Method for calculating maximum torque of ultrasonic motor based on finite element simulation analysis

Abstract

This invention discloses a method for calculating the maximum torque of an ultrasonic motor based on finite element simulation analysis. Using ANSYS Workbench finite element analysis software, the method combines the structural transient analysis module with the piezoelectric module to calculate the time-varying behavior of the stator and rotor of a traveling wave ultrasonic motor. By applying a torque that gradually increases in the opposite direction to the motor's rotation, the maximum torque of the traveling wave ultrasonic motor is determined at the moment the motor reverses direction. This method is simple and can preliminarily determine the maximum torque of a traveling wave ultrasonic motor, laying the foundation for subsequent structural optimization and experiments, and has significant practical value.

Description

Technical Field

[0001] This invention designs a traveling wave rotating ultrasonic motor, and in particular, designs a method for calculating the maximum torque of the ultrasonic motor based on finite element simulation analysis. Background Technology

[0002] Spaceflight is one of the most challenging and far-reaching high-tech fields in the world today, and my country is accelerating its efforts to become a space power, continuously expanding the depth and breadth of space applications. Spacecraft are the carriers of space applications, and various high-precision, long-life space mechanisms are widely deployed on them, such as laser pointing mechanisms (CPA), control moment gyroscopes (CMG), laser scanning three-dimensional imaging mechanisms (LVDS), space robotic arms, and antenna drive mechanisms (GDA), to meet the needs of different applications for precise control, accurate observation, and stable operation. Achieving lightweight and rapid, stable motion performance of space mechanisms has become a fundamental capability that urgently needs to be improved to support my country's development into a space power. Motors are the driving source for the motion of various space mechanisms and play a crucial role in their overall performance. Unlike the electromagnetic motors commonly used in space mechanisms, which transmit power through electromagnetic force, ultrasonic motors use piezoelectric ceramics to excite the stator to generate controllable micro-vibrations, which are then converted into macroscopic rotor rotation through stator-rotor friction. Based on this working principle, ultrasonic motors, within the strict volume and weight constraints of space mechanisms, can fully demonstrate their advantages such as light weight, high torque, fast response, and self-locking. Their application in space mechanisms can better achieve system lightweighting and significantly improve response characteristics. Therefore, to meet the typical operating requirements of space mechanisms—high precision, long lifespan, ultra-low speed, high speed ratio, and reciprocating oscillation—and especially since the load capacity of ultrasonic motors is the most important capability for space mechanisms, it is essential to study the maximum torque of ultrasonic motors. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a method for calculating the maximum torque of an ultrasonic motor based on finite element simulation analysis.

[0004] The technical solution adopted to solve the above-mentioned technical problems is as follows:

[0005] The method for calculating the maximum torque of an ultrasonic motor based on finite element simulation analysis includes the following steps:

[0006] Step 1), determine the geometry and material definitions of the stator and rotor of the ultrasonic motor;

[0007] Step 2), mesh the model and establish a finite element simulation model of the ultrasonic motor;

[0008] Step 3) Set constraint boundary conditions and contact boundary conditions for the finite element simulation model of the ultrasonic motor;

[0009] Step 4) Set the material properties of the piezoelectric material in the ultrasonic motor, and determine its polarization direction, piezoelectric constant, and dielectric constant;

[0010] Step 5) Perform modal analysis on the ultrasonic motor to determine the magnitude of the stator working modal frequency of the ultrasonic motor;

[0011] Step 6) Establish a transient dynamics simulation analysis module and set the calculation time for each load step according to the working modal frequency of the ultrasonic motor stator;

[0012] Step 7), define substeps in the load step settings;

[0013] Step 8) Set the voltage load. Using the load step as a reference, set the voltage for each load step in each cycle and perform a cycle to obtain the curve of the rotation angle of the ultrasonic motor rotor changing with time.

[0014] Step 9), apply torque. Based on the load step, do not apply the opposite torque before 0.005s. After the motor enters steady speed, start applying the torque that gradually increases to 1Nm to obtain the opposite torque curve.

[0015] Step 10): Based on the curve of the rotation angle of the ultrasonic motor rotor changing with time, it is determined that the ultrasonic motor is in the starting working state when the slope of the curve is negative, and the maximum electronic torque is when the slope of the curve begins to turn positive.

