ISO/PAS 5101:2021

PUBLICLY ISO/PAS
AVAILABLE 5101
SPECIFICATION
First edition
2021-10
Road vehicles — Field load
specification for brake actuation and
modulation systems
Véhicules routiers — Spécification de la charge pour les systèmes
d'actionnement et de modulation des freins
Reference number
ISO/PAS 5101:2021(E)
© ISO 2021

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ISO/PAS 5101:2021(E)
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ISO/PAS 5101:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 2
5 Percentiles of field coverage .3
6 Base assumptions and boundary conditions . 4
6.1 General . 4
6.2 Lifetime specifications . 4
6.2.1 Vehicle lifetime . 4
6.2.2 Standstill events, slopes and durations . 5
6.2.3 Standstill duration distribution . 5
6.2.4 Brake duration distribution . 5
6.3 Number of brake operations . 6
6.4 Temperature distributions . 7
6.4.1 Global environmental temperature distribution T . 7
env
6.4.2 Temperature distribution at installation location T . 8
inst
6.4.3 Exceptional high temperatures at the installation location . 9
6.4.4 Function specific occurrence and distributions over temperature ranges . 10
6.5 Brake pedal application profile . 11
6.5.1 Parameters for brake pedal apply and release time . 11
6.5.2 Modulation of deceleration during brake events .12
7 Braking system usage .13
7.1 Base brake function .13
7.2 Dynamic stability functions . 14
7.2.1 Electronic brake force distribution (EBD) . 14
7.2.2 Antilock braking system (ABS) . 14
7.2.3 Traction control (TCS). 16
7.2.4 Electronic stability control (ESC) . 20
7.2.5 Trailer sway control (TSC) . 24
7.2.6 Roll-over mitigation functions . 24
7.3 Brake torque optimizing functions . 25
7.3.1 Brake booster support functions . 25
7.3.2 Hydraulic brake assist (HBA) . 36
7.3.3 Hydraulic rear-brake boost (HRB) . 37
7.3.4 Fading support . 37
7.3.5 Brake preconditioning .38
7.4 Assistance functions .40
7.4.1 Standstill management .40
7.4.2 Hill descent control . 45
7.4.3 Adaptive cruise control (ACC) .46
7.4.4 Parking assist (PA). 51
8 Substitution methods .55
8.1 Dependent functions . 55
8.1.1 Substitution of ABS functions . 55
8.1.2 Substitution of hold functions .56
8.1.3 Substitution of fading support manoeuvres . 57
8.1.4 Substitution of brake disc wiping manoeuvres . 57
8.1.5 Substitution of base brake functions .58
Bibliography .59
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ISO/PAS 5101:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,
Vehicle dynamics and chassis components.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/PAS 5101:2021(E)
Introduction
Vehicle development programs tend to grow in complexity and integration of the braking system with
chassis dynamics and mechatronics, demanding more robust and comprehensive evaluation programs.
Also, to remain competitive, braking systems and their components’ functionality and application
across multiple vehicle architectures and platforms are increased.
The proper selection and adaptation of field load spectra and profiles to the specific program ensure
functionality, reliability and braking system availability. This document defines a library of field
load schedules to help developing simulation and testing programs tailored to the vehicle or system
specification and requirements. Specific cycles and load collectives including the main functions
associated with everyday driving and operation and exceptional load cases are described to ensure safe
braking behaviour. This document's field load was typically derived from analysing field data collected
from almost 1 million vehicles having driven more than 45 billion km. Several vehicle and brake system
suppliers from vehicles used in different regions worldwide contributed to this field data collection. In
addition, data from driving studies with specific measurement equipment was used. Wherever the data
available from field or studies was not sufficient, existing specifications or expert judgement served to
derive conservative assumptions.
This document provides field loads independent of the vehicle technology, vehicle specification,
intended use and field usage. It remains the manufacturer's responsibility to include and adapt the field
loads to the specific vehicle configuration. The adaptation includes at least:
— define sampling and testing plans, including vehicle configuration(s), road conditions selection of
the specific profiles and load spectra of this document;
— define level of evaluation and integration of simulation, Hardware-in-the-Loop, physical testing
methods, along with other components and software functions part of the testing program;
— agree on performance and reliability criteria (including statistical tools and metrics);
— reflect specific system architectures and control technologies for the unit(s) under testing.
