Long-stroke fast tool servo system with integrated axial cutting force detection actuator

Abstract

The present invention provides a long-stroke fast tool servo system integrated with an axial cutting force detection mechanism, comprising: a long-stroke fast tool servo mechanism, which is used to drive an air-floating guide shaft to move in a linear direction; an axial cutting force detection actuator, which is installed on the air-floating guide shaft and moves linearly with the air-floating guide shaft; an end actuator, which is installed on the axial cutting force detection actuator and is used to install a tool; the axial cutting force detection actuator detects the axial cutting force exerted on the tool and outputs the same thrust to offset the axial cutting force; compared with the existing long-stroke fast tool servo mechanism and force detection means, the system of the present invention can integrate the force detection mechanism into the long-stroke fast tool servo system, and can monitor the size of the cutting force in real time during ultra-precision machining, so as to compensate for defects in the machining later.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-precision machining, and in particular to a long-stroke fast tool servo system integrated with an axial cutting force detection actuator. Background Art

[0002] Ultra-precision cutting is one of the important processing methods for the surface microstructure of key components in the fields of semiconductors, optics, aerospace, etc. Ultra-precision single-point diamond cutting is to drive the diamond tool through an ultra-precision machine tool with nanometer positioning accuracy, cooperate with the spindle rotation movement, and form a spatial cutting trajectory to process the geometric surface. In order to process the surface microstructure array with higher precision and efficiency, the fast tool servo system is produced. The fast tool servo system is a mechanical cutting system based on a single-point diamond tool. It uses a high-frequency response servo mechanism to drive the single-point diamond tool and cooperates with the machine tool axis movement for ultra-precision cutting. It is an indispensable processing device for processing microstructure optical devices.

[0003] With the continuous development of optical technology, various high-performance optical components are developing towards more complex surface shapes, denser microstructure arrays and more extreme sizes, which puts higher requirements on fast tool servo systems. For example, the processing technology of some free-form surfaces with large curvature and deep vector height requires a fast tool servo system with a stroke of millimeters. However, the currently commonly used piezoelectric ceramic-driven fast tool servo system cannot meet the requirements because its stroke is usually tens of microns. The magnetostrictive fast tool servo system and the Maxwell force-driven fast tool servo system are difficult to meet the requirements of ultra-high processing accuracy due to their nonlinear and magnetostrictive effects. Therefore, linear drives based on the Lorentz magnetic principle are widely used in long-stroke fast tool servo systems. The long-stroke fast tool servo system with voice coil motor as the drive can reach a stroke of hundreds of microns or even several millimeters, and the frequency response can reach hundreds of hertz. At the same time, it can also achieve nanometer-level positioning accuracy. It is an important equipment for processing optical free-form surfaces.

[0004] Cutting force is an important indicator reflecting the cutting state. Micro-defects on the microstructure surface are often generated at the position where the cutting force is abnormal. In order to grasp the cutting state of the long-stroke fast tool servo mechanism cutting complex surface microstructures and ensure the integrity of the processed surface microstructure, it is necessary to monitor the cutting force generated during the cutting process in real time. At present, there are two main ways to effectively measure the cutting force in the ultra-precision machining process. The first is to use a commercial dynamometer, and the second is to use a fast tool servo system with an integrated force sensor. Commercial dynamometers are large in size, expensive, and have a high force measurement resolution, which makes them difficult to use in the field of ultra-precision cutting. Existing integrated force sensors are mostly integrated in fast tool servo systems with smaller strokes. It is difficult to take into account the characteristics of high resolution, high stiffness and a large range at the same time, and cannot be applied to long-stroke fast tool servo systems. On the other hand, there are currently single-axis fast tool servo systems with integrated piezoelectric force sensors, but due to the inherent defect of charge leakage, they cannot accurately measure static cutting forces.

