STEERING-IN-THE-LOOP TEST BENCH

SOLUTIONS FOR VIRTUAL TEST DRIVING

Table of Contents

Motivation 3

System at a Glance 4

General Description 6

Block Diagram (example configuration) 7

Use Cases 8

Optimization Tasks – ECU Optimization

Optimization Tasks – Steering System Optimization

Approval and Release Tasks – Validation of Safety-Critical Components

Approval and Release Tasks – Release Tests

Best-in-Class Features 10

Add-ons and Integration Potential 11

Synergy Effects Using CarMaker/HIL

Integration of Further ECUs and the FailSafeTester

Coupling with the SystemExperiencePlatform (SEP)

Scope of Delivery 12

Technical Data Sheet 13

Test Bench Results 13

Explanation of Terms

Steering Wheel Actuator Controller Performance

Linear Actuator Controller Performance

2

© pixelcaos – fotolia

State-of-the-art steering systems require increased effort during the entire development process. Particularly the

complexity of interaction between mechanical components and ECUs in all electric steer-by-wire systems leads to

more stringent requirements compared to conventional systems.

Real driving tests are not sustainable and available due to reproducibility and financial reasons at least in early de-

velopment phases. In addition, the increased number of links between ECUs interacting with the steering system

can only be covered by more and more diversity in the types of maneuver.

In order to get validated and fully verified data it is necessary to cut out physical parts as much as possible.

Even with respect to highly automated and autonomous driving, efficient development and validation of steering

systems is still becoming increasingly important since testing and validation becomes more challenging with the

numerous active vehicle subsystems that are intertwined with the steering system.

Motivation

3

Steering Rack Actuator

Induces and measures forces at

steering rack side with high

positioning accuracy

Power Rack

Provides 400 V,

125 A power supply

for actuators

Xpack4 IntegrationHIL

Contains the real-time system

including CarMaker, the test bench

controller with power supply unit as

well as optional additional units

4

System at a Glance

Steering Wheel Actuator

Induces torque and angle at

steering wheel side

Steering System

Full steering system as unit

under test

5

The Steering-in-the-Loop test bench is a turnkey solution for test and validation of real steering components – from the steering wheel up to the steering rack with tie rods.

The main components include:

� Low-vibration and vibration-damping base plate

� Power rack (power supply unit)

� Two linear actuators

� Steering wheel actuator

� Guide and adjusting unit for the steering unit

� Xpack4 real-time system for the activation of the actuators and data recording by the sensors

The system is flexible and can be easily and quickly adapted to different customized steering systems. All actu-

ators can be individually controlled depending on force, position (linear actuators on the track rod) or torque or

angle (steering wheel actuator). In combination with sensors and the CarMaker simulation environment, a closed-

loop system is formed with which steering maneuvers can be realistically reproduced and steering characteristics

investigated.

Torque transmission on the steering rack, in this steering system test bench, takes place on both sides, using

electric linear motors, and has complete hardware-in-the-loop capability. This way, innovative steering systems

can hereby be tested under realistic loading. With the test bench, excitations resulting from forces or potholes on

the road can be tested with a wide range of frequencies and amplitudes through the high-precision adjustability

of the actuators in order to accurately determine the transfer function in the steering system. In order to perform

release tests, the real steering system can be coupled on a vehicle using the test bench. In addition to open loop

tests, random steering maneuvers, such as changing lanes or entire tracks such as the Nuerburgring, can be reali-

stically tested to the limits of driving dynamics by using the IPGDriver model. In particular, closed-loop maneuvers

of virtually any complexity can be very easily structured, implemented and tested by coupling with the CarMaker

integration and test platform. Additional advantages of shifting tests to the test bench arise through operational

load simulations that are reproducible.

General Description

6

Block Diagram (example configuration)

For illustration purposes, the schema shows an

example of a configuration with the associated

physical signal and data flows.

7

Identical communication

as below

CarMaker Host-PC

Project Data

CarMaker Xpack4

Driver Model

Road Model

Vehicle Model

Test Rig Control

Hardware Interface

Ethernet

ECUCAN Signals

Angle or torque control

Displacement or force control

Position / velocity / acceleration measurement

Force measurement

Ang. / vel. / acc. measurement

Torque measurement

Use Cases

� Failsafe testing: All types of electrical errors can be reproducibly generated in real-time.

Failsafe tests are notably critical for the investigation of the error behavior and the secu-

ring of electric steering systems.

� Functional testing: The entire spectrum of the control device behavior can be tested

using the test bench on a targeted and automated basis.

� Performance testing: Complete man-

euvers and situations on the limits of

driving dynamics can also be effectively

and reproducibly performed on the test

bench – without posing any risks for the

testing persons or material.

� ECU calibration: In addition to easy

exchange of the entire steering system,

direct control devices and software versions can also be installed or replaced. This way,

different parameter settings and applications can be tested and optimized in short time.

