WO2001060682A1 - Compensation automatique de l'hysterese de servodirection electrique - Google Patents

Compensation automatique de l'hysterese de servodirection electrique Download PDF

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Publication number
WO2001060682A1
WO2001060682A1 PCT/US2000/040844 US0040844W WO0160682A1 WO 2001060682 A1 WO2001060682 A1 WO 2001060682A1 US 0040844 W US0040844 W US 0040844W WO 0160682 A1 WO0160682 A1 WO 0160682A1
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WO
WIPO (PCT)
Prior art keywords
value
steering
values
steering wheel
torque
Prior art date
Application number
PCT/US2000/040844
Other languages
English (en)
Inventor
William H. Wittig
Original Assignee
Delphi Technologies, Inc.
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 Delphi Technologies, Inc. filed Critical Delphi Technologies, Inc.
Publication of WO2001060682A1 publication Critical patent/WO2001060682A1/fr

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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
    • B62D5/0466—Controlling the motor for returning the steering wheel to neutral position

Definitions

  • This invention relates to electric power steering, and more particularly, to automatic hysteresis compensation for electric power steering systems.
  • Typical vehicle steering systems are constructed in such a way that the steering wheel will tend to return to center when let go by the operator of the vehicle.
  • the center is defined as a straight line of travel.
  • This return-to- center function is in response to road forces acting upon the turned front tires of the moving vehicle that tend to force the turned tires to the neutral (or center) position.
  • friction in the steering system can interfere with the return- to-center function of the steering.
  • One known method to prevent this is to reduce the overall steering ratio of the steering system, but this has the effect of increasing steering sensitivity, which is not always desirable.
  • a known technique for preventing steering system friction from interfering with the return-to-center function is to generate a command, in relation to vehicle speed, that commands an electric power steering actuator to provide a return-to-center position force.
  • the force exerted by the actuator overcomes the steering friction and allows the return-to-center function.
  • electric power steering motors are controlled either in a current mode or voltage mode.
  • Current mode control provides certain advantages because the inherent control damping and speed dependability of voltage mode control are eliminated. However the elimination of the control damping that is present in the voltage mode can prevent the system from obtaining stable closed-loop poles.
  • One solution provided is by creating an apparatus that includes a torque sensor coupled to a vehicle steering system for measuring steering wheel torque provided by a vehicle operator and, a steering angle sensor coupled to the steering system for measuring steering wheel angle. Furthermore, the apparatus may also include a controller, responsive to the measured steering wheel angle and vehicle speed, that provides a sum return-to- center command, as well as a motor responsive to the sum return-to-center command, a detailed description of which is described in Kaufmann et al., US 5,668,722, issued 16SEP1997, for an Electric Power Steering Control.
  • a change in hysteresis also known as friction or lash, occurs. This change in hysteresis adversely affects the performance of the steering system because the system is operating with a different hysteresis value from what the controller was designed to accommodate.
  • SUMMARY OF THE INVENTION Disclosed herein are a method and an apparatus by which the hysteresis of a steering system is measured by the steering system controller and used to compute a value of friction compensation that is optimum for a current system state.
  • a controller continuously monitors the torque and position of the steering system handwheel and records a value of the torque signal each time the position sensor indicates a zero position. These torque values are then separated into two groups, one group denotes a set of torque values for clockwise handwheel movement, and another group denotes a set of torque values for counter-clockwise handwheel movement. A difference between these two groups of data, when suitably filtered for a predetermined period of time forms a measurement of the current system hysteresis.
  • an enhancement that facilitates consistent performance of the electric power steering feel may be provided.
  • the enhancement equalizes the differences that may exist among different individual electric power steering systems.
  • this invention is based upon a measurement of a hysteresis of the electric power steering system during its operation.
  • the measurement is possible because a set of sensors senses parameters such as torque or position of the electric power steering system.
  • the relationship of torque and position parameters can be plotted and a symmetrical hysteresis loop curve may be drawn. It is noted that under practical operational circumstances, the loop curve may not be perfectly symmetrical. However, a symmetrical hysteresis curve may be used to best illustrate the concept of the instant invention.
  • FIG. 1 is a schematic diagram showing an electric power steering control system according to this invention
  • Figure 2 illustrates the operation of a method for compensating for an electric power steering system hysteresis
  • Figure 3 illustrates the operation of the method in Fig. 2 wherein a detailed illustration is described
  • Figure 4 illustrates an ideal hysteresis loop curve.
  • reference numeral 10 generally designates a motor vehicle power steering system suitable for implementation of this invention.
  • the steering mechanism 12 is a rack-and-pinion type system and includes a toothed rack (not shown) and a pinion gear (also not shown) located under gear housing 14.
  • the upper steering shaft 18 connected to the lower steering shaft 20 through universal joint 22, turns the pinion gear.
  • Rotation of the pinion gear moves the toothed rack that moves tie rods 24 (only one shown) that in turn move the steering knuckles 26 (only one shown), that turn wheels 28 (only one shown).
