As the power source for various electrical appliances and machines, electric motors are used by almost every engineer and electronics enthusiast, whether in industrial applications or personal projects. They play a significant role despite their small size. Here, we'll discuss the issue of motor motion control algorithms.
I. DSP and TI
Why do many people immediately think of DSPs when discussing motor control? And when talking about DSP control, TI is always mentioned. Firstly, a DSP chip is a microprocessor with a special architecture. Internally, it uses a Harvard architecture that separates program and data processing, has a dedicated hardware multiplier, and provides special instructions for quickly implementing various digital signal processing algorithms. A control system based on a DSP chip is essentially a monolithic system; therefore, all the functions required for control can be implemented by the DSP chip. This reduces the size of the target system, the number of external components, and increases system reliability. Its advantages include good stability, high precision, and fast processing speed, and it is currently widely used in the frequency converter and servo industries. Major DSP manufacturers include Texas Instruments (TI), Analog Devices (ADI), Motorola, and others. Among them, TI's TMS320 series, primarily focused on digital control and motion control, is very popular due to its low price, ease of use, and powerful functionality.
II. Common Motor Control Algorithms and Research Methods
1. Motor control can be classified by power supply type into DC motors and AC motors. It can also be classified by structure and working principle into DC motors, asynchronous motors, and synchronous motors. Different motors use different driving methods. This article mainly introduces servo motors. Servo motors primarily rely on pulses for positioning. When a servo motor receives one pulse, it rotates by the angle corresponding to that pulse, thus achieving displacement. Therefore, servo motors inherently possess the function of emitting pulses. For each angle rotation, the servo motor emits a corresponding number of pulses, forming a closed loop with the pulses received by the servo motor, thereby precisely controlling the motor's rotation and achieving precise positioning down to 0.001mm. Compared to ordinary motors, servo motors offer advantages in control precision, low-frequency torque, overload capacity, and response speed, making them widely used in robotics, CNC machine tools, injection molding, textiles, and other industries, as shown in the diagram below.
2. Traditional control platforms only focus on motor characteristics. The new motion control platform consists of a motor and loading system, a motor driver debugging system, a data acquisition system, and a power supply system. It constructs a complete hardware and software experimental environment from motor to drive, providing fully open hardware and software interfaces, rich scalability for teaching experiences, and comprehensive and reliable protection measures. It can perform tests such as motor identification, stall testing, motor efficiency testing, motor parameter measurement, motor TN curve testing, motor motion control, encoder vector torque, and sensorless vector speed analysis. The system is shown in the figure above.
III. PWM Control and Test Results
Pulse width modulation (PWM) is a highly effective technique that uses the digital output of a microprocessor to control analog circuits. It is widely used in many fields, from measurement and communication to power control and conversion. PWM is an analog control method that modulates the bias of the base of a transistor or the gate of a MOSFET according to changes in the corresponding load, thereby changing the conduction time of the transistor or MOSFET and thus changing the output of the switching power supply. The MES-100 test waveform is shown in the figure below.
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