TWI572853B - A Method for Measuring Rigidity of Objects in Rotating State - Google Patents

Description

Method for measuring the rigidity of an object in a rotating state

The present invention relates to a method for measuring the rigidity of an object, and more particularly to a method for measuring the rigidity of an object in a rotating state.

A spindle of a machine tool is an important component that affects the cutting accuracy of the machine tool. Knowing the stiffness of the spindle at high speeds helps to design a better machine tool quality.

Referring to FIG. 1 and FIG. 2, a measuring device 1 for measuring the overall maneuvering stiffness of a milling machine spindle in a rotating state, as disclosed in the Chinese Patent No. CN 103419085 A (hereinafter referred to as the foregoing), mainly comprises a base unit 11 and an electromagnetic The excitation unit 12, a simulation tool 131 sandwiched between a holder 13, and a measuring unit 14. The base unit 11 includes a base 111, a rectangular frame 112 disposed on the base 111, a concave partition 113, and a plurality of adjustable lifting brackets 114. The concave partition 113 divides the rectangular frame 112 into a front chamber 115 and a rear chamber 116. The adjustable lifting brackets 114 are respectively disposed on the rectangular frame 112 and located on the left, right and rear sides of the rear chamber 116. The simulated cutter 131 sandwiched by the shank 13 is surrounded by the adjustable lifting brackets 114. Wrap around. The electromagnetic excitation unit 12 includes an AC power source 121 electrically connected to each other, an electromagnetic excitation component 122 disposed in the chamber 115 before the rectangular frame 112, and a frequency generating member 125. The electromagnetic excitation component 122 has a core frame 123 and a spiral coil 124 wound around the core frame 123. The measuring unit 14 includes a force measuring plate 141, a plurality of laser displacement sensing members 142, and a plurality of eddy current sensing members 143. The force measuring plate 141 is connected to the base 111. The laser displacement sensing members 142 are respectively disposed on the left and right sides of the rear chamber 116 of the rectangular frame 112 to measure the simulated tool 131 relative to the base. A dynamic displacement of the seat unit 11. The eddy current sensing members 143 are respectively disposed on the adjustable lifting brackets 114 to measure the radial dynamic displacement and the longitudinal dynamic displacement of the shank 13.

In detail, the measuring method of the measuring device 1 disclosed in the foregoing method first outputs a signal to the AC power source 121 through the frequency generating member 125 of the electromagnetic excitation unit 12 to generate an electromagnetic excitation. The alternating current of the helical coil 124 of the component 122 forms an alternating magnetic field that causes the alternating magnetic field to generate an alternating electromagnetic force to the simulated tool 131 to cause relative vibration of the simulated tool 131 relative to the base unit 11. The dynamic displacement of the simulated tool 131 relative to the base unit 11 is further measured by the laser displacement sensing members 142, and the radial dynamic displacement of the tool holder 13 is measured by the eddy current sensing members 143. The longitudinal dynamic displacement is matched with the force plate 141 to measure a dynamic force of the electromagnetic excitation unit 12. Finally, the dynamic stiffness of the simulated tool 131 is obtained according to Newton's third law of motion.

The applicant provides a force versus time diagram as shown in FIG. 3 according to the alternating electromagnetic force generated by the measuring device 1 disclosed in the previous case. However, referring to FIG. 3, the electromagnetic excitation component 122 acts on the simulation tool 131 only by the alternating electromagnetic force in a single direction, so that the simulation tool 131 is still subjected to a bias force F ₀ , resulting in a bias force F ₀ . The simulated tool 131 produces a nonlinear deformation, resulting in an increase in the error of the stiffness measurement.

According to the above description, how to avoid the nonlinear deformation generated when the simulated tool performs the rigidity measurement under high-speed rotation is a difficult problem to be solved by those skilled in the technical field.

Accordingly, it is an object of the present invention to provide a method of measuring the rigidity of an object in a rotated state.

Therefore, the method for measuring the rigidity of the object in the rotating state of the present invention comprises a step (a), a step (b), and a step (c).

The step (a) is to continuously input a first alternating current to a first electromagnet and a second electromagnet respectively disposed on opposite sides of the object to be tested continuously rotating along an axis. An alternating current signal and a second alternating current signal, the first electromagnet and the second electromagnet respectively generate an action on the object to be tested along an effective line perpendicular to the axis a first electromagnetic force and a second electromagnetic force, so that the object to be tested generates a displacement along the line of action, wherein a phase difference between the first alternating current signal and the second alternating current signal is The phase difference) is 90 degrees.

