JPH0772749B2 - Motion prediction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motion prediction method for predicting and displaying a target course and speed from target position information such as a tracking target detected by a radar or the like.

(Prior Art) Conventionally, in the case of predicting and displaying the course and speed of a target (for example, a ship) in a target tracking device, especially a target tracking device using a radar signal, as shown in FIG. The target detecting means 22 obtains the target position signal of the target from the radar video signal of the target obtained at each antenna scanning period, and the motion predicting means 23 predicts the target course and speed based on the target position signal, and further the vector generation. A vector signal is generated from the target course and velocity signal output from the motion prediction means 23 by the means 24, and the vector signal output from the vector generation means 24 is displayed on the display 25 while being superimposed on the radar video signal. .

FIG. 5 shows an example of the display of the display 25, and the course and speed of the targets 9a to 9e in the radar image display are set to the target 9a.
Display with vectors 10a to 10e starting from ~ 9e.
Here, each direction of the vectors 10a-10e represents the course of the targets 9a-9e, and each length of the vectors 10a-10e represents the velocity of the targets 9a-9e.

By the way, the radar video signal contains clutter noise and receiver noise in addition to the target signal, and further, since the target signal also has fluctuations, the target position signal output from the target detection means 22 is Includes an error. Therefore, the motion predicting means 23 uses a cyclic filter such as a Kalman filter or an α-β filter in order to stably predict the course and velocity, or the course and the route which are obtained from the time difference between the two different observation times. It was necessary to perform smoothing by applying a moving average to the speed or combining the two.

(Problems to be Solved by the Invention) However, in such a conventional motion prediction method, when the target is performing constant-velocity linear motion, good course and speed are predicted, and a stable vector is obtained. Although it is displayed, the response when the target is changed or the gear is changed becomes very slow, and the vector is displayed as if the constant velocity straight movement was continued despite the change of the needle or the change in gear. There is a problem that the speed and the actual target course and speed are significantly different.

FIG. 6 is a diagram for specifically explaining the above problem and shows an example of a vector display of a course and a speed when a target, which is performing a uniform linear motion, suddenly changes its needle.

In FIG. 6, L is the trajectory of the target motion, and P0, P1, P2 are the target positions of the motion process. At the point P0 where the target is moving at a constant speed, the vector 10 correctly represents the target course and speed. At the point P1 shortly after the target starts changing needles, the vector 10 is displayed as if the target continues to move at a constant linear velocity. Furthermore, at the point P2 where the target has changed significantly, the course and speed represented by the vector 10, particularly the course, is greatly delayed from the target change in course, and is significantly different from the actual target course and speed.

As described above, in the conventional method, it is not possible to promptly predict the target variable speed change state at the time of changing the target needle and changing gears, which is a big problem in knowing the trend of the target with a high risk of collision and making an escape plan. There is.

(Means for Solving the Problems) The present invention has been made with the above points in mind, and in accordance with the degree of danger of the target to be tracked, a target with a low possibility of collision is In addition to the conventional stable motion prediction, the target course and speed can be predicted appropriately by performing motion prediction with good followability for a target with high risk. It is intended to provide a forecasting method.

In order to achieve this object, the present invention emphasizes the smoothness of the target position signal obtained from the target position detection device to perform the motion prediction, and also emphasizes the followability of the target position signal. Any one of the second motion predicting means for predicting motion, the own ship course signal, the own ship speed signal, the target position signal, and the first or second motion predicting means obtained from the own ship motion detecting device. Collision calculation means for calculating a collision judgment signal for judging the possibility of collision between the target and the ship based on the target course speed signal obtained by the above, collision judgment signal obtained by the collision calculation means, and preset reference The determination means for comparing the value with a value for outputting a determination signal indicating the degree of collision, and the determination output for determining that the possibility of collision are low.
The output of the motion predicting means and the output of the second motion predicting means are switched and selected based on the determination output that the possibility of collision is high and output to the collision calculating means.

(Operation) According to the motion prediction method of the present invention having such a configuration, the first motion prediction means for predicting a stable target course velocity signal with emphasis on smoothness, and the target with emphasis on followability. A second motion predicting means for predicting a target course speed signal that quickly follows the change in needle speed and the speed is provided, and the possibility of a collision between the target and the own ship is judged by the judging means based on the collision judging signal obtained from the collision calculating means. The target course speed signal output from either the first motion predicting means or the second motion predicting means is automatically selected by the switching means based on the judgment result. That is, when the possibility of collision is low, the stable target course speed signal with importance placed on smoothness obtained by the first motion prediction means is obtained by the second motion prediction means when the possibility of collision is high. The target course velocity signal in which the following followability is emphasized is selected, and it is possible to appropriately predict the target motion in automatic tracking or the like for collision prevention.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, 1 is a ship motion detection device, 2 is a target detection device, 3 is first motion prediction means, 4 is second motion prediction means, 5 is switching means, 6 is collision calculation means, and 7 is Determination means,
Reference numeral 8 is a display means.

