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Space Robotics

Motors

A space motor has to deliver torque for years through large thermal swings, in vacuum or a thin carbon dioxide atmosphere, with no maintenance and, in a sealed or open configuration, a lubrication and brush problem that terrestrial catalog parts do not carry. Heat leaves a vacuum-mounted winding only by conduction, so dissipation rather than torque often sets the size [13]. This page covers the motor families that flew or were qualified, the electronics that drive them, the lubricant and thermal constraints that govern them, and what is not established.

Two failure modes recur in the qualification records below, and neither is electrical. On IPEx the accelerated life test of the wheel actuator was ended by the harmonic drive wave generator migrating axially into the flex cup, which broke the springs preloading the motor rotor bearings [1]. On the Apollo Lunar Roving Vehicle the sealed motor was selected over an open brushless alternate, and the contractor was obliged to carry the alternate design until the sealed baseline had been shown to work in simulated lunar conditions [3].

Motors selected and flown

Section titled “Motors selected and flown”
PartManufacturerUsed bySource
LSI 75-12ThinGapipex (wheel actuators)[1]
LSI 75-30ThinGapipex (bucket drum and arm actuators)[1]
Series-wound four-pole brush motor, 1/4 hpGarrett Corporationapollo-lrv[3]
Six-pole brushless motor, 80:1 spurGeneral Electricapollo-lrv, alternate not flown[3]
2214X024BXTH with 22GPT gearhead at 862:1Faulhaberipex (radiator cover actuator)[1]

Ratings and qualification results

Section titled “Ratings and qualification results”
  • LSI 75-12, ThinGap: a frameless slotless brushless DC motor kit [1]. Ratings: paired with Honeywell SS511AT Hall sensors and a Harmonic Drive CSF 14-80LW 80:1 gearset. Sizing load cases run to 7.45 N m at the gearbox and 0.24 N m at the motor at 150 rpm, with the long-duration driving cases at 1530 rpm [1]. High pole count gives usable low-speed commutation from Hall sensors alone. Qualification: characterized under vacuum from 0 to 15 N m in 3 N m steps and from 10 rpm to 1700 rpm, at 35 and 40 C surface temperature and bus voltages of 47.6, 53.2 and 58.8 V; varying bus voltage across that range had negligible effect on motor response [1]. Accelerated life test at 3-sigma load ran 6,547,036 input revolutions against a mission requirement of 5.7 million before failing. Root cause was the harmonic drive wave generator moving axially into the flex cup, which failed the motor rotor bearing springs, not the motor itself [1]. The published output is a characterization curve and fitted equation, Fig. 6, rather than a single torque constant.
  • LSI 75-30, ThinGap: a frameless brushless DC motor kit [1]. Ratings: same outside diameter as the wheel actuator motor, chosen for commonality; drives a Harmonic Drive CSF 20-160LW gearset [1]. Qualification: covered by the same four-stage KSC actuator qualification campaign as the wheel actuator, with the arm and bucket drum units run at 2-sigma load rather than 3-sigma. Only the wheel actuator result is published [1].
  • Series-wound four-pole brush motor, 1/4 hp, Garrett Corporation: a hermetically sealed brush DC traction motor [5]. Ratings: one per wheel at 36 Vdc nominal with pulse-width-modulated speed control from the drive controller, coupled to a United Shoe Machinery 80:1 harmonic drive and instrumented for thermal monitoring on the crew display [5]. Motor and wave generator run together in a sealed 5.17 N/cm2 dry nitrogen atmosphere, transmission lubricated with Krytox 143AZ oil [3]. Qualification: selected as the baseline and flown on Apollo 15, 16 and 17. The sealed traction drive holds 7.5 psia internal pressure [5]. The contract required the alternate open-to-vacuum design to be carried in parallel until the sealed baseline was demonstrated under simulated lunar conditions [3].
  • Six-pole brushless motor, 80:1 spur, General Electric: a permanent magnet brushless DC traction motor with 80:1 planetary spur gearing, open to vacuum, carried as the Apollo LRV alternate design and not flown [3]. Ratings: same 80:1 overall reduction as the baseline, entire drive open to vacuum rather than sealed. Qualification: carried as the contractual alternate and not selected. Its stall torque against current was characterized alongside the series-wound baseline, Fig. on p. 4 [3].
  • 2214X024BXTH with 22GPT gearhead at 862:1, Faulhaber: a brushed DC motor with planetary gearhead [1]. Ratings: gearhead rated 1.8 N m continuous and 2.5 N m peak against a computed 1.84 N m peak requirement; motor runs at 431 rpm to open the cover in 30 s. Gearhead is orderable vacuum-rated with vacuum grease preinstalled [1]. Qualification: not yet qualified. The Hall effect sensor part number inside the motor could not be identified, which the paper records as an open qualification item, and the actuator has still to run the four-stage campaign applied to the drive actuators [1].

Sizing against the seals

Section titled “Sizing against the seals”

The IPEx Gen 1 actuator was instrumented specifically to separate motor losses from gearbox, bearing, seal and resolver losses, because manufacturer motor curves and gear efficiencies assume a particular grease, temperature and ambient pressure [2]. The measured maximum seal drag across that campaign was 0.03 N m, under one percent of the overall load, which is why the layered labyrinth, felt and PTFE seal stack was kept. For a motor sized against a lunar duty cycle the seal is not the constraint; the harmonic drive interface is [1][2].

One further selection is published without a test result and is therefore not tabled. RASSOR 2.0 uses a Parker Bayside K089050 frameless kit motor direct-driving a Harmonic Drive SHG 32-160 at 161:1 in its shoulder actuator, with factory-installed Hall sensors, chosen because the kit format removes the separate housing and coupling [4].

Why a brush material is qualified against its ambient

Section titled “Why a brush material is qualified against its ambient”

A sliding electrical contact is lubricated by a transfer film, and the film is a function of the ambient rather than of the brush. A graphite-carbon body sliding at 216 cm/s under a 9.8 N load at 20 C holds a carbon transfer film on the chromium and iron oxides of AISI 440C down to 1e-9 torr, which caps its friction coefficient at about 0.2; on electrolytic silver, silver oxide is thermodynamically unstable below about 1 torr, no carbon film forms, the carbon strips metallic silver and the coefficient rises to about 0.5 with silver sliding on silver [6]. Wear of graphite sliding bodies becomes very high below 1e-5 torr as the adsorbed moisture the film depends on is pumped away, which is the mechanism behind high-altitude generator brush dusting. The Apollo traction motor above never sees that regime: it runs sealed in dry nitrogen at 5.17 N/cm2 rather than open to the lunar surface [3], so its brush heritage is heritage at an ambient pressure the vehicle’s exterior mechanisms did not have.

Motors qualified by Mars surface programs

Section titled “Motors qualified by Mars surface programs”

Three flown programs published motor qualification campaigns against a part number. The failures they record are at the brush, the commutator and the lubricant, and none is an electrical failure of the winding [8][9].

PartManufacturerUsed bySource
M32 flat motormaxonperseverance[7]
M32 detent brakemaxonperseverance[7]
M20 gearmotormaxonperseverance[7]
RE016maxonsojourner (wheel drives)[8]
Brush DC motor lotmaxonspirit, opportunity (arm)[9]
USR30E3 ultrasonic motorShinseiMarsArmII wrist, MicroArm[10]
USR60S1 ultrasonic motorShinseiMicroArm shoulder and elbow[10]
Iron-core motor, SG54-27 brushesATCMars Polar Lander study[8]
BMG planetary gearmotorNot namedKSC dynamometer article[11]
DRV8412 motor driverTexas InstrumentsJPL avionics screen[12]

