Dynamic characterization system for measuring dynamic response

Abstract

The present disclosure relates to a system for measuring a dynamic response of a machine tool. The system includes a vibration mechanism, an accelerometer, a controller, and a housing. The vibration mechanism is operable to generate an excitation signal, and the accelerometer is operable to measure dynamic energy in response to the excitation signal and output a dynamic response signal indicative of the dynamic energy. The controller includes a communication interface and operates the vibration mechanism to output the excitation signal and send a vibration input signal over the communication interface based on the excitation signal. The housing houses the vibration mechanism and the controller.

Description

Technical Field

[0001] This disclosure relates to a system for measuring the dynamic response of a machine tool. Background Technology

[0002] The descriptions in this section are provided only as background information in relation to this disclosure and may not constitute prior art.

[0003] Computer numerical control (CNC) machine tools can be operated to perform high-speed machining of workpieces (such as aluminum blocks) to form parts. When machining at high cutting speeds, especially for thin-walled workpieces, the structural dynamics of the machine tool can become a concern in preventing excessive or unstable vibrations. Existing Condition Indicator Analysis Box (CIAB) systems measure vibrations during the cutting process but cannot be used to determine the structural dynamics of the machine tool (i.e., natural frequencies and vibration modes).

[0004] Currently, manual offline testing is used to calibrate and eliminate unstable vibrations. For example, when a CNC machine tool is offline, the operator strikes the CNC machine tool with an instrumented hammer at one or more points along the machine and uses an accelerometer to measure the vibration. This operation is susceptible to operator error and can be inaccurate due to unknown and varying forces applied to the machine tool.

[0005] Furthermore, the wear and tear on tools used in CNC machine tools is largely unpredictable and requires regular preventative maintenance. This results in costly replacement of parts with significant remaining lifespans, outages for machine tools, and operators being preoccupied with unnecessary maintenance. These and other issues are addressed through the teachings of this disclosure. Summary of the Invention

[0006] This section provides a brief overview of this disclosure and is not a full disclosure of the entire scope or all features of this disclosure.

[0007] In one form, this disclosure relates to a dynamic characterization system comprising a vibration mechanism operable to generate an excitation signal, an accelerometer, a controller including a communication interface, and a housing. The accelerometer is operable to measure dynamic energy in response to the excitation signal and output a dynamic response signal indicating the dynamic energy. The controller is configured to operate the vibration mechanism to output the excitation signal and transmit a vibration input signal via the communication interface based on the excitation signal. The housing houses the vibration mechanism and the controller.

[0008] In another form, the housing contains the accelerometer.

[0009] In another form, the controller sends vibration signals via a communication interface based on the dynamic response signals from the accelerometer.

[0010] In one configuration, the accelerometer is positioned separately from the housing.

[0011] In another form, the dynamic characterization system also includes a power source for supplying power to at least one of the vibration mechanisms or controllers, and the housing contains the power source.

[0012] In another form, the power source is a turbine generator.

[0013] In another form, the vibrating mechanism is a piezoelectric actuator.

[0014] In one form, the communication interface includes a wireless transceiver.

[0015] In another form, the vibration mechanism can be operated to output different excitation signals.

[0016] In one form, this disclosure relates to a dynamic characterization system for measuring the dynamic response of an object. The system includes a piezoelectric actuator operable to generate an excitation signal, an accelerometer, a controller including a wireless transceiver, and a housing. The accelerometer is operable to measure dynamic energy in response to the excitation signal and generate a dynamic response signal indicating the dynamic energy. The housing is configured to attach to and detach from the object. The housing also houses a vibration mechanism and the controller. The controller is configured to operate the piezoelectric actuator to output the excitation signal and to output data based on the excitation signal via the wireless transceiver.

[0017] In another form, the system also includes a power source for supplying power to the vibration mechanism and the controller.

[0018] In one configuration, the housing contains an accelerometer, which outputs a dynamic response signal to the controller.

