To develop an application for on-line monitoring and data logging of random vibrations experienced by automotive test components in a randomly vibrated test Bench and thus studying the effects of vibration on different automotive components.

The Real-Time 3-Dimensional Vibration monitoring system is based on National Instrument’s Compact Reconfigurable Input Output (cRIO). It uses the NI Compact RIO Reconfigurable Control & Acquisition System which is a small, rugged embedded platform with modular industrial grade I/O modules and the unprecedented flexibility of NI RIO™ technology.

The system acquires vibration signal from tri-axial IEPE (Integrated Electronics Piezo Electric) accelerometer. As the accelerometer used was tri-axial the vibration experienced by the component in all the three directions could be monitored and analyzed hence also called as 3-Dimensional vibration monitoring system. The acquired data is transferred to cRIO-9002 real time controller in blocks of 4096 data points where the vibration data is processed and logged. A serial operating terminal is provided that was connected to the RS232 port available on the cRIO real time controller. The Serial Operator Panel is used to start and stop the process as well as display the calculated real time parameters. It uses MODBUS protocol to communicate with the Real-Time Controller cRIO-9002, which provided the system self sufficiency making it a stand alone unit. Detailed Offline analysis of data was done after transferring the data from Real-Time Controller cRIO-9002 to Laptop using ftp (file transfer protocol).

The automotive component manufactured is subjected to random vibration to study the behavior of the component before the product is released.

The system will provide accurate Real-Time Analysis to Study the effect of vibrations on the component. The vibration analysis was previously done offline with very limited online monitoring and analysis provision. Hence the user had to work with small chunks of data repeatedly at pre-selected intervals missing crucial failure points. The storage of the test results for the entire duration of the test process facilitates easy Offline Analysis. Figure 1.0 shown below displays the functional modules used in the portable real time vibration monitoring system.

Software implementation can be divided into the following modules:

• Real Time Acquisition
• Real Time Floating point operation and data logging
• Offline Data Analysis

Upon receiving start signal from the serial terminal LCD display panel a check will be done to determine the space available in the compact flash of Real-Time Controller cRIO-9002. If the size is not sufficient an indication will be sent to the serial terminal LCD display so that the data can be copied to laptop/PC before continuing with the test. If the space is sufficient for logging then Acquisition will start. The cRIO-9233 samples voltage signal transmitted from the IEPE accelerometer and transfers the data to the Real-Time Controller cRIO-9002

Real-Time Floating-point operation including Logging

The Real-Time Floating point operations include determining RMS, Peakpegel value and FFT for each block of data consisting of 4096 data points. The peakpegel value is used to eliminate accidental peaks in the acquired vibration data this is determined using a proprietary algorithm. The RMS and Peak pegel values are logged throughout the entire duration of the test with a fixed interval of 5 minutes. The duration of test will be up to 150 Hours. The FFT is logged once during the first five minute interval, then during the last five minute interval and then according to user configured intermediate intervals. The user can configure the intermediate interval according to the run duration.

The calculated parameters RMS and Peakpegel value is also transmitted to the operator panel and updated every second. The operator can thus monitor the vibration level experienced by the component during run and determine if the vibration level is within expected limits.

Offline Analysis

The GUI provided on the Laptop allows the user to carry out offline analysis for already completed tests.

The sequence of operation is as mentioned below:

       1.  Select required test data
       2.  View Offline data
       3.  Generate Report

The main offline screen is shown in Figure 3.0 shown above. Here the FFT, Peak pegel and rms plot are displayed. FFT is displayed on plots shown on left side of the screen and peakpegel and rms are displayed on the plots shown on the right side of the screen.

There is provision to zoom each of the screens by double clicking on the required plots. The zoom screen is shown in figure 4.0 below. The zoom screen has provision to further zoom selected portion of the plot.

After selecting the required test data and viewing the waveform, an option is provided for the user to generate reports of the waveform viewed by clicking on the generate report button shown in screen 3.0 above.

The generated report contains information about the operator, component tested, the model number, serial number of accelerometer used, and the intended customer details along with the RMS, Peakpegel value and FFT plots of the component during the test duration.

Conclusion:

The portable real time vibration monitoring solution provided a customized and convenient means of doing vibration analysis compared to the costlier and bulkier vibration analyzers available in the market. It provided a reliable and rugged Standalone solution using the capability of NI RIO™ technology combined with the Flexibility of Lab VIEW. The system provided real time analysis of vibration thereby facilitating immediate corrective action in case of failure of component. It saved the user 6-8 hours per component that needed testing at 30% of the cost of available analyzers.