Servo motor shaft resistance calculation method and system suitable for wire feeding system

Abstract

The invention discloses a servo motor shaft resistance calculation method and system suitable for a wire feeding system, and belongs to the technical field of welding wires. The method comprises the following steps: acquiring an encoder electrical angle and a three-phase current of the servo motor; calculating the rotating shaft current of the servo motor according to the encoder electrical angle and the three-phase current of the servo motor; calculating the electromagnetic torque of the servo motor according to the rotating shaft current of the servo motor; and calculating the shaft resistance of the servo motor according to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor. When the servo motor is used for wire feeding, the real-time shaft resistance of the servo motor is calculated by utilizing the real-time control block diagram of the wire feeding system, so that the wire feeding performance of the servo motor is remarkably improved, that is, the forward and reverse rotation frequency of reciprocating wire feeding is remarkably improved, the transition frequency of welding wire molten drops is improved in the welding process, and the welding performance is improved; and splashing is reduced or even avoided.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a method and system for calculating shaft resistance of a servo motor suitable for a wire feeding system. Background Art

[0002] With the development of welding technology, especially for thin plate and low current welding, the traditional method of improving welding performance by adjusting welding current and voltage is becoming less and less effective. Therefore, adjusting welding current, voltage and wire feeding speed has become a consensus among more and more people, such as CMT technology, AWP technology, etc. Their common feature is that during the welding process, the wire feeding speed is matched with the current and voltage to continuously feed the wire back and forth during the welding process.

[0003] The main method to achieve the reciprocating wire feeding is to use a servo driver to drive the servo motor. During the wire drawing welding process, the servo motor needs to drive the welding wire to be fed in a high-frequency forward and reverse manner according to the short-circuit arcing state of the welding arc. However, how to calculate the servo motor shaft resistance during the wire drawing and feeding process has not yet been solved. Therefore, the design of a servo control calculation method determines the performance of wire drawing and feeding. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a servo motor shaft resistance calculation method and system suitable for a wire feeding system, which can solve the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0006] On the one hand, the present invention provides a method for calculating the shaft resistance of a servo motor applicable to a wire feeding system, comprising:

[0007] Get the encoder electrical angle and three-phase current of the servo motor;

[0008] Calculating the shaft current of the servo motor according to the encoder electrical angle and the three-phase current of the servo motor;

[0009] Calculating the electromagnetic torque of the servo motor according to the shaft current of the servo motor;

[0010] The servo motor shaft resistance is calculated according to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor.

[0011] Optionally, the shaft current of the servo motor is calculated using a parameter transformation method, and the shaft current of the servo motor is expressed as:

[0012] [ I d I q ] = [ c o s θ s i n θ − s i n θ c o s θ ] [ I α I β ] ;

[0013] [ I α I β ] = [ 1 − 1 2 − 1 2 0 3 2 − 3 2 ] [ I u I v I w ] ;

[0014] In the formula, Indicates the servo motor Shaft current; Indicates the servo motor Shaft current; Indicates the encoder electrical angle of the servo motor; represents the first intermediate current; represents the second intermediate current; Indicates the first phase current of the three-phase current of the servo motor; Indicates the second phase current of the servo motor's three-phase current; Indicates the third phase current of the servo motor's three-phase current.

[0015] Optionally, the electromagnetic torque of the servo motor is expressed as:

[0016] ;

[0017] In the formula, Indicates the electromagnetic torque of the servo motor; Indicates the number of pole pairs of the servo motor; Indicates the servo motor Shaft current; Indicates the flux linkage of the servo motor.

[0018] Optionally, the servo motor and welding wire are connected via a PI-controlled wire feeding system;

[0019] The shaft resistance of the servo motor is expressed as:

[0020] ;

[0021] In the formula, Indicates the actual electrical angular velocity of the servo motor; Indicates the inertia of the servo motor; represents the first parameter of the PI controller; represents the second parameter of the PI controller; Indicates the electromagnetic torque of the servo motor.