[0019] In another configuration, the controller is configured to filter the dynamic response signal from the accelerometer and use a wireless transceiver to output data indicating the filtered dynamic response signal.

[0020] In another form, the controller transfers the dynamic response signal from the measured position to the desired position.

[0021] In one configuration, the accelerometer is positioned on an object at a location separate from the housing.

[0022] In one form, this disclosure relates to a system for measuring the dynamic response of a machine tool. The system includes a piezoelectric actuator operable to generate an excitation signal, an accelerometer, a controller, and a housing. The accelerometer is operable to output a dynamic response signal indicating the dynamic energy of the machine tool. The controller is configured to operate the piezoelectric actuator to output the excitation signal and output data indicating the excitation signal. The housing houses the piezoelectric actuator and the controller and is configured to be attached to the machine tool.

[0023] In one configuration, the housing contains the accelerometer.

[0024] In another form, the accelerometer is positioned on a machine tool separate from the housing.

[0025] In another form, the system also includes a turbine generator for supplying power to at least one of the controller or piezoelectric actuator.

[0026] Other areas of application will become apparent from the description provided herein. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0027] To facilitate a good understanding of this disclosure, its various forms will now be described by way of example with reference to the accompanying drawings, wherein:

[0028] Figure 1 This invention describes a computer numerical control (CNC) machine tool system equipped with a dynamic characterization (DC) system in accordance with the teachings of this disclosure;

[0029] Figure 2 This describes one form of a DC system located at the spindle of a CNC machine tool in accordance with the teachings of this disclosure;

[0030] Figure 3 This is a block diagram of a DC controller for a DC system according to the teachings of this disclosure; and

[0031] Figure 4 This illustrates another form of a DC system positioned at the spindle according to the teachings of this disclosure.

[0032] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way. Detailed Implementation

[0033] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or its uses. It should be understood that throughout the drawings, corresponding reference numerals indicate similar or corresponding parts and features.

[0034] refer to Figure 1The computer numerical control (CNC) machine tool system 100 (hereinafter referred to as the “CNC system”) is equipped with the dynamic characterization (DC) system 102 of this disclosure. The CNC system 100 includes a CNC system controller 104 and a multi-axis CNC machining center 106 (hereinafter referred to as the “CNC machine tool”), operable to form parts (e.g., engine blocks) from a workpiece 107 (e.g., a metal casting). The CNC machine tool 106 includes a spindle 108 and a tool (not shown) attached to an end of the spindle 108. The tool is selected from a plurality of tools housed in a tool magazine 112. The spindle 108 and / or the workpiece can be moved relative to each other along multiple axes such that the spindle 108 is aligned with a portion of the workpiece 107 to be machined. The teachings of this disclosure are applicable to other machine tools and should not be limited to the depicted CNC system 100.

[0035] The CNC system controller 104 is configured to operate the CNC machine tool 106 using one or more pre-stored programs. Therefore, together with other components of the CNC machine tool 106, the CNC system controller 104 controls the torque, position, orientation, and other operating parameters of the spindle 108 to form parts. The operator can access the CNC system controller 104 through a user interface 111.

[0036] The CNC system controller 104 is also configured to perform diagnostics on the CNC system 100 to ensure that the system 100 operates within certain parameters. In one form, using the DC system 102 of this disclosure, the CNC system controller 104 performs a vibration analysis of the CNC machine tool 106 to determine the structural dynamics of the machine tool 106. The DC system 102 measures the dynamic energy of the CNC machine tool 106 in response to a controlled excitation signal generated by the DC system 102. Based on the received data, the CNC system controller 104 performs diagnostics to determine whether the machine tool is operating within predefined parameters.

