阅读说明：本技术 一种基于次级电流检测的电阻焊质量监控方法 (Resistance welding quality monitoring method based on secondary current detection ) 是由 李维维 于 2021-08-16 设计创作，主要内容包括：本发明提供了一种基于次级电流检测的电阻焊质量监控方法,包括以下步骤：步骤S01：通过采样系统采集焊接时间T和焊接过程中的电流值数组I-(N)；步骤S02：通过计算在焊接时间T内电流的均方根值,得到电流的有效值I,步骤S03：计算在焊接过程中的热量等效值W,W=W=I～(2)*R*T；步骤S04：将I值或W值和设置的上下限阈值对比,如果超出范围则发出警报。本发明针对不同电流特性的电阻焊接设备,拥有广泛的自适应性,同时采用嵌入式采集,用软件算法替代传统的电流测试仪的复杂电路,有效降低了成本,使得电阻焊接大规模使用第三方电流热量监控成为可能,并且采用对于不同特性电流的自适应算法使得用户不需要对采集层面的参数做任何设置。(The invention provides a resistance welding quality monitoring method based on secondary current detection, which comprises the following steps of: step S01: collecting welding time T and current value array I in welding process through sampling system N (ii) a Step S02: obtaining an effective value I of the current by calculating the root mean square value of the current during the welding time T, step S03: calculating a heat equivalent value W, W = W = I during welding 2 R T; step S04: and comparing the I value or the W value with the set upper and lower limit threshold values, and giving an alarm if the I value or the W value is out of the range. The resistance welding device has wide adaptivity aiming at resistance welding devices with different current characteristics, simultaneously adopts embedded acquisition, replaces a complex circuit of a traditional current tester with a software algorithm, effectively reduces the cost, enables the resistance welding to use third-party current heat monitoring on a large scale, and enables a user not to refer to the acquisition level by adopting the adaptive algorithm for the current with different characteristicsThe number is set arbitrarily.)

1. A resistance welding quality monitoring method based on secondary current detection comprises the following steps: step S01: acquisition by a sampling systemWelding time T and current value array I in welding process_N(ii) a Step S02: obtaining an effective value I of the current by calculating the root mean square value of the current during the welding time T, step S03: calculating a heat equivalent value W, W = I during welding²R T; step S04: and comparing the I value or the W value with the set upper and lower limit threshold values, and giving an alarm if the I value or the W value is out of the range.

2. The method of claim 1, wherein: in step S01, measured current data is acquired by the rogowski coil, and welding time data is acquired by the timer.

3. The method of claim 2, wherein: the counting length of the timer is 32-bit word length.

4. The method of claim 1, wherein: the sampling system is an embedded CPU and parallel AD sampling system.

5. The method of claim 2, wherein: the Rogowski coil has consistency through impedance matching.

6. The method of any one of claims 1 to 5, wherein: in step S01, a plurality of sets of output data of the rogowski coil are collected in parallel within the collection time to perform a filtering algorithm, the filtering algorithm removes the maximum value and the minimum value of the plurality of sampling values, averages the remaining values to obtain a current differential value within the collection time, obtains a current value by an integration method, and stores the current value in the corresponding collection array I_N。

7. The method of claim 6, wherein: the acquisition time was 10 us.

8. The method of any one of claims 1 to 5, wherein: the method for collecting the welding time comprises the following steps: for sampled current values and settingsIs compared with the threshold value, and when the threshold value is larger than the set threshold value, the time mark is taken as the initial time mark of welding and is marked as T_ONAnd recording the current coil sampling value into a storage space, judging whether the current coil sampling value meets an acquisition ending threshold value or not in the welding process, and updating a counter T if the current coil sampling value does not meet the acquisition ending threshold value_PRecording and storing the sampling value of the coil in a storage space; if the acquisition ending threshold is met, stopping acquisition, and counting by a counter T_PStopping updating and obtaining T_PThe count value is denoted as T_OFFAccording to T = T_OFF-T_ONThe entire current duration, i.e. the welding time, is obtained.

9. The method of any one of claims 1 to 5, wherein: in step S04, an alarm is determined to be over-limit when the upper limit is exceeded, and an alarm is determined to be under-limit when the lower limit is fallen below, the upper and lower limits being preset by the customer according to the actual product process.

10. The method of any one of claims 1 to 5, wherein: the alarm is a mode of combining an independent buzzer and an independent LED lamp and matching with a liquid crystal display alarm content.

Technical Field

The invention belongs to the field of resistance welding engineering, and relates to a resistance welding quality monitoring method based on secondary current detection.

