Abstract
Keywords - Automotive, Suspension, Shock Absorbers Tester, Parameter Identification,
Diagnostics.
Abstract - The automotive suspension system plays a critical role in determining the contact forces between tires and road. The suspension is also responsible for isolating the sprung mass from the terrain irregularities, to provide comfortable conditions to the occupants. Therefore, any deficiency on a component of the suspension system can significantly impact the active safety, in addition to decrease the sensation of comfort of the passengers.
Dynamic simulation is a common tool to test performances of vehicles in real emergency situations, since the high difficulty to program and carry out such maneuvers. Additionally, simulation permits to assess the influence of several design and operative parameters on its active safety. The low success rates of accurate simulation studies regarding the performances of vehicles in use are due manly to the unavailability of precise methods to identify the real dynamic characteristics of the components of automotives. The current suspension testers are not able to identify, and even less to quantify, the deterioration of shock absorbers. The only accurate method to comprehensive test these components involves their disassembly, which is a high cost and slow task.
This paper presents a method for comprehensive identification of the dynamic curves of automotive shock absorbers by testing them assembled on the suspension systems.
The method is based on the use of excitation plates to generate vertical vibration motions of controlled frequency and amplitude at the wheels, simulating the terrain irregularities. The vertical displacement of the plates, the wheels and the sprung mass at both sides of the car are collected. The outputs motions are used as inputs for a four degrees of freedom mathematical model of each axle of the vehicle. Finally, parameters accurate representing the dynamic characteristics of the shock absorbers are computed by using proper mathematical treatment of the 4 DOF model.
The test bench builds in excitation control equipment and a data acquisition system. Displacement signals from six reflective laser sensors are recorded and conditioned on real time. The data are used as inputs for the 4 DOF model of each axle of the vehicle.
The paper shows the success of the method by comparing the dynamic curves of automotive shock absorbers computed by the novel technique with the same curves computed by conventional shock absorber testers that involve their disassembly. The results are presented for several suspension systems with different types of shock absorbers.