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PUBLICLY AVAILABLE SPECIFICATION ISO/PAS 5101:2021(E)
Road vehicles — Field load specification for brake
actuation and modulation systems
1 Scope
This document specifies expected field loads for functions provided by the braking system actuator and
modulator and applies to passenger cars and light commercial vehicles (classes M1 and N1, according
to UNECE).
Functions addressed in this document are:
— dynamic stability functions (e.g. electronic stability control);
— brake torque optimizing functions (e.g. electronic brake force distribution);
— brake assistance functions (e.g. hill start assist).
This document only covers functions where data of appropriate maturity are available. There are
additional functions of a braking system, which are not covered by this document.
By describing the expected field loads, this document specifies representative manoeuvres and
occurrences for different functions. These serve as an orientation for the derivation of test procedures.
This document applies to vehicles up to conditional automation (SAE J 3016 level 3) with a maximum of
30 % automated brake operations.
NOTE Field loads for automation levels above level 3 are under consideration for future editions.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
brake booster
part of the actuation unit, excluding master cylinder, in systems with separate actuator and modulator
Note 1 to entry: A brake booster is not part of braking systems with integrated actuator and modulator (see
Figure 1).
3.2
fading
decrease of braking torque as a function of temperature or vehicle speed at constant application force
Note 1 to entry: Amongst others, the decrease of the friction by the temperature is the most important effect.
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ISO/PAS 5101:2021(E)
[SOURCE: ISO 611:2003, 7.1.7, modified — The original term was "brake fade", the word “vehicle” and
Note 1 to entry were added, and the examples were removed.]
3.3
brake friction coefficient
ratio between the tangential force and the normal force, acting between linings and drum or disc
[SOURCE: ISO 611:2003, 9.19.1, modified — The symbols and formula were removed, the original term
was "coefficient of friction".]
3.4
coefficient of adhesion
µ
ratio between the tangential force transmitted to the road by a tyre and the normal force
[SOURCE: ISO 611:2003, 9.19.2, modified — "k" was changed to "µ", the symbols, formula and note were
removed.]
3.5
control time
duration the braking system is controlling the pressure
3.6
fully active brake operation
deceleration intended by the driver and automatically initiated and operated by the braking system
3.7
nominal runout pressure
lowest master cylinder pressure where maximum support from the actuator is reached in quasi-static
operation
Note 1 to entry: Only applies to separated actuator and modulator.
Note 2 to entry: For vacuum-based actuation systems, the nominal runout pressure refers to sea level.
Note 3 to entry: Above this pressure, only the unsupported pressure increase is possible.
3.8
partially active brake operation
deceleration initiated by the driver and supported by the modulation of the wheel brake pressure
3.9
standstill
stopping situation during a trip in which the vehicle is not moving
EXAMPLE Stopping at traffic lights or in heavy traffic situations.
Note 1 to entry: Standstill does not include parking situations.
3.10
steering angle
mean value of angle of left and right front wheel relative to the longitudinal axis of the vehicle
Note 1 to entry: Rear-wheel steering is not considered in this document.
4 General
This document describes use cases represented by manoeuvres and their occurrences for various
functions of the braking system to describe the expected field loads for a braking system. Unless
otherwise specified, these manoeuvres and occurrences are derived from empirical values and
collected field data.
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ISO/PAS 5101:2021(E)
The manoeuvres and occurrences described in this document serve as an orientation to develop test
procedures. The applicability of the generalized field loads detailed in this document needs to consider
the specific braking system and vehicle configuration.
Figure 1 depicts the components of the braking system addressed in this document.
Figure 1 — Components of the braking system
5 Percentiles of field coverage
The braking system supports multiple vehicle dynamics functions. The probability of high usage of all
functions in an individual vehicle is much lower than the probability of high usage of only one single
th
function in an individual vehicle. A specification aiming to cover the 100 percentile vehicle for every
individual function would lead to an over-specification.
The field load for electronic brake force distribution (EBD), antilock braking system (ABS) and adaptive
th
cruise control (ACC) aims to describe the 99 percentile vehicle usage. All other functions described
th
in Clause 7 cover the 95 percentile vehicle usage for each function. However, it is unlikely that all
functions – given the multitude of functions - are used up to the specification limit in one individual
vehicle. This approach leads to a field coverage significantly above 99 %.
th
NOTE 1 ABS, EBD and the standard brake function are specified to cover the 99 percentile vehicle usage
because products only providing this set of functions exist and therefore, the combination effect is weak. ACC is
th
specified to cover the 99 percentile because it is an automation of the standard braking function.