Ratings and qualification results

Section titled “Ratings and qualification results”
  • M32 flat motor, maxon. Brushless flat motor at ten flight actuator locations on Perseverance. Ratings: torque constant 50 mNm/A to an acceptance criterion of plus or minus 10 percent, tested at 12, 20 and 28 V in both directions at ambient [7]. Qualification: 99 units were delivered across three lot builds, 10 engineering model, 35 in the first flight lot and 54 in the second [7].
  • M32 detent brake, maxon. Passive magnetic detent brake on the same motor. Ratings: 10 and 20 mNm holding torque options over 24 detents per revolution, matching the motor commutation state changes, accepted at plus or minus 10 percent measured at 2 rpm over two revolutions [7]. Qualification: the axially charged detent magnet produced stray flux at the Hall sensor, causing commutation switching errors and reduced detent strength until it was compensated [7]. A passive brake changed the behavior of the sensor that commutates the motor it brakes.
  • M20 gearmotor, maxon. Smaller gearmotor from the same qualification campaign. Ratings: gearmotor torque constant 1620 Nm/A to plus or minus 10 percent, verified at plus 70, plus 22 and minus 70 C, with static holding torque required above 50 mNm after one thermal cycle from plus 113 to minus 135 C and two from plus 70 to minus 135 C [7]. Qualification: rotary life testing ran 40400 revolutions at 0.2 N m, 12400 at 0.3, 2100 at 0.4 and 1500 at 0.5, split between directions and alternating between plus 70, plus 22, minus 55 and minus 70 C, completing with minimal wear. Thermal life testing accumulated 3015 cycles representing 4.5 Mars years over 1.5 years of running, on seasonal profiles of minus 80 to plus 85 C for summer and minus 115 to plus 50 C for winter, and was still running when the source was written [7]. Bake-out was 288 hours at 113 C and 1.3e-3 Pa, followed by 40 hours of 80 percent relative humidity at plus 80 C as an accelerated corrosion exposure.
  • RE016, maxon. Brush DC motor in the Sojourner wheel drives. Ratings: the mission requirement was about one million revolutions for 100 m of driving [8]. Qualification: two complete actuators ran 30 to 40 million revolutions to failure under load and start-stop, part of it at -70 C in low pressure carbon dioxide, and two motors ran 40 million revolutions unloaded at plus 20 C in low pressure air without failing. Retested for the Mars Polar Lander robotic arm at 30 V rather than Sojourner’s 15.5 V, 29 motors averaged under 10 million revolutions, failing by rotor shorting from conductive commutator debris, by brush galling and micro-welding to the commutator, and in one or two cases by an open winding [8]. Doubling the bus voltage cost the design more than a factor of three in life.
  • Brush DC motor lot, maxon, for the Mars Exploration Rover and Phoenix arm actuators. Ratings: lot of 211 motors [9]. Qualification: 168 were fully tested and flight qualified with no indication of degraded or broken brushes. Brushes broke only in component-level simulated pyro shock, at a maximum tolerated 2600 G peak shock response spectrum against a 4000 G requirement, and never in assembly-level pyro shock, which the review attributes to component-level testing being a routine overtest [9].
  • USR30E3 ultrasonic motor, Shinsei. Traveling wave piezoelectric motor at the MarsArmII wrist and the MicroArm shoulder and elbow. Ratings: 1 in-lb of stall torque and 300 rpm unloaded, both manufacturer figures, with a minimum rated temperature of -10 C [10]. Qualification: repeatable operation down to -50 C in a 20 mTorr inert atmosphere, with seizure at about -50 C attributed to differential thermal expansion at the stator-rotor interface [10]. One unit was tested, in an inert atmosphere rather than in Martian carbon dioxide, and no lifetime or cycle count is reported.
  • USR60S1 ultrasonic motor, Shinsei. Larger traveling wave motor for the same joints. Ratings: 100 rpm unloaded maximum speed [10]. Qualification: stall torque measured on the bench at 4.5 in-lb at room temperature and one atmosphere, against 6 in-lb stated for the same joints in the same paper’s abstract, which the source does not reconcile [10].
  • Iron-core motor, SG54-27 brushes, ATC, with silver-graphite brushes. Ratings: complete mechanisms cycled under high load, one test per condition. Qualification: 102 million revolutions to brush wear-out at -70 C in 1.0 kPa carbon dioxide, 36 million at -70 C in 1.0 kPa nitrogen, and 62 million in ambient air, with no-load life exceeding 100 million revolutions and 300 to 500 million extrapolated from brush wear [8]. The same program’s vacuum tests were no-load only, and SG54-27 brushes failed in as few as 3 million revolutions in vacuum, with up to 20 million for SG59 [15]. The authors draw no conclusion from the carbon dioxide against nitrogen difference, and with one article per condition the ordering carries no spread.
  • BMG planetary gearmotor, vendor not named, with Cu43Zr43Al7Be7 bulk metallic glass gearing and an iKote dry film. Ratings: run at 1 N m of output torque and 2000 rpm under vacuum, direction reversed every 2000 revolutions [11]. Qualification: 10 million motor revolutions to stall at ambient temperature against 1.5 million below 100 K on the Kennedy Space Center Space Environment Dynamometer, one article per condition [11]. Cold costs this gearmotor a factor of about seven in life, measured rather than derated.
  • DRV8412 motor driver, Texas Instruments. Commercial dual full-bridge motor driver screened for a JPL avionics build. Ratings: biased at 13 V on the power supply pin against a 52.5 V rating [12]. Qualification: no latchup above 42.8 MeV-cm2/mg at 25 C and 90 C with silver-109 over 1e7 ions/cm2, with a recoverable functional interrupt observed [12]. A cross section of the die found 12.76 micrometers of copper redistribution above the active silicon, and 287 MeV bromine-81 has only about 17 micrometers of range in that stackup, so an ion that reaches the die in a bare part does not reach it here.

Ion range, not linear energy transfer alone, decides whether a motor driver has been tested at all [12]. The same campaign measured silver at 2954 MeV reaching 113 micrometers in silicon and bromine at 287 MeV reaching 36, against a redistribution layer thick enough to stop the lighter of the two.

Design space and why selections converged

Section titled “Design space and why selections converged”

Four families have been used or proposed. Brush DC motors need no commutation electronics, which mattered for Sojourner’s 80C85 processor, and were judged viable on Mars because the 1.0 kPa carbon dioxide atmosphere is not vacuum [8]. Brushless permanent magnet motors move the dissipating windings onto the stator, where the chassis acts as a heat sink in vacuum; the Apollo LRV study found an overrated brushless motor with a pulse width modulated controller the best fit for 88 N m per wheel at 11.0 rad/s, because a directly sized motor would have needed 596 W/kg dissipation capability against about 200 W/kg considered the reliability ceiling [13]. The statically commutated brushless traction motor itself predates the lunar program, with Army-funded development from 1962 [14]. Frameless kit motors with Hall commutation, as on IPEx and RASSOR, remove the housing and coupling [1][4]. Piezoelectric motors remove the gearhead and brush, at the cost of a narrow cold envelope [10].

The LRV result shows how schedule can override the technical preference: the General Electric brushless alternate was preferred technically, but the schedule did not allow qualifying brushes for vacuum, so the sealed brush baseline flew [3]. Mars programs made the opposite choice for the opposite reason, qualifying commercial maxon flat brushless motors for Perseverance after changing the construction of the catalog part [7]. Both are flight-proven; frameless brushless kits on IPEx are ground-qualified at TRL 5 and have not flown [1][2].

Joint motors for manipulators

Section titled “Joint motors for manipulators”

Manipulator joints add requirements that wheel drives lack: holding torque, smooth low-speed motion and a brake. A 1987 survey of ten transmission families found harmonic drives needing about 30 percent additional torque to overcome static friction, with efficiency falling from the usual 80 to 90 percent with wet lubricant to as low as 50 percent dry [25]. The European Robotic Arm joint motor unit pairs a redundantly wound permanent magnet synchronous motor and a 454:1 epicyclic stage with look-up-table current shaping that cut torque ripple from about 15 percent of mean torque to under 0.3 percent peak to peak [23]. Its plasma sprayed chromium oxide brake works only after in-vacuo running in of at least 12000 revolutions, and its air and vacuum torque cannot be correlated one to one, which limits how much brake testing can be done at higher assembly levels [23]. The arm’s joint gearbox is a four stage planetary at 1:450 with oil lubricated bearings preloaded against launch vibration [24]. Mars Pathfinder’s lander actuators used brushless motors through an 8277:1 gearbox for airbag retraction and a 31,552:1 harmonic drive for petal opening, and eliminated Nedox plating on gear planets after delamination [26].

