Joint-space impedance control for tendon-driven manipulators

A method for providing torque control of a tendon-driven manipulator, said method comprising:

• calculating by a processor, actuator reference positions or motor commands by projecting a torque error into a tendon position space using a single linear operation;
• calculating the torque error using sensed tendon tensions, a reference torque and internal tension;
• limiting minimum and maximum tendon tensions by projecting the torque error into the tendon tension space and then projecting the torque error into a joint space including converting a tendon limiting value from the joint space to the tendon space, limiting the tendon tensions, and converting the tendon tension back from the tendon space to the joint space;
• providing a proportional-integral controller to control torque and internal tension or joint space impedance;
• calculating a command actuator position by adding a velocity feedback term and a torque error term to a current actuator position;
• and
• calculating a torque error reference using the torque error term by multiplying a joint error by a stiffness constant to realize a positive stiffness.