CN104655063A - High-accuracy calibration method of joint coordinate measuring machine - Google Patents

Abstract

The invention discloses a high-accuracy calibration method of a joint coordinate measuring machine, which comprises the following steps that the measuring machine acquires a plurality of pairs of taper holes in each calibration plate with different poses for many times; each pose corresponds to a group of joint angles and a measuring head coordinate; a plurality of groups of joint angle vectors and measuring head coordinates are obtained; a plurality of groups of two-point distance values between the taper holes in the calibration plates are calculated; a standard deviation formula of x, y and z coordinates of each measuring point is obtained; standard deviations of the measuring points are summed; the two-point distance value Li of each calibration plate at the measuring point i subtracts a point distance truth value Lr; standard deviations are obtained and summed; delta xyz and delta L are summed to serve as an objective function of a nonlinear quadratic programming problem; and a structure parameter error value of the joint coordinate measuring machine is obtained by a sequential quadratic programming algorithm.

Description

The high-precision calibrating method of articulated coordinate machine

Technical field

The present invention relates to coordinate measuring technology field, be specifically related to the high-precision calibrating method of six-freedom joint type coordinate measurement machine.

Background technology

Articulated coordinate machine is the three coordinate measuring machine of the nonopiate co-ordinate-type of a kind of multiple degrees of freedom, usually has 6 degree of freedom.It copies human synovial structure, is connected in series Special composition open-chain structure, thus instead of linear measure longimetry benchmark with measurement of angle benchmark by three gage beams and a gauge head by six (rotation) joints.When using measuring machine to measure, gauge head coordinate is the function of measuring machine kinematics parameters and its six joint angles.Compared with traditional orthogonal coordinate system formula three coordinate measuring machine, the advantages such as measurement range is large, convenient, flexible, precision is higher, physical construction is simple, good environmental adaptability that it has.But its structure is a kind of cascaded structure on the other hand, and error component is many, and Transmitting error cofficient is large, control errors is complicated, thus its precision is difficult to be guaranteed.At present, articulated coordinate machine is applied to the lower field of Product Reverse Engineering design equally accurate mostly, makes it apply and is subject to larger restriction.For improving the measuring accuracy of measuring machine, demarcation calibration must be carried out to it before the use, to guarantee that its measuring accuracy is within the accuracy rating of design.The error source of articulated coordinate machine has multiple, and wherein main error is by process and assembling causes geometric error, and namely measuring machine is based on the structural parameters error measuring equation.Demarcate be exactly by carrying out identification to measuring machine measurement model parameter to obtain its precision architecture parameter, calibration be then utilize obtain parameters revision measuring machine structure to obtain more accurate coordinates.

At present, the method for articulated coordinate machine structural parameters calibration has a variety of, such as based on the scaling method of three coordinate measuring machine, optical calibration method, scaling method based on plane and distance.These existing methods are all be placed on by measuring machine to be calibrated in the measurement space of more high-precision coordinate surveying instrument (as orthogonal three coordinate measuring machine, total powerstation etc.) usually.In this measurement space, have two coordinate systems, one is the conventional coordinates provided by high-precision coordinate surveying instrument, and another is machine coordinate system to be calibrated.The transformation relation of two kinds of coordinate systems need be set up during measurement by high-precision coordinate surveying instrument, namely determine the origin position of machine to be calibrated; Fixed or change the joint angles of machine to be calibrated by utility appliance, thus obtain the various spatial attitude of machine to be calibrated, for each attitude, except the gauge head coordinate of gauge head in coordinate system to be calibrated, also have the coordinate figure of gauge head in conventional coordinates; By the coordinate figure of gauge head under two kinds of coordinate systems, the error information under each attitude can be obtained, adopt corresponding computing method to obtain the error parameter of machine to be calibrated.Said method can realize the identification of structural parameters, but their realization all depends on the high-acruracy survey equipment of timing signal, cannot accomplish on-site proving; These methods use conventional numeric analytical approach (as least square method mostly simultaneously, singular value decomposition method) obtain analytic solution, this just needs through being several times as much as the repeated measurement solving number of parameters, complex operation, and these class methods require high to initial value, under initial value chooses inappropriate situation, often can only obtain local solution, affect the measuring accuracy of measuring machine.

