CN109285117A - A kind of more maps splicing blending algorithm based on map feature - Google Patents

A kind of more maps splicing blending algorithm based on map feature Download PDF

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CN109285117A
CN109285117A CN201811029781.1A CN201811029781A CN109285117A CN 109285117 A CN109285117 A CN 109285117A CN 201811029781 A CN201811029781 A CN 201811029781A CN 109285117 A CN109285117 A CN 109285117A
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map
point
feature
algorithm
rigid body
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郭健
朱禹璇
李胜
吴益飞
龚勋
危海明
赵超
袁佳泉
施佳伟
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Nanjing University of Science and Technology
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Nanjing University of Science and Technology
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00Geometric image transformations in the plane of the image
    • G06T3/40Scaling of whole images or parts thereof, e.g. expanding or contracting
    • G06T3/4038Image mosaicing, e.g. composing plane images from plane sub-images
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00Geometric image transformations in the plane of the image
    • G06T3/60Rotation of whole images or parts thereof

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Abstract

The invention discloses a kind of, and more maps based on map feature splice blending algorithm, include the following steps: the edge pixel point for extracting grating map to be spliced, establish rigid body translation mathematical model, convert image registration minimization problem for map Bonding Problem;Based on improved SURF algorithm, feature is extracted from map to be spliced, determines optimal initial splicing parameter;Parameter will initially be spliced and substitute into mathematical model, improved ICP algorithm is based on, solves accurate rigid body translation result;It rotated, translated and is merged accordingly as a result, treating stitching image according to accurate rigid body translation, obtain the accurate splicing result of grating map.The present invention has initial splicing speed faster, is conducive to fairly large map splicing;There is stronger robustness and higher precision to biggish map environment.

