Road surface spectrum test trailer device

Abstract

The invention discloses a road surface spectrum test trailer device, which relates to the field of vehicle engineering, and comprises a frame, a traction device arranged on one side of the frame, and a walking mechanism and a test mechanism arranged below the frame, the frame comprises a cross beam, a longitudinal beam and a joint for connecting the cross beam and the longitudinal beam which are arranged on the bottom plate; the traction device comprises a traction frame, a pull head and a traction frame joint, the traction frame is connected with the pull head through a traction frame front connecting shaft, and the other end of the traction frame is connected with the traction frame joint through a traction frame connecting shaft; the walking mechanism is composed of four universal trundles with the tire diameter of 200 mm and the rated load of 1600 N; the testing mechanism comprises an acceleration sensor magnetic seat arranged on a testing wheel support, an acceleration sensor is arranged on the acceleration sensor magnetic seat, and the pavement unevenness testing is achieved by collecting acceleration signals of vertical jumping of the testing wheel in the pavement driving process and vehicle speed signals.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle engineering, and in particular to a road spectrum testing trailer device. Background Art

[0002] In recent years, with rapid economic development and improved living standards, the mileage of highways and the number of vehicles in use have continued to grow. The total mileage of graded highways exceeds 4.57 million kilometers, and the number of civilian vehicles has exceeded 256 million. Road surface roughness, as a key indicator for determining road quality and an input for vehicle operation, holds significant research significance in road and automotive engineering. In road engineering research, some roads have developed bumps, depressions, and cracks during use, and even landslides over time, seriously impacting road drivability. These phenomena are often attributed to a lack of thorough research on road surface roughness, which increases road maintenance costs.

[0003] Therefore, a road spectrum testing trailer device is provided to solve the above problems. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a road spectrum test trailer device, which realizes road roughness testing by collecting acceleration signals and vehicle speed signals of the test wheels bouncing up and down during driving on the road.

[0005] To achieve the above-mentioned object, the present invention provides a road spectrum test trailer device, comprising a frame, a traction device arranged on one side of the frame, a traveling mechanism and a testing mechanism arranged below the frame;

[0006] The vehicle frame includes a crossbeam, a longitudinal beam and a joint for connecting the crossbeam and the longitudinal beam arranged on the bottom plate;

[0007] The traction device includes a traction frame, a pulling head and a traction frame joint. The traction frame and the pulling head are connected through a front connecting shaft of the traction frame, and the other end of the traction frame is connected to the traction frame joint through a traction frame connecting shaft.

[0008] The traveling mechanism consists of four swivel casters with a tire diameter of 200mm and a rated load of 1600N;

[0009] The testing mechanism includes an acceleration sensor magnetic base arranged on a test wheel bracket, an acceleration sensor is arranged on the acceleration sensor magnetic base, the bottom of the test wheel bracket is connected to the test wheel, the middle part of the test wheel bracket is connected to the test wheel mounting bracket, and a vertical bearing is arranged between the test wheel mounting bracket and the test wheel.

[0010] Preferably, the structure of the joint is set as an aluminum elbow rectangular pipe, and the structure of the cross beam is set as an aluminum rectangular pipe. The cross beam includes a first cross beam, a middle cross beam, and a tail cross beam; the joint includes a first joint, a middle joint, and a tail joint; the longitudinal beam is set as two parallel aluminum rectangular pipes, with a length of 1300 mm, a width of 50 mm, a height of 70 mm, and a thickness of 3 mm. There are 12 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the longitudinal beam for fixing the longitudinal beam and the bottom plate. There are also 2 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the longitudinal beam for fixing the longitudinal beam and the universal caster. There are 4 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the longitudinal beam for fixing the longitudinal beam and the first joint.

[0011] Preferably, the number of the first cross beam is set as one, with a length of 800 mm, a width of 50 mm, a height of 70 mm, and a thickness of 3 mm. The first cross beam is connected to one end of the two longitudinal beams through the first joint. There are 4 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the first cross beam for fixing the first cross beam and the universal caster. There are 8 positioning bolt holes with a diameter of 12 mm on both the left and right sides of the first cross beam for fixing the first cross beam and the towing frame joint.

[0012] Preferably, the number of the middle cross beams is set as 2, with a length of 700 mm, a width of 50 mm, a height of 70 mm, and a thickness of 3 mm. The 2 middle cross beams are arranged on the front and rear sides of the test wheel bracket and are connected to the two longitudinal beams through the first joint. There are 8 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the middle cross beam for fixing the middle cross beam to the longitudinal beam, the test wheel bracket, and the bottom plate.

[0013] Preferably, the number of the tail cross beam is set as one, with a length of 800 mm, a width of 50 mm, a height of 70 mm, and a thickness of 3 mm. The tail cross beam is connected to the two longitudinal beams through the tail joint. There are 4 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the tail cross beam for fixing the tail cross beam and the longitudinal beam.

