PROCESS CONTROL METHOD AND APPARATUS

Description

FIELD OF THE INVENTION

The subject matter disclosed herein relates to a process control method and apparatus without the need for additional sensors. More particularly, the subject matter discloses a process control method and apparatus that controls optimum feed rates without the need for sensors to process parameters related to captured power output.

BACKGROUND

Silicon carbide is a synthetically produced crystalline compound of silicon and carbon (SiC) that can be used to form a ceramic matrix composite (CMC) by combining a SiC matrix phase with a SiC fiber phase using various processing methods. SiC/SiC CMCs have high thermal, mechanical, and chemical stability while at the same time having a high strength to weight ratio.

The hardness of a SiC/SiC CMC is second only to that of diamond tooling. In addition, the SiC fiber reinforced phase adds anisotropy and heterogeneity material properties to the compound. Thus, it is challenging to develop a high quality, efficient and cost-effective way to machine a SiC/SiC CMC.

Ultrasonic impact grinding (UIG) has been used to drill diffuser-type holes and slots in CMCs.

Therefore, it is necessary to develop a machining strategy and method to meet the targeted requirement.

SUMMARY OF THE INVENTION

An ultrasonic impact grinding system is disclosed. The ultrasonic impact grinding system includes an ultrasonic vibration tool having a tool tip. The ultrasonic impact grinding system also includes a slurry having a slurry nozzle to deliver a slurry having abrasive particles in an area of the tool tip. The tool tip of the ultrasonic vibration tool engages the abrasive particles to machine a workpiece. The ultrasonic impact grinding system also includes an ultrasonic power supply to provide power to the ultrasonic vibration tool. The ultrasonic impact grinding system also includes a controller to receive captured power output by the ultrasonic vibration tool and to control a feed rate to the ultrasonic vibration tool from the ultrasonic power supply. The power output includes a vibration amplitude as the tool tip engages the abrasive particles. The controller is configured to determine when the captured power output based on the vibration amplitude reaches a specified level. The controller also is configured to modify the feed rate to the ultrasonic vibration tool based on reaching the specified level.

A method is disclosed. The method includes machining a workpiece using an ultrasonic vibration tool to engage abrasive particles in a slurry. The method also includes capturing power output from the ultrasonic vibration tool. The power output is related to a vibration amplitude of a tool tip of the ultrasonic vibration tool. The method also includes receiving the captured power output at a controller connected to an ultrasonic power supply that supplies power to the ultrasonic vibration tool. The method also includes determining the captured power has reached a specified level. The method also includes modifying power to the ultrasonic vibration tool by a control signal from the controller to the ultrasonic power supply.

A method is disclosed. The method includes repetitively determining a magnitude of a power output signal used to power an ultrasonic vibration tool used in an ultrasonic impact grinding machine to generate a corresponding data signal. The method also includes repetitively determining an x-y-z position of the ultrasonic vibration tool during a grinding operation to generate a corresponding position signal. The method also includes adaptively processing the corresponding data signal and the corresponding position signal to generate a control signal for controlling an operation of a drive feed system for the ultrasonic vibration tool.

BRIEF DESCRIPTION OF THE FIGURES

Implementations of the inventive concepts disclosed herein may be better understood when consideration is given to the following detailed description thereof. Such description makes reference to the included drawings, which are not necessarily to scale, and which some features may be exaggerated and some features may be omitted or may be represented schematically in the interest of clarity. Like reference numerals in the drawings may represent and refer to the same or similar element, feature, or function. In the drawings:

FIG. 1 illustrates an ultrasonic vibration tool according to the disclosed embodiments.

FIG. 2 illustrates a machining process implemented by the ultrasonic vibration tool according to the disclosed embodiments.

FIG. 3 illustrates a weaving pattern for a CMC according to the disclosed embodiments.

FIG. 4A illustrates how the relative content of fiber and matrix changes during a machining operation.

FIG. 4B further illustrates how the relative content of fiber and matrix changes during a machining operation.

