JPH0661097B2 - Self-moving state extraction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a self-moving state extraction method for extracting a translation direction and rotation of a moving body that moves with translation and rotation. .

<Prior Art> From the spatiotemporal information of the outside world obtained in the field of view of an image pickup device such as a camera corresponding to human eyes, the self-moving state of the moving body equipped with this image pickup device, that is, the translational direction of the moving body, Extracting rotation accurately and rationally and easily is a technology that is expected to be realized in many industrial fields even in the future.

Even if it is simply considered, there are applications such as for self-control of mobile robots, and conversely, since information on an object viewed from a moving object can be obtained, three-dimensional structural analysis of that object is possible. It can also be a powerful help in etc.

For this reason, many people have been engaged in this kind of research in the past, but among them, the flow of objects in the field of view due to the movement of a moving body, the so-called optical flow (represented by angular velocity) A method of extracting the self-moving state from the flow pattern of is represented by the following documents.

: Parzdny, K. “Egomotion and relative depth map from optical fl
ow. ”Biol.Cyernet.36,87-102 (1980): Longuet-Higgins, HC and Prazdny, K.“ The interpretation of a moving retinal imge. ”Proc.R.Soc.Lond.B, 208,385-397 ( 1980) The method shown in the above-mentioned document is characterized in that all three rotation variables are changed to select one that meets the conditions, and the method described in the above-mentioned document is that the angular velocity of the first and second orders of the angular velocity is weak. It is characterized in that it uses many spatial derivatives.

On the other hand, the active method disclosed by the applicant at the Institute of Electronics and Communication Engineers on March 26, 1985 and filed a separate patent on June 28, 1985 based on this is also not known. It can be mentioned as a conventional example.

This is conveniently referred to as the “filed invention”, which follows the object so that it is clearly visible.

The retina of an animal's eye is close to a sphere, and the peripheral part of the visual field contributes to the perception of self-movement. It is an active model that imitates the structure and behavior of the eye possessed by higher animals. And the summary is as follows.

A self-moving state extraction method for extracting the translational direction and rotation of a moving body consisting of translation and rotation based on the angular velocity field associated with the flow pattern of the external world; The projection surface is a sphere; and a rotation for tracking the object in the center of the visual field is added independently of the rotation of the moving body; the tracking rotation causes the object when only the translational motion exists in the moving body. A field equivalent to an angular velocity field generated when an object is tracked with a basic rotation axis of a predetermined latitude; extracting the translational direction and rotation of a moving body based on the equivalent field; Self-moving state extraction method. That is, according to the above-mentioned invention of the present application, in addition to the rotation (original rotation) of the moving body, an independent tracking rotation capable of actively tracking the object in the center of the visual field is added to perform translation and rotation. The angular velocity (optical velocity) generated in the central part of the visual field and the peripheral visual field when the object is tracked with the basic rotation axis of the predetermined latitude when it is assumed that the moving body is not rotating but only translating. You can create the equivalent of the flow field.

Therefore, in general, if the basic rotation axis is set to a 90-degree latitude axis, the translation of the moving body can be performed from the equivalent optical flow field by a normal simple geometrical or vector operation. And the original rotation can be extracted most easily and reliably.

<Problems to be Solved by the Invention> As clearly described in the above-mentioned invention already filed by the applicant,
Conventional methods, such as those shown in the literature, are still
The result is not satisfactory at all.

Each of them is very complicated, takes a lot of time for calculation, and has a drawback such as instability, but in principle, a camera corresponding to the eyes is set for a moving object and is active. Since it is assumed that the object does not move, the object in the direction of the line of sight moves with respect to the retina of the "eye", and there is a drawback that the object cannot be clearly seen.

On the other hand, the above-mentioned invention of the present application overcomes these drawbacks as described above.

However, even in the present invention, the latitude at the time of tracking rotation for tracking the object in the center of the field of view is not constant. Therefore, when actually implementing this method, tracking in an arbitrary direction is performed. It has the drawback that it must be able to rotate, and the tracking mechanism must be complicated, and the extraction and analysis of the optical flow must be performed twice.
There is also some work to do.

The present invention has been made in view of these points, and as a method for extracting a self-moving state of a moving body, in addition to the drawbacks of the passive method shown in the above document, the active method separately disclosed by the present applicant. The main purpose was to solve the remaining drawbacks of the traditional method.

Therefore, in other words, this invention is to provide a more practical active self-moving state extraction method by solving the drawbacks of the above-mentioned invention.

<Means for Solving Problems> In order to achieve the above object, the present invention provides an active self-moving state extraction method having the following configuration.

