Improving first order sliding mode control on second order mechanical systems

In this paper is proposed a control algorithm based on the first order sliding mode technique. The control design adds an exponential reaching law and a disturbance estimator to improve performance, achieving a reduction of the convergence time to the reference, as well as a reduction of the reaching time towards the sliding surface. Also, by compensating the estimated disturbance, it is possible to reduce the amplitude of the chattering in the control signal. As the control design is intended to be applied in mechanical systems, a velocity observer design is also proposed. Bringing together the above aspects, the proposed controller renders an improved performance over the classical first order sliding mode controller. The stability of the closed-loop system is proved using quadratic functions. The performance of the proposed control structure is illustrated and compared with other controllers via numerical simulations and real-time experiments in a mechanical system.