Abstract: A test system and a method includes applying a test drive signal to a physical test rig having a compliant actuator assembly for imparting loads to a test specimen. An actual response signal of the physical test rig and the test specimen to the test drive signal is obtained and an error as a function of the actual response signal and a selected response signal is calculated. If the error has not reached a selected threshold a new drive signal based on the error and a relaxation gain factor is obtained. The new drive signal is obtained and applied until the error reaches the selected threshold.

Abstract: A loading assembly used in a vehicle spindle test fixture includes a wheel adapter housing that is mountable to a vehicle spindle. A pair of vertical struts are provided. Each vertical strut is joined to the wheel adapter housing at spaced-apart first pivot connections. A bell crank is coupled to each end of the vertical struts at spaced-apart second pivot connections. An actuator is pivotally coupled to the bell crank at a third pivot connection. The location of the second pivot connections relative to the third pivot connection approximates the location of the first pivot connections relative to the spindle axis.

Abstract: A brake torque loading linkage for vehicle spindle test fixtures permits applying a brake torque load while other loads are being applied, particularly vertical loading, where substantial movement is encountered, without requiring substantial compensation. The brake torque loading actuator is mounted to move with the vertical loading linkage. The reference for the brake torque is thus on the linkage that moves for applying the vertical load and there is no need to compensate for vertical movements of the spindle being tested when applying the brake torque. The linkage utilized comprises a bell crank loading linkage that is used for applying the torque to a spindle and in particular is useful for testing spindles mounted on pivoting swing arm mountings.