Guidance method and system for an automotive vehicle
First Claim
1. A method of guiding an automotive vehicle in accordance with at least three navigational electromagnetic wave signals transmitted from at least three fixed stations, which comprises the following steps:
- (a) receiving the at least three navigational electromagnetic wave signals synchronously transmitted from the at least three fixed stations;
(b) detecting the differences in receive time between two pairs of said at least three navigational electromagnetic wave signals;
(c) determining at least two hyperbolas in accordance with the detected differences in receive time between the pairs of navigational electromagnetic wave signals;
(d) calculating a point of intersection of the at least two determined hyperbolas to obtain a vehicle position on the basis of navigational electromagnetic wave signals;
(e) storing sequentially the vehicle position calculated on the basis of navigational electromagnetic wave signals;
(f) detecting vehicle orientation in which the vehicle is travelling;
(g) detecting vehicle speed at which the vehicle is travelling;
(h) calculating a distance over which the vehicle has travelled in accordance with the detected vehicle orientation and the detected vehicle speed;
(i) adding the distance calculated on the basis of detected vehicle orientation and detected vehicle speed to the current stored vehicle position calculated on the basis of navigational electromagnetic wave signals in order to obtain a vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed;
(j) detecting the field strengths of the at least three navigational electromagnetic wave signals;
(k) comparing the detected field strengths with a predetermined lower limit; and
(l) selecting and displaying the vehicle position calculated on the basis of navigational electromagnetic wave signals when the detected field strengths are all beyond the predetermined lower limit and the vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed when any one of the detected field strengths is below the predetermined lower limit.
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Accused Products
Abstract
A guidance method and system for an automotive vehicle which switches from an electronic navigational signal method to a dead reckoning method when any of the field strengths of three navigational electromagnetic wave signals drops below a predetermined lower limit or vice versa when the field strengths of the three navigational electromagnetic wave signals all exceed the lower limit. Therefore, even if the navigational wave signals are obstructed by buildings or mountains, it is possible to continuously determine and display the vehicle position. The guidance system according to the present invention comprises a receive-state detection unit for detecting three field strengths and for comparing the detected field strengths with a predetermined lower limit, and a selector for selectively outputting vehicle position signals on the basis of navigational signals or dead reckoning, in addition to the conventional electronic navigation system and dead reckoning system.
69 Citations
10 Claims
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1. A method of guiding an automotive vehicle in accordance with at least three navigational electromagnetic wave signals transmitted from at least three fixed stations, which comprises the following steps:
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(a) receiving the at least three navigational electromagnetic wave signals synchronously transmitted from the at least three fixed stations; (b) detecting the differences in receive time between two pairs of said at least three navigational electromagnetic wave signals; (c) determining at least two hyperbolas in accordance with the detected differences in receive time between the pairs of navigational electromagnetic wave signals; (d) calculating a point of intersection of the at least two determined hyperbolas to obtain a vehicle position on the basis of navigational electromagnetic wave signals; (e) storing sequentially the vehicle position calculated on the basis of navigational electromagnetic wave signals; (f) detecting vehicle orientation in which the vehicle is travelling; (g) detecting vehicle speed at which the vehicle is travelling; (h) calculating a distance over which the vehicle has travelled in accordance with the detected vehicle orientation and the detected vehicle speed; (i) adding the distance calculated on the basis of detected vehicle orientation and detected vehicle speed to the current stored vehicle position calculated on the basis of navigational electromagnetic wave signals in order to obtain a vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed; (j) detecting the field strengths of the at least three navigational electromagnetic wave signals; (k) comparing the detected field strengths with a predetermined lower limit; and (l) selecting and displaying the vehicle position calculated on the basis of navigational electromagnetic wave signals when the detected field strengths are all beyond the predetermined lower limit and the vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed when any one of the detected field strengths is below the predetermined lower limit.
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2. A method of guiding an automotive vehicle in accordance with at least three navigational electromagnetic wave signals transmitted from at least three fixed stations, which comprises the following steps:
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(a) receiving the at least three navigational electromagnetic wave signals synchronously transmitted from the at least three fixed stations; (b) detecting the differences in receive time between two pairs of said at least three navigational electromagnetic wave signals; (c) determining at least two hyperbolas in accordance with the detected difference in receive time between the pairs of navigational electromagnetic wave signals; (d) calculating a point of intersection of the at least two determined hyperbolas to obtain a vehicle position on the basis of navigational electromagnetic wave signals; (e) storing sequentially the vehicle position calculated on the basis of navigational electromagnetic wave signals; (f) detecting vehicle orientation in which the vehicle is travelling; (g) detecting vehicle speed at which the vehicle is travelling; (h) calculating a distance over which the vehicle has travelled in accordance with the detected vehicle orientation and the detected vehicle speed; (i) adding the distance calculated on the basis of detected vehicle orientation and detected vehicle speed to the current stored vehicle position calculated on the basis of navigational eleectromagnetic wave signals in order to obtain a vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed; (j) detecting the field strengths of the at least three navigational electromagnetic wave signals; (k) comparing the detected field strengths with a predetermined lower limit; (l) generating a signal indicative of an erroneous vehicle position on the basis of navigational electromagnetic wave signals when any one of the detected field strengths is below the predetermined lower limit; (m) calculating the vehicle speed according to the generated signal indicative of the erroneous vehicle position calculated on the basis of navigational electromagnetic wave signals; (n) comparing the calculated vehicle speed with the detected vehicle speed and generating an output signal indicative thereof; and (o) selecting and displaying the vehicle position calculated on the basis of navigational electromagnetic wave signals when the difference between the calculated vehicle speed and the detected vehicle speed is less than a predetermined amount and the vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed when the calculated vehicle speed is greater than the detected vehicle speed by said predetermined amount. - View Dependent Claims (3)
