What is Motion Control?

What is Motion Control?

The application of motion control in the field of robots and CNC machine tools is more complicated than the application in special machines because the latter has a simpler motion form and is usually called general motion control (GMC). Motion control is widely used in packaging, printing, textile, and assembly industries.

In the field of industrial control and automation, what exactly does motion control mean?

In summary, motion control is mainly divided into two directions, one is a motion control, which is usually used in the mechanical field; the other is process control, which is usually used in the chemical industry. And motion control refers to a kind of servo system that originated in the early days, based on the control of the motor, to realize the control of the change of the angular displacement, torque, speed, and other physical quantities of the object.

In the above definition, motor control is mentioned, but motor control and motion control are different. From the point of concern, motor control (herein referred to as a servo motor) is mainly concerned with controlling one or more of the torque, speed, and position of a single motor to a given value. The focus of motion control is to coordinate multiple motors to complete the specified motion (composite trajectory, composite speed), and focus more on trajectory planning, speed planning, and kinematics conversion; for example, CNC machine tools need to coordinate XYZ axis motors to complete interpolation action.

Motor control is often used as a link of the motion control system (usually a current loop, working in torque mode), and it focuses more on the control of the motor. It generally includes three control loops: position control, speed control, and torque control. Generally, there is no plan. (Some drives have simple position and speed planning capabilities); motion control is often for products, including mechanical, software, electrical, and other modules, such as robots, drones, motion platforms, etc., which are for mechanical motion the position and speed of the components are controlled and managed in real-time so that they can be controlled following the expected motion trajectory and prescribed motion parameters.

Part of motor control and motion control overlap: the position loop/speed loop/torque loop can be implemented in the drive of the motor or the motion controller, so the two are easy to confuse.

The basic structure of the motion control system

The basic structure of a motion control system includes a motion controller: used to generate track points (desired output) and close the position feedback loop. Many controllers can also close a speed loop internally.

Motion controllers are mainly divided into three categories, namely PC-Based, dedicated controllers, and PLC. Among them, PC-Based motion controllers are widely used in electronics, EMS, and other industries; the representative industries of dedicated controllers are wind power, photovoltaics, robots, molding machinery, etc.; PLC is favored in rubber, automotive, metal metallurgy, and other industries.

Drive or amplifier: used to convert the control signal from the motion controller into a higher power current or voltage signal. The more advanced intelligent drive can close the position loop and speed loop by itself to obtain more precise control.

Actuators: such as hydraulic pumps, cylinders, linear actuators, or motors to output motion. Feedback sensor: such as photoelectric encoder, resolver, or Hall effect device, etc., used to feedback the position of the actuator to the position controller to realize the closure of the position control loop.
Numerous mechanical components are used to convert the motion form of the actuator into the desired motion form, including gearboxes, shafts, ball screws, toothed belts, couplings, and linear and rotary bearings.

The emergence of motion control has promoted electromechanical control solutions. For example, in the past, both cams and gears needed to be realized by mechanical structures. Now they can be realized by electronic cams and electronic gears, which eliminates the return, friction, and wear of the mechanical realization process.

Mature and stable motion control products not only need to provide path planning, forward-looking control, motion coordination, interpolation, kinematics forward and inverse solutions, and drive motor command output, but also need to have engineering configuration software, syntax interpreter, and simple PLC Function, PID control algorithm realization, HMI interactive interface, fault diagnosis interface, advanced motion controller can also realize safety control and so on.

The development trend of motion control technology and market

According to the market research report released by Markets and Markets, the global motion control market (including spare parts: AC motors, motors, motion controllers, AC drives, electronic drives; applications: packaging, material processing, metal processing, conversion, positioning) is expected to be Reached 22.84 billion U.S. dollars, growing at a compound annual growth rate of 5.5% between 2016 and 2022.

As far as motion controllers are concerned, with the expansion of industry applications, China's motion control market has gradually matured. Good development has been achieved in most downstream machinery industries such as machine tools, engraving machines, semiconductors, industrial robots, EMS, and material handling. Especially in industries such as lithium batteries, industrial robots, semiconductors, and EMS, European, American, and Japanese motion control manufacturers have outstanding performance and have strong comprehensive 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, but how to meet the requirements correctly and in real-time is the most important function; plus, various products now The requirements for precision are getting higher and higher, and the requirements for the manufacturing process are getting more and more stringent. Motion control emphasizes real-time and precision. To achieve optimization, various related technologies must be integrated. Such integration is regarded as the most difficult control technology.

Dedicated controllers will remain the main type of motion controller in the industrial robot industry for a while. The PC-Based motion control market in the semiconductor industry is developing steadily, with a growth rate of about 17%. The increasing demand for machine vision functions in the logistics industry has led to a gradual increase in the proportion of PC-Based. The traditional printing machinery is still dominated by PLC motion controllers. The application of PC-Based motion controllers has just started. It is used more in emerging digital printing machinery and will grow slightly in the future. According to expert analysis and prediction, the market demand for motion controllers will become larger and larger in the next few years, which will be one of the foundations of future industrial development.