Background

The resistance welding is a welding technology based on the fusion of the contact resistance of a welded workpiece heated by a large current instantaneously, and has the advantages of no need of auxiliary welding flux, low cost and high speed; the stability of the welding technique is dependent on the stability of the welding current. The stability is divided into the magnitude of the current value and the length of time. The welding current is usually tens of thousands of amperes, such a large current is always a difficult point of testing, and with the development of resistance welding technology, various characteristics of the welding current also appear, such as various waveforms of sinusoidal alternating current, correction wave alternating current, pulse direct current, pulse group direct current and the like. For such large (tens of thousands) ampere-level and various current waveforms, no corresponding self-adaptive large-current detection equipment exists at present, and no welding quality monitoring device based on large-current detection exists.

The current detection method is usually implemented by matching a current transformer, a Hall sensor and a Rogowski coil with an integrator. The current transformer is usually used for collecting alternating current below kiloamperes, the hall sensor is usually used for collecting alternating current below kiloamperes, and the scheme that the rogowski coil is matched with the integrator is usually applied to the collection occasions of alternating sinusoidal current of tens of thousands of amperes.

Disclosure of Invention

1. The technical problem to be solved is as follows:

in resistance welding, the current collection of different levels needs corresponding collection tools, and there is no corresponding self-adaptive high-current detection equipment, and even no welding quality monitoring device based on high-current detection.

2. The technical scheme is as follows:

in order to solve the above problems, the present invention provides a resistance welding quality monitoring method based on secondary current detection, comprising the steps of: step S01: collecting welding time T and current value array I in welding process through sampling system_N(ii) a Step S02: obtaining an effective value I of the current by calculating the root mean square value of the current during the welding time T, step S03: calculating a heat equivalent value W, W = W = I during welding²R T; step S04: and comparing the I value or the W value with the set upper and lower limit threshold values, and giving an alarm if the I value or the W value is out of the range.

In step S01, measured current data is acquired by the rogowski coil, and welding time data is acquired by the timer.

The sampling system is an embedded CPU and parallel AD sampling system.

The Rogowski coil has consistency through impedance matching.

In step S01, a plurality of sets of output data of the rogowski coil are collected in parallel within the collection time to perform a filtering algorithm, the filtering algorithm removes the maximum value and the minimum value of the plurality of sampling values, averages the remaining values to obtain a current differential value within the collection time, obtains a current value by an integration method, and stores the current value in the corresponding collection array I_N。

The method for collecting the welding time comprises the following steps: comparing the sampled current value with a set threshold value, and when the sampled current value is larger than the set threshold value, taking the sampled current value as a starting time mark of welding and marking the time mark as T_ONAnd recording the current coil sampling value into a storage space, judging whether the current coil sampling value meets an acquisition ending threshold value or not in the welding process, and updating a counter T if the current coil sampling value does not meet the acquisition ending threshold value_PRecording and storing the sampling value of the coil in a storage space; if the acquisition ending threshold is met, stopping acquisition, and counting by a counter T_PStopping updating and obtaining T_PThe count value is denoted as T_OFFAccording to T = T_OFF-T_ONThe entire current duration, i.e. the welding time, is obtained. If the starting threshold requirement is not met, the I stored in the S01 is used_NAnd (6) clearing.

In step S04, an alarm is determined to be over-limit when the upper limit is exceeded, and an alarm is determined to be under-limit when the lower limit is fallen below, the upper and lower limits being preset by the customer according to the actual product process.

The alarm is a mode of combining an independent buzzer and an independent LED lamp and matching with a liquid crystal display alarm content.

3. Has the advantages that:

the invention aims at resistance welding equipment with different current characteristics and has wide adaptivity. The invention adopts embedded acquisition, replaces the complex circuit of the traditional current tester by a software algorithm, effectively reduces the cost and makes the large-scale use of third-party current heat monitoring for resistance welding possible. The invention adopts the self-adaptive algorithm for different characteristic currents, so that the user does not need to set the parameters of the acquisition layer at all. The device designed by the invention monitors the resistance welding quality based on large current detection, can generate an alarm signal for welding the current effective value or the heat equivalent value exceeding the preset alarm upper and lower limits, and is convenient for users to screen out unqualified welding workpieces.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the drawings and examples.

As shown in fig. 1, a resistance welding quality monitoring method based on secondary current detection includes the following steps: step S01: collecting welding time T and current value array I in welding process through sampling system_N(ii) a Step S02: obtaining an effective value I of the current by calculating the root mean square value of the current during the welding time T, step S03: calculating a heat equivalent value W, W = I during welding²R T; step S04: and comparing the I value or the W value with the set upper and lower limit threshold values, and giving an alarm if the I value or the W value is out of the range.

