Development of 3-degree-of-freedom HMI for omnidirectional wheelchair typed mobile assistive robot using simple force detection mechanism

Abstract

In recent years, electric powered wheelchairs have become indispensable in long-term care. Up so far, many electrically powered wheelchairs have been developed to reduce the burden of caregivers, in which omnidirectional electrically powered wheelchairs attracted researchers' attentions because these types of EPWs can be used without stress in narrow and/or crowded spaces. In this research, we have developed an omnidirectional wheelchair typed mobile assistive robot with power assistance. In addition, traditional electric powered wheelchairs use a joystick or a force sensor as the operation interface. Joysticks cannot be used by the elderly or disabled, and force sensors are too expensive to be used for wheelchairs. In this study, we have developed a new type of Human Machine Interface (HMI) using a mechanism that can detect force at low cost by using linear potentiometers and compression coil springs instead of a force sensor.The accuracy of the developed HMI is verified, and its effectiveness is confirmed in practical use. Further, we conducted power assisted experiments in forward/backward and lateral directions and turn on the spot using an admittance control with the developed HMI attached to our omnidirectional wheelchair robot. From the experimental results, the developed HMI control accurately measures the forces applied on the wheelchair by the user. Finally, a power-assisted experiment was conducted in the straight direction on a 5-degree slope. These experiments proved that our HMI-based power assist system is effective for omnidirectional wheelchairs.