Haptic Consensus in Bilateral Teleoperation

In this paper, haptic consensus is introduced for networked robotics; specifically teleoperation systems. Haptic consensus basically employs distributed consensus algorithms, forcing the networked robots to agree on system states such as position, acceleration and force. Once the systems agree on these states they have a haptic coupling. Any force applied on one robot is felt by others and they can move in perfect harmony, repeating what a master does. Network topology is represented by graphs and it is shown by using graph Laplacians that the topology is very critical for the stability of the overall teleoperation system. In this paper, the simplest form of haptic consensus in a 2 robot network -bilateral teleoperation-is shown. Because bilateral teleoperation requires acceleration control, modified consensus algorithms are developed. For haptic consensus in bilateral teleoperation we introduce two new consensus algorithms; one for the acceleration consensus and one for a common acceleration feedforward. Acceleration consensus is realized by an algorithm similar to a PD controller, whereas the acceleration feedforward is determined by force consensus filters measuring the forces applied on the robots. When these algorithms are used together, it is shown that haptic consensus can be realized. The results presented in this paper can be extended to teleoperation systems with multiple robots without loss of generality.