The big guy explained the measurement and control system (5), the design scheme of the wind power measurement and control system (the second part)

The importance of the measurement and control system is self-evident. Among many systems, the measurement and control system is an indispensable component. In the last article, the editor has made a preliminary introduction to the design of wind power measurement and control system. In this paper, the remaining contents of the wind power measurement and control system will be discussed.

1. Vibration and noise collection

For the acquisition of vibration and noise signals, the test method is concerned with the phase relationship of the vibration signals at 24 test points, so the system is required to collect the vibration signals synchronously. The system uses an 8-channel NIPXI-4472 dynamic signal analyzer to collect noise and vibration signals. According to the test standard, the gearbox test is concerned with 24 channels of vibration and 2 channels of noise signals, and 4 pieces of PXI-4472 are required. PXI-4472 channels can achieve synchronous acquisition. In order to solve the synchronization problem between each module, the 10MHz system clock on the PXI-1050 backplane is used, and this unified clock signal is transmitted to each module through the PXI clock trigger synchronization bus.

To achieve true synchronization between modules, in addition to the unification of clock signals, a trigger signal is also required to trigger each module to start working at the same time. The PXI-4472 is used as a slave card (SlaveDevice) to send a trigger signal from the motherboard card. The signal reaches each slave card through the star trigger bus (StarTrigger). The circuit design ensures that the star trigger line is transmitted to each module. The time is equal, the skew of the trigger signal is less than 1ns, and the delay between the main board and each slave board does not exceed 5ns. Using the highly integrated clock trigger feature of PXI, the synchronous data acquisition of multiple vibration and noise channels is completed with a high cost performance.

Taking a main board card and a slave board card as an example, the code for the above synchronization triggering work through LabVIEW programming is shown in Figure 3.

The big guy explained the measurement and control system (5), the design scheme of the wind power measurement and control system (the second part)

2. Embedded Controller

The gear box test standard requires vibration and noise signal acquisition and real-time frequency domain Fourier analysis to be performed every 15 minutes during the test. The frequency resolution of interest is 0.5Hz, the bandwidth is 20kHz, and the 16th spectral average is required. For vibration signals, frequency band energy is required. For calculation, the noise signal needs to be calculated by the equivalent sound pressure level. This requires that the time-domain vibration noise signal is collected for 2s at a sampling rate of 80kS/s for each calculation, and 16 times of continuous collection and calculation are performed. The program code of a real-time processing is shown in Figure 4.

In addition to the above-mentioned vibration and noise acquisition and calculation, the processor also needs to perform multiple tasks such as process execution, environmental parameter acquisition, motion control communication, and digital I/O communication, which places higher requirements on the speed and memory of the processor. In addition, since the system needs to monitor the DC governor and the running state of the motor in real time, the controller must run continuously and stably, and has the ability to make emergency decisions on dangerous situations. Therefore, in order to ensure the time accuracy and performance reliability of the controller, the PXI-8106 embedded The real-time operating system runs on the controller, which is responsible for time-critical tasks such as process execution, data acquisition, and data real-time processing. It uses the TCP/IP protocol to communicate with the upper monitoring terminal industrial computer through the Gigabit Ethernet card, and configures, displays, stores, and reports. And non-real-time tasks such as query are transferred to the monitoring terminal program for processing.

If the monitoring terminal application program and the embedded real-time controller program are merged into a PC running the Windows operating system (the configuration is the same as that of the PXI-8106), the acquisition program and the calculation code shown in Figure 4 need to run 16 consecutive times. 4 to 5 minutes. During the calculation process, the resources are basically exhausted, and sometimes memory overflow occurs. The system application program can run independently in the real-time controller to ensure the priority execution of high-priority data acquisition and control tasks, and the real-time operating system does not require peripheral devices, a single-task running platform, and fewer background programs and services. In such a system design Under the guarantee, the memory and CPU resources are divided. The above code only needs 40s to execute 16 times, and the time accuracy and stability of the application are improved. In addition, because the application running on the real-time operating system uses multi-threading technology programming, and monitoring The communication of the terminal is basically not affected during the calculation execution process, and the performance of the system is greatly improved.

3. Signal electrical connector

The data acquisition and control part of the system is designed based on the PXI bus, which has the characteristics of high integration and modularization of the equipment and the flexibility and expansibility that it brings. In order to ensure the scalability, replaceability, and maintenance simplicity of the entire system, a signal electrical connector with strong scalability and reliability must be provided between the test system and the field sensor actuator.

In order to achieve a reliable connection between the test system resources and the test signal of the DUT, the signal electrical connector device must have the power capacity, signal frequency and service life required by the test, and the additional signal attenuation and interference introduced by the electrical connector must be controlled within within the range allowed by the test.

The system is designed with a mixed module connector to realize the electrical connection to the field. The signals are divided into three groups of electrical connections: environmental parameters, digital I/O signals, and noise and vibration signals. They are packaged in DIN standard shells and aluminum frames, and the interface uses wire spring connectors. The number of times of plugging and unplugging is more than 20,000 times, and it has the advantages of strong modular scalability, small contact resistance, large load current, good seismic performance and light plugging and unplugging force. Use high-quality, high-temperature shielded cables for connection.

The Links:   LM151X05-A3 LM215WF3-SDB1

Bookmark the permalink.

Comments are closed.