CN102155887A - Method for measuring flexibility of mass centre - Google Patents

Abstract

The invention provides a method for measuring the flexibility of a mass centre, relating to a mass centre measuring method. The invention aims to provide a method for measuring the flexibility of the mass centre, which can execute measurement only by changing two different postures without needs of the adjustment of the horizontality of a measuring table, the position relation restriction on a product and the measuring table and strict horizontal and vertical postures of the product. Sphere centre coordinates of four small weighing sensor spheres are measured by using a laser tracker, and coordinates of contact points of the weighing sensors and the measuring table can be obtained by the sphere centre coordinates; a product mass centre passing straight line equation L1' under a coordinate system of the product is obtained; the product is placed on a measuring table surface in another posture to obtain a product mass centre passing straight line equation L2' under the coordinate system of the product; the straight line L1' and the straight line L2' both pass the mass centre of the product and are both positioned under the same coordinate system of the product; and an intersection point of the two straight lines is calculated to obtain product mass centre coordinates. The method of the invention has the advantages of product positioning accuracy, good measuring tooling generality and the like.

Description

Barycenter flexible measuring method

Technical field

The present invention relates to a kind of barycenter measuring method.

Background technology

The barycenter of guided missile is one of most important parameter in the guided missile mass property parameter, and these parameters have fundamental influence to the actual use of product.The degree that do not overlap of the guided missile centre of form and barycenter will directly influence attitude and its skyborne trajectory of MISSILE LAUNCHING.Therefore, set up development and the production cycle of its static parameter measurement system to accelerating this type of type product, the emission security and the operational reliability that improve product have very important significance.

Traditional barycenter measuring method mainly contains the method for waving, suspension method, balance weighing, line-of-sight course, four-point method.The time line-of-sight course or the four-point method that mainly use when general spacecraft or guided missile barycenter are measured, these two kinds of methods utilize principle of moment balance to cooperate with LOAD CELLS, mechanical frock etc., centroid position can be calculated by computer software at last.

But this kind technical method has certain limitation.At first, the required parameter of the location of product and result of calculation depends on the mechanical frock that designs, and the fine degree of mechanical frock making directly has influence on last measurement result, and is therefore very high to the technological requirement of mechanical frock.

Secondly, be subjected to the constraint of mathematics computing model, require to measure table top and must keep level, before measurement products, need the test desk level-off has been reduced the efficient of product test.The skew that can make test desk generation angle that increases along with measuring number of times so also can increase the error that product is measured.

The 3rd, when product is measured, product needed is in strict accordance with measuring under two kinds of pose states (level and vertical state), this kind method is during for the less product of volume, it is relatively easy to operate, if when needing the bigger product of measurement volumes, such as products such as big carrying compartment sections, no matter be placement product pose conversion also time of product, it is all cumbersome to operate.And certain test desk can only be measured at one or several products of fixing model, if will measure the product of other models the time, must make test desk with matching.

Summary of the invention

The purpose of this invention is to provide a kind ofly do not need to adjust test desk level, product and do not have the constraint of position relation yet with test desk, the pose of product does not need strict level and the barycenter flexible measuring method that vertically, only needs two kinds of different poses of conversion just can measure yet.

The present invention solves the problems of the technologies described above the technical scheme of taking to be:

Barycenter flexible measuring method of the present invention realizes according to following steps:

Step 1, establish the measurement coordinate system (X at laser tracker place _Survey, Y _Survey, Z _Survey) the xyz axle be α, β, γ with straight up angular separation respectively; P1, P2, P3, P4 are respectively following four LOAD CELLSs of test desk;

Utilize laser tracker to measure the sphere centre coordinate of 4 sensor beads, then the contact point coordinate (x of sensor and test desk _i, y _i, z _i) can obtain by sphere centre coordinate, the frock gravity when first weighing frock is unloaded is placed on product on the frock then, can obtain frock gravity and product gravity:

F wherein ₁'～F ₄' be frock when unloaded 4 sensors to the support force of frock, F ₁～F ₄Be respectively frock when loading product 4 sensors to the support force of test desk and product;

The support force F of step 2,4 sensors that frock is subjected to when unloaded ₁'～F ₄' and be subjected to the support force F of 4 sensors when loading product ₁～F ₄And product gravity F _ProduceRespectively along the X that measures coordinate system _Survey, Y _Survey, Z _SurveyDirection of principal axis decomposes the support force F that draws ₁'～F ₄', F ₁～F ₄With product gravity F _ProduceComponent because product is in poised state, each component is zero with respect to measuring each reference axis moment of coordinate system, utilizes the component that calculates and the coordinate (x of sensor and test desk contact point _i, y _i, z _i), can be to measuring coordinate system X _Survey, Y _Survey, Z _SurveyAxle row torque equilibrium equation obtains through arrangement:

Arrangement (2) formula can obtain straight line equation L1:

$L1:\left\{\begin{array}{c}x=f_1\left(t\right)\\ y=f_2\left(t\right)\\ z=f_3\left(t\right)\end{array}\right.---\left(3\right)$