[0037] refer to Figure 2In one embodiment, the dynamic characterization system 102 includes a housing 202, a vibration mechanism 204, a power supply 206, an accelerometer 208, and a dynamic characterization (DC) controller 210. As illustrated, the housing 202 houses the vibration mechanism 204, the power supply 206, the accelerometer 208, and the DC controller 210. In one embodiment, the housing 202 is configured to engage with the spindle 108 such that the DC system 102 can be easily attached to and detached from the spindle 108. For example, the DC system 102 may be stored in a tool library 112 of the CNC machine tool 106, and in the event of a vibration analysis, the CNC system controller 104 operates the CNC machine tool 106 to retrieve the DC system 102 from the tool library 112 and attach the system 102 to the spindle 108. In another embodiment, the DC system 102 is positioned on the CNC machine tool 106 by the operator and can be attached to different locations on the CNC machine tool 106. Therefore, the physical configuration of the housing 202 can be changed based on the environment in which the DC system 102 is used.

[0038] Vibration mechanism 204 is operable to generate a predefined excitation signal to induce a dynamic response from spindle 108. In one form, vibration mechanism 204 is a piezoelectric actuator operable by DC controller 210. In another form, vibration mechanism 204 is an unbalanced body mounted on the spindle to generate an excitation signal (i.e., input force). In this form, DC system 102 can deliver more energy at a frequency associated with the spindle speed 108 to excite heavier components of CNC machine tool 106.

[0039] Power source 206 provides power to one or more components of DC system 102. For example, power source 206 supplies power to at least one of DC controller 210, vibration mechanism 204, and / or accelerometer 208. In one form, power source 206 is a turbine generator that converts the mechanical energy (such as compressed air) of its self-shaft into electrical energy. Other power sources (such as batteries) are also within the scope of this disclosure.

[0040] Accelerometer 208 measures dynamic energy (i.e., acceleration) along one or more axes in response to an excitation signal. More specifically, the excitation signal generated by vibration mechanism 204 causes vibration along spindle 108, and accelerometer 208 measures the intensity of the vibration. In one embodiment, accelerometer 208 sends data indicating the dynamic energy of spindle 108 as a dynamic response signal to DC controller 210. In other embodiments, the accelerometer may output a signal to CNC system controller 104, as described below.

[0041] The DC controller 210 is configured to control the operation of the vibration mechanism 204 and communicate with the CNC system controller 104 of the CNC system 100. (Reference) Figure 3In one form, the DC controller 210 includes a communication interface 302, a vibration control module 304, and a signal analysis module 306. In addition to the various components discussed below, the DC controller 210 also includes electronic components such as a microcontroller, filters (e.g., a fast Fourier transform chip), a transceiver, capacitors for maintaining charge, and other suitable electronic devices for performing the various functions described herein.

[0042] Communication interface 302 establishes communication with an external system (such as CNC system controller 104). In one form, communication interface 302 includes a Bluetooth transceiver for establishing wireless communication using the Bluetooth protocol. Communication interface 302 may use other wireless communication protocols, such as Wi-Fi, radio frequency communication, and Zigbee, and should not be limited to the Bluetooth protocol.

[0043] The vibration control module 304 controls the vibration mechanism 204 to generate an excitation signal, which may also be referred to as an input force. The vibration control module 304 can be configured in various suitable ways to output the excitation signal. For example, in one form, the vibration control module 304 stores one or more signal distribution curves and selects an excitation signal from one or more signal distribution curves based on a command from the CNC system controller 104 that identifies the desired signal distribution curve for the excitation signal. In another form, the vibration control module 304 is programmed to select certain signal distribution curves once the DC controller 210 receives power, and therefore, no further instructions from the CNC system controller 104 are required.

[0044] The excitation signal serves as the input force that induces vibrations (e.g., dynamic energy) along the CNC machine tool 106. In one form, the excitation signal includes, but is not limited to, a sinusoidal waveform with a set frequency or a linearly modulated signal whose frequency varies over time (i.e., increases or decreases). Because the excitation signal is based on a known signal distribution curve, the input force applied to the CNC machine tool is consistent and unaffected by operator error.

