John J. Craig

Articulated Hands Force Control and Kinematic Issues

Kinematic and control issues are discussed in the context of an articulated, multifinger mechanical hand. Hand designs with particular mobility properties are illustrated, and a definition of accuracy points within manipulator workspace is given. Optimization of tlte physical dimensions of the Stanford-JPL hand is described. Several architectures for position and force control of this multiloop mechanism are described, including a way of dealing with the internal forces inherent in such systems. Preliminary results are shown for the joint torque subsystem used in the hand controller.

Adaptive control of mechanical manipulators

When an accurate dynamic model of a mechanical manipu lator is available, it may be used in a nonlinear, model-based scheme to control the manipulator. Such a control formula tion yields a controller that suppresses disturbances and tracks desired trajectories uniformly in all configurations of the manipulator. Use of a poor dynamic model with this kind of model-based decoupling and linearizing scheme, however, may result in performance that is inferior to a much simpler, fixed-gain scheme. In this paper, we develop a parameter-adaptive control scheme in a set of adaptive laws that can be added to the nonlinear, model-based controller. The scheme is unique be cause it is designed specifically for the nonlinear, model- based controller and has been proven stable in a full, nonlin ear setting. After adaptation, the error dynamics of the joints are decoupled with uniform disturbance rejection in all ma nipulator configurations. The issues of sufficient excitation and the effect of disturbances are also discussed. The theory is demonstrated with simulation results and also with data from an implementation for an industrial robot, the Adept One.

Industrial robot programming languages: A comparative evaluation

Eight commercially available high-level robot programming languages developed by industrial robot builders and research laboratories are evaluated. These languages are: AL; AML; Help; Jars; MCL; Rail; RPL; and Val. The historical background of the languages is reviewed. The languages are evaluated on the basis of data types, control structures, motion specification, use of sensors, and interface with external machines and devices. Common and uncommon features are noted. Facilities for program editing, entry, debugging, and teaching are compared. Conclusions are given regarding their present status and future development.