And the L1 straight line is through the product barycenter, once more with the measurement of coordinates of laser tracker to the product key point, the foundation rule of good according to the rules product coordinate system is set up the product coordinate system then, the transition matrix T that utilize to measure coordinate system and product coordinate system with the equation of L1 from measurement coordinate system (X _Survey, Y _Survey, Z _Survey) be transformed into product coordinate system (X _Produce, Y _Produce, Z _Produce), obtain the linear equation L1 ' under the product coordinate system:

${L1}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′}\left(t\right)\\ y^{\′}={f_2}^{\′}\left(t\right)\\ z^{\′}{=f_3}^{\′}\left(t\right)\end{array}\right.---\left(4\right)$

Step 3, product is changed into another pose again and be placed on and measure on the table top, utilize above-mentioned step once to calculate the straight line L2 of second again through the product barycenter, still the foundation rule before utilizing, set up the product coordinate system, equation with straight line L2 after setting up well is transformed under the product coordinate system, obtains equation L2 ':

$L{2}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′\′}\left(t\right)\\ y^{\′}={f_2}^{\′\′}\left(t\right)\\ z^{\′}{=f_3}^{\′\′}\left(t\right)\end{array}\right.---\left(5\right)$

Step 4, straight line L1 ' and L2 ' pass through the product barycenter, and under the identical product coordinate system, therefore ask the intersection point of two straight lines to obtain the product center-of-mass coordinate.

The invention has the beneficial effects as follows:

Designing the general barycenter of a kind of flexibility measures and computational methods, this measuring method does not need test desk adjustment level, product and test desk do not have the constraint of position relation yet, the pose of product does not need strict level and vertical yet, only need two kinds of different poses of conversion just can measure, this has solved to a certain extent, and product orientation is inaccurate, large component problem such as 90 ° of difficult upsets and measurement frock versatility difference when measuring.

The method must have coordinate measuring system, and we select laser tracker to carry out the measurement of coordinates of key point.Can according to circumstances select three sensors or four sensors during measurement.

The invention effect

Because this measurement and computational methods are aimed at the measurement design of ordinary circumstance, so measurement has versatility for barycenter.The parameter that the algorithm the inside relates to is many, and Mathematical Modeling is also comparatively complicated, but realizes by computer software programming.

The flexible measuring method at be generally speaking measurement, promptly test desk is out-of-level, product and frock relativeness pose fixing and that product is placed on the test desk is fixing.Original measuring method then is at special circumstances, i.e. test desk level, and product and the pose that the frock relativeness is fixed and product is placed on the test desk are fixed.So only some parameters in the flexible algorithm need be provided with, just can finish ordinary circumstance and conversion in particular cases.So just made things convenient for measurement.

Owing to added laser tracker, make the coordinate of some key points that we can be by measurement products surface or bottom surface set up the product coordinate system, and can pass through Coordinate Conversion, the data transaction of measuring under the coordinate system is arrived under the product coordinate system.So it is unrestricted on this theoretical method for the position and the pose of product itself of product on frock.

This method has solved and has used a certain test desk can only measure a kind of restriction of type product barycenter simultaneously.Owing to do not need when measuring to 90 ° of product upsets, thus for large-scale products such as cabin section, handled easily not only, and reduced the possibility that meets accident.Therefore, the invention solves that product orientation is inaccurate, large component is difficult for 90 ° of upsets when measuring and measure problem such as frock versatility difference.

Description of drawings

Fig. 1 is a kind of principle schematic of measuring state of the present invention, and Fig. 2 is the principle schematic of another kind of measurement state of the present invention.

The specific embodiment

The specific embodiment one: as depicted in figs. 1 and 2, the detailed process of the described barycenter flexible measuring of present embodiment method is:

Because the method has versatility and generality, as shown in Figure 1, establishes the x of the measurement coordinate system at laser tracker place _Survey, y _Survey, z _SurveyAxle is α, β, γ with straight up angular separation respectively.P1, P2, P3, P4 are respectively following 4 LOAD CELLSs of test desk;

Utilize laser tracker to measure the sphere centre coordinate of 4 sensor beads, then the contact point coordinate (x of sensor and test desk _i, y _i, z _i) can obtain by sphere centre coordinate, the frock gravity when first weighing frock is unloaded is placed on product on the frock then, can obtain frock gravity and product gravity:

F wherein ₁'～F ₄' be frock when unloaded 4 sensors to the support force of frock, F ₁～F ₄Be respectively frock when loading product 4 sensors to the support force of test desk and product;

With the support force of each sensor and product gravity respectively along the x that measures coordinate system _Survey, y _Survey, z _SurveyDirection of principal axis decomposes, because product is in poised state, each component is zero with respect to measuring each reference axis moment of coordinate system, by the component that calculated just now and the coordinate figure of sensor and test desk contact point, and can be to measurement coordinate system x _Survey, y _Survey, z _SurveyAxle row torque equilibrium equation:

Arrangement (2) formula can obtain straight line equation L1:

$L1:\left\{\begin{array}{c}x=f_1\left(t\right)\\ y=f_2\left(t\right)\\ z=f_3\left(t\right)\end{array}\right.---\left(3\right)$

And the L1 straight line is through the product barycenter, once more with the measurement of coordinates of laser tracker to the product key point, the foundation rule of good according to the rules product coordinate system is set up the product coordinate system then, the transition matrix T that utilize to measure coordinate system and product coordinate system with the equation of L1 from measurement coordinate system (X _Survey, Y _Survey, Z _Survey) be transformed into product coordinate system (X _Produce, Y _Produce, Z _Produce), obtain the linear equation L1 ' under the product coordinate system:

${L1}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′}\left(t\right)\\ y^{\′}={f_2}^{\′}\left(t\right)\\ z^{\′}{=f_3}^{\′}\left(t\right)\end{array}\right.---\left(4\right)$

Product being changed into another pose is placed on the measurement table top again, utilize above-mentioned step once to calculate the straight line L2 of second again through the product barycenter, still the foundation rule before utilizing, set up the product coordinate system, equation with straight line L2 after setting up well is transformed under the product coordinate system, obtains equation L2 ';

$L{2}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′\′}\left(t\right)\\ y^{\′}={f_2}^{\′\′}\left(t\right)\\ z^{\′}{=f_3}^{\′\′}\left(t\right)\end{array}\right.---\left(5\right)$

Straight line L1 ' and L2 ' pass through the product barycenter, and under the identical product coordinate system, therefore ask the intersection point of two straight lines to obtain the product center-of-mass coordinate.In actual measurement, exist error promptly not have intersection point owing to measure by two barycenter antarafacials that may cause trying to achieve at last, can be approximately the product centroid position this moment with the mid point of two straight line common vertical line sections.

Claims (1)

1. barycenter flexible measuring method, it is characterized in that: described method realizes according to following steps:

Step 1, establish the measurement coordinate system (X at laser tracker place _Survey, Y _Survey, Z _Survey) the xyz axle be α, β, γ with straight up angular separation respectively; P1, P2, P3, P4 are respectively following four LOAD CELLSs of test desk;

Utilize laser tracker to measure the sphere centre coordinate of 4 sensor beads, then the contact point coordinate (x of sensor and test desk _i, y _i, z _i) can obtain by sphere centre coordinate, the frock gravity when first weighing frock is unloaded is placed on product on the frock then, can obtain frock gravity and product gravity:

F wherein ₁'～F ₄' be frock when unloaded 4 sensors to the support force of frock, F ₁～F ₄Be respectively frock when loading product 4 sensors to the support force of test desk and product;

The support force F of step 2,4 sensors that frock is subjected to when unloaded ₁'～F ₄' and be subjected to the support force F of 4 sensors when loading product ₁～F ₄And product gravity F _ProduceRespectively along the X that measures coordinate system _Survey, Y _Survey, Z _SurveyDirection of principal axis decomposes the support force F that draws ₁'～F ₄', F ₁～F ₄With product gravity F _ProduceComponent because product is in poised state, each component is zero with respect to measuring each reference axis moment of coordinate system, utilizes the component that calculates and the coordinate (x of sensor and test desk contact point _i, y _i, z _i), can be to measuring coordinate system X _Survey, Y _Survey, Z _SurveyAxle row torque equilibrium equation obtains through arrangement:

Arrangement (2) formula can obtain straight line equation L1:

$L1:\left\{\begin{array}{c}x=f_1\left(t\right)\\ y=f_2\left(t\right)\\ z=f_3\left(t\right)\end{array}\right.---\left(3\right)$

And the L1 straight line is through the product barycenter, once more with the measurement of coordinates of laser tracker to the product key point, the foundation rule of good according to the rules product coordinate system is set up the product coordinate system then, the transition matrix T that utilize to measure coordinate system and product coordinate system with the equation of L1 from measurement coordinate system (X _Survey, Y _Survey, Z _Survey) be transformed into product coordinate system (X _Produce, Y _Produce, Z _Produce), obtain the linear equation L1 ' under the product coordinate system:

${L1}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′}\left(t\right)\\ y^{\′}={f_2}^{\′}\left(t\right)\\ z^{\′}{=f_3}^{\′}\left(t\right)\end{array}\right.---\left(4\right)$

Step 3, product is changed into another pose again and be placed on and measure on the table top, utilize above-mentioned step once to calculate the straight line L2 of second again through the product barycenter, still the foundation rule before utilizing, set up the product coordinate system, equation with straight line L2 after setting up well is transformed under the product coordinate system, obtains equation L2 ':

$L{2}^{,}:\left\{\begin{array}{c}{x}^{\′}={f_1}^{\′\′}\left(t\right)\\ y^{\′}={f_2}^{\′\′}\left(t\right)\\ z^{\′}{=f_3}^{\′\′}\left(t\right)\end{array}\right.---\left(5\right)$

Step 4, straight line L1 ' and L2 ' pass through the product barycenter, and under the identical product coordinate system, therefore ask the intersection point of two straight lines to obtain the product center-of-mass coordinate.

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