ISO 4138-2021 pdf free download – Passenger cars — Steady-state circular driving behaviour — Open-loop test methods.
8Test procedure8.1warm-up
The warm-up shall be carried out in accordance with ISO 15037-1:2019,7.1.8.2 Initial driving condition
The conditions shall be in accordance with IS0 15037-1:2019,7.2.1 and 7.2.3,and with 8.3 to 8.6 asfollows, according to which method and variation is used.
8.3General test description
All necessary variables shall be recorded throughout the manoeuvre. Data shall be taken for both leftand right turns.A minimum of three repetitions is recommended.
For tests utilizing discrete increments of speed, radius or steering-wheel angle, all of the test data maybe taken in one turning direction followed by all the data in the other turning direction, as experiencehas shown that this minimizes data scatter. However, to obtain more even tyre wear and reduced tyreheating, data may be taken in alternating turning directions at each test speed/radius/steering-wheelangle.
The method chosen shall be noted on the test report, in the section on test-method-specific data for testconditions (see IS0 15037-1:2019,Annex B).At a minimum, data shall be taken at increments of lateralacceleration no larger than 0,5 m/s2.Annex C provides general information for the test methods.
NOTE where data vary rapidly with changes in lateral acceleration it can be useful to decrease the speed/radius/steering-wheel angle increments.
The test should be repeated several times so that the results can be examined for repeatability andaveraged.
Caution should be exercised during testing so that tyre heating is minimized as much as possible. Tyreheating is a particular concern for test methods using continuous speed increase, with attendant longperiods of data acquisition, and for all test methods at high levels of lateral acceleration.The tyresshould be cooled to normal operating temperatures between test runs.
8.4Method 1-Constant radius
8.4.1 Description
This test method requires driving the test vehicle at several speeds over a circular path of knownradius. The standard radius of the path shall be 100 m, but larger and smaller radi may be used, with40 m as the recommended lower value and 30 m as the minimum.
The directional-control response characteristics are determined from data obtained while driving thevehicle at successively higher speeds on the constant-radius path. This procedure can be conducted in arelatively small area. The procedure can be adapted to existing test track facilities by selecting a circleor path of appropriate radius. A constant-radius (in plane) road will often suffice for a test facility.
The constant-radius test exists in two variations. In the first, the vehicle is driven on the circular pathat discrete constant speeds. Data are taken when steady-state is attained. The test can be run on anylevel constant-radius path of sufficient length to attain and hold on-radius steady-state for at least a3 s measurement period. In the second, the vehicle remains on the circle with a continuous, slow speedincrease, during which data are taken.
8.4.2Procedure8.4.2.1 General
First drive the vehicle on the desired circular path at the lowest possible speed.Record data with thesteering-wheel and throttle positions fixed, so that the approximate Ackermann steer angle can berecorded.
Then drive the vehicle at the next speed at which data are to be taken.
Increase the level of the lateral acceleration and take data until it is no longer possible to maintainsteady-state conditions.
8.4.2.2With discrete test speeds
Drive the vehicle onto the circle at each test speed.After attaining steady-state, in which the desiredpath radius is held within ± 0,5 m, the steering wheel and throttle positions shall be held constant forat least 3 s.
8.4.2.3With continuous speed increase
Steadily increase the speed and record data continuously for as long as the vehicle remains on thedesired circular path within ±0,5 m.The maximum rate of increase of lateral acceleration should be0,1 m/s2-/s.The maximum permissible rate of increase of lateral acceleration shall be 0,2 m/s2/s.ISO 4138 pdf download.