Piezoelectric and other non-electromagnetic actuation

Section titled “Piezoelectric and other non-electromagnetic actuation”

Rotary ultrasonic motors drove the 2.3 m all-composite MarsArmII through harmonic drives [10]; the cold seizure of the tested unit is in the Mars table above. Piezoelectric percussive drills avoid a motor on the percussion path: Auto-Gopher-2 used a 5.2 kHz piezoelectric percussor with a 65 kg drill drawing under 500 W and reached 7.52 m in gypsum in a field test [37]. A single slotted-horn piezoelectric stack produced both hammering and bit rotation at about 100 rpm for about 100 W in a laboratory prototype, removing the rotary motor [38]. None of these has flown as a surface drill. The two piezoelectric ground tests are not motor qualifications in the sense of the tables here.

Motor drive and control electronics

Section titled “Motor drive and control electronics”

Perseverance’s motors are verified together with the controller that commutates them. Its control architecture runs a 64 Hz telemetry and command cadence, a 512 Hz PID loop, 31.25 kHz commutation and 23.5 kHz brake current control across 33 actuators; PWM ground bounce at 31.25 kHz coinciding with a 4 MHz ADC sample flipped bits in the 12-bit current reading and tripped overcurrent protection during mast deployment testing [17]. The actuator test suite covered winding resistance, brake engage and disengage, cogging and torque ripple, and dynamometer runs at -70, +22 and +70 C on 94 motors and actuators, with an unresolved torque-constant discrepancy of up to 10 percent in the report [16].

The Europa Lander motor controller is a ground development, not flight hardware. It moves drive electronics onto the actuator in a 0.3 kg package rated -55 to +85 C in operation, motivated by MSL cabling exceeding 50 kg [18]. Its point-of-load regulator drifted out of specification at 256 krad against a 200 krad part rating and a 300 krad requirement, closed by tantalum shielding [18]. Closing all three control loops in an FPGA required at least 5 kHz on the current loop and 2 kHz on the velocity loop [19]. A power conversion card with its own microcontroller digitizes telemetry where it is generated [20]. A Standard CAN bus cannot carry the 512 Hz loop closed over the bus, but fits with about a fifth of the bandwidth spare if the loop is closed locally and only 64 Hz telemetry crosses it [21]. A hardware-in-the-loop simulator for the 24-motor controller is a proposal-stage build [22]. A published actuator model for the Sample Retrieval Lander arm underpredicts real bandwidth by design, so passing sequences should transfer with margin [36].

Lubrication and thermal constraints

Section titled “Lubrication and thermal constraints”

Wet lubricants set the thermal envelope. On MSL the Braycote viscosity sets a -70 C minimum, all 31 actuators were qualified by soak at -70 C, and 15 C of margin gives a -55 C minimum allowable flight temperature [27]. In thermal vacuum, bearing conductance in a low pressure atmosphere is about three times the published vacuum value and gear contact is a real heat path, which cut model error from 5.8 to 2.8 C [28]. Because the original dry-lubricated actuators failed qualification, Curiosity pre-heats actuators with the computer off, which would otherwise have cost about 50 W of a roughly 114 W supply [29]. An oscillating heat pipe inside the actuator structure is simulation only, predicting a gradient cut from 75 C to 3.4 C at 12.7 W [30]. Among lubricants, silahydrocarbons beat Pennzane on low temperature fluidity and unformulated wear scar but have vapor pressure at least an order of magnitude above 815Z [31]. Chromium content of the counterface, not the lubricant, drove the life of Fomblin Z-25 in a rolling element vacuum tribometer [32]. Bulk metallic glass gearing removes wet lubricant entirely and is covered in the Mars table above.

Failures in service and standards

Section titled “Failures in service and standards”

The Curiosity drill feed motor stalled at current limit on sol 1536 with no shaft motion after the brake was released, traced to a high friction zone about one third of a revolution wide, best explained by the ferrous brake plate partially disengaging; feed extended drilling later resumed [33]. A VIPER engineering model test found that loss of power to a drive motor raised slip by 200 percent on a 15 degree slope and by a factor of 25 on a 3 degree slope [34]. Torque margins quoted from programs qualified before 2023 were computed with the 2015 mechanisms standard, which carries factors of 1.25 and 2.0 for test of flight-like hardware and 4x life testing for loss-of-life mechanisms [35].

What is not established

Section titled “What is not established”

Cross-program comparison is limited by single-article tests: the carbon dioxide against nitrogen brush life ordering has one test per condition [15], and the bulk metallic glass cold life result is one article per condition [11]. The Apollo steering anomaly is left open with motor or gear train binding as most likely cause [5]. The M20 thermal life test was still running when reported [7], and the Europa Lander controller work is ground development with no flight record [18][19]. Vacuum friction data are clean-vacuum laboratory values and bound real mechanisms from above, with no regolith or cryogenic data [6]. The IPEx 75-30 arm and bucket actuator result and the Faulhaber radiator actuator qualification are unpublished [1].

References

  1. Schuler, J. M., Smith, J. D., Nick, A. J., Buckles, B. C., Dyas, J. E., Ortega, V. V., Cloud, J. M., Dokos, A. G., Zhang, E. L., Wang, J. J., Baron, M. A., Muller, T. J., Clark, C. J. and Howe, M. W. (2024). ISRU Pilot Excavator (IPEx) Technology Readiness Level 5 Design Overview . AIAA AVIATION Forum and ASCEND, 20240008162. Source
    BibTeX
    @inproceedings{schuler2024isru,
  title = {ISRU Pilot Excavator (IPEx) Technology Readiness Level 5 Design Overview},
  author = {Schuler, Jason M. and Smith, Jonathan D. and Nick, Andrew J. and Buckles, Bradley C. and Dyas, Jeffrey E. and Ortega, Victoria V. and Cloud, Joseph M. and Dokos, Adam G. and Zhang, Elizabeth L. and Wang, Jerry J. and Baron, Michael A. and Muller, Thomas J. and Clark, Casey J. and Howe, Musashi W.},
  booktitle = {AIAA AVIATION Forum and ASCEND},
  number = {20240008162},
  institution = {NASA},
  year = {2024},
  doi = {10.2514/6.2024-4890},
  abstract = {This paper details the mechanical and mechatronic design of the Technology Readiness Level (TRL)-5 In-Situ Resource Utilization (ISRU) Pilot Excavator (IPEx). IPEx is a robotic excavator designed for a technology demonstration of regolith mining in the lunar south pole region. The novel design uses pairs of counter-acting excavation tools called bucket drums, that dig at the same time in opposing directions to reduce the reaction force needed, thereby enabling mining with a small, low-mass, robotic system. IPEx builds on the prior work of the Regolith Advanced Surface Systems Operations Robot (RASSOR), which is the TRL-4 implementation of this concept. The TRL-5 IPEx subsystems that are discussed in this paper include: Regolith Delivery Subsystem (RDS), Mobility Subsystem (MS), Cameras and Dust Mitigation Subsystem (CDMS), and Thermal Control Subsystem (TCS). Each subsystem is described in detail with rationale for design selections. Dust tolerance is a key feature for IPEx, and this paper details a thermal control system with an actuated radiator cover and phase change material as well as camera modules with removable electrodynamic dust shields (EDS). Additional components such as actuators, wheels, and bucket drums are discussed in detail. Due to their complexity, the avionics and software subsystems will be discussed in a separate publication.}
}
  2. Clark, C. J., Smith, J. D., Nick, A. J., Ortega, V. V., Schuler, J. M., Dyas, J. E. and Lahl, J. (2025). Design and Testing of TRL5 IPEx Actuators . IEEE Aerospace Conference, 20250000003. Source
    BibTeX
    @inproceedings{clark2025design,
  title = {Design and Testing of TRL5 IPEx Actuators},
  author = {Clark, Casey J. and Smith, Jonathan Drew and Nick, Andrew J. and Ortega, Victoria V. and Schuler, Jason M. and Dyas, Jeffrey E. and Lahl, John},
  booktitle = {IEEE Aerospace Conference},
  number = {20250000003},
  institution = {NASA},
  address = {Big Sky, MT},
  year = {2025},
  url = {https://ntrs.nasa.gov/citations/20250000003},
  abstract = {NASA is advancing In-Situ Resource Utilization (ISRU) by focusing on missions aimed at establishing sustainable infrastructure on the Moon and Mars. On the Moon, regolith serves as the most abundant resource. To support ISRU objectives, a 30-kg-class robot called ISRU Pilot Excavator (IPEx) is being developed to excavate 10,000 kg of lunar regolith during a future technology demonstration mission. IPEx uses novel excavation tools, called bucket drums, which are hollow cylinders with scoops staggered around the outside. Regolith is collected with the scoops and flows into the drum where it is captured by an internal baffle system. The excavator can then transport the regolith in the drum and reverse the direction of the drum rotation to dispense the regolith out. IPEx uses two sets of bucket drums that dig simultaneously in opposing directions and results in counteracting excavation forces. This combination of bucket drum excavation tools and counteracting excavation forces enables low mass robotic excavators to effectively dig in reduced gravity environments. This is a significant departure from terrestrial excavators that rely on high mass to produce tractive forces to counteract the forces of excavation.

