SUMMARY Work relevant to the state of the art as regards passenger cars towing trailers is referenced and reviewed. Not only included is the very limited amount of work specifically dealing with passenger cars towing trailers, but also reviewed is the much larger body of work having a bearing on car-trailer systems. Topics included are aerodynamic forces, tire forces, the compliance concept, relevant work on vehicles without trailers, vehicles with trailers, and the role of the driver. The types of stability problems exhibited by car-trailer systems are discussed. The state of the art as regards ability to predict vehicle response to specific steering inputs is shown to be fairly advanced. Recent significant advances include the appearance of experimental data useful for validating theoretical models. However, the state of the art as regards definition of what constitute desirable handling characteristics is still at a primitive stage, largely because of a lack of understanding of the roles played by driv...

Handling Characteristics of Car-Trailer Systems; A State-of-the-Art Survey

SUMMARY This paper is concerned with the description of the open loop response of road vehicles to steering inputs. The important literature is reviewed for both steady state and transient response behaviour. The measures available for steady state response covering the whole range of lateral acceleration are discussed in detail, and sample measured data are presented. It is shown that the important quantities are the effective cornering stiffnesses of the front and rear tyres, how they are related, and how they vary with lateral acceleration. Transient response is only considered for the region of linear behaviour, where it is seen that a control theory approach is appropriate. A sample set of frequency response curves and step input responses are presented. It is concluded that satisfactory methods of measurement and description are available but that ‘desirable’ levels cannot yet be firmly specified.

Analysis and Interpretation of Steady-State and Transient Vehicle Response Measurements

State-of-the-Art-Vehicle Control and Road Holding

A seven-degree-of-freedom four-wheeled vehicle-handling model was developed for the purpose of investigating differences in the behaviours of front-wheel drive (FWD) and rear-wheel drive (RWD) vehicles. The handling treatments of the two cases have been studied on horizontal, sloping, and low-friction roads by applying step steer angle inputs. The difference between the behaviours of two layouts on a horizontal road was found to be small; it became pronounced on low-friction roads and severe on sloping roads. On horizontal roads, both layouts showed understeering behaviours up to the limit lateral accelerations. On sloping roads, however, the RWD vehicle tended to oversteer whereas the FWD vehicle remained in an understeering mode. The variation in the parameters showed that increasing the velocity or slope and decreasing the friction coefficient reveals the differences in the behaviours of the two layouts. A small perturbation technique was also applied to the model and the resulting linearized e...

Effect of Front-Wheel Drive or Rear-Wheel Drive on the Limit Handling Behaviour of Passenger Vehicles

THE NEED TO CONSIDER AUTOMOBILE DYNAMIC PROBLEMS, IN WHICH THE VEHICLE IS SUBJECT TO LONGITUDINAL AND LATERAL FORCES SIMULTANEOUSLY, IS OUTLINED. TETHERED TESTING IS PROPOSED AS A METHOD FOR MEASURING VEHICLE BEHAVIOR UNDER THESE CONDITIONS, AND UP TO THE MAXIMUM LATERAL FORCE THAT CAN BE OBTAINED. EQUIPMENT AND DATA ANALYSIS PROCEDURES ARE DESCRIBED. IT IS SHOWN THAT THE RATE OF CHANGE OF STEER ANGLE WITH LATERAL ACCELERATION AND THE RATE OF CHANGE OF STEER ANGLE WITH SLIP ANGLE ARE SUITABLE QUANTITIES FOR CHARACTERIZING VEHICLE STEADY STATE BEHAVIOR. RESULTS ARE PRESENTED IN TERMS OF THESE QUANTITIES TO ILLUSTRATE THE EFFECTS OF COMBINED CORNERING AND TRACTION FOR FRONT AND REAR WHEEL DRIVE VEHICLES. /HSL/

N F Barter

Papers

Traction effects while cornering