Experimental verification of “hardware fail-safe chopper” for electrical wheelchair

摘要

The role of electrical wheelchair has been more important in recent aging society. However, currently used electrical wheelchair is not always better solution considering human safety. For example, when the electrical wheelchair contacts a large step, it is dangerous to roll over the step with an ordinary speed. In addition, a human will be exposed to risk when a controller fails during step over. To solve these problems, we propose hardware fail-safe chopper to realize safe and secure electrical wheelchairs. In the proposed system, a wheelchair stops in front of a large step temporarily and the energy to climb the step is charged from battery to supercapacitor. Then, a large torque can be generated in the wheel with motor to achieve step-climbing by discharging the stored energy of the supercapacitor in short time. Therefore, the proposed chopper circuit operates as a buck converter on a flat ground and as a boost converter which is supplied the energy from the supercapacitor in the case of the step-climbing. An absolutely fail-safe operation can be provided by the hardware-based restriction of the motor torque. A validity of the proposed system is confirmed by the simulation and experiments.