ANSYS finite element analysis-based pendulum assembly closed-loop dynamics modeling method

Abstract

The invention relates to a pendulum assembly closed-loop dynamics modeling method based on ANSYS finite element analysis, belongs to the technical field of accelerometer dynamics simulation modeling, and solves the problem that a traditional motion equation is difficult to accurately describe the real-time motion state of an accelerometer pendulum assembly in a closed-loop working state. The method comprises the following specific steps: S1, establishing a quartz pendulous reed dynamic closed-loop feedback control simulation model based on a quartz accelerometer system box schematic diagram; s2, an ANSYS simulation platform is determined; s3, establishing a three-dimensional model of the quartz flexible accelerometer pendulum assembly; s4, material parameters of the pendulum assembly are set; s5, carrying out grid division on the pendulum assembly; s6, determining the time step length of simulation; s7, a load is added to the pendulum assembly, and the work response of the sensor is obtained through calculation; and S8, post-processing the working response of the sensor to obtain an output result.

Description

Technical Field

[0001] The invention relates to the technical field of accelerometer dynamics simulation modeling, and in particular to a closed-loop dynamics modeling method of a pendulum component based on ANSYS finite element analysis. Background Art

[0002] The quartz flexible accelerometer is based on the principle of torque balance, that is, the balance between the inertia torque and the feedback torque, and measures the acceleration through the displacement change of the sensitive pendulum assembly. When the quartz accelerometer is working, the sensitive acceleration in the input axis direction is excited, and the pendulum assembly deflects under the action of the inertia torque. The differential capacitor detection circuit senses the deflection of the pendulum assembly and outputs a current signal to the torquer coil. The torquer coil is acted upon by the Ampere force in the magnetic field, generating a feedback torque equal to the inertia torque and opposite in direction, so that the resultant torque on the pendulum assembly is zero, so that the pendulum assembly is always controlled near the zero position.

[0003] Ideally, the flexible pendulum beam that limits the movement of the pendulum assembly is highly flexible in the direction of the input axis and highly strong in the direction of the output axis, so that the motion state of the pendulum assembly is movement in the direction of the input axis. However, the actual flexible pendulum beam is not infinitely flexible, and the pendulum assembly exhibits different vibration shapes at each modal frequency. In addition, the noise frequency of the external interference to the accelerometer during operation is as high as 2000Hz, which includes the first three modal frequencies of the pendulum assembly, causing the pendulum assembly to exhibit a multi-degree-of-freedom superposition motion state when the accelerometer is working. The traditional motion equation is difficult to accurately describe the motion state of the pendulum assembly. In addition, there is a lack of research on the meter model. Since the quartz flexible accelerometer is a typical closed-loop detection sensor, the current open-loop mechanical simulation model lacks the loading of feedback force and cannot describe the closed-loop working state of the pendulum assembly.

[0004] In summary, the motion state of the pendulum assembly in the meter head is directly related to the measurement accuracy of the quartz accelerometer, and the multi-degree-of-freedom superposition motion equation of the pendulum assembly is difficult to solve. The current open-loop simulation model cannot fully describe the accelerometer working in the closed loop. Therefore, there is a lack of a model that accurately describes the closed-loop working state of the pendulum assembly. Summary of the invention

[0005] In view of the above problems, the present invention provides a closed-loop dynamic modeling method of a pendulum assembly based on ANSYS finite element analysis, which solves the problem that traditional motion equations are difficult to accurately describe the real-time motion state of the accelerometer pendulum assembly in a closed-loop working state.

[0006] The present invention discloses a closed-loop dynamic modeling method of a pendulum assembly based on ANSYS finite element analysis, and the specific steps are as follows:

[0007] S1. Establish a closed-loop feedback control simulation model of quartz pendulum dynamics based on the block diagram of the quartz accelerometer system;

[0008] S2. Determine the ANSYS simulation platform;

[0009] S3, establishing a three-dimensional model of the quartz flexible accelerometer pendulum assembly;

[0010] S4, setting the material parameters of the pendulum assembly;

[0011] S5, dividing the pendulum assembly into grids;

[0012] S6, determine the time step of the simulation;

[0013] S7, based on the simulation time step, adding load to the pendulum assembly and solving to obtain the working response of the sensor;

[0014] S8. Post-process the working response of the sensor to obtain an output result.

[0015] Optionally, according to the working principle of the quartz flexible accelerometer, a principle block diagram of the quartz accelerometer system is established.

[0016] Optionally, the material parameters of the pendulum assembly include material parameters of the flexible pendulum piece, coil and skeleton.

