China
Africa
Explore chapters and articles related to this topic
Suspension systems
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
The Citroën Hydractive principle has been subject to continuous development and in the current third generation version, introduced in 2001, an electronically controlled variable ride height function has been incorporated in the system. This is accomplished by varying the amount of fluid in the hydraulic levelling circuitry, depending on car speed and road surface conditions, and is signalled by fast-acting electronic sensors. The benefits of a variable ride height system have previously been explained in connection with air suspension (Section 23.4). Provision is also made for an overriding push-button control of the system by the driver, which caters for the extremes of a high position to facilitate wheel changing and a low position for coupling a caravan.
VTT – a virtual test truck for modern simulation tasks
Published in Vehicle System Dynamics, 2021
Georg Rill, Florian Bauer, Mathias Kirchbeck
The axles of commercial on-road trucks are often suspended by air springs. Besides a ride-cushioning effect an air suspension provides a level control that maintains the steady-state ride height regardless of load. The air springs of two or three rear axles are usually coupled to provide a waking-beam like performance of the axle combination. Figure 5 shows two air springs that are coupled by a pipe.Each air spring is characterised by the polytropic exponent κ, the effective cross-section area , the excessive pressure in design position , an the volume in design position. The polytropic state change delivers The time derivative of the transfer volume is given by where denotes the cross-section of the connecting pipe and is the velocity of the air flow. According to Bernoulli the flow dynamics is defined by where is assumed, λ denotes the pipe friction factor, ℓ and d describe the length and the diameter of the connecting pipe, ξ is a pressure loss factor, and represents the laminar pressure loss at the reference flow velocity . For the sake of simplicity is set in this approach. Combining (4) with (5) finally delivers a first-order differential equation for the transfer volume where collects all turbulent losses.