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Robots have stringent design requirements for power density, waste heat, and volume. Mirmex Motor last month said it has developed a new method of producing high-power-density electric micromotor windings. The company said its use of artificial intelligence and flexible printed circuits “completely revolutionizes traditional winding design and manufacturing methods.”
Research and development for the new approach began in 2013 at Université catholique de Louvain, Belgium’s largest French-speaking university. In 2017, the team founded Mirmex Motor to commercialize the technology, and the Mont-Saint-Guibert, Belgium-based company has raised several million euros from local investors and the European Commission.
“In Belgium, interest in robotics is increasing, in particular for medical robotics such as active prosthetics, surgical, and for manufacture of vaccines,” said Cedric Van Rossum, CEO of Mirmex Motor. “Many in medtech or biomedical are investing in automation, including robotized actuators.”
Researchers turn to flexible circuit boards
“Seven years ago, François Baudart, a UCLouvain professor [now chief technology officer of Mirmex Motor], wanted to create a winding for a new motor, and he realized how painful it could be to develop custom-made, high-performance brushless DC electric motors,” Van Rossum told The Robot Report. “The classical way is with copper wire turning. He started looking for different flexible winding — 3D printing, metal cutting. In the end, the best way was creating a cylindrical shape with a flexible printed circuit board [PCB] roll.”
“It didn’t work the first time, so François had to explore why,” Van Rossum explained. “He tried to model a way to build such a winding, so subsequent prototypes could be made. There’s real interest in innovative technologies on a flexible substrate. This could never be done with traditional winding.”
“It was perfect timing: Flexible PCBs are being used more and more in electronics, batteries, and computers, or to replace harnesses in bigger consumer electronics applications,” said Van Rosssum. “François worked with many vendors to develop a tool to optimize motor winding for the best possible architecture. The next step was to create special patterns with modules to explore different possibilities to increase coupling between winding and minimize losses.”
Mirmex Motor uses AI for custom motors
Mirmex Motor said its proprietary software enables it to customize motor designs while also simplifying production and reducing tooling costs. It uses algorithms to automate the creation of winding topologies and validate the printing on flexible PCB strips. This also means that such motors can be manufactured more quickly than with traditional single copper-winding techniques, the company said.
Slotless permanent magnet motors have existed for 40 years, but neither synchronous machines nor slotless brushless direct current (SBLDC) machines have changed much in that time, said Mirmex. In addition to making custom motors easier to design and make than SBLDC motors, the company said its system “meets the demands of users looking for increased performance and the convenience of compactness.”
The company claimed that its motors can be up to 50% more compact, 70% more dynamic, lose three times less heat, and be assembled 10 times faster than most motors using conventional copper coils.
“Our use of AI is similar to what’s called ‘generative design’ in CAD [computer-aided design],” Van Rossum said. “We give some constraints to the algorithm, and then it is able to think of multiple possibilities to build the optimal system for every space, such as a cubic millimeter. It determines where to put copper fiber, how thick to make it, or where to put insulation. The AI is trying multiple possibilities at the motor level and the winding level, and it will come up with the best solutions for a given curvature or thickness of substrate, for example.”
Meeting customer demands
“We got feedback from customers seeking two different things,” Van Rossum said. “First, if you have a winding with higher performance, we can offer more compactness for a given torque or volume than with regular technology, depending on the application. For example, prosthetics for young people are difficult to build. You need motors strong enough to take things in hand but at the cost of weight or difficult manipulation. You typically make it with smaller motors for agility, but then the strength and torque are too low to effectively pick up heavy things.”
“Second, a lot of Mirmex customers are looking for more customization,” he added. “Most motors are sold from thick catalogs, so designers and manufacturers are forced to compromise on whaat can be obtained. For example, you might need 23 mm diameter, but the vendor catalog has only 20 or 25 mm. It’s the same with the length, number of poles, sensors, and electronics. Dozens of compromises can push a design far from its optimal point.”
“When we talk with clients for the first time, they’re surprised that we can optimize for temperature, size, and the main performance area they want to improve such as degrees of freedom,” said Van Rossum. “They were not capable of visualizing all the things they could do, which enables them to rethink and improve their designs as they start asking themselves these questions.”
“We remove some complexity of choices,” he said. “We can clearly show the costs of their design decisions in terms of optimum reach. Or, if they selected one material, they can decrease cost by 20% but increase torque by 1%. Customers can modify length, diameter, interconnections, parallel path arrangements until fairly late in the cycle.
“Mirmex can even create two designs in parallel — such as a single- or double-pole pair — which robotics startups usually can’t afford to do,” Van Rossum said. “With traditional winding, it used to take a minimum investment of $50,000 to $100,000, but now it’s $4,0000 to $10,000, depending on the application.”
Mirmex Motor said its motor technology is useful for robotics, surgical devices, aerospace, and high-performance industrial tools. The company also licenses its patented technology to OEMs.