Dynamic Test Rig
The Wollongong University Civil Engineering department has an ongoing research project to investigate railway line foundations. As part of this project the University recently purchased a low cost dynamic actuator for use in a test rig of their own design. The actuator is a standard design developed by CMA, and includes the following components:-
- 200 Bar rated servo actuator, complete with position feedback transducer, servo valve, pressure and tank line accumulators, and isolation valves.
- Control System based upon CMA’s FATC real time hydraulic controller. The control system provides both position and force control, following either oscillatory (wave) or ramped motion.
- PC based operator interface allowing full control over the actuator, graphing and data-logging.
The cost of the system has been kept low by using a conventional NFPA tie-rod type cylinder as the starting point for the actuator, and by using a standard CMA FATController running software specifically designed for test machine applications.
Specifications:
- Dynamic wave generator operating from 0.1 to 100 Hz.
- 100mm stroke and up to 40kN dynamic load.
- 35 Hz @ +/-2.5mm typical max position oscillation.
- 80Hz @ 0-30kN & +/-0.25mm force oscillation.
- Slow position ramping to .01mm/sec for conventional stress/strain testing.
- Slow force ramping to 1N/sec.
- Built-in pressure and tank line accumulators allowing remote oil supply without pipework cavitation.
- Programmable range position and force testpoints for external data logging.
- Cycle counter.
Adaptive Control
A feature of particular value is CMA’s adaptive control used to ensure optimum accuracy during wave based motion. This feature allows the system to self-compensate for attentuation and offsetting at high dynamic test specifications. Adaptive control allows the operators to focus on the test, rather than having to spend time and effort tuning the system for different loads and test specifications.
Operator Interface
A simple and intuitive PC operator interface is provided that allows the students to move the actuator for configuration of the test rig, and to specify and run tests. Self-help information on each page of the interfacing program explains the variables and modes of operation available. Calibration and accuracy testing of the system are also quickly and easily carried out from the PC interface.