Abstract
Inherent compliance and assistive behavior are assumed to be essential properties for safe human-robot interaction. Rehabilitation robots demand the highest standards in this respect because the machine interacts directly with weak persons who are often sensitive to pain. Using novel soft fluidic actuators with rotary elastic chambers (REC actuators), compact, lightweight, and cost-effective therapeutic devices can be developed. This article describes modular design and control strategies for new assistive acting robotic devices for upper and lower extremities. Due to the inherent compliance and natural back-drivability of pneumatic REC actuators, these movement therapy devices provide gentle treatment, whereby the interaction forces between humans and the therapy device are estimated without the use of expensive force/torque sensors. An active model-based gravity compensation based on separated models of the robot and of the individual patient’s extremity provides the basis for effective assistive control. The utilization of pneumatic actuators demands a special safety concept, which is merged with control algorithms to provide a sufficient level of safeness and to catch any possible system errors and/or emergency situations. A self-explanatory user interface allows for easy, intuitive handling. Prototypes are very comfortable for use due to several control routines that work in the background. Assistive devices have been tested extensively with several healthy persons; the knee/hip movement therapy device is now under clinical trials at the Clinic for Orthopaedics and Trauma Surgery at the Klinikum Stuttgart.
This work was supported by the German Federal Ministry of Education and Research through grant 01EZ0769 from the cooperative research project KoBSAR “Compact assistive/restorative motion therapy devices of new generation based on fluidic soft actuators with rotary elastic chambers”. The concepts for the new movement therapy devices with REC actuators were discussed in detail with the cooperation of the following partners: C. Koch, E. Frank, H.-D. Haas, and D. Anhalt from the Dr. Paul Koch GmbH company (Frickenhausen) as well as Dr. P. Reize and M. Mahner from the Clinic for Orthopaedics and Trauma Surgery at Klinikum Stuttgart. The authors appreciate the nylon-polyurethane air pads manufactured and provided by Dr. Winkler GmbH & Co. KG company (Ainring-Mitterfelden; general manager, Dr. R. Resinger). The contribution of Erwin Wendland and Elke Sorgenicht to the mechanical design as well as the technical support of Heinz Weissig are gratefully acknowledged.
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