Redundant underactuated robot with multi-mode control framework

A method for controlling a robotic system having a jointed mechanism that includes a plurality of actively-controlled joints, a plurality of passive joints that are redundant with the actively-controlled joints, and an end-effector connected to and positioned distally with respect to the passive joints, the method comprising:

• measuring joint positions of the passive joints using a plurality of position sensors;
• transmitting the measured joint positions to a controller;
• selectively controlling the actively-controlled joints via the controller in response to the measured joint positions using a modeled impedance of the robotic system in which the robotic system is modeled as a spring-mass-damper system having a stiffness parameter and a damping parameter, including manipulating at least one of the stiffness parameter and the damping parameter, and using a plurality of control modes, the control modes including an Autonomous Mode in which an operator does not physically interact with the end-effector and a Cooperative Control Mode in which the end-effector is configured to be physically interacted with by the operator;
• and
• executing force control over the end-effector in one or both of the Autonomous Mode and the Cooperative Control Mode to thereby limit a force applied by the end-effector to an object.

A robotic system comprising:

• a jointed mechanism having a plurality of actively-controlled joints and a plurality of passive joints;
• an end-effector connected to and positioned distally with respect to the passive joints and configured to apply a regulated force to an object, wherein the end-effector is configured for physical interaction with an operator during a Cooperative Control Mode;
• a plurality of position sensors operable for measuring joint positions of the passive joints;
• and
• a controller in communication with the position sensors, and programmed to selectively control a position of the actively-controlled joints using a modeled impedance of the robotic system in response to the measured joint positions to thereby command application of the regulated force to the object via the end-effector;
• wherein the modeled impedance is modeled via the controller as a spring-mass-damper system having stiffness and damping parameters, and wherein the controller is programmed to control the jointed mechanism by manipulating at least one of the stiffness parameter and the damping parameter and to execute force control over the end-effector in the Cooperative Control Mode to thereby limit a force applied by the end-effector to the object.