A mass comparator eccentric load identification method and system

Abstract

The present invention discloses a method and system for identifying overload of a mass comparator, which performs identification in the following manner: normalizing the AD value of the analog-to-digital conversion output of each weighing sensor, and judging whether the normalized value is within the range of the normalized maximum output value and minimum output value of the corresponding weighing sensor; the present invention automatically identifies the placement of the weight during the weight verification process, and if the overload at the weight placement position is large, prompts the verification personnel that the overload error is large, thereby solving the problem of large overload error of the mass comparator during actual use.

Description

Technical Field

[0001] The present invention belongs to the field of mass measurement, and in particular to a method and system for identifying an eccentric load when a mass comparator is used. Background Art

[0002] A mass comparator is an important measuring instrument in mass measurement, primarily used to transfer mass values. Its primary traceability principle is to place a standard weight and a test weight on the comparator and calculate the difference between the test weight and the standard weight. By knowing the mass of the standard weight, the value of the test weight can be determined.

[0003] Mass comparators used for transferring large weight values ​​typically use a multi-load cell structure. These typically consist of three or four strain gauge load cells, and having multiple cells can introduce eccentric load errors.

[0004] Offset error can affect the accuracy of a mass comparator's weighing results. This is primarily due to factors such as the dispersed sensitivity of multi-channel load cells, the stiffness and strength of the load carrier, and internal stresses, mechanical deformation, and dimensional errors caused by the mass comparator's processing and installation. This can lead to different weighing results depending on where the weight is placed on the mass comparator, known as offset error. Since it's difficult for the test weight and the reference weight to be placed in the same position on the mass comparator during calibration, a significant offset error can lead to inaccurate calibration results, impacting traceability.

[0005] Traditional multi-sensor weighing systems typically utilize an analog junction box, where the angular difference is adjusted by adjusting the potentiometers corresponding to each load cell on the junction box. However, this approach requires extensive practical experience and repeated debugging, which is time-consuming and laborious. Furthermore, it can only address off-center load errors within a small area at the center of the mass comparator. However, in actual use, it is difficult for the calibration personnel to ensure that the test weight and the standard weight are placed in the center of the mass comparator scale. Consequently, large off-center load errors can affect the accuracy of weighing results.

[0006] Based on the above reasons, many large-mass comparators do not perform well in actual applications, have large eccentric load errors, and are difficult to meet usage requirements. Summary of the Invention

[0007] The object of the present invention is to provide a method and system for identifying eccentric loading when a mass comparator is in use, so as to solve the problem of large eccentric loading error of the mass comparator when it is actually used.

[0008] The technical solutions for achieving the purpose of the present invention are:

[0009] A method for identifying eccentric load of a mass comparator includes the following steps: identifying by:

[0010] Normalize the AD value of the analog-to-digital conversion output of each weighing sensor, and determine whether the normalized value is within the normalized maximum output value and minimum output value range of the corresponding weighing sensor;

[0011] The normalization process of the AD value of the weighing sensor output analog-to-digital conversion is as follows:

[0012]

[0013] in P i Output the AD value of analog-to-digital conversion for the i-th weighing sensor F i The normalized value of k i is the angular difference coefficient of the i-th weighing sensor; M The mass of the weight displayed after the mass comparator stabilizes;

[0014] Among them, the coefficients of the weighing sensor are obtained by solving the following super-positive definite equations by the least squares method:

[0015]

[0016] in W is the weight of the weight placed on the scale, m is the number of placements, n is the number of load cells, f ji Then it is the AD value output by the i-th weighing sensor after analog-to-digital conversion after the j-th weight is placed.

