4569846498
Share Embed Flag
Download ePaper

4569846498

lollypop413
01.05.2017 Views

Modelling and assembly of the full vehicle 365 Translational joint to ground Steering rack part TRANS MOTION Steering motion inputs applied at the rack to ground translational joint Front suspension INPLANE TRANS MOTION Fig. 6.39 Front suspension steering ratio test model Toe out – road wheel steer (deg) – toe in 10.0 8.0 6.0 4.0 2.0 0.0 2.0 4.0 6.0 8.0 FRONT RIGHT SUSPENSION – STEERING RATIO TEST 100 mm rebound _ _ _ _ _ _ _ _ Static position _______________ 100 mm bump ___ ___ ___ ___ 10.0 150.0 90.0 30.0 30.0 90.0 150.0 180.0 120.0 60.0 0.0 60.0 120.0 180.0 Left turn – steering wheel angle (deg) – right turn Fig. 6.40 Results of steering ratio test for MSC.ADAMS front right suspension model In the following example the geometric ratio between the rotation of the steering column and the travel of the rack is already known, so it is possible to apply a motion input at the rack to ground joint that is equivalent to handwheel rotations either side of the straight ahead position. The jack part shown in Figure 6.39 can be used to set the suspension height during

366 Multibody Systems Approach to Vehicle Dynamics a steering test simulation. Typical output is shown in Figure 6.40 where the steering wheel angle is plotted on the x-axis and the road wheel angle is plotted on the y-axis. The three lines plotted represent the steering ratio test for the suspension in the static (initial model set up here), bump and rebound positions. Having decided on the suspension modelling strategy and how to manage the relationship between the handwheel rotation and steer change at the road wheels the steering inputs from the driver and the manoeuvre to be performed need to be considered. 6.12.3 Steering inputs for vehicle handling manoeuvres The modelling of steering inputs suggests for the first time some representation of the driver as part of the full vehicle system model. Any system can be considered to consist of three elements – the ‘plant’ (the item to be controlled), the input to the plant and the output from the plant (Figure 6.41). Inputs to the system (i.e. handwheel inputs) are referred to as ‘open loop’ or ‘closed loop’. An open loop steering input requires a time dependent rotation to be applied to the part representing a steering column or handwheel in the simulation model. In the absence of these bodies an equivalent translational input can be applied to the joint connecting a rack part to the vehicle body or chassis, assuming a suspension linkage modelling approach has been used. Examples will be given here where the time dependent motion is based on a predetermined function or equation to alter the steering inputs or a series of measured inputs from a vehicle on the proving ground. Any system can be considered to consist of three elements – the ‘plant’ (the item to be controlled), the input to the plant and the output from the plant (Figure 6.41). When a closed-loop controller is added to the system, its goal is to allow the input to the plant to be adjusted so as to produce the desired output. The desired output is referred to as the ‘reference’ state; a difference between the actual output and the reference is referred to as an ‘error’ state. The goal of the control system is to drive the error to zero. We can consider an example of a closed loop steering input that requires a torque to be applied to the handwheel or steering column such that the vehicle will follow a predetermined path during the simulation. A mechanism must be modelled to measure the deviation of the vehicle from the path and process this in a manner that feeds back to the applied steering torque. Error Input Reference Plant Output Gain Fig. 6.41 grey Feedback An open-loop system, in black, is a subset of a closed-loop system, in

Modelling and assembly of the full vehicle 365<br />

Translational joint<br />

to ground<br />

Steering rack<br />

part<br />

TRANS<br />

MOTION<br />

Steering motion inputs<br />

applied at the rack to<br />

ground translational joint<br />

Front<br />

suspension<br />

INPLANE<br />

TRANS<br />

MOTION<br />

Fig. 6.39<br />

Front suspension steering ratio test model<br />

Toe out – road wheel steer (deg) – toe in<br />

10.0<br />

8.0<br />

6.0<br />

4.0<br />

2.0<br />

0.0<br />

2.0<br />

4.0<br />

6.0<br />

8.0<br />

FRONT RIGHT SUSPENSION – STEERING RATIO TEST<br />

100 mm rebound<br />

_ _ _ _ _ _ _ _<br />

Static position _______________<br />

100 mm bump ___ ___ ___ ___<br />

10.0<br />

150.0 90.0 30.0 30.0 90.0 150.0<br />

180.0 120.0 60.0 0.0 60.0 120.0 180.0<br />

Left turn – steering wheel angle (deg) – right turn<br />

Fig. 6.40 Results of steering ratio test for MSC.ADAMS front right<br />

suspension model<br />

In the following example the geometric ratio between the rotation of the<br />

steering column and the travel of the rack is already known, so it is possible<br />

to apply a motion input at the rack to ground joint that is equivalent<br />

to handwheel rotations either side of the straight ahead position. The jack<br />

part shown in Figure 6.39 can be used to set the suspension height during

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!