In addition, recent years delivers some documents successively and proposes different scaling methods, but still comes with some shortcomings." research of Arm Flexible coordinate measuring machine calibration technique " (Harbin Institute of Technology's journal, 2008) adopting spherical displacer to measure ten centre ofs sphere utilizes least square method to demarcate, this method still needs three coordinate measuring machine to provide " true value ", and measure, the matching centre of sphere time introduce error large, affect precision, its method of sampling provided cannot meet the articulated coordinate machine space error regularity of distribution simultaneously, is more difficult to get optimum noninferior solution." the articulated coordinate machine parameter calibration based on laser tracker " (China Science & Technology University's journal, 2009) laser tracker is utilized to demarcate, timing signal adopts the attitude of unit clamp fixation measuring machine, measures 30 points, adopts Gauss-Newton method to ask least square solution; Owing to relating to coordinate conversion, need demarcate 31 parameters, this brings certain difficulty for solving; Meanwhile, because attitude is fixed, though use to measure and count more, but still do not meet back propagation net." mathematical modeling of anti-person joint's formula coordinate measuring machine and scaling method " (Central China University of Science and Technology's journal, 2007) timing signal still needs to use high accuracy three coordinate machine and sets up world coordinate system and ask for error, still relates to centre of sphere matching and coordinate transform; Meanwhile, although gather 30 points, demarcate and only carry out at part measurement space, unmeasured to other region." design of articulated arm coordinate measuring machine calibration system " (computer measurement and control, 2009) reversal process each structural parameters to measuring machine are adopted to carry out indirect inspection, but experimentation is complicated, need complicated clamping tool and high precision orthogonal formula coordinate measuring machine." six-freedom degree articulated flexible COMERO high precision calibration method " (patent, 2007) adopt high precision instrument and unit clamp to complete demarcation equally, demarcate attitude and fix, do not consider the duplicate measurements to single-point." Parameters Identification of A Flexible Coordinate Measuring Machine " (agricultural mechanical journal, 2007) have employed the scaling method of single-point cone nest, a cone nest is fixed on a position of measurement space, use articulated flexible COMERO to cone nest summit continuous sampling 200 point, this method does not need other exact instrument, but timing signal only considered single-point repeatability, and does not consider length measurement precision; Meanwhile, measured zone is fixing also have impact on calibration result." a kind of optimization sampling policy of portable articulated coordinate machine structural parameters calibration " adopts two ends to demarcate with the quartz pushrod of cone nest, quartz pushrod is placed on six circumferential positions that measuring machine is the center of circle, 500 groups of data are measured by a calibration, Different Plane rotating quartz rod in each position, amounts to 3000 groups of data; Although such sampling policy can meet whole measurement space, implementation process is complicated, does not consider this precision index of single-point repeatability carrying out timing signal simultaneously.

These methods are at timing signal still Shortcomings above, and as most method does not consider the measuring machine error space regularity of distribution, sampling exists the phenomenon that measuring machine attitude is single, measured zone is narrow, calibration result is only in local optimum; At timing signal for repeatability precision and the length measurement precision index of weighing measuring machine precision, only considered one, making calibration result not satisfactory when evaluating measuring machine precision; And demarcation realization depends on other high precision measuring instrument, can not on-site proving.

To sum up, for Problems existing in above-mentioned calibration technique, need a kind of easy, be easy to operate scaling method, both single-point repeatability precision and the length measurement precision of measuring machine had been taken into account, can global solution be obtained again, effectively improve Precision of Parameters Identification, and then improve the overall precision of measuring machine.

Summary of the invention

The object of the present invention is to provide a kind of articulated coordinate machine scaling method, the method timing signal can be demarcated the single-point repeatability precision of measuring machine and length measurement precision simultaneously, meet joint arm measuring machine method of evaluating performance (U.S. ASMEB89.4.22), global solution can be obtained again, effective raising Precision of Parameters Identification, and then the overall precision improving measuring machine.