[0017] A mass comparator eccentric load identification system includes the following steps: providing an eccentric load identification module and an alarm module;

[0018] The data acquisition module is used to collect the weight mass displayed by the mass comparator after stabilization, and each weighing sensor outputs the AD value of analog-to-digital conversion;

[0019] The overload identification module identifies whether the weight is placed in the weighing area in the following manner:

[0020] Normalize the AD value of the analog-to-digital conversion output of each weighing sensor, and determine whether the normalized value is within the normalized maximum output value and minimum output value range of the corresponding weighing sensor;

[0021] The normalization process of the AD value of the weighing sensor output analog-to-digital conversion is as follows:

[0022]

[0023] in P i Output the AD value of analog-to-digital conversion for the i-th weighing sensor F i The normalized value of k i is the angular difference coefficient of the i-th weighing sensor; M The mass of the weight displayed after the mass comparator stabilizes;

[0024] Among them, the coefficients of the weighing sensor are obtained by solving the following super-positive definite equations by the least squares method:

[0025]

[0026] in W is the weight of the weight placed on the scale, m is the number of placements, n is the number of load cells, f ji Then it is the AD value output by the i-th weighing sensor after analog-to-digital conversion after the j-th weight is placed;

[0027] When it is recognized that the weight is not placed in the weighing area, the alarm module will issue an alarm prompt.

[0028] Compared with the prior art, the present invention has the following significant advantages:

[0029] The present invention provides a method for identifying eccentric loading when using a mass comparator, which automatically identifies the weight placement position during the weight verification process. If the weight placement position has a large eccentric loading, the verification personnel are prompted that the eccentric loading error is large, thereby avoiding affecting the verification result. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the sensor data fusion algorithm area delineation.

[0031] Figure 2 This is a physical picture of the mass comparator overload identification system.

[0032] Figure 3 (a) shows the weight placed normally at the center, and (b) is the corresponding displayed numerical diagram.

[0033] Figure 4 (a) shows the weight placed in a position with large eccentric load, and (b) shows the corresponding alarm prompt diagram. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] A method for identifying eccentric load of a mass comparator according to the present invention comprises the following steps:

[0036] Step 1: Area Delineation. This involves defining the weighing area of ​​the mass comparator's scale. Within this area, the eccentric load error meets the weighing requirements. Outside this area, the eccentric load error fails to meet the requirements. This step only needs to be performed when the mass comparator is first installed or after the mass comparator has been relocated.

[0037] Step 1.1: Determine the angular coefficient of each load cell. The angular coefficient of each load cell must be re-determined after the mass comparator is first installed or relocated. This patented method uses analog-to-digital conversion for each load cell and solves a set of super-positive equations to determine the angular coefficient.

[0038] First, place weights of a certain weight at different positions on the scale. Use weights of the same weight when placing weights, and try to place the weights with the center of gravity within the center of the scale. Figure 1 The dot is the center of gravity where the weights are placed each time.

[0039] Let the number of placements be m , the number of weighing sensors is n , the weight of the weight placed is W , n The coefficient of a load cell is k 1, k 2, … , k i , … , k n , f It is the output value of the load cell after analog-to-digital conversion after the weight is placed and stabilized, for example f ji Then it is the AD value output by the i-th weighing sensor after analog-to-digital conversion after the j-th weight is placed, 1≤i≤ n , 1≤j≤ m . According to each loading, the equations are:

[0040] (1)

[0041] Converted to matrix expression:

[0042] (2)

[0043] In the formula m > n ,suggestion m ≥3 n .

[0044] Then, the coefficient of each weighing sensor can be obtained by solving the super positive definite equation system (2) using the least squares method. k 1, k 2, … , k i , … , k n .

[0045] Step 1.2 Determine the weighing area.

[0046] Basic idea: Determine the weighing area based on the placement of the weights when solving the angular difference of the weighing sensor in step 1.1. The area within the weight placement range is defined as the weighing area. If it exceeds this range, it is considered that the data has a large eccentric load error.

[0047] like Figure 1 As shown, four load cells ( n= 4) Take the mass comparator as an example, that is, to determine the positions of the four points A, B, C, and D. First, the AD value matrix of the load cell analog-to-digital conversion output in equation (2) is split into equation (3):

[0048] (3)

[0049] The column values ​​in formula (2) are the AD values ​​output by the same weighing sensor when the weight is placed in different positions. Then find the maximum and minimum values ​​of each column:

[0050]

[0051] (4)

[0052] in f imax is the maximum output value of the i-th load cell when the weight is placed in different positions in step 1.1;

[0053] in f imin is the minimum output value of the i-th load cell when the weight is placed in different positions in step 1.1;

