Speed measuring device and speed measuring method for digital drive control motor in laser welding system

Abstract

The invention discloses a motor speed measuring device, belongs to the technical field of laser welding systems, and particularly relates to a speed measuring device and method for a digital drive control motor in a laser welding system, and the device comprises a master controller MCU, a sensor interface, a fully differential operational amplifier circuit, a differential to single-ended circuit, a differentiating circuit and a voltage follower circuit. Two paths of sensor signals of a motor are obtained through the fully differential circuit, the signals of the fully differential circuit are amplified and then connected to the differential-to-single-end circuit, the differentiating circuit and the voltage following circuit to be further processed, the processed signals are connected to an AD port of the MCU, and the MCU can obtain data of the voltage change rate through the device. According to the speed measurement device and method, the change value of the position voltage in unit time is calculated by hardware, and the voltage value sampled by the ADC directly corresponds to the speed value, so that high-frequency speed measurement can be carried out without a high-resolution ADC.

Description

Technical Field

[0001] The present invention belongs to the technical field, and in particular relates to a speed measuring device and a speed measuring method for a digital drive control motor in a laser welding system. Background Art

[0002] Laser welding systems are mainly used in the manufacturing industry. In the manufacturing industry, laser welding systems are used to produce electronic products such as robots, mobile phones, computers, as well as automotive parts, electrical parts, etc. Laser welding systems can achieve high-efficiency production and processing, reduce labor costs, and improve production efficiency. Through the precise control of the focal position and energy density of the laser beam, rapid heating and precise control of small areas can be achieved, thereby greatly improving the welding speed; the laser welding system has the characteristics of high precision, and can achieve micron-level welding accuracy, smooth welds without impurities, and ensure the stable performance of electronic equipment. The accuracy of the laser welding system can reach ±0.01mm, and the consistency is as high as 99% or more.

[0003] In the laser welding system, it is mainly controlled by DC motor. In the process of DC motor control, the traditional speed measurement method is to sample the voltage value of the position per unit time, and feedback the speed by calculating the difference between the voltage values ​​of two interval positions. The biggest defect of the traditional method is that as the speed measurement frequency increases, the corresponding sampling frequency must also be increased. If the accuracy of the ADC is not enough, the ADC conversion value per unit time will also change very little, resulting in extremely low speed resolution. The new method proposed in this paper uses hardware to calculate the change value of the position voltage per unit time. The voltage value sampled by the ADC directly corresponds to the speed value, so that high-frequency speed measurement can be performed without a high-resolution ADC. Summary of the invention

[0004] Purpose of the invention: To provide a digital drive control motor speed measuring device and speed measuring method in a laser welding system to solve the above-mentioned problems.

[0005] Technical solution:

[0006] In the first aspect, a digital drive control motor speed measuring device in a laser welding system, the speed measuring device comprises: a main controller MCU, a sensor interface, a fully differential operational amplifier circuit, a differential to single-ended circuit, a differential circuit and a voltage follower circuit;

[0007] The input end of the sensor interface is connected to the position sensor of the motor, and the output end is connected to the input end of the fully differential operational amplifier circuit, the output end of the fully differential operational amplifier circuit is connected to the main controller MCU, the input end of the differential to single-ended circuit is connected to the output end of the fully differential operational amplifier circuit, and the output end is connected to the output end of the differential circuit, the output end of the differential circuit is connected to the input end of the voltage follower circuit, and the output end of the voltage follower circuit is connected to the main controller MCU, and the main controller MCU controls the motor.