[0022] Optionally, the shaft resistance of the servo motor includes a first shaft resistance, and calculation of the first shaft resistance includes:

[0023] If the electromagnetic torque of the servo motor is zero, the first shaft resistance of the servo motor is obtained, and the first shaft resistance of the servo motor is expressed as:

[0024] .

[0025] Optionally, the shaft resistance of the servo motor further includes a second shaft resistance, and calculation of the second shaft resistance includes:

[0026] If the preset mechanical speed of the servo motor is zero, the second shaft resistance of the servo motor is obtained, and the second shaft resistance of the servo motor is expressed as:

[0027] .

[0028] In a second aspect, the present invention provides a servo motor shaft resistance calculation system applicable to a wire feeding system, comprising:

[0029] Data acquisition module, which obtains the encoder electrical angle and three-phase current of the servo motor;

[0030] A shaft current calculation module, which calculates the shaft current of the servo motor according to the encoder electrical angle and the three-phase current of the servo motor;

[0031] An electromagnetic torque calculation module, which calculates the electromagnetic torque of the servo motor according to the shaft current of the servo motor;

[0032] The shaft resistance calculation module calculates the shaft resistance of the servo motor according to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor.

[0033] In a third aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implements the steps of the method for calculating the shaft resistance of a servo motor applicable to a wire feeding system as described in the first aspect.

[0034] In a fourth aspect, the present invention provides a computer device, comprising:

[0035] Memory, for storing computer instructions;

[0036] A processor is used to execute the computer instructions to implement the steps of the servo motor shaft resistance calculation method applicable to the wire feeding system described in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention can calculate the real-time shaft resistance of the servo motor by utilizing the real-time control block diagram of the wire feeding system when the servo motor is feeding the welding wire, thereby significantly improving the wire feeding performance of the servo motor, that is, the forward and reverse frequency of the reciprocating wire feeding is significantly improved, thereby increasing the transition frequency of the welding wire droplet during the welding process, improving the welding performance, and reducing or even eliminating spatter. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1It is a schematic flow chart of a method for calculating shaft resistance of a servo motor applicable to a wire feeding system in one embodiment of the present invention;

[0040] Figure 2 Shown is a schematic diagram of the wire feeding principle of a wire feeding system of the present invention in one embodiment;

[0041] Figure 3 Shown is a schematic structural diagram of a wire feeding system of the present invention in one embodiment;

[0042] Figure 4 Shown is a control block diagram of a wire feeding system in one embodiment of the present invention.

[0043] Figure 5 Shown is a control block diagram of the wire feeding system of the present invention in a second embodiment;

[0044] Figure 6 Shown is a control block diagram of the wire feeding system of the present invention in a third embodiment.

[0045] In the figure: 1-driving wheel; 2-driven wheel; 3-servo motor shaft; 4-welding wire. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0047] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment introduces a method for calculating the shaft resistance of a servo motor suitable for a wire feeding system. During the wire drawing welding process, the servo motor needs to drive the welding wire to feed in a high-frequency forward and reverse rotation according to the short-circuit arc state of the welding arc. The wire feeding principle diagram is shown in FIG. Figure 2 As shown in the figure, in a cycle T, the servo motor drives the welding wire to be fed in a high frequency forward and reverse rotation. Taking one cycle as an example, in [t 1 , t 2 ] During this time period, the servo motor runs at a speed of V 1 Drive the welding wire to feed forward; 2 , t 3] During this time period, the servo motor runs at a speed of V 2 Drive the welding wire to feed in reverse direction.

