As someone working in industrial control, I often talk about motion control . So, what exactly does motion control refer to in the field of industrial control and automation ?
What is the difference between motor control and motion control?
What are the basic structural components?
What are the development trends of motion control?
......
Let's find out together!
Industrial control is mainly divided into two directions: motion control, which is usually used in the mechanical field, and process control, which is usually used in the chemical industry. 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
The definition above mentions motor control, but 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 achieve given values. Motion control, on the other hand, focuses on coordinating multiple motors to complete specified motions (synthetic trajectories, synthetic velocities), emphasizing trajectory planning, velocity planning, and kinematic transformations; for example, in CNC machine tools , 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 the 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 planning capabilities (although some drivers have simple position and speed planning capabilities).
Motion control is often applied to products and includes mechanical, software, and electrical modules, such as robots , drones, and motion platforms. It involves real-time control and management of the position and speed of mechanical moving parts, enabling them to move according to the expected trajectory and specified motion parameters.
There is some overlap between the two: the position loop/speed loop/torque loop can be implemented in the motor driver or in the motion controller, so the two are easily confused.
Basic architectural components
The basic architecture of a motion control system includes:
Motion controller: Used to generate trajectory points (desired output) and close the position feedback loop. Many controllers can also internally close a velocity loop.
Motion controllers are mainly divided into three categories: PC-based, dedicated controllers, and PLCs. PC-based motion controllers are widely used in industries such as electronics and EMS; dedicated controllers are represented by industries such as wind power, photovoltaics, robotics, and molding machinery; while PLCs are favored in industries such as rubber, automobiles, and metallurgy.
Drives 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 position and speed loops for more precise control.
Actuators: such as hydraulic pumps, cylinders, linear actuators, or motors, used to output motion.
Feedback sensors , such as photoelectric encoders, rotary transformers, or Hall effect devices, are used to provide feedback on the position of the actuator to the position controller in order to achieve the closure of the position control loop.
Numerous 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 has further facilitated electromechanical control solutions. For example, cams and gears used to require mechanical structures, but now they can be implemented using electronic cams and electronic gears, eliminating the backlash, friction, and wear associated with mechanical implementation.
Mature motion control products not only need to provide path planning, look-ahead control, motion coordination, interpolation, forward and inverse kinematics solutions, and instruction output for driving motors, but also need to have engineering configuration software (such as SIMOTION's SCOUT), a syntax interpreter (not only its own language, but also support for IEC-61131-3 PLC languages), basic PLC functions, PID control algorithm implementation, HMI interactive interface, fault diagnosis interface, and advanced motion controllers can also achieve safety control, etc.
Development Trends of Motion Control
Regarding motion controllers, the Chinese motion control market has gradually matured with the expansion of industry applications, achieving good development in most downstream machinery industries such as machine tools, engraving machines, semiconductors, industrial robots, EMS, and material handling. Particularly in industries such as lithium batteries, industrial robots, semiconductors, and EMS, motion control manufacturers from Europe, the United States, and Japan have performed exceptionally well, possessing strong overall competitive advantages.
Since the goal of motion control is to complete the production line process to manufacture products, the motion control process in the middle is not the most important thing. Instead, the most important function is to achieve the requirements correctly and in real time. In addition, the precision requirements of various products are getting higher and higher, and the requirements of the process 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 in the industrial robot industry for some time. The PC-based motion control market in the semiconductor industry 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 proportion of PC-based controllers. 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.
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