JP5029173B2 - Coating unevenness evaluation device - Google Patents

Description

  The present invention relates to a coating unevenness evaluation apparatus for accurately determining and evaluating a coating unevenness of a workpiece.

  For example, the current method for inspecting unevenness in metallic paint used in automobile bodies relies on sensory inspection by a skilled inspector. It is very difficult to distinguish the coating unevenness, and it is easy to determine the unevenness that is clearly recognized as a coating unevenness by a skilled inspector.

  If such a coating unevenness that is difficult to discriminate can be performed by an automatically processed inspection device without using a skilled inspector, it is possible to efficiently perform the coating unevenness determination on a production line of a mass-produced vehicle. .

  For example, Patent Documents 1 and 2 can be cited as conventional techniques for automatically determining coating unevenness as described above. In Patent Document 1, an image obtained by picking up a surface to be coated with a CCD camera is divided into a plurality of small areas, the average amount of light received in each area is obtained and the dispersion value is obtained, and a large area formed by collecting the small areas. An apparatus and a method for determining the maximum and minimum difference values of the average received light amount in the region and determining the coating unevenness based on these values are disclosed. On the other hand, Patent Document 2 discloses a method for calculating the intensity of a specific wavelength component in the intensity waveform of received / reflected light, and trying to identify coating unevenness based on the intensity.

JP 2005-106764 A JP-A-5-288690

  In Patent Document 1, the captured image information of the CCD camera is processed, and the results are greatly different depending on the surrounding environmental conditions (brightness, temperature, paint color, etc. in the factory). High reliability is difficult to obtain. Further, in Patent Document 2, although attention is paid to the wavelength component of unevenness, whether or not unevenness has actually occurred as described above because the analysis result of wavelength separation is finally subjected to integral calculation. It is not suitable for such delicate judgments.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a coating unevenness evaluation apparatus that can accurately determine and evaluate coating unevenness without requiring a skilled inspector.

  In order to achieve the above object, the coating unevenness evaluation apparatus according to the present invention is a coating unevenness evaluation apparatus that evaluates the coating unevenness of a workpiece, and the coating unevenness evaluation apparatus includes a light emitting unit that irradiates light onto a painted surface of a workpiece. Built in the body with wheels is a light receiving means for receiving reflected light, a calculation means for executing calculation using received light data received by the light receiving means, and a display means for displaying a calculation result by the calculation means The calculation means reads the received light data at predetermined intervals when the coating unevenness evaluation apparatus is moved a predetermined distance on the coating surface, and executes the movement of the predetermined distance a plurality of times to perform the first operation. The moving average value is obtained, the interval is changed, the coating unevenness evaluation apparatus is moved a plurality of times to obtain the second moving average value, and the interval is changed to obtain the (n−1) th and nth moving average values. The first step to seek And the difference between the nth moving average value and the (n-1) th moving average value is obtained to obtain a difference value n-1 of the moving average value, and the difference value n-2,. The second step of obtaining the standard deviations n-1 ′, n-2 ′,..., 1 ′ of the difference values of the moving average values, and arbitrarily adding two standard deviations from the standard deviations The third step is to perform the third step of taking out the non-uniformity characteristic value on the long wavelength side and the non-uniformity characteristic value on the short wavelength side, and determining the presence / absence region of the coating nonuniformity with these two types of nonuniformity characteristic values. is there.

  The coating unevenness evaluation apparatus of the present invention continuously emits light from a light emitting means composed of a light emitting element or the like to a painted surface of a work, or emits light at every minute interval in the moving direction of the apparatus, and receives reflected light from the painted surface as a light receiving element or the like. The received light is received by the light receiving means, and the received light data is stored in the apparatus, and the received light data is calculated by an appropriate calculating means to determine and evaluate the coating unevenness. This evaluation device is configured in a small handy type, and the inspector can manually run the painted surface and read the received light data at that time, which requires running with a large manipulator etc. And not.

