Toll object detection in a GNSS system using particle filter
First Claim
1. A method for assessing passages by a vehicle through a tolling object utilizing a global navigation satellite system (GNSS) comprising an on-board unit (OBU) in every vehicle to be surveyed by the system, said OBU receiving signals from satellites to consistently and frequently estimate position coordinates for the vehicles, comprising the steps of:
- (A) obtaining an initial vehicle position including a degree of uncertainty (50),(B) using computer hardware and software to assign (51) a predetermined number of particles for each vehicle, in a meaning understood by the Sequential Monte Carlo mathematical method, comprising a process model, a measurement model and a probability distribution,(C) using computer hardware and software to assign to each particle;
(i) a common initial probability, and(ii) an initial state comprising at least three dimensional spatial position,(D) using computer hardware and software to define epochs in time within each of which the following procedure is conducted;
(i) in a prediction step (52), using said process model to predict with uncertainty the state of each particle in the next epoch, generally represented as xt=φ
t(xt-1)+η
t, wherein xt is a state vector, φ
t(xt-1) is a function used to predict the state xt in one epoch from information of the state in the previous epoch, and η
t is a process noise term, the predictions of all particles within each epoch thereby representing the probability distribution of the state vector xt given all previous measurements zt,(ii) in an updating step (53), using computer hardware and software to update the probability of the particles according to how well each particle'"'"'s state from the prediction step agrees with GNSS pseudo range measurements, according to the equation zt=ht(xt)+ε
t, wherein zt is a measurement vector, ht(xt) is a possibly time-varying function of the state, and ε
t is measurement noise, thereby updating the probability distribution,(iii) using computer hardware and software to assess passage or non-passage (54) by mathematically comparing the spatial definition of the tolling objects in question with the updated particle information from the prediction step (52) while applying a defined confidence level,(iv) recursively repeating steps (D)(i) through (D)(iii) at a predetermined rate.
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Abstract
A particle filter, also known as Sequential Monte Carlo Method, used to estimate vehicle position based on GNSS pseudo range measurements and other sensors. The particle filter creates an ensemble of particles and road user charging (road tolling) can be performed on each particle. The resulting distribution of assessed vehicle passages is analyzed to assess if the event actually took place or not. The use of particle filter overcomes limitations occurring while employing traditional Kalman filter based methods.
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Citations
20 Claims
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1. A method for assessing passages by a vehicle through a tolling object utilizing a global navigation satellite system (GNSS) comprising an on-board unit (OBU) in every vehicle to be surveyed by the system, said OBU receiving signals from satellites to consistently and frequently estimate position coordinates for the vehicles, comprising the steps of:
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(A) obtaining an initial vehicle position including a degree of uncertainty (50), (B) using computer hardware and software to assign (51) a predetermined number of particles for each vehicle, in a meaning understood by the Sequential Monte Carlo mathematical method, comprising a process model, a measurement model and a probability distribution, (C) using computer hardware and software to assign to each particle; (i) a common initial probability, and (ii) an initial state comprising at least three dimensional spatial position, (D) using computer hardware and software to define epochs in time within each of which the following procedure is conducted; (i) in a prediction step (52), using said process model to predict with uncertainty the state of each particle in the next epoch, generally represented as xt=φ
t(xt-1)+η
t, wherein xt is a state vector, φ
t(xt-1) is a function used to predict the state xt in one epoch from information of the state in the previous epoch, and η
t is a process noise term, the predictions of all particles within each epoch thereby representing the probability distribution of the state vector xt given all previous measurements zt,(ii) in an updating step (53), using computer hardware and software to update the probability of the particles according to how well each particle'"'"'s state from the prediction step agrees with GNSS pseudo range measurements, according to the equation zt=ht(xt)+ε
t, wherein zt is a measurement vector, ht(xt) is a possibly time-varying function of the state, and ε
