Robust and stable robotic force control

To perform many complex tasks, modern robots often require robust and stable force control. Linear, fixed- gain controllers can only provide adequate performance when they are tuned to specific task requirements, but if the environmental stiffness at the robot/task interface is unknown or varies significantly, performance is degraded. This paper describes the design of a robotic force controller that has a simple architecture yet is robust to bounded uncertainty in the environmental stiffness. Generic stability conditions for the controller are developed and a simple design methodology is formulated. The controller design is tested on an experimental robot, and is shown to perform favourably in the presence of large changes in environmental operating conditions.