FIG. 4C further illustrates how the relative content of fiber and matrix changes during a machining operation.

FIG. 5 illustrates a graph of load signals obtained during the machining of a CMC workpiece according to the disclosed embodiments.

FIG. 6 illustrates a graph of the load signals obtained during the machining of a CMC workpiece according to the disclosed embodiments.

FIG. 7 illustrates a block diagram of an embodiment of the ultrasonic tool cutting system for which the present invention may be used according the disclosed embodiments.

FIG. 8 illustrates a flowchart for controlling the ultrasonic vibration tool according to the disclosed embodiments.

FIG. 9 illustrates an embodiment of a measuring device for measuring the length of a tool tip.

FIG. 10 illustrates a block diagram of a one embodiment of the control unit shown in FIG. 7 according to the disclosed embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining at least one embodiment of the inventive concepts disclosed herein in detail, it is to be understood that the inventive concepts are not limited in their application to the details of construction and the arrangement of the components or steps or methodologies set forth in the following description or illustrated in the drawings. In the following detailed description of the embodiments of the inventive concepts, numerous specific details are set forth in order to provide a more thorough understanding of the inventive concepts. It will be apparent to one skilled in the art, however, having the benefit of the instant disclosure that the inventive concepts disclosed herein may be practiced without these specific details.

As used herein, a letter following a reference numeral is intended to reference an embodiment of the feature or element that may be similar, but not necessarily identical, to a previously described element or feature bearing the same reference numeral, such as 1, 1a, or 1b. Such shorthand notations are used for purposes of convenience only, and should not be construed to limit the inventive concepts disclosed herein in any way unless expressly stated to the contrary.

Moreover, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elements and components of embodiments of the instant inventive concepts. This is done merely for convenience and to give a general sense of the inventive concepts, and “a” and “an” are intended to include one or at least one and the singular also includes plural unless it is obvious that it is meant otherwise. It will be further understood that the terms “comprises” or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, any reference to “one embodiment,” “alternative embodiments,” or “some embodiments” means that particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the inventive concepts disclosed herein. The appearances of the phrase “in some embodiments” in various places in the specification are not necessarily all referring to the same embodiment, and embodiments of the inventive concepts disclosed may include one or more of the features expressly described or inherently present herein, or any combination or sub-combination of two or more such features, along with any other features that may not necessarily be expressly described or inherently present in the instant disclosure.

The inventive concepts may be described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

Inventive concepts may be implemented as a computer process, a computing system or as an article of manufacture such as a computer program product of computer readable media. The computer program product may be a computer storage medium readable by a computer system and encoding computer program instructions for executing a computer process. When accessed, the instructions cause a processor to enable other components to perform the functions disclosed below.

A method and system are disclosed. The method and system set and control optimum feed rates for ultrasonic impact grinding of CMCs without any additional sensors. The term “sensorless” or “sensor less” may refer to the feature of not adding sensors to an existing system. In other words, additional sensors may not be needed to enable the functionality disclosed herein. Instead of the pre-programmed feed rates of the current methods, the disclosed method utilizes the power data from an ultrasonic generator to adaptively adjust the feed rate the UIG's Computer Numerical Control (CNC) controller. It has been found that for a given vibration frequency, the power level in the ultrasonic generator is a good indicator of the average force on the tool. The disclosed method uses this power to set the appropriate feed rate to maintain a desired force. The force level needed for a particular tool design, slurry composition, and CMC material may be determined using modeling.

FIG. 1 depicts an ultrasonic vibration tool 1 according to the disclosed embodiments. Ultrasonic vibration tool 1 includes a transducer 2, an energy-forming horn 3, an ultrasonic tool tip 4, and a tool tip edge 5. The electrical energy input to transducer 2 is converted to mechanical vibrations at a high frequency (usually at 20-40 kHz) along longitudinal axis 6 of tool 1. The excited vibration is subsequently transmitted through energy-focusing horn 3 to tool tip 4 in order to amplify the vibration amplitude which is delivered to tool tip edge 5. Tool 1 is located directly above the workpiece (not shown in FIG. 1) and vibrates along its longitudinal axis 6 at a desired amplitude.

