Mike Blundell

Dual extended Kalman filter for vehicle state and parameter estimation

The article demonstrates the implementation of a model-based vehicle estimator, which can be used for combined estimation of vehicle states and parameters. The estimator is realised using the dual extended Kalman filter (DEKF) technique, which makes use of two Kalman filters running in parallel, thus ‘splitting’ the state and parameter estimation problems. Note that the two problems cannot be entirely separated due to their inherent interdependencies. This technique provides several advantages, such as the possibility to switch off the parameter estimator, once a sufficiently good set of estimates has been obtained. The estimator is based on a four-wheel vehicle model with four degrees of freedom, which accommodates the dominant modes only, and is designed to make use of several interchangeable tyre models. The paper demonstrates the appropriateness of the DEKF. Results to date indicate that this is an effective approach, which is considered to be of potential benefit to the automotive industry.

The influence of rubber bush compliance on vehicle suspension movement

Abstract The work described in this paper forms part of a large study into aspects of suspension and tyre modelling on computer simulations of vehicle handling during the design process. The section of work included here aims to describe the influence of rubber bush compliance on changes in suspension geometry during vertical movement relative to the vehicle body. The emphasis is placed on the use of multibody systems analysis software to predict suspension characteristics and hence provide information for vehicle designers regarding the potential handling behaviour of a new vehicle design. Analysis work has been carried out to illustrate how joints in a vehicle suspension can be modelled and the issues involved where a detailed treatment of the rubber bush material is considered. The paper concludes by outlining the trend towards suspension designs which will increasingly depend on the behaviour of rubber bushes, and the implications for complex computer simulations such as vehicle handling and braking.

The modelling and simulation of vehicle handling Part 3: Tyre modelling:

Abstract This is the third in a series of four papers (Parts 1 to 4) looking at the application of computer-based analysis methods to model vehicles and simulate vehicle handling. The material contained in these papers is based on a study carried out in order to investigate the influence of suspension and tyre modelling on the outputs predicted by vehicle handling simulations. The papers deal with analysis methods, vehicle modelling (both in the previous Issue), tyre modelling and handling simulation. In this paper an overview of the use of tyre models in vehicle dynamics is provided. This is followed by a more detailed description of three tyre modelling approaches that can be used for handling simulations. A description is also provided of a computer-based modelling system where FORTRAN routines represent the various models and a computer model of a tyre test rig is used to interrogate the models and data before integrating these into a full vehicle handling simulation. The use of this system to compare the accuracy of the tyre models under consideration is also presented. The examples used to illustrate the concepts explained throughout this series of papers have been generated using the ADAMS (Automatic Dynamic Analysis of Mechanical Systems) program.

Kalman filter as a virtual sensor: applied to automotive stability systems

This paper demonstrates the use of an extended Kalman filter (KF) as a virtual sensor for non-measurable vehicle states and unknown vehicle parameters. The purpose of obtaining these values is to make them available within the control algorithms of the various automotive stability systems. Based on an extensive four-wheel vehicle model, an estimator is implemented on data from a test vehicle. Using available reference data, the suitability of the extended KF technique as a virtual sensor is demonstrated.

Effects of roof crush loading scenario upon body in white using topology optimisation

This paper investigates the effects of variations in modelling of roof crush loading scenarios upon topology and mass of a body in white (BIW) for a hybrid electric vehicle (HEV). These variations incorporated the proposed changes to the Federal Motor Vehicle Safety Standards (FMVSS) 216 standard. The base model used for the investigation in this paper was based upon a series of optimisation studies. The overall purpose was to minimise the BIW mass of an HEV subjected to multiple crash scenarios including high-speed front impact, offset deformable barrier (ODB), side impact, pole impact, high-speed rear impact and low-speed rear impact in addition to a roof crush scenario. For the purpose of achieving this goal, finite element (FE) topology optimisation was employed. Owing to the limitations of present-day FE optimisation software, all models utilised linear static load cases. In addition, all models made use of inertia relief (IR) boundary conditions. With the above approach, the BIW topology was investigated.

