A preview approach to force control of robot manipulators

Automated assembly operations that utilize robots tend to constrain the robot's motion due to the task geometry. This constrained motion is termed compliant motion. Complaint motion can be actively controlled using a method of force feedback based upon servo-loop compensation, or it can be passively controlled by mechanical devices integrated into the robot structure. The “preview approach” to force control presented in this paper is a scheme based on predictive calculation of the contact forces that develop at the interface between mating parts. The preview approach utilizes predicted, present and past information to execute motion control. Contact forces are calculated using a mathematical model of the assembly process and are then used to control the compliant motion through suitable compensation torques. The control algorithm used here is more efficient than the standard methods that rely on data from force sensors and use no preview.