A creep state identification and compensation method for high-precision weighing sensor

Abstract

The present invention relates to the technical field of weighing sensors, and in particular to a method for identifying and compensating a creep state of a high-precision weighing sensor, comprising the following steps: the high-precision weighing sensor is powered on and the generated voltage is continuously transmitted to a voltage amplification module, the voltage amplification module transmits the voltage to an AD module after amplification, and the AD module converts the voltage into a digital quantity and transmits it to a microprocessor; the microprocessor calculates the rate of change of the voltage change rate and then determines whether it is within a fixed threshold range close to zero. If it is within a fixed threshold range close to zero, the high-precision weighing sensor is judged to be in a creep state. If it is not within a fixed threshold range close to zero, the difference is compensated on the voltage value measured this time and converted into a real pressure value and displayed on a display screen of the high-precision weighing sensor. The method provided by the present invention avoids the situation where a small load is added to a high-precision sensor and it is judged as creep, and increases the universality and accuracy of judging the creep state.

Description

Technical Field

[0001] The present invention relates to the technical field of weighing sensors, and in particular to a creep state identification and compensation method for a high-precision weighing sensor. Background Art

[0002] In a measurement system, the measuring range of a weighing sensor can be equally divided into multiple minimum divisions that the sensor can accurately measure. At the same time, according to the comprehensive performance of the sensor, the weighing sensor can be divided into four accuracy levels: A, B, C, and D. Among them, the high-precision weighing sensor is a Class A weighing sensor with a high accuracy level and a high maximum verification division value. It has the advantages of high accuracy and high sensitivity. Creep is an important indicator for detecting the performance of a weighing sensor. It describes the phenomenon that the strain of a solid material gradually increases over time while keeping the stress constant. For a high-precision weighing sensor, the error caused by its creep error will also be greater. Therefore, the requirements for creep compensation of a high-precision weighing sensor will be higher, and the effect of its hardware compensation method will not be very significant. It is very difficult to distinguish between creep state and non-creep state for digital creep compensation, which makes creep compensation of high-precision sensors extremely difficult. The existing fuzzy compensation method for creep error determines whether it is a non-creep section or a creep section through the maximum membership principle in fuzzy identification. However, the membership function in this method is obtained based on a random sampling survey within the industry. Since the sample may not fully represent the entire industry, there may be sampling deviations, resulting in inaccurate results. When a small load is added to the sensor, it will be judged as a creep state. For creep compensation of high-precision weighing sensors, the accuracy requirements for creep state judgment will be higher. If the creep state judgment is wrong, it will have a greater impact on the measurement accuracy of the high-precision weighing sensor.

[0003] At present, there are other compensation methods for creep compensation of high-precision sensors, such as hardware compensation and compensation by establishing mathematical models. For hardware compensation, the manufacturing process of the strain gauge on the sensor is very high and hardware compensation can only be applied to creep compensation at room temperature, and the compensation effect is not ideal for low and high temperatures. Compensation by establishing mathematical models requires connecting to a computer, which is costly and not real-time and extensive. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for identifying and compensating the creep state of a high-precision weighing sensor, which can accurately determine whether the high-precision weighing sensor is in a creep state, and then compensate the measurement value of the high-precision weighing sensor, thereby avoiding the situation where a small load is added to the high-precision sensor and it will be judged as creep, thereby increasing the universality and accuracy of judging the creep state.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for identifying and compensating creep state of a high-precision weighing sensor comprises the following steps:

[0007] S1: The high-precision weighing sensor is powered on and continuously transmits the voltage generated by the strain gauge to the voltage amplifier module. The voltage amplifier module amplifies the voltage and transmits it to the AD module. The AD module converts the voltage analog quantity into digital quantity and transmits it to the microprocessor.

[0008] S2: The microprocessor records the received voltage information and calculates the voltage change rate, and then further calculates the change rate of the voltage change rate;

[0009] S3: The microprocessor determines whether the rate of change of the voltage change rate is within a fixed threshold range close to zero. If the rate of change of the voltage change rate is within the fixed threshold range close to zero, the high-precision weighing sensor is determined to be in a creep state, and the process returns to step S1 to continue testing until the rate of change of the voltage change rate is no longer within the fixed threshold range close to zero. The high-precision weighing sensor is determined to be in a non-creep state and the process proceeds to the next step.

[0010] S4: The microprocessor takes the difference between the voltage value measured last time and the voltage value measured for the first time as the completed creep value and subtracts it from the voltage value measured this time to obtain the real voltage value of this measurement, and then converts the real voltage value of this measurement into a real pressure value and displays it on the high-precision weighing sensor display screen.

