What Is a Servo Controller?
A servo controller is a control device that achieves high-speed, high-precision drive control of various industrial machines.
There are several servo controllers for different applications, such as sequencer-based and industrial PC-based controllers. A servo controller must be selected for each control application.
In recent years, there have been cases where a large-scale servo control system has been built by integrating the servo controller and a cloud-based system using IoT technology.
Uses of Servo Controllers
Servo controllers are mainly used for high-speed, high-precision drive control of various industrial machines in the industrial field. Servo controllers can be broadly classified into two types: sequencer-based and industrial PC-based.
Sequencer-based servo controllers are used for integrated control of servo motors mounted on a single piece of equipment or multiple pieces of equipment, while industrial PC-based controllers are used for large-scale systems that centrally control an entire production line.
Examples of servo controller applications include the following:
- Magnet wire winding equipment in electric motor production lines.
- Multi-axis control in a PET bottle beverage transport line.
Principle of Servo Controllers
A servo motor does not operate by itself; it requires a servo amplifier, which is the driver that operates the servo motor, and a servo controller, which acts as a control tower.
The servo controller transmits command signals to the servo amplifier, which in turn supplies power to the servo motor.
1. Command Signal of Servo Controller
The role of the servo controller is to output target values of position, speed, and rotation force to move the servo motor as command signals.
2. Power Supply to the Servo Amplifier
The servo amplifier supplies power to the servo motor based on the command signals received from the servo controller. It is not always the case that the servo motor is moving according to the target value. Therefore, the servo amplifier receives feedback signals from the servo motors as described below.
3. Feedback From Servo Motor
The servo motor has an encoder inside. The encoder detects the actual rotation position and speed of the servo motor and converts them into electrical signals. This electrical signal is sent to the servo amplifier as a feedback signal.
The servo amplifier compares the feedback signal with the target value received from the servo controller and controls the power supply to the servo motor to minimize the error.
Other Information on Servo Controller
Servo Motor Control
Servo motors, including servo controllers, are controlled by feedback control. There are two types of control: open-loop control and closed-loop control.
1. Open-Loop Control
This control uses a mathematical model on the current state and control system to perform calculations on inputs. It is used for simple processes. Sequence control is a typical example, in which each step of the control proceeds sequentially according to a predetermined order.
The advantage of an open-loop system is that the system is less susceptible to measurement noise and instability. The disadvantage is that the control is design-specific.
2. Closed-Loop Control
This technique provides feedback of the system’s output to the input and is more accurate than open-loop control. Closed-loop systems have superior robustness, but the disadvantage is that they can cause uncontrolled behavior in the system.
Another disadvantage is that they are vulnerable to measurement noise. Motor servomotors use closed-loop control, which enables precise rotation speeds and rotational speeds to be achieved.