t is measurement noise, thereby updating the probability distribution,(iii) using computer hardware and software to assess passage or non-passage (54) by mathematically comparing the spatial definition of the tolling objects in question with the updated particle information from the prediction step (52) while applying a defined confidence level, (iv) recursively repeating steps (D)(i) through (D)(iii) at a predetermined rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for assessing distance driven by a vehicle utilizing a global navigation satellite system (GNSS) comprising an on-board unit (OBU) in every vehicle to be surveyed by the system, said OBU receiving signals from satellites to consistently and frequently estimate position coordinates for the vehicles, comprising the steps of:
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(A) obtaining an initial vehicle position including a degree of uncertainty (50), (B) using computer hardware and software to assign (51) a predetermined number of particles for each vehicle, in a meaning understood by the Sequential Monte Carlo mathematical method, comprising a process model, a measurement model and a probability distribution, (C) using computer hardware and software to assign to each particle; (i) a common initial probability, and (ii) an initial state comprising at least three dimensional spatial position, (D) using computer hardware and software to define epochs in time within each of which the following procedure is conducted; (i) in a prediction step (52), using said process model to predict with uncertainty the state of each particle in the next epoch, generally represented as xt=φ
t(xt-1)+η
t, where xt is the state vector, φ
t(xt-1) is a function used to predict the state xt in one epoch from information of the state in the previous epoch, while η
t is a process noise term, the predictions of all particles within each epoch thereby representing the probability distribution of the state vector xt given all previous measurements zt,(ii) in an updating step (53), using computer hardware and software to update the probability of the particles according to how well each particle'"'"'s state from the prediction step agrees with GNSS pseudo range measurements, according to the equation zt=ht(xt)+ε
t, where zt is a measurement vector, ht(xt) is a possibly time-varying function of the state, and ε
t is measurement noise, thereby updating the probability distribution,(iii) using computer hardware and software to assess distance driven by creating the probability distribution (63) of the actual distance from individual particle distances as derived by step (D)(ii), by applying a defined confidence level, (iv) recursively repeating steps (D)(i) through (D)(iii) at a predetermined rate.
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19. A system for assessing passages by a vehicle through a tolling object utilizing a global navigation satellite system (GNSS) comprising an on-board unit (OBU) in every vehicle to be surveyed by the system, said OBU receiving signals from satellites to consistently and frequently estimate position coordinates for the vehicles, comprising computer hardware and adapted computer software programmed to perform the following steps:
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(A) obtaining an initial vehicle position including a degree of uncertainty (50), (B) using computer hardware and software to assign (51) a predetermined number of particles for each vehicle, in a meaning understood by the Sequential Monte Carlo mathematical method, comprising a process model, a measurement model and a probability distribution, (C) using computer hardware and software to assign to each particle; (i) a common initial probability, and (ii) an initial state comprising at least three dimensional spatial position, (D) using computer hardware and software to define epochs in time within each of which the following procedure is conducted; (i) in a prediction step (52), using said process model to predict with uncertainty the state of each particle in the next epoch, generally represented as xt=φ
t(xt-1)+η
t, where xt is the state vector, φ
t(xt-1) is a function used to predict the state xt in one epoch from information of the state in the previous epoch, while η
t is a process noise term, the predictions of all particles within each epoch thereby representing the probability distribution of the state vector xt given all previous measurements zt,(ii) in an updating step (53), using computer hardware and software to update the probability of the particles according to how well each particle'"'"'s state from the prediction step agrees with GNSS pseudo range measurements, according to the equation;
zt=ht(xt)+ε
t, wherein zt is a measurement vector, ht(xt) is a possibly time-varying function of the state, and ε
t is measurement noise, thus updating the probability distribution,(iii) using computer hardware and software to assess passage or non-passage by (54) mathematically comparing the spatial definition of the tolling objects in question with the updated particle information from the prediction step (52) while applying a defined confidence level, (iv) recursively repeating steps (D)(i) through (D)(iii) at a predetermined rate. - View Dependent Claims (20)
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Specification