[0054] According to formula (4), we can get Figure 1 in f 1max , f 1min , f 2max , f 2min , f 3max , f 3min ,f 4max , f 4min When the weight is placed at point A in step 1.1, it is closest to load cell 1 and farthest from load cell 3. Therefore, load cell 1 outputs the maximum value and load cell 3 outputs the minimum value. f 1max and f 3min Similarly, when the weight is placed at point B in step 1.1, we can get f 2max and f 4min ; At point C f 3max and f 1min ; At D o'clock f 4max and f 2min Therefore, the weighing area (the area formed by ABCD in the figure) can be determined according to the output extreme value of the weighing sensor.

[0055] Then the maximum output value and the minimum output value of the weighing sensor are normalized.

[0056]

[0057] (5)

[0058] in p imax for f imax Normalized value;

[0059] in p imin for f imin Normalized value;

[0060] according to p imax and p imin The normalized maximum and minimum values ​​of the i-th load cell can be determined. When placing weights in normal use, if the normalized value of the i-th load cell is P i satisfy , it means that there is no overload. If it exceeds this range, it means that a large overload has occurred and an alarm is required.

[0061] Step 2: Identify eccentric loads

[0062] Depend on Figure 1 It can be seen that when the weight is placed in the weighing area, the normalized value of each weighing sensor should be greater than the normalized minimum value calculated in step 1.2 and less than the normalized maximum value.

[0063] When the mass comparator is in use, the weight is placed on the mass comparator scale. After the mass comparator stabilizes, the weight is displayed as M After the mass comparator is stable, the AD value of each weighing sensor output analog-to-digital conversion is ( F 1, F 2, … , F i , … F n ). Then the output value of each weighing sensor is normalized:

[0064] (6)

[0065] According to formula (6), we can get Figure 1 in P 1, P 2, P 3. P 4.

[0066] judge P i Is the value in [ p imin , p imax ], if p imin ≤ P i ≤ p imax , the weight is considered to be placed in the weighing area; if P i < p imin or P i > p imax It is considered that the weight is placed beyond the designated weighing area, which is likely to cause a large eccentric load error. The instrument will issue an alarm to complete the entire eccentric load identification process.

[0067] Based on the above-mentioned method, the present invention provides a mass comparator overload identification system. The identification system includes a data acquisition module, an overload identification module, and an alarm module. The data acquisition module is used to collect the weight mass displayed by the mass comparator after stabilization, and each weighing sensor outputs the analog-to-digital conversion AD value. The overload identification module uses the algorithm in step 2 above to determine whether the weight is placed within the weighing area. The details will not be repeated here. If the alarm module determines that the weight is not placed within the weighing area, it will issue an alarm.

[0068] Example 1

[0069] In order to verify the feasibility of the algorithm, a self-developed large-mass comparator is used as a test platform. The hardware diagram of the large-mass comparator is as follows: Figure 2 As shown in the figure, the large mass comparator adopts a four-load cell structure.

[0070] First determine the angular difference coefficient of each weighing sensor, using 1 t The weights are placed at different positions on the scale, namely ( W =1 t ). Number of placements m =15, number of weighing sensors n = 4. The AD values ​​output at each position are shown in the following table.

[0071]

[0072] Based on the above data, the angular difference coefficients of each weighing sensor are obtained by solving the super positive definite equation group according to formula 2.

[0073] k 1=0.14193005859

[0074] k 2=0.13988704979

[0075] k 3=0.13975673913

[0076] k 4=0.13981688022

[0077] According to formula 4, we can get:

[0078] f 1max =1862127, f 1min =1313566

[0079] f 2max =2263848, f 2min=1654663

[0080] f 3max =1870659, f 3min =1348181

[0081] f 4max =2309755, f 4min =1471109

[0082] Then according to formula 5:

[0083] p 1max =0.264291793, p 1min =0.186434993

[0084] p 2max =0.316683024, p 2min =0.231465925

[0085] p 3max =0.261437207, p 3min =0.188417380

[0086] p 4max =0.322942734, p 4min =0.205685871

[0087] When the mass comparator is in use, after the weights are loaded and the displayed value is stable, M By using formula (6), we can find P 1, P 2, P 3. P 4. By judgment , , , It can be determined whether overloading occurs.