Ultrasonic vibration tool 1 is used to machine a CMC component such as to form holes, slots, and the like. Tool 1 is attached to a work fixture (not shown) using a suitable fastener 7. Tool 1 also includes back portion 8, flange 9 and front portion 10 that enhance delivery of the mechanical vibrations from tool tip 4 to horn 3. These features may be arranged in various configurations to achieve the functionality disclosed above.

FIG. 2 depicts a machining process implemented by ultrasonic vibration tool 1 according to the disclosed embodiments. Tool tip 4 is vibrated toward and away from a surface 206 of workpiece 23 in a direction 204 that is, for example, perpendicular to the surface of the workpiece. In some embodiments, tool tip 4 may be vibrated toward and away at other angles related to workpiece 23. Workpiece 23 may be a substrate that is part of the CMC component. An abrasive slurry 20 is constantly fed into machining area 21 by slurry source 202. Slurry 20 contains abrasive particles 24, made of abrasive material, such as diamond, boron carbide, and the like, that is suspended in water, oil, or other solutions. Slurry 20 also flushes away debris from machining area 21.

The vibration of tool tip 4 causes abrasive particles 24 contained in slurry 20 located between the tool tip and workpiece 23 to impact surface 206 and subsequent surfaces, thereby the removal of material by microchipping as generally indicated by reference number 25 in FIG. 2. Because the actual machining is carried out by abrasive particles 24, tool tip 4 may be softer than the workpiece 23. Thus, the UIG process can be treated as a micro scale material fracture process using abrasive particles 24 as the cutting edges.

The fracture toughness of a SiC matrix may be increased by its fiber reinforcement. The removal process of fibers, however, does not always occur simultaneously with the SiC matrix. This condition indicates that the failure mechanisms vary between machining the SiC matrix and the fibers.

The fracture mechanism of a SiC matrix is relatively uniform. Fiber fracture forms may be related to fiber orientation and density. SiC fibers are first de-bonded from the SiC matrix due to extrusion by tool 1. One or more of a bending-induced fracture, a compression-induced fracture and a shear-induced fracture occur in different orientations of the SiC fibers.

Material removal rate mainly depends on vibration amplitude 208, applied static pressure, abrasive concentration, and size distribution of the abrasive particles. Once the slurry solution is selected to be used, primarily only vibration amplitude 208 and feed rates can be adjusted to achieve the desired material removal. Vibration amplitude 208 refers to the peak-to-peak amplitude at tool edge 5 of tool tip 4. Tool edge 5 vibrates in direction 204. The amplitude of this vibration, or vibration amplitude 208, varies as tool 1 operates.

Woven reinforced materials such as CMCs may include three different constituents: fibers, matrix, and porosities. Particularly in CMCs, due to the complex manufacturing method followed and especially during the stage of Chemical Vapor Infiltration (CVI), big porosities can be found within the material and therefore need to be considered to get an in-depth understanding of the machining mechanism.

FIG. 3 depicts a typical microstructure of a workpiece 23 comprised of CMC material 301 having fiber tows 302 and 303 which are formed of CMC fiber, and are interwoven. Workpiece 23 may be an intermediate product being machined to form a component, such as a blade outer air seal, a static vane, a turbine blade, other components for gas turbine engines, and other components for other applications. CMC material 301 also includes a CMC matrix such as shown at 304, as well as pores or voids in the matrix.

