As someone working in industrial control, I often encounter the topic of motion control. So, what exactly does motion control refer to within the scope of industrial control and automation?
What is the difference between motor control and motion control?
What are the fundamental architectural components?
What are the trends in the development of motion control?
......
Let's find out together!
Industrial control is primarily divided into two directions: motion control, which is generally used in the mechanical field, and process control, which is generally used in the chemical field. Motion control refers to a type of system that originated from early servo systems, based on the control of electric motors, to control changes in physical quantities such as angular displacement, torque, and speed of an object.
Motor control and motion control
Motor control and motion control are different.
In terms of focus, motor control (referring to servo motors) primarily focuses on controlling one or more parameters of a single motor, such as torque, speed, and position, to reach a given value. Motion control, on the other hand, primarily focuses on coordinating multiple motors to complete a specified motion (forming a trajectory, forming a speed), emphasizing trajectory planning, speed planning, and kinematic transformation; for example, in a CNC machine tool, the XYZ axis motors need to be coordinated to complete interpolation movements.
Motor control is often used as a component of motion control systems (usually a current loop, operating in torque mode), focusing more on the control of the motor. It generally includes three control loops: position control, speed control, and torque control. It generally does not have the ability to design (some drivers have simple position and speed design capabilities).
Motion control is often applied to products, including mechanical, software, and electrical modules, such as robots, drones, and motion channels. It involves real-time control and management of the position, speed, and other parameters of mechanical moving parts, enabling them to move according to expected motion trajectories and rules.
There is some overlap between the two: the orientation loop/speed loop/torque loop can be completed in the motor driver or in the motion controller, so the two are easily confused.
Fundamental architectural components
The basic architecture of a motion control system includes:
Motion controller: Used to generate trajectory points (desired output) and close the orientation response loop. Many controllers are also capable of closing a velocity loop internally.
Motion controllers are primarily divided into three categories: PC-based, dedicated controllers, and PLCs. PC-based motion controllers are widely used in industries such as electronics and machine tools; dedicated controllers are represented by industries such as wind power, photovoltaics, robotics, and molding machinery; while PLCs are favored in industries such as rubber, automotive, and metallurgy.
Drivers or amplifiers: These convert control signals (typically speed or torque signals) from the motion controller into higher-power current or voltage signals. More advanced intelligent drives can close their own orientation and speed loops to achieve more accurate control.
Actuators: such as hydraulic pumps, cylinders, linear actuators, or motors, used to output motion.
Reaction sensors, such as photoelectric encoders, rotary transformers, or Hall effect devices, are used to indicate the position of the actuator to the position controller, thereby completing the closure of the position control loop.
Many mechanical components are used to convert the motion of an actuator into the desired motion. These include gearboxes, shafts, ball screws, toothed belts, couplings, and linear and rotary bearings.
Motion Control from the Perspective of Motion Controllers
The emergence of motion control is increasingly promoting electromechanical control solutions. For example, cams and gears used to require mechanical structures to complete, but now electronic cams and electronic gears can be used to complete the task, eliminating the backlash, friction, and wear in the mechanical process.
Experienced motion control products not only require supply path planning, look-ahead control, motion coordination, interpolation, forward and inverse kinematics solutions, and instruction output for drive motors, but also need to have engineering configuration software, syntax interpreter, basic PLC functions, PID control algorithm implementation, HMI interactive interface, fault diagnosis interface, and advanced motion controllers can also perform safety control.
The Development Trend of Motion Control
As for motion controllers, with the expansion of professional applications, my country's motion control market has gradually matured, and has achieved good development in most downstream machinery industries such as machine tools, engraving machines, semiconductors, industrial robots, EMS, and material handling.
Since the goal of motion control is to complete the production line process and manufacture products, the motion control process itself is not the most important thing. Rather, the most important function is to accurately and in real time meet the requirements. In addition, the precision requirements of various products are getting higher and higher, and the process requirements are becoming more and more stringent. Motion control emphasizes real-time and precision. To achieve optimization, various related technologies must be integrated. Such integration is considered the most difficult control technology.
Dedicated controllers will remain the primary type of motion controller for industrial robots for some time. The PC-based motion control market in the electronics and semiconductor industries is developing steadily, with a growth rate of around 17%. The increasing demand for machine vision functions in the logistics industry is also leading to a gradual increase in the PC-based market share. In traditional printing machinery, PLC motion controllers still dominate, while the application of PC-based motion controllers is just beginning, with more use in emerging digital printing machinery, and is expected to see slight growth in the future.
