CN-116490315-B - Method for determining an estimated value of an arc voltage

CN116490315BCN 116490315 BCN116490315 BCN 116490315BCN-116490315-B

Abstract

In order to improve the estimation of the arc voltage for use in the welding process, it is proposed that the welding line (4) is modeled with a welding line model (13) as a transmission system with an order greater than one, and that the estimated value of the arc voltage is determined as the difference between the measured voltage at the measuring location (19) and the determined line voltage drop.

Inventors

P. Rhett Heng
H. Ensborina
D. Solinger
G. Wallinger

Assignees

弗罗纽斯国际有限公司

Dates

Publication Date: 20260505
Application Date: 20211123
Priority Date: 20201125

Claims (11)

1. A method for determining an estimated value û LB of an arc voltage of an arc (10) burning between a welding electrode (9) and a workpiece (7), wherein a line voltage drop u S of the welding line (4) between a measuring location (19) on the welding line (4) and the arc (10) is determined with a welding line model (13) having model parameters p M , and wherein the welding line model (13) models the welding line (4) as a transmission system with a welding current i S flowing through the welding line (4) or a measured voltage u M applied at the measuring location (19) as an input parameter u and with a line voltage drop u S as an output parameter y, in order to determine a current estimated value for the line voltage drop u S for the current welding current i S or the current measured voltage u M , and an estimated value û LB of the arc voltage is determined with a known relationship between the line voltage drop u S and the arc voltage u LB , characterized in that for the estimated voltage u 35, the welding line model (13) is determined with a difference between the measured voltage u 3274 of the welding line (4) as a step and the estimated value of the measured voltage u 3274 as the transmission parameter y.
2. A method according to claim 1, characterized in that the transfer system is modeled as transfer functions G(s), G z (z) as a quotient of the output parameter y and the input parameter u.
3. Method according to any one of claims 1 to 2, characterized in that during a short-circuit between the welding electrode (9) and the workpiece (7) or a weld pool on the workpiece (7), a suitable output variable y is measured for a number N of input variables u, and model parameters p M are identified by means of a parameter estimation method from these N input variables u and output variable y.
4. A method according to claim 3, characterized in that the model parameter p M is identified during the short-circuit phase during welding.
5. A method according to claim 3, characterized in that the model parameters p M are identified before welding for a predefined time profile of the input variable u and the associated output variable y.
6. A method as claimed in claim 3, characterized in that a time profile of the input variable u is generated, which time profile has a plurality of rising edges, the slope of at least two edges being different.
7. The method according to claim 6, characterized in that the different slope of the at least two edges for the welding current i S as input parameter is selected in the range between 100A/ms and 10000A/ms.
8. A method according to claim 3, characterized in that the deviation between the measured value of the output parameter and the estimation of the output parameter, which is determined for the input parameter using the welding line model, is minimized in a parameter estimation method in order to determine the model parameters of the welding line model.
9. A method according to claim 3, characterized in that the model parameters are identified a plurality of times, the development of the value of at least one of the model parameters over time is investigated in order to obtain conclusions about faults in the welding line or to obtain conclusions about an unfavorable laying of the welding line.
10. Method according to claim 1 or 2, characterized in that a pulse of welding current i S is continuously applied to the welding line (4) until the value of the measurement voltage u M at the measurement location (19) is constant and that the ohmic resistance R 1 of the welding line model (13) is determined from the quotient of the measurement voltage u M and the applied welding current i S .
11. Welding power supply for carrying out a welding process, having a welding regulation unit (11), wherein a welding line model (13) having a model parameter p M is implemented in an evaluation unit (16) of the welding regulation unit (11), which describes a welding current i S flowing through a welding line (4) of the welding power supply (1) as an input variable u in the form of a transmission system or a measured voltage u M applied at a measuring point (19) of the welding line (4) in relation to a line voltage drop u S at the welding line (4) as an output variable y, and the welding line model (13) determines a current evaluation value for a line voltage drop u S for a current welding current i S or a current measured voltage u M , and the welding regulation unit (11) thereby determines an evaluation value û LB of an arc voltage from a known relation between the line voltage drop u S and the arc voltage u LB , characterized in that the welding line model (13) is modeled in the evaluation unit (16) to a transmission system of a number greater than one and the measured voltage drop u 3723 is implemented as a difference between the measured voltage drop u û LB and the measured voltage u û LB of the estimated voltage u position (16) is determined.