[0050] Therefore, during the reciprocating wire feeding process, due to the inertia generated by the reciprocating motion of the main wire feeding wheel and the pressure of the wire feeding wheel on the welding wire, the wire drawing and feeding system will exert different resistances on the servo motor shaft, and the servo motor needs to overcome this ever-changing resistance to accurately feed the wire at high speed. The structure of the wire drawing and feeding system is as follows: Figure 3 As shown, its working principle is: during the normal wire feeding process of the wire feeding system, the driven wheel 2 and the driving wheel 1 press the welding wire 4, and the servo motor drives the driving wheel 1 to rotate forward and reversely. Due to the friction between the welding wire 4 and the wire feeding wheel, the welding wire 4 can be driven to reciprocate. During the reciprocating motion, the friction resistance will also be applied to the servo motor shaft 3 in the reverse direction. Therefore, this method can detect the size of the resistance applied to the servo motor shaft 3 in real time. In the subsequent servo motor control process, the corresponding electromagnetic force is applied in advance according to the size of the resistance of the servo motor shaft 3, thereby increasing the corresponding speed of the motor.

[0051] The method specifically comprises the following steps:

[0052] Step 1: Get the encoder electrical angle of the servo motor 、Encoder electrical angular velocity and three-phase current , , The electrical angle of the servo motor RDC encoder is read in real time through the resolver transformer angle speed acquisition module. and electrical angular velocity ; Read the three-phase current of the servo motor in real time through the current sampling chip , , .

[0053] Step 2: According to the electrical angle of the servo motor encoder and three-phase current , , , using the parameter transformation method, the shaft current of the servo motor is calculated, and the shaft current of the servo motor is expressed as:

[0054] [ I d I q ] = [ c o s θ s i n θ − s i n θ c o s θ ] [ I α I β ] ;

[0055] [ I α I β ] = [ 1 − 1 2 − 1 2 0 3 2 − 3 2 ] [ I u I v I w ] ;

[0056] In the formula, Indicates the servo motor Shaft current; Indicates the servo motor Shaft current; Indicates the encoder electrical angle of the servo motor; represents the first intermediate current; represents the second intermediate current; Indicates the first phase current of the three-phase current of the servo motor; Indicates the second phase current of the servo motor's three-phase current; Indicates the third phase current of the servo motor's three-phase current.

[0057] Step 3: Calculate the electromagnetic torque of the servo motor according to the shaft current of the servo motor , the electromagnetic torque of the servo motor It is expressed as:

[0058] ;

[0059] In the formula, Indicates the number of pole pairs of the servo motor; Indicates the servo motor Shaft current; represents the flux linkage of the servo motor, and These two parameters are known constants of the servo motor and can be found in the motor product manual.

[0060] Step 4: According to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor , calculate the servo motor shaft resistance .

[0061] The servo motor and welding wire are connected through a PI-controlled wire feeding system. The initial block diagram of the s-domain continuous system of the wire feeding system with PI control as the controller is as follows: Figure 4 As shown, the control equation of the PI controller is expressed as:

[0062] ;

[0063] In the formula, represents the control equation of the PI controller; represents the first parameter of the PI controller; Represents the second parameter of the PI controller.

[0064] According to the wire feeding system, the shaft resistance of the two servo motors is obtained , .

[0065] When the electromagnetic torque of the servo motor is zero, When Figure 5As shown, the wire feeding system is represented as follows:

[0066] ;

[0067] At this time, according to the actual electrical angular velocity of the servo motor , get the first axis resistance of the servo motor , the first axis resistance of the servo motor It is expressed as:

[0068] .

[0069] When the actual electrical angular velocity of the servo motor is zero, When Figure 6 As shown, the wire feeding system is represented as follows:

[0070] ;

[0071] At this time, according to the electromagnetic torque of the servo motor , get the second axis resistance of the servo motor , the second axis resistance of the servo motor It is expressed as:

[0072] .

[0073] During the actual operation of the system, the shaft resistance of the servo motor is the shaft resistance of the two servo motors , The sum is:

[0074] ;

[0075] In the formula, Indicates the inertia of the servo motor.

