Dual-loop control for backlash correction in trajectory-tracking of a planar 3-RRR manipulator

The presence of backlash in the gearheads is an inherent problem in manipulators using geared motors. This paper looks at a potential solution to this problem via the implementation of a dual-loop control strategy, in which feedback is taken from the motors as well as the end-effector of the manipulator. Using the redundant sensed information, the actual error in the joint-space is computed and used to rectify the desired trajectory for the joint-space trajectory-tracking control scheme. Experiments done on a 3-RRR planar parallel manipulator show significant improvement in the tracking performance due to the introduction of dual-loop control scheme.