� Benchmarking and characterization:

Benchmark tests can be performed in the early development phases. Causes for dif-

ferences between units under test can be effectively identified and analyzed thanks to

constant parameters. The complete steering system can be investigated under labora-

tory conditions. With virtually free parameter setting of test setups, characteristic curves

can be efficiently determined and the steering’s characteristic properties identified.

� Steering (feeling)

calibration:

Pre-calibrated ECU’s can be

automatically set off on the

test bench. Subjective evalu-

ation criteria of the steering

behavior, such as precision,

comfort or center point fee-

ling, can be transferred, se-

cured and optimized step by

step in hard system parame-

ters. The precise integration

of the test piece in the

test environment and the

complete reproducibility of the

test make it possible to accurately quantify the test results. Handling and comfort criteria

from open and closed loop maneuvers can be determined, analyzed and evaluated with

high statistical significance.

Optimization Tasks – Steering System Optimization

Optimization Tasks – ECU Optimization

© fotomek – fotolia

8

MIL

SIL HIL

VIL

OEM

MIL

SIL HIL

VIL

OEM

Tier 1

Objective confirmation

Simulation of steering & handling

Virtual optimization

parameters

Subjective steering feel

Objective steering & handling

REAL

VIRTUAL

The test bench design enables additional integration of other components in the hard-

ware and software models and the study of effects and correlations as well as the va-

lidation of these components. The ASIL analyses, stipulated in ISO 26262 (particularly

ASIL-C and ASIL-D), can be performed.

� Hardware control systems such as SSP (Steering Stability Program)

can be integrated in the system, either entirely or in parts, and their influences on

the steering system analyzed. With

regards to automated driving, com-

plex composite systems can also

be implemented with the respecti-

ve steering interventions.

� Software control systems can

be tested in early phases and their

effects on the system be analyzed.

This enables to perform tests and

protect steering-related functiona-

lities especially for highly automa-

ted and autonomous driving.

Approval and Release Tasks – Release Tests

The complete closed-loop applicability of the test bench makes it possible to also simulate

complex maneuvers. This means that virtual test drives can be performed and analyzed

before the real release tests for basically all steering system release maneuvers (e.g.

parking functions, escape turns, etc.). As a result, the use of expensive real test drives

is substantially reduced.

© fotomek – fotolia

9

MIL

SIL HIL

VIL

OEM

Tier 1

Approval and Release Tasks – Val idation of Safety-Crit ical Components

Best-in-Class Features

� Test bench hardware, software and connectivity concept from the same source, enable extremely short laten-

cy times and latency compensation in the transmission of signal and data, and makes it possible to perform

the most complex of closed-loop maneuvers.

� Custom-made actuators for the respective requirements enable a very high force resolution and thus great

precision in the obtained results.

� Coupling with Test Manager and the use of Test Ware allows the fully-automated sequence control of com-

plete test catalogues that are designed for steering optimization. Corresponding diagnostics and analyses can

hereby also be done.

Further Advantages at a Glance

� The use of the test bench enables significant efficiency improvement in the benchmarking procedure. Real

steering systems can be analyzed and evaluated under laboratory conditions, thereby saving time that would

otherwise be used in real test drives.

� Validations can be performed in the early development phases. Real experimental vehicles, materials or other

prototypes are thus not necessary. This saves time and largely reduces the costs.

� Prototypical steering systems can be tested in a short time for a variety of vehicle models. The complex in-

stallation, re-installation and de-installation procedures in a real test are reduced to a simple mount on the test

bench. The larger validation scope results in a higher safety level.

� Improved validation quality leads to effort reduction for vehicle testing.

� Test results and validation are completely reproducible and independent of human influence or environmental

conditions. Risk to persons performing the tests and the material used is largely minimized.

10

Synergy Effects Using CarMaker/HIL

Use open integration opportunities at the highest level:

� Simulation of all other vehicle components and the whole environment in

hard real-time conditions.

� Validated model libraries (e.g. tires, suspension, MBS axles) can

easily be used and integrated.

� IPGDriver model for sophisticated closed loop driving tasks.

Integration of Further ECUs and the Fai l Safe Tester

� The Xpack4 IntegrationHIL system provides possibilities for further plug-in test boxes extending the test cases

range of the whole system. Functional tests and interactions between steering system (including the optional

EPS-ECU) and components like ESC in complex settings with highest reproducibility.

� Fail Safe Tester provides opportunities for testing power supply, torque sensor signals, CAN signals and motor

control.

Coupling with the System Experience Platform (SEP)

� Replace selectively steering wheel actuator and

virtual driver algorithms or models by a human test

driver by mouse click especially for subjective

steering feel experiences in closed-loop maneuvers.

� Vice versa the Steering-in-the-Loop test bench

provides realistic steering behavior for the SEP.