  • Electric power steering assist is provided through the unit generally designated by reference numeral 30 and includes a controller 32 and the electric motor 34.
  • the controller 32 is powered by a vehicle power supply 36 through line 38.
  • the controller 32 receives a signal representative of the vehicle velocity on line 40.
  • Steering pinion gear angle is measured through position sensor 42 (which may be an optical encoding type sensor, variable resistance type sensor or any other suitable type of position sensor) and fed to the controller 32 through line 44.
  • position sensor 42 which may be an optical encoding type sensor, variable resistance type sensor or any other suitable type of position sensor
  • a torque sensor 43 senses the torque applied to the steering wheel 16 by the vehicle operator.
  • the torque sensor 43 may include a torsion bar (not shown) and a variable resistive-type sensor (also not shown) that outputs a variable resistance signal to controller 32 through line 46 in relation to the amount of twist on the torsion bar. Although this is the preferable torque sensor, any other suitable torque-sensing device used with known signal processing techniques will suffice.
  • the controller 32 In response to the inputs on lines 40,44, and 46, the controller 32 sends a current command through line 48 to the electric motor 34.
  • the motor 34 in turn supplies a torque assist to the steering system through a worm 50 and a worm gear 52, in such a way as to providing the torque assist to the vehicle steering in addition to a driving force exerted by the vehicle operator.
  • reference numeral 60 generally designates a method for implementing the method for automatic compensation for electric power steering system within the controller 32.
  • a measure of torque for instance in Newton meters (Nm) is defined.
  • a measure of position for instance in degrees (deg) of moving away from the center line either clockwise or counter-clockwise is defined. Attention is drawn to the fact that the measure of torque and the measure of position is based on outputs of sensors.
  • Torque data flows toward block 64 along line 70.
  • the measured torque value is recorded and stored in a memory (not shown).
  • the memory can be temporary registers in the controller 32 or other form of memories outside the controller 32 such as a random access memory, erasable programmed read only memory, or other suitable forms of memory.
  • the recorded and stored torque values in block 64 then flow along line 72 toward block 66 wherein the recorded and stored torque values are weighted or adjusted according to a friction compensation table or schedule.
  • a friction compensation table or schedule is established through the utilization of sensors based, for instance, upon vehicle operating history, certain predetermined formulae, etc. It can be appreciated that a series of compensation settings are determined for a range of possible system hysteresis values. An optimum compensation setting can be determined using various known methods or formulae.
  • a difference of the adjusted torque values and the measure of position that is processed in block 62 and transmitted along line 76 is computed and transmitted as output along line 78.
  • data flowing through lines 70, 72, 74, and 76 can be processed according to known methods such that undesirable noise, flowing along data streams or lines 70, 72, 74, and 76, can be reduced.
  • defining a moving average as a basis for eliminating undesirable data may be used, etc.
  • reference numeral 80 generally designates a detailed method for implementing the method for automatic compensation for electric power steering of Figure 2.
  • a flow chart is depicted.
  • a set of input value including input torque and position values is generated and flows through line 84.
  • the set of input values may be supplied by a set of sensors that sense and measure the set of requisite values.
  • the input values from block 82 are branched into lines 86 and 88 containing essentially the same information.
  • the input values are checked at diamond block 90 for position information. If the position value is greater than a predetermined limit, the information flows through line 92, and exits the instant flow-chart. If the steering wheel position is not within a programmable limit, the process stops, thus ensuring that the data used to determine a hysteresis estimate is within an appropriate region of a hysteresis loop curve.
  • the information flows through line 94, the information flows toward diamond block 96 for determination of a current steering wheel turning direction.
  • the filtered data is separated into two groups depending upon current turning direction of the steering wheel. If the current steering wheel turning direction is clockwise, the information flows along line 98 toward block 100 wherein an accumulated clockwise zero crossing data is determined. The information then flows through line 102 toward block 104 for a calculation of hysteresis. Complementarily, if the current steering wheel turning direction is counter-clockwise, the information flows along line 106 toward block 108 wherein an accumulated counter-clockwise zero crossing data is determined.
  • a known technique in filtering data may be used at this juncture. For example, a filtering technique using exponentially weighted moving average may be used.
  • the information then flows through line 1 10 toward block 104 for a calculation of hysteresis.
  • a hysteresis value is determined as a difference between a clockwise zero torque cross point and a counter-clockwise zero torque cross point.
  • the calculated hysteresis information then flows along line 112 into block
  • an output is calculated.
  • the output may be used to adjust or create a compensation by increasing a return-to-center command or increasing an amount > of assist to offset the hysteresis.
  • the output then flows out along an output line
  • reference numeral 120 generally designates an ideal hysteresis loop.
  • the horizontal co-ordinate denotes steering wheel position measured in degrees as shown.
  • the vertical co-ordinate denotes steering wheel torque measured in Newton Meters as shown.

