Selection and design of various functional components of the control system:
1. The single-chip microcomputer used in this system is the 8031 from Intel. This microcontroller serves as the core of the control system, handling signal processing through the parallel 8255 port. It receives signals for torque, valve position, opening and closing actions, and provides the necessary control signals to the three-phase PWM wave generator. It also processes fault and alarm signals, handles analog inputs such as current, voltage, and position, and sends working state information to the display. Additionally, it executes control commands from the system and feeds back relevant data.
2. For generating three-phase PWM waves, a digital approach is preferred over analog methods. While analog circuits are complex and prone to temperature drift, digital methods offer better precision. However, they require significant memory resources. To meet the requirements of the intelligent power module, the SA8282 from MITEL is used. This dedicated IC features an independent microprocessor interface and contains waveform, frequency, and amplitude control data, making it ideal for high-performance applications.
3. The motor power supply uses the IPM (Intelligent Power Module) PM50RSA120 from Japan. This module integrates power switches, driver circuits, and braking functions, along with built-in protection mechanisms such as overcurrent, short-circuit, undervoltage, and overheating detection. It is suitable for three-phase asynchronous motors up to 5.5 kW with a rated voltage of 380 V and a power factor of 0.75.
4. Position detection is crucial for the actuator’s performance. Traditional sensors like potentiometers and differential transformers have limitations in terms of lifespan and accuracy. A pulse digital sensor is used instead, offering non-contact operation, high precision, stability, and no temperature restrictions, making it ideal for long-term use.
5. Voltage and current detection are essential for monitoring motor torque and diagnosing faults. Hall-effect current transformers are used for real-time current sensing, while a voltage divider circuit is employed for voltage measurement. These components ensure accurate feedback for fault detection and protection.
6. For communication, the MAX232 chip is used to convert TTL levels to RS-232 standards, enabling serial communication between the microcontroller and other devices. This facilitates remote control and system networking.
7. A clock circuit based on the DS12887 ensures accurate timing for sampling, control cycles, and calendar functions. It includes 114 bytes of non-volatile RAM for storing critical data over time.
8. An LCD unit, specifically the MGLS12832 module, is used for human-machine interaction. It supports text and graphics, allowing users to adjust parameters such as valve position, torque, and communication settings through a menu-based interface.
9. A program self-recovery circuit using the MAX705 ensures system stability. If the program encounters interference and resets, the circuit detects the failure, triggers a reset, and restores normal operation. This improves system reliability and fault tolerance.
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