Multi-angle adjustable heavy load tire hydraulic loading system and control method

Abstract

The application discloses a multi-angle adjustable heavy-load tire hydraulic loading system and a control method, and the method comprises the following steps: constructing and acquiring loading platform parameters, and calculating the final displacement of all servo loading cylinders respectively; setting a target position and motion parameters, planning a seven-segment S-shaped speed curve, generating a position virtual shaft and a real-time position instruction thereof; taking the position virtual shaft as a main shaft and all servo loading cylinders as slave shafts, a master-slave following relationship is established by using a Poly5 electronic cam algorithm, four servo loading cylinders are driven to move synchronously, and the loading platform reaches a preset pose; on the basis that the loading platform keeps the set posture, a pressure virtual shaft is constructed, a tension change trajectory is generated according to a target tension value, and a control strategy of a pressure outer ring and a position inner ring is adopted for execution. The application realizes impact-free flexible reproduction of complex multi-angle working conditions of heavy-load tires and high-precision dynamic variable load loading under a constant posture.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic control technology, and specifically relates to a multi-angle adjustable heavy-duty tire hydraulic loading system and control method. Background Technology

[0002] Heavy-duty tires are core components of transportation and operational equipment such as heavy-duty trucks, construction machinery, and mining vehicles, and their performance directly affects vehicle driving safety. In actual operation, heavy-duty tires inevitably experience wear. Due to factors such as uneven load distribution, complex road conditions, and variable steering and braking conditions, tire wear often exhibits non-uniformity, with different areas of the tire showing varying degrees of wear. This leads to shortened tire life, reduced grip and braking performance, and causes vehicle vibration and noise, severely impacting vehicle handling stability and driving safety.

[0003] To delve into the non-uniform wear mechanism of heavy-duty tires and explore effective control methods, accurately simulating the stress state of tires under various working conditions is crucial. In tire non-uniform wear research, real-vehicle road tests more closely resemble real-world performance; however, they suffer from drawbacks such as long testing cycles, high costs, uncontrollable environmental factors (affected by seasonal changes, road maintenance, etc.), and difficulties in data collection, making reproducible and parameterized systematic research challenging. Therefore, indoor bench testing serves as an important supplementary and even alternative method, providing a more controlled testing environment and facilitating data collection, making it an ideal platform for systematic research.

[0004] Chinese invention patent application CN105445040A discloses an experimental rig for testing the steering performance of multi-axle vehicles. The rig includes a support frame and an axle fixed to the support frame. Tires are mounted on both ends of the axle, and a road surface simulation plate is mounted on one or both sides of the axle, contacting the tires. A hydraulic servo cylinder is fixedly connected to the underside of the road surface simulation plate. This design focuses on simulating static or unidirectional loads and cannot meet dynamic requirements. It fails to realistically reproduce complex loads and can only achieve loading in a single direction.

[0005] Chinese invention patent application CN111474850A discloses a control method for optimizing a PID hydraulic leveling system based on an improved sine and cosine algorithm. The method includes the following steps: establishing a mathematical model of the controlled object through system identification; determining the upper bound of the performance index of the control system's excitation response based on the requirements of the controlled system, and constructing the comprehensive fitness function J of the optimization algorithm by combining the comprehensive performance index ITAE of the control system; optimizing the parameters Kp, Ki, and Kd of the PID controller in the solution space using an improved sine and cosine algorithm, and assigning the algorithm's result to the PID controller; using the deviation from the platform's preset angle as the system input, the PID controller sends a control signal, which, through the actuator, changes the angle of the work platform. A dual-axis sensor feeds back the detected angle signal to the controller, and this process repeats until the platform's levelness requirement is met. This method uses a traditional vertical loading structure with a single-stage position loop PID control combined with a step displacement input. This not only makes it difficult for the loading platform to maintain a constant horizontal reference plane, easily causing angle deviations, but also triggers a huge initial impact during startup.

[0006] To achieve higher control accuracy and robustness, Chinese invention patent application CN118034057A discloses a neural network adaptive superspiral sliding mode control method for a hydraulic press leveling system. This method includes the following steps: establishing a mathematical model of a passive four-corner leveling system for a hydraulic press considering a moving beam model; approximating the unknown parts of the system model based on the RBF neural network principle; combining the RBF neural network with sliding mode control according to the established mathematical model to design a superspiral sliding mode position closed loop, using the highest cylinder displacement as the virtual axis, with the four leveling cylinders tracking the virtual axis to achieve four-cylinder synchronous control; designing an adaptive law based on the designed neural network superspiral sliding mode controller and tuning the controller gain online; and ensuring the stability and convergence of the entire closed-loop system based on the Lyapunov method for the designed neural network adaptive superspiral sliding mode controller. In this scheme, the online computation and weight update of the RBF network greatly increase the computational burden and affect the real-time response of the system. At the same time, the tuning of complex superspiral sliding mode parameters is extremely difficult, and the stability guaranteed by the Lyapunov method depends on the ideal model. Actual unmodeled dynamics and noise may cause the actual performance to deviate from the theoretical expectations. Summary of the Invention

[0007] This invention provides a multi-angle adjustable heavy-duty tire hydraulic loading system and control method, aiming to solve the problems of existing technologies being unable to meet the real simulation requirements of complex dynamic coupled loads, as well as low control accuracy and poor stability during multi-degree-of-freedom loading processes.

