CN115609514A

CN115609514A - Intelligent wrench based on torque angle method and screwing control method

Info

Publication number: CN115609514A
Application number: CN202211341529.0A
Authority: CN
Inventors: 王直; 陈昭明
Original assignee: Jiangsu University of Science and Technology
Current assignee: Jiangsu University of Science and Technology
Priority date: 2022-10-28
Filing date: 2022-10-28
Publication date: 2023-01-17

Abstract

The invention discloses an intelligent wrench based on a torque angle method and a tightening control method, wherein the intelligent wrench comprises a microcontroller, a torque measuring module, an angle measuring module, a memory and a working power supply, wherein the torque measuring module, the angle measuring module, the memory and the working power supply are electrically connected with the microcontroller; the torque measuring module is used for measuring the torque of the intelligent wrench, the angle measuring module adopts an inertial sensor and is used for measuring the deflection angle of the intelligent wrench, the inertial sensor comprises a gyroscope, an accelerometer and a magnetometer, and the microcontroller controls the intelligent wrench to be screwed down by adopting a torque angle method. The method does not use the conventional method for calculating the angular attitude by the quaternion of the inertia device, only reduces the complicated operation and the attitude calculation by establishing the wrench coordinate system based on the torque wrench, and has the characteristics of high calculation efficiency, high precision, low cost, low power consumption and long endurance.

Description

Intelligent wrench based on torque angle method and screwing control method

Technical Field

The invention relates to an intelligent wrench, in particular to an intelligent wrench based on a torque and angle method and a tightening control method.

Background

A torque wrench is a tightening tool that acts on the head of a bolt to tighten bolts of different types by applying different torques to ensure the reliability of the mechanical equipment connection. In the fields of ships, railways, aviation and the like, the application quantity of threaded fasteners is increasing, and the functions of the threaded fasteners are also more and more important. Due to the common and potential severity of threaded fastener failures, ensuring the reliability of the bolted connection is critical. The reliability of the bolt connection is related to the applied pretightening force, and the pretightening force is determined by the tightening mode. The torque method is a common torque method in bolt tightening modes, and obtains a mathematical model through the relation between tightening torque and pretightening force, so as to obtain the tightening torque range under different pretightening forces. However, the bolt can enter a plastic deformation area due to the large pretightening force, and the torque and the pretightening force are not in a linear relation at the moment. Therefore, in some fields where pre-tightening force is required, the torque method is not applicable. At the moment, a torque angle turning method is selected, and the method can effectively reduce the dispersity of the bolt pretightening force so as to improve the connection reliability of the bolt, reduce the torque deviation and meet the requirement of higher bolt pretightening force. The torque cornering method is essentially a step-wise tightening strategy, where the bolts are first tightened to an initial torque and then to a certain angle on the basis of the initial torque. In order to implement the torque-angle method, functions of measuring torque and measuring angle are required.

The torque measuring methods are various and can be divided into three categories according to the measuring principle: equilibrium force method, energy conversion method, and transmission method. The transmission method is widely applied to various situations for measuring torque. When transmitting torque, the elastic shaft physical parameters generate changes, the changes of the physical parameters reflect the changes of the torque, and the transmission method measures the torque by measuring the changes of the physical parameters. These varying physical parameters can be classified into three categories according to the way the signal is generated: deformation, stress and strain types. The deformation type mainly comprises capacitance type, optical type, magnetoelectric type, photoelectric type and mechanical type; the stress type is mainly divided into a photoelastic type and a magnetic elastic type; the strain type torque measurement method mainly refers to a resistance strain gauge type measurement method. The resistance strain effect refers to that when mechanical deformation is generated under the action of external force, the resistance value of a conductor or a semiconductor material changes correspondingly, and the resistance strain type measurement method is based on the resistance strain effect to measure torque. The strain gauge is adhered to the rotating shaft, and when torque acts on the rotating shaft, the strain gauge can detect the torque according to the change of the resistance value.