Figure 2 illustrates an example of the usage of an individual function.
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ISO/PAS 5101:2021(E)
Key
X load or stress level with consistent engineering units
Y probability density
a th
99 percentile.
Figure 2 — Schematic example of the probability density function P for the load σ
NOTE 2 Few vehicles experience a very low load; few vehicles experience a very high load; most vehicles
experience a medium level of load.
NOTE 3 Typically, braking system components can endure loads above their specification. Furthermore, the
load a component experiences is typically lower than the load described.
6 Base assumptions and boundary conditions
6.1 General
This clause defines the assumptions for the vehicle lifetime and braking system lifetime. These
assumptions serve as the baseline for the manoeuvres and occurrences of the functions described in
Clause 7.
NOTE Clause 7 describes the field load for braking system functions but not for wearing parts such as brake
pads and brake discs.
6.2 Lifetime specifications
6.2.1 Vehicle lifetime
The field loads described in this document correspond to a vehicle lifetime of either 300 000 km or
8 000 h ignition-on time or 15 years, whichever occurs first.
The expected amount of trips is up to 50 000 over a vehicle lifetime.
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ISO/PAS 5101:2021(E)
6.2.2 Standstill events, slopes and durations
The expected amount of brake operations that lead to a standstill is 480 000 over a vehicle lifetime.
Table 1 shows the distribution of slopes at the standstill events. The values shown include uphill and
th
downhill slopes and cover the 99 percentile. An even distribution between up- and downhill situations
is assumed.
Table 1 — Distribution of standstill events versus slope angle
Slope at a standstill Probability
[%] [%]
> 30 - 50 0,006
> 20 - 30 0,194
> 15 - 20 0,8
> 10 - 15 2
> 5 - 10 9
≤ 5 88
6.2.3 Standstill duration distribution
In total 480 000 standstill events are defined over vehicle lifetime. Table 2 shows the distribution of
their duration. The durations are independent of any active function when the vehicle ignition is on.
th
The distribution covers the 99 percentile usage.
NOTE The parking times between two trips are not considered.
Table 2 — Distribution of standstill duration
Standstill duration Frequency
[s]
0 - 2 126 000
2 - 10 162 000
10 - 30 100 000
30 - 60 47 000
60 - 180 34 000
180 - 900 9 000
> 900 2 000
Sum 480 000
6.2.4 Brake duration distribution
Table 3 shows values of the brake duration distribution of an average driver.
Table 3 — Distribution of brake duration
Brake duration Percentage per class
[s] [%]
0 – 2 57
2 – 5 25
5 - 10 9
10 - 60 8
> 60 1
Sum 100
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ISO/PAS 5101:2021(E)
6.3 Number of brake operations
th
Over a vehicle lifetime, the 99 percentile of brake operations corresponds to 2,2 million brake
operations. Of these 2,2 million brake operations, 600 000 events take place during standstill.
The frequency of brake operations during standstill represents brake operations that begin and end
during vehicle standstill.
Table 4 shows the number of brake operations in deceleration classes of 0,05 g.
The frequencies shown in Table 4 include the base brake function and all functions intended to
decelerate or hold the vehicle.
This document assumes 10 000 kPa is equivalent to 1,0 g for a typically laden vehicle.
Table 4 — Distribution of brake operations versus deceleration and brake pedal force
Deceleration Brake pedal Frequency per class Frequency per class Frequency per class
a
[g] force while driving during standstill
[N]
0,00 ≤ x ≤ 0,05 20 205 033 84 569 289 602
0,05 < x ≤ 0,10 20 639 927 243 706 883 633
0,10 < x ≤ 0,15 29 404 300 115 070 519 370
0,15 < x ≤ 0,20 38 200 177 56 182 256 359
0,20 < x ≤ 0,25 48 84 266 25 350 109 616
0,25 < x ≤ 0,30 57 35 147 16 912 52 059
0,30 < x ≤ 0,35 67 14 463 12 771 27 234
0,35 < x ≤,0,40 77 7 168 9 810 16 978
0,40 < x ≤ 0,45 86 3 893 7 793 11 686
0,45 < x ≤ 0,50 96 2 144 5 892 8 036
0,50 < x ≤ 0,55 105 1 252 4 585 5 837
0,55 < x ≤ 0,60 115 745 3 474 4 219
0,60 < x ≤ 0,65 124 466 2 718 3 184
0,65 < x ≤ 0,70 134 332 2 218 2 550
0,70 < x ≤ 0,75 143 198 1 613 1 811
0,75 < x ≤ 0,80 153 91 1 067 1 158
0,80 < x ≤ 0,85 163 77 995 1 072
0,85 < x ≤ 0,90 172 63 917 980
0,90 < x ≤ 0,95 182 52 831 883
0,95 < x ≤ 1,00 191 41 739 780
1,00 < x ≤ 1,05 201 32 640 672
1,05 < x ≤ 1,10 210 25 534 559
1,10 < x ≤ 1,15 220 19 421 440
1,15 < x ≤ 1,20 230 14 301 315
1,20 < x ≤ 1,25 239 10 175 185
1,25 < x ≤ 1,30 249 9 105 114
> 1,30 > 250 56 612 668
1 600 000 600 000 2 200 000
a
Including brake operations leading to a vehicle standstill.
