The Serpentine Robot is a prototype hyper-redundant (snake-like) manipulator system developed at the Jet Propulsion Laboratory. It is designed to navigate and perform tasks in obstructed and constrained environments in which conventional 6-DOF manipulators cannot similarly function. This paper describes the Serpentine Robot mechanical design, a low level inverse kinematic algorithm for the joint assembly, a brief synopsis of control development to date, and the applications of this technology.

The teleprogramming system is a supervisory control approach to time delayed teleoperation that incorporates predictive graphics and reactive skills to accomplish dexterous manipulation tasks in the presence of significant time delay. This paper presents an experimental effort to validate the teleprogramming system using the GRASP Laboratory of the University of Pennsylvania as the operator station and the TROPICS Laboratory of the Jet Propulsion Laboratory as the remote site. The teleprogramming experiment involved operator supervisory control of a robot performing puncture and slice operations on the thermal blanket securing tape of a satellite repair mission sub-task This experiment was successfully performed in August, 1994 using the Internet as the sole medium of communication. During experimentation, messages experienced time-varying time delay between three and fifteen seconds with an average delay of approximately six seconds.

When multiple arms are used to manipulate a large object, it is beneficial and sometimes necessary to maintain and control contacts between the object and the effector (the contacting surface of an arm) through force closure. Rolling and/or sliding can occur at these contacts, and the system is, in general, characterized by holonomic as well as nonholonomic (including unilateral) constraints. In this paper, the control of planar rolling contacts is investigated. Multi-arm manipulation systems are typically redundant. In the authors' approach, a minimal set of inputs is employed to control the trajectory of the system while the surplus inputs control the contact conditions. The trajectory includes the gross motion of the object as well as the rolling motion at each contact. A nonlinear feedback scheme for simultaneous control of motion as well as contact conditions is presented. A new algorithm which adapts a two-effector grasp with rolling contacts to external loads and the trajectory is developed. Simulations and experimental results are used to illustrate the salient features in control and planning.>

The authors address force control in overconstrained dynamic systems with special emphasis on robot control. Previous approaches to force control are studied, and many of these are shown to be unsuitable for dynamic force control. Practical and theoretical considerations for designing force control algorithms are discussed. Experimental and simulation results that validate the theoretical findings are presented for a single-degree-of-freedom pneumatic force controller.>

The authors present a unified formulation for the control problem of multiple arm systems which accommodates both holonomic and nonholonomic constraints. Several unique control properties of nonholonomic systems are discussed. Several useful results regarding input-output linearization and the zero dynamics in such systems are proved. The analysis and controller design are discussed for multi-arm systems. Results from computer simulations are presented to demonstrate the control algorithms. Simulation results illustrate that rolling and sliding can be effectively controlled.>

An object much larger than a robot end-effector can not be rigidly grasped. Instead, it is necessary to support the object with multiple effectors. The effectors need not be grippers-they may be surfaces on the arm(s). Multiple arm manipulation without rigid grasps is investigated. The interaction between a robot and the object is characterized by unilateral constraints. The closed chain topology, redundancy in actuation, and the nonlinear coupled equations of motion make the problem formidable. The approach used is to utilize a minimal set of inputs to control the trajectory. The surplus inputs are used to control the contact conditions (rolling, sliding, etc.).>