A suspension supplier took the customization route to obtain a comprehensive apparatus for testing and verifying in-development technology for passenger vehicles.
"The typical shock absorber dynamometer rig is capable of only displacing the damper. In our active air systems, the damper and the variable spring rate air suspension is a single unit. Our system incorporates the controls to make adjustments to the air system pressures on-the-fly while evaluating the damper," explained Brian Saylor, Manager of ArvinMeritor's Vehicle Dynamics Technology Center.
Because ArvinMeritor's Active Air Suspension (AAS) system is unlike anything on the market today, "there has never been anything designed to test and develop this sort of product," said Saylor, who adds that the test rig's custom controls "allow us to test an infinitely variable spring rate easily."
A component test bench can run the AAS module without the presence of the electronic control unit, and it can control pressures within the air spring and piston based on force and pressure. An external input into the spring module can be generated via load or displacement.
"The test bench and supporting equipment is capable of measuring the response time of all components in the system and the system itself. Response rates are as fast as 80 ms for full inflation, and the response rate for partial adjustments is even quicker. In addition, batch tests can be run to generate Design of Experiments data," noted Jeff Lloyd, Advanced Chassis Engineering Team Leader for ArvinMeritor.
Testing and development work on the AAS system has been under way for about two years. End of 2008 testing involves "validating durability, all-weather performance, and NVH performance on select vehicle-specific applications to meet the start of production requirement of 2011," said Lloyd.
ArvinMeritor also developed a customized testing rig for its adaptive damping technology. "For valve development, we wanted a flow bench that could be operated bi-directionally so we could evaluate compression and rebound in the same test setup. It was important to be able to measure accurately high flow rates up to 80 L/min and low flow rates less than 2 L/min. In addition, we wanted the ability to have servo-control over the valve environment via pressure and flow control so we could properly characterize and evaluate the valve performance over a wide range of parameters," explained Jim Keane, Advanced Chassis Engineering Team Leader for ArvinMeritor.
The supplier's Adaptive Damping technology goes into production in early 2009 for an off-highway seat suspension application. Testing for adaptive damping, AAS, and other advanced products is done at ArvinMeritor's Vehicle Dynamics Technology Center in Troy, MI. "We look at our testing capabilities as an advantage over other companies," said Saylor.
Developing customized test rigs for advanced products is definitely common at ArvinMeritor. "For products that are unique to the testing environment, we will start with a rig that is close and make the necessary modifications. If nothing is close, then we can design the test rig 100% to fit our needs," said Saylor.