Simulation and real-time control of a seven-degree-of-freedom manipulator

A simple and efficient numerical scheme for local optimization of complex performance criteria is presented to generate the joint trajectory of a seven-degree-of freedom redundant manipulator. Several practical issues arising from the implementation of local optimization are discussed. A comparison is made of the joint trajectories obtained by optimizing different performance criteria. The seven-degree-of-freedom Robotics Research Corporation (RRC) manipulator is used as a test-bed in this research. A program for real-time control and 3-D graphics simulation of the RRC manipulator is developed on the IRIS-4D/50 GT Silicon Graphics workstation. The user-interface created for this program has several trajectory planning features. It also includes a capability to evaluate joint trajectories in real-time by using plots in 3-D space represented by the end-effector trajectory, self-motion, and the cost function or performance criterion. All the software is written in C programming language for easy portability, and can be used for other seven-degree-of-freedom manipulators. A JR³ force/torque sensor and an ultrasonic sensor were integrated to the RRC manipulator for force control and obstacle avoidance, respectively.