CN110715783A

CN110715783A - Method for detecting vibration characteristic of cab of long-head truck

Info

Publication number: CN110715783A
Application number: CN201911066027.XA
Authority: CN
Inventors: 张代胜; 王海涛; 李瑞峰; 俞俊兆
Original assignee: Hefei Polytechnic University
Current assignee: Hefei University of Technology; Hefei Polytechnic University
Priority date: 2019-11-04
Filing date: 2019-11-04
Publication date: 2020-01-21

Abstract

The invention provides a method for detecting vibration characteristics of a cab of a long-head lorry, which only comprises the following steps: 1) a cab modal test; 2) testing the bending and torsional rigidity of the cab; 3) performing a CAE simulation test; 4) and (3) road test: for the problems found in a cab modal test, a cab bending and torsional rigidity detection test and a CAE simulation test, the relationship between the problems and the engine speed and the automobile running speed is analyzed by a road test method, and the cab vibration characteristic is detected from the angle of the whole automobile. The detection method tightly combines the test, the analysis and the real vehicle test, combines the vibration problem of the cab with the whole vehicle from the development and design stage, and achieves advanced design. In addition, compared with a flat head vehicle, the domestic long head vehicle has less data accumulation of the vibration performance, the detection method can effectively analyze the reason that the cab generates the vibration problem under different working conditions, provide data for fully knowing the vibration performance of the long head vehicle, and accumulate the experience for the development of long head vehicle products.

Description

Method for detecting vibration characteristic of cab of long-head truck

Technical Field

The invention relates to a method for detecting vibration characteristics of a long-head truck, in particular to a method for detecting vibration characteristics of a cab of the long-head truck.

Background

A truck is a form of vehicle used to carry cargo and goods. In the age of the great development of the transportation industry, which is promoted by the technological progress, trucks are more and more widely used because of the advantages of high transportation efficiency, low cost, low oil consumption and the like. However, the running road surface is severe, the whole vehicle or the local vibration is obvious because the vehicle is easily influenced by the road surface and the excitation of an engine in the running process. When resonance occurs, violent vibration and noise are generated, the comfort of drivers and passengers is seriously influenced, the drivers and passengers are more easily fatigued, the structure is damaged, and the service life of a vehicle body is shortened.

Compared with a flat head vehicle, the long head vehicle has the advantages that in terms of safety, as the head of the long head vehicle is long, when the long head vehicle encounters a collision condition, the front end of the head of the long head vehicle has a longer buffer distance to a driver, and a front collision energy absorption area is larger, so that the safety is good; in the aspect of comfort, the engine is arranged on the head part, so that the position of a cab is not occupied, the cab space is large, more space is used for installing facilities such as a refrigerator and a sleeper, and the cab is close to the ground and is convenient to move up and down. Therefore, the comfort is better; in the aspect of installation and maintainability, the engine cabin of the long-head vehicle is larger in position, so that the engine with larger size and stronger dynamic property can be installed, and the installation and maintainability are more convenient. Currently, long-head vehicles will meet a larger development space due to the relaxation of the overall length dimension of the long-head vehicle by national policy.

Meanwhile, in order to improve the competitive power of brands in the automobile industry, designers and manufacturers pay more and more attention to the noise and vibration level of the trucks, and the vibration performance of the system is clearly controlled. Non-metallic new materials used in the aerospace industry are also widely used in vehicle bodies to improve the fatigue life of the cab and the riding comfort. At present, the occupancy of the long-head vehicle in the domestic market is low, the technology research and development accumulation is less, the research method for the vibration characteristic of the cab of the long-head vehicle mainly refers to the flat-head vehicle, and a mature system is not formed. And the performance of the product is exposed through the test and then corrected by a simple standard test, so that the time is consumed, and the performance of the product cannot be controlled. Therefore, it is necessary to establish a long-head vehicle cab vibration characteristic evaluation system.

