Method of determining a directional change during vehicle navigation, apparatus for carrying out such a method, and vehicle comprising such an apparatus

• US 5,908,466 A
• Filed: 06/28/1995
• Issued: 06/01/1999
• Est. Priority Date: 07/04/1994
• Status: Expired due to Fees

• Current Assignee: Mannesmann VDO AG (Continental AG)
• Original Assignee: Mannesmann VDO AG (Continental AG)
• Inventors: Van Kessel, Antoon M. M., Veugen, Leonardus M. M., Hermans, Hans G. M.
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/494,532
• Time in Patent Office: 1,434 Days
• Field of Search: 364/457, 364/450, 364/453, 364/449, 364/551.01, 364/559, 364/561, 364/565, 364/571.01, 340/988, 303/168, 303/174, 701/224, 701/217, 701/220, 701/207, 702/92, 702/93
• US Class Current: 701/224
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 22/025 Differential odometers

Abstract

A method of determining a directional change of a vehicle carries out dead-reckoning for which it utilizes sensors provided on two wheels. In order to compensate for differences between the wheels, the method utilizes given parameters in processing the data from the wheel sensors. The invention provides an extension of the method by estimating the parameters during normal operation of the vehicle, so that they are adapted to changing circumstances encountered by the vehicle. Estimation is performed by comparing data from the wheel sensors with independently determined directional data for a given period of time.

Claims

1. A method of determining a directional change during navigation of a vehicle comprising a left wheel sensor and a right wheel sensor, each of said left and right wheel sensors being operative to supply pulses which are a measure of excursion of an associated wheel, said method comprising the steps:

recording a number of pulses pL from the left wheel sensor and a number of pulses pR from the right wheel sensor for a predetermined sampling interval;

supplying a left correction factor ratioL and a right correction factor ratioR;

determining a first directional change of said vehicle based at least in part on said left and right correction factors; and

executing the above steps during operation of the vehicle for a given number of sampling intervals,

determining a second directional change independently from said left and right wheel sensors during each sampling interval; and

calculating a corrected left correction factor and a corrected right correction factor using the values for pL and pR and the independently determined second directional change as a function of statistical values derived from said first direction changes and said second directional changes said given number of sampling intervals, said corrected left correction factor and said corrected right correction factor being used in subsequent determinations of a directional change during navigation of said vehicle.

2. A method as claimed in claim 1, wherein said step of determining a second directional change independently from said left and right wheel sensors comprises using a compass sensor.

3. A method as claimed in claim 2, wherein the step of calculating a corrected left correction factor and a corrected right correction factor is only performed after said given number of sampling intervals and, moreover, only when a cumulative directional change, between a beginning and an end of said given number of sampling intervals, is below a given amount.

4. A method as claimed in claim 1, wherein said step of determining a second directional change independently from said left and right wheel sensors comprises using cartographic data.

5. A method as claimed in claim 4, wherein execution of the steps of the method is subject to the condition that, on the basis of the cartographic data, the vehicle will travel a minimum predetermined distance on a straight road segment, and subject to a number of conditions relating to a direction of travel of the vehicle and operation of the wheel sensors.

6. A method as claimed in claim 4, wherein said step of calculating a corrected left correction factor and a corrected right correction factor is only performed when the vehicle leaves a road segment and, moreover, when the collected values of pL and pR relate to a travelled road segment having at least a given minimum length.

7. A method as claimed in claim 1, wherein said method further comprises low-pass filtering said corrected left correction factor and said right correction factor, said low-pass filtered corrected left and right correction factors being used to subsequently determine the directional change.

8. A method of determining a directional change during navigation of a vehicle comprising a left wheel sensor and a right wheel sensor, each of said left and right wheel sensors being operative to supply pulses which are a measure of excursion of an associated wheel, said method comprising the steps:

recording a number of pulses pL from the left wheel sensor and a number of pulses pR from the right wheel sensor for a predetermined sampling interval;

supplying a left correction factor ratioL and a right correction factor ratioR;

determining a first directional change of said vehicle based at least in part on said left and right correction factors; and

executing the above steps during operation of the vehicle for a given number of sampling intervals,

determining a second directional change independently from said left and right wheel sensors during each sampling interval using a compass sensor;

calculating a corrected left correction factor and a corrected right correction factor using the values for pL and pR and the independently determined second directional change for said given number of sampling intervals, said corrected left correction factor and said corrected right correction factor being used in subsequent determinations of a directional change during navigation of said vehicle; and

wherein execution of the steps of the method is interrupted if at least one condition out of a group of conditions, including speed of the vehicle, direction of travel of the vehicle, operation of the wheel sensors and operation of the compass sensor is not satisfied.

9. An apparatus comprising:

a left input for receiving a signal pL representative of number of left pulses;

right input for receiving a signal pR which is representative of the number of right pulses;

storage means for storing a left correction factor ratioL and a right correction factor ratioR; and

arithmetic means coupled to the left input, the right input and the storage means for calculating (ratioL×

pL-ratioR×

pR),

wherein the apparatus further comprises;

means for receiving information, independently of said left and said right inputs, relating to a series of directional changes; and

means for associating the series of directional changes with a respective series of left pulses and right pulses for calculating a corrected left correction factor and a corrected right correction factor.

10. An apparatus as claimed in claim 9, means for low-pass said corrected left correction factor and said corrected right correction factor, respectively.

