Analysis of Bilateral Systems with Time Delay

Bilateral control is an effective method for reproduction of tactile sense. Therefore many researches have been conducted so far. That is about not only stability but also performance. In this paper, one of evaluation indices of bilateral systems, "Transparency" is applied to the case with time delay. Both master and slave site of the system used in this research come with acceleration control system by disturbance observer. Therefore the system is very robust to disturbance and parameter variation. The relation of force and position information of both master and slave is formulated using hybrid matrix. Then frequency responses of the elements of hybrid matrix are analyzed taking band- width of disturbance observer and reaction force observer, time delay into account. From those frequency responses, it is found out that there exists unfamiliar phenomenon (an infinite number of resonances) induced by the dimensionless characteristic of time delay. Therefore the relation of time delay and the phenomenon is discussed and clarified using Pade approximation. Then using the result, new stabilization method is proposed. It is based on phase-lead compensation.