WO2010082086A1 - Absolute rotation angle sensing device, electric power assisted steering system comprising such a rotation angle sensing device and method for sensing an absolute angle - Google Patents

Absolute rotation angle sensing device, electric power assisted steering system comprising such a rotation angle sensing device and method for sensing an absolute angle Download PDF

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Publication number
WO2010082086A1
WO2010082086A1 PCT/IB2009/051975 IB2009051975W WO2010082086A1 WO 2010082086 A1 WO2010082086 A1 WO 2010082086A1 IB 2009051975 W IB2009051975 W IB 2009051975W WO 2010082086 A1 WO2010082086 A1 WO 2010082086A1
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WO
WIPO (PCT)
Prior art keywords
sensing
rotation angle
rotating part
sensing elements
signals
Prior art date
Application number
PCT/IB2009/051975
Other languages
French (fr)
Inventor
Franck Debrailly
Stéphane MOISY
Alexis Gatesoupe
Original Assignee
Aktiebolaget Skf
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.)
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Publication date
Application filed by Aktiebolaget Skf filed Critical Aktiebolaget Skf
Priority to PCT/IB2009/051975 priority Critical patent/WO2010082086A1/en
Publication of WO2010082086A1 publication Critical patent/WO2010082086A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
    • G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/245—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains using a variable number of pulses in a train
    • G01D5/2454—Encoders incorporating incremental and absolute signals
    • G01D5/2455—Encoders incorporating incremental and absolute signals with incremental and absolute tracks on the same encoder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D15/00—Steering not otherwise provided for
    • B62D15/02—Steering position indicators ; Steering position determination; Steering aids
    • B62D15/021—Determination of steering angle
    • B62D15/0235—Determination of steering angle by measuring or deriving directly at the electric power steering motor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D15/00—Steering not otherwise provided for
    • B62D15/02—Steering position indicators ; Steering position determination; Steering aids
    • B62D15/021—Determination of steering angle
    • B62D15/0245—Means or methods for determination of the central position of the steering system, e.g. straight ahead position

Definitions

  • the present invention relates to an absolute rotation angle sensing device, for an electric energy assisted steering (EPAS) system. Furthermore, the present invention relates to an EPAS system comprising such an absolute rotation angle sensing device. Besides, the present invention relates to a method for sensing an absolute rotation angle of an EPAS system.
  • EPAS electric energy assisted steering
  • a motor vehicle In a motor vehicle, the driver turns the steering wheel, which is fast in rotation with the steering column, to steer the vehicle.
  • An EPAS system assists in steering the vehicle by means of an electric motor having a rotor which actuates a steering rack.
  • the steering rack cooperates with the steering column via a pinion.
  • Such a pinion usually has a reduction factor of about 1/40, so that 1 revolution of the steering wheel corresponds to 40 revolutions of the electric motor in the case where the electric motor and the rack are concentric.
  • Prior art rotation angle sensors may be classified as either absolute rotation angle sensors or relative rotation angle sensors.
  • a relative rotation angle is the angle separating an initial zero position, for instance when the ignition is turned on, and the current position of the rotating part. Such an initial zero position is variable, i.e. it does not refer to any static part.
  • an absolute rotation angle is the angle separating the current position of a rotating part from the initial steering wheel position, which is constant and set by reference to a static part.
  • An absolute rotation angle sensor can be located directly on the steering column of a vehicle. However, such a location requires an absolute rotation sensor with a very high resolution, which is hence expensive, to get accurate measurements of the rotation angle.
  • the rotation angle of the rotor corresponds to the position of the steered wheels with respect to the ground.
  • an absolute rotation angle sensor can have its rotating part fast in rotation with a rotor of an EPAS system of the vehicle.
  • the rotor of the EPAS system is mobile around a rotation axis.
  • the steering wheel can rotate through several revolutions, usually three to six, in both directions of revolution, namely clockwise and counter-clockwise. Therefore, the rotor can rotate approximately 40 times these three to six revolutions, also in both directions of revolution, due to the reduction factor.
  • a prior art absolute rotation angle sensor generally comprises a rotating part and magnetic poles fast in rotation with the rotor, several sensing elements arranged to sense these magnetic poles when said rotating part rotates and to output signals representative of an angular position of this rotating part and supply means providing current to the sensing elements.
  • a prior art method for sensing an absolute rotation angle of an EPAS system usually comprises the steps of: supply means provide current to the sensing elements; when said rotating part rotates, the sensing elements sense the magnetic poles and output signals representative of an angular position of the rotating part; an electronic control unit uses these signals to determine the rotation angle of the rotating part.
  • the signals are processed by the electronic control unit to determine the rotation angle and the direction of rotation of the steering column, hence of the steering wheel.
  • a solution would be to keep providing electrical energy to the sensing elements, even when the engine ignition is turned off, so that the prior art absolute rotation angle sensor keeps measuring the rotation angle. Yet, such a permanent measurement significantly increases the power consumption of the absolute rotation angle sensor, which is contrary to most specification requirements.
  • One object of the present invention is to solve the here-above described problems, by providing a cost effective, energy saving absolute rotation angle sensor which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off.
  • an absolute rotation angle sensing device for an electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis and through several revolutions, said absolute rotation angle sensing device comprising: a rotating part configured to be fast in rotation with said rotor ; at least one pair of magnetic poles disposed oppositely around said rotation axis, said magnetic poles being fast in rotation with said rotating part; a first sensing group comprising at least three first sensing elements, said first sensing elements being distributed around said rotation axis, said first sensing elements being arranged so as to sense said magnetic poles when said rotating part rotates and to output first signals representative of an angular position of said rotating part within one or all of said revolutions ; first supply means configured to provide electrical energy to said first sensing elements when said EPAS system is in an operation mode ;
  • This absolute rotation angle sensing device is characterized in that it further comprises: - a second sensing group comprising two second sensing elements, said second sensing elements being arranged so as to sense said magnetic
  • An absolute angle sensor can identify in which revolution is positioned the rotor of the EPAS system. Hence, the absolute rotation angle cannot be "lost" when the steering wheel is rotated while the engine ignition is turned off. According to other advantageous but optional features of the present invention, considered on their own or in any technically possible combination:
  • said first sensing elements and said second sensing elements are Hall- effect cells
  • At least one of said sensing elements is common to said first sensing group and to said second sensing group;
  • said absolute rotation angle sensing device comprises a certain number of pairs of magnetic poles, the respective positions of said second sensing elements being separated by a shift angle of 90° (modulo 360 °) divided by said number of pairs of magnetic poles;
  • said first supply means are connected to an accumulator, which is loaded by an alternator of a vehicle, and in that said second supply means are connected either to a battery or to a capacitor, which are independent from said alternator.
  • Another object of the present invention is to provide a cost effective, energy saving electric power assisted steering (EPAS) system which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off.
  • an electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis and through several revolutions, characterized in that it comprises an absolute rotation angle sensing device as here-above described and an electronic control unit configured to control said absolute rotation angle sensing device.
