Effect of link flexibility of an adaptive tracking controller for a robot manipulator

The authors study the effects of flexible links on an adaptive tracking controller (ATC) for a robot manipulator. To obtain the effects of the flexible links on the controller, a rigid-based ATC is implemented with a rigid and a flexible dynamic model, respectively. The Lagrange-Euler equation is used to formulate a workable state variable model for both dynamic systems. The link flexibility is incorporated in the flexible dynamic model by using the method of the assumed mode. Three different flexural link rigidities were used in the simulation studies by selecting three cross sections of links. Two existing model reference adaptive control techniques, the gradient approach by using the modified MIT (MMIT) rule and the exact matching method, were applied. The exact matching adaptation mechanism was used as the comparative reference. Numerical simulation results indicate that the gradient approach has superior performance over other designs. A comparison of the tracking performance was also made for the MIT rule and the MMIT rule