[0045] In one embodiment, the signal analysis module 306 sends signals indicating the excitation signal and the dynamic response signal from the accelerometer 208. For example, the signal analysis module 306 is configured to transform the excitation signal into a frequency domain signal and send the corresponding signal as a vibration input signal to the CNC system controller 104 via the communication interface 302. As another example, the signal analysis module 306 is configured to transform the dynamic response signal from the accelerometer 208 into a frequency domain signal and further filter the transformed signal. That is, the transformed signal is transferred from its measurement position (i.e., the position of the accelerometer) to the desired position (e.g., the end of the spindle). The filtered signal is then sent as a vibration signal to the CNC system controller 104 via the communication interface 302.

[0046] In an exemplary operation, DC system 102 is stored in tool library 112 of CNC machine tool 106, and CNC system controller 104 operates CNC machine tool 106 to retrieve DC system 102 when vibration analysis of CNC machine tool 106 is to be performed. In one form, when the power source is a turbine generator, system controller 104 outputs air from spindle 108 to drive the turbine generator and thereby power the components of DC system 102. DC controller 210 operates vibration mechanism 204 to generate an excitation signal, and accelerometer 208 measures the vibration of CNC machine tool. DC controller 210 sends data to CNC system controller 104 based on the excitation signal and the dynamic response signal from accelerometer 208.

[0047] CNC system controller 104 uses data from DC controller 210 to evaluate the stability of the machine tool. In one form, the CNC system controller performs a frequency response function (FRF) measurement to determine the stability lobe diagram of the CNC machine tool 106. Other possible analyses performed by CNC system controller 104 using data from DC system 102 are also within the scope of this disclosure. Once the vibration analysis is complete, CNC system controller 104 operates CNC machine tool 106 to return DC system 102 to the tool library 112. Other operations and / or methods using DC system 102 are also within the scope of this disclosure. For example, the operator can position the DC system at other locations on CNC machine tool 106 to measure the dynamic response of CNC machine tool 106.

[0048] The DC system 102 disclosed herein includes a dedicated accelerometer for measuring the dynamic energy of a CNC machine tool 106. Alternatively, the DC system is configured to utilize the accelerometer of the CNC machine tool 106. Reference Figure 4The DC system 402 includes a housing 202, a vibration mechanism 204, a power supply 206, and a DC controller 410. Similar to the DC controller 210, the DC controller 410 is configured to operate the vibration mechanism 204 and send data indicating excitation signals to the CNC system controller 104.

[0049] The CNC machine tool 106 includes an accelerometer 412 mounted on the spindle 108 for measuring the dynamic energy of the CNC machine tool 106. In one embodiment, the accelerometer 412 provides data indicating the dynamic energy during normal machining operations and / or during diagnostics performed by the CNC system controller 104.

[0050] The DC system 402 is further simplified by removing the accelerometer and utilizing the existing accelerometer on the CNC machine tool 106. For example, the DC controller 410 is configured to provide data about the excitation signal and does not need to process the signal from the accelerometer 412.

[0051] With the DC system disclosed herein, the CNC system receives machine tool dynamics based on known force inputs (i.e., predetermined excitation signals) rather than on operator experience. Furthermore, the CNC system 100 can perform vibration analysis without going offline. That is, the CNC system 100 can automatically acquire the dynamic response of the CNC machine tool 106 without operator assistance. The CNC system is able to characterize the entire working stroke, not just the dynamic response of a few fixed configurations, which may not include structural weaknesses at all input frequencies. In other words, the DC system can characterize the entire workspace, including areas inside the machine tool that are not safely accessible to the operator, and therefore can study structurally weak points in the machine tool structure that cannot be measured manually when the machine tool is in operating mode.

[0052] The description in this disclosure is exemplary in nature only, and therefore, any changes that do not depart from the substance of this disclosure are intended to fall within its scope. Such changes should not be considered as departing from the spirit and scope of this disclosure.