A self-moving state extraction method for extracting the translation direction and rotation of a moving body, which is composed of translation and rotation, based on an angular velocity field associated with an external flow pattern; The surface is assumed to be a sphere; the rotation for tracking the object in the center of the visual field is added independently of the rotation of the moving body; and the theory is to rotate around the defined axis in order to set the tracking rotation axis at a specific latitude. A supplementary rotation obtained by calculation (hereinafter referred to as "thinking supplementary rotation") is added; by this, when there is only translational motion in the moving body, the object is a base of a predetermined latitude. A method of extracting a self-moving state, which comprises: creating a field equivalent to an angular velocity field generated when tracking is performed on a rotation axis; and extracting a translation direction and a rotation of a moving body based on the equivalent field.

<Operation> In the self-moving state extraction method according to the configuration of the present invention, the object is visually tracked so that it can be seen clearly, the retina of the eye of an animal is close to a spherical surface, and the peripheral part of the visual field contributes to the perception of self-movement. It is an active model imitating the structure and behavior of the eyes of higher animals such as.

Then, in addition to the rotation of the moving body (original rotation), independent tracking rotation that can actively track the object in the center of the visual field is added, and the moving body that is translating and rotating does not rotate. To create a field equivalent to the angular velocity (optical flow) field generated in the center of the visual field and the peripheral visual field that occurs when the object is tracked with the basic rotation axis of the predetermined latitude when only translation is performed. You can

Therefore, in general, if the above basic rotation axis is an axis with a latitude of 90 degrees, translation and original rotation of the moving body can be performed by ordinary simple geometrical or vectorial operations from the above-mentioned equivalent optical flow. And can be extracted most easily and reliably.

Moreover, since the auxiliary rotation for thought is added and analyzed, unlike the already-filed invention described above, the tracking rotation axis can be set to a desired specific latitude, and only in the mild direction, the entire axis can be set. Since it only needs to be rotatable, the tracking mechanism can be greatly simplified, and the arithmetic system can be simplified and speeded up.

Generally, it is convenient to set the tracking rotation axis to 90 degrees latitude, and accordingly, the rotation axis of the auxiliary rotation in thought is a line segment connecting the center of the visual field and the projection center thereof. .

<Examples> The projection plane of the external world that defines the field of view may be a plane, a spherical surface, or the like. However, in the present invention, for the reasons described above, as shown in the preferred embodiment in the accompanying drawings, the external world is It is projected on the hemisphere by polar projection with the point O as the projection center.

For convenience of explanation, the projection hemisphere is shown upside down so as to be point-symmetric with respect to the point O, and the radius is normalized to "1" for handling.

In this embodiment, for the sake of simplicity, it is assumed that the optical flow extraction portion is provided only on the center portion A of the visual field at latitude 0 degrees and on the great circle at latitude 90 degrees. What is prepared in the corner extraction unit on the great circle is for storing the latitude component U _θ of the optical flow, which is the angular velocity, the longitude component U _φ , the angle α formed by the meridian, and the magnitude V of. It is a register.

A bar is drawn above the value V, "" indicates a vector, and the same applies to the following alphabetical symbols.

Optical flow at center A of the field of view The size of V _A , There is a register that stores the angle φ _A formed by the horizontal line.

What you want to extract is the latitude θ of the intersection T of the translation direction and the spherical surface.
_There are five parameters: _T and longitude φ _T , latitude θ _R and longitude φ _{R at} the intersection R of the rotation axis and the spherical surface, and rotation speed W.
The rotation vector is a three-dimensional vector whose magnitude is W and whose direction is along the rotation axis.

First, from the two parameters that define the direction of translation, we will start by extracting the longitude φ _T.

To clearly see the object in the center of the field of view, the optical flow at that point It is only necessary to add the rotation ₁ that cancels out.

But the optical flow Since the rotation axis of the tracking rotation ₁ that cancels out is the axis perpendicular to the optical flow, its lightness is uniquely determined to be φ _A + π / 2, but the latitude is uncertain.

Therefore, in the present invention, this is set to a specific latitude. In this example, the particular latitude is chosen to be the most common 90 degrees.

Rotational speed _{W 1} of the rotary ₁ is equal to A _V. And the characteristic of the optical flow that occurs at this time is
Auxiliary rotation in thought around the line segment connecting point O and point A
By adding ₂ , it is possible to create a "state in which the object in the center of the field of view is tracked by the" basic rotation "of the rotational axis OR at 90 degrees latitude when the moving body is only in translational motion". .

Under this state, all latitude components of the optical flow on the great circle AT connecting the translation direction T and the center A of the visual field can be eliminated. Therefore, at each point on the great circle that passes through the center of the field of view, we obtain W ₂ (θ, φ) = U _θ (θ, φ) / sin… 1) , The longitude of the great circle becomes the longitude φ _T in the translation direction.