[0014] Preferably, the number of the first joints is set as 2, with a thickness of 3 mm. The longitudinal beam is connected to the first cross beam through the first joint. There are 3 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the first joint for fixing the universal caster. There are 2 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the first joint for fixing the longitudinal beam. There are 4 positioning holes with a diameter of 12 mm on the front side of the first joint and 2 positioning holes with a diameter of 12 mm on the rear side of the first joint for fixing the first cross beam and the towing frame joint.

[0015] Preferably, the number of tail joints is set to 2, and the thickness is set to 3 mm, which are used to fix the longitudinal beam and the tail cross beam. There are 3 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the tail joint for fixing the universal caster wheels. There are 2 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the tail joint for fixing the longitudinal beam. There are 2 positioning holes with a diameter of 10 mm on the front and rear sides of the tail joint for fixing the tail cross beam.

[0016] Preferably, the length of the bottom plate is set to 1406 mm, the width is set to 806 mm, and the thickness is set to 3 mm. There are 16 through holes with a diameter of 14 mm on the bottom plate, and 4 through holes are fixed to the universal caster wheels by bolts. There are also 48 through holes with a diameter of 10 mm on the bottom plate, and 6 through holes are fixed to the middle joint by bolts.

[0017] Preferably, there are 2 through holes with a diameter of 25 mm at the head of the towing frame joint, through which it is connected to the towing frame. There are 2 positioning holes with a diameter of 25 mm at the head of the towing frame, through which it is connected to the draw head. There is a cylinder with a diameter of 25 mm at the head of the draw head, through which it is connected to the vehicle towing hook.

[0018] Preferably, a spring is provided on the outside of the connection between the middle part of the test wheel bracket and the test wheel mounting bracket. The test wheel mounting bracket is a centrosymmetric structure. The outer frame includes hollow rectangular aluminum tubes, and the inner frame includes four rib plates and a hollow cylinder. There are 2 positioning holes on the upper and lower surfaces of the hollow rectangular aluminum tubes respectively. A vertical bearing with an inner diameter of 30 mm and an outer diameter of 45 mm is installed between the test wheel mounting bracket and the test wheel. The test wheel has a diameter of 150 mm, a wheel width of 40 mm, and a mounting hole diameter of 15 mm.

[0019] Therefore, the present invention adopts the above-mentioned pavement spectrum test trailer device, determines the specific renovation objects and quantification indexes according to the built environment and the current situation of thermal comfort of specific cases, so as to improve the thermal comfort of the human body near the ground. The research results have improved the comprehensive and accurate observation and evaluation method system of the thermal environment in the use stage after the project is completed, and provided guidance and reference data for the optimization of thermal comfort in micro-scale outdoor spaces. This method has great practical potential and can provide valuable references for the research and application in related fields.

[0020] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Brief Description of the Drawings

[0021] Figure 1 It is a device diagram of a pavement spectrum test trailer device in the present invention;

[0022] Figure 2 It is a front view of a pavement spectrum test trailer device in the present invention;

[0023] Figure 3 It is the assembly drawing of the vehicle frame in the embodiment of the present invention;

[0024] Figure 4 It is the engineering drawing of the longitudinal beam in the embodiment of the present invention;

[0025] Figure 5 It is the engineering drawing of the first cross beam in the embodiment of the present invention;

[0026] Figure 6 It is the engineering drawing of the middle cross beam in the embodiment of the present invention;

[0027] Figure 7 It is the engineering drawing of the tail cross beam in the embodiment of the present invention;

[0028] Figure 8 It is the engineering drawing of the first joint in the embodiment of the present invention;

[0029] Figure 9 It is the engineering drawing of the middle joint in the embodiment of the present invention;

[0030] Figure 10 It is the engineering drawing of the tail joint in the embodiment of the present invention;

[0031] Figure 11 It is the engineering structure drawing of the bottom plate in the embodiment of the present invention;

[0032] Figure 12 It is the structure drawing of the traction device in the embodiment of the present invention;

[0033] Figure 13 It is the assembly drawing of the test wheel in the embodiment of the present invention;

[0034] Figure 14 It is the engineering drawing of the test wheel mounting bracket in the embodiment of the present invention;

[0035] Figure 15 It is the engineering drawing of the test wheel support in the embodiment of the present invention;

[0036] Figure 16 It is the flow chart of the test method for a pavement spectrum test trailer device in the embodiment of the present invention;

[0037] Reference numerals

[0038] 1. Test wheel mounting bracket; 2. Middle joint; 3. Middle crossbeam; 4. Longitudinal beam; 5. Traction frame joint; 6. First and last joint; 7. Bottom plate; 8. Tail joint; 9. Pull head; 10. Test wheel bracket; 11. Test wheel; 12. Caster bracket; 13. Universal caster; 14. Caster mounting shaft; 15. Spring; 16. Vertical bearing; 17. Traction frame connecting shaft; 18. Traction frame front connecting shaft; 19. Traction frame; 20. First crossbeam; 21. Tail crossbeam; 22. Acceleration sensor magnetic seat; 23. Bolt; 24. Photoelectric sensor bracket. Detailed implementation mode

[0039] The technical solution of the present invention will be further described below through the drawings and embodiments.

