Discrete-time velocity control of redundant robots with acceleration/torque optimization properties

The paper addresses the following problem for redundant robots. Given a second-order inverse differential scheme that realizes instantaneously a desired task acceleration and has some specified properties in terms of joint acceleration or torque, define a discrete-time joint velocity command that shares the same characteristics under suitable hypotheses. The goal is to obtain simpler implementations of possibly complex robot control laws that i) can be directly interfaced to the low-level servo loops of a robot, ii) require less task information and on-line computations, iii) are still provably good with respect to some target performance. The method is illustrated by considering the conversion into discrete-time velocity commands of control schemes for redundant robots that minimize the (possibly, weighted) norm of joint acceleration or joint torque, or that add null-space damping to overcome floating motion of the robot joints. Numerical results are presented for the kinematic control of a 7R KUKA LWR.