Driving Machines Intelligently
According to the International Federation of Robotics, more than half a million robots are installed around the world, covering tasks as diverse as handling, welding, assembly, dispensing and processing. But this isn’t the only area of growth. Collaborative robots (cobots) and Autonomous Guided Vehicles (AGVs) are also increasing in market share. Rather than being stuck behind safety screens, these devices operate alongside human operators. Their roles range from moving workpieces around factories and storage facilities to participating in the manufacturing process. Beyond robots, manufacturing continues to demand traditional drives for conveyor belts, actuators, compressors and pumps.
Motor suppliers and the semiconductor industry have been innovating to develop solutions that provide higher efficiency and lower system cost. As a result, brushless motors have grown in popularity, but innovative approaches are needed to control them without the mechanical commutation of brushed motors. Sensors are an obvious solution to monitor the rotor but they add to the expense and are another potential point of failure. That has led to the development of software control algorithms that determine rotor angles by other means.
Devices such as dsPIC33 Digital Signal Controllers (DSCs) combine the real-time control capabilities of an MCU with the math support of a digital signal processor. Operating at up to 100 MHz and providing up to two cores, these cost-optimized devices are well suited for sensorless brushless DC motor control, vector or Field-Oriented Control (FOC) of AC induction and Permanent Magnet Synchronous Motors (PMSMs).
However, this domain demands more than processor performance. This is why the dsPIC33 family of DSCs also integrates high-resolution Pulse-Width Modulation (PWM) with dead-time compensation, high-speed 12-bit Analog-to-Digital Converters (ADCs), analog comparators, op amps and Programmable Gain Amplifiers (PGAs). All these blocks are also tightly coupled with the CPU to create fast and predictable control loops. Zero-Speed/Maximum-Torque (ZS/MT) control algorithms are also available, providing sensorless control at zero and low speeds while delivering maximum torque with Interior Permanent Magnet (IPM) motors.
For those looking for an MCU, there are plenty of 32-bit devices with peripherals tuned to motor control applications. The SAM S70, powered by a 300-MHz Arm® Cortex®-M7 core, is a great option for dual-motor designs that include FOC. For integration of IEEE 1588 Ethernet and CAN FD, the SAM E70 MCU offers exceptionally fast control loops alongside industrial connectivity. For cost-constrained designs, devices like the PIC32CM MCU include a dedicated motor control PWM with a Positional Decode (PDEC). For more connectivity, you should consider SAM D2x and C2x devices. Driven by Arm Cortex-M0+ cores with up to 256 KB of Flash, these MCUs offer 5V operability and support everything from basic BLDC and FOC to PMSM.
32-bit MCUs for Motor Control
FPGAs are an alternative to DSCs and MCUs in motor control. Thanks to their programmable logic blocks, they can be tuned to the application’s demands to provide high-speed control interfaces and supporting multiple motors is as easy as replicating functional blocks. The SmartFusion® 2 System-on-Chip (SoC) FPGA combines an FPGA with an Arm Cortex-M3 processor and embedded Flash and is available in a dual-axis motor control starter kit. Using the demonstration code provided, you can explore using FPGAs for sensorless PMSM control and micro-stepping of stepper motors.
SmartFusion 2 FPGAs for Multi-axis Motor Control
Drive circuitry is a critical part of a motor control design, linking the outputs of the DSC or FPGA with the MOSFETs or IGBTs selected. Fast, predictable delays and switching times are essential, along with low-capacitance inputs and high-voltage, high-current outputs. As drives shrink so they can be mounted on the motor being controlled, the need for innovative and compact packaging becomes another critical design requirement.
Microchip offers a comprehensive range of MOSFETs drivers, covering low-side, high-side, half- and full-bridge, and three-phase needs. Suited to low figure of merit (FOM) MOSFETs are drivers such as the MCP14700, a high-speed synchronous solution with both high and low-side drivers. Peak output current lies at 2 A and can drive loads of 3,300 pF in 10 ns. Available in a 3 × 3 × 0.9 mm DFN package, they offer space savings over traditional surface outline devices.
MOSFET Drivers
The drive for more efficiency, higher power density, and reduced forced cooling is pushing some developers to evaluate wide bandgap alternatives to silicon MOSFETs. Silicon carbide (SiC) offers higher switching speeds, greater robustness, and less RDS(ON) variation over temperature, enabling these design requirements to be met.
The MSC090SMA70 is ideal for motor drives offering as low as 15 mΩ in compact, surface-mount D3PAK or traditional leaded TO-247 three and four-pin package.
Finally, control algorithms are an essential requirement for any engineering team. Support is available through the motorBench® Development Suite that generates source code for the MPLAB® X Integrated Development Environment (IDE), accelerating the deployment of FOC algorithms.
You can also use Simulink®, motor models provided by MathWorks® and MPLAB IDE device blocks to generate and deploy embedded code directly to a DSC.
Find Out More
dsPIC33 DSCs for Advanced Motor Control
PMSM Control
motorBench Development Suite
