Tula Turns Its Tech Toward EV Motor Control

Scott Bailey, Tula Technology president and CEO

San Jose-based Tula Technology is best known for its innovative Dynamic Skip Fire technology. DSF uses sophisticated firing-control algorithms to adjust, on a cycle by cycle basis, the effective displacement of an IC engine. It’s been proven on over a half-million GM V8s, providing optimum efficiency at each load point. DSF is considered a high-value solution for reducing CO2 emissions and for extending the ICE’s market viability.

But with the future looking increasingly electrified, what’s next for Tula? Editor-in-chief Lindsay Brooke caught up with Scott Bailey, the company’s president and CEO, to find out. Highlights of their conversation follow.

What’s the status of DSF development for 4- and 3-cylinder engines?

We’ve done quite a bit of work in Asia on the four-cylinder DSF and have successfully wrapped up some advanced development projects. We’re not yet at the point where I can give you a defined production date. The 3-cylinder project with an OEM is tied into mild hybrid, what we call eDSF. [See SAE Technical Paper 2018-01-0864, available online.] It has full range of capability to deactivate any and all cylinders, in any sequence. Pairing eDSF with a 48-V mild hybrid system enables increased regen braking and other hybrid synergies. And our eDSF plus Miller cycle is also being evaluated.

With the electric machine on board, we can do torque smoothing. This allows us to go into firing fractions and get a little more fuel efficiency. We can also do some torque augmentation that will allow us to stay in better fuel-consumption operating points by using a very small amount of the electric machine’s output.

The BEV tidal wave is building. How is Tula responding to this?

Honestly, the second half of 2018 was hard for us to engage in IC engine conversations with people because the electrification challenge was so significant. The powertrain organizations were just so focused on finding solutions. It was a frustration for us, and understandable. But we’re seeing what I think is a more normalized mix again. The realities of EV market acceptance, infrastructure, cost, and life-cycle CO2 impacts are driving a more balanced conversation now. So, we’re getting renewed engine programs and reopened dialogue. And there are related tailwinds, including China’s New Energy Vehicle regulations. The Chinese government is driving a meaningful advancement in IC engines, as well as in EVs.

Last time we spoke, you indicated Tula was filing some patents related to EVs.

‘Dynamic Motor Drive’ is what we call our technology for electric machines. We’ve been working on it for the last 18 months. DMD uses some of the same control philosophies we have in DSF. It’s a bit of pulse motor control to broaden the islands of an electric machine’s optimal operating efficiency. That’s required a lot of work on motors, inverter design and power electronics.

Using permanent magnet machines, we’ve proved that our control methodology does work. We’re getting a nice efficiency gain out of the inverter, with fewer losses, and nice gains out of the electric motor itself. But primarily at high rpm. That caused us to search for gains at lower rpm as well. So, we turned our attention to the Permanent Magnet-Assisted Synchronous Reluctance machines.

We have a lot of work going on with these motors. We’re redesigning the rotors to take maximum advantage of our pulse-control schemes. We’ve done more than 4,000 tweaks in modeling and simulation. We’ve got a rotor design that we feel very good about. But we’re not 100 percent done with it. We’ll insert the new rotor into a fairly conventional stator, then confirm our sim results with true hardware testing.

This motor type is very amenable to the controls that we’ve developed. Everyone likes to see test data. This fall we’ll have that data to prove what we believe the benefits of this approach to electric motor control will be — not only for vehicle propulsion but for applications such as EV heat pumps as well.

We’re feeling pretty encouraged. Our goal at Tula is to be a full propulsion-system-efficiency company.