Exploiting autonomous corner modules to resolve force constraints in the tyre contact patch

This paper presents a general force allocation strategy for over-actuated vehicles, utilising technologies where tyre forces can be morefreely controlled than in conventional vehicles. For the purpose of illustration, this strategy has been applied and evaluated using adesign proposal of an autonomous corner module (ACM) chassis during a transient open-loop response test. In this work, the vehicle hasbeen forced to follow a trajectory, identical to the performance of a conventional front-steered vehicle during the manoeuvre studied. Anoptimisation process of tyre force allocation has been adopted along with tyre force constraints and cost functions to favour a desiredsolution. The vehicle response has been evaluated as open-loop, where tyre forces are shown to be allocated in a different mannerthan in conventional front-steered vehicles. A suggested approach for a control scheme of steering actuators is presented, where theactuator limitation is related to the lateral force possible. Finally, the force allocation strategy involves the ability to control vehicleslip independently from vehicle yaw rate. This opportunity has been adapted in the ACM vehicle in order to relax vehicle slip from theoriginal trajectory description. In such circumstances, the ACMs demonstrate better utilisation of the adhesion potential

Stability of an electric vehicle with permanent-magnet in-wheel motors during electrical faults

This paper presents an analysis of the stability of an electric vehicle equipped with in-wheel motors ofpermanent-magnet type during a class of electrical faults. Due to the constant excitation from the permanentmagnets, the output torque from a faulted wheel cannot easily be removed if an inverter shuts down, which directlyaffects the vehicle stability. In this paper, the impact of an electrical fault during two driving scenarios isinvestigated by simulations; using parameters from a 30 kW in-wheel motor and experimentally obtained tire data.It is shown that the electrical fault risks to seriously degrading the vehicle stability if the correct counteraction isnot taken quickly. However, it is also demonstrated that vehicle stability during an electrical fault can be maintainedwith only minor lateral displacements when a closed-loop path controller and a simple method to allocate theindividual tire forces are used. This inherent capacity to handle an important class of electrical faults is attractive;especially since no additional fault-handling strategy or hardware is needed

Control of electric vehicles with autonomous corner modules: implementation aspects and fault handling

In this paper, vehicle dynamics for electric vehicles equippedwith in-wheel motors and individual steering actuators are studied adoptingthe principles of optimal tyre-force allocation. A simple method fordescribing the constraints owing to tyre and actuator limitations is described.The control architecture is evaluated by investigating its response to realisticfault conditions. The evaluation demonstrates that the control architecture’sability to ensure vehicle stability generally is good. However, during majorfaults and extreme driving situations, vehicle stability is not maintainedunless the constraints in the optimisation process used for tyre-force allocationare adapted to the specific fault

The influence of tyre lateral force for control allocation of yaw torque

The present paper provides a thorough analysis and revealsthe yaw torque generated by tyre lateral forces, due to the well-knowncombined slip effect. The indirect yaw torque here is captured by a tyremodel simplifiation designed for the real-time control allocation purpose.Experiments were carried out by a driving robot, controlling steeringwheel, gas and brake pedal at various manoeuvres. The test vehicleis equipped with high precision measurement-wheel mounted at eachwheel. It was found that the simplified model correlates with the experimentalresults, where the relation between the wheel torque distributionof front/rear axles and the yaw torque generated by tyre lateral forcesare highly dependent on the vehicle lateral acceleration and drive torquerequest

The Alaska Workers’ Compensation Law: Fact-Finding, Appellate Review, and the Presumption of Compensability

This paper presents a fault handling strategy for electric vehicles with in-wheel motors. The ap-plied control algorithm is based on tyre-force allocation. One complex tyre-force allocation meth-od, which requires non-linear optimization, as well as a simpler tyre force allocation method are developed and applied. A comparison between them is conducted and evaluated against a standard reference vehicle with an Electronic Stability Control (ESC) algorithm. The faults in consideration are electrical faults that can arise in in-wheel motors of permanent-magnet type. The results show for both tyre-force allocation methods an improved re-allocation after a severe fault and thus re-sults in an improved state trajectory recovery. Thereby the proposed fault handling strategy be-comes an important component to improve system dependability and secure vehicle safety.QC 20130611</p