  Here, the reading of the received light data is performed by changing the reading interval in the moving direction of the apparatus. Specifically, in the case of a total travel (movement) distance of 20 cm, a step of reading light reception data at intervals of 2 mm, a step of reading light reception data at intervals of 5 mm, and thereafter, 10 mm intervals, 15 mm intervals, 20 mm intervals, 25 mm intervals The step of reading the received light data is repeated at intervals of 30 mm, etc., and each read data is stored in the apparatus. By measuring the data interval from a short one to a long one in this way, it is possible to obtain a non-uniform long wavelength component to a short wavelength component. By separating the wavelength components by such a simple method, it is possible to eliminate the need for a large-scale apparatus and software for obtaining a superior frequency component (wavelength component) by, for example, fast Fourier transform (FFT). The purpose of decomposing into wavelength components in this way is that the wavelength component of the reflected light is on the longer wavelength side on the coating surface that can be clearly seen as coating unevenness, whereas the reflection is on the coating surface that can be identified as non-uniformity. This is because it is specified that the wavelength component of light is on the short wavelength side, and thus it is intended to determine the presence or absence of unevenness by paying attention to such characteristics.

  In addition, each reading step is repeated twice or more, and the average value thereof is taken, whereby the median value of the data with an arbitrary width interval can be specified, noise can be removed, and measurement accuracy can be improved. In this step, a moving average value for each reading interval (for example, the first moving average value when the 2 mm interval is executed twice to the nth moving average value when the 30 mm interval is executed twice) is obtained.

  Next, a difference between adjacent moving average values is obtained, and respective standard deviations are obtained. For example, in the above example, with respect to the short wavelength component, the difference between the first moving average value obtained by executing the 2 mm interval twice and the second moving average value obtained by executing the 5 mm interval twice is obtained. By obtaining the standard deviation, it is possible to identify the wavelength component that peaks in the short wavelength side band. On the other hand, in the above example, it is possible to identify the wavelength component that peaks in the long wavelength side band by obtaining the moving average in the same manner at intervals of 25 mm and 30 mm, calculating the difference, and obtaining the standard deviation.

  Next, two standard deviations are arbitrarily extracted from the obtained standard deviations, and the uneven characteristic value on the long wavelength side and the uneven characteristic value on the short wavelength side are set. For example, in the above example, the standard deviation at the intervals of 2 mm and 5 mm is selected and set to the non-uniformity characteristic value on the short wavelength side, and the standard deviation at the intervals of 25 mm and 30 mm is selected to determine the nonuniformity on the long wavelength side. Set to the characteristic value.

  Next, for example, a coordinate system is set with the vertical axis representing the non-uniformity characteristic value on the short wavelength side and the horizontal axis representing the nonuniformity characteristic value on the long wavelength side, and the actual read received light data is plotted in this coordinate system.

  Next, the boundary line of each group of the plot group evaluated as having no unevenness, the plot group being evaluated as having unevenness, and the plot group in which the presence or absence of unevenness is difficult (evaluation varies depending on the evaluator) is statistically determined. Set by discriminant analysis method. Note that the boundary lines may be set after the respective plots and the results obtained by the skilled engineer determining whether or not there is unevenness are linked and the groups are specified in the coordinates.

  By plotting the received light data in a coordinate system consisting of the above-mentioned two characteristic values, that is, the uneven characteristic value on the long wavelength side and the uneven characteristic value on the short wavelength side, and evaluating the presence or absence of unevenness in the coordinate system, high The presence or absence of unevenness can be specified with accuracy and instantaneously.

  The evaluation result can be instantaneously displayed on the display means of the apparatus comprising a liquid crystal screen or the like, and the inspector simply moves the apparatus by a predetermined distance, for example, twice at a plurality of light receiving intervals. The boundary line of each group is set by and the judgment result of the coating unevenness can be visually recognized.