The invention provides a kind of high-precision calibrating method of articulated coordinate machine, described scaling method comprises the steps:

Using six-freedom joint type coordinate measurement machine as machine to be calibrated, with the pedestal of measuring machine for initial point sets up cartesian coordinate system, with the base central of measuring machine for the center of circle, be many mean lines by whole circle circumference equal dividing, polylith scaling board is placed in described mean line respectively accordingly;

Measuring machine respectively gathers repeatedly with different attitude the multipair taper hole on each scaling board, and each attitude correspondence obtains one group of joint angles and a gauge head coordinate, so obtains many group joint angles vectors and gauge head coordinate;

According to measuring the gauge head coordinate figure obtained, calculate many groups of 2 somes distance numerical value between often pair of taper hole on each scaling board;

Described gauge head coordinate is the function of the angle vector value of corresponding attitude and the structure parameter vectors of machine to be calibrated, therefore, uses θ _i,jthe angle vector that the jth time being characterized in measuring point i is measured, A characterisation of structures parameter vector, then the gauge head coordinate that measuring point i measures in jth time is expressed as:

$\left\{\begin{array}{c}{1}_{i,j}^x=f_x({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^y=f_y({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^z=f_z({\mathrm{\θ}}_{i,j},A)\end{array}\right....\left(1\right);$

According to above measuring point equation in coordinates, the standard deviation formula of each measuring point at x, y, z coordinate can be write out:

${\mathrm{\σ}}_x={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-x_r)}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_y={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_i-y_r)}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_z={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(z_i-z_r)}^{1/2}}{n-1}\right]}^{1/2}...\left(2\right);$

Wherein x _ry _rz _rthe coordinate true value of measuring point i on x, y, z three-dimensional direction,

The standard deviation of whole m measuring point is sued for peace, namely

${\mathrm{\δ}}_{\mathrm{xyz}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}({\mathrm{\σ}}_x^i+{\mathrm{\σ}}_y^i+{\mathrm{\σ}}_z^i)...\left(3\right);$

By two the somes distance value Ls of each scaling board at measuring point i place _iwith a distance true value L _rsubtract each other, ask standard deviation and sue for peace, formula is as follows:

${\mathrm{\σ}}_L={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(L_i-L_r)}^2}{n}\right]}^{1/2},{\mathrm{\δ}}_L=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{\σ}}_L^i...\left(4\right);$

Wherein, n is the gauge head number of coordinates that each measuring point place measurement obtains, and m is measuring point quantity, δ _xyzand δ _lthe function of structure parameter vectors A, δ the most at last _xyzwith δ _lbe added the objective function as quadratic nonlinearity planning problem, that is:

$\left\{\begin{array}{c}\min {\mathrm{\δ}}_{\mathrm{xyz}}\left(A\right)+{\mathrm{\δ}}_L\left(A\right)\\ A_{\min }\≤A\≤A_{\max }\end{array}\right....\left(5\right);$

Utilize sequential quadratic programming algorithm can obtain the structural parameters error amount of articulated coordinate machine.

Preferably, for each scaling board, there are many group gauge head coordinate figures at measuring point i place, it averaged, can obtain as the coordinate true value of measuring point i;

Preferably, machine to be calibrated is placed in the measurement space of high precision measuring instrument, is demarcated the taper hole position coordinates on scaling board by high precision measuring instrument, as the coordinate true value of measuring point i.

Preferably, machine to be calibrated is the 1st, 2 grade of joint fixable change arm coordinate measuring machine, and its 1st, 2 grade of joint has locking device, for the position of fixing front two-stage gage beam.

Preferably, each scaling board is in differing heights in measurement space and different radii circumference.

Preferably, described scaling board is cylinder iron made, and its front has the taper hole of multiple different size, and each taper hole is uniformly distributed in whole scaling board plane, and described taper hole is constructed to be permeable to gauge head stabilizing base is put wherein.

Should be appreciated that description and the follow-up detailed description of aforementioned cardinal principle are exemplary illustration and explanation, should not be used as the restriction to the claimed content of the present invention.

Accompanying drawing explanation

With reference to the accompanying drawing of enclosing, the following description by embodiment of the present invention is illustrated by the more object of the present invention, function and advantage, wherein:

The to be calibrated machine schematic diagram of Fig. 1 for adopting in the specific embodiment of the invention.

Its special calibrating plate schematic diagram of Fig. 2 for adopting in the specific embodiment of the invention.

Fig. 3 is the calibration position relation schematic diagram in the specific embodiment of the invention between machine to be calibrated and its special calibrating plate.

Embodiment

Hereinafter, embodiments of the invention will be described with reference to the drawings.In the accompanying drawings, identical Reference numeral represents same or similar parts, or same or similar step.