[0008] To address the aforementioned technical problems, this invention proposes a multi-angle adjustable hydraulic loading control method for heavy-duty tires, comprising the following steps: Construct a loading platform supported by multiple servo loading cylinders, obtain the loading platform parameters, and calculate the final target displacement corresponding to each servo loading cylinder. Set the target position and motion parameters, plan a seven-segment S-shaped velocity curve including acceleration, uniform acceleration, deceleration, constant speed, deceleration, uniform deceleration and deceleration, and generate a virtual position axis and its real-time position command. Using the virtual axis of the position as the master axis and all servo loading cylinders as slave axes, the master-slave following relationship is established using the Poly5 electronic cam algorithm; and combining the initial state of each slave axis with the boundary conditions of the final target displacement, the Poly5 motion curve position command of each servo loading cylinder is calculated in real time, driving the four servo loading cylinders to move synchronously, so that the loading platform reaches the preset pose; While maintaining the set posture on the loading platform, a virtual pressure axis is constructed, and a tension change trajectory is generated based on the target tension value; a control strategy of outer pressure loop and inner position loop is adopted. The outer pressure ring outputs a position compensation amount based on the deviation between the real-time collected tension feedback value and the tension command value generated by the pressure virtual axis through PID calculation. The inner position loop superimposes the position compensation amount onto the real-time position of the virtual position axis, which serves as the final position input for each servo loading cylinder, driving the servo loading cylinder to move.

[0009] Preferably, the method further includes a cyclic pressure loading step: Once the outer pressure control system reaches a steady state, the loading frequency is set to make the tension setpoint fluctuate within the preset range of the target tension. The setpoint of the tension after real-time calculation of fluctuations is used as the input of the outer pressure ring, and the position compensation amount is continuously output to the inner position ring to drive the servo loading cylinder to perform dynamic loading.

[0010] Preferably, the method further includes a motion stop and reset step: After receiving the stop command, the controller re-plans the seven-segment S-shaped speed curve of the virtual position axis, starting from the current position of the loading platform center and ending at the zero position. Using the current position of the four servo loading cylinders as the initial state and the zero position as the final target displacement, the zero-return trajectory of each axis is recalculated using the Poly5 electronic cam algorithm. The four servo loading cylinders are driven to move synchronously to the standby zero position, thereby achieving system unloading and reset.

[0011] Preferably, the loading platform is a four-corner hydraulic loading platform, driven by servo loading cylinders located at the four corners of the loading platform; A spatial rectangular coordinate system is established with the center point of the loading platform surface at the standby position as the origin. An X-axis and a Y-axis are set on the horizontal plane, with the X-axis parallel to the tire rolling direction. The loading platform parameters include the target position of the loading platform center. Pitch angle Roll angle and half the distance between the two cylinders in the X-axis direction. Half the distance between the two cylinders in the Y-axis direction ; The final target displacement is calculated as follows:

[0012] In the formula, , , , These represent the final displacements of the four servo-loaded cylinders.

[0013] Preferably, the seven-segment S-shaped velocity curve is specifically as follows: Using the target position at the center of the platform as the final target position of the virtual axis, and the set speed as the uniform speed segment, trapezoidal velocity planning calculation is performed in combination with the set acceleration, deceleration and jerk. The motion process is divided into seven time periods: acceleration phase, deceleration phase, and acceleration phase. Uniform acceleration segment Deceleration / Acceleration Section Uniform speed segment Deceleration / Acceleration Section Uniform deceleration section and deceleration phase ; exist , , , The acceleration changes linearly in stages. , The acceleration remains constant during the phase. The acceleration during the phase is zero.

[0014] Preferably, the method for establishing a master-slave follower relationship using the Poly5 electronic cam algorithm includes the following steps: Define normalized variables Map the real-time position of the virtual axis to the interval [0,1]:

[0015] In the formula, The target position is generated in real time for the virtual axis of position. Let L be the initial position of the virtual axis, and L be the total travel distance of the virtual axis. Establish each servo loading cylinder based on The fifth-order polynomial equation:

[0016] In the formula, These are the real-time position commands for the four servo loading cylinders. Let represent the undetermined polynomial coefficients of the i-th servo loading cylinder.

[0017] Preferably, the calculation method for the Poly5 motion curve position command is as follows: Calculate the lower-order coefficients using the initial boundary conditions. , and ; Construct boundary conditions containing higher-order coefficients using the terminal states , and A system of linear equations; Based on the initial position and final target displacement of the servo loading cylinder, the higher-order coefficients are obtained by solving the system of linear equations. , and ; Substitute all the solved coefficients into the fifth-order polynomial equation to calculate the position commands of each servo loading cylinder in real time.

[0018] Preferably, the generation of the tension change trajectory specifically involves: Using the current tension value as the starting force, and the target tension as the final target force along the virtual axis of tension; Set the parameters for the velocity, acceleration, deceleration, and jerk of the tension change, and generate a tension command with a trapezoidal velocity trajectory and a non-linear S-shaped target tension trajectory.

[0019] Preferably, the inner position ring superimposes the position compensation amount onto the real-time position of the virtual position axis, specifically in the following manner: The position compensation amount output by the outer pressure loop is added to the current real-time position command of the virtual axis to obtain the corrected virtual axis position command. The corrected virtual axis position command is used as the vertical displacement parameter of the loading platform center in the inverse kinematics solution. It is then substituted back into the target displacement calculation formula of the four servo loading cylinders to calculate the final position input of the four servo loading cylinders at the current moment, including pressure compensation.

[0020] On the other hand, the present invention also proposes a multi-angle adjustable heavy-duty tire hydraulic loading system, including a high-pressure oil source, an oil tank, a loading platform, four servo loading cylinders arranged in a rectangle and supporting the loading platform, a sensor group, and a controller. The four servo loading cylinders belong to four identical loading subsystems, each of which includes: a reversing valve, a safety valve, a servo proportional valve, and a check valve. In each loading subsystem, the reversing valve is a two-position three-way valve, and its output end is connected to the pilot control port of the check valve to control the opening and closing of the check valve. The P port of the servo proportional valve is connected to a high-pressure oil source, the T port is connected to an oil tank, the A port is connected to the rod chamber of the corresponding servo loading cylinder, and the B port is connected to the rodless chamber of the corresponding servo loading cylinder. Safety valves and check valves are installed in parallel or in series on the pipeline between the A port of the servo proportional valve and the rod chamber of the servo loading cylinder, and on the pipeline between the B port of the servo proportional valve and the rodless chamber of the servo loading cylinder. The sensor group includes: Displacement sensors, each installed on a servo-loaded cylinder, are used to detect the piston rod stroke; Pressure sensors are installed at the inlet of the rod-side and rodless chambers of each servo loading cylinder, respectively. The gyroscope sensor installed on the loading platform is used to detect the attitude angle of the loading platform; And a tension sensor installed at the center of the loading platform to detect the force between the tire and the loading platform; The controller is electrically connected to the servo proportional valve, directional valve and sensor group of each loading subsystem, and is configured to execute the heavy-duty tire hydraulic loading control method as described in the first aspect of the present invention.

