Supermileage Systems Enterprise Brushless DC Motor Controller Project

The SAE Supermileage Enterprise team is branching out and competing in a new competition! The Shell Eco-Marathon competition challenges students to design and build an ultra energy-efficient vehicle, covering the most distance using the least amount of energy. The SAE Supermileage team has taken on this new challenge and is attacking it with a Brushless Direct Current Motor, or BLDC. This is a new and exciting project for the Supermileage team as we are branching out into the world of electric motors. Electric motors come in many different types. Each type has different internal structure that can completely change how they should be controlled. The benefit of using more complex electric motors is that they are typically more energy efficient. Since Shell Eco-Marathon is judged based off of efficiency, we decided to brave the challenges presented by a more complex motor type. The motor we chose to use is of the Brushless DC type (also known as a Permanent-Magnet AC motor) and is a 300 Watt motor. This type has powerful permanent magnets in the rotor (the part that spins), which are repelled by magnetic fields produced by wire coils in the stator (the outer shell). Using embedded computers and power electronics, we can carefully control the magnetic fields produced by the coils so that they always apply as much force to the rotor as possible.

The purpose of our project is to design, build, and test the device that controls the magnetic fields in the stator. Building a motor controller is a daunting task, requiring us to bring together knowledge of motors, controls, power electronics, and solid-state materials. So far, we have completed our initial design, and have already started prototyping. The complete prototyped vehicle has a theoretical drag coefficient of 0.09 and an overall weight of 136 lbs. We have a goal of achieving 500 km/kWh, which converts to roughly 9000 MPGe. Upon achieving this goal we would take first place at the competition with a large lead, based on results from previous years. The new Tesla P85D gets 93 MPGe and the Nissan Leaf gets 114 MPGe. When putting our goal into perspective with electric vehicles already on the road, our projected 9000 MPGe is roughly 90 times the efficiency of current production battery electric vehicles (BEV) on the market today!

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