In the control domain, the position and angle of the load are considered as control objects. For example:

Previously, servomotors and servomotor controllers are often used to fulfill the position control. Along with the development of the common inverter technology, AC inverter transmission has been used more and more extensively in position control. Sanken has made helpful attempts in this aspect.

1. Common characteristics of position control:
There are various simple and complicated control modes depending on the purposes. (open-loop position control, manual position determination, close-loop position control);
The position of the control object changes in the form of rotation speed integral.
Even if the position sensor is not installed directly on the load, it is possible to estimate the position very accurately by the rotation angle of the motor in most cases.
Reversible operation is needed.

2. Close-loop position control method:
The following diagram shows the position control with speed feedback hoops. No direct position commands are given to the inverter; instead, pulse rows are inputted. The accumulated value of these pulse numbers is used as the position command. To increase this position command, add the pulse row to the positive rotation input. To decrease, add the pulse row to the negative rotation input. Control the accumulated value of this input pulse row and the accumulated value of the PG feedback pulse row to make them identical.

Let's take positive rotation for example. Calculate the command-inputted pulse (plus operation in the counter) and PG feedback pulse (minus operation in the counter) in a same counter ever and again. Use the accumulated value of the counter as the speed command. Therefore, once the target position is reached, the accumulated value of the counter will be zero and the motor will stop at this position. Moreover, when the accumulated value of the counter turns very small, a position determination ending signal is sent from the position determination judgment circuit to notify of the termination of the position control.

In this application, PG produces two pulse rows with 90o phase difference. The rotation direction can be judged by monitoring the ascending sequence of these pulse signals. In addition, once the motor rotates for one resolution, a display pulse will be generated at the special rotor position, which can be used for determination of the position origin.

The feedback pulse of PG will be subject to the descending circuit before entering the counter. In the descending circuit, the PG pulse row is frequency divided into a part of an integral in order to change the position change quantity (gain) of an input pulse. Therefore, if it is frequency divided into 1/n, an input pulse PG will need n pulses to make the motor rotate.

3. Application example:
In the production line of a copper tube production enterprise in Jiangsu, the point-to-point function of Samco-VM05 is used to replace the servo system. The purpose of reducing the cost is achieved under the basis of meeting the process conditions.

Summary:
1. The position control depends on the correctness of the feedback pulse to a great extent, so the problem of pulse must be resolved first of all. Otherwise, there may be phenomena such as high operation current, large fluctuation of feedback rotation speed display, unstable motor operation, etc.
3. Normally the adjustment of close-loop speed control is performed. Cd088 and Cd089 are adjusted to appropriate values. Then the adjustment of position control Cd606 is made.
2. The motor and the inverter shall be grounded properly to prevent interference.
4. In accordance with the process requirements, the command pulse rows can be given by the PLC for continuous path control.