Disclosure of Invention

In view of the above-described drawbacks of the prior art, it is an object of the present invention to provide a vibration characteristic detection method suitable for cab detection of a long-head truck.

In order to achieve the above and other related objects, the present invention provides a method for detecting vibration characteristics of a cab of a long-head truck, comprising the steps of:

1) cab modal testing: the test object is a white body of a cab of the long-head truck, a free mode is adopted, and the modal parameters of the cab are obtained through tests;

2) cab bending and torsional stiffness test: the test object is a white body of a cab of the long-head lorry, loading forces with different magnitudes are applied to different positions of the cab in a front-end rigid constraint and rear-end loading mode, meanwhile, a plurality of test points are arranged on the cab, the displacement change magnitude of each test point under the action of different positions and different guiding loading forces is detected, and the rigidity condition of the cab is analyzed;

3) performing CAE simulation test, comparing the test result in the step 1) and the step 2) with the CAE simulation test, verifying the accuracy of the simulation, finding out common problems, and improving the problems exposed by the test in the model simulation;

4) and (3) road test: for the problems found in a cab modal test, a cab bending and torsional rigidity detection test and a CAE simulation test, the relationship between the problems and the engine speed and the automobile running speed is analyzed by a road test method, and the cab vibration characteristic is detected from the angle of the whole automobile.

Preferably, the excitation is performed by a single-point excitation method in the cab mode test.

Preferably, when performing a cab modal test, the cab is first divided into a plurality of grids by area, each grid being set as a test point.

Preferably, when performing the cab mode test, the vehicle cab is supported by an air spring to keep the cab stable, so that the restrained state of the cab is close to the free state.

Preferably, when a cab bending and torsional rigidity detection test is carried out, firstly, according to the actual structure of the cab, measuring points are arranged along 7 points of a left sill beam, a right sill beam, a left longitudinal beam, a right longitudinal beam, 2 points of a diagonal line of a front windshield of the cab, and 2 points of a diagonal line of a left door frame and a right door frame, so that relatively complete measuring point distribution is formed, deformation of each measuring point of the cab under bending and torsional working conditions and change conditions of the diagonal lines of each door frame and each window frame are measured through displacement sensors of each measuring point, and the rigidity condition of the cab is analyzed according to the deformation and the change.

Preferably, when the cab bending and torsional rigidity detection test is carried out, the torsional rigidity test is carried out by adopting a jack at the rear ends of left and right side members of a body-in-white cab according to load grades of 50kg, 100kg, 150kg, 200kg, 250kg, 300kg, 400kg and 600kg, wherein 600kg is an overload condition, and the test is carried out only once.

Preferably, the cab torsional rigidity test is divided into a left loading working condition and a right loading working condition, each test load under each working condition is subjected to two times of loading and unloading measurement, a torsional deformation curve is drawn according to the average of the two measured values, and the torsional rigidity of the vehicle body is calculated.

Preferably, the cab bending stiffness test is carried out by adopting graded loading, four pedestals are arranged at the bottom of the cab according to requirements and fix the carrying pole beam, weights are sequentially loaded at two ends according to different load grades, and the graded loading is as follows: 100kg, 200kg, 300kg, 400kg were loaded in this order.

Preferably, the cab bending stiffness test is divided into a left loading working condition and a right loading working condition, three groups of repeated measurement are carried out on each working condition, and deformation data are obtained according to the average value of three times.

Preferably, the road test is divided into two parts: (1) evaluation of occupant perception: with the speed of 40-120KM/h as the test speed, the vibration performance of the sample car cab is evaluated through the subjective feeling of passengers in the cab; (2) and (3) testing and evaluating an instrument: carrying out real vehicle idle speed test on idle speed vibration problems exposed in both the test and the simulation; the test was carried out at 60KM/h, 90KM/h and 120KM/h, respectively, on the test roads. And repeating the two rounds to reduce random errors. The test process maintains the vehicle to run along a straight line at a constant speed as much as possible, and the sampling time is maintained at about 120 s.

