Control method and device of pulse power supply for electric spark machining based on stepped wave discharge current output

Abstract

The application discloses a control method and device of an electrical discharge machining pulse power supply based on stepped wave discharge current output, and belongs to the technical field of electrical discharge special machining, wherein the discharge current output in a single pulse discharge period is sequentially composed of a rising edge multi-step increasing stepped section, a stable discharge section and a falling edge multi-step decreasing stepped section; the rising edge is sequentially turned on by a plurality of power switching tubes according to a first order to realize step-by-step current increasing; the falling edge is sequentially turned off by the plurality of power switching tubes according to a second order to realize step-by-step current decreasing; the interelectrode voltage signal is collected in real time to identify the discharge state and calculate the effective spark discharge rate, and the stepped wave parameters are adjusted in a closed loop according to the effective spark discharge rate; the control method and device of the electrical discharge machining pulse power supply based on the stepped wave discharge current output can simultaneously improve machining efficiency, machining precision and electrode loss, and is suitable for various machining scenes such as rough machining, semi-finishing machining and finishing machining.

Description

Technical Field

[0001] This invention relates to the field of electrical discharge machining (EDM) technology, and in particular to an EDM pulse power supply control method and device based on stepped wave discharge current output. Background Technology

[0002] Electrical discharge machining (EDM) is a non-contact machining technology that applies pulsed electrical energy between a tool electrode and a workpiece, using the instantaneous high temperature generated by the spark discharge between the electrodes to melt, vaporize, and erode the workpiece material. Compared to traditional machining, EDM has no macroscopic cutting force, avoiding problems such as microstructural deformation and loss of precision control caused by contact machining. It can process precision parts with high hardness, high melting point, and complex structures, and is widely used in mold manufacturing, aerospace, precision machinery, microelectronics, and medical devices. In the EDM system, the pulse power supply is the core execution unit, and the controllability of its output discharge energy is the core factor determining machining efficiency and quality. The leading and trailing edge change rate, amplitude stability, and parameter adjustability of the discharge current waveform output by the pulse power supply directly determine the wear rate of the tool electrode, the surface roughness of the workpiece, the discharge stability of the machining process, and the consistency of batch processing.

[0003] In the current field of electrical discharge machining (EDM), the mainstream pulse power supply technologies are divided into two categories: square wave pulse power supplies and approximate triangular wave pulse power supplies. Square wave pulse power supplies output a standard square wave current with steep rising and falling edges and large slopes, providing rapid peak discharge energy and high processing efficiency, making them suitable for rough machining of high-hardness materials. However, the steep rising edge of the current in square wave pulse power supplies results in excessively large instantaneous discharge impact energy, easily leading to severe vaporization loss at the electrode end, increasing processing costs. Simultaneously, steep-edge discharge causes molten spatter on the workpiece surface, resulting in poor surface roughness and failing to meet the requirements of high-precision finishing. Furthermore, steep-edge impacts easily induce arc discharge, short circuits, and other adverse discharge phenomena, leading to poor processing stability and a high workpiece scrap rate. Approximate triangular wave pulse power supplies, on the other hand, output a near-triangular wave current with gentle rising and falling edges, eliminating steep-edge impacts, resulting in low electrode loss and good surface quality, making them suitable for precision micro-machining. However, the current energy rises slowly and the peak energy duration is short, resulting in insufficient effective processing energy and extremely low processing efficiency. It cannot meet the processing needs of high-hardness and difficult-to-machine materials and can only be used in low-efficiency micro-fine machining scenarios, severely limiting its application scope.

[0004] The existing pulse power supply solutions described above can only meet single-dimensional processing requirements and cannot simultaneously address the three core indicators of processing efficiency, processing accuracy, and low electrode loss. Facing the increasingly stringent processing demands of new and difficult-to-machine materials such as high-temperature alloys, titanium alloys, and ceramic matrix composites in the aerospace field, as well as the industry's core requirements for high precision, low cost, high efficiency, and full-process adaptability, the shortcomings of existing pulse power supplies are becoming increasingly apparent. Furthermore, the waveform parameters of the two existing power supplies are fixed, failing to achieve flexible programmable adaptation of waveform parameters, and cannot dynamically adjust current output characteristics according to real-time changes in processing conditions. This makes it difficult to adapt to the processing requirements of roughing, semi-finishing, and finishing processes, resulting in poor workpiece consistency during batch processing and failing to meet the large-scale production requirements of high-end manufacturing. The industry urgently needs an EDM pulse power supply that can achieve segmented controllable discharge energy, adaptive adjustment under operating conditions, and full-process adaptability. Summary of the Invention

[0005] The purpose of this invention is to provide a pulse power supply control method and device for electrical discharge machining based on stepped wave discharge current output. It aims to solve the core technical bottleneck of existing electrical discharge machining pulse power supplies that cannot simultaneously achieve high machining efficiency, low electrode loss, and high machining accuracy. By using a multi-step stepped current waveform, the discharge energy can be output in segments and controllable. At the same time, the machining conditions can be dynamically and adaptively adjusted to meet the needs of electrical discharge machining in the whole process, multiple scenarios, and multiple materials.

[0006] To achieve the above objectives, the present invention provides a method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output, comprising the following steps: Step S1: Collect processing condition parameters and match them to generate target parameters for stepped wave discharge current. The target parameters for stepped wave discharge current include the number of steps N, the duration of each current step, the duration of single-pulse stable discharge, and the pulse interval duration. Step S2: In each single pulse discharge cycle, according to the target parameters of the matched stepped wave discharge current, the main control MCU of the pulse power supply system generates M synchronous timing control signals, and controls the M power switches to turn on in the first order. The time interval between the turn-on of two adjacent power switches is the duration of each current step, and the output rise edge is a multi-step incremental step segment; where M is equal to the step number N, N≥2; Step S3: When the number of conduction paths reaches the step number N, keep all M power switches in the conduction state and continuously output a stable discharge segment for a duration equal to the single-pulse stable discharge duration. Step S4: When the duration of the stable discharge segment reaches the duration of the single-pulse stable discharge, the main control MCU controls the M-channel synchronous timing control signals to turn off the M-channel power switches in the second order, which is the opposite of the first order. The turn-off time interval between two adjacent power switches is the duration of each current step, and the output is a multi-step decreasing ladder segment with a falling edge. Step S5: After all M power switching transistors are turned off, the current output stops, and after the timer reaches the pulse interval duration, it jumps to step S2 and executes repeatedly. Step S6: Real-time acquisition of the inter-electrode voltage signal and identification of the inter-electrode discharge state during each individual pulse discharge cycle, calculation of the effective spark discharge rate, and dynamic adjustment of the step wave discharge current target parameter based on the effective spark discharge rate.

[0007] Preferably, in step S2, the main control MCU increments the IO register of the main control MCU step by step using a bitwise OR assignment method, controlling the M power switches to turn on in the first order; in step S4, the main control MCU decrements the IO register step by step using a bitwise AND assignment method, controlling the M power switches to turn off in the second order; the timing synchronization error of the M synchronization timing control signals is less than or equal to 10ns.

[0008] Preferably, the discharge current output within a single pulse discharge cycle The following piecewise function relationship is satisfied: When it is in the rising edge of a multi-step increasing ladder segment ; When in the stable discharge phase ; When in a descending step with multiple decreasing steps ; in, For the time variable within a single pulse discharge cycle, This is the current step index of the rising step segment. For the current step index of the descending step segment, For the first The magnitude increment of the current at each step, and the magnitude increment of the current at each step. Equal or unequal, This is the peak current. The duration of each current is denoted as . This refers to the duration of a single-pulse stable discharge.

[0009] Preferably, in steps S2 to S5, a four-state machine consisting of idle state, discharge breakdown state, discharge state, and pulse interval state is used to achieve closed-loop control throughout the entire process. The machine remains idle when there are no processing commands. Upon receiving the processing instruction, switch to the discharge breakdown state and execute step S2; After reaching the currently set step number N, switch to the discharge state and execute step S3; After the single-pulse stable discharge duration is reached, step S4 is executed. After all power switching transistors are turned off, the pulse interval state is switched to execute step S5. After the pulse interval duration is reached, the system jumps back to the discharge breakdown state and repeats the cycle.

[0010] Preferably, the adjustment range of the step number N is 2 to 16; the adjustment range of the duration of each current step is 1 to 10 μs; the adjustment range of the duration of the single-pulse stable discharge is 1 to 1000 μs; and the adjustment range of the pulse interval duration is 1 to 1000 μs. The duration of each step along the rising edge in step S2 and the duration of the corresponding step along the falling edge in step S4 are set independently.

[0011] Preferably, in step S6, the inter-electrode discharge state includes an open circuit state, a spark discharge state, and a short circuit state. When a short circuit is detected, the M-channel power switch is immediately turned off to stop current output; When the effective spark discharge rate is lower than the first preset threshold, the pulse interval duration is extended or the step number N is reduced, or the pulse interval duration and the step number N are extended simultaneously. When the effective spark discharge rate is higher than the second preset threshold, the step number N is increased or the single-pulse stable discharge duration is extended, or the step number N and the single-pulse stable discharge duration are increased simultaneously.

[0012] An electrical discharge machining pulse power supply control device based on stepped wave discharge current output, comprising: The main control MCU unit is used to generate M synchronous timing control signals by directly assigning values ​​to the IO registers of the main control MCU unit; The power amplifier output unit is connected to the main control MCU unit and includes M parallel power switch branches. Each power switch branch is connected in series with a current-limiting resistor and a power switch. The M power switch branches correspond one-to-one with the M synchronous timing control signals and are used to synthesize the output stepped discharge current step by step according to the synchronous timing control signals. M is equal to the step number N. The discharge status monitoring unit is connected in parallel across the machining electrode space between the tool electrode and the workpiece, and is connected to the main control MCU unit. It is used to collect the electrode voltage signal in real time and identify the electrode discharge status by threshold comparison. The human-machine interface unit is bidirectionally connected to the main control MCU unit and is used to input machining parameters and display machining status. The DC power supply unit is connected to the main control MCU unit, the power amplifier output unit, the discharge status monitoring unit, and the human-machine interaction unit, respectively, and is used to provide DC power to the above units.

[0013] Preferably, the discharge state monitoring unit calculates the effective spark discharge rate in the following manner. : ; in, This represents the number of pulses identified as spark discharge states within a preset time window. This represents the total number of pulses within a preset time window. The main control MCU unit based on the effective spark discharge rate Dynamically adjust the stepped wave parameters: when When the accuracy is less than 70%, increase the pulse interval duration or decrease the step number N, or simultaneously increase the pulse interval duration and decrease the step number N; when When the success rate is greater than or equal to 90%, increase the step number N or extend the duration of stable single-pulse discharge, or increase both the step number N and extend the duration of stable single-pulse discharge.

[0014] Preferably, the main control MCU unit is an industrial-grade MCU with a multi-channel IO controller or hardware PWM timer and a main frequency greater than or equal to 100MHz; The main control MCU unit uses a fixed interrupt period as the timing timestamp and directly assigns values ​​to the IO register to achieve synchronous control of multiple signals. The fixed interrupt period is 1μs.

[0015] Preferably, the discharge state monitoring unit is provided with voltage sampling thresholds, which include: open circuit voltage threshold greater than or equal to 80V, spark discharge voltage threshold 20 to 60V, arc discharge voltage threshold 10 to 20V, and short circuit voltage threshold less than 10V. When the inter-electrode voltage is detected to be lower than the short-circuit voltage threshold, the main control MCU unit immediately shuts down the M power switching transistors. When the effective spark discharge rate When the value is below 70%, the main control MCU unit automatically adjusts the pulse interval duration.

[0016] Therefore, the present invention employs the above-mentioned method and apparatus for controlling the pulse power supply of electrical discharge machining based on stepped wave discharge current output, which has the following beneficial effects: (1) Full-cycle stepped control of discharge current is achieved; This invention adopts a three-segment waveform structure consisting of a multi-stage increasing stepped segment on the rising edge, a stable discharge segment, and a multi-stage decreasing stepped segment on the falling edge. This reduces the discharge impact caused by abrupt current changes, which not only helps reduce electrode wear caused by abrupt changes on the rising edge, but also helps suppress secondary discharge and workpiece surface damage caused by abrupt changes on the falling edge. Thus, improvements are achieved in processing efficiency, processing accuracy, and electrode wear. Experimental verification shows that under the same processing conditions, the molybdenum wire electrode wear using this invention is reduced by more than 20% compared to the square wave pulse power supply, the surface roughness Ra is reduced by more than 15% compared to the square wave pulse power supply, and the secondary discharge rate is reduced by more than 60% compared to the square wave pulse power supply.

[0017] (2) The timing control logic is simplified, balancing control accuracy and hardware cost. This invention adopts the direct assignment method of the I / O registers of the main control MCU, realizing step-by-step incremental turn-on control on the rising edge through bitwise OR assignment, and step-by-step incremental turn-off control on the falling edge through bitwise AND assignment. Synchronous control of multiple power switches can be achieved without complex programmable logic devices such as FPGAs, and the timing synchronization error can be controlled within 10ns. This control method effectively utilizes the deterministic timing characteristics of MCU register operations, avoiding timing deviations caused by interrupt response delays and uncertainties in software instruction execution time. Compared with the stepped wave control scheme implemented using FPGA, the hardware structure of this invention is simpler, and while achieving high-performance stepped wave output, it can effectively control the manufacturing cost of the pulse power supply.

[0018] (3) Strong adaptability to processing scenarios; In this invention, the number of steps, the duration of each current step, the duration of single-pulse stable discharge, and the pulse interval duration can all be adjusted independently. The number of steps can be configured from 2 to 16 steps according to the processing accuracy requirements, and the amplitude of each current step can be configured using equal or variable amplitude methods. Before processing, the corresponding stepped wave parameter group can be matched and called from the built-in database of the control system according to the workpiece material properties, target processing accuracy, and preset processing efficiency. During processing, based on the real-time collected inter-electrode discharge state parameters, the system can perform closed-loop adaptive adjustment of the stepped wave parameters to adapt to changes in the processing gap state. Through the above configuration and adjustment mechanism, this invention can adapt to the needs of different processing stages such as roughing, semi-finishing, and finishing, and cover multiple processing applications on the same equipment.

[0019] (4) It helps reduce the defective discharge rate and improve processing stability and consistency. This invention reduces defective discharge phenomena such as arc discharge and short circuit caused by sudden current changes through smooth current change control throughout the entire cycle. Experimental verification shows that under the same processing conditions, the defective discharge rate of the scheme using this invention is reduced by more than 50% compared with the square wave pulse power supply. At the same time, with real-time discharge status monitoring and closed-loop adaptive adjustment, the system can automatically adjust the stepped wave parameters according to the changes in the effective spark discharge rate, maintaining the discharge state within the set stable range, thereby helping to reduce dimensional dispersion and surface quality fluctuations in batch processing.

[0020] (5) It has multi-level safety protection functions; the present invention collects the inter-electrode voltage in real time through the discharge state monitoring unit, and identifies the inter-electrode state based on four threshold levels: open circuit voltage, spark discharge voltage, arc discharge voltage and short circuit voltage. When a short circuit state is detected, the system can quickly turn off all power switching tubes and terminate the current output, which helps to reduce the risk of electrode burnout and workpiece scrapping, and extend the service life of the equipment.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a block diagram of an electrical discharge machining pulse power supply control device based on stepped wave discharge current output according to the present invention. Figure 2 This is a flowchart of an electrical discharge machining pulse power supply control method based on stepped wave discharge current output according to the present invention. Figure 3 This is a waveform diagram of the stepped discharge current within a single pulse discharge cycle according to an embodiment of the present invention; Figure 4 This is a measured waveform diagram of the stepped discharge current according to an embodiment of the present invention; Figure 5 This is a measured waveform of the stepped discharge current in another embodiment of the present invention. Detailed Implementation

[0023] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely illustrates selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] Example like Figure 1 As shown, the present invention provides an electrical discharge machining pulse power supply device based on stepped-wave discharge current output, comprising a main control MCU unit, a power amplifier output unit, a discharge status monitoring unit, a human-machine interface unit, and a DC power supply unit. The main control MCU unit, as the core of the device, is connected to the power amplifier output unit, the discharge status monitoring unit, and the human-machine interface unit. The DC input terminal of the power amplifier output unit is connected to an external DC bus, and the AC output terminal is connected between the tool electrode and the workpiece machining electrode in the electrical discharge machining process. The sampling terminal of the discharge status monitoring unit is connected in parallel across the machining electrode between the tool electrode and the workpiece, and the signal output terminal is connected to the main control MCU unit. The human-machine interface unit is bidirectionally connected to the main control MCU unit. The input terminal of the DC power supply unit is connected to the power grid, and the output terminal is connected to the main control MCU unit, the power amplifier output unit, the discharge status monitoring unit, and the human-machine interface unit.

[0025] The core functions of the main control MCU unit include: receiving operating parameters from the human-machine interface unit and matching them to generate target parameters for a stepped wave; generating high-precision synchronous timing control signals to drive the power amplifier output unit to produce a stepped wave discharge current; receiving inter-electrode status signals uploaded by the discharge status monitoring unit and executing a closed-loop adaptive adjustment algorithm; and immediately triggering protection actions and stopping output to protect the tool electrode and workpiece when abnormal states such as short circuits are detected. The main control MCU unit uses an industrial-grade MCU with a multi-channel I / O controller or hardware pulse width modulation (PWM) timer and a main frequency of not less than 100MHz to ensure that the timing control accuracy meets the requirements.

[0026] The power amplifier output unit is used to synthesize a stepped discharge current with corresponding amplitude stepwise by controlling the timing signals of the main control MCU unit and switching multiple power switches sequentially, thereby converting electrical energy into processing discharge energy. The power amplifier output unit adopts a multi-parallel branch topology. Each branch is connected in series with a current-limiting resistor and a power metal-oxide-semiconductor field-effect transistor (MOSFET) switch. All branches are connected in parallel between the DC bus and the processing electrode. Each branch corresponds to a fixed current output amplitude. When a branch is turned on, the total output current is superimposed on the corresponding amplitude to achieve a stepped current output. The number of branches matches the maximum step size N, and the preferred value of N is 2 to 16.

[0027] The discharge status monitoring unit is used to acquire the voltage signal between the processing electrodes in real time. It identifies the discharge status between the electrodes through threshold comparison and logical judgment. The discharge status between the electrodes includes open circuit status, spark discharge status, arc discharge status and short circuit status. The status signal is uploaded to the main control MCU unit in real time to provide feedback basis for the dynamic adjustment of the stepped wave parameters.

[0028] The human-machine interaction unit can be implemented using a touch screen. Its core functions include: receiving processing condition parameters input by the user and sending them to the main control MCU unit to match and generate the target parameters of the stepped wave; displaying the processing status and processing parameters in real time, including statuses such as standby, processing, short circuit, and abnormal alarm; and supporting users to modify the stepped wave parameters online to realize manual intervention in the processing process.

[0029] The DC power supply unit is used to provide a stable DC power supply for the entire device, including providing DC bus voltage for the power amplifier output unit and providing isolated and regulated DC power for the main control MCU unit, discharge status monitoring unit and human-machine interaction unit.

[0030] like Figure 2As shown, the core of the electrical discharge machining pulse power supply control method based on stepped wave discharge current output provided by this invention lies in the following: within a single pulse discharge cycle, the rising edge of the output discharge current is a multi-level increasing stepped waveform; after reaching the set maximum number of steps, it enters a stable discharge stage, providing stable machining energy; after a single pulse reaches the set maximum pulse discharge duration, the falling edge of the output discharge current is a multi-level decreasing stepped waveform; simultaneously, through real-time monitoring of the machining inter-electrode state, closed-loop dynamic adjustment of waveform parameters is achieved. Figure 3 As shown, the stepped discharge current waveform within a single pulse discharge cycle exhibits a three-segment structure, consisting of a rising edge multi-step increasing segment, a stable discharge segment, and a falling edge multi-step decreasing segment.

[0031] Combination Figures 1 to 3 The control method of the present invention specifically includes the following steps.

[0032] Step S1: Collect processing condition parameters and match them to generate target parameters for stepped wave discharge current. Collect processing condition indicators such as the material properties of the workpiece to be processed, processing accuracy requirements, electrode type and specifications, and preset processing efficiency. Match these indicators to generate corresponding target parameters for stepped wave discharge current, and store them in the database of the pulse power supply control system. The stepped wave discharge current parameters include: the number of steps N (N≥2, a positive integer), and the duration of each current step. Single-pulse stable discharge duration Pulse interval duration The control system database can pre-store multiple sets of parameters adapted to different processing scenarios, for example, it can store 1 to 999 sets of parameters, where the step number N is preferably 2 to 16 steps; the duration of each step current. Preferably 1 to 10 μs; single-pulse stable discharge duration Preferably 1 to 1000 μs; pulse interval duration The preferred value is 1 to 1000 μs.

[0033] Step S2: In each single pulse discharge cycle, based on the matched stepped discharge current target parameters, the main control MCU of the pulse power supply system generates M synchronous timing control signals, which sequentially control the conduction of M power switches according to the first order. The conduction time interval between two adjacent power switches is the duration of each current step, outputting a multi-step ascending stepped segment with rising edges; where M equals the step number N, and N≥2. Specifically, based on the matched stepped discharge target parameters, the main control MCU generates N sets of synchronous timing control signals, each set of signals corresponding to the conduction of one power MOSFET switch, and each switch corresponding to the current output of one stepped segment. The timing signals are triggered strictly according to the order of the stepped segments, and the trigger interval between adjacent rising stepped segment signals is... The timing synchronization error is no greater than 10ns, ensuring no sudden changes or spikes in current. The specific turn-on logic is as follows: In the first interrupt cycle after entering the discharge breakdown state, the main control MCU controls the first I / O port output, driving the first power MOSFET Q1 to turn on, outputting the first-order current; at the first T0 time, the first I / O port remains in the output state, the second I / O port starts outputting, Q1 remains on, Q2 is on, outputting the second-order superimposed current; in the second… At any given time, the first and second I / O ports remain in output state, while the third I / O port begins outputting. Q1 and Q2 remain on, and Q3 is on, outputting the third-order superimposed current. This continues until the set maximum number of conduction steps N is reached, completing the multi-order stepped current output on the rising edge. The pulse power supply system uses timer interrupts to generate stable timing signals, with an optimal interrupt interval of 1μs. A synchronous PWM signal is generated using the main control MCU's hardware timer, and values ​​are assigned to the main control MCU's I / O registers via bitwise OR assignment to achieve precise synchronization of multi-channel timing. For example: during the first interrupt cycle, IO_register |= 0X0001; the first... At time IO_register|= 0X0003; the second one At time IO_register |= 0X0007; the third one At time IO_register |= 0X000F, and so on.

[0034] Step S3: When the number of conduction paths reaches the step order N, keep all M power switches fully on, continuously outputting a stable discharge segment for a duration equal to the single-pulse stable discharge duration. When the set maximum on-current step order N is reached, the pulse power supply system enters a stable discharge state. The main control MCU keeps all N power MOSFETs fully on, providing stable discharge energy of constant amplitude for EDM. The single-pulse stable discharge duration is... .

[0035] Step S4: After the duration of the stable discharge segment reaches the single-pulse stable discharge duration, the main control MCU controls the M-channel synchronous timing control signals to sequentially turn off the M-channel power switches in a second order, which is the reverse of the first order. The turn-off time interval between two adjacent power switches is the duration of each current step, and the output is a multi-step decreasing gradient segment with a falling edge. When the single-pulse stable discharge duration reaches the set time... Subsequently, the main control MCU controls N sets of synchronous timing control signals to turn off sequentially, corresponding to N sets of power MOSFETs turning off sequentially. The timing signals are executed in reverse logic of the turn-on control in step S2, that is, the last MOSFET turned on turns off first, and the first MOSFET turned on turns off last; the turn-off interval between adjacent falling step signals is... The timing synchronization error is no greater than 10ns, ensuring no sudden changes or reverse spikes in the current. The specific turn-off logic is as follows: taking a maximum conduction order N=10 as an example, it achieves... During the first interrupt cycle after the timeout, IO_register &= 0x03FF; the second... At time IO_register&= 0X01FF; the third At each step, IO_register &= 0X00FF is set, and so on, until all power MOSFETs are turned off, completing the falling edge multi-step current output.

[0036] Step S5: After all M power switches are turned off, current output stops. After the timer reaches the set pulse interval duration, the process jumps to step S2 and repeats. After all N groups of power MOSFETs are sequentially turned off, the pulse power supply stops current output, and the pulse power supply system enters the pulse interval state. The interrupt period is used as the timestamp for timing; when the timer reaches the set pulse interval duration... Then, jump to step S2 and execute it repeatedly until the processing program ends.

[0037] Step S6: During each single pulse discharge cycle, the inter-electrode voltage signal is acquired in real time, and the inter-electrode discharge state is identified. The effective spark discharge rate is calculated, and one or more of the target parameters of the stepped wave discharge current are dynamically adjusted based on the effective spark discharge rate. During each pulse cycle, the voltage signal between the machining electrodes is acquired in real time through the discharge state monitoring unit, and the inter-electrode discharge state (including open circuit, spark discharge, arc discharge, and short circuit) is identified. The state data is then uploaded to the main control MCU in real time. Based on the real-time discharge state, the main control MCU dynamically adjusts the stepped wave target parameters: if a short circuit state is detected, all power MOSFETs are immediately turned off, current output is stopped, and the tool electrode and workpiece are protected; if the spark discharge state is unstable, the stepped wave number N and the duration of each step are dynamically adjusted. Single pulse duration Pulse interval duration One or more parameters are used to achieve closed-loop adaptive control of the processing process.

[0038] In steps S2 to S4, as follows Figure 3 As shown, the discharge current output during a single pulse discharge cycle The following piecewise function relationship is satisfied: When in a rising multi-step ladder segment: ; When in a stable discharge phase: ; When in a descending step segment with multiple decreasing steps: ; in, For the time variable within a single pulse discharge cycle, This is the current step index of the rising step segment. For the current step index of the descending step segment, For the first The magnitude increment of the current at each step, and the magnitude increment of the current at each step. Equal or unequal, This is the peak current. The duration of each current is denoted as . This refers to the duration of a single-pulse stable discharge.

[0039] In steps S2 to S5, this invention employs a four-state machine—idle state, discharge breakdown state, discharge state, and pulse interval state—to achieve closed-loop control throughout the entire process. When there is no processing instruction, the system remains in the idle state. Upon receiving a processing instruction, it switches to the discharge breakdown state and executes step S2. After reaching the currently set step number NN, it switches to the discharge state and executes step S3. After reaching the single-pulse stable discharge duration, it executes step S4. After all power switches are turned off, it switches to the pulse interval state and executes step S5. After reaching the pulse interval duration, it jumps back to the discharge breakdown state, and the process repeats cyclically.

[0040] In step S6, the discharge state monitoring unit calculates the effective spark discharge rate in the following manner. : ; in, This represents the number of pulses identified as spark discharge states within a preset time window. This represents the total number of pulses within a preset time window. The main control MCU unit based on the effective spark discharge rate Dynamically adjust the stepped wave parameters: when When the accuracy is less than 70%, increase the pulse interval duration or decrease the step number N, or simultaneously increase the pulse interval duration and decrease the step number N; when When the success rate is greater than or equal to 90%, increase the step number N or extend the duration of stable single-pulse discharge, or increase both the step number N and extend the duration of stable single-pulse discharge.

[0041] The present invention will be further described in detail below through specific embodiments.

[0042] Example 1: Method and apparatus for controlling pulse power supply of 4th order stepped wave wire EDM.

[0043] The hardware configuration of the device in this embodiment is as follows: The main control MCU unit uses an STM32F407ZGT6 industrial-grade MCU with a main frequency of 168MHz and a built-in advanced hardware timer, which can realize microsecond-level timer interrupts; a set of 16-bit IO peripherals is used as the synchronous timing signal generator, and the timing synchronization error is no more than 10 nanoseconds. The power amplifier output unit adopts a 4-way parallel branch topology, with one IRF540N power MOSFET connected in series in each constant current branch, and each branch is equipped with a 10Ω current-limiting resistor. The maximum output current is 5A, and the peak output current is 20A when all 4 channels are fully on. The discharge status monitoring unit uses an AD8138 high-speed differential operational amplifier to build the sampling circuit, with a sampling bandwidth of 20MHz. The voltage sampling thresholds are set as follows: open circuit voltage not less than 80V, spark discharge voltage 20 to 60V, arc discharge voltage 10 to 20V, and short circuit voltage less than 10V. The human-machine interaction unit uses a 5-inch industrial touch screen, which supports processing parameter input, real-time display of processing status, and abnormal alarm prompts. The DC power supply unit inputs AC220V industrial power grid and outputs an adjustable DC bus voltage from 0 to 100V to power the power amplifier output unit; at the same time, it outputs isolated +5V and +24V DC power supplies to power the main control MCU unit, discharge status monitoring unit and human-machine interaction unit.

[0044] This embodiment pre-stores three sets of parameters, respectively adapted to roughing, semi-finishing, and finishing scenarios. Roughing scenario: number of steps N=4, duration of each step... =5 microseconds, stable single-pulse discharge duration =100 microseconds, pulse interval duration =300 microseconds, peak current 20A. Semi-finishing scenario: number of steps N=3, duration of each step =3 microseconds, stable single-pulse discharge duration =50 microseconds, pulse interval duration =150 microseconds, peak current 15A. Finishing scenario: number of steps N=2, duration of each step... =1 microsecond, duration of stable single-pulse discharge =5 microseconds, pulse interval duration =30 microseconds, peak current 10A.

[0045] The specific control process is as follows: The user selects the processing scene through the human-machine interaction unit, inputs the workpiece material and electrode specifications, and the main control MCU matches the corresponding parameter group. The pulse power supply system enters the discharge breakdown state, and the main control MCU triggers the conduction of 4 MOSFETs sequentially through a 1-microsecond timer interrupt: In the first interrupt cycle, Q1 conducts, outputting a 5A first-order current; after 5 microseconds, Q2 conducts, outputting a 10A second-order current; after 10 microseconds, Q3 conducts, outputting a 15A third-order current; after 15 microseconds, Q4 conducts, outputting a 20A fourth-order current, completing the rising-edge 4-step output, as shown below. Figure 3 The rising edge is shown in a multi-step ascending sequence. Entering a stable discharge state, Q1 to Q4 remain fully conductive, discharging continuously for 100 microseconds to provide stable energy for processing, as shown... Figure 3 The process is shown in the stable discharge phase. After reaching the stable discharge duration, it enters the falling edge control phase, sequentially turning off the MOSFETs according to the reverse logic: In the first interrupt cycle, Q4 turns off, and the current drops to 15A; after 5 microseconds, Q3 turns off, and the current drops to 10A; after 10 microseconds, Q2 turns off, and the current drops to 5A; after 15 microseconds, Q1 turns off, and the current drops to 0, completing the four-stage falling edge output, as shown below. Figure 3 The process is illustrated by a multi-step decreasing sequence on the falling edge. It enters a pulse interval state, with no output for 300 microseconds, then jumps to the rising edge control flow, executing cyclically. During processing, the discharge status monitoring unit collects the inter-electrode voltage in real time. If the short-circuit voltage is detected to be below 10V, all MOSFETs are immediately turned off, output stops, and an alarm is triggered. If the spark discharge ratio is detected to be below 80%, the pulse interval duration T_MJ is automatically adjusted to improve discharge stability. Figure 4 This is a measured waveform of the stepped discharge current in this embodiment.

[0046] Example 2: Method and apparatus for controlling pulse power supply in 8th-order stepped wave electrical discharge machining.

[0047] The hardware configuration of the device in this embodiment is as follows: The main control MCU unit uses an STM32H7 industrial-grade MCU with a main frequency of 400MHz and a built-in advanced hardware timer, which can realize microsecond-level timer interrupts; a set of 16-bit IO peripherals is used as the synchronous timing signal generator, and the timing synchronization error is no more than 10 nanoseconds. The power amplifier output unit adopts an 8-way parallel branch topology, with one IRFP250MPBF power MOSFET connected in series in each constant current branch, and a current-limiting resistor installed in each branch, of which the current-limiting resistors of the first two branches are 15Ω and the current-limiting resistors of the last six branches are 10Ω. The discharge state monitoring unit uses an AD8138 high-speed differential operational amplifier to build a sampling circuit with a sampling bandwidth of 20MHz. The voltage sampling thresholds are set as follows: open circuit voltage not less than 80V, spark discharge voltage 20 to 60V, arc discharge voltage 10 to 20V, and short circuit voltage less than 10V. The configuration of the remaining units is the same as in Embodiment 1.

[0048] This embodiment uses a stepped amplitude configuration, with the first two steps at the rising edge having an amplitude of 3A each, and the next six steps having an amplitude of 5A each, with each step lasting for a duration of [duration missing]. =1.5 microseconds, single-pulse stable discharge duration =30 microseconds, pulse interval duration =60 microseconds, step number N=8. The specific control process is consistent with the core logic of Example 1, and an adaptive parameter adjustment function is added: the pulse power system counts the discharge status every 10 pulse cycles. If the effective spark discharge ratio is not less than 90%, the step current is automatically increased by 1 step to improve processing efficiency; if the effective spark discharge ratio is less than 70%, the step current is automatically reduced by 1 step to extend the pulse interval to ensure processing stability. Figure 5 This is a measured waveform of the stepped discharge current in this embodiment.

[0049] Example 3: Method and apparatus for controlling pulse power supply in second-order stepped wave micro-electrical discharge machining.

[0050] The hardware configuration of the device in this embodiment is as follows: The main control MCU unit uses an STM32F407ZGT6 industrial-grade MCU with a main frequency of 168MHz and a built-in advanced hardware timer, which can realize microsecond-level timer interrupts; a set of 16-bit IO peripherals is used as the synchronization timing signal generator, and the timing synchronization error is no more than 10 nanoseconds. The power amplifier output unit adopts a two-way parallel constant current branch topology, with one IRFP250MPBF power MOSFET connected in series in each constant current branch. The output current amplitude of each constant current branch is 0.5A, and the peak output current is 1A when both are fully on. The discharge state monitoring unit uses a rail-to-rail high-speed operational amplifier to build a micro-voltage sampling circuit with a sampling accuracy of no more than 0.1V, which is suitable for low-voltage and low-current scenarios in micro-machining. The configuration of the remaining units is the same as in Embodiment 1.

[0051] The core parameters of this embodiment are: number of steps N=2, duration of each step. =1 microsecond, duration of stable single-pulse discharge =2 microseconds, pulse interval duration =8 microseconds, peak current 1A. The specific control process is consistent with the core logic of Example 1, and the protection logic is optimized for micro-machining scenarios: when abnormal fluctuations in the inter-electrode voltage are detected, the output is stopped immediately to avoid microelectrode burn-out and microstructure deformation.

[0052] Example 4: Full-parameter adaptive stepped wave pulse power supply closed-loop control method.

[0053] This embodiment presents a general closed-loop control method, adaptable to all hardware devices in embodiments 1 to 3. Its core lies in achieving adaptive adjustment of all parameters during the machining process. Before machining, the user inputs the workpiece material, target machining accuracy, target machining efficiency, and electrode type. The main control MCU generates an initial set of stepped wave parameters using its built-in expert database. During machining, the discharge state monitoring unit collects inter-electrode voltage data every pulse cycle and calculates four core indicators: effective spark discharge rate, arc discharge rate, short-circuit rate, and machining energy utilization rate. The main control MCU dynamically adjusts the stepped wave parameters using a fuzzy proportional-integral-derivative (PID) control algorithm: if the machining efficiency is lower than the target value, and the effective spark discharge rate is not lower than 90%, the stepped wave order N is increased, the peak current is increased, and the stable discharge time is extended. If the sum of the arc discharge rate and the short circuit rate is not less than 10%, then the single pulse duration should be shortened. Extend the pulse interval Reduce the step current amplitude until the abnormal discharge rate is below 5%. The pulse power supply system records the parameters and effect data of the processing process in real time, automatically optimizes the expert database, and realizes self-learning function to improve the consistency of batch processing.

[0054] Therefore, the present invention adopts the above-mentioned method and device for controlling the pulse power supply of electrical discharge machining based on stepped wave discharge current output. Within a single pulse discharge cycle, it outputs a multi-step increasing stepped segment on the rising edge, a stable discharge segment, and a multi-step decreasing stepped segment on the falling edge. The power switch is controlled by direct assignment of values ​​to the IO register of the main control MCU to achieve stepped current output throughout the cycle. At the same time, the stepped wave parameters are adjusted in a closed loop according to the effective spark discharge rate, which can adapt to various scenarios such as roughing, semi-finishing, and finishing.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output, characterized in that, Includes the following steps: Step S1: Collect processing condition parameters and match them to generate target parameters for stepped wave discharge current. The target parameters for stepped wave discharge current include the number of steps N, the duration of each current step, the duration of single-pulse stable discharge, and the pulse interval duration. Step S2: In each single pulse discharge cycle, according to the target parameters of the matched stepped wave discharge current, the main control MCU of the pulse power supply system generates M synchronous timing control signals, and controls the M power switches to turn on in the first order. The time interval between the turn-on of two adjacent power switches is the duration of each current step, and the output rise edge is a multi-step incremental step segment; where M is equal to the step number N, N≥2; Step S3: When the number of conduction paths reaches the step number N, keep all M power switches in the conduction state and continuously output a stable discharge segment for a duration equal to the single-pulse stable discharge duration. Step S4: When the duration of the stable discharge segment reaches the duration of the single-pulse stable discharge, the main control MCU controls the M-channel synchronous timing control signals to turn off the M-channel power switches in the second order, which is the opposite of the first order. The turn-off time interval between two adjacent power switches is the duration of each current step, and the output is a multi-step decreasing ladder segment with a falling edge. Step S5: After all M power switching transistors are turned off, the current output stops, and after the timer reaches the pulse interval duration, it jumps to step S2 and executes repeatedly. Step S6: Real-time acquisition of the inter-electrode voltage signal and identification of the inter-electrode discharge state during each individual pulse discharge cycle, calculation of the effective spark discharge rate, and dynamic adjustment of the step wave discharge current target parameter based on the effective spark discharge rate.

2. The method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output according to claim 1, characterized in that: In step S2, the main control MCU increments the IO register step by step using a bitwise OR assignment method, controlling the M power switches to turn on in the first order; in step S4, the main control MCU decrements the IO register step by step using a bitwise AND assignment method, controlling the M power switches to turn off in the second order; the timing synchronization error of the M synchronization timing control signals is less than or equal to 10ns.

3. The method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output according to claim 2, characterized in that, Discharge current output during a single pulse discharge cycle The following piecewise function relationship is satisfied: When in a rising multi-step ladder segment: ； When in a stable discharge phase: ； When in a descending step segment with multiple decreasing steps: ； in, For the time variable within a single pulse discharge cycle, This is the current step index of the rising step segment. For the current step index of the descending step segment, For the first The magnitude increment of the current at each step, and the magnitude increment of the current at each step. Equal or unequal, This is the peak current. The duration of each current is denoted as . This refers to the duration of a single-pulse stable discharge.

4. The method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output according to claim 1, characterized in that, In steps S2 to S5, a four-state machine consisting of idle state, discharge breakdown state, discharge state, and pulse interval state is used to achieve closed-loop control throughout the entire process. The machine remains idle when there are no processing commands. Upon receiving the processing instruction, switch to the discharge breakdown state and execute step S2; After reaching the currently set step number N, switch to the discharge state and execute step S3; After the single-pulse stable discharge duration is reached, step S4 is executed. After all power switching transistors are turned off, the pulse interval state is switched to execute step S5. After the pulse interval duration is reached, the system jumps back to the discharge breakdown state and repeats the cycle.

5. The method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output according to claim 1, characterized in that: The adjustment range of the step number N is 2 to 16; the adjustment range of the duration of each current step is 1 to 10 μs; the adjustment range of the duration of a single pulse stable discharge is 1 to 1000 μs; and the adjustment range of the pulse interval duration is 1 to 1000 μs. The duration of each step along the rising edge in step S2 and the duration of the corresponding step along the falling edge in step S4 are set independently.

6. The method for controlling an electrical discharge machining pulse power supply based on stepped-wave discharge current output according to claim 1, characterized in that: In step S6, the inter-electrode discharge states include open circuit state, spark discharge state, and short circuit state. When a short circuit is detected, the M-channel power switch is immediately turned off to stop current output; When the effective spark discharge rate is lower than the first preset threshold, the pulse interval duration is extended or the step number N is reduced, or the pulse interval duration and the step number N are extended simultaneously. When the effective spark discharge rate is higher than the second preset threshold, the step number N is increased or the single-pulse stable discharge duration is extended, or the step number N and the single-pulse stable discharge duration are increased simultaneously.

7. A pulse power supply control device for electrical discharge machining based on stepped-wave discharge current output, used to implement the pulse power supply control method for electrical discharge machining based on stepped-wave discharge current output as described in any one of claims 1-6, characterized in that, include: The main control MCU unit is used to generate M synchronous timing control signals by directly assigning values ​​to the IO registers of the main control MCU unit; The power amplifier output unit is connected to the main control MCU unit and includes M parallel power switch branches. Each power switch branch is connected in series with a current-limiting resistor and a power switch. The M power switch branches correspond one-to-one with the M synchronous timing control signals and are used to synthesize the output stepped discharge current step by step according to the synchronous timing control signals. M is equal to the step number N. The discharge status monitoring unit is connected in parallel across the machining electrode space between the tool electrode and the workpiece, and is connected to the main control MCU unit. It is used to collect the electrode voltage signal in real time and identify the electrode discharge status by threshold comparison. The human-machine interface unit is bidirectionally connected to the main control MCU unit and is used to input machining parameters and display machining status. The DC power supply unit is connected to the main control MCU unit, the power amplifier output unit, the discharge status monitoring unit, and the human-machine interaction unit, respectively, and is used to provide DC power to the above units.

8. The electrical discharge machining pulse power supply control device based on stepped wave discharge current output according to claim 7, characterized in that, The discharge status monitoring unit calculates the effective spark discharge rate as follows: : ； in, This represents the number of pulses identified as spark discharge states within a preset time window. This represents the total number of pulses within a preset time window. The main control MCU unit based on the effective spark discharge rate Dynamically adjust the stepped wave parameters: when When the accuracy is less than 70%, increase the pulse interval duration or decrease the step number N, or simultaneously increase the pulse interval duration and decrease the step number N; when When the success rate is greater than or equal to 90%, increase the step number N or extend the duration of stable single-pulse discharge, or increase both the step number N and extend the duration of stable single-pulse discharge.

9. The electrical discharge machining pulse power supply control device based on stepped wave discharge current output according to claim 7, characterized in that: The main control MCU unit is an industrial-grade MCU with a multi-channel IO controller or hardware PWM timer and a main frequency greater than or equal to 100MHz; The main control MCU unit uses a fixed interrupt period as the timing timestamp and directly assigns values ​​to the IO register to achieve synchronous control of multiple signals. The fixed interrupt period is 1μs.

10. The electrical discharge machining pulse power supply control device based on stepped wave discharge current output according to claim 8, characterized in that: The discharge status monitoring unit is equipped with voltage sampling thresholds, which include: open circuit voltage threshold greater than or equal to 80V, spark discharge voltage threshold 20 to 60V, arc discharge voltage threshold 10 to 20V, and short circuit voltage threshold less than 10V. When the inter-electrode voltage is detected to be lower than the short-circuit voltage threshold, the main control MCU unit immediately shuts down the M power switching transistors. When the effective spark discharge rate When the value is below 70%, the main control MCU unit automatically adjusts the pulse interval duration.

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