Hybrid CPM and CAM Physiotherapy Device by Using Intelligent Feedback Control

Continuous passive motion (CPM) and continuous active motion (CAM) physiotherapy devices are commonly used to promote rehabilitation of damaged synovial joints. CPM devices use an electric motor to move the joint through a range of motion (ROM) without muscle activity of the patient. CAM devices use some form of mechanical resistance to patient muscle activity. This paper presents a combined CAM/CPM device which functions conventionally in the CPM mode, but in the CAM mode uses the motor to exert a constant force against patient activity, simulating the effect of a spring load. In the CAM mode, the motor is embedded in a feedback loop with two sensors, one a force sensor, the other an angular position sensor. The simulated-spring-load system operation is smooth and natural. Recording is detailed. Enhancement of the operating program would allow detailed recording and analysis of patient tremor, micro-tremor, moments of weakness, etc, for advanced diagnosis of patients. The presented design will be of use for diagnosis, therapy and research.