[0088] The algorithm was used to verify the eccentricity detection of the mass comparator using a 1-ton weight placed at different positions. Figures 3 and 4 show that the weight is normally placed at the center. Figure 3 (a) shows the weight displayed when the weight is normally placed at the center. Figure 3 (b) shows the normal value when the weight is normally placed at the center. Figure 4 (a) shows the weight placed at a position with a large eccentricity. Figure 4 (b) shows the instrument alarm when the eccentricity is large.

Claims

1. A method for identifying eccentric load of a mass comparator, characterized in that: The following steps are involved: Identification is done by: Normalize the AD value of each load cell output analog-to-digital conversion and determine whether the normalized value is within the normalized maximum and minimum output values ​​of the corresponding load cell. This can be obtained by: where p imax f imax The maximum output value after normalization; p imin f imin The minimum output value after normalization; f imax is the maximum output value of the i-th weighing sensor when the weight is placed in different positions, f imin is the minimum output value of the i-th load cell when the weight is placed in different positions; The normalization process of the AD value of the weighing sensor output analog-to-digital conversion is as follows: Among them, P i The AD value F of the analog-to-digital conversion output of the i-th weighing sensor i The normalized value of k i is the angular difference coefficient of the i-th weighing sensor; M is the weight mass displayed by the mass comparator after stabilization; Among them, the coefficients of the weighing sensor are obtained by solving the following super-positive definite equations by the least squares method: Where W is the weight of the weight placed on the platform, m is the number of placements, n is the number of weighing sensors, and f ji Then it is the AD value output by the i-th weighing sensor after analog-to-digital conversion after the j-th weight is placed; Judgment P i Is the value of [p imin ,p imax ], if p imin ≤P i ≤p imax , the weight is considered to be placed in the weighing area; if P i <p imin or P i >p imax It is considered that the weight is placed beyond the designated weighing area, and the overload identification is completed.

2. The mass comparator eccentric load identification method according to claim 1, characterized in that: in 。 3. The mass comparator eccentric load identification method according to claim 2, characterized in that: It is used to determine the weighing area, and the maximum normalized value and the minimum normalized value output by the weighing sensor when determining the angular difference coefficient of each weighing sensor are used as the boundaries of the weighing area.

4. A mass comparator eccentric load identification system, characterized in that: Equipped with data acquisition module, eccentric load identification module and alarm module; The data acquisition module is used to collect the weight mass displayed by the mass comparator after stabilization, and each weighing sensor outputs the AD value of analog-to-digital conversion; The overload identification module identifies whether the weight is placed in the weighing area in the following manner: Normalize the AD value of each load cell output analog-to-digital conversion and determine whether the normalized value is within the normalized maximum and minimum output values ​​of the corresponding load cell. This can be obtained by: where p imax f imax The maximum output value after normalization; p imin f imin The minimum output value after normalization; f imax is the maximum output value of the i-th weighing sensor when the weight is placed in different positions, f imin is the minimum output value of the i-th load cell when the weight is placed in different positions; The normalization process of the AD value of the weighing sensor output analog-to-digital conversion is as follows: Among them, P i The AD value F of the analog-to-digital conversion output of the i-th weighing sensor i The normalized value of k i is the angular difference coefficient of the i-th weighing sensor; M is the weight mass displayed by the mass comparator after stabilization; Among them, the coefficients of the weighing sensor are obtained by solving the following super-positive definite equations by the least squares method: Where W is the weight of the weight placed on the platform, m is the number of placements, n is the number of weighing sensors, and f ji Then it is the AD value output by the i-th weighing sensor after analog-to-digital conversion after the j-th weight is placed; Judgment P i Is the value of [p imin ,p imax ], if p imin ≤P i ≤p imax , the weight is considered to be placed in the weighing area; if P i <p imin or P i >p imax If the weight is placed beyond the designated weighing area, the overload identification is completed; When it is recognized that the weight is not placed in the weighing area, the alarm module will issue an alarm prompt.

Images