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Motor control: Hardware versus software

Motor control: Hardware versus software

In the early 1820s, as part of his extensive studies into electro-magnetic induction, the scientist Michael Faraday first observed how a wire carrying a current could be made to rotate around a magnet. From these rudimentary beginnings, electric motors have developed into a huge global business, with billions of units being shipped every year serving applications in the industrial, automotive and consumer electronics sectors.

Though there has been a great deal of progress in the efficiency levels that motors can achieve, there is still room for further enhancements. This can be brought about both through advances in the motors themselves and the semiconductor devices that are used to drive them.

Brushless DC (BLDC) motors deliver significant improvements in reliability, size and cost than more traditional (and increasingly outdated) brushed AC and DC motors. As a result, the proportion of the motion control market based on BLDC motors is growing at pace, a recent report from Technavio forecasting double digit growth in this segment between now and 2020. As they do not feature a commutator, these motors require more sophisticated supporting electronics to take care of torque control.

A variety of methods (and accompanying technologies) have been developed through which this can be addressed. And over the course of the last decade the way in which torque control is applied to BLDC motors has evolved. Because of its noisy operation and limited accuracy, trapezoidal motor control has, in many cases, been supplanted by smoother sinusoidal control techniques. This requires access to high-precision rotor position data though, and consequently the substantial processing effort associated with it can potentially cause system lag. This, in turn, can impinge upon efficiency levels when the motor is running at higher speeds.

Field oriented control (FOC) of BLDC motors can circumvent both the noise issues of trapezoidal control and the inherent inefficiency at of sinusoidal control at high speeds. In effect, it can support highly efficient operation regardless of speed. Furthermore, as FOC is a sensor-less motor control technique, it can present savings in relation to component count, space, weight and power consumption. The challenge posed by FOC is, however, that it is reliant on sensed stator current signals being rapidly converted into the necessary voltage control signals. If this is dealt with via software it will put considerable strain onto the motor system’s processing capabilities.

Rather than using a processing-heavy, software-oriented approach, an alternative that is gaining a lot of interest from the engineering community is to employ some form of dedicated FOC hardware. The problem, until now, with hardware-based solutions of this kind is that they have lacked the flexibility needed by engineers to match the system’s operation parameters with their particular application needs - meaning that compromises had to be made. Through its unique Vector Engine (VE) offering, Toshiba has been able to overcome these constraints and supply the market with an adaptable and highly effective FOC motor control platform which requires the allocation of only relatively limited software resource.

For more details on how Toshiba’s VE technology is helping revolutionise motor control, please click here:

Click here to learn more about Toshiba's range of microcontrollers that use VE for motor control

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