[0040] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those with ordinary skills in the field to which the present invention belongs.

[0041] The words such as "including" or "containing" used in the present invention mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements. The orientation or positional relationship indicated by terms such as "inside", "outside", "above", "below", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, terms such as "attached" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present invention can be understood according to specific circumstances.

[0042] Embodiment

[0043] As Figures 1 - 15 shown, a road surface spectrum test trailer device includes a vehicle frame, a traction device provided on one side of the vehicle frame, a traveling mechanism provided under the vehicle frame, and a test mechanism;

[0044] The vehicle frame includes a crossbeam, a longitudinal beam 4 provided on the bottom plate 7, and joints for connecting the crossbeam and the longitudinal beam 4;

[0045] The traction device includes a traction frame, a pull head 9 and a traction frame joint 5. The traction frame 19 is connected to the pull head 9 through the traction frame front connecting shaft 17, and the other end of the traction frame 19 is connected to the traction frame joint 5 through the traction frame connecting shaft 18;

[0046] The walking mechanism is four universal casters 13 with a tire diameter of 200 mm and a rated load of 1600 N. The universal casters 13 are arranged on the caster support 12 through caster mounting shafts 14;

[0047] The testing mechanism includes an acceleration sensor magnetic seat 22 arranged on the test wheel support 10. An acceleration sensor is arranged on the acceleration sensor magnetic seat 22. The bottom of the test wheel support 10 is connected to the test wheel 11. The middle part of the test wheel support 10 is connected to the test wheel mounting bracket 1. A vertical bearing 16 is arranged between the test wheel mounting bracket 1 and the test wheel 11.

[0048] The structure of the joint is set as an aluminum elbow rectangular pipe, and the structure of the cross beam is set as an aluminum rectangular pipe. The cross beam includes a head cross beam 20, a middle cross beam 3 and a tail cross beam 21. The joint includes a head joint 6, a middle joint 2 and a tail joint 8; The longitudinal beam 4 is set as two parallel aluminum rectangular pipes, with a length of 1300 mm, a width of 50 mm, a height of 70 mm and a thickness of 3 mm. There are 12 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the longitudinal beam 4 for fixing the longitudinal beam 4 and the bottom plate 7. There are also 2 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the longitudinal beam 4 for fixing the longitudinal beam 4 and the universal caster 13. There are 4 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the longitudinal beam 4 for fixing the longitudinal beam 4 and the head joint 6.

[0049] The number of the head cross beam 20 is set as one, with a length of 800 mm, a width of 50 mm, a height of 70 mm and a thickness of 3 mm. The head cross beam 20 is connected to one end of the two longitudinal beams 4 through the head joint 6. There are 4 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the head cross beam 20 for fixing the head cross beam 20 and the universal caster 13. There are 8 positioning bolt holes with a diameter of 12 mm on both the left and right sides of the head cross beam 20 for fixing the head cross beam 20 and the towing frame joint 5.

[0050] The number of the middle cross beams 3 is set as 2, with a length of 700 mm, a width of 50 mm, a height of 70 mm and a thickness of 3 mm. The 2 middle cross beams 3 are arranged on the front and rear sides of the test wheel support 10 and are connected to the two longitudinal beams 4 through the head joint 6. There are 8 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the middle cross beam 3 for fixing the middle cross beam 3 to the longitudinal beam 4, the test wheel support 10 and the bottom plate 7.

[0051] The number of the rear crossbeam 21 is set to 1, its length is set to 800 mm, width to 50 mm, height to 70 mm, and thickness to 3 mm. The rear crossbeam 21 is connected to two longitudinal beams 4 through the rear joint 8. There are 4 positioning bolt holes with a diameter of 10 mm on both the upper and lower sides of the rear crossbeam 21 for fixing the rear crossbeam 21 and the longitudinal beam 4.

[0052] The number of the first joints 6 is set to 2, and the thickness is set to 3 mm. The longitudinal beam 4 is connected to the first crossbeam 20 through the first joints 6. There are 3 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the first joints 6 for fixing the universal caster 13. There are 2 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the first joints 6 for fixing the longitudinal beam 4. There are 4 positioning holes with a diameter of 12 mm on the front side of the first joints 6, and 2 positioning holes with a diameter of 12 mm on the rear side of the first joints 6 for fixing the first crossbeam 6 and the towing frame joint 5.