Inflammatory Characteristics of Stenotic Aortic Valves: A Comparison between Rheumatic and Nonrheumatic Aortic Stenosis.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.Background. Although our comprehension of nonrheumatic aortic stenosis (NRAS) has increased substantially during the last decade, less is known about the histopathology of rheumatic aortic stenosis (RAS). The aim of this study was to investigate rheumatic aortic stenosis by means of analyses previously used in nonrheumatic stenosis. Material and Methods. Valve specimens were obtained from 39 patients referred to hospital due to significant aortic stenosis. According to established macroscopic criteria the valves were divided into two groups consisting of 29 NRAS and 10 RAS valves. Mononuclear inflammatory cells and apolipoproteins were investigated using immunohistochemical analyses. Results. The localisation of calcification differed in tricuspid nonrheumatic valves when compared to bicuspid nonrheumatic and rheumatic valves. The RAS valves revealed a lower degree of T lymphocyte infiltration compared with the NRAS valves. Infiltration of macrophages was seen in all valves and there were no differences regarding deposition of apolipoprotein. Conclusion. Rheumatic and nonrheumatic aortic stenotic valves show a similar and significant chronic inflammation. The similarities regarding the localisation of calcification indicate that the valve anomaly/morphology can influence the pathogenesis of aortic stenosis. Finally, our findings highlight the question of a postinflammatory valvular disease of other causes than rheumatic fever.Swedish Heart-Lung Foundation, Östergötland County Council, Linköping University Hospital

Autonomous corner modules as an enabler for new vehicle chassis solutions

Demands for new functions and refined attributes in vehicle dynamics areleading to more complex and more expensive chassis design. To overcome this, there hasbeen increasing interest in a novel chassis design that could be reused in the developmentprocess for new vehicle platforms and mainly allow functions to be regulated by software.The Autonomous Corner Module (ACM) was invented at Volvo Car Corporation (VCC) in1998. The invention is based upon actively controlled functions and distributed actuation. Themain idea is that the ACM should enable individual control of the functions of each wheel;propulsion/braking, alignment/steering and vertical wheel load. This is done by using hubmotorsand by replacing the lower control arm of a suspension with two linear actuators,allowing them to control steering and camber simultaneously. Along with activespring/damper and wheel motors, these modules are able to individually control each wheel\u27ssteering, camber, suspension and spin velocity. This provides the opportunity to replacemechanical drive, braking, steering and suspension with distributed wheel functions which, inturn, enable new vehicle architecture and design.The aim of this paper is to present the vehicle dynamic potential of the ACM solution, bydescribing its possible uses and relating them to previous research findings. Associated worksuggests chassis solutions where different fractions of the functions of the ACM capabilityhave been used to achieve benefits in vehicle dynamics. For instance, ideas on how to useactive camber control have been presented. Other studies have reported well-knownadvantages, such as, good transient yaw control from in-wheel motor propulsion and stablechassis behaviour from four-wheel steering, when affected by side wind. However, thistechnology also presents challenges. One example is how to control the relatively largeunsprung mass that occurs due to the extra weight from the in-wheel motor. The negativeinfluence from this source can be reduced by using active control of vertical forces. Theimplementation of ACM, or similar technologies, requires a well-structured hierarchy andcontrol strategy. Associated work suggests methods for chassis control, where tyre forces canbe individually distributed from a vehicle path description. The associated workpredominately indicates that the ACM introduces new opportunities and shows itself to be apromising enabler for vehicle dynamic functions

Closed-loop controller for post-impact vehicle dynamics using individual wheel braking and front axle steering

This paper presents a vehicle path controller for reducing the maximum lateral deviation (Ymax) after an initial impact in a traffic accident. In previous research, a Quasi-Linear Optimal Controller (QLOC) was proposed and applied to a simple vehicle model with individually controlled brake actuators. QLOC uses non-linear optimal control theory to provide a semiexplicit approximation for optimal post-impact path control, and in principle can be applied to an arbitrary number of actuators. The current work extends and further validates the control method by analysing the effects of adding an active front axle steering actuator at different post-impact kinematics, as well as increasing the fidelity of the vehicle model in the closed-loop controlled system. The controller performance is compared with the results from open-loop numerical optimisation which uses the same vehicle model. The inherent robustness properties of the QLOC algorithm are demonstrated by its direct application to an independent high-fidelity multi-body vehicle model. Towards real-time implementation, the algorithm is further simplified so that the computational efficiency is enhanced, whereas the performance is shown not to be degraded

Steering Redundancy for Self-Driving Vehicles using Differential Braking

This paper describes how differential braking can be used to turn a vehicle in the context of providing fail-operational control for self-driving vehicles. Two vehicle models are developed with differential input. The models are used to explain the bounds of curvature that differential braking provides and they are then validated with measurements in a test vehicle. Particular focus is paid on wheel suspension effects that significantly influence the obtained curvature. The vehicle behaviour and its limitations due to wheel suspension effects are, owing to the vehicle models, defined and explained. Finally, a model-based controller is developed to control the vehicle curvature during a fault by differential braking. The controller is designed to compensate for wheel angle disturbance that is likely to occur during the control event