Two Synchronization Methods for Motion Control and Data Acquisition in Test Systems

There are generally two types of synchronization methods adopted in the test system: one is that the motion control card controls the motor to move to a certain specified position, and the data acquisition card can collect data at the position in real time. This method is called interruption; the other synchronization method is that if the data acquisition card collects a signal that meets certain conditions when the motor moves to a certain position, it is necessary to record the current movement position of the motor. This method is called capture.

Interrupt mode

interrupts are divided into absolute position interrupts, relative position interrupts and periodic position interrupts. Absolute position interrupt means that when the motor moves to a certain absolute position, the motion control card will generate an external interrupt signal; relative position interrupt means that when the difference between the motor's movement position and the position when the motor is allowed to generate an interrupt meets the set conditions, an interrupt signal is generated; modulo position interrupt means that each interrupt signal will be generated relative to a certain set position. Therefore, the interrupt method can be determined according to the different needs of the test system.

The principle of synchronization

When the motion control card controls the motor to move to a certain position, once the position signal returned by the encoder meets the set position condition, an interrupt signal will be issued. This signal can be used as a trigger condition for the data acquisition card to collect the signal, so that the acquisition card can collect the required data in real time. The motion control card and the data acquisition card can achieve synchronization between the two through the RTSI bus. The interrupt signal generated by the motion control card is transmitted to the RTSI output pin through the internal circuit. Currently, there are 7 RTSI output pins (RTSIO-RTSl6). The RPSI output pin can be connected to the RTSI pin of the data acquisition card through an external cable. The RTSI pin of the acquisition card can also be connected to its control signal (see Figure 1) through the internal circuit to achieve synchronization between the two.

When the motion control card controls the motor to move to a specified position, an interrupt signal will be generated. The interrupt output signal can be connected to the RTSI pin of the motion control card, and the RTSI pin of the motion control card is connected to the RTSI pin of the data acquisition card. In the acquisition card, the RTSI pin signal is used as the system scan clock and is connected to the sampling clock signal. Therefore, every time the motion control card generates an interrupt signal, the data acquisition card performs a channel scan to read the data collected from each sensor. The data will be stored in the set buffer. Once the data in the buffer is full, it will be displayed on the screen through multi-threading. In this way, synchronization between motion control and data acquisition is achieved.