[0053] The number of the rear joints 8 is set to 2, and the thickness is set to 3 mm for fixing the longitudinal beam 4 and the rear crossbeam 21. There are 3 positioning bolt holes with a diameter of 14 mm on both the upper and lower sides of the rear joints 8 for fixing the universal caster 13. There are 2 positioning bolt holes with a diameter of 10 mm on both the left and right sides of the rear joints 8 for fixing the longitudinal beam 4. There are 2 positioning holes with a diameter of 10 mm on the front and rear sides of the rear joints 8 for fixing the rear crossbeam 21.

[0054] The length of the bottom plate 7 is set to 1406 mm, width to 806 mm, and thickness to 3 mm. There are 16 through holes with a diameter of 14 mm on the bottom plate 7. 4 through holes are fixed to the universal caster 13 through bolts 23. There are also 48 through holes with a diameter of 10 mm on the bottom plate 7. 6 through holes are fixed to the middle joint 2 through bolts 23.

[0055] There are 2 through holes with a diameter of 25 mm at the head of the towing frame joint 5, through which it is connected to the towing frame. There are 2 positioning holes with a diameter of 25 mm at the head of the towing frame, through which it is connected to the pull head 9. There is a cylinder with a diameter of 25 mm at the head of the pull head 9, through which it is connected to the vehicle towing hook.

[0056] There is a photoelectric sensor bracket 24 on the test wheel bracket 10. There is a spring 15 on the outside of the connection between the middle part of the test wheel bracket 10 and the test wheel mounting bracket 1. The test wheel mounting bracket 1 is a centrosymmetric structure. The outer frame includes hollow rectangular aluminum tubes, and the inner frame includes four rib plates and a hollow cylinder. There are 2 positioning holes on the upper and lower surfaces of the hollow rectangular aluminum tube respectively. A vertical bearing 16 with an inner diameter of 30 mm and an outer diameter of 45 mm is installed between the test wheel mounting bracket 1 and the test wheel 11. The diameter of the test wheel 11 is 150 mm, the wheel width is 40 mm, and the mounting hole diameter is 15 mm.

[0057] Working principle: The road surface spectrum test trailer is connected to the tractor through a traction device, and the traction force is provided by the towing trailer. A spring is installed between the test wheel and the test wheel mounting bracket to keep the test wheel tire in constant contact with the road surface to ensure the accuracy of the road surface spectrum test. An acceleration sensor and a speed sensor are installed on the test wheel bracket to collect the longitudinal acceleration signal of the test wheel and the driving speed signal of the trailer.

[0058] As Figure 16 shown, a test method for a road surface spectrum test trailer device specifically includes the following steps:

[0059] S1: Determine that the test vehicle speed v of the trailer is 5 - 30 km / h, and the sampling frequency fs of the triaxial acceleration sensor installed at the center of gravity position of the trailer body is ≥200 Hz;

[0060] S2: Use different types of trailers to drive on roads with different road surface flatnesses, and use the gravity acceleration sensor to collect the acceleration value a(t) at the center of gravity position of the trailer body. Preprocess the acceleration value, specifically including using a digital filtering method to remove interference factors such as noise and zero drift;

[0061] S3: Use a fourth-order Butterworth band-pass filter (cutoff frequency 0.1 - 50 Hz, passband ripple ≤0.5 dB to remove noise) to remove noise

[0062] It is used to calculate the power spectral density of the signal (F(t)), which is an important formula in the field of signal processing. Where T is the time interval, F(t) is a function of time t, ω is the angular frequency, and j is the imaginary unit.

[0063] S4: Perform a Fourier transform on the preprocessed acceleration signal a(t) to obtain the frequency-domain representation A(f) of the acceleration signal. The calculation formula is where f is the frequency and j is the imaginary unit.

[0064] S5: In the Welch method, the number of segments M ≥ 10, and the overlap rate is 50%;

[0065] S6: Use linear regression or nonlinear regression method to establish a fitting model between the power spectrum density Sa(f) of the same type of trailer and the road surface spectrum index, and calculate the power spectrum density Sa(f) of the acceleration signal using the periodogram method or the Welch method;

[0066] Taking the periodogram method as an example, the calculation formula for power spectral density is: Where T is the sampling time length of the signal;

[0067] The power spectrum density (S a (f) The fitting model of the road surface spectrum index (such as road surface roughness coefficient, etc.) can be fitted by linear regression, nonlinear regression and other methods. Assume that the fitting model is: (

[0068] Among them, Y is the road spectrum index, β0,β1,…,β n is the fitting coefficient.

