Small advances in efficiency lead to enhanced range in electric vehicles. Reduce drag, adjust the acceleration curve, and improve regenerative braking for a few extra kilometers. Tula, a car technology firm, has developed yet another approach to improve efficiency.
The Dynamic Motor Drive (DMD) method pulses the electric motor to operate inside an efficiency “sweet spot.” DMD improves efficiency while eliminating one of the more contentious components found in EV motors: rare earth metals.
As a result, efficiency gains of roughly 3% are realized. That’s not a significant increase, but if your vehicle has 300 miles of range, for example, you’ll have nine extra miles of road to cover.
However, the system is also designed to function in a future where there are fewer rare earth magnets.
Rare earth magnets are expensive for automakers and do not fit with the environmentally friendly image of EVs. The majority of the neodymium used in these magnets, which make up 90% of the materials used in the EV sector, comes from China.
The cost of those materials has climbed by nearly 90% since late 2021. There are proposals to expand rare earth mining in the US, but it won’t be cheap given the necessary environmental safeguards.
The environmental cost of mining and processing neodymium is significant. The fact that mining for the magnets used in EVs might release hazardous chemicals into waterways is not good for the image of what is intended to be a cleaner alternative to gas-powered automobiles.
The issue is the continued use of these interior permanent magnet (IPM) motors in the majority of EVs on the road. Electrically excited synchronous motors (EESM) are currently being used in the construction of vehicles by Nissan and BMW.
At some point in the future, it’s conceivable that others will change. John Fuerst, senior vice-president of DMD and engineering at Tula, mentioned during a presentation that OEMs are primarily aiming on EESM for their vehicles.
But despite having magnet-free motors, neither BMW nor Nissan have developed a car that can use DMD. The majority of the DMD secret sauce, according to Tula, is in the software that manages the motor, but some minor hardware adjustments are necessary.
Finding a way to force the motor to pulse within the vehicle’s performance sweet zone is the hardest challenge. Each vehicle has a certain point where the motor speed and torque are balanced to provide the optimum energy efficiency.
Tula provided a graph as an illustration, indicating a point where a car is producing roughly 75 lb-ft of torque at 3,000 rpm. The DMD system will pulse the motor 20 times per second while forcing it to produce 75 lb-ft of torque if the vehicle is moving at a speed that requires less torque—say let’s 25 lb-ft—in that case.
It is a pulsed delivery of power as opposed to a continuous one. Tula has been adjusting the system to lessen that sensation so that driving won’t seem like rolling in a car that is suffering a series of mini-earthquakes.
The business aims to send the OEMs the DMD software to install on their vehicles, not to construct cars for automakers. Tula would receive a licensing fee from automakers, probably between $50 and $70 each vehicle. But it won’t happen for a few more years; even the most optimistic forecasts put the release of DMD in late 2025.
Tula is not new to the game of efficiency. It developed a technique called Dynamic Skip Fire, which switches off cylinders in big engines to raise a car’s miles per gallon rating.
Tula can see where the market is going. EVs are the wave of the future, and if you want to be a part of it, you need to find a method to tempt automakers with effective solutions that work with less expensive motors to have less of an impact on the environment. If it works, you won’t even be aware of it.