Description

Method for determining an estimated value of an arc voltage Technical Field The invention relates to a method for determining an estimate of the arc voltage of an arc burning between a welding electrode and a workpiece, wherein a line voltage drop of the welding line between a measuring location on the welding line and the arc is determined with a welding line model having model parameters, and the welding line model models the welding line as a transmission system, which takes as input variables the welding current flowing through the welding line or the measured voltage applied at the measuring location and takes as output variables the line voltage drop in order to determine a current estimate of the line voltage drop for the current welding current or the current measured voltage, and the known relationship between the line voltage drop and the arc voltage is used to determine the estimate of the arc voltage. The invention also relates to a welding power supply in which such a welding line model is implemented. Background The main task of a welding power supply for carrying out a welding process is to generate, control and adjust the process parameters, i.e. the welding current and/or the welding voltage and, if appropriate, the wire feed, in accordance with the welding task in such a way that a good welding result with the desired weld quality and thus a good welded connection is ultimately produced. The regulation of the welding current has a special effect here, since the welding process is powered by the welding current. In order to regulate the welding process, an arc voltage is also required, as it is an important parameter for the welding process. The arc voltage that drops at the arc is related to the arc length and thus also to the spacing between the welding electrode and the workpiece (or puddle). However, the arc voltage cannot be measured directly in practice, and one therefore relies on reconstructing the arc voltage from indirect measurements. A welding line consisting of a welding current line (a line leading from the welding power supply to the welding torch or to the welding electrode) and a ground line (a line leading back from the workpiece to the welding power supply) connects the welding power supply to the welding torch, i.e. to the welding electrode and the workpiece. The welding line is typically connected to a welding power source in a connection socket. The socket voltage between the connection sockets, i.e. between the welding current line and the ground line, and the socket current flowing through the welding line can be simply measured on the welding power supply. The socket current may be the same as the welding current, as the current in parallel with the arc during welding is mostly negligible. But the socket voltage does not correspond to the arc voltage due to the voltage drop across the weld line. In order to reconstruct the arc voltage from the socket voltage, a line model is used in the known prior art, which models the welding line as a series circuit of line resistance and line inductance (R/L model) in order to determine the voltage drop over the welding line. Then, an estimate of the arc voltage can be obtained using the measured socket voltage and the measured socket current and the line model. Thus, the voltage drop across the weld line is compensated for by the line model to obtain an estimate of the arc voltage. This is known, for example, from WO2000/74888A1 or DE102005005771B 4. Since in this model only one accumulator or dynamic component is used to describe the (line inductance L) hose bundle, the model is first-order. The parameters of the R/L line model, i.e., line resistance and line inductance, are known or identified. The parameter identification may be performed during the welding or also in the welding pauses. For example, the welding electrode (or contact tube of the welding torch) may be shorted to the workpiece. The line resistance is then determined when the current is constant. The current pulse can then be switched on and the line inductance can be determined therefrom. For example, a current pulse that does not interfere with the welding process may be modulated onto the welding current during welding and model parameters determined from the reaction. Model parameters can also be determined continuously from the formula relation of the existing measured values, as in DE102005005771B 4. Thus, the arc voltage may be estimated during operation of the welding power source. However, in practice it has been demonstrated that using a general R/L line model, significant estimation errors can occur in reconstructing the arc voltage, which can negatively impact the welding process. It is known from the applicant's studies that the laying of the welding line has a great influence on the reconstruction of the arc voltage. It has been observed that the welding lines are often arranged in the vicinity of the electrically conductive member/component/struc