The exoskeleton market is at a tipping point. With an aging population, increases in chronic disease and no end in sight for serious labor shortages, exoskeletons offer tremendous potential. In fact, market reports estimate that the exoskeleton market will grow at a compound annual growth rate of nearly 40% between now and 2028 — when it will reach $3.7 billion.
Engineers are currently hard at work to develop exoskeletons that help restore movement for those with motor impairments and even augment natural human performance. But the segment isn’t without its challenges. As wearable devices, exoskeletons must be comfortable, reliable and safe — a tall order given their extremely complex mechanics.
Engineers must consider three main criteria when designing exoskeletons for commercial viability: temperature, safety and mobility.
Keeping Operating Temperatures Low
Engineers know all too well that heat generated from motors can be an issue in temperature-sensitive applications. Unlike with traditional machine design, however, exoskeleton engineers don’t have the usual motor cooling options (fans, water, insulation, etc.) at their disposal due to size and weight constraints.
While typical motors operate at a maximum winding temperature of 155 degrees Celsius (over 300 degrees Fahrenheit), motors chosen for exoskeleton design must perform adequately at much lower temperatures, without the advantage of the aforementioned cooling systems. Unfortunately, exoskeleton engineers are often presented with frameless motor designs made for industrial robotics applications, which are running at temps that may exceed practical levels for exoskeleton equipment—given that it will come into close contact with a user’s body.
Engineers must instead find thermally efficient motors that operate at temperatures as low as 50-60 degrees C to minimize the impact of close-to-body contact. These low operating winding temps, however, may drastically impair the performance of typical frameless motors. Engineers should work with a partner that not only offers thermally efficient motors, but also motion design tools that can simulate motor performance levels at specified torque, speed and temperature levels. This will allow better planning for a range of application needs and motor sizing requirements.
Sizing for Safety & Mobility
One of the biggest hurdles to viable exoskeleton design is sizing. Not only must engineers account for the sizing differences inherent in the human population, but they must also keep their designs as slim, streamlined and lightweight as possible to allow for maximum comfort, safety and mobility.
Particularly in medical rehabilitation applications, engineers must account for the fact that a user may have little to no function in certain limbs. Here, lighter-weight designs are crucial to ensure safety in the case of falls or accidents.
Lighter-weight designs are also important for comfort, especially if OEMs hope to widen exoskeleton adoption, and for applications that require more sustained or regular use of the exoskeleton. For example, workers and patients using exoskeletons for rehabilitation or mobility will not be willing to endure excessive weight or uncomfortable pressure on the body. In addition to discomfort, designers must account for and reduce common risks to the wearer, including:
- Injury or discomfort caused from friction/direct contact between the exoskeleton and the user
- Joint hyperextension and overexertion
- Unintended contact, collision, and vibration exposure
Finally, streamlined, sleek designs are a must to allow the user to navigate tighter spaces and to reduce the risk of the exoskeleton snagging on nearby objects.
These strict size and weight considerations require frameless motors that are compact yet powerful enough to meet the needs of the given exoskeleton application.
Motors Designed for Exoskeletons
The majority of high-performance, frameless motors are designed for general automation or, at best, robotic joint applications — and therefore may not meet the more intensive demands of exoskeleton designers. Kollmorgen’s TBM2G motors, however, were made for the task.
They deliver consistent torque across the full range of speed — all in a more compact package. Engineers will enjoy high performance within the required temperature range, without having to oversize the motor. TBM2G motors were made to integrate easily with harmonic-drive-type mechanisms most commonly used in exoskeleton joints, with optional integrated Hall sensors that don’t increase motor length.
Finally, TBM2G motors come in seven diameters ranging from 50 mm to 115 mm and three stack lengths ranging from 8 mm to 26 mm — so exoskeleton OEMs can more easily scale to meet varying human sizes and application requirements.
Choosing the Right Partner
When it comes to exoskeleton engineering, selecting the right partner is as important as the design components themselves. As the exoskeleton market quickly develops, Kollmorgen can help engineers stay ahead of the curve.
Kollmorgen is the global leader in frameless, brushless motor design and manufacturing — with the motor selection, engineering guidance and service to support any exoskeleton application.
Contact us to discuss your needs and goals with a Kollmorgen exoskeleton expert.
