WO2011061753A1 - An electric power steering system - Google Patents

An electric power steering system Download PDF

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Publication number
WO2011061753A1
WO2011061753A1 PCT/IN2010/000715 IN2010000715W WO2011061753A1 WO 2011061753 A1 WO2011061753 A1 WO 2011061753A1 IN 2010000715 W IN2010000715 W IN 2010000715W WO 2011061753 A1 WO2011061753 A1 WO 2011061753A1
Authority
WO
WIPO (PCT)
Prior art keywords
steering
ecu
assistance
steering system
power steering
Prior art date
Application number
PCT/IN2010/000715
Other languages
French (fr)
Inventor
Ashfaque Ahmed Ansari
Hari Srinivas Babu Aggarapu
Preesty J. Thomas
Abhijeet A. Shirguppe
Original Assignee
Tata Motors Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tata Motors Limited filed Critical Tata Motors Limited
Publication of WO2011061753A1 publication Critical patent/WO2011061753A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input

Definitions

  • the present invention relates to power steering system in vehicles and more particularly to electric power steering system to provide power assistance during parking and at low speed of vehicle.
  • the Electric Power Steering (EPS) system for an automobile comprises of steering wheel, an electric motor along with reduction mechanisms, a controller, various sensors, steering column, and steering rack & pinion.
  • the electric motor is coupled to the steering column through a gear mechanism.
  • Conventional electric power steering system requires expensive sensors namely torque sensor & steering wheel angle sensor and Electronic Control Unit (ECU) with high processing capabilities to take care of power assistance at all manoeuvring events.
  • ECU Electronic Control Unit
  • the conventional steering assistance system provides assistance at all manoeuvring events and till the maximum speed is achieved which increases the complexity and overall cost of the system.
  • FAW Front Axle Weight
  • the embodiments herein provide an electric power steering system.
  • the EPS system comprises a steering angle sensor mounted on steering column, a vehicle speed sensor, an electric motor coupled to reduction gearbox and an electronic control unit (ECU).
  • the electric motor with a reduction gear is coupled to the steering column with steering wheel at one end and rack & pinion arrangement towards the other end.
  • the ECU is provided to monitor the output of said steering angle sensor and vehicle speed sensor to rotate said motor in clockwise or counter-clockwise direction to provide power assistance to said steering system in desired direction at low speeds.
  • the present invention provides an electric power steering system with park-assist feature active only at low vehicle speeds and decoupling as soon as high vehicle speeds are achieved. Accordingly when the vehicle ignition key is inserted, the ECU is powered ON. Also other vehicle signals like Vehicle speed and steering angle are detected by the ECU. In static vehicle condition or at very low vehicle speeds, if driver intends to take left/right turn, he/she will start rotating the Steering wheel in right/left direction. As soon as the driver start rotating the steering wheel, the steering wheel sensor senses the direction of the steering wheel movement and provide this signal to the ECU.
  • the ECU computes the steering rate and then based on the computed steering rate, vehicle speed value and programmed logic in the ECU, the motor will start rotating in clockwise or counter clockwise direction, thus providing required steering assist to the driver.
  • the motor assistance seizes when the vehicle speed is greater than 15kmph and when the steering rate becomes zero.
  • FIG.l shows an electric power steering system, according to present invention.
  • FIG. 2 shows a schematic diagram illustrating a coupling of gear box output shaft with steering column, according to present invention.
  • FIG. 3 shows a block diagram of an electric power steering system, according to present invention.
  • FIG. 4 shows a flow chart to illustrate a working of electric power steering system, according to present invention.
  • the EPS system comprises a steering angle sensor 2 mounted on steering column 6, a vehicle speed sensor 3, an electric motor coupled to reduction gearbox 5 and an electronic control unit (ECU) 4.
  • the electric motor with a reduction gear 5 is coupled to the steering column 6 with steering wheel 1 at one end and rack & pinion 7 assembly towards the other end.
  • the signal from vehicle speed sensor 3, steering angle sensor 2 and vehicle battery 8 is fed to the ECU 4.
  • the ECU 4 is provided to monitor the output of said steering angle sensor 2 and vehicle speed sensor 3 to rotate said motor in clockwise or counter-clockwise direction to provide power assistance to said steering system in desired direction at low speeds.
  • gear box output shaft 9 with steering column 6 is as shown in FIG. 2.
  • the motor and gear box assembly is coupled to the steering column 6 through gear box output shaft 9 and locked using locking mechanism 10.
  • the electric motor with a reduction gear 5 is coupled to the steering column 6 with steering wheel 1 at one end and rack & pinion 7 arrangement towards the other end.
  • FIG. 3 The block diagram of an electric power steering system according to present invention is as shown in FIG. 3.
  • said steering angle sensor 2 sends signal to ECU 4 to compute the steering rate to rotate the motor in clockwise or counterclockwise direction.
  • the ECU 4 computes the steering rate based on the steering angle signal.
  • the steering rate is used to cut-off the steering assistance in case the driver holds the steering wheel 1 at one position continuously or when the steering rate is zero.
  • the vehicle speed sensor 3 signal is fed to the ECU 4 to limit the steering assistance feature at low vehicle speeds only.
  • the motor assistance seizes when the vehicle speed increases and/ or when the steering rate becomes zero.
  • the ECU 4 provides variable steering assist with respect to varying steering wheel 1 angle.
  • the ECU 4 also provides constant steering assistance with respect to varying steering wheel 1 angle.
  • a display unit is provided to indicate the status of the steering assistance system.
  • the flow chart as shown in FIG. 4 illustrates working of the electrical power steering system. Accordingly when the vehicle ignition key is inserted (12), the ECU 4 is powered ON. Also other vehicle signals like Vehicle speed and steering angle are detected by the ECU 4 (1 ). In static vehicle condition or at very low vehicle speeds (10 - 15 mph), if driver intends to take left / right turn, he / she will start rotating the Steering wheel 1 in right / left direction. As soon as the driver start rotating the steering wheel 1, the steering wheel sensor senses the direction of the steering wheel 1 movement and provide this signal to the ECU 4.
  • the ECU 4 computes the steering rate and then based on the computed steering rate, vehicle speed value and programmed logic in the ECU 4 (14 & 15), the motor will start rotating in clockwise or counter clockwise direction, thus providing required steering assist to the driver. If The motor assistance seizes when the vehicle speed is greater than 15kmph and/ or when the steering rate becomes zero. If there is no supply to the motor, then go to start (16).

