Servos are what enable robot movement to be initiated - with six of them usually incorporated into modern robot arms, and even more being needed for mobile AGV units and suchlike. The use of BLDCs to drive the servos in robotic designs offers a lot of advantages over brushed motors. These include greater operational efficiency, longer operational lifespan and reduced noise. They do, however, require more sophisticated control. Accurate rotor positioning data in relation to each individual motor in the robotic system will be essential.
The control of these BLDCs can be broken down into three key elements. These are the controller (optimized for Field-Oriented-Control using appropriate switching technology to maximise operational efficiency, so that energy reserves are not wasted), the power delivery ( with very low power losses leading to reduced heat generation), and the feedback loop (with data on the exact position of the rotor being continuously updated). The amount of time and effort involved in all this can be daunting for most engineers, and this is why being able to address everything using an optimised development platform would be hugely beneficial.
In order to assist engineers looking to develop motor systems for robotic use cases, so that they can get a useful head start there, the Toshiba Servo Drive Reference Model has been developed. The MCU employed in this hardware leverages an Arm® Cortex®-M4 processing core which is capable of running at speeds of up to 160MHz, with a floating point unit (FPU) plus 512kB of Flash memory resource. The MCU’s Vector Engine is able to undertake all the necessary vector control calculations. The control element is complemented by a power delivery element, which comprises six 100V-rated MOSFETs. These MOSFETS are based on Toshiba’s latest generation U-MOS IX-H trench process. This process mitigates some of the power losses normally experienced, by being able to provide a better trade-off between charge characteristics and on-resistance.
Details on this reference model can be found in a whitepaper that Toshiba has published on robotic servo drives. This can be downloaded below: