Introduction
One of our customers — National Institutes for Quantum and Radiological Science and Technology (QST) — is a set of integrated research institutions involved in studies of quantum science and technology. They analyze the effect of radiation on humans, radiation emergency medicine, and the medical use of radiation. QST utilizes the most advanced technologies and tools in the research process in its labs and institutes.
Requirements
Part of the innovative QST research and development groups is currently engaged in designing a field remote control robot. The robot, among other applications, will be involved in maintenance and repair of a nuclear plant.
The conditions of operation may be rather extreme, so extensive testing is very important in production of such a sophisticated device.
Solutions
The QST ‘s engineers provided a whole set of necessary testing procedures for checking the reliability, stability, durability of their robots.
For these purposes they applied vibration control system RL-C21 by RULA.
They used not only the standard control by accelerometers, but also displacement and velocity control to monitor the object under test all along the required frequency range. Besides, an important part of testing is resonance search and tracking, which will be described in the next blocks.
Image: Resonance search and tracking testing in RSTD software
Resonance search
There are 3 resonance search methods: transmissibility, first transmissibility derivative and Q-factor. The QST ‘s engineers used the last two.
The first transmissibility derivative is calculated numerically, any change of derivative sign from plus to minus is considered a resonance.
Q-factor is calculated as the ratio of the center frequency of the resonance to its half-power bandwidth and determines how sharp the resonance is, and, therefore, how much damage it can do.
Image: Transmissibility line and derivative lines before and after the resonance
Resonance tracking
Also QST's engeneers used phase as the resonance tracking method. The software starts at the resonance frequency and calculates the difference between the current and demanded phase. If the difference is less than the allowed accuracy, the software holds the frequency, and starts dwelling until the point with the appropriate phase is found. The Transmissibility vs Phase graph allows the user to asses how the resonance is tracked.
Image: Transmissibility vs. Phase
Results
With the help of the RL-C21 controllers, the QST engineers detected a 31,3 Hz resonant frequency in the structure and changed the construction of their Blanket Remote Handling System. After that the resonance disappeared. The robot can now be operated.