The scheme of measuring the angle mainly adopts an inertial sensor which is mainly divided into a gyroscope and an accelerometer. However, most of the existing schemes for measuring angles by inertial sensors rely on a single sensor, and it is difficult to obtain an accurate angle measurement result by only relying on measurement data of the single sensor, so data fusion of various sensors needs to be performed by an algorithm, and the selection of a chip is mainly based on integration of various inertial sensors. An existing digital display type angle torque wrench adopts a torque angle method, and angle attitude calculation is carried out by using a DMP integrated in a control chip. The DMP attitude calculation directly outputs quaternion according to data acquired by a gyroscope without filtering and correcting, and the precision is not high. The quaternion angle attitude algorithm for performing complementary filtering correction on the data added into the accelerometer is used for solving absolute coordinates in a coordinate system in the northeast, the solving process is complicated, the solving efficiency is low, the calculation cannot be performed in time when the posture of the wrench changes rapidly, the data hysteresis phenomenon can occur, and the precision of the rotation angle can be influenced in the using process of the wrench. Meanwhile, as the posture of the wrench in the using process is changed, a special working state which cannot be described by using a northeast coordinate system exists, so that a dead zone which cannot describe the posture exists in the method. Secondly, in view of the existing electronic wrench, when the electronic wrench rotates in the horizontal direction, the angle measurement errors of the torque structure of the electronic wrench are all about +/-3%, and when the electronic wrench rotates in the vertical direction, the angle measurement error of the torque tool with the best precision is up to +/-6.2%. Not only be limited to the level and screw up in the in-service use of spanner, have multiple occasion to need the bolt of screwing up of multi-angle, can see that current torque tool with measure the angle function can not satisfy practical application's demand from this.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention provides the intelligent wrench based on the torque angle method and the tightening control method, which are applied to a scene with high requirement on the pretightening force of the bolt, can improve the resolving efficiency of angle measurement, and can achieve higher precision standard in the measurement of the rotation angle in the wrench operation process.

The technical scheme is as follows: the invention adopts the technical scheme that an intelligent wrench based on a torque and angle method comprises the following steps: the device comprises a microcontroller, a torque measuring module, an angle measuring module, a memory and a working power supply, wherein the torque measuring module, the angle measuring module, the memory and the working power supply are electrically connected with the microcontroller; the torque measuring module is used for measuring the torque of the intelligent wrench, the angle measuring module adopts an inertial sensor and is used for measuring the deflection angle of the intelligent wrench, and the inertial sensor comprises a gyroscope, an accelerometer and a magnetometer. The system also comprises a communication module for transmitting data to the PC end, a display screen for interaction, a key and an audible and visual alarm module. The microcontroller controls the intelligent wrench to be screwed down by adopting a torque angle method, and the measurement of the deflection angle of the intelligent wrench in the torque angle method comprises the following steps:

(1) Respectively acquiring attitude data by adopting a wrench coordinate system, and integrating course angular acceleration acquired by a gyroscope to obtain a course angle alpha';

(2) After Kalman filtering is carried out on attitude data acquired by an accelerometer and a gyroscope, a pitch angle and a roll angle are calculated;

(3) Calculating the pitch angle and the roll angle in combination with attitude data collected by the magnetometer to obtain a course angle alpha;

(4) Complementary filtering is carried out according to the course angle alpha obtained by combining magnetometer data analysis and the course angle alpha' output by the gyroscope to obtain the corrected course angle alpha ₁ Namely the deflection angle of the intelligent wrench.

The method adopts a torque angle method to control the wrench to tighten, and the measurement of the deflection angle of the intelligent wrench in the torque angle method comprises the following steps:

(1) Respectively acquiring attitude data by adopting a wrench coordinate system, a gyroscope, an accelerometer and a magnetometer, wherein the heading angular acceleration acquired by the gyroscope is integrated to obtain a heading angle alpha';

Wherein the difference formula of the complementary filtering is:

α ₁ ＝Aα+(1-A)[α ₀ +α’]

in the formula, alpha ₁ Is the course angle fused at the current moment, A is the complementary filter coefficient, A = KT/(1 +KT), K is the weight factor in the filter transfer function expression, T is the time constant, alpha is the course angle obtained by combining the magnetometer data analysis, and alpha is the course angle obtained by combining the magnetometer data analysis ₀ The course angle after the complementary filtering processing at the last moment, and alpha' is the course angle output by the gyroscope.