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4. A system of guiding an automotive vehicle in accordance with at least three navigational electromagnetic wave signals transmitted from at least three fixed stations, which comprises:
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(a) a receiver for receiving the at least three navigational electromagnetic wave signals synchronously transmitted from the at least three fixed stations and for generating signals corresponding thereto; (b) a position detection unit connected to said receiver for detecting differences in receive time between at least two pairs of said at least three navigational electromagnetic wave signals, for determining at least two hyperbolas in accordance with the detected difference in receive time, for calculating a point of intersection of the at least two determined hyperbolas, and for outputting a signal indicative of a vehicle position calculated on the basis of said navigational electromagnetic wave signals; (c) a vehicle orientation sensor for detecting vehicle orientation in which the vehicle is travelling and for outputting signals corresponding thereto; (d) a vehicle speed sensor for detecting vehicle speed at which the vehicle is travelling and for outputting signals corresponding thereto; (e) a position calculating unit connected to said vehicle orientation sensor, said speed sensor, and said position detection unit for calculating a distance over which the vehicle has travelled in accordance with the detected vehicle orientation and the detected vehicle speed, for sequentially storing the vehicle position calculated on the basis of navigational wave signals, for adding the distance calculated on the basis of detected vehicle orientation and detected vehicle speed to the current stored vehicle position calculated on the basis of navigational electromagnetic wave signals, and for outputting a signal indicative of a vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed; (f) a receive-state detection unit connected to said receiver for detecting field strengths of the at least three navigational electromagnetic wave signals, for comparing the detected field strengths with a predetermined lower limit, and for outputting no signal when the detected field strengths are all beyond the lower limit and for outputting an output signal when any one of the detected field strengths is below the lower limit; (g) a selector connected to said position calculating unit, said position detection unit, and said receive-state detection unit for selecting the signal generated from said position detection unit when said receive-state detection unit outputs no signal and the signal generated from said position calculating unit when said receive-state detection unit outputs an output signal; and (h) a display unit connected to said selector for receiving said selected signal for displaying the signals generated from said position detection unit and from said position calculating unit; whereby the vehicle positions are displayed on the basis of navigational electromagnetic wave signals when the field strengths are all beyond the predetermined lower limit and on the basis of detected vehicle orientation and detected vehicle speed when any one of the field strengths is below the predetermined lower limit.
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5. A system of guiding an automotive vehicle in accordance with at least three navigational electromagnetic wave signals transmitted from at least three fixed stations, which comprises:
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(a) a receiver for receiving the at least three navigational electromagnetic wave signals synchronously transmitted from the at least three fixed stations, for detecting field strengths of said received signals, for comparing the detected field strengths with a predetermined lower limit, and for generating signals corresponding to the results of said comparison; (b) a position detection unit connected to said receiver for detecting differences in receive time between at least two pairs of said at least three navigational electromagnetic wave signals, for determining at least two hyperbolas in accordance with the detected differences in receive time, for calculating a point of intersection of the at least two determined hyperbolas, for outputting signals indicative of a vehicle position calculated on the basis of navigational wave signals when the field strengths of the navigational electromagnetic wave signals are all beyond said predetermined lower limit and signals indicative of an erroneous vehicle position when any one of the detected field strengths is below the predetermined lower limit; (c) a vehicle orientation sensor for detecting vehicle orientation in which the vehicle is travelling and for outputting signals corresponding thereto; (d) a vehicle speed sensor for detecting vehicle speed, V, at which the vehicle is travelling and for outputting signals corresponding thereto; (e) a memory connected to said position detection unit for storing the signals from said position detection unit and outputting same after a predetermined delay; (f) a position calculating unit connected to said vehicle orientation sensor, said vehicle speed sensor, and said memory, for calculating a distance over which the vehicle has travelled in accordance with the detected vehicle orientation and the detected vehicle speed, for sequentially receiving the outputted signals from the memory, for adding the distance calculated on the basis of detected vehicle orientation and detected vehicle speed to the stored vehicle position represented by said outputted signals from said memory, and for outputting a signal indicative of a vehicle position calculated on the basis of detected vehicle orientation and detected vehicle speed; (g) a speed calculating unit connected to said position detection unit for calculating vehicle speed Vs according to the output signals from said position detection unit indicative of the vehicle position calculated on the basis of navigational electromagnetic wave signals; (h) a comparator connected to said position calculating unit and said speed calculating unit for comparing the calculated vehicle speed with the detected vehicle speed and for outputting no signal when the difference between the calculated vehicle speed and the detected vehicle speed is less than a predetermined amount and an output signal when the calculated vehicle speed is greater than the detected vehicle speed by said predetermined amount; (i) a selector connected to said position calculating unit, said position detection unit, and said comparator for selecting the signal generated from said position detection unit when said comparator outputs no signal and the signal generated from said position calculating unit when said comparator outputs an output signal; (j) a display unit connected to said selector for receiving said selected signal and for displaying the selected signals; whereby the vehicle positions are displayed on the basis of navigational electromagnetic wave signals when the field strengths are all beyond the predetermined lower limit and on the basis of detected vehicle orientation and detected vehicle speed when any one of the field strengths is below the predetermined lower limit. - View Dependent Claims (6, 7, 8, 9, 10)
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Specification