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

The embodiments of the present invention provide an electric power steering system. The EPS system comprises a steering angle sensor (2) mounted on steering column (6), a vehicle speed sensor (3), an electric motor coupled to reduction gearbox (5) and an electronic control unit (ECU) (4). The electric motor with a reduction gear (5) is coupled to the steering column (6) with a steering wheel (1 ) at one end and rack & pinion (7) arrangement towards the other end. The ECU (4) is provided to monitor the output of said steering angle sensor (2) and vehicle speed sensor (3) to rotate said motor in clockwise or counter-clockwise direction to provide power assistance to said steering system in desired direction at low speeds.

Description

AN ELECTRIC POWER STEERING SYSTEM
FIELD OF INVENTION
The present invention relates to power steering system in vehicles and more particularly to electric power steering system to provide power assistance during parking and at low speed of vehicle.
BACKGROUND OF INVENTION
The Electric Power Steering (EPS) system for an automobile comprises of steering wheel, an electric motor along with reduction mechanisms, a controller, various sensors, steering column, and steering rack & pinion. The electric motor is coupled to the steering column through a gear mechanism. Conventional electric power steering system requires expensive sensors namely torque sensor & steering wheel angle sensor and Electronic Control Unit (ECU) with high processing capabilities to take care of power assistance at all manoeuvring events. The conventional steering assistance system provides assistance at all manoeuvring events and till the maximum speed is achieved which increases the complexity and overall cost of the system. For the vehicles with comparatively less Front Axle Weight (FAW) it is found that, steering effort required by the driver is considerably high when the vehicle is in parking condition or at very low speeds only. However, the steering effort reduces drastically as the vehicle speed increases. Hence, for such vehicles with lower FAW (in the range of 250 ~ 350 kg) , full fledge and high cost EPS system with assistance at all manoeuvring events is not necessary and is also complex in terms of functionality and development. Hence there is a need to provide a steering assistance to the vehicle during parking or till the vehicle pickup the speed. There is a need to activate the steering assistance feature only at low vehicle speeds and decoupling as soon as the high vehicle speeds are achieved.
OBJECT OF THE INVENTION
The primary object of the present invention is to provide an electric power steering system with steering assistance active only during parking condition and at low vehicle speeds and decoupling as soon as high vehicle speeds are achieved. Another object of this invention is to provide assistance to driver with a simple and low cost system.
SUMMARY OF THE INVENTION
The embodiments herein provide an electric power steering system. The EPS system comprises a steering angle sensor mounted on steering column, a vehicle speed sensor, an electric motor coupled to reduction gearbox and an electronic control unit (ECU). The electric motor with a reduction gear is coupled to the steering column with steering wheel at one end and rack & pinion arrangement towards the other end. The ECU is provided to monitor the output of said steering angle sensor and vehicle speed sensor to rotate said motor in clockwise or counter-clockwise direction to provide power assistance to said steering system in desired direction at low speeds.
The present invention provides an electric power steering system with park-assist feature active only at low vehicle speeds and decoupling as soon as high vehicle speeds are achieved. Accordingly when the vehicle ignition key is inserted, the ECU is powered ON. Also other vehicle signals like Vehicle speed and steering angle are detected by the ECU. In static vehicle condition or at very low vehicle speeds, if driver intends to take left/right turn, he/she will start rotating the Steering wheel in right/left direction. As soon as the driver start rotating the steering wheel, the steering wheel sensor senses the direction of the steering wheel movement and provide this signal to the ECU. The ECU computes the steering rate and then based on the computed steering rate, vehicle speed value and programmed logic in the ECU, the motor will start rotating in clockwise or counter clockwise direction, thus providing required steering assist to the driver. The motor assistance seizes when the vehicle speed is greater than 15kmph and when the steering rate becomes zero.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.l shows an electric power steering system, according to present invention.