[0017] Optionally, the expression for the simulation time step is:

[0018] Δt=1 / (20f)

[0019] Wherein, f is the first-order modal vibration frequency of the flexible pendulum.

[0020] Optionally, the specific steps of adding a load to the pendulum assembly and solving to obtain the sensor in S7 are as follows:

[0021] Step 71. Use APDL language to add fixed constraints to the six upper and lower bosses of the outer ring of the flexible pendulum, add an initial acceleration load to the flexible pendulum as a whole, and add an initial feedback force load to the pendulum coil;

[0022] Step 72. Obtain the real-time displacement of the current step and process it through the proportional integral link to obtain the Ampere force current; obtain the feedback force load of the next step from the Ampere force current;

[0023] Step 73. Obtain the acceleration load for the next step;

[0024] Step 74. Obtain the real-time displacement of the pendulum assembly in the next step based on the feedback force load in the next step and the acceleration load in the next step;

[0025] Step 75. Determine whether the calculation time reaches the calculation time threshold. If so, output the working response of the sensor. If not, return to step 72 based on the simulation time step.

[0026] Optionally, the acceleration load includes a magnitude and a direction of the load.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1. The present invention adopts finite element simulation technology, which can effectively describe the motion state of the pendulum assembly:

[0029] In the actual working environment of the accelerometer, the pendulum assembly will be disturbed by environmental noise and present a motion vibration mode with superimposed degrees of freedom. Compared with the traditional motion equation, it is difficult to accurately describe the motion state of the pendulum assembly. The finite element simulation can effectively describe the motion state of the pendulum assembly, the results are accurate, the calculation time is greatly saved, and the experimental efficiency is improved.

[0030] 2. The present invention adopts a closed-loop simulation modeling method of the pendulum assembly dynamics based on ANSYS finite element analysis, which effectively describes the closed-loop working state of the pendulum assembly:

[0031] The quartz flexible accelerometer is a typical closed-loop feedback sensor. Most existing simulation models are forward channel simulation verifications, lacking a description of the closed-loop working state of the pendulum assembly. This closed-loop dynamic modeling method is based on ANSYS finite element simulation software. By simultaneously loading acceleration and feedback force loads, where the feedback force load is obtained by solving the displacement at the previous moment, it simulates the motion state of the quartz accelerometer pendulum assembly in the closed-loop working state, providing theoretical support and simulation platform for the structural optimization design of the quartz accelerometer head. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a block diagram of the quartz accelerometer system in the present invention;

[0033] Figure 2 Schematic diagram of the closed-loop feedback control simulation model of the quartz pendulum dynamics in the present invention;

[0034] Figure 3 is a schematic diagram of a three-dimensional model of a pendulum assembly in the present invention;

[0035] Figure 4 A schematic diagram of the mesh division result of the pendulum assembly in the present invention;

[0036] Figure 5 A schematic diagram of the pendulum assembly being loaded with load in the present invention;

[0037] Figure 6 It is the dynamic response of the pendulum assembly in the present invention when operating in an open loop under sinusoidal acceleration;

[0038] Figure 7 It is the closed-loop working step response of the pendulum assembly in the present invention;

[0039] Figure 8 This is the logarithmic swept frequency response of the pendulum assembly in the present invention in closed loop operation. DETAILED DESCRIPTION

[0040] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0041] A specific embodiment of the present invention, as Figure 1-Figure 8 , discloses a closed-loop dynamic modeling method of a pendulum assembly based on ANSYS finite element analysis, the specific steps are as follows:

[0042] S1. Based on the block diagram of the quartz accelerometer system, a simulation model of the quartz pendulum dynamic closed-loop feedback control is established.

[0043] like Figure 1 As shown, according to the working principle of quartz flexible accelerometer, a principle block diagram of quartz accelerometer system is established;

[0044] Specifically, the simulation object is clearly defined as the pendulum assembly, and the signal transmission process of the quartz accelerometer system principle block diagram is: input load (acceleration a, feedback force), acting on the pendulum assembly, outputting the pendulum displacement Δd, inputting the differential capacitance sensor, outputting the differential capacitance value Δc, then inputting the differential capacitance detection circuit, outputting the output voltage ΔU, then inputting the digital closed-loop detection circuit, and finally outputting the digital output Y of the sensor. Among them, the digital closed-loop detection circuit will also output a feedback current I proportional to Y, which is input into the torquer, and the torquer outputs a feedback force, forming one of the input loads, and then acting on the pendulum to form a closed-loop control.

[0045] like Figure 2 As shown, the quartz pendulum dynamic closed-loop feedback control simulation model includes the determined input load (acceleration a, feedback force) and output (pendulum displacement Δd, digital output Y), and the determined transmission relationship between the controllers.