  • a further object of the present invention is to provide a cost effective, energy saving method for sensing an absolute rotation angle which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off.
  • a method for sensing an absolute rotation angle of an electric energy assisted steering (EPAS) system comprising: a rotor mobile around a rotation axis and through several revolutions ; - a rotating part configured to be fast in rotation with said rotor ; at least one pair of magnetic poles disposed oppositely around said rotation axis, said magnetic poles being fast in rotation with said rotating part; wherein, when said EPAS system is in an operation mode, said method comprises the steps of: - first supply means provide electrical energy to a first sensing group comprising at least three first sensing elements; when said rotating part rotates, said first sensing elements sense said magnetic poles and output first signals representative of an angular position of said rotating part within one or all of said revolutions ; - an electronic control unit determines, based upon said first signals, the rotation angle of said rotating part ;
  • EPAS electric energy assisted steering
  • This method is characterized in that, when said EPAS system is in a standby mode, it comprises the steps of: said first supply means stop providing electrical energy to said first sensing group ; second supply means provide electrical energy to two second sensing elements belonging to a second sensing group ; when said rotating part rotates, said second sensing elements sense said magnetic poles and output respective second signals having a predetermined phase shift ; said electronic control unit identifies, based upon said second signals, in which one of said revolutions is positioned said rotating part.
  • this method further comprises the steps of:
  • said first supply means provide electrical energy at a first voltage
  • said second supply means provide electrical energy at a second voltage, which is lower than said first voltage ;
  • a voltage comparator determines whether said EPAS system is in said operation mode or in said standby mode, based upon a comparison between the voltage supplied by said first supply means and a threshold voltage.
  • said first voltage is 5 V, in that said second voltage is 3 V and in that said threshold voltage is about 4 V;
  • a counter means outputs the direction of revolution and the number of revolutions covered by said rotating part and stores them in a memory; - when said EPAS system resumes in said operation mode, said electronic control unit retrieves from said memory said direction of revolution and said number of revolutions;
  • FIG. 2 is a functional diagram comprising the absolute rotation angle sensing device of figure 1 and
  • FIG. 3 is a view analogous to figure 1 of an absolute rotation angle sensing device according to a second embodiment of the present invention.
  • Figure 1 depicts an absolute rotation angle sensor 1 comprising a rotating part 2 and an encoder or a magnet 5.
  • Rotating part 2 is configured to be fast in rotation with a non-shown rotor belonging to an electric energy assisted steering
  • Rotating part 2 has a shape of an annular ring with symmetry of revolution around axis Xi .
  • Rotating part 2 can rotate around a rotation axis Xi through several revolutions, namely hundred and twenty to two hundred and forty revolutions.
  • Angle sensor 1 can be either integrated into the motor or located close to the motor.
  • Magnet 5 has one pair of magnetic poles, i.e. a north (N) pole 3 and a south (S) pole 4. Magnet 5 extends along the whole circumference of axis Xi.
  • Magnet 5 forms an annular ring around axis Xi .
  • Magnetic poles 3 and 4 are fast in rotation with rotating part 2.
  • N pole 3 and S pole 4 are disposed oppositely around axis Xi.
  • Angle sensor 1 further comprises three first Hall-effect cells 11 , 12 and 13, which together form a first sensing group.
  • First Hall-effect cells 11 , 12 and 13 are angularly evenly distributed around axis Xi. In other words, the first Hall-effect cells 11 , 12 and 13 are separated two by two by a mechanical angle of 120°.
  • First Hall-effect cells 11 , 12 and 13 are arranged at static positions and at a detection distance from magnet 5, so as to sense N pole 3 and S pole 4 when rotating part 2 rotates.
  • First Hall-effect cells 11 , 12 and 13 are adapted to output first signals which are representative of the current absolute angular position of rotating part around axis Xi such as disclosed in WO-A-2007/077389.
  • Each Hall- effects cell 11 , 12, or 13 is supplied with a constant voltage and generates an output voltage which varies according to the magnetic field generated by the magnet and sensed by the Hall-effect cell.
  • Angle sensor 1 further comprises two seconds Hall-effect cells 21 and 22.
  • Second Hall-effect cells 21 and 22 both constitute a second sensing group of sensing elements, aside of first sensing group formed by first-Hal l-effect cells 11 , 12 and 13.
  • Second Hall-effect cells 21 and 22 are arranged on a static part of angle sensor 1 , at static positions separated by a 90°(modulo 180°) angle.
  • Second Hall-effect cells 21 and 22 are located at a detection distance from magnet 5, so as to sense N pole 3 and S pole 4 when rotating part 2 rotates.
  • Second Hall-effect cells 21 and 22 are mutually positioned so as to output respective second signals having a predetermined phase shift of 90°. Since second Hall-effect cells 21 and 22 output sine-wave signals and since they are separated by a shift angle of 90°(modulo 180°) they output respective second signals with a phase shift of 90°. Hence, when seco nd Hall-effect cell 21 outputs a sine signal, second Hall-effect cell 22 output a cosine signal. These second signal, sine and cosine, are representative of the revolution in which is positioned rotating part 2, hence the rotor of the EPAS system.
  • angle sensor 1 further comprises a first wire 15 connected to first Hall-effect cells 11 , 12 and 13, in order to provide them with electrical energy.
  • first wire 15 is connected to a first power supply consisting of an accumulator 31 which is loaded by an alternator of the vehicle. Accumulator 31 can provide electrical current at a first voltage of 5 V.
  • First wire 15 thus forms first supply means configured to provide electrical current to first Hall- effect cells 11 , 12 and 13.
  • Angle sensor 1 also comprises a second wire 25 connected to second Hall- effect cells 21 and 22, in order to provide them with electrical energy.
  • Second wire 25 is connected to a second power supply, which consists of a battery 32 independent from the alternator of the vehicle.
  • Battery 32 can provide electrical current at a second voltage of 3 V, which is lower than the first voltage.
  • Second wire 25 thus forms second supply means configured to provide electrical current to second Hall-effect cells 21 and 22.
  • second power supply may consist of a capacitor independent from the alternator of the vehicle and loaded by the accumulator of the vehicle.
  • Angle sensor 1 is connected to a control system S, which retrieves first and second signals respectively emitted by first 11 , 12, 13 and second 21 , 22 Hall- effect cells.
  • Control system S comprises an interpolating unit 6 which integrates the first signals from first Hall-effect cells 11 , 12 and 13.
  • Interpolating unit 6 is directly connected to first Hall-effect cells 11 , 12 and 13.
  • filters can be inserted between interpolating unit 6 and every first Hall-effect cell 11 , 12 or 13, in order to clean up the first signals.
  • Control system S also comprises a counter 7 connected to both second Hall- effect cells 21 and 22 on the one hand. On the other hand, counter 7 is connected to a memory 8. Interpolating unit 6 and memory 8 are both connected to an output connector 9, which is itself connected to an electronic control unit 40. Output connector and electronic control unit 40 both belong to the control system S. Interpolating unit 6, counter 7, memory 8 and output connector 9 are made of analogical components and therefore transmit analogical signals.
