Michael Garrett

Lightweight Rovers for Mars Science Exploration and Sample Return

We report on the development of new mobile robots for Mars exploration missions. These lightweight survivable rover (LSR) systems are of potential interest to both space and terrestrial applications, and are distinguished from more conventional designs by their use of new composite materials, collapsible running gear, integrated thermal-structural chassis, and other mechanical features enabling improved mobility and environmental robustness at reduced mass, volume, and power. Our first demonstrated such rover architecture, LSR-1, introduces running gear based on 2D composite struts and 3D machined composite joints, a novel collapsible hybrid composite-aluminum wheel design, a unit-body structural- thermal chassis with improved internal temperature isolation and stabilization, and a spot-pushbroom laser/CCD sensor enabling accurate, fast hazard detection and terrain mapping. LSR-1 is an approximately .7

LEMUR: Legged Excursion Mechanical Utility Rover

MIL 1.0 meter(Lambda) 2(W X L) footprint six-wheel (20 cm dia.) rocker-bogie geometry vehicle of approximately 30 cm ground clearance, weighing only 7 kilograms with an onboard .3 kilogram multi-spectral imager and spectroscopic photometer. By comparison, NASA/JPLs recently flown Mars Pathfinder rover Sojourner is an 11+ kilogram flight experiment (carrying a 1 kg APXS instrument) having approximately .45 X .6 meter(Lambda) 2(WXL) footprint and 15 cm ground clearance, and about half the warm electronics enclosure (WEE) volume with twice the diurnal temperature swing (-40 to +40 degrees Celsius) of LSR- 1 in nominal Mars environments. We are also developing a new, smaller 5 kilogram class LSR-type vehicle for Mars sample return -- the travel to, localization of, pick-up, and transport back to an Earth return ascent vehicle of a sample cache collected by earlier science missions. This sample retrieval rover R&D prototype has a completely collapsible mobility system enabling rover stowage to approximately 25% operational volume, as well an actively articulated axle, allowing changeable pose of the wheel strut geometry for improved transverse and manipulation characteristics.

Gravity‐independent Rock‐climbing Robot and a Sample Acquisition Tool with Microspine Grippers

Although future orbital facilities will have immense scale, details will require intricate operations in restrictive, confined quarters. LEMUR is a small, agile and capable six-legged walking robot that has been built at the Jet Propulsion Laboratory to perform dexterous small-scale assembly, inspection and maintenance. It is intended to expand the operational envelope of robots in its size class (sub-5 kg) through the flexible use of its limbs and effectors, as well as through the modular changeout of those effectors. In short, LEMUR is intended as a robotic instantiation of a six-limbed primate with Swiss Army knife tendencies.LEMURs layout consists of six independently operated limbs arranged in two rows of three. The front two limbs have four active degrees of freedom while the rear four limbs have three each. Each limb is reconfigurable to allow the integration of a variety of mechanical tools.

Robot work crews for planetary outposts: close cooperation and coordination of multiple mobile robots

A rock-climbing robot is presented that can free climb on vertical, overhanging, and inverted rock faces. This type of system has applications to extreme terrain on Mars or for sustained mobility on microgravity bodies. The robot grips the rock using hierarchical arrays of microspines. Microspines are compliant mechanisms made of sharp hooks and flexible elements that allow the hooks to move independently and opportunistically grasp roughness on the surface of a rock. This paper presents many improvements to early microspine grippers, and the application of these new grippers to a four-limbed robotic system, LEMUR IIB. Each gripper has over 250 microspines distributed in 16 carriages. Carriages also move independently with compliance to conform to larger, cm-scale roughness. Single gripper pull testing on a variety of rock types is presented, and on rough rocks, a single gripper can support the entire mass of the robot (10 kg) in any orientation. Several sensor combinations for the grippers were evaluated using a smaller test-gripper. Rock-climbing mobility experiments are also described for three characteristic gravitational orientations. Finally, a sample acquisition tool that uses one of the robots grippers to enable rotary percussive drilling is shown.

