Simple switching control for hybrid dynamics of a planar hopping robot

Abstract

This paper presents a new prospect of switching controller for the hybrid dynamics of a hopping robot. The hopping robot studied in this paper jumps using only its single leg, and its dynamics is considered as a hybrid system. The robot dynamics has the aerial phase and the ground-contact phase, and the phase change is driven by the touchdown and lift-off events. Thus, it is an event-driven dynamically intermittent system, i.e. a hybrid system. The hybrid dynamics including the two phases usually requires a distinct controller for each phase because legged robots have completely different dynamics for each phase. In contrast, this paper presents one form of controller applied to both phases. The controller is flexible enough that only desired variables and gains are switched and the switching is driven by the phase change events. This controller proposed and applied in this paper is in the likely simplest form. From a practical point of view, this minimalist approach is desirable for robotics applications due to their nature of being real-time embedded control systems in implementation. For analyzing simulation and experimental data, the Poincare map is introduced. Resulting motion is shown and discussed in the context of discrete system stability.