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
  • G01D5/20—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 by varying inductance, e.g. by a movable armature
  • G01D5/2006—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 by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
  • G01D5/2013—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 by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils by a movable ferromagnetic element, e.g. a core
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
  • G01B7/04—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving

Definitions

• the invention relates generally to determination of the position of a movable operating mechanism and more specifically to the determination of the position in a coil of a movable core connected to such an operating mechanism.
• the grade of accuracy is affected by how often the measurements take place and by variations of the resistance of the coil due to coil temperature changes.
• a method for compensating the temperature of an inductive sensor is known from US- 5331066-A.
• the temperature compensation is performed every time the voltage across a coil is measured and requires that a steady state voltage value across the coil is reached before the temperature compensation is obtained.
• the basis for this method seems to be good, it may in practice not suit applications where the position of a movable operating mechanism has to be determined with shorter intervals than would normally be possible if the steady state voltage would have to be reached every time before the initiation of a new control voltage pulse.
• An example of such an application is the measurement of a current position of a vehicle clutch.
• the object of the invention is to provide an alternative temperature compensating method for determining the position of a vehicle element connected to a movable core in a coil, said method also being adapted for vehicle applications where the position of the vehicle element has to be determined relatively frequently.
• the invention relates to a method in a vehicle for determining position of a movable operating mechanism connected to a core in a coil.
• the coil is connected with its one end to one terminal of a voltage source and with its other end in series with a pulse controlled switch and a resistor to the other terminal of the voltage source.
• the method comprises the steps of:
• An embodiment of the invention comprises the step of only generating the shorter pulses if a predetermined operation is occurring or is initiated in the vehicle.
• the invention also relates to a computer program for determining position of a movable operating mechanism in a vehicle, the operating mechanism being connected to a core in a coil, which is connected with its one end to one terminal of a voltage source and with its other end in series with a pulse controlled switch and a resistor to the other terminal of the voltage source.
• the computer program comprises computer readable program code elements which when run on a computer connected to the switch and the resistor causes the computer
• the computer program may comprise computer readable program code elements which when run on the computer causes the computer to only generate the shorter pulses if a predetermined operation is occurring or is initiated in the vehicle. Furthermore the invention relates to a computer program product comprising the computer program and a computer usable medium on which the computer program is stored.
• the invention relates to a vehicle comprising a movable operating mechanism connected to a movable core in a coil connected with its one end to one terminal of a voltage source and with its other end in series with a pulse controlled switch and a resistor to the other terminal of the voltage source, and a computer comprising a storage unit and a computer program stored in the storage unit, the computer program comprising computer readable program code elements which when run on the computer connected to the switch and the resistor causes the computer
• the operating mechanism is in one embodiment a clutch operating mechanism, such as a clutch actuator piston affecting a lever in an automatic clutch manoeuvring system for a friction clutch.
• the operating mechanism may also be a gearbox operating mechanism.
• the operation may be a gear shifting operation.
• the operation may also be a clutch disengagement or clutch engagement.
• Other embodiments may include more predetermined operations or combinations of the operations mentioned above for inhibiting the generation of the wider pulses.
• the intervals of wider pulses may in some embodiments be between 1 and 10 s, and the wider pulses may have a width of at least 5 ms.
• Fig. 1 is a schematic illustration of an embodiment of the invention
• Fig. 2 is a schematic flow chart illustrating steps of an embodiment of a method according to the invention
• Fig. 3 A is a schematic illustration of an embodiment of a pulse train generated in accordance with the invention
• Fig. 3B is a schematic illustration of voltages resulting from the pulses of the pulse train in Fig. 3 A.
• movable operating mechanism e.g. a clutch operating mechanism or a gear box operating mechanism in a vehicle A
• vehicle A is not illustrated in any further detail.
• the movable operating mechanism 1 is connected to a movable core 2 in a coil 3 forming a position sensor for the movable operating mechanism 1.
• the coil 3 in Fig. 1 is connected with its one end to a positive terminal +U of a voltage source and with its other end in series with a switch 4 and a resistor 5 to the ground terminal G of the voltage source.
• the switch 4 can be e.g. a field effect transistor and is pulse controlled by means of a train of pulses generated by a computer 6 in the form of an electronic control unit (ECU) that comprises a processor 7.
• ECU electronice control unit
• the processor 7 is connected to a computer program product 8 in the form of a storage unit that stores a computer program 9 and another storage unit that stores a memory 10 for tables and limit values.
• the storage units can be e.g. ROMs 5 PROMs 5 EPROMs 5 EEPROMs and flash memories.
• the processor 7 is connected to one output port 11 and one input port 12 of the computer 6.
• the train of pulses generated by the computer 6 under control of computer program 9 to repeatedly close the switch 4 is supplied via output port 11 to the switch 4.
