Improving transparency in bilateral teleoperation systems based on model-mediated approach

Transparency is an evaluation criterion for teleoperation systems based on force and position error. Generally, conventional control architectures do not lead to a high transparency to preserve the stability. A novel method is the model-mediated teleoperation approach which estimates the environment impedance on slave site and transmits it to master, where the force is calculated locally by creating a virtual environment. This procedure increases the transparency without degrading stability and with time delays in system. Correctly locating the virtual environment has a significant effect on improving the transparency of the system; however, the proposed methods for this aim either require simplifying environment model or adversely affect the transparency. In this paper a novel, yet very simple, algorithm is presented for determining the location of the virtual environment and collision time. The main feature of this algorithm is that firstly it is independent of environment model and thus is applicable to all environments, and secondly it increases the transparency of the system without using additional sensors. The proposed approach is implemented on a single-degree-of-freedom bilateral teleoperation system with time delay. For estimating environment impedance, novel accurate and robust methods are utilized. Impedance and sliding-mode controllers are used for controlling the master and slave, respectively, and the performance of the system is investigated in interaction with hard and soft environments. Simulation results indicate that the transparency of the system is suitably high in interaction with both environments; however, model jump occurs merely at the first moment of contact with the hard environment.