Description

A kind of more maps splicing blending algorithm based on map feature
Technical field
The invention belongs to robot control fields, and in particular to a kind of more maps splicing fusion calculation based on map feature Method.
Background technique
Mobile robot (Robot) is the automatic installations for executing work, it can not only receive mankind commander, but also can be with The program of preparatory layout is run, can also can assist in or replace according to principle program action formulated with artificial intelligence technology The mankind complete dangerous work, such as can put into mobile robot in this extreme environment of mountain area substation.Therefore draw Domestic and foreign scholars have been played more and more to pay attention to.Robot, which wants to realize, to be explored and navigates in circumstances not known, needs first to complete map Creation.The prior art is mostly to create smaller or medium scale environmental map, however, with the continuous expansion of environment scale, As still carried out map building using the prior art, the map of creation precision, robustness and in terms of will all deposit In problem, the demand of extensive environment can not be adapted to.
Summary of the invention
The purpose of the present invention is to provide a kind of, and more maps based on map feature splice blending algorithm.
The technical solution for realizing the aim of the invention is as follows: a kind of more maps splicing blending algorithm based on map feature, Include the following steps:
Step 1, the edge pixel point for extracting grating map to be spliced, establish rigid body translation mathematical model, map are spliced Problem is converted into image registration minimization problem;
Step 2 is based on improved SURF (Speeded Up Robust Features) algorithm, mentions from map to be spliced Feature is taken, determines optimal initial splicing parameter;
Step 3 will initially splice parametric results substitution mathematical model, be based on improved ICP (iterative closest Point) algorithm solves accurate rigid body translation result;
Step 4 is rotated accordingly, translated and is merged as a result, treating stitching image according to accurate rigid body translation, is obtained Obtain the accurate splicing result of grating map.
Compared with prior art, the present invention its remarkable advantage are as follows: 1) present invention has initial splicing speed faster, favorably Splice in fairly large map;2) present invention has stronger robustness and higher essence for biggish map environment Degree;3) present invention utilize SURF algorithm, available more effective feature to optimal initial splicing parameter.
Detailed description of the invention
Fig. 1 is that the present invention is based on the flow charts of more maps of map feature splicing blending algorithm.
Fig. 2 is the flow chart of the improved SURF algorithm of the present invention.
Fig. 3 is the flow chart that the present invention obtains optimal solution.
Fig. 4 is the scale space figure that the present invention constructs.
Specific embodiment
The principle of the present invention and scheme are further illustrated with reference to the accompanying drawings and detailed description.
As shown in Figure 1, the process of more maps splicing blending algorithm based on map feature are as follows:
Step 1: extracting the edge pixel point of grating map to be spliced, establish rigid body translation mathematical model, map is spliced Problem is converted into image registration minimization problem.
For there are overlapping region two-dimensional grid map G and W, Boundary extracting algorithm is utilized from grating map to be spliced Edge pixel point is extracted respectivelyWithNgAnd NwRespectively indicate the element of edge pixel point set G and W Number.It will be in map G and the edge pixel point set G of the overlapping region map WεIt indicates, it is the subset of G, overlapping percentages ε To indicate.
Map Bonding Problem can be regarded as image registration problem, and calculating acquires rigid body translation parameter T={ R, t }, and R is one A Two Dimensional Rotating transformation matrix, t ∈ R is two-dimension translational transformation vector, so that transformed treated point set T (G) can be well It is matched with point set W, and then grating map Bonding Problem is expressed as minimization problem, such as following formula:
s.t.RTR=I2×2, Δ (R)=1
In formula, λ is control parameter, | | represent element number in set, minimum overlay percentage εminIt indicates.
Step 2: using the vector for improving SURF algorithm and extracting the SURF feature of grating map to be spliced, determine it is optimal just Begin splicing parameter;
In order to solve the rigid body translation in above formula, preferable feature extraction is needed initially to splice parameter (R0,t0), therefore adopt Initially splice parameter based on to improvement SURF algorithm with a kind of to obtain.SURF algorithm is improved to filter using integral image, box With Haar small echo accelerating algorithm, stable margin is all had to the complicated variation such as scale, noise, illumination and visual angle difference, is had Body realizes that steps are as follows:
Step 2.1, building scale space
Since box filtering and integral image is utilized in SURF algorithm, it is unrelated with picture size to calculate time-consuming, therefore in spy SURF algorithm ratio SIFT efficiency of algorithm is higher when sign detection, and SURF algorithm is exactly that original image and box filter are accelerated using the property The convolution algorithm of wave.The scale space pyramid bottom of SURF algorithm is filtered using the box that a size is 9x9, box filter Minimum 6 pixel step lengths of wave size conversion, the 2nd layer of minimum 15x 15.The box of current size filters corresponding Gauss scale-value Calculation formula it is as follows:Current box filtering size is indicated with N.As shown in figure 4, as a kind of specific reality Mode is applied, constructs 4 degree 4 layers of scale space, the size variation of cassette filter is respectively 6,12,24,48 in each layer.
Step 2.2, detection characteristic point
