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
Textbook Module5 MDPS (Motor Driven Power Steering) Module5 MDPS (Motor Driven Power Steering) 5.1 O nl y LESSON Overview 123 5.1.1 Introduction 123 5.1.2 History 124 5.1.3 Categorization by Motor Location 125 5.2 Layout .127 Components .129 lU 5.3 se 5.2.1 System Configuration 127 5.2.2 Input / Output Elements 128 na 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 5.5 High Vehicle Speed 136 Over Heat Protection 137 Over Load Protection 138 Restoration Control 139 uc a 5.4.2 5.4.3 5.4.4 5.4.5 tio 5.4.1 Low Vehicle Speed 135 Maintenance .141 Fo r Ed 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 Basic Chassis Technology 121 Textbook Fo r Ed uc a tio na lU se O nl y Module5 MDPS (Motor Driven Power Steering) 122 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) 5.1 Overview 5.1.1 Introduction Fo r Ed uc a tio na lU se O nl y Motor Driven Power Steering (MDPS) uses an electric motor to assist the steering power Because of friction between the front tires and the road, especially in parking, steering power to turn the steering wheel is required Basic Chassis Technology 123 Module5 MDPS (Motor Driven Power Steering) History O nl y 5.1.2 Textbook se Figure 5-1 Hydraulic Power Steering (left) / Electric Power Steering (right) lU MDPS operates the motor according to the steering condition, thus offering an optimal steering characteristic 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 is expected to replace hydraulic power steering system for the following reasons na ▪ The system is environment friendly since no steering oil is used tio ▪ Due to the lower weight and less components the fuel consumption is reduced Fo r Ed uc a ▪ A speed-responsive function can be implemented 124 Basic Chassis Technology Textbook Categorization by Motor Location O nl y 5.1.3 Module5 MDPS (Motor Driven Power Steering) ▪ Pinion-type: Suitable for mid-size vehicles Fo r Ed uc a tio na ▪ Rack-type: Suitable for large-size vehicles lU ▪ Column-type: Suitable for small to mid-size vehicles se 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-size vehicles However, design cost increases as a more complex layout is required Basic Chassis Technology 125 Textbook Fo r Ed uc a tio na lU se O nl y Module5 MDPS (Motor Driven Power Steering) 126 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) Layout 5.2.1 System Configuration lU se O nl y 5.2 Steering Wheel na The driver turns the steering wheel, the initial input terminal of MDPS, to transfer driving intentions (direction, speed, etc) to the vehicle tio Torque & Angle Sensor (integrated) Recognizes the force (torque) and direction of the driver's steering ECU uc a Combines input values (torque, direction, speed, variant code, etc) and applies the desired assist torque to the motor BLAC Motor Ed The motor rotates according to the signal received from ECU Shaft Fo r 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 Rack & Pinion Gear Rotational movement is converted to a straight-line movement through the combination of the rack gear and pinion gear, and this determines the direction of the wheels Basic Chassis Technology 127 Module5 MDPS (Motor Driven Power Steering) 5.2.2 Textbook Input / Output Elements Input Elements Output Elements ▪ Battery Voltage ▪ Vehicle Speed ▪ Motor ▪ Engine Speed ▪ ESP Warning Lamp O nl y ▪ Torque Sensor ▪ Angle Sensor Function se Configuration 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 Engine Speed This signal is received by the Engine Control Module (idle up function) In order to operate, a engine speed higher than 500rpm needs to be detected by the MDPSCM Torque Sensor Measures the twisting of the torsion bar Angle Sensor The sensor delivers information about turning speed and the neutral position of the steering wheel The amount of restoration current is calculated by the MDPSCM based on the Steering Angle- and Vehicle tio na lU Battery Voltage Motor uc a Speed sensor signal The Warning Lamp is on for approximately seconds when the ignition is turned on It is continuously turned on when a fault is detected or during communication with the Scan Tool Fo r Ed Warning Lamp The torque output of the motor is controlled by varying the current Low current = low torque, High current = high torque 128 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) Components 5.3.1 Torque & Angle Sensor tio na lU se O nl y 5.3 uc a Figure 5-2 MDPS Ass’y Ed Some of vehicle model have integrated torque and angle sensor which is more advanced As shown in the picture, two portions for the torque and angle detection have been integrated in one unit, referred to as ‘a torque and angle sensor.’ Fo r 1) Torque Sensor The torque sensor is installed in the middle of the steering column and is composed of a main and a sub sensor 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 a change 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 Basic Chassis Technology 129 Textbook O nl y Module5 MDPS (Motor Driven Power Steering) This Magnetic field is proportion to torque The Hall IC detects this change of magnetic field and send signal in voltage form The voltage is proportion to rotating angle from -4.5˚ to 4.5˚ se The torque sensor has two output signal and MDPS ECU compares these signal and for detecting sensor fault uc a tio na lU 2) Angle Sensor Fo r Ed As the steering rotates, the main gear may rotate Two planetary gears with different number of gear teeth will rotate at the same time and the magnet attached in the planetary gear rotates The Hall IC detects the change of rotating angle and outputs the voltage signals to the control module Finally the control module will calculate the steering angle by processing