  • Control system S further comprises an electronic control unit (ECU) 40 having a signal processor 41 , an analogical/digital converter 42, a calculating processor 43 and an integrating unit 44. Signal processor 41 adjusts the offset and the gain of the signals transmitted by the output connector 9. ECU 40 and its components transmit digital signals.
  • ECU 40 and its components transmit digital signals.
  • control system S comprises a voltage comparator 33 which determines whether EPAS system works in operation mode or in standby mode. To this aim, voltage comparator 33 compares the first voltage supplied by the accumulator 31 , namely the first power supply, to a threshold voltage. Since first voltage is 5 V and second voltage is 3 V, this threshold voltage can be set at 4 V.Voltage comparator 33 hence is at the intersection of first wire 15 and second wire 25. Voltage comparator 33 can be made of an analogical or digital component which is incorporated into angle sensor 1.
  • voltage comparator 33 actuates battery 32, when the EPAS system is in standby mode, or transmits the current provided by the accumulator 31 , when the EPAS system is in operation mode. More accurately, battery 32 is activated if the voltage supplied by the accumulator 31 is lower than the 4 V threshold voltage, most often when this first voltage is 0 V. The latter occurs when the engine ignition is turned off, hence when the EPAS system is in standby mode. In this mode, the first sensing group is shutdown and it does not need any current supply.
  • first wire 15 provides electrical energy to the first sensing group, i.e. to first Hall-effect cells 11 , 12 and 13. Then, when rotating part 2 rotates, ECU 40 determines, based on the first signals transmitted by first Hall-effect cells 11 , 12 and 13, an accurate rotation angle of rotating part 2, hence of the rotor of the EPAS system, within one specific revolution.
  • Another counter and another memory located in the ECU 40 can further count the number of revolutions of the rotating part 2, which is typically within the range [-60 revolutions ; +60 revolutions] for a 3 revolutions steering wheel, and within the range [-120 revolutions ; +120 revolutions] for a 6 revolutions steering wheel. ECU 40 can then calculate the absolute angular position of the rotating part 2 within the full range of revolutions.
  • the counter 7 and the memory 8, used for the second sensing group as earlier described can also be used in combination with the first sensing group so as to determine in which revolution stands the rotating element 2 during operation mode of the EPAS system.
  • the rotation angle can be calculated by the calculating processor 43 after interpolating unit 6 has combined the first signals under sine- and cosine-wave forms.
  • second Hall-effect cells 21 and 22 can sense N pole 3 and S pole 4 and consequently transmit second signal to counter 7. Second signals respectively transmitted by second Hall-effect cells 21 and 22 have a 90° phase shift, one signal correspon ding to a sine and the other one corresponding to a cosine.
  • ECU 40 can identify, based upon the second signals, in which revolution is positioned rotating part 2, hence the rotor of the EPAS system.
  • ECU 40 uses counter 7 and memory 8.
  • Counter 7 outputs the direction of revolution and the number of revolutions covered by rotating part 2. Indeed counter 7 emits one pulse signal at every revolution covered by rotating part 2.
  • Memory 8 backs up and compiles direction and number of revolutions.
  • integrating unit 44 retrieves from memory 8 the direction and the number of revolutions covered by rotating part 2 during the standby mode.
  • ECU 40 can hence accurately determine the absolute rotation angle of rotating part 2.
  • ECU 40 thusly gathers the rotation angle when the EPAS system is in an operation mode and the number of revolutions of rotating part 2 when the EPAS system is turned off.
  • calculating processors 43 may calculate the rotation angle, which is then used by the integrating unit 44, together with the direction and the number of revolutions compiled by memory 8.
  • Figure 3 illustrates an absolute rotation angle sensor 301 according to another embodiment of the present invention.
  • Angle sensor 301 is quite similar to angle sensor 1.
  • the description of angle sensor 1 given above can therefore be transposed to angle sensor 301.
  • the reference number of a part of angle sensor 301 can be directly derived, by adding 300 to it, from the reference number of the corresponding part of angle sensor 1.
  • Angle sensor 301 mainly differs from angle sensor 1 by its number of Hall- effect cells and its number of magnetic poles.
  • Magnet 305 indeed comprises four magnetic poles, i.e. N poles 303.1 and 303.2 and S poles 304.1 and 304.2.
  • Each magnetic pole namely N 303.1 or 303.2 and S 304.1 or 304.2, extends around axis X 301 on a range of 90°.
  • N poles 303.1 and 303.2 and S p oles 304.1 and 304.2 are alternately distributed around axis X 3 oi- Magnetic poles 303.1 , 303.2, 304.1 and 304.2 extend on the whole circumference of axis X 30 i .
  • Angle sensor 301 also differs from angle sensor 1 by the fact that it comprises only four Hall-effect cells instead of five.
  • First Hall-effect cells 311 , 312 and 313 correspond to first Hall-effect cells 11 , 12 and 13 in structure and in function.
  • angle sensor 301 comprises only one single second Hall-effect cell 322 instead of the two seconds Hall-effect cells 21 and 22 of angle sensor 1.
  • Hall-effect cell 312 also achieves the function of a second Hall-effect cell.
  • Hall-effect cell 312 is common to first sensing group and to second sensing group.
  • First sensing group consists of Hall-effect cells 311 , 312 and 313, while second sensing group consists of Hall-effect cells 312 and 322.
  • Second Hall-effect cells 312 and 322 are separated by a 45 * (modulo 180 * ) mechanical angle, instead of the 90°(nnodulo 180") m echanical angle separating second Hall-effect cells 21 and 22. Second Hall-effect cells 312 and 322 are mutually positioned so as to output respective second signals having a 90° electrical phase shift, which corresponds to 90° me chanical angle when the magnet 5 or encoder is bipolar. Second Hall-effect cells 312 and 322 transmit sine- and cosine-wave signals. More generally, the magnet can comprise any given number or pairs of magnetic poles N and S, with second sensing elements separated by a shift angle of 90°(nnodulo 360") divided by this given number of pairs of magnetic poles.
  • an angle sensor according to the invention can comprise three pairs of magnetic poles with second sensing elements separated by mechanical shift angles of 30°(nnodulo 120°).
  • second sensing el ements transmit respective second signals having a predetermined electrical phase shift of 90°.
  • the present invention permits to significantly decrease the power consumption when the EPAS system is turned off, while nonetheless keeping track of the absolute rotation angle by taking account of the direction and the number of revolutions made during standby mode, until the first Hall-effect cells 311 , 312 and 313 are activated again when the EPAS system resumes in operation mode.
  • An angle sensor according to the present invention permits to save about 7 mA per first Hall-effect cell turned off during standby mode, which represents a significant energy saving, thus complying with specification requirements.
  • Positioning the second Hall-effect cell at 90°(modu lo 180°) electrical shift angle permits to automatically produce sine and cosine signals, thus making it possible to keep measuring an absolute position angle over one revolution, though its accuracy can be lower than the one obtained with the first sensing group used in the operating mode of the EPAS system.
