A brushless motor controller uses electronic control circuitry to regulate the voltage and current fed into a servo drive. It enables the actuator to execute motion commands by sequentially energizing motor windings, propelling the rotor and providing a range of speeds.
Consider your application speed performance requirements when choosing a motor controller. Also consider whether sensor-based or sensorless methods are preferred, and if you need a fast EtherCAT communication interface.
Accurate Rotor Position Sensing
The main function of a brushless motor controller is to provide accurate position sensing, which is vital for positioning and torque control. This ensures high performance and optimal efficiency, along with a low torque variation and immunity to stray magnetic fields. It should also be flexible for different motor designs and sensor placements.
Compared to traditional DC brushed motors, brushless motors have no brushes and perform commutation electronically at certain rotor positions, rather than mechanically using brushes and sparks to transfer current between the windings. The electronic circuits perform similar timed power distribution as the commutator assembly, but they have much higher efficiency and are less susceptible to mechanical wear.
To achieve this, a motor controller uses pulse-width modulation (PWM) to regulate the current injected into the motor windings. The PWM signals can create sinusoidal back-EMFs from Hall sensors, which directly correspond to the motor driving signals in a closed-loop system.
When determining mechanical position, the sensor signals must be properly analyzed to determine the rotor angle based on the number of pole pairs. However, the error values associated with the Hall sensor state do not necessarily match those of the mechanical angle. To overcome this issue, a new algorithm searches for the maximum error value stored in the non-volatile EEPROM memory and finds the most probable mechanical position.
Advanced Torque Control
Brushless motors eliminate the need for brushes and a commutator system to distribute current to the rotor windings. They use permanent magnets to generate torque. They require an electronic controller to perform the same timed power distribution, but it can be done with much more accuracy and less susceptibility to mechanical wear. This also allows for advanced capabilities not possible with brushed DC motors, such as microstepping operation and holding torque at rest.
Brushed DC motors have a maximum torque when stationary, and their maximum torque decreases linearly as they speed up. By contrast, the maximum torque of a brushless DC motor increases with speed. It’s important to choose the right control method for your application based on speed performance requirements (maximum/minimum, changes, accuracy) and load/ambient conditions.
To control motor speed, brushless motor controller a motor controller can utilize closed-loop feedback to regulate input power by changing the PWM duty cycle. This produces sinusoidal current waveforms, which help the commutation process run smoother.
BLDC motor controllers used in power electronics deal with high currents and voltage, which necessitates a fast switching frequency. To reduce the size of their circuits, these devices may employ discrete components, including external high-power transistors such as IGBT or GaN. This reduces cost and complexity while improving reliability. This is an example of a design principle known as dimension reduction, where the use of discrete components reduces the number of dimensions needed to describe the system.
Variable Speed Control
A brushless motor controller with variable speed control capabilities allows you to vary the current flowing to the rotor, thereby controlling its rotational speed. This helps ensure a precise level of force or torque output, which is essential in precision applications such as CNC machines and medical devices.
A microprocessor-based motor controller uses sensors to detect the rotor’s position, then sequentially energizes the correct motor windings to generate a magnetic field that propels the rotor. Because this technique eliminates the need for mechanical commutation, it results in fewer failure points, lower maintenance requirements, and lower levels of electromagnetic interference (EMI) and noise.
Most brushed DC motors use sinusoidal regulation to adjust their current output, but some models utilize a more advanced form of governance called field-oriented control. This governance method removes time dependence from calculations, allowing you to achieve the desired moment of force and flux values without sacrificing efficiency at higher speeds.
Some brushed DC motor controllers can be configured to perform PID control, which reduces motion errors and improves responsiveness. The PID algorithm feeds back the proportional, integral, and differential controls – representing the error, the brushless motor controller manufacturer percentage of variance to the target value, and the change in acceleration, respectively – and works to minimize these errors. The control unit then uses the data to optimize motor operations.
High-Resolution Sensors
Brushless motor controllers have built-in sensors that enable advanced control features. These include rotor position sensing to ensure precise control. It’s also possible to incorporate feedback sensors such as encoders for precise speed and torque monitoring.
In comparison, traditional motors use brushes and a commutator that act as switches when current flows through them. The instantaneous opening and closing of these switches causes arcing at the brushes, which generates significant electrical noise. This noise can be picked up by sensitive circuits and create a problem.
High-resolution sensors allow the motor controller to detect the exact rotor position and enable sinusoidal commutation for noise reduction. This allows the motor to start up more quickly and with lower vibrations. It also improves accuracy and precision in demanding applications.
A robust circuit design is crucial for ensuring durability in rough environments. This is achieved through modern manufacturing methods that result in streamlined designs, strong connections and robust components. It’s also essential to incorporate efficient cooling methods to prevent overheating.
A reliable motor controller will be less prone to damage and maintenance, saving money over the life of the device. It will also be able to operate with maximum efficiency for reduced energy consumption and lower heat generation.