Double-wire double-pulse MIG welding power supply system based on fractional calculus and control method

Abstract

The invention discloses a double-wire double-pulse MIG welding power supply system based on fractional calculus. The double-wire double-pulse MIG welding power supply system comprises a host power supply, a slave power supply, a DSP control module, a master wire arc load and a slave wire arc load. One end of the host power supply is connected with a three-phase AC power grid, and the other end is connected with the main wire arc load. One end of the slave power supply is connected with the three-phase alternating current power grid, and the other end is connected with the slave wire arc load; the host power supply and the slave power supply are respectively connected with the same DSP control module, and the DSP control module is integrated with a fractional calculus control module; and the fractional calculus control module outputs four paths of pulse width modulation (PWM) signals to respectively control on and off of a switching tube of the host power supply and a switching tube of the slave power supply, so that the system enters a double-pulse mode to work. Complex nonlinear and time-varying dynamic characteristics of a welding arc and a molten pool system can be described and matched more accurately.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a dual-wire dual-pulse MIG welding power supply system and control method based on fractional calculus. Background Technology

[0002] MIG welding, as a highly efficient and flexible welding process, has been widely used in automotive manufacturing, shipbuilding, pressure vessels, and aerospace. Twin-wire pulsed MIG welding offers significant improvements in welding speed and quality compared to single-wire pulsed MIG welding. However, due to the closer distance between the two welding wires in twin-wire pulsed MIG welding, the master and slave arcs interact during welding, causing mutual interference. Therefore, the arc stability in twin-wire pulsed MIG welding is worse than that in single-wire welding. The arc behavior of the master and slave welding wires under the influence of high pulsed current directly affects the droplet transfer behavior. The interference from the dual arcs causes corresponding offset behavior, which directly affects the weld formation characteristics and quality.

[0003] To optimize the interference of dual arcs and its impact on droplet transfer and weld formation, waveform control is employed in the process. Dual pulses, through alternating strong and weak pulses, achieve dynamic regulation of arc energy and directional droplet separation. Specifically, high-frequency pulses precisely control the droplet separation process, ensuring a stable transition of one droplet per pulse, while low-frequency pulses regulate heat input and molten pool stirring intensity, effectively reducing spatter rate and total heat input, and minimizing the heat-affected zone. This is suitable for welding thin-walled parts to avoid deformation and burn-through risks. Simultaneously, it achieves high consistency in waveform output and uniform weld penetration, improving weld formation quality and mechanical properties. Furthermore, the dynamic stirring mechanism of the molten pool refines the weld grain structure, suppressing crack and porosity defects, and optimizing the droplet transfer mode to improve penetration and deposition efficiency, making it suitable for the high-precision requirements of automated production lines.

[0004] Currently, research on welding systems often involves simplifying minor factors or making assumptions to establish system models and implement intelligent control. These models are mostly integer-order systems, frequently losing realistic information about the system and its behavior. Fractional calculus, however, considers response information of arbitrary orders in the modeling and analysis of nonlinear systems, compensating for the shortcomings of integer-order calculus. Integer-order calculus only considers local information with integer properties during modeling and analysis, while fractional calculus considers all information about each state point and its behavior for any real number during model analysis and design. Mathematically, it represents the influence of past states or information on the current state in a weighted form. The most significant characteristic of fractional-order control systems is their memory property; all states during system operation have varying degrees of influence or constraints on the current state, accumulating overall system information within a certain range. Mathematical models analyzed and designed based on fractional calculus can better describe the real behavior and representation information of the system, enriching the design methods and engineering applications of dynamic control systems. With the continuous promotion and in-depth research of fractional calculus theory, its applications are increasingly broad in various engineering disciplines such as mechanics, physics, bioengineering, and earthquake analysis.

[0005] As described above, dual-wire dual-pulse welding technology and advanced fractional-order control theory each have their advantages. Combining the two organically can fully leverage the inherent advantages of dual-wire dual-pulse technology in high deposition efficiency and flexible heat input control, while utilizing the superior dynamic response and high-precision control capabilities of fractional-order control to achieve more precise and stable control of the welding arc morphology and droplet transfer process, thereby significantly improving the weld formation quality and overall mechanical properties. Therefore, this invention proposes a dual-wire dual-pulse MIG welding power supply system and control method based on fractional-order calculus. Summary of the Invention

[0006] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a dual-wire dual-pulse MIG welding power supply system and control method based on fractional calculus.

[0007] This invention proposes a fractional-order calculus control method based on the commonly used dual-wire dual-pulse MIG welding, overcoming the shortcomings of integer-order calculus. This control system achieves superior control performance with small overshoot, fast response, and strong parameter robustness by performing more accurate fractional-order modeling and compensation of the dynamic characteristics of the welding process.

[0008] The objective of this invention is achieved through the following technical solution: A dual-wire dual-pulse MIG welding power supply system based on fractional calculus includes a host power supply, a slave power supply, a DSP control module, a host wire arc load, and a slave wire arc load. One end of the main power supply is connected to a three-phase AC power grid, and the other end is connected to the main wire arc load; one end of the slave power supply is connected to a three-phase AC power grid, and the other end is connected to the slave wire arc load. The host power supply and the slave power supply are respectively connected to the same DSP control module, which integrates a fractional calculus control module; The fractional-order calculus control module outputs four pulse width modulation (PWM) signals, which control the switching transistors of the master power supply and slave power supply to turn on and off, enabling the system to operate in dual-pulse mode.

[0009] Furthermore, the host power supply and the slave power supply have the same structure, both including a main circuit, a high-frequency drive module, a fault protection module, and a voltage and current detection module; The main circuit includes an input rectifier and filter module, a high-frequency inverter module, a power transformer module, and an output rectifier and filter module that are electrically connected in sequence. One end of the high-frequency drive module is connected to the high-frequency inverter module, and the other end is connected to the DSP control module; One end of the fault protection module is connected to the three-phase AC input power grid, and the other end is connected to the DSP control module; One end of the voltage and current detection module is connected to the arc load, and the other end is connected to the DSP control module.

[0010] Furthermore, the main circuits of the host power supply and slave power supply adopt a half-bridge hard switch, full-bridge hard switch, phase-shifted full-bridge soft switch, or half-bridge or full-bridge LLC resonant soft switch main circuit topology.

[0011] Furthermore, the fractional-order calculus control module includes: a fractional-order control unit, a fractional-order operator implementation unit, an offline parameter pre-tuning unit, and a dual-wire collaborative management unit.

[0012] Furthermore, the transfer function model of the fractional-order control unit is as follows: G c (s)= K p + K i s -λ + K d s μ ,in, K p , K i , K d These are the proportional, integral, and differential coefficients, respectively, and λ and μ are real numbers greater than zero, representing the fractional orders of the integral and differential, respectively.

[0013] Furthermore, the fractional-order operator implementation unit is used to physically implement the s in the fractional-order control unit within the digital control environment. -λ and s μ Operator.

[0014] Furthermore, the offline parameter pre-tuning unit performs offline global optimization of five parameters of the fractional-order control unit based on a genetic algorithm. These five parameters are specifically... K p , K i , K d , μ , λ ; Specifically: First, a simulation model of the welding system is established, and the parameters of a set of fractional-order control units are encoded into a chromosome. The integral performance index of the system error is used as the fitness function. The integral performance index includes the time-to-absolute-error integral, the error-squared integral, or the absolute-error integral. Subsequently, through iterative evolution via selection, crossover, and mutation operations using a genetic algorithm, the optimal parameter set of the fractional-order control unit that optimizes the fitness function is found in the simulation environment.

[0015] Furthermore, the dual-filament collaborative management unit pre-stores the optimal parameter set of the master filament and slave filament fractional-order control unit, which is optimized by the offline parameter pre-tuning unit; In actual control, the dual-wire collaborative management unit calls the optimal parameter set and executes the anti-coupling strategy. By utilizing the strong robustness of the optimized fractional-order controller, it actively suppresses the mutual interference between the master and slave wire arcs, thereby achieving stable collaborative operation of the dual arcs.

[0016] A control method for a dual-wire, dual-pulse MIG welding power supply system based on fractional calculus, comprising: A fractional-order control unit is used to perform closed-loop control on the output current of the output rectifier and filter module, thereby achieving constant current output from the output rectifier and filter module. To achieve dual-pulse current output from the output rectifier and filter module; Achieving dual pulses on the master and slave wires, and achieving precise control of the current waveform by adjusting the fractional order and integral-derivative coefficients of the fractional-order control unit; The phase shift between the master wire dual pulse and the slave wire dual pulse is achieved, with a phase shift range of 0° to 180°. The precise control of the dual pulse current phase is achieved through tracking control by the fractional-order control unit. The constant current output specifically refers to the output of a given peak current. I p Or given base current Ib Feedback current I of the current detection circuit f The deviation is calculated, and the phase shift angle of the modulation signal PWMA and the modulation signal PWMB is obtained by constant current fractional-order calculus control based on the deviation. The phase shift angle is set as the phase difference between PWMA and PWMB. This process is repeated until constant current is achieved.

[0017] Furthermore, within one pulse cycle, the current transition points of the host power supply and slave power supply are segmented. Specifically, this means segmenting the median waveform, dividing the current waveform within each pulse cycle into N segments. t n This indicates the time for each stage. The timer is set to generate an interrupt every 1ms, and the counter is incremented by 1. exist t n During this phase, the host's current setpoint is set to... I x1 The slave current setpoint is set to I y2 At the same time, the counter is cleared to 0, and then the timer is started until the counter value equals 0. t n The loop exits when n is reached; then the value of n is incremented by 1, and the next stage is entered. It is then determined whether all stages have been traversed. If all stages have been successfully traversed, the loop ends and the next pulse cycle begins. Otherwise, the current setpoint is reacquired, and the above operation process is repeated.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) By introducing two additional adjustable dimensions, the integral order λ and the differential order μ, the complex nonlinear and time-varying dynamic characteristics of the welding arc and molten pool system can be described and matched more accurately. (2) Fractional calculus has inherent “memory” and “heredity”, which enables it to make comprehensive use of historical state information in control, thereby achieving a faster, non-overshoot, and high-precision dynamic response than traditional integer PID, and significantly improving arc length stability and droplet transition consistency.

[0019] (3) To address the challenges of manually tuning the five parameters of a fractional-order controller and its tendency to get trapped in local optima, a genetic algorithm is used for offline global optimization. This algorithm uses system performance indices such as ITAE and ISE as fitness functions. By simulating the natural evolution process, it can automatically and efficiently find the optimal parameter combination for the overall performance of the control system in a complex parameter space, ensuring the full realization of the performance potential of the fractional-order controller and solving the core obstacle to its engineering application.

[0020] (4) A single DSP control module is used to coordinate the control of the dual-wire dual-pulse MIG welding host power supply and slave power supply based on fractional calculus, reducing the number of controllers and simplifying the control system structure. It saves the controller timer, has strong anti-interference ability, and eliminates communication interference and communication delay problems between the host power supply and slave power supply; (5) The dual pulse can effectively stir the molten pool through low-frequency thermal pulses while ensuring the droplet transition one drop at a time, thereby significantly reducing porosity and spatter, and obtaining a weld with beautiful shape and excellent internal quality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2(a) is a schematic diagram of the current waveform of the dual-pulse phase of the host and slave of the present invention at 0°. Figure 2(b) is a schematic diagram of the current waveform of the master and slave devices of the present invention with a dual-pulse phase of 180°; Figure 2(c) shows that the bipulse phase of the host and slave devices of this invention is a random phase. φ (0°< φ< A schematic diagram of the current waveform at 180°. Figure 3 This is the main welding program flowchart of the present invention; Figure 4 This is a flowchart of multi-phase control of dual-wire dual-pulse MIG welding current based on fractional calculus. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0023] Example like Figure 1 As shown, a dual-wire dual-pulse MIG welding power supply system based on fractional calculus includes a main power supply, a slave power supply, a DSP control module, a main wire arc load, and a slave arc load. One end of the main power supply is connected to a three-phase AC power grid, and the other end is connected to the main wire arc load; one end of the slave power supply is connected to a three-phase AC power grid, and the other end is connected to the slave wire arc load.

[0024] The host power supply and slave power supply are respectively connected to the same DSP control module, which integrates a fractional calculus control module.

[0025] The host power supply and slave power supply have the same structure, both including a main circuit, a high-frequency drive module, a fault protection module, and a voltage and current detection module.

[0026] The main circuit includes an input rectifier and filter module, a high-frequency inverter module, a power transformer module, and an output rectifier and filter module, which are electrically connected in sequence. The high-frequency inverter module is an IGBT full-bridge inverter, and the power transformer module is a transformer. The high-frequency drive module is an IGBT drive circuit.

[0027] One end of the high-frequency drive module is connected to the high-frequency inverter module, and the other end is connected to the control circuit.

[0028] One end of the fault protection module is connected to the three-phase AC input power grid, and the other end is connected to the DSP control module.

[0029] One end of the voltage and current detection module is connected to the arc load, and the other end is connected to the DSP control module; The main circuits of the host power supply and slave power supply adopt a half-bridge or full-bridge hard switching, phase-shifted full-bridge soft switching, or half-bridge or full-bridge LLC resonant soft switching main circuit topology.

[0030] The DSP control module uses a TMS320F280049C or TMS320F28379D digital signal processor. This invention uses only one DSP control module to control the coordinated control of two power supplies, which has strong anti-interference ability. Furthermore, one DSP control module coordinates the control of the master power supply and the slave power supply, eliminating communication interference and communication delay issues between the master and slave power supplies. Commonly used dual-wire pulse MIG welding technology uses two separate power supplies, which coordinate the control between the two power supplies through a communication protocol, inevitably causing interference and affecting the welding process.

[0031] The fractional-order calculus control module outputs four pulse width modulation (PWM) signals, which control the switching transistors of the host power supply and slave power supply to turn on and off, respectively, so that the welding power supply system enters dual-pulse mode.

[0032] The fractional-order calculus control module includes: a fractional-order control unit, a fractional-order operator implementation unit, an offline parameter pre-tuning unit, and a dual-wire collaborative management unit.

[0033] Furthermore, the fractional-order control unit is the system's transfer function model as follows: G c (s)= K p + K i s -λ + K d s μ That is, fractional-order PID control, where, K p , K i ,K d These are the proportional, integral, and differential coefficients, respectively, and λ and μ are real numbers greater than zero, representing the fractional orders of the integral and differential, respectively.

[0034] Furthermore, the fractional-order operator implementation unit is responsible for physically implementing the s in the fractional-order controller within the digital control environment. -λ and s μ Operator. This module discretizes continuous fractional operators into an equivalent, microprocessor-executable integer-order high-order IIR digital filter using a preset digital approximation algorithm (such as the Oustaloup recursive approximation algorithm), thereby realizing the "memory" and "inheritance" characteristics of fractional calculus in discrete-time systems.

[0035] Furthermore, the core of the offline parameter pre-tuning unit is based on a genetic algorithm to adjust the five parameters of the fractional-order controller. K p , K i , K d , μ , λ Offline global optimization is performed. In this module, a simulation model of the welding system is first established, and a set of controller parameters is encoded into a chromosome. The fitness function is based on the integral performance index of the system error (such as ITAE (integral of time multiplied by absolute error), ISE (integral of squared error), or IAE (integral of absolute error) criterion). Subsequently, through the selection, crossover, and mutation operations of a genetic algorithm, the optimal combination of controller parameters that optimizes the fitness function is searched in the simulation environment. Finally, the optimized parameter set is preset and stored in the memory of the control system, and can be directly called during actual welding.

[0036] Furthermore, the dual-wire collaborative management unit pre-stores the optimal parameter sets of the master and slave wire fractional-order controllers, respectively, optimized by the offline parameter pre-tuning module. During actual control, this module calls their respective parameter sets and executes an anti-coupling strategy, utilizing the strong robustness of the optimized fractional-order controllers to actively suppress mutual interference between the master and slave wire arcs, thereby achieving stable collaborative operation of the two arcs.

[0037] Further explanation: The anti-coupling strategy employs a feedforward compensation method: when a change in the voltage or current of the master wire arc is detected, this change is used as a feedforward input into the slave wire control loop to eliminate the dynamic disturbance caused by the master wire to the slave wire; conversely, the same applies. This feedforward compensation achieves coupling suppression between the master and slave wires.

[0038] like Figures 2(a)-2(c)As shown, the current waveforms of the dual pulses of the host power supply and the slave power supply at different phases can be adjusted by adjusting the phase difference between the PWM of the host power supply and the PWM of the slave power supply, so that the phase of the dual pulses of the host and slave can be adjusted between 0° and 180°, which is beneficial to the control of the current phase.

[0039] like Figure 3 As shown, a control method for a fractional-order dual-wire dual-pulse MIG welding power supply system is as follows: A fractional-order PID controller is used to perform closed-loop control on the output current of the output rectifier and filter module, thereby achieving constant current output from the output rectifier and filter module. To achieve dual-pulse current output from the output rectifier and filter module, specifically: To achieve dual-pulse current, set the phase angle between the low-frequency pulses from the master and slave devices, and set a given peak current. I p , I p and the peak feedback current acquired through the current detection circuit I pf A constant peak current is obtained by applying constant current fractional-order PID control. Then, a given base current is set. I b , I b and the base feedback current acquired through the current detection circuit I bf Together, they undergo constant current fractional-order PID control to obtain a constant base current.

[0040] Achieving dual pulses on the master and slave wires, and achieving precise control of the current waveform by adjusting the fractional order and integral / derivative coefficients of the fractional-order PID controller; The phase shift between the master wire dual pulse and the slave wire dual pulse is achieved, with a phase shift range of 0° to 180°. The phase shift is precisely controlled by the fractional-order PID controller through tracking control.

[0041] Furthermore, the constant current output of the output rectifier and filter module is achieved specifically as follows: Given peak current I p Or given base current I b Feedback current of the current detection circuit I f The deviation is calculated, and the phase shift angle of the modulation signal PWMA and the modulation signal PWMB is obtained by constant current fractional-order calculus control based on the deviation. The phase shift angle is set as the phase difference between PWMA and PWMB. This process is repeated until constant current is achieved.

[0042] like Figure 4The diagram shows the multi-phase control flowchart of dual-wire dual-pulse MIG welding current based on fractional calculus. The specific steps are as follows: Within one pulse cycle, the current transition points of the master power supply and slave power supply are segmented. Specifically, the median waveform is segmented, dividing the current waveform within each pulse cycle into N segments. t n This indicates the time for each stage, with the timer set to generate an interrupt every 1ms and the counter incremented by 1. t n During this phase, the host current setpoint is set to... I x1 The slave current setpoint is set to I y2 At the same time, the counter is cleared to 0, and then the timer is started until the counter value equals 0. t n The loop exits when n is reached; then the value of n is incremented by 1, and the next stage is entered. It is then determined whether all stages have been traversed. If all stages have been successfully traversed, the loop ends and the next pulse cycle begins. Otherwise, the current setpoint is reacquired, and the above operation process is repeated.

[0043] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A dual-wire, dual-pulse MIG welding power supply system based on fractional calculus, characterized in that, Includes main power supply, slave power supply, DSP control module, main wire arc load and slave wire arc load; One end of the main power supply is connected to a three-phase AC power grid, and the other end is connected to the main wire arc load; one end of the slave power supply is connected to a three-phase AC power grid, and the other end is connected to the slave wire arc load. The host power supply and the slave power supply are respectively connected to the same DSP control module, which integrates a fractional calculus control module; The fractional-order calculus control module outputs four pulse width modulation (PWM) signals, which control the switching transistors of the master power supply and slave power supply to turn on and off, enabling the system to operate in dual-pulse mode.

2. The dual-wire dual-pulse MIG welding power supply system according to claim 1, characterized in that, The host power supply and slave power supply have the same structure, both including a main circuit, a high-frequency drive module, a fault protection module and a voltage and current detection module; The main circuit includes an input rectifier and filter module, a high-frequency inverter module, a power transformer module, and an output rectifier and filter module that are electrically connected in sequence. One end of the high-frequency drive module is connected to the high-frequency inverter module, and the other end is connected to the DSP control module; One end of the fault protection module is connected to the three-phase AC input power grid, and the other end is connected to the DSP control module; One end of the voltage and current detection module is connected to the arc load, and the other end is connected to the DSP control module.

3. The dual-wire dual-pulse MIG welding power supply system according to claim 1, characterized in that, The main circuits of the host power supply and slave power supply adopt a half-bridge hard switch, full-bridge hard switch, phase-shifted full-bridge soft switch, or half-bridge or full-bridge LLC resonant soft switch main circuit topology.

4. The dual-wire dual-pulse MIG welding power supply system according to claim 1, characterized in that, The fractional-order calculus control module includes: a fractional-order control unit, a fractional-order operator implementation unit, an offline parameter pre-tuning unit, and a dual-wire collaborative management unit.

5. The dual-wire dual-pulse MIG welding power supply system according to claim 4, characterized in that, The transfer function model of the fractional-order control unit is as follows: G c (s)= K p + K i s -λ + K d s μ ,in, K p , K i , K d These are the proportional, integral, and differential coefficients, respectively, and λ and μ are real numbers greater than zero, representing the fractional orders of the integral and differential, respectively.

6. The dual-wire dual-pulse MIG welding power supply system according to claim 5, characterized in that, The fractional-order operator implementation unit is used to physically implement the s in the fractional-order control unit in a digital control environment. -λ and s μ Operator.

7. The dual-wire dual-pulse MIG welding power supply system according to claim 6, characterized in that, The offline parameter pre-tuning unit performs offline global optimization of five parameters of the fractional-order control unit based on a genetic algorithm. These five parameters are specifically... K p , K i , K d , μ , λ ; Specifically: First, a simulation model of the welding system is established, and the parameters of a set of fractional-order control units are encoded into a chromosome. The integral performance index of the system error is used as the fitness function. The integral performance index includes the time-to-absolute-error integral, the error-squared integral, or the absolute-error integral. Subsequently, through iterative evolution via selection, crossover, and mutation operations using a genetic algorithm, the optimal parameter set of the fractional-order control unit that optimizes the fitness function is found in the simulation environment.

8. The dual-wire dual-pulse MIG welding power supply system according to claim 7, characterized in that, The dual-filament collaborative management unit pre-stores the optimal parameter set of the master filament and slave filament fractional-order control unit, which is optimized by the offline parameter pre-tuning unit; In actual control, the dual-wire collaborative management unit calls the optimal parameter set and executes the anti-coupling strategy. By utilizing the strong robustness of the optimized fractional-order controller, it actively suppresses the mutual interference between the master and slave wire arcs, thereby achieving stable collaborative operation of the dual arcs.

9. A control method for a dual-wire, dual-pulse MIG welding power supply system based on fractional calculus as described in any one of claims 1-8, characterized in that, include: A fractional-order control unit is used to perform closed-loop control on the output current of the output rectifier and filter module, thereby achieving constant current output from the output rectifier and filter module. To achieve dual-pulse current output from the output rectifier and filter module; Achieving dual pulses on the master and slave wires, and achieving precise control of the current waveform by adjusting the fractional order and integral-derivative coefficients of the fractional-order control unit; The phase shift between the master wire dual pulse and the slave wire dual pulse is achieved, with a phase shift range of 0° to 180°. The precise control of the dual pulse current phase is achieved through tracking control by the fractional-order control unit. The constant current output specifically refers to the output of a given peak current. I p Or given base current I b Feedback current I of the current detection circuit f The deviation is calculated, and the phase shift angle of the modulation signal PWMA and the modulation signal PWMB is obtained by constant current fractional-order calculus control based on the deviation. The phase shift angle is set as the phase difference between PWMA and PWMB. This process is repeated until constant current is achieved.

10. The control method according to claim 9, characterized in that, Within one pulse cycle, the current transition points of the master power supply and slave power supply are segmented. Specifically, the median waveform is segmented, dividing the current waveform within each pulse cycle into N segments. t n This indicates the time for each stage. The timer is set to generate an interrupt every 1ms, and the counter is incremented by 1. exist t n During this phase, the host's current setpoint is set to... I x1 The slave current setpoint is set to I y2 At the same time, the counter is cleared to 0, and then the timer is started until the counter value equals 0. t n Exit the loop when prompted; Then the value of n is incremented by 1, and the next stage is entered. It is then determined whether all stages have been traversed. If all stages have been successfully traversed, the loop ends and the next pulse cycle begins. Otherwise, the current setpoint is reacquired, and the above operation process is repeated.

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