The design of a friction compensation control architecture for a heavy lift precision manipulator in contact with the environment

Joint friction is a major obstacle in heavy-lift precision manipulator performance. Friction compensation is vital to the performance of these manipulators. This paper presents a friction compensation architecture for a six degree-of-freedom heavy lift manipulator which utilizes sensor-based compensation in some joints, and a combination of adaptive, and model-based compensation in the remaining joints. The adaptive approach is used when the manipulator is not in contact with the environment, and the model-based compensation is used when the manipulator or its payload nears the environment. The parameters of the model-based approach are updated by the adaptive compensation during the non-contact phase of the task. This approach is validated in simulation