[0016] Step 11): At the trough of the curve showing the change in the rotation angle of the motor rotor over time, the time when the motor is reversed by the opposite torque is obtained. Based on the reversal time, the torque is determined on the opposite torque curve, which is the maximum torque of the motor.

[0017] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0018] 1. Time Saving. Previously, testing the maximum torque of ultrasonic motors typically involved experimental methods. These methods suffer from drawbacks such as long part processing times and unpredictable performance. This new method allows for the prediction of ultrasonic motor performance before part processing, thereby reducing redundant experiments and saving time.

[0019] 2. The method is simple. Utilizing the powerful integration and parametric capabilities of ANSYS Workbench finite element analysis software, various simulations can be performed as long as the material parameters of each material are known. ANSYS Workbench has powerful post-processing functions, facilitating data extraction and analysis. Attached Figure Description

[0020] Figure 1 Flowchart of the method of this invention;

[0021] Figure 2 A schematic diagram of the traveling wave rotating ultrasonic motor in an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of the finite element analysis mesh model of the stator of the traveling wave rotating ultrasonic motor in an embodiment of the present invention;

[0023] Figure 4 Schematic diagram of the polarization direction and voltage application method of the stator ceramic sheet in this embodiment of the invention;

[0024] Figure 5 The B09 mode shape of the traveling wave rotating ultrasonic motor stator in this embodiment of the invention;

[0025] Figure 6 A schematic diagram of the harmonic response of the stator of the traveling wave rotating ultrasonic motor in an embodiment of the present invention;

[0026] Figure 7 A schematic diagram of the finite element analysis mesh model of the entire traveling wave rotating ultrasonic motor in an embodiment of the present invention;

[0027] Figure 8 A schematic diagram of the operation of the traveling wave rotating ultrasonic motor in an embodiment of the present invention;

[0028] Figure 9 The embodiments of the present invention include the angular rotation curve of the traveling wave rotating ultrasonic motor and the curve of opposite torque application. Specific implementation methods:

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, this invention discloses a method for calculating the maximum torque of an ultrasonic motor based on finite element simulation analysis. The following detailed description uses a traveling wave rotating ultrasonic motor as an example. The structure of the traveling wave rotating ultrasonic motor is as follows: Figure 2 As shown, the rotor, friction plates, stator base, and ceramic plates are included, and their various material parameters are shown in the table below:

[0031]

[0032] Import the established simulation analysis model into the finite simulation analysis software (ANSYS Workbench).

[0033] Step 1) Define the materials for the components in the model, establish a coordinate system, and set the polarization direction for the piezoelectric element, such as... Figure 3 As shown.

[0034] Step 2), mesh generation. Determine the mesh size based on the thruster dimensions. The mesh twist should be less than 0.5, and the mesh orthogonality should be greater than 0.8. The generated stator mesh is shown below. Figure 3 As shown, the overall mesh is as follows Figure 7 ;

[0035] Step 3) Set boundary conditions. The boundary conditions should be consistent with the actual situation. In this embodiment, the web of the ultrasonic motor stator is in a fixed support state.

[0036] Configure the contact settings. The connection method for each component is set according to the actual situation. In this embodiment, except for the friction plate and the stator, which is a frictional connection, all other connections are bonded.

[0037] Step 4) Set the material properties of the piezoelectric material in the finite element simulation model of the ultrasonic motor, and determine the piezoelectric constant, dielectric constant, and polarization direction of the piezoelectric ceramic.

[0038] Step 5) Suppress the rotor and friction plates, perform modal analysis on the stator, and determine the stator's operating mode as mode B09, with phase A frequency of 24558 Hz and phase B frequency of 24577 Hz. Figure 5 As shown.

[0039] Harmonic response analysis was performed on the nail, and the operating voltage was determined to be 500Vpp. For example... Figure 6 As shown.

[0040] Step 6) Establish a transient dynamics simulation analysis module and set the calculation time for each load step according to the working modal frequency of the ultrasonic motor stator;

[0041] Remove the suppression of the rotor and friction plates, add a transient structural module, and set the calculation time for the appropriate load steps as needed. Determine the time for each load step based on the resonant frequency f obtained from modal analysis, with the mode shapes as follows: Figure 4 As shown. One cycle time is 1 / f. If one cycle is subdivided into 8 load steps, then the calculation time for each load step is (1 / 8f) s.

[0042] Step 7) Define substeps in the load step settings. The total number of substeps in one cycle should be greater than or equal to 20. In this embodiment, the number of substeps is set to 5, that is, each load step is divided into 5 substeps, and the number of calculation steps in each cycle is 40.

