A comparative evaluation of adaptive and non-adaptive Sliding Mode, LQR & PID control for platform stabilization

During the uniform locomotion of compliant legged robots and other terrain vehicles, the body of the robot often exhibits complex oscillations which may have a disturbing effect on onboard sensors. For a camera mounted on such a robot, due to perspective projection, the effects of angular disturbances are particularly pronounced as compared to translational disturbances. This paper is motivated by the particular problem of legged robots exhibiting angular body motions and attempts to evaluate the performance of baseline and state-of-the-art controllers for compensating this undesired motion. For this comparative evaluation, a simplified planar camera platform is considered in a Matlab-Simulink based simulation environment but motion disturbances are collected on a physical experimental robot platform. Although the full stabilization problem is in 3D with three independent axes of rotation, we currently consider a planar case on the pitch axis with a kinematic structure very similar to many parallel actuated 3D platforms. We believe that despite the simplified analysis, the presented performance evaluation provides significant insight into the general problem. The work consist of the derivation of the planar platform model followed by the implementation and comparative testing of 4 different controllers, namely Proportional-Integral-Derivative (PID), Linear Quadratic Regulator (LQR), Sliding Mode (SMC) and Adaptive Sliding Mode (ASMC) controllers. Experimental setup, disturbance collection and finally, the controller performance test results are presented and discussed.