[0011] Further, in step S2, the voltage change rate is calculated according to formula (1), and the change rate of the voltage change rate is calculated according to formula (2):

[0012] (1);

[0013] (2);

[0014] in: is the serial number of the test times, is the serial number of the voltage change rate, is the serial number of the rate of change of voltage change rate, The microprocessor receives the Voltage value, For the The voltage change rate, For the The rate of change of voltage change rate.

[0015] The optimized fixed threshold range close to zero in step S3 is .

[0016] Furthermore, in step S4, the actual voltage value measured this time is calculated according to formula (3):

[0017] (3);

[0018] in: is the actual voltage value measured this time, The microprocessor receives the Voltage value, is the voltage value measured for the first time.

[0019] Beneficial effects of the invention:

[0020] The present invention determines whether the rate of change of the voltage change rate is within a fixed threshold range close to zero by calculating the rate of change of the voltage change rate of the high-precision weighing sensor, thereby determining the creep state. There is no need to set different thresholds or functions in advance according to different types of high-precision weighing sensors. The present invention can accurately determine whether the high-precision weighing sensor is in a creep state, and then compensate for the measured value of the high-precision weighing sensor, thereby avoiding the situation where a small load is added to the high-precision sensor and the sensor is judged as creep, thereby increasing the universality and accuracy of judging the creep state. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention.

[0022] Figure 2 It is a schematic diagram of the system of the present invention.

[0023] Figure 3 It is a schematic diagram of the voltage variation curve of the present invention.

[0024] In the figure: 1. Strain gauge, 2. Voltage amplifier module, 3. AD module, 4. Microprocessor, 5. High-precision weighing sensor display screen. DETAILED DESCRIPTION

[0025] A method for recognizing and compensating creep state of a high-precision weighing sensor, the flow chart is as follows Figure 1 As shown in the system diagram Figure 2 As shown, the specific steps include:

[0026] S1: The high-precision weighing sensor is powered on and continuously transmits the voltage generated by the strain gauge 1 to the voltage amplifier module 2. The voltage amplifier module amplifies the voltage and transmits it to the AD module 3. The AD module converts the voltage analog quantity into a digital quantity and transmits it to the microprocessor 4.

[0027] The bridge circuit in the strain gauge of the high-precision weighing sensor has a voltage generated due to the change in load, which causes the resistance change to destroy the balance of the bridge. The generated voltage has a certain relationship with the pressure on the high-precision weighing sensor. The generated voltage can be amplified by the voltage amplifier module and then converted into a digital value through the AD module, and then transmitted to the microprocessor. The microprocessor converts the voltage value into a pressure value based on the relationship between the generated voltage and the pressure on the high-precision weighing sensor and displays it on the high-precision weighing sensor display.

[0028] S2: The microprocessor records the received voltage information and calculates the voltage change rate, and then further calculates the change rate of the voltage change rate;

[0029] S3: The microprocessor determines whether the rate of change of the voltage change rate is within a fixed threshold range close to zero. If the rate of change of the voltage change rate is within the fixed threshold range close to zero, the high-precision weighing sensor is determined to be in a creep state, and the process returns to step S1 to continue testing until the rate of change of the voltage change rate is no longer within the fixed threshold range close to zero. The high-precision weighing sensor is determined to be in a non-creep state and the process proceeds to the next step.

[0030] S4: The microprocessor takes the difference between the voltage value measured last time and the voltage value measured for the first time as the completed creep value and subtracts it from the voltage value measured this time to obtain the real voltage value of this measurement, and then converts the real voltage value of this measurement into a real pressure value and displays it on the high-precision weighing sensor display screen 5.

[0031] The present invention provides a method for recognizing and compensating the creep state of a high-precision weighing sensor, which abandons the traditional method of setting different thresholds or functions in advance according to the types of different weighing sensors, and then calculating the compensation value for compensation. The present invention first judges the creep state each time it detects, and when judging the creep state, it directly judges whether the high-precision weighing sensor is in a creep state based on whether the rate of change of the voltage change rate is within a fixed threshold range infinitely close to zero, until the high-precision weighing sensor is in a non-creep state, the compensation value is calculated, and then the measured value of the non-creep state is compensated. It does not need to set different thresholds or functions in advance according to the type of each weighing sensor, avoids the situation where a small load is added to the high-precision sensor and it will be judged as creep, increases the universality and accuracy of judging the creep state, ensures the accuracy of the final measurement result of the high-precision weighing sensor, and is applicable to various weighing sensors.

[0032] Further, in step S2, the voltage change rate is calculated according to formula (1), and the change rate of the voltage change rate is calculated according to formula (2):

[0033] (1);

[0034] (2);

[0035] in: is the serial number of the test times, is the serial number of the voltage change rate, is the serial number of the rate of change of voltage change rate, The microprocessor receives the Voltage value, For the The voltage change rate, For the The rate of change of voltage change rate.