By reference to one exemplary embodiment, object of the present invention and function and the method for realizing these objects and function will be illustrated.But the present invention is not limited to following disclosed one exemplary embodiment; Can be realized it by multi-form.The essence of instructions is only help various equivalent modifications Integrated Understanding detail of the present invention.

Be described in detail in conjunction with schematic diagram for the present invention; when describing the embodiment of the present invention in detail, for ease of illustrating, represent that the sectional view of device architecture can be disobeyed general ratio and be made partial enlargement; and described schematic diagram is example, it should not limit the scope of protection of the invention at this.In addition, the three-dimensional space of length, width and the degree of depth should be comprised in actual fabrication.

Below with reference to the accompanying drawings, the specific embodiment of the present invention is described.

Scaling method of the present invention with general six-freedom joint type coordinate measurement machine, as machine to be calibrated.

Machine to be calibrated shown in Fig. 1 is articulated flexible COMERO, has six degree of freedom.Machine to be calibrated comprises: pedestal 101, three sections of gage beams 102,103,104, joint 111,112,113,114,115,116, and gauge head 105.

On pedestal 101, six rotatable joint 111,112,113,114,115,116 Special composition open-chain structures of being connected by three sections of gage beams 101,102,103, the end of this open-chain structure is the gauge head 105 of measuring machine.Each joint 111,112,113,114,115,116 can be rotated around the axis of himself, and the angle of articulation is controlled to obtain by the high accuracy circular Grating Angle Sensor that it is installed.Due to physical construction restriction, wherein joint 111,113,115 can rotate in 0 ~ 2 π angular range, and joint 112,114,116 can rotate in the angular range of-π ~ 0.

Preferably, machine to be calibrated is joint fixable change arm coordinate measuring machine, and its joint 111,112 has locking device, gage beam 111,112 position can be made to fix by it.The measurement result precision becoming the measurement result ratio any attitude measurement acquisition of arm coordinate measuring machine when arthrodesis is high, become arm measure machine owing to can fix in joint simultaneously, corresponding different positions and pose of applying when measuring is wanted easily, not need supplemental support device.

Articulated coordinate machine similar apery mobile phone mechanical arm, but to the not requirement of measurement pose, therefore to same measurement point, any attitude can be adopted to measure, so just can be organized arbitrarily gauge head coordinate, due to the existence of error, make these gauge head coordinates can not be identical, this be referred to as the reproducibility error of measuring machine.At present, namely the accuracy standard weighing articulated coordinate machine adopts repeatability precision and length measurement precision.The present embodiment has taken into full account this feature of articulated coordinate machine, different attitude repetitive measurement is adopted to same measurement point, simultaneously in order to meeting spatial back propagation net, multiple points of diverse location are measured, and using the point between the measurement point on same scaling board apart from the basis as length measurement precision.So, the present invention considers repeatability precision and the length measurement precision of articulated coordinate machine simultaneously.

In addition, articulated coordinate machine is as a kind of serial mechanism adopting spherical coordinate system, its measurement space can be the sphere with different radii, and be nonlinear in the distribution of its error of whole measurement space, less compared with its error of zonule, but along with the extension of measurement space, its error increases gradually.Therefore carrying out timing signal, data sampling will interval from small to large, to ensure that packet contains whole audience control information, to these data acquisitions High Accuracy Parameter discrimination method, obtains the Minimum Area solution of measuring machine uncertainty, thus realizes the demarcation of measuring machine.

According to above-mentioned consideration, the invention provides a kind of exemplary calibration method, as described below.

As shown in Figure 3, with the pedestal 101 of measuring machine for initial point sets up cartesian coordinate system, with the base central of measuring machine for the center of circle, whole circle circumference is divided into 6 mean lines by 60 degree, 6 pieces of scaling boards 301,302,303,304,305,306 are placed in 6 mean lines respectively.In addition, in sampling, should cover at the coordinate range of timing signal institute sampled point the scope that coordinate machine can measure as far as possible, if six each comfortable different radiis in position, and there is respective height, calibration result is optimum, but the corresponding like this difficulty too increasing placement scaling board.Therefore, in the present embodiment, there is the layout type of difference in height, semidiameter the position taking adjacent scaling board, namely have three scaling boards 301,303 and 305 to be in sustained height and with Radius circumference 311, another three scaling boards 302,304 and 306 are in another height and another the radius circumference 312 different from last height and radius circumference.As for difference in height, also can adopt as long as meet other layout type that also can cover measurement range in z-axis direction as far as possible more than enoughly.