  Further, in a preferred embodiment of the coating unevenness evaluation apparatus according to the present invention, the calculation means executes the first step and the second step with one moving line, and the first step with different moving lines. And up to the second step, the average value of the standard deviation corresponding to each moving line is obtained to obtain the average standard deviation. In the third step, two average standard deviations are arbitrarily selected from the average standard deviations. It is taken out and is made into the non-uniformity characteristic value on the long wavelength side and the nonuniformity characteristic value on the short wavelength side.

  Since the painted surface has a surface spread, multiple measurement lines (moving lines of the device) are set on the painted surface, the moving average is calculated for each reading interval for each moving line, and the difference is calculated. After that, the standard deviation is obtained, and the average value of the standard deviation is obtained for each corresponding reading interval to obtain the average standard deviation. By extracting two average standard deviations that determine the long wavelength side unevenness characteristic value and the short wavelength side unevenness characteristic value from this average standard deviation and setting the coordinate system, Highly accurate coating unevenness evaluation results can be obtained.

  Furthermore, in a preferred embodiment of the coating unevenness evaluation apparatus according to the present invention, the light emission from the light emitting means is executed at an angle inclined by 15 degrees from a perpendicular or normal to the painted surface of the workpiece, and the light receiving means Light reception is performed on the normal line or the normal line.

  When evaluating coating unevenness accurately, in order to receive the reflected light that has the highest reflected light intensity from the paint surface and is not specularly reflected, As a combination, light is emitted at an angle inclined by 15 degrees from a normal or normal to the painted surface of the workpiece, and light is received on the normal or normal.

  As can be understood from the above description, according to the coating unevenness evaluation apparatus of the present invention, there are two components, that is, the long wavelength side component of reflected light indicating the presence of unevenness and the short wavelength side component of reflected light indicating no unevenness. By evaluating the presence / absence of unevenness by element, it is possible to perform more accurate evaluation of coating unevenness. Further, according to the coating unevenness evaluation apparatus of the present invention, it is a handy type, its calculation algorithm is also executed by a simple method, and furthermore, the evaluation result can be visually recognized instantly, so it is suitable for application to a mass production line of automobiles. It is.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of the coating unevenness evaluation apparatus of the present invention, and FIG. 2 is a configuration diagram showing the internal configuration of the coating unevenness evaluation apparatus of the present invention. FIG. 3 is a block diagram showing the inside of the calculation means, and FIG. 4 is a flowchart of the unevenness evaluation method by the coating unevenness evaluation apparatus. FIG. 5 is a graph showing that the amplitude contraction rate of the moving average for each read data interval of reflected light is different. FIG. 6 shows the difference of the moving average for each adjacent read data interval, and the wavelength for each difference. FIG. 7 is a graph showing the peak, and FIG. 7 is a measurement data waveform for each read data interval of reflected light, and shows the amplitude of the waveform as a standard deviation. FIG. 8 is a diagram showing a coordinate system composed of long-wavelength side unevenness characteristic values and short-wavelength side unevenness characteristic values, in which unevenness areas, unevenness areas, and difficult evaluation areas are set.

  FIG. 1 is a diagram showing an embodiment of a coating unevenness evaluation apparatus. This coating unevenness evaluation apparatus 10 is formed in a compact handy type, and grips the body 1 by hand and moves it on the painted surface of the workpiece with four wheels 4 attached to the lower end of the body 1. It is. Further, a liquid crystal screen 7 is provided on the upper surface of the body 1, and an unevenness evaluation result is displayed after being moved a predetermined distance and a predetermined number of times as will be described later.

  FIG. 2 is a configuration diagram showing the internal configuration of the coating unevenness evaluation apparatus. The light receiving element 3 is disposed in the normal or perpendicular direction of the workpiece W, and the light emitting element 2 is disposed in a manner in which the light emitting direction is adjusted to an angle inclined by 15 degrees from the light receiving element 3.

  A rotary encoder 5 is mounted on one wheel 4 so that the moving distance can be measured. For example, the moving distance is set to 20 cm, and when moving 20 cm, the end of movement is displayed or the movement is stopped. Can be executed.

