Apparatus for estimating state of vehicle located in frontward field

• US 20090040095A1
• Filed: 08/08/2008
• Published: 02/12/2009
• Est. Priority Date: 08/10/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ogawa, Takashi
• Granted Patent: US 7,920,087 B2
• Time in Patent Office: Days
• US Class Current: 342/70
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection

Abstract

An estimation apparatus estimates a state of a vehicle located in a frontward field. Positional coordinates of a plurality of positions on an object are measured by radiating radar waves toward the frontward field and receiving reflected radar waves from an object in the frontward field. A position, direction and size of a graphical pattern are obtained by approximating the graphical pattern into a profile pattern of the object. The graphical pattern is modeled as a profile of a vehicle. A direction and size of the graphical pattern are unknown. The profile pattern is expressed by the positional coordinates. As the state of the vehicle located ahead, a position of the vehicle, a direction of the vehicle, and one of a whole length and a whole width of the vehicle are estimated based on the position, the direction, and the size of the graphical pattern.

Claims

1. An estimation apparatus for estimating a state of a vehicle located in a frontward field which is present in front of the estimation apparatus, comprising:

measurement means for measuring positional coordinates of a plurality of positions on an object to be targeted, by radiating radar waves toward the frontward field and receiving reflected radar waves from an object located ahead in the frontward field;

analysis means for obtaining a position, a direction and a size of a graphical pattern by approximating the graphical pattern into a profile pattern of the object located ahead, the graphical pattern being modeled as a profile of a vehicle, a direction and a size of the graphical pattern being unknown, the profile pattern being expressed by the positional coordinates measured by the measuring means; and

estimation means for estimating, as the state of the vehicle located ahead, a position of the vehicle, a direction of the vehicle, and one of a whole length and a whole width of the vehicle based on the position, the direction, and the size of the graphical pattern obtained by the analysis means.

2. The estimation apparatus of claim 1, wherein

the analysis means comprises is configured i) to use, as the graphic pattern, a first graphic pattern consisting of a single segment that models one surface of the vehicle and a second graphic pattern being L-shaped and consisting of a pair of mutually-orthogonal segments that models a front or rear surface of the vehicle and a side surface of the vehicle, so as to approximate the profile pattern of the object by each of the first and second graphic patterns, and ii) obtain the position, direction and size of each of the first and second graphic patterns and an approximation error between each of the first and second graphic patterns and the approximated profile pattern, and

the estimation means is configured to estimate the position of the vehicle, the direction of the vehicle, and at least one of the whole length and the whole width of the vehicle based on the obtained position, direction, and size of each of the first and second graphic patterns and the obtained approximation error.

3. The estimation apparatus of claim 2, wherein

the analysis means is configured to obtain a position, direction and length of each segment composing each of the first and second graphic patterns and an approximation error between each segment composing each of the first and second graphic patterns and the profile pattern as the position, direction and size of each of the first and second graphic patterns and the approximation error between each of the first and second graphic patterns and the approximated profile pattern, and

the estimation means is configured to estimate the position of the vehicle, the direction of the vehicle, and at least one of the whole length and the whole width of the vehicle based on the obtained position, direction, and length of each segment of each of the first and second graphic patterns and the approximation error between each segment composing each of the first and second graphic patterns and the profile pattern.

4. The estimation apparatus of claim 3, wherein the estimation means comprises

probability calculation means for calculating, as for each of the three segments of the first and second graphic patterns, a probability that each segment is a segment that approximates the front or rear surface of the vehicle and a probability that each segment is a segment that approximates the side surface of the vehicle based on the position, direction and length of each segment and the approximation error between each segment and the profile pattern;

selection means for selecting a most probable graphic pattern directed to the profile of the vehicle from a set of the graphic patterns in response to calculated probabilities by the probability calculating means, under a condition where the object is regarded as the vehicle; and

means for estimating, as to the selected graphic pattern, the position of the vehicle, the direction of the vehicle, and at least one of the whole length and the whole width of the vehicle based on the obtained position, direction, and length of each segment of each of the first and second graphic patterns and the approximation error between each segment composing each of the first and second graphic patterns and the profile pattern.

5. The estimation apparatus of claim 4, wherein

the measurement means is operable repeatedly at execution cycles and the analysis means and the estimation means are operable repeatedly together with the repletion of the measurement means,

the apparatus comprises prediction means for predicting, prior to estimating the state of the vehicle, the state of the vehicle in the next execution cycle of the estimation means by applying, to a predetermined motion model of the vehicle, the sate of the vehicle estimated by the estimation means in the past cycle, and

the probability calculating means is configured to calculate the probabilities based on the position, length, and direction of each segment and the approximation error between each segment and the profile pattern, which are obtained in the current execution cycle, and the state of the vehicle predicted by the prediction means.

6. The estimation apparatus of claim 5, wherein

the probability calculating means comprises

means for calculating, for each segment, the probabilities based on the length of each segment and the approximation error obtained by the analysis means,

means for calculating, for each segment, a likelihood corresponding to each prior probability based on the position, direction and length of each segment obtained by the analysis means and the state of the vehicle predicted by the prediction means,

means for calculating, for each segment, as the probabilities, a posterior probability that each segment approximates the front or rear surface of the vehicle and a posterior probability that each segment approximates the side surface of the vehicle by applying a Bayesian estimation technique to the calculated prior probabilities and the calculated likelihoods.

7. The estimation apparatus of claim 6, wherein

the prediction means is configured to use the state of the vehicle estimated in the past by the estimation means to i) predict, according to the predetermined motion model, the state of the vehicle to be estimated by the estimating means in the next execution cycle and ii) predict, according to the predetermined motion model, a travel direction of the vehicle to be estimated by the estimation means in the next execution cycle, and

the likelihood calculating means is configured to calculate, for each segment, the likelihoods based on i) the state of the vehicle and the travel direction of the vehicle both predicted by the prediction means and ii) the direction, position and length of each segment obtained by the analysis means in the current execution cycle.

8. An estimation apparatus for estimating a motion state of a vehicle located in a frontward field which is present in front of the estimation apparatus, comprising:

measurement means for measuring positional coordinates of a plurality of positions on a surface of an object to be targeted, by radiating radar waves toward the frontward field and receiving reflected radar waves from an object located ahead in the frontward field; and

estimation means for estimating the motion state of the vehicle based on the positional coordinates measured by the measurement means and a predetermined non-linear motion model for the vehicle.

9. The estimation apparatus of claim 8, wherein the estimation means is configured to estimate, as the motion state of the vehicle, in addition to the angular velocity, one or more from a group of physical quantities consisting of a position of the vehicle, a direction of the vehicle, a speed of the vehicle, and a travel direction of the vehicle.

10. The estimation apparatus of claim 8, wherein

the estimation means uses a Kalman filter adapted to the non-linear motion model to estimate the state of the vehicle.

11. The estimation apparatus of claim 8, wherein

the Kalman filter is an unscented Kalman filter.

12. The estimation apparatus of claim 10, wherein the non-linear motion model is an uniform circular motion model.

13. The estimation apparatus of claim 10, wherein the measurement means is operable repeatedly at execution cycles and the estimation means is operable repeatedly together with the repletion of the measurement means, and

the estimation means comprise means for determining whether or not the angular velocity estimated in the current execution cycle is zero;

means for changing the motion model to estimate the state of the vehicle from the non-linear motion model to a predetermined linear motion model when the angular velocity estimated in the current execution cycle is zero; and

means for estimating the state of the vehicle according to the linear motion model.