[0005] Therefore, in view of the above-mentioned shortcomings in the field of ultra-precision machining, a new long-stroke fast tool servo system with an integrated axial cutting force detection mechanism is proposed. Summary of the invention

[0006] The invention provides a novel long-stroke fast tool servo system integrated with an axial cutting force detection mechanism, which can solve the ultra-precision cutting process with high resolution, high rigidity and a large range.

[0007] Long-stroke fast tool servo system with integrated axial cutting force detection actuator, including:

[0008] Long-stroke fast tool servo mechanism, which is used to drive the air-floating guide shaft to move in a linear direction;

[0009] An axial cutting force detection actuator is mounted on the air-floating guide shaft and moves linearly with the air-floating guide shaft;

[0010] An end actuator, which is mounted on the axial cutting force detection actuator and is used to install a tool; the axial cutting force detection actuator is used to detect the axial cutting force applied to the end actuator and output the same thrust to offset the axial cutting force;

[0011] A displacement detection mechanism, which is used to detect the axial displacement of the long-stroke fast tool servo mechanism;

[0012] A host computer system, which is used to control the actions of the long-stroke fast tool servo mechanism and the axial cutting force detection actuator;

[0013] The axial cutting force detection actuator includes a first voice coil motor, a flexible hinge and a capacitive displacement sensor; the end actuator is installed on the flexible hinge, and the end actuator is subjected to the axial cutting force and transmits it to the flexible hinge; when the flexible hinge is deformed by the force, the capacitive displacement sensor measures the deformation displacement of the flexible hinge and transmits it to the host computer system; the host computer system controls the first voice coil motor to output the same thrust to offset the axial cutting force.

[0014] Preferably, the long-stroke fast tool servo mechanism comprises a second voice coil motor, an air-floating guide shaft sleeve and an air-floating guide shaft; the second voice coil motor drives the air-floating guide shaft to produce axial displacement, and the air-floating guide shaft sleeve is used to guide and constrain the air-floating guide shaft.

[0015] Preferably, the displacement detection mechanism is a linear grating encoder, which can detect the axial displacement of a long-stroke fast tool servo mechanism.

[0016] Preferably, the host computer system includes a data acquisition card and a host computer; the input end of the data acquisition card is connected to the output end of the linear grating encoder and the output end of the capacitive displacement sensor, and is used to collect displacement signals of the driving end and the force detection end respectively; the output end of the data acquisition card is respectively connected to the input ends of two linear drivers for driving the first voice coil motor and the second voice coil motor, and is used to generate output voltage signals for controlling the displacement of the first voice coil motor and the second voice coil motor respectively;

[0017] The upper computer host is connected to the control end of the data acquisition card, and is used to receive the displacement digital coding signal and the displacement voltage signal collected by the data acquisition card, and calculate the displacement value and the dynamic force size of the cutting force generated by the two voice coil motors based on the signal, and control the voltage signal to be output, which is transmitted to the first voice coil motor and the second voice coil motor by the linear driver through the data acquisition card to accurately control the displacement generated by the voice coil motors.

[0018] Preferably, the force measuring base is fixedly mounted on the front end of the air floating guide rail shaft; an open chamber is provided inside the force measuring base, and the first voice coil motor is mounted in the chamber of the force measuring base;

[0019] A flexible hinge is fixedly mounted on the front side of the force measuring base; the deformable portion of the flexible hinge is located on the front side of the first voice coil motor;

[0020] The first voice coil motor comprises a first voice coil motor stator and a first voice coil motor mover; the first voice coil motor stator is directly fixedly installed in the chamber of the force measuring base; the first voice coil motor mover is fixedly connected to the deformable part of the flexible hinge;

[0021] A tool holder is installed on the outer side of the deformable part of the flexible hinge, and the tool holder is used to install a diamond tool;

[0022] A sleeve is also installed on the force measuring base, and the sleeve extends into the interior of the force measuring base and faces the flexible hinge; the capacitive displacement sensor is installed at the front end of the sleeve, and the detection end of the capacitive displacement sensor is close to the deformable part of the flexible hinge; when the diamond tool is subjected to axial cutting force and transmitted to the flexible hinge, the flexible hinge will produce axial deformation, and the capacitive displacement sensor can measure the deformation displacement of the flexible hinge in a non-contact manner.

