A quick and accurate method for aligning a spherical rotary table

Abstract

The application provides a kind of spherical rotary table fast and accurate alignment method, comprising the following steps: step 1. import spherical rotary table model into three-dimensional software, read the unbalance information of rotary table, divide the rotary table, divide into 8 parts with the xy, xz and yz plane of three-dimensional model coordinate system as the reference, obtain the load size information by calculating the reduced alignment position range;Step 2. use the servo control unit of rotary table itself torque motor group, connect the test circuit, the output torque of rotary table working state is represented by the current value of control unit;Step 4. according to the optimal configuration scheme obtained, the current value and the observation moment difference of counterweight are observed.The method greatly improves the production efficiency without repeated trial and error for each device by the installer;The servo control unit is constructed by using the stable output characteristics of the torque motor of the rotary table, and the change of current value in the alignment process is used as the concrete discrimination index, and the rotary table after preliminary alignment is balanced and checked.

Description

Technical Field

[0001] This invention relates to the field of turntable balancing technology, and in particular to a method for rapid and accurate balancing of a spherical turntable. Background Technology

[0002] A spherical turntable is a complex, modern piece of equipment integrating optoelectronics and electromechanical systems, widely used in aerospace, defense, and other fields. Due to its structure and internal loads, the turntable's center of mass and center of rotation often do not coincide, generating unbalanced torques during movement that affect its stability. Therefore, balancing is an indispensable step in the turntable's production and assembly process. Traditional manual trial-and-error methods for balancing spherical turntables are inefficient and lack precision.

[0003] Currently, the mainstream method for balancing turntables is the traditional manual trial-and-error method. A spherical turntable has at least two axes: azimuth and pitch. The loads on these two axes are coupled during balancing, requiring assemblers to repeatedly trial and error while considering both axes, leading to low production efficiency. Furthermore, the traditional manual trial-and-error method cannot accurately determine whether the spherical turntable has reached a balanced state; relying solely on the assembler's personal experience often fails to meet the accuracy requirements for subsequent assembly and adjustment. Therefore, there is an urgent need to research a method that can quickly and accurately balance spherical turntables. Summary of the Invention

[0004] To address the issues of low efficiency and poor accuracy in balancing spherical turntables using traditional manual trial-and-error methods, this invention provides a rapid and accurate balancing method for spherical turntables. This method simultaneously detects and balances the equilibrium of all axis systems during the balancing process. Under the premise that the required balance is achieved, a multi-objective optimization algorithm is used to obtain the optimal solution with the minimum counterweight. The method is characterized by the following steps:

[0005] Step 1. Import the spherical turntable model into the 3D software, read the turntable imbalance information, divide the turntable into 8 parts based on the xy, xz and yz planes of the 3D model coordinate system, and obtain the load size information by calculating and narrowing the balancing position range.

[0006] Step 2. Build a servo control unit using the turntable's own torque motor, connect it to the test circuit, and characterize the output torque of the turntable under working conditions by measuring the current value of the control unit: control the turntable to rotate at a constant speed in the azimuth and pitch axes, observe the current value of the control unit, and the point where the current value is the maximum is where the eccentric torque is the maximum. The maximum eccentric torque of that axis can be calculated by measuring the current value.

[0007] Step 3. Using a multi-objective optimization method, substitute the data obtained in the previous steps into the formula and constraints, and use MATLAB to calculate the optimal configuration scheme.

[0008] Step 4. Adjust the counterweights according to the obtained optimal configuration scheme, observe the torque difference and current value. If the balance requirement is met, the balance can be considered successful. If not, analyze the cause, fine-tune the number of counterweights, and repeat this step until the balance requirement is met.

[0009] Furthermore, during the initial balancing of the turntable using 3D software, the unbalance needs to be accurately applied to each component to obtain the material density information, and the corresponding load of a certain area on the turntable needs to be calculated. The assembly and adjustment personnel need to make judgments and selections based on the actual situation.

[0010] Furthermore, in the process of building the servo control unit, it is necessary to consult the technical manual to obtain the torque constant K of the motor, prepare the debugged control board, the host computer for debugging, the regulated power supply, the feedback device that can read the current value (such as an ammeter), and connect the test circuit.

[0011] Furthermore, during the test, the azimuth axis system must be kept running at a constant speed and smoothly, and the pitch axis system must be repeatedly rotated in both directions to observe the system current value and adjust the counterweight accordingly.

[0012] Furthermore, during the adjustment of the counterweight, the following conditions must be met: , or ,in This represents the change in torque between the turntable's power-on and stable operation states. Let represent the change in system current, and m and L represent the weight of the added counterweight and the distance from the center of rotation, respectively.

