Delayed teleoperation system in presence of moving virtual fixture

This paper presents a hybrid PD-Based controller for delayed teleoperation systems in presence of moving virtual fixtures. Virtual fixtures in such systems are used to prevent slave robots from entering the undesired areas of the workspace. For example, in Minimal Invasive Surgery (MIS), it is very important to restrain the surgical robot. It appears that employing virtual fixtures in bilateral teleoperation systems can make them unstable. In other words, virtual and software constraints, sampling rate and data quantization can cause instability and vibrate the slave robot entering into unauthorized areas. Another possible reason for instability is time delay in the communication channel. This factor has not been investigated in such systems so far. To carry out the stability of the closed loop system, passivity theorem is utilized. Moreover experimental results demonstrate the performance of the proposed controller with a reasonable accuracy.