SAN JOSE, CALIF.—Electric cars are all about small gains in efficiency that translate into increased range. Reduce friction, tweak the acceleration curve and increase the regenerative braking and you’ll get a few more miles. Automotive technology company Tula has proposed another solution to improve efficiency.
The system, called Dynamic Motor Drive (DMD), pulses the electric motor to operate within the “sweet spot” of efficiency. DMD improves efficiency and removes one of the more controversial materials found in EV engines: rare earth metals. The result is an efficiency gain of about 3 percent. That’s not a huge boost, but if your car has a range of 300 miles, for example, you get an extra nine miles of road you can cover. But the system is also setting itself up to work in a world with fewer rare-earth magnets.
These rare earth magnets cost automakers quite a lot, and they don’t fit EVs’ green stance. Currently, 90 percent of the EV industry’s materials for these magnets (mainly neodymium) come from China. Since the end of 2021, the price of these materials has increased by about 90 percent. There is It plans to increase rare earth production in the United Statesbut considering the environmental measures that need to be taken, it still won’t be cheap.
The extraction and processing of neodymium causes great damage to the environment. Electric cars are supposed to be a greener answer to gas-powered cars, so it doesn’t seem like a good idea to remove the magnets that go into an EV. responsible for the introduction of toxic chemicals into waterways.
The thing is, most EVs on the road still use these internal permanent magnet (IPM) motors. Currently, BMW and Nissan have vehicles in production that use electrically excited synchronous motors (EESMs) in their vehicles. Others will likely make the transition at some point in the future. During the presentation, John Fuerst, Tulane’s DMD and senior vice president of engineering, noted that OEMs are primarily working on EESM for their vehicles.
Even with their magnetless engines, neither BMW nor Nissan have yet built a DMD-capable vehicle. Tula notes that some minor hardware changes must occur, but most of the DMD secret sauce is in the software that controls the motor.
The biggest challenge is getting the engine to pulse within the car’s efficiency. Every vehicle has a point at which engine speed and torque are adjusted to ensure the best use of energy. As an example, Tula shared a graph showing the point at which a car makes about 75 lb-ft of torque at 3,000 rpm. If the car is traveling at a speed that uses less torque – 25 lb-ft, say the DMD system will pulse the motor 20 times per second and produce 75 lb-ft of torque.
Not a continuous supply of power, but a pulsed delivery of power. To make sure it doesn’t create a driving experience similar to rolling in a car experiencing a series of small earthquakes, Tula tweaks the system to reduce this sensation.