According to the invention, the welding time and the welding current are collected to obtain the heat equivalent value, the current effective value and the heat equivalent value are compared with the preset upper and lower alarm limits, and an alarm signal is generated when the alarm condition is met, so that a user can screen out unqualified welding workpieces according to the alarm signal.

In one embodiment, measured current data is acquired through the Rogowski coil, the Rogowski coil with the appropriate turn ratio is selected to match corresponding coil impedance, the Rogowski coil is essentially a hollow inductor, the inductance value of the hollow inductor is influenced by the total length, the cross-sectional area and the shape of the inductor and the winding process of the inductor coil, high consistency is difficult to achieve particularly in products of different batches and different manufacturers, and the traditional use method of the Rogowski coil is that a Rogowski coil manufacturer configures a matched integrator, and a hardware integrator link is not needed in the application, so that impedance matching needs to be performed on the purchased Rogowski coil, the internal resistance of the Rogowski coil is adjusted, and the Rogowski coil has high consistency.

In one embodiment, the sampling system is an embedded CPU and parallel AD sampling system, embedded acquisition is adopted, a software algorithm is used for replacing a complex circuit of a traditional current tester, the cost is effectively reduced, and the large-scale use of third-party current heat monitoring for resistance welding becomes possible.

The Rogowski coil output value is acquired at a high speed, the CPU is provided with fast filtering sampling original data by a parallel multipath homologous signal acquisition method, the CPU obtains an accurate sampling value according to the fast filtering calculation of the original data, the processing can eliminate the system error of AD sampling as much as possible, the calculation intensity during subsequent filtering is greatly reduced, and the real-time performance is reliably improved.

Parallelly collecting multiple sets of Rogowski coil output data in collection time to perform a filtering algorithm, wherein the filtering algorithm is to remove the maximum value and the minimum value in multiple sampling values, average the rest values to obtain a current differential value in the collection time, obtain a current value in an integral mode, and store the current value in a corresponding collection array I_N。

The acquisition time is 10us, and the acquisition frequency is 100 khz.

In one embodiment, the method for collecting the welding time comprises the following steps: comparing the sampled current value with a set threshold value, and when the sampled current value is larger than the set threshold value, taking the sampled current value as a starting time mark of welding and marking the time mark as T_ONAnd recorded in a memory space, T_ONThe method can be embodied as the operation of clearing a counter, wherein the counting length of the counter is 32-bit word length and is enough to support the time accumulation in the working process of the welding current.

In the welding process, judging whether the current coil sampling value meets the acquisition ending threshold value or not, and if not, updating the counter T_PRecording and storing the sampling value of the coil in a storage space; if the acquisition ending threshold is met, stopping acquisition, and counting by a counter T_PStopping updating and obtaining T_PThe count value is denoted as T_OFFAccording to T = T_OFF-T_ONThe entire current duration, i.e. the welding time, is obtained.

In step S02, data I is recorded_NPerforming root mean square operation based on T time, wherein I_NFor collecting arrays, the value of N is from 0 to the counting value of the current collection point,and acquiring the effective value I of the whole current process.

Based on the practical application scenario, the consistency of the materials in the same batch in the production process is very high, so that the contact resistance in the welding process is almost consistent, and under the condition that the resistance is consistent by default, the resistance value of the current contact resistance can be assumed to be a constant R, according to the formula W = I²R T obtains the heat value of the welding, as long as the pressure is normal in the welding of the parts, the material batches are the same, R can be regarded as a constant, and therefore W can be regarded as an equivalent value W = I for resistance R²×T。

In step S04, the obtained I and W are compared to each other at upper and lower limits, and if the I and W exceed the upper limit, an alarm is determined as an overrun alarm, and if the I and W fall below the lower limit, the I and W are stored in a monitor in a standard manner preset by a user. The sound-light alarm is a mode of combining an independent buzzer and an independent LED lamp and matching with a liquid crystal display alarm content. When the overrun alarm occurs, the buzzer rings, the LED lamp is lightened, meanwhile, four words of overrun alarm occur on the screen, the buzzer stops after 2 seconds of ringing, the LED lamp is maintained until the next welding meets the detection standard, and the word of the screen and the LED display time are synchronous. The occurrence of the under-limit alarm is similar to the action, and the difference is that the screen displays the word of 'under-limit alarm'.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.