Garrett Motion’s world-leading advances in high-speed electric motors, which solve a variety of industry challenges across vehicle traction, cooling, air supply, and more, are rooted in in-house investments across e-motor design, power electronics and the enabling motor control systems.

Together, these three elements are creating e-motors capable of rotational speeds exceeding 200,000 RPM, ready for application in fuel cell, hybrid, and full electric powertrains. The result is impressive efficiency, torque and overall performance for Garrett’s E-Turbo, E-Compressor, E-Axle, and E-Cooling technologies. These innovations are key enablers for the automotive industry as it shifts gears toward the low and zero-emissions era of mobility.

Garrett’s rich mechanical engineering legacy informs the company’s electrification success, even for the motor control software and algorithms that make it possible for inverter technology to modulate the voltage at 30,000 times per second. That’s the equivalent of the control system making up to 12,000 adjustments to electrical voltage literally in the blink of an eye.

Uniquely, these speeds and modulations are achieved without the sensors that would conventionally measure rotor angle and speed – in Garrett e-motors, this functionality is determined by algorithms developed by the in-house team. Operating in a sensorless algorithm environment allows Garrett to achieve very high speeds by effectively removing the need for an encoder or resolver traditional drives would use, improving costs – a consideration for automakers.

Controls Expertise with Global Reach

The controls team forms part of Garrett’s Electrification Center of Excellence (ECOE), a global network of engineers fusing hardware and software with expertise in e-motor design, power electronics and control technology, as well as overall system integration and validation.

This investment in capabilities has driven world leading innovations, including the E-Turbo, which integrates a small electric motor on the turbo shaft to help deliver air on demand and boost fuel efficiency and transient performance. Garrett motor control engineers played a key role in enabling this turbo advancement and are currently involved in numerous other OEM projects at a system level for hybrid, fuel cell and battery electric vehicles.

Controls expertise, expressed through algorithms and software coding, is fundamental to Garrett’s leadership in e-motor design, notably in pushing the envelope for what’s achievable with microcontrollers. These house all the software and algorithms that control the inverter and the motor.

“Essentially, this software is the brain governing how our power electronics control the electric motor,” says Ali Najmabadi, Garrett’s motor control software leader. “Our algorithms utilize the power electronics to drive the motor. To drive this motor, you need AC currents and AC voltages, which you have to synthesize. You don’t have access to a perfect AC voltage source in a vehicle, so we synthesize this from battery DC voltage using the inverter. This is where the power electronics comes in. We use the power electronics to drive this motor.”

In this realm, there’s increasing demand to switch faster. Garrett is pushing its algorithms to support very high e-motor rotational speeds, upwards of 200,000 RPM. As speeds increase, so does the switching frequency, presenting a challenge to minimize the number of samples per electrical cycle to reduce demand on processing power and inverter cost without losing accuracy and controllability. Garrett has succeeded in maintaining 200,000 RPM at 10 samples per electrical revolution, which is difficult to achieve.

“We are motor control engineers, expressing control algorithms in the language of software,” says Ali. “While there are lots of organizations and institutions involved in electrification, very few are able to control electric motors at the speeds and power we now call standard.”

Pushing the Boundaries of Test & Simulation

Garrett’s decision to build in-house capability for its e-motor technologies means that everything is cultivated internally, so there is full ownership of the end-to-end process and the enabling systems. As such, there is none of the risk associated with outsourcing software and algorithm development.

The uniqueness of this capability means that the controls team has had to develop its own simulation and test procedures, notably in modelling in the digital world the ultra-high e-motor speeds in the physical world.

At lower RPM speeds in the tens of thousands, it’s relatively feasible to test machinery and understand its characteristics. However, the challenge increases significantly at speeds up to 200,000 RPM. There are no off the shelf solutions to measure angle and speed at such high speeds easily, so Garrett developed new and innovative ways to leverage speed and position sensors.

“We’re pushing the boundaries to such an extent that conventional tools fall short,” says Ali. “When peers learned about our methodology to capture speeds exceeding 200,000 RPM and angles at these extreme levels, they were astounded by our innovation. This truly underscores the pioneering nature of our work.”

This approach also fits with the Garrett ethos of investing in its own capabilities to maintain control of every stage of the development process, to promote the innovation culture that ensures products stay ahead of the curve.

Meeting – and Exceeding – Customer Requirements

For new projects, the start point means taking account of customer requirements and assessing whether existing algorithms fit or need recalibration. This also means understanding the full physical system – from the motor to the inverter to the conditions they operate under. For instance, in the case of a speed controller, this would include not just the software and e-drive hardware but also elements like aerodynamics.

The preliminary evaluations involve simple models simulated environment to emulate real-world physical systems. From here, the team delves into the detail, considering various algorithmic architectures, weighing their pros and cons, taking account of simulation data from Garrett’s database, and engaging with experts across multiple departments.

Says Ali: “As motor control engineers, we’re bridging power electronics and motor design and expressing it in a language of algorithms and software to control physical systems.”

The end goal? An algorithm that can be implemented on the microcontroller with maximum computational speed and minimum memory footprint and ultimately pass a series of rigorous tests to ensure that customer requirements are met.

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