Accordingly, a CVI CMC structure may include the fiber-rich region, matrix-rich region and porosities, and their relative content can be expressed as:

C CMC = C fiber + C matrix + C porosity = 1 ( 1 )

FIGS. 4A-C depicts how the relative content of fiber (λ) and matrix (v) changes along the hole and depending on where a hole 400 is machined within the CMC workpiece. Hole 400 may refer to a slot, an indentation, and the like. Referring to FIG. 4A, as workpiece 23 is being machined, tool tip 4 and tool tip edge 5 may initially encounter tow 303. One can appreciate that the relative content of tows 302 and 303 (fibers) as well as the matrix and porosity is changing along hole axis Y. It also may vary depending on where hole 400 is machined. More than one hole may be machined into workpiece 23. Thus, variation may be encountered between the content of workpiece 23 at the distinct area. For example, directly to the left of hole axis Y, the respective materials of workpiece 23 would differ in order.

Referring to FIG. 4B, tool tip 4 encounters a tow 302, with a slight bit of matrix 304 having porosity. As may be appreciated, tool tip edge 5 moves further along tool axis Y. This further movement along tool axis Y may result in a greater vibration amplitude 208 for tool tip 4. Referring to FIG. 4C, a subsequent step shows where tool tip 4 is machined through tow 302 and is again encountering matrix 304 having porosity at area 402. In a subsequent step, tool tip 4 will have moved through area 402 of matrix 304 with porosities and will again encounter a portion of tow 302. These steps also result in further movement of tool tip edge 5 along tool axis Y, which may result in an increased vibration amplitude 208 for tool tip 4.

As depicted in FIGS. 4A-C, the relative content of fiber, matrix and porosity is changing along tool axis Y, and it also varies depending on where the hole is machined. Therefore, two stochastic variables are defined to describe the structure of the material; the relative content of fiber is defined as λ while the relative content of matrix as v. Hence, the total relative content of material at a specific instant of the drilling process (t) or drilling depth (d) for a certain size of a tool(s) can be defined as:

C CMC ( s , t ) = C fiber + C matrix + C porosity = λ + v + ( 1 - λ - v ) ( 2 )

One may appreciate that, depending on how the material is distributed along the drilling path, tool 1 might encounter different resultant axial loads. Due to the stochastic nature of λ and v, a probabilistic approach defining how the resultant cutting load tends to fluctuate depending on the cutting depth (d), can offer an understanding of how the heterogeneous material property affects the level of dynamics of the system.

FIG. 5 depicts a graph 500 of measured machining loads of CMCs, which have different magnitude due to the heterogeneous nature. This is due to the different material constituents (fibers, matrix and porosities), which are in contact with the tool tip at each instant of the machining process. Graph 500 includes axis 502, which provides values for the machining depth of tool 1 in millimeters. Graph 500 also includes axis 504, which provides values for machining loads in Newtons. As shown in FIG. 5, after every 9-11 mils, one or more peak loads 506 may be observed, which correlates to the depth of each tow/ply, and the pattern is repeatable. From machining perspective, the fluctuated loads are not desirable for creating precision features and can cause overloading of tooling for some cases. Thus, it is desirable to perform adaptive control of axial loads to improve process efficiency.

Without a precise follow-up control of frequency and amplitude of the electric signal feeding the ultrasonic stack, the output power of a power supply for tool 1 will fluctuate strongly during machining process resulting in bad quality of the process. In the UIG process, the average power P can be estimated with the following equation:

P = F × V ≈ F × f × A

• • F—Average load applied in the cutting zone (N)
  • V—Velocity of down speed (m/s)
  • f—Vibration frequency (kHz)
  • A—Vibration amplitude (m) as shown by vibration amplitude 208 in FIG. 2.

In addition to the CMC materials and the distribution of SiC fibers, the average load also depends on the feed rate along the machining direction, or tool axis Y. FIG. 6 depicts graph 600 having axis 602 providing values for time in seconds and axis 604 providing values for force in Newtons. When the feed rates are suitable to the material removal capability of the process, the average load tends to be small and stable other than a few peak loads 606 that occur where the area has higher ratio of SiC fibers as shown in graph 600.

On the other hand, when feed rates are beyond, or exceeds, the material removal capability of the process, the cutting load increases quickly, and sometimes it can cause tool breakage and deflection if the applied load is over its yield strength. Thereafter it is necessary to monitor and control the power output to avoid overloading the tool.

