BS ISO 14793 pdf download Road vehicles — Heavy commercial vehicles and buses — Lateral transient response test methods
This International Standard specifies test methods for determining the transient response behaviour of heavycommercial vehicles, heavy commercial vehicle combinations, buses and articulated buses， as defined inISO 3833 for trucks and trailers above 3,5 t and buses above 5t maximum weight, and in UNECE(UnitedNations Economic Commission for Europe) and EC vehicle classification, categories M3,N2,N3,03 and O4.
NOTE The open-loop manoeuvres specified in this International Standard are not representative of real drivingconditions, but are nevertheless useful for obtaining measures of vehicle transient behaviour particularly with respect tothat which the driver experiences — in response to several specific types of steering input under closely controlled testconditions. For combinations where the response of the last vehicle unit is of importance, see ISO 14791.
The following referenced documents are indispensable for the application of this document.For datedreferences,only the edition cited applies. For undated references， the latest edition of the referenceddocument (including any amendments) applies.
ISO 1176:1990, Road vehicles – Masses – Vocabulary and codesISO 3833:1977, Road vehicles -Types -Terms and definitions
ISO/TR 8725:1988,Road vehicles —Transient open-loop response test method with one period of sinusoidalinput
ISO/TR 8726:1988,Road vehicles — Transient open-loop response test method with pseudo-random steeringinput
ISO 8855:1991, Road vehicles —Vehicle dynamics and road-holding ability —Vocabulary
ECERegulation No.30, Uniform provisions concerning the approval of pneumatic tyres for motor vehicles andtheir trailers
3Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8855 and the following apply.3.1
unit of a vehicle combination which is connected with a yaw-articulation jointEXAMPLE Tractor, semitrailer, dolly.
NOTE The number of vehicle units is one more than the number of articulation joints.
IMPORTANT—The method of data analysis in the frequency domain is based on the assumption thatthe vehicle has a linear response.Over the whole range of lateral acceleration this is unlikely to be thecase, the standard method of dealing with such a situation being to restrict the range of the input sothat linear behaviour can be assumed and, if necessary, to perform more than one test at differentranges of inputs which,together, cover the total range of interest.
The objective of these tests is to determine the transient response of a vehicle.Characteristic values andfunctions of both linear and nonlinear behaviour are considered necessary for fully characterizing vehicletransient response. Linear characteristic values and functions are determined with tests in the frequencydomain and nonlinear characteristic values and functions with tests in the time domain. In the case of vehiclecombinations, it is primarily the response of the first vehicle unit that is evaluated.
lmportant characteristics in the time domain are
– time lags between steering-wheel angle, lateral acceleration and yaw velocity,
– response times of lateral acceleration and yaw velocity (see 9.2.1),
– lateral acceleration gain (lateral acceleration divided by steering-wheel angle),- yaw velocity gain (yaw velocity divided by steering-wheel angle), and
– overshoot values (see 9.2.3).
lmportant characteristics in the frequency domain are the transfer functions of- lateral acceleration related to steering-wheel angle, and
– yaw velocity related to steering-wheel angle,
expressed as gain and phase functions between input and output variables.
There are several test methods for obtaining these characteristics in the time and frequency domains, asfollows, the applicability of which depends in part on the size of the test track available.
1) step input;
2sinusoidal input (one period).b)frequency domain:
1) random input;2)pulse input;
3) continuous sinusoidal input.