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Integrated chassis control Brakenet 2002
- 1. Integrated Vehicle ControlSystemsIntegrated Vehicle Control Systems Vehicle Chassis SystemsVehicle Chassis Systems ControlControl andand IntegrationIntegration September, 2002September, 2002 Dr. Mark N.W. HowellDr. Mark N.W. Howell
- 2. Integrated Vehicle ControlSystem • IntroductionIntroduction • Systems IntegrationSystems Integration • Subsumption ArchitectureSubsumption Architecture • ExamplesExamples • ConclusionsConclusions Presentation OutlinePresentation Outline
- 3. Integrated Vehicle ControlSystem • Safety • Predictable behaviour • Responsive Handling • Ride Comfort • Maximise efficiency & performance of the vehicle • Flexibility, modular, ‘plug and play’ architecture IntroductionIntroduction
- 4. Integrated Vehicle ControlSystem OEMOEMRequirementsRequirements Based on car type/OEM requirements select required systems for interaction Brand DNA Product Differentiation Performance FeelPerformance Feel Ease of UseEase of Use ReliabilityReliability IntegrityIntegrity SafetySafety ComfortComfort
- 5. Integrated Vehicle ControlSystem Whole Vehicle Objectives Braking Steering Suspension Powertrain 6 D.O.F Longitudinal Lateral Bounce Pitch Roll Yaw Characteristics Safe Predictable Responsive Handling Ride ComfortNVH, Energy, Reliability, Cost ...
- 6. Integrated Vehicle ControlSystem • Braking Systems - ABS, TRC • Steering - AFWS, 4WS • Suspension - Active, Semi-active, Roll Control • Drivetrain - Differential/ IVT/CVT • + Cruise Control, Intelligent/Adaptive Cruise Control • Yaw moment control, X-by-wire • Future systems: Collision Avoidance, Parking • Need a coherent way of integrating systems The Need for IntegrationThe Need for Integration
- 7. Integrated Vehicle ControlSystem • Modular • Respect IPR of suppliers • Avoid excessive complexity • Incorporate fault detection, diagnosis and tolerance • Open architecture Design RequirementsDesign Requirements
- 8. Integrated Vehicle ControlSystem Subsumption ArchitectureSubsumption Architecture Sensors S T I M U L U S C O O R D I N A T I O N O Actuators Behaviour 1 Behaviour 2 Behaviour n A modular, behaviour based, distributed architecture Behaviours are layers of control architectures that are event driven One layer can subsume control over another layer Higher level behaviour can suppress a lower-level behaviour.
- 9. Integrated Vehicle ControlSystem • Distributed Layered Control – Control distributed across parallel layers each with multiple modules • Behavioural Decomposition – different layers support different ‘task-achieving’ behaviours’ – decomposes into behavioural rather than function units • Increasing ‘Levels of competence’ – Ascending level adds capabilities resulting in higher overall competence. – Higher levels often operate by modulating the activities of lower levels. • Incremental Construction – incremental control system designing – intermediate architecture tested and debugged before next layer added. • Conflict resolution and communication between levels – Higher layers subsume the roles of lower ones by suppressing their outputs and substituting their own. Key Aspects of SubsumptionKey Aspects of Subsumption
- 10. Integrated Vehicle ControlSystem SubsumptionSubsumption Advantages • Modular • Very flexible • Robust to system change • Incremental control design Disadvantages • Complex overall system with a large number of behaviours • Verification difficult of overall system behaviour
- 11. Integrated Vehicle ControlSystem Collision Avoidance Straight Line Stability Neutral Steer Parking Aid Safety Distance from Obstacles Anti - Dive Anti - Squat Yaw Stability Roll Stability Ride Comfort Load Transfer Forward Speed Layer 4 Behaviour Layer 3 Behaviour Layer 2 Behaviour Layer 1 Behaviour Layer 0 Hardware ABS TCS Side Slip Control Controllable Suspension Driver SensorandInformationBus Integrated Layers Non Integrated Layers (mostly single loop) Lane Detection and Tracking Brakes Engine Transmission Suspension Steering Subsumption SubsystemsSubsumption Subsystems