When the magnetometer is not in the horizontal position, the magnetic induction data measured by the magnetometer needs to be compensated:

wherein: m is a group of _x 、M _y 、M _z Each being 3 axis data, H 'output from the magnetometer' _x And H' _y Corrected X-axis and Y-axis magnetic induction data, respectively.

Has the beneficial effects that: compared with the prior art, the invention has the following advantages: the invention does not use the conventional method for solving the quaternion of an inertia device to solve the angle attitude, and only reduces the complex operation and the attitude calculation by establishing a wrench coordinate system taking a torque wrench as a reference. The spanner coordinate system is a relative position coordinate system, so that the response to the change is quicker and more accurate, and the efficiency and the precision of angle attitude calculation can be obviously improved. The measurement scheme designed by the invention has the capability of measuring angles through experimental verification, and the measurement scheme obviously improves the measurement precision and inhibits the random walk and zero drift of the gyroscope under static or dynamic conditions. Secondly, most of like products in the market are expensive, and the production cost is high. The invention is developed based on STM32, has the functions of basic digital display, key control, acousto-optic early warning and data storage and transmission, and has the characteristics of low cost, low power consumption and long endurance.

Drawings

FIG. 1 is a block diagram of the general construction of a smart wrench;

FIG. 2 is a schematic view of two coordinate systems of the intelligent wrench of the present invention;

FIG. 3 is a flow chart of a tightening control method according to the present invention;

FIG. 4 is a schematic diagram of the basic principle of complementary filtering according to the present invention;

FIG. 5 is a view showing the data of the change of the course angle of the horizontally disposed intelligent wrench at rest according to the present invention;

FIG. 6 is a graph of the change data of the course angle of the intelligent wrench in an inclined position when the intelligent wrench is at rest according to the present invention;

FIG. 7 is a view of the data of the change of the course angle of the intelligent wrench in horizontal movement during the dynamic state;

FIG. 8 is the data of the change of the course angle of the intelligent wrench in free movement during dynamic state.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

The structure block diagram of the intelligent wrench based on the torque angle method is shown in figure 1, and the intelligent wrench comprises a microcontroller MCU, a memory electrically connected with the MCU, and modules electrically connected with the MCU: the device comprises a torque measuring module, an angle measuring module and a working power supply. The system also comprises a display screen and a key for interaction and an audible and visual alarm module. In this embodiment, a data transmission function is implemented using a communication module.

In the selection of the controller, DSP and FPGA are expensive and large in size, and are not in accordance with the design requirements of low cost and convenience, STM32L433RBT6 contains various industrial applications such as PWM and ADC and various communication interfaces such as SPI, 12C, CAN and Ethernet, and the characteristic of ultralow power consumption meets the requirement of stable endurance, so that the Microcontroller (MCU) in the design is selected as the Microcontroller.

The power supply circuit provides a reliable working power supply for the system, ensures the normal and stable operation of the intelligent wrench, and is an important component of the intelligent wrench. The system is powered by a rechargeable lithium battery in consideration of the portability of the torque wrench. Compared with the traditional zinc-manganese dry battery, the rechargeable lithium battery can avoid frequent battery replacement, and has the advantages of low self-discharge rate, long cycle life, high energy density, environmental friendliness and the like. The specific model of the power management chip is LD39015M33R, and the characteristics of ultra-low voltage drop, low quiescent current and low noise make the power management chip suitable for low-power battery power supply application. The ceramic capacitor can ensure that the battery can still work normally under the condition of low electric quantity. And the on-off mode can be controlled by the enabling logic, and the controllable power supply design is adopted for the power supplies of other functional modules through the characteristic. When the modules are required to work, the MCU controls the power supplies of the modules to be switched on, the modules supply power to start working, and when the modules are not required to work, the MCU controls the power supplies of the modules to be switched off, and the system enters a low power consumption state.