these signals Note that the operating principle is same as one for the absolute steering angle in the ESC system Therefore, it is necessary to the sensor calibration after replacing the sensor 130 Basic Chassis Technology Module5 MDPS (Motor Driven Power Steering) O nl y Textbook Fo r Ed uc a tio na lU se As the steering rotates, the main gear may rotate Two planetary gears with different number of gear teeth will rotate at the same time and the magnet attached in the planetary gear rotates The Hall IC detects the change of rotating angle and outputs the voltage signals to the control module Finally the control module will calculate the steering angle by processing these signals Note that the operating principle is same as one for the absolute steering angle in the ESC system Therefore, it is necessary to the sensor calibration after replacing the sensor Basic Chassis Technology 131 Module5 MDPS (Motor Driven Power Steering) ECU O nl y 5.3.2 Textbook Fo r Ed uc a tio na lU se If the driver moves the steering wheel, a sensor registers the steering torque exerted and sends this information as an electrical signal to the ECU This calculates the supporting steering torque and activities the servo-motor on the basis of the calculated result 132 Basic Chassis Technology Textbook Motor O nl y 5.3.3 Module5 MDPS (Motor Driven Power Steering) Currently, brushless AC motors are used the most, and depending on the required steering performance, the torque generated by these motors is to Nm Fo r Ed uc a tio na lU se The direction of rotation of the motor depends on the direction of motion of steering wheel Basic Chassis Technology 133 Module5 MDPS (Motor Driven Power Steering) 5.3.4 Textbook Rack & Pinion Fo r Ed uc a tio na lU se O nl y 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 by suitably indirect ratio around the center of the steering At the same time, it is possible with a direct ratio arrangement in the range of medium and large steering angles to reduce the necessary steering angle requirement when turning from lock to lock 134 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) Control Logic 5.4.1 Low Vehicle Speed lU se O nl y 5.4 Fo r Ed uc a tio na 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 the steering effort for the driver Basic Chassis Technology 135 Module5 MDPS (Motor Driven Power Steering) 5.4.2 Textbook High Vehicle Speed se O nl y At high vehicle speed the twisting of the torsioning bar is low The MDPSCM supplies a low current to the motor in order to increase the steering effort for the driver, thus offering higher steering stability Fo r Ed uc a tio na lU Figure 5-3 Over Heat Protection 136 Basic Chassis Technology Textbook 5.4.3 Module5 MDPS (Motor Driven Power Steering) Over Heat Protection Fo r Ed uc a tio na lU se O nl y Turning the steering wheel left and right continuously causes overcurrents in the motor, which can lead to internal 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 of motor running time Steering feels heavier when overheat protection is enabled Basic Chassis Technology 137 Module5 MDPS (Motor Driven Power Steering) 5.4.4 Textbook Over Load Protection se O nl y Fully turning the steering wheel by 780 or -780 degrees rapidly increases current consumption Overload protection reduces currents to protect the motor The vehicle is slightly understeered even if the steering wheel is fully turned when overload protection is enabled Fo r Ed uc a tio na lU Figure 5-4 Restoration Control 138 Basic Chassis Technology Textbook 5.4.5 Module5 MDPS (Motor Driven Power Steering) Restoration Control Fo r Ed uc a tio na lU se O nl y Restoration control is a function that helps the steering wheel return to its starting position after a turn for straight-line driving After steering and finishing a turn, the steering wheel automatically returns to its starting position without having to steer in the opposite direction Basic Chassis Technology 139 Textbook Fo r Ed uc a tio na lU se O nl y Module5 MDPS (Motor Driven Power Steering) 140 Basic Chassis Technology Textbook Maintenance Figure 5-5 MDPS S/W Management Variant Coding se 5.5.1 O nl y 5.5 Module5 MDPS (Motor Driven Power Steering) Fo r Ed uc a tio na lU 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 a light steering feel, while European and North American drivers prefer a heavier one Depending on each vehicle model and region, a steering feel can be selected by using a diagnostic tool, and the process for recognizing the specifications must be carried out when the MDPS system is replaced If the process is not conducted, an error code(C1702 Specification Recognition Error) is output If the specification for another region is selected, a different steering feel is set Basic Chassis Technology 141 Module5 MDPS (Motor Driven Power Steering) 5.5.2 Textbook SAS Calibration Fo r Ed uc a tio na lU se O nl y This function has to be performed after replacement of the Motor Driven Power Steering Control Module (MDPSCM) or the Absolute Position Sensor (APS) Successful calibration is displayed under current data's of the Scan Tool “Calibration Status.” 142 Basic Chassis Technology ... lU se O nl y Module5 MDPS (Motor Driven Power Steering) 140 Basic Chassis Technology Textbook Maintenance Figure 5- 5 MDPS S/W Management Variant Coding se 5. 5.1 O nl y 5. 5 Module5 MDPS (Motor... Technology 1 25 Textbook Fo r Ed uc a tio na lU se O nl y Module5 MDPS (Motor Driven Power Steering) 126 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) Layout 5. 2.1 System... Ed uc a tio na lU se O nl y Module5 MDPS (Motor Driven Power Steering) 122 Basic Chassis Technology Textbook Module5 MDPS (Motor Driven Power Steering) 5. 1 Overview 5. 1.1 Introduction Fo r Ed