[0053] According to the present invention, a dynamic characterization system for measuring the dynamic response of an object is provided, the system comprising: a piezoelectric actuator operable to generate an excitation signal; an accelerometer operable to measure dynamic energy in response to the excitation signal and generate a dynamic response signal indicating the dynamic energy; a controller including a wireless transceiver, wherein the controller is configured to operate the piezoelectric actuator to output the excitation signal and output data via the wireless transceiver based on the excitation signal; and a housing configured to attach to and detach from the object, wherein the housing houses the vibration mechanism and the controller.

[0054] According to an embodiment, the invention is further characterized by the power supply providing power to the vibration mechanism and the controller.

[0055] According to an embodiment, the power source is a turbine generator.

[0056] According to an embodiment, the housing houses the accelerometer, and the accelerometer outputs a dynamic response signal to the controller.

[0057] According to an embodiment, the controller is configured to filter the dynamic response signal from the accelerometer and use a wireless transceiver to output data indicating the filtered dynamic response signal.

[0058] According to an embodiment, the controller transfers the dynamic response signal from the measured position to the desired position.

[0059] According to an embodiment, the accelerometer is positioned on an object at a location separate from the housing.

[0060] According to the present invention, a system for measuring the dynamic response of a machine tool is provided, the system comprising: a piezoelectric actuator operable to generate an excitation signal; an accelerometer operable to output a response signal indicating the dynamic energy of the machine tool; a controller configured to operate the piezoelectric actuator to output the excitation signal and output data indicating the excitation signal; and a housing housing the piezoelectric actuator and the controller and configured to be attached to the machine tool.

[0061] According to an embodiment, the housing contains the accelerometer.

[0062] According to an embodiment, the accelerometer is positioned on a machine tool separate from the housing.

[0063] According to an embodiment, the invention is further characterized by a turbine generator for supplying power to at least one of the controller or piezoelectric actuator.

Claims

1. A system for a machine tool, the system comprising: a machine tool, the machine tool comprising a spindle; and a dynamic characterization system attachable to the machine tool and comprising: a piezoelectric actuator operable to generate a predefined excitation signal; an accelerometer operable to measure dynamic energy of the machine tool in response to the excitation signal and output a dynamic response signal indicative of the dynamic energy; a controller comprising a communication interface, wherein the controller is configured to: store a plurality of known signal profile curves, select a known signal profile curve of the predefined excitation signal from the plurality of known signal profile curves, operate the piezoelectric actuator to output the excitation signal having the selected known signal profile curve; and transmit, through the communication interface, a vibration input signal indicative of the excitation signal having the selected known signal profile curve; and a housing housing the piezoelectric actuator and the controller, wherein the housing is attachable to and detachable from an end of the spindle; and a system controller operating the machine tool to cause the machine tool to retrieve the dynamic characterization system and conduct a vibration analysis through the dynamic characterization system without being necessarily offline when a vibration analysis of the machine tool is to be performed, and operating the machine tool to cause the dynamic characterization system to be returned to a tool library of the machine tool once the vibration analysis is completed.

2. The system of claim 1, wherein the housing further houses the accelerometer.

3. The system of claim 1, wherein the controller transmits a vibration signal through the communication interface based on the dynamic response signal from the accelerometer.

4. The system of claim 1, wherein the accelerometer is positioned separately from the housing.

5. The system of claim 1, wherein the communication interface comprises a wireless transceiver.

6. The system of claim 1, wherein the piezoelectric actuator is operable to output different excitation signals.

7. The system of claim 5, wherein the housing houses the accelerometer, and the accelerometer outputs the dynamic response signal to the controller.

8. The system of claim 7, wherein the controller is configured to filter the dynamic response signal from the accelerometer and output data indicative of the filtered dynamic response signal using the wireless transceiver.

9. The system of claim 7, wherein the controller shifts the dynamic response signal from a measured location to a desired location.

10. The system of any one of claims 1 to 9, wherein the dynamic characterization system further comprises a power source to power at least one of the piezoelectric actuator or the controller, wherein the housing houses the power source.

11. The system of claim 10, wherein the power source is a turbine generator.

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