Clearance control of mechanism with sliding mode controller

Due to the design, manufacturing, and assembly processes, joint clearance inevitably occurs in mechanisms. To reduce the undesirable effects of this phenomenon, in this work a practical control method to decrease these effects is presented. This control method ensures permanent joint contact and follows the desired path based on the actuators in the system. As a result, because the controller seeks to achieve two control demands using one actuator, these mechanisms are known as an under-actuated system. For this purpose, an improved second-order sliding-mode controller (IS-SMC) is proposed. This choice is based on its robustness and its ability to meet control demands in a finite time, as well as its high accuracy for sub-excitation systems. In this research, the control method is applied to the crank-slider and the four-bar mechanisms. For this purpose, at first, the equations of these mechanisms have been expressed in an ideal form, and then the nonlinear equations have been extracted with the imperfect joint. The Lankarani-Nikravesh and the Ambrosio models have been used for modeling the clearance and friction force in the joint, respectively. In addition, verification of controller is implemented in Adams software.