IPEx is made up of several custom actuators that all need to be verified for their intended application. This paper focuses on the initial design, testing and modifications of three actuators: the mobility actuator, the shoulder actuator, and the excavation actuator.

Each actuator was tested under four separate test profiles: ambient motor characterization, hot and cold motor characterization, accelerated life test (ALT), and concept of operations (ConOps) test. The motor characterization tests enabled derivation of torque equations for each actuator to estimate output torque without implementing sensors. The accelerated life tests were successful for each actuator and verified the motors’ ability to survive the mission. For the ConOps test, only the bucket drum actuator performed a complete ConOps without the need to restart the test. Overall, the first series of testing resulted in various failure modes and minor design alterations for each actuator. The test results, failure modes, and design alterations are highlighted within this paper. This paper focuses on discussing the mobility, excavation, and shoulder actuator design, testing principles, and results that qualified it as a TRL 5 system.}
}
  3. Jones, C. S. J. and Nola, F. J. (1971). Mobility systems activity for lunar rovers at MSFC . NASA, NASA-TM-. Source
    BibTeX
    @techreport{jones1971mobility,
  title = {Mobility systems activity for lunar rovers at MSFC},
  author = {Jones, C. S., Jr. and Nola, F. J.},
  number = {NASA-TM-},
  institution = {NASA},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720004516},
  abstract = {The Apollo Lunar Roving Vehicle (LRV) mobility system is described. Special emphasis is given to the redundancy aspects and to the selection of the drive motors. A summary chart of the performance on the lunar surface during the Apollo 15 flight is included. An appendix gives details on some development work on high efficiency drive systems and compares these systems to the selected system.}
}
  4. Mueller, R. P., Smith, J. D., Schuler, J. M., Nick, A. J., Gelino, N. J., Leucht, K. W., Townsend, I. I. and Dokos, A. G. (2016). Design of an Excavation Robot: Regolith Advanced Surface Systems Operations Robot (RASSOR) 2.0 . ASCE Earth and Space Conference, 20210011366. Source
    BibTeX
    @inproceedings{mueller2016design,
  title = {Design of an Excavation Robot: Regolith Advanced Surface Systems Operations Robot (RASSOR) 2.0},
  author = {Mueller, Robert P. and Smith, Jonathan D. and Schuler, Jason M. and Nick, Andrew J. and Gelino, Nathan J. and Leucht, Kurt W. and Townsend, Ivan I. and Dokos, Adam G.},
  booktitle = {ASCE Earth and Space Conference},
  number = {20210011366},
  pages = {163-174},
  institution = {NASA},
  year = {2016},
  doi = {10.1061/9780784479971.018},
  abstract = {To continue on a sustainable and flexible path, NASA needs to address the challenge of collecting and moving large amounts of regolith at the destination. Acquiring the water resources on Mars will require mining significant quantities of regolith, and this is not possible with the state-of-the-art low mass excavation systems. Low gravity environments (Mars = 3/8G) and launch mass restrictions limit the traction and the resulting reaction force of the vehicle, making current terrestrial techniques impractical. This project addressed this challenge by developing a completely new technology that can mine large quantities of regolith on Mars. Recent measurements by the “Curiosity” rover on Mars have found that the regolith contains ~2% water by weight globally, ~4% in Jezero Crater (Human Architecture Team’s reference landing site), and much more at the poles. RASSOR 2.0 is a planetary excavator, which has a mass of 66 kg, with a 0.38 kg vehicle mass per kilogram, per hour of excavation rate and power usage of 4 W per kg of regolith excavation rate. A single RASSOR 2.0 can excavate a minimum of 2.7 metric tons of regolith per day. This is accomplished by using counteracting excavation forces on two opposing digging implements called bucket drums and an autonomous mining control system. This work has addressed several major research areas outlined in the NASA Technology Area (TA) 04 Robotics and Autonomous Systems and TA 07 Human Destination Systems roadmaps. This project started at Technology Readiness Level (TRL) 4 as a low fidelity “proof of concept” prototype which has successfully demonstrated basic regolith simulant excavation functionality in a lab-scale gravity off load test. The foundational technology described here was awarded US patent number: US 9027265 for a “Zero horizontal reaction force excavator” on May 12, 2015.}
}
  5. NASA Manned Spacecraft Center. (1971). Apollo 15 Mission Report . NASA Manned Spacecraft Center, MSC-05161. Source
    BibTeX
    @techreport{anon1971apollo,
  title = {Apollo 15 Mission Report},
  author = {{NASA Manned Spacecraft Center}},
  number = {MSC-05161},
  institution = {NASA Manned Spacecraft Center},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720021182},
  abstract = {A detailed discussion is presented of the Apollo 15 mission, which conducted exploration of the moon over longer periods, greater ranges, and with more instruments of scientific data acquisition than previous missions. The topics include trajectory, lunar surface science, inflight science and photography, command and service module performance, lunar module performance, lunar surface operational equipment, pilot's report, biomedical evaluation, mission support performance, assessment of mission objectives, launch phase summary, anomaly summary, and vehicle and equipment descriptions. The capability of transporting larger payloads and extending time on the moon were demonstrated. The ground-controlled TV camera allowed greater real-time participation by earth-bound personnel. The crew operated more as scientists and relied more on ground support team for systems monitoring. The modified pressure garment and portable life support system provided better mobility and extended EVA time. The lunar roving vehicle and the lunar communications relay unit were also demonstrated.}
}
  6. Buckley, D. H. (1971). Friction, Wear, and Lubrication in Vacuum . National Aeronautics and Space Administration. Source
    BibTeX
    @book{buckley1971friction,
  title = {Friction, Wear, and Lubrication in Vacuum},
  author = {Buckley, Donald H.},
  series = {NASA SP-277},
  publisher = {National Aeronautics and Space Administration},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720012801},
  abstract = {A review of studies and observations on the friction, wear, and lubrication behavior of materials in a vacuum environment is presented. The factors that determine and influence friction and wear are discussed. They include topographical, physical, mechanical, and the chemical nature of the surface. The effects of bulk properties such as deformation characteristics, fracture behavior, and structure are included.}
}
  7. Loschiavo, M., Phillips, R., Mikhaylov, R. and Braunschweig, L. (2020). Mars 2020 Maxon Commercial Motor Development from COTS to Flight Qualified Motors, Gearbox, and Detent Brake: Issues Overcome and Lessons Learned . Aerospace Mechanisms Symposium. Source
    BibTeX
    @inproceedings{loschiavo2020mars,
  title = {Mars 2020 Maxon Commercial Motor Development from COTS to Flight Qualified Motors, Gearbox, and Detent Brake: Issues Overcome and Lessons Learned},
  author = {Loschiavo, Michael and Phillips, Robin and Mikhaylov, Rebecca and Braunschweig, Lynn},
  booktitle = {Aerospace Mechanisms Symposium},
  publisher = {JPL Open Repository},
  year = {2020},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/52357}
}
  8. Reid, L. K., Braun, D. F. and Noon, D. E. (1999). Robotic Arm and Rover Actuator Systems for Mars Exploration . Aerospace Mechanisms Symposium. Source
    BibTeX
    @inproceedings{reid1999robotic,
  title = {Robotic Arm and Rover Actuator Systems for Mars Exploration},
  author = {Reid, Lisa K. and Braun, David F. and Noon, Don E.},
  booktitle = {Aerospace Mechanisms Symposium},
  organization = {Jet Propulsion Laboratory, California Institute of Technology},
  year = {1999},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/18020}
}
  9. McManamen, J. P., Pellicciotti, J. W., De Kramer, C., Dube, M. J., Peeler, D., Muirhead, B. K., Sevilla, D. R., Sabahi, D. and Knopp, M. D. (2007). Independent Review Support for Phoenix Mars Mission Robotic Arm Brush Motor Failure . NASA, NASA/TM-2007-215084, NESC-RP-07-13/06-050-E. Source
    BibTeX
    @techreport{mcmanamen2007independent,
  title = {Independent Review Support for Phoenix Mars Mission Robotic Arm Brush Motor Failure},