[0023] Preferably, when the axial cutting force detection actuator follows the displacement of the air-floating guide shaft, the host computer system controls the first voice coil motor to generate a thrust in the opposite direction to offset the influence of the inertia force in the reciprocating motion of the axial cutting force detection actuator, so that the diamond tool and the force measuring base always remain in a state of no relative displacement.

[0024] Preferably, the second voice coil motor comprises a second voice coil motor stator and a second voice coil motor mover; the second voice coil motor stator is fixed to the back plate of the housing by screws, and the air-floating guide rail sleeve is installed on the bottom plate of the housing; the second voice coil motor mover is connected to the air-floating guide rail shaft by a connecting plate, and the air-floating guide rail shaft is constrained by the air-floating guide rail sleeve and can only slide axially; when the control current flows through the second voice coil motor, the second voice coil motor mover is affected by the Lorentz magnetic force and drives the air-floating guide rail shaft to move within the stroke.

[0025] Preferably, the linear grating encoder is used to detect the displacement of the air-floating guide shaft; the grating scale of the linear grating encoder is fixed on the air-floating guide shaft through a support frame; the reading head of the linear grating encoder is connected to the side plate of the outer shell through a connecting plate; the grating scale moves with the air-floating guide, and then the reading head can measure the displacement of the air-floating guide shaft.

[0026] The beneficial effects of the present invention are as follows:

[0027] (1) Compared with the existing long-stroke fast tool servo mechanism and force detection means, the system of the present invention can integrate the force detection mechanism into the long-stroke fast tool servo system, and can monitor the magnitude of the cutting force in real time during ultra-precision machining, so as to compensate for defects in the machining later; it can also be separated into the long-stroke fast tool servo system and the force detection system, so as to be used as two separate systems;

[0028] (2) Compared with the existing axial cutting force measurement mechanism for ultra-precision turning, the axial cutting force detection mechanism in the system of the present invention has the characteristics of high force detection resolution, large range and high rigidity. Its force measurement resolution is 5mN, the force measurement range is 0~15N, and the static rigidity is 50N / μm;

[0029] (3) Compared with the existing piezoelectric force sensor, the axial cutting force monitoring mechanism in the system of the present invention can measure the static cutting force more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall appearance of the long-stroke fast tool servo system integrated with the axial cutting force detection mechanism in the present invention.

[0031] Figure 2 It is a schematic diagram of the overall structure of the long-stroke fast tool servo system integrated with the axial cutting force detection mechanism in the present invention.

[0032] Figure 3 It is a three-dimensional stereoscopic view of the axial cutting force detection mechanism of the present invention.

[0033] Figure 4 It is a front view of the axial cutting force detection mechanism of the present invention.

[0034] Figure 5 for Figure 4 Cross-sectional view in the AA direction. DETAILED DESCRIPTION

[0035] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0036] The embodiment of the present invention provides a novel long-stroke fast tool servo system integrated with an axial cutting force detection mechanism, comprising:

[0037] A long-stroke fast tool servo mechanism, which is used to drive the air-floating guide shaft 18 to move in a linear direction;

[0038] An axial cutting force detection actuator, which is mounted on the air-floating guide shaft 18 and moves linearly with the air-floating guide shaft 18;

[0039] An end actuator, which is mounted on the axial cutting force detection actuator and is used to install the tool 2; the axial cutting force detection actuator is used to detect the axial cutting force applied to the end actuator and output the same thrust to offset the axial cutting force;

[0040] A displacement detection mechanism, which is used to detect the axial displacement of the long-stroke fast tool servo mechanism;

[0041] The host computer system is used to control the actions of the long-stroke fast tool servo mechanism and the axial cutting force detection actuator.

