Scheme 44
Description of ESC
Optimum driving safety now has a name: ESC, the Electronic Stability Control.
ESC is based on the MGH 40 ABS Hydraulic System. ESC recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by wheel-individual braking and engine control intervention with no need for actuating the brake or the gas pedal.
ESC adds a further function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and EDC functions. Whereas the ABS/TCS function controls wheel slip during braking and acceleration and, thus, mainly intervenes in the longitudinal dynamics of the vehicle, active yaw control stabilizes the vehicle about its vertical axis.
This is achieved by individual wheel brake intervention and adaptation of the momentary engine torque with no need for any action to be taken by the driver.
ESC essentially consists of three assemblies: the sensors, the electronic control unit, and the actuators.
The electronic control unit incorporates the technological experience accumulated in connection with the MGH 40 system, but has been substantially expanded in terms of capacity and monitoring concept in order to permit the additional sensor signals and arithmetic operations to be processed and converted into corresponding valve, pump, and engine control commands. Two 16-bit processors and one 8-bit processor, which monitor each other, cooperate to handle these requirements.
Of course, the stability control feature works under all driving and operating conditions. Under certain driving conditions, the ABS/TCS function can be activated simultaneously with the ESC function in response to a command by the driver.
In the event of a failure of the stability control function, the basic safety function, ABS, is still maintained.
Scheme 45
Description of ESC control
ESC system includes ABS/EBD, TCS, and AYC function.
ABS/EBD function: The ECU changes the active sensor signal (current shift) coming from the four wheel sensors to the square wave. By using the input of above signals, the ECU calculates the vehicle speed and the acceleration & deceleration of the four wheels and, the ECU judges whether the ABS/EBD should be actuated or not.
The TCS function prevents the wheel slip of drive direction by adding brake pressure and engine torque reduction via CAN communication. The TCS function uses the wheel speed sensor signal to determine the wheel slip as far as ABS function.
The AYC function prevents unstable maneuver of the vehicle. To determine the vehicle maneuver, the AYC function uses the maneuver sensor signals (Yaw Rate Sensor, Lateral Acceleration Sensor, Steering Wheel Angle Sensor). If a vehicle maneuver is unstable (over-steer or under-steer), the AYC function applies brake pressure on certain wheels, and sends an engine torque reduction signal by CAN.
After the ignition key-ON, the ECU continually checks for system failure (self-diagnosis). If system failure is detected, the ECU informs the driver of the system failure through the BRAKE/ABS/ESC warning lamp (fail-safe warning).
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Scheme 47
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Scheme 49
- ESC Non-operation: normal braking. ESC FUNCTION CHART (ESC NON-OPERATION: NORMAL BRAKING) Solenoid valve Continuity Valve Motor pump TC Valve IN (NO) OFF OPEN OFF OFF OUT (NC) OFF CLOSE
- ESC operation ESC FUNCTION CHART ( ESC OPERATION) Solenoid valve Continuity Valve Motor pump TC Valve Under-steering (Only inside of rear wheel) IN (NO) OFF OPEN ON ON OUT (NC) OFF CLOSE Over-steering (Only outside of front wheel) IN (NO) OFF OPEN OUT (NC) OFF CLOSE
Description
When the vehicle is turning with respect to a vertical axis, the yaw rate sensor detects the yaw rate electronically by the vibration change of the plate fork inside the yaw rate sensor.
If yaw velocity reaches a specific velocity after it detects the vehicle yawing, the ESC control is reactivated.
The Lateral G sensor senses vehicle's lateral G forces. A small element inside the sensor is attached to a deflectable lever arm.
Direction and magnitude of the lateral G forces can be communicated by changes in electrostatic capacity according to lateral G forces. Signals are interchanged with HECU through an extra CAN line, which is only used for communication between the HECU and the sensor.
Scheme 50
Specifications
| Description | Specification | Remarks | |
|---|---|---|---|
| Operating voltage | 10 ~ 16V | ||
| Output signal | CAN Interface | ||
| Operating temperature | 40 ~ 85°C (-40 ~ 185°F) | ||
| Yaw-rate sensor | Measurement range | 75 ~ 75°/sec | |
| Frequency response | 18 ~ 22Hz | ||
| Lateral G sensor | Measurement range | 1.5 ~ 1.5g | |
| Frequency response | 50Hz±60% | ||
YAW-RATE AND LATERAL G SENSOR SPECIFICATIONS
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Scheme 52
- Turn ignition switch OFF and disconnect the negative (-) battery cable.
- Remove the crash pad assembly. (For Coupe, refer to «CRASH PAD»(ref-362224-S30236245892010060400000) . For Sedan, refer to «CRASH PAD»(ref-362245-S13817783762010060400000) .)
- Remove the heater & blower unit. (Refer to «HEATER»(ref-362219) and «BLOWER»(ref-362289) )
- Disconnect the yaw rate & lateral G sensor connector.
- Remove the mounting bolts (A). Tightening torque: 7.9 ~ 10.8 N.m (0.8 ~ 1.1 kgf.m, 5.8 ~ 8.0 lb-ft)
- Installation is the reverse of removal.
- The ESC OFF switch is for the user to turn off the ESC system.
- The ESC OFF lamp is on when ESC OFF switch is engaged.
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Scheme 54
- Turn ignition switch OFF and disconnect the negative (-) battery cable.
- Remove the lower crash pad switch assembly by using the scraper and then disconnect the connectors.
- Check the continuity between the switch terminals as the ESC OFF switch is engaged.
The Steering Wheel Angle Sensor detects rotating direction of the vehicle. Rotating direction detected by the sensor is communicated with the HECU as a CAN signal, involving information about the angle through the CAN communication line. The HECU detects the speed of the steering wheel handling and the angle with this CAN signal. The HECU also uses this signal as the input signal to control anti-roll.
