The GMW14201 specification from General Motors Corporation is a rotational vibration measurement test performed on the inside and outside of rearview mirrors. It measures the rotational response of a mirror when subjected to vertical input vibration.
Accelerometers are placed on the reflective surface of an inside or outside rearview mirror in a triangular pattern. The test engineers then mount the mirror to a rigid fixture mounted to the head of a shaker. The shaker uses the random vibration profile specified by GMW14201 to shake the mirror vertically.
Random Test in VibrationVIEW
VibrationVIEW includes a form for the user to enter the distance between the accelerometers for later calculation. During the test, VibrationVIEW records the accelerometers’ input and response values at a high sample rate. Recording waveform data requires the RecorderVIEW option on the VR controller.
After the test is complete, a MATLAB script computes the remaining calculations. The accelerometers are arranged so that the difference in acceleration between two accelerometers divided by the distance between them equates to the angular acceleration between them.
The MATLAB script outputs a series of graphs: Transmissibility vs. Frequency and Rotation vs. Frequency.
Multi-Axis Rotational Control
Control angular or rotational acceleration with multi-axis rotational control, which enables 360-degree movement with plate and tilt adjustment.
VR recommends the following software and hardware for conducting the GMW14201 specification.
- GMW14201 Specification from General Motors Corporation
- VR9500 or VR10500 Vibration Controller
- Random Test Module
- RecorderVIEW waveform recording option
- GMW14201 MATLAB script
- MATLAB 7(r14) or newer
- Three light-weight single-axis matched 100 mV/g accelerometers with low transverse sensitivity
- One shaker control accelerometer
- A shaker with fixturing capable of running the specification
Random Test Module
A random vibration test is a realistic method of bringing a product to failure. A random test excites all frequencies in a defined spectrum at any given time. By exciting all the resonances of the device under test, engineers can determine the interaction between multiple resonances.
With up to 26,000 lines of control, the VibrationVIEW Random test module provides the highest possible control in an easy-to-use format. Analyze random data with a comprehensive suite of graph display options or generate a test from recorded data with our advanced test development options.
With RecorderVIEW, there’s no need to buy extra equipment to collect data. The VR9500 and VR10500 controller hardware can connect to a notebook PC and function as a portable data acquisition system. Record field acceleration measurements directly to the PC’s hard drive. Plus, access all the features of the VR9500/VR10500 including a low noise floor, 24-bit resolution inputs, built-in accelerometer constant current supply, TEDS transducer interface, and a unique DC offset that allows a measurement to true DC with constant current type accelerometers.