[0042] The overall appearance of the system is as follows Figure 1 As shown in the figure, the shell of the system is composed of 6 aluminum alloy plates, namely the front plate 1, the rear plate 9, the side plates 8 and 11, the top plate 10 and the bottom plate 6. All structures in the system are connected to the bottom plate and the rear plate, and the shell can also play the role of electromagnetic shielding. When in use, the system is connected to the machine tool through the right-angle connecting plates 4 and 7 fixed on the left and right sides of the shell 6.

[0043] The axial cutting force detection actuator includes a first voice coil motor, a flexible hinge 5 and a capacitive displacement sensor 23; the end actuator is installed on the flexible hinge 5, and the end actuator is subjected to the axial cutting force and transmitted to the flexible hinge; when the flexible hinge is deformed by force, the capacitive displacement sensor 23 measures the deformation displacement of the flexible hinge and transmits it to the host computer system; the host computer system controls the first voice coil motor to output the same thrust to offset the axial cutting force. When the flexible hinge 5 is reset to the initial position, the forces on both sides of the flexible hinge 5 are balanced.

[0044] Preferably, the long-stroke fast tool servo mechanism includes a second voice coil motor, an air-floating guide shaft sleeve 19 and an air-floating guide shaft 18 ; the second voice coil motor drives the air-floating guide shaft 18 to produce axial displacement, and the air-floating guide shaft sleeve 19 is used to guide and constrain the air-floating guide shaft 18 .

[0045] Preferably, the displacement detection mechanism is a linear grating encoder, which can detect the axial displacement of a long-stroke fast tool servo mechanism.

[0046] Preferably, the host computer system includes a data acquisition card and a host computer; the input end of the data acquisition card is respectively connected to the output end of the linear grating encoder and the output end of the capacitive displacement sensor 23, the data acquisition card collects the displacement signal of the second voice coil motor from the output end of the linear grating encoder, and the data acquisition card collects the displacement voltage signal of the flexible hinge from the output end of the capacitive displacement sensor 23;

[0047] The host computer is connected to the control end of the data acquisition card, and is used to receive the displacement digital coding signal and the displacement voltage signal collected by the data acquisition card, and calculate the displacement value and the dynamic force size of the cutting force generated by the two voice coil motors based on the signal, and control the voltage signal to be output; the host computer is directly connected to or indirectly transmitted to the input end of the linear driver of the first voice coil motor and the second voice coil motor through the data acquisition card, and accurately controls the displacement generated by the voice coil motor.

[0048] Preferably, the force measuring base 17 is fixedly mounted on the front end of the air floating guide rail shaft 18 by bolts; an open chamber is provided inside the force measuring base 17, and the first voice coil motor is installed in the chamber of the force measuring base 17;

[0049] A flexible hinge is fixedly mounted on the front side of the force measuring base 17; the deformable portion of the flexible hinge is located on the front side of the first voice coil motor;

[0050] The first voice coil motor comprises a first voice coil motor stator 24 and a first voice coil motor mover 16; the first voice coil motor stator 24 is directly fixedly installed in the cavity of the force measuring base 17; the first voice coil motor mover 16 is fixedly connected to the deformable part of the flexible hinge;

[0051] A tool holder 3 is installed on the outer side of the deformable part of the flexible hinge, and the tool holder is used to install the diamond tool 2;

[0052] The force measuring base is also provided with a sleeve 26, and a gasket 25 is provided between the base part of the sleeve 26 and the force measuring base. The sleeve 26 extends into the force measuring base and faces the flexible hinge; the capacitive displacement sensor 23 is installed at the front end of the sleeve 26, and the detection end of the capacitive displacement sensor 23 is close to the deformable part of the flexible hinge; when the diamond tool is subjected to the axial cutting force transmitted to the flexible hinge, the flexible hinge will produce axial deformation, and the capacitive displacement sensor can measure the deformation displacement of the flexible hinge in a non-contact manner.

