Robust Control Design for a Hopping Robot in Flight Phase using the Sliding Mode Approach

Abstract

Nowadays, legged mobile robots have increased the interest of the robotics community because such mechanisms have higher versatility and autonomy compared to wheeled mobile robots. Although single-leg or multi-leg mechanisms can cross any terrain, some disadvantages are related to their increased complexity in mechanical design, modeling and control, and higher power consumption. A first case study for the balance and motion planning problem is the hopping robot, which is a nonholonomic system whose motion dynamics of each hopping cycle can be split into flight and stance phases. In this work, we consider the modeling and control design of a one-legged hopping robot in the flight phase by using the sliding mode approach, due to its well-known ability to deal with parametric uncertainties and nonlinear disturbances. Then, two nonlinear controllers are designed and implemented to automatically stabilize the robot joints during the flight in the presence of perturbations caused by the neglected high-order nonlinear terms in the modeling process, unmodeled dynamics and measurement noise. The Lyapunov stability theory is used to demonstrate the stability and robustness properties of the overall closed-loop control systems. Numerical simulations and a comparative analysis are provided to illustrate the performance and feasibility of the proposed control methodology.