Closed-loop driver/vehicle model for automotive control

This paper demonstrates the implementation of a comprehensive vehicle model combined with a driver model in closed loop for the purpose of developing and testing of vehicle stability systems. As an example of such a stability system, a model of an active front steering controller is considered. The operation of this controller is based on vehicle states available my means of a state estimator. The functional efficiency of these combined models is demonstrated using a double-lane change manoeuvre. The use of the stability controller shows clear improvement in terms of the vehicle dynamical stability.

Influence of vehicle secondary impact following an emergency braking on an unbelted occupant's neck, head and thorax injuries

Passive safety has for many years reduced the number of fatalities on the roads. However, its effect on occupants’ safety has now stabilised, meaning that new active safety features are needed to reduce further the number of casualties. These active safety features, like autonomous emergency braking (AEB), aim to prevent vehicle collisions and reduce the vehicle kinetic energy on impact. A previous study has shown that unbelted occupants kinematics are affected by the pre-braking phase, suggesting that the occupants hand positions on the steering wheel, combined with a bracing behaviour, could cause the occupant to miss the deploying airbag in the case of a secondary rigid wall impact. This paper will investigate the variations of the secondary vehicle impact crash patterns by calculating crash pulses based on typical vehicle frontal accident scenarios and conclude on these effects on the human occupants neck, head and thorax injuries.

The simulation of pedestrian impact with a combined multibody finite elements system model

This paper describes a study carried out to develop and apply Madymo models combining multibody and finite element components to simulate accidents between vehicles and pedestrians. The work is in response to new European legislation and will support the automotive industry and the requirement to design future vehicles that afford pedestrians more protection. The simulations performed aim to represent pedestrian accidents as they occur in the real world. The problems of validating computer models of a pedestrian, a vehicle and the mechanics of impact are discussed. In particular, the modelling of the pedestrian presents challenges in terms of establishing the bio-fidelity of the model. The work presented here has been carried out with collaboration from the Motor Industry Research Association (MIRA Ltd) and involved managing a large number of computer simulations to cover a matrix of varying critical variables such as vehicle speed and pedestrian posture. To facilitate the process, a design of experiments statistical approach has been adopted here where the model has been used to provide predictions of pedestrian injury criteria and post-impact kinematics.

A multi-body systems approach to simulate helicopter occupant protection systems

This paper reports on the work of computer simulations carried out at Coventry University as part of the European 6th Framework HeliSafe TA project, which considered the potential improvements in occupant safety for civil helicopters. A multi-body systems approach with additional use of finite elements for critical components such as a pilot airbag and the harnesses was adopted in the computer models to simulate helicopter crash/rollover scenarios and to investigate the effectiveness of occupant protection systems deployed during helicopter crash scenarios. ADAMS and Madymo simulations of helicopter impact/rollover events were demonstrated. A cabin/cockpit model of a Bell UH-1D helicopter was developed to replicate the physical crash test setup and a parametric study for the pilot airbag and a range of harness concepts was performed. The use of validated multi-body systems-based cabin/cockpit models has proved to be effective in the development of new restraint system concepts for occupant protection.

Computer simulation of real-world vehicle–pedestrian impacts

This paper describes a study carried out to develop and apply computer analysis tools to simulate real-world accidents between vehicles and pedestrians. The main focus has been the incorporation of realistic pedestrian pre-impact gait motion and to investigate the outcome of real-world impacts. A combination of multi-body, FACET and finite element based vehicle models in conjunction with validated human body models developed by MADYMO were used to simulate and analyse vehicle–pedestrian accident scenarios. European regulations and consumer tests for passenger cars now address vehicle front aggressiveness, and vehicle manufactures have effectively developed design solutions for meeting these requirements. Vehicle frontal geometry and pedestrian pre-impact characteristics play a major role in determining the post-impact kinematics and severity of injury sustained during pedestrian–vehicle contact stage. A unique aspect of this study has been the application of the Injury Severity Index method developed for automotive occupant injury assessment to pedestrians. The injury results from the simulations were measured and the severity assessed by applying a quantitative rating method.