[0053] Preferably, when the axial cutting force detection actuator follows the displacement of the air-floating guide shaft 18, the host computer system controls the first voice coil motor to generate thrust in the opposite direction to offset the influence of the inertial force in the reciprocating motion of the axial cutting force detection actuator, so that the diamond tool and the force measuring base always remain in a state of no relative displacement, which makes the axial force measuring mechanism have a larger axial stiffness. Therefore, the cutting force detection mechanism can have the characteristics of high force detection resolution, large range and high stiffness at the same time. Its force measurement resolution is 5mN, the force measurement range is 0~15N, and the static stiffness is 50N / μm. This means that the integrated force measuring mechanism will not affect the cutting performance of the original long-stroke fast tool servo system.

[0054] Preferably, the second voice coil motor includes a second voice coil motor stator 22 and a second voice coil motor mover 20; the second voice coil motor stator 22 is fixed to the housing back plate 9 by screws, and the air-floating guide shaft sleeve 19 is installed on the housing bottom plate 6; the second voice coil motor mover 20 is connected to the air-floating guide shaft 18 through the connecting plate 21, and the air-floating guide shaft 18 is constrained by the air-floating guide shaft sleeve 19 and can only slide axially; when the control current flows through the second voice coil motor, the second voice coil motor mover is affected by the Lorentz magnetic force and drives the air-floating guide shaft to move within the stroke. The motion generated by the upper computer system driving the second voice coil motor and the air-floating guide shaft is displacement feedback through a linear grating encoder.

[0055] Preferably, the linear grating encoder is used to detect the displacement of the air-floating guide shaft; the grating scale 14 of the linear grating encoder is fixed on the air-floating guide shaft 18 through a support frame 15; the reading head 13 of the linear grating encoder is connected to the housing side plate 11 through a connecting plate 12; the grating scale moves with the air-floating guide, and then the reading head can measure the displacement of the air-floating guide shaft. The host computer system then performs position closed-loop feedback control on the long-stroke fast tool servo system through an algorithm. In this example, the positioning resolution of the long-stroke fast tool servo system is 20nm, and the full stroke length is 10mm.

Claims

1. A long-stroke fast tool servo system with an integrated axial cutting force detection actuator, characterized in that: include: A long-stroke fast tool servo mechanism, which is used to drive the air-floating guide shaft (18) to move in a linear direction; An axial cutting force detection actuator, which is mounted on the air-floating guide shaft (18) and moves linearly with the air-floating guide shaft (18); An end actuator, which is mounted on the axial cutting force detection actuator and is used to install a tool; the axial cutting force detection actuator is used to detect the axial cutting force applied to the end actuator and output the same thrust to offset the axial cutting force; A displacement detection mechanism, which is used to detect the axial displacement of the long-stroke fast tool servo mechanism; A host computer system, which is used to control the actions of the long-stroke fast tool servo mechanism and the axial cutting force detection actuator; The axial cutting force detection actuator comprises a first voice coil motor, a flexible hinge and a capacitive displacement sensor; the end actuator is mounted on the flexible hinge, and the end actuator is subjected to the axial cutting force and transmits it to the flexible hinge; when the flexible hinge is deformed by the force, the capacitive displacement sensor measures the deformation displacement of the flexible hinge and transmits it to the host computer system; the host computer system controls the first voice coil motor to output the same thrust to offset the axial cutting force; The long-stroke fast tool servo mechanism comprises a second voice coil motor, an air-floating guide shaft sleeve (19) and an air-floating guide shaft (18); the second voice coil motor drives the air-floating guide shaft (18) to generate axial displacement, and the air-floating guide shaft sleeve (19) is used to guide and constrain the air-floating guide shaft (18).

2. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 1, characterized in that: The displacement detection mechanism is a linear grating encoder, which can detect the axial displacement of a long-stroke fast tool servo mechanism.

3. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 2, characterized in that: The host computer system includes a data acquisition card and a host computer; the input end of the data acquisition card is connected to the output end of the linear grating encoder and the output end of the capacitive displacement sensor, and is used to collect displacement signals of the driving end and the force detection end respectively; the output end of the data acquisition card is respectively connected to the input ends of two linear drivers for driving the first voice coil motor and the second voice coil motor, and is used to generate output voltage signals for controlling the displacement of the first voice coil motor and the second voice coil motor respectively; The upper computer host is connected to the control end of the data acquisition card, and is used to receive the displacement digital coding signal and the displacement voltage signal collected by the data acquisition card, and calculate the displacement value and the dynamic force size of the cutting force generated by the two voice coil motors based on the signal, and control the voltage signal to be output, which is transmitted to the first voice coil motor and the second voice coil motor by the linear driver through the data acquisition card to accurately control the displacement generated by the voice coil motors.

4. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 3, characterized in that: A force measuring base (17) is fixedly mounted on the front end of the air floating guide rail shaft (18); an open chamber is arranged inside the force measuring base (17), and the first voice coil motor is mounted in the chamber of the force measuring base (17); A flexible hinge is fixedly mounted on the front side of the force measuring base (17); a deformable portion of the flexible hinge is located on the front side of the first voice coil motor; The first voice coil motor comprises a first voice coil motor stator (24) and a first voice coil motor mover (16); the first voice coil motor stator (24) is directly fixedly installed in the chamber of the force measuring base (17); the first voice coil motor mover (16) is fixedly connected to the deformable part of the flexible hinge; A tool holder (3) is installed on the outer side of the deformable part of the flexible hinge, and the tool holder is used to install the diamond tool (2); The force measuring base is also provided with a sleeve (26), which extends into the force measuring base and faces the flexible hinge; the capacitive displacement sensor (23) is provided at the front end of the sleeve (26), and the detection end of the capacitive displacement sensor (23) is close to the deformable part of the flexible hinge; when the diamond tool is subjected to an axial cutting force which is transmitted to the flexible hinge, the flexible hinge will produce an axial deformation, and the capacitive displacement sensor can measure the deformation displacement of the flexible hinge in a non-contact manner.

5. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 4, characterized in that: When the axial cutting force detection actuator follows the displacement of the air-floating guide rail shaft (18), the host computer system controls the first voice coil motor to generate thrust in the opposite direction to offset the influence of the inertia force in the reciprocating motion of the axial cutting force detection actuator, so that the diamond tool and the force measuring base are always kept in a state of no relative displacement.

6. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 5, characterized in that: The second voice coil motor comprises a second voice coil motor stator (22) and a second voice coil motor mover (20); the second voice coil motor stator (22) is fixed on the housing back plate (9) by screws, and the air-floating guide rail shaft sleeve (19) is installed on the housing bottom plate (6); the second voice coil motor mover (20) is connected to the air-floating guide rail shaft (18) through a connecting plate (21), and the air-floating guide rail shaft (18) is constrained by the air-floating guide rail shaft sleeve (19) and can only slide axially; when the control current flows through the second voice coil motor, the second voice coil motor mover is acted upon by the Lorentz magnetic force and drives the air-floating guide rail shaft to move within a stroke.

7. The long-stroke fast tool servo system integrated with an axial cutting force detection actuator as claimed in claim 6, characterized in that: The linear grating encoder is used to detect the displacement of the air-floating guide shaft; the grating scale (14) of the linear grating encoder is fixed on the air-floating guide shaft (18) through a support frame (15); the reading head (13) of the linear grating encoder is connected to the housing side plate (11) through a connecting plate (12); the grating scale moves with the air-floating guide, and the reading head can measure the displacement of the air-floating guide shaft.

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