The torque measuring module selects a resistance type strain gauge. The resistance-type strain gauge can realize the deformation of a measuring object through the resistance change, thereby obtaining the magnitude of the torque. The device has simple structure, low cost and higher reliability, and can adapt to severe environment. Other transfer-based measurement methods are not suitable for use in the present invention: the sensor of the magnetoelectric measuring method has large size and weight, the capacitance measuring method is not suitable when the rotating shaft has overlarge size, the optical fiber measuring method is difficult to debug, and the measuring precision of the magnetic sensitive measuring method is low. Some new measurement techniques, such as wireless surface acoustic wave measurement, are not mature, and laser doppler measurement is costly. In consideration of the fact that the development of strain gauges is mature, most of the digital display type torque wrenches in the market adopt a resistance strain gauge measurement method to measure torque, so that in the torque measurement part of the invention, a resistance strain gauge is selected to measure torque. The strain gauge is generally connected in a bridge form, and voltage signals are acquired in a bridge circuit, belong to analog signals and need to be subjected to A/D conversion. The invention selects the low-power-consumption small-signal 24-bit AD conversion chip ADS1220 as the processing chip of the torque module, the voltage difference of the electric bridge formed by the strain gauge is input to the ADS1220, and the digital quantity is sent to the MCU through the SPI communication interface for data processing, thus completing the torque measurement.

To the selection of angle measurement module, there are many varieties of products on the market at present and can satisfy the requirement of measuring the angle, and six shaft class products mainly include: ICM-20600, ICM-20649, ICM-20689, MPU-6000, etc., nine shaft class products mainly include: ICM-20948, MPU-9250, and the like. Many angle-measurable torque wrenches on the market rely on the DMP of MPU6050 (six-axis series) for attitude solution. The design scheme needs to use the magnetometer, and the accuracy is improved by adding the magnetometer to assist in measurement and calculation, so that nine-axis series MPU9250 is selected. The MPU9250 has a 3-axis MEMS gyroscope, a 3-axis MEMS accelerometer, and a 3-axis magnetometer.

This intelligent spanner has following function: and (1) measuring the angle and the torque. The angle measurement is performed after the torque measurement, and the range of the angle measurement is 0 to ± 720 °. The measurement error should be kept within ± 1.5%. And (2) key control and data display. The total number of the four keys is set up as an up-down key, an A key and a B key. The up and down keys are used for menu selection and numerical value addition and subtraction, the key A is used for confirmation, the key B is used for return, and long-time pressing can be switched between a working state and a low-power-consumption state. And an OLED display screen is selected to realize data display. And (3) acousto-optic early warning. When the wrench is used, the early warning prompt is carried out on the torque value or the angle value which is about to reach the set torque value or angle value. The LED lamp is combined by a buzzer and an LED indicator lamp. And (4) data storage and data transmission. The measured and processed data are stored, a read only memory (EEPROM) is designed and selected, the wrench is communicated with the PC end in a WIFI mode, and the data are uploaded. And (5) the power supply can continue to charge. The system has a power management function, is not provided with a switch, and is controlled to operate by the low-power consumption MCU. Meanwhile, the system adopts a rechargeable lithium battery for power supply, meets the requirement of low power consumption, reduces the frequency of battery replacement and is environment-friendly.

The tightening control method of the present invention, the flowchart of which is shown in fig. 3, includes the following processes:

(1) And respectively acquiring attitude data by adopting a wrench coordinate system, and outputting a course angle alpha' by the gyroscope, the accelerometer and the magnetometer.

The data collected by the gyroscope, the accelerometer and the magnetometer do not use a northeast coordinate system, but use a torque tool coordinate system (namely, a wrench coordinate system), and a new coordinate system is established in the attached figure 2. Because the posture of the wrench in the using process is variable and the working state cannot be described in a northeast coordinate system, the method for calculating the angular posture by using quaternion is not used in the design, and the complex operation and posture calculation are reduced only by establishing a wrench coordinate system based on the torque wrench. As shown in fig. 2, the xyz coordinate system is an internal coordinate system of the angle detection sensor, and the origin is at the center of the chip; the XYZ coordinate system is the torque wrench coordinate system with the origin at the center of the axis of rotation. The X-axis of the XYZ coordinate system is parallel to the X-axis of the XYZ coordinate system, and is set as the center of the axis of rotation and the central axis of the rigid structure. The Y-axis of the XYZ coordinate system is parallel to the Y-axis of the XYZ coordinate system, and the direction is set to a direction perpendicular to the central axis on the horizontal plane of the rotation axis. The Z-axis of the XYZ coordinate system and the Z-axis of the XYZ coordinate system are parallel, and all directions of angles are defined such that the counterclockwise direction facing the origin is negative and the clockwise direction is positive.