- 12. Integrated Vehicle ControlSystem Sensors (physical) Sensors (Soft) State Estimation/ Observers Near Traffic Condition Driver Model True Vehicle Model 'Desired' Vehicle Model Road Condition Estimation Bahaviours Lane Detection Sensor and Information BusSensor and Information Bus
- 13. Integrated Vehicle ControlSystem Behaviour 4 Behaviour 3 Behaviour 2 Behaviour 1 ACTION MAX (B1, B2,B3,B4) Behaviour 4 Behaviour 3 Behaviour 2 Behaviour 1 ACTION Respond of highest active behaviour Response of behaviour with the highest activation signal Behaviour 4 Behaviour 3 Behaviour 2 Behaviour 1 ACTION Voting based (Neural) Behaviour 4 Behaviour 3 Behaviour 2 Behaviour 1 ACTION Fuzzy Rule based (A) (B) (C) (D)
- 14. Integrated Vehicle ControlSystem Scope for Integration - ActuationScope for Integration - Actuation • 4 Independent Brake 4 • Engine 1+(...) • Driveline (Transmission/differential) 1,2+ • Individual Wheel Steering 4 • Active Suspension 4 Total : 15+
- 15. Integrated Vehicle ControlSystem • Stiff suspension model - nonlinear tyre model • 7 DOF: Yaw, Sideslip, Longitudinal, Wheel spin + Control States • Independent wheel braking • Rudimentary Powertrain (torque demand) • Active Front Wheel Steer Simple StudySimple Study
- 16. Integrated Vehicle ControlSystem • Integrated Systems • Non-integrated control Driver Throttle Brake Input Steer Angle Input Brake torque Front Steer Angle Throttle Low ‘ABS’ Independent Wheel Slip Control Front Slip angle control Yaw/ Sideslip Control Directional Control HighIntermediate Vehicle Simple study - levels of behaviourSimple study - levels of behaviour
- 17. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -10 -5 0 5 10 15 20 25 30 time [s] speed[m/s] Vehicle Forward Speed noctrl S sigma S beta10S allS
- 18. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -200 -150 -100 -50 0 50 100 150 200 time [s] beta[o ] Vehicle Side Slip Angle noctrl S sigma S beta10 S all S
- 19. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -4 -3 -2 -1 0 1 2 3 4 time [s] beta[o ] Vehicle Side Slip Angle noctrl S sigma S beta10 S all S
- 20. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -60 -40 -20 0 20 40 60 time [s] delta[o ] Steer Angle noctrlS sigma S beta10 S all S
- 21. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 time [s] r[rad/s] Yaw Rate noctrl S sigma S beta10 S all S
- 22. Integrated Vehicle ControlSystem 0 2 4 6 8 10 12 14 16 18 20 -8 -6 -4 -2 0 2 4 6 8 time [s] a lat [m/s2 ] Lateral Acceleration noctrl S sigma S beta10 S all S
- 23.
- 24. Integrated Vehicle ControlSystem • Technical and commercial considerations restrict the ways that integrated vehicle control systems are implemented in practice • Limiting total system complexity is a priority • Layered ‘subsumption’ architectures are particularly applicable to the control implementation, but detailed methodologies are not yet well developed • Issues of conflict resolution in real-time, may be solved by extending commonly available control techniques Main ConclusionsMain Conclusions
- 25. Integrated Vehicle ControlSystem Any Questions ?Any Questions ?
Editor's Notes
- #4 Different vehicle manufactures (OEMs) want different characteristics from a vehicle - the brand DNA - the system needs to be tuneable to meet the performance feel of that make of care. They also demand high levels of comfort, safety etc as well as safe, predictable responsive vehicles that have good handling and ride comfort characteristics. To achieve these objective and maximise the efficiency and performance of the vehicle systems they need to be integrated together. It is that integration that is examined in this talk. In order to achieve the above a flexible, modular tuneable ‘plug and play’ architecture is desirable.
