What is a motion controller?
A motion controller is a dedicated controller that controls the operation of an electric motor. For example, a limit switch controls an AC contactor to move an object upwards to a designated position and then downwards. Alternatively, a time relay can control the motor to rotate forward and backward or to rotate intermittently. The application of motion control in robotics and CNC machine tools is more complex than its application in specialized machines because the latter have simpler motion patterns and are often referred to as general motion control (GMC).
Features of motion controllers
(1) The hardware composition is simple. The system can be formed by inserting the motion controller into the PC bus and connecting the signal lines.
(2) Development can be carried out using the rich software already available on PCs;
(3) The motion control software has good code universality and portability;
(4) There are many engineers who can carry out development work, and they can carry out development without much training.
What is a PLC?
A programmable logic controller (PLC) is a digital electronic system specifically designed for industrial applications. It employs a programmable memory that stores instructions for performing logical operations, sequential control, timing, counting, and arithmetic operations, controlling various types of machinery or production processes through digital or analog inputs and outputs.
What is a motion controller? What is the difference between a motion controller and a PLC?
Features of PLC
(1) High reliability. Since most PLCs use single-chip microcomputers, they have a high degree of integration. In addition, the corresponding protection circuits and self-diagnostic functions improve the reliability of the system.
(2) Easy to program. PLC programming mostly uses relay control ladder diagrams and command statements, which are much fewer in number than microcomputer instructions. Except for mid-range and high-end PLCs, most small PLCs only have about 16 instructions. Because ladder diagrams are intuitive and simple, they are easy to learn and use, and even programming can be done without computer expertise.
(3) Flexible configuration. Because PLC adopts a modular structure, users can easily change the function and scale of the control system by simply combining them. Therefore, it is applicable to any control system.
(4) Complete input/output function modules. One of the biggest advantages of PLC is that it has corresponding modules for different field signals (such as DC or AC, switch quantity, digital quantity or analog quantity, voltage or current, etc.) that can be directly connected to industrial field devices (such as buttons, switches, current transmitters, motor starters or control valves, etc.) and connected to the CPU motherboard through the bus.
(5) Easy installation. Compared with computer systems, PLCs do not require a dedicated computer room or strict shielding measures. When in use, simply connect the detection device to the actuator and the I/O interface terminals of the PLC correctly, and it will work normally.
(6) Fast operating speed. Since the control of PLC is executed by program control, its reliability and operating speed are incomparable to those of relay logic control. In recent years, the use of microprocessors, especially with the widespread adoption of single-chip microcomputers, has greatly enhanced the capabilities of PLCs and narrowed the gap between PLCs and microcomputer control systems, especially for high-end PLCs.
The difference between motion controllers and PLCs
Motion control mainly involves the control of stepper motors and servo motors. The control structure is generally: control device + driver + (stepper or servo) motor.
The control device can be a PLC system or a dedicated automation device (such as a motion controller or motion control card). When a PLC system is used as a control device, although it has the flexibility and certain versatility of a PLC system, it is difficult to achieve high precision, such as interpolation control, and requires sensitive response, or programming is very difficult, and the cost may be high.
With technological advancements and accumulated expertise, motion controllers have emerged, embedding some common and specialized motion control functions—such as interpolation instructions. Users only need to configure and call these function blocks or instructions, thus reducing programming difficulty and offering advantages in performance and cost.
Alternatively, it can be understood as follows: a PLC is used as a common motion control device. A motion controller is a special type of PLC, specifically designed for motion control.