[0036] By using the above method to calculate the rate of change of the voltage change rate, and then judging whether it is infinitely close to zero, it is possible to judge whether the high-precision weighing sensor is in a creep state. Compared with the traditional method of setting different thresholds or functions in advance according to the types of different weighing sensors, and then calculating the compensation value for compensation, this method is simpler, more practical, and more applicable. It can be applied to various types of weighing sensors, especially high-precision weighing sensors.

[0037] The optimized fixed threshold range close to zero in step S3 is .

[0038] Furthermore, in step S4, the actual voltage value measured this time is calculated according to formula (3):

[0039] (3);

[0040] in: is the actual voltage value measured this time, The microprocessor receives the Voltage value, is the voltage value measured for the first time.

[0041] By compensating the measured values ​​in the above manner, the influence of creep can be eliminated and the situation where a small load is added to a high-precision weighing sensor and the sensor is judged as creep can be avoided. This not only increases the universality and accuracy of judging the creep state, but also makes the measured values ​​more accurate and applicable to high-precision sensors.

[0042] The specific verification method is as follows:

[0043] Set up a scenario where a weighing sensor is used to detect a heavy object, and the detection time interval is set to 0.01 seconds.

[0044] First apply = 100 kg weight, the weighing sensor display will display the change of pressure value in real time until the pressure tends to be constant, that is, the voltage change curve is finally horizontal, and in the microprocessor part, a voltage value change curve will be obtained.

[0045] On this basis, continue to apply =50 kg of weight, at this time the load cell will continue to increase its output voltage analog value due to the increase of weight, thus generating a new voltage change curve based on the previous one.

[0046] At this point, the weights applied in the first two times are larger, so it is clear which section of the voltage change curve is caused by creep. The first method uses the value of the voltage change rate to make the judgment, and the other method uses the rate of change of the voltage change rate to make the judgment.

[0047] The first method sets the voltage change rate threshold as The second method sets the voltage change rate to the threshold value. After the first two loads were applied, both methods could accurately determine the cause of the voltage change.

[0048] Then the third loading is performed, and the weight of the added weight is = 1 kg, for load cells that can detect loads of 100 kg or more, will be greater than of order of magnitude, assuming exist of magnitude, exist of the order of magnitude, or even less than When a 1 kg weight is added, although there is also a 10 N pressure, it can be regarded as a small load compared to the 1500 N pressure previously applied, and its voltage change curve is slower than the curves of the previous two times. The change rate of the load voltage applied for the third time is less than At this time, it will be mistakenly judged that the change in voltage value is caused by creep.

[0049] We use the second judgment method. Even if the rate of change of the voltage value is close to the rate of change of the voltage value caused by creep after adding a 100 kg weight, the rate of change of the voltage value between two adjacent time intervals after the load is applied will be at least 2 times the rate of change of the original voltage value. Here, compared with the change in the rate of change of the voltage value caused by the creep of the sensor itself, the change in the voltage value caused by the small change caused by the load can also be considered as an instantaneous change in the Δt time interval, so the rate of change of the voltage change is greater than , so that it can be accurately determined whether the voltage change is caused by creep.

[0050] The above steps are for the analysis of loading of a weighing sensor. The following is an example analysis of weighing sensors with different ranges:

[0051] Three sensors with different measuring ranges are used, namely, 10 tons, 100 kg and 10 grams. The difference between the first two is 100 times, and the difference between the latter two is Use these three weighing sensors to measure the corresponding weights. =9 tons, =99 kg, = 9 grams. After the value on the display stabilizes, add a weight of one thousandth of its range to each of the three weighing sensors. At this time, if the rate of change of the voltage value is used to determine whether it is in a creep state, it will lead to misjudgment due to the different ranges and voltage change rate thresholds of different sensors. For example, after weighing with a 10-ton weighing sensor, After adding a 10 kg weight, the voltage change rate threshold of the 10-ton weighing sensor is ,The voltage change rate threshold of the 100 kg sensor is , if you use To judge, the voltage change at this time is non-creep. Judgment is creep.

