Analysis of Force/Stiffness Control of Variable Stiffness Tendon Driven Arms

Under the human environment, robot arms are desired to have safety and versatility. There is a tendon drive arm using nonlinear springs as a mechanism that meets the requirement. By using springs in the power transmission path of this arm, safety at the time of contact can be secured. Also, utilizing the nonlinearity of the springs, the mechanical stiffness of the arm can be adjusted. In this paper, we analyze the natural angular frequency and the damping factor of the force control system for the mechanical stiffness of the tendon drive arm using the nonlinear springs and the contact environmental change using the root locus. In particular, it is possible to increase the response speed without changing the control stiffness by making the mechanical stiffness variable.