For the scale space of building, candidate extreme point is detected by Hessian matrix, finds candidate extreme point postscript Its positions and dimensions is recorded, image space and scale space are then found to extreme point neighborhood territory pixel interpolation using Harriss algorithm In sub-pixel precision characteristic point, eliminate the extreme point of wherein low contrast, remaining is the position of characteristic point;
Step 2.3 determines characteristic point direction
After the position for determining characteristic point, to make characteristic point that there are the characteristics such as invariable rotary, a determination one need to be characterized Principal direction, while robustness is improved using Haar small echo.First centered on characteristic point, by the 6 δ (scale where characterized by δ Value) it is that radius work is justified, the Haar small echo response that the point in border circular areas is 4 δ in the x and y direction is calculated, and with Gaussian template pair Obtained response results do the cumulative principal direction to get this feature point, more meet reality.As a kind of specific embodiment, with Centered on characteristic point, the fan-shaped region that central angle is 60 ° be unit, traverse entire response image with 5 ° for step-length, 6 fans can be obtained Shape region, the haar small echo response in each fan-shaped region on the direction accumulation calculating x and y generate a new vector, will be new Principal direction of the direction of modulus value maximum vector as this feature point in vector.
Step 2.4 generates feature point description symbol
To ensure that rotational invariance rotates reference axis to SURF characteristic point principal direction, along principal direction with characteristic point it is The heart constructs the square window that 20 δ are side length, which is uniformly divided into 16 sub-blocks, with 2 δ in each subregion Haar small echo template with 5x5 size for 1 fritter interval sampling, calculate in each fritter test point relative to principal direction x and y The response dx and d of axis directionyThe response and its absolute value of 25 sampled points in each fritter are added up, just formed 14 dimensional vector of the subregion describe sub- ν=(∑ dx,∑dy,∑|dx|,∑|dy|).By the processing of the above process, often A characteristic point just obtains 1 64 dimension description vectors, can remove the influence of brightness change after feature vector is normalized, finally obtains The vector descriptor of SURF feature.
After obtaining the vector descriptor of feature, validity feature pair is obtained using RANSAC algorithm, determines initial spell Connect parameter.Grating map G and W are extracted and are established N group SURF feature pairWherein Pi,GAnd Pi,WIt respectively indicates I-th group of feature of map G and W, they use P in the position of grating map respectivelyi,GAnd Pi,WIt indicates.If T={ R, t } is splicing The approximate solution of parameter, and { Pi,G,Pi,W}I=1For one group of effective feature pair, that is, they are for the same position in two-dimensional coordinate It sets, then | | Rpi,G+t-pi,W||2≈0.Two groups of features such as { P are randomly selected from SURF feature pairi,G,Pi,W}I=n, mIt calculates newest Parameter T to be spliceds={ Rs,ts, wherein variable s is the number of iterations, initial value 0;Calculate di=| | Rpi,G+t-pi,W||2, root According to the threshold value d of settingth, count di≤dthSURF feature pair group number;It repeats above step and reaches set maximum value to s, benefit Optimal initial splicing parameter T is obtained to calculating with the N number of effective SURF feature foundbest
Step 3 will initially splice parameter substitution mathematical model, be based on improved ICP algorithm, solve accurate rigid body translation As a result;
Step 3.1 establishes point to relationship
(R is changed by the rigid body that preceding an iteration obtainsk-1,tk-1), establish the corresponding relationship put between point set:
In order to accelerate ICP algorithm speed, using the nearest neighbor search algorithm based on k-d tree, by giWith corresponding points Between Euclidean distanceRetain, establishes point to relationship
Step 3.2 calculates εkAnd it updates
According to the point of foundation to relationship, overlapping percentages ε is calculatedk, and update corresponding subset
According to the Euclidean distance retainedBy ascending order mode to all-pairIt is ranked up, cumulative time Point after going through sequence determines the corresponding point of minimum target functional value to position in the queue the target function value in simultaneously calculating formula Set label Ck, for calculating the current optimum superposing percentage ε of grating map to be splicedk=(Ck/Ng), and use preceding CkA point is to more New subset
Step 3.3 calculates rigid body translation result
To updated subsetNewest rigid body translation result (R is calculated using least square methodk,tk):
IfUsing above formula respectively to parameter (θ, tx,ty) seek local derviation Number, then can get three equations, and three equations of simultaneous can be obtained current newest rigid body translation result.
Step 3.4 repeats above step, until | ξkk-1| < ξ or the number of iterations k reaches the maximum times K of formulation Then stop iteration, whereinAccurate rigid body translation knot can be obtained Fruit (εk,Rk,tk)。
Step 4 is rotated accordingly, translated and is merged as a result, treating stitching image according to accurate rigid body translation, is obtained Obtain the accurate splicing result of grating map;
Splicing parameter is obtained by previous step algorithm and solves rigid body translation as a result, map G can thus be carried out Corresponding rotation and translation obtains transformed map T (G).If directly transformed map T (G) is added to map W On, it is possible that then splicing result is inevitably wrong the case where partial occlusion.Therefore, it in order to splice the integrality of map, needs Transformed map T (G) and W are merged.Before map fusion, a width is defined first for storing map fusion knot to be spliced The blank map L of fruit is determined the size of map L by map T (G) and the direct stack result of W, then selected reference point, by map W Coordinate origin align with this point, one by one traverse and determine map L in each pixel pixel value, finally can get grating map Accurate splicing result, complete the fusion of map.

