Control system design for a continuous passive motion machine

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The Ohio State University

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The knee is a complex joint that is essential for walking, running, kneeling, and climbing stairs. Injuries and trauma to the knee joint commonly require surgical treatment followed by post-operative physical therapy rehabilitation. Successful physical therapy treatment plans involve repetitive flexion and extension of the knee immediately following surgery. A continuous passive motion machine is commercially available to generate cyclic passive flexion and extension of the patient's leg. Continuous passive motion has been shown to reduce joint stiffness, swelling, and restore the normal range of motion in the knee post-operatively. However, the number of cycles, the maximum and minimum angles of flexion, and the speed of the device are input parameters that currently have no standard setting. Defining a standard physical therapy treatment methodology that specifies the settings of the continuous passive motion device could decrease the overall treatment time and may improve the patient's outcome. Biomechanical evaluation of a knee during continuous passive motion can help to define standard settings for the input parameters. A testing device similar to a commercially available continuous passive motion machine can provide researchers with the means to measure the effects of the input settings. The testing device must have user-friendly operation with input parameters for the angular flexion velocity and flexion angle of the knee. The purpose of this project is to develop closed-loop control for the testing device through a graphical user interface control of the device. The software, mechanical hardware, and electrical hardware operate the device based on the user input parameters. The testing device will be used for future work in the Neuromuscular Biomechanics Laboratory to study the biomechanical properties of the knee undergoing continuous passive motion.



passive, control, knee, motion