Sliding Mode Control of a Differential Drive Mobile Robot

Abstract

This report presents the sliding mode control (SMC) design of a Differential Drive Mobile Robot (DDMR) following a trajectory using the SMC techniques. Control of DDMR generally follows two approaches, trajectory following, positioning motion. In this report, the kinematic and dynamical models of DDMR are found such that mathematical analysis can be done. The model is nonlinear, and its control needs two state variables of which only one can be measured; another one is estimated with the help of the observer. Particularly to follow any trajectory, we required global coordinates of the path. However, in our application, we neither can sense that nor we measure, so we have to estimate the global coordinates of the path with the help of an observer. In this report, we proposed one of the robust observer sliding mode observer (SMO). Project work includes the designing, analysis and implementation of a nonlinear sliding mode observer. Then we implemented the SMO in place of linear Luenberger observer and verified the model again with MATLAB/Simulink software. While using the SMC approach, we have also analyzed various reaching laws, i.e. constant reaching law and power rate reaching law and found that chattering was significantly reduced because of the power rate reaching law. One modality of movement includes forward movement. To find the proper control action, the Lyapunov theorem for nonlinear systems is applied. Verification of the model, including SMC and SMO, is done with the help of simulation in MATLAB/Simulink software. Results/Diagrams obtained from the simulation are shown in this report. The future work includes hardware implementation of this model.