In the field of electric drive system for electric vehicle, permanent magnet synchronous motor (PMSM) has become the mainstream choice because of its high power density and high efficiency. As a leading semiconductor solution provider, Microchip offers a complete range of solutions for PMSM control. This paper will deeply analyze Microchip's PMSM control method, from core technology to practical application, to provide a comprehensive reference for engineers.
ROLO: The Core Technology of Sensorless Control
Sensorless FOC control is the main trend of PMSM control, which can improve the reliability of the system and reduce the cost by replacing physical sensors with algorithms. Microchip's ROLO is an efficient means of BEMF (back electromotive force) observation.
The core idea of ROLO is to construct a state observer based on the ODE (ordinary differential equation) model of PMSM. By measuring the voltage and current of the motor, the observer can estimate the rotor position and speed information in real time. Compared with the traditional full-order observer, the reduced-order design only observes the necessary state variables, which significantly reduces the computational burden and enables the system to run on resource-limited MCUs such as Cortex-M0+.
Digital Signal Controller: Hardware Platform Optimized for Motor Control
dsPIC Series Digital Signal Controllers
Ideal hardware platform for PMSM control with specialized motor control peripherals
Microchip's dsPIC series DSC (Digital Signal Controller) is an ideal hardware platform for PMSM control. Taking dsPIC33FJ32MC204 as an example, it integrates special peripherals for motor control and powerful DSP functions, and provides a solid foundation for complex control algorithms.
Hardware Multiply Accumulator (MAC)
Complete multiplication and addition operations in a single cycle, greatly improving the execution efficiency of algorithms such as vector transformation and PID regulation.
High Resolution PWM Module
Generates accurate complementary PWM signals, supports dead-time control, and directly drives three-phase inverter bridges.
High-Speed ADC Module
1Msps conversion rate, multiple inputs can be sampled at the same time to meet the synchronization requirements of current sensing.
Dedicated Motor Control PWM
Flexible configuration of PWM mode, supporting direct generation of space vector modulation.
These features enable the dsPIC DSC to efficiently execute the FOC algorithm for precise control of the PMSM. Compared with general MCU, DSC has obvious performance advantages and higher integration in motor control applications.
Current Sensing Schemes: Single Shunt vs Multi-Resistor Sampling
Current detection is the basis of PMSM vector control, and different sampling schemes directly affect the system performance and cost. Microchip offers a variety of current sensing solutions to suit different application needs.
| Sampling Scheme | Principle and Characteristics | Advantage | Applicable Scenarios |
|---|---|---|---|
| Single Resistor Sampling | A single sampling resistor is placed on the DC bus to reconstruct the three-phase current by multiple sampling. | Lowest cost, simple hardware | Cost-sensitive applications such as home appliances |
| Dual Resistance Sampling | A sampling resistor is respectively connected in series with the lower bridge of the U phase and the V phase | The sampling time is more flexible and the precision is higher | Common Solutions for TI C2000 Series |
| Three-Resistor Sampling | The lower bridge of each phase is connected with a sampling resistor in series, and the sampling phase is selected according to the sector. | High sampling accuracy and relatively simple algorithm | STM32 Common Solutions, High Performance Applications |
Microchip's single-resistor sampling scheme minimizes cost while maintaining performance through clever sampling timing and signal processing algorithms.
Complete Development Ecosystem: From Evaluation Kits to Software Libraries
Microchip offers a complete development ecosystem for PMSM control, significantly reducing time to market. Core components include a hardware evaluation platform, software libraries, and development tools.
The MPLAB Harmony 3 motor control module is the core of the Microchip solution, which integrates the ROLO algorithm implementation and the hardware abstraction layer. Developers can quickly start development directly using the provided routines, such as the PMSM_FOC_rolo_Sam_c21.
Hardware Platforms
Supports low-voltage MCLV2 and high-voltage MCHV3 evaluation kits, covering a wide range of applications from home appliances to industrial drives.
Software Libraries
MPLAB Harmony 3 motor control module with ROLO algorithm implementation and hardware abstraction layer.
Development Tools
MPLAB Harmony Configurator (MHC) for CPU and peripheral configuration, with graphical tools for monitoring and adjustment.
Development Process
1. Configure with MHC
2. Modify parameters
3. Compile and download
4. Monitor and adjust
This highly integrated development environment allows engineers to focus on algorithm optimization and performance tuning, rather than driver development.
Electric Vehicle Oriented Optimization Features
Microchip's PMSM control scheme specifically addresses the special needs of new energy vehicle applications:
Wide Voltage Range Operation
Supports operating voltages from 10V to 48V, covering the 12V/24V/48V electrical systems of new energy vehicles.
Four-Quadrant Operation Capability
Realize forward, reverse and braking operation to meet the requirements of electric vehicle drive and energy recovery.
Flux-Weakening Speed Expansion
The speed range of the motor is expanded through the flux-weakening control technology to improve the high-speed running performance of the vehicle.
These features make Microchip's solutions particularly suitable for auxiliary motor applications in new energy vehicles, such as water pumps, oil pumps, fans and compressors.
Microchip's PMSM control scheme combines advanced algorithms with a dedicated hardware platform to provide a complete solution from low cost to high performance. ROLO technology enables sensorless FOC to be implemented on MCUs with limited resources, laying the foundation for large-scale applications.
With the increasing requirements of electric vehicle on the efficiency of electric drive system and the increasing demand for functional safety, Microchip is expected to further integrate functional safety features (such as ASIL certification) and improve the adaptive ability of the algorithm to cope with the challenges brought by the change of motor parameters and aging.
For engineers, mastering Microchip's PMSM control scheme not only helps the development of current projects, but also lays a technical foundation for more complex electric drive system design in the future.
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