Real-time zone-adaptive control of SCARA-type robot arm

A piecewise-linear control strategy is applied to a 2 d.o.f. manipulator performing under variable-load and variable-path conditions is presented. Each axis of the robot arm is modeled as a separate SISO (single-input, single-output) system with a single nonlinear parameter, inertia, which varies according to the load carried and position of the manipulator. The trajectory of the robot arm is divided into zones. Within each zone, an estimate of the inertial load for each axis is obtained. The inertial value for each axis is then assumed to be constant throughout the zone. A PID controller is designed within each zone for each axis which minimizes an integrated time and absolute error performance index for the estimated value of inertia. The result of this algorithm is a robust controller which tunes its parameters at specific times and can withstand a wide range of variations of the payload and path. The implemented controller was found to perform as theoretically predicted. It was also able to reduce manipulator vibration due to mechanical resonance