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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.
© IP
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SOLUTIONS FOR VIRTUAL TEST DRIVING