[0021] Compared with the prior art, the present invention has the following technical effects: 1. The heavy-duty tire hydraulic loading control method proposed in this invention employs a parallel motion mechanism driven by a four-column electro-hydraulic servo. Through differential displacement control of the four servo loading cylinders, it can accurately simulate the complex postures of a vehicle such as pitch and roll on slopes and uneven road surfaces. This allows the test bench to reproduce the stress state of uneven load distribution of heavy-duty tires in actual operation, providing a more realistic indoor test environment for studying the non-uniform tire wear mechanism.

[0022] 2. The heavy-duty tire hydraulic loading control method proposed in this invention ensures the continuity of acceleration through a seven-segment S-shaped speed planning, eliminating the rigid impact of the hydraulic system at the moment of start-up and stop; by using the normalized Poly5 interpolation algorithm to establish a master-slave following relationship, it solves the problem of synchronization difficulties caused by the different strokes of the four hydraulic cylinders, ensuring that the four corners of the loading platform are strictly synchronized during the attitude adjustment process, and maintaining the stability and high rigidity during the movement process.

[0023] 3. The heavy-duty tire hydraulic loading control method proposed in this invention employs a cascade decoupling control strategy of an outer pressure loop and an inner position loop. By superimposing the compensation output of the pressure loop onto the common vertical displacement parameter of the virtual spindle, and combining it with inverse kinematics to redistribute the stroke of each axis, independent and precise adjustment of the vertical load is successfully achieved without changing the predetermined tilt angle of the platform.

[0024] 4. The heavy-duty tire hydraulic loading control method proposed in this invention supports a cyclic pressure loading mode based on sine waves, which can simulate the dynamic alternating load of the tire during driving. Combined with a high-frequency response servo proportional valve and a high-precision sensor closed loop, the system can not only perform static stiffness testing, but also long-term dynamic durability and fatigue testing, greatly expanding the application range of the test bench. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of the heavy-duty tire hydraulic loading control method described in this invention; Figure 2 This is a flowchart of the displacement synchronization control described in an embodiment of the present invention; Figure 3 This is a flowchart of the alternating pressure control described in an embodiment of the present invention; Figure 4 This is a schematic diagram of the heavy-duty tire hydraulic loading system according to an embodiment of the present invention; Figure 5 This is a loading diagram of an embodiment of the present invention.

[0026] Reference numerals in the attached diagram: 1. High-pressure oil source; 2. Oil tank; 3. Reversing valve; 4. Safety valve; 5. Servo proportional valve; 6. Displacement sensor; 7. Pressure sensor; 8. Servo loading cylinder; 9. Gyroscope sensor; 10. Tension sensor; 11. Check valve. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present application and with reference to the accompanying drawings.

[0028] This embodiment uses a rectangular four-corner hydraulic loading platform as an example to illustrate the technical solution. The loading platform is driven by four servo loading cylinders located at the four corners of the loading platform.

[0029] Example 1 This embodiment describes a multi-angle adjustable hydraulic loading control method for heavy-duty tires, such as... Figure 1 As shown, it includes the following steps one through four: Those skilled in the art will understand that, prior to step one, when the system is started or in standby mode, it is necessary to ensure that all actuators are in a defined initial position. Specifically, the control system drives the first to fourth loading subsystems into a standby reset state: When the four directional valves 3 are energized and in the left position, high-pressure oil enters the pilot control port of the check valve 11, forcibly opening the main channel of the check valve 11, causing it to lose its one-way shut-off function and allowing the oil to flow freely in both directions; at the same time, the four servo proportional valves 5 are energized in the right position, so that the rodless chamber of the four servo loading cylinders 8 is connected to the oil tank 2, and the oil in the rod chamber is unloaded.

[0030] In this state, due to the return oil in the rodless chamber, the piston rods of the four servo loading cylinders 8 retract to their lowest positions under the action of gravity. The system defines this lowest position as the zero position (i.e., standby position) of the servo loading cylinder 8, and resets or calibrates the readings of the displacement sensors 6 corresponding to each servo loading cylinder 8 to their initial values.

[0031] Step 1: Construct a loading platform supported by multiple servo loading cylinders. The system obtains the target pose parameters and geometric parameters of the loading platform through the host computer or user input, and calculates the final target displacement corresponding to each servo loading cylinder.

[0032] A spatial rectangular coordinate system is established with the center point of the loading platform surface at the standby position as the origin. An X-axis and a Y-axis are set on the horizontal plane, with the X-axis parallel to the tire rolling direction. The loading platform parameters include: Target location of loading platform center ; Pitch angle (That is, the angle of rotation around the Y-axis causes a height difference in the X-axis direction); Roll angle (That is, the angle of rotation around the X-axis causes a height difference in the Y-axis direction); and half the distance between the two cylinders in the X-axis direction (The distance from the center of the loading cylinder to the geometric center of the platform along the X-axis); Half the distance between the two cylinders in the Y-axis direction (The distance from the center of the loading cylinder to the geometric center of the platform in the Y-axis direction).

[0033] Based on the spatial geometric parameters obtained above, the controller calculates the final target displacement required for each servo loading cylinder to reach the target posture using an inverse kinematics algorithm. In this embodiment, the distribution of the four servo loading cylinders (denoted as the first servo loading cylinder, the second servo loading cylinder, the third servo loading cylinder, and the fourth servo loading cylinder) in the coordinate system corresponds to the positive and negative sign logic in the formula, and the calculation method for their final displacement is shown in the following set of equations:

[0034] In the formula, , , , These represent the final displacements of the four servo loading cylinders. The controller uses these four calculated displacements as target values ​​in the subsequent virtual axis position control strategy, combining S-shaped speed planning and the Poly5 electronic cam algorithm to drive the hydraulic system.

