Digital Force Control in Rehabilitation Robotics

Robots can successfully be applied in rehabilitation of the disabled. Force sensors are used to control the contacts between the robotic arms and the patients’ body parts either during the teaching-in of the robot, or during its operation. The use of certified standard industrial robots inserted into an outer force control loop results low sampling frequency, and the experiments call the attention for the corresponding destabilizing digital effects. The stability of the force based teaching-in method is analysed with application for upper limb motion therapy. The stability limits are presented in the parameter space of the sampling time, control gains and mechanical parameters of the sensor. The least force error is calculated in closed form. Real parameter case study and experiments confirm the analytical predictions.

[1]  Gábor Stépán,et al.  Vibrations of machines subjected to digital force control , 2001 .

[2]  Miklós Farkas,et al.  Periodic Motions , 1994 .

[3]  Friedrich Lange,et al.  Learning force control with position controlled robots , 1996, Proceedings of IEEE International Conference on Robotics and Automation.

[4]  George Haller,et al.  Quasiperiodic oscillations in robot dynamics , 1995, Nonlinear Dynamics.

[5]  John J. Craig,et al.  Hybrid position/force control of manipulators , 1981 .

[6]  Hermano Igo Krebs,et al.  MIT-MANUS: a workstation for manual therapy and training. I , 1992, [1992] Proceedings IEEE International Workshop on Robot and Human Communication.

[7]  Benjamin C. Kuo,et al.  Digital Control Systems , 1977 .

[8]  William Harwin,et al.  Error correction movement for machine assisted stroke rehabilitation , 2001 .

[9]  John J. Craig,et al.  Introduction to Robotics Mechanics and Control , 1986 .