Analysis of Bowden cable Transmission performance for orthosis applications

A Bowden cable performance analysis, based on a design of experiments (DoE) is presented for orthosis applications. The need for analysing these cables is based on the construction of IKO (IKerlan´s Orthosis) with five actuated degrees of freedom (DoF) to help the human arm. The aim is for an individual to be capable of lifting weight without any great effort using this exoskeleton, which should be portable and readily dressed (and, therefore, lightweight). In order to transmit the power from the actuators to the joints, Bowden cables are used due to their flexibility and light weight. Transmission performance has been analysed in terms of load loss and cable deformation in order to estimate actuator requirements and positioning accuracy. A test bench has been built to measure the cable deformation and load loss occurring between the two ends of the cable in different situations. This has been applied to cables with two different diameters and at different loads. The variables for which the effect has been analysed are weight, the angle formed by the cable at the point where it leaves the sheath, the cable flexion angle, cable length, cable flexion curvature radius and cable type.