[0035] Step Two: Set the target position and motion parameters, plan a seven-segment S-shaped velocity curve including acceleration, uniform acceleration, deceleration, constant speed, deceleration, uniform deceleration, and deceleration, and generate the virtual position axis and its real-time position command. After completing the final target displacement of each servo loading cylinder ( , , , After the calculation, the controller enters the displacement adjustment stage. To avoid hydraulic shock caused by traditional step signals and to ensure strict time synchronization (i.e., simultaneous start-up, simultaneous arrival, and trajectory coordination) of the four hydraulic cylinders as they reach different target positions, this embodiment adopts a master-slave control strategy using a virtual position axis and a Poly5 electronic cam. The specific steps are as follows: The controller first constructs a virtual axis that does not exist in the physical entity to represent the target position at the center of the platform. The final target position for motion along the virtual axis. Receives parameters from the four-axis displacement loop PID control: set speed. acceleration deceleration and jerk Based on the above parameters, trapezoidal velocity planning calculations are performed, generating a trapezoidal velocity trajectory and a non-linear five-order S-shaped displacement curve for the target position trajectory. The five-order S-shaped displacement curve is a seven-segment S-curve, including three acceleration segments, one constant velocity segment, and three deceleration segments. These are the acceleration and deceleration segments (…). ), uniform acceleration segment ( ), deceleration phase ( ), uniform speed segment ( ), deceleration phase ( ), uniform deceleration section ( ) and deceleration phase ( The corresponding time for each segment of motion is recorded as follows: , , , , , , The calculation formula is as follows:

[0036] The piecewise kinematic formulas are as follows: Acceleration phase The acceleration increases linearly from 0 to its maximum value. Time range: 0 < < ,in .

[0037]

[0038] Uniform acceleration segment The acceleration remains at a constant maximum value, uniform acceleration. ), time range < < ,in ,in a 1, v 1. s 1 represents the final state of acceleration.

[0039]

[0040] deceleration phase The acceleration decreases linearly from its maximum value to 0, and the deceleration ( ), time range < < ,in ,in a 2, v 2. s 2 represents the final state of acceleration.

[0041]

[0042] constant speed segment The velocity remains constant, the acceleration is 0, and the time range is... < < ,in ,in a 3, v 3. s 3 represents the final state of deceleration.

[0043]

[0044] deceleration phase The acceleration increases linearly from 0 in the opposite direction, acceleration and deceleration ( ), time range < < ,in ,in a 4, v 4. s 4 represents the final state of uniform velocity.

[0045]

[0046] Uniform deceleration section The acceleration remains a constant negative value, and the deceleration is uniform. ), time range < < ,in ,in a 5, v 5. s 5 represents the final state of acceleration / deceleration.

[0047]

[0048] Deceleration section The acceleration linearly reverts from its negative maximum value to 0, while the deceleration... ), time range < < ,in ,in a 6, v 6. s 6 represents the final state of uniform deceleration.

[0049]

[0050] exist , , , The acceleration changes linearly in stages. , The acceleration remains constant during the phase. The acceleration during the phase is zero.

[0051] Step 3: Using the virtual axis of position as the master axis and all servo loading cylinders as slave axes, establish a master-slave following relationship using the Poly5 (fifth-order polynomial) electronic cam algorithm; and combine the initial state of each slave axis with the boundary conditions of the final target displacement, calculate the Poly5 motion curve position command of each servo loading cylinder in real time, drive the four servo loading cylinders to move synchronously, and make the loading platform reach the preset pose. Please refer to [link / reference] for details. Figure 2 (Flowchart of displacement synchronization control for the four-corner hydraulic loading system).

[0052] Specifically, the method for establishing a master-slave follower relationship using the Poly5 electronic cam algorithm includes the following steps: Define normalized variables Map the real-time position of the virtual axis to the interval [0,1]:

[0053] In the formula, The target position is generated in real time for the virtual axis of position. Let L be the initial position of the virtual axis, and L be the total travel distance of the virtual axis. Establish each servo loading cylinder based on The fifth-order polynomial equation:

[0054] In the formula, These are the real-time position commands for the four servo loading cylinders. Let represent the undetermined polynomial coefficients of the i-th servo loading cylinder.

[0055] To ensure the smoothness of the motion's starting and ending points (without abrupt changes in position, velocity, or acceleration), the aforementioned coefficients are solved using boundary conditions. The specific calculation methods are as follows (S31-S33): S31: Utilizing the initial state ( Given the boundary conditions, calculate the lower-order coefficients. , and ; lower order coefficients :

[0056] lower order coefficients :

[0057]

[0058] lower order coefficients :

[0059]

[0060] S32: Utilizing the terminal state ( The boundary conditions are constructed by including higher-order coefficients. , and A system of linear equations, in which ; Position constraints ),in The equations for the coefficients of each servo-loaded cylinder can be obtained as follows:

[0061]

[0062] Speed ​​constraints ),in The equations for the coefficients of each servo-loaded cylinder can be obtained as follows:

[0063]

[0064] Acceleration constraints ),in The equations for the coefficients of each servo-loaded cylinder can be obtained as follows:

[0065]

[0066] S33: Based on the initial position and final target displacement of the servo loading cylinder, solve the linear equations to obtain higher-order coefficients. , and Specifically, based on the combination of the above equations for position constraints, velocity constraints, and acceleration constraints, we can obtain:

[0067] Write it in the form of a system of linear equations:

[0068] Calculate the coefficient determinant , , and :

[0069]

[0070]

[0071]

[0072] Calculate the lower-order coefficients , and for:

[0073] Substitute all the solved coefficients into the fifth-order polynomial equation to calculate the position commands of each servo loading cylinder in real time:

[0074] In the above formula, This represents the real-time position command for the i-th servo loading cylinder, where .