[0069] S7: Conduct a suitability test on the fitting model of the power spectrum density and road spectrum index of different types of trailers, using statistical test methods such as F test or t test;

[0070] S8: Eliminate the influence of different types of trailers on the fitting model and obtain a universal fitting model of power spectrum density and road spectrum index. The specific method is as follows:

[0071] Calculate the average power spectral density S when the trailer is stationary a0 (f), using the average power spectrum density value S when the trailer is traveling a1 (f) minus the average power spectral density S at rest a0 (f), and the power spectrum density (S(f)=S a1 (f)-S a0 (f);

[0072] The general fitting model is:

[0073] Y=α0+α1S(f)+α2S 2 (f)+…+α n S n (f)

[0074] Among them, (α0,α1,…,α n ) is the general fitting coefficient;

[0075] The universal fitting model and the collected acceleration signal are used to reconstruct the road surface spectrum through inverse Fourier transform. The calculation formula of inverse Fourier transform is:

[0076] Among them, A(f) is calculated according to the general fitting model and the power spectral density S(f). After obtaining the time-domain representation a(t) of the acceleration signal through inverse Fourier transform, the acceleration signal is further converted into road surface spectrum information according to the vehicle dynamics model and related theories.

[0077] S9: Based on the vehicle frequency response function H(f) = 1 / (1+(f / f0) 4 )(f0 = 2Hz), reconstruct the road surface elevation. According to the reconstructed road surface spectrum information, evaluate and analyze the characteristics of the road surface such as flatness and roughness.

[0078] A test system for a road surface spectrum test trailer device includes an acceleration sensor, a data acquisition module, a signal processing module, a model establishment module, an inverse Fourier transform module, an evaluation and analysis module, a cloud server module, and a machine learning module;

[0079] The acceleration sensor is installed at the center of gravity position of the trailer body and is used to collect the acceleration value of the trailer during driving;

[0080] The data acquisition module is connected to the acceleration sensor and is used to collect and store the acceleration signal output by the acceleration sensor;

[0081] The signal processing module is connected to the data acquisition module and is used to preprocess, perform Fourier transform, calculate power spectral density, etc. on the collected acceleration signal, and preprocess the collected acceleration signal using digital filtering methods;

[0082] The model establishment module is used to establish a fitting model between the power spectral density and the road surface spectrum index, perform applicability tests and eliminate the influence of vehicle models, and obtain a general fitting model;

[0083] The inverse Fourier transform module performs inverse Fourier transform according to the general fitting model and the collected acceleration signal to reconstruct the road surface spectrum;

[0084] The evaluation and analysis module evaluates and analyzes the characteristics of the road surface such as flatness and roughness according to the reconstructed road surface spectrum information.

[0085] The cloud server module is used to store multi-vehicle calibration data and update the general fitting model in real time;

[0086] The machine learning module optimizes the frequency response function parameters based on historical data.

[0087] The main design indicators of the road surface spectrum test trailer are as follows.

[0088] (1) The height of the road surface spectrum test trailer frame from the ground is 514 mm, the width of the frame is 806 mm, and the length is 1406 mm.

[0089] (2) The spring in the test wheel mechanism should have a certain preload force, the size of which should be sufficient to keep the test wheel in constant contact with the ground and prevent it from coming off the ground due to the trailer bouncing during travel.

[0090] (3) The maximum test speed of the trailer is designed to be no more than 30 km / h.

[0091] (4) Recommended range of accelerometer: -50g-50g.

[0092] (5) A photoelectric speed sensor can be installed on the test wheel bracket.

[0093] When the installation position of other components conflicts with the test wheel mechanism, you should first ensure that the test wheel mechanism is located in the center of the vehicle body to ensure the accuracy of the test wheel mechanism's measurement data.

[0094] Example 1

[0095] Body frame: It is made of welded aluminum alloy rectangular tubes. The body size is 1406mm long, 806mm wide and 514mm high, ensuring lightweight and structural strength.

[0096] Testing agency:

[0097] The test wheel (150 mm in diameter, 40 mm in wheel width) is connected to the test wheel stand via a vertical bearing (30 mm in inner diameter, 45 mm in outer diameter), allowing for free up and down movement.

[0098] A preload spring is installed between the test wheel and the bracket. The spring stiffness is designed according to the weight of the trailer to ensure that the test wheel always contacts the road surface.

[0099] Install the accelerometer:

[0100] The triaxial accelerometer (range ±50g) is fixed to the magnetic base on the top of the test wheel bracket to collect the vertical acceleration signal a z (t).

[0101] The triaxial acceleration sensor is located at the center of gravity of the trailer and is rigidly connected to the frame longitudinal beam by bolts to ensure signal accuracy.

[0102] Data acquisition and transmission module:

[0103] Data acquisition unit: integrated high-precision AD converter (sampling frequency f s ≥200Hz), connected to the acceleration sensor through a shielded cable, real-time acquisition of a z (t).

[0104] GPS module: records the trailer's location and speed v, and stores the data synchronously in the vehicle's memory.

[0105] Wireless communication module: Transmits the original data to a remote server or a mobile terminal.

