Technical Bulletin

Robot Friction Measurementfor LSS Testing
Version 1.0
10th March 2022
TB 038TitleVersionDocument NumberAuthor
Date
Related Documents
Application Date

Robot Friction Measurement for LSS Testing
1.0
TB 038A Hellmann (BASt), J Ellway (Euro NCAP)
10th March 2022
AEB C2C, AEB VRU & LSS testing protocols
1st January 2023

Copyright © Euro NCAP 2022 - This work is the intellectual property of Euro NCAP. Permission is granted for this material
to be shared for non-commercial, educational purposes, provided that this copyright statement appears on thereproduced materials and notice is given that the copying is by permission of Euro NCAP. To disseminate otherwise or to
republish requires written permission from Euro NCAP.

Preface
DISCLAIMER: Euro NCAP has taken all reasonable care to ensure that the information
published in this document is accurate and reflects the technical decisions taken by theorganisation. In the unlikely event that this protocol contains a typographical error or any otherinaccuracy, Euro NCAP reserves the right to make corrections and determine the assessment
and subsequent result of the affected requirement(s).

EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP)

Table of Contents
1.

Introduction ................................................................................................................... 1

2.
2.1
2.2

Steering Robot Friction Measurement Procedure ..................................................... 2
Measuring device ............................................................................................................ 2
Procedure ........................................................................................................................ 2Annex I ...................................................................................................................................... 4

1.

Introduction

This Technical Bulletin (TB 038) defines the friction requirements for steering robots that areused in the assessment of Lane Support Systems (LSS) as well as Emergency Steering Support(ESS) systems. It also serves as a check for possible incorrect and constrained mounting of thesteering robot resulting in high friction, which can negatively impact the performance of a Lane
Keep Assist (LKA), ELK (Emergency Lane Keeping) or ESS systems.
During Euro NCAP LSS testing, the steering robot is switched to ‘free-mode’ once a system
reaction has been anticipated. The ‘free-mode’ sets the robot to a passive status where only theresidual friction remains to be overcome by the lane support system to redirect the car back.
In the event that a vehicle demonstrates abnormal performance during an LSS test, theOEM may request that the Euro NCAP test laboratory performs a friction measurementin accordance with the following procedure. In the event the performance was not as
predicted by the OEM (with a friction level up to l.5Nm), the Euro NCAP Secretariat
shall be informed. Where the OEM can demonstrate that the limitations with test
equipment are adversely influencing the system performance, alternative test methods
will be considered.
This document should be used in conjunction with the Euro NCAP AEB C2C, LSS VRU &LSS Testing protocols.

Version 1.0
10th March 2022

12.

Steering Robot Friction Measurement Procedure

The procedure quantifies the influence of a steering robot during the critical part of a test run
where the steering robot is deactivated, and the action of the lane support system is expected.
2.1
2.1.1
2.1.2
2.1.3

Measuring device
A steering robot with accurate torque measurement is needed.
An example test execution is detailed in Annex I.
The measured torque values shall be filtered with a low-pass 4 pole Butterworth filterand 6Hz cut-off frequency.

2.2
Procedure
2.2.1 Ensure that the vehicle remains stationary throughout the entire procedure.
2.2.2 The friction of the robot actuator is measured by manually turning the steering wheelwith an amplitude of ±45 degrees, where 0 degrees being the centred steering wheel
position (driving in a straight line), and the robot being in the same state as during thecritical manoeuvre (‘free-mode’). Then the average torque T, considering the turning
direction and the linked prefix is calculated.
2.2.3 This test must be executed three times, and the following must be checked:
2.2.4 The recorded torque value must not exceed:
Tmax=1.5 Nm
2.2.5 The recorded torque value must exceed:
Tmin=0.2 Nm(Simulating hands on situation during the LSS)
2.2.6 To ensure constant and steady friction, the standard deviation must also be checked inaccordance with the formula:𝑛12𝑇𝑠𝑡𝑑𝑑𝑒𝑣 = √ ∑ 𝑇𝑖2 − 𝑇𝑚𝑒𝑎𝑛< 0.4 Nm
𝑛𝑖=1n= number of torque measurement samples
2.2.7 The measurement of friction must be verified for both rotation directions independently
and for the 3 tests in each direction (6 verifications in total).
2.2.8 It is important to make sure the test starts with a steering angle greater than 45 degrees
or less than -45 degrees to avoid any discontinuities in the measurement trace. See
Figure 1.

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10th March 2022

2

Example of friction curve:

SR60 friction torque with centred robot
1.6
1.2

SR TorqueTolerance corridors

Torque [Nm]

0.8

-45

0.4

-35

-25-150-5-0.4

51525

35

45

-0.8
-1.2
-1.6

Steering angle [°]Figure 1: Example friction output

Version 1.0
10th March 2022

3

Annex I
Example procedure utilising SR15 Orbit or other similar steering robots
1.
2.
3.
4.

Ensure that the vehicle remains stationary throughout the entire procedure.
Attach robot according to normal installation instructions.
Swap tie-down rod for load cell & sucker mount assembly.
Ensure that load cell runs perpendicular to the arm of the robot and is in plane with the gearring.

5. Power up robot with steering robot in '0' position to ensure the SR angle is zeroed.
6. Create a ‘Learn Test’ as a record of data.
7. Edit ADC channels by opening: 'Vehicle Edit/Test' > 'Test & Results' > 'Set up Transducers'> ' ADC channels'.
8. Find corresponding ADC channel for connected load cell and configure the sensitivity andunits.
9. Zero the current reading to compensate for the force read due to the weight of the robot arm
and load cell assembly.
10. Torque is calculated as:
Calculated channel:
𝑇𝐹𝑟𝑖𝑐𝑡𝑖𝑜𝑛 = 𝐹𝑑
𝑇𝐹𝑟𝑖𝑐𝑡𝑖𝑜𝑛 = 𝑁?∗ 0.52
Where F = Force in link (N)Where "?" = ADC Channel number
And d = link separation (m)11. Take an initial reading by slowly rotating (<40 °/s) the steering wheel by hand.
12. If there is a prominent sinusoidal torque pattern occurring once per cycle, recentre the Orbitgear ring to the steering column to reduce the effects of vertical force translated to the loadcell.
13. Take a secondary reading. You may wish to centre the hysteresis curve about 0 by increasingor decreasing the analogue offset.
14. Take 3 further readings according to step 11.
15. Review data and a apply a filter to reduce noise that would likely not be detected by thevehicle's ADAS (in this report, a 6Hz, 4 pole Butterworth filter was applied).

Version 1.0
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416. Crop graph to area of interest (-45 to 45 degrees) for increasing SR angle and fit a trend lineof least squares regression for each plot. This will be used to determine the average friction
value.
17. Repeat step 12 for decreasing SR angle.
18. If the resultant friction torque is too high, try loosening the two thumb screws of the motor
assembly by a ¼ turn (see image below) and repeat steps 11-17:

Version 1.0
10th March 20225