The scaling board used in the present invention is articulated coordinate machine its special calibrating plate, cylinder iron make, as shown in Figure 2, its front has 56 taper holes, 201,6 20 taper holes 203 and 8 10 taper holes 202, each taper hole is uniformly distributed in whole scaling board plane, can be put in wherein to measure for gauge head stabilizing base.

Here, the effect of scaling board mainly can provide a gauged distance, and the distance before demarcation on scaling board between each hole is all demarcated by more high-precision surveying instrument.And due to scaling board be cast iron manufacture, stable performance, so when demarcating onsite application, it on, each pitch-row is from constant, the true taper hole therefore demarcated on the scaling board that obtains can be used for repeatability precision and to demarcate and length measurement precision is demarcated.Another effect of scaling board can be easier to carry out sampling patters, on a scaling board present position, provides multiple taper hole that can be used as measurand.In addition because the profile design of taper hole becomes to be suitable for gauge head at same position stably measured, make coordinate machine carry out the sampling of multidigit appearance at a measuring point, meet the objective function of calibration algorithm well to the requirement of measurement data amount.

In the present embodiment, have employed 6 scaling boards, measuring machine respectively gathers 50 times to two taper holes any on each scaling board with different attitude, each pose corresponding one group of angle vector sum gauge head coordinate, then 6 scaling board positions then can obtain 600 groups of joint angles vectors and 600 gauge head coordinates, and 300 groups of distance values.

Concrete sampling process is as follows:

1, before use scaling board, on scaling board, arbitrfary point is obtained apart from being measured by high precision measuring instrument (orthogonal three-coordinate measuring machine, comparator etc.).

2, machine to be calibrated is steadily placed on platform or square chest.With machine base center to be calibrated for initial point, be oriented to x-axis, set up cartesian coordinate system with the grating encoder zero-bit in joint 111, surveyed coordinate is all under this coordinate system thereafter.

3,6 scaling boards are placed as shown in Figure 3.Be similar to when scaling board is placed and be placed in mean line.Three scaling boards 301,303 and 305 are in sustained height and with Radius circumference 311, another three scaling boards 302,304 and 306 are in another height and another the radius circumference 312 different from aforementioned height and radius circumference.

4, according to shown in Fig. 3, an optional taper hole on scaling board 301, gauge head is probeed into taper hole, gauge head ball is contacted completely with cone-shaped wall, 6 joints are rotated arbitrarily in range of motion, enable measuring machine with different attitude measurement taper hole 50 times, record the angle vector that gauge head coordinate and six joint angles thereof are formed simultaneously.It should be noted that research shows, in 6 joints of measuring machine, 1,2 pairs, the joint final Accuracy of measuring machine is maximum, therefore should Rotating with Uniform in the FROM of joint 111,112 as far as possible, to obtain the combination of more complete joint.For arm changeable type coordinate measuring machine, the locking device by joint 1,2 has been assisted.

5, after completing the measurement of a taper hole, then on scaling board 301 another taper hole optional, repeat step 4.

6, when completing sampling to scaling board 301, successively step 4,5 being repeated to scaling board 302-306, until complete whole 600 samplings, obtaining 600 groups of joint angles vectors, 600 gauge head coordinates.

After sampling, data are processed.

Concrete data handling procedure is:

1, according to measuring 600 the gauge head coordinate figures obtained, calculating 2 somes distance Li on each scaling board, 300 points can be obtained altogether apart from values.

2, there are 50 groups of gauge head coordinate figures for each measuring point i place, it is averaged, can obtain because articulated coordinate machine is generally used for relative measurement, not high to position accuracy demand, and duplicate measurements also eliminates stochastic error, therefore average coordinates value can be similar to the coordinate true value thinking measuring point i, so both can carry out self-calibration, the scene without the need to high precision measuring instrument is assisted.

