Vandresen, M., Dutra, C., Almeida, M., and Sbardelotto, V., "Closed-Loop Control of a Bench Test Drive System for Automotive Shock Absorbers," SAE Technical Paper 2015-36-0288, 2015, doi:10.4271/2015-36-0288.
In a test bench for automotive shock absorbers the angular velocity of the "scotch yoke" mechanism must be constant, but the load (resulting from shock forces) varies in function of the speed, resulting in fluctuations in the speed along the course of the test, in function of the frequency variator response time controlling the electric motor. Employing a closed loop control system for the automotive shock absorber tests will result in tests with better quality at higher speeds and loads, thus enabling a better representation of the shock absorber condition. The paper presents the state of the art and research in development that is linked to closed loop control mechanisms. It is developed a control system which allows maintaining a constant test speed, independent of the load reaction to a range of shock absorber tested, as a function of resultant load. The mathematical modeling of the problem is presented, quantifying the magnitudes involved. The concepts will be tested on a prototype test bench and the test results with and without the developed control, will be presented for conventional shock absorbers and competition shock absorber with adjustments.