This paper describes a system design concept to enable automated sample acquisition on planetary surfaces without the use of additional sensor information such as cameras and force/torque sensors. A simple and robust solution is presented to the unique problems encountered in in situ science applications with its tight constraints on mass, power, computing resources and lack of flight-qualified hardware. Problems addressed include end-effector contact detection, trajectory generation, hardware fault monitoring and autonomous determination of terrain profile.

On January 24, 2004, the Mars Exploration Rover named Opportunity successfully landed in the region of Mars known as Meridiani Planum, a vast plain dotted with craters where orbiting spacecraft had detected the signatures of minerals believed to have formed in liquid water. The first pictures back from Opportunity revealed that the rover had landed in a crater roughly 20 meters in diameter - the only sizeable crater within hundreds of meters - which became known as Eagle Crater. And in the walls of this crater just meters away was the bedrock MER scientists had been hoping to find, which would ultimately prove that this region of Mars did indeed have a watery past. Opportunity explored Eagle Crater for almost two months, then drove more than 700 meters in one month to its next destination, the much larger Endurance Crater. After surveying the outside of Endurance Crater, Opportunity drove into the crater and meticulously studied it for six months. Then it went to examine the heat shield that had protected Opportunity during its descent through the Martian atmosphere. More than a year since landing, Opportunity is still going strong and is currently en route to Victoria Crater - more than six kilometers from Endurance Crater. Opportunity has driven more than four kilometers, examined more than eighty patches of rock and soil with instruments on the robotic arm, excavated four trenches for subsurface sampling, and sent back well over thirty thousand images of Mars - ranging from grand panoramas to up close microscopic views. This paper details the experience of driving Opportunity through this alien landscape from the point of view of the Rover Planners, the people who tell the rover where to drive and how to use its robotic arm.

NASA's Mars Exploration Rovers are two six-wheeled, 175-kg robotic vehicles which have operated on Mars for over a year as of March 2005. Each rover is controlled by a team who must understand the rover's surroundings and develop command sequences on a daily basis. The tight tactical planning timeline and ever-changing environment call for tools that allow quick assessment of potential manipulator targets and traverse goals, since command sequences must be developed in a matter of hours after receipt of new data from the rovers. Reachability maps give a visual indication of which targets are reachable by each rover's manipulator, while slope and solar energy maps show the rover operator which terrain areas are safe and unsafe from different standpoints.

Spirit is one of two rovers that landed on Mars in January 2004 as part of NASA's Mars Exploration Rover mission. As of July 2005, Spirit has traveled over 4.5 kilometers across the Martian surface while investigating rocks and soils, digging trenches to examine subsurface materials, and climbing hills to reach outcrops of bedrock. Originally designed to last 90 sols (Martian days), Spirit has survived over 500 sols of operation and continues to explore. During the mission, we achieved increases in efficiency, accuracy, and traverse capability through increasingly complex command sequences, growing experience, and updates to the on-board and ground-based software. Safe and precise mobility on slopes and in the presence of obstacles has been a primary factor in development of new software and techniques.

This paper describes the operations of the 5 degree-of-freedom instrument deployment device (IDD), a dexterous robotic manipulator on the Mars Exploration Rovers, spirit and opportunity. The unprecedented flawless operations of the IDD enabled precise and reliable placement of at least 3 in situ instruments in sequential order on a designated target position on Martian rock/soil any time during the Martian diurnal cycle (day or night). These placements demonstrated a repeatability of /spl sim/1 mm in position and /spl sim/1 degree in orientation. This operations breakthrough is underappreciated, but it alone enabled the scientist to characterize a wide range of rocks and soils in a timely manner in the hunt for geological clues that revealed that the planet was once rich in water. In this paper we describe the IDD planning and command sequence generation process used to place and hold in situ instruments directly against rock and soil targets of interest within the IDD work volume.

