- Position command generator. A machine reads command from its storage and interprets into a format compatibly with a controller. Usually, there are two types of path that machine has to be able to traveling, straight line motion (linear) and circular motion. After machine knows what is a motion type, it send a motion information to its interpolation, a system that take a path conformations and feed a position controller a position that motor have to rotate to at given time.
- Position Controller. A sub-system that receives a position command and driver a motion to that position.
A position controller, is mainly consist of hardware box. There are two types of position controller, a open and close loop position controller.
Open loop position control
Like its name, this controller need not a feedback device. A rotation has a pre-define, certain amount of traveling. This mean, with a one command, a device will travel with one position unit.
A block diagram of system is shown below,
Example of this kind of device is stepper motor controller system. see picture below,
Close loop position control
A block diagram is shown below,
It has a PID calculator, a driver and a feedback device. An big advantage of close loop over open loop is, close loop has an error detection device and use that device as a part of controlling. Some open loop system has an error detector but use to indicate or stop operation if a system enter an position error that cannot acceptable.
Servo motor and Servo driver .
An industrial market has introduced a device used to control a motion of object that is attached to it, that device is consist of a motor and a drive system to be convenient and flexible to build or fix a machine. There is invention a servo motor and servo driver.
Actually, server motor and servo drive has to work together to provide ability to control a motion of object attach to it. Anyway, it was separated a driver and motor because it is easy to upgrade, fix only a driver or motor. Need not to change both of them.
Picture below show a categorize of server system.
Feedback device.
For a close loop control system, it has to has a feedback device. It tells a system how much actual position differ from a desire command. There are two types of feedback device, analog and digital feedback device.
- Analog feedback device. Use with analog control system. It can be used with digital system by integrate with analog to digital converter. Usually convert a distance to electrical signal, a voltage or current. Example of this device,
- Potentiometer
- Tachometer
- Digital feedback device. Use with digital control system. With more accurate and good noise rejection. A digital feedback device is widely use more than an analog. These device, topically use an optical technique. Example of device.
- Absolute encoder
- Give a certain position for any movement. Is used for a short distance of movement.
- Incremental encoder
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