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FEATURE MOTION CONTROL
55thannIversary
from DC motors t miCron-level
While the first electric motors were invented nearly 200 years ago, the basis
Karen Whittaker T
oday, DC and brushless DC (BLDC) motors are relied on for applications that demand the highest levels of motion
precision. Their compact footprint is vital for purposes that demand small size and low weight, while their ease of integration and robust characteristics make them suitable for the most demanding environments. While the role of the motor is to generate
motion, increasingly motors are specified as one component within a wider drive system. Along with the motor, a gear reduces speed and increases torque, while to achieve precise control, a sensor and controller manage the motion characteristics. As a result of advances in drive system
technology, today this enables us to reach micron-level precision in fields such as robotic surgery, through to applications such as controlling the movement of equipment onboard rover vehicles exploring other planets.
Development of DC anD aC motors But to get this far, the development of the technology has come a long way. In 1832, William Sturgeon demonstrated an early commutated electric motor. Later in the nineteenth century, engineers including Frank J. Sprague helped make DC motors practical for industrial use. The brushed DC motor operates by supplying direct current to the rotor through brushes and a commutator, creating a magnetic field that interacts with the stator to produce continuous rotation. Later that century, a competing technology
was developed with the invention of the AC induction motor in 1887 by Nikola Tesla. Powered by alternating current, the AC induction motor creates a rotating magnetic field in the stator that drives the rotor without the need for brushes or a commutator. An important difference between these
designs is that DC motors were traditionally easier to control. For a DC motor, speed is controlled by varying the supply voltage, while torque is directly related to the current. In the early days, voltage change was achieved by variable resistors and then thyristor and transistor controllers. For an AC motor, where speed change relies on management of the mains supply frequency, control wasn’t generally possible until the development of the variable speed drive in the 1970s and, as a result, AC motors were restricted to continuous speed applications.
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of the technology is still relied on to achieve the pinnacle of motion control today, with endeavours ranging from robotic surgery to
space exploration. maxon UK & Ireland marketing manager, Karen Whittaker, explores how the technology emerged – and where it’s going
Surgical robots require precision drive systems
ironless winDings anD Core The toy industry, including the spread of model railways, was significant to the development of DC motors, particularly between the 1930s and 1950s. One such advance in DC motor technology was the invention of the ironless winding, which had its origins in the 1930s but was perfected by maxon in 1970 with the patent of the manufacturing process for the ironless rotor with the diamond shaped winding. In a brushed DC motor, the key design
advantage of an ironless winding is the removal of the iron core from the rotor. This eliminates cogging, the small fluctuations in torque caused by the magnetic attraction between the iron rotor and the magnets in the stator. Without this drawback, the ironless winding enables the motor to deliver smoother rotation and greater control precision. The design also eliminates iron losses in the rotor and reduces rotor inertia, enabling faster acceleration and deceleration, and improving dynamic response.
4 DesIGn sOLUtIOns 1971-2026 JULY/AUGUST 2026
maxon motor was founded in Sachseln,
Switzerland, nine years before making its first major breakthrough. Established in 1961 by the Braun family – their name made famous as owners of the German electrical appliance company Braun – the company was first known as Interelectric AG. Originally manufacturing shaving foils for electric razors, the company’s transformation into a precision motor manufacturer began after Braun was sold to Gillette in 1967.
emergenCe of BlDC teChnology While engineers at the Sachseln plant were making their mark with the ironless winding, the 1960s also saw the emergence of electronically commutated brushless DC motor designs. Like a conventional DC motor, a brushless DC (BLDC) motor is powered by direct current, but it replaces mechanical brushes and the commutator with an electronic controller that switches current in sequence between the stator
www.designsolutionsmag.co.uk
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