In the field of motor applications, sensored motors are equipped with position sensors (such as Hall sensors or encoders) that provide precise rotor position and speed information, enabling efficient and stable operation. Compared with sensorless motors, sensored motors offer significant advantages in low-speed startup, dynamic response, and load adaptability. As a result, they are widely used in industrial automation, robotics, electric vehicle drives, and household appliances. So, what are the common control methods for sensored motors? Let’s take a closer look.
Open-Loop Control
Open-loop control is the most basic motor control method. It does not rely on feedback signals; instead, the motor is driven with fixed voltage or current. This approach is simple and low-cost, but since there is no real-time feedback, accuracy and dynamic performance are limited. In sensored motors, open-loop control is mostly used in scenarios where load changes are minimal or precision requirements are low, such as small fans and pumps.
Closed-Loop Control
Closed-loop control uses sensors to continuously collect rotor speed or position data. The feedback is compared with the setpoint, and the input current is adjusted accordingly. This significantly improves stability and dynamic performance. Closed-loop control is suitable for applications that require both precision and reliability, such as CNC machines, automated production lines, and electric vehicle drive systems.
Vector Control (FOC, Field Oriented Control)
Vector control is one of the most common and advanced methods for sensored motors. It works by mathematically transforming the three-phase current into torque and flux components, which are controlled independently, achieving a performance similar to that of DC motors.
Advantages: Fast torque response, excellent low-speed performance, and high efficiency.
Applications: Widely used in electric vehicles, servo motors, robotics, and other areas that demand smooth operation and efficient energy management.
Direct Torque Control (DTC)
Direct Torque Control is based on space vector modulation principles, directly controlling motor torque and flux. It eliminates the need for current decoupling, achieving faster response.
Advantages: Simple control structure and excellent dynamic performance.
Disadvantages: Torque ripple at low speeds, and higher requirements for hardware and computational power.
Applications: Suitable for industrial drives requiring fast response and high efficiency, such as high-speed motors and variable frequency drive systems.
V/F Control (Volts per Hertz Control)
V/F control keeps the ratio between voltage and frequency constant to maintain basic torque stability. While simpler in principle, it is less precise and less efficient than vector control or DTC.
Advantages: Easy to implement and cost-effective.
Applications: Commonly used in large fans, pumps, and other load scenarios with low precision requirements.
Conclusion
Thanks to rotor position detection, sensored motors can adopt a variety of control methods. From simple open-loop control to more accurate closed-loop control, and from advanced vector control (FOC) to direct torque control (DTC), the choice depends on application requirements.
For cost-sensitive, low-precision scenarios, open-loop or V/F control is sufficient.
For high-precision, high-efficiency needs, FOC or DTC is recommended.
For reliable industrial and transportation applications, closed-loop control remains the core solution.
In short, selecting the right control method is key to unlocking the performance of sensored motors, extending equipment lifespan, and improving system efficiency.