Module 3 ESC (electronic stability control) eng

: Bộ điều khiển độ ổn định điện tử (ESC) làm tăng sự an toàn chủ động trong mọi điều kiện lái xe.Đặc biệt khi vào cua, hay nói cách khác, khi các lực li tâm đang hoạt động, ESC sẽ ổn định xe và giữ cho xe an toàn trên làn đường. ESC nhận biết các điều kiện lái xe quan trọng, chẳng hạn như phản ứng hoảng loạn trong các tình huống nguy hiểm, và ổn định xe bằng cách tự phân bổ lực phanh bánh xe và can thiệp vào hệ thống điều khiển động cơ mà không cần phải đạp phanh hoặc bàn đạp ga.ESC phản ứng xử lý nhanh vượt xa khả năng nhận biết nguy hiểm của người lái xe và tự động “điều khiển” chiếc xe trở lại đúng hướng bằng cách sử dụng phanh có chọn lọc. Nói cách khác, ESC đảm bảo rằng chiếc xe hoạt động, vận hành bình thường ngay cả trong những tình huống khắc nghiệt nhất.

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Control)

LESSON

3.1 Overview 71

3.1.1 Introduction 71

3.1.2 History of ESC 72

3.1.3 ESC Logic 73

3.2 System Components 77

3.2.1 Main Components 77

3.2.2 Wheel Speed Sensor 78

3.2.3 Yaw-rate & 2 G-Sensor 79

3.2.4 Steering Angle Sensor 80

3.2.5 ESC OFF Switch 82

3.2.6 Brake Switch 83

3.2.7 ESC HECU 84

3.2.8 Warning Lamp & Indicator Lamp 89

3.3 Maintenance 91

3.3.1 Variant Coding 91

3.3.2 HECU Air Bleeding 92

3.3.3 Steering Angle Sensor Calibration 94

3.3.4 G-Sensor Calibration 95

[Learning Objective]

▪ Describe the history of ESC

▪ Describe the system layout and list the locations, mechanisms and functions of components

▪ Describe the valve operation that takes place in the oil pressure circuit during normal operation, ABS operation and ESC operation

▪ Take the necessary measures after changing parts

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▪ Europe: ESP (Electronic Stability Program)

▪ North America/global: ESC (Electronic Stability Control)

▪ Korea: VDC (Vehicle Dynamic Control)

Anti-wheel lock Independent wheel control Wheel/steering wheel control

ABS (Anti-lock Brake System) is designed to generate maximum brake force the driver can't with pedalwork A vehicle skidding out of control can't be controlled ABS rapidly repeats the application/release ofbrakes when tires are skidding to restore a vehicle's pre-skid brake force

While ABS only adjusts a vehicle's brake force, TCS (Traction Control System) adjusts brake force as well

as the power transmitted to the wheels from the engine TCS is designed for harsh driving conditions, such

as snow or mud It applies the brakes only to a spinning wheel or redistributes power to be transmitted to

a spinning wheel to other wheels for increased stability When functioning in conjunction with ABS, TCScontrol is executed through ABS, and when accelerating, TCS control is executed through engine output.ESC (Electronic Stability Control) detects a vehicle's skidding and controls brake pressure applied toindividual wheels and the engine output Without the driver applying the brakes, ESC safely prevents avehicle from skidding ESC's primary function is prevention of understeering and oversteering ABS, TCSand EBD all fall into the category of ESC

VSM (Vehicle Stability Management) maintains a stable vehicle position by applying ESC and MDPS (MotorDriven Power System) to braking and steering when a vehicle is spinning, understeered or oversteered

1) Driver Intension & Actual Vehicle Behavior

The driver's intention is measured by the steering wheel angle (e.g where does the driver wants to go)and the braking pressure (e.g is the driver applying the brake) To verify whether the vehicle is moving asthe driver intends, actual vehicle behavior is measured by vehicle rotation angle (yaw angle) and vehiclespeed

2) Comparison between Driver Intension and Actual Vehicle Behavior (ESC control)

As long as the actual vehicle behavior matches the drivers’ intention, the situation is judged as normaloperation and ESC will not become active If there is a large difference between actual vehicle behaviorand driver’s intention the situation is judged as unstable driving condition

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3) Oversteering & Understeering

With unstable driving conditions, understeering and oversteering can occur Understeering refers to a state

in which the vehicle's turn angle is larger than the steering wheel angle, and the vehicle slides out whenturning a corner Oversteering refers to a state in which the vehicle's turn angle is smaller than the steeringwheel angle when turning a corner

● Left Understeer

a An obstacle appears ahead on the right The driver turns the steering wheel to the left, butundersteering occurs and the vehicle keeps moving forward toward the obstacle

b ESC HECU detects the understeer through the steering angle sensor and Yaw-rate sensor, and

instantly brakes the rear left wheel

c Consequently, the vehicle is guided into the driver's intended direction

b ESC HECU detects the oversteer through the steering angle sensor and Yaw-rate sensor, and

instantly brakes the front left wheel

c Consequently, the vehicle is guided into a straight line without skidding

TIP Vehicle without ESC

If a driver suddenly turns the steering wheel to evade an object that suddenly appeared in front whiledriving on a highway in a vehicle without ESC, the action causes the vehicle to slide and becomesuncontrollable

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Wheel Speed Sensor Detects the speed of each wheel.