  author = {McManamen, John P. and Pellicciotti, Joseph W. and De Kramer, Cornelis and Dube, Michael J. and Peeler, Deborah and Muirhead, Brian K. and Sevilla, Donald R. and Sabahi, Dara and Knopp, Michael D.},
  number = {NASA/TM-2007-215084, NESC-RP-07-13/06-050-E},
  institution = {NASA},
  year = {2007},
  url = {https://ntrs.nasa.gov/citations/20070035083},
  abstract = {The Phoenix Project requested the NASA Engineering and Safety Center (NESC) perform an independent peer review of the Robotic Arm (RA) Direct Current (DC) motor brush anomalies that originated during the Mars Exploration Rover (MER) Project and recurred during the Phoenix Project. The request was to evaluate the Phoenix Project investigation efforts and provide an independent risk assessment. This includes a recommendation for additional work and assessment of the flight worthiness of the RA DC motors. Based on the investigation and findings contained within this report, the IRT concurs with the risk assessment Failure Cause / Corrective Action (FC/CA) by the project, "Failure Effect Rating "3"; Major Degradation or Total Loss of Function, Failure Cause/Corrective Action Rating Currently "4"; Unknown Cause, Uncertainty in Corrective Action."}
}
  10. Schenker, P., Bar-Cohen, Y., Brown, D., Lindemann, R., Garrett, M., Baumgartner, E., Lee, S., Lih, S.-S. and Joffe, B. (1999). A Composite Manipulator Utilizing Rotary Piezoelectric Motors: New Robotic Technologies For Mars in-situ Planetary Science . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{schenker1999composite,
  title = {A Composite Manipulator Utilizing Rotary Piezoelectric Motors: New Robotic Technologies For Mars in-situ Planetary Science},
  author = {Schenker, P. and Bar-Cohen, Yoseph and Brown, David and Lindemann, R. and Garrett, Mike and Baumgartner, E. and Lee, S. and Lih, Shyh-Shiuh and Joffe, B.},
  booktitle = {IEEE Aerospace Conference},
  publisher = {JPL Open Repository},
  year = {1999},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/20580}
}
  11. Kennett, A. and Dillon, R. `. (2024). Development of a Bulk Metallic Glass Planetary Gearmotor for Unheated Actuation in Cryogenic Environments . International Conference on Advanced Robotics. Source
    BibTeX
    @inproceedings{kennett2024development,
  title = {Development of a Bulk Metallic Glass Planetary Gearmotor for Unheated Actuation in Cryogenic Environments},
  author = {Kennett, Andrew and Dillon, Robert ``Peter''},
  booktitle = {International Conference on Advanced Robotics},
  publisher = {JPL Open Repository},
  year = {2024},
  doi = {10.48577/jpl.bhhjka},
  abstract = {Bulk metallic glasses (BMGs), a class of amorphous metal alloys, were selected for development of gears for unheated actuators that can be used in cryogenic environments such as Mars, the Moon, and outer planetary icy bodies (e.g., Enceladus and Europa). Specifically, an alloy of Cu43Zr43Al7Be7 was used to successfully develop a BMG planetary gearbox and prototype and flight gearmotors for operation at ≤-180 C. In additional to lessons learned from all phases of development, components and configurations, testing (including shock and vibration), and qualification for use in the Cold Operable Lunar Deployable (robotic) Arm (COLDArm) system are presented.}
}
  12. Daniel, A. C. and Allen, G. R. (2018). Heavy-Ion Test Results of Several Commercial Components for Use in a JPL Class D Interplanetary Mission Payload . JPL Open Repository. Source
    BibTeX
    @inproceedings{daniel2018heavy,
  title = {Heavy-Ion Test Results of Several Commercial Components for Use in a JPL Class D Interplanetary Mission Payload},
  author = {Daniel, Andrew C. and Allen, Gregory R.},
  publisher = {JPL Open Repository},
  year = {2018},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/48478}
}
  13. Jones, C. S. J., Nola, F. J. and Doran, B. J. (1969). Traction drive system design considerations for a lunar roving vehicle . SAE Technical Paper Series, NASA-TM-. Source
    BibTeX
    @inproceedings{jones1969traction,
  title = {Traction drive system design considerations for a lunar roving vehicle},
  author = {Jones, C. S., Jr. and Nola, F. J. and Doran, B. J.},
  booktitle = {SAE Technical Paper Series},
  volume = {1},
  number = {NASA-TM-},
  institution = {NASA},
  year = {1969},
  doi = {10.4271/700023},
  abstract = {<div class="htmlview paragraph">For an optimum design, the weight, energy consumption, and operational flexibility of the traction drive system for a lunar roving vehicle must be considered along with the power supply, motor, and power train.</div> <div class="htmlview paragraph">Other problems considered in this paper include: environment and motor dissipation; motor type (a-c or d-c) and commutation if d-c; motor controller (switching of large currents); delivery of torque at varying speeds; the power train; use of regenerative braking and conservation of energy; and power supply voltage variation. These problems are studied in the light of certain general system specifications, which fall into weight, performance, and environment categories. Tradeoff studies are considered for purposes of optimization in each of these areas.</div> <div class="htmlview paragraph">Special consideration is given to the controller and system design as it pertains to regenerative braking and the conservation of energy. Some aspects of changing the modes of motor operation to satisfy extreme performance requirements of speed and torque are discussed.</div>}
}
  14. Slabiak, W. and Collins, G. C. (1968). Brushless Synchronous Propulsion Motor . SAE Technical Paper Series. Source
    BibTeX
    @inproceedings{slabiak1968brushless,
  title = {Brushless Synchronous Propulsion Motor},
  author = {Slabiak, Walter and Collins, George C.},
  booktitle = {SAE Technical Paper Series},
  volume = {1},
  publisher = {SAE International},
  year = {1968},
  doi = {10.4271/680455},
  abstract = {<div class="htmlview paragraph">The development of a brushless synchronous motor with d-c motor characteristics suitable for vehicle propulsion applications is described. The motor is statically commutated, using thyristors triggered by rotor position logic. It may be operated from d-c power sources such as batteries or from a-c sources such as engine driven alternators, depending on the commutation circuit used with the motor.</div> <div class="htmlview paragraph">The motor has high speed capability, coupled with high torque ability, thus providing the operating range required for severe applications such as military and off highway vehicles.</div> <div class="htmlview paragraph">The three basic elements of the motor system: the motor, power converter, and trigger circuits are discussed in detail. Mechanical, electrical, and control characteristics are reviewed.</div> <div class="htmlview paragraph">Performance data on motors built for vehicular application are also presented.</div>}
}
  15. Noon, D. E. and Braun, D. (1998). Long Life DC brush motor for use on the Mars Surveyor Program . Jet Propulsion Laboratory, 20210003097. Source
    BibTeX
    @techreport{noon1998long,
  title = {Long Life DC brush motor for use on the Mars Surveyor Program},
  author = {Noon, Don E. and Braun, D.},
  number = {20210003097},
  institution = {Jet Propulsion Laboratory},
  year = {1998},
  url = {https://ntrs.nasa.gov/citations/20210003097},
  abstract = {DC brush motors have several qualities which make them very attractive for space flight applications.}
}
  16. Edelson, K., Benjamin, B., Dominguez, L., Fuller, D. and Kennett, A. (2018). System-level actuator testing for mars rover application . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{edelson2018system,
  title = {System-level actuator testing for mars rover application},
  author = {Edelson, Kevin and Benjamin, Brandon and Dominguez, Luis and Fuller, Daniel and Kennett, Andrew},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-8},
  publisher = {IEEE},
  year = {2018},
  doi = {10.1109/aero.2018.8396491},
  abstract = {The Mars 2020 mission utilizes heritage designs from the Mars Science Laboratory rover, while integrating new actuators for the Sample Caching Subsystem (SCS). The Motion Control Subsystem system-level test program was executed to identify potential areas of risk as well as qualify actuators and the Rover Motor Controller Assembly (RMCA). Actuators were tested in a flight-like configuration in a thermal chamber at ambient temperature, +70 °C, and -70 °C. The tests performed include Winding Resistance, Brake Disengage/Engage, Startup/Halt Sensitivity, No Load, Cogging Profile/Powered Torque Ripple, and Dynamometer. The test setups and methods for understanding results were outlined. Early test results identified areas of risk which resulted in an engineering change: a new RMCA FPGA rate estimator algorithm and changes to the controller conductance loop. The continuation of this testing and future work will inform development of flight software and operational procedure.}
