Impedance and Interaction Control

Internal models in sensorimotor integration: perspectives from adaptive control theory

“…According to the equilibrium-point hypothesis, the motor command may modulate the stiffness and viscosity of the muscles which act as a spring to "pull" the hand back to some equilibrium positions of the muscles regardless of external disturbances. Impedance control is an extension of the equilibrium-point hypothesis in the context of engineering robotics, where robotic control is achieved by regulating its output impedance which characterizes the dynamic behavior of the robot at the port of interaction with the environment (Hogan 1985;Hogan and Buerger 2005). Output impedance is intrinsic to the robotic control system and does not require precise knowledge of the environment (Hogan and Buerger 2005).…”

“…Impedance control is an extension of the equilibrium-point hypothesis in the context of engineering robotics, where robotic control is achieved by regulating its output impedance which characterizes the dynamic behavior of the robot at the port of interaction with the environment (Hogan 1985;Hogan and Buerger 2005). Output impedance is intrinsic to the robotic control system and does not require precise knowledge of the environment (Hogan and Buerger 2005). This gives impedance control its appeal since in general a complete model of the environment is lacking and the environment may vary from task to task.…”

“…5) with an implicit impedance control law given by the stiffness and viscosity of the arm muscles during movement and a continuous gain-switching schedule that is determined by hand position. This form of impedance control is analogous to a PD controller with a resultant torque given by the deviations of the instantaneous hand position and velocity from their corresponding virtual trajectories: (13) where K is the stiffness matrix, B is the viscosity matrix, and θ o is the virtual trajectory for impedance control, which is equivalent to the reference trajectory for PD control (Hogan and Buerger 2005).…”

Learning and generalizing force control policies for sculpting

“…Using position control in our scenario, however, is rather inappropriate since a kinematic plan incompatible with the environment or endeffector's mechanical resistance would result in high impact forces or even task failure. Instead, a compliant control policy is of interest to be learned which regulates interaction [4]. The proposed generalization algorithm is significantly less complex than computationally expensive incremental learning techniques [12] since it only allows for policy prediction given new inputs without integrating new information into the learning structure.…”

Human-friendly robotic manipulators: safety and performance issues in controller design

“…Their operation surely includes interaction with various objects and thus require an interaction controller which allows a stable operation against range of environmental behaviors including cases of contact, no contact and the transition between the two. Because of the inadequacy of direct force controllers to manage unstructured environments [170] and their sensitivity to coupled instability [52,79], impedance control is used as the interaction controller of choice in this thesis. Impedance control technique o↵ers easier task planning and its e↵ectiveness is reported in various applications such as human-robot cooperation, dynamic whole-body mobile manipulation, vision guided manipulation, dual-arm cooperation and human-assist systems [28,81,186,43,133,27].…”