2SamandTable of Contents...IntroductionTEVES MK20MANDO
3Samand Introduction… The Consequences Of Wheels Locking: Locking Driver are familiar with the consequences of wheels locking, due to braking too hard for road surface adherence conditions:The braking distance is longer,There is no lateral guidance:-The locked rear wheels often start to skid causing a spin,-The locked front wheels lose their steer ability, the vehicle continues straight ahead.There is abnormal tyre wear,There is an increased risk of accident.Even an experienced driver, in an extreme case, can lose control over the type and intensity of his braking.Only an automatic control system can prevent the wheels from locking. But to anticipate locking, the system must be able to continually analyse the changes in the speed of each of the wheels, and to do so, it uses sensors.Longer stopping distanceNo lateral guidanceACCIDENTTyre Wear
4Samand TEVES MK20… 1. Operation Graph : When the Vehicle is moving, the ABS ECU continuously monitors the Wheel Speed Data received from the Wheel Sensors and calculates the Reference Speed ( VREF )Based on the Reference Speed, the Wheel Slip Threshold ( ) can then be determined based on internal programmed mapsIf, under braking situations, any of the vehicle wheel speeds drop below the Reference Speed (VREF), the ABS ECU will automatically control the braking pressure in the system via the ARU hydraulic block assembly.
5SamandTEVES MK20…2. Influence EBD system in ABS system:
7SamandTEVES MK20…4. Location Of ABS ECU and Additional Regulation Unit :
8Samand TEVES MK20… 5. Wheel Speed Sensors: These are used to give the wheel speed information to the ABS electronic control unit (ECU), depending on which is fitted, in order to anticipate regulation in order to prevent the wheels from locking.To acquire the wheel speeds, inductive sensors are used which measure the speed of each of the vehicle wheels on a toothed or magnetic pulse wheel.
9Samand TEVES MK20… 6. Inductive Sensors: Two-pole sensors have the advantage of delivering a stronger signal than a signal-pole sensor, and are less sensitive to out-of-round *. Furthermore, in order to obtain higher sensor sensitivity, the teeth on the pulse wheel must be such that a tooth is opposite one pole while the flat is opposite the other pole. A two-pole sensor can be compared to a sensor composed of two permanent magnets each of which has a winding. The aim is to filter spurious signals caused by pole gap vibration.Out-of-round: pulse wheel axis off-centre in relation to the wheel axis witch causes variations in the gap over one rotation.
15SamandTEVES MK20…8. Inductive Sensors (rear):Location of sensors.
16SamandTEVES MK20…8. Inductive Sensors (rear):Air gap0.8 – 1.2 mm
17Samand TEVES MK20… 9. Testing the inductive sensors: Measuring the signal with an oscilloscope at low speed:The signal from these sensors may be tested by connecting an oscilloscope or AC voltmeter between its two conductors and turning the wheel.To test the condition of the sensor, its resistance must be measured on its connector terminals.
18Samand TEVES MK20… 9. Testing the inductive sensors: Measuring the signal with an oscilloscope at high speed:The signal amplitude and frequency increase in proportion to the wheel rotation speed.
19Samand TEVES MK20… 10. Bleeding: To diagnosis and bleeding should be use diagnosis tools.
20Samand TEVES MK20… 11. Warning light: In the event of a ABS function fault.
21Samand TEVES MK20… 11. Warning light: In the event of a Electronic Braking Distribution (EBD) fault
22Low speed output characteristics SamandMANDO…1. Review of accommodation:Passive SensorActive sensorPower supplierN/RProvided from battery via ECUTypeInductiveHall effectAir gap0.8 – 1.2 mm0.5 – 1.5 mmOutputVoltage / variable amplitude(dependant at vehicle speed)Current / pulse(independent at vehicle speed)I – V conversionRequiredProtection circuitLow speed output characteristics2KPH Min.0.14KPH Min.