In automotive component stress testing applications, perfectly tuned hydraulic systems are often essential in providing reliable, repeatable results. One developer of special purpose machines for assembly, fabrication and testing of automobiles is Suyash Engineers & Automation Pvt. Ltd. (SEAPL) of Pune, India. They are a supplier to the Tata Motors Ltd. Engineering Research Center, a unit of Tata Motors, India's largest automobile manufacturer. The Engineering & Research Center deals with prototype development and testing activities.
SEAPL has used different controllers to operate their test systems over the years, from various local and foreign sources. Many of their test systems have used PCI, PXI, and PCIEcompatible interface hardware to connect with PCs running National Instruments’ LabVIEW software for data logging and analysis. The platform changes were necessary because the systems often provided less than satisfactory results. “We were facing problems like inaccuracy in position and load, sluggish response, the need for frequent re-tuning of PID parameters, complications in programming logic and so on,” said Sujay Wayse, SEAPL Managing Director.
A recent project gave them the opportunity to develop a new solution. SEAPL was asked to develop a system for testing leaf spring suspension assemblies to be used in a wide range of utility vehicles, from small trucks to heavy trucks. The system needed to perform fatigue/endurance testing of various springs under simulated road conditions in order to verify spring quality and provide the manufacturer with information on the component life cycles. To ensure that road conditions are being modeled exactly, load data was acquired during rigorous road testing and then the same loading is applied precisely to the suspension assemblies under test for a specified number of cycles.
The response of the spring force is logged to learn the component failure point, to measure hysteresis in deflection or load as the test progresses (which can be an early warning of impending component failure), and to also know the initial stiffness and change in stiffness after a certain number of cycles (which is also an indicator of component quality). Therefore, the system needed to not only apply a predetermined amount of force and count the cycles, but it also needed to be able to monitor precisely how the test specimen responds to the force. The tester does this by measuring the deflection of the spring that occurs each cycle, In light of the problems that SEAPL had with other hydraulic controllers, they sought out a new solution to control the hydraulics of the leaf spring tester. “We had a pretty good experience with a controller manufactured by Delta Computer Systems when we were working with a servo-hydraulic compression molding press in 2002,” said Sujay Wayse. “So we searched for Delta motion controllers on the internet and contacted the company to receive more information. ”The controller that they selected was an RMC75E twoaxis unit.