Backstepping Control of Variable Stiffness Robots

Robots with elastic joints arouse an increasing interest in the robotics community. Especially, variable stiffness robots promise to be beneficial regarding robustness and task adaptability. However, the control of variable stiffness multijoint robots is challenging due to their highly nonlinear behavior. Here, we present a backstepping approach for tracking control of multijoint variable stiffness robots. To cope with the problem of noisy-state measurements and the need for higher order state derivatives, command filters are used. A stability proof of the complete control approach including filtering is given. Finally, the simulations and measurements on a variable stiffness joint and a multijoint variable stiffness robot validate the approach.