  • the different electronic circuits used with the first sensing group can advantageously by used to process also the first signals and the second signals generated by the second sensing group.
  • the predetermined phase shift between the respective second sensing elements can be different from 90°.
  • an angle sensor must comprise at least two second sensing elements.
  • One second sensing element is enough to determine whether one full revolution has been made, for instance by detecting the zero, the maximum or the minimum value of a sine-wave signal.
  • Another second sensing element is needed in order to determine the direction of revolution, namely clockwise or counter-clockwise, as the steering rack can operate the wheels to the left or to the right.
  • the direction of revolution can be determined by detecting which one of the two sine- wave signals is in advance with respect to the other.
  • the first sensing group can comprise more than three sensing elements, say five, depending on the accuracy and on the response time required for the absolute rotation angle sensor.
  • these first sensing elements can be evenly or unevenly distributed around the rotation of an axis.
  • all the sensing elements of the second sensing group can advantageously be used in the first sensing group.
  • first sensing elements and/or second sensing elements can be of another nature. Furthermore, first sensing elements can differ from second sensing elements.
  • the first sensing group can comprise three or more first sensing elements, say Hall-effects cells, two of which form the second sensing group.
  • the first supply means and the second supply means can be made of two distinct wires, like 15 and 25.
  • the first and second supply means can comprise one single wire plus a switching element to control the current supply to the one sensing element which is solely a first sensing element, i.e. which solely belongs to the first sensing group.
  • the three sensing elements are supplied with current, with this switching element in a closed position.
  • the switching element In standby mode, the switching element is open and the sole first sensing element is turned off.
  • a voltage comparator determines whether the EPAS system is in operation mode or in standby mode. This voltage comparator consequently actuates, namely opens or closes, this switching element.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Abstract

This absolute rotation angle sensing device (1 ), for an EPAS system comprising a rotor mobile around a rotation axis (X1 ; X301 ), comprises: a rotating part (2); a pair of magnetic poles (3, 4) fast in rotation with said rotating part (2); at least three first sensing elements (11, 12, 13) distributed around said axis (X1; X301 ) and arranged to sense said magnetic poles (3, 4) so as to output first signals representative of an angular position of said rotating part (2); first supply means (15) to provide energy to said first sensing elements (11, 12, 13) during operation mode. This absolute rotation angle sensing device (1 ) further comprises: at least two second sensing elements (21, 22) arranged so as to sense said magnetic poles (3, 4) and mutually positioned so as to output respective second signals having a predetermined phase shift, said second signals being representative of the revolution in which is positioned said rotating part (2); second supply means (25) to provide energy to said second sensing elements (21, 22) during standby mode.

Description

ABSOLUTE ROTATION ANGLE SENSING DEVICE, ELECTRIC POWER
ASSISTED STEERING SYSTEM COMPRISING SUCH A ROTATION ANGLE
SENSING DEVICE AND METHOD FOR SENSING AN ABSOLUTE ANGLE
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an absolute rotation angle sensing device, for an electric energy assisted steering (EPAS) system. Furthermore, the present invention relates to an EPAS system comprising such an absolute rotation angle sensing device. Besides, the present invention relates to a method for sensing an absolute rotation angle of an EPAS system.
BACKGROUND ART OF THE INVENTION
In a motor vehicle, the driver turns the steering wheel, which is fast in rotation with the steering column, to steer the vehicle. An EPAS system assists in steering the vehicle by means of an electric motor having a rotor which actuates a steering rack. The steering rack cooperates with the steering column via a pinion. Such a pinion usually has a reduction factor of about 1/40, so that 1 revolution of the steering wheel corresponds to 40 revolutions of the electric motor in the case where the electric motor and the rack are concentric. Prior art rotation angle sensors may be classified as either absolute rotation angle sensors or relative rotation angle sensors. A relative rotation angle is the angle separating an initial zero position, for instance when the ignition is turned on, and the current position of the rotating part. Such an initial zero position is variable, i.e. it does not refer to any static part. In contrast, an absolute rotation angle is the angle separating the current position of a rotating part from the initial steering wheel position, which is constant and set by reference to a static part.
An absolute rotation angle sensor can be located directly on the steering column of a vehicle. However, such a location requires an absolute rotation sensor with a very high resolution, which is hence expensive, to get accurate measurements of the rotation angle. The rotation angle of the rotor corresponds to the position of the steered wheels with respect to the ground.
Instead, an absolute rotation angle sensor can have its rotating part fast in rotation with a rotor of an EPAS system of the vehicle. The rotor of the EPAS system is mobile around a rotation axis. The steering wheel can rotate through several revolutions, usually three to six, in both directions of revolution, namely clockwise and counter-clockwise. Therefore, the rotor can rotate approximately 40 times these three to six revolutions, also in both directions of revolution, due to the reduction factor.
A prior art absolute rotation angle sensor generally comprises a rotating part and magnetic poles fast in rotation with the rotor, several sensing elements arranged to sense these magnetic poles when said rotating part rotates and to output signals representative of an angular position of this rotating part and supply means providing current to the sensing elements.
A prior art method for sensing an absolute rotation angle of an EPAS system usually comprises the steps of: supply means provide current to the sensing elements; when said rotating part rotates, the sensing elements sense the magnetic poles and output signals representative of an angular position of the rotating part; an electronic control unit uses these signals to determine the rotation angle of the rotating part.
Then, the signals are processed by the electronic control unit to determine the rotation angle and the direction of rotation of the steering column, hence of the steering wheel.
However, when the EPAS system is in a standby mode, namely when the ignition of the vehicle engine is turned off, a prior art absolute rotation angle sensor is unable to determine an angle of rotation of the EPAS system. Hence, if the steering wheel or the wheels of the vehicle are turned while the engine is not running, e.g. during maintenance of the vehicle, an inconsistency occurs when the engine ignition resumes, because the actual absolute rotation angle differs from the absolute rotation angle stored by the EPAS system before the engine ignition was turned off. Such an inconsistency hinders the control of the EPAS system, because its memory stored an incorrect absolute rotation angle.
A solution would be to keep providing electrical energy to the sensing elements, even when the engine ignition is turned off, so that the prior art absolute rotation angle sensor keeps measuring the rotation angle. Yet, such a permanent measurement significantly increases the power consumption of the absolute rotation angle sensor, which is contrary to most specification requirements.
SUMMARY OF THE INVENTION One object of the present invention is to solve the here-above described problems, by providing a cost effective, energy saving absolute rotation angle sensor which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off.