FIG. 2 shows a schematic diagram illustrating a coupling of gear box output shaft with steering column, according to present invention. FIG. 3 shows a block diagram of an electric power steering system, according to present invention.
FIG. 4 shows a flow chart to illustrate a working of electric power steering system, according to present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
An electric power steering system according to present invention is as shown in FIG. 1. The EPS system comprises a steering angle sensor 2 mounted on steering column 6, a vehicle speed sensor 3, an electric motor coupled to reduction gearbox 5 and an electronic control unit (ECU) 4. The electric motor with a reduction gear 5 is coupled to the steering column 6 with steering wheel 1 at one end and rack & pinion 7 assembly towards the other end. The signal from vehicle speed sensor 3, steering angle sensor 2 and vehicle battery 8 is fed to the ECU 4. The ECU 4 is provided to monitor the output of said steering angle sensor 2 and vehicle speed sensor 3 to rotate said motor in clockwise or counter-clockwise direction to provide power assistance to said steering system in desired direction at low speeds.
The coupling of gear box output shaft 9 with steering column 6 is as shown in FIG. 2. The motor and gear box assembly is coupled to the steering column 6 through gear box output shaft 9 and locked using locking mechanism 10. The electric motor with a reduction gear 5 is coupled to the steering column 6 with steering wheel 1 at one end and rack & pinion 7 arrangement towards the other end.
The block diagram of an electric power steering system according to present invention is as shown in FIG. 3. When the steering wheel 1 is rotated said steering angle sensor 2 sends signal to ECU 4 to compute the steering rate to rotate the motor in clockwise or counterclockwise direction. The ECU 4 computes the steering rate based on the steering angle signal. The steering rate is used to cut-off the steering assistance in case the driver holds the steering wheel 1 at one position continuously or when the steering rate is zero. The vehicle speed sensor 3 signal is fed to the ECU 4 to limit the steering assistance feature at low vehicle speeds only. The motor assistance seizes when the vehicle speed increases and/ or when the steering rate becomes zero. As the motor has less working cycle being active only at low speed and when there is need of assistance, so the operation saves energy and it is achieved by a smaller motor with low capacity and high overload possibility, which saves the cost of the motor significantly. The ECU 4 provides variable steering assist with respect to varying steering wheel 1 angle. The ECU 4 also provides constant steering assistance with respect to varying steering wheel 1 angle. A display unit is provided to indicate the status of the steering assistance system.
The flow chart as shown in FIG. 4 illustrates working of the electrical power steering system. Accordingly when the vehicle ignition key is inserted (12), the ECU 4 is powered ON. Also other vehicle signals like Vehicle speed and steering angle are detected by the ECU 4 (1 ). In static vehicle condition or at very low vehicle speeds (10 - 15 mph), if driver intends to take left / right turn, he / she will start rotating the Steering wheel 1 in right / left direction. As soon as the driver start rotating the steering wheel 1, the steering wheel sensor senses the direction of the steering wheel 1 movement and provide this signal to the ECU 4. The ECU 4 computes the steering rate and then based on the computed steering rate, vehicle speed value and programmed logic in the ECU 4 (14 & 15), the motor will start rotating in clockwise or counter clockwise direction, thus providing required steering assist to the driver. If The motor assistance seizes when the vehicle speed is greater than 15kmph and/ or when the steering rate becomes zero. If there is no supply to the motor, then go to start (16).
ADVANTAGE:
• Simple in construction and assembly.
• Low Cost.
• Use of available signals from vehicle.
• Selection of Low capacity motor with 3 ~ 4 times overload possibility (as the duty cycle is found to be only 5%).
• Low cost Electric Power Steering system with Park-Assist feature active only at low vehicle speeds and decoupling as soon as high vehicle speeds are achieved. The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

Claims

CLAIMS :
1. An electric power steering system, comprising;
a steering angle sensor mounted on steering column, a vehicle speed sensor an electric motor coupled to reduction gearbox and an electronic control unit (ECU); said electric motor with low capacity and high overload possibility is coupled to said steering column by a reduction gear mechanism, said steering column has a steering wheel at one end and rack & pinion arrangement towards other end;
said ECU is provided to monitor the output of said steering angle sensor and vehicle speed sensor to rotate said motor in clockwise or counter- clockwise direction to provide power assistance to said steering system in desired direction at low speed of vehicle.
2. The power steering system according to claim 1, wherein when said steering wheel is rotated said steering angle sensor sends signal to ECU to compute the steering rate to rotate the motor in clockwise or counter-clockwise direction.
3. The power steering system according to claim 1, wherein said ECU computes the steering rate based on the steering angle signal.
4. The power steering system according to claim 1, wherein said steering rate is used to cut-off the steering assistance in case the driver holds the steering wheel at one position continuously or when the steering rate is zero.
5. The power steering system according to claim 1, wherein said vehicle speed sensor signal is fed to the ECU to limit the steering assistance feature at low vehicle speeds.
6. The power steering system according to claim 1, wherein said motor assistance seizes when the vehicle speed increases and when the steering rate becomes zero.
7. The power steering system according to claim 1, wherein said ECU provides variable steering assist with respect to varying steering wheel angle.
8. The power steering system according to claim 1, wherein said ECU also provide constant steering assistance with respect to varying steering wheel angle.
9. The power steering system according to claim 1 , wherein a display unit is provided to indicate the status of the steering assistance system.
10. The power steering system according to claim 1, wherein as herein described and illustrated in figures of accompanying drawings.
PCT/IN2010/000715 2009-11-23 2010-11-01 An electric power steering system WO2011061753A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN2214MU2009 2009-11-23
IN2214/MUM/2009 2009-11-23

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WO2011061753A1 true WO2011061753A1 (en) 2011-05-26

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PCT/IN2010/000715 WO2011061753A1 (en) 2009-11-23 2010-11-01 An electric power steering system

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103879441A (en) * 2012-12-21 2014-06-25 现代自动车株式会社 Steering apparatus for hev and method of controlling the same

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2226285A (en) * 1988-11-30 1990-06-27 Fuji Heavy Ind Ltd An electric power steering system for an automobile
US4954957A (en) * 1988-01-25 1990-09-04 Nissan Motor Company, Limited Control system for adapting suspension characteristics and steering characteristics to vehicle driving condition
JP2005067262A (en) * 2003-08-28 2005-03-17 Nissan Motor Co Ltd Electric power steering control device
JP2005231416A (en) * 2004-02-17 2005-09-02 Toyota Motor Corp Vehicle steering device
KR20060035873A (en) * 2004-10-21 2006-04-27 주식회사 만도 Free apatrness absorp structure of electrical power steering system
EP1808357A2 (en) * 2006-01-12 2007-07-18 Mando Corporation Electric power steering apparatus equipped with steering angle sensor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4954957A (en) * 1988-01-25 1990-09-04 Nissan Motor Company, Limited Control system for adapting suspension characteristics and steering characteristics to vehicle driving condition
GB2226285A (en) * 1988-11-30 1990-06-27 Fuji Heavy Ind Ltd An electric power steering system for an automobile
JP2005067262A (en) * 2003-08-28 2005-03-17 Nissan Motor Co Ltd Electric power steering control device
JP2005231416A (en) * 2004-02-17 2005-09-02 Toyota Motor Corp Vehicle steering device
KR20060035873A (en) * 2004-10-21 2006-04-27 주식회사 만도 Free apatrness absorp structure of electrical power steering system
EP1808357A2 (en) * 2006-01-12 2007-07-18 Mando Corporation Electric power steering apparatus equipped with steering angle sensor

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103879441A (en) * 2012-12-21 2014-06-25 现代自动车株式会社 Steering apparatus for hev and method of controlling the same
US20140180545A1 (en) * 2012-12-21 2014-06-26 Hyundai Motor Company Steering apparatus for hev and method of controlling the same
US9199664B2 (en) * 2012-12-21 2015-12-01 Hyundai Motor Company Steering apparatus for HEV and method of controlling the same
CN103879441B (en) * 2012-12-21 2017-10-31 现代自动车株式会社 The transfer and its control method of hybrid vehicle

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