[0008] In a further embodiment, the fully differential operational amplifier circuit includes: resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C1, and fully differential circuit U1;

[0009] One end of the resistor R4 and one end of the resistor R5 input the position signals V01+ and V01- of the motor in the laser welding system, pin 1 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R4, one end of the capacitor C1 and one end of the resistor R1, pin 4 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C1 and one end of the resistor R2, one end of the capacitor C3 is simultaneously connected to the other end of the resistor R2, the other end of the resistor R1 and one end of the capacitor C4 and outputs a signal V01+_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C3 is grounded, pin 8 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R5, the One end of the capacitor C6 is connected to one end of the resistor R7, pin 5 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C6 and one end of the resistor R6, one end of the capacitor C5 is simultaneously connected to the other end of the resistor R6, the other end of the resistor R7, and the other end of the capacitor C4, and outputs a signal V01-_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C5 is grounded, pin 6 of the fully differential circuit U1 is grounded, pin 3 of the fully differential circuit U1 is simultaneously connected to one end of the capacitor C2 and one end of the resistor R3, the other end of the capacitor C2 is grounded, and pin 7 of the fully differential circuit U1 and the other end of the resistor R3 input a 3.3V voltage.

[0010] In a further embodiment, the differential-to-single-ended circuit includes: a differential-to-single-ended chip U2, a capacitor C11, and a capacitor C9;

[0011] Pin 1 of the differential-to-single-ended chip U2 is grounded, pins 2 and 3 of the differential-to-single-ended chip U2 are connected to the fully differential op amp circuit and input signals V01+_1 and V01-_1, pin 4 of the differential-to-single-ended chip U2 inputs a voltage of -5V0 and is connected to one end of the capacitor C11, and the other end of the capacitor C11 is grounded, pins 5 and 6 of the differential-to-single-ended chip U2 output a signal V01 to the differential circuit, pin 5 of the differential-to-single-ended chip U2 inputs a voltage of +5V0 and is connected to one end of the capacitor C9, and the other end of the capacitor C9 is grounded.

[0012] In a further embodiment, the differential circuit includes: capacitor C10, resistor R9, amplifier U3A, resistor R8, capacitor C7, capacitor C8, capacitor C12;

[0013] One end of the capacitor C10 is connected to the differential to single-ended circuit and inputs the signal V01, and the other end is connected to one end of the resistor R9. Pin 2 of the amplifier U3A is simultaneously connected to the other end of the resistor R9, one end of the resistor R8 and one end of the capacitor C7. Pin 3 of the amplifier U3A is grounded. Pin 1 of the amplifier U3A is simultaneously connected to the other end of the capacitor C7 and the other end of the resistor R8 and outputs the signal SPEED of the voltage follower circuit. Pin 4 of the amplifier U3A inputs a voltage of -5V0 and is connected to one end of the capacitor C8. The other end of the capacitor C8 is grounded. Pin 8 of the amplifier U3A inputs a voltage of +V0 and is connected to an end of the capacitor C12. One end of the capacitor C12 is grounded.

[0014] In a further embodiment, the voltage follower circuit includes: an amplifier U3B, a resistor R11, a resistor R12, a resistor R10, and a voltage regulator D1;

[0015] One end of the resistor R11 is connected to the differential circuit and inputs the signal SPEED, pin 5 of the amplifier U3B is simultaneously connected to the other end of the resistor R11 and one end of the resistor R12, the other end of the resistor R12 inputs a voltage of 3.3V, pins 6 and 7 of the SPEED are connected and connected to one end of the resistor R10, the other end of the resistor R10 is connected to the negative electrode of the voltage regulator D1 and outputs the signal SPEED1 to the main controller MCU, and the positive electrode of the voltage regulator D1 is grounded.

[0016] In the second aspect, a method for measuring the speed of a digitally driven motor in a laser welding system is implemented by the digitally driven motor speed measuring device in the laser welding system described above. The speed measuring method obtains two sensor signals of the motor through the fully differential operational amplifier circuit, the fully differential circuit signal is amplified and connected to the differential to single-ended circuit, the differential circuit and the voltage follower circuit further process the signal, and the processed signal is connected to the AD port of the MCU. The MCU can obtain the data of the voltage change rate through this device.

[0017] In a further embodiment, the position signal of the motor in the laser welding system is a differential output, and the fully differential circuit U1 in the fully differential operational amplifier circuit amplifies the motor position signal by a certain multiple to reach a voltage level that meets the voltage collected by the main controller MCU. The specific gain method is as follows:

[0018] AV=Rf / Rg=R7 / R5

[0019] The resistance of resistor R4 is the same as the resistance of resistor R5, and the resistance of resistor R1 is the same as the resistance of resistor R7, so that the amplification ratios at both ends of the feedback are the same.