This object is achieved by an absolute rotation angle sensing device, for an electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis and through several revolutions, said absolute rotation angle sensing device comprising: a rotating part configured to be fast in rotation with said rotor ; at least one pair of magnetic poles disposed oppositely around said rotation axis, said magnetic poles being fast in rotation with said rotating part; a first sensing group comprising at least three first sensing elements, said first sensing elements being distributed around said rotation axis, said first sensing elements being arranged so as to sense said magnetic poles when said rotating part rotates and to output first signals representative of an angular position of said rotating part within one or all of said revolutions ; first supply means configured to provide electrical energy to said first sensing elements when said EPAS system is in an operation mode ; This absolute rotation angle sensing device is characterized in that it further comprises: - a second sensing group comprising two second sensing elements, said second sensing elements being arranged so as to sense said magnetic poles when said rotating part rotates, said second sensing elements being mutually positioned so as to output respective second signals having a predetermined phase shift, said second signals being representative of the revolution in which is positioned said rotating part; second supply means configured to provide electrical energy to said second sensing elements when said EPAS system is in a standby mode. An absolute angle sensor according to the invention can identify in which revolution is positioned the rotor of the EPAS system. Hence, the absolute rotation angle cannot be "lost" when the steering wheel is rotated while the engine ignition is turned off. According to other advantageous but optional features of the present invention, considered on their own or in any technically possible combination:
- said first sensing elements and said second sensing elements are Hall- effect cells;
- at least one of said sensing elements is common to said first sensing group and to said second sensing group;
- all the sensing elements of the second sensing group are comprised in the first sensing group;
- said predetermined phase shift is of 90°
- said absolute rotation angle sensing device comprises a certain number of pairs of magnetic poles, the respective positions of said second sensing elements being separated by a shift angle of 90° (modulo 360 °) divided by said number of pairs of magnetic poles;
- said first supply means are connected to an accumulator, which is loaded by an alternator of a vehicle, and in that said second supply means are connected either to a battery or to a capacitor, which are independent from said alternator.
Another object of the present invention is to provide a cost effective, energy saving electric power assisted steering (EPAS) system which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off. This object is achieved by an electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis and through several revolutions, characterized in that it comprises an absolute rotation angle sensing device as here-above described and an electronic control unit configured to control said absolute rotation angle sensing device. A further object of the present invention is to provide a cost effective, energy saving method for sensing an absolute rotation angle which is able to correctly determine the absolute rotation angle, even when the engine ignition has been turned off. This object is achieved by a method for sensing an absolute rotation angle of an electric energy assisted steering (EPAS) system, said EPAS system comprising: a rotor mobile around a rotation axis and through several revolutions ; - a rotating part configured to be fast in rotation with said rotor ; at least one pair of magnetic poles disposed oppositely around said rotation axis, said magnetic poles being fast in rotation with said rotating part; wherein, when said EPAS system is in an operation mode, said method comprises the steps of: - first supply means provide electrical energy to a first sensing group comprising at least three first sensing elements; when said rotating part rotates, said first sensing elements sense said magnetic poles and output first signals representative of an angular position of said rotating part within one or all of said revolutions ; - an electronic control unit determines, based upon said first signals, the rotation angle of said rotating part ;
This method is characterized in that, when said EPAS system is in a standby mode, it comprises the steps of: said first supply means stop providing electrical energy to said first sensing group ; second supply means provide electrical energy to two second sensing elements belonging to a second sensing group ; when said rotating part rotates, said second sensing elements sense said magnetic poles and output respective second signals having a predetermined phase shift ; said electronic control unit identifies, based upon said second signals, in which one of said revolutions is positioned said rotating part. According to other advantageous but optional features of the present invention, considered on their own or in any technically possible combination: - this method further comprises the steps of:
- said first supply means provide electrical energy at a first voltage ;
- said second supply means provide electrical energy at a second voltage, which is lower than said first voltage ; - a voltage comparator determines whether said EPAS system is in said operation mode or in said standby mode, based upon a comparison between the voltage supplied by said first supply means and a threshold voltage. - said first voltage is 5 V, in that said second voltage is 3 V and in that said threshold voltage is about 4 V;
- when said EPAS system is in said standby mode, a counter means outputs the direction of revolution and the number of revolutions covered by said rotating part and stores them in a memory; - when said EPAS system resumes in said operation mode, said electronic control unit retrieves from said memory said direction of revolution and said number of revolutions;
- said first signals and said second signals are sine-wave signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention and its advantages will be better understood on the basis of the following description, which is given as an illustrative example without restricting the scope of the invention, in relation with the annexed drawings, among which: - Figure 1 is a schematic and partial view of an absolute rotation angle sensing device according to a first embodiment of the invention,
- Figure 2 is a functional diagram comprising the absolute rotation angle sensing device of figure 1 and
- Figure 3 is a view analogous to figure 1 of an absolute rotation angle sensing device according to a second embodiment of the present invention.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
Figure 1 depicts an absolute rotation angle sensor 1 comprising a rotating part 2 and an encoder or a magnet 5. Rotating part 2 is configured to be fast in rotation with a non-shown rotor belonging to an electric energy assisted steering
(EPAS) system. Rotating part 2 has a shape of an annular ring with symmetry of revolution around axis Xi . Rotating part 2 can rotate around a rotation axis Xi through several revolutions, namely hundred and twenty to two hundred and forty revolutions. Angle sensor 1 can be either integrated into the motor or located close to the motor.
Magnet 5 has one pair of magnetic poles, i.e. a north (N) pole 3 and a south (S) pole 4. Magnet 5 extends along the whole circumference of axis Xi.
Magnet 5 forms an annular ring around axis Xi . Magnetic poles 3 and 4 are fast in rotation with rotating part 2. N pole 3 and S pole 4 are disposed oppositely around axis Xi.
Angle sensor 1 further comprises three first Hall-effect cells 11 , 12 and 13, which together form a first sensing group. First Hall-effect cells 11 , 12 and 13 are angularly evenly distributed around axis Xi. In other words, the first Hall-effect cells 11 , 12 and 13 are separated two by two by a mechanical angle of 120°.
First Hall-effect cells 11 , 12 and 13 are arranged at static positions and at a detection distance from magnet 5, so as to sense N pole 3 and S pole 4 when rotating part 2 rotates. First Hall-effect cells 11 , 12 and 13 are adapted to output first signals which are representative of the current absolute angular position of rotating part around axis Xi such as disclosed in WO-A-2007/077389. Each Hall- effects cell 11 , 12, or 13 is supplied with a constant voltage and generates an output voltage which varies according to the magnetic field generated by the magnet and sensed by the Hall-effect cell.
Angle sensor 1 further comprises two seconds Hall-effect cells 21 and 22. Second Hall-effect cells 21 and 22, both constitute a second sensing group of sensing elements, aside of first sensing group formed by first-Hal l-effect cells 11 , 12 and 13. Second Hall-effect cells 21 and 22 are arranged on a static part of angle sensor 1 , at static positions separated by a 90°(modulo 180°) angle. Second Hall-effect cells 21 and 22 are located at a detection distance from magnet 5, so as to sense N pole 3 and S pole 4 when rotating part 2 rotates.
Second Hall-effect cells 21 and 22 are mutually positioned so as to output respective second signals having a predetermined phase shift of 90°. Since second Hall-effect cells 21 and 22 output sine-wave signals and since they are separated by a shift angle of 90°(modulo 180°) they output respective second signals with a phase shift of 90°. Hence, when seco nd Hall-effect cell 21 outputs a sine signal, second Hall-effect cell 22 output a cosine signal. These second signal, sine and cosine, are representative of the revolution in which is positioned rotating part 2, hence the rotor of the EPAS system.
