Delay dependent stability limits in high performance real-time visual servoing systems

This paper addresses the long-standing problem that visual feedback delay can drive a high bandwidth visual servoing system unstable. While some architectures become unstable with increasing image processing delay, we propose a novel visual servo implementation whose stability is independent of delay time. Performance decreases as image processing delay increases, but the system always remains stable. We demonstrate our new approach experimentally on a camera-pointing device. For those visual servo implementations that will become unstable with increased time delay, we propose an analytical method to find the upper limit of acceptable delay, using equations derived from the Nyquist stability criterion. The approach described in this paper is not only a useful tool for design and implementation of stable visual servoing systems, but also has general application to other dynamic systems with delay elements.