A 4-poster or four poster is an automotive test system specifically designed for the testing of
vehicle
A vehicle () is a machine designed for self-propulsion, usually to transport people, cargo, or both. The term "vehicle" typically refers to land vehicles such as human-powered land vehicle, human-powered vehicles (e.g. bicycles, tricycles, velo ...
s.
These test systems consist of 4
hydraulic actuator
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment ( engineering vehicles ...
s on top of which the wheels of the vehicle are placed. Movements of the
actuator
An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an ...
s simulate the road surface and forces exerted by the road on the wheels. The movements of the system are tightly controlled by a
digital test controller. During the research phase of a vehicle, a 4-poster system is used to test newly designed
suspension
Suspension or suspended may refer to:
Science and engineering
* Car suspension
* Cell suspension or suspension culture, in biology
* Guarded suspension, a software design pattern in concurrent programming suspending a method call and the calling ...
systems and their durability. In production, 4-poster systems are typically used to test every vehicle at the end of the production line on squeak and rattle, which is a check to make sure the vehicle doesn't have any loose parts. Multiple kinds of tests are possible: sine test (sweep in frequency), simple wave form on each actuator, open loop test (driven by an external tension signal). There is also a particular testing method called ICS control, which allows to reproduce on a car an actual service environment, starting from those data coming from the outdoor acquisition sessions.
See also
*
7 post shaker
The 7 post shaker is a piece of test equipment used to perform technical analysis on race cars. By applying shaking forces the shaker can emulate banking loads, lateral load transfer, longitudinal weight transfer and ride height sensitive downfor ...
References
Automotive engineering
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