CN112129485B - Single-vector loading method for wind tunnel mechanical balance - Google Patents
Single-vector loading method for wind tunnel mechanical balance Download PDFInfo
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- CN112129485B CN112129485B CN202011309851.6A CN202011309851A CN112129485B CN 112129485 B CN112129485 B CN 112129485B CN 202011309851 A CN202011309851 A CN 202011309851A CN 112129485 B CN112129485 B CN 112129485B
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Abstract
The invention discloses a wind tunnel mechanical balance single vector loading method, wherein the mechanical balance single vector loading comprises a force transfer system, a force generation system and a control system, the force transfer system transfers force generated by a force source to a loading point through a steel wire, the force direction borne by the loading point and the X, Y, Z direction respectively form a fixed included angle, the loading force can be decomposed into three directions which respectively correspond to the resistance, the lifting force and the lateral force of a balance, the offset of the loading point and the coordinate center of the balance determines the moment applied to the balance, and the scheme can simultaneously obtain the loading load with six components through one loading point; the invention realizes accurate control of force through a computer control technology, realizes automatic loading, improves the automation level of loading, selects a proper loading point according to the characteristics of a mechanical balance, realizes vector loading, realizes simultaneous loading of six components through one loading point, and improves the loading efficiency.
Description
Technical Field
The invention relates to the field of wind tunnel tests, in particular to a method for loading a wind tunnel mechanical balance single vector.
Background
The wind tunnel mechanical strain balance is widely applied to the abdominal support force measurement test of the wind tunnel due to the advantages of large measurement range, convenience in use, strong stability and the like. The mechanical balance is a mechanical structure which decomposes a pneumatic load into three components of force and three components of moment, and the force and the moment are transmitted to a measuring element through a force transmission mechanism to obtain values of the force and the moment.
The balance performance needs to be calibrated or detected before use, the balance calibration method at present is that a loading frame needs to be installed for loading, a manual weight moving loading method is adopted for loading, and the detection method has the disadvantages of complex installation of the loading frame, low efficiency, time and labor waste. Meanwhile, the loading of the artificial weight causes that the final loading capacity is influenced by the environment and errors possibly occur, so that the final measurement is not accurate.
Disclosure of Invention
The invention aims to design a single-vector loading method for a balance based on the prior art, which utilizes the applied force in one direction and accurately decomposes the applied force into forces and moments in three directions through closed-loop control to be used for calibrating a target balance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a wind tunnel mechanical balance single vector loading method is disclosed, wherein the establishment of a balance and single vector calculation model comprises the following processes:
s1, establishing a coordinate system XYZ by taking the calibration center of the balance as a coordinate origin A;
s2, setting a force application point O in one quadrant in any one of plane coordinate systems XAY, XAZ and YAZ in the coordinate systems XYZ;
s3, applying a vector force F to the force application point, wherein the direction of the vector force and three axes of a coordinate system XYZ respectively have included angles beta, alpha and gamma, taking the force application point O as an origin, the force parallel to the X axis is denoted as Fx, the force parallel to the Y axis is denoted as Fy, the force parallel to the Z axis is denoted as Fz, and the moments around the X axis, the Y axis and the Z axis are denoted as Mx, My and Mz respectively;
s4, measuring the force on the balance according to the definition of the coordinate system, and calculating three components of vector force at the force application point O:
and S5, calculating the moment stressed by the balance according to the deviation delta Y of the force application point O relative to the point A in the negative direction of the Y axis and the deviation delta Z in the Z direction:
My=-Fx ×Δz，Mx=Fz ×Δy-Fy×Δz，Mz=-Fx×Δy；
s6: and correspondingly comparing the force and the moment calculated in the S4 and the S5 with six components actually measured by the balance, and adjusting the difference value of the force and the moment to realize the calibration of the balance.
In the technical scheme, the balance vector force loading process comprises the following steps:
a1: selecting one or all of six components of the current loading amount, and setting a loading point number, a positive-stroke repetition number and a negative-stroke repetition number;
a2, the initial load is the first load of the loading points, and the subsequent loading points are sequentially added with increments on the basis to form a loading sequence;
a3, controlling the loading vector force to a specified load by a control system, and acquiring data to acquire data of six component sensors of the balance after the load is stable;
and A4, under the condition of finishing A3, controlling the loading vector force to the next specified load, starting to acquire data after the load is stable, and repeating the process until the loading sequence is finished and the loading process is finished.