[0043] Step 8) Set the voltage load. Using the load step as a reference, set the voltage for each load step in each cycle and perform a cycle to obtain the curve of the rotation angle of the ultrasonic motor rotor changing with time.

[0044] In the structural transient module, the constitutive parameters of the piezoelectric material are assigned values;

[0045] In the structural transient analysis, a voltage load is added to the load step. The voltage is set for each of the eight load steps in each cycle, based on the load step, and the cycle is repeated periodically. In one cycle, a sinusoidal voltage load with a peak-to-peak value of v is applied sequentially according to time.

[0046] In the structural transient analysis, a voltage load is added to the load step. The voltage is set for each of the eight load steps in each cycle based on the load step and is cycled periodically. In one cycle, a cosine voltage load with a peak-to-peak value of v is applied sequentially according to time.

[0047] Set opposite torque loads. Based on the load step, set the motor rotation direction opposite to the load step in each cycle for 5 load steps. According to the previous simulation, the motor enters a stable rotation state after 0.005 seconds. After that, apply 0.0005 Nm for each small step. After increasing to 1 Nm, all the remaining steps are all 1 Nm increments.

[0048] Next, the transient dynamics finite element method is performed.

[0049] Step 9), apply torque. Based on the load step, do not apply the opposite torque before 0.005s. After the motor enters steady speed, start applying the torque that gradually increases to 1Nm to obtain the opposite torque curve.

[0050] Step 10): Based on the curve of the rotation angle of the ultrasonic motor rotor changing with time, it is determined that the ultrasonic motor is in the starting working state when the slope of the curve is negative, and the maximum electronic torque is when the slope of the curve begins to turn positive.

[0051] Step 11): At the trough of the curve showing the change in the rotation angle of the motor rotor over time, the time when the motor is reversed by the opposite torque is obtained. Based on the reversal time, the torque is determined on the opposite torque curve, which is the maximum torque of the motor.

[0052] After the transient dynamics finite element solution is completed, the model runs as follows: Figure 8 As shown, read the amplitude change over time graph, as follows. Figure 9 As shown, the motor starts to reverse at 0.006048055s, so its maximum torque is determined to be 0.2725Nm.

[0053] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0054] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the maximum torque of an ultrasonic motor based on finite element simulation analysis, characterized in that, Includes the following steps: Step 1) Determine the geometry and material definitions of the stator and rotor of the ultrasonic motor; Step 2), mesh generation and establish the finite element simulation model of the ultrasonic motor; Step 3) Set constraint boundary conditions and contact boundary conditions for the finite element simulation model of the ultrasonic motor; Step 4) Set the material properties of the piezoelectric material in the ultrasonic motor, and determine its polarization direction, piezoelectric constant, and dielectric constant; Step 5) Perform modal analysis on the ultrasonic motor to determine the magnitude of the stator working modal frequency of the ultrasonic motor; Step 6) Establish a transient dynamics simulation analysis module and set the calculation time for each load step according to the working modal frequency of the ultrasonic motor stator; Remove the suppression of the rotor and friction plates, add a structural transient module, and determine the time of each load step based on the resonant frequency f obtained from modal analysis. The time of one cycle is 1 / f. Subdivide one cycle into 8 load steps, and the calculation time of each load step is 1 / 8f seconds. Step 7) Define substeps in the load step settings, set the number of substeps to 5, that is, divide each load step into 5 substeps, and the number of calculation steps in each cycle is 40 steps; Step 8) Set the voltage load. Using the load step as a reference, set the voltage for each load step in each cycle and perform a cycle to obtain the curve of the rotation angle of the ultrasonic motor rotor changing with time. Step 9), apply torque. Based on the load step, do not apply the opposite torque before 0.005s. After the motor enters steady speed, start applying the torque that gradually increases to 1Nm to obtain the opposite torque curve. Step 10): Based on the curve of the rotation angle of the ultrasonic motor rotor changing with time, the ultrasonic motor is in the starting working state when the slope of the curve is negative, and the maximum torque of the motor is when the slope of the curve begins to turn positive. Step 11): At the trough of the curve showing the change in the rotation angle of the motor rotor over time, the time when the motor is reversed by the opposite torque is obtained. Based on the reversal time, the torque is determined on the opposite torque curve, which is the maximum torque of the motor.

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