It is more efficient to access all process data in real-time. Based on the available information from machine tools and ultrasonic power supplies, an adaptive process control approach is proposed in this invention to improve the machining stability and performance as shown in FIGS. 7 and 8.

FIG. 7 depicts a closed loop adaptive ultrasonic system 800 according to the disclosed embodiments. The system includes an ultrasonic power supply 801, which receives incoming electrical power at power terminal 802. Power supply 801 supplies electrical power to ultrasonic vibration tool 1 via power terminal 804. Tool 1 includes tool tip 4, which is used to perform a machining operation on workpiece 23. Workpiece 23 is mounted on machine table 807, which in turn is driven in x-y-z directions by drive system 808 under the control of CNC controller 809. Ultrasonic power supply 801 may also supply electrical power to drive system 808 and CNC controller 809, or theses elements can be powered from other sources.

When tool 1 is fixed in a stationary position, drive system 808 can position workpiece 23 under tool tip 4 as needed in order to carry out the machining operation under the control of CNC controller 809. Alternatively, workpiece 23 can remain stationary and tool 1 can be carried by its own drive system similar to drive system 808 also under control of a CNC controller, similar to CNC controller 809.

The power output from ultrasonic power supply 801 is captured during the machining operation by data acquisition device and signal processing device 810. In particular, voltages and currents are captured for processing by control unit 811, as disclosed below.

After appropriate filtering to remove unwanted artifacts, if necessary, the data signal from device 810 is suppled to control unit 811. Control unit 811 also controls the operation of CNC controller 809. The data signal is used by control unit 811 to control the operation of CNC controller 809 to, in turn, control the feed rates of drive system 808 to maintain desired loads on tool 1. Speed and position data from axis encoder scalar unit 812 is also supplied in real time to control unit 811. Based on all of this data, control unit 811 can determine the motion and rate of motion along the machining axis of tool 1 required in order to achieve the desired and most efficient machining process. This feature allows control unit 811 to CNC controller 809, accordingly. Control unit 811 can also control the operation of tool 1, e.g., turning the tool on and off, controlling various operating parameters, and turning slurry source 202 on and off.

Database 830 is included in system 800. During the disclosed processes, all process data, including machining conditions, reference and actual load as well as amplitude profiles are stored in database 830. The data may be saved for analysis. If the targeted process performance is achieved to meet the quality inspection requirements of parts subject to ultrasonic machining by tool 1, then the reference process signature and the measured signature may be fused as an adjusted baseline signature. The adjusted baseline signature may be saved to database 830. In machining subsequent CMC parts, the adjusted baseline signature may be used for process monitoring and control by following the same processes used to machine the previous workpieces.

This iterative process may be repeated until all parts are machined. Over time, with physics-guided machine learning, a reliable historical dataset may be built as an up-to-date representation of the physical operation of system 100. Thus, a process profile with high fidelity may be built, which can be used to evaluate the current condition. It also may be used to predict future behavior, refine the control of tool 1, and optimize operations within system 100.

FIG. 8 depicts a flowchart 700 for controlling ultrasonic vibration tool 1 according to the disclosed embodiments. Flowchart 700 may refer to FIGS. 1-7 for illustrative purposes. Flowchart 800, however, is not limited by the embodiments disclosed by FIGS. 1-7.

Step 702 executes by providing power to tool 1. Ultrasonic power supply 801 provides power to tool 1. The power output of ultrasonic power supply 801 may control a tool speed to maintain a desired load on tool 1. Step 704 executes by machining a workpiece 23 using tool 1 to engage abrasive particles 24 in slurry 20. Abrasive particles 24 machine workpiece 23 and are washed away by slurry 20.

