Active front steering
Upcoming SlideShare
Loading in...5
×
 

Active front steering

on

  • 726 views

 

Statistics

Views

Total Views
726
Views on SlideShare
726
Embed Views
0

Actions

Likes
0
Downloads
5
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Active front steering Active front steering Document Transcript

  • Active front steeringBasic systemActive front steering (AFS) is technology designed to make the front wheels turn a certainnumber of degrees in accordance with the speed of the vehicle. It was originally developedby Bavarian Motor Works (BMW) in 2003 and the ZF Lenksysteme method used is prettymuch the same used in the AFS of other cars. The slower the speed, the greater number ofdegrees the wheels are turned per degree of movement of the steering wheel; more frontwheel turning is required than at higher speeds. This prevents over and under-steering, as inparking situations or high speed highway driving, when the former involves more turning ofthe wheels and the latter does not. One stark example is locking the steering wheel afterparking. It should take less than half a turn. In normal vehicles, it can take more than twoturns of the steering wheel to lock, as opposed to AFS, where fewer than two turns is needed.Sensors located in the steering column and detecting steering angle recognize where thedriver wants to go and activate the AFS. If the electronics shuts down, the planetary gear inthe differential controlled by the AFS is locked, and fixed ratio steering takes over. In theevent of a planetary gear problem conventional steering then takes over, as there is a secondshaft running from the steering rack running from the to the planetary gear assembly.A typical AFS looks like the following: [1] -1--------------------------------------------------------------------------------------------------------------------------------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • with a detailed configuration being: [2] 1. Main gear 2. Servotronic valve 3. AFS actuator including the synchronous motor 4. Upper position gear system 5. AFS electronic control system with the AFS Electronic Control Unit (ECU) 6. Motor angle sensor 7. Electromagnetic locking unit 8. Pinion angle sensor 9. Steering pump 10. Oil reservoir with filter 11. HosesOther: Respective electrical connections of the ECU and the required software modules -2--------------------------------------------------------------------------------------------------------------------------------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • The typical motor and electromagnetic locking units is:and the AFS actuator: [3]Active front steering and driveline dynamics functionsTwo methods exist for steering adjustment, the ZF Lenksysteme approach and the Ackermanmethod. With the ZF Lenksysteme the variable steering ratio (VSR) is the ratio between thesteering wheel angle and the average road wheel angle and this is changed in accordancewith the driving environment, as a function of such factors as velocity. The VSR also dependsupon the pinion gear angles, or the rack displacement, it being less at higher speeds thanlower ones. This means more precision for smaller steering angles and reduced steeringeffort at larger steering angles [4]. This system has steering lead function (SLF) that adapts -3--------------------------------------------------------------------------------------------------------------------------------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • the steering response to signals about the vehicle situation, such as wheel angular velocitythat determines the desired SLF. The whole system has a feedback system, where thedrivers actions help control AFS actuator motion and the system response is fed back to thedriver.The Ackerman method adjusts the steering angle by computing the difference between areference yaw rate (movement around the vehicles vertical axis) and actual yaw rate.Steering ability depends upon vehicle mass, road conditions, and velocity, among otherfactors, so better control is achieved by controlling the yaw rate [5].Most systems use the ZF Lenksysteme. Want to learn more about the latest technologies and developments in braking systems? Visit our download centre for more articles, whitepapers and interviews: http://bit.ly/steering-articlesReferences (Subject is indicated by URL – accessed 9 July 2011)[1] Willy Klier, Gerd Reimann and Wolfgang Reinelt, Concept and Functionality of the ActiveFront Steering System, ZF Lenksysteme GmbH, Schwäbisch Gmünd, Germany, No. 2004-21-0073, 2003 SAE International (2003), pp. 1-3[2] Ibid.[3] Ibid.[4] Ibid., p. 3[5] http://resources.metapress.com/pdf-preview.axd?code=22113q1143813182&size=largest -4--------------------------------------------------------------------------------------------------------------------------------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de