[0020] In a further embodiment, the differential to single-ended circuit converts the double-ended signal into a single-ended signal, that is, the voltage range is calculated as follows:

[0021] V out =V +in -V -in

[0022] Converted into a voltage value with the center point of the motor stroke as the reference, that is, the position signal.

[0023] In a further embodiment, the differential circuit eliminates the invariant and highlights the variable. The differential circuit converts the rectangular wave into a sharp pulse wave. The width of the output sharp pulse waveform is related to the capacitance C*resistance R, that is, the time constant of the circuit. The output voltage of the differential circuit is:

[0024]

[0025] In the above formula, the smaller the capacitance C*resistance R is, the sharper the spike pulse waveform is, and vice versa; the capacitance C*resistance R of the differential circuit is less than the width of the input waveform. The function of C7 in the differential circuit is to suppress high-frequency signals in the circuit and prevent interference signals from causing saturation of the operational amplifier.

[0026] In a further embodiment, the voltage follower circuit is used for buffering, isolation, and improving load capacity, and the resistance value of the resistor R11 in the voltage follower circuit is the same as the resistance value of the resistor R12, and the measured speed of the motor is calculated as follows:

[0027]

[0028] We can get:

[0029]

[0030] Among them, speed The unit is V / ms, that is, volt / millisecond; then:

[0031] V speed1 =1.65-1.23V

[0032] The measured speed of the motor is

[0033] Beneficial effect: The present invention utilizes a fully differential circuit to obtain two-way sensor signals of the motor. After the fully differential circuit signal is amplified, it is connected to a differential to single-ended circuit. The differential circuit and the voltage follower circuit further process the signal. The processed signal is connected to the AD port of the MCU. The MCU can obtain the data of the voltage change rate through this device. The speed measuring device and method of the present invention use hardware to calculate the change value of the position voltage per unit time. The voltage value sampled by the ADC directly corresponds to the speed value, so that high-frequency speed measurement can be performed without a high-resolution ADC. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a system structure diagram of the speed measuring device of the present invention.

[0035] Figure 2 It is a schematic diagram of a fully differential operational amplifier circuit of the present invention.

[0036] Figure 3 It is a schematic diagram of a differential to single-ended circuit of the present invention.

[0037] Figure 4 It is a signal waveform diagram of the differential to single-ended circuit of the present invention.

[0038] Figure 5 It is a schematic diagram of a differential circuit of the present invention.

[0039] Figure 6 It is the differential circuit signal waveform diagram of the present invention.

[0040] Figure 7 It is a schematic diagram of a voltage follower circuit of the present invention.

[0041] Figure 8 It is a graph showing the relationship between the actual speed measured by the motor and the theoretical calculated speed according to the speed measurement method of the present invention.

[0042] Fig. 9 It is a measured waveform diagram of the speed measurement method of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] First embodiment:

[0045] like Figure 1 As shown, a digital drive control motor speed measuring device in a laser welding system, the speed measuring device includes: a main controller MCU, a sensor interface, a fully differential operational amplifier circuit, a differential to single-ended circuit, a differential circuit and a voltage follower circuit;

[0046] The input end of the sensor interface is connected to the position sensor of the motor, and the output end is connected to the input end of the fully differential operational amplifier circuit, the output end of the fully differential operational amplifier circuit is connected to the main controller MCU, the input end of the differential to single-ended circuit is connected to the output end of the fully differential operational amplifier circuit, and the output end is connected to the output end of the differential circuit, the output end of the differential circuit is connected to the input end of the voltage follower circuit, and the output end of the voltage follower circuit is connected to the main controller MCU, and the main controller MCU controls the motor.