As described above, the present invention has the following advantageous effects: the detection method tightly combines the test, the analysis and the real vehicle test, combines the vibration problem of the cab with the whole vehicle from the development and design stage, and achieves advanced design. In addition, compared with a flat head vehicle, the domestic long head vehicle has less data accumulation of the vibration performance, the detection method can effectively analyze the reason that the cab generates the vibration problem under different working conditions, provide data for fully knowing the vibration performance of the long head vehicle, and accumulate the experience for the development of long head vehicle products.

Drawings

Fig. 1 is a schematic diagram of a cab modal testing system.

Fig. 2 is a cab grid diagram.

Fig. 3 is a view of the arrangement of the cab stations.

FIG. 4 is a fundamental frequency torsional mode diagram of a vehicle body.

Fig. 5 is a first order torsional mode diagram of the vehicle body (side panel + roof).

Fig. 6 shows the back panel + ceiling front bend.

Fig. 7 is a vehicle body curve (floor + quarter curve).

Fig. 8 is a vehicle body curve (side panel + back panel curve).

Fig. 9 is a first-order bending (floor + tailgate high-order bending) of the vehicle body.

FIG. 10 is a graph of bending and torsional stiffness test point distribution.

FIG. 11 is a basic principle diagram of a static rigidity test of a vehicle body.

Fig. 12 is a view showing a structure for fixing a shoulder pole in a bending rigidity test of a vehicle body.

Fig. 13 is a plan view schematically illustrating a bending rigidity test of a vehicle body.

Fig. 14 is a graph showing bending deformation data of the left side member under each level of load of the underbody.

Fig. 15 is a data graph of the bending deformation of the right side member under each level of load of the underbody.

FIG. 16 is a graph of right side load left stringer torsional deflection data.

Fig. 17 is a graph of left side load right stringer torsional deflection data.

Fig. 18 is a deformation diagram of the right side of the left and right door frames under a torsional load.

Fig. 19 is a deformation diagram of the left and right door frames under a left-side torsional load.

Fig. 20 is a deformation diagram under a torsional load on the right side of the front windshield.

Fig. 21 is a deformation diagram under a torsional load on the left side of the front windshield.

Fig. 22 is a general flowchart of the failure detection of the abnormal vibration problem in the cab of the vehicle.

Fig. 23 is a general flow chart of fault detection of abnormal vibration problem of the automobile chassis.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

The invention discloses a method for detecting vibration characteristics of a cab of a long-head lorry, which only comprises the following steps: 1) a cab modal test; 2) testing the bending and torsional rigidity of the cab; 3) performing CAE simulation test, comparing the test result in the step 1) and the step 2) with the CAE simulation test, verifying the accuracy of the simulation, finding out common problems, and improving the problems exposed by the test in the model simulation; 4) and (3) road test: for the problems found in a cab modal test, a cab bending and torsional rigidity detection test and a CAE simulation test, the relationship between the problems and the engine speed and the automobile running speed is analyzed by a road test method, and the cab vibration characteristic is detected from the angle of the whole automobile. The method of each step is described in detail below.

Cab mode detection method

1, summarizing: a white body modal test of a cab of a certain long-head truck is completed on a special test device for the modal test, and a test object is a cab white body without glass and adopts a free modal mode. Structural parameters such as natural frequency, modal shape and the like of the cab are obtained through tests, and data information is accumulated for evaluating the dynamic characteristics of the existing structural system, verifying the reliability of finite element analysis results and predicting and optimizing the dynamic characteristics of a new train type.

2 purpose of the test: and performing modal test and analysis on a certain long-head truck cab to obtain modal parameters of a body-in-white of the cab. Compared with the vibration performance data of the marker post vehicle and the analysis result of the cab, the vibration performance of the cab can be more comprehensively known.

