I. INTRODUCTION
In the field of industrial automation control, PLC (Programmable Logic Controller) is widely used in various industrial scenarios as an important control device. Among the control methods of PLC, pulse control and bus control are two common control strategies. In this paper, we will discuss the difference between pulse control and bus control of PLC in detail, and analyze it from various aspects, such as control principle, application scenarios, and performance characteristics, so that readers can have a deeper understanding of the differences between these two control methods.
II. Pulse Control
Control principle
Pulse control is a control technology that uses pulse signals as a means of control. In PLC, pulse control usually generates high-speed pulse signals through specific output ports, and these pulse signals are transmitted to the control components of the controlled object, thus controlling the movement or state of the controlled object. Parameters such as the frequency and duty cycle of the pulse signals can be precisely adjusted through the PLC program to achieve different control effects.
Application Scenarios
Pulse control is suitable for applications where precise control of position, speed or acceleration is required. For example, in automated production lines, pulse control can be used to control servo motors and stepping motors to realize precise position control and speed adjustment; in robot control systems, pulse control can be used to control the robot's joint motion to realize high-precision trajectory planning and motion control; in numerical control machine tools, pulse control can be used to control the rotational speed of the main spindle and the moving speed of the feed axis to improve machining In CNC machine tools, pulse control can be used to control the spindle rotation speed and feed axis movement speed to improve processing accuracy and efficiency.
Performance characteristics
(1) High precision: Pulse control can realize high-precision position control and speed adjustment to meet various high-precision control requirements.
(2) High frequency: The high-speed pulse signal generated by PLC has high frequency, which can realize fast response and precise control.
(3) High stability: pulse control has high stability, can be stable in a variety of harsh environments.
III. Bus control
Control principle
Bus control is the technology of control through the bus communication protocol. In PLC, bus control sends instructions to multiple controlled objects through the bus to realize parallel control. The bus communication protocol specifies parameters such as data transmission format, transmission rate, and transmission method to ensure the accuracy and reliability of data during transmission.
Application Scenarios
Bus control is suitable for applications where multiple objects or devices need to be controlled simultaneously. For example, in industrial automation assembly lines, warehouse integration and other systems, bus control can simultaneously control multiple motors, sensors, actuators and other devices to realize complex control logic and automation operations. In addition, bus control is also widely used in building automation, intelligent transportation and other fields.
Performance characteristics
(1)Support multi-device connection: bus control adopts open structure design, supports many different device connections, and can realize networking control of various devices.
(2) Efficient and reliable: The bus control adopts efficient communication protocols and reliable transmission methods to ensure the accuracy and reliability of data in the transmission process.
(3)Flexible: bus control supports a variety of communication methods, you can choose the appropriate communication method according to the actual needs, to achieve flexible and diverse control strategies.
(4) Easy maintenance: The bus control adopts modular design, which is easy to maintain and expand. When a device fails, the device can be easily replaced or repaired without affecting the normal operation of the entire system.
IV. Comparison of pulse control and bus control
Control mode
Pulse control is to directly control the movement or state of the controlled object through pulse signals, while bus control is to send commands to multiple controlled objects through the bus communication protocol to realize parallel control. Therefore, in terms of control mode, pulse control focuses more on precise control of a single object, while bus control focuses more on parallel control of multiple objects.
Control accuracy
Pulse control can realize high-precision position control and speed adjustment to meet various high-precision control needs. Although bus control can also realize precise control, its control accuracy may be slightly lower than that of pulse control.
Number of control objects
Pulse control can generally control only one object, such as motor control in a microcontroller. Bus control, on the other hand, can control multiple objects at the same time. When controlling large-scale industrial automation assembly lines, warehouse integration and other systems, bus control is a more suitable control method.
Synchronization and anti-interference
In terms of synchronization and anti-jamming, bus control has significant advantages. Due to the high bus signal transmission rate, the synchronization error of multiple motor control can be achieved at the microsecond level, almost no synchronization error. At the same time, the bus control adopts twisted twisted signal lines and cables with shielding layer, which have strong anti-interference. On the other hand, pulse control is prone to synchronization error and weak anti-jamming ability due to limited pulse transmission speed and cable length.
Wiring Layout and Expandability
In terms of wiring layout and expandability, bus control also performs well. Bus type wiring is very simple, PLC and other host computer only need to connect out two wires can be completed dozens or even hundreds of motor control wiring, simplify the wiring step line difficulty, saving wire. At the same time, bus control, whether it is a motor drive and other slave stations or PLC and other master stations, generally can be configured for multiple network control, these reserved interfaces can be realized configuration, for the later increase in functionality or control changes are very helpful. Pulse-type control in the hardware interface has been limited to not be able to realize the configuration, later if you need to increase the function or change the control mode will be very difficult.
V. Conclusion
In summary, PLC pulse control and bus control in the control principle, application scenarios, performance characteristics and other aspects of the significant differences. Pulse control is suitable for precise control of a single object, while bus control is more suitable for complex systems that require simultaneous control of multiple objects or devices. In practical applications, the appropriate control method should be selected according to specific needs and scenarios.