Power steering position feedback for an all-terrain wheelchair

Molten Rock Equipment was formed in 2004 by a group of wheelchair users who were frustrated with the limited capabilities of assistive equipment that did not reflect their lifestyle interests in adventurous outdoor sports. The company's highly successful Boma7 range all-terrain wheelchair began manufacture in 2007.

With a distinctive and ergonomic design that allows users easy access and straightforward operation, the electrically powered Boma7 range enables simple outdoor activities such as walking a dog or visiting a local park but is equally at home as an all-terrain wheelchair for use in more challenging landscapes. Harsh weather environments and steep gradients with mud, rain and ice mean that the chassis, suspension and especially the steering mechanism are subjected to high levels of shock and vibration. 

The steering system specification includes a robust Linak linear actuator and a Dynamic Controls joystick control system. The ELPM's pedigree - the motorsports industry uses it in position measurement for ride height, suspension and steering angle - helped the company decide on putting the sensor through its paces on the Boma7 joystick version, where it provides steering position feedback as part of the wheelchair's servo control system.

The ELPM is available in measurement ranges from 12.5mm to 150mm and feature a conductive plastic resistance element built up by the application of several layers of special inks combined with a wiper assembly comprising an elastomer-damped, multi-fingered precious metal brush arrangement. This patented measurement technology ensures smooth and uninterrupted contact with low electrical noise.

The sensor also includes an improved felt and O-ring sealing arrangement that provides IP67 ingress protection. With a serviceable rated life of more than 25 million operations, the lightweight, slimline sensor features self-aligning spherical bearing mounts and a compact retracted mounting distance for straightforward installation. An optional quick release version (the ELPM-Pop) includes snap-on fittings for fast replacement.