[0013] The beneficial effects of this invention are as follows:

[0014] (1) Use three-dimensional software to perform balancing analysis on the turntable. Especially for the production of turntables of the same model in large quantities, the preliminary balancing information of the batch of turntables can be obtained by one calculation, saving the time of assembly and adjustment personnel to try and assemble each piece of equipment individually, and greatly improving work efficiency.

[0015] (2) By using the turntable’s own torque motor to build a servo control unit, the torque that is not easy to observe and measure is converted into a visible current value, providing a concrete indicator for turntable balance verification, avoiding errors caused by human experience judgment, and ensuring the accuracy of balancing. Attached Figure Description

[0016] Figure 1 This is a flowchart of the balancing method. Figure 2 A schematic diagram of the azimuth and pitch axis system and motion in a three-dimensional coordinate system. Figure 3 Schematic diagram of the first type of counterweight Figure 4 Schematic diagram of the second type of counterweight Figure 5 Schematic diagram of the third type of counterweight Figure 6 Schematic diagram of servo control unit Figure 7 Diagram showing the counterweight installation location Detailed Implementation

[0017] The following is in conjunction with the appendix Figure 1-7 The technical solution of the present invention will be described in detail below.

[0018] like Figure 1 As shown, this embodiment provides a fast and accurate balancing method for a spherical turntable. The goal is to obtain the optimal counterweight scheme through a multi-objective optimization method while ensuring balance requirements. The method includes three main parts: partitioning the turntable using computer 3D software and a solid model of the turntable to obtain load information, constructing a servo control unit to perform balance verification on the turntable, and obtaining and verifying the minimum weight counterweight scheme through multi-objective optimization.

[0019] In this example, the spherical turntable carries multiple loads and its design is not perfectly symmetrical. The center of mass of the machined turntable does not coincide with its center of rotation. This offset center of mass generates an unbalanced moment, affecting the turntable's balance and motion stability. Therefore, the machined turntable needs to be balanced to eliminate the adverse effects of the unbalanced moment. Furthermore, because the eccentric moment is large and the internal space is limited before balancing, the balancing area is significantly restricted. During the balancing process, the weight of the counterweight in each counterweight area must be strictly controlled; otherwise, the turntable may fail to achieve the required balance.

[0020] Step 1. Import the spherical turntable model into the 3D software, read the turntable imbalance information, divide the turntable into 8 parts based on the xy, xz and yz planes of the 3D model coordinate system, reduce the balancing position range by calculation, and obtain the load size information.

[0021] In this embodiment, a spherical turntable model is imported into 3D software. Density information is added to each component, and the center of rotation is aligned with the origin of the 3D coordinate system. The unbalance information between the turntable's center of mass and the axis system is then read. The 3D model is divided into eight installation areas based on the xy, xz, and yz planes of the coordinate system, resulting in the counterweight installation areas and corresponding load magnitudes (the 3D coordinate system is as follows). Figure 2 (As shown). Taking into account factors such as the turntable structure, existing counterweights, and installation methods, a suitable installation area was selected from eight installation zones.

[0022] Based on the internal shape characteristics of the turntable and the actual working environment, the counterweight of the spherical turntable can be designed into three types: 1. The first type of counterweight is a large-weight, regularly shaped counterweight with a cross-sectional axisymmetric structure, such as... Figure 3 As shown, this type of counterweight is mainly used to balance the large eccentric moment generated when the pitch axis rotates. During installation, its axis needs to coincide with the axis of the spherical turntable in the horizontal plane to balance the eccentric moment caused by the mass concentrated near the axis of the turntable. It is usually used for initial balancing to offset most of the eccentric moment; 2. The second type of counterweight is an axisymmetric, arc-shaped regular counterweight, such as... Figure 4 As shown, this type of counterweight has a regular shape cut out on its inner side to more accurately match the eccentric torque caused by the small masses at both ends of the pitch axis and the mass of the outer ring of the azimuth axis; 3. The third type of counterweight is a thin rectangular counterweight with a regular shape, such as... Figure 5 As shown, this type of counterweight is used to balance the eccentric torque caused by uneven mass on one side and to precisely repair the remaining eccentric torque.

[0023] Step 2. Build a servo control unit using the turntable's own torque motor, connect it to the test circuit, and characterize the output torque of the turntable under working conditions by measuring the current value of the control unit: control the turntable to rotate at a constant speed in the azimuth and pitch axes, observe the current value of the control unit, and the point where the current value is the maximum is where the eccentric torque is the maximum. The maximum eccentric torque of that axis can be calculated by measuring the current value.

[0024] In this example, both the torque motor and the driver are components of the turntable itself. The torque constant K of the turntable orientation torque motor in this example was obtained by consulting the technical manual. fw The torque constant K of the pitch torque motor fy .like Figure 6 The driver controls the torque motor to drive the load to move and forms a closed loop with the feedback device. It is connected to the power supply and debugging circuit. After the turntable is powered on, the current under working conditions can be obtained from this.