The step (b) is to measure a total force of the first electromagnetic force and the second electromagnetic force acting on the object to be tested and the displacement of the object to be tested at the step (a).

The step (c) is after the step (b), the total force and the displacement are Fourier transformed to calculate a rigidity of the object to be tested in the step (a).

The effect of the present invention is to input the first alternating currents respectively input to the first electromagnet and the second electromagnet through the first electromagnet and the second electromagnet disposed on opposite sides of the object to be tested. The phase difference between the signal and the second alternating current signal is 90 degrees, such that the first electromagnetic force and the second electromagnetic force are symmetrically distributed on opposite sides of the object to be tested, so that the total force is averaged and The problem of unbiased force increases the accuracy of the rigidity of the object to be measured measured at the time of rotation.

2‧‧‧Measurement device

21‧‧‧First electromagnet

22‧‧‧Second electromagnet

23‧‧‧ force sensing parts

24‧‧‧ Displacement sensing parts

3‧‧‧ objects to be tested

4‧‧‧Tool machine

41‧‧‧Clip seat

L ₀ ‧‧‧ axis

L ₁ ‧‧‧action line

F ₁ ‧‧‧First electromagnetic force

F ₂ ‧‧‧second electromagnetic force

F‧‧‧ total force

I ₁ ‧‧‧First AC current signal

I ₂ ‧‧‧Second alternating current signal

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a perspective view showing the rotation of a milling machine spindle as disclosed in Chinese Patent No. CN 103419085 A. Measuring device for maneuvering stiffness; 2 is a plan view showing an electromagnetic excitation unit and its detailed components of the measuring device for the overall maneuvering stiffness in the rotating state of the spindle of the milling machine; FIG. 3 is a force versus time diagram illustrating the applicant according to the measuring device. FIG. 4 is a front view showing a measuring device used in an embodiment of the method for measuring the rigidity of an object in a rotating state according to the present invention; FIG. 5 is a measuring device used in FIG. A partially enlarged view illustrating a force situation of an object to be tested in the embodiment; FIG. 6 is a current versus time diagram illustrating a first alternating current signal and a first step in a step (a) of the embodiment. 2 alternating current signal; and FIG. 7 is a force-to-time relationship diagram illustrating a first electromagnetic force, a second electromagnetic force, and a total force in the step (a).

Referring to FIG. 4, an embodiment of the method for measuring the rigidity of an object in a rotating state according to the present invention uses a measuring device 2 as shown in FIG. 4 to measure the mechanical properties of an object 3 to be measured, and the object to be tested 3 is an axis. A clamping seat 41 of a power tool 4 is driven by a driving source (not shown) of the power tool 4 to continuously rotate at an axis of ₀ to 6000 rpm along an axis L _{0 of} the clamping seat 41. rotation. This embodiment of the invention comprises a step (a), a step (b), and a step (c).

Referring to FIG. 5, FIG. 6 and FIG. 7, step (a) is the opposite sides of the measuring means are disposed in the continuously along the rotation axis L ₀ of the object to be measured 3 in a first 2 The electromagnet 21 and the second electromagnet 22 continuously input a first alternating current signal I ₁ and a second alternating current signal I ₂ , so that the first electromagnet 21 and the second electromagnet 22 are respectively substantially perpendicular An action line L _{1 of} the axis L ₀ generates a first electromagnetic force F ₁ and a second electromagnetic force F ₂ acting on the object 3 to be tested, so that the object 3 to be tested generates a line along the line of action L _{1 .} Displacement. As shown in FIGS. 5 and 6, in order to make a phase difference between the first electromagnetic force F ₁ and the second electromagnetic force F ₂ 180 degrees (ie, a half cycle), the first electromagnetic force F ₁ and the A total force F of the second electromagnetic force F ₂ is not biased, and a phase difference between the first alternating current signal I ₁ and the second alternating current signal I ₂ must be controlled at 90 degrees (ie, the time difference is T/ 4, T is the period). In this embodiment of the present invention, the first alternating current signal I ₁ and the second alternating current signal I ₂ are exemplified by a sinusoidal wave, but are not limited thereto, and may be Other periodic functions.

In the step (b), a force transducer 23 and a displacement sensing member 24 of the measuring device 2 respectively measure the action on the object 3 to be tested. The total force F and the displacement of the object 3 to be tested. In order to avoid the first electromagnet 21, the electromagnet 22 causes the second force to the sensing element 23 the height difference force measurement error, the force sensing member 23 is disposed on the action line L _1, The first electromagnet 21 and the second electromagnet 22 are maintained at the same height. Preferably, in the embodiment, the force sensing member 23 is an axial type piezoelectric power sensor; the displacement sensing member 24 is a Laser Doppler velocimeter.

