Digital Signal Controllers Provide Advanced Motor Control
for Emission-Free Electric Scooters

When developing the new Vectrix emission-free electric scooter, scheduled for release in late 2005, the manufacturer integrated a digital signal controller in the motor control system. The controller also handles system startup, lights, safety features, and battery recharge management and supervision.

The aluminum frame scooter also consists of a 125-V nickel-metal-hydride (NMH) battery and a directdrive, brushless DC motor that peaks at 20 kW with currents up to 275 amperes. An innovative planetary gearbox was integrated in the rear wheel to provide a smooth ride without shifting.

Operation
Integrating a digital signal controller into the scooter’s design enabled the implementation of algorithms (e.g., tuning the motor’s phase angle advance)

and reduced the size and complexity of the system’s electronics; all of the control functionality could be put on a single board for savings in space and manufacturing costs. Increased circuit reliability was also recognized, which is especially important with the high currents and mechanical and environmental stresses of a transportation system.

Regenerative braking is essential in electrically powered vehicles because it converts mechanical braking energy back into electrical energy for reuse, extending the scooters range by up to 12 percent.

DSP-based control technology simplified the implementation of regenerative braking, which the rider controls with a patented bidirectional throttle. The DSP’s flexibility allowed regenerative braking performance to be tailored to the capabilities and experience of the rider. The characteristics are software determined.

DSP software programmability saved development time by making design modifications easier and enabling the rapid introduction of features for user comfort and safety. New features currently indevelopment include DSPbased remote technology for keyless entry and interactive vehicle information and diagnostics.

Additionally, programmability allows for the development of additional scooters with different features and performance characteristics based on the same control platform, extending the product line while saving hardware redesign effort.

More Information
For more information on Vectrix’s emissionfree technology, contact Peter Hughes, Vectrix Corporation’s vice president of technology, at phughes@vectrixusa.com or Jonathan Banks, director of marketing, at jbanks@vectrixusa.com. Visit Vectrix online at http://info.ims.ca/5081-330.

Learn more about Texas Instruments’ DSP technology at http://info.ims.ca/5081-331.