  FIG. 3 is a block diagram showing the inside of the calculation means. When an operation switch (not shown) is turned on, a digital command signal is transmitted from the light emitting unit 61, and a signal is transmitted to the light emitting element 2 via the D / A converter 62. On the other hand, the reflected light (analog signal) from the painted surface is transmitted to the light receiving unit 63 via the A / D converter 64, and this is sent to the calculation unit 65 for storage.

  An unevenness evaluation method using the coating unevenness evaluation apparatus, in particular, a calculation algorithm in the calculation unit 65 will be described based on the flow of FIG. The wheel rotation speed recognition sensor (rotary encoder) controls the movement of the coating unevenness evaluation device 10 on the coating surface by a predetermined distance (step S1), receives reflected light at predetermined intervals and reads the received light data ( Step S2), moving the predetermined distance a plurality of times to obtain a first moving average value, changing the interval, moving the coating unevenness evaluation device a plurality of times to obtain a second moving average value, By changing the interval, the (n-1) -th and n-th moving average values are obtained (step S3).

  Next, the difference between the n-th moving average value and the (n−1) -th moving average value, and the difference between the n−1-th moving average value and the n−2th moving average value in sequence are obtained to obtain the difference between the moving average values. The values n-1, n-2,..., 1 are obtained (step S4), and the standard deviations n-1 ′, n-2 ′,. Obtained (step S5).

  Here, in order to evaluate the unevenness with higher accuracy in consideration of the spread of the painted surface, the calculation unit 65 executes steps S1 to S5 with one moving line, and the moving lines are different. Steps S1 to S5 are executed, and the average value of the standard deviation corresponding to each moving line is obtained (step S6). The calculation results are accumulated in the calculation result storage unit 66. Note that the movement line is preferably changed about 10 times.

  Finally, two optimal average values are extracted from the average values of the standard deviations in the calculation result storage unit 66 (which standard deviation is extracted in advance by the measurer), and unevenness on the long wavelength side A coordinate system is formed as a characteristic value and a non-uniformity characteristic value on the short wavelength side, and actually read received light data is plotted in this coordinate system, a plot group evaluated as having no unevenness, a plot group being evaluated as having unevenness, The boundary line of each plot group in which the presence or absence of unevenness is difficult (evaluation varies depending on the evaluator) is set by a statistical discriminant analysis method and the presence or absence of unevenness is displayed (step S7). The above steps are executed by the CPU 67 in the calculation unit 6.

  FIG. 5 is a graph showing the moving average amplitude contraction rate at each reading interval. From the figure, it can be seen that the short wavelength component disappears as the reading interval increases.

  FIG. 6 is a graph obtained by using the moving average amplitude contraction rate of FIG. 5 to determine the difference of moving averages for each adjacent read data interval and to determine the wavelength peak for each difference. From the figure, M4 having a difference in moving average of short wavelength components has a peak around 10 mm, and M1 having a difference in moving average of long wavelength components has a peak around 50 to 70 mm. In FIG. 6, four wavelength regions are separated, and M3 and M4 can be used for the short wavelength side unevenness characteristic value, and M2 and M1 can be used for the long wavelength side unevenness characteristic value.

  FIG. 7 illustrates a measurement waveform of a moving average (weighted moving average) twice at each reading interval, and the amplitude of the waveform is represented by a standard deviation value when the average value is normalized to 1. ing.

  In the figure, the highlight is the received light data itself, and it can be seen that the wavelength becomes longer and the standard deviation value becomes smaller as the reading interval increases.

  FIG. 8 is a diagram showing a coordinate system composed of a long wavelength side unevenness characteristic value and a short wavelength side unevenness characteristic value. Each coordinate axis is represented by a numerical value obtained by multiplying the standard deviation by 1000. It is a figure in which a non-uniformity area and a difficult evaluation area are set. In the figure, the A area is an area where there is no coating unevenness, the C area is an area where there is uneven coating, and the B area is an area where it is difficult to evaluate the presence or absence of coating unevenness.

