Development of a Four Wheel Steering System for Cars

DEVELOPMENT OF FOUR WHEEL STEERING SYSTEM FOR A CAR
K. Lohith1, Dr. S. R. Shankapal2, M. H. Monish Gowda3 1- M. Sc. [Engg.] Student, 2-President, 3- Assistant professor Automotive and Aeronautical Engineering Department, M. S. Ramaiah School of Advanced Studies, Bangalore – 58.

Abstract
Production cars are designed to understeer and rarely do they oversteer. If a car could automatically compensate for an understeer/oversteer problem, the driver would enjoy nearly neutral steering under varying operating conditions. Four-wheel steering is a serious effort on the part of automotive design engineers to provide near-neutral steering. Also in situations like low speed cornering, vehicle parking and driving in city conditions with heavy traffic in tight spaces, driving would be very difficult due to vehicle’s larger wheelbase and track width. Hence there is a requirement of a mechanism which result in less turning radius and it can be achieved by implementing four wheel steering mechanism instead of regular two wheel steering. In this project Maruti Suzuki 800 is considered as a benchmark vehicle. The main aim of this project is to turn the rear wheels out of phase to the front wheels. In order to achieve this, a mechanism which consists of two bevel gears and intermediate shaft which transmit 100% torque as well turns rear wheels in out of phase was developed. The mechanism was modelled using CATIA and the motion simulation was done using ADAMS. A physical prototype was realised. The prototype was tested for its cornering ability through constant radius test and was found 50% reduction in turning radius and the vehicle was operated at low speed of 10 kmph. Nomenclature L R a2 δif δof δir δif R1 Wf W C1 C2 wf wr δ δi δo Wheelbase (mm) Turning radius (mm) Distance of CG from rear axle (mm) Inner angle of front tire (degree) Outer angle of front tire (degree) Inner angle of rear tire (degree) Outer angle of rear tire (degree) Distance between instantaneous centre and the

References: Fig. 19 Constant radius test conducted for four wheel steer. 6.7 Comparison [1] Unknown, Four wheel steering report, http://www.scribd.com/doc/34677964/FourWheel-Steering-report, Retrived on 13th Sep 2012. [2] Unknown, Four wheel steering, http://www.wisegeek.com/what-is-four-wheelsteering.htm, Retrived on 13th Sep 2012. [3] Unknown, Four wheel steering, http://what-whenhow.com/automobile/four-wheel-steering-4wsautomobile/, Retrived on 14th Sep 2012. [4] “Honda Prelude Si 4WS: It Will Never Steer You Wrong,” Car and Driver, Vol. 33, No. 2, pps. 4045, August 1987. [5] Sano s et al, “Operational and design features of the steer angle dependent four wheel steering system.” 11th International conference on Experimental safety vehicles, Washington D C 1988, 5P. [6] Jack Erjavec., Automotive Technology, A System Approach, 5th Edition, 2010. [7] Farrokhi, Four wheel steering, http://www.iust.ac.ir/files/ee/farrokhi_0a5f0/journa l_papers/j13.pdf, Retrived on 20th Oct 2012. [8] M. Abe, "Vehicle Dynamics and Control for Improving Handling and Active Safety: From Four-Wheel-Steering to Direct Yaw Moment Control," in Proc. Institution of Mechanical Engineers, Part K, Journal of Milti-body Dynamics, vol. 213, no. 4, 1999. [9] Lee, A.Y., “Vehicle Stability Augmentation Systems Designs for Four Wheel Steering Vehicles,” ASME Journal of Dynamical Systems, Measurements and Control, Vol. 112, No. 3, pps. 489-495, September 1990. [10] four wheel steering system for future International Journals tjprc.org/download.php?fname=223...5...%20FOUR%20%20... [11] Nalecz A G and Bindemann A C, “ Analysis of the dynamic response of four wheel steering vehicles at high speed.” International journal of vehicle design, Vol 9, No 2, 1988, pp. 179-202. [12] Unkown, Maruti Suzuki, http://www.carfolio/maruti-suzuki-800.htm, Retrived on 4th Nov 2012. [13] Reza.N.Jazar., Vehicle Dynamics, Theory and applications, 2008. Fig. 20 Comparison circle of 2WS and 4WS Table 2. Comparison for two wheel steer and four wheel steer Turning radius By calculation By experiment Four wheel steer 2.59 m 2.85 m Two wheel steer 4.4 m 5.75 m Table 2 gives the comparison between the turning radius for two wheel steer and four wheel steer by calculation and experiment. By calculation we can conclude that there is 41.13 % reduction in turning radius and by experiment it’s 50.43%. 7. CONCLUSION By the analytical and experimental analysis and results we conclude that; • • Four wheel steering concept was generated The four wheel concept was simulated in ADAMS to check for functionality of mechanism SAS TECH Journal 97 Volume 12, Issue 1, April 2013