}
  17. Walker, L., Austin, J., Kennett, A. and Borne, D. (2022). Actuator and Motor Control End-to-End V&V on the Mars 2020 Rover . JPL Open Repository. Source
    BibTeX
    @inproceedings{walker2022actuator,
  title = {Actuator and Motor Control End-to-End V&V on the Mars 2020 Rover},
  author = {Walker, Luke and Austin, Jesse and Kennett, Andrew and Borne, Davis},
  publisher = {JPL Open Repository},
  year = {2022},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/55967}
}
  18. Bolotin, G., Hunter, D., Sheldon, D., Lias, M. and Stell, C. (2019). Cold Survivable Distributed Motor Controller (CSDMC) . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{bolotin2019cold,
  title = {Cold Survivable Distributed Motor Controller (CSDMC)},
  author = {Bolotin, Gary and Hunter, Donald and Sheldon, Doug and Lias, Malcolm and Stell, Chris},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-10},
  publisher = {IEEE},
  year = {2019},
  doi = {10.1109/aero.2019.8742005},
  abstract = {This paper presents the results of NASA's COLDTECH development entitled “Cold Survivable Distributed Motor Controller (CSDMC)”. This work addresses the need to lower the mass, power and volume of the motor control electronics and its associated cabling. Landed payload mass of ocean world missions typically requires a spacecraft launch mass of 7-10x the landed mass due to the required propellant to get the payload to the surface. Reduction of landed mass leads to cheaper, more frequent missions and/or increased science return. This work addresses this need by developing a distributed electronics architecture, which places control and power electronics near or at actuators and instruments. The outcome of this effort will result in a 10X reduction in harness mass, enabling a significant increase in science payload which then enables more capable sample acquisition, delivery and analysis systems on these missions. Placing the control and power conversion electronics at or near the actuators or instruments is the cornerstone of our distributed architecture. To do this, we developed the technology necessary to distribute the electronics and place them on a shared interface and power bus. This enables a significant reduction in cable mass along with its associated complexity. This allows spacecraft designers to take advantage of volume at the extremities that would normally not be utilized. In this paper we discuss the technologies and system design to achieve these goals in support of ocean world missions. These technologies include the development of our motor control modules, a point of load regulator and isolated converter modules along with the packaging technology necessary to allow our electronics to survive the extreme temperatures.}
}
  19. Lias, M., Katanyoutanant, S., Bolotin, G., Hunter, D. and Cheng, B. (2022). Cold Survivable Electronics Motor Control Law Implementation . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{lias2022cold,
  title = {Cold Survivable Electronics Motor Control Law Implementation},
  author = {Lias, Malcolm and Katanyoutanant, Sumant and Bolotin, Gary and Hunter, Donald and Cheng, Ben},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-7},
  publisher = {IEEE},
  year = {2022},
  doi = {10.1109/aero53065.2022.9843688},
  abstract = {For the last seven years JPL has been developing motor control electronics for use on future missions to extreme environments such as Europa and Mars. The packaging technology developed will allow the electronics to survive the extremes seen on the surface. This packaging technology allows us to package everything to control a number of motors on a single card including the closedloop control. In order to improve the performance of the motor control we have developed FPGA code to close the position, velocity and current control loops of the motor controller. This code allowed for a significant improvement in loop rate allowing the control of the motors to be more accurate. This allows for more accurate control of descent engines, more precise control of robotic arm motors. In this paper we will present the design of the control algorithm, the performance of the sensors and the test results of the resulting system.}
}
  20. Cheng, B., Bolotin, G., Hunter, D. and Lias, M. (2022). Power Converter Design for the Europa Lander Motor Controller . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{cheng2022power,
  title = {Power Converter Design for the Europa Lander Motor Controller},
  author = {Cheng, Ben and Bolotin, Gary and Hunter, Don and Lias, Malcolm},
  booktitle = {IEEE Aerospace Conference},
  pages = {01-07},
  publisher = {IEEE},
  year = {2022},
  doi = {10.1109/aero53065.2022.9843831}
}
  21. Tran, H., Bolotin, G., Cheng, B., Sirota, A. and Lias, M. (2021). An evaluation of the CAN bus for use on the Europa Lander motor controller . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{tran2021evaluation,
  title = {An evaluation of the CAN bus for use on the Europa Lander motor controller},
  author = {Tran, Hieu and Bolotin, Gary and Cheng, Ben and Sirota, Allen and Lias, Malcolm},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-9},
  publisher = {IEEE},
  year = {2021},
  doi = {10.1109/aero50100.2021.9438294},
  abstract = {This paper will present the application of the Controller Area Network (CAN) for communication between the Motor Control Processor and the Europa Lander Motor Control Cards. The Europa Lander preproject team is concerned about lowering the estimated mass, volume, and power of the mission concept so that it could maximize its science return. The motor controller uses multiple Motor Control Cards to control the 24 motors that will be operating in the extremes of the Europa environment. The CAN bus was considered because of its multi-drop nature, low power interface, and simple communication protocol. Beyond communication with the motor controller cards we also use the CAN bus interface to gather telemetry from the Power Conversion Card. Our system requires the collection of telemetry at a rate of 64Hz from the Power Conversion Card and all active motor controllers along with the sending of control packets and the receipt of control parameters at 512 Hz. In the paper we will address the ability of the CAN bus to meet these requirements along with our Arduino based test system used to learn about the CAN bus standard and verify our analysis.}
}
  22. Bolotin, G., Sirota, A., Lias, M., Bakker, C., Cox, B., Snover, B. and Walker, R. (2021). The Implementation of a Motor Simulator for the Development of the Europa Lander Motor Controller . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{bolotin2021implementation,
  title = {The Implementation of a Motor Simulator for the Development of the Europa Lander Motor Controller},
  author = {Bolotin, Gary and Sirota, Allen and Lias, Malcolm and Bakker, Chris and Cox, Brian and Snover, Burt and Walker, Roy},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-9},
  publisher = {IEEE},
  year = {2021},
  doi = {10.1109/aero50100.2021.9438155},
  abstract = {JPL is developing a motor controller capable of controlling the motors required for landed missions on icy worlds such as Europa and Enceladus. To support this effort, JPL, together with Tech180, is developing a motor simulator capable of simulating various types of motors required for these missions and their operation in the ambient environment. This system is being designed to support three 3-phase brushless DC motors with the ability to expanded to 24 motors. The simulator is able to simulate motors with current draw up to 10 amps, and sensors that range from resolvers, hall sensors, and encoders. The motor simulator design utilizes NI components and LabViewsoftware, along with high-speed FPGA hardware. This paper will present an overview of our motor controller, the requirements for the motor simulator, and details of its design along with the test results to date.}
}
  23. Baker, F. C., Favre, E., Mozzon, J.-M., Crausaz, A. and Juriens, P. (1999). European Robotic Arm (ERA) Manipulator Joint System Motor Unit and Tribological Brake . European Space Mechanisms and Tribology Symposium. Source
    BibTeX
    @inproceedings{baker1999european,
  title = {European Robotic Arm (ERA) Manipulator Joint System Motor Unit and Tribological Brake},
  author = {Baker, F. C. and Favre, E. and Mozzon, J.-M. and Crausaz, A. and Juriens, P.},
  booktitle = {European Space Mechanisms and Tribology Symposium},
  address = {Toulouse},
  year = {1999},
  url = {https://www.esmats.eu/esmatspapers/pastpapers/pdfs/1999/baker.pdf}
