The Quarter Vehicle serves for the testing of active-suspension control algorithms. The aim of the control loop is to compensate road undulations and other disturbances, so that the driver of the vehicle notices as little pitch and rolling motion as possible. The laboratory model consists of three masses, which are vertically displaceable. The top mass (blue) represents the quarter vehicle body, which is connected by two springs with the middle mass, the "wheel" of the car (red). The active suspension mechanism is placed between vehicle mass and wheel mass and consists of a DC-motor. The middle mass is again linked by two springs to the lowest mass (grey) which represents the street. It can be shifted by a DC motor to simulate different road profiles.