[0075] In a specific hydraulic loading system, a displacement sensor monitoring the piston rod displacement in the servo loading cylinder acquires the displacement signal of the servo loading cylinder in real time and transmits it to the controller. When the user clicks the displacement enable button, the virtual axis starts running and outputs its real-time position. The controller calculates normalized variables based on the real-time position, substitutes them into the Poly5 equations for each axis, and calculates the current target position command for the four servo loading cylinders in real time. , , and The controller uses the difference between the target position command and the actual displacement signal for each axis as the input to the position loop PID controller, calculates the output control quantity (such as valve port voltage signal), and applies it to each servo proportional valve. The valve port voltage signal of the four servo proportional valves adjusts the hydraulic oil flow, driving the servo loading cylinder to follow the command. The controller compares the difference between the actual displacement and the final target displacement of the four servo loading cylinders in real time. When the difference of all axes is less than or equal to a preset threshold (e.g., 0.2mm), the position and angle adjustment is determined to be complete, the "displacement indicator" is illuminated, and the current position is maintained in a closed loop, awaiting the next pressure loading command.

[0076] Step 4: Once the loading platform has been adjusted to the preset target position and attitude (i.e., displacement control is complete), the controller automatically enters the alternating pressure control stage. This embodiment adopts a cascade control strategy of "pressure outer loop - position inner loop," that is, while maintaining the set attitude of the loading platform (i.e., pitch angle)... and roll angle Based on a constant load, a virtual pressure axis is constructed, and a tension change trajectory is generated according to the target tension value to achieve precise variable load application on the tire. The outer pressure ring outputs a position compensation amount based on the deviation between the real-time collected tension feedback value and the tension command value generated by the pressure virtual axis through PID calculation. The inner position loop superimposes the position compensation amount onto the real-time position of the virtual position axis, which serves as the final position input for each servo loading cylinder, driving the servo loading cylinder to move.

[0077] Please see Figure 3 (Flowchart of alternating pressure control for four-corner hydraulic loading system) First, the system enters the pressure control mode. The displacement sensor continuously collects the displacement signals of the four servo loading cylinders in real time, and the tension sensor collects the actual tension signal perpendicular to the loading plane in real time, and transmits the above signals to the controller synchronously.

[0078] The controller constructs a virtual pressure axis to generate a smooth tension change trajectory, avoiding damage to the tire from sudden load changes. Specifically, the generation of the tension change trajectory involves: The controller uses the tension value collected by the current tension sensor as the starting force and the target tension set by the user as the final target force for the pressure virtual axis. The controller sets parameters for the velocity, acceleration, deceleration, and jerk of the tension change. Based on these parameters, it performs trapezoidal velocity planning calculations to generate real-time tension commands with a trapezoidal velocity trajectory and a non-linear S-shaped target tension trajectory.

[0079] In the outer loop (pressure loop) of the cascade control, the controller uses the real-time tension command as the set target value and the actual tension value collected in real time by the tension sensor as the feedback process variable. After the difference between the two is calculated, the result is processed by a PID algorithm to output the vertical position compensation amount required to maintain the target tension. This compensation amount represents the fine-tuning distance that the center of the loading platform needs to make in the vertical direction to achieve the target tension at the current moment.

[0080] In the inner loop (position loop) of the cascade control, in order to ensure that the original tilt angle of the platform remains unchanged while pressure is applied, the controller performs the following decoupling calculation: The position compensation amount output by the outer pressure loop is added to the current real-time position command of the virtual axis to obtain the corrected virtual axis position command; specifically, the position compensation amount output by the outer pressure loop... Real-time position command of virtual axis superimposed on the current position The corrected vertical position command for the platform center is obtained. .

[0081] The corrected virtual axis position command is used as the vertical displacement parameter of the loading platform center in the inverse kinematics solution, and then substituted back into the target displacement calculation formula for the four servo loading cylinders to calculate the final position input of the four servo loading cylinders at the current moment, including pressure compensation. Specifically, in this embodiment, the corrected virtual axis position command is used as the vertical displacement parameter of the loading platform center in the inverse kinematics solution. As new inverse kinematic parameters, combined with the pitch angle that has been locked and remains unchanged in step two. and roll angle and platform geometry parameters ( Substituting the values ​​back into the target displacement calculation formula, the final displacement input of the four servo loading cylinders, including pressure compensation, is calculated at the current moment. The calculation formula is as follows:

[0082] The controller calculates Using the setpoints for the inner loop of each axis position and the feedback values ​​from the displacement sensors of each axis as feedback, position loop PID calculations are performed separately. The output control signals drive four servo proportional valves to adjust the extension and retraction of the hydraulic cylinders. In this way, the four hydraulic cylinders superimpose the same displacement increment in the vertical direction. Meanwhile, the relative height difference between each cylinder remains unchanged, thus achieving precise loading of the target pressure while maintaining a constant loading plane inclination angle.

[0083] The controller compares the actual feedback value of the tension sensor with the target tension setting value in real time. When the absolute value of the difference is continuously less than or equal to the preset threshold (e.g., 10N), it is determined that the tension value loaded by the platform has reached the target tension value. At this time, the controller lights up the "pressure indicator light" to indicate that the single pressure loading is completed.

[0084] After completing the static target tensile loading (i.e., Embodiment 3 above), in order to simulate the dynamic stress conditions of a heavy-duty tire driving on a real road surface, and to ensure safe reset after the test, this embodiment further performs a cyclic pressure loading step and a motion stop reset step. Therefore, the method described in this embodiment also includes step five.

[0085] Step 5: Cyclic pressure loading. Once the outer loop pressure control system reaches a steady state, set the loading frequency to ensure the tension setpoint fluctuates within the preset range of the target tension. After the system detects that static tension loading is complete (i.e., the "pressure indicator light" illuminates), the operator can set the loading frequency via the host computer. (For example Then click the "Cyclic Loading" enable button. At this time, the controller will set the static target tension value. Converted to a certain range (e.g.) The dynamic tension setting fluctuates to simulate the dynamic loading environment of the tire.

[0086] Dynamic tension setting value The calculation formula is as follows:

[0087] In the formula, It is a time variable.

[0088] During this process, the system continues to execute the cascade control strategy of "pressure outer loop - position inner loop": the setpoint of the tension after fluctuation is calculated in real time as the input of the pressure outer loop, and the position compensation is continuously output to the position inner loop to drive the servo loading cylinder for dynamic loading. When the test task ends or needs to be stopped midway, the operator clicks the "motion stop" button, and the system enters the reset process.

[0089] When the test task ends or needs to be stopped midway, the operator clicks the "Stop Movement" button, and the system enters the reset process. Therefore, the method described in this embodiment also includes step six.

[0090] Step Six: Motion Stop and Reset Procedure. Upon receiving the stop command, the controller uses the current position of the loading platform center as the starting point and the zero-point position as the ending point to re-plan the seven-segment S-shaped velocity curve of the virtual position axis. Specifically, the controller reads the current real-time position of the loading platform center as the starting point and the zero-point position (standby position) as the ending point. This is combined with the preset zero-return speed. acceleration deceleration And accelerometer Then, the trapezoidal velocity planning calculation is performed again to generate a virtual axis S-shaped motion trajectory that smoothly transitions from the current position to the zero point (its velocity profile is trapezoidal and its position profile is S-shaped).

[0091] Using the current positions of the four servo loading cylinders as the initial state and zero position as the final target displacement, the Poly5 electronic cam algorithm is used to recalculate the zero-return trajectory for each axis. The controller uses the virtual axis's S-shaped motion trajectory, smoothly transitioning from the current position to zero, as the master axis, and the four servo loading cylinders as slave axes. The real-time position, velocity, and acceleration of the four servo loading cylinders are acquired as the initial state (initial velocity parameters). Initial acceleration parameters Set zero position (displacement is 0), zero velocity, and zero acceleration as the final state (final velocity parameter). =0, final acceleration parameter (0). Using the normalization algorithm and Cramer's rule, the coefficients of the five polynomials are recalculated to construct the fifth-order Poly5 curve equations for the four servo loading cylinders to return to zero from their current irregular positions.

[0092] The four servo loading cylinders are driven to move synchronously to the standby zero position, realizing system unloading and reset. The controller activates the displacement motion enable, and the virtual spindle begins its return-to-zero motion. Based on the real-time virtual axis position, the four servo loading cylinders calculate the real-time position command of each axis using the Poly5 equation. The controller calculates the difference between the real-time position command of each axis and the feedback signal from the displacement sensor, and outputs the control voltage to the four servo proportional valves through the position loop PID calculation, driving the hydraulic cylinders to retract synchronously.

[0093] The controller compares the actual displacement of the four servo loading cylinders with the zero position in real time. When the difference of all axes is less than or equal to the preset threshold (e.g., 0.2mm), the system is determined to have been safely reset, the "standby position" indicator light illuminates, and the system completes unloading and returns to standby mode.

[0094] Example 2 This embodiment describes a multi-angle adjustable heavy-duty tire hydraulic loading system, such as... Figure 4 As shown, the system mainly consists of four parts: a hydraulic power unit, an actuator, a sensor detection unit, and a controller.

[0095] In terms of overall architecture, the system includes a high-pressure oil source 1 (which serves as a hydraulic power source to provide constant system pressure), an oil tank 2 (for storing and recovering hydraulic oil), a high-rigidity loading platform, and four servo loading cylinders 8 that are arranged in a rectangular shape to support the loading platform.

[0096] To achieve independent driving and coordinated control of the four corners of the loading platform, the four servo loading cylinders 8 belong to four structurally identical loading subsystems (i.e., the first to the fourth loading subsystems). For simplicity, the following description will focus on one of the loading subsystems (e.g., the subsystem driving the first servo loading cylinder) and its corresponding pipelines, valve groups, and sensors. The structures and connections of the other three loading subsystems are identical.

[0097] Regarding the loading subsystem, each loading subsystem includes core control components and auxiliary safety components, specifically including: directional valve 3, safety valve 4, servo proportional valve 5, and check valve 11.

[0098] The core control element is the servo proportional valve 5, which precisely adjusts the flow rate and direction of the hydraulic cylinder according to the controller's instructions. The P port (inlet) of the servo proportional valve 5 is connected to the high-pressure oil source 1 via a pipeline, the T port (return port) is connected to the oil tank 2, and the A port (working port A) is connected to the rod chamber of the servo loading cylinder 8 via the main oil circuit; the B port (working port B) of the servo proportional valve 5 is connected to the rodless chamber of the servo loading cylinder 8 via the main oil circuit. The controller can control the extension, retraction, and stop of the servo loading cylinder 8 by adjusting the valve core opening of the servo proportional valve 5.

[0099] To ensure reliable locking of the hydraulic cylinder (e.g., preventing pressure drop due to internal leakage) and to enable standby unloading, a check valve 11 is installed on the main oil line between the servo proportional valve 5 and the servo loading cylinder 8. Specifically, a first hydraulically controlled check valve is connected in series on the pipeline between port A of the servo proportional valve 5 and the rod-side chamber of the servo loading cylinder 8; a second hydraulically controlled check valve is connected in series on the pipeline between port B of the servo proportional valve 5 and the rodless chamber of the servo loading cylinder 8. The pilot control ports (i.e., control oil ports) of these two check valves 11 are connected to the output end of the directional valve 3 after converging through the control pipeline.

[0100] The directional valve 3 is a two-position three-way solenoid valve. Its inlet is connected to the high-pressure oil source 1 (or the pressure oil circuit before the servo valve), and its return port is connected to the oil tank 2. When the directional valve 3 is energized (or in the left position), high-pressure control oil enters the pilot control port of the check valve 11, forcibly opening the valve core of the check valve 11, causing it to lose its one-way shut-off function and allowing the oil to flow freely in both directions. At this time, the servo loading cylinder 8 can move with the servo proportional valve 5 or return oil to unload. When the directional valve 3 is de-energized (or in the right position), the pilot control port of the check valve 11 is depressurized, and the check valve 11 resumes its one-way shut-off function, thereby acting as a hydraulic lock to ensure the safety of position holding.

[0101] To prevent system overload from causing pipe bursts or component damage, overload protection is installed on the oil inlet lines of both chambers of the servo loading cylinder 8. Specifically, a safety valve 4 is connected in parallel on the oil inlet line of the rod chamber of the servo loading cylinder 8, with its outlet connected to the oil tank 2; another safety valve 4 is connected in parallel on the oil inlet line of the rodless chamber of the servo loading cylinder 8, with its outlet also connected to the oil tank 2. When the pressure in either chamber exceeds the set safety threshold, the corresponding safety valve 4 opens to overflow, draining the high-pressure oil back to the oil tank, thereby protecting the actuator.

[0102] Regarding the sensor detection unit, the system is equipped with a multi-dimensional sensor group for real-time feedback of the system's motion state and force conditions, forming a fully closed-loop control: Displacement detection: Each servo loading cylinder 8 is equipped with a displacement sensor 6 (such as a magnetostrictive displacement sensor or a grating ruler) on its side or inside, which is used to detect the extension stroke of the piston rod in real time and provide feedback on the absolute position information of the four corners.

[0103] Pressure detection: Pressure sensors 7 are installed at the inlet of the rod chamber and the inlet of the rodless chamber of each servo-loaded cylinder 8. These two pressure sensors 7 are used to monitor the pressure difference between the two chambers of the hydraulic cylinder in real time. The controller can use this to calculate the output force of a single cylinder or for feedback in the force control loop.

[0104] Attitude detection: A high-precision gyroscope sensor 9 (or tilt sensor) is installed on the upper surface of the loading platform to directly detect the spatial attitude of the loading platform, specifically including pitch, roll and yaw, to provide feedback for the multi-axis synchronous leveling algorithm.

[0105] Load detection: A tension sensor 10 (or a three-dimensional force sensor) is installed at the geometric center of the loading platform (below the tire contact area) to directly detect the vertical force and dynamic load between the tire and the loading platform. It is the core feedback source for pressure virtual spindle control.

[0106] The system controller (such as a PLC, industrial computer, or dedicated motion controller) is connected to each of the above components via electrical wiring: Output: Connected to the control coil of the servo proportional valve 5 in the four loading subsystems (outputs analog voltage / current signals), and the electromagnet of the solenoid directional valve 3 (outputs switching signals).

[0107] Input terminal: Collects signals from displacement sensor 6, pressure sensor 7, gyroscope sensor 9, and tension sensor 10.

[0108] The controller is pre-programmed with a control program for the hydraulic loading method as described in Embodiment 1, and is configured to execute all control methods including pose calculation, virtual spindle planning, Poly5 electronic cam synchronization, cascade pressure control, and cyclic loading.

[0109] A schematic diagram of a single loading platform after loading a tire is shown below. Figure 5 As shown, the system adopts a parallel motion mechanism design with four-column electro-hydraulic servo drive. The specific structure includes a stable base fixed at the bottom, four servo loading cylinders (red columnar components in the figure) distributed in a rectangular array, and a high-rigidity loading platform (white rectangular plate in the figure) located at the top.

[0110] During testing, the heavy-duty tire to be tested is placed above the loading platform. The cylinder bodies of the four servo loading cylinders are vertically fixed to the base. The piston rods are not rigidly connected to the loading platform, but rather connected to its lower surface via ball joints. This flexible connection method removes the constraints on rotational freedom and is the key structural basis for achieving multi-angle deflection of the platform. When the system executes multi-angle loading commands, the controller drives the four servo loading cylinders to extend different stroke lengths. By controlling the stroke difference between the front and rear hydraulic cylinders, the loading platform is driven to rotate around the lateral axis, achieving pitch angle adjustment; by controlling the stroke difference between the left and right hydraulic cylinders, the loading platform is driven to rotate around the longitudinal axis, achieving roll angle adjustment.

[0111] With the help of this four-corner independent drive and ball joint support structure, this system can flexibly simulate the tire force posture of a vehicle under complex working conditions such as driving on slopes, turning and tilting, or uneven road surfaces. In combination with the aforementioned virtual spindle and Poly5 electronic cam control algorithm, it can complete high-precision static or dynamic loading tests.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A multi-angle adjustable heavy-duty tire hydraulic loading control method, characterized in that, Includes the following steps: Construct a loading platform supported by multiple servo loading cylinders, obtain the loading platform parameters, and calculate the final target displacement corresponding to each servo loading cylinder. Set the target position and motion parameters, plan a seven-segment S-shaped velocity curve including acceleration, uniform acceleration, deceleration, constant speed, deceleration, uniform deceleration and deceleration, and generate a virtual position axis and its real-time position command. Using the virtual axis of the position as the master axis and all servo loading cylinders as slave axes, a master-slave following relationship is established using the Poly5 electronic cam algorithm; and combining the initial state of each slave axis with the boundary conditions of the final target displacement, the Poly5 motion curve position command of each servo loading cylinder is calculated in real time, driving all servo loading cylinders to move synchronously, so that the loading platform reaches the preset pose; While maintaining the set posture on the loading platform, a virtual pressure axis is constructed, and a tension change trajectory is generated based on the target tension value; a control strategy of outer pressure loop and inner position loop is adopted. The outer pressure ring outputs a position compensation amount based on the deviation between the real-time collected tension feedback value and the tension command value generated by the pressure virtual axis through PID calculation. The inner position loop superimposes the position compensation amount onto the real-time position of the virtual position axis, which serves as the final position input for each servo loading cylinder, driving the servo loading cylinder to move.

