Design, Modeling and Fabrication of an Isokinetic Exercise Device for Back Muscles Strength and Endurance

Abstract

Low back pain is one of the most common pains that people experience in their lives. This pain is mainly associated with the weakness of back muscles that increases the risk of spine damage. Proper exercise can increase muscle strength and improve spine stability and protect it against damages. A new exercise device intended for back muscles is developed here based on biomechanical, rehabilitation and engineering requirements. A novel mechanism has been designed and fabricated such that the flexion/extension and lateral bending tests and trains can be conducted in sitting/standing positions with a single actuation and monitoring system all in one device, enhancing functionality and reducing costs. The muscles torque is monitored via a mechanism composed of two single-point load cells. An electrical motor with closed loop control is used to provide the required constant speed (in the isokinetic operation mode). The parameters in the dynamic model of the electrical motor are estimated through system identification. Two controllers (including a PI and a repetitive controller) are designed and implemented. Both controllers demonstrated good tracking and disturbance rejection in the steady state performance. The test results associated with the isokinetic and isometric operation modes obtained in the training of an adult subject are also presented and discussed.