Expert Blog
Compact DC motors: Why premium designs can achieve better value
For applications where compact DC motors are mission-critical, from space missions to medical surgery, engineers specify designs for their precision and durability. But even when the stakes aren’t as high, premium motor technology can increase application performance and prove more cost-effective in the long term. Tamas Hertelendi, maxon UK & Ireland’s engineering lead for Southern England, explains.
When sending a space rover over 40 million miles to Mars to search for previous signs of life, you don’t look to make cost savings by procuring low-cost motor technology. That’s why NASA’s engineers installed high-performance, ultra-reliable maxon DC motors in their Perseverance rover, currently exploring the red planet and the ground-breaking Ingenuity drone - the first drone ever to fly on another planet.
Not every organisation has NASA’s budget. But then again, the relative cost of a premium DC motor isn’t beyond the financial power of most OEMs or end users who rely on them. Instead, the decision usually comes down to short-term procurement cost compared to the value that can be achieved long term.
Reducing size and weight
Compact DC motors must typically fit within a particular space envelope, an area where innovation in motor design has a distinct advantage. Leading technology, such as coreless rotors, optimised windings, and multi-pole configurations, assists in generating a high level of torque relative to motor size. As a result, a much smaller motor can be used, or more torque can be generated for the same space envelope.
Weight savings are also critical for applications such as aerospace, ROVs (remote-operated vehicles), and AMRs (autonomous mobile robots). Lower mass can increase application dynamics, while reduced weight could enable a higher payload or the installation of additional battery power.
maxon recently received an ROV application design that included four drive motors based on large, 42mm diameter designs, reaching nearly 200mm long. The motors we specified were just a third of the size – and still outperformed the original ones in torque generation. We also integrated maxon’s compact miniMACS6 programmable multi-axis controller. Combined, this gave the customer a huge space-saving, enabling them to double the battery size and dramatically increase the range of their vehicle.
Technology such as a coreless design, optimised windings, and more powerful magnets also contribute to higher efficiency, another important advantage for designers of battery-powered devices.
maxon - DCX motors designed for high performance at an attractive cost
The value of enhanced reliability
Enhancing efficiency also leads to improved thermal management, which is also crucial to ensure motor reliability. A recent project involving a humanoid robot head required specifying over 25 motors to control features such as the eyes, nose, and mouth. Within such a space-constrained footprint and with so many motors operating together, it was imperative to rely on designs that would run at a relatively low temperature. This principle applies to thermal management and covers all aspects of motor design that impact reliability, whether the bearings, electrical integrity, or sealing from ingress.
For applications where motor operation is critical, like drone flight or implanted medical devices, the need to ensure reliability is clear: motors used in these applications require product compliance, such as SN EN ISO 13485 for medical devices, EN 9100 for aerospace, and DO-160-G for aviation.
However, should engineers use inexpensive commodity motors if motors are not mission-critical? Depending on the application, opting for a durable motor that lasts ten times longer than a low-cost design could help balance the long-term replacement costs. The expense of downtime resulting from a failed motor could also be significantly higher than the price of the motor itself.
Optimising performance
Premium compact motors are also often characterised by the precision and dynamism they can achieve. Many engineers will already specify appropriate motor technology for applications that rely on high performance. While precision is critical for applications such as surgical robotics, and dynamism is vital for systems like high-performance automotive brake control, designers from widespread sectors can enhance their applications by optimising the specification of the complete drive system.
To achieve precision, technology such as a coreless motor design that removes cogging torque is typically involved, along with the right gear head, encoder, and precise motor controls. Meanwhile, a low inertia approach combined with responsive control is crucial to optimise dynamism and enable rapid changes in torque, speed, and position.
Expertise in specification and support
Whether the requirement of the drive system is to optimise performance, reliability, design integration - or elements of various criteria - engineering expertise in support can be key. The potential to discuss design needs with a drive system engineer helps ensure the correct specification is achieved, and advice can enhance the design to improve the overall application.
Customisation of the motor or gear might also be advisable to achieve specific characteristics or meet certain environmental conditions. Even for urgent demands, customisation of production-based designs can be quickly achieved – around 80% of maxon’s projects usually involve some customisation.
An engineering partnership
Engineering partnerships like this are increasingly called on thanks to globally changing needs, including sustainability. Many OEMs and end users, too, require components that will last a long time and that can be recycled or safely managed at the end of life. Responsible material sourcing, ethical manufacture, and partnerships are aspects that we’re now commonly asked to prove. Ultimately, these demands are helping to enhance sustainable practices throughout the entire lifecycle of electric motors.
Engaging with a drive system specialist who takes a holistic approach to quality, from product design to service support, ultimately improves application reliability and performance. For many applications, this can also increase value long term.
Contact Tamas Hertelendi, Sales Engineer, at tamas.hertelendi@maxongroup.com to discuss your application.