[0106] Data processing terminal:

[0107] Configures a high-performance embedded processor to run signal processing algorithms, including filtering, Fourier transform, power spectral density calculation, etc.

[0108] Signal processing and road surface spectrum reconstruction process:

[0109] Step 1: Signal acquisition and preprocessing

[0110] Acceleration signal acquisition: The semi-trailer travels at a test vehicle speed v ≤ 30 km / h, and the sensor samples the vertical acceleration a s (t) at the sampling frequency f z (t).

[0111] Digital filtering: A band-pass filter (cutoff frequency 0.1 Hz - 50 Hz) is used to remove high-frequency noise and zero drift, and the preprocessed signal is denoted as a(t).

[0112] During the road surface spectrum measurement process, the part greater than 50 Hz is excluded. There are mainly reasons such as measurement principle limitations, actual road surface characteristics, equipment limitations, and data analysis requirements. The following is a specific introduction:

[0113] For sensors used in road surface spectrum measurement, such as acceleration sensors, etc., they all have their specific frequency response ranges. Generally speaking, in the low-frequency band, the sensor can measure and reflect the actual road surface conditions more accurately, but as the frequency increases, the response of the sensor may deviate or distort. When the frequency is greater than 50 Hz, the sensor may not be able to measure accurately, and the data obtained may have large errors and cannot truly reflect the actual situation of the road surface, so this part of the data needs to be excluded.

[0114] Some road surface spectrum measurement methods are based on continuous sampling and analysis of road surface flatness and other characteristics. In actual operation, due to factors such as sampling frequency and measurement time interval limitations, the measurement of the high-frequency part may not reach sufficient accuracy. For example, if the sampling frequency is low, according to the Nyquist sampling theorem, for signals above a certain frequency (such as 50 Hz), spectral aliasing may occur, resulting in inaccurate measurement results. Therefore, the high-frequency part needs to be excluded to avoid the influence of incorrect data.

[0115] The excitation generated by road surface unevenness and other factors on the vehicle is mainly of low-frequency characteristics. During the vehicle's driving process, the interaction with the road surface is mainly reflected in the long-wavelength road surface undulations and other situations. The vibration and excitation frequencies caused by these factors are relatively low, usually below 50Hz. The high-frequency components above 50Hz account for a very small proportion in the actual excitation of the road surface on the vehicle, and the impact on the study of the relationship between the road surface spectrum and vehicle response can be ignored. Therefore, in order to highlight the main road surface characteristics and excitation factors, the part above 50Hz will be removed.

[0116] The materials and structures of the road surface itself have certain filtering characteristics. For example, asphalt road surfaces or cement road surfaces, etc., have a certain attenuation effect on high-frequency vibrations and excitations, making the actual high-frequency components that can be transmitted and measured very weak. From this perspective, the part above 50Hz has little significance in the mechanical transmission and performance of the actual road surface. Removing this part of the data can reduce unnecessary interference.

[0117] When analyzing road surface spectrum data, the main focus is on the low-frequency information that can reflect the main characteristics of the road surface flatness, roughness, etc. The high-frequency part above 50Hz often contains some random noises and tiny fluctuations that are insignificant for the overall assessment of the road surface condition. Removing this part can make the data analysis more focused on the key road surface characteristic parameters and improve the accuracy and efficiency of the analysis.

[0118] Many models and algorithms for road surface spectrum analysis are based on low-frequency assumptions or designed for low-frequency characteristics. For example, some statistical models of road surface unevenness and vehicle dynamics models have good accuracy and applicability when dealing with low-frequency signals, while they may not be able to handle or interpret high-frequency signals well. In order to make the measured data match these models and algorithms for subsequent calculations and analyses, the part above 50Hz is usually removed.

[0119] During the road surface spectrum measurement process, environmental factors and the measurement equipment itself will introduce noises. Such as the driving noises of surrounding vehicles, the electronic noises of the measurement equipment, etc. These noises usually have relatively high-frequency components and may cover up the true road surface spectrum signal. When the frequency is greater than 50Hz, the influence of the noise may be more significant. In order to obtain pure road surface spectrum data, removing this part of high-frequency noise can improve the quality and reliability of the data. During the road surface spectrum measurement process, there are usually the following special processing requirements for the part below 50Hz.

[0120] Although mainly the part above 50Hz is removed, for the part below 50Hz, low-pass filtering optimization adjustments may also be required. For example, according to the specific measurement equipment and road surface characteristics, select a low-pass filter with a suitable cut-off frequency around 30Hz - 40Hz to further filter out the relatively high-frequency noises that may exist and have a small impact on the measurement results, making the measurement signal purer.

[0121] To prevent aliasing during subsequent data processing and sampling, it is necessary to ensure that signals below 50 Hz are effectively anti-aliased filtered so that the signals meet the requirements of the sampling theorem and ensure that the spectrum of the sampled signal can truly reflect the spectrum of the original signal.

