Optimising miniature motor design

Miniature motors are integral to providing motion in space-critical, high-performance applications. The design and manufacture of these motors take cutting edge engineering expertise and a keen understanding of customer requirements is essential when deciding which performance features must be developed. Sunil Kumar reports

One of the most common requirements of an OEM design engineer is customisation flexibility. Every application has different demands on the miniature motor and motion control solution, which can seldom be completely fulfilled from a standard specification. For this reason, Portescap’s design approach has always included the widest range of customisation options. While the success of many customised designs means that they eventually become standard products among our miniature motor range, all customised development has to originate from a foundational technology platform.

To arrive at these optimum bases of miniature motor development, customer input is vital. It’s important to maintain a clear vision of our customers’ landscape of competitive development. Responding to the needs of the customer always remains the most important consideration. At Portescap, the framework we use to understand these insights most accurately is based on a process called the Voice of the Customer.

This process integrates years of design experience combined with real-life field application expertise to understand customer wants and needs, right down to the most detailed level. This includes collaborating with OEM design engineers, working alongside them as well as their end user customers, specific to industries and applications. The final outcome is the generation of detailed product and solution design specifications, with significant input from our customers’ technical insights. Ultimately, these customer requests become key aspects of future product designs that are then developed by our engineers to solve complex problems for critical applications.

After detailed investigation, we need to understand the development path for the customer-inspired initiative. It’s crucial to know whether customer requests can work together and be aligned into a single product or solution. It’s also vital to determine whether a product concept is scalable and viable for manufacture to meet the price point that the market demands, and we achieve this understanding with the application of lean management principles.

For all new projects, we use the established stage-gate product development process. The stage-gate process navigates a product idea from concept to business case to production, using a list of well-defined actions. Dedicated teams then take ownership of the product at each step, and a fundamentally important aspect is receiving user reviews and feedback throughout the entire development journey. The final result is a technology platform that is not only cost-effective for OEM integration but is also true to the customers’ initial design requests.

Applying customer insights to product design

By listening to the customer to address their specific and developing needs, our Voice of the Customer process has delivered many innovative new motor platforms, all of which remain fully customisable. A particular example is the development of brushless DC (BLDC) motors for robotic applications. As well as being robust, long-lasting and able to operate at high speeds, they’re also small enough to fit into compact areas like robot joints.

With footprint being critical, user feedback led us to create a proprietary u-shaped coil with a much smaller size compared to those found within typical BLDC motors. The coil integrates larger copper fittings that enable higher performance than a standard straight coil. It also has minimal iron losses, which means improved efficiency and cooler operation. This new design allows a two-pole motors, for example, to deliver 30% more torque compared to motors of a similar size with traditional coil design. Taking the design further, BLDC slotless motors that incorporate u-coils can be tailored for high-speed, high-torque or a balance of both.

Another common requirement for robotic applications received through the Voice of the Customer process is high dynamic response. Robotic grippers need a combination of fast, incremental precision that a stepper motor can provide, as well as the speed and acceleration typical of BLDC motors. A new way of achieving and combining the benefits of both motor types is by introducing a rare earth magnet, designed in a thin disc form. The result of this new design is increased step resolutions compared to permanent magnet stepper motors. This is combined with significantly higher capabilities of acceleration due to low inertia, as well as greater top speed than conventional stepper motors because of the new design’s shorter magnetic circuit which provides lower iron losses.

While low inertia disc magnet technology was developed as a result of Voice of the Customer research within robotics, it’s also a good example of how advances can be transferred to the benefit of wider applications. The low-inertia disc magnet technology can also apply to actuators, enabling quick linear acceleration and deceleration within one low-profile package, which saves process time. That means engineers can simplify their designs as they solve complex application challenges.

Robots can involve both linear and rotary motion. The challenge is that both modes typically require additional control components which expand footprint. However, we know from our research that reduced size is a key attribute that customers need. As a result, our innovative development of the Dual Motion Can Stack Actuator allows simultaneous linear and rotary motion that combines two permanent stepper motors into one lightweight, compact package. The actuator design delivers pure linear motion in any direction without shaft rotation. It also achieves pure rotational motion, clockwise or anti-clockwise, with no shaft translation along its axis. With this design, it’s also possible to combine linear motion and rotation simultaneously in any direction.

These examples enable engineers to understand the real needs of our customers and integrate them into our product development cycles. When our product developers move on to customise motors and control solutions for specific projects, Voice of the Customer research enables them to quickly and accurately achieve a bespoke design that precisely matches the specification thanks to the customer-insight led technology foundation. This in turn allows us to integrate new features into our standard product range that is in tune with current demand.

Sunil Kumar is Product Manager at Portescap.