[0076] Example 2

[0077] This embodiment introduces a servo motor shaft resistance calculation system applicable to a wire feeding system, including:

[0078] Data acquisition module, obtains the electrical angle of the servo motor encoder 、Encoder electrical angular velocity and three-phase current , , The electrical angle of the servo motor RDC encoder is read in real time through the resolver transformer angle speed acquisition module. and electrical angular velocity ; Read the three-phase current of the servo motor in real time through the current sampling chip , , .

[0079] The shaft current calculation module calculates the actual mechanical rotation angle of the servo motor. and three-phase current , , , using the parameter transformation method, the shaft current of the servo motor is calculated, and the shaft current of the servo motor is expressed as:

[0080] [ I d I q ] = [ c o s θ s i n θ − s i n θ c o s θ ] [ I α I β ] ;

[0081] [ I α I β ] = [ 1 − 1 2 − 1 2 0 3 2 − 3 2 ] [ I u I v I w ] ;

[0082] In the formula, Indicates the servo motor Shaft current; Indicates the servo motor Shaft current; Indicates the encoder electrical angle of the servo motor; represents the first intermediate current; represents the second intermediate current; Indicates the first phase current of the three-phase current of the servo motor; Indicates the second phase current of the servo motor's three-phase current; Indicates the third phase current of the servo motor's three-phase current.

[0083] The electromagnetic torque calculation module calculates the electromagnetic torque of the servo motor according to the shaft current of the servo motor. It is expressed as:

[0084] ;

[0085] In the formula, Indicates the number of pole pairs of the servo motor; Indicates the servo motor Shaft current; represents the flux linkage of the servo motor, and These two parameters are known constants of the servo motor and can be found in the motor product manual.

[0086] The shaft resistance calculation module is based on the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor , using the wire feeding system, calculate the servo motor shaft resistance The initial block diagram of the s-domain continuous system of the wire feeding system with PI control as the controller is as follows: Figure 4 As shown, the control equation of the PI controller is expressed as:

[0087] ;

[0088] In the formula, represents the control equation of the PI controller; represents the first parameter of the PI controller; Represents the second parameter of the PI controller.

[0089] According to the wire feeding system, the shaft resistance of the two servo motors is obtained , .

[0090] When the electromagnetic torque of the servo motor is zero, When Figure 5 As shown, the wire feeding system is represented as follows:

[0091] ;

[0092] At this time, according to the actual electrical angular velocity of the servo motor , get the first axis resistance of the servo motor , the first axis resistance of the servo motor It is expressed as:

[0093] .

[0094] When the actual electrical angular velocity of the servo motor is zero, When Figure 6 As shown, the wire feeding system is represented as follows:

[0095] ;

[0096] At this time, according to the electromagnetic torque of the servo motor , get the second axis resistance of the servo motor , the second axis resistance of the servo motor It is expressed as:

[0097] .

[0098] During the actual operation of the system, the shaft resistance of the servo motor is the shaft resistance of the two servo motors , The sum is:

[0099] ;

[0100] In the formula, Indicates the inertia of the servo motor.

[0101] Example 3

[0102] Based on Example 1, this embodiment introduces a specific experimental design of a servo motor shaft resistance calculation method suitable for a wire feeding system, including the following steps:

[0103] Through experiments, we can get Kp=0.1, ki=20 for PI controller, and the moment of inertia J of servo motor , the number of pole pairs of the servo motor =4, the magnetic flux of the servo motor =0.0379, the current sampling chip of the servo motor collects the three-phase current of the servo motor in real time , , and encoder electrical angle , control the CPU to calculate the servo motor in real time Shaft current , the servo motor encoder collects the encoder electrical angular velocity in real time Finally, the load resistance of the servo motor shaft can be calculated by the calculation formula:

[0104] .

[0105] Example 4

[0106] This embodiment introduces a computer-readable storage medium on which computer instructions are stored. When the computer instructions are executed by a processor, the steps of the servo motor shaft resistance calculation method applicable to the wire feeding system described in Embodiment 1 or 3 are implemented.