Claims (6)

1. more maps based on map feature splice blending algorithm, which comprises the steps of:
Step 1, the edge pixel point for extracting grating map to be spliced, establish rigid body translation mathematical model, by map Bonding Problem It is converted into image registration minimization problem;
Step 2 is based on improved SURF algorithm, extracts feature from map to be spliced, determines optimal initial splicing parameter;
Step 3 will initially splice parameter substitution mathematical model, be based on improved ICP algorithm, solve accurate rigid body translation knot Fruit;
Step 4 is rotated accordingly, translated and is merged as a result, treating stitching image according to accurate rigid body translation, and grid are obtained The accurate splicing result of lattice map.
2. more maps according to claim 1 based on map feature splice blending algorithm, which is characterized in that in step 1, For there are overlapping region two-dimensional grid map G and W, if being with the edge pixel point set of map W in map GWithNgAnd NwRespectively indicate the element number of edge pixel point set G and W, in the map G and overlapping region map W Edge pixel point set is Gε, it is the subset of G, ε is overlapping percentages, and by calculating rigid body translation parameter T={ R, t }, R is one Two Dimensional Rotating transformation matrix, t ∈ R are two-dimension translational transformation vectors, and grating map Bonding Problem is converted into image registration problem, So that transformed, treated that point set T (G) can be matched with point set W well, such as following formula:
s.t.RTR=I2×2, Δ (R)=1
In formula, λ is control parameter, | | represent element number in set, minimum overlay percentage εminIt indicates.
3. more maps according to claim 2 based on map feature splice blending algorithm, which is characterized in that in step 2, Improved SURF algorithm pass through respectively building scale space, detect characteristic point, determine characteristic point direction, extract SURF feature to Amount, specifically:
Step 2.1, building scale space: the scale space pyramid bottom is filtered using the box that a size is 9x9, box Minimum 6 pixel step lengths of size conversion, the 2nd layer of minimum 15x15 are filtered, box filters the calculation formula of corresponding Gauss scale-value It is as follows:Wherein current box filtering size is indicated with N;
Step 2.2, detection characteristic point: for the scale space of building, candidate extreme point is detected by Hessian matrix, is found Its positions and dimensions is recorded after candidate extreme point, using Harriss algorithm to extreme point neighborhood territory pixel interpolation, finds image space With the sub-pixel precision characteristic point in scale space, the extreme point of wherein low contrast is eliminated, remaining is the position of characteristic point It sets;
Step 2.3 determines characteristic point direction: centered on characteristic point, justifying by radius work of 6 δ, the point calculated in border circular areas exists It is responded on the direction x and y for the Haar small echo of 4 δ, and obtained response results is made of Gaussian template and are added up to get this feature point Principal direction, the scale-value where wherein δ is characterized;
Step 2.4, the vector descriptor for forming SURF feature: constructing 20 δ centered on characteristic point along principal direction is side The region is uniformly divided into 16 sub-blocks by long square window, in each subregion with the Haar small echo template of 2 δ with 5x5 size is 1 fritter interval sampling, calculates response d of the test point relative to principal direction x and y-axis direction in each fritterx And dy, the response and its absolute value of 25 sampled points in each fritter are added up, 14 dimension of the subregion is formed The sub- ν of vector description=(∑ dx,∑dy,∑|dx|,∑|dy|), by the processing of the above process, each characteristic point just obtains 1 64 dimension description vectors, after feature vector is normalized, finally obtain the vector descriptor of SURF feature.
4. more maps according to claim 3 based on map feature splice blending algorithm, which is characterized in that in step 2, Obtain initial splicing parameter method particularly includes:
Firstly, randomly selecting two groups of feature such as P from SURF feature pairi,G,Pi,W}I=n, m, calculate newest parameter T to be spliceds= {Rs,ts, wherein variable s is the number of iterations, initial value 0;
Then, it calculatesAccording to the threshold value d of settingth, count di≤dthSURF feature pair group Number;
Finally, repeating to utilize the N number of effective SURF feature pair found up to reaching maximum number of iterations with above-mentioned steps, count It calculates and obtains optimal initial splicing parameter Tbest
5. more maps according to claim 1 based on map feature splice blending algorithm, which is characterized in that in step 4, Based on improved ICP algorithm, accurate rigid body translation is solved as a result, being specifically:
Step 3.1 changes (R by the rigid body that preceding an iteration obtainsk-1,tk-1), establish the corresponding relationship put between point set:
In order to accelerate ICP algorithm speed, using the nearest neighbor search algorithm based on k-dtree, by giWith corresponding pointsBetween Euclidean distanceRetain, establishes point to relationship
Step 3.2, according to the point of foundation to relationship, calculate overlapping percentages εk, and update corresponding subset
According to the Euclidean distance retainedBy ascending order mode to all-pairIt is ranked up, the traversal that adds up row Point after sequence determines that the corresponding point of minimum target functional value marks position in the queue to the target function value in simultaneously calculating formula Number Ck, for calculating the current optimum superposing percentage ε of grating map to be splicedk=(Ck/Ng), and use preceding CkA point is sub to updating Collection;
Step 3.3, to updated subsetFormula is calculated using least square method and calculates newest rigid body translation result (Rk, tk):
IfUsing above formula respectively to parameter (θ, tx,ty) partial derivative is sought, Three equations are obtained, three equations of simultaneous are up to current newest rigid body translation result;
Step 3.4 repeats step 3.1 to 3.3, until ξkk-1| < ξ or the number of iterations k reach maximum times K, obtain accurate Rigid body translation result (εk,Rk,tk), wherein
6. more maps according to claim 1 based on map feature splice blending algorithm, which is characterized in that in step 4, Before map fusion, the blank map L that a width is used to store map fusion results to be spliced is defined first, it is straight by map T (G) and W The size that stack result determines map L is connect, then selected reference point, the coordinate origin of map W is aligned with this point, is traversed one by one And determine the pixel value of each pixel in map L, it finally can get the accurate splicing result of grating map, complete melting for map It closes.
CN201811029781.1A 2018-09-05 2018-09-05 A kind of more maps splicing blending algorithm based on map feature Pending CN109285117A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109839153A (en) * 2019-01-30 2019-06-04 江苏理工学院 A kind of computer system applied to city stratification environmental monitoring and simulation
CN109978767A (en) * 2019-03-27 2019-07-05 集美大学 The ground laser SLAM drawing method based on multirobot collaboration
CN110321398A (en) * 2019-06-26 2019-10-11 浙江吉利控股集团有限公司 A kind of dead space is parked method for building up, device and the terminal of map
CN110415174A (en) * 2019-07-31 2019-11-05 达闼科技(北京)有限公司 Map amalgamation method, electronic equipment and storage medium
WO2020259361A1 (en) * 2019-06-28 2020-12-30 Oppo广东移动通信有限公司 Map update method and apparatus, and terminal and storage medium
CN112991187A (en) * 2021-04-28 2021-06-18 四川大学 Convolution twin-point network blade profile splicing system based on multiple spatial similarities
CN114581498A (en) * 2022-05-05 2022-06-03 环球数科集团有限公司 Iterative model registration system combining vector data and raster image
CN114699013A (en) * 2022-03-29 2022-07-05 深圳优地科技有限公司 Fixed-point cleaning method and device, electronic equipment and storage medium

