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Resolver-based stepper motors ‘open up new applications’

12 December, 2019

Two Japanese companies – the stepper motor manufacturer MinebeaMitsumi and the semiconductor specialist Renesas Electronics – have collaborated to develop a new type of resolver-based stepping motor that, they say, will allow precision motor control even in harsh environments, and will expand the uses for stepper motors. The motors are aimed at applications such as robotics, office and medical equipment, that need compact motors with precision controls, and resistance to environmental influences such as heat, dust and vibration.

The developers claim that the new motors will develop up to three times more torque than existing products and can carry heavy loads without step-out. The high torque levels will, in turn, allow smaller motors to be used. They offer a resolution of 200,000 P/R, allowing precision positioning to be achieved.

Other characteristics of the new motor and controls include low power consumption (achieved using servo control that responds to the actual load to optimise the current), and the ability to drive at broadband and ultra-low speeds. The motors are resistant to electromagnetic noise, and built-in filters allow them to detect positions reliably with a signal-to-noise ratios of 1:2 (where noise levels are twice the signal levels). The motor’s cost/performance characteristics are described as “superlative”.

The development is based on a new resolver-to-digital converter (RDC) developed by Renesas that supports MinebeaMitsumi's new motors. Renesas has also developed driver software for controlling the RDC with a 32-bit RX microcontroller. To help application developers, a resolver-based stepping motor control kit has been produced that includes development tools, a 42mm square motor with resolver, and an evaluation board incorporating the RDC.

MinebeaMitsumi has a track record of producing resolver sensors for automotive applications. It says that the new development will allow resolver-based stepper motors to be used in consumer and industrial equipment applications for the first time. Katsutoshi Suzuki, who is in charge of electronics engineering at MinebeaMitsumi, predicts that the development “will allow us to acquire new markets”.

MinebeaMitsumi's resolver-based stepper motors incorporate resolver-to-digital chips and microcontrollers developed by Renesas

In robots or AGV (automated guided vehicle) development, for example, the motors will help to achieve precision motion even in harsh environments such as warehouses or outdoors, while cutting costs and allowing equipment to be reduced in size by using smaller motors.

MinebeaMitsumi plans to start shipping samples of its new resolver-based stepping motors in January 2020 with mass production starting in April 2020. Renesas' resolver-based stepping motor control kit will be available in January 2020

Using servo control, the stepper motors can be used up to maximum torque, and high-speed rotational speeds are possible. Motor sizes can be reduced compared to open-loop control methods.



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