3, according to the mathematical model of articulated coordinate machine, the gauge head coordinate of gauge head in articulated coordinate machine is the function of the angle vector value of corresponding attitude and the structure parameter vectors of machine to be calibrated, therefore, uses θ _i,jthe angle vector that the jth time being characterized in measuring point i is measured, A characterisation of structures parameter vector, then the gauge head coordinate that measuring point i measures in jth time is expressed as:

$\left\{\begin{array}{c}{1}_{i,j}^x=f_x({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^y=f_y({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^z=f_z({\mathrm{\θ}}_{i,j},A)\end{array}\right....\left(1\right);$

4, solve by the structural parameters error vector A of the machine to be calibrated demarcated.According to above-mentioned gauge head coordinate formula (1), 600 gauge head coordinates can obtain 1800 equations:

$\begin{array}{cc}{1}_{\mathrm{1,1}}^x=f_x({\mathrm{\θ}}_{\mathrm{1,1}},A)& \left(1\right)\\ 1_{\mathrm{1,1}}^y=f_y({\mathrm{\θ}}_{\mathrm{1,1}},A)& \left(2\right)\\ 1_{\mathrm{1,1}}^z=f_z({\mathrm{\θ}}_{\mathrm{1,1}},A)& \left(3\right)\\ 1_{\mathrm{1,2}}^x=f_x({\mathrm{\θ}}_{\mathrm{1,2}},A)& \left(4\right)\\ \·\·\·& \\ 1_{\mathrm{12,50}}^z& \left(1800\right)\end{array}...\left(2\right),$

In the system of equations that this is made up of 1800 equations, the structure parameter vectors A having machine to be calibrated only is uncertain, is also unique parameter to be calibrated.Articulated coordinate machine is according to DH establishing equation kinematics model, and therefore its structural parameters have 27, due to the length of gage beam 1 on measuring machine precision without impact, therefore the present invention only demarcates other 26 structural parameters.

A can be drawn to this solving equations.Here, be the problem avoiding traditional algorithm to be all easily absorbed in local solution, problem solving is quadratic nonlinearity planning problem by multiple goal chess game optimization question variation by the present invention.

According to above measuring point equation in coordinates, the standard deviation formula of each measuring point x, y, z coordinate can be write out

${\mathrm{\σ}}_x={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{x})}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_y={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_i-\stackrel{\‾}{y})}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_z={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(z_i-\stackrel{\‾}{z})}^{1/2}}{n-1}\right]}^{1/2}...\left(3\right);$

This standard deviation formula reflects the multiplicity error of measuring machine spot measurement.By demarcate institute survey 12 standard deviation sue for peace, namely

${\mathrm{\δ}}_{\mathrm{xyz}}=\underset{i=1}{\overset{12}{\mathrm{\Σ}}}({\mathrm{\σ}}_x^i+{\mathrm{\σ}}_y^i+{\mathrm{\σ}}_z^i)...\left(4\right);$

To be subtracted each other with some distance true value apart from value by the point of scaling board 6 positions and ask standard deviation and sue for peace, formula is as follows:

${\mathrm{\σ}}_L={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(L_i-L_r)}^2}{n}\right]}^{1/2},{\mathrm{\δ}}_L=\underset{i=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_L^i...\left(5\right);$

Wherein, n=50, L _rfor truly putting apart from value.δ _xyzand δ _lthe function of structure parameter vectors A, δ the most at last _xyzwith δ _lbe added the objective function as quadratic nonlinearity planning problem, that is:

$\left\{\begin{array}{c}\min {\mathrm{\δ}}_{\mathrm{xyz}}\left(A\right)+{\mathrm{\δ}}_L\left(A\right)\\ A_{\min }\≤A\≤A_{\max }\end{array}\right....\left(6\right);$

The system of equations that 1800 equations are formed is converted into single-objective nonlinear programming problem by this objective function, and recycling sequential quadratic programming algorithm can obtain the structural parameters error amount of articulated coordinate machine.Then according to obtained structural parameters error amount, can demarcate.

Here preferably adopt sequential quadratic programming algorithm, its result is stablized, and precision increase rate is large simultaneously, and demarcating success ratio is 100%.Concrete, after emulation is demarcated, single-point repeatability precision improves 88.9%, and linear measure longimetry precision improves 92.7%.

In above-described embodiment, to put 6 scaling boards, it is example that each scaling board respectively measures 2 points, and the present invention can also take other sampling policies, such as:

With measuring machine base central for the center of circle, being similar to differing heights by scaling board is placed in six round mean lines, measuring machine respectively gathers 50 times to two taper holes any on scaling board with different attitude, and 6 positions can obtain 600 groups of joint angles, gauge head coordinate and 300 groups of distance values.