Further, the configuration of each block will be described in detail together with the operation. First, the own ship motion detection device 1 is configured by a device such as a gyro and a Doppler log, and the motion state of the own ship, that is, the own ship course and the own ship It becomes a sensor that detects the ship speed.

The target detection device 2 detects the target from the video video signal of the target obtained by the radar device and outputs the target position signal.

The first and second motion prediction means 3 and 4 are the target detection device 2
The target course and speed are predicted based on the target position signal obtained from the above, and the target course and speed signal is output. The prediction of the target course and velocity is obtained by decomposing the target position signal into Cartesian coordinate components, performing motion prediction for each Cartesian coordinate component, and converting the resulting target velocity signal into polar coordinates. be able to.

Further, the target motion prediction can be realized by using, for example, an α-β filter. For example, motion prediction by a one-dimensional α-β filter is expressed as follows.

Xs (k) = Xp (k) + α [Xm (k) −Xp (k)] Vs (k) = Vs (k−1) + β [Xm (k) −Xp (k)] / T Xp (k + 1) = Xs (k) + Vs (k-1) ・ T Xm: Target position Xs: Target smooth position Xp: Target predicted position Vs: Target speed α, β: Filter constant T: Observation interval This α-β filter is a kind of This is a low-pass filter, and when the value of α or β is made small (close to 0), the smoothing characteristic of the filter becomes remarkable, and α or β
When the value of is increased (close to 1), the tracking characteristic of the filter becomes remarkable. The frequency characteristic of the α-β filter is described in, for example, the document [DEMayiatis “Comparsion of
α-β and Kalman filter in track while scan rada
rs "].

Therefore, in the first motion prediction means 3, by setting the values of α and β of the α-β filter to small values, it is possible to obtain a target course and speed prediction result with excellent smoothness. By setting the values of α and β of the α-β filter to large values, the predicting means 4 can obtain a target course and speed prediction result with excellent followability.

That is, the filter constant of the first motion prediction means 3 is set to α1,
β1 and the filter constant of the second motion prediction means 4 are α2,
Assuming β2, the relationship between α and β can be summarized as follows.

α1 <α2 β1 <β2 Next, the switching means 5 causes the target course and the target course obtained as a result of the speed prediction of the target course having different characteristics obtained by the first and second motion predicting means 3 and 4, respectively. Either one of the speed signals is selected and output.

Further, the collision calculation means 6 is any one of the own vessel course signal and the own vessel speed signal obtained from the own vessel motion detection apparatus 1, the target position signal obtained from the target detection apparatus 2, and the selected one obtained from the switching means 5. DCPA (closest approach distance) and TCPA (time to reach the closest approach distance), which are the target collision determination signals, are calculated from the target course / speed signal of.

DCPA and TCPA obtained by the collision calculating means 5 will be described with reference to FIG.

Fig. 2 shows the movements of the ship and the target in the relative coordinate system. 31 is the ship itself, 32 is the target, Rd is the distance between the ship and the target, θ
b is the target direction, Vr is the target relative speed, and θr is the target relative course. The values of Rd, θb, Vr, and θr are easily calculated from the own ship course signal, the own ship speed signal, the target position signal, and the target course speed signal.

Here, DCPA and TCPA can be calculated as follows.

TCPA = Rd * cos θ / Vr DCPA = Rd * sin θ θ = θb−θr + π For details on how to determine DCPA and TCPA, refer to the document [Japan Radio Technique, NO8 1974, “Collision preventive device and its sea test”]. It is shown.

DCPA indicates the distance between the target and the expected point where the ship will be closest (hereinafter called CPA) and the ship, and TCP
A represents the time until the goal reaches CPA. Therefore, if the DCPA shows a small value, the target is expected to pass through the waters close to the ship, and it can be judged that there is a high possibility of collision.If the TCPA shows a small value, there is a margin time until the target comes closest. Since it is small, it can be judged that the risk is high.

The judging means 7 judges the possibility of a collision between the target and the own ship from the values of DCPA and TCPA obtained by the collision calculating means 6, and outputs a switching signal to the switching means 5 according to the result.

Here, a method of determining the possibility of collision can be performed by comparing a predetermined reference DCPA, reference TCPA with a target DCPA, TCPA.

For example, if (DCPA) ≤ (reference DCPA) and (TCPA) ≤ (reference TCPA), it is judged as a dangerous target with a high possibility of collision, and (DCPA)> (reference DCPA) or (TCPA)> In the case of (standard TCPA), the possibility of collision is low and it is judged as a safe target.