[0122] Step 2: Fourier transform and power spectral density calculation

[0123] Frequency domain conversion: The discrete Fourier transform (DFT) is performed on a(t) to obtain the frequency domain signal A(f):

[0124] where Δt = 1 / f s , and N is the number of sampling points.

[0125] Power spectral density (PSD) calculation: The Welch method is used for segment averaging, and the calculation formula is:

[0126]

[0127] where w(n) is the Hanning window function, L is the segment length, and M is the number of segments.

[0128] Step 3: Establish a general fitting model *

[0129] Static reference calibration: Measure the background noise power spectrum S a0 (f) when the trailer is stationary.

[0130] Dynamic signal correction: Subtract the static reference from the power spectrum S a1 (f) during driving to obtain the effective power spectrum S(f) S(f) = S a1 (f) - S a0 (f)

[0131] Model fitting: Use non-linear regression to establish the mapping relationship between S(f) and the road surface unevenness coefficient IRI:

[0132] IRI = α0 + α1S(f) + α2S 2 (f) where the coefficients α0, α1, α2 are determined through calibration experiments.

[0133] Step 4: Inverse Fourier transform and road surface spectrum reconstruction

[0134] Frequency domain to road surface spectrum conversion: Based on the corrected power spectrum S(f), generate the road surface elevation time domain signal h(t) through inverse Fourier transform: where H(f) is the vehicle system frequency response function, which is determined by the trailer dynamics model.

[0135] Step 5: Road surface characteristic evaluation

[0136] Roughness analysis: Calculate the International Roughness Index (IRI) and the power spectral density level according to h(t).

[0137] Roughness classification: Classify the road surface grades (grades A - E) according to the ISO8608 standard.

[0138] Conduct an applicability test on the fitting model of the power spectral density of the same type of trailer and the road surface spectral index. Use the F - test and t - test methods to test the significance and goodness of fit of the model. In MATLAB, the regstats function can be used for regression analysis and testing.

[0139] In the stationary state, collect the acceleration signal for a period of time (such as 30s), and perform signal pre - processing, Fourier transform, and power spectral density calculation according to the above steps to obtain the average power spectral density S a0 (f) of the trailer when it is stationary.

[0140] Process the acceleration signal collected during the vehicle's driving to obtain the average power spectral density S a1 (f) during driving.

[0141] Use the formula S(f) = S a1 (f) - S a0 (f) to calculate the general power spectral density.

[0142] Substitute the general power spectral density S(f) into the fitting model and refit to obtain the general fitting model of the power spectral density and the road surface spectral index.

[0143] According to the general fitting model and the collected acceleration signal, reconstruct the road surface spectrum through inverse Fourier transform. In MATLAB, the ifft function can be used to implement the inverse Fourier transform.

[0144] After obtaining the time - domain representation a(t) of the acceleration signal through inverse Fourier transform, further convert the acceleration signal into road surface spectrum information according to the vehicle dynamics model and relevant theories.

[0145] Therefore, the present invention adopts the above - mentioned road surface spectrum test trailer device, evaluates and analyzes the characteristics such as the flatness and roughness of the road surface according to the reconstructed road surface spectrum information, compares the reconstructed road surface spectrum information with the results measured by professional road surface detection equipment to verify the effectiveness and accuracy of this method. At the same time, according to the evaluation and analysis results, provide a basis for road construction, maintenance, and vehicle driving performance evaluation.

[0146] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements do not cause the modified technical solutions to depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A road spectrum test trailer device, characterized in that: It includes a vehicle frame, a traction device arranged on one side of the vehicle frame, a traveling mechanism and a testing mechanism arranged under the vehicle frame; The vehicle frame includes a crossbeam, a longitudinal beam and a joint for connecting the crossbeam and the longitudinal beam arranged on the bottom plate; The traction device includes a traction frame, a pulling head and a traction frame joint. The traction frame and the pulling head are connected through a front connecting shaft of the traction frame, and the other end of the traction frame is connected to the traction frame joint through a traction frame connecting shaft. The traveling mechanism consists of four swivel casters with a tire diameter of 200mm and a rated load of 1600N; The testing mechanism includes an acceleration sensor magnetic base arranged on a test wheel bracket, an acceleration sensor is arranged on the acceleration sensor magnetic base, the bottom of the test wheel bracket is connected to the test wheel, the middle part of the test wheel bracket is connected to the test wheel mounting bracket, and a vertical bearing is arranged between the test wheel mounting bracket and the test wheel.

