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Autonomous corner modules as an enabler for new vehicle chassis solutions
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0002-4048-3452
2006 (English)In: FISTA TransactionArticle in journal (Refereed) Published
Abstract [en]

Demands for new functions and refined attributes in vehicle dynamics are leading to more complex and more expensive chassis design. To overcome this, there has been increasing interest in a novel chassis design that could be reused in the development process 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) in 1998. The invention is based upon actively controlled functions and distributed actuation. The main 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 hubmotors and by replacing the lower control arm of a suspension with two linear actuators, allowing them to control steering and camber simultaneously. Along with active spring/damper and wheel motors, these modules are able to individually control each wheel's steering, camber, suspension and spin velocity. This provides the opportunity to replace mechanical drive, braking, steering and suspension with distributed wheel functions which, in turn, enable new vehicle architecture and design.

The aim of this paper is to present the vehicle dynamic potential of the ACM solution, by describing its possible uses and relating them to previous research findings. Associated work suggests chassis solutions where different fractions of the functions of the ACM capability have been used to achieve benefits in vehicle dynamics. For instance, ideas on how to use active camber control have been presented. Other studies have reported well-known advantages, such as, good transient yaw control from in-wheel motor propulsion and stable chassis behaviour from four-wheel steering, when affected by side wind. However, this technology also presents challenges. One example is how to control the relatively large unsprung mass that occurs due to the extra weight from the in-wheel motor. The negative influence from this source can be reduced by using active control of vertical forces. The implementation of ACM, or similar technologies, requires a well-structured hierarchy and control strategy. Associated work suggests methods for chassis control, where tyre forces can be individually distributed from a vehicle path description. The associated work predominately indicates that the ACM introduces new opportunities and shows itself to be a promising enabler for vehicle dynamic functions.

Place, publisher, year, edition, pages
2006.
Keyword [en]
Chassis control, vehicle dynamics, steering, propulsion, active suspension
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6769OAI: oai:DiVA.org:kth-6769DiVA: diva2:11573
Note
QC 20100721Available from: 2007-02-14 Created: 2007-02-14 Last updated: 2010-07-21Bibliographically 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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