In this case, when the optical flow extraction unit is prepared only for latitude 90 degrees, ζ = | U _θ (π / 2, φ) −U _θ (π / 2, φ + π) ... 2) If we find φ that minimizes, it becomes φ _T , which is one parameter of the translational direction to be obtained.

Thus, the rotational speed W ₂ of the auxiliary rotary _{2, W 2 = U θ (π} / 2, φ T) ... 3) , and this auxiliary rotary ₂ is used for correction of the optical flow extractor.

Next, the extraction of "rotation" and the extraction of θ _T will be described.

According to the definition described above, the latitude θ _R ″ of the intersection R ″ of the rotation axis of the composite rotation ″ and the spherical surface is π / 2, and the longitude φ _R ″ is φ _T −.
π / 2. Therefore, after that, W ″ and θ _T should be known.

However, the optical flow of the point R ″ being tracked Does not include a rotation component, so The angle a _R ″ formed by and the meridian becomes θ _T as it is.

Optical flow at point T , The velocity W ″ of the synthetic rotation (= basic rotation) is V _T , because it does not include a translational component, but here, only at the center of the field of view and at the 90 ° latitude, the optical flow Since the extraction unit is provided, another extraction method for the combined rotation speed W ″ based on this will be described.

This rotation speed W ″ is an arbitrary point Q on the great circle with a latitude of 90 degrees.
(π / 2, φ) optical flow From the latitude component U _θ (φ), the longitude component U _φ (φ), and the angle a (= θ _T −φ) formed by the great circle AT and the great circle AQ 4).

That is, the angle formed by the great circle AT and the arc QT is t,
From the spherical geometry, tan θ _T = tan t / sin a ... And from the local plane geometry at the point Q, tan t = U _θ (φ) / (U _φ (φ) −W ″ · cos a)・ ・
Therefore, tan t is eliminated from these equations, and W ″
Solving this gives the following equation 4).

The above formula is “optical flow of point Q (π / 2, φ)” Is obtained by subtracting the contribution of rotation "from the direction of point T".

If the optical flow does not exist at the point R ″, W ″ and θ _T can also be obtained simultaneously by applying the above rule at two points where the optical flow exists.

As described above, tracking rotation ₁ , auxiliary rotation for thought
_2, and "so is known, = from the relationship previously described" synthesis rotation - 1 _- by 2 _... 5), the original rotation to be obtained, i.e. it is possible to determine the rotation of the moving body.

It should be noted that, in the above-described embodiment, the tracking rotation is incorporated so that “when the moving object makes only a translational motion,
We introduced the concept of "tracking with 90" rotation axis OR "rotation", but generalizing this concept, "when the moving body is only in translation, the object is at a predetermined latitude x degree". It may be changed to "the state of tracking by the basic rotation of the rotation axis", and the latitudes of the rotation axes of the tracking rotation ₁ and the auxiliary rotation ₂ are set to other than 90 degrees and 0 degrees respectively, as described above. You can try as much as possible,
Even so, since it is simpler and has advantages as compared with the conventional method, this is the case in the gist of the present invention.

However, it is also true that the angular relationship as shown in the above example is actually desirable.

<Effects of the Invention> As described above, according to the present invention, an object that is impossible with the conventional self-moving state extraction method of this type is clearly seen (the optical flow of the object is erased). In addition to the above, it is possible to extract the self-moving state only by the optical flow around the center of the visual field and around the visual field, and the spatial differentiation is not performed. You can get advantages such as being strong.

Further, even with respect to the invention already filed by the applicant as an active method, it is possible to exert a more excellent effect by simplifying the analysis of the rotation mechanism for tracking rotation and the optical flow. .

[Brief description of drawings]

The drawings are explanatory views for explaining an embodiment of the present invention. In the figure, A is the center of the field of view, O is the center of polar projection, T is the intersection of the translation direction and the projection sphere, R is the intersection of the rotation axis of the original rotation and the projection sphere, and R ₁ is the tracking rotation and the projection sphere. , R ″ is the intersection of the composite rotation and the projection sphere, and ₁ , ₁ , ₂ ″ are the respective rotation vectors.

Claims (1)

[Claims] 1. A self-moving state extraction method for extracting the translation direction and rotation of a moving body, which is composed of translation and rotation, based on an angular velocity field associated with a flow pattern of the outside world. The projection surface of the flow pattern of is a spherical surface; and the rotation for tracking the object in the center of the visual field is added independently of the rotation of the moving body; and the tracking rotation axis is set to a specific latitude. Auxiliary rotation obtained by theoretical calculation is added about the axis; this makes it possible to estimate the angular velocity generated when the object is tracked by the basic rotation axis of a predetermined latitude when only the translational motion exists in the moving body. Creating a field equivalent to the field; extracting the translational direction and rotation of the moving body based on the equivalent field;