With measuring machine base central for the center of circle, being similar to differing heights by scaling board is placed in six round mean lines, measuring machine respectively gathers 100 times to two taper holes any on scaling board with different attitude, and 6 positions can obtain 1200 groups of joint angles, gauge head coordinate and 600 groups of distance values.

With measuring machine base central for the center of circle, being divided to be similar to differing heights by scaling board is placed in six round mean lines, measuring machine respectively gathers 50 times to four taper holes any on scaling board with different attitude, and 6 positions can obtain 1200 groups of joint angles, gauge head coordinate and 1800 groups of distance values.

With measuring machine base central for the center of circle, scaling board is placed in six round mean lines so that differing heights is approximate at twice, measuring machine respectively gathers 50 times to two taper holes any on scaling board with different attitude, and 12 positions can obtain 1200 groups of joint angles, gauge head coordinate and 600 groups of distance values.

With measuring machine base central for the center of circle, scaling board is placed in six round mean lines so that differing heights is approximate at twice, measuring machine respectively gathers 100 times to two taper holes any on scaling board with different attitude, and 12 positions can obtain 2400 groups of joint angles, gauge head coordinate and 1200 groups of distance values.

With measuring machine base central for the center of circle, scaling board is placed in six round mean lines so that differing heights is approximate at twice, measuring machine respectively gathers 50 times to 4 taper holes any on scaling board with different attitude, and 12 positions can obtain 2400 groups of joint angles, gauge head coordinate and 3600 groups of distance values.

Scheme described by above embodiment is only a kind of lowest accuracy and requires sampling plan, in concrete enforcement, and can according to accuracy requirement to scaling board putting position number, sampling number, the corresponding increase of duplicate measurements number of times.But more than operation must meet scaling board and puts requirement, and namely adjacent position is in different measuring radius and there is difference in height.Because the measurement space of coordinate machine be one spherical, therefore in demarcation sampling, make calibration point be scattered in spherical as far as possible, comparatively even on measurement space like this, coverage is also large, avoids the demarcation failure caused in the sub-fraction that measurement time institute's mark fixes a point only to be distributed in measurement space because of similar demarcation in the past.

Compared with the prior art, invention increases success ratio and the precision of demarcation, its beneficial effect is embodied in:

1, in the present invention, the conic hole on the scaling board of design used is apart from providing the gauged distance demarcated, that is the distance before demarcation on scaling board between each hole is all demarcated by more high-precision surveying instrument, due to many constraints of gauged distance (namely survey the distance of certain several calibration point), make to demarcate stable, success ratio is high.Compare, if do not have gauged distance to retrain, also there will be result be local optimum result (namely only more current measurement point precision is improved, if but newly increase some and measure check posts, then precision deterioration is occurred to these new points) or to demarcate unsuccessfully.

2, sampled point of the present invention can increase as required voluntarily, because data processing method has used distance value, therefore along with sampled point increases, the corresponding increase of distance value, and data volume is beyond sample point coordinate value, a large amount of sampled datas is that high-precision calibrating provides the foundation.

3, the present invention also can when not increasing sampled point, more sampled data is obtained by increasing sampling pose, measure owing to adopting taper hole, therefore be easy to the acquisition realizing various pose data, increase the overall precision that little basis effectively ensure that machine to be calibrated in surveying work amount.

4, sampled point approaches uniformity of the present invention distributes whole measurement space, fully can extract the control information of joint measurment machine in effective measurement space, the overall precision of machine to be calibrated is guaranteed.

5, in scaling method of the present invention, instead of true value with mean value, make can not introduce high precision measuring instrument at timing signal, make on-site proving become possibility, given full play to the dirigibility of articulated coordinate machine, calibration cost obtains saving simultaneously.

6, the present invention is not when needing on-site proving, machine to be calibrated can be placed in the measurement space of high precision measuring instrument, the true value of the taper hole position coordinates on scaling board as institute's measuring point is demarcated by high precision measuring instrument, utilize this value and measured value to ask for error amount to process, effectively can improve the overall precision of machine to be calibrated.

In conjunction with the explanation of the present invention disclosed here and practice, other embodiments of the present invention are all easy to expect and understand for those skilled in the art.Illustrate and embodiment be only considered to exemplary, true scope of the present invention and purport limited by claim.

