ASM-BrakeHydraulics Nachdruck-10-2007 E 02 …...As well as gasoline and diesel engines, there are models for vehicle dynamics and brake hydraulics. Combined models interoperate in

dSPACE

dSPACE Automotive Simulation Models – ASM

Brake Hydraulics Model

ASM – Brake Hydraulics Model

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Automotive Simulation Models

ASM – Brake Hydraulics Model

Real-time brake hydraulics model

Key Features Open MATLAB®/Simulink® model

Real-time simulation and offline simulation

Complete hydraulics system with full ESP support

Description Application AreasThe ASM – Brake Hydraulics Model is an open Simulink model that simulates the brake hydraulics system required for vehicle dynamics controls like ABS (Antilock Brake System), TCS (Traction Control System), and ESP (Electronic Stability Program). It is typically used together with a vehicle model on a dSPACE Simulator for hardware-in-the-loop testing of the vehicle’s ESP electronic control unit (which usually includes ABS and TCS) or during the design phase of ESP controller algorithms for early validation by offline simulation.

Key BenefitsAll the Simulink blocks in the model are visible, so it is easy to add or replace components with custom models to adapt the brake hydraulics properties perfectly to individual projects. The ASM – Brake Hydraulics Model is a complete hy-draulics system that includes all the features and functions required for ESP controls. The model can be parameterized completely via ModelDesk’s graphical user interface and takes full advantage of ModelDesk’s comprehensive parameter man-agement and handling features.

Simulation Model CharacteristicsThe modeled ESP braking system consists of a dual-circuit hydraulics system. The model con-tains all the components like valves, chambers, accumulators, and braking cylinders that are necessary for simulating a standard state-of-the-art ESP braking system (for example, Bosch, ContinentalTeves, TRW).

Offline and Online SimulationThe ASM – Brake Hydraulics Model can be used in combination with real controllers in a hard-ware-in-the-loop environment (HIL or online mode), or it can be used for simulating an ESP braking system in combination with software controller algorithms (PC or offline mode). The model supports real-time code generation via Real-Time Workshop from The MathWorks and dSPACE’s RTI for online simulation on a dSPACE real time system.

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Main Features and Benefits

Feature Description Benefit

Open Simulink model All model blocks are visible Custom models can easily be added or used to replace model components

ModelDesk Graphical user interface with parameter management

Easy parameter handling and management

Online simulation Real-time simulation on real-time hardware Hardware-in-the-loop simulations with ECUs

Offline simulation Simulations as early as the design phase Controller validation in early development stages

ASMSignalBus Simulation signals are part of a structured Simulink signal bus

Standardized and fast access to model variables (p. 8)

Online tunable parameters

Direct parameter access during real-time simulations Online parameter optimizations and behavior studies (p. 9)

Model interoperability ASM models are easy to combine to create a virtual vehicle

An entire virtual vehicle can be simulated (p. 10)

Order Information

Order Number

ASM – Brake Hydraulics Model ASM_L_BH

Relevant Software and Hardware

Hardware

Required Minimum system Pentium 3 processor, 800 MHz 512 MB RAM

Recommended system Pentium 4 processor, 1.4 GHz or higher Memory ≥ 1024 MB RAM

dSPACE Simulator, equipped with DS1005 or DS1006

Software for Online Simulation

Required Integrated development environment MATLAB®/Simulink® from The MathWorks®

Real-Time Workshop®

dSPACE implementation software Real-Time Interface (RTI)

dSPACE experiment software ControlDesk

dSPACE experiment software ModelDesk

Operating system www.dspace.com/goto?os_compatibility

Optional Other dSPACE ASM Packages –

Software for Offline Simulation

Required Integrated development environment MATLAB®/Simulink® from The MathWorks®

dSPACE experiment software ModelDesk

Operating system www.dspace.com/goto?os_compatibility

Optional Other dSPACE ASM Packages –

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Pre-Charge Valve 1 Change-Over Valve 1

Inlet Valve FL Inlet Valve RR

Outlet Valve FL Outlet Valve RR

Pump 1

ConnectionChamber 1

Damper Chamber 1

Reservoir 1

Non-Return ValveReservoir 1

Non-ReturnValve FL

Brake Cylinder FL

Master Brake Cylinder

Brake Cylinder RR

Non-ReturnValve RL

Pre-Charge Valve 2Change-Over Valve 2

Inlet Valve FRInlet Valve RL

Outlet Valve FROutlet Valve RL

Pump 2

ConnectionChamber 2

Damper Chamber 2

Reservoir 2

Non-Return ValveReservoir 2

Brake Cylinder FRBrake Cylinder RL

Non-ReturnValve RR

Non-ReturnValve FR

M

ASM Brake Hydraulics

Feature Overview Features at a Glance Contains all the components of a state-of-

the-art ESP braking system Linear and physical master brake cylinder

model Valves with continuously controllable

cross-sections Nonlinear, look-up-table-based wheel

brake cylinder Offline and online simulation

Real-time capable Graphical user interface for

parameterization Easy to insert in ASMVehicleDynamics Numerical integration stabilized via local

oversampling Modular, library-based implementation Easy variable access Fully integrated into dSPACE tool chain


Hydraulics Model ConceptThe brake hydraulics model consists of the master brake cylinder and the two independent braking circuits. The braking circuit system calculates the pressure in each wheel brake cylinder.

Schematics of the brake hydraulics.