11. A vehicle comprising:

a left side and a right side wheel; and

a system for indicating a directional change for said vehicle, said system including;

a left side wheel sensor for generating pulses during movement of said vehicle corresponding to a wheel excursion of said left side wheel;

a right side wheel sensor for generating pulses during movement of said vehicle corresponding to a wheel excursion of said right side wheel;

first storing means for storing a left correction factor ratioL and a right correction factor ratioR;

recording means, coupled to said left and right wheel sensors, for recording, during a sampling interval a number of pulses, pL from said left side wheel sensor and a number of pulses pL from said right wheel sensor;

multiplying means for multiplying the left correction factor ratioL stored in said first storing means by the number of pulses pL recorded in said recording means, and for multiplying the right correction factor ratioR stored in said first storing means by the number of pulses pR recorded in said recorded means;

means for calculating the difference between the two multiplied quantities, said difference being equal to the direction change of said vehicle;

means for determining a second direction change quantity independently of said right and left side wheel sensors;

second storing means for storing numbers of pulses from said left wheel sensor and numbers of pulses from said right wheel sensor for a given number of sampling intervals;

third storing means for storing second direction change quantities for said given number of sampling intervals;

estimating means for estimating a corrected right correction factor ratioR and a corrected left correction factor ratioL based on statistical values derived from said numbers of pulses from said left wheel sensor and said numbers of pulses from said right wheel sensor stored in said second storing means, and on said second direction change quantities stored in said third storing means; and

means for storing said corrected left correction factor and said corrected right correction factor in said first storing means.

12. A method of determining a distance travelled during navigation of a vehicle comprising a left wheel sensor and a right wheel sensor, each of said left and right wheel sensors being operative to supply pulses which are a measure of excursion of an associated wheel, said method comprising the steps:

recording a number of pulses pL from the left wheel sensor and a number of pulses pR from the right wheel sensor, for a given sampling interval; and

calculating a first distance Δ

s travelled from

space="preserve" listing-type="equation">Δ

s=dpp×

(pL+pR)/2,

where dpp is a correction factor;

wherein the method also comprises;

determining a second distance travelled independent of said left and right wheel sensors;

executing the above steps during operation of the vehicle and for a given number of sampling intervals, while storing for each sampling interval values of said first and said second distance travelled; and

calculating a value for dpp by comparison of the values collected for Δ

s and the independently determined distance travelled.

13. A method of determining a directional change for a vehicle, said method comprising the steps:

recording during a sampling interval, a number of pulses pL from a left side wheel sensor, and a number of pulses pL from a right side wheel sensor during movement of said vehicle, said number of pulses corresponding to respective wheel excursions;

calculating, during said sampling interval, a first direction change quantity by multiplying said number of pulses pL by a stored left correction factor thereby forming a first product, multiplying said number of pulses pR by a stored right correction factor thereby forming a second product, and subtracting the second product from the first product;

determining, during said sampling interval, a second direction change quantity independently of said right and left side wheel sensors;

repeating the above steps for a given number of sampling intervals while storing said first and second direction change quantities for each sampling interval;

calculating a corrected right correction factor and a corrected left correction factor using said stored first and second direction change quantities for said given number of sampling intervals; and

storing said corrected left and right correction factors for a subsequent determination of a directional change for the vehicle.

14. The method as claimed in claim 13, wherein the given number of sampling intervals is about 80.

15. A system for indicating a directional change for a vehicle having a left and a right side wheel, said system comprising:

a left side wheel sensor for generating pulses during movement of said vehicle corresponding to a wheel excursion of said left side wheel;

a right side wheel sensor for generating pulses during movement of said vehicle corresponding to a wheel excursion of said right side wheel;

recording means, coupled to said left and right wheel sensors, for recording, during a sampling interval, the number of pulses pL from said left side wheel sensor and the number of pulses pL from said right side wheel sensor;

means for determining a direction change quantity independently of said right and left side wheel sensors;

estimating means for estimating a right correction factor ratioR and a left correction factor ratioL based on said independently determined direction change quantity;

storing means for storing said estimated left correction factor and said estimated right correction factor;

multiplying means for multiplying the estimated left correction factor ratioL by the number of pulses pL recorded in said recording means and multiplying the estimated right correction factor ratioR by the number of pulses pR recorded in said recorded means;

means for calculating the difference between the two multiplied quantities, said difference being equal to the direction change of said vehicle.

16. An apparatus for determining a directional change during navigation of a vehicle, the apparatus comprising:

a left wheel sensor,

a right wheel sensor, each of said left and right wheel sensors being operative to supply pulses which are a measure of excursion of an associated wheel;

a memory recording a number of pulses pL from the left wheel sensor and a number of pulses pR from the right wheel sensor for a predetermined sampling interval;

a means for supplying a left correction factor ratioL and a right correction factor ratioR, wherein a first directional change of said vehicle is determined based at least in part on said left and right correction factors, and executes the above steps during operation of the vehicle for a given number of sampling intervals,

a means for determining a second directional change independently from said left and right wheel sensors during each sampling interval using a compass sensor and calculating a corrected left correction factor and a corrected right correction factor using the values for pL and pR and the independently determined second directional change for said given number of sampling intervals, said corrected left correction factor and said corrected right correction factor being used in subsequent determinations of a directional change during navigation of said vehicle; and

an interruption means for interrupting determinations made if at least one condition out of a group of conditions, including speed of the vehicle, direction of travel of the vehicle, operation of the wheel sensors and operation of the compass sensor is not satisfied.