This section provides overview, applications, and principles of motion controllers. Also, please take a look at the list of 58 motion controller manufacturers and their company rankings.
A motion controller is a device used to control the motion of equipment driven by servomotors or linear motors.
Users program the motion they wish to achieve in advance and have the motion controller execute it to control the motion of the equipment.
Motion controller is similar to PLCs in that they automatically control equipment with programs customized by the user. However, they specialize in controlling motors.
In contrast, PLCs can perform various types of control, not limited to motors. In other words, the characteristics of motion controller and PLCs differ in terms of generality.
Motion controllers are used to control equipment driven by servomotors and linear motors. They are used to control a wide variety of equipment, but the most common applications are industrial robots and industrial machines that perform grinding and cutting.
Motion controllers, rather than PLCs, are often used for motion control. One advantage of motion controllers are that they are suited to control multiple axes and synchronization when the total number of axes is large.
While a PLC has a limited number of axes that can be controlled by a single unit, motion controllers can control far more axes than that. For this reason, motion controllers are used in industrial machine tools and robots that require precise, multi-axis control.
To select motion controllers, it is necessary to understand the differences in interpolation control. Interpolation control is a control method for synchronous control, such as simultaneous starts and stops between multiple axes. There are two types of motion controllers: linear interpolation and circular interpolation.
Linear interpolation is a control method in which, when positioning with two motors, the motors are controlled simultaneously to move linearly to the desired position. The CPU calculates and controls the motors so that they move in a straight line in a diagonal direction rather than moving horizontally and then vertically.
Since linear interpolation enables oblique linear movement, the time required for positioning can be reduced. For this reason, in machine tools, linear interpolation is used for tool movement in sections where no cutting is performed.
Circular interpolation is a control method in which, as with linear interpolation, when two motors are simultaneously controlled for positioning, the CPU calculates the movement to draw a circular arc. Since the movement path is not linear, it has the disadvantage that it takes more time to reach the target position than linear interpolation.
By using arc interpolation, if there are obstacles on the route to positioning, it is possible to avoid the obstacles.
PLCs are often compared to motion controllers, and the principle of PLCs and motion controllers differs in the CPU's processing method.
PLCs are characterized by the fact that every line of the program is read at each execution. PLCs are characterized by the fact that all lines of the program are read at each execution, and they have multitasking control in which all lines are executed simultaneously.
For this reason, the PLC must read every line of the program. The disadvantage of this rate-limiting reading time is that PLCs do not have enough computing time to perform complex control.
Especially in the case of complex control, the program capacity also increases and loading takes even more time. However, this program loading method differs significantly between PLCs, motion controllers, and ordinary PCs.
Unlike PLCs, motion controllers read and execute programs one line simultaneously, just like a regular PC. Therefore, motion controllers are less expensive and faster in computation per task than PLCs.
A further advantage of motion controllers are that increasing program capacity does not affect the time required for a single line of processing. Therefore, for complex systems such as servo motors, control using motion controllers are more efficient than control using a PLC, allowing complex systems to be processed at higher speeds.
There are three types of motion controllers output methods that enable complex, high-speed control: pulse method/common pulse method, pulse method, and phase difference input method/90-degree phase difference method.
The pulse method/common pulse method is a method in which the direction of rotation is determined according to the H/L level of the DIR signal when a pulse is input to the CLK signal. In actual control, the DIR signal determines the direction of rotation (H: forward, clockwise, right rotation; L: reverse, counterclockwise, left rotation), and pulses are input to the CLK signal at the timing for rotation.
The pulse method is a method in which the direction of rotation is determined when a pulse is input to either the CW or CCW signal. CCW stands for Counter Clock Wise and indicates reverse, counterclockwise, or left rotation.
The phase difference input method/90-degree phase difference method is a method in which the direction of rotation is determined from the phase shift of pulses input to the phase A and B pulse signals.
If the phase A pulse signal is out of phase with the phase B pulse signal by -90 degrees, the rotation is counterclockwise or left.
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