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
唐宏伟: "基于SURF特征的多机器人栅格地图拼接方法", 《电子测量与仪器学报》 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109839153A (en) * 2019-01-30 2019-06-04 江苏理工学院 A kind of computer system applied to city stratification environmental monitoring and simulation
CN109978767A (en) * 2019-03-27 2019-07-05 集美大学 The ground laser SLAM drawing method based on multirobot collaboration
CN109978767B (en) * 2019-03-27 2023-09-15 集美大学 Laser SLAM map method based on multi-robot cooperation
CN110321398A (en) * 2019-06-26 2019-10-11 浙江吉利控股集团有限公司 A kind of dead space is parked method for building up, device and the terminal of map
WO2020259361A1 (en) * 2019-06-28 2020-12-30 Oppo广东移动通信有限公司 Map update method and apparatus, and terminal and storage medium
CN110415174A (en) * 2019-07-31 2019-11-05 达闼科技(北京)有限公司 Map amalgamation method, electronic equipment and storage medium
CN112991187A (en) * 2021-04-28 2021-06-18 四川大学 Convolution twin-point network blade profile splicing system based on multiple spatial similarities
CN114699013A (en) * 2022-03-29 2022-07-05 深圳优地科技有限公司 Fixed-point cleaning method and device, electronic equipment and storage medium
CN114581498A (en) * 2022-05-05 2022-06-03 环球数科集团有限公司 Iterative model registration system combining vector data and raster image
CN114581498B (en) * 2022-05-05 2022-07-29 环球数科集团有限公司 Iterative model registration system combining vector data and raster image

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Application publication date: 20190129