NOTE 1 Table 4 shows data over a vehicle lifetime according to 6.2.1.
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ISO/PAS 5101:2021(E)
NOTE 2 Brake pedal forces are derived from the deceleration to brake pedal force characteristic of vehicles
which delivered the corresponding field data.
NOTE 3 Brake pedal forces values are used for brake pedal applies during standstill, deceleration values for
brake pedal applies during driving.
NOTE 4 For vehicle configurations differing from those assumptions, the relation between brake pressure
and deceleration is determined individually.
Figure 3 illustrates the corresponding cumulative distributions from Table 4.
Key
X cumulative number of load cycles in counts
g deceleration level in g
1 total cumulative brake operations
2 cumulative brake operations while driving
3 cumulative brake operations during standstill
Figure 3 — Cumulative distribution per class
6.4 Temperature distributions
6.4.1 Global environmental temperature distribution T
env
The distribution of the environmental temperatures, as shown in Table 5, uses the following principles:
— global coverage of typical, low and high-temperature profiles;
— weighting according to human population density, cities with less than 1 000 inhabitants are not
considered;
— extreme temperature events, which do not occur regularly within 10 years, are not covered.
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ISO/PAS 5101:2021(E)
Table 5 — Distribution of environmental temperature
T Probability
env
[°C] [%]
‒ 40 0,5
‒ 30 2
‒ 20 5
‒ 10 5
0 7,5
10 15
20 25
30 25
40 14
50 1
Sum 100
6.4.2 Temperature distribution at installation location T
inst
Table 6 provides the estimated probability distribution as a function of the temperature at the
installation location T .
inst
The temperature at installation location T reflects the superposition of the environmental
inst
temperature T outside the vehicle with the temperature increase dT at the installation location in a
env
combustion engine compartment during vehicle operation.
The dT in electric vehicles is lower and therefore is assumed to be covered by this specification. Use
Formula (1) to determine the temperature distribution at the installation location.
T = T + ΔT (1)
inst env
where
T is the temperature at the installation location of the brake actuation and modulation sys-
inst
tems;
T is the distribution of worldwide environmental temperature outside the vehicle (vehicle
env
independent, see 6.4.1);
ΔT is the temperature increase by vehicle usage at installation location (vehicle dependent,
typical vehicle resulting distribution for T given in Clause 6).
At environmental temperatures of -40 °C, no increase of T by vehicle usage is assumed due to the
inst
airflow's high cooling capability.
Moderate and high environmental temperatures lead to a ΔT of up to 55 K.
Specific temperature effects may be considered when the brake system components directly interact
(have thermal conductivity) through a mechanical connection.
EXAMPLE Direct cooling effect by the connection of an actuator to the passenger compartment.
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ISO/PAS 5101:2021(E)
Table 6 — Distribution of temperature at the installation location
T Probability
inst
[°C] [%]
‒ 40 0,5
‒ 20 2,5
20 28
60 40
80 26
105 3
Sum 100
6.4.3 Exceptional high temperatures at the installation location
Higher ΔT can occur as a combination of exceptional events and devices' proximity with significantly
increased temperatures.
EXAMPLE Stopover after long steep uphill driving at low speed with fully laden trailer and vehicle.
NOTE 1 This occurs only in rare vehicle configurations.
To also cover such exceptional situations, Figure 4 shows representative manoeuvres, including 120 °C.
Phase 1 defines the starting condition. The braking system is heated thoroughly until 105 °C to ensure
all system components start with this initial temperature.
Phase 2 represents the h
...