The Mars Polar Lander (MPL) mission was the first planetary mission to use Internet-based distributed ground operations where scientists and engineers collaborate in daily mission operations from multiple geographically distributed locations via the Internet. This paper describes the operations system, the Web interface for telescience (WITS), which was used by the MPL mission for Internet-based operations. WITS was used for generating command sequences for the lander's robotic arm and robotic arm camera, and as a secondary tool for sequence generation for the stereo camera on the lander. WITS was also used as a public outreach tool. Results are shown from the January 2000 field test in Death Valley, California.

This paper describes the control system design concepts for the Mars Volatiles and Climate Surveyor (MVACS) Robotic Arm which supports the scientific investigations to be conducted as part of the Mars Surveyor '98 Lander project. Novel solutions are presented to some of the unique problems encountered in this demanding space application with its tight constraints on mass, power, volume, and computing resources. Problems addressed include the 4-DOF forward and inverse kinematics, trajectory planning to minimize potential impact damage, joint drive train protection, Lander tilt prevention, hardware fault monitoring, and collision avoidance.

An impedance function is proposed to achieve accurate force tracking under the presence of uncertainties in robot dynamics and environment models. The new impedance function is formulated on the basis of PID control of the force tracking error which compensates for the unknown environment stiffness and position. The robot dynamics uncertainties are compensated by a simple time-delayed robust control algorithm. Stability and convergence of the control scheme are analyzed. Simulation studies with a three link rotary robot manipulator are shown. Furthermore, experimental results on a PUMA 560 arm are carried out to confirm the proposed impedance controller's performance.

A robust internal force-based impedance control scheme for coordinating manipulators is introduced. Internal force-based impedance control enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects and requires no knowledge of the object dynamic model. Each manipulator's nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty and payload variation. The controller is only weakly-dependent on each manipulator's inertia matrix. Stability of the system is analyzed. The scheme is computationally inexpensive and suitable for general-purpose microcomputer implementation. Rigorous experimental investigations are performed and the results presented which validate the proposed concepts.

An internal force-based impedance control scheme for two coordinating robots manipulating a rigid object via palm grasping is introduced. The minimal internal force required to maintain the grasp on the object is computed from the frictional constraints and sensed forces. A closed-form solution to the minimization problem is developed which makes the algorithm suitable for real-time control. The controller uses sensed moments at the palm interface to maintain proper orientation of the palms to achieve maximum surface contact. Each manipulator's nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty and payload variation. The controller is only weakly-dependent on each manipulator's inertia matrix. Stability of the system is analyzed. Rigorous experimental investigations are are performed and the results presented which validate the proposed concepts.

An internal force-based impedance control scheme for cooperating manipulators is introduced which controls the motion of the objects being manipulated and the internal force on the objects. The controller enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects. Each manipulator is directly given the properties of an impedance by the controller; thus, eliminating the gain limitation inherent in the structure of previously proposed schemes. The controller uses the forces sensed at the robot end effectors to compensate for the effects of the objects' dynamics and to compute the internal force using only kinematic relationships. Thus, knowledge of the objects' dynamics is not required. Stability of the system is proven using Lyapunov theory and simulation results are presented validating the proposed concepts. The effect of computational delays in digital control implementations is analyzed vis-a-vis stability and a lower bound derived on the size of the desired manipulator inertia relative to the actual manipulator endpoint inertia. The bound is independent of the sample time.

The decomposition of forces on an object grasped by multiple manipulators is analyzed using the theory of metric spaces and generalized inverses. In general, the space of forces exerted on the object is nonhomogenous and suitable metrics must be used to decompose the space into motion-inducing and internal force subspaces. A common theoretical framework is proposed in this paper which solves the decomposition problem for rigid, palm-type, and frictional point-contact grasps. New solutions are derived for systems with palm-type and mixed grasps. Previous decompositions for the rigid and frictional point contact grasps are analyzed within the theoretical framework. It is shown that previous solutions in the rigid grasp case are equivalent to the minimization of a norm based on a kinetic energy metric associated with the object. >