Active isotropic compliance in redundant manipulators

The isotropic compliance property is examined in the Special Euclidean Group SE(3) in the case of redundant manipulators. The redundancy problem is solved by means of the QR decomposition of the transposed Jacobian matrix, and the compliance property is achieved by means of active stiffness regulation. Thanks to the defined control matrices, the control system realizes the isotropy condition. The local optimization of the joint torques is discussed. In particular, the joint control torques work is minimized obtaining an analytic solution through a Lyapunov equation. The proposed approach is applied to a 7R and to a 9R serial manipulator, and verified by means of multibody dynamics simulations.