In the above technical solution, the vector force is provided by a loading device, the loading device including:
a base, a bracket arranged on the base and a pulley arranged on the upper part of the bracket, a rope is wound on the pulley, one end of the rope is connected with a balance, the other end of the rope is connected with a motor arranged on the base,
a tension sensor is arranged between the balance and the rope, one end of the tension sensor is connected with the balance, and the other end of the tension sensor is connected with the rope.
In the technical scheme, a spring is arranged between the motor and the rope, one end of the spring is connected with the motor, and the other end of the spring is connected with the rope.
In the technical scheme, the pulley is an eccentric pulley, the stress point of the balance is connected by adopting a universal ball hinge, and the stress point of the balance and the stress point of the pulley are positioned on the same straight line.
In the technical scheme, a double closed-loop control algorithm is adopted in the process of loading the vector force, the balance is controlled to automatically load according to a loading sequence, the motor is controlled, and balance output is collected until the loading sequence is finished.
In the technical scheme, an inner ring of the double closed-loop control algorithm is a position ring and is used for converting the loading force into the motor position, and an outer ring forms force closed-loop control for force feedback.
In the above technical solution, the double closed loop control process is:
b1: the control system acquires a fixed value of an applied acting force, and compares the fixed value with a current tension value acquired by a tension sensor;
b2, calculating a control quantity according to the comparison difference in the B1, and acquiring the movement displacement of the motor according to the power output of the motor by using the control quantity;
b3, after the motor is controlled to move to the designated displacement, the control system acquires the position information of the motor and acquires the tension value on the current tension sensor again;
b4, comparing the tension value obtained in the B3 with a fixed value in the control system, and repeating the processes of B1-B4 until the difference between the given force value and the obtained current force value is less than the error requirement.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
according to the mechanical balance single-vector automatic loading method, the loading load is generated by adopting a mode of combining an electric servo force generator and a force measuring sensor according to the structural characteristics of the mechanical balance, the accurate control in the loading is realized by a computer control technology, the automatic loading is realized, and the automatic level of the loading is improved. The automatic loading system has the advantages that the proper loading points are selected according to the characteristics of the mechanical balance, vector loading is realized, simultaneous loading of six components is realized through one loading point, the loading efficiency is improved, the system structure is simple and practical, the control process is flexible, rapid and convenient, the working performance is stable and reliable, the problem of single-vector automatic loading of the wind tunnel mechanical balance is well solved, the cost is reduced, and the efficiency is improved.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a force resolution schematic diagram of a single vector loading apparatus;
FIG. 2 is a schematic block diagram of a control system for a single vector loading unit;
FIG. 3 is a block diagram of a force source system architecture;
wherein: the device comprises a base 1, a servo motor 2, an electric cylinder 3, an electric push rod 4, a spring 5, a pulley 6, a steel wire 7, a force sensor 8 and a support 9.
Detailed Description
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
The force measuring system is mainly composed of a force transmission system, a force generation system and a control system, wherein the force generation system control and the force measurement are completed on a computer. The force transmission system transmits the force generated by the force source to a balance loading point and consists of a steel wire, a pulley block and the like. The device comprises a force generation system control system, a servo motor, an electric cylinder, a spring, a high-precision sensor and the like. The force generated by the force source is transmitted to the loading point through the steel wire, the force direction borne by the loading point and the X, Y, Z direction respectively form a fixed included angle, and the loading force can be decomposed into three directions which respectively correspond to the resistance, the lifting force and the lateral force of the balance. The offset of the loading point from the coordinate center of the balance determines the moment applied to the balance, and the scheme can simultaneously obtain six-component loading load through one loading point.
As shown in fig. 1, the force analysis diagram is a principle diagram of force analysis, in which point a is a balance calibration center and is also a force analysis center, a coordinate system XYZ is established with point a as a coordinate origin, point O is a force application point of a loading device, an offset amount of point O with respect to point a in a negative Y-axis direction is Δ Y, an offset amount in a Z-direction is Δ Z, angles between vector forces F generated by a force source system and three XYZ axes are β, α, and γ, respectively, a received point O is an origin, a force parallel to the X-axis is Fx, a force parallel to the Y-axis is Fy, a force parallel to the Z-axis is Fz, and moments around the X-axis, the Y-axis, and the Z-axis are Mx, My, and Mz, respectively. According to the geometrical relationship in the figure 1, the force and the moment applied to the balance can be obtained, and the relationship between the force and the loaded vector force F is as follows:
the force versus moment relationship is expressed as:
My=-Fx ×Δz （1）
Mx=Fz ×Δy-Fy×Δz （2）
Mz=-Fx×Δy （3）
the relationship between the force applied to the load point and the three components is:
Fy=F×cos(α) （5）
Fx=F×cos(β) （6）
Fz=F×cos(γ) （7）
according to the analysis, the load is applied to the balance through the force source system, and meanwhile, the load of the balance six-fold component can be obtained, so that the loading efficiency is effectively improved.