Add-ons and Integration Potential

Communication via CAN

11

Scope of Delivery

The test bench is delivered with the following components in the basic configuration (without ECU integration):

Steering-in-the-Loop Test Bench

Engineering – Construction, Bui ld-up and Integration

Xpack4 Real-Time Computer with Subrack

� Power rack unit – 400 V, 125 A

supply for actuators

� Steering rack actuator

unit left/right

� Steering rack adjustment unit

� Steering wheel actuator

� Steering wheel / steering column

height adjustment unit

� Baseplate

� Basic mechanical safety parts

� Power rack unit

� Steering rack actuator

unit left/right

� Steering rack adjustment unit

� Steering wheel actuator

� Steering wheel / steering column

height adjustment unit

� Baseplate

� Mechanical safety elements

including wiring

� Test bench controlling software

extension

� Functionality tests

� Documentation

� SBC-F23P01-3U F23P01 Core i7 Single Board Computer / 3U cPCI Intel 2.4 GHz quad core, 16 GB RAM, 2x GigEthernet, USB

� IO-D203-08 cPCI Carrier Board D203-08 - 6U, slots for 4 M-Modules, A24 support

� SR19-3-C 19“/3U SubrackcPCI

� IO-M410 – CAN/CAN FD

communication interface 4 galvanically isolated CAN / CAN FD channels, high bandwidth

� IO-M36N-00 – Analog inputs,

16 Bits, single-ended 16 bit analog input, 16 single-ended channels, autonomous scan

� IO-M31 – Binary inputs

common ground 16 binary inputs, load on ground

The stated scope does not include any possible adjustments to the respective individual safety regulations, requi-

rements or conventions. Additional components, such as the CarMaker software or integration of electric steering

control units, are required for operation.

12

Linear Actuator Module

Max. force (each actuator)

Max. force (combined)

Active width of actuator

Maximum velocity

Static accuracy (deviation)

Dynamic accuracy (deviation)

Latency

12500 N

25000 N

+- 200 mm

+- 1m/s

< 6 N

< 55 N

3 ms

Steering Wheel Actuator Module

Peak torque

Mean torque

Max. steering wheel velocity

Static accuracy (deviation)

Dynamic accuracy (deviation)

Latency

120 Nm

50 Nm

1800 deg/s

< 0.02 deg

< 1.3 deg

5 ms

Xpack4 Real-Time System (basic configuration)

Real-time computer

CAN interface

Analog input

Binary input

F23P01 (single board computer)

M410 (IO-Card)

M36N00 (IO-Card)

M31 (IO-Card)

Technical Data Sheet

Explanation of Terms

� Latency Time: Time from request of new set value to response of actuator. Caused by communication delays

and frequency converter internal delays.

� Response Time: Time delay of whole control loop to set new value. E.g. force control, time delay until force

sensor measures requested value.

� Accuracy: Difference between requested value and measured sensor value.

Test Bench Results

13

Control Loop

Response Time Posit ion Control

Maneuver:

� Slalom 18m, v=55 km/h, aymax=8.6 m/s²

~ 5ms

CarMaker requested angle

Measured angle (sensor)

Latencies and responses during the control loop

Constant driving

Driving straight, v=55 km/h

Slalom 18m

aymax=8.6 m/s² (at vehicle limit)

Mean deviation 0.004 deg -0.005 deg

Standard deviation 0.014 deg 1.256 deg

14

Use of internal position controller

Servo motor +angle sensor

CM Requested

Angle Hiperface

~2ms = Position

Ctrl 3Phase AC

1ms = CM Requested

Angle CAN

1ms = Measured

Angle CAN

Accuracy Posit ion Control

Constant driving

Slalom 18m

Xpack4 Real-time System

Frequency Converter

Steering Wheel Actuator Controller Performance

Linear Actuator

Measured Force

Analog Signal

~2ms = Force

3Phase AC1ms = Set Force CAN

Control Loop

Response Time Force Control

For slalom 18m at vehicle limits:

Force gradient: ~ 6000 N/s, force response time: ~ 0 ms (latency compensation by force control loop)

Constant driving

Driving straight, v=55 km/h

Slalom 18m

aymax=8.6 m/s² (at vehicle limit)

Mean deviation - 0.62 N 0.37 N

Standard deviation 5.7 N 54.3 N

Accuracy Force Control

Constant driving

Slalom 18m

CarMaker requested force

Measured force (sensor)

Latencies and responses during the control loop

15

Frequency Converter

Xpack4 Real-time System

Force controller with use of sensor signal

Linear Actuator Controller Performance

1ms = Actual Force CAN

IPG Automotive GmbH • Bannwaldallee 60 • 76185 Karlsruhe • Tel.: +49 721 98520 0 • ipg-automotive.com

As a global leader in virtual test driving technology, IPG Automotive develops innovative simulation solutions for vehicle

development. Designed for seamless use, the software and hardware products can be applied throughout the entire

development process, from proof-of-concept to validation and release. The company’s virtual prototyping technology

facilitates the automotive systems engineering approach, allowing users to develop and test new systems in a virtual

whole vehicle.

IPG Automotive is an expert in the field of virtual development methods for the application areas of ADAS & Automated

Driving, Powertrain, and Vehicle Dynamics, committed to providing support to master the growing complexity in these

domains. Together with its international clients and partners, the company is pioneering simulation technology that is

increasing the efficiency of development processes.

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SOLUTIONS FOR VIRTUAL TEST DRIVING