As can be seen on figure 2, angle sensor 1 further comprises a first wire 15 connected to first Hall-effect cells 11 , 12 and 13, in order to provide them with electrical energy. To this aim, first wire 15 is connected to a first power supply consisting of an accumulator 31 which is loaded by an alternator of the vehicle. Accumulator 31 can provide electrical current at a first voltage of 5 V. First wire 15 thus forms first supply means configured to provide electrical current to first Hall- effect cells 11 , 12 and 13. Angle sensor 1 also comprises a second wire 25 connected to second Hall- effect cells 21 and 22, in order to provide them with electrical energy. Second wire 25 is connected to a second power supply, which consists of a battery 32 independent from the alternator of the vehicle. Battery 32 can provide electrical current at a second voltage of 3 V, which is lower than the first voltage. Second wire 25 thus forms second supply means configured to provide electrical current to second Hall-effect cells 21 and 22. Alternatively, second power supply may consist of a capacitor independent from the alternator of the vehicle and loaded by the accumulator of the vehicle.
Angle sensor 1 is connected to a control system S, which retrieves first and second signals respectively emitted by first 11 , 12, 13 and second 21 , 22 Hall- effect cells. Control system S comprises an interpolating unit 6 which integrates the first signals from first Hall-effect cells 11 , 12 and 13. Interpolating unit 6 is directly connected to first Hall-effect cells 11 , 12 and 13. Alternatively, filters can be inserted between interpolating unit 6 and every first Hall-effect cell 11 , 12 or 13, in order to clean up the first signals.
Control system S also comprises a counter 7 connected to both second Hall- effect cells 21 and 22 on the one hand. On the other hand, counter 7 is connected to a memory 8. Interpolating unit 6 and memory 8 are both connected to an output connector 9, which is itself connected to an electronic control unit 40. Output connector and electronic control unit 40 both belong to the control system S. Interpolating unit 6, counter 7, memory 8 and output connector 9 are made of analogical components and therefore transmit analogical signals. Control system S further comprises an electronic control unit (ECU) 40 having a signal processor 41 , an analogical/digital converter 42, a calculating processor 43 and an integrating unit 44. Signal processor 41 adjusts the offset and the gain of the signals transmitted by the output connector 9. ECU 40 and its components transmit digital signals.
According to embodiments not shown, digital components 41 , 42, and/or 43 might be replaced by analogical components. Conversely, analogical components 6, 7, 8 and/or 9 might be replaced by digital components. Part or all of these analogical components can be incorporated into absolute rotation angle sensor 1. Moreover, control system S comprises a voltage comparator 33 which determines whether EPAS system works in operation mode or in standby mode. To this aim, voltage comparator 33 compares the first voltage supplied by the accumulator 31 , namely the first power supply, to a threshold voltage. Since first voltage is 5 V and second voltage is 3 V, this threshold voltage can be set at 4 V.Voltage comparator 33 hence is at the intersection of first wire 15 and second wire 25. Voltage comparator 33 can be made of an analogical or digital component which is incorporated into angle sensor 1.
Depending on the result of this voltage comparison, voltage comparator 33 actuates battery 32, when the EPAS system is in standby mode, or transmits the current provided by the accumulator 31 , when the EPAS system is in operation mode. More accurately, battery 32 is activated if the voltage supplied by the accumulator 31 is lower than the 4 V threshold voltage, most often when this first voltage is 0 V. The latter occurs when the engine ignition is turned off, hence when the EPAS system is in standby mode. In this mode, the first sensing group is shutdown and it does not need any current supply.
In a method according to the present invention, during operation mode of the EPAS system, first wire 15 provides electrical energy to the first sensing group, i.e. to first Hall-effect cells 11 , 12 and 13. Then, when rotating part 2 rotates, ECU 40 determines, based on the first signals transmitted by first Hall-effect cells 11 , 12 and 13, an accurate rotation angle of rotating part 2, hence of the rotor of the EPAS system, within one specific revolution.
Another counter and another memory located in the ECU 40 can further count the number of revolutions of the rotating part 2, which is typically within the range [-60 revolutions ; +60 revolutions] for a 3 revolutions steering wheel, and within the range [-120 revolutions ; +120 revolutions] for a 6 revolutions steering wheel. ECU 40 can then calculate the absolute angular position of the rotating part 2 within the full range of revolutions. Alternatively, the counter 7 and the memory 8, used for the second sensing group as earlier described, can also be used in combination with the first sensing group so as to determine in which revolution stands the rotating element 2 during operation mode of the EPAS system. The rotation angle can be calculated by the calculating processor 43 after interpolating unit 6 has combined the first signals under sine- and cosine-wave forms.
Furthermore, when the EPAS system is in standby mode, i.e. when engine ignition is turned off, first wire 15 stops providing current to first Hall-effect cells 11 , 12 and 13, whereas second wire 25 provides current to second Hall-effect cells 21 and 22. Thus, when rotating part 2 rotates, second Hall-effect cells 21 and 22 can sense N pole 3 and S pole 4 and consequently transmit second signal to counter 7. Second signals respectively transmitted by second Hall-effect cells 21 and 22 have a 90° phase shift, one signal correspon ding to a sine and the other one corresponding to a cosine.
Thus, ECU 40 can identify, based upon the second signals, in which revolution is positioned rotating part 2, hence the rotor of the EPAS system. To this aim, ECU 40 uses counter 7 and memory 8. Counter 7 outputs the direction of revolution and the number of revolutions covered by rotating part 2. Indeed counter 7 emits one pulse signal at every revolution covered by rotating part 2. Memory 8 backs up and compiles direction and number of revolutions. When the EPAS resumes in operation mode, integrating unit 44 retrieves from memory 8 the direction and the number of revolutions covered by rotating part 2 during the standby mode.
ECU 40 can hence accurately determine the absolute rotation angle of rotating part 2. ECU 40 thusly gathers the rotation angle when the EPAS system is in an operation mode and the number of revolutions of rotating part 2 when the EPAS system is turned off. After the analogical/digital converter 42 has converted the first and second signals, calculating processors 43 may calculate the rotation angle, which is then used by the integrating unit 44, together with the direction and the number of revolutions compiled by memory 8.
Figure 3 illustrates an absolute rotation angle sensor 301 according to another embodiment of the present invention. Angle sensor 301 is quite similar to angle sensor 1. The description of angle sensor 1 given above can therefore be transposed to angle sensor 301. The reference number of a part of angle sensor 301 can be directly derived, by adding 300 to it, from the reference number of the corresponding part of angle sensor 1. One can thus define a rotating part 302, a magnet 305, a rotation axis X30i and Hall-effect cells 311 , 312, 313 and 322.