}
  24. Cruijssen, H. J., Ellenbroek, M., Henderson, M., Petersen, H., Verzijden, P. and Visser, M. (2014). The European Robotic Arm: A High-Performance Mechanism Finally on its way to Space . Aerospace Mechanisms Symposium, NASA Goddard Space Flight Center, 20150004070. Source
    BibTeX
    @inproceedings{cruijssen2014european,
  title = {The European Robotic Arm: A High-Performance Mechanism Finally on its way to Space},
  author = {Cruijssen, H. J. and Ellenbroek, M. and Henderson, M. and Petersen, H. and Verzijden, P. and Visser, M.},
  booktitle = {Aerospace Mechanisms Symposium, NASA Goddard Space Flight Center},
  number = {20150004070},
  institution = {NASA},
  year = {2014},
  url = {https://ntrs.nasa.gov/citations/20150004070},
  abstract = {This paper describes the design and qualification of the European Robotic Arm (ERA), which is planned to be launched by the end of 2015. After years of changes, a shift of launcher and new loads, launch preparation is underway. The European Robotic Arm ERA has been designed and manufactured by Dutch Space and its subcontractors such as Astrium, SABCA and Stork with key roles for the mechanical aspects. The arm was originally designed to be launched by the STS (mounted on a Russian module for the ISS) in 2001. However, due to delays and the STS disaster, a shift was made to the Russian Proton rocket. ERA will be launched on the Multipurpose Laboratory Module (MLM). This module, which is now planned for launch to the ISS in 2015, will carry the ERA. The symmetrical design of the arm with a complete 3 degree-of-freedom wrist and general-purpose end effector on both sides, allows ERA to relocate on the station by grappling a new base point and releasing the old one, and move to different working locations.
}
}
  25. Chun, W. and Brunson, P. (1987). Actuators for a Space Manipulator . NASA, 19890000730. Source
    BibTeX
    @techreport{chun1987actuators,
  title = {Actuators for a Space Manipulator},
  author = {Chun, W. and Brunson, P.},
  number = {19890000730},
  institution = {NASA},
  year = {1987},
  url = {https://ntrs.nasa.gov/citations/19890000730},
  abstract = {The robotic manipulator can be decomposed into distinct subsytems. One particular area of interest of mechanical subsystems is electromechanical actuators (or drives). A drive is defined as a motor with an appropriate transmission. An overview is given of existing, as well as state-of-the-art drive systems. The scope is limited to space applications. A design philosophy and adequate requirements are the initial steps in designing a space-qualified actuator. The focus is on the d-c motor in conjunction with several types of transmissions (harmonic, tendon, traction, and gear systems). The various transmissions will be evaluated and key performance parameters will be addressed in detail. Included in the assessment is a shuttle RMS joint and a MSFC drive of the Prototype Manipulator Arm. Compound joints are also investigated. Space imposes a set of requirements for designing a high-performance drive assembly. Its inaccessibility and cryogenic conditions warrant special considerations. Some guidelines concerning these conditions are present. The goal is to gain a better understanding in designing a space actuator.}
}
  26. Gillis-Smith, G. R. (1996). Mars Pathfinder Lander Deployment Mechanisms . JPL Open Repository. Source
    BibTeX
    @inproceedings{gillissmith1996mars,
  title = {Mars Pathfinder Lander Deployment Mechanisms},
  author = {Gillis-Smith, Greg R.},
  publisher = {JPL Open Repository},
  year = {1996},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/24167}
}
  27. Novak, K. S., Liu, Y., Lee, C.-J. and Hendricks, S. (2010). Mars Science Laboratory rover actuator thermal design . International Conference on Environmental Systems. Source
    BibTeX
    @inproceedings{novak2010mars,
  title = {Mars Science Laboratory rover actuator thermal design},
  author = {Novak, Keith S. and Liu, Yuanming and Lee, Chern-Jiin and Hendricks, Steven},
  booktitle = {International Conference on Environmental Systems},
  publisher = {American Institute of Aeronautics and Astronautics},
  year = {2010},
  doi = {10.2514/6.2010-6196},
  abstract = {NASA will launch a 900 kg rover, part of the Mars Science Laboratory (MSL) mission, to Mars in October of 2011. The MSL rover is scheduled to land on Mars in August of 2012. The rover employs 31, electric-motor driven actuators to perform a variety of engineering and science functions including: mobility, camera pointing, telecommunications antenna steering, soil and rock sample acquisition and sample processing. This paper describes the MSL rover actuator thermal design. The actuators have stainless steel housings and planetary gearboxes that are lubricated with a wet lubricant. The lubricant viscosity increases with decreasing temperature. Warm-up heaters are required to bring the actuators up to temperature (above -55 C) prior to use in the cold wintertime environment of Mars (when ambient atmosphere temperatures are as cold as -113 C). Analytical thermal models of all 31 MSL actuators have been developed. The actuators have been analyzed and warm-up heaters have been designed to improve actuator performance in cold environments. Thermal hardware for the actuators has been specified, procured and installed. This paper presents actuator thermal analysis predicts, and describes the actuator thermal hardware and its operation. In addition, warm-up heater testing and thermal model correlation efforts for the Remote Sensing Mast (RSM) elevation actuator are discussed.}
}
  28. Redmond, M., Kempenaar, J. and Novak, K. (2017). Mars 2020 Mobility Actuator Thermal Testing and Model Correlation . International Conference on Environmental Systems. Source
    BibTeX
    @inproceedings{redmond2017mars,
  title = {Mars 2020 Mobility Actuator Thermal Testing and Model Correlation},
  author = {Redmond, Matthew and Kempenaar, Jason and Novak, Keith},
  booktitle = {International Conference on Environmental Systems},
  publisher = {JPL Open Repository},
  year = {2017},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/47695}
}
  29. Lee, G. Y. and Donaldson, J. A. (2013). Dreaming on Mars: how Curiosity performs actuator warm-up while sleeping . International Conference on System of Systems Engineering. Source
    BibTeX
    @inproceedings{lee2013dreaming,
  title = {Dreaming on Mars: how Curiosity performs actuator warm-up while sleeping},
  author = {Lee, Gene Y. and Donaldson, James A.},
  booktitle = {International Conference on System of Systems Engineering},
  pages = {123-128},
  publisher = {IEEE},
  year = {2013},
  doi = {10.1109/sysose.2013.6575254}
}
  30. Maghsoudi, E., Furst, B. I., Jasper, J. D., Daimaru, T. and Odagiri, K. (2020). Efficient Thermal Management for Sampling Arm Actuators . JPL Open Repository. Source
    BibTeX
    @inproceedings{maghsoudi2020efficient,
  title = {Efficient Thermal Management for Sampling Arm Actuators},
  author = {Maghsoudi, Elham and Furst, Ben I. and Jasper, Jay D. and Daimaru, Takuro and Odagiri, Kimihide},
  publisher = {JPL Open Repository},
  year = {2020},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/53057}
}
  31. Jones, W. R. J., Jansen, M. J., Gschwender, L. J., Snyder, C. E. J., Sharma, S. K., Predmore, R. E. and Dube, M. J. (2001). The Tribological Properties of Several Silahydrocarbons for Use in Space Mechanisms . Journal of Synthetic Lubrication, NASA/TM-2001-211196. Source
    BibTeX
    @article{jones2001tribological,
  title = {The Tribological Properties of Several Silahydrocarbons for Use in Space Mechanisms},
  author = {Jones, W. R., Jr. and Jansen, M. J. and Gschwender, L. J. and Snyder, C. E., Jr. and Sharma, Shiv K. and Predmore, R. E. and Dube, Michael J.},
  journal = {Journal of Synthetic Lubrication},
  volume = {20},
  number = {NASA/TM-2001-211196},
  pages = {303-315},
  institution = {NASA},
  address = {Liege},
  year = {2001},
  doi = {10.1002/jsl.3000200404},
  abstract = {Abstract Silahydrocarbons are members of a relatively new class of liquid lubricants with great potential for use in space mechanisms. They are unimolecular species consisting of silicon, carbon, and hydrogen. They possess unique wear, viscosity, and volatility properties while retaining the ability to solubilise conventional additives. The tribological properties of several members of this class, including tri‐, tetra‐, and penta‐compounds, are presented. These properties include viscosity‐temperature, viscosity—pressure, vapour pressure, lubricant life, traction, and reciprocating and four‐ball wear rates. Lubricant lifetimes were determined using a vacuum ball bearing simulator, the spiral orbit tribometer. Wear was measured using a Cameron Plint reciprocating tribometer and wear rates with a vacuum four‐ball tribometer. Conventional viscometry was used for viscosity—temperature measurements and a Knudsen cell for vapour pressure. Thermogravimetric analysis was also used for volatility measurements. Pressure—viscosity coefficients (α—values) were estimated from elastohydrodynamic lubrication film thickness measurements. These properties are compared to those of existing state‐of‐the‐art space lubricants.}