Yaw Rate Sensor Measures the rotation angle of the vehicle via vertical axis

Steering Angle Sensor Detects the driver's directional intention

Pressure Sensor Measures brake pressure to identify the driver's braking intention

ESC OFF Switch ESCcan be stopped at the driver's will

Brake Switch This switch is mounted on the pedal assembly and is used to send the status

of the brake pedal to the HECU

ESC HECU Receives signal from each sensor and computes the signals and uses the

data to engage brake for each wheel

Warning Lamp ABS / EBD / ESC / DBC Notifies system trouble to the driver

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1) Exploded View of Wheel Speed Sensor and Its Role

The wheel speed sensor detects the speed of each wheel, then transfers the information to the ESC HECU

to calculate the vehicle speed and determine whether the wheel is locked or not It is located in the wheelhub area There are two types of WSS: Passive (Coil Type) and Active (Hall IC Type) Active WSS is notaffected by air gaps and detections can be made from a speed of 0km/h; as such, active WSS is in wideruse than passive WSS

2) Coil Type & Hall IC Type

Category Coil Type Hall IC Type

Type

it energizes the coil

The internal resistance of Hall IC may bealternated upon the rotating of tone wheeland it generates the different current

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3.2.3 Yaw-rate & 2 G-Sensor

1) Exploded View of Yaw-rate & 2 G-Sensor and Its Role

Yaw-rate sensor measures the rotation angle speed based on the vehicle's vertical axis, side wayacceleration caused by centrifugal force, and longitudinal acceleration for determining sudden braking

or road incline It sends the data signal to ESC HECU, which uses the data for vehicle stability control.Yaw-rate sensor includes latitude and longitudinal acceleration sensors that allows all condition detectionwith a single sensor It's data is also used for ESC auxiliary functions or for EPB Install the Yaw-ratesensor at the bottom of the center floor console facing ahead

2) Mechanism

Alternating voltage causes the oscillator of the Yaw-rate sensor to transform and oscillate left and right

at a set rate If the vehicle makes a turn at a constant angular velocity in this state, the detector in thesensor tilts toward the direction of the oscillation and at a right angle, due to Coriolis force, and producesalternating voltage An AC waveform is generated from the detecting element and is used to detect thecornering direction and magnitude, outputting an analog signal in the process

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1) Exploded View of Steering Angle Sensor and Its Role

Steering Angle Sensor is integrated with Torque Sensor It detects the the steering wheel turn angle andtorque to determine driver's steering intention ESC HECU compares the steering wheel angle receivedfrom the steering angle sensor with the vehicle's actual turn angle received from the yaw rate sensor todetermine understeer/oversteer

There are two types of steering wheel sensor: optical type and magnetic type Generally, optical type isused for low output models, and magnetic type is used for high output models

Installation locations are as follows

▪ In case of vehicles with MDPS.: The Steering angle sensor is installed in MDPS assembly.

▪ Vehicle without MDPS: The Steering angle sensor is installed upper side of the clock spring of steering

is composed of an input shaft rotor (magnet) and an output shaft rotor For the steering angle, the maingear matches the column shaft, rotating two planetary gears that each have a different number of gearteeth Then, a phase difference is created and the rotation angle is detected via Hall IC which uses that

● Optical Sensor

An optical sensor uses light for detection and is made up of a quill shaft, dust cover, light guide,input/output disk and PCB assembly If the light emitting element (LED A/B) generates light, it passesthrough two input/output discs via a light pipe The light is then received by the photodetector inPCB and a steering angle and torque are detected based on the volume of light received When theinput/output disc is in a neutral state, the left and right angles are identical, so the amount of light thatpasses through it is the same However, when steering is applied, one side of the disc is blocked, andthe amount of light is reduced The angle and distortion are determined by the change in light Thekey here is the base point of the input shaft disc, called the index point If the MDPS is replaced, thesteering angle value which is transmitted to the ECU is different from the steering angle of the actualvehicle, so set to zero point the steering angle sensor to find the index point

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1) Exploded View of ESC OFF Switch and Its Role

The ESC off switch allows the driver to stop ESC When the "off" signal is sent to HECU, the ESC OFFindicator comes on The ESC off switch is used in the following circumstances