[0052] We use the rate of change of the rate of change to judge. No matter how large the range is, the threshold of the rate of change of the rate of change is , because as long as it is a loading process, relative to creep, it is considered as a transient change, just as Figure 3 As shown in the figure: Indicates loading =The voltage change curve caused by a weight of 100 kg, Indicates loading =The voltage change curve caused by a weight of 50 kg, Indicates loading = The voltage change curve caused by the creep state of a 100 kg weight, Indicates loading = The voltage change curve caused by the creep state of a 50 kg weight. The circled C1 part indicates the load =100 kg weight creep voltage change, we can see that the rate of change of the curve and the rate of change of the rate of change are close to 0, and the circle marked C2 indicates the loading =1 kg of weight, even if the rate of change is very close to the creep state, the rate of change of the rate of change will have a dramatic increase process, and may even reach a change of 100 orders of magnitude. That is, when a tiny weight is added in this section, the rate of change of voltage is very small, while the rate of change of the rate of change will increase exponentially during the period of adding the weight, so it is easy to judge whether the voltage change is caused by creep.

[0053] Through the above example, we can judge whether the sensor is in a creep state by judging the rate of change of the voltage value, which is more accurate. And for sensors with different ranges, the same voltage change rate threshold can be set for judgment. Compared with the traditional judgment method using the voltage change rate threshold, the applicable range of the threshold is greatly expanded, the workload of sensor factory calibration is reduced, and the adjustment difference of the threshold of different sensor models is reduced. This will improve efficiency, save costs, and save the steps of setting different thresholds.

[0054] When a small load is added to the strain gauge load cell, if only the voltage change rate is used to determine whether it is in a creep state, it is very likely to incorrectly determine whether the current sensor is caused by the load or creep.

[0055] When measuring voltage values, the time interval used is very small. When the rate of change is derived again, the value will increase by the square of the decimal point of time, thereby amplifying the unrecognizable value to a clearly recognizable range, and then it is easy to distinguish whether the value is caused by the load or the creep of the sensor.

[0056] When weighing objects with high-precision weighing sensors, no matter whether the rate of change or the rate of change of the rate of change is used to judge, there will be a value to define whether the value change of the sensor is caused by creep or by the applied weight. According to the creep characteristics of the sensor, when a small load is added, for a high-precision sensor, the rate of change of its voltage value may still be within the limit of the creep state, and it will be mistakenly judged as a creep state. The rate of change of its voltage change rate reflects the change of the slope of the voltage value change curve within two extremely short time intervals. Therefore, when a small load is applied, the rate of change of the voltage value change rate within a relatively short time interval will exceed the defined value.

[0057] The reason for the above explanation is that the creep of the sensor is caused by the slow deformation of the material under constant stress, so the change in the voltage value is also slow. Therefore, the method proposed in this patent shows that the rate of change of the voltage value in the creep state will be within a range close to zero, that is, within the range of the boundary value given by us.

[0058] In summary, the present invention provides a method for identifying and compensating the creep state of a high-precision weighing sensor, which avoids the situation where a small load applied to a high-precision sensor will be judged as creep, increases the universality and accuracy of judging the creep state, ensures the accuracy of the final measurement results of the high-precision weighing sensor, and is applicable to various weighing sensors.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for identifying and compensating creep state of a high-precision weighing sensor, characterized in that: The steps include: S1: The high-precision weighing sensor is powered on and continuously transmits the voltage generated by the strain gauge to the voltage amplifier module. The voltage amplifier module amplifies the voltage and transmits it to the AD module. The AD module converts the voltage analog quantity into digital quantity and transmits it to the microprocessor. S2: The microprocessor records the received voltage information, calculates the voltage change rate according to formula (1), and then further calculates the change rate of the voltage change rate according to formula (2): （1）； （2）； in: is the serial number of the test times, is the serial number of the voltage change rate, is the serial number of the rate of change of voltage change rate, The microprocessor receives the Voltage value, For the The voltage change rate, For the The rate of change of the voltage change rate; S3: The microprocessor determines whether the rate of change of the voltage change rate is within a fixed threshold range close to zero. If the rate of change of the voltage change rate is within the fixed threshold range close to zero, the high-precision weighing sensor is determined to be in a creep state, and the process returns to step S1 to continue testing until the rate of change of the voltage change rate is no longer within the fixed threshold range close to zero. The high-precision weighing sensor is determined to be in a non-creep state and the process proceeds to the next step. S4: The microprocessor takes the difference between the voltage value measured last time and the voltage value measured for the first time as the completed creep value and subtracts it from the voltage value measured this time to obtain the real voltage value of this measurement, and then converts the real voltage value of this measurement into a real pressure value and displays it on the high-precision weighing sensor display screen.

2. A method for identifying and compensating creep state of a high-precision weighing sensor according to claim 1, characterized in that: The fixed threshold value close to zero in step S3 is .

3. A method for identifying and compensating creep state of a high-precision weighing sensor according to claim 1, characterized in that: In step S4, the actual voltage value measured this time is calculated according to formula (3): （3）； in: is the actual voltage value measured this time, The microprocessor receives the Voltage value, is the voltage value measured for the first time.

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