[0047] Embodiment 1:

[0048] like Figure 2 As shown, the fully differential operational amplifier circuit includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C1, and a fully differential circuit U1;

[0049] One end of the resistor R4 and one end of the resistor R5 input the position signals V01+ and V01- of the motor in the laser welding system, pin 1 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R4, one end of the capacitor C1 and one end of the resistor R1, pin 4 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C1 and one end of the resistor R2, one end of the capacitor C3 is simultaneously connected to the other end of the resistor R2, the other end of the resistor R1 and one end of the capacitor C4 and outputs a signal V01+_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C3 is grounded, pin 8 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R5, the One end of the capacitor C6 is connected to one end of the resistor R7, pin 5 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C6 and one end of the resistor R6, one end of the capacitor C5 is simultaneously connected to the other end of the resistor R6, the other end of the resistor R7, and the other end of the capacitor C4, and outputs a signal V01-_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C5 is grounded, pin 6 of the fully differential circuit U1 is grounded, pin 3 of the fully differential circuit U1 is simultaneously connected to one end of the capacitor C2 and one end of the resistor R3, the other end of the capacitor C2 is grounded, and pin 7 of the fully differential circuit U1 and the other end of the resistor R3 input a 3.3V voltage.

[0050] Embodiment 2:

[0051] like Figure 3 As shown, the differential to single-ended circuit includes: a differential to single-ended chip U2, a capacitor C11 and a capacitor C9;

[0052] Pin 1 of the differential-to-single-ended chip U2 is grounded, pins 2 and 3 of the differential-to-single-ended chip U2 are connected to the fully differential op amp circuit and input signals V01+_1 and V01-_1, pin 4 of the differential-to-single-ended chip U2 inputs a voltage of -5V0 and is connected to one end of the capacitor C11, and the other end of the capacitor C11 is grounded, pins 5 and 6 of the differential-to-single-ended chip U2 output a signal V01 to the differential circuit, pin 5 of the differential-to-single-ended chip U2 inputs a voltage of +5V0 and is connected to one end of the capacitor C9, and the other end of the capacitor C9 is grounded.

[0053] Embodiment 3:

[0054] like Figure 5 As shown, the differential circuit includes: capacitor C10, resistor R9, amplifier U3A, resistor R8, capacitor C7, capacitor C8, capacitor C12;

[0055] One end of the capacitor C10 is connected to the differential to single-ended circuit and inputs the signal V01, and the other end is connected to one end of the resistor R9. Pin 2 of the amplifier U3A is simultaneously connected to the other end of the resistor R9, one end of the resistor R8 and one end of the capacitor C7. Pin 3 of the amplifier U3A is grounded. Pin 1 of the amplifier U3A is simultaneously connected to the other end of the capacitor C7 and the other end of the resistor R8 and outputs the signal SPEED of the voltage follower circuit. Pin 4 of the amplifier U3A inputs a voltage of -5V0 and is connected to one end of the capacitor C8. The other end of the capacitor C8 is grounded. Pin 8 of the amplifier U3A inputs a voltage of +V0 and is connected to an end of the capacitor C12. One end of the capacitor C12 is grounded.

[0056] Embodiment 4:

[0057] like Figure 7 As shown, the voltage follower circuit includes: an amplifier U3B, a resistor R11, a resistor R12, a resistor R10, and a voltage regulator tube D1;

[0058] One end of the resistor R11 is connected to the differential circuit and inputs the signal SPEED, pin 5 of the amplifier U3B is simultaneously connected to the other end of the resistor R11 and one end of the resistor R12, the other end of the resistor R12 inputs a voltage of 3.3V, pins 6 and 7 of the SPEED are connected and connected to one end of the resistor R10, the other end of the resistor R10 is connected to the negative electrode of the voltage regulator D1 and outputs the signal SPEED1 to the main controller MCU, and the positive electrode of the voltage regulator D1 is grounded.

[0059] Second embodiment:

[0060] In the laser welding system, the motor swings and finally reflects a red light in the shape of a "one". According to the actual situation, this circuit needs to give a control signal of 0.1V peak to peak value for the 1mm width of the red light reflected by the motor swing. The swing speed of the motor can be changed by setting the red light width and the swing frequency. Because the position of the motor is reflected by the voltage, the rate of change of the voltage can be considered as the speed of the motor.

[0061] like Figure 1 As shown, a method for measuring the speed of a digitally driven motor in a laser welding system is implemented by using a digitally driven motor speed measuring device in the laser welding system. The speed measuring method obtains two sensor signals of the motor through the fully differential operational amplifier circuit. The fully differential circuit signal is amplified and then connected to the differential to single-ended circuit. The differential circuit and the voltage follower circuit further process the signal. The processed signal is connected to the AD port of the MCU. The MCU can obtain the data of the voltage change rate through the device.

[0062] Embodiment 5:

[0063] like Figure 2 As shown, the position signal of the motor in the laser welding system is a differential output. The fully differential circuit U1 in the fully differential operational amplifier circuit amplifies the motor position signal (small voltage signal) by a certain multiple to reach a voltage level that meets the voltage level collected by the main controller MCU. The specific gain method is as follows:

[0064] AV=Rf / Rg=R7 / R5

[0065] The resistance of resistor R4 is the same as the resistance of resistor R5, and the resistance of resistor R1 is the same as the resistance of resistor R7, so that the amplification ratios at both ends of the feedback are the same.

[0066] This circuit actually uses R5=1K, R7=147K, and the final voltage range collected by the MCU is 0~3.3v.

[0067] Embodiment 6:

[0068] like Figure 3 and Figure 4 As shown, in a further embodiment, the differential to single-ended circuit converts the double-ended signal into a single-ended signal, that is, the voltage range is calculated as follows:

[0069] V out =V +in -V -in

[0070] Converted into a voltage value with the center point of the motor stroke as the reference, i.e. the position signal. The final voltage range is -3.3V to 3.3V.

[0071] Specifically, the measured waveform is as follows: Figure 4 As shown, CH1 is V +in signal, CH2 is V -in signal, CH3 is V out From the signal, we can see that the oscilloscope's built-in Math channel and CH3 completely overlap, verifying the above formula. Here, since the output amplitude variation range has doubled, the subsequent speed should be twice the actual speed.

[0072] Embodiment 7:

[0073] like Figure 5 and Figure 6 As shown, the differential circuit reduces the invariant and highlights the variable. The differential circuit converts the rectangular wave into a sharp pulse wave. The output waveform of the circuit only reflects the sudden change of the input waveform. That is, there is output only when the input waveform suddenly changes. The circuit is as shown in Figure 5As shown. There is no output for the constant part. The width of the output spike waveform is related to the capacitance C*resistance R, that is, the time constant of the circuit. The output voltage of the differential circuit is:

[0074]

[0075] In the above formula, the smaller the capacitance C*resistance R is, the sharper the spike pulse waveform is, and vice versa. The capacitance C*resistance R of the differential circuit is less than the width of the input waveform. The capacitance C*resistance R of this circuit must be much less than the width of the input waveform, otherwise the waveform transformation function is lost and it becomes a general RC coupling circuit. Generally, the capacitance C*resistance R is less than or equal to 1 / 10 of the width of the input waveform of the differential circuit. The function of C7 in the differential circuit is to suppress high-frequency signals in the circuit and prevent interference signals from causing saturation of the operational amplifier.

[0076] Embodiment 8:

[0077] like Figure 7 As shown, the voltage follower circuit is used for buffering, isolation, and improving the load capacity, and the resistance value of the resistor R11 in the voltage follower circuit is the same as the resistance value of the resistor R12. The measured speed of the motor is calculated as follows:

[0078]

[0079] We can get:

[0080]

[0081] Among them, speed The unit is V / ms, that is, volt / millisecond; then:

[0082] V speed1 =1.65-1.23V

[0083] The measured speed of the motor is

[0084] Embodiment 9:

[0085] Combination Figure 8 Fig. 9 , the output of the differential to single-ended circuit U2 is differentiated, and the result is the rate of change of the voltage, that is, the speed of the motor. By increasing the bias signal 3.3V, the final output can meet the acquisition range of the MCU. The microcontroller can calculate the speed value through the voltage value of Vspeed1. The actual test data is shown in Table 1.

[0086] Table 1 Relationship between the measured speed and voltage change rate of the motor

[0087]

[0088]

[0089]

[0090] Through Table 1, Figure 8 , Fig. 9 It can be seen that the device is accurate in detecting the motor speed. The MCU of the device only needs to collect the ADC voltage value to know the motor speed, which eliminates the intermediate calculation steps and has a faster response.

[0091] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A digital drive control motor speed measuring device in a laser welding system, characterized in that: The speed measuring device comprises: a main controller MCU, a sensor interface, a fully differential operational amplifier circuit, a differential to single-ended circuit, a differential circuit and a voltage follower circuit; The input end of the sensor interface is connected to the position sensor of the motor, and the output end is connected to the input end of the fully differential operational amplifier circuit, the output end of the fully differential operational amplifier circuit is connected to the main controller MCU, the input end of the differential to single-ended circuit is connected to the output end of the fully differential operational amplifier circuit, and the output end is connected to the output end of the differential circuit, the output end of the differential circuit is connected to the input end of the voltage follower circuit, and the output end of the voltage follower circuit is connected to the main controller MCU, and the main controller MCU controls the motor.

2. According to the digital drive control motor speed measuring device in the laser welding system of claim 1, it is characterized in that: The fully differential operational amplifier circuit includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C1, and a fully differential circuit U1; One end of the resistor R4 and one end of the resistor R5 input the position signals V01+ and V01- of the motor in the laser welding system, pin 1 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R4, one end of the capacitor C1 and one end of the resistor R1, pin 4 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C1 and one end of the resistor R2, one end of the capacitor C3 is simultaneously connected to the other end of the resistor R2, the other end of the resistor R1 and one end of the capacitor C4 and outputs a signal V01+_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C3 is grounded, pin 8 of the fully differential circuit U1 is simultaneously connected to the other end of the resistor R5, the One end of the capacitor C6 is connected to one end of the resistor R7, pin 5 of the fully differential circuit U1 is simultaneously connected to the other end of the capacitor C6 and one end of the resistor R6, one end of the capacitor C5 is simultaneously connected to the other end of the resistor R6, the other end of the resistor R7, and the other end of the capacitor C4, and outputs a signal V01-_1 to the main controller MCU and the differential to single-ended circuit, the other end of the capacitor C5 is grounded, pin 6 of the fully differential circuit U1 is grounded, pin 3 of the fully differential circuit U1 is simultaneously connected to one end of the capacitor C2 and one end of the resistor R3, the other end of the capacitor C2 is grounded, and pin 7 of the fully differential circuit U1 and the other end of the resistor R3 input a 3.3V voltage.

3. The digital drive control motor speed measuring device in a laser welding system according to claim 1 is characterized in that: The differential to single-ended circuit comprises: a differential to single-ended chip U2, a capacitor C11 and a capacitor C9; Pin 1 of the differential-to-single-ended chip U2 is grounded, pins 2 and 3 of the differential-to-single-ended chip U2 are connected to the fully differential op amp circuit and input signals V01+_1 and V01-_1, pin 4 of the differential-to-single-ended chip U2 inputs a voltage of -5V0 and is connected to one end of the capacitor C11, and the other end of the capacitor C11 is grounded, pins 5 and 6 of the differential-to-single-ended chip U2 output a signal V01 to the differential circuit, pin 5 of the differential-to-single-ended chip U2 inputs a voltage of +5V0 and is connected to one end of the capacitor C9, and the other end of the capacitor C9 is grounded.

4. The digital drive control motor speed measuring device in a laser welding system according to claim 1 is characterized in that: The differential circuit includes: capacitor C10, resistor R9, amplifier U3A, resistor R8, capacitor C7, capacitor C8, capacitor C12; One end of the capacitor C10 is connected to the differential to single-ended circuit and inputs the signal V01, and the other end is connected to one end of the resistor R9. Pin 2 of the amplifier U3A is simultaneously connected to the other end of the resistor R9, one end of the resistor R8 and one end of the capacitor C7. Pin 3 of the amplifier U3A is grounded. Pin 1 of the amplifier U3A is simultaneously connected to the other end of the capacitor C7 and the other end of the resistor R8 and outputs the signal SPEED of the voltage follower circuit. Pin 4 of the amplifier U3A inputs a voltage of -5V0 and is connected to one end of the capacitor C8. The other end of the capacitor C8 is grounded. Pin 8 of the amplifier U3A inputs a voltage of +V0 and is connected to an end of the capacitor C12. One end of the capacitor C12 is grounded.

5. The digital drive control motor speed measuring device in a laser welding system according to claim 1 is characterized in that: The voltage follower circuit includes: an amplifier U3B, a resistor R11, a resistor R12, a resistor R10, and a voltage regulator tube D1; One end of the resistor R11 is connected to the differential circuit and inputs the signal SPEED, pin 5 of the amplifier U3B is simultaneously connected to the other end of the resistor R11 and one end of the resistor R12, the other end of the resistor R12 inputs a voltage of 3.3V, pins 6 and 7 of the SPEED are connected and connected to one end of the resistor R10, the other end of the resistor R10 is connected to the negative electrode of the voltage regulator D1 and outputs the signal SPEED1 to the main controller MCU, and the positive electrode of the voltage regulator D1 is grounded.

6. A method for measuring the speed of a digital drive control motor in a laser welding system, implemented by using the digital drive control motor speed measuring device in a laser welding system according to any one of claims 1 to 5, characterized in that: The speed measurement method obtains two-way sensor signals of the motor through the fully differential operational amplifier circuit. The fully differential circuit signal is amplified and connected to the differential to single-ended circuit. The differential circuit and the voltage follower circuit further process the signal. The processed signal is connected to the AD port of the MCU. The MCU can obtain voltage change rate data through the device.

7. The method for measuring speed of a digital drive control motor in a laser welding system according to claim 6, characterized in that: The position signal of the motor in the laser welding system is a differential output. The fully differential circuit U1 in the fully differential operational amplifier circuit amplifies the motor position signal by a certain multiple to reach a voltage level that meets the voltage collected by the main controller MCU. The specific gain method is as follows: AV=Rf / Rg=R7 / R5 The resistance of resistor R4 is the same as the resistance of resistor R5, and the resistance of resistor R1 is the same as the resistance of resistor R7, so that the amplification ratios at both ends of the feedback are the same.

8. The method for measuring speed of a digital drive control motor in a laser welding system according to claim 6, characterized in that: The differential to single-ended circuit converts a double-ended signal into a single-ended signal, that is, the voltage range is calculated as follows: V out =V +in -V -in Converted into a voltage value with the center point of the motor stroke as the reference, that is, the position signal.

9. The method for measuring speed of a digital drive control motor in a laser welding system according to claim 6, characterized in that: The differential circuit eliminates the invariant and highlights the variable. The differential circuit converts the rectangular wave into a sharp pulse wave. The width of the output sharp pulse waveform is related to the capacitance C*resistance R, that is, the time constant of the circuit. The output voltage of the differential circuit is: In the above formula, the smaller the capacitance C*resistance R is, the sharper the spike pulse waveform is, and vice versa; the capacitance C*resistance R of the differential circuit is less than the width of the input waveform. The function of C7 in the differential circuit is to suppress high-frequency signals in the circuit and prevent interference signals from causing saturation of the operational amplifier.

10. The method for measuring speed of a digital drive control motor in a laser welding system according to claim 9, characterized in that: The voltage follower circuit is used for buffering, isolation, and improving the load capacity, and the resistance value of the resistor R11 in the voltage follower circuit is the same as the resistance value of the resistor R12. The measured speed of the motor is calculated as follows: We can get: Among them, speed The unit is V / ms, that is, volt / millisecond; then: V speed1 =1.65-1.23V The measured speed of the motor is

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