Step 706 executes by capturing a power output from tool 1 using data acquisition and signal processing device 810. The power output is related to a vibration amplitude 208 of a tool tip 4 of tool 1. In some embodiments, a larger vibration amplitude may be used to efficiently machine the fiber tow, such as tows 302 and 303, during operations. Based on Equation 2 disclosed above, a profile for vibration amplitude 208 may be estimated to overcome nonuniform fracture toughness along the machining path, shown by hole axis Y. A smaller vibration amplitude 208 may be provided for regions with a higher ration of pores in matrix 304. A larger vibration amplitude 208 may be provided for regions with an increased concentration ratio of fiber tows. This estimated amplitude may be used as a reference for adaptive process control of system 800.

Step 708 executes by receiving the captured power output at a controller, such as control unit 811, from device 810. Step 710 executes by determining whether the captured power output received at control unit 811 has reached a specified level. As noted above, a reference amplitude may be used to compare against the captured power output having vibration amplitude 208. Control unit 811 may process the power output to determine a vibration amplitude 208 currently being experienced by tool 1.

If step 710 is no, then flowchart 700 proceeds back to step 704 to continue machining workpiece 23 with tool 1. If the actual feed rate, or vibration amplitude 208, is within a reasonable range by not reaching a specified level, then the process continues until a peak load condition is observed or machining is completed.

If step 710 is yes, then step 712 executes by modifying power to tool 1 by a control signal from the controller, or control unit 811, to ultrasonic power supply 801. Thus, if the feed rate is out of the normal range, or has reached a specified level, even with higher vibration amplitude 208, then the power to tool 1 may be modified to avoid problems associated with excessive or peak loads using the tool. The feed rates are adjusted proportionally to ultrasonic power consumption. The power, or feed rates, are reduced to avoid severe tool wear and undesirable conditions. Thus, the disclosed embodiments may control vibration amplitude 208 using an adaptive process by increasing power to tool 1 to overcome higher fracture toughness in workpiece 23 for areas with a high concentration ration of fiber tows by modifying the power at a specified level or outside a specified range to prevent undesirable effects from the increased power.

Step 714 executes by storing the data associated with the analysis and modification of the power to tool 1 for this instance in database 830. As disclosed above, database 830 may store the data captured and generated by control unit 811 and device 810 to update the references for adaptive process control of system 800.

Step 716 also executes after step 712 by determining whether the modification in power to tool 1 is significant. If the feed rate is out of the normal range even with a higher vibration amplitude 208, then the on-machine tool measurement may be used to check tool length and diameter. The difference between the tool penetration depth and tool wear may be the actual machining rate. If the observed machining rate is significantly less than a desired rate, then the disclosed embodiments should replace the tooling or flush used slurry out of the machining area. Further, when tool 1 is not engaged in machining, ultrasonic power supply 801 may be turned off to save energy.

If step 716 is no, then flowchart 700 returns to step 704 to continues machining workpiece 23 with the modified power from ultrasonic power supply 801. If step 716 is yes, then step 718 executes by stopping operations to engage in measuring tool tip 4 to check length and diameter. This process is disclosed in FIG. 9.

FIG. 9 depicts one embodiment of a measuring device for measuring the length of tool tip 4. Tool tip 4 will wear during machining. Thus, it is important to periodically measure the length of tool tip 4 in order to compensate for wear and to trigger an alert when wear has become sufficient to impair the operation of the tool tip. An optical transmitter 902, which can be a laser diode, transmits a light beam 906 to optical receiver 905 with its focal point 907 at the end of tool tip 4. Optical transmitter 903 and optical receiver 905 are coupled to control unit 811 via respective nodes 903 and 904

FIG. 10 depicts a block diagram of a one embodiment of control unit 811 shown in FIG. 7 according to the disclosed embodiments. Control unit 811 includes central processing unit (CPU) 1001, which is used to execute computer software instructions. CPU 1001 is coupled, via bus 1002, to ROM memory 1003, flash memory 1004, RAM memory 1005, mass storage 1006 and I/O interface 1007.

ROM memory 1003 and flash memory 1004 may be used to store computer software instructions for execution by CPU 1001. RAM memory 1005 may also be used for storing computer software instructions, and especially for storing information that is only needed for a short period of time. Mass storage 1006 is used for longer and larger data storage needs as may be required to be retain for data analysis over time.