[0046] It will be appreciated that the digital output Y is the output of the accelerometer.

[0047] S2. Determine the ANSYS simulation platform.

[0048] Preferably, the simulation platform is the parametric design language APDL in ANSYS, which facilitates the writing of closed-loop circuits.

[0049] S3. Establish a three-dimensional model of the quartz flexible accelerometer pendulum assembly.

[0050] For example, Taking the accelerometer as an example, a three-dimensional model of the quartz flexible accelerometer pendulum assembly is established, such as Figure 3 shown.

[0051] S4. Set the material parameters of the pendulum assembly.

[0052] The pendulum assembly includes a flexible pendulum piece, a coil and a frame, and the material parameters of the flexible pendulum piece, the coil and the frame are set.

[0053] Exemplarily, as shown in Table 1, the material parameters of the pendulum assembly parts include density, elastic modulus and Poisson's ratio.

[0054] Table 1 Material parameters of the pendulum assembly of the quartz accelerometer

[0055]

[0056]

[0057] S5. Divide the pendulum components into grids.

[0058] Specifically, a smaller grid constraint is added to the swing beam of the flexible swing piece, and a multi-layer scanning grid is used; a coarser grid constraint is used for the remaining structural parts. The division results are as follows: Figure 4 shown.

[0059] S6. Determine the simulation time step, the expression is:

[0060] Δt=1 / (20f)

[0061] Wherein, f is the first-order modal vibration frequency of the flexible pendulum.

[0062] For example, the 30 μm quartz beam pendulum assembly with the largest stiffness is taken as the critical value for calculation, and its natural frequency is 15.79 Hz, so the maximum time step can be Δt=1 / (20f) = 0.0032s.

[0063] S7. Based on the simulation time step, add load to the pendulum assembly and solve to obtain the working response of the sensor. The specific steps are as follows:

[0064] Step 71. Use APDL language to add fixed constraints to the six upper and lower bosses of the outer ring of the flexible pendulum, add an initial acceleration load to the flexible pendulum as a whole, and add an initial feedback force load to the coil.

[0065] Furthermore, the acceleration load includes the magnitude and direction of the load.

[0066] Step 72. Obtain the Ampere force current (i.e., in step 1) of the real-time displacement of the current step processed by the proportional integral link; obtain the feedback force load of the next step from the Ampere force current;

[0067] Step 73. Obtain the acceleration load for the next step;

[0068] Step 74. Obtain the real-time displacement of the pendulum assembly in the next step based on the feedback force load in the next step and the acceleration load in the next step;

[0069] Step 75. Determine whether the calculation time reaches the calculation time threshold. If so, obtain the working response of the sensor. If not, return to step 72 based on the simulation time step.

[0070] The feedback force is provided by the Ampere force exerted on the coil in the magnetic field. The magnitude of the Ampere force current is calculated by the real-time displacement calculated in the previous sub-step through the proportional integral link. The load loading diagram is as follows: Figure 5 shown.

[0071] It can be understood that in step S7, the working response of the sensor is solved at each step under the simulation time step Δt determined in S6.

[0072] S8. Post-process the working response of the sensor to obtain an output result.

[0073] Specifically, the output result of the working response of the sensor includes the displacement response of the pendulum assembly and the output response of the accelerometer.

[0074] Furthermore, the output response of the accelerometer may include a steady-state response, a sinusoidal response, a swept frequency response, a random vibration response, an impulse response, and the like.

[0075] The dynamic closed-loop simulation model of the pendulum assembly based on ANSYS finite element analysis is compared and verified in open-loop and closed-loop operation, and the displacement response of the sampling point on the accelerometer pendulum assembly model and the equivalent digital value of the accelerometer output are output.

[0076] (1) Open-loop response of pendulum assembly

[0077] Under the condition of no feedback force, sinusoidal accelerations of different frequencies are input, and the displacement of the center of mass of the pendulum assembly is taken at each time step. It is normalized with the input sinusoidal acceleration excitation, and the dynamic tracking effect of the pendulum assembly at different frequencies when working in open loop can be obtained, such as Figure 6 shown.

[0078] from Figure 6It can be seen that when the acceleration excitation frequency of the pendulum assembly is slow (f=0.1Hz), it can be seen from the displacement of the center of mass of the pendulum assembly that the dynamic tracking effect of the pendulum assembly on the input excitation is better, and the tracking delay is smaller; when the input excitation frequency of the pendulum assembly is large (f=1Hz), it can be seen from the displacement of the center of mass of the pendulum assembly that its dynamic performance deteriorates, the tracking delay is large, the tracking amplitude is greatly reduced, and the open-loop bandwidth is small.

