Robust Model Reference Adaptive Control Design for 1DOF Flexible Arm with Payload Variations based on Fractional Order MIT Law

Flexible manipulators, due to their inherent structural flexibility, present significant control challenges, especially when manipulating non-fixed payloads. This paper introduces a fractional-order model reference adaptive control (FOMRAC) design to deal with the problem of controlling a single-link flexible manipulator which is subject to joint friction and variation in the load. This control system allows removing the effects of nonlinear friction by implementing an adaptive regulator for the motor position that compensates the coupling torque and Coulomb friction. The tip position control is carried out by decoupling the system dynamics using a positive feedback closed loop around the tip position and then applying a FOMRAC adaptive regulator for the decoupled system when the tip load is varying. Simulations of ideal and disturbed control scenarios are given to validate the efficiency of the proposed fractional-order adaptive control algorithms applied to a single-link flexible manipulator and demonstrate its superior performance when managing variations in payload and disturbance rejection comparatively with the standard integer MRAC scheme.