  According to the verification by the present inventors, when there is no coating unevenness, the short wavelength component of the reflected light from the coating surface is superior, and conversely, when there is coating unevenness, the long wavelength component of the reflected light is excellent. This is clearly shown in FIG.

  Note that the boundary line of each region in FIG. 8 can be set by a known discriminant analysis method in statistics.

  By evaluating the coating unevenness using a compact coating unevenness evaluation apparatus having a simple arithmetic algorithm of the present invention, it becomes possible to obtain an evaluation result with high evaluation accuracy and the presence or absence of unevenness in a short time, It is particularly suitable for application to a mass production line of vehicles.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

It is an external appearance perspective view of the coating nonuniformity evaluation apparatus of this invention. It is the block diagram which showed the internal structure of the coating nonuniformity evaluation apparatus of this invention. It is the block diagram which showed the inside of a calculating means. It is a flowchart of the nonuniformity evaluation method by a coating nonuniformity evaluation apparatus. It is the graph which showed that the amplitude shrinkage rate of the moving average for every reading data interval of reflected light was different. It is the graph which calculated | required the difference of the moving average for every adjacent reading data interval, and calculated | required the wavelength peak for every difference. FIG. 7 is a measurement data waveform for each reflected light reading data interval, in which the amplitude of the waveform is represented by a standard deviation. FIG. 7 is a diagram showing a coordinate system composed of long wavelength side unevenness characteristic values and short wavelength side unevenness characteristic values, and is a view in which unevenness areas, unevenness areas, and difficult evaluation areas are set.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Light emitting element, 3 ... Light receiving element, 4 ... Wheel, 5 ... Rotary encoder, 6 ... Calculation part (calculation means), 7 ... Liquid crystal screen (display means), 10 ... Paint unevenness evaluation apparatus

Claims (2)

A coating unevenness evaluation device that evaluates the unevenness of coating of a workpiece,
The coating unevenness evaluation apparatus includes: a light emitting unit that irradiates light on a painted surface of a workpiece; a light receiving unit that receives reflected light; a calculation unit that performs calculation using light reception data received by the light receiving unit; The display means for displaying the calculation result by the calculation means, and the body with wheels are built in,
In the calculating means, reads in the received light data of a predetermined interval of time obtained by predetermined distance at hand in a single movement lines on the painted surface coating unevenness evaluation device, a plurality of times perform the movement of a predetermined distance by the manual together with first obtains a moving average value of the time was, by changing the interval at said one mobile line is moved several times uneven paint evaluation device at said change intervals and to read received data, according to the manual The second moving average value is obtained by executing a predetermined distance of movement a plurality of times , and the interval is further changed in the one movement line, and the coating unevenness evaluation device is moved a plurality of times at the changed interval to receive light data. And a first step of obtaining the n−1th and nth moving average values by performing a plurality of manual movements of a predetermined distance a plurality of times ,
The difference between the n-th moving average value and the (n−1) -th moving average value is obtained to obtain the moving average value difference value n−1, and the difference values n−2,. a second step of determining of the standard deviation of the difference value of each moving average value,
The first step and the second step are performed for each of a plurality of moving lines by changing the moving line, and a difference value of the moving average value for each predetermined interval is obtained in each moving line, and each moving average value The standard deviation of the difference value is obtained, and two standard deviations are arbitrarily extracted from the plurality of standard deviations obtained for each moving line to obtain the long wavelength side unevenness characteristic value and the short wavelength side unevenness characteristic value. A coating unevenness evaluation apparatus that executes the third step of obtaining the presence / absence region of unevenness of coating with various types of unevenness characteristic values. Light emitted from the light emitting means is intended to be performed at an angle inclined 15 degrees from the perpendicular or normal to the coated surface of the workpiece, light receiving by said light receiving means is performed on the perpendicular line or normal, to claim 1 The coating unevenness evaluation device described.

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