[0025] The spherical turntable in this example has an azimuth range of 0° to 360° and a pitch range of -5° to 85°. First, without any counterweights, the pitch axis is rotated uniformly at a speed of 5° / s with the azimuth axis perpendicular to the horizontal plane, and the maximum current value I is recorded. fy And the corresponding upper computer angle θ at this time fy The maximum resultant eccentric moment corresponding to the pitch axis is T. fy =K fy ×I fy Then, using a special fixture, the azimuth axis was rotated 90° to the horizontal plane while the pitch axis was perpendicular to the horizontal plane. Without any counterweight, the azimuth axis was rotated perpendicular to the horizontal plane at a constant speed of 5° / s, and the maximum current value I was recorded. fw And the corresponding upper computer angle θ at this timefw The maximum resultant eccentric moment corresponding to the pitch axis is T. fw =K fw ×I fw .

[0026] Step 3. Using a multi-objective optimization method, substitute the data obtained in the previous steps into the formula and constraints, and use MATLAB to calculate the optimal configuration scheme.

[0027] After completing the above measurements, the minimum weight optimization balancing begins. By assigning density values ​​to various parts of the 3D model, suitable installation areas for balancing can be identified. Considering the convenience of disassembly, maintenance, and debugging, the final placement of the counterweight is determined within these installation areas. The lever arms of different installation positions under different axis systems are then precisely measured in the 3D model. In this example, the final placement of the counterweight is determined through the above steps. Figure 7 Three counterweight installation positions: The first type of counterweight is installed at the center of the farthest end of the back cover, with the center of the circle coinciding with the center of the sphere. The second type of counterweight is placed in the center in the upper part of the rear of the turntable, with a part of the regular rectangular pattern cut out off-center in the middle. The third type of counterweight is installed on top of the second type of counterweight, placed in the center.

[0028] This invention employs a linear programming algorithm. Linear programming is a mature method for handling linear objective functions and linear constraints. Its standard form requires minimizing the objective function, ensuring that constraints are equal and variables are non-negative, which aligns with the application scenario of finding the minimum weight while maintaining balance during balancing. The optimization objective and constraints are listed below in this example:

[0029]

[0030] Where x1, x2, and x3 are the weights of the counterweights at the three installation locations;

[0031] M is the total weight of all counterweights;

[0032] K fw I fw and K fy I fy These represent the maximum eccentric moment in the two cases without adding a counterweight;

[0033] L 1fw L 2fw and L 3fw The lever arm of the three types of counterweights relative to the azimuth axis;

[0034] L 1fy L 2fy and L 3fy These are the lever arms of the three types of counterweights relative to the pitch axis.

[0035] The MATLAB function for linear optimization in this example is:

[0036] x=linprog(f,A,b,Aeq,beq,lb,ub)

[0037] Where f is the objective function to be minimized, i.e., M = x1 + x2 + x3;

[0038] Aeqx=beq is the constraint matrix, corresponding to two equilibrium equations;

[0039] lb is the lower limit of weight;

[0040] ub represents the maximum weight.

[0041] In actual calculations, due to limited installation space, the available installation space needs to be measured in advance based on the model before optimization. The corresponding weight is calculated based on the density of the selected counterweight material, and this weight is the upper limit of x1, x2, and x3. Additionally, when measuring the counterweight lever arm, if the counterweight is thick, the influence of the counterweight thickness on the lever arm needs to be considered. The ratio of the lever arm L from the center of mass to the center of rotation to its thickness b is used as a reference. If L / b >> 5, the influence of the counterweight height change on the lever arm can be considered negligible; otherwise, it is necessary to reselect the counterweight material and other parameters, or to perform torque calculations considering height differences.

[0042] Step 4. Adjust the counterweights according to the obtained optimal configuration scheme, observe the torque difference and current value. If the balance requirement is met, the balance can be considered successful. If not, analyze the cause, fine-tune the number of counterweights, and repeat this step until the balance requirement is met.

[0043] In this example, after calculating the weight corresponding to the available installation area using MATLAB, counterweights are applied. A rotational speed of 5° / s is sent to the servo control unit to control the turntable's orientation axis system to rotate at a constant speed for verification. The operating current I of the system under the current balancing condition and stable operation is recorded. The change in motor torque under the current operating condition can be obtained from T=K×I. Under stable movement of the turntable's orientation axis system, a rotational speed of 3° / s is sent to the servo control unit to control the turntable's pitch axis system to rotate at a constant speed for verification.

[0044] Based on the torque difference and current fluctuation of the motor under the two states obtained in the previous step, if the error range does not reach the specified value, the turntable is in an unbalanced state. Calculate the counterweight required to balance this difference. After adjustment, repeat the previous step for verification.

