Refine Your Search

Search Results

Viewing 1 to 6 of 6
Journal Article

The Aerodynamics of a Small Car Overtaking a Truck

The influence of a large truck on the aerodynamics of a small passenger car in an overtaking manoeuvre on the motorway was considered, many years ago, during the 1970's, to be a potential problem for the vehicle aerodynamicist. The concern never became significant as vehicle architecture evolved and car weights increased. The current drive for improved fuel economy is advocating that a considerable reduction in vehicle mass is desirable and therefore it may be time to readdress the significance of the truck passing manoeuvre. A quasi-steady experiment has been undertaken at small model scale to examine the aerodynamic characteristics of a small car in proximity to a large truck. Measurements at yaw were included to crudely simulate the effects of a crosswind. The wind tunnel data is presented and the limitations of the experimental procedure are discussed.
Technical Paper

Preliminary Investigation of the Influence of a Ground-Plane Boundary Layer on the Aerodynamic Characteristics of Road Vehicle Models Tested Over a Fixed Ground

Results from a series of experimental measurements are presented in order to investigate the influence of the ground-plane boundary layer on the overall characteristics of a scale model road vehicle. The wind tunnel model is a generic bluff body which has a streamlined forebody, simple wheel representation and interchangeable rear end sections. The aerodynamic forces and moments were measured via an external 3-component balance at a free stream velocity of 24 m/s. corresponding to Reynolds number of 5.5 × 105 based on model length, over a range of ride heights and yaw angles. The ground plane boundary layer thickness was varied artificially. The influence of wheels and underbody roughness were also investigated.
Journal Article

New Slip Control System Considering Actuator Dynamics

A new control strategy for wheel slip control, considering the complete dynamics of the electro-hydraulic brake (EHB) system, is developed and experimentally validated in Cranfield University's HiL system. The control system is based on closed loop shaping Youla-parameterization method. The plant model is linearized about the nominal operating point, a Youla parameter is defined for all stabilizing feedback controller and control performance is achieved by employing closed loop shaping technique. The stability and performance of the controller are investigated in frequency and time domain, and verified by experiments using real EHB smart actuator fitted into the HiL system with driver in the loop.
Technical Paper

Millimetre-Wave Automotive Radar Advance Path Measurement

Millimetre wave radar sensors are being actively developed for automotive applications including Intelligent Cruise Control (ICC), Collision Warning (CW), and Collision Avoidance (CA). Knowledge of the road geometry is of fundamental importance to these future intelligent automotive systems. The interest in such systems is evidenced by manufacturers now starting to incorporate radars in production luxury vehicles. Determination of the road geometry, day and night, under all weather conditions, is a challenging problem requiring both fundamental research and systems studies. Current automotive radar systems rely heavily on the use of extrapolating yaw rate data generated within the vehicle to produce a prediction of the path of the road ahead. This use of historical data is only satisfactory if the road trajectory is uniform. Sudden discontinuities in the path, such as bends, cause this method of path prediction to produce significant errors.
Technical Paper

Comparing Static and Dynamic Testing Techniques for the Crosswind Sensitivity of Road Vehicles

An accurate simulation of a ground vehicle interacting with a crosswind gust can be achieved by using a moving model mounted on a track such that it can traverse the working section of a conventional atmospheric boundary layer wind tunnel. This paper will briefly describe the facility that is being developed at Cranfield University and detail comparisons between static and dynamic data from tests on three basic model configurations. Under the same nominal wind input, data from static tests compares well with that from dynamic tests at yaw angles below 15°. At higher yaw angles, after the onset of “large scale” separation, the dynamic values of the forces and moments become larger than the static values.
Technical Paper

Assessing the Effects of Shear and Turbulence During the Dynamic Testing of the Crosswind Sensitivity of Road Vehicles

With increasing speeds and the anticipated reduction in weight of modern cars, the issue of crosswind sensitivity is becoming increasingly important. In a previous paper by the same authors, the normal method of testing such aerodynamic characteristics at model scale, using static models at yaw to the freestream, was compared with dynamic testing, in which the model is propelled across a ‘gust’ simulated by a wind tunnel. A direct comparison using a similar gust profile for both static and dynamic tests was made with the conclusion that the simple static test technique was underestimating the true transient loads. Further tests have been carried out, on a generic squareback (or estate) model, during which the effect of varying both the vertical velocity profile and the turbulence intensity within the gust was considered.