Claims (6)

1. a high-precision calibrating method for articulated coordinate machine, described scaling method comprises the steps:

Using six-freedom joint type coordinate measurement machine as machine to be calibrated, with the pedestal of measuring machine for initial point sets up cartesian coordinate system, with the base central of measuring machine for the center of circle, be many mean lines by whole circle circumference equal dividing, polylith scaling board is placed in described many mean lines respectively accordingly;

Measuring machine respectively gathers repeatedly data to each in the multipair taper hole on each scaling board with different attitude, and each attitude correspondence obtains one group of joint angles and a gauge head coordinate, so obtains the multiple gauge head coordinate of many group joint angles vector sums;

According to measuring the multiple gauge head coordinate figures obtained, calculate 2 somes distance numerical value between often pair of taper hole on each scaling board respectively;

Described gauge head coordinate is the function of the angle vector value of corresponding attitude and the structure parameter vectors of machine to be calibrated, therefore, uses θ _i,jthe angle vector that the jth time being characterized in measuring point i is measured, with A characterisation of structures parameter vector, then the gauge head coordinate that measuring point i measures in jth time is expressed as:

$\left\{\begin{array}{c}{1}_{i,j}^x=f_x({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^y=f_y({\mathrm{\θ}}_{i,j},A)\\ 1_{i,j}^z=f_z({\mathrm{\θ}}_{i,j},A)\end{array}\right....\left(1\right);$

According to above measuring point equation in coordinates, the standard deviation formula of each measuring point x, y, z coordinate can be write out:

${\mathrm{\σ}}_x={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-x_r)}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_y={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_i-y_r)}^2}{n-1}\right]}^{1/2},{\mathrm{\σ}}_z={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(z_i-z_r)}^{1/2}}{n-1}\right]}^{1/2}...\left(2\right);$

Wherein x _r, y _r, z _rthe coordinate true value of measuring point i on x, y, z three-dimensional direction,

The standard deviation of whole m measuring point is sued for peace, namely

${\mathrm{\δ}}_{\mathrm{xyz}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}({\mathrm{\σ}}_x^i+{\mathrm{\σ}}_y^i+{\mathrm{\σ}}_z^i)...\left(3\right);$

By two the somes distance value Ls of each scaling board at measuring point i place _isubtract each other with a distance true value Lr, ask standard deviation and sue for peace, formula is as follows:

${\mathrm{\σ}}_L={\left[\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(L_i-L_r)}^2}{n}\right]}^{1/2},{\mathrm{\δ}}_L=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{\σ}}_L^i...\left(4\right);$

Wherein, n is the gauge head number of coordinates that each measuring point place measurement obtains, and m is measuring point quantity,

δ the most at last _xyzwith δ _lbe added the objective function as quadratic nonlinearity planning problem, that is:

$\left\{\begin{array}{c}\min {\mathrm{\δ}}_{\mathrm{xyz}}\left(A\right)+{\mathrm{\δ}}_L\left(A\right)\\ A_{\min }\≤A\≤A_{\max }\end{array}\right....\left(5\right);$

Utilize sequential quadratic programming algorithm can obtain the structural parameters error amount of articulated coordinate machine, then according to obtained structural parameters error amount, can demarcate.

2. scaling method as claimed in claim 1, wherein for each scaling board, has many group gauge head coordinate figures, averages, can obtain it at measuring point i place as the coordinate true value x of measuring point i _r, y _r, z _r.

3. scaling method as claimed in claim 1, is wherein placed in the measurement space of high precision measuring instrument, is demarcated the taper hole position coordinates on scaling board by high precision measuring instrument, as the coordinate true value x of measuring point i by machine to be calibrated _r, y _r, z _r.

4. scaling method as claimed in claim 1, wherein machine to be calibrated is the 1st, 2 grade of joint fixable change arm coordinate measuring machine, and its 1st, 2 grade of joint has locking device, for the position of fixing front two-stage gage beam.

5. scaling method as claimed in claim 1, wherein each scaling board is in differing heights in measurement space and different radii circumference.

6. scaling method as claimed in claim 1, wherein said scaling board is cylinder iron made, and its front has the taper hole of multiple different size, and each taper hole is uniformly distributed in whole scaling board plane, and described taper hole is constructed to be permeable to gauge head stabilizing base is put wherein.