Impulsive torque control of biped gait with power packets

Many strategies for an actuated biped gait generation have been proposed based on the passive dynamic gait. Among them, this study focuses on an impulsive excitation at the toe-off instance. The strategy offers advantages in its experimental implementation; for example, it is not required to measure and control the trajectory of the legs all the time. However, there has been no study on a realistic design of the impulsive torque itself. In this paper, we propose an impulsive actuation method based on a power packet dispatching system. Power packet is a unit of electric power transfer in a pulse shape with information tags attached in voltage waveforms. According to the tag, power packets are transferred from sources to loads. On the basis of the power packetization, the torque input is configured as a result of a power packet supply to electric motors in a realistic setup. The proposed scheme controls the supply in a digitized way, that is, by changing the number of power packets supplied in a gait step. We confirm the successful gait generation with the power packets through numerical simulations

Energy Shaping of Hybrid Systems via Control Lyapunov Functions

Abstract-This paper presents a method for adding robustness to periodic orbits in hybrid dynamical systems by shaping the energy. This energy shaping method is similar to existing methods but improves upon them by utilizing control Lyapunov functions which allow for formal results on stability. The main theoretical result, Theorem 1, states that, given an exponentially-stable limit cycle in a hybrid dynamical system, application of the presented energy shaping controller results in a closed-loop system which is exponentially stable. As illustrated through simulation on the compass gait biped, this method turns out to be useful in practice, providing an improvement in robustness and convergence properties while maintaining existing stability