Module 5 MDPS (hệ thống trợ lưc lái điện) eng

Hệ thống trợ lực lái điện hoạt động theo trạng thái của vô lăng lái, do đó, nó cung cấp đặc tính lái tối ưu. Mặt khác, trợ lực lái sử dụng áp suất thủy lực để làm giảm lực đán lái, nó cho phép người lái dễ dàng điều khiển vô lăng. Trợ lực lái điện trên ô tô thay thế trợ lực lái thủy lực vì những lý do sau đây: Thân thiện với mội trường do không dung dầu trợ lực lái Nhẹ hơn và kết cấu đơn giản nên suất tiêu hao nhiên liệu tốt hơn Khả năng đáp ứng nhanh theo tốc độ

Educational

Use

Steering)

LESSON

5.1 Overview 123

5.1.1 Introduction 123

5.1.2 History 124

5.1.3 Categorization by Motor Location 125

5.2 Layout 127

5.2.1 System Configuration 127

5.2.2 Input / Output Elements 128

5.3 Components 129

5.3.1 Torque & Angle Sensor 129

5.3.2 ECU 132

5.3.3 Motor 133

5.3.4 Rack & Pinion 134

5.4 Control Logic 135

5.4.1 Low Vehicle Speed 135

5.4.2 High Vehicle Speed 136

5.4.3 Over Heat Protection 137

5.4.4 Over Load Protection 138

5.4.5 Restoration Control 139

5.5 Maintenance 141

5.5.1 Variant Coding 141

5.5.2 SAS Calibration 142

[Learning Objectives]

▪ Describe the history of MDPS

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

▪ Verify the control logic in the current data

▪ Take the necessary measures after changing parts

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5.1.2 History

Figure 5-1 Hydraulic Power Steering (left) / Electric Power Steering (right)

MDPS operates the motor according to the steering condition, thus offering an optimal steeringcharacteristic On the other hand, power steering uses hydraulic pressure for reduction of steering effort,enabling the driver to easily operate the steering wheel EPS-equipped cars are increasing and EPS isexpected to replace hydraulic power steering system for the following reasons

▪ The system is environment friendly since no steering oil is used.

▪ Due to the lower weight and less components the fuel consumption is reduced.

▪ A speed-responsive function can be implemented.

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5.1.3 Categorization by Motor Location

EPS is divided into three types according to the motor location, Column type, Pinion type, Rack type.Torque increases as the motor is located closer to the wheels, a characteristic suitable for mid to large-sizevehicles However, design cost increases as a more complex layout is required

▪ Column-type: Suitable for small to mid-size vehicles

▪ Pinion-type: Suitable for mid-size vehicles

▪ Rack-type: Suitable for large-size vehicles

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2 Torque & Angle Sensor (integrated)

Recognizes the force (torque) and direction of the driver's steering

The combined force of torque created by the driver's steering and the motor's assist torque is applied

to the shaft; the force is then transferred to the pinion gear from the worm gear

6 Rack & Pinion Gear

Rotational movement is converted to a straight-line movement through the combination of the rackgear and pinion gear, and this determines the direction of the wheels

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5.2.2 Input / Output Elements

Input Elements Output Elements

Battery Voltage This input is used for monitoring the system voltage and alternator load in

order to increase the engine idle rpm

Vehicle Speed The Control Module calculates the current for the motor based on the vehicle

speed sensor input

The sensor delivers information about turning speed and the neutral position

of the steering wheel The amount of restoration current is calculated by theMDPSCM based on the Steering Angle- and Vehicle

Speed sensor signal

current = low torque, High current = high torque

Warning Lamp

The Warning Lamp is on for approximately 5 seconds when the ignition isturned on It is continuously turned on when a fault is detected or duringcommunication with the Scan Tool

1) Torque Sensor

The torque sensor is installed in the middle of the steering column and is composed of a main and a subsensor When the steering wheel is turned, the torsion bar is twisted in proportion to the steering resistance.The offset of the input- in relation to the output shaft causes a change in magnetic field, thus causing achange of current With the change of input signal current the Motor Driven Power Steering Control Module(MDPSCM) also detects the turning direction of the Steering wheel

as one for the absolute steering angle in the ESC system Therefore, it is necessary to do the sensorcalibration after replacing the sensor.

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5.3.4 Rack & Pinion

As an alternative to a constant reduction ratio on the rack, suitable toothing of the rack allows the ratio to

be varied as a function of travel In this way, the straight running stability of the vehicle can be improved bysuitably indirect ratio around the center of the steering At the same time, it is possible with a direct ratioarrangement in the range of medium and large steering angles to reduce the necessary steering anglerequirement when turning from lock to lock

5.4.1 Low Vehicle Speed

At low vehicle speed (measured by the vehicle speed sensor) the twisting of the torsioning bar (measured

by the torque sensor) is high The MDPSCM supplies a high current to the motor in order to reduce thesteering effort for the driver

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5.4.2 High Vehicle Speed

At high vehicle speed the twisting of the torsioning bar is low The MDPSCM supplies a low current to themotor in order to increase the steering effort for the driver, thus offering higher steering stability

Figure 5-3 Over Heat Protection

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5.4.3 Over Heat Protection

Turning the steering wheel left and right continuously causes overcurrents in the motor, which can lead tointernal damage in the motor Overheat protection reduces motor currents to prevent this from happening.For this function, temperature is measured not by the temperature sensor, but by the ECU's calculation ofmotor running time Steering feels heavier when overheat protection is enabled

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5.4.4 Over Load Protection

Fully turning the steering wheel by 780 or -780 degrees rapidly increases current consumption Overloadprotection reduces currents to protect the motor The vehicle is slightly understeered even if the steeringwheel is fully turned when overload protection is enabled

Figure 5-4 Restoration Control

Use

Variant coding takes place through EPS type recognition in GDS The steering feel drivers need differs

by region; as such, steering feel is set according to region and vehicle model Korean drivers prefer alight steering feel, while European and North American drivers prefer a heavier one Depending on eachvehicle model and region, a steering feel can be selected by using a diagnostic tool, and the process forrecognizing the specifications must be carried out when the MDPS system is replaced If the process is notconducted, an error code(C1702 Specification Recognition Error) is output If the specification for anotherregion is selected, a different steering feel is set