3, test system:

(1) an excitation part: comprises a signal generator, a power amplifier, a vibration exciter and the like;

(2) a collection part: the device comprises a force sensor, an acceleration sensor, an adjuster and the like;

(3) analysis, display and recording part: comprises a dynamic signal acquisition, analysis and processing system (DH5920), a computer and the like;

(4) a support portion: jacks and air springs;

a schematic of the modal testing system is shown in figure 1.

4 test subjects:

in the test, the cab structure weighed 408kg in body-in-white and the approximately square structure had 2520 × 2430 × 2260mm in profile size. A total of 430 stations were arranged, and the frequency range was analyzed at 200 Hz.

5 protocol of the test:

5.1 mounting means

Because the cab has larger volume and mass, the test adopts an air spring supporting mode to keep the cab stable, thereby leading the constraint state of the cab to be close to a free state and reducing the influence on the test.

5.2 excitation method

There are usually two alternative excitation methods, one of which is to excite a point on the structure and measure the response of all points, i.e. the single point excitation method. The other is to excite multiple points of the structure simultaneously and measure the response of each point, which is known as a multipoint excitation method. The advantage of single-point excitation is that in the mode test, only the signals of excitation and response are measured and recorded at the same time, and then the frequency response function corresponding to the freedom degree of response excitation can be obtained through digital signal processing, thus being simple and easy to implement and wide in application. And multiple point excitation needs to adopt several sets of vibration exciters for excitation, and excitation signals of the vibration exciters are not related to each other, so that the magnitude and the phase of input force of each vibration exciter need to be debugged repeatedly, and time is consumed. In the modal test, single-point excitation or multi-point excitation is adopted depending on the difficulty of the overall excitation of the test piece. If the response of any point on the test piece can be measured by single-point excitation, and the response amplitude is large enough, single-point excitation is adopted.

The test researches the modal parameters of the white body of the cab, so that the white body is easy to be excited, and the low-frequency band is the frequency band which is interested by people, so that the test adopts a single-point excitation method.

5.3 Point selection

For the modal test, the measurement point selection follows the principle that the measurement points are as few as possible and the modal shape characteristics can be clearly displayed on the premise of basically reflecting the outline of the vehicle body.

Due to the fact that the white body of a cab is large in volume, a vehicle body is divided into grids by 10 x 10cm before measuring points are determined. Measuring points are selected from the grid nodes, and 430 measuring points are arranged in total. The cab grid and station layout is shown in fig. 2 and 3.

5.4 parameter setting, System debugging and sampling

After the equipment installation is completed, the storage rule, the signal source and the channel parameter are set in the measurement setting. In the channel setting, the range, sensitivity, and the like of each channel need to be set.

As the cab test has more test points, in order to facilitate the identification of subsequent modal parameters, 10 test points can be used as a group, and all the test points are divided into 43 groups to be tested and analyzed step by step. When each group of test is carried out, the frequency response and the coherence condition of each measuring point, the time history and the self-spectrum of the exciting force and the like are recorded and analyzed, and the accuracy of the current test is judged in time according to the data condition.

6 analysis of test results:

the respective step shapes of the cab are shown in FIGS. 4-9 and Table 1

Since the cab structure is composed of a frame and plates and is approximately of a square structure, the vibration mode of the cab structure is different from that of a common car body, and more box-shaped structure vibration characteristics are shown, namely, the car body is bent in multiple directions. Wherein the torsion of the vehicle body is represented by the combination form of a side wall and a rear wall, and the side wall and a ceiling; the bending form of the vehicle body is more, wherein the rear coaming and the ceiling are bent along the X direction of a vehicle body coordinate system; the bottom plate and the back panel are bent along the Z direction of a vehicle body coordinate system; the bending of the side coamings and the back coamings is in a bidirectional vibration form (in the X direction and the Y direction); the high-order mode is mostly a local mode or a multi-component multi-direction mode.