State estimation and vehicle localization for the FIDO Rover

We report on the development of cooperating multiple robots. This work builds form our earlier research on autonomous planetary rovers and robot arms. Here, we seek to closely coordinate the mobility and manipulation of multiple robots to perform site construction operations- as an example, the autonomous deployment of a planetary power station- a task viewed as essential to a sustained robotic presence and human habitation on Mars. There are numerous technical challenges; these include the mobile handling of extended objects, as well as cooperative transport/navigation of such objects over natural, unpredictable terrain. We describe an extensible system concept, related simulations, a hardware implementation, and preliminary experimental results. In support of this work we have developed an enabling hybrid control architecture wherein multi-robot mobility and sensor-based controls are derived as group compositions and coordination of more basic behaviors under a task-level multi-agent planner. We summarize this Control Architecture for Multi-robot Planetary Outposts (CAMPOUT), and its application to physical experiments where two rovers carry an extended payload over natural terrain.

TRESSA: Teamed robots for exploration and science on steep areas

This paper describes the means for generating rover localization information for NASA/JPLs FIDO rover. This is accomplished using a sensor fusion framework which combines wheel odometry with sun sensor and inertial navigation sensors to provide an integrated state estimate for the vehicles position and orientation relative to a fixed reference frame. This paper describes two separate state estimation approaches built around the extended Kalman filter formulation and the Covariance Intersection formulation. Experimental results from runs in JPLs MarsYard are presented in order to compare the state estimates generated using each formulation.

Dexterous robotic sampling for Mars in-situ science

Long-duration robotic missions on lunar and planetary surfaces (for example, the Mars Exploration Rovers have operated continuously on the Martian surface for close to 3 years) provide the opportunity to acquire scientifically interesting information from a diverse set of surface and subsurface sites and to explore multiple sites in greater detail. Exploring a wide range of terrain types, including plains, cliffs, sand dunes, and lava tubes, requires the development of robotic systems with mobility enhanced beyond that which is currently fielded. These systems include single as well as teams of robots. TRESSA (Teamed Robots for Exploration and Science on Steep Areas) is a closely coupled three-robot team developed at the Jet Propulsion Laboratory (JPL) that previously demonstrated the ability to drive on soil-covered slopes up to 70 deg. In this paper, we present results from field demonstrations of the TRESSA system in even more challenging terrain: rough rocky slopes of up to 85 deg. In addition, the integration of a robotic arm and instrument suite has allowed TRESSA to demonstrate semi-autonomous science investigation of the cliffs and science sample collection. TRESSA successfully traversed cliffs and collected samples at three Mars analog sites in Svalbard, Norway as part of a recent geological and astrobiological field investigation called AMASE: Arctic Mars Analog Svalbard Expedition under the NASA ASTEP (Astrobiology Science and Technology for Exploring Planets) program.

A Composite Manipulator Utilizing Rotary Piezoelectric Motors: New Robotic Technologies For Mars in-situ Planetary Science

Robotic exploration of the Martian surface will provide important scientific data on planetary climate, life history, and geologic resources. In particular, robotic arms will assist in the detailed visual inspection, instrumented analysis, extraction, and earth return of soil and rock samples. To this end, we are developing new robotic manipulation concepts for use on landers and rovers, wherein mass, volume, power and the ambient Mars environment are significant design constraints. Our earlier work led to MarsArmI, a 2.2 meter, 3-dof hybrid metal/composite, dc-motor actuated arm operating under coordinated joint-space control; NASAs Mars Surveyor 98 mission utilizes this design concept. More recently, we have conceived and implmented new, all- composite, very light robot arms: MarsArmII, a 4.0 kilogram, 2.3 meter arm for lander operations, and MicroArm-1 and MicroArm-2, two smaller 1.0+ kilogram, .7 meter rover arms for mobile sample acquisition and Mars sample return processing. Features of these arms include our creation of new 3D machined composites for critical load-bearing parts; actuation by high-torque density ultrasonic motors; and, visually-designated inverse kinematics positioning with contact force adaptation under a novel task-level, dexterous controls paradigm. Our demonstrated results include robotic trenching, sample grasp-manipulation-and-transfer, and fresh rock surface exposure-probing via the science operators point-and-shoot visual task designation in a stereo workspace. Sensor-referenced control capabilities include real-time adaptation to positioning error and environmental uncertainties (e.g., variable soil resistance and impediments), and the synthesis of power optimal trajectories for free space manipulation.