[0079] (2) Closed-loop dynamic response of pendulum assembly

[0080] When acceleration excitation and feedback force excitation are added at the same time, the pendulum assembly forms a closed-loop working state, in which the feedback force load is calculated by the displacement calculated by the previous step length solution.

[0081] Step response: When the pendulum assembly is in closed-loop working state, a step accelerometer load of 1g is input, and the closed-loop step response of the pendulum assembly can be obtained, such as Figure 7 shown. Figure 7 In the figure, the ordinate is the digital output Y of the accelerometer. When an acceleration excitation of 1g is input, the output is 3284^, from which the scale factor of the accelerometer can be calculated.

[0082] Sweep frequency response: When the pendulum assembly is in closed-loop working state, a logarithmic sine sweep frequency signal with an amplitude of 1g is input, the sweep frequency range is 10-2000Hz, and the sweep time is 1s. The closed-loop sweep frequency response of the pendulum assembly can be obtained, such as Figure 8 shown. Figure 8 In the process of increasing the frequency of the external excitation signal, the tracking error gradually increases, and the output amplitude attenuation ratio is different at different frequency points. When the amplitude attenuation is 0.707 times the scale, the frequency is 546.3Hz, and the closed-loop bandwidth of the pendulum component is 546.3Hz.

[0083] It can be concluded that the closed-loop simulation modeling method of the pendulum assembly dynamics based on ANSYS finite element analysis of the present invention can effectively simulate the open-loop displacement response and closed-loop dynamic response of the quartz flexible accelerometer pendulum assembly. After comparison and verification with the theoretical model, the establishment of the closed-loop dynamic model of the pendulum assembly is basically reasonable.

[0084] Therefore, the closed-loop dynamic modeling method of the pendulum assembly based on ANSYS finite element analysis of the present invention is used to establish a dynamic model of the quartz flexible accelerometer pendulum assembly, which is more in line with the working environment of the actual pendulum piece, and can effectively simulate the closed-loop motion state of the quartz accelerometer pendulum assembly, effectively avoiding the complex solution calculation of multi-order degree-of-freedom motion equations, saving a lot of verification time, and providing theoretical support and simulation platform for the structural optimization design of the quartz accelerometer head and preliminary indicator verification.

[0085] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A closed-loop dynamic modeling method for a pendulum assembly based on ANSYS finite element analysis, characterized in that: The specific steps are as follows: S1. Establish a closed-loop feedback control simulation model of quartz pendulum dynamics based on the block diagram of the quartz accelerometer system; S2. Determine the ANSYS simulation platform; S3, establishing a three-dimensional model of the quartz flexible accelerometer pendulum assembly; S4, setting the material parameters of the pendulum assembly; S5, dividing the pendulum assembly into grids; S6, determine the time step of the simulation; S7, based on the simulation time step, adding load to the pendulum assembly and solving to obtain the working response of the sensor; S8. Post-process the working response of the sensor to obtain an output result.

2. The closed-loop dynamic modeling method of a pendulum assembly according to claim 1, characterized in that: According to the working principle of quartz flexible accelerometer, the principle block diagram of quartz accelerometer system is established.

3. The closed-loop dynamic modeling method of a pendulum assembly according to claim 1, characterized in that: The material parameters of the pendulum assembly include the material parameters of the flexible pendulum piece, coil and frame.

4. The closed-loop dynamic modeling method of a pendulum assembly according to claim 1, characterized in that: The expression for the simulation time step is: Δt=1 / (20f) Wherein, f is the first-order modal vibration frequency of the flexible pendulum.

5. The closed-loop dynamic modeling method of a pendulum assembly according to claim 1, characterized in that: The specific steps for adding loads to the pendulum assembly and solving to obtain the sensor in S7 are as follows: Step 71. Use APDL language to add fixed constraints to the six upper and lower bosses of the outer ring of the flexible pendulum, add an initial acceleration load to the flexible pendulum as a whole, and add an initial feedback force load to the pendulum coil; Step 72. Obtain the real-time displacement of the current step and process it through the proportional integral link to obtain the Ampere force current; obtain the feedback force load of the next step from the Ampere force current; Step 73. Obtain the acceleration load for the next step; Step 74. Obtain the real-time displacement of the pendulum assembly in the next step based on the feedback force load in the next step and the acceleration load in the next step; Step 75. Determine whether the calculation time reaches the calculation time threshold. If so, output the working response of the sensor. If not, return to step 72 based on the simulation time step.

6. The closed-loop dynamic modeling method of a pendulum assembly according to claim 5, characterized in that: Acceleration loads include the magnitude and direction of the load.

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