Fatigue Test Device for Stance Phase Control Knee Orthoses

Mechanical endurance testing is critical to ensuring durability and safety of novel orthosis components. Stance phase control knee orthoses present challenges in this area because of the lock/release mechanisms, dynamic range of joint motion, and in some cases, the capability of locking at different joint positions. A new mechanical fatigue tester has been developed to evaluate stance phase control knee orthosis joint designs. Electromechanical and pneumatic elements of the fatigue tester are under computer control. The user can determine applied maximum load, applied load at release, and range of motion and can set specific failure criteria. The computer control algorithm also provides automated data logging and system diagnostic information. This system has been in operation for more than 2,000,000 cycles. The time to complete one test cycle is 4.3 seconds under a 44.7-Nm load and 50° range of motion.