- #7 The need for integration becomes apparent when we look at the various different subsystems that are on the car - there are four main subsystem groups namely Braking, Suspension Steering and Powertrain/Engine each of which has had a number of different functions designed for a specific behaviour. For instance braking systems involve ABS and traction control, active suspensions and active roll control are also now available. Many other systems exist as well such as yaw moment control, x-by-wire systems as well as cruise control adaptive cruise control. Other systems such as collision avoidance and parking assist are also being developed. These systems all need to be integrated together in a coherent way One other thing worth noting is that there are a lot more systems than actuators many of these individual systems share actuation requirements and so they a decision needs to be made by in system architecture as to which subsystem has control at any one time.
- #8 To link all these systems together and to tie up was has previously been stated we require a modular architecture so that different combinations of systems can be added together. This architecture needs to be able to respect the IPR of the suppliers of the various systems We also need to involve excessive complexity - it does not make sense to design a single controller for everything which will become extremely complex especially as extra code will be need to protect the system integrity. It is likely that the design of such a system would become prohibitively expensive. We also require an open architecture approach with a standard interface design so that the subsystems can take commands in and give an indication as to the reliability of the information being supplied.
- #10 The main properties of a subsumption approach are listed here.
- #12 In order to put these ideas into context the following diagram shows the different layers of control that could be involved in an integrated chassis system design. The lowest level controls the actual vehicle hardware - the engine, brakes, transmission suspension and steering systems. Above this we have single behaviour systems independent controlled and mostly responsible for a single task. The ABS here for instance is independent wheel ABS and purely responsible for preventing a wheel from locking. The driver is on this level this is only part of the drivers function and is just to show that he cannot influence the other subsystems on this level - however some can be considered to be subsuming his control. Above this we have higher behaviours that can make use of the behaviours in the layer below them. For instance yaw stability will need to make use of and steering control that is available as well as perhaps change the brake distribution. Cruise control can be seen as the forward speed control that would make use of the ABS and traction control and the layer above this represents adaptive cruise control where the desired behaviour is to maintain a safe distance from the car in front.
- #13 In order to put these ideas into context the following diagram shows the different layers of control that could be involved in an integrated chassis system design. The lowest level controls the actual vehicle hardware - the engine, brakes, transmission suspension and steering systems. Above this we have single behaviour systems independent controlled and mostly responsible for a single task. The ABS here for instance is independent wheel ABS and purely responsible for preventing a wheel from locking. The driver is on this level this is only part of the drivers function and is just to show that he cannot influence the other subsystems on this level - however some can be considered to be subsuming his control. Above this we have higher behaviours that can make use of the behaviours in the layer below them. For instance yaw stability will need to make use of and steering control that is available as well as perhaps change the brake distribution. Cruise control can be seen as the forward speed control that would make use of the ABS and traction control and the layer above this represents adaptive cruise control where the desired behaviour is to maintain a safe distance from the car in front.
- #15 What scope is there to implement this integration. Well consider this example we have 4 independent brake controllers, an engine control for the traction control system but there may be others that could be added in here. Transmission control with active differentials controlling both the torque distribution left right and front rear. Individual wheel steer and active suspension also add many other potential actuators.
- #16 As a simple example of the principles discusses a 7DOF stiff suspension model with nonlinear tyre characteristics was developed. This allows for yaw, sideslip, longitudinal control and wheel spin. The model had individual wheel braking a rudimentary torque demand for the powertrain control and active front wheel steer.
- #17 The system showing how this integration philosophy applies. At the top we have on integrated control where the driver command just feed through to the vehicle. In the lower diagram individual wheel ABS and front slip angle control are added. The yaw/sideslip control is a higher level that augments the ABS control decision and above that direction control can be added which override this and the drivers control decision.