Abstract : This paper introduces a control system and operation process for damping testing of in-use Ag shock absorbers using frequency response function fitting technology. Related issues are analyzed and discussed from the aspects of testing equipment and requirements, as well as speed control unit and control program. Keywords : Automotive shock absorber; frequency converter; frequency response function; damping ratio. According to the EUSAMA standard, the performance of automotive suspension is evaluated using the minimum adhesion percentage (Amin). Since shock absorber damping is a major factor affecting suspension performance, Amin is often used to evaluate the performance of in-use automotive shock absorbers. However, the value of Amin is also related to many factors such as suspension mass, tire stiffness, and dynamic load. Therefore, by testing the damping of shock absorbers, a more comprehensive and accurate evaluation of the performance of in-use automotive shock absorbers can be made. 1. Test Apparatus and Requirements As mentioned in the text, the structural parameters [m1, m2, K1, K2] and damper damping coefficient c1 of the automotive suspension system can be obtained using frequency response function fitting technology. This method requires establishing a system to excite the automotive suspension and measuring the dynamic load Δfd(t) and amplitude x3(t) at different excitation frequencies wk. Then, the measured value of the frequency response function Gpk (P is the number of discrete points within 2 periods) is obtained: [b][align=center]For details, please click: In-use Automotive Shock Absorber Damping Test Method[/align][/b]