2. The road spectrum test trailer device according to claim 1, characterized in that: The structure of the joint is set as an aluminum elbow rectangular tube, the structure of the crossbeam is set as an aluminum rectangular tube, the crossbeam includes a first crossbeam, a middle crossbeam and a tail crossbeam, and the joint includes a first joint, a middle joint and a tail joint; the longitudinal beam is set as two parallel aluminum rectangular tubes with a length of 1300mm, a width of 50mm, a height of 70mm and a thickness of 3mm. There are 12 positioning bolt holes with a diameter of 10mm on the upper and lower sides of the longitudinal beam for fixing the longitudinal beam and the base plate. There are also 2 positioning bolt holes with a diameter of 14mm on the upper and lower sides of the longitudinal beam for fixing the longitudinal beam and the universal caster. There are 4 positioning bolt holes with a diameter of 10mm on the left and right sides of the longitudinal beam for fixing the longitudinal beam and the first joint.

3. The road spectrum test trailer device according to claim 2, characterized in that: The number of the first crossbeam is set to one, the length is set to 800mm, the width is set to 50mm, the height is set to 70mm, and the thickness is set to 3mm. The first crossbeam is connected to one end of the two longitudinal beams through the first joint. There are 4 positioning bolt holes with a diameter of 14mm on the upper and lower sides of the first crossbeam for fixing the first crossbeam and the universal caster. There are 8 positioning bolt holes with a diameter of 12mm on the left and right sides of the first crossbeam for fixing the first crossbeam and the traction frame joint.

4. The road spectrum test trailer device according to claim 2, characterized in that: The number of median cross beams is set to 2, the length is set to 700mm, the width is set to 50mm, the height is set to 70mm, and the thickness is set to 3mm. The two median cross beams are set on the front and rear sides of the test wheel bracket and connected to the two longitudinal beams through the first joint. There are 8 positioning bolt holes with a diameter of 10mm on the upper and lower sides of the median cross beam for fixing the median cross beam to the longitudinal beam, the test wheel bracket and the base plate.

5. The road spectrum test trailer device according to claim 2, characterized in that: The number of tail cross beams is set to 1, the length is set to 800mm, the width is set to 50mm, the height is set to 70mm, and the thickness is set to 3mm. The tail cross beam is connected to the two longitudinal beams through the tail joint. There are 4 positioning bolt holes with a diameter of 10mm on the upper and lower sides of the tail cross beam for fixing the tail cross beam and the longitudinal beam.

6. The road spectrum testing trailer device according to claim 2, characterized in that: The number of the first joints is set to 2, and the thickness is set to 3mm. The longitudinal beam is connected to the first crossbeam through the first joint. There are 3 positioning bolt holes with a diameter of 14mm on the upper and lower sides of the first joint for fixing the universal casters. There are 2 positioning bolt holes with a diameter of 10mm on the left and right sides of the first joint for fixing the longitudinal beam. There are 4 positioning holes with a diameter of 12mm on the front side of the first joint, and 2 positioning holes with a diameter of 12mm on the rear side of the first joint for fixing the first crossbeam and the traction frame joint.

7. The road spectrum testing trailer device according to claim 2, characterized in that: The number of tail joints is set to 2, and the thickness is set to 3mm, which is used to fix the longitudinal beam and the tail crossbeam. Three positioning bolt holes with a diameter of 14mm are set on the upper and lower sides of the tail joint for fixing the universal casters. Two positioning bolt holes with a diameter of 10mm are set on the left and right sides of the tail joint for fixing the longitudinal beam. Two positioning holes with a diameter of 10mm are set on the front and rear sides of the tail joint for fixing the tail crossbeam.

8. The road spectrum testing trailer device according to claim 1, characterized in that: The length of the base plate is set to 1406mm, the width is set to 806mm, and the thickness is set to 3mm. There are 16 through holes with a diameter of 14mm on the base plate, 4 of which are fixed to the universal casters with bolts. There are also 48 through holes with a diameter of 10mm on the base plate, 6 of which are fixed to the center joint with bolts.

9. The road spectrum testing trailer device according to claim 1, characterized in that: The head of the traction frame joint is provided with two through holes with a diameter of 25mm, which are connected to the traction frame through the through holes. The head of the traction frame is provided with two positioning holes with a diameter of 25mm, which are connected to the pulling head through the positioning holes. The head of the pulling head is provided with a cylinder with a diameter of 25mm, which is connected to the vehicle towing hook through the cylinder.

10. The road spectrum testing trailer device according to claim 1, characterized in that: A spring is provided on the outside of the connection between the middle part of the test wheel bracket and the test wheel mounting bracket. The test wheel mounting bracket is a centrally symmetrical structure. The external frame includes a hollow rectangular aluminum tube, and the internal frame includes four ribs and a hollow cylinder. Two positioning holes are respectively provided on the upper and lower surfaces of the hollow rectangular aluminum tube. A vertical bearing with an inner diameter of 30mm and an outer diameter of 45mm is installed between the test wheel mounting bracket and the test wheel. The test wheel has a diameter of 150mm, a wheel width of 40mm, and a mounting hole diameter of 15mm.

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