International Journal of Control, Vol.85, No.9, 1313-1326, 2012
Lyapunov stable displacement-mode haptic manipulation of hydraulic actuators: theory and experiment
In this article, a stable control scheme is designed and experimentally evaluated for haptic-enabled teleoperated control of hydraulic actuators. At the actuator (slave) side, the controller allows the hydraulic actuator to have a stable position tracking. At the master side, the haptic device provides a kind of ` feel' of telepresence to the operator by creating a force that acts like a virtual spring, coupling the displacement of the haptic device to the displacement of the hydraulic actuator. In free motion, this virtual spring restricts the operator's hand to move fast when the slave manipulator is behind/ahead in terms of tracking the master manipulator's displacement. On the other hand, when interacting with the environment, the constrained force imposed on the hydraulic actuator is indirectly reflected through this virtual spring force. Extension of Lyapunov's stability theory to non-smooth systems is first employed to prove the stability of the resulting control system. Effectiveness of the controller is then validated via experimental studies. It is shown that the control scheme performs well in terms of both positioning the hydraulic actuator and providing a haptic feel to the operator. The control scheme is easy to implement since very little knowledge about system parameters is needed and the required on-line measurements are actuator's supply and line pressures and displacement.
Keywords:hydraulic actuator;haptic;telemanipulation;displacement-mode;Lyapunov's stability;Filippov's solution