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∆ p1

q2

∆ p2

q1

Inlet Valve RL

Non-ReturnValve RL

∆ p3

q3

Change-Over Valve

Master Brake CylinderThe master brake cylinder transforms the brake pedal position into a cylinder pressure. It consists of a cylinder with a piston that delivers pressure to both braking circuits. There are two models, one linear and one physical. The linear model can be used to convert the pedal position into

a pressure directly, for example, if a brake pedal position of 70 percent must produce exactly 70 percent of the maximum braking pressure. The physical model can be used for realistic vehicle simulations or if the data measured for the brake pedal position is to be reused in simulations.

Components and Characteristics Linear model: Linear conversion of brake

pedal position to cylinder pressure Physical model: Massless piston which can

move longitudinally in the cylinder body

One piston of the master brake cylinder.

Hydraulic ValvesValves are used to control the flow of the hydraulic fluid. The flow control valves are mod-eled as orifices with continuously controllable cross-sections.

Components and Characteristics All valves except the non-return valve have

continuously controllable cross-sections Model based on the Bernoulli equation Different types of valves included Precharge valve with two different cross-

sections in the opening state. The cross- section depends on the pressure difference

Change-over valve with pressure relief function in the closed state

Inlet valve Outlet valve Non-return valve

∆ p1 [bar]

q1 [cm³/s]

q3 [cm³/s]

∆ p3 [bar]

∆ p2 [bar]

q2 [cm³/s]

A selection of the valve systems: non-return, inlet, and change-over valves with their characteristics diagrams.


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Pump

Damper Chamber q

∆ p

Chambers and AccumulatorsThe chamber is modeled as a fixed volume that is filled with a compressible fluid.

Components and Characteristics Chamber with fixed volume filled with a

compressible fluid, model based on the continuity law

Hydropneumatic accumulator, model based on the Hagen-Poisson equation

A damper camber.

Wheel Brake CylinderThe wheel brake cylinder is based on a look-up table that calculates the cylinder pressure from the cylinder volume.

Components and Characteristics Nonlinear Look-up-table based

Graph of cylinder pressure versus cylinder volume.

Hydraulics PumpThe hydraulic pump transports brake fluid back from the accumulator to the master brake cylin-der. Its second function is to deliver braking fluid to the inlet valves during active braking without driver intervention.

Components and Characteristics Look-up-table based

Hydraulics pump with damper chamber.

Pump

Damper Chamber q

∆ p


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Simulation Results The hydraulic model, executed in conjunction with a real ECU, generates a modulated pressure in each brake cylinder as the brake pressure rises.

The vehicle model supplies the required wheel and vehicle speeds.

Parameter Manage-ment in ModelDesk

Parameterization ModelDesk is a graphical user interface for intui-tive model parameterization and parameter set management. It also provides project handling and allows parameter sets to be downloaded to offline and online simulations. Its overall look

and feel, basic handling, and workflows are identical to those of other software tools from dSPACE. For manual parameter entry, ModelDesk provides parameter pages with illustrations for each component.

Graph of modulated cylinder pressure and the resulting wheel and vehicle speeds.

Parameter page for the precharge and change-over valves with graph of valve characteristics.


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1ms

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Technical Aspects

Numerical Stability

Subsystem OversamplingTo quarantee numerically stable integration of submodels with stiff behavior, local subsystem oversampling is used. The Simulink For Iterator subsytem evaluates stiff differential equations n-times during one major simulation step.

Subsystem oversampling for a step response of a first-order delay element.

Parameters Sets The model is preconfigured with default data, so that all the tables and parameters have useful values and are fully functional.

Signal and Parameter Management

ASMSignalBusThe ASMSignalBus comprises the relevant signals of all model components in a hierarchical structure. Signals for I/O access with an inter-

face board or for display with a Simulink Scope can be chosen conveniently via a Simulink Bus- Selector.

ASMSignalBus displays all the relevant signals in a clear structure.

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Parameters Tunable Online Every parameter in the model is implemented as a single constant block and can be tuned dur-ing real-time simulation on a dSPACE Simulator. ControlDesk provides access to the parameters in online mode.

The brake hydraulics Simulink model with the main components and signals.

Signal and Parameter Management

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ASM Philosophy

Concept Model Design PhilosophyFor optimum support of customer-specific requirements dSPACE has chosen an open model concept. This means that models are visible to users right down to the level of standard Simulink blocks. Thus the dSPACE Automotive Simulation Models provide enormous flexibility for projects that require dedicated simulation models. The open model approach allows perfect adaptation to individual projects and requirements. This can be achieved by modifying models or by replacing or adding components.

Virtual VehicledSPACE Automotive Simulation Models are a collection of well coordinated models that you can easily combine to build anything from extended models to a whole virtual vehicle. As well as gasoline and diesel engines, there are models for vehicle dynamics and brake hydraulics. Combined models interoperate in one simulation.

Several ASM packages can be combined to make up a virtual car.

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dSPACEwww.dspace.com

France

dSPACE Sarl Parc Burospace Bâtiment 20 Route de la Plaine de Gisy91573 Bièvres CedexTel.: +33 1 6935 5060 Fax: +33 1 6935 5061 [email protected]

USA and Canada

dSPACE Inc.50131 Pontiac TrailWixom . MI . USA 48393-2020 Tel.: +1 248 295 4700Fax: +1 248 295 [email protected]

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dSPACE Ltd. Unit B7 . Beech HouseMelbourn Science ParkMelbourn Hertfordshire . SG8 6HBTel.: +44 1763 269 020Fax: +44 1763 269 [email protected]

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Documents

ASM-BrakeHydraulics Nachdruck-10-2007 E 02 …...As well as gasoline and diesel engines, there are models for vehicle dynamics and brake hydraulics. Combined models interoperate in