The body mode reflects the dynamic property of the body on one hand and is matched with the performance of other parts on the other hand. Because the floor of the vehicle body is supported by a plurality of longitudinal and transverse beams, the floor has higher rigidity, less vibration modes or smaller relative amplitude; the ceiling is integrally constructed by the glass fiber reinforced plastics, so that the rigidity is high, and the bending and torsion amplitudes are relatively small; the rear coaming piece has large size, a hole is formed in the middle, and the bending vibration mode is more (the rear window glass can be changed after being installed); the left side wall and the right side wall are locally weaker, and the integral bending torsion vibration mode and the local bending vibration mode appear in sequence; particularly, the connection rigidity of the upper part of the side wall B column is relatively weak, and low-order vibration modes repeatedly appear, so that the side wall B column is a part worth focusing.

Method for detecting bending and torsional rigidity of cab

1, summarizing: the test vehicle type belongs to a long-head heavy truck, and in order to verify the design scheme of the product, improve the performance of the product, test the bending and torsional rigidity of the body-in-white in a cab, and independently develop and accumulate precious test data for the vehicle type. The bending and torsional rigidity test of the white body of the cab is completed on a special test bench for the torsional rigidity of the body. According to the structure and the bearing condition of the cab, front end rigid constraint is adopted, and rear end loading is adopted.

Data are obtained through tests, and foundations are established for further improving the rigidity of the cab, improving the deformation condition of the door and window frame, verifying CAE analysis and optimization and the like.

2, purpose: and (3) carrying out bending and torsional rigidity test and analysis on a white body of a cab of a certain long-head truck, obtaining corresponding bending and torsional rigidity values through the test, drawing a torsional curve, and verifying a CAE analysis result.

3, testing instruments and equipment:

a. a torsional stiffness test bed;

b. a static displacement tester;

c. displacement sensor and support

d. A door and window deformation gauge;

e. jacks and force sensors;

f. a computer and a data acquisition system;

g. other installation tools.

4 test subjects:

in the test, the cab structure weighed 408kg in body-in-white and the approximately square structure had 2520 × 2430 × 2260mm in profile size.

5, measuring point arrangement scheme:

according to the actual structure of the cab, the measuring points are distributed along 7 points of a left sill beam, a right sill beam, a left longitudinal beam and a right longitudinal beam, 2 points are distributed on the diagonal line of a front windshield of the cab, and 2 points are distributed on the diagonal lines of a left door frame and a right door frame, so that relatively complete measuring point distribution is formed, as shown in fig. 10. And measuring the deformation of each measuring point of the cab under the bending and torsion working conditions and the change condition of the diagonal line of each door and window frame by using each measuring point displacement sensor, and analyzing the rigidity condition of the cab according to the deformation.

The basic principle of the static rigidity test of the vehicle body can be seen in fig. 11, the preparation work before the test mainly comprises the steps of preparing a test fixture, manufacturing a test gauge, determining a vehicle body installation scheme and the like, and a preparatory loading test is also carried out before the formal test so as to ensure that the whole set of test system is reliable and effective. Depending on the actual structure of the cab and the form of suspension mounting, a special fixture is provided. The bolt holes of the front suspension points of the left and right longitudinal beams of the white body of the cab are utilized to be rigidly fixed on a front bracket of a test bed through a connecting piece; the bolt holes near the suspension points at the rear ends of the left and right longitudinal beams are utilized to be rigidly fixed on the rotating cross beam of the test bed through the connecting piece, the front and the rear of the vehicle body are horizontally aligned, and the center line is adjusted to be consistent with that of the twisting cross beam.

The torsional rigidity test adopts jacks to carry out the tests on the rear ends of left and right longitudinal beams of a white body in a cab according to the load grades of 50kg, 100kg, 150kg, 200kg, 250kg, 300kg, 400kg and 600 kg. 600kg is an overload condition, and only one test is carried out. The bending is divided into a left loading working condition and a right loading working condition, each test load under each working condition is subjected to two times of measurement of loading and unloading, a torsional deformation curve is drawn according to the average of the two measured values, and the torsional rigidity of the vehicle body is calculated.

