Moving with the times

5 min read

There is an opportunity to move ahead in the market if DC motor efficiency can be maximised rather than compromised.

Defining the future trends in motors is not straightforward because these trends not only cover the technology but also the engineers who are using it. To take the second point first, design teams are getting smaller.

In the past a mechanical engineer would design the mechanical movement and pass it over to an electrical engineer who would design the circuitry to control it all, but very few design engineers carry the tag mechanical or electrical anymore – they are just engineers. Somewhere in this evolution certain areas of expertise can become lost and motor expertise is potentially one such area.

Engineers understand that motors run at different efficiencies depending on the speed that they are going, but increasingly the motor will be selected based on the space available or the average power required, even though this results in a solution that may be over or under-specified. Take robotics for example where the movement is not constant. Instead of using a DC motor calculated to cover constant and maximum operation, it can be more efficient to over-run an under-powered motor for short sharp movements as it will then have time to cool down.

Overall efficiency is a balance between different parts of a drivetrain – the controller, motor and gearbox. Just selecting a motor in isolation based on its headline power rating will not always provide the most efficient system.

The message here is that every application is different and motor expertise is no longer a regular part of the engineer’s skill set. So with leading edge designs, the sooner that the motor supplier, assuming it is a supplier with a strong technical support team, can become involved the better.

Time to market pressures are nothing new but continue to drive engineering productivity. I predict that these pressures will continue be passed straight on to the supply chain and the motor, often the heart of the machine, needs to be defined at an early stage in order to streamline the design flow. For this reason tools like maxon motors’ 'Configure to Order' will play an importantrole for engineers with a good knowledge of motor technology, or even as a starting point with prototypes for those who don’t. It is an online tool that will help configure the right motor for the application, starting with diameter, length, power and speed and moving into torque and commutation type. Tools like this keep designs moving and as we make to order the actual bespoke part that is configured by the customer is only 11 days away when the prototyping begins. This allows the customer to be testing the exact part and not a compromise in their prototype or development machine.

Technology development

So the engineering role is changing, and will continue to do so. Technology will also continue to progress although the current efficiency of DC motors and their controllersare such – in the order of 90 – 95% - that improvements by this parameter alone are likely to be in very small increments. The efficiency of the DC motor and controllers is hugely dependant on how they are used.

We are constantly looking at the quality of the magnets – higher quality more powerful magnets means smaller ones can be used for the same purpose and so a smaller motor can be produced. Equally the copper quality and ways of packing the windings into a smaller frame can offer down-sizing possibilities. Directly within the motor then, the trend will be more towards smaller rather than more efficient.

Gearing will have a bigger impact on the efficiency as it is the least efficient part of the system. It is a curious dilemma. The phenomenon known as backlash is important here. Tightly fitting gears can be very precise, important in high accuracy pick and place applications for example, but because of friction they can suffer from an efficiency perspective. On the other hand, backlash might be unimportant in more in forgiving applications, like a prosthetic arm, and allow a more efficient system to be used.

So it will be the gear boxes, rather than the motors themselves, that will provide the next opportunity for major efficiency advances. I use the word opportunity because having the most efficient gearbox is not necessarily going to provide the most efficient system – it is choosing the right controller, right motor and right gearbox for the application that is important.

New materials will also play their part. Ceramic gears and shafts are very tough wearing and also provide efficiency advantages. Ceramics are not always suitable for very high vibration environments, like motor sport because when they break they break, they don’t gradually wear like metal parts. They are also up to 20% more expensive, but for long life applications they are ideal.

Making it in the UK

In the UK there are a number of industries that are promise strong growth in coming years. One is aerospace and there are a number of factors influencing motor use within it. For one thing all valves on a traditional airliner have been hydraulically controlled, but now the option of small motors and cables, rather than a big hydraulic unit and pipes, has become a lighter and therefore more attractive option. Also within the aerospace sector is the space end of the market. maxon motor has had products in all of NASA’s six Mars rovers, but that is clearly a limited market. What is burgeoning in the UK is the development of the small satellite industry, particularly cube sats. The volumes are ramping up for these tiny satellites but they are still not cheap to get into space and so having space-proven products (and being space certified with EN 9100) as maxon does, is very important for the satellite engineers.

Medical, and particularly prosthetics, is another sector that will be strong in the coming years. Prosthetic hands have come a long way in the past few years, they have become lighter, more complex, more realistic and, most importantly, more useful. Having smaller, lighter motors in there has been an enabling technology for this and further developments in motors and gears will be the foundation for future improvements. It is an interesting area though, some people are sticking with the hardware they already have and are concentrating on the algorithms and muscle movements required to provide more natural movement. maxon has a separate medical division and production facility that has been awarded the medical certification ISO 13485 to invest in future medical technologies.

From robotics to oil and gas there are a many areas where UK companies look set to lead the field in coming years. Our message to engineers is to not overlook the huge difference that using the right drive components can make, nor the specialist expertise that is both important and available, when designing a successful and efficient product.

maxon motors

Since 1961 maxon motor’s micro motors have moved everything that has to be rotated with high precision and reliability.

maxon motor is the worldwide leading provider of high-precision drive systems up to 500 W. For over 50 years, we have focused on customer-specific solutions, quality and innovation. Worldwide, maxon motor has more than 2200 employees and sales companies in 30 countries. maxon motor has production sites at the headquarters in Switzerland, as well as in Germany and Hungary.

Numerous companies from various industries count on drive systems of maxon motor for their mission-critical applications. Our drive systems can be found wherever precision and reliability have top priority, for example in: Medical technology; Industrial automation and robotics; Aerospace; and Automotive.