As shown in fig. 2, the control system is composed of an industrial personal computer, a motion controller, a servo driver, a high-precision tension sensor, a data acquisition system and the like. The realization process is as follows:
the control system structure adopts a double closed-loop control structure, the inner loop adopts a position loop, the loading force is converted into the motor position, and the position closed-loop control is realized by adopting a PID control algorithm, so that the system is stable and controllable. The outer ring adopts force feedback to form force closed-loop control, and adopts a PI control algorithm to improve the control precision of the system.
Firstly, a control system obtains a given force value, the given force value is compared with a current force value obtained by the system through collecting the force applied by a force sensor, a control quantity is calculated through a control algorithm according to the difference of the two force values, the control quantity is converted into a given position of a motor, a servo system controls the motor to move to the given position according to the given position of the motor, and the closed-loop control of the position of the servo motor is realized. And the control system continuously acquires the current force value, and repeats the process until the difference between the given force value and the acquired current force value is smaller than the error requirement, so that the control process is finished, and the closed-loop control of the force is realized.
In the control process, a segmented PI control method is adopted, different control parameters are used according to different error bands, PI control parameters are dynamically adjusted, and the control efficiency and the control precision are further improved.
As shown in fig. 3, the vector force is composed of a loading device including a servo motor, an electric cylinder, a spring, a high-precision sensor, and the like. The device comprises a base, wherein a bracket is arranged on the base, and a pulley is arranged on the top of the bracket; the electric cylinder is arranged on the base, and an electric push rod on the electric cylinder stretches up and down under the control of the servo motor. The end part of the electric push rod is provided with a spring, the other end of the spring is connected to a steel wire, the steel wire is connected with a tension sensor after passing around the pulley, and the force is transmitted to the balance through the tension sensor.
In the process, the tension sensor is used for acquiring the tension of the balance, and the two springs have two functions, so that on one hand, the springs convert the displacement of the electric cylinder into force, and on the other hand, the springs can reduce the ratio of the applied load to the linear movement distance of the ball screw, thereby improving the loading precision; the pulley is designed to be an eccentric pulley, so that the stress point of the pulley can be ensured to naturally point to the stress point of the balance, the stress points of the balance are connected by adopting a universal ball hinge, the stress directions of the two points are positioned on the same straight line, and the loss of force in the transmission process is reduced.
In this embodiment, the servo motor is controlled by a control system, and a TCP/IP protocol and a dynamic connection library technology are used to control the force source system and the data acquisition system. The system adopts a TCP/IP protocol to communicate with the motion controller and the data acquisition system, adopts a dynamic link library technology to realize information interaction with the motion controller and the data acquisition system, controls the power source system to generate a given load, and acquires load data of six components of the balance acquired by the data acquisition system, thereby realizing automatic loading of the balance and improving the loading efficiency.
In this embodiment, a double closed-loop control algorithm is used to achieve closed-loop precise control of the force. The force source control system adopts a closed-loop control structure, load generated by the force source system is obtained and compared with given load, and a segmented PI control algorithm is adopted to calculate control quantity, so that accurate control of force is realized.
In the embodiment, the automation degree is high, and the use is simple. And the system software automatically controls the force source system according to the loading sequence according to the balance loading process and collects balance output until the loading sequence is operated, and calculates the loading result. The whole loading process runs automatically without human intervention, and the balance loading efficiency is high.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.