The bending stiffness test is carried out by adopting graded loading, four pedestals are arranged at the bottom of the cab according to requirements, the shoulder pole beam is fixed, and hanging baskets for loading are arranged at two ends of the shoulder pole beam, as shown in figures 12 and 13. And sequentially loading weights at two ends according to different load levels. The grading load is: 100kg, 200kg, 300kg, 400kg were loaded in this order. 400kg of the test sample is an overload condition, and only one test is carried out. The bending is divided into a left loading working condition and a right loading working condition, three groups of repeated measurement are carried out on each working condition, and deformation data are obtained according to the average value of three times.

7 analysis of test results:

(1) flexural rigidity test

The test results are shown in fig. 14, 15 and table 2, and table 2 shows the test data at each point under bending load. Fig. 16 to 21 and tables 3 and 4 show graphs of the torsional rigidity test data.

Table 2 test data for each station under bending load.

TABLE 3

Load class kg	50	100	150	200	250	300	400	500	600
										Equivalent torque Nm	441	882	1323	1764	2205	2646	3528	4410	5292

TABLE 4

Rigidity tests show that the torque rigidity of the cab presents a sectional characteristic and a nonlinear change characteristic.

1. Under the action of bearing left-side loading torque or right-side loading torque, the longitudinal beam bears combined action of bending and twisting loads due to the eccentric bearing effect of the actual longitudinal beam, the longitudinal beam is subjected to bending and twisting combined deformation, and when a certain torque value is exceeded, the left-side loading left longitudinal beam is greatly deformed, and the right-side loading right longitudinal beam is greatly deformed, so that the asymmetric deformation characteristic is shown. The cross section of the longitudinal beam is a closed thin-wall rectangle, and under the action of bending load, the longitudinal beam structure should have warping stress, which is different from the torsion deformation and stress of a common vehicle body.

2. The vehicle body floor has a longitudinal-transverse beam connection, but the connection between the transverse beam and the longitudinal beam is weak, and only a part of load is transmitted to the right side when the vehicle body is twisted on the left side, and the phenomenon is also reflected when the vehicle body is twisted on the right side. When one side of the vehicle body is twisted, the longitudinal beam body structure is twisted when a certain torque value is exceeded, but the torsional load is not effectively transmitted to the other side.

3. The relation curve of the torque and the torsion angle is in a typical nonlinear characteristic, and a small change of the torsion angle brings a large change of the torsional rigidity, namely the sensitivity of the torsional rigidity to the data of the change of the torsion angle of the automobile body.

4. The torsional rigidity index of the long-head car body is less than the data, and the performance is different from the torsional rigidity of the general car body. However, referring to the diagonal line indexes of the torsion door frame and the wind window of the bearing type car body, the deformation values of the door frame and the wind window of the car body are far smaller than those of the car body.

Third, road verification and detection method

1 purpose of the test:

the method is used for carrying out real vehicle road test aiming at the problems found in the test and simulation of the cab of the long-head truck. The main purpose of the road vibration test is to verify the test and simulation results, expose the vibration problem of the sample vehicle and enhance the understanding of the vibration characteristic of the long-head vehicle. The road test is divided into two parts:

(1) evaluation of occupant perception: and (3) evaluating the vibration performance of the cab of the sample car by subjective feelings of passengers in the cab by taking 40-120KM/h as a test vehicle speed.

(2) And (3) testing and evaluating an instrument: carrying out real vehicle idle speed test on idle speed vibration problems exposed in both the test and the simulation; the test was carried out at 60KM/h, 90KM/h and 120KM/h, respectively, on the test roads. And repeating the two rounds to reduce random errors. The test process maintains the vehicle to run along a straight line at a constant speed as much as possible, and the sampling time is maintained at about 120 s.