Angle sensor 301 mainly differs from angle sensor 1 by its number of Hall- effect cells and its number of magnetic poles. Magnet 305 indeed comprises four magnetic poles, i.e. N poles 303.1 and 303.2 and S poles 304.1 and 304.2. Each magnetic pole, namely N 303.1 or 303.2 and S 304.1 or 304.2, extends around axis X301 on a range of 90°. N poles 303.1 and 303.2 and S p oles 304.1 and 304.2 are alternately distributed around axis X3oi- Magnetic poles 303.1 , 303.2, 304.1 and 304.2 extend on the whole circumference of axis X30i .
Angle sensor 301 also differs from angle sensor 1 by the fact that it comprises only four Hall-effect cells instead of five. First Hall-effect cells 311 , 312 and 313 correspond to first Hall-effect cells 11 , 12 and 13 in structure and in function. Besides, angle sensor 301 comprises only one single second Hall-effect cell 322 instead of the two seconds Hall-effect cells 21 and 22 of angle sensor 1. Indeed, Hall-effect cell 312 also achieves the function of a second Hall-effect cell. In other words, Hall-effect cell 312 is common to first sensing group and to second sensing group. First sensing group consists of Hall-effect cells 311 , 312 and 313, while second sensing group consists of Hall-effect cells 312 and 322.
Second Hall-effect cells 312 and 322 are separated by a 45*(modulo 180*) mechanical angle, instead of the 90°(nnodulo 180") m echanical angle separating second Hall-effect cells 21 and 22. Second Hall-effect cells 312 and 322 are mutually positioned so as to output respective second signals having a 90° electrical phase shift, which corresponds to 90° me chanical angle when the magnet 5 or encoder is bipolar. Second Hall-effect cells 312 and 322 transmit sine- and cosine-wave signals. More generally, the magnet can comprise any given number or pairs of magnetic poles N and S, with second sensing elements separated by a shift angle of 90°(nnodulo 360") divided by this given number of pairs of magnetic poles. For instance, an angle sensor according to the invention can comprise three pairs of magnetic poles with second sensing elements separated by mechanical shift angles of 30°(nnodulo 120°). Thus, second sensing el ements transmit respective second signals having a predetermined electrical phase shift of 90°.
The present invention permits to significantly decrease the power consumption when the EPAS system is turned off, while nonetheless keeping track of the absolute rotation angle by taking account of the direction and the number of revolutions made during standby mode, until the first Hall-effect cells 311 , 312 and 313 are activated again when the EPAS system resumes in operation mode.
An angle sensor according to the present invention permits to save about 7 mA per first Hall-effect cell turned off during standby mode, which represents a significant energy saving, thus complying with specification requirements.
Positioning the second Hall-effect cell at 90°(modu lo 180°) electrical shift angle permits to automatically produce sine and cosine signals, thus making it possible to keep measuring an absolute position angle over one revolution, though its accuracy can be lower than the one obtained with the first sensing group used in the operating mode of the EPAS system. The different electronic circuits used with the first sensing group can advantageously by used to process also the first signals and the second signals generated by the second sensing group. According to another non-shown embodiment, the predetermined phase shift between the respective second sensing elements can be different from 90°.
Be the electrical phase shift equal or not to 90° an angle sensor according to the invention must comprise at least two second sensing elements. In the simplest configuration, there are only two second sensing elements spaced apart angularly. One second sensing element is enough to determine whether one full revolution has been made, for instance by detecting the zero, the maximum or the minimum value of a sine-wave signal. Another second sensing element is needed in order to determine the direction of revolution, namely clockwise or counter-clockwise, as the steering rack can operate the wheels to the left or to the right. For instance, the direction of revolution can be determined by detecting which one of the two sine- wave signals is in advance with respect to the other.
According to a non-shown embodiment, the first sensing group can comprise more than three sensing elements, say five, depending on the accuracy and on the response time required for the absolute rotation angle sensor.
Besides, these first sensing elements can be evenly or unevenly distributed around the rotation of an axis.
Besides, all the sensing elements of the second sensing group can advantageously be used in the first sensing group.
Moreover, instead of Hall-effect cells, first sensing elements and/or second sensing elements can be of another nature. Furthermore, first sensing elements can differ from second sensing elements.
According to a further non-shown embodiment, two sensing elements are common to the first and second sensing groups. For instance, the first sensing group can comprise three or more first sensing elements, say Hall-effects cells, two of which form the second sensing group.
In such a case, the first supply means and the second supply means can be made of two distinct wires, like 15 and 25. Alternatively, the first and second supply means can comprise one single wire plus a switching element to control the current supply to the one sensing element which is solely a first sensing element, i.e. which solely belongs to the first sensing group.
In the latter case, in operation mode, the three sensing elements are supplied with current, with this switching element in a closed position. In standby mode, the switching element is open and the sole first sensing element is turned off.
Alike previous embodiments, a voltage comparator determines whether the EPAS system is in operation mode or in standby mode. This voltage comparator consequently actuates, namely opens or closes, this switching element.

Claims

1. Absolute rotation angle sensing device (1 ; 301 ), for an electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis (Xi ; X301) and through several revolutions, said absolute rotation angle sensing device comprising: a rotating part (2 ; 302) configured to be fast in rotation with said rotor; at least one pair of magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) disposed oppositely around said rotation axis (Xi ; X301), said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) being fast in rotation with said rotating part (2 ; 302); a first sensing group comprising at least three first sensing elements (11 , 12, 13 ; 311 , 312, 313), said first sensing elements (11 , 12, 13 ; 311 , 312, 313) being distributed around said rotation axis (Xi ; X3oi), said first sensing elements (11 , 12, 13 ; 311 , 312, 313) being arranged so as to sense said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) when said rotating part (2 ; 302) rotates and to output first signals representative of an angular position of said rotating part (2 ; 302) within one or all of said revolutions; first supply means (15) configured to provide electrical energy to said first sensing elements (11 , 12, 13 ; 311 , 312, 313) when said EPAS system is in an operation mode; characterized in that said absolute rotation angle sensing device (1 ; 301 ) further comprises: a second sensing group comprising two second sensing elements (21 , 22 ; 312, 322), said second sensing elements (21 , 22 ; 312, 322) being arranged so as to sense said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) when said rotating part (2 ; 302) rotates, said second sensing elements (21 , 22 ; 312, 322) being mutually positioned so as to output respective second signals having a predetermined phase shift, said second signals being representative of the revolution in which is positioned said rotating part (2; 302); second supply means (25) configured to provide electrical energy to said second sensing elements (21 , 22 ; 312, 322) when said EPAS system is in a standby mode.
2. Absolute rotation angle sensing device (1 ; 301 ) according to claim 1 , characterized in that said first sensing elements (11 , 12, 13 ; 311 , 312, 313) and said second sensing elements (21 , 22 ; 312, 322) are Hall-effect cells.
3. Absolute rotation angle sensing device (301 ) according to any preceding claim, characterized in that at least one (312) of said sensing elements (311 , 312, 313, 322) is common to said first sensing group and to said second sensing group.
4. Absolute rotation angle sensing device according to claim 3, characterized in that all the sensing elements of the second sensing group are comprised in the first sensing group.
