The Optimal Design and Application of Rim Motors for a Novel Powered Wheelchair

This thesis proposes the design of a powered wheelchair propelled by a 4th generation rim motor module. This novel powered wheelchair changes the driving structure of the traditional powered wheelchair equipped with reduction gears to one that is direct-driven by two rim motors hidden in the push rim. This design simultaneously provides the advantages of lower weight and more hand-drive space. Long torque arm is supplied in the hand-driven mode and high torque and torque density are supplied in the motor-driven mode.
First of all, determination of the torque, speed and power based on dynamic evaluation is necessary. After deciding the proper winding type and tooth/pole combination, the magnetic circuit model is constructed. The optimal values of the motor can then be set through sensitivity analysis and an optimal search method. The optimal results are then verified by the Finite Element Analysis (FEA). The magnet and tooth shapes are modified to reduce the torque ripple. Some parameters of the motor are adjusted to reduce the weight without decreasing the output performance. Finally, the d-/q-axis inductances are used to find the maximum torque per ampere (MTPA).
The performance test of the rim motor shows that the design goal is achieved. The maximum torque is 26.8 and the maximum speed is 87 rpm. The road test reveals that the maximum speed is 9 km/hr on a level surface and 4 km/hr on an upward slope. Under the same speed on level ground, the powered wheelchair equipped with rim motor modules consumes only one-third the electric power of existing powered wheelchairs available on the current market and is 40 percent lighter in weight. The advantages of energy savings and light weight make this novel powered wheelchair competitive.