Wireless control of passive systems subject to actuator constraints

Actuator constraints such as saturation can impose severe constraints on networked control systems. For instance delays in wireless control systems of unstable plants combined with actuator constraints may make it impossible to stabilize a system. In this paper the conditions are derived that show when actuator saturation, a common memoryless nonlinearity, in series with a passive system causes the loss of passivity. However, using a non-linear controller known as a inner-product recovery block, the overall passivity of the system is recovered. Furthermore, we note specific sector conditions in which strictly-input passivity and strictly-output passivity can be recovered. Finally, it is shown how the inner-product recovery block can be used to maintain an l₂ ^m-stable wireless control network.