Braking performance detector for agricultural machinery based on Beidou satellite single point positioning mode

Abstract

The application discloses a farm machine braking performance detector based on a Beidou satellite single point positioning mode, and belongs to the technical field of braking performance detection. The signal collector is internally provided with a satellite signal receiving module compatible with BDS and GPS, and the host is internally provided with a sequence parameter extraction module, an integral distance measurement module, an error correction module, a slope solution module and a performance evaluation module. Through the collection of three-dimensional motion data of the measured farm machine, the uncorrected braking distance is calculated by using the complex Simpson integral algorithm, the error correction distance caused by the single point positioning signal drift is obtained based on the back propagation neural network, and the farm machine braking distance is solved in combination with the slope correction value, so that the braking performance qualification condition of the measured farm machine is finally determined. The application does not need to erect a ground differential reference station and external supporting components, solves the problem of complicated field detection deployment, eliminates signal drift and road slope interference, and improves detection convenience and accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of brake performance detection, and particularly relates to a farm machine brake performance detector based on a Beidou satellite single-point positioning mode. BACKGROUND

[0002] The farm machine brake performance detector is a special measurement test equipment specially used for measuring the brake system efficiency of various agricultural machines such as tractors and combine harvesters. The brake performance is listed as a core index of the farm machine safety technical inspection by the agricultural machinery safety supervision and management department, aiming to ensure the brake safety of the farm machine during road driving and field operation. The main function of the farm machine brake performance detector is to collect various kinematic parameters such as the initial speed, brake time and brake distance of the farm machine during braking, and to determine the qualified condition of the brake performance according to the relevant national standards. In the prior art, the brake performance detection mainly relies on a contact type five-wheel detector, a non-contact type photoelectric sensor and a satellite navigation positioning system. The satellite navigation positioning system can solve the speed and displacement information of the measured farm machine in real time by receiving space satellite signals, and provides a technical basis for the automatic and digital detection of the farm machine brake performance, and becomes an important technical means for the annual inspection and road inspection of the current farm machine safety supervision organization.

[0003] In order to solve the problem of difficult acquisition of high-precision brake parameters in the non-structured road environment in the wild, the prior art adopts a laser Doppler sensing measurement and real-time dynamic carrier phase difference positioning technology. However, the laser sensing measurement equipment needs to be erected with an external support component and strictly aligned with the optical path, and the real-time dynamic carrier phase difference positioning technology depends on the field layout of the ground difference reference station, thereby causing problems of complicated detection equipment installation and deployment process, insufficient overall carrying convenience and low field flow detection efficiency. SUMMARY

[0004] The application aims to provide a farm machine brake performance detector based on a Beidou satellite single-point positioning mode, which does not need to erect a ground difference reference station and an external support component, solves the problem of complicated field detection deployment, eliminates signal drift and road slope interference, and improves detection convenience and accuracy.

[0005] To solve the above technical problems, the technical solution adopted by the application is as follows:

[0006] The farm machine brake performance detector based on the Beidou satellite single-point positioning mode comprises a signal collector and a host computer. The signal collector is internally provided with a satellite signal receiving module compatible with the Beidou satellite navigation system and the global positioning system. The host computer is internally provided with:

[0007] The sequence parameter extraction module is configured to collect and pre-process three-dimensional motion data of the agricultural machine under test, generate smooth horizontal velocity sequences and smooth vertical velocity sequences, and obtain effective horizontal velocity sequence segments, effective vertical velocity sequence segments, steady-state velocity variance, braking initial velocity, and braking duration.

[0008] The integral distance measurement module is configured to perform time integration on the effective horizontal velocity sequence segments by using a complex Simpson integral algorithm to obtain an uncorrected braking distance.

[0009] The error correction module is configured to obtain an error correction distance caused by single-point positioning signal drift by using a back propagation neural network based on the steady-state velocity variance and the braking duration.

[0010] The slope calculation module is configured to calculate a slope correction value based on the effective horizontal velocity sequence segments and the effective vertical velocity sequence segments, and calculate the agricultural machine braking distance by combining the uncorrected braking distance and the error correction distance.

[0011] The performance evaluation module is configured to retrieve standard limits in a standard database according to the braking initial velocity, compare the standard limits with the agricultural machine braking distance, judge whether the braking performance is qualified, and take corresponding measures.

[0012] Preferably, the signal collector is of a magnetic type, including a shell and a magnetic base arranged at the bottom of the shell, and a satellite signal receiving module is packaged in the shell. The main machine is handheld, including a processor, a memory, a power module, a touch display screen, and a buzzer. The processor is electrically connected with the memory, the power module, the touch display screen, and the buzzer, and is used to run the sequence parameter extraction module, the integral distance measurement module, the error correction module, the slope calculation module, and the performance evaluation module.

[0013] Preferably, in the sequence parameter extraction module, the process of collecting the three-dimensional motion data of the agricultural machine under test includes:

[0014] The signal collector is fixed by the magnetic base arranged at the bottom to the geometric center position on the top of the cab of the agricultural machine under test, the antenna posture is adjusted to ensure that the antenna gain direction of the satellite signal receiving module is vertically oriented to the sky, and there is no metal cover around;

[0015] The handheld main machine is placed in the cab of the agricultural machine under test, and a data transmission channel is established with the signal collector in one of the wired data cable or wireless communication link;

[0016] The system power is started, and the satellite signal receiving module compatible with the Beidou satellite navigation system and the global positioning system in the signal collector automatically searches and locks the radio frequency signals of visible satellites. When the number of locked visible satellites meets the positioning calculation requirements, the measurement is ready.

[0017] Three-dimensional motion data includes time series data, horizontal Doppler velocity series data, and vertical Doppler velocity series data;

[0018] The satellite signal receiving module receives radio frequency signals from visible satellites, demodulates the radio frequency signals to obtain satellite navigation messages, extracts satellite ephemeris data and time information of the current sampling time from the satellite navigation messages, measures the Doppler frequency shift value and carrier-to-noise ratio of the carrier signal in the radio frequency signal, constructs a velocity observation equation based on the Doppler frequency shift principle and combined with satellite ephemeris data, and calculates the three-dimensional velocity vector of the signal acquisition device in the geocentric-ground-fixed coordinate system.

[0019] The three-dimensional velocity vector in the geocentric-fixed coordinate system is projected and transformed to the local tangent plane coordinate system, and the eastward velocity component, the northward velocity component, and the celestial velocity component are decomposed.

[0020] Based on the eastward and northward velocity components, the Pythagorean theorem is used to calculate the horizontal Doppler velocity data, and the celestial velocity component is directly used as the vertical Doppler velocity data.

[0021] The sequence parameter extraction module collects time information, horizontal Doppler velocity data, vertical Doppler velocity data, and carrier-to-noise ratio in real time through the data transmission channel according to the set sampling frequency, and constructs and outputs three-dimensional motion data.

[0022] Preferably, in the sequence parameter extraction module, the process of generating smooth horizontal velocity sequences and smooth vertical velocity sequences includes:

[0023] The time length of the sliding filter window is set based on the carrier-to-noise ratio in the 3D motion data. When the carrier-to-noise ratio is lower than the preset threshold, the time length is increased.

[0024] For horizontal and vertical Doppler velocity sequence data in 3D motion data, data processing queues corresponding to time lengths are constructed respectively.

[0025] Arrange the speed values ​​in the data processing queue in ascending order, and select the value in the middle position as the filtered speed value at the center of the sliding filter window.

[0026] The sliding filter window is moved point by point according to the sampling time interval to traverse the entire horizontal Doppler velocity sequence data and the vertical Doppler velocity sequence data, remove outlier noise points, and generate smooth horizontal velocity sequence and smooth vertical velocity sequence respectively.

[0027] Preferably, in the sequence parameter extraction module, the process of obtaining the effective horizontal velocity sequence segment, the effective vertical velocity sequence segment, the steady-state velocity variance, the initial braking velocity, and the braking duration includes:

[0028] A negative braking trigger acceleration threshold is set. When the instantaneous acceleration feature values ​​of three consecutive sampling times are all less than the braking trigger acceleration threshold, the first sampling time in the corresponding instantaneous acceleration feature sequence is marked as the braking start time.

[0029] Set a stopping speed threshold. When the value of the smoothed horizontal speed sequence is continuously less than the stopping speed threshold, mark the first sampling time corresponding to that time as the vehicle stopping time.

[0030] Based on the determined braking start time and vehicle stopping time, data within the corresponding time period is extracted from the smooth horizontal velocity sequence to generate a valid horizontal velocity sequence segment. Simultaneously, data within the same time period is extracted from the smooth vertical velocity sequence to generate a valid vertical velocity sequence segment.

[0031] The instantaneous acceleration characteristic sequence of the agricultural machinery is obtained by performing a first-order difference operation on the smoothed horizontal velocity values ​​at adjacent sampling times in the effective horizontal velocity sequence segment.

[0032] Before the braking start time, the data of the smoothed horizontal velocity sequence within a preset steady-state time window is extracted, and the variance of the smoothed horizontal velocity sequence data within the steady-state time window is calculated as the steady-state velocity variance before braking.

[0033] Read the values ​​of the smooth horizontal velocity sequence at the moment of braking start and mark the values ​​as the initial braking velocities;

[0034] Calculate the time difference between the moment the vehicle stops and the moment braking begins, and record the time difference as the braking duration.

[0035] Preferably, in the integral ranging module, the process of using the complex Simpson integral algorithm to perform time integration on the effective horizontal velocity sequence segment to obtain the uncorrected braking distance includes:

[0036] The integral ranging module receives a valid horizontal velocity sequence segment output by the sequence parameter extraction module. The valid horizontal velocity sequence segment contains smoothed horizontal velocity values ​​at each sampling time from the start of braking to the time the vehicle stops.

[0037] Obtain the total length of the effective horizontal velocity sequence segment and the time interval between adjacent sampling points. If the total length of the sequence is even, discard the last data point of the sequence.

[0038] The smoothed horizontal velocity values ​​of the first and last data points of the processed effective horizontal velocity sequence segment are added together as boundary terms.

[0039] Extract the data points at each odd-indexed position in the sequence, calculate the sum of the smoothed horizontal velocity values ​​of each odd-indexed data point and multiply it by a coefficient of 4, and use it as the weighted sum of the odd-numbered terms;

[0040] Extract the data points at each even-indexed position after removing the first and last data points from the sequence, calculate the sum of the smooth horizontal velocity values ​​of each even-indexed data point and multiply it by a coefficient of 2, and use it as the weighted sum of the even-numbered terms.

[0041] The weighted sums of boundary terms, odd-numbered terms, and even-numbered terms are added together to obtain the total weighted velocity sum. The total weighted velocity sum is then multiplied by one-third of the sampling time interval to calculate the uncorrected braking distance.

[0042] Preferably, in the error correction module, the process of obtaining the error correction distance caused by the drift of the single-point positioning signal based on the steady-state velocity variance and braking duration using a backpropagation neural network includes:

[0043] The error correction module uses a pre-trained backpropagation neural network for calculation, and receives the steady-state velocity variance and braking duration output by the sequence parameter extraction module. The backpropagation neural network adopts a three-layer fully connected topology, which includes an input layer, a hidden layer and an output layer with neurons.

[0044] Construct an input layer vector corresponding to the input layer, and map the steady-state velocity variance and braking duration to the first and second components of the input layer vector, respectively.

[0045] The input layer vector is input into the hidden layer, multiplied by the weight matrix of the hidden layer, and then the bias vector is added to calculate the net input vector of the hidden layer.

[0046] The output vector of the hidden layer is obtained by performing an element-wise transformation on the net input vector using a nonlinear activation function.

[0047] The output vector of the hidden layer is input to the output layer, multiplied by the connection weight vector from the hidden layer to the output layer, and then the bias value of the output layer is added to calculate the error correction distance caused by the drift of the single-point positioning signal.

[0048] Preferably, in the slope calculation module, the process of calculating the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment includes:

[0049] The slope calculation module receives the effective horizontal velocity sequence fragment and the effective vertical velocity sequence fragment output by the sequence parameter extraction module;

[0050] Calculate the arithmetic mean of the smoothed horizontal velocity values ​​at each sampling point in the effective horizontal velocity sequence segment to obtain the horizontal average velocity during the braking process. Calculate the arithmetic mean of the smoothed vertical velocity values ​​at each sampling point in the effective vertical velocity sequence segment to obtain the vertical average velocity during the braking process.

[0051] The ratio of the vertical average velocity to the horizontal average velocity is calculated using the arctangent function, thus obtaining the average slope angle during braking.

[0052] The slope calculation module receives the uncorrected braking distance output by the integral distance measuring module, and based on the principle of energy conservation, uses the average slope angle to calculate the impact of the change in gravitational potential energy caused by the slope on the braking distance of the agricultural machinery, thus obtaining the slope correction value.

[0053] Preferably, in the slope calculation module, the process of calculating the braking distance of the agricultural machinery by combining the uncorrected braking distance and the error-corrected distance includes:

[0054] The slope calculation module receives the error correction distance output by the error correction module;

[0055] The final braking distance of the agricultural machine is calculated by subtracting the error correction distance from the uncorrected braking distance and adding the slope correction value.

[0056] Preferably, in the performance evaluation module, the process of retrieving standard limits from the standard database based on the initial braking speed, comparing them with the braking distance of the agricultural machine, determining the compliance of braking performance, and taking corresponding measures includes:

[0057] The performance evaluation module receives the initial braking velocity output by the sequence parameter extraction module;

[0058] In the preset standard database, a table lookup is performed based on the initial braking speed. The standard database stores the standard limit values ​​of braking distance corresponding to different initial speed ranges.

[0059] Match the speed range containing the initial braking velocity, and extract the standard limit value corresponding to the speed range as the current judgment benchmark;

[0060] The performance evaluation module receives the farm machinery braking distance output by the slope calculation module;

[0061] Compare the driving distance of agricultural machinery with the standard limit numerically;

[0062] If the braking distance of the agricultural machine is less than or equal to the standard limit, the braking performance of the tested agricultural machine is deemed qualified, and a qualified instruction is generated. The touch screen of the drive host displays a green qualified mark, and the speed-time change curve of the braking process is plotted and displayed on the screen with time as the horizontal axis and smooth horizontal speed as the vertical axis.

[0063] If the braking distance of the agricultural machine exceeds the standard limit, the braking performance of the tested agricultural machine is deemed unqualified, and an unqualified warning command is generated. The buzzer alarm of the drive host emits an alarm sound, and a red unqualified warning mark and the value exceeding the standard are displayed on the touch screen. The three-dimensional motion data, the braking distance of the agricultural machine, and the judgment result of this test are marked as abnormal data and stored in the memory of the host.

[0064] The beneficial effects of this invention are as follows:

[0065] This invention employs a magnetic signal acquisition device in conjunction with a handheld host, eliminating the need for a ground differential reference station and external support components required for photoelectric testing. It can be directly installed on the surface of the agricultural machinery under test to acquire satellite signals compatible with both BDS (BeiDou Navigation Satellite System) and GPS (Global Positioning System). This enables rapid deployment and flexible dismantling of the testing equipment in fields and unstructured road environments, significantly improving the operational efficiency and portability of agricultural machinery safety supervision agencies in mobile testing scenarios.

[0066] This invention utilizes an integral ranging module combined with an error correction module. By analyzing the steady-state velocity variance and braking time, it uses a backpropagation neural network to obtain the error correction distance caused by the drift of the single-point positioning signal. Without the need for real-time dynamic carrier phase differential positioning equipment, it compensates for the uncorrected braking distance, achieving high-precision calculation of agricultural machinery braking distance, reducing the hardware cost of agricultural machinery safety detection and ensuring the accuracy of detection data.

[0067] This invention proposes to collect three-dimensional motion data of the agricultural machinery under test through a sequence parameter extraction module, calculate the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment using a slope calculation module, and calculate the braking distance of the agricultural machinery by combining the uncorrected braking distance and the error-corrected distance. This eliminates the interference of farmland topography undulation and road surface slope factors on the braking distance measurement results, and ensures the objectivity and reliability of the agricultural machinery braking performance evaluation results under complex terrain conditions. Attached Figure Description

[0068] Figure 1 This is a schematic diagram illustrating a usage scenario of the present invention;

[0069] Figure 2 This is a schematic diagram of the module connection of the present invention;

[0070] Figure 3 The figure shows the simulation test results during the verification process of this invention.

[0071] In the diagram: 1. Signal acquisition device; 2. Main unit; 3. Agricultural machinery under test. Detailed Implementation

[0072] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0073] like Figure 1 and Figure 2 As shown, the detector includes a signal acquisition unit 1 and a main unit 2. The signal acquisition unit 1 has a built-in satellite signal receiving module compatible with both the BeiDou Navigation Satellite System and the Global Positioning System. Figure 1The dotted line in the diagram represents the data transmission channel. Host 2 contains:

[0074] The sequence parameter extraction module is used to collect and preprocess the three-dimensional motion data of the agricultural machine under test 3, generate a smooth horizontal velocity sequence and a smooth vertical velocity sequence, and obtain effective horizontal velocity sequence segments, effective vertical velocity sequence segments, steady-state velocity variance, braking initial velocity and braking duration.

[0075] The integral ranging module is used to perform time integration on the effective horizontal velocity sequence segment using the complex Simpson integral algorithm to obtain the uncorrected braking distance;

[0076] The error correction module is used to obtain the error correction distance caused by the drift of the single-point positioning signal based on the steady-state velocity variance and braking time using a backpropagation neural network.

[0077] The slope calculation module is used to calculate the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment, and to calculate the braking distance of the agricultural machinery by combining the uncorrected braking distance and the error correction distance.

[0078] The performance evaluation module is used to retrieve standard limits from the standard database based on the initial braking speed, compare them with the braking distance of the agricultural machinery, determine the compliance of the braking performance, and take corresponding measures (alarm or record).

[0079] The signal acquisition unit 1 is magnetic, including a housing and a strong magnetic base at the bottom of the housing. The satellite signal receiving module is encapsulated inside the housing. The main unit 2 is handheld, including a processor, memory, power module, touch screen and buzzer. The processor is electrically connected to the memory, power module, touch screen and buzzer, and is used to run the sequence parameter extraction module, integral ranging module, error correction module, slope calculation module and performance evaluation module.

[0080] In the sequence parameter extraction module, the process of acquiring the three-dimensional motion data of the tested agricultural machinery 3 includes:

[0081] The signal acquisition device 1 is attached to the geometric center of the top of the cab of the agricultural machine under test 3 by means of the magnetic base set at the bottom. The antenna attitude is adjusted to ensure that the antenna gain direction of the satellite signal receiving module is vertically facing the sky and there are no metal obstructions covering the surrounding area.

[0082] Place the handheld host 2 in the cab of the agricultural machine 3 under test, and establish a data transmission channel with the signal acquisition device 1 through a wired data cable or a wireless communication link.

[0083] When the system power is turned on, the satellite signal receiving module built into the signal acquisition unit 1, which is compatible with the Beidou satellite navigation system and the global positioning system, automatically searches for and locks the radio frequency signals of visible satellites. When the number of locked visible satellites meets the positioning calculation requirements, it enters the measurement ready state.

[0084] Three-dimensional motion data includes time series data, horizontal Doppler velocity series data, and vertical Doppler velocity series data;

[0085] The satellite signal receiving module receives radio frequency signals from visible satellites, demodulates the radio frequency signals to obtain satellite navigation messages, extracts satellite ephemeris data and time information of the current sampling time from the satellite navigation messages, measures the Doppler frequency shift value and carrier-to-noise ratio of the carrier signal in the radio frequency signal, constructs a velocity observation equation based on the Doppler frequency shift principle and combined with satellite ephemeris data, and calculates the three-dimensional velocity vector of signal acquisition device 1 in the geocentric-ground-fixed coordinate system.

[0086] The three-dimensional velocity vector in the geocentric-fixed coordinate system is projected and transformed to the local tangent plane coordinate system, and the eastward velocity component, the northward velocity component, and the celestial velocity component are decomposed.

[0087] Based on the eastward and northward velocity components, the Pythagorean theorem is used to calculate the horizontal Doppler velocity data, and the celestial velocity component is directly used as the vertical Doppler velocity data.

[0088] The sequence parameter extraction module collects time information, horizontal Doppler velocity data, vertical Doppler velocity data, and carrier-to-noise ratio in real time through the data transmission channel according to the set sampling frequency, constructs and outputs three-dimensional motion data, and sets the sampling frequency range to 10Hz to 50Hz.

[0089] In the sequence parameter extraction module, the process of generating smooth horizontal velocity sequences and smooth vertical velocity sequences includes:

[0090] The time length of the sliding filter window is set based on the carrier-to-noise ratio in the 3D motion data. When the carrier-to-noise ratio is lower than the preset threshold, the time length is increased.

[0091] For horizontal and vertical Doppler velocity sequence data in 3D motion data, data processing queues corresponding to time lengths are constructed respectively.

[0092] Arrange the speed values ​​in the data processing queue in ascending order, and select the value in the middle position as the filtered speed value at the center of the sliding filter window.

[0093] The sliding filter window is moved point by point according to the sampling time interval to traverse the entire horizontal Doppler velocity sequence data and the vertical Doppler velocity sequence data, remove outlier noise points, and generate smooth horizontal velocity sequence and smooth vertical velocity sequence respectively.

[0094] The sequence parameter extraction module includes the following steps to obtain the effective horizontal velocity sequence segment, the effective vertical velocity sequence segment, the steady-state velocity variance, the initial braking velocity, and the braking duration:

[0095] A negative braking trigger acceleration threshold is set. When the instantaneous acceleration feature values ​​of three consecutive sampling times are all less than the braking trigger acceleration threshold, the first sampling time in the corresponding instantaneous acceleration feature sequence is marked as the braking start time.

[0096] Set a stopping speed threshold. When the value of the smoothed horizontal speed sequence is continuously less than the stopping speed threshold, mark the first sampling time corresponding to that time as the vehicle stopping time.

[0097] Based on the determined braking start time and vehicle stopping time, data within the corresponding time period is extracted from the smooth horizontal velocity sequence to generate a valid horizontal velocity sequence segment. Simultaneously, data within the same time period is extracted from the smooth vertical velocity sequence to generate a valid vertical velocity sequence segment.

[0098] The instantaneous acceleration characteristic sequence of the agricultural machinery is obtained by performing a first-order difference operation on the smoothed horizontal velocity values ​​at adjacent sampling times in the effective horizontal velocity sequence segment.

[0099] Before the braking start time, the data of the smoothed horizontal velocity sequence within a preset steady-state time window is extracted, and the variance of the smoothed horizontal velocity sequence data within the steady-state time window is calculated as the steady-state velocity variance before braking.

[0100] Read the values ​​of the smooth horizontal velocity sequence at the moment of braking start and mark the values ​​as the initial braking velocities;

[0101] Calculate the time difference between the moment the vehicle stops and the moment braking begins, and record the time difference as the braking duration.

[0102] In the integral ranging module, the process of using the complex Simpson integral algorithm to integrate the effective horizontal velocity sequence segment over time to obtain the uncorrected braking distance includes:

[0103] The integral ranging module receives a valid horizontal velocity sequence segment output by the sequence parameter extraction module. The valid horizontal velocity sequence segment contains smoothed horizontal velocity values ​​at each sampling time from the start of braking to the time the vehicle stops.

[0104] Obtain the total length of the effective horizontal velocity sequence segment and the time interval between adjacent sampling points. If the total sequence length is even, discard the last data point of the sequence to keep the total number of data points participating in the integration calculation odd, so as to meet the odd number of nodes requirement of the complex Simpson integral algorithm.

[0105] The smoothed horizontal velocity values ​​of the first data point of the processed effective horizontal velocity sequence segment. Smoothed horizontal velocity values ​​of the last data point Add them together as boundary terms;

[0106] Extract the data points at each odd-indexed position in the sequence, and calculate the smoothed horizontal velocity value of each data point at each odd-indexed position. The sum of these terms is multiplied by a coefficient of 4 to obtain the weighted sum of the odd-numbered terms. ;

[0107] Let be the logarithm of the subintervals of the integration interval. The total number of odd data points after processing, i is the loop variable for the summation operation, and represents the index of the sub-interval;

[0108] Extract the data points at even-numbered indices from the sequence after removing the first and last data points, and calculate the smoothed horizontal velocity value for each even-numbered index data point. The sum of these terms is multiplied by a coefficient of 2 to obtain the weighted sum of the even-numbered terms. ;

[0109] The weighted sums of boundary terms, odd-numbered terms, and even-numbered terms are added together to obtain the total weighted velocity sum. This total weighted velocity sum is then multiplied by one-third of the sampling time interval to calculate the uncorrected braking distance in meters.

[0110] ;

[0111] In the formula, The sampling time interval is in seconds.

[0112] In the error correction module, the process of obtaining the error correction distance caused by the drift of the single-point positioning signal, based on the steady-state velocity variance and braking duration, using a backpropagation neural network, includes:

[0113] The error correction module uses a pre-trained backpropagation neural network for calculation, and receives the steady-state velocity variance and braking duration output by the sequence parameter extraction module. The backpropagation neural network adopts a three-layer fully connected topology, which includes an input layer, a hidden layer and an output layer with neurons.

[0114] Construct an input layer vector corresponding to the input layer, and map the steady-state velocity variance and braking duration to the first and second components of the input layer vector, respectively.

[0115] The input layer vector is input into the hidden layer, multiplied by the weight matrix of the hidden layer, and then the bias vector is added to calculate the net input vector of the hidden layer.

[0116] The output vector of the hidden layer is obtained by performing an element-wise transformation on the net input vector using a nonlinear activation function.

[0117] The output vector of the hidden layer is input to the output layer, multiplied by the connection weight vector from the hidden layer to the output layer, and then the bias value of the output layer is added to calculate the error correction distance caused by the drift of the single-point positioning signal.

[0118] In the slope calculation module, the process of calculating the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment includes:

[0119] The slope calculation module receives the effective horizontal velocity sequence fragment and the effective vertical velocity sequence fragment output by the sequence parameter extraction module;

[0120] Calculate the arithmetic mean of the smoothed horizontal velocity values ​​at each sampling point in the effective horizontal velocity sequence segment to obtain the horizontal average velocity during the braking process. Calculate the arithmetic mean of the smoothed vertical velocity values ​​at each sampling point in the effective vertical velocity sequence segment to obtain the vertical average velocity during the braking process.

[0121] The ratio of the vertical average velocity to the horizontal average velocity is calculated using the arctangent function, yielding the average slope angle in radians during braking. If the average slope angle is greater than zero, it indicates an uphill slope; if the average slope angle is less than zero, it indicates a downhill slope; if the average slope angle is equal to zero, it indicates a flat road surface.

[0122] The slope calculation module receives the uncorrected braking distance output by the integral distance measurement module. Based on the principle of energy conservation, and utilizing the average slope angle The effect of the change in gravitational potential energy caused by slope on the braking distance of agricultural machinery was calculated, and the slope correction value in meters was obtained:

[0123] ;

[0124] In the formula, K is an empirical weighting coefficient based on the type of agricultural machinery, used to compensate for the differences in braking performance of different models on slopes.

[0125] In the slope calculation module, the process of calculating the braking distance of the agricultural machinery, combining the uncorrected braking distance and the error-corrected distance, includes:

[0126] The slope calculation module receives the error correction distance output by the error correction module;

[0127] The final braking distance of the agricultural machine is calculated by subtracting the error correction distance from the uncorrected braking distance and adding the slope correction value.

[0128] In the performance evaluation module, the process of retrieving standard limits from the standard database based on the initial braking speed, comparing them with the braking distance of the agricultural machinery, determining the compliance of braking performance, and taking corresponding measures includes:

[0129] The performance evaluation module receives the initial braking velocity output by the sequence parameter extraction module;

[0130] In the preset standard database, a table lookup is performed based on the initial braking speed. The standard database stores the standard limit values ​​of braking distance corresponding to different initial speed ranges.

[0131] Match the speed range containing the initial braking velocity, and extract the standard limit value corresponding to the speed range as the current judgment benchmark;

[0132] The performance evaluation module receives the farm machinery braking distance output by the slope calculation module;

[0133] Compare the driving distance of agricultural machinery with the standard limit numerically;

[0134] If the braking distance of the agricultural machine is less than or equal to the standard limit, the braking performance of the tested agricultural machine 3 is deemed qualified, and a qualified instruction is generated. The touch screen of the drive host 2 displays a green qualified pass mark, and plots and displays the speed-time change curve of the braking process on the screen with time as the horizontal axis and smooth horizontal speed as the vertical axis.

[0135] If the braking distance of the agricultural machine exceeds the standard limit, the braking performance of the tested agricultural machine 3 is deemed unqualified, and an unqualified warning command is generated. The buzzer alarm of the main unit 2 is activated, and a red unqualified warning mark and the value exceeding the standard are displayed on the touch screen. The three-dimensional motion data, braking distance of the agricultural machine, and judgment result of this test are marked as abnormal data and stored in the memory of the main unit 2.

[0136] In summary, the complete testing process of the agricultural machinery braking performance testing instrument based on BeiDou satellite point positioning in this embodiment is as follows:

[0137] The magnetic signal acquisition device 1 is attached to the geometric center of the top of the cab of the agricultural machine 3 under test. The antenna attitude is adjusted to ensure that there is no obstruction. The handheld host 2 is placed in the cab and a communication connection is established. The power is turned on and the signal acquisition device 1 enters the measurement ready state after locking the Beidou and GPS satellite signals.

[0138] The satellite signal receiving module demodulates the radio frequency signal to obtain satellite ephemeris data and time information, measures the Doppler frequency shift and carrier-to-noise ratio, and calculates the three-dimensional velocity vector. The sequence parameter extraction module collects and constructs three-dimensional motion data in real time at a frequency of 10Hz to 50Hz. Based on the carrier-to-noise ratio, it adaptively sets a sliding filter window to generate smooth horizontal velocity sequences and smooth vertical velocity sequences. It performs differential operations and combines the braking trigger acceleration threshold and the stopping velocity threshold to automatically extract effective horizontal velocity sequence segments and effective vertical velocity sequence segments, as well as extract steady-state velocity variance, braking initial velocity, and braking duration.

[0139] The integral ranging module receives effective horizontal velocity sequence segments and uses the complex Simpson integral algorithm to integrate the effective horizontal velocity sequence segments over time to calculate the uncorrected braking distance. The error correction module uses a pre-trained backpropagation neural network, inputs the steady-state velocity variance and braking time, and obtains and outputs the error correction distance caused by the drift of the single-point positioning signal. The slope calculation module calculates the slope angle based on the effective horizontal velocity sequence segments and the effective vertical velocity sequence segments, calculates the slope correction value based on the principle of energy conservation, and finally subtracts the error correction distance from the uncorrected braking distance and adds the slope correction value to calculate the braking distance of the agricultural machine.

[0140] The performance evaluation module retrieves the corresponding standard limit from the standard database based on the initial braking speed, compares the braking distance of the agricultural machine with the standard limit, and if the braking distance of the agricultural machine is less than or equal to the standard limit, it is deemed qualified, a green pass mark is displayed on the screen and a speed-time change curve is plotted, if the braking distance of the agricultural machine is greater than the standard limit, it is deemed unqualified, a buzzer alarm is triggered, a red warning mark and the value exceeding the standard are displayed, and the abnormal data is marked and stored.

[0141] To verify the ability of the agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning in this embodiment to achieve high-precision braking distance calculation and automated qualification judgment under the influence of satellite signal noise interference and road slope, a simulation experiment was conducted.

[0142] A wheeled tractor with an initial braking speed of 22.92 km / h was used as the test object. The test scenario was an unstructured road with random drift noise superimposed by Beidou single-point positioning and a 3-degree downhill slope. The simulation results are as follows: Figure 3 As shown.

[0143] Figure 3 In the graph, the horizontal axis represents time (in seconds), and the vertical axis represents speed (in meters per second). The curve visually displays the speed change trend throughout the braking process. Furthermore, the panel displays real-time monitoring data and performance evaluation reports processed by the main unit 2. The displayed content includes:

[0144] Real-time monitoring data: Time 4.58s, Speed ​​0.00m / s; Performance evaluation report information: Sequence parameter extraction stage, initial braking speed 22.92km / h, braking duration 1.40s; Distance calculation stage, uncorrected braking distance 4.35m, agricultural machine braking distance 4.20m; Judgment results: The standard limit is 9.50m, the braking performance of this agricultural machine meets the requirements, and it is judged as qualified (PASS). A buzzer alarm icon is also provided on the panel to display alarm status.

[0145] like Figure 3 As shown in the curve (corresponding to the sequence parameter extraction stage): the dark gray dotted line represents the original horizontal Doppler velocity sequence data collected by the signal acquisition device 1, which contains obvious random noise fluctuations. The black solid line represents the smooth horizontal velocity sequence generated after processing by the sequence parameter extraction module. It can be seen that this embodiment effectively removes outlier noise points in the original signal and generates a smooth and realistic velocity change process.

[0146] like Figure 3 The vertical dashed line indicates (corresponding to the effective segment extraction stage): the black vertical dashed line marks the braking start time identified by the agricultural machinery braking performance tester based on the braking trigger acceleration threshold, and the black vertical dotted line marks the vehicle stopping time identified by the agricultural machinery braking performance tester. It accurately locks the start and end points of the braking process and calculates the braking duration as 1.40s.

[0147] like Figure 3 The gray-filled area (corresponding to the integral ranging stage) shows the effective horizontal velocity sequence segment between the black vertical dashed line and the black vertical dotted line. The integral ranging module uses the complex Simpson integral algorithm to perform time integration on the gray-shaded area, and the calculated uncorrected braking distance is 4.35m.

[0148] Panel Information and Central Label (Correction and Evaluation Phase): The initial braking speed extracted by the agricultural machinery braking performance tester is 22.92 km / h. The error correction module, based on the steady-state speed variance and braking duration, uses a backpropagation neural network to obtain the error correction distance caused by the drift of the single-point positioning signal. The slope calculation module calculates the slope correction value based on the effective horizontal and vertical speed sequence segments. Both modules together compensate for the uncorrected distance (corrected from 4.35m to 4.20m), resulting in a final agricultural machinery braking distance of 4.20m. The performance evaluation module retrieves the standard limit value corresponding to this initial braking speed from the standard database, which is 9.50m. Since 4.20m is less than 9.50m, the agricultural machinery braking performance tester determines the braking performance of the tested object to be "Pass" and prominently displays the "[Pass]" label in the center of the screen. Furthermore, the buzzer alarm icon on the panel is silent, indicating that the braking distance does not exceed the standard and the buzzer alarm is not triggered, conforming to the pass / fail judgment logic.

[0149] The simulation process verified that this embodiment effectively solved the problem of insufficient ranging accuracy caused by signal drift under single-point positioning by combining the complex Simpson integral algorithm and the backpropagation neural network error correction mechanism. Through slope calculation compensation, the objectivity of braking performance test data in non-flat road environment was guaranteed.

Claims

1. An agricultural machinery braking performance testing instrument based on BeiDou satellite single-point positioning, characterized in that, The detector includes a signal acquisition unit and a main unit. The signal acquisition unit has a built-in satellite signal receiving module compatible with both the BeiDou Navigation Satellite System and the Global Positioning System. The main unit contains: The sequence parameter extraction module is used to collect and preprocess the three-dimensional motion data of the agricultural machinery under test, generate smooth horizontal velocity sequence and smooth vertical velocity sequence, and obtain effective horizontal velocity sequence segments, effective vertical velocity sequence segments, steady-state velocity variance, braking initial velocity and braking duration. The integral ranging module is used to perform time integration on the effective horizontal velocity sequence segment using the complex Simpson integral algorithm to obtain the uncorrected braking distance; The error correction module is used to obtain the error correction distance caused by the drift of the single-point positioning signal based on the steady-state velocity variance and braking time using a backpropagation neural network. The slope calculation module is used to calculate the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment, and to calculate the braking distance of the agricultural machinery by combining the uncorrected braking distance and the error correction distance. The performance evaluation module is used to retrieve standard limits from the standard database based on the initial braking speed, compare them with the braking distance of agricultural machinery, determine the compliance of braking performance, and take corresponding measures.

2. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning as described in claim 1, characterized in that, The signal acquisition unit is magnetically attached, including a housing and a magnetic base located at the bottom of the housing. The satellite signal receiving module is encapsulated inside the housing. The main unit is handheld and includes a processor, memory, power module, touch screen, and buzzer alarm. The processor is electrically connected to the memory, power module, touch screen, and buzzer alarm, and is used to run the sequence parameter extraction module, integral ranging module, error correction module, slope calculation module, and performance evaluation module.

3. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 2, characterized in that, In the sequence parameter extraction module, the process of acquiring the three-dimensional motion data of the agricultural machinery under test includes: The signal acquisition device is attached to the geometric center of the top of the cab of the agricultural machinery under test by magnetic base at the bottom. The antenna attitude is adjusted to ensure that the antenna gain direction of the satellite signal receiving module is vertically facing the sky and there are no metal obstructions around it. Place the handheld host in the cab of the agricultural machinery under test, and establish a data transmission channel with the signal acquisition device through either a wired data cable or a wireless communication link. When the system power is turned on, the built-in satellite signal receiving module of the signal acquisition unit, which is compatible with the Beidou satellite navigation system and the global positioning system, automatically searches for and locks the radio frequency signals of visible satellites. When the number of locked visible satellites meets the positioning calculation requirements, it enters the measurement ready state. Three-dimensional motion data includes time series data, horizontal Doppler velocity series data, and vertical Doppler velocity series data; The satellite signal receiving module receives radio frequency signals from visible satellites, demodulates the radio frequency signals to obtain satellite navigation messages, extracts satellite ephemeris data and time information of the current sampling time from the satellite navigation messages, measures the Doppler frequency shift value and carrier-to-noise ratio of the carrier signal in the radio frequency signal, constructs a velocity observation equation based on the Doppler frequency shift principle and combined with satellite ephemeris data, and calculates the three-dimensional velocity vector of the signal acquisition device in the geocentric-ground-fixed coordinate system. The three-dimensional velocity vector in the geocentric-fixed coordinate system is projected and transformed to the local tangent plane coordinate system, and the eastward velocity component, the northward velocity component, and the celestial velocity component are decomposed. Based on the eastward and northward velocity components, the Pythagorean theorem is used to calculate the horizontal Doppler velocity data, and the celestial velocity component is directly used as the vertical Doppler velocity data. The sequence parameter extraction module collects time information, horizontal Doppler velocity data, vertical Doppler velocity data, and carrier-to-noise ratio in real time through the data transmission channel according to the set sampling frequency, and constructs and outputs three-dimensional motion data.

4. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 3, characterized in that, In the sequence parameter extraction module, the process of generating smooth horizontal velocity sequences and smooth vertical velocity sequences includes: The time length of the sliding filter window is set based on the carrier-to-noise ratio in the 3D motion data. When the carrier-to-noise ratio is lower than the preset threshold, the time length is increased. For horizontal and vertical Doppler velocity sequence data in 3D motion data, data processing queues corresponding to time lengths are constructed respectively. Arrange the speed values ​​in the data processing queue in ascending order, and select the value in the middle position as the filtered speed value at the center of the sliding filter window. The sliding filter window is moved point by point according to the sampling time interval to traverse the entire horizontal Doppler velocity sequence data and the vertical Doppler velocity sequence data, remove outlier noise points, and generate smooth horizontal velocity sequence and smooth vertical velocity sequence respectively.

5. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 4, characterized in that, The sequence parameter extraction module includes the following steps to obtain the effective horizontal velocity sequence segment, the effective vertical velocity sequence segment, the steady-state velocity variance, the initial braking velocity, and the braking duration: A negative braking trigger acceleration threshold is set. When the instantaneous acceleration feature values ​​of three consecutive sampling times are all less than the braking trigger acceleration threshold, the first sampling time in the corresponding instantaneous acceleration feature sequence is marked as the braking start time. Set a stopping speed threshold. When the value of the smoothed horizontal speed sequence is continuously less than the stopping speed threshold, mark the first sampling time corresponding to that time as the vehicle stopping time. Based on the determined braking start time and vehicle stopping time, data within the corresponding time period is extracted from the smooth horizontal velocity sequence to generate a valid horizontal velocity sequence segment. Simultaneously, data within the same time period is extracted from the smooth vertical velocity sequence to generate a valid vertical velocity sequence segment. The instantaneous acceleration characteristic sequence of the agricultural machinery is obtained by performing a first-order difference operation on the smoothed horizontal velocity values ​​at adjacent sampling times in the effective horizontal velocity sequence segment. Before the braking start time, the data of the smoothed horizontal velocity sequence within a preset steady-state time window is extracted, and the variance of the smoothed horizontal velocity sequence data within the steady-state time window is calculated as the steady-state velocity variance before braking. Read the values ​​of the smooth horizontal velocity sequence at the moment of braking start and mark the values ​​as the initial braking velocities; Calculate the time difference between the moment the vehicle stops and the moment braking begins, and record the time difference as the braking duration.

6. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 5, characterized in that, In the integral ranging module, the process of using the complex Simpson integral algorithm to integrate the effective horizontal velocity sequence segment over time to obtain the uncorrected braking distance includes: The integral ranging module receives a valid horizontal velocity sequence segment output by the sequence parameter extraction module. The valid horizontal velocity sequence segment contains smoothed horizontal velocity values ​​at each sampling time from the start of braking to the time the vehicle stops. Obtain the total length of the effective horizontal velocity sequence segment and the time interval between adjacent sampling points. If the total length of the sequence is even, discard the last data point of the sequence. The smoothed horizontal velocity values ​​of the first and last data points of the processed effective horizontal velocity sequence segment are added together as boundary terms. Extract the data points at each odd-indexed position in the sequence, calculate the sum of the smoothed horizontal velocity values ​​of each odd-indexed data point and multiply it by a coefficient of 4, and use it as the weighted sum of the odd-numbered terms; Extract the data points at each even-indexed position after removing the first and last data points from the sequence, calculate the sum of the smooth horizontal velocity values ​​of each even-indexed data point and multiply it by a coefficient of 2, and use it as the weighted sum of the even-numbered terms. The weighted sums of boundary terms, odd-numbered terms, and even-numbered terms are added together to obtain the total weighted velocity sum. The total weighted velocity sum is then multiplied by one-third of the sampling time interval to calculate the uncorrected braking distance.

7. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning as described in claim 1, characterized in that, In the error correction module, the process of obtaining the error correction distance caused by the drift of the single-point positioning signal, based on the steady-state velocity variance and braking duration, using a backpropagation neural network, includes: The error correction module uses a pre-trained backpropagation neural network for calculation, and receives the steady-state velocity variance and braking duration output by the sequence parameter extraction module. The backpropagation neural network adopts a three-layer fully connected topology, which includes an input layer, a hidden layer and an output layer with neurons. Construct an input layer vector corresponding to the input layer, and map the steady-state velocity variance and braking duration to the first and second components of the input layer vector, respectively. The input layer vector is input into the hidden layer, multiplied by the weight matrix of the hidden layer, and then the bias vector is added to calculate the net input vector of the hidden layer. The output vector of the hidden layer is obtained by performing an element-wise transformation on the net input vector using a nonlinear activation function. The output vector of the hidden layer is input to the output layer, multiplied by the connection weight vector from the hidden layer to the output layer, and then the bias value of the output layer is added to calculate the error correction distance caused by the drift of the single-point positioning signal.

8. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 5, characterized in that, In the slope calculation module, the process of calculating the slope correction value based on the effective horizontal velocity sequence segment and the effective vertical velocity sequence segment includes: The slope calculation module receives the effective horizontal velocity sequence fragment and the effective vertical velocity sequence fragment output by the sequence parameter extraction module; Calculate the arithmetic mean of the smoothed horizontal velocity values ​​at each sampling point in the effective horizontal velocity sequence segment to obtain the horizontal average velocity during the braking process. Calculate the arithmetic mean of the smoothed vertical velocity values ​​at each sampling point in the effective vertical velocity sequence segment to obtain the vertical average velocity during the braking process. The ratio of the vertical average velocity to the horizontal average velocity is calculated using the arctangent function, thus obtaining the average slope angle during braking. The slope calculation module receives the uncorrected braking distance output by the integral distance measuring module, and based on the principle of energy conservation, uses the average slope angle to calculate the impact of the change in gravitational potential energy caused by the slope on the braking distance of the agricultural machinery, thus obtaining the slope correction value.

9. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning as described in claim 1, characterized in that, In the slope calculation module, the process of calculating the braking distance of the agricultural machinery, combining the uncorrected braking distance and the error-corrected distance, includes: The slope calculation module receives the error correction distance output by the error correction module; The final braking distance of the agricultural machine is calculated by subtracting the error correction distance from the uncorrected braking distance and adding the slope correction value.

10. The agricultural machinery braking performance testing instrument based on Beidou satellite single-point positioning method according to claim 3, characterized in that, In the performance evaluation module, the process of retrieving standard limits from the standard database based on the initial braking speed, comparing them with the braking distance of the agricultural machinery, determining the compliance of braking performance, and taking corresponding measures includes: The performance evaluation module receives the initial braking velocity output by the sequence parameter extraction module; In the preset standard database, a table lookup is performed based on the initial braking speed. The standard database stores the standard limit values ​​of braking distance corresponding to different initial speed ranges. Match the speed range containing the initial braking velocity, and extract the standard limit value corresponding to the speed range as the current judgment benchmark; The performance evaluation module receives the farm machinery braking distance output by the slope calculation module; Compare the driving distance of agricultural machinery with the standard limit numerically; If the braking distance of the agricultural machine is less than or equal to the standard limit, the braking performance of the tested agricultural machine is deemed qualified, and a qualified instruction is generated. The touch screen of the drive host displays a green qualified mark, and the speed-time change curve of the braking process is plotted and displayed on the screen with time as the horizontal axis and smooth horizontal speed as the vertical axis. If the braking distance of the agricultural machine exceeds the standard limit, the braking performance of the tested agricultural machine is deemed unqualified, and an unqualified warning command is generated. The buzzer alarm of the drive host emits an alarm sound, and a red unqualified warning mark and the value exceeding the standard are displayed on the touch screen. The three-dimensional motion data, the braking distance of the agricultural machine, and the judgment result of this test are marked as abnormal data and stored in the memory of the host.

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