The step (c) is after the step (b), after performing the Fourier transform on the total force F and the displacement, calculating the object 3 to be tested in the step (a) by using a calculation formula. A rigid. Specifically, the calculation formula is Where X ( ω ) is a function of the Fourier transform of the displacement, F ( ω ) is a function of the total force F after Fourier transform, and k is the time of the object 3 to be tested at the step (, a) For a rigid, detailed derivation process, see Ewins, DJ Modal testing 2: Theory, practice and application, Research Studies Press, 2000, page 36-45.

In detail, the embodiment of the present invention is configured to firstly mount the object 3 to be tested on the clamping seat 41 of the machine tool 4, and is rotated by the driving source (not shown) of the machine tool 4 to A specific speed. Then, the first alternating current signal I ₁ and the second alternating current signal I _{2 are respectively} applied to the first electromagnet 21 and the second electromagnet 22 to make the first electromagnet 21 and the second electromagnetic The iron 22 generates the first electromagnetic force F ₁ and the second electromagnetic force F _{2 respectively} , so that the first electromagnetic force F ₁ and the second electromagnetic force F ₂ act together on the object 3 to be tested, and the The measuring object 3 generates the displacement; at the same time, the force sensing member 23 passing through the measuring device 2 and the displacement sensing member 24 measure the first electromagnetic force F ₁ acting on the object 3 to be tested and the first The electromagnetic force F ₂ and the displacement of the object 3 to be tested. Finally, the total force F and the displacement are respectively Fourier transformed, and then the rigidity of the object to be tested 3 in the rotation state can be derived through the above calculation formula.

It is to be noted that the first electromagnet 21 and the second electromagnet 22 are disposed on opposite sides of the object 3 to be tested, and the first alternating current signal I ₁ and the second alternating current signal I The phase difference between the _two is controlled at 90 degrees, and the first electromagnetic force F ₁ and the second electromagnetic force F _{2 in} opposite directions can be generated, so that the total force F is averaged to zero, not as described in the previous case. Has a biasing force F ₀ . Therefore, the error of the rigidity measured by the object 3 to be measured in the rotation state is reduced.

In summary, the method for measuring the rigidity of the object in the rotating state of the present invention generates the interaction between the first electromagnet 21 and the second electromagnet 22 disposed on opposite sides of the object 3 to be tested. Measuring the first electromagnetic force F ₁ of the object 3 and the second electromagnetic force F ₂ , and the phase difference between the first alternating current signal I ₁ and the second alternating current signal number I ₂ is controlled at 90 degrees, so that This total force F does not generate a biasing force and thus reduces the measurement error. Therefore, the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and the simple equivalent changes and modifications made by the scope of the patent application and the patent specification of the present invention are It is still within the scope of the invention patent.

2‧‧‧Measurement device

21‧‧‧First electromagnet

22‧‧‧Second electromagnet

23‧‧‧ force sensing parts

24‧‧‧ Displacement sensing parts

3‧‧‧ objects to be tested

4‧‧‧Tool machine

41‧‧‧Clip seat

L ₀ ‧‧‧ axis

L ₁ ‧‧‧action line

Claims (3)

A method for measuring the rigidity of an object in a rotating state comprises the following steps: a step (a) is a first electromagnet disposed on opposite sides of an object to be tested continuously rotated along an axis And continuously inputting a first alternating current signal and a second alternating current signal with a second electromagnet, so that the first electromagnet and the second electromagnet respectively act on the line of action substantially perpendicular to the axis a first electromagnetic force and a second electromagnetic force of the object to be tested, so that the object to be tested generates a displacement along the line of action, wherein a phase difference between the first alternating current signal and the second alternating current signal a step (b), in the step (a), measuring a total force of the first electromagnetic force acting on the object to be tested and the second electromagnetic force and the object to be tested Displacement; and a step (c), after the step (b), performing a Fourier transform on the total force and the displacement to calculate a rigidity of the object to be tested in the step (a). The method for measuring the rigidity of an object in a rotating state as described in claim 1, wherein the first alternating current signal and the second alternating current signal in the step (a) each have a sinusoidal waveform. In the method of measuring the rigidity of the object in the rotating state according to Item 1 of the claim, in the step (b), the total force and the displacement are respectively measured by a force sensing member and a displacement sensing member. And the force sensing member is located on the line of action.