Inertia simulation system and method for tractor test bench based on digital twinning

Abstract

This invention relates to a tractor test bench inertia simulation system and method based on digital twins. The system includes a central control unit, wheel-side loading units, sensors, and couplings. The central control unit establishes a tractor-wide dynamic model and an adaptive observer of the drive wheel rotational inertia based on the parameters of the tractor under test. It then calculates the target resistance torque of the drive wheels according to the set test conditions and controls the wheel-side loading units to apply electric inertia. The system acquires the motion state of the drive wheels in real time through sensors, dynamically corrects the drive wheel rotational inertia in the dynamic model using the observer, achieves adaptive parameter matching between the digital twin model and the actual tractor, and adjusts the target resistance torque in real time based on the corrected model. This invention overcomes the problems of discontinuous mechanical inertia adjustment and large simulation errors caused by fixed electric inertia models in traditional methods, significantly improving the realism, accuracy, and efficiency of tractor indoor testing.

Description

Technical Field

[0001] This invention belongs to the field of tractor testing, specifically relating to a tractor test bench inertia simulation system and method based on digital twins. Background Technology

[0002] As a core power equipment in modern agriculture, the reliability of tractors directly affects agricultural production efficiency and operating costs. During the research and development phase, conducting reliability tests by simulating field loads on indoor test benches is a key method to shorten development cycles and reduce testing risks and costs. Currently, inertia simulation on test benches mainly employs two methods: mechanical inertia and electrical inertia. Mechanical inertia simulation simulates inertia through combinations of mechanical flywheels of different masses and sizes. This requires physical switching of inertia values ​​via mechanical devices such as clutches and gearboxes, and necessitates a large, precision-machined flywheel assembly, a robust support structure, a complex clutch transmission mechanism, and a large installation space. This method suffers from problems such as inability to continuously and smoothly adjust inertia, time-consuming and labor-intensive switching processes, and significant simulation errors. In contrast, electrical inertia simulation uses control algorithms to drive the motor's output speed and torque to simulate inertia. This allows for rapid and precise adjustment of inertia values ​​and significantly reduces the manufacturing cost, size, and weight of the test bench, minimizing maintenance requirements and achieving "lightweight" and miniaturized test benches.

[0003] Traditional tractor electric inertia simulation test benches typically employ controllers based on fixed transfer functions or rely on preset empirical data to generate target torque and speed. These methods fail to adequately consider the inherent characteristics of different tractor models, as well as the dynamic changes in load spectra under various operating conditions such as transport, plowing, and rotary tillage. This results in significant deviations between the simulated resistance torque and actual conditions, making the test results unable to accurately reflect the true stress state of the tractor and greatly diminishing the reliability and guiding value of the test data. Therefore, there is an urgent need in this field for a novel electric inertia simulation technology that can deeply integrate physical mechanisms and real-time data to overcome the aforementioned shortcomings of traditional test benches and achieve high-fidelity, high-efficiency, and high-consistency tractor reliability testing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a tractor test bench inertia simulation system and method based on digital twins. By establishing a high-fidelity tractor dynamics model and forming a real-time interactive closed-loop system with the actual tractor under test, the system uses an adaptive observer of drive wheel rotational inertia to correct the tractor dynamics parameters based on the real-time status feedback of the tractor under test, ensuring that the tractor dynamics model matches the dynamic response of the actual tractor under test. Simultaneously, the system calculates the theoretical drive wheel resistance torque conforming to the target working condition based on the corrected tractor dynamics model, and uses this torque to drive the wheel-side loading unit for high-fidelity inertia simulation loading. Based on the aforementioned closed-loop simulation mechanism of "virtual-real interaction and parameter feedback," this invention can significantly improve the realism and accuracy of the simulated load on the test bench, making the reliability testing of the entire tractor closer to the real field operating environment.

[0005] To achieve the above objectives, the first technical solution adopted by the present invention is: a tractor test bench inertia simulation system based on digital twins, comprising: a central control unit, a wheel-side loading unit, sensors, and couplings; The central control unit is electrically connected to the wheel-side loading unit and the sensor respectively, and the wheel-side loading unit is mechanically connected to the drive wheel of the tractor under test through a coupling; The central control unit is used for: Establish a dynamic model of the tractor as a whole and an adaptive observer of the rotational inertia of the drive wheels based on the parameters of the tractor under test. Based on the test conditions and the initial position, speed, and front wheel angle of the tractor under test, the target resistance torque of the drive wheel is calculated using the tractor's overall dynamics model, and the wheel-side loading unit is controlled to apply inertia loading to the drive wheel. The difference between the actual angular acceleration of the tractor's drive wheel and the theoretical angular acceleration of the drive wheel in the tractor's dynamic model is calculated, and the moment of inertia of the drive wheel in the tractor's dynamic model is corrected by using an adaptive observer of the moment of inertia of the drive wheel. The theoretical position and speed of the tested tractor are updated by sensor information, and the target resistance torque of the drive wheels is adjusted in real time according to the overall dynamic model of the tractor.

[0006] Furthermore, the central control unit includes a real-time industrial computer, a data acquisition card, and a motor controller; the real-time industrial computer is used to establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheel; the data acquisition card is used to receive and process information from the sensors; and the motor controller is used to control the wheel-side loading unit to perform inertia loading according to the target resistance torque.

[0007] Furthermore, the wheel-side loading unit includes a loading motor and a cooling system.

[0008] Furthermore, the sensor is at least used to acquire real-time information on the speed, torque, and angular acceleration of the drive wheels of the tested tractor, and to send the information to the central control unit.

[0009] The second technical solution proposed in this invention is: a method for simulating the inertia of a tractor test bench based on digital twins. This method uses the inertia simulation system described above and includes the following steps: S1. Based on the parameters of the tractor under test, establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheels, and set the initial state of the tractor. S2. The central control unit calculates the target resistance torque at the drive wheel based on the test conditions and the tractor's initial position, speed, and front wheel angle using the tractor's overall dynamics model, and sends control commands to the wheel-side loading unit. S3. The wheel-side loading unit applies inertia loading to the drive wheel according to the control command of the central control unit. S4. The sensor acquires the speed, torque, and angular acceleration information at the drive wheel of the tested tractor in real time and sends the information to the central control unit. S5. The central control unit calculates the difference between the actual angular acceleration of the tractor's drive wheel and the theoretical angular acceleration of the drive wheel in the tractor's dynamic model, and corrects the moment of inertia of the drive wheel in the tractor's dynamic model through the drive wheel moment of inertia adaptive observer. S6. The central control unit updates the theoretical position and speed state of the tested tractor through the actual motion parameters obtained by the sensors, and adjusts the target resistance torque at the drive wheel in real time according to the corrected tractor overall dynamics model. S7. Determine whether the experiment is complete. If not, proceed to S4; if complete, export the experiment data and exit the inertia simulation system.

[0010] Furthermore, the tractor overall dynamics model established in step S1 is a multibody dynamics model that includes longitudinal, lateral, yaw motion and wheel rotation dynamics.

[0011] Furthermore, in step S1, the adaptive observer of the driving wheel's moment of inertia adopts a proportional-integral-derivative control law.

[0012] Furthermore, the actual motion parameters in step S6 include the rotational speed and torque of the drive wheel.

[0013] The beneficial effects of this invention are: 1. By establishing a digital twin model of the tractor's overall dynamics and introducing an adaptive observer of the driving wheel's rotational inertia, the system can dynamically correct the model parameters according to the real-time response of the tested tractor, ensuring that the virtual model and the actual physical object always maintain dynamic consistency, greatly improving the authenticity and accuracy of the bench simulation load, and making the indoor test closer to the real field operation conditions.

[0014] 2. This invention employs a fully electric inertia loading method, completely eliminating the complex mechanical structures of traditional mechanical flywheel assemblies, clutches, gearboxes, etc., and achieving continuous, smooth, and rapid adjustment of the inertia value. This not only significantly reduces the manufacturing cost, floor space, and equipment weight of the test bench, but also significantly improves the system's response speed and adjustment accuracy.

[0015] 3. The system of this invention can quickly construct corresponding dynamic models based on the parameters of different tractor models, and supports the simulation of various typical working conditions such as plowing, rotary tilling, and transportation. By integrating physical mechanisms with real-time data, the system can automatically adapt to the dynamic changes of different load spectra, overcoming the drawbacks of traditional electric inertia test benches that rely on fixed transfer functions or empirical data, and significantly improving the reliability of test data and its engineering guidance value.

[0016] 4. The entire simulation process is completed automatically under the closed-loop control of the central control unit, including model building, drag torque calculation, inertia loading, parameter correction, and state updates, without any manual intervention. Data can be automatically exported after the test, greatly shortening test preparation and execution time, improving test repeatability and consistency, and providing technical support for the standardization and mass production of tractor reliability testing. Attached Figure Description

[0017] Figure 1 This is a simplified structural diagram of the tractor test bench according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the tractor dynamics model according to Embodiment 2 of the present invention; Figure 3 This is a flowchart of the inertia simulation method according to Embodiment 2 of the present invention; The diagram shows: 100, Central Control Unit; 101, Real-time Industrial PC; 102, Data Acquisition Card; 103, Motor Controller. 200. Wheel-side loading unit; 201. Loading motor; 202. Cooling system; 300, sensor; 400, coupling; 500, tractor under test. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments, but this should not be construed as limiting the invention in any way.

[0019] Example 1 like Figure 1 As shown, a tractor test bench inertia simulation system based on digital twin is installed on the tractor test bench and includes a central control unit, wheel-side loading unit, sensors and couplings.

[0020] The central control unit includes a real-time industrial computer, a data acquisition card, and a motor controller. The wheel-side loading unit includes a loading motor and a cooling system. The central control unit is electrically connected to the wheel-side loading unit and the sensor, respectively. The wheel-side loading unit is mechanically connected to the drive wheel of the tractor under test via a coupling.

[0021] The real-time industrial control computer is used to establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheels. The data acquisition card is used to receive and process sensor information, and the motor controller is used to control the loading motor to load electrical inertia.

[0022] The central control unit has the following functions: (1) Establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheels based on the parameters of the tractor under test; (2) Calculate the target resistance torque of the drive wheel using the tractor's overall dynamic model based on the test conditions and the initial position, speed and front wheel angle of the tractor under test, and control the wheel-side loading unit to apply inertia loading to the drive wheel. (3) Calculate the difference between the actual angular acceleration of the tractor drive wheel and the theoretical angular acceleration of the drive wheel in the tractor dynamics model, and correct the moment of inertia of the drive wheel in the tractor dynamics model by using the drive wheel moment of inertia adaptive observer; (4) Update the theoretical position and speed of the tested tractor through sensor information, and adjust the target resistance torque of the drive wheel in real time according to the tractor's overall dynamic model.

[0023] Example 2 This embodiment takes plowing as an example, and the method for inertia simulation using the inertia simulation system described in Embodiment 1 includes the following steps: S1, the following parameters are specified for the tractor under test: overall mass m, wheelbase l, front axle track d1, rear axle track d2, distance a from the center of mass to the front axle, distance b from the center of mass to the rear axle, and height h from the center of mass to the ground. g Specific parameters such as the front wheel radius r1 and the rear wheel radius r2 are input to the central control unit, which then constructs a tractor dynamics model under plowing conditions based on the tractor parameters. In the formula, v x v is the longitudinal speed of the tractor yFor the lateral speed of the tractor, The first derivative of the longitudinal velocity of the tractor. Let ω be the first derivative of the tractor's lateral velocity, and ω be the tractor's yaw rate. δ is the first derivative of the tractor's yaw rate. f For the front wheel steering angle, F xfl F is the longitudinal force on the left front wheel. xfr F is the longitudinal force on the right front wheel. yfl For the lateral force on the left front wheel, F yfr F is the lateral force on the right front wheel. xrl F is the longitudinal force on the left rear wheel. xrr F is the longitudinal force on the right rear wheel. yrl For the lateral force on the left rear wheel, F yrr F is the lateral force on the right rear wheel. r For the total resistance of the tractor, I z Let be the moment of inertia of the tractor about the z-axis of the vehicle body coordinate system.

[0024] Since the tractor operates at a low speed during plowing, the effect of air resistance on the tractor can be ignored. Therefore, the resistance equation for a tractor traveling at a stable speed is: (2) In the formula, F D For the resistance of tractor plowing, F f This refers to the rolling resistance of the tractor.

[0025] Load transfer significantly affects tire adhesion. To more realistically reflect the dynamic response of the tractor under complex working conditions, it is necessary to consider load transfer caused by lateral and longitudinal movements and resistance. Therefore, the vertical load model for each tire is as follows: In the formula, F zfl For the vertical load on the left front wheel, F zfr For the vertical load on the right front wheel, F zrl For the vertical load on the left rear wheel, F zrr The vertical load on the right rear wheel is m. l h is the mass of the plow D T is the height of the point of application of the traction resistance above the ground. f1 T is the rolling resistance torque of the front wheel. f2 This is the rolling resistance torque of the rear wheel.

[0026] The Dugoff tire model is used to describe the relationship between the tractor's driving state and tire forces. The Dugoff tire model is as follows: in, In the formula, F x For the longitudinal force of the tire, F y F is the lateral force of the tire. z Where μ is the vertical load on the tire, s is the coefficient of road adhesion, and C is the wheel slip ratio. x C represents the longitudinal slip stiffness of the tire. y Let α be the tire lateral slip stiffness, α be the tire slip angle, and ε be the speed factor.

[0027] The tire slip angle model for the four drive wheels is as follows: In the formula, α fl The left front wheel slip angle, α fr The right front wheel slip angle, α rl The left rear wheel slip angle, α rr This refers to the right rear wheel's side slip angle.

[0028] The wheel rotation model of the tested tractor is as follows: In the formula, J f J is the moment of inertia of the front wheel. r For the moment of inertia of the rear wheel, The first derivative of the angular velocity of the left front wheel. The first derivative of the angular velocity of the right front wheel. The first derivative of the angular velocity of the left rear wheel. T is the first derivative of the angular velocity of the right rear wheel. dfl For the left front wheel drive torque, T dfr For the right front wheel drive torque, T drl For the left rear wheel drive torque, T drr For the right rear wheel drive torque, T bfl For the braking torque of the left front wheel, T bfr T is the braking torque of the right front wheel. brl For the braking torque of the left rear wheel, T brr This is the braking torque for the right rear wheel.

[0029] The longitudinal velocity of the wheel center of the tractor being tested is: In the formula, v fl v is the longitudinal velocity at the center of the left front wheel. fr v is the longitudinal velocity at the center of the right front wheel. rl v is the longitudinal velocity of the left rear wheel center. rr This represents the longitudinal velocity of the right rear wheel center.

[0030] The formula for calculating the wheel slip ratio of the tested tractor is: In the formula, s fl The slip ratio of the left front wheel, s fr The slip ratio of the right front wheel, s rl The left rear wheel slip ratio, s rr The slip ratio of the right rear wheel.

[0031] The control law for the adaptive observer of the driving wheel's moment of inertia is: In the formula, J a (t) represents the increment of the driving wheel's rotational inertia at time t, e(t) is the difference between the actual tractor driving wheel angular acceleration at time t and the theoretical driving wheel angular acceleration from the tractor dynamics model, and K p For proportional gain, K i For integral gain, K d This is the differential gain.

[0032] S2 defines the tractor's initial position, speed, and front wheel angle, and sets the plowing resistance, rolling resistance, and acceleration resistance experienced by the tractor based on the test conditions. Plowing resistance, rolling resistance, and acceleration resistance can be based on data collected from field tests, or data generated from physical and empirical formulas. Plowing resistance F D The calculation formula is: In the formula, Z represents the number of plowshares, and B... l h is the width of a single plowshare. k For deep cultivation, k l For soil specific resistance.

[0033] The formula for calculating rolling resistance is: In the formula, F f1 F is the rolling resistance of the front wheel. f2 denoted as , where f is the rolling resistance of the rear wheel.

[0034] Acceleration resistance F i The calculation formula is: In the formula, δ is the tractor rotational mass conversion factor.

[0035] The central control unit calculates the target resistance torque based on the longitudinal force and tire radius of each drive wheel, and sends control commands to the wheel-side loading unit.

[0036] S3, the wheel-side loading unit applies electric inertia loading to the drive wheel according to the control command of the central control unit.

[0037] S4, the sensor acquires information such as the rotational speed, torque, and angular acceleration at the drive wheel of the tractor under test, and sends the information to the central control unit.

[0038] S5, the central control unit calculates the difference between the actual angular acceleration of the tractor's drive wheel and the theoretical angular acceleration of the drive wheel in the tractor dynamics model based on the information obtained by the sensor, inputs the difference to the adaptive observer of the drive wheel's rotational inertia, calculates the increase in the rotational inertia of the drive wheel in the tractor dynamics model at the current moment, and corrects the rotational inertia of the drive wheel.

[0039] S6, the central control unit calculates the theoretical position and front wheel angle of the tractor according to the speed and torque information obtained by the sensor and according to the formulas (1) to (9), and adjusts the target resistance torque in real time according to the set test conditions.

[0040] Determine whether the experiment is complete. If not, proceed to step S4; if complete, export the experiment data and exit the inertia simulation system.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the specific implementation of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the pending claims.

Claims

1. A tractor test bench inertia simulation system based on digital twinning, characterized in that, include: Central control unit, wheel-side loading unit, sensors, and couplings; The central control unit is electrically connected to the wheel-side loading unit and the sensor respectively, and the wheel-side loading unit is mechanically connected to the drive wheel of the tractor under test through a coupling; The central control unit is used for: Establish a dynamic model of the tractor as a whole and an adaptive observer of the rotational inertia of the drive wheels based on the parameters of the tractor under test. Based on the test conditions and the initial position, speed, and front wheel angle of the tractor under test, the target resistance torque of the drive wheel is calculated using the tractor's overall dynamics model, and the wheel-side loading unit is controlled to apply inertia loading to the drive wheel. The difference between the actual angular acceleration of the tractor's drive wheel and the theoretical angular acceleration of the drive wheel in the tractor's dynamic model is calculated, and the moment of inertia of the drive wheel in the tractor's dynamic model is corrected by using an adaptive observer of the moment of inertia of the drive wheel. The theoretical position and speed of the tested tractor are updated by sensor information, and the target resistance torque of the drive wheels is adjusted in real time according to the overall dynamic model of the tractor.

2. The tractor test bench inertia simulation system of claim 1, wherein, The central control unit includes a real-time industrial computer, a data acquisition card, and a motor controller; the real-time industrial computer is used to establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheels; the data acquisition card is used to receive and process information from the sensors. The motor controller is used to control the wheel-side loading unit to perform inertia loading according to the target resistance torque.

3. The tractor test bench inertia simulation system of claim 1, wherein, The wheel-side loading unit includes a loading motor and a cooling system.

4. The tractor test bench inertia simulation system of claim 1, wherein, The sensor is used at least to acquire real-time information on the speed, torque, and angular acceleration of the drive wheels of the tractor under test, and to send the information to the central control unit.

5. A tractor test bench inertia simulation method based on digital twinning, characterized in that, This method employs the inertia simulation system as described in any one of claims 1-4, and includes the following steps: S1. Based on the parameters of the tractor under test, establish the overall dynamic model of the tractor and the adaptive observer of the rotational inertia of the drive wheels, and set the initial state of the tractor. S2. The central control unit calculates the target resistance torque at the drive wheel based on the test conditions and the tractor's initial position, speed, and front wheel angle using the tractor's overall dynamics model, and sends control commands to the wheel-side loading unit. S3. The wheel-side loading unit applies inertia loading to the drive wheel according to the control command of the central control unit. S4. The sensor acquires the speed, torque, and angular acceleration information at the drive wheel of the tested tractor in real time and sends the information to the central control unit. S5. The central control unit calculates the difference between the actual angular acceleration of the tractor's drive wheel and the theoretical angular acceleration of the drive wheel in the tractor's dynamic model, and corrects the moment of inertia of the drive wheel in the tractor's dynamic model through the drive wheel moment of inertia adaptive observer. S6. The central control unit updates the theoretical position and speed state of the tested tractor through the actual motion parameters obtained by the sensors, and adjusts the target resistance torque at the drive wheel in real time according to the corrected tractor overall dynamics model. S7. Determine whether the experiment is complete. If not, proceed to S4; if complete, export the experiment data and exit the inertia simulation system.

6. The tractor test bench inertia simulation method according to claim 5, characterized in that, The tractor's overall dynamics model established in step S1 is a multibody dynamics model that includes longitudinal, lateral, yaw motion and wheel rotation dynamics.

7. The tractor test bench inertia simulation method according to claim 5, characterized in that, In step S1, the adaptive observer of the driving wheel's moment of inertia adopts a proportional-integral-derivative control law.

8. The tractor test bench inertia simulation method according to claim 5, characterized in that, The actual motion parameters mentioned in step S6 include the rotational speed and torque of the drive wheel.

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