Instrumentation and control of a high power BLDC motor for small vehicle applications

Brushless DC (BLDC) motors are becoming an increasingly popular motor of choice for low powered vehicles such as mopeds, power assisted bicycles, mobility scooters, and in this reported application, motorised mountain boards. With rapid developments in technology, high energy density batteries such as Lithium-ion Polymer batteries are becoming more affordable and highly suitable for such vehicles due to the superior charge rate and light weight of the lithium chemistry batteries. This combined with the high power, light weight, and low cost BLDC motor results in the BLDC motor being a very favourable solution over an internal combustion engine for low power vehicles with power requirements of up to 7kW. A BLDC motor controller was developed specifically for the motorised mountain board application. The motor controller is a sensored BLDC motor controller which takes inputs from Hall Effect sensors to determine the rotor position. Many other sensors are used to monitor the variables that are critical to the operation of the motor controller such as the motor phase current, battery voltage, motor temperature, and transistor temperature. The reported system is further enhanced by several additional features such as output for an LCD screen, regenerative braking, timing advance, cruise control, and soft start functions. These topics are discussed briefly in this paper.