Tractor cab active suspension control method based on road surface working condition recognition

Abstract

The invention belongs to the technical field of self-adaptive control, and particularly relates to a tractor cab active suspension control method based on road surface working condition recognition, which comprises the following steps of: performing frequency domain analysis on pure vertical acceleration data, and acquiring a frequency domain characteristic index of a road surface working condition according to a ratio of low-frequency and high-frequency energy integral values and a root-mean-square value; a basic comfort damping coefficient is obtained in combination with the pressure fluctuation rate and the frequency domain characteristic index; according to the deviation distance of the pure telescopic displacement data relative to the mechanical neutral point, a protection factor is calculated in combination with the instantaneous movement speed and the movement direction of a piston of the suspension oil cylinder; and generating a control instruction based on the product of the basic comfort damping coefficient and the protection factor. According to the method, the road surface working condition can be accurately recognized, damping can be dynamically adjusted, and soft limiting protection of the suspension stroke is achieved while the riding comfort is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of adaptive control technology. More specifically, this invention relates to an active suspension control method for a tractor cab based on road condition recognition. Background Technology

[0002] Tractors, as core power equipment in modern agricultural production, operate in a variety of complex environments, ranging from tilling soft, undulating fields to high-speed transport on hard surfaces. The front axle hydraulic suspension system, a key component connecting the wheels and the chassis, primarily functions to attenuate vibrations and impacts caused by uneven road surfaces through the coordinated action of hydraulic cylinders and accumulators, thereby improving driver comfort and overall machine handling stability. With the continuous increase in the operating speed of high-power tractors, higher demands are placed on the control precision and response strategies of the suspension system. How to achieve adaptive adjustment of damping characteristics under vastly different operating conditions and ensure the system's safety under extreme conditions has become a pressing technical problem to be solved in this field.

[0003] In the prior art, Chinese patent application CN103713535B discloses an electric suspension control device for a tractor. This device consists of a controller, control panel, DC motor, angle sensor, limit switch, force sensor, etc. The DC motor drives the lifting arm through a cylindrical gear reduction mechanism and a worm gear reduction mechanism, thereby actuating the suspension rods. This control device achieves integrated control of tillage depth, driving force, and slippage by collecting angle, force, and wheel speed signals.

[0004] However, the existing technologies mentioned above employ a rigid mechanical transmission structure based on a DC motor and worm gear. Although the self-locking characteristic is suitable for maintaining the working depth of agricultural implements, it lacks the elasticity and damping energy absorption characteristics of a hydraulic suspension system. It cannot effectively absorb and filter high-frequency vibrations and impacts transmitted from the road surface, making it difficult to meet the requirements of front axle suspension for ride comfort. The control logic in the existing technologies mainly focuses on adjusting the working load and slip ratio, and cannot distinguish between the low-frequency undulations in the field and the high-frequency bumps on the road from the frequency domain dimension. This results in the inability to adaptively adjust the vibration reduction strategy for different road conditions. Summary of the Invention

[0005] To address the technical problems mentioned above, such as the lack of flexible damping and energy absorption characteristics in rigid mechanical transmission structures, which makes it difficult to guarantee ride comfort; the inability to accurately identify field and road conditions due to reliance solely on time-domain signals, resulting in poor adaptability of vibration reduction strategies; and the reliance on limit switches for positioning, which makes suspended components prone to mechanical hard impacts at extreme positions, this invention provides an active suspension control method for tractor cabs based on road condition identification. This method includes: acquiring vertical acceleration data of the tractor front axle, extension / relocation data of the suspension cylinder, and pressure data of the suspension cylinder; performing noise reduction and bandpass filtering on the vertical acceleration data, extension / relocation data, and pressure data to obtain clean vertical acceleration data, clean extension / relocation data, and clean pressure data; performing frequency domain analysis on the clean vertical acceleration data, and based on a preset low-frequency... The frequency domain characteristic index of the road surface condition is obtained by combining the spectral energy integral value within the segment with the spectral energy integral value within the preset high-frequency band, as well as the root mean square value of the pure vertical acceleration data. The pressure fluctuation rate is obtained based on the difference between the pure pressure data and the preset equilibrium pressure value. The basic damping coefficient of the suspension system is obtained based on the frequency domain characteristic index of the road surface condition, the pressure fluctuation rate, and the preset basic damping value of the highway condition. The instantaneous velocity of the suspension cylinder piston is obtained by performing differential calculations on the pure telescopic displacement data. A protection factor is obtained based on the deviation distance of the pure telescopic displacement data from the pre-recorded mechanical midpoint data, combined with the instantaneous velocity and direction of the suspension cylinder piston. The target damping control value is obtained based on the basic damping coefficient and the protection factor, and the final control command is generated based on the target damping control value.

[0006] This invention, by performing frequency domain analysis on vertical acceleration data and obtaining the frequency domain characteristic index of road conditions, can accurately distinguish between field conditions characterized by large low-frequency fluctuations and highway conditions characterized by dense high-frequency bumps from the perspective of frequency energy distribution. This guides the suspension system to adaptively switch between a soft mode that adapts to large-stroke energy absorption and a hard mode that maintains driving stability. This invention corrects the basic damping coefficient through pressure fluctuation changes. When abnormal and drastic fluctuations in the suspension cylinder pressure are detected, the execution weight of the soft suspension strategy can be automatically reduced, preventing the risk of instability caused by the control system forcibly implementing flexible adjustments in an unstable hydraulic circuit state. At the same time, this invention calculates a protection factor. When it identifies that the piston is approaching the stroke limit at high speed and continues to move away from the center position, it forcibly and significantly increases the system damping to implement emergency braking, achieving soft limit protection for the suspension mechanism. This effectively avoids damage to the cab comfort and suspension structure life caused by mechanical hard impacts, thus achieving comprehensive safety protection while ensuring ultimate comfort.

[0007] Preferably, the acquisition of the vertical acceleration data of the tractor front axle, the telescopic displacement data of the suspension cylinder, and the pressure data of the suspension cylinder includes: acquiring the vertical acceleration data of the front axle through an acceleration sensor installed at the axle head of the tractor front axle; acquiring the real-time telescopic displacement data of the suspension cylinder through a displacement sensor installed at the front end of the frame; and reading the real-time pressure data of the rodless chamber and the rod chamber of the suspension cylinder through a pressure sensor in the hydraulic circuit.

[0008] Preferably, the frequency domain analysis of the pure vertical acceleration data includes: performing a fast Fourier transform on the pure vertical acceleration data to convert the time domain signal into a frequency domain power spectral density function, and presetting low-frequency and high-frequency bands.

[0009] Preferably, the frequency domain characteristic index satisfies the following relationship: In the formula, For the frequency domain characteristic index of road surface conditions, Low-frequency energy value, This is a high-frequency energy value. This represents the root mean square value of the pure vertical acceleration data. It is a linear normalization function.

[0010] This invention constructs a frequency domain characteristic index that includes the ratio of low-frequency energy to high-frequency energy, and uses an S-shaped activation function to map the wide range of energy ratios to a standard range. This allows the calculated frequency domain characteristic index to sensitively reflect the frequency tendency of road excitation. When vibration energy is concentrated at low frequencies, the index value is significantly increased to drive the system to switch to soft suspension mode, and vice versa to decrease the index value to maintain hard suspension mode. This achieves continuous and nonlinear evaluation of road surface types and improves the resolution of working condition identification.

[0011] Preferably, