A three-dimensional carving processing device and three-dimensional carving processing process for salt sculptures

Abstract

The present application relates to the technical field of numerical control engraving processing, and discloses a three-dimensional engraving processing device and three-dimensional engraving processing technology for salt sculptures, which comprises a control calculation module, a processing execution mechanism, a state sensing module and a synchronous acquisition module. The state sensing module acquires the frequency band elastic wave signal, the load phase current and the absolute mechanical angle during cutting. The synchronous acquisition module performs timestamp alignment on the above signals to generate a heterogeneous data sequence. The control calculation module calculates the cutting state energy index based on the sequence. The processing technology is as follows: within the interpolation cutting period, if the energy index exceeds the upper limit of safety, the absolute mechanical angle is extracted to deduce the normal space vector, the target attitude compensation angle is calculated in combination with the interference boundary, and the cutting tool is deflected under the premise that the tool tip point follows the invariable. Through time domain synchronization of multiple source signals and adaptive intervention of the cutting tool attitude, the present application prevents the brittle material of the salt sculpture from breaking and collapsing.

Description

Technical Field

[0001] This invention relates to the field of CNC engraving technology, specifically to a three-dimensional engraving equipment and process for salt carving. Background Technology

[0002] Salt sculpture is a craft made by pressing salt powder mixed with binder or by using natural salt blocks as raw materials. Its material characteristics are characterized by uneven internal density and high overall brittleness. In the three-dimensional carving process, existing CNC milling equipment relies on pre-generated fixed trajectory codes to remove materials. When monitoring the cutting state, such equipment often relies on a single spindle load current. Due to the difference in sampling rates between acoustic sensors, current sensors and position encoders, the multi-source physical signals are misaligned in the time domain. The system cannot achieve synchronization and alignment of the timestamps of the underlying data, making it difficult to establish a correlation between the sudden change in cutting resistance and the specific mechanical phase of the current rotation of the cutting edge. Therefore, it is impossible to deduce the actual normal force direction that causes the material to break.

[0003] When encountering sudden changes in local material hardness or signs of fracture, existing equipment can only passively reduce the feed rate or stop the machine directly. Due to the lack of a dynamic attitude intervention model for spatial interference envelope calculation and tool tip tracking in the CNC system, the equipment cannot actively change the cutting force direction by deflecting the tool tilt angle in real time while maintaining the original tool tip translation trajectory. This static execution logic makes it impossible for the detailed contours and thin-walled structures of salt carvings to be released in time when the cutting stress is concentrated, ultimately leading to irreversible chipping and fracture of the workpiece, reducing the product yield. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a three-dimensional carving equipment and process for salt sculptures, which solves the problem that brittle salt sculpture materials will chip and break due to the lack of multi-source physical state synchronous sensing and tool posture adaptive compensation mechanism in existing processing equipment.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a three-dimensional carving processing equipment for salt sculpture, comprising: a control calculation module, a processing execution mechanism, a status sensing module, and a synchronous acquisition module; The control calculation module is used to issue basic spatial interpolation commands and basic rotation speed commands to the machining actuator; The machining execution mechanism includes a five-axis robotic arm and an electric spindle. The electric spindle is installed at the end flange of the five-axis robotic arm and holds a single-edged carbide tool. The five-axis robotic arm is used to receive basic spatial interpolation commands and attitude deflection commands, and the electric spindle is used to receive basic speed commands and speed adjustment commands. Together, they execute spatial trajectory motion and enter the material cutting state. The state perception module is used to acquire the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle of the machining actuator in the cutting state; The synchronous acquisition module performs analog-to-digital conversion on the frequency band elastic wave signal and the load phase current sequence, and aligns them with the absolute mechanical angle in discrete digital signal form using timestamps to generate a heterogeneous data sequence. The control calculation module receives the heterogeneous data sequence, performs sub-band division and energy integration on the frequency band elastic wave signal to obtain the cutting state energy index. When the cutting state energy index is higher than the upper limit of the safety threshold range, it extracts the sudden peak from the load phase current sequence in the heterogeneous data sequence, and extracts the absolute mechanical angle corresponding to the sudden peak as the fracture characteristic phase and positively maps it to the normal space vector. Based on the normal space vector and the physical interference limit boundary, it calculates the target attitude compensation angle, and issues an attitude deflection command including tool tip point following control to the machining actuator, driving the machining actuator to deflect to the target attitude compensation angle.

[0006] The innovative principle of the above solution is as follows: the equipment monitors multi-source physical signals and converts them into heterogeneous data sequences in a unified time domain. The energy index of the cutting state is used to quantitatively assess the fracture risk of the material. When the energy index exceeds the safety limit, the normal space vector is back-derived by extracting the fracture characteristic phase, and the compensation angle to avoid the fracture direction is calculated. The tool attitude tilt angle is adjusted without changing the translational trajectory of the tool tip, forming a machining compensation closed loop to prevent material fracture.

[0007] Furthermore, the state perception module includes an acoustic emission sensor, a phase current sensor, and an encoder. The acoustic emission sensor is installed on the structural interface between the electric spindle and the five-axis robotic arm. The phase current sensor is connected in series in the drive circuit of the electric spindle. The encoder is located at the tail of the electric spindle.

[0008] Furthermore, the control calculation module calculates the physical interference limit boundary by combining the current interpolation cutting depth of the machining actuator and the geometric dimensions of the single-edged carbide tool. The physical interference limit boundary constitutes the effective spatial conical envelope surface for the deflection of the single-edged carbide tool. Based on the constraint of the physical interference limit boundary, the control calculation module calculates the target attitude compensation angle of the single-edged carbide tool axis deviating from the normal spatial vector without exceeding the physical interference limit boundary.

[0009] By calculating the conical envelope, physical interference between the tool and the machined surface or the unmachined blank is avoided when the tool deflects.

[0010] Furthermore, the control and calculation module sends an attitude deflection command to the five-axis robotic arm, driving the five-axis robotic arm to deflect to the target attitude compensation angle. The tip position of the single-edged carbide tool follows the translational trajectory specified by the basic spatial interpolation command. After the cutting energy index falls back to within the safe threshold range, the control and calculation module controls the five-axis robotic arm to restore the initial machining posture corresponding to the basic spatial interpolation command.

[0011] Furthermore, the control and calculation module extracts the high-frequency subband energy parameters that characterize the fracture features, and calculates the ratio of the high-frequency subband energy parameters to the total energy of the entire frequency band to obtain the cutting state energy index of the current interpolation cycle.

[0012] Furthermore, when the cutting energy index is less than the lower limit of the safety threshold range, the control calculation module sends a speed adjustment command to the electric spindle to control the electric spindle to increase the speed on the basis of the original basic speed command to perform chip removal action; When the cutting state energy index is greater than or equal to the lower limit of the safety threshold range and less than or equal to the upper limit of the safety threshold range, the control calculation module continues to send basic spatial interpolation commands and basic speed commands.

[0013] This control logic improves chip removal conditions through speed regulation, preventing salt powder accumulation that could lead to secondary cutting and extrusion.

[0014] Furthermore, the synchronous acquisition module integrates a field-programmable gate array (FPGA) chip and a temperature-controlled crystal oscillator (TCSCR). The TCSCR generates a basic clock beat and inputs it into the internal phase-locked loop (PLL) of the FPGA chip. The FPGA chip generates multiple synchronous trigger pulses with phase-locked relationships based on the basic clock beat. The synchronous acquisition module distributes the synchronous trigger pulses in parallel to the multi-channel analog-to-digital converter hardware and performs sampling actions concurrently to acquire the frequency band elastic wave signal and the load phase current sequence. At the same time, the FPGA chip latches the absolute mechanical angle signal based on the synchronous trigger pulses to establish a unified sampling start zero point.

[0015] The underlying frequency division trigger establishes a unified clock reference, enabling time-domain synchronization between high-frequency elastic wave signals and low-frequency mechanical motion data.

[0016] Furthermore, the synchronous acquisition module assigns absolute timestamps to discrete digital signals within the field-programmable gate array chip, uses low-frequency reference alignment logic to map and merge the frequency band elastic wave signal to the time axis of the load phase current sequence, uses a fixed positive integer ratio of high-frequency and low-frequency sampling rates as the interval span, and establishes the start and end indexes of high-frequency data by multiplying the low-frequency timestamp nodes sequentially by the fixed positive integer ratio to generate a data matrix containing unified time domain labels.

[0017] Furthermore, the digital signal processor inside the synchronous acquisition module uses a finite-length unit impulse response low-pass filter to filter out high-frequency glitches for the load phase current sequence, performs threshold judgment for the frequency band elastic wave signal and removes jump points whose amplitude exceeds the physical limit of the range. The cleaned data is encapsulated and packaged according to a fixed frame header structure and check bits to generate a heterogeneous data sequence of fixed byte length and sent to the control and calculation module.

[0018] The second aspect of this invention provides a three-dimensional carving process for salt sculptures, the process comprising the following steps: The machining actuator receives the basic spatial interpolation command and the basic rotation speed command and enters the cutting state; During the interpolation motion cycle, the state perception module acquires the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle of the machining actuator during the cutting process, and the synchronous acquisition module establishes a heterogeneous data sequence with the same time domain reference. The control and calculation module performs sub-band division and energy integration calculations on the frequency band elastic wave signals in the heterogeneous data sequence to obtain the cutting state energy index; When the cutting energy index is below the lower limit of the safety threshold range, the control calculation module sends a speed adjustment command; when the cutting energy index is within the safety threshold range, the control calculation module continues to send basic spatial interpolation commands and basic speed commands; when the cutting energy index is above the upper limit of the safety threshold range, the control calculation module extracts the sudden peak value from the load phase current sequence, and extracts the absolute mechanical angle corresponding to the sudden peak value as the fracture characteristic phase positive mapping as the normal space vector, and calculates the target attitude compensation angle in combination with the physical interference limit boundary, and sends an attitude deflection command including tool tip point following control, driving the machining actuator to deflect to the target attitude compensation angle to complete the adaptive compensation closed loop of the current cycle.

[0019] This invention provides a three-dimensional carving equipment and process for salt sculpture. It offers the following advantages: 1. The field-programmable gate array chip and the temperature-controlled crystal oscillator inside the synchronous acquisition module of this invention perform hardware-level pulse edge alignment on high-frequency elastic wave signals, low-frequency phase current sequences and absolute mechanical angles. Combined with low-frequency reference alignment logic, a data matrix containing a unified time-domain label is generated, which overcomes the time-domain misalignment defect caused by the difference in sampling rate of multi-source physical quantities. This enables the sudden change in cutting resistance to correspond precisely with the current rotation phase of the spindle, providing accurate data support for the subsequent judgment of the machining state.

[0020] 2. This invention utilizes a control calculation module to calculate the cutting state energy index to quantify the fracture risk. When the energy index exceeds the safety limit, the absolute mechanical angle corresponding to the current mutation is extracted and positively mapped into a normal space vector. Combined with the tool tip point following control, the equipment can actively deflect the tool tilt angle according to the normal space vector to change the cutting force direction while keeping the original cutting trajectory unchanged, releasing local cutting stress and preventing the salt carving brittle material from chipping or breaking.

[0021] 3. This invention, when performing tool attitude compensation calculation, combines the current interpolation cutting depth and tool geometry to pre-calculate the physical interference limit boundary of the conical envelope surface constituting the tool deflection space. The normal space vector is placed under the constraint of this boundary to calculate the target attitude compensation angle, ensuring that the tool and electric spindle will not mechanically collide with the machined surface or unmachined blank during the process of the five-axis robotic arm driving the tool deflection and unloading, thus ensuring the equipment safety of the machining process. Attached Figure Description

[0022] Figure 1 This is a perspective view of the present invention; Figure 2 This is a schematic diagram of the system timing interaction of the present invention; Figure 3 This is a schematic diagram of the method flow of the present invention; Figure 4 This is a schematic diagram of the structural layout and motion mechanism of the processing actuator of the present invention; Figure 5 This is a comparison and verification diagram of the time-domain evolution of the cutting state parameters of the present invention; Figure 6 This is a comparison and verification diagram of the attitude compensation vector space mapping of the present invention.

[0023] Among them, 10 is the control calculation module; 20 is the machining execution mechanism; 21 is the five-axis robotic arm; 22 is the single-edged carbide tool; 30 is the status perception module; and 40 is the synchronous acquisition module. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] See attached document Figures 1-2 The present invention provides a three-dimensional carving processing equipment for salt sculpture, including: a control calculation module 10, a processing execution mechanism 20, a status sensing module 30, and a synchronous acquisition module 40.

[0026] The control calculation module 10 is communicatively connected to the machining execution mechanism 20 and the synchronous acquisition module 40, respectively. It is used to parse the geometric features of the imported three-dimensional model and send basic spatial interpolation commands and basic speed commands to the machining execution mechanism 20. It also receives the heterogeneous data sequence sent by the synchronous acquisition module 40, calculates the current cutting state energy index based on the heterogeneous data sequence, calculates the target attitude compensation angle in combination with spatial interference constraints, and sends speed adjustment commands or attitude deflection commands including tool tip point following control to the machining execution mechanism 20, forming a machining state feedback closed loop.

[0027] The machining execution mechanism 20 includes a five-axis robotic arm 21 and an electric spindle. The electric spindle is installed at the end flange of the five-axis robotic arm 21 and holds a single-edged carbide tool 22. The machining execution mechanism 20 is communicatively connected to the control and calculation module 10. The five-axis robotic arm 21 is used to receive basic spatial interpolation commands and attitude deflection commands issued by the control and calculation module 10 to execute spatial translational and rotational motions. The electric spindle is used to receive basic speed commands and speed adjustment commands to provide rotational cutting power. The two work together to execute spatial trajectory motion and material cutting state.

[0028] The state sensing module 30 is arranged on the structural component of the machining execution mechanism 20 and is unidirectionally connected to the synchronous acquisition module 40. It is used to acquire the changes of multi-source physical quantities of the machining execution mechanism 20 in the cutting state. The state sensing module 30 contains an acoustic emission sensor, a phase current sensor and an encoder. The acoustic emission sensor is installed on the structural interface between the electric spindle and the five-axis robotic arm 21 and is used to capture the frequency band elastic wave signal generated in the machining area. The phase current sensor is connected in series to the drive circuit of the electric spindle and is used to acquire the load phase current sequence during the operation of the electric spindle. The encoder is arranged at the tail of the electric spindle and is used to measure the absolute mechanical angle of the rotor.

[0029] The synchronous acquisition module 40 is communicatively connected to the state sensing module 30 and the control calculation module 10, respectively. It is used to perform synchronous data acquisition on multi-channel hardware based on a unified clock trigger source, and to perform analog-to-digital conversion processing on the received frequency band elastic wave signal and load phase current sequence. It aligns the received signal with the absolute mechanical angle in the form of discrete digital signal and generates a heterogeneous data sequence which is sent to the control calculation module 10.

[0030] See attached document Figure 3 This invention provides a three-dimensional carving process for a salt sculpture three-dimensional carving equipment, comprising the following steps: S1, the control calculation module 10 analyzes the geometric features of the imported three-dimensional model, outputs basic spatial interpolation command and basic rotation speed command to the machining execution mechanism 20, and drives the machining execution mechanism 20 into the cutting state; S2, during the interpolation motion cycle, the state perception module 30 acquires the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle of the machining actuator 20 during the cutting process. The synchronous acquisition module 40 receives the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle and establishes a heterogeneous data sequence with the same time domain reference, and transmits the heterogeneous data sequence to the control calculation module 10. S3, the control and calculation module 10 receives the heterogeneous data sequence, performs sub-band division and energy integration on the frequency band elastic wave signal in the heterogeneous data sequence to extract the high-frequency sub-band energy parameters that characterize the fracture features and calculate the ratio, obtains the cutting state energy index of the current interpolation cycle, and compares the cutting state energy index with the safety threshold range set in the system, and determines the intervention logic branch based on the range of the value. S4, when the cutting energy index is less than the lower limit of the safety threshold range, the control calculation module 10 sends a speed adjustment command to the electric spindle in the machining execution mechanism 20 to perform chip removal and returns to S2; when the cutting energy index is greater than or equal to the lower limit of the safety threshold range and less than or equal to the upper limit of the safety threshold range, the control calculation module 10 continues to send the basic spatial interpolation command and the basic speed command and returns to S2. When the cutting state energy index is greater than the upper limit of the safety threshold range, the control calculation module 10 extracts the sudden peak value from the load phase current sequence of the heterogeneous data sequence, and extracts the absolute mechanical angle corresponding to the sudden peak value as the fracture characteristic phase. Combined with the initial phase offset of the cutting edge of the single-edged carbide tool 22 relative to the encoder zero point, the current attitude transformation matrix of the five-axis robot arm 21 and the electric spindle is used to positively map it into the normal space vector. Combined with the current interpolation cutting depth of the machining execution mechanism 20 and the geometric dimensions of the single-edged carbide tool 22, the physical interference limit boundary is calculated. Based on the normal space vector and the physical interference limit boundary, the target attitude compensation angle is calculated, and the five-axis robot arm 21 in the machining execution mechanism 20 is driven to deflect to the target attitude compensation angle. After the cutting state energy index falls back to the safety threshold range, the initial machining attitude corresponding to the basic space interpolation command is restored, the adaptive compensation closed loop of the current cycle is completed, and S2 is returned.

[0031] See attached document Figure 4The control and calculation module 10 receives the heterogeneous data sequence sent by the synchronous acquisition module 40 and performs state determination and parameter intervention during the cutting process of the salt carving material based on the heterogeneous data sequence. The control and calculation module 10 performs sub-band division and energy integration calculation on the frequency band elastic wave signal in the heterogeneous data sequence. The brittle fracture and plastic removal generated by the salt carving material during the cutting process excite elastic waves of different frequency bands. By selecting a specific wavelet basis to decompose the frequency band elastic wave signal, the high-frequency sub-band energy parameter characterizing the fracture characteristics is extracted. The control and calculation module 10 calculates the ratio of the high-frequency sub-band energy parameter to the total energy of the entire frequency band to obtain the cutting state energy index of the current interpolation cycle. The specific formula for calculating the cutting state energy index is as follows: ; In the formula, I e E represents the cutting state energy index, with a value ranging from 0 to 1; t1 is the start time of the current interpolation cycle; t2 is the end time of the current interpolation cycle; h (t) represents the high-frequency component of the band elastic wave signal reconstructed after sub-band division, which characterizes the fracture features; dt is the differential element of the time variable; E(t) is the original band elastic wave signal. The specific algorithm steps and the number of decomposition layers for wavelet packet decomposition can be conventionally set according to the signal sampling frequency and processor performance.

[0032] After obtaining the cutting state energy index, the control calculation module 10 compares the cutting state energy index with the safety threshold range set in the system. The safety threshold range includes a lower safety threshold and an upper safety threshold, and is obtained by calibration based on historical machining test data. In this embodiment, the lower safety threshold ranges from 0.2 to 0.35, and the upper safety threshold ranges from 0.75 to 0.85. When the cutting state energy index is less than the lower limit of the safety threshold range, it indicates that the material removal is in a viscous state. The control calculation module 10 sends a speed adjustment command to the electric spindle in the machining execution mechanism 20 to control the electric spindle to increase the speed based on the original basic speed command to perform chip removal. When the cutting state energy index is greater than or equal to the lower limit of the safety threshold range and less than or equal to the upper limit of the safety threshold range, the control calculation module 10 continues to send basic spatial interpolation commands and basic speed commands. When the cutting state energy index rises from less than the lower limit of the safety threshold range back to within the safety threshold range, the control calculation module 10 resumes the basic speed command.

[0033] When the cutting state energy index is greater than the upper limit of the safety threshold range, the control calculation module 10 starts the adaptive attitude compensation logic. The control calculation module 10 extracts the sudden peak value caused by the cutting edge of the single-edged carbide tool 22 cutting into hard particles from the load phase current sequence of the heterogeneous data sequence. The specific extraction logic is as follows: the control calculation module calculates the difference between the current value of the current sampling point and the average current value of the historical stable period. When the absolute value and the slope of the difference both exceed the set tolerance threshold, it is determined to be the sudden peak value caused by cutting into hard particles.

[0034] After locking the time node of the sudden peak, the control and calculation module extracts the absolute mechanical angle corresponding to the time node of the sudden peak as the fracture characteristic phase. Combined with the initial phase offset of the cutting edge of the pre-calibrated single-edged carbide tool 22 relative to the encoder zero point, the control and calculation module 10 uses the current attitude transformation matrix of the five-axis robot arm 21 and the electric spindle to positively map the fracture characteristic phase into the normal space vector in the workpiece coordinate system. The calculation principle of the normal space vector is to transform the actual cutting edge phase angle in the spindle rotation plane to the workpiece coordinate system through the homogeneous coordinate transformation matrix conventional in this field. The normal space vector indicates the direction of the normal stress that causes the sudden change in cutting resistance.

[0035] The control and calculation module 10 reads the current interpolation cutting depth and calculates the physical interference limit boundary in combination with the geometric dimensions of the single-edged carbide tool 22. The specific calculation process is as follows: the current tool tip coordinates of the single-edged carbide tool 22 are taken as the vertex of the spatial cone, the diameter of the bottom surface of the cone is determined by the diameter of the tool holder of the single-edged carbide tool 22 combined with the preset safety clearance, and the current interpolation cutting depth is taken as the height of the cone. The mathematical model of the cone is constructed by the spatial analytical geometry method. The space defined by the mathematical model is the physical interference limit boundary. The physical interference limit boundary constitutes the effective spatial conical envelope of the deflection of the single-edged carbide tool 22. Based on the calculated normal space vector, under the constraint of the physical interference limit boundary, the control solution module 10 calculates the target attitude compensation angle of the single-edged carbide tool 22 axis deviating from the normal space vector without crossing the physical interference limit boundary, with the minimum attitude deflection angle as the optimization target. The control solution module 10 generates an attitude deflection command including tool tip point following control to drive the five-axis robot arm 21 in the machining execution mechanism 20 to deflect to the target attitude compensation angle. Due to the tool tip point following control, the tool tip position of the single-edged carbide tool 22 maintains the translational trajectory specified by the basic spatial interpolation command. After the cutting state energy index falls back to the safe threshold range, the control solution module 10 controls the five-axis robot arm 21 to restore the initial machining attitude corresponding to the basic spatial interpolation command.

[0036] The physical structure of the machining actuator 20 includes a five-axis robotic arm 21 and an electric spindle. The five-axis robotic arm 21 adopts a series joint configuration and provides three spatial translational degrees of freedom and two rotational degrees of freedom. The three spatial translational degrees of freedom correspond to the linear axes of the spatial orthogonal coordinate system, and the two rotational degrees of freedom correspond to the pitch axis and yaw axis, which change the spatial attitude of the tool. The electric spindle is installed at the end flange of the five-axis robotic arm 21 by means of rigid connectors and bolt fastening. The front end of the electric spindle is equipped with a chuck and holds a single-edged carbide tool 22. The five-axis robotic arm 21 drives the electric spindle to produce corresponding movements in three-dimensional space according to various instructions issued by the control calculation module 10. After the motor stator inside the electric spindle is energized, it generates a rotating magnetic field to drive the rotor to rotate at high speed and drive the single-edged carbide tool 22 to provide rotational cutting power.

[0037] The machining actuator 20 receives the basic spatial interpolation command and basic speed command issued by the control calculation module 10. The basic spatial interpolation command includes the spatial position sequence and feed speed information in the three-dimensional coordinate system. The motion controller inside the five-axis robotic arm 21 parses the basic spatial interpolation command and converts the spatial position sequence into pulse drive signals for each joint motor through the inverse kinematics algorithm. The joint motors rotate in coordination, causing the electric spindle to carry the single-edged carbide tool 22 to perform spatial translation along a predetermined straight line or arc trajectory. The frequency converter inside the electric spindle parses the basic speed command and outputs three-phase AC power of the corresponding frequency to the motor stator winding. The motor stator winding causes the rotor to maintain the set basic speed. The specific solution matrix for the inverse kinematics algorithm can be derived based on the specific link parameters of the five-axis robotic arm 21.

[0038] When the intervention logic is triggered, the machining actuator 20 receives an attitude deflection command that includes tool tip follow control. The attitude deflection command requires changing the spatial tilt angle of the tool axis without changing the spatial coordinates of the tool tip of the single-edged carbide tool 22. The motion controller of the five-axis robotic arm 21 establishes the tool tip coordinate system. The motion controller reads the position vector and attitude rotation matrix of the end flange in the base coordinate system and combines them with the pre-set tool length vector to calculate the actual position coordinates of the current tool tip in the base coordinate system in real time using the vector addition and coordinate system transformation principle. The translation joints and various rotation joints of the five-axis robotic arm 21 are coupled and linked under the attitude deflection command so that the translation displacement cancels the tool tip position deviation caused by the rotation in real time. The machining actuator 20 synchronously changes the output frequency of the frequency converter driver according to the speed adjustment command to realize the dynamic increase and decrease of the electric spindle speed.

[0039] The state sensing module 30 is arranged on the machining execution mechanism 20 and is unidirectionally connected to the synchronous acquisition module 40. The state sensing module 30 is used to acquire the changes of multi-source physical quantities during the cutting process of the machining execution mechanism 20. The state sensing module 30 includes an acoustic emission sensor installed on the structural joint surface of the electric spindle and the five-axis robotic arm 21. The sensing end of the acoustic emission sensor is coated with acoustic coupling agent and fastened to the structural joint surface with bolts. The acoustic coupling agent fills the micro gaps on the surface and directly changes the acoustic conduction medium properties of the joint surface, causing the acoustic impedance mismatch to attenuate. The frequency band elastic wave signal generated by the fracture of the salt carving material is transmitted to the joint surface through the single-edged carbide tool 22, causing the piezoelectric ceramic wafer in the acoustic emission sensor to undergo micro-deformation. The piezoelectric ceramic wafer converts the mechanical deformation into a voltage signal output based on the positive piezoelectric effect to complete the acquisition of the frequency band elastic wave signal.

[0040] The state sensing module 30 contains a phase current sensor, which is connected in series in the drive circuit of the electric spindle. The phase current sensor is arranged on the line between the output terminal of the frequency converter and the input terminal of the motor stator winding. The phase current sensor uses the closed-loop Hall effect principle to monitor the transient current flowing through the drive circuit. When the single-edged carbide tool 22 driven by the electric spindle encounters a sudden change in cutting resistance during cutting, the electromagnetic torque in the motor stator winding undergoes a corresponding physical change. The change in electromagnetic torque causes the load phase current in the drive circuit to fluctuate synchronously at high frequency. The Hall element inside the phase current sensor senses the change in the magnetic field around the conductor and outputs a proportional secondary current. The secondary current is converted into a voltage value by the internal sampling resistor to form a low-voltage analog signal characterizing the load phase current sequence. The specific circuit configuration of the closed-loop Hall current sensor can be conventionally set according to the voltage level.

[0041] The state sensing module 30 contains an encoder located at the tail of the electric spindle. The encoder spindle is coaxially connected to the tail of the electric spindle rotor via a rigid coupling. The rigid coupling eliminates angular backlash during transmission by mechanically locking, forming a mechanical transmission structure that allows the encoder's code disk to rotate synchronously with the rotor. The encoder is an absolute photoelectric encoder with multiple concentric code tracks marked with light-transmitting and light-shielding areas. The light beam emitted by the light source passes through the rotating code disk and illuminates the photosensitive receiving element, forming a digital encoded signal that changes with the rotor position. The encoder's decoding circuit decodes the digital encoded signal and outputs the absolute mechanical angle representing the rotor's current absolute position. The absolute mechanical angle and the load phase current sequence establish a physical mapping relationship on the time axis within the rotor rotation cycle. After acquisition, the multi-source physical quantities are transmitted in parallel to the synchronous acquisition module 40 via the data bus.

[0042] The synchronous acquisition module 40 integrates a field-programmable gate array (FPGA) chip and is equipped with a temperature-controlled crystal oscillator. The temperature-controlled crystal oscillator generates a basic clock beat and inputs it into the internal phase-locked loop of the FPGA chip. The FPGA chip generates multiple synchronous trigger pulses with phase-locked relationships based on the basic clock beat by frequency division. After receiving the acquisition start signal from the control and calculation module 10, the synchronous acquisition module 40 distributes synchronous trigger pulses to the multi-channel analog-to-digital converter hardware in parallel. The multi-channel analog-to-digital converter hardware triggers the sampling action at the edge of the synchronous trigger pulse to acquire the frequency band elastic wave signal and load phase current sequence transmitted by the state perception module 30. At the same time, the field programmable gate array chip directly latches the absolute mechanical angle digital encoding signal transmitted by the state perception module 30 at the edge of the synchronous trigger pulse. The synchronous acquisition module 40 establishes a unified sampling start zero point based on the pulse edge alignment mechanism at the hardware level.

[0043] The sampling rate of the band elastic wave signal is on the order of megahertz, and the sampling rates of the load phase current sequence and absolute mechanical angle are on the order of kilohertz. The synchronous acquisition module 40 receives discrete digital signals and assigns absolute timestamps in the field programmable gate array chip. The synchronous acquisition module 40 uses low-frequency reference alignment logic to map and merge the band elastic wave signal to the time axis of the load phase current sequence. The synchronous acquisition module 40 extracts high-frequency sampling points within the low-frequency sampling period according to the index mapping rule and integrates them into a high-frequency data subset. The specific mapping association logic is to use a fixed positive integer ratio of the high-frequency and low-frequency sampling rates as the interval span and to establish the start and end index of the high-frequency data by multiplying the low-frequency timestamp nodes sequentially by the fixed positive integer ratio. In this embodiment, the value range of the fixed positive integer ratio is 500 to 2000. The synchronous acquisition module 40 generates a data matrix containing a unified time domain label according to the mapping association logic. Multi-channel data timing control is a well-known technology in this field.

[0044] After timestamp alignment, the synchronous acquisition module 40 performs noise reduction and cleaning rules and post-processing operations on the data matrix. The digital signal processor inside the synchronous acquisition module 40 uses a finite-length unit impulse response low-pass filter to filter out high-frequency glitches generated by the switching frequency of the frequency converter driver for the load phase current sequence. The digital signal processor performs threshold judgment for the frequency band elastic wave signal and directly removes jump points whose amplitude exceeds the physical limit of the acoustic emission sensor range. In this embodiment, the voltage amplitude threshold corresponding to the physical limit of the acoustic emission sensor range is in the range of -5 volts to +5 volts. The cleaned frequency band elastic wave signal, the load phase current sequence, and the absolute mechanical angle are encapsulated and combined according to a fixed frame header structure and check bits. The synchronous acquisition module 40 packages the structured encapsulated multi-source physical quantities into a heterogeneous data sequence of fixed byte length. The synchronous acquisition module 40 sends the heterogeneous data sequence to the control calculation module 10 through the peripheral component interconnection bus. The synchronous acquisition module 40 maintains periodic streaming data push to complete the data transmission for continuous monitoring.

[0045] Application Examples: See attached document Figure 5-6 During the processing stage where the local moisture content of the salt carving material increases, the material removal mechanism undergoes a physical transformation from brittle fracture to plastic flow. The plastic flow state causes the high-frequency component of the band elastic wave signal generated when the single-edged carbide tool 22 is separated from the material to decrease sharply. When the control calculation module 10 detects that the cutting state energy index is lower than the lower limit of the safety threshold, it triggers the speed adjustment logic. The control calculation module 10 outputs a speed increase command to the frequency converter driver, causing the electric spindle to accelerate the rotation of the single-edged carbide tool 22. The increase in rotational angular velocity directly increases the centrifugal force on the agglomerates in the tool chip groove and throws out the cutting waste. The physical chip removal action restores the cutting edge's entry space, allowing the cutting process to regain the physical conditions for generating the high-frequency component of the band elastic wave signal. When the cutting state energy index stabilizes within the safety threshold range, the control system restores the basic speed command.

[0046] When the single-edged carbide tool 22 cuts into the dense crystalline particles inside the salt carving material on the predetermined interpolation trajectory, the stator winding of the spindle motor needs to output higher electromagnetic torque to overcome the cutting resistance. The sudden increase in electromagnetic torque is directly reflected in the load phase current sequence as a current jump waveform with peak characteristics. The control calculation module 10 extracts the absolute mechanical angle corresponding to the current jump waveform and maps it to the workpiece coordinate system to form a normal space vector representing the direction of force. The motion controller of the five-axis robotic arm 21 reconstructs the tilt angle of the axis of the single-edged carbide tool 22 based on the normal space vector and the set physical interference limit boundary. Each joint motor drives the spindle to perform attitude yaw action without changing the current spatial coordinate of the tool tip. The attitude yaw action causes the cutting angle of the cutting edge relative to the crystalline particles to change geometrically, thereby decomposing the concentrated radial cutting force. The decomposition of the cutting force causes the cutting state energy index to fall back to the safe threshold range and avoids the single-edged carbide tool 22 from breaking.

[0047] The control and calculation module 10 continuously receives multi-source physical quantity data matrices synchronously acquired by the underlying hardware through the synchronous acquisition module 40. The cutting state energy index and normal space vector calculation mechanism within the algorithm framework constitute an adaptive closed-loop control system in the non-uniform material carving process. During the execution of basic spatial interpolation commands, the five-axis robotic arm 21 and the electric spindle superimpose speed adjustment commands or attitude deflection commands in real time based on the dynamic drift of the cutting state energy index. The multi-degree-of-freedom coupling linkage at the hardware level, combined with the multi-source heterogeneous data mapping analysis at the software level, realizes the physical intervention and adjustment of the processing state. The carving process adaptively eliminates the mechanical impact and vibration caused by the sudden change in material properties without interrupting the feed trajectory. The real-time feedback of the physical state and the dynamic matching of the underlying control commands ensure the geometrical accuracy and cutting surface quality of the final complex curved contour.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional carving processing equipment for salt sculptures, characterized in that, include: The machining actuator (20) includes a five-axis robotic arm (21) and an electric spindle. The electric spindle is installed at the end flange of the five-axis robotic arm (21) and holds a single-edged carbide tool (22). The five-axis robotic arm (21) is used to receive basic spatial interpolation commands and attitude deflection commands. The electric spindle is used to receive basic speed commands and speed adjustment commands, and together they execute spatial trajectory motion and material cutting state. The state perception module (30) is used to acquire the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle of the machining actuator (20) in the cutting state; The synchronous acquisition module (40) is used to perform analog-to-digital conversion processing on the frequency band elastic wave signal and the load phase current sequence, and to align the frequency band elastic wave signal and the load phase current sequence after analog-to-digital conversion with the absolute mechanical angle in the form of discrete digital signals to generate a heterogeneous data sequence. The control calculation module (10) receives the heterogeneous data sequence, performs sub-band division and energy integration on the frequency band elastic wave signal to obtain the cutting state energy index. When the cutting state energy index is higher than the upper limit of the safety threshold range, it extracts the sudden peak from the load phase current sequence in the heterogeneous data sequence, and extracts the absolute mechanical angle corresponding to the sudden peak as the fracture characteristic phase and positively maps it to the normal space vector. Based on the normal space vector and the physical interference limit boundary, it calculates the target attitude compensation angle and sends an attitude deflection command containing tool tip point following control to the machining execution mechanism (20) to drive the machining execution mechanism (20) to deflect to the target attitude compensation angle.

2. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The state sensing module (30) contains an acoustic emission sensor, a phase current sensor and an encoder. The acoustic emission sensor is installed on the structural interface between the electric spindle and the five-axis robotic arm (21). The phase current sensor is connected in series to the drive circuit of the electric spindle. The encoder is located at the tail of the electric spindle.

3. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The control calculation module (10) calculates the physical interference limit boundary by combining the current interpolation cutting depth of the machining execution mechanism (20) and the geometric dimensions of the single-edged carbide tool (22). The physical interference limit boundary constitutes the effective spatial conical envelope surface of the deflection of the single-edged carbide tool (22). The control calculation module (10) calculates the target attitude compensation angle of the axis of the single-edged carbide tool (22) deviating from the normal space vector without crossing the physical interference limit boundary, based on the constraint of the normal space vector.

4. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The control calculation module (10) sends the attitude deflection command to the five-axis robotic arm (21) to drive the five-axis robotic arm (21) to deflect to the target attitude compensation angle. The tip position of the single-edged carbide tool (22) follows the translational trajectory specified by the basic spatial interpolation command. After the cutting state energy index falls back to the safe threshold range, the control calculation module (10) controls the five-axis robotic arm (21) to restore the initial machining posture corresponding to the basic spatial interpolation command.

5. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The control calculation module (10) extracts the high-frequency subband energy parameters characterizing the fracture features, and calculates the ratio of the high-frequency subband energy parameters to the total energy of the entire frequency band to obtain the cutting state energy index of the current interpolation cycle.

6. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, When the cutting state energy index is less than the lower limit of the safety threshold range, the control calculation module (10) sends a speed adjustment command to the electric spindle to control the electric spindle to increase the speed and perform chip removal action based on the original basic speed command; when the cutting state energy index is greater than or equal to the lower limit of the safety threshold range and less than or equal to the upper limit of the safety threshold range, the control calculation module (10) continues to send the basic spatial interpolation command and the basic speed command.

7. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The synchronous acquisition module (40) integrates a field-programmable gate array (FPGA) chip and is equipped with a temperature-controlled crystal oscillator. The temperature-controlled crystal oscillator generates a basic clock beat and inputs it into the internal phase-locked loop of the FPGA chip. The FPGA chip generates multiple synchronous trigger pulses with phase-locked relationships based on the basic clock beat. The synchronous acquisition module (40) distributes the synchronous trigger pulses in parallel to the multi-channel analog-to-digital converter hardware and performs sampling to obtain the frequency band elastic wave signal and the load phase current sequence. At the same time, the FPGA chip latches the absolute mechanical angle signal based on the synchronous trigger pulse to establish a unified sampling start zero point.

8. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The synchronous acquisition module (40) assigns absolute timestamps to the frequency band elastic wave digital signal, the load phase current digital signal, and the absolute mechanical angle digital encoding signal after analog-to-digital conversion within the field-programmable gate array chip. It uses low-frequency reference alignment logic to map and merge the frequency band elastic wave signal to the time axis of the load phase current sequence. It uses a fixed positive integer ratio of the sampling rate of the frequency band elastic wave signal to the sampling rate of the load phase current sequence as the interval span, and establishes the start and end indexes of the frequency band elastic wave data by multiplying the timestamp nodes of the load phase current sequence by the fixed positive integer ratio, thereby generating a data matrix containing a unified time domain label.

9. The three-dimensional carving equipment for salt sculpture according to claim 1, characterized in that, The digital signal processor inside the synchronous acquisition module (40) uses a finite-length unit impulse response low-pass filter to filter out high-frequency glitches in the load phase current sequence, performs threshold judgment on the frequency band elastic wave signal and removes jump points whose amplitude exceeds the physical limit of the range, and encapsulates and combines the cleaned frequency band elastic wave signal and the load phase current sequence with the absolute mechanical angle according to a fixed frame header structure and check bit to generate the heterogeneous data sequence of fixed byte length and sends it to the control calculation module (10).

10. A three-dimensional carving process for salt sculptures, using the three-dimensional carving equipment for salt sculptures as described in any one of claims 1 to 9, characterized in that, The process includes the following steps: The machining actuator (20) receives the basic spatial interpolation command and the basic rotation speed command and enters the cutting state; During the interpolation cycle, the state perception module (30) acquires the frequency band elastic wave signal, load phase current sequence and absolute mechanical angle of the machining actuator (20) during the cutting process, and the synchronous acquisition module (40) establishes a heterogeneous data sequence with the same time domain reference. The control calculation module (10) performs sub-band division and energy integration calculation on the frequency band elastic wave signal in the heterogeneous data sequence to obtain the cutting state energy index; When the cutting state energy index is less than the lower limit of the safety threshold range, the control calculation module (10) sends a speed adjustment command to the electric spindle; when the cutting state energy index is greater than or equal to the lower limit of the safety threshold range and less than or equal to the upper limit of the safety threshold range, the control calculation module (10) continues to send the basic spatial interpolation command and the basic speed command; when the cutting state energy index is greater than the upper limit of the safety threshold range, the control calculation module (10) extracts the sudden peak value from the load phase current sequence, and extracts the absolute mechanical angle corresponding to the sudden peak value as the fracture characteristic phase positive mapping to the normal space vector, and calculates the target attitude compensation angle in combination with the physical interference limit boundary, and sends the attitude deflection command including tool tip point following control, driving the machining execution mechanism (20) to deflect to the target attitude compensation angle to complete the adaptive compensation closed loop of the current cycle.

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