[0045] In this example, the turntable reaches a balanced state when the fluctuation range of rotational speed and torque is no greater than 0.3%.

[0046] This example only applies to a single spherical turntable of this model. If balancing is required for multiple turntables of the same model, balancing and fine-tuning can be performed directly on subsequent turntables based on the results calculated for the first turntable. This eliminates the need for repeated calculations, significantly saving working time and improving work efficiency.

[0047] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit the scope of this disclosure. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure. Although this application has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and not intended to limit the application of this application. The protection scope of this application is defined by the appended claims and may include various variations, modifications, and equivalent solutions made to the invention without departing from the protection scope and spirit of this application.

Claims

1. A method for rapid and accurate balancing of a spherical turntable, characterized in that, Specifically, the following steps are included: Step 1. Import the spherical turntable model into the 3D software, read the turntable imbalance information, divide the turntable into 8 parts based on the xy, xz and yz planes of the 3D model coordinate system, and obtain the load size information by calculating and narrowing the balancing position range. The counterweights for the spherical turntable are designed in three types based on the turntable's internal shape and actual working environment: The first type is a large, regularly shaped counterweight with a cross-sectional axisymmetric structure, used to balance the large eccentric moment generated during the rotation of the pitch axis. During installation, its axis needs to coincide with the axis of the spherical turntable in the horizontal plane to balance the eccentric moment caused by the mass concentrated near the axis of the turntable, initially balancing and offsetting most of the eccentric moment; the second type is an axisymmetric, regularly shaped arc counterweight with a regular shape carved out on the inside, used to more accurately match the eccentric moment caused by the small masses at both ends of the pitch axis and the mass of the outer ring of the azimuth axis; the third type is a regularly shaped, thin rectangular counterweight, used to balance the eccentric moment caused by uneven mass on one side, and to precisely repair the remaining eccentric moment; Step 2. Build a servo control unit using the turntable's own torque motor, connect it to the test circuit, and characterize the output torque of the turntable under working conditions by the current value of the control unit: control the turntable to rotate at a constant speed in the azimuth and pitch axes, observe the current value of the control unit, and the point where the current value is the maximum is the point where the eccentric torque is the maximum. Calculate the maximum eccentric torque of the pitch axis by the current value. Step 3. Using a multi-objective optimization method, substitute the data obtained in the previous steps into the formula and constraints, and use MATLAB to calculate the optimal configuration scheme; To meet the lightweight requirements, and under the premise of achieving balance, an optimization algorithm is used to optimize the weight distribution at each location. The minimum weight combination is then calculated using MATLAB. The optimization objective and constraints are as follows: ； Where x1, x2, and x3 are the weights of the counterweights at the three installation locations; M is the total weight of all counterweights; K fw I fw and K fy I fy These represent the maximum eccentric moment in the two cases without adding a counterweight; L 1fw L 2fw and L 3fw The lever arm of the three types of counterweights relative to the azimuth axis; L 1fy L 2fy and L 3fy The lever arm of the three types of counterweights relative to the pitch axis; Step 4. Adjust the counterweights according to the obtained optimal configuration scheme, observe the torque difference and current value. If the balance requirement is met, the balance can be considered successful. If not, analyze the cause, fine-tune the number of counterweights, and repeat this step until the balance requirement is met.

2. The method for rapid and precise balancing of a spherical turntable according to claim 1, characterized in that: Step 1 involves reading the positions of the turntable model's center of mass and rotation center, as well as the unbalance in the two axis directions, in the 3D modeling software to calculate the load information and balancing position information.

3. The method for rapid and precise balancing of a spherical turntable according to claim 1, characterized in that: The turntable torque motor used in step 2 has the characteristic of stable torque output. After the turntable is powered on and operating smoothly, the motor needs to output a certain amount of torque to drive the turntable and counteract the imbalance. Given that the motor torque constant K is known, when the imbalance in the pitch axis direction changes... The change in output torque is characterized by the change in system current.

4. The method for rapid and precise balancing of a spherical turntable according to claim 1, characterized in that: The servo control unit assembled in step 2 should include at least a torque motor, a control board, a driver and a host computer, a regulated power supply and feedback devices; wherein, the torque motor provides power and eliminates unbalanced torque, the control board, the driver and the host computer are used to control the turntable to move, and the regulated power supply and feedback devices provide stable current and readings.

5. The method for rapid and precise balancing of a spherical turntable according to claim 1, characterized in that: In step 2, the turntable is controlled to rotate at a constant speed. When measuring the azimuth and pitch axes, it needs to be rotated multiple times in both directions.

6. The method for rapid and precise balancing of a spherical turntable according to claim 1, characterized in that: The adjustment of the counterweight in step 4 must meet the following requirements. or ,in Let m be the torque of the variable torque of the machine, and L be the weight of the added counterweight and the distance from the center of rotation of the motion, respectively.

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