2. The method according to claim 1, characterized in that, The method also includes a cyclic pressure loading step: Once the outer pressure control system reaches a steady state, the loading frequency is set to make the tension setpoint fluctuate within the preset range of the target tension. The setpoint of the tension after real-time calculation of fluctuations is used as the input of the outer pressure ring, and the position compensation amount is continuously output to the inner position ring to drive the servo loading cylinder to perform dynamic loading.

3. The method according to claim 1, characterized in that, The method also includes motion stopping and reset steps: After receiving the stop command, the controller re-plans the seven-segment S-shaped speed curve of the virtual position axis, starting from the current position of the loading platform center and ending at the zero position. Using the current position of the four servo loading cylinders as the initial state and the zero position as the final target displacement, the zero-return trajectory of each axis is recalculated using the Poly5 electronic cam algorithm. The four servo loading cylinders are driven to move synchronously to the standby zero position, thereby achieving system unloading and reset.

4. The method according to claim 1, characterized in that, The loading platform is a four-corner hydraulic loading platform, driven by servo loading cylinders located at the four corners of the loading platform; A spatial rectangular coordinate system is established with the center point of the loading platform surface at the standby position as the origin. An X-axis and a Y-axis are set on the horizontal plane, with the X-axis parallel to the tire rolling direction. The loading platform parameters include the target position of the loading platform center. Pitch angle Roll angle and half the distance between the two cylinders in the X-axis direction. Half the distance between the two cylinders in the Y-axis direction ; The final target displacement is calculated as follows: In the formula, , , , These represent the final displacements of the four servo-loaded cylinders.

5. The method according to claim 1, characterized in that, The seven-segment S-shaped velocity curve is specifically as follows: Using the target position at the center of the platform as the final target position of the virtual axis, and the set speed as the uniform speed segment, trapezoidal velocity planning calculation is performed in combination with the set acceleration, deceleration and jerk. The motion process is divided into seven time periods: acceleration phase, deceleration phase, and acceleration phase. Uniform acceleration segment Deceleration / Acceleration Section Uniform speed segment Deceleration / Acceleration Section Uniform deceleration section and deceleration phase ; exist , , , The acceleration changes linearly in stages. , The acceleration remains constant during the phase. The acceleration during the phase is zero.

6. The method according to claim 4, characterized in that, The method for establishing a master-slave follower relationship using the Poly5 electronic cam algorithm includes the following steps: Define normalized variables Map the real-time position of the virtual axis to the interval [0,1]: In the formula, The target position is generated in real time for the virtual axis of position. Let L be the initial position of the virtual axis, and L be the total travel distance of the virtual axis. Establish each servo loading cylinder based on The fifth-order polynomial equation: In the formula, These are the real-time position commands for the four servo loading cylinders. Let represent the undetermined polynomial coefficients of the i-th servo loading cylinder.

7. The method according to claim 6, characterized in that, The calculation method for the Poly5 motion curve position command is as follows: Calculate the lower-order coefficients using the initial boundary conditions. , and ; Construct boundary conditions containing higher-order coefficients using the terminal states , and A system of linear equations; Based on the initial position and final target displacement of the servo loading cylinder, the higher-order coefficients are obtained by solving the system of linear equations. , and ; Substitute all the solved coefficients into the fifth-order polynomial equation to calculate the position commands of each servo loading cylinder in real time.

8. The method according to claim 1, characterized in that, The generation of the tension change trajectory is specifically as follows: Using the current tension value as the starting force, and the target tension as the final target force along the virtual axis of tension; Set the parameters for the velocity, acceleration, deceleration, and jerk of the tension change, and generate a tension command with a trapezoidal velocity trajectory and a non-linear S-shaped target tension trajectory.

9. The method according to claim 1, characterized in that, The inner position loop superimposes the position compensation amount onto the real-time position of the virtual position axis. Specifically, the execution method is as follows: The position compensation amount output by the outer pressure loop is added to the current real-time position command of the virtual axis to obtain the corrected virtual axis position command. The corrected virtual axis position command is used as the vertical displacement parameter of the loading platform center in the inverse kinematics solution. It is then substituted back into the target displacement calculation formula of the four servo loading cylinders to calculate the final position input of the four servo loading cylinders at the current moment, including pressure compensation.

10. A multi-angle adjustable heavy-duty tire hydraulic loading system, comprising a high-pressure oil source (1), an oil tank (2), a loading platform, four servo loading cylinders (8) arranged in a rectangular shape and supporting the loading platform, a sensor group, and a controller; Its features are, The four servo loading cylinders (8) belong to four identical loading subsystems. Each loading subsystem includes: a reversing valve (3), a safety valve (4), a servo proportional valve (5), and a check valve (11). In each loading subsystem, the reversing valve (3) is a two-position three-way valve, and its output end is connected to the pilot control port of the check valve (11) to control the opening and closing of the check valve. The P port of the servo proportional valve (5) is connected to the high-pressure oil source (1), the T port is connected to the oil tank (2), the A port is connected to the rod chamber of the corresponding servo loading cylinder (8), and the B port is connected to the rodless chamber of the corresponding servo loading cylinder (8). Safety valves (4) and check valves (11) are installed in parallel or in series on the pipeline between port A of the servo proportional valve (5) and the rod chamber of the servo loading cylinder, and on the pipeline between port B of the servo proportional valve (5) and the rodless chamber of the servo loading cylinder (8). The sensor group includes: Displacement sensors (6) are installed on each servo loading cylinder (8) to detect the piston rod stroke; Pressure sensors (7) are installed at the inlet of the rod chamber and rodless chamber of each servo loading cylinder (8); The gyroscope sensor (9) installed on the loading platform is used to detect the attitude angle of the loading platform; And a tension sensor (10) installed at the center of the loading platform to detect the force between the tire and the loading platform; The controller is electrically connected to the servo proportional valve (5), directional valve (3) and sensor group of each loading subsystem, and is configured to perform the heavy-duty tire hydraulic loading control method as described in any one of claims 1-9.

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