1991 Volume 27 Issue 3 Pages 333-340
A trajectory accuracy improvement scheme for a “serial-parallel-drive”, SCARA type robot arm is proposed. The serial-parallel-drive robot arm has the forearm motor on the upper arm coaxially, which drives the forearm through a parallel link mechanism. The scheme is composed of invariant dynamics design, decoupling compensation control, and inverse system computation. It cancels the inertia variation effects, coupling inertia effects, centrifugal and Coriolis torque effects, and response lag of the servo system. It simplifies the arm drive system dynamics into decoupled, linear, time-invariant one. Therefore, the computation requirement of the inverse system is reduced compared to the conventional inverse dynamics method. The scheme is applied to a SCARA type direct-drive robot arm with a 8bit MPU controller, and verified to be effective through simulation and real-time operation experiments.