It can be seen that the coordinate system of the MPU is parallel to the three axes of the torque tool coordinate system, respectively, such that the angle of rotation about the X-axis is consistent with the angle of rotation about the X-axis, the angle of rotation about the Y-axis is consistent with the angle of rotation about the Y-axis, and the angle of rotation about the Z-axis is consistent with the angle of rotation about the Z-axis, and thus the angle of rotation about the XYZ axes can be derived by measuring the angle of rotation about the XYZ axes. In this coordinate system, the rotation angle of the torque wrench is reduced to the rotation angle around the Z-axis, i.e. the angular heading angle α of the sensor around the Z-axis. The coordinate axis definition solves the influence of the posture of the torque wrench during working on the rotating angle, realizes the xyz triaxial decoupling, avoids a large number of calculation tasks such as quaternion, euler angle, direction cosine and the like, and needs to ensure the parallelism of three pairs of axes of two coordinate systems during circuit design and circuit board installation.

During the actual use of the wrench, due to the characteristics of the gyroscope, integral errors are caused and data drift is caused as the measuring time increases. To improve the accuracy of angle measurement and long-term use, it is not enough to rely on the measurement data of a single sensor, and the data fusion of multiple sensors needs to be performed through an algorithm. The present design uses magnetometer data and gyroscope data fusion to increase measurement accuracy.

The design provides a combined algorithm of Kalman filtering and complementary filtering, firstly, kalman filtering is carried out on data measured by an accelerometer and a gyroscope, then, the Kalman filtering is substituted into a formula (11) and a formula (12) to obtain a course angle alpha solved by the magnetometer, then, complementary filtering is carried out on the course angle alpha and a course angle alpha' output by the gyroscope, and finally, a more accurate course angle is obtained.

(2) And performing Kalman filtering on data measured by the accelerometer and the gyroscope, and calculating to obtain more accurate pitch angle rho and roll angle phi data.

Kalman filtering is a data processing method for optimal estimation with good effect in a linear system. According to the design, a Kalman filtering algorithm is used for fusing data of an accelerometer and a gyroscope, interference caused by random noise is removed, and an accurate pitch angle rho and a roll angle phi are obtained. Firstly, approximately regarding the measurement process as a linear system, establishing a state equation and a measurement equation as follows:

the state equation is as follows:

x _k ＝Ax _k - ₁ +BU _k +w _k (1)

the measurement equation is as follows:

y _k ＝Hx _k +v _k (2)

in the formula: x is the number of _k Is a state vector; u shape _k Inputting a control vector for the system; w is a _k Is system process white noise; yk is an observation vector; v. of _k To measure system noise.

Assuming that the noise thereof follows a normal distribution, the 5 core formulas thereof are as follows.

Pre-estimation of state quantities:

current state estimation:

error covariance pre-estimation:

P _k|k-1 ＝APk- ₁ A ^T +Q (5)

kalman gain:

K _k ＝P _k|k-1 H ^T (HP _k|k-1 H ^T +R) ^-1 (6)

error covariance:

P _k ＝(I-K _k H)P _k|k-1 (7)

wherein:

to the actual value K of the current state _k (ii) is estimated;

is based on k-1 pre-estimation of k times; k is _k To observe the deviation

The modified weighting of (1); p _k A covariance matrix of the current state estimation value; p _k|k-1 Pre-estimating an error covariance matrix; q is the covariance of the white noise in the system process, and R is the covariance of the measured system noise.