• Input port 12 of the computer 6 is connected to the interconnection point between the switch 4 and the resistor 5 to sense the voltage across the resistor 5 when current flows through the coil 3 and the resistor 5 when the switch 4 is closed.
• Information about the position of the core 2 in the coil 3, i.e. information about the current position of the operating mechanism 1 as determined by the processor 7 under control of computer program 9 is supplied to e.g. a control loop (not shown).
• Step Sl in Fig. 2 a pulse train PT as illustrated in Fig. 3 A is generated by the computer 6 to repeatedly close the switch 4.
• the pulse train PT has in this embodiment three shorter pulses during which coarse positions of the core 2 are determined and two wider pulses during which also the coil resistance compensation coefficient is determined.
• Fig. 3B the corresponding voltages obtained across the resistor 5 during the pulses of the pulse train PT 5 i.e. when the switch 4 is closed, are illustrated.
• the shorter pulses of the pulse train PT for measuring the time for the voltage across the resistor 5 to reach the predetermined limit value UP is generated at a pulse rate of e.g. between 500 Hz and 1 kHz.
• the wider pulses of the pulse train PT for measuring not only the time for the voltage across the resistor 5 to reach the predetermined limit value UP but also the voltage across the resistor 5 at maximum steady-state value of the current through the coil 3 and the resistor 5 are e.g. of a width of at least 5 ms, and the time interval between the wider pulses is e.g. between 1 and 10 s.
• the time for the voltage U5 across the resistor 5 to reach a predetermined limit value UP set in memory 10 is measured by means of the computer 6 under control of the computer program 9 in Step S2a every time the switch 4 is closed.
• Fig. 3B the times for the voltage U5 across the resistor 5 to reach the predetermined limit value UP during the pulses of the pulse train PT in Fig. 3 A are denoted ⁇ 41, ⁇ 42, ⁇ 43, ⁇ 44 and ⁇ 45. Should the measured times differ, the core 2 is moving in the coil 3.
• the computer 6 determines a first, coarse value of the position of the core 2 in the coil 3 in Step S3a, e.g. by checking which time value ⁇ 41, ⁇ 42, ⁇ 43, ⁇ 44 and ⁇ 45 correspond to which coarse core position value in a pre-established table stored in memory 10. Such a table is established by using the nominal resistance value of the coil 3 even though coil resistance actually is dependent on coil temperature.
• the coarse value of the core position value determined in Step S3 a from the measured time does normally not exactly represent the actual core position value due to the fact that the resistance of the coil 3 will vary with the temperature of the coil 3.
• the voltage U5 across the resistor 5 is measured in Step S2b when the current through the coil 3 and the resistor 5 has reached its maximum steady-state value.
• the wider pulses of the pulse train PT generated by the computer 6 have to be of such a width that the current through the coil 3 and the resistor 5 is allowed to reach its maximum steady-state value during the pulses, i.e. when the switch 4 is closed. It is to be understood that the maximum steady-state value of the current through the coil 3 and the resistor 5 will vary with the temperature of the coil 3. Thus, also the resulting voltage across the resistor 5 at the maximum steady-state value of the current through the coil 3 and the resistor 5 will vary with the temperature of the coil 3.
• the voltages across the resistor 5 at maximum steady-state value of the current through the coil 3 and the resistor 5 during the two wider pulses of the pulse train PT are denoted UM41 and UM42.
• the voltage value UM41 is illustrated as being higher than the voltage value UM42 implying that the temperature of the coil 3 has changed during the time period in question.
• the predetermined limit voltage value UP can be set to e.g. 4 V.
• the resulting voltage value UM3 at maximum steady-state value of the current through the coil 3 and the resistor 5 will then be around 7 V.
• Step S3b determines the actual resistance value of coil 3, e.g. by checking which measured voltage value corresponds to which temperature dependent resistance value in a table stored in memory 10.
• Step S3b From the actual resistance value of coil 3 determined in Step S3b, the computer 6 under control of computer program 9 determines a coil resistance compensation coefficient in Step S4b that is used in Step S5 to compensate the coarse position determined in Step S3 a in order to arrive at a fine value P of the position of the core 2 in the coil 3.
• the grade of accuracy of the coarse position and, thereby, also of the compensated coarse position will be higher.
• the generation of the wider pulses in accordance with Fig. 4A is inhibited by the computer 6 when a clutch operation is initiated, i.e. when the core 2 is moving in the coil 3.
• the generation of the wider pulses is inhibited by the computer 6 when it receives a message that a gear shift is initiated by e.g. an automatic gear shifting system. This is done in order to maintain the high accuracy attained by determining the coarse position at a higher pulse rate.
• the shorter pulses are generated by the computer 6 during the clutch operation and a gear shifting operation respectively.
• the latest temperature dependent coil resistance compensation coefficient determined by the computer 6 before the clutch operation was initiated by the computer 6 is thereafter used to compensate every determined coarse position until the clutch operation is finished by the computer 6. This can be done due to the fact that the temperature of the coil 3 does not change as quickly as the position of the core 2 in the coil 3 as indicated above.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Hydraulic Clutches, Magnetic Clutches, Fluid Clutches, And Fluid Joints (AREA)
• Reciprocating, Oscillating Or Vibrating Motors (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (4)

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• 2005
  • 2005-01-03 SE SE0500005A patent/SE0500005D0/sv unknown
  • 2005-12-22 WO PCT/SE2005/002032 patent/WO2006073349A1/en active Application Filing
  • 2005-12-22 DE DE112005003242.6T patent/DE112005003242B8/de not_active Expired - Fee Related
  • 2005-12-22 GB GB0711099A patent/GB2435772B/en not_active Expired - Fee Related

Patent Citations (4)

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