}
  32. Pepper, S. V. (1998). Tribometer for Lubrication Studies in Vacuum . NASA, 20050177172. Source
    BibTeX
    @techreport{pepper1998tribometer,
  title = {Tribometer for Lubrication Studies in Vacuum},
  author = {Pepper, Stephen V.},
  number = {20050177172},
  institution = {NASA},
  year = {1998},
  url = {https://ntrs.nasa.gov/citations/20050177172},
  abstract = {The NASA Lewis Research Center has developed a new way to evaluate the liquid lubricants used in ball bearings in space mechanisms. For this evaluation, a liquid lubricant is exercised in the rolling contact vacuum tribometer shown in the photo. This tribometer, which is essentially a thrust bearing with three balls and flat races, has contact stresses similar to those in a typical preloaded, angular contact ball bearing. The rotating top plate drives the balls in an outward-winding spiral orbit instead of a circular path. Upon contact with the "guide plate," the balls are forced back to their initial smaller orbit radius; they then repeat this spiral orbit thousands of times. The orbit rate of the balls is low enough, 2 to 5 rpm, to allow the system to operate in the boundary lubrication regime that is most stressful to the liquid lubricant. This system can determine the friction coefficient, lubricant lifetime, and species evolved from the liquid lubricant by tribodegradation. The lifetime of the lubricant charge is only few micrograms, which is "used up" by degradation during rolling. The friction increases when the lubricant is exhausted. The species evolved by the degrading lubricant are determined by a quadrupole residual gas analyzer that directly views the rotating elements. The flat races (plates) and 0.5-in.-diameter balls are of a configuration and size that permit easy post-test examination by optical and electron microscopy and the full suite of modern surface and thin-film chemical analytical techniques, including infrared and Raman microspectroscopy and x-ray photoelectron spectroscopy. In addition, the simple sphere-on-a-flat-plate geometry allows an easy analysis of the contact stresses at all parts of the ball orbit and an understanding of the frictional energy losses to the lubricant. The analysis showed that when the ball contacts the guide plate, gross sliding occurs between the ball and rotating upper plate as the ball forced back to a smaller orbit radius. The friction force due to gross sliding is sensed by the piezoelectric force transducer behind the guide plate and furnishes the coefficient of friction for the system. This tribometer has been used to determine the relative lifetimes of Fomblin Z-25, a lubricant often used in space mechanisms, as a function of the material of the plates against which it was run. The balls were 440C steel in all cases; the plate materials were aluminum, chromium (Cr), 440C steel (17 wt % Cr), and 4150 steel (1 wt % Cr). As shown in the bar graph, the lifetime is greatest for the plate material with least chromium, thus implicating chromium as a tribochemically active element attacking Fomblin Z-25.}
}
  33. Kinnett, R., Green, T., Klein, D. and Lin, M. R. (2022). Remote Diagnosis and Operational Response to an In-Flight Failure of the Drill Feed Mechanism Onboard the Mars Science Laboratory Rover . Aerospace Mechanisms Symposium. Source
    BibTeX
    @inproceedings{kinnett2022remote,
  title = {Remote Diagnosis and Operational Response to an In-Flight Failure of the Drill Feed Mechanism Onboard the Mars Science Laboratory Rover},
  author = {Kinnett, Ryan and Green, Thomas and Klein, Douglas and Lin, Megan Richardson},
  booktitle = {Aerospace Mechanisms Symposium},
  publisher = {JPL Open Repository},
  year = {2022},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/56163}
}
  34. Pavlov, C. A., Rogg, A. and Johnson, A. M. (2022). Assessing Impact of Joint Actuator Failure on Lunar Rover Mobility, 20220006267. ntrs.nasa.gov/citations/20220006267
    BibTeX
    @misc{pavlov2022assessing,
  title = {Assessing Impact of Joint Actuator Failure on Lunar Rover Mobility},
  author = {Pavlov, Catherine A. and Rogg, Arno and Johnson, Aaron M.},
  howpublished = {Presentation at the NASA},
  number = {20220006267},
  type = {Presentation},
  year = {2022},
  url = {https://ntrs.nasa.gov/citations/20220006267}
}
  35. NASA. (2015). NASA-STD-5017A: Design and Development Requirements for Mechanisms . NASA Office of the Chief Engineer. Source
    BibTeX
    @techreport{nasa2015mechanisms,
  title = {NASA-STD-5017A: Design and Development Requirements for Mechanisms},
  author = {{NASA}},
  institution = {NASA Office of the Chief Engineer},
  year = {2015},
  url = {https://standards.nasa.gov/standard/nasa/nasa-std-5017}
}
  36. Rogers, P., Bowkett, J. and Backes, P. (2026). A High-Fidelity Actuator Model for Robotic Autonomy in Space and Beyond . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{rogers2026high,
  title = {A High-Fidelity Actuator Model for Robotic Autonomy in Space and Beyond},
  author = {Rogers, Preston and Bowkett, Joseph and Backes, Paul},
  booktitle = {IEEE Aerospace Conference},
  publisher = {JPL Open Repository},
  year = {2026},
  doi = {10.48577/jpl.wgjtid}
}
  37. BarCohen, Y., Sherrit, S., Badescu, M., Lee, H. J., Bao, X. and Chang, Z. (2019). Drilling mechanisms using piezoelectric actuators. dataverse.jpl.nasa.gov/dataset.xhtml
    BibTeX
    @misc{barcohen2019drilling,
  title = {Drilling mechanisms using piezoelectric actuators},
  author = {BarCohen, Yoseph and Sherrit, Stewart and Badescu, Mircea and Lee, Hyeong Jae and Bao, Xiaoqi and Chang, Zensheu},
  howpublished = {Presentation at the Engineering Mechanics Institute Conference},
  year = {2019},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/50758}
}
  38. Sherrit, S., Domm, L., Bao, X., Bar-Cohen, Y., Chang, Z. and Badescu, M. (2012). Single Piezo-Actuator Rotary-Hammering (SPaRH) drill . Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems. Source
    BibTeX
    @inproceedings{sherrit2012single,
  title = {Single Piezo-Actuator Rotary-Hammering (SPaRH) drill},
  author = {Sherrit, Stewart and Domm, Lukas and Bao, Xiaoqi and Bar-Cohen, Yoseph and Chang, Zensheu and Badescu, Mircea},
  booktitle = {Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems},
  series = {SPIE Proceedings},
  volume = {8345},
  pages = {83452B},
  publisher = {SPIE},
  year = {2012},
  doi = {10.1117/12.915379},
  abstract = {The search for present or past life in the Universe is one of the most important objectives of NASA's exploration missions. Drills for subsurface sampling of rocks, ice and permafrost are an essential tool for astrobiology studies on other planets. Increasingly, it is recognized that drilling via a combination of rotation and hammering offers an efficient and effective rapid penetration mechanism. The rotation provides an intrinsic method for removal of cuttings from the borehole while the impact and shear forces aid in the fracturing of the penetrated medium. Conventional drills that use a single actuator are based on a complex mechanism with many parts and their use in future mission involves greater risk of failure and/or may require lubrication that can introduce contamination. In this paper, a compact drill is reported that uses a single piezoelectric actuator to produce hammering and rotation of the bit. A horn with asymmetric grooves was designed to impart a longitudinal (hammering) and transverse force (rotation) to a keyed free mass. The drill requires low axial pre-load since the hammering-impacts fracture the rock under the bit kerf and rotate the bit to remove the powdered cuttings while augmenting the rock fracture via shear forces. The vibrations 'fluidize' the powdered cuttings inside the flutes reducing the friction with the auger surface. This action reduces the consumed power and heating of the drilled medium helping to preserve the pristine content of the acquired samples. The drill consists of an actuator that simultaneously impacts and rotates the bit by applying force and torque via a single piezoelectric stack actuator without the need for a gearbox or lever mechanism. This can reduce the development/fabrication cost and complexity. In this paper, the drill mechanism will be described and the test results will be reported and discussed.}
}