Sensors for an omni-directional mobile platform

Moving heavy objects in the workplace has resulted in an increased number of accident compensation claims throughout the western world. For this reason it is common to hire dedicated persons to move heavy equipment in a workplace. The aim of this work is to design and build a midsized omni-directional 4-wheeled mobile platform that can be easily controlled in a confined space to move heavy objects. For very accurate motion of the platform and dexterous control, it is essential to have accurate speed feedback of the wheels. An alternative method of sensing the speed of the wheels has been employed. It relies on measuring the back EMF of the motors which are driving the wheels. This voltage based speed measurement technique has been experimentally evaluated and benchmarked against the traditional quadrature encoder based digital system for viability and accuracy. Experimental results show that with appropriate post possessing, the voltage based speed measurement system is a suitable low-cost replacement. Several other sensors, such as inclinometer, joystick and battery level sensor, have been incorporated in the mobile platform. These sensors combine to add functionality and safety to the system through sensor fusion and redundancy. These topics are briefly discussed in this paper.