Ethan Frick details how software-based PCB stator motors offer custom, high-performance solutions
Historically, designing custom-built electric motors has been a long and labour-intensive process, and the transition from prototyping to full-scale production has further limited the viability of these custom machines. Thus, many engineers are pressured into selecting a “best-fit” motor from a catalogue of existing solutions rather than investing in a “perfect-fit”. Unfortunately, these best-fit, off-the-shelf motors are commonly over-sized, inefficient and ignore many application specifics such as thermal conditions. As the world becomes more electrified and the incentive to decrease carbon footprint grows, it is clear that this best fit model is no longer acceptable.
ECM PCB Stator Technology is a Boston, USA-based start-up aiming to change the relationship between engineers and motor design with its novel design-to-manufacture software platform. With PrintStator, purpose-built electric motor designs, ready for manufacture, are automatically generated from any set of motor specifications, eliminating human error and enabling a new degree of design flexibility. With ECM’s platform, a nearly infinite number of motor designs is possible. Whether improving an existing system or creating a new technology, motors designed with this new solution have been proven to provide remarkable system level efficiency improvements in a considerably smaller footprint.
Motor as Software
Using a proprietary PCB stator axial flux motor design, which replaces the copper windings used in conventional motors with a PCB that works in conjunction with permanent magnets, ECM’s software platform fundamentally changes the way motors are designed and manufactured. A cloud-based CAD/CAM SaaS platform, PrintStator creates custom PCB stator-based motors for distinct requirements. Any set of motor specifications can be fed into the software, which will then use given optimisation parameters such as “maximum efficiency” or “minimum radius”, to produce unique, application-specific solutions.
Leveraging the existing PCB manufacturing industry, the platform also enables rapid prototyping and full-scale production. Along with each custom design, the software provides design files that can be used to immediately print the stator at any PCB house, globally.
This system is already being used to prototype and design ECM machines by key players in a wide range of industries. In the medical industry, a 40W PCB stator motor designed to actuate the elbow joint of an adult orthosis, resulted in a greatly reduced system size and increased patient capability. For an e-mobility partner, the system was used to design and implement several mid-drive e-bike solutions that provided double the peak power output when compared to legacy motors, without increasing motor mass or volume. New autonomous vehicle technologies have also highlighted the platform, which has been shown to increase propulsion motor efficiency by 15%. Within a broad range of applicability, a motor designed and developed with PrintStator will almost always be lighter, smaller and more efficient in an application than an off-the-shelf motor.
High Efficiency Motors for the HVACR Sector
The heating, ventilation, air conditioning and refrigeration (HVACR) industry is one of the largest consumers of electricity in the world, accounting for 10% of the total US electricity consumption alone. Purpose-built motors offering system level efficiency improvements could have a significant impact on the industries carbon footprint. Using PrintStator, custom PCB stator motors have been shown to improve HVACR solutions across a number of key metrics including energy efficiency, size, weight, and noise.
The platform uses optimisation algorithms to enable stator designs with superior efficiencies and less raw material. The motors designed with the platform are ultra-thin, have efficiency levels in the low- to mid-90s and are up to 70% lighter than comparable machines. Further, the platform’s optimisation of magnet, steel and copper mass offers up to 80% reduction in raw material. For the HVACR industry, ECM has prototyped high-performance motors including a 750W motor with 90% efficiency, a 2.2KW with 93% efficiency and a 4.5kW with 94% efficiency.
To measure the feasibility of PCB stator technology for maritime HVACR, ECM was commissioned to replace a 2.2kW air handler motor on MARAD’s USTS Kennedy with a 2.2kW PCB stator motor. The first iteration reduced motor weight by 66%, from 45kg to 15kg, and increased motor efficiency to 91.6%. In a second retrofit the existing air handler belt drive system was replaced with a direct PCB stator drive system to further boost system efficiency to 93%. In comparison to the legacy 2.2kw induction motor with 5kg of copper windings, ECM’s motor only used 600g of copper, an 88% reduction.
Robotics is one of the fastest growing industries in 2021 and the demand for increased production and lower costs is accelerating the transition to automation. Mckinsey and Company predicts that 88% of businesses plan on using robotics to automate processes in the near future. PCB motors can integrate seamlessly into a range of these robotic and actuator applications to provide compact, efficient, torque-dense solutions with minimal axial length and weight.
Unlike many conventional electric machines, ECM motors do not have any cogging torque. Since PCB stators have no iron, there are no preferred rotor positions, enabling a superior quality of motion. ECM has designed PCB stator motors for gimbal and other precision motion applications offering exceptional pointing accuracy, a 24-bit encoder offers 16,777,216 discrete positions. The lack of cogging also reduces vibration and audible noise. In certain noise critical applications, a reduction of 20-30dB have been reported.
Recently, ECM partnered with Cone Drive, a subsidiary of Timken, to integrate its harmonic drive into the PCB stator actuators. The form factor flexibility of PrintStator allows ECM to design PCB stators as thin annular rings, enabling the compact integration with a variety of torque multipliers, including Cone Drive’s harmonic drive, resulting in high torque density. The hollow shaft actuator was significantly more efficient, two thirds of the weight and half the axial length of competing integrations, increasing max load by up to 76%. In a second actuator, with the harmonic drive nested in front of the motor rather than in the motor cavity, the motor offered a 66% reduction in weight and 48.25Nm/kg of torque.
Custom PCB stator motors, designed with ECM’s software can offer remarkable system level improvements across a wide range of industries, including HVACR, robotics, unmanned vehicles, precision motion control, e-mobility, haptic systems, physical therapy and medical devices.
Ethan Frick is with ECM PCB Stator Technologies