Real-Time Stabilization Control of a Rotary Inverted Pendulum Using LQR-Based Sliding Mode Controller

Inverted pendulum has been a benchmark system in dynamics and control theory. This system has an inherit feature of being nonlinear, unstable and underactuated. Due to which, it is widely known as a test bench to evaluate the capability and performance of emerging control algorithms. Furthermore, the inverted pendulum system is also known to resemble many real-world problems including Segway’s, humanoid robots, to name a few. The literature on inverted pendulum system reveals a wide range of controllers. The linear quadratic regulator (LQR) is one of the well-known optimal controllers; however, it lags in robustness. The sliding mode controller is known for its robustness characteristics; however, it has a problem of non-robust reachability phase. To solve the problems in both the controllers while retrieving their advantages, this paper presents the design of a hybrid controller which is a combination of LQR and sliding mode controller for the robust control of rotary inverted pendulum. This controller uses LQR as a baseline controller for optimal performance and a sliding mode controller to robustly control the system against matched uncertainties. The robustness of the proposed controller is validated on a real-time rotary inverted pendulum subjected to an input disturbance. The obtained simulation as well as experimental results show that the proposed controller performed satisfactorily with robustness to matched uncertainties. Furthermore, the problem of chattering in the controller is dealt by smoothening the control input with insignificant loss in robustness.