[0107] Example 5

[0108] This embodiment introduces a computer device, including:

[0109] Memory, for storing computer instructions;

[0110] A processor is used to execute the computer instructions to implement the steps of the servo motor shaft resistance calculation method applicable to the wire feeding system described in Example 1 or 3.

[0111] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0112] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0113] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0114] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0115] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A method for calculating the shaft resistance of a servo motor suitable for a wire feeding system, characterized in that: include: Get the encoder electrical angle and three-phase current of the servo motor; Calculating the shaft current of the servo motor according to the encoder electrical angle and the three-phase current of the servo motor; Calculating the electromagnetic torque of the servo motor according to the shaft current of the servo motor; The servo motor shaft resistance is calculated according to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor.

2. The method for calculating the shaft resistance of a servo motor suitable for a wire feeding system according to claim 1, characterized in that: The shaft current of the servo motor is calculated by using the parameter transformation method. The shaft current of the servo motor is expressed as: ； ； In the formula, Indicates the servo motor Shaft current; Indicates the servo motor Shaft current; Indicates the encoder electrical angle of the servo motor; represents the first intermediate current; represents the second intermediate current; Indicates the first phase current of the three-phase current of the servo motor; Indicates the second phase current of the servo motor's three-phase current; Indicates the third phase current of the servo motor's three-phase current.

3. The method for calculating the shaft resistance of a servo motor suitable for a wire feeding system according to claim 1, characterized in that: The electromagnetic torque of the servo motor is expressed as: ； In the formula, Indicates the electromagnetic torque of the servo motor; Indicates the number of pole pairs of the servo motor; Indicates the servo motor Shaft current; Indicates the flux linkage of the servo motor.

4. The method for calculating the shaft resistance of a servo motor suitable for a wire feeding system according to claim 1, characterized in that: The servo motor and welding wire are connected through a PI-controlled wire feeding system; The shaft resistance of the servo motor is expressed as: ； In the formula, Indicates the actual electrical angular velocity of the servo motor; Indicates the inertia of the servo motor; represents the first parameter of the PI controller; represents the second parameter of the PI controller; Indicates the electromagnetic torque of the servo motor.

5. The method for calculating the shaft resistance of a servo motor suitable for a wire feeding system according to claim 5, characterized in that: The shaft resistance of the servo motor includes a first shaft resistance, and the calculation of the first shaft resistance includes: If the electromagnetic torque of the servo motor is zero, the first shaft resistance of the servo motor is obtained, and the first shaft resistance of the servo motor is expressed as: 。 6. The method for calculating the shaft resistance of a servo motor suitable for a wire feeding system according to claim 5, characterized in that: The shaft resistance of the servo motor also includes a second shaft resistance, and the calculation of the second shaft resistance includes: If the preset mechanical speed of the servo motor is zero, the second shaft resistance of the servo motor is obtained, and the second shaft resistance of the servo motor is expressed as: 。 7. A servo motor shaft resistance calculation system suitable for a wire feeding system, characterized in that: include: Data acquisition module, which obtains the encoder electrical angle and three-phase current of the servo motor; A shaft current calculation module, which calculates the shaft current of the servo motor using a parameter transformation method according to the encoder electrical angle and three-phase current of the servo motor; An electromagnetic torque calculation module, which calculates the electromagnetic torque of the servo motor according to the shaft current of the servo motor; The shaft resistance calculation module calculates the shaft resistance of the servo motor according to the electromagnetic torque of the servo motor and the actual electrical angular velocity of the servo motor and using the wire feeding system.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the computer instruction is executed by the processor, the steps of the servo motor shaft resistance calculation method applicable to the wire feeding system described in any one of claims 1 to 6 are implemented.

9. A computer device, characterized in that: include: Memory, for storing computer instructions; A processor is used to execute the computer instructions to implement the steps of the servo motor shaft resistance calculation method applicable to the wire feeding system according to any one of claims 1 to 6.

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