Furthermore, as the switching signal to the switching means 5 based on the determination result of the determination means 7, when the target is determined to be a safe target with a low possibility of collision, the output result of the first motion prediction means 3 is selected. Thus, the switching signal is output so that the output result of the second motion prediction means 4 is selected when the target is determined to be a dangerous target with a high possibility of collision.

The display means 8 superimposes and displays the target course / speed signal obtained from the switching means 5 on the radar image signal obtained from the target detection device 2 as a vector display.

FIG. 3 is a block diagram showing another embodiment of the present invention.

That is, in the embodiment shown in FIG. 1, the first motion prediction means 3 and the second motion prediction means 4 having different motion prediction characteristics are provided as means for obtaining the target course velocity signal, and the output signal is switched by the switching means 5. Although selected, the embodiment of FIG. 3 is characterized in that one motion predicting means is used and the motion predicting characteristic of the motion predicting means is switched by the output signal of the judging means 7.

In FIG. 3, the ship motion detection device 1, the target detection device 2, the collision calculation means 6, the determination means 7 and the display means 8 are the same as in FIG. Reference numeral 40 denotes a motion predicting means which is a means for selecting a motion predictive characteristic according to a switching signal which is an output signal of the judging means 7 to predict a target motion and outputting a target course / speed signal.

As the motion predicting means 40, for example, by setting the values of the filter constants α and β of the α-β filter for performing motion prediction to small values, the predicted result of the target course and speed with excellent smoothness is obtained. And α-β
By setting the values of the filter constants α and β of the filter to large values, it is possible to obtain a target course and speed prediction result with excellent followability.

That is, by switching between large and small values of the filter constants α and β according to the switching signal from the judging means 7, the smoothness is emphasized to predict a stable target course speed, or the followability is emphasized to change the target needle. In this case, it is possible to realize a motion predicting means that predicts a target course speed that quickly follows, or selects one of the motion prediction characteristics to perform target motion prediction, and outputs a target course speed signal.

Here, as the switching signal output from the judging means 7,
When the target has a low possibility of collision and can be determined to be a safe target, a switching signal is output so that the motion prediction characteristic of the motion prediction means 40 is selected as a prediction characteristic with emphasis on smoothness, and the target has a collision. If it is determined to be a likely and dangerous goal,
A switching signal is output so as to select the motion prediction characteristic as a prediction characteristic that emphasizes followability.

Although a radar device is used as an example of the target detection device 2 in the above embodiment, the present invention can be similarly applied to a sensor such as a sonar or a laser device that can detect target position information.

Further, as the above-mentioned embodiment, the motion prediction system for a ship has been described, but the present invention is not limited to this, and the motion prediction method for an aircraft, the control of an industrial robot, and the like can be used for an appropriate moving object. It is possible.

(Effects of the Invention) As described above, according to the present invention, a target with a low risk of collision is automatically predicted with stable course and speed, and a high risk of collision is obtained. For the target, the motion prediction that promptly follows the change in the course and speed is performed, and thus it is possible to avoid a collision with the target and perform safe and appropriate navigation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a relationship between a ship and a target for collision calculation,
FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG.
FIG. 5 is a block diagram showing an example of a conventional method, FIG. 5 is an explanatory diagram showing an example of display on a display device, and FIG. 6 is an explanatory diagram showing an example of conventional vector display of course and speed. 1: Own ship motion detection device 2: Target detection device 3: First motion prediction means 4: Second motion prediction means 5: Switching means 6: Collision calculation means 7: Judgment means 8: Display means 9: Tracking target 10 : Vector 21: Radar 22: Target detection means 23: Motion estimation means 24: Vector generation means 25: Display 31: Own ship 32: Target 40: Motion prediction means

Claims (1)

[Claims] 1. A motion prediction method for predicting a target course and speed from a target position signal output from a target detection device, wherein a target course / speed signal predicted with emphasis placed on smoothness rather than the target position signal is used. A first motion predicting means for outputting; a second motion predicting means for outputting a target course / velocity signal predicted with emphasis on followability rather than the target position signal; the first or second motion prediction Collision calculating means for outputting a collision judgment signal for judging the possibility of a collision with the target based on the target course / speed signal and the own course / speed signal obtained from one of the means; When the collision determination signal obtained from the calculation means is compared with a preset reference value to determine the degree of collision possibility, and the determination means outputs a determination output that the possibility of collision is low. To the first The second is when the output of the motion prediction means, also resulted in determination output to a high possibility of collision
And a switching means for selectively switching the output of the motion predicting means and outputting the output to the collision calculating means.