Claims (7)
1. A wind tunnel mechanical balance single vector loading method is used for establishing a calculation model of a balance and a single vector, and is characterized by comprising the following steps:
s1, establishing a coordinate system XYZ by taking the calibration center of the balance as a coordinate origin A;
s2, setting a force application point O in one quadrant in any one of plane coordinate systems XAY, XAZ and YAZ in the coordinate systems XYZ;
s3, applying a vector force F to the force application point, wherein the direction of the vector force and three axes of a coordinate system XYZ respectively have included angles beta, alpha and gamma, taking the force application point O as an origin, the force parallel to the X axis is denoted as Fx, the force parallel to the Y axis is denoted as Fy, the force parallel to the Z axis is denoted as Fz, and the moments around the X axis, the Y axis and the Z axis are denoted as Mx, My and Mz respectively;
s31: selecting one or all of six components of the current loading amount, and setting a loading point number, a positive-stroke repetition number and a negative-stroke repetition number;
s32, the initial load is the first load of the loading point, and the subsequent loading points are sequentially added with increments on the basis to form a loading sequence;
s33, controlling the loading vector force to a specified load by the control system, and starting to acquire data of six component sensors of the balance after the load is stable;
s34, under the condition of finishing A3, controlling the loading vector force to the next specified load, after the load is stable, starting to collect data, repeating the process until the loading sequence is finished and the loading process is finished;
s4, measuring the force on the balance according to the definition of the coordinate system, and calculating three components of vector force at the force application point O:
and S5, calculating the moment stressed by the balance according to the deviation delta Y of the force application point O relative to the point A in the negative direction of the Y axis and the deviation delta Z in the Z direction:
My=-Fx ×Δz，Mx=Fz ×Δy-Fy×Δz，Mz=-Fx×Δy；
s6: and correspondingly comparing the force and the moment calculated in the S4 and the S5 with six components actually measured by the balance, and adjusting the difference value of the force and the moment to realize the calibration of the balance.
2. The wind tunnel mechanical balance single vector loading method according to claim 1, wherein the vector force is provided by a loading device, and the loading device comprises:
a base, a bracket arranged on the base and a pulley arranged on the upper part of the bracket, a rope is wound on the pulley, one end of the rope is connected with a balance, the other end of the rope is connected with a motor arranged on the base,
a tension sensor is arranged between the balance and the rope, one end of the tension sensor is connected with the balance, and the other end of the tension sensor is connected with the rope.
3. The wind tunnel mechanical balance single vector loading method according to claim 2, wherein a spring is arranged between the motor and the rope, one end of the spring is connected with the motor, and the other end of the spring is connected with the rope.
4. The wind tunnel mechanical balance single vector loading method according to claim 2, wherein the pulley is an eccentric pulley, the force bearing point of the balance is connected by a universal ball hinge, and the force bearing point of the balance and the force bearing point of the pulley are on the same straight line.
5. The wind tunnel mechanical balance single vector loading method according to claim 2, wherein a double closed loop control algorithm is adopted in the vector force loading process, the balance is controlled to automatically load according to a loading sequence, a motor is controlled, and balance output is collected until the loading sequence is finished.
6. The wind tunnel mechanical balance single vector loading method according to claim 5, wherein an inner ring of the double closed-loop control algorithm is a position ring for converting the loading force into the motor position, and an outer ring forms force closed-loop control for force feedback.
7. The wind tunnel mechanical balance single vector loading method according to claim 6, wherein the double closed loop control process is as follows:
b1: the control system acquires a fixed value of an applied acting force, and compares the fixed value with a current tension value acquired by a tension sensor;
b2, calculating a control quantity according to the comparison difference in the B1, and acquiring the movement displacement of the motor according to the power output of the motor by using the control quantity;
b3, after the motor is controlled to move to the designated displacement, the control system acquires the position information of the motor and acquires the tension value on the current tension sensor again;
b4, comparing the tension value obtained in the B3 with a fixed value in the control system, and repeating the processes of B1-B4 until the difference between the given force value and the obtained current force value is less than the error requirement.
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| US6629446B2 (en) * | 2001-01-08 | 2003-10-07 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Single vector calibration system for multi-axis load cells and method for calibrating a multi-axis load cell |
| CN101419118B (en) * | 2008-12-05 | 2010-09-08 | 中国航天空气动力技术研究院 | Support reaction type wind-tunnel balance shafting static calibration method |
| US9354134B2 (en) * | 2013-03-08 | 2016-05-31 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Adminstration | In-situ load system for calibrating and validating aerodynamic properties of scaled aircraft in ground-based aerospace testing applications |
| CN107462395B (en) * | 2017-08-16 | 2019-03-19 | 中国空气动力研究与发展中心超高速空气动力研究所 | Interference coefficient calibration method between a kind of balance component |
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