Position/force control with a frequency-based switch for robots interacting with a compliant environment

Position/force control coordination can be achieved in many ways. This paper looks at different control coordination strategies, and the possible effects of transition from free to constrained motion. In hybrid position/force controllers for example, position and force controlled directions are separated and explicitly controlled. A selection matrix switches position and force control modes accordingly. Another approach based on the accommodation strategy allows for explicit position and force control without using any sensor dependent switch. It can be seen that an element in the accommodation control could be regarded as a frequency-based switch. A generalization can be written for this class of controllers. A single link robot example is given to illustrate the characteristics of this class of structure