I/O interface 1007 allows the control unit to communicate via bus 1008 to other parts of the system, such as data acquisition and signal processing device 810, axis encoder scalar unit 812, and CNC controller 809, all shown in FIG. 7. Also coupled to control unit 811 may be human interface device 1009, which allows an operator of the system to input control commands to the system via switches, knobs, keyboards and the like and to receiver information from the system via lights, displays, audio devices and the like.

A network interface 1010 may also be provided that allows control unit 811 to communicate with Internet hosted services such as Cloud Storage Units web applications and the like that consume data provided via control unit 811 for analysis and subsequent retrieval.

The functionality shown in FIG. 10 may also be integrated into CNC controller 809.

Thus, using real time data obtained during machining, it is possible to perform closed-loop process control of UIG to achieve targeted machining performance without any additional sensors. Further, the ultrasonic power supply connected to the CNC controller adaptively provides the targeted power to ultrasonic tooling to achieve desired vibration amplitude.

Based on the input parameters, such as the fracture toughness of fiber tow and matrix, constituent ratio of fibers tow, matrix and pores, tow depth together with tooling geometries and machining conditions, the physics-based model is used to predict the load profile along the drilling depth. If some of these parameters are unknown, it is necessary to perform tests to calibrate the loads, so that an estimated load profile can be obtained as the reference for the real time process control. Ideally, a larger vibration amplitude can be used to efficiently break the fiber tow during drilling. Based on Equation (2) above, a vibration amplitude profile can be estimated to overcome nonuniform fracture toughness along the drilling path, smaller vibration amplitude for regions with higher ratio of pores, and larger vibration amplitude for regions with high concentration ratio of fiber tows.

This estimated amplitude will then be used as a reference for adaptive process control. During actual drilling process, the power signals are used to control the tool speed to maintain the prescribed loads as mentioned above.

Without any additional sensors, the feed rates are adjusted proportionally to the ultrasonic power consumption, sometimes it could significantly reduce feed rates when high loads occurred to avoid severe tool wear and undesirable conditions. So, the novelty here is to adaptive control the vibration amplitude by increasing power to the ultrasonic system to overcome higher fracture toughness for areas with high concentration ratio of fiber tows. If the actual feed rate is within a reasonable range, the process continues until the end of the NC program. On the other hand, if the feed rate is out of the normal range even with higher vibration amplitude, the on-machine tool measurement is then used to check tool length and diameter.

The difference between the tool penetration depth and tool wear is the actual machining rate. If the observed machining rate is significantly less than the desired one, it needs to either replace the tooling or flush used slurry out of machining area. Moreover, when the cutter is not engaged in cutting, the ultrasonic power supply can be turned off to save energy. With the encoder signals from the CNC controller, the tool position is known, so the tool could also slow down during the breakthrough of holes to avoid edge chipping using the look-ahead function embedded in CNC controller.

During the process, all process data, including machining conditions, reference and actual load and amplitude profile are saved and analyzed. If targeted process performance is achieved to meet the quality inspection requirement of parts, the reference process signature and measured one will be fused as an adjusted baseline signature, which will then be saved to the historical database. In the drilling of subsequent CMC parts, the adjusted baseline signature will be used for process monitoring and control by following the same procedure used to machine the previous parts. This iterative process will be repeated until all parts are machined. Over the time, with the physics-guided machine learning, a reliable historical dataset can be built as an up-to-date representation of the physical operation. Thus, a process profile with high fidelity is built, which can be used to evaluate the current condition and more importantly to predict future behavior, refine the control and optimize operations.

As will be appreciated by one skilled in the art, the present invention may be embodied as a system, method or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module,” or “system.” Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer-usable program code embodied in the medium.

The corresponding structures, material, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material or act for performing the function in combination with other claimed elements are specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for embodiments with various modifications as are suited to the particular use contemplated.