In order to further suppress the drift of the gyroscope, the angular velocity offset of the gyroscope needs to be processed, and equation (3) can be described by the following equation:

wherein: t is _s Is a sampling period; omega _k Representing a gyroscope k timeAngular velocity of the moment.

The gyroscope measures the angular velocity of the rotation, and the corresponding angular value needs to be obtained through integration, as shown in the formula (9):

θ _k ＝(ω _k -ω _{bias_k} )dt+θ _k-1 (9)

wherein: theta _k And theta _k-1 The angle values of adjacent moments; omega _k Is a rotational angular velocity; omega _{bias_k} Is the offset of the angular velocity of rotation.

The accelerometer can obtain three-axis acceleration components, and angle calculation is required through an equation (10).

Wherein: a. The _x 、A _y 、A _z Acceleration components of three axes, respectively; ρ is the pitch angle; phi is the roll angle.

(3) And calculating the attitude angles rho and phi obtained by calculation and magnetometer data to obtain a heading angle alpha.

The magnetometer mainly measures the three-axis magnetic induction. In the horizontal position, the course angle can be obtained by equation (11).

Wherein H _x And H _y Respectively, the magnetic induction data measured by the magnetometer on the X-axis and the Y-axis. When the magnetometer is not in a horizontal position, equation (11) is needed to compensate:

wherein: m _x 、M _y 、M _z 3 axes of data respectively output by the magnetometers.

When the wrench is used for a long time, the accuracy of the course angle output by the gyroscope is insufficient, the reference value is not high, and the course angle value calculated by the magnetometer is relatively accurate. The complementary filtering algorithm can be used for correcting the gyroscope by using the magnetometer, so that the drift of the gyroscope is effectively inhibited while the accuracy of information is improved.

(4) And performing complementary filtering on the course angle alpha and the course angle alpha' output by the gyroscope to finally obtain a more accurate course angle. I.e. the calculated deflection angle.

The basic principle of complementary filtering is shown in fig. 4. In the figure, theta is an actual rotation angle value; omega is the angular velocity measured by a gyroscope; theta ₁ The angle value obtained for the magnetometer(s),

the angle value estimated after the complementary filtering algorithm; n is ₁ High frequency noise introduced into the magnetometer measurements; n is a radical of an alkyl radical ₂ Low frequency noise introduced in the gyroscope measurements. By means of a low-pass filter G ₁ (s) eliminating high frequency noise n in magnetometers ₁ Using a high-pass filter G ₂ (s) cancelling Low-frequency noise n in a gyroscope ₂ . The transfer functions of the two filters are designed as shown in equations (13) and (14).

The selected filter transfer function is required to satisfy G ₁ (s)+G ₂ (s) =1, and the appropriate cut-off rate of the high-pass filter and the low-pass filter in the system can be achieved by selecting the appropriate value of the weight factor K. The following equation holds:

the processed attitude angle θ estimate is then:

equation (16) corresponds to the difference equation:

in the formula, A = KT/(1 KT); t is a time constant; theta ₁ (k) Calculating an angle value of the gyroscope in k time; theta ₂ (k) Is the angular data resolved by the magnetometer.

The difference formula can be written as:

α ₁ ＝Aa+(1-A)[α ₀ +α’] (18)

wherein: alpha is alpha ₀ Is the course angle after the filtering processing at the previous moment; alpha is alpha ₁ Is the course angle fused at the current moment; α' is the heading angle resolved by the gyroscope; α is the heading angle resolved from magnetometer data, α ₁ Is the final calculated wrench rotation angle.

And (3) testing the effect of the scheme:

fig. 5 and 6 are heading angle change data for a horizontal and an inclined position, respectively, with the wrench at rest. The magnetometer has a certain zero offset phenomenon, the whole magnetometer fluctuates up and down near a zero offset value, and the offset is within the range of +/-0.5; the gyroscope has obvious drift phenomenon, and the accumulated error obtained by the integral angle gradually increases along with time; the course angle curve after the combined filtering is smooth and stable, and the deviation is within the range of +/-0.1, which shows that the angle measurement algorithm of the scheme can inhibit the drift of the gyroscope and improve the angle accuracy of measurement.

