Vibration Image Acquisition Using Timestamp Remapping
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Solution Overview
Problem
Conventional vibration testing systems require expensive high-speed cameras and significant time and effort due to the lack of synchronization between shaker table vibrations and camera exposure triggers, leading to accuracy issues with low-speed cameras when using under-sampling techniques.
Innovation Solution
A shaker test apparatus that employs timestamping and remapping of image sequences from low-speed cameras, allowing for synchronized triggering and accurate reconstruction of vibration data even at higher excitation frequencies, using a shaker table, vibration controller, cameras, trigger signal controller, and processing computer to reorder image frames based on timestamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-speed cameras are used to ensure adequate image sampling rate, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
A timestamping mechanism is introduced as an intermediary between the camera and the vibration excitation system. The timestamp records the exact capture time of each image frame, enabling post-processing synchronization with the vibration signal. This intermediary allows low-speed cameras to be used effectively by decoupling the camera's native frame rate from the required sampling rate for accurate vibration measurement.
2Device complexity
If low-speed cameras are used with under-sampling technique, then device complexity is reduced, but measurement precision deteriorates due to jitter
Solution Approach 1:
The system implements feedback by recording timestamps for each captured image frame and using these timestamps during post-processing to determine the exact temporal position of each frame within the vibration cycle. This feedback mechanism compensates for jitter in the camera's frame capture timing, allowing accurate reconstruction of the vibration signal even when using low-speed cameras with under-sampling.
3Measurement precision
If synchronized triggering is implemented, then measurement precision is improved, but loss of time increases due to complex coordination
Solution Approach 1:
The system performs preliminary action by recording timestamps for each captured image frame during the acquisition phase. This preliminary time-stamping action enables flexible post-processing where frames can be sorted and synchronized with the vibration signal without requiring complex real-time coordination during the actual test execution, thereby reducing setup time while maintaining measurement precision.
Data Source
AI summary
A shaker test apparatus is provided along with a method of collecting and processing images, wherein a shaker table is driving the device under test by a vibration controller at a known vibration frequency and period, wherein a device under test obtains a steady-state vibration characteristic of that excitation frequency when mounted on the shaker table. While the device under test is being excited, a trigger signal controller triggers a camera to capture a series of still image frames at a regular sampling frequency that is less than the vibration frequency (under-sampling), and a timer associated with the camera records a timestamp of an image capture time for each image frame. A computer processor uses the timestamps to remap the order of the image frames, shifting each frame's capture time backwards by a specified multiple of vibration periods in order to correctly represent a single vibration period beginning with an earliest captured image.