Simulating a Car suspension

Objectives

• Display two Simcenter Amesim systems

• Select a region of the sketch

• Use the copy/cut/paste

• Use of dynamic blocks

• Use a simple control system

Figure 41: Car suspension

The system you will use is shown in the figure above and is made up of three sub-systems:

• On the left: the system used on the Quarter car example

• In the center: the theoretical modification known as the sky-hook suspension

• On the right: the active damper system that approximates to the sky-hook

The idea of the sky-hook is to have an additional damper fixed to the body of the car and to a point in the sky vertically above the car. Naturally this arrangement is difficult to obtain! Note that the main damper experiences the velocity of the wheel and the velocity of the car body. In contrast the sky-hook damper only experiences the velocity of the car body.

In the active suspension approximation an important feature is the inclusion of two velocity sensors to provide the velocity of the wheel and the velocity of the car body. To replicate the main damper these signals are differenced and passed through a gain with a value corresponding to the main damper rating. For the sky-hook damper only the velocity of the car body is used and this is attached to a gain corresponding to the sky-hook damper rating. The two signals are combined and transmitted as forces to the mass of the car and of the wheel.

The road profile is defined in a single duty cycle submodel. The output is then duplicated and sent to the three sub-systems. This makes it 100% certain that the three subsystems are receiving the same signal!

To build the system you will copy the Quarter car system into a new system. To do this we need to display two systems simultaneously.