Realization of an FPGA-based Motion control system for electric standing wheelchairs

Abstract

With the characteristics of convenience and mobility, electric standing wheelchairs (ESW) enable patients to freely move and stand up. Being extensively utilized, electric wheelchairs have already been one of the indispensable medical rehabilitation devices. Without doubt, the increase of standing function on electric wheelchairs would be further beneficial to patients. The controller system of the ESW is mainly based on the SoPC (System on a Programmable Chip) constructed by FPGA (Field Programmable Gate Array) and one Nios II processor produced by Altera company. The electric wheels are built up by two DC rim motors while the standing frame is composed of a linear motion mechanism and a parallel four-bar linkage mechanism. The motion controller IC is realized by PDL with the function of standing frame and two DC rim motors' speed control. The controller of standing frame consists of one motor drive and four channels of PWM (Pulse Width Modulation) signal outputs. Therefore, the necessary all digital drive controller of ESW is realized in one FPGA. This ESW enable not only the two-wheel machine to locate, synchronize, turn left or right, move forward or backward, brake and stop, but also the standing frame to lift and fall. Finally, this work completes one experiment system including a FPGA board, three converters, one two-wheel drive standing wheelchair platform that further evidences both the effectiveness and accuracy of the FPGA-based motion controller for ESW.