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Exploiting autonomous corner modules to resolve force constraints in the tyre contact patch
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2008 (English)In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 46, no 7, 553-573 p.Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
2008. Vol. 46, no 7, 553-573 p.
Keyword [en]
autonomous corner module; force allocation; steering actuator; tyre constraints; vehicle control; vehicle dynamics
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-6772DOI: 10.1080/00423110701504215ISI: 000257029700001Scopus ID: 2-s2.0-46349108582OAI: oai:DiVA.org:kth-6772DiVA: diva2:11576
Note
QC 20100629Available from: 2007-02-14 Created: 2007-02-14 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Aspects of autonomous corner modules as an enabler for new vehicle chassis solutions
Open this publication in new window or tab >>Aspects of autonomous corner modules as an enabler for new vehicle chassis solutions
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis adopts a novel approach to propelling and controlling the dynamics of a vehicle by using autonomous corner modules (ACM). This configuration is characterised by vehicle controlled functions and distributed actuation and offers active and individual control of steering, camber, propulsion/braking and vertical load.

Algorithms which control vehicles with ACMs from a state-space trajectory description are reviewed and further developed. This principle involves force allocation, where forces to each tyre are distributed within their limitations. One force allocation procedure proposed and used is based on a constrained, linear, least-square optimisation, where cost functions are used to favour solutions directed to specific attributes.

The ACM configuration reduces tyre force constraints, due to lessen estrictions in wheel kinematics compared to conventional vehicles. Thus, the tyres can generate forces considerably differently, which in turn, enables a new motion pattern. This is used to control vehicle slip and vehicle yaw independently. The ACM shows one important potential; the extraordinary ability to ensure vehicle stability. This is feasible firstly due to closed-loop control of a large number of available actuators and secondly due to better use of adhesion potential. The ability to ensure vehicle stability was demonstrated by creating actuator faults.

This thesis also offers an insight in ACM actuators and their interaction, as a result of the force allocation procedure.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. viii, 22 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2006:101
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4275 (URN)978-91-7178-559-6 (ISBN)
Presentation
2007-02-22, Sal D41, KTH, Lindstedtsvägen 17, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101117Available from: 2007-02-14 Created: 2007-02-14 Last updated: 2010-11-17Bibliographically approved
2. Exploiting individual wheel actuators to enhance vehicle dynamics and safety in electric vehicles
Open this publication in new window or tab >>Exploiting individual wheel actuators to enhance vehicle dynamics and safety in electric vehicles
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on individual wheel actuators in road vehicles intended for vehicle motion control. Particular attention is paid to electro-mechanical actuators and how they can contribute to improving vehicle dynamics and safety. The employment of individual wheel actuators at the vehicle's four corner results in a large degree of over-actuation. Over-actuation has a potential of exploiting the vehicle's force constraints at a high level and of controlling the vehicle more freely. One important reason for using over-actuated vehicles is their capability to assist the driver to experience the vehicle as desired. This thesis demonstrates that critical situations close to the limits can be handled more efficiently by over-actuation.

To maximise the vehicle performance, all the available actuators are systematically exploited within their force constraints.  Therefore, force constraints for the individually controlled wheel are formulated, along with important restrictions that follow as soon as a reduction in the degrees of freedom of the wheel occurs. Particular focus is directed at non-convex force constraints arising from combined tyre slip characteristics.

To evaluate the differently actuated vehicles, constrained control allocation is employed to control the vehicle. The allocation problem is formulated as an optimisation problem, which is solved by non-linear programming.

To emulate realistic safety critical scenarios, highly over-actuated vehicles are controlled and evaluated by the use of a driver model and a validated complex strongly non-linear vehicle model.

it is shown that, owing to the actuator redundancy, over-actuated vehicles possess an inherent capacity to handle actuator faults, with less need for extra hardware or case-specific fault-handling strategies.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. x, 84 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:33
Keyword
autonomous wheel corner, actuators, vehicle dynamics, control allocation, electric vehicles, vehicle modelling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-11005 (URN)978-91-7415-387-3 (ISBN)
Public defence
2009-09-25, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100722Available from: 2009-09-08 Created: 2009-09-03 Last updated: 2010-07-22Bibliographically approved

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