Fig. 7 and 8 are heading angle change data for horizontal movement and free movement of the wrench while dynamic. It can be seen that in the motion state, both the gyroscope and the magnetometer can track the angle change in time. Comparing the two curves can know that the gyroscope has better dynamic response and the magnetometer has more obvious noise and certain hysteresis in the motion state; in the free motion of fig. 7, the magnetometer still fluctuates greatly under algorithm compensation, and the curve after complementary filtering is smooth and stable, so that the noise of the magnetometer is suppressed, the angle error is reduced, and the precision is remarkably improved.

Comparative test experiments:

the invention carries out precision comparison test with two common angle measuring wrenches from the market, wherein the angle measuring wrenches on the market are marked as A and B. Wherein, A uses DMP carried by gyroscope chip to resolve attitude, B uses MPU6050 of integrated Kalman filtering algorithm. The comparative test was performed using a torque testing jig.

The torque wrench is arranged on the rotary table to be fixed, and the rotation angular velocity provided by the rotary table is the rotation angular velocity of the torque wrench, so that different wrenches can rotate at the same angular velocity. The experiment was carried out at 30dps, taking four test points of 45 °, 90 °, 135 ° and 180 °. The test data are shown in the following table, where table 1 is the measured difference between the rotation angle in the horizontal position and the measured angle of the wrench, and table 2 is the measured difference between the rotation angle in the inclined position and the measured angle of the wrench.

TABLE 1 measured differences in horizontal placement

	A	B	MY
				45°	0.36	0.41	0.36
90°	2.41	1.42	0.32
				135°	2.36	0.39	0.39
180°	2.38	1.42	0.38

TABLE 2 measurement of the difference in inclined position

	A	B	MY
				45°	1.39	0.37	0.34
90°	1.38	0.39	0.39
				135°	1.36	1.36	0.36
180°	3.34	1.39	-0.64

In the table, a and B are two commercially available measurable angle wrenches, wherein a uses DMP carried by a gyroscope chip to perform attitude solution, and B uses MPU6050 of an integrated kalman filter algorithm. MY is the wrench designed by the invention. It can be known from the table above, no matter be under level or the slope is put, the difference that the intelligent spanner of this paper design surveyed at four test points is littleer, and the error that can calculate by the error formula is within 1%, accords with the original intention of design precision, proves best on the angle measurement function performance, has certain competitiveness compared with like product.

Claims

1. An intelligent spanner based on torque angle method, characterized in that: the device comprises a microcontroller, a torque measuring module, an angle measuring module, a memory and a working power supply, wherein the torque measuring module, the angle measuring module, the memory and the working power supply are electrically connected with the microcontroller; the torque measurement module is used for measuring the torque of intelligent spanner, the angle measurement module adopts inertial sensor for measure the deflection angle of intelligent spanner, inertial sensor includes gyroscope, accelerometer and magnetometer, microcontroller adopts the torque corner method to control intelligent spanner and screws up, the measurement to intelligent spanner deflection angle in the torque corner method includes following step:

(3) Calculating the pitch angle and the roll angle in combination with attitude data acquired by the magnetometer to obtain a course angle alpha;

2. The intelligent torque-angle-based wrench of claim 1, wherein: the system also comprises a communication module used for transmitting data to the PC terminal.

3. The torque-angulation-based smart wrench of claim 1, wherein: the system also comprises a display screen and a key used for interaction, and an audible and visual alarm module.

4. The intelligent wrench tightening control method is characterized in that the method controls the wrench tightening by adopting a torque angle method, and the measurement of the deflection angle of the intelligent wrench in the torque angle method comprises the following steps:

5. The intelligent wrench tightening control method according to claim 4, characterized in that: the difference formula of the complementary filtering is:

α ₁ ＝Aα+(1-A)[α ₀ +α’]

6. The intelligent wrench tightening control method according to claim 4, characterized in that: when the magnetometer is not in a horizontal position, the magnetic induction data measured by the magnetometer needs to be compensated:

wherein: m _x 、M _y 、M _z Each being 3 axis data, H 'output from the magnetometer' _x And H' _y Corrected X-axis and Y-axis magnetic induction data, respectively.