Impedance force control of free-joint manipulators with one motor under gravity

In this paper, free-joint manipulators under gravity potential are to be considered. Although free-joint manipulators under gravity are namely pendulum systems, there is difference that pendulums are controlled to the gravitational equilibriums and these free-joint manipulators are controlled to the other configuration. Dynamical behaviors under vibrational input to the first joint are analyzed via averaging analysis. It is clarified that dynamical stabilization onto a configuration other than the gravitational equilibriums can be realized using a kind of artificial potential produced by vibrational input against gravity. Passive impedance property is clarified for the dynamically stabilized systems to an external disturbance and an impedance force control method to attenuate desired impedance property is proposed.