New planetary rovers for long-range Mars science and sample return

We report a significant advance in space robotics design based on innovation of 3D composite structures and piezoelectric actuation. The essence of this work is development of a new all-composite robotic manipulator utilizing rotary ultrasonic motors (USM). MarsArmII is 40% lighter than a prior MarsArmI JPL design based in more massive, bulky hybrid metal-composite, joint-link system architecture and dc-motor driven actuation. MarsArmII is a four d.o.f. torso-shoulder- elbow, wrist-pitch robot of over two meters length, weighing four kilograms, and carrying a one kilogram multi-functional science effector with actuated opposable scoops, micro-viewing camera, and active tooling (abrader). MarsArmII construction is composite throughout, with all critical load-bearing joints and effector components being based in a new 3D air layup carbon fiber RTM composite process of our design, and links formed of 2D graphite epoxy. The 3D RTM composite is machinable by traditional metal shop practice, and in early tests such parts bench-marked favorably with aluminum based designs. Each arm link incorporates a surface mounted semiconductor strain gauge, enabling forced-referenced closed loop positioning. The principal arm joints are six in-lb rotary USMs acting under optically encoded PID servo control through harmonic drives. We have demonstrated the MarsArmII system for inverse kinematics positioning tasks (utilizing computer vision derived stereo workspace coordinates) that include simulated Martian soil trenching, sample acquisition and instrument transfers, and fresh rock surface exposure by abrasion.

Video presentation of a rock climbing robot

There are significant international efforts underway to place mobile robots (`rovers) on the surface of Mars. This follows on the recent successful NASA Mars Pathfinder flight of summer 1997. In that mission, the 11+ Kg Sojourner rover explored a small 50 meter locale about its lander over a several week period. Future planned science missions of the Mars Surveyor Program are more aggressive, seeking to autonomously survey planetary climate, life and resources over multiple kilometers and many months duration. These missions will also retrieve collected sample materials back to a Mars Ascent Vehicle for more detailed analysis on Earth. In support of these future missions we are developing and field testing new rover technology concepts. We first overview the design and initial operations of SRR-1 (Sample Return Rover), a novel 10 kg-class four wheel, hybrid composite-metal vehicle for rapid (10 - 30 cm/sec) autonomous location, rendezvous, and retrieval of collected samples under integrated visual and beacon guidance. SRR is a light 88 X 55 X 36 (LWH) cm3 vehicle collapsing to less than one third its deployed field volume, and carrying a powerful, visually-servoed all-composite manipulator. We then sketch development of the FIDO rover (Field Integrated Design and Operations), a new 50+ kg, six wheel, approximately 100 X 80 X 50 (LWH) cm3, high mobility, multi-km range science vehicle which includes mast-mounted multi-spectral stereo, bore-sighted IR point spectrometer, robot arm with attached microscope, and body- mounted rock sampling corer. Currently in integration phase, FIDO rover will first be tested in September, 1998, `MarsYard (JPL) operations, followed by CY99 full-scale terrestrial field simulations of a planned Mars 03 multi- kilometer roving mission (Athena-based science rover payload), demonstrating remote science selection, autonomous navigation, in situ sample analysis, and robotic sample collection functions.