2 test instruments and equipment:

a. a portable dynamic signal testing and analysis system;

b. an acceleration sensor;

c. an inverter and a storage battery;

f. a computer and a data acquisition system;

d. dynamic data processing and analysis software.

And 3, measuring point arrangement:

TABLE 5 measurement Point arrangement

4, test results:

(1) under the test vehicle speed of 60-120KM/h, the subjective feeling of passengers in the cab is abnormal vibration attenuation;

(2) under the idle working condition that the problems are exposed in both the test and the simulation, the vibration of the cab is obvious. The display rotating speed of the instrument panel is 600 r/min, the test frequency is 31.25Hz, and the corresponding rotating speed is 625 r/min; the amplitude of a measuring point of the suspension, the frame and the swing arm is 0.34, and the amplitude of a measuring point of a guide rail of a driver seat is 0.31.

An idle vibration solution is proposed-frequency avoidance, damping addition, vibration absorbers, re-optimization of structure (frame/body), and adjustment of idle speed.

5, test thinking:

the vibration problem of the cab of the long-head vehicle is analyzed by a road test to be related to the rotating speed of an engine and the running speed of the vehicle. When the vibration phenomenon of a cab occurs in an actual vehicle test, firstly, the rotating speed of an engine is changed on the premise of keeping the vehicle speed unchanged so as to analyze the vibration problem related to the rotating speed; if the vibration problem cannot be solved, the vibration problem is considered to be related to the chassis, a road test is carried out after the tire pressure is adjusted, and the test vehicle speed is changed to analyze the vibration problem related to the vehicle speed. Fig. 22 shows a flow chart of the failure detection of the abnormal vibration problem of the cab of the vehicle when an abnormality occurs, and fig. 23 shows a flow chart of the failure detection of the abnormal vibration problem of the chassis of the vehicle.

The method for detecting the vibration characteristic of the cab of the long-head vehicle is mainly used for products which are developed in the forward direction and optimized and improved, and can be used for testing and verifying the vibration characteristic of the products in the stages of design development and optimization and improvement.

1 modal test.

And performing modal testing on the cab, and analyzing to obtain a vibration pattern diagram of the cab under different frequencies. The cab mode can reflect the dynamic property of the cab body on one hand, and requires the performance of other components to be matched in a coordinated manner on the other hand, so that resonance is avoided.

2. Rigidity test

The actual constraint condition of the cab is simulated, the bending and torsional rigidity of the cab is tested, and the rigidity of the cab is a comprehensive capability reflecting the cab under different working conditions. The key of the cab rigidity test and analysis lies in verifying whether the vehicle body structure is reasonable, obtaining key data indexes such as the vehicle body integral torsional rigidity value, the vehicle body deformation, the door and window frame deformation, the vehicle body rigidity curve and the like through the static bending and torsional rigidity test, and objectively evaluating the cab rigidity state.

3. Comparative CAE analysis

Comparing and analyzing the test result with a CAE simulation result, verifying the accuracy of simulation and finding out a common problem; secondly, the problem exposed by the test needs to be improved in the model simulation,

4. road test

For automobile products before production or after optimized modification, road tests are the most important work for verifying the vibration performance of the cab. The detection method is used for analyzing the relation between the problems found by modal and rigidity tests and simulation and the rotating speed of an engine and the running speed of an automobile by a road test method. The vibration characteristic of the cab is detected from the angle of the whole vehicle.

For example, the problem of cab vibration found by testing and simulation occurs in an actual vehicle test, and the rotating speed of an engine is changed on the premise of firstly ensuring that the vehicle speed is not changed so as to analyze the problem of vibration related to the rotating speed; if the vibration problem cannot be solved, the vibration problem is considered to be related to the chassis, a road test is carried out after the tire pressure is adjusted, and the test vehicle speed is changed to analyze the vibration problem related to the vehicle speed.

