Low-cost SVM motor control system on an 8-bit MCU
The STMicroelectronics Nucleo-8S208RB kit provides a platform to develop solutions for the STM8S series of 8-bit MCUs. SPINnaker is supplied with a PC GUI to support motor control project development and is rated for operation at temperatures up to 150°C.
SPINnaker uses the space vector modulation (SVM) method of motor control, a technique which is usually too resource intensive for 8-bit MCUs. The motor control software running on the STM8S MCU occupies a Flash memory footprint of less than 8kbyte and requires less than 1.5kbyte RAM. The software includes a unique algorithm for speed control and flux reduction that was developed in-house by Future, and has the ability to control motor position at a resolution of 384 steps per revolution.
SVM provides several advantages over block commutation, including low acoustic noise and no torque ripple, but these advantages usually come at the price of a higher system cost, due to the need for a more complex 32-bit MCU. The SPINnaker design implements a low-cost, three-phase power stage composed of six 60V STL20N6F7 MOSFETs from STMicroelectronics. SPINnaker itself runs with up to 24V.
It also includes a USB Type-C power supply controlled by an STMicroelectronics STUSB4500, and a Panasonic supercapacitor-based back-up power supply. In addition, the SPINnaker board’s Panasonic POSCAP polymer capacitors demonstrate the superior characteristics of this device type in an application that would traditionally use multi-layer ceramic capacitors.
Etienne Lanoy, Director of the Future Electronics Centres of Excellence, said: ‘There are numerous motor-control development boards available for designers working in a 32-bit MCU environment, but precise motor-control schemes implemented on an 8-bit MCU have been much harder to find. Future Electronics’ development of the SPINnaker board now puts this right, providing a ready-made implementation of space vector modulation on the popular STM8S series of MCUs.’
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