▪ Rocking to free the vehicle in deep snow or loose surface material

▪ Driving with snow chains

▪ Operation of the vehicle on a brake test bench

2) ESC 2–Step OFF Switch

Improving from the conventional ESC on/off switch, late-model vehicles have a 2-step ESC control switch.Turning ESC off by one step (semi-ESC) only turns off engine control for sporty acceleration after making

a turn and escaping puddles without reduced engine torque from spinning

● ESC Step 1 OFF

• Switch: Press ESC OFF for less than 3 seconds

• Indicator & buzzer: ESC OFF indicator on, no buzzer

• Display: "Traction control off" displayed on dashboard

• Control: Engine torque control (TCS) OFF, brake control on

● ESC Step 2 OFF

• Switch: Press and hold ESC OFF for more than 3 seconds

• Indicator & buzzer: ESC OFF indicator on, dashboard buzzer sounded once

• Display: "VDC off" displayed on dashboard

• Control: Engine torque control (TCS) off, brake control off

1) Exploded View of Brake Switch and Its Role

When the brake pedal is depressed, current is fed via the brake light switch to the control module TheBrake Switch Signal is required for monitoring the Pressure Sensor Usually the Pressure Sensor shouldrecognize an increase in pressure when the brake pedal is applied (Brake Switch Status ON) And Thebrake light switch indicates brake pedal status to the ABS control unit

The stop lamp switch signal is required for the hydraulic brake assist, electronic stability, downhill brakecontrol and hill start assist function Furthermore the brake signal is required for the pump motor test which

is performed at speeds above 30km/h every time the ignition is turned on

▪ ECU identifies the driver's intention (steering wheel position + vehicle speed + accel pedal)

▪ ECU analyzes the vehicle's movement (vehicle turning speed + side pulling force)

▪ Significant inconsistency between the driver's intention and vehicle movement is recognized as a safety

hazard and hydraulic control devices adjust the braking of individual wheels It also controls the engineoutput via communication line connected to the engine to safely control the vehicle out of a potentiallydangerous situation The indicators and warning lamps are also controlled according to vehicle state

2) Components

Configuration Function

ECU Receives signals from input elements and produces control signals if a spin,

understeer or oversteer is detected

HCU Hydraulic regulator

Motor Powers the pump with power supplied by ECU

Pump Pump is engaged by motor during decompression and returns the oil back to the

master cylinder

Pressure Sensor Measures brake pressure to identify the driver's braking intention Detects sudden

braking from pressure drops

Solenoid Valve Receives Open and Close commands from ECU and opens/closes flows for

individual wheel pressure control

• Inlet Solenoid Valve (ISV)

This valve connects or disconnects the hydraulic path between master cylinder and the wheelcylinders The valve remains normally open but it is closed when the dump and hold mode beginsduring ABS operation Purpose of the check valve is to help the brake fluid returning from the wheelcylinder to the master cylinder when the brake pedal is released

• Outlet Solenoid Valve (OSV)

The outlet solenoid valves are normally closed The valve is opened when the dump mode begins torelease the wheel cylinder pressure

• Electric Shuttle Valve (ESV)

The Electric Shuttle Valve is normally closed When ESC is in progress, the valve is opened andbrake fluid is supplied to the pump elements

• Traction Control Valve (TCV)

The Traction Control Valve is normally open and the brake pressure from the master cylinder is applied

to the wheel cylinders While TCS or ESC is in progress, the TCV is closed and the generated pressure

is applied to the front wheel cylinders without returning to the master cylinder The TCV includes arelief valve and a check valve When excessive pressure is supplied from the motor, the relief valve

is opened and the pressure is relieved

• Pressure Sensor (P/U)

The Pressure Sensor monitors the pressure of the brake line This sensor signal is the basic data forhydraulic brake assistance control Additionally this sensor input is required when ESC is in progress

• Solenoid Valve Operation

Valve Electrically Condition

of the pressurized brake fluid when the Outlet Control Valve (OCV) is opened The pump draws thebrake fluid out of the accumulators.

• Solenoid Valve Operation

- Normal braking

Valve Electrically Condition

- Hold mode

Valve Electrically Condition

to prevent an excessive pressure built up within the circuit The pump basically pumps the brake fluidthrough the pipes without creating pressure.

• Solenoid Valve Operation

is a self-diagnosis process If all the system is normal, the warning lamps turn OFF If any of the lampsremain turned ON, it signifies failure of the corresponding system.

2) Indicator/Warning Lamp Function

Configuration Function

ESC Warning Lamp ESC indicator blinks when the ESC system is on ESC warning lamp switched

on when the ESC system is faulty

ESC OFF Warning

Lamp

The ESC off switch allows the driver to stop ESC When the "off" signal is sent

to HECU, the ESC OFF indicator comes on ESC can be disabled for sportydriving and vehicle inspections

EBD Warning Lamp

As the EBD system uses brake warning lamps, brake force is not distributed

to front and rear wheels if the ABS warning lamp and brake warning lamp are

on at the same time

DBC Indicator

Pressing DBC On turns on the indicator to show that DBC is ready for use(stand-by); the indicator blinks when DBC is on The indicator turns red if theDBC system is faulty

ABS Warning Lamp The ABS warning lamp staying on while driving indicates an ABS fault.

However, the brakes continue to function normally