At present, the method for detecting the vibration characteristic of the cab of the long-head vehicle mainly refers to a flat-head vehicle. The idea that the simple vibration test and analysis of a cab is not tightly combined with an actual vehicle test and the integral vibration detection of an automobile is not consistent with the integrity is considered; the product performance is exposed through a large amount of road tests and then corrected through a simple standard alignment test, time and financial resources are consumed, and the product performance cannot be controlled essentially. The detection method tightly combines the test, the analysis and the real vehicle test, combines the vibration problem of the cab with the whole vehicle from the development and design stage, and achieves advanced design. In addition, compared with a flat head vehicle, the domestic long head vehicle has less data accumulation of the vibration performance, the detection method can effectively analyze the reason that the cab generates the vibration problem under different working conditions, provide data for fully knowing the vibration performance of the long head vehicle, and accumulate the experience for the development of long head vehicle products. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A method for detecting vibration characteristics of a cab of a long-head truck is characterized by comprising the following steps:

2. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: and when the cab modal test is carried out, a single-point excitation method is adopted for excitation.

3. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: when carrying out a cab modal test, firstly, a cab is divided into a plurality of grids according to the area, and each grid is set as a test point.

4. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: when the cab modal test is carried out, the automobile cab adopts an air spring supporting mode to keep the cab stable, so that the restrained state of the cab is close to the free state.

5. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: when a cab bending and torsional rigidity detection test is carried out, firstly, according to the actual structure of the cab, measuring points are arranged along 7 points of a left sill beam, a right sill beam, 7 points of a left longitudinal beam, 2 points of a diagonal line of a front windshield of the cab, and 2 points of a diagonal line of a left door frame and a right door frame to form complete measuring point distribution, deformation of each measuring point of the cab under bending and torsional working conditions and change conditions of the diagonal lines of the door frames and the window frames are measured through displacement sensors of the measuring points, and accordingly the rigidity condition of the cab is analyzed.

6. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: when a cab bending and torsional rigidity detection test is carried out, a jack is adopted in the torsional rigidity test to carry out tests on the rear ends of left and right longitudinal beams of a body-in-white cab according to the load grades of 50kg, 100kg, 150kg, 200kg, 250kg, 300kg, 400kg and 600kg, wherein 600kg is an overload working condition and is only carried out once.

7. The method for detecting cab vibration characteristics of a long-head truck according to claim 6, characterized in that: the cab torsional rigidity test is divided into a left loading working condition and a right loading working condition, each test load under each working condition is subjected to two times of loading and unloading measurement, a torsional deformation curve is drawn according to the average of the two measured values, and the torsional rigidity of the vehicle body is calculated.

8. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: the cab bending stiffness test is carried out by adopting graded loading, four benches are arranged at the bottom of the cab according to requirements and fix the carrying pole beam, weights are sequentially loaded at two ends according to different load grades, and the graded loading is as follows: 100kg, 200kg, 300kg, 400kg were loaded in this order.

9. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: the bending stiffness test of the cab is divided into a left loading working condition and a right loading working condition, three groups of repeated measurement are carried out on each working condition, and deformation data are obtained according to the average value of three times.

10. The method for detecting vibration characteristics of a cab of a long-head truck according to claim 1, characterized in that: the road test is divided into two parts: (1) evaluation of occupant perception: with the speed of 40-120KM/h as the test speed, the vibration performance of the sample car cab is evaluated through the subjective feeling of passengers in the cab; (2) and (3) testing and evaluating an instrument: carrying out real vehicle idle speed test on idle speed vibration problems exposed in both the test and the simulation; the test was carried out at 60KM/h, 90KM/h and 120KM/h, respectively, on the test roads. And repeating the two rounds to reduce random errors. The test process maintains the vehicle to run along a straight line at a constant speed as much as possible, and the sampling time is maintained at about 120 s.