Differential odometer dynamic calibration method and apparatus therefor

A method for continuously calibrating a differential odometer of a vehicle, said vehicle having a left wheel and a right wheel, wherein the left wheel is located a known track distance opposite the right wheel, said differential odometer including a left wheel sensor coupled to the left wheel, and a right wheel sensor coupled to the right wheel, said left wheel sensor providing a left wheel pulse count as the left wheel rotates, and said right wheel sensor providing a right wheel pulse count as the right wheel rotates, said method comprising the steps of:

• determining vehicle heading and vehicle distance traversed using a product of the left wheel pulse count and a left distance per pulse coefficient and a product of the right wheel pulse count and a right distance per pulse coefficient;
• providing a correction value corresponding to a measured ratio of the right wheel pulse count to the left wheel pulse count, when a predetermined another vehicle distance has been traversed while said measured ratio is bounded within a predetermined range for a predetermined vehicle distance traversed;
• determining a new left distance per pulse coefficient, corresponding to the provided correction value, and a new right distance per pulse coefficient, corresponding to the provided correction value;
• and
• substituting the left distance per pulse coefficient with the new left distance per pulse coefficient, and the right distance per pulse coefficient with the new right distance per pulse coefficient, thereby causing calibration of said differential odometer, consistent with the provided correction value.

A method for calibrating a differential odometer of a vehicle, said vehicle having a left wheel and a right wheel, wherein the right wheel is located a known track distance opposite the left wheel, said differential odometer including a left wheel sensor coupled to the left wheel, and a right wheel sensor coupled to the right wheel, said sensors for providing electrical pulses as the associated wheel rotates, said sensors for determining, vehicle heading and vehicle distance traversed, said method comprising the steps of:

• counting the electrical pulses provided by each wheel and periodically providing a left wheel pulse count corresponding to a totalized number of electrical pulses provided by the left wheel sensor within a period, and periodically providing a right wheel pulse count corresponding to a totalized number of electrical pulses provided by the right wheel sensor within said period;
• determining said vehicle heading by dividing a difference of a product of the left wheel pulse count and a left distance per pulse coefficient and a product of the right wheel pulse count and a right distance per pulse coefficient by the track distance;
• determining said vehicle distance traversed by dividing a sum of the product of the left wheel pulse count and the left distance per pulse coefficient and the right wheel pulse count and the right distance per pulse coefficient by two;
• filtering the right wheel pulse count and the left wheel pulse count and providing a correction ratio corresponding to a measured ratio of the right wheel pulse count to the left wheel pulse count, when a predetermined vehicle distance has been traversed while said measured ratio is bounded within a predetermined range for a predetermined vehicle distance traversed;
• determining a new left distance per pulse coefficient for the left wheel corresponding to the provided correction ratio, and a new right distance per pulse coefficient for the right wheel corresponding to the provided correction ratio;
• and
• substituting the left distance per pulse coefficient with the new left distance per pulse coefficient, and the right distance per pulse coefficient with the new right distance per pulse coefficient, thereby causing calibration of said differential odometer, consistent with the provided correction ratio.

A method for continuously calibrating a differential odometer of a vehicle, said vehicle having a left wheel and a right wheel, wherein the left wheel is located a known track distance opposite the right wheel, said differential odometer including a left wheel sensor coupled to the left wheel, and a right wheel sensor coupled to the right wheel, said method comprising the steps of:

• providing a left wheel pulse count as the left wheel rotates, wherein a left wheel distance traversed is determined by a product of the left wheel pulse count and a left distance per pulse coefficient;
• providing a right wheel pulse count as the right wheel rotates, wherein a right wheel distance traversed is determined by a product of the right wheel pulse count and a right distance per pulse coefficient;
• determining vehicle heading by dividing a difference of the left wheel distance traversed and the right wheel distance traversed by the track distance;
• determining a vehicle distance traversed by dividing the sum of the left wheel distance traversed and the right wheel distance traversed by two;
• filtering the right wheel pulse count and the left wheel pulse count and providing a correction ratio corresponding to a measured ratio of the right wheel pulse count to the left wheel pulse count, when a predetermined continuous vehicle distance has been traversed while said measured ratio is continuously bounded within a predetermined range for a predetermined vehicle distance traversed;
• determining an autonomous vehicle heading using a to be provided compass;
• determining an intensity of the correction ratio responsive to a measured relationship between the determined vehicle heading and the autonomously determined vehicle heading, and providing a revised correction ratio corresponding to the provided ratio and the determined intensity;
• determining a new left distance per pulse coefficient, corresponding to the provided revised correction ratio, and a new right distance per pulse coefficient, corresponding to the provided revised correction ratio;
• and
• substituting the left distance per pulse coefficient with the new left distance per pulse coefficient, and the right distance per pulse coefficient with the new right distance per pulse coefficient, thereby causing calibration of said differential odometer, consistent with the provided revised correction ratio.

An apparatus for continuously calibrating a differential odometer of a vehicle, said vehicle having a left wheel and a right wheel, wherein the left wheel is located a known track distance opposite the right wheel, said differential odometer including a left wheel sensor coupled to the left wheel, and a right wheel sensor coupled to the right wheel, said left wheel sensor providing a left wheel pulse count as the left wheel rotates, wherein a left wheel distance traversed is determined by a product of the left wheel pulse count and a left distance per pulse coefficient, and said right wheel sensor providing a right wheel pulse count as the right wheel rotates, wherein a right wheel distance traversed is determined by a product of the right wheel pulse count and a right distance per pulse coefficient, wherein vehicle heading is determined using the left wheel distance traversed and the right wheel distance traversed, and wherein vehicle distance traversed is determined by the left wheel distance traversed and the right wheel distance traversed, said apparatus comprising:

• means for providing a correction value corresponding to a measured relationship between the left wheel pulse count and the right wheel pulse count;
• means for determining a new left distance per pulse coefficient, corresponding to the provided correction value, and a new right distance per pulse coefficient, corresponding to the provided correction value;
• and
• means for substituting the left distance per pulse coefficient with the new left distance per pulse coefficient, and the right distance per pulse coefficient with the new right distance per pulse coefficient, thereby causing calibration of said differential odometer, consistent with the provided correction value.

An apparatus for continuously calibrating a differential odometer of a vehicle, said vehicle having a left wheel and a right wheel, wherein the left wheel is located a known track distance opposite the right wheel, said differential odometer including a left wheel sensor coupled to the left wheel, and a right wheel sensor coupled to the right wheel, said left wheel sensor providing a left wheel pulse count as the left wheel rotates, and said right wheel sensor providing a right wheel pulse count as the right wheel rotates, said apparatus comprising:

• means for determining vehicle heading using a product of the left wheel pulse count and a left distance per pulse coefficient and a product of the right wheel pulse count and a right distance per pulse coefficient;
• means for determining a vehicle distance traversed using a product of the left wheel pulse count and a left distance per pulse coefficient and a product of the right wheel pulse count and the right distance per pulse coefficient;
• means for providing a correction ratio corresponding to the ratio of the right wheel pulse count to the left wheel pulse count, when a predetermined vehicle distance has been traversed while said measured correction ratio is bounded within a predetermined range for a predetermined vehicle distance traversed;
• means for determining a new left distance per pulse coefficient, corresponding to the provided correction ratio, and a new right distance per pulse coefficient, corresponding to the provided correction ratio;
• and
• means for substituting the left distance per pulse coefficient with the new left distance per pulse coefficient, and the right distance per pulse coefficient with the new right distance per pulse coefficient, thereby causing calibration of said differential odometer, consistent with the provided correction ratio.