In a motion system, the controller is used to manipulate stages and actuators so that they move or stop in a desired manner.
In CNC machine motion control system contains a commanded position, the actual position, and the error signal which is the difference between the actual and commanded position.
A motion controller performs four fundamental tasks:
- decoding position feedback,
- generating the commanded position or motion profile,
- closing the position loop
- compensating stability.
Of these four tasks, the most fundamental are decoding the motor position and closing the loop. The motor position is determined from the feedback signal (PG) , often an incremental encoder, and compared with the commanded position. The difference between the actual and the commanded motor position is known as the position error.
The controller’s task is to minimize the position error without oscillating the load.
STRUCTURE OF A MOTION CONTROL SYSTEM
The motion controller for a servomotor consists of the components:
- Controller Hardware: This includes the physical device or circuitry responsible for processing control signals and sending them to the servomotor. It may include a microcontroller or a dedicated motion control board.
- Feedback System: Servomotors are equipped with feedback devices such as encoders or resolvers to provide information about the motor’s actual position, speed, or torque. The motion controller uses this feedback data to ensure accurate and precise control over the motor’s movement.
- Communication Interfaces: Motion controllers often include various communication interfaces such as Ethernet, USB, or serial ports to connect with external devices or systems. These interfaces enable the motion controller to receive commands or send feedback information to a supervisory control system or human-machine interface (HMI).
- Control Modes and Features: Motion controllers for servomotors may offer different control modes, such as position control, velocity control, or torque control. They may also include advanced features like trajectory planning, motion profiling, acceleration and deceleration control, and integration with other automation components.
The motion controller receives high-level commands or instructions, processes them based on the control algorithm and feedback information, and generates appropriate control signals to drive the servomotor. The control signals typically involve adjusting voltage, current, or pulse-width modulation (PWM) signals to achieve the desired motion or position.
FUNCTIONS OF A MOTION CONTROLLER
A motion controller for a servomotor is a device or system that manages the movement and position of a servomotor. Servomotors are commonly used in industrial automation, robotics, CNC machines, and other applications where precise control of position, speed, and torque is required.
A motion controller for a servomotor typically performs the following functions:
- Position Control: The controller calculates and adjusts the position of the servomotor based on the desired position setpoint. This involves sending control signals to the motor to achieve accurate positioning.
- Speed Control: The controller can regulate the speed of the servomotor, ensuring it reaches the desired speed and maintains it during operation. This is important for applications requiring controlled acceleration and deceleration.
- Torque Control: Some applications require precise control over the torque exerted by the servomotor. The motion controller can manage the motor’s torque output to match the application’s requirements.
- Feedback Loop: Motion controllers often use feedback devices like encoders or resolvers to provide real-time information about the motor’s actual position, speed, and sometimes even torque. This feedback allows the controller to make adjustments and corrections to achieve accurate motion control.
- Trajectory Planning: For complex motion profiles, the motion controller can generate trajectories that dictate how the motor should move over time. These trajectories take into account factors like acceleration, deceleration, and jerk to ensure smooth and efficient motion.
- Closed-Loop Control: A closed-loop control system constantly compares the desired motion profile with the actual motion feedback from the servomotor. It then adjusts the control signals to minimize any discrepancies between the two, providing accurate and stable motion.
- Communication Interface: Modern motion controllers often come with communication interfaces such as Ethernet, USB, or serial ports. the communication interface allowing them to be integrated into larger control systems and communicate with other devices or a central control unit.
- Software Configuration: Motion controllers usually have software interfaces that allow users to configure various parameters, set motion profiles, tune control loops, and monitor the performance of the system.
The motion controller’s can vary depending on the manufacturer, intended application, and complexity of the motion control needs.
Suppliers of motion controller
The best known suppliers of motion controllers for servomotors are :
- Leadshine is a Chinese manufacturer of motion control products. They offer a wide range of motion controllers for servomotors, including open-loop and closed-loop controllers, as well as controllers with integrated encoders.
- Delta is a Taiwanese manufacturer of automation products. They offer a variety of motion controllers for servomotors, including high-performance controllers for demanding applications.
- Omron is a Japanese manufacturer of industrial automation products. They offer a range of motion controllers for servomotors, including controllers for general-purpose applications and controllers for harsh environments.
- Parker Hannifin is an American manufacturer of motion control products. They offer a wide range of motion controllers for servomotors, including controllers for high-precision applications and controllers for robotics applications.
- ABB is a Swiss-Swedish multinational corporation that provides technology products and services. They offer a variety of servo drives and motion controllers for a variety of industries.
- Fanuc is a Japanese manufacturer of automation products. They offer a wide range of servo drives and motion controllers for industrial applications.
- Siemens is a German manufacturer of industrial automation products. They offer a range of motion controllers for servomotors, including servo drives, servo amplifiers, and servo motors.
- Schneider Electric is a French multinational company that manufactures a variety of industrial products, including motion controllers for servomotors.
The best vendor for you will depend on your specific application requirements. Keep in mind that you should get quotes from several suppliers before making a decision.