5. Absolute rotation angle sensing device (1 ; 301 ) according to any preceding claim, characterized in that said predetermined phase shift is of 90°.
6. Absolute rotation angle sensing device (1 ; 301 ) according to claim 5, characterized in that it comprises a certain number of pairs of magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2), the respective positions of said second sensing elements (21 , 22 ; 312, 322) being separated by a shift angle of 90°(modulo 360°) divided by said number of pair s of magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2).
7. Absolute rotation angle sensing device (1 ; 301 ) according to any preceding claim, characterized in that said first supply means (15) are connected to an accumulator (31 ), which is loaded by an alternator of a vehicle, and in that said second supply means (25) are connected either to a battery (32) or to a capacitor, which are independent from said alternator.
8. Electric power assisted steering (EPAS) system comprising a rotor mobile around a rotation axis (Xi ; X301) and through several revolutions, characterized in that it comprises an absolute rotation angle sensing device (1 ; 301 ) according to any preceding claim and an electronic control unit (40) configured to control said absolute rotation angle sensing device (1 ; 301 ).
9. Method for sensing an absolute rotation angle of an electric energy assisted steering (EPAS) system, said EPAS system comprising: a rotor mobile around a rotation axis (Xi ; X301) and through several revolutions ; a rotating part (2 ; 302) configured to be fast in rotation with said rotor ; at least one pair of magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) disposed oppositely around said rotation axis (Xi ; X301), said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) being fast in rotation with said rotating part (2 ; 302) ; wherein, when said EPAS system is in an operation mode, said method comprises the steps of: - first supply means (15) provide electrical energy to a first sensing group comprising at least three first sensing elements (11 , 12, 13 ; 311 , 312, 313) ; when said rotating part (2 ; 302) rotates, said first sensing elements (11 , 12,
13 ; 311 , 312, 313) sense said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 ,
304.2) and output first signals representative of an angular position of said rotating part (2 ; 302) within one or all of said revolutions ; an electronic control unit (40) determines, based upon said first signals, the rotation angle (A2 ; A302) of said rotating part (2; 302); characterized in that, when said EPAS system is in a standby mode, said method comprises the steps of: - said first supply means (15) stop providing electrical energy to said first sensing group ; second supply means (25) provide electrical energy to two second sensing elements (21 , 22 ; 312, 322) belonging to a second sensing group ; when said rotating part (2 ; 302) rotates, said second sensing elements (21 , 22 ; 312, 322) sense said magnetic poles (3, 4 ; 303.1 , 303.2, 304.1 , 304.2) and output respective second signals having a predetermined phase shift ; said electronic control unit (40) identifies, based upon said second signals, in which one of said revolutions is positioned said rotating part (2; 302).
10. Method according to claim 9, characterized in that it further comprises the steps of: said first supply means (15) provide electrical energy at a first voltage ; - said second supply means (25) provide electrical energy at a second voltage, which is lower than said first voltage ; a voltage comparator (33) determines whether said EPAS system is in said operation mode or in said standby mode, based upon a comparison between the voltage supplied by said first supply means (15) and a threshold voltage.
11. Method according to claim 10, characterized in that said first voltage is 5 V, in that said second voltage is 3 V and in that said threshold voltage is about 4 V.
12. Method according to any of claims 9 to 11 , characterized in that, when said EPAS system is in said standby mode, a counter means (7) outputs the direction of revolution and the number of revolutions covered by said rotating part (2; 302) and stores them in a memory (8).
13. Method according to claim 12, characterized in that, when said
EPAS system resumes in said operation mode, said electronic control unit (40) retrieves from said memory (8) said direction of revolution and said number of revolutions.
14. Method according to any preceding claim, characterized in that said first signals and said second signals are sine-wave signals.
PCT/IB2009/051975 2009-01-13 2009-01-13 Absolute rotation angle sensing device, electric power assisted steering system comprising such a rotation angle sensing device and method for sensing an absolute angle WO2010082086A1 (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013063205A1 (en) * 2011-10-26 2013-05-02 The Timken Company Rotational encoder with additional independent hall effekt sensor
WO2014060040A1 (en) 2012-10-19 2014-04-24 Aktiebolaget Skf A system for shifting an analogical output signal of a sensor device, a sensor-bearing unit and a shifting method
WO2014106545A1 (en) 2013-01-07 2014-07-10 Aktiebolaget Skf System for shifting an analogical output signal of a sensor device, sensor-bearing unit, shifter module and shifting method
EP3361221A1 (en) * 2017-02-13 2018-08-15 Marantec Antriebs- und Steuerungstechnik GmbH & Co. KG. Sensor for determining the position of a drive system
US10466311B2 (en) 2014-09-04 2019-11-05 The Timken Company Hall effect sensor circuit with offset compensation
FR3089251A1 (en) * 2018-11-29 2020-06-05 Continental Automotive France Device and method for detecting a change in position of a target of an internal combustion engine.
WO2021206109A1 (en) * 2020-04-08 2021-10-14 日本精工株式会社 Rotation angle detection device and electric power steering device
DE102020208675A1 (en) 2020-07-10 2022-01-13 Aktiebolaget Skf Method of positioning a magnetic device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080036454A1 (en) * 2003-10-22 2008-02-14 Aktiebolaget Skf Multi-Revolution Absolute High-Resolution Rotation Measurement System And Bearing Equipped With Such A System
DE102006048771A1 (en) * 2006-10-12 2008-04-17 Sensitec Gmbh Encoders on a magnetic basis
US20080157705A1 (en) * 2006-12-28 2008-07-03 Harmonic Drive Systems Inc. Magnetic Absolute Encoder
US20080272834A1 (en) * 2004-05-21 2008-11-06 Kabushiki Kaisha Yaskawa Denki Absolute Multi-Revolution Encoder
WO2009001399A1 (en) * 2007-06-22 2008-12-31 Harmonic Drive Systems Inc. Apparatus for detecting position of rotation of motor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080036454A1 (en) * 2003-10-22 2008-02-14 Aktiebolaget Skf Multi-Revolution Absolute High-Resolution Rotation Measurement System And Bearing Equipped With Such A System
US20080272834A1 (en) * 2004-05-21 2008-11-06 Kabushiki Kaisha Yaskawa Denki Absolute Multi-Revolution Encoder
DE102006048771A1 (en) * 2006-10-12 2008-04-17 Sensitec Gmbh Encoders on a magnetic basis
US20080157705A1 (en) * 2006-12-28 2008-07-03 Harmonic Drive Systems Inc. Magnetic Absolute Encoder
WO2009001399A1 (en) * 2007-06-22 2008-12-31 Harmonic Drive Systems Inc. Apparatus for detecting position of rotation of motor

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WO2021206109A1 (en) * 2020-04-08 2021-10-14 日本精工株式会社 Rotation angle detection device and electric power steering device
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US11511803B2 (en) 2020-04-08 2022-11-29 Nsk Ltd. Rotation angle detection device, electric power steering device and method of controlling electric power steering device
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