Carlos Canudas de Wit

Switching and PI control of walking motions of planar biped walkers

A companion paper has addressed the problem of designing controllers that induce exponentially stable, periodic walking motions at a fixed walking rate for a planar, biped robot with one degree of underactuation. This note provides two additional control features: 1) the ability to compose such controllers to obtain walking at several discrete walking rates with guaranteed stability during the transitions; and 2) the ability to regulate the average walking rate to a continuum of values.

Optimal Radio-Mode Switching for Wireless Networked Control

Energy efficiency is a major issue in wireless networked control systems. In this chapter, we address this problem by considering more specifically the energy-consumption of the radio chip of sensor nodes. There exists an interesting and rich literature on the topics of intermittent and event-based control, allowing to turn off the sensor’s radio for longer time than what is possible with a classical periodic sampling. Such a literature only addresses policies using two radio-modes (Transmitting and Sleep), while this contribution aims at exploiting the use of various radio-modes, both transmitting modes having different transmission power, where increased power results in better transmission quality (fewer errors) but higher energy cost, and non-transmitting modes which correspond to switching off only some components of the chip, and result in having higher energy cost than Sleep but faster/less costly transition to transmission. We propose an event-based radio-mode switching policy to perform a trade-off between energy saving and performance of the control application. The switching policy is derived jointly with the feedback law using a switched model taking into account control and communication. We compute the optimal joint switching policy and feedback law using Dynamic Programming and we illustrate the results in simulations.