Abstract

L'invention concerne un procédé et un appareil permettant l'amélioration du mouvement de retour au centre d'un volant de direction (16). Ledit procédé consiste à déterminer une première et une deuxième valeur ; à dériver un ensemble de deux valeurs à partir de la première valeur ; à calculer une troisième valeur à partir de l'ensemble de deux valeurs et de la première valeur, selon une formule prédéterminée ; et à calculer une instruction de direction au moyen de la troisième valeur et de la deuxième valeur, de manière que le mouvement de retour au centre soit amélioré.
PCT/US2000/040844 2000-02-18 2000-09-07 Compensation automatique de l'hysterese de servodirection electrique WO2001060682A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US18359600P 2000-02-18 2000-02-18
US60/183,596 2000-02-18

Publications (1)

Publication Number Publication Date
WO2001060682A1 true WO2001060682A1 (fr) 2001-08-23

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2000/040844 WO2001060682A1 (fr) 2000-02-18 2000-09-07 Compensation automatique de l'hysterese de servodirection electrique

Country Status (1)

Country Link
WO (1) WO2001060682A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003097428A1 (fr) * 2002-05-16 2003-11-27 Zf Lenksysteme Gmbh Procede de fonctionnement d'un systeme de direction d'un vehicule automobile et systeme de direction
EP1275937A3 (fr) * 2001-07-12 2004-03-03 Kabushiki Kaisha Toyota Chuo Kenkyusho Appareil d'estimation d'une grandeur physique; appareil d'estimation d'un coefficient de frottement de surface d'une route, de la position neutre d'angle de braquage et de la réduction de pression de l'air
EP1401696A2 (fr) * 2001-07-03 2004-03-31 Trw Inc. Systeme de direction assiste par energie electrique avec compensation de friction, et procede de commande dudit systeme
CN102806942A (zh) * 2011-02-16 2012-12-05 操纵技术Ip控股公司 电力动力转向控制方法和系统

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4393694A (en) * 1981-05-18 1983-07-19 Sun Electric Corporation Vehicle steering and front-end alignment defect detector
US5422810A (en) * 1994-05-05 1995-06-06 Ford Motor Company Method and apparatus for determining steering position of automotive steering mechanism
US5446660A (en) * 1992-09-22 1995-08-29 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Electronically controlled power steering apparatus and method therefor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4393694A (en) * 1981-05-18 1983-07-19 Sun Electric Corporation Vehicle steering and front-end alignment defect detector
US5446660A (en) * 1992-09-22 1995-08-29 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Electronically controlled power steering apparatus and method therefor
US5422810A (en) * 1994-05-05 1995-06-06 Ford Motor Company Method and apparatus for determining steering position of automotive steering mechanism

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1401696A2 (fr) * 2001-07-03 2004-03-31 Trw Inc. Systeme de direction assiste par energie electrique avec compensation de friction, et procede de commande dudit systeme
EP1401696A4 (fr) * 2001-07-03 2007-04-25 Trw Inc Systeme de direction assiste par energie electrique avec compensation de friction, et procede de commande dudit systeme
EP1275937A3 (fr) * 2001-07-12 2004-03-03 Kabushiki Kaisha Toyota Chuo Kenkyusho Appareil d'estimation d'une grandeur physique; appareil d'estimation d'un coefficient de frottement de surface d'une route, de la position neutre d'angle de braquage et de la réduction de pression de l'air
US6802226B2 (en) 2001-07-12 2004-10-12 Kabushiki Kaisha Toyota Chuo Kenkyusho Physical amount estimating apparatus, road surface friction condition estimating apparatus, steering angle neutral point estimating apparatus and air pressure reduction estimating apparatus
WO2003097428A1 (fr) * 2002-05-16 2003-11-27 Zf Lenksysteme Gmbh Procede de fonctionnement d'un systeme de direction d'un vehicule automobile et systeme de direction
US7035722B2 (en) 2002-05-16 2006-04-25 Zf Lenksysteme Gmbh Method for operating a steering system for a motor vehicle and steering system
CN100344489C (zh) * 2002-05-16 2007-10-24 Zf操作系统有限公司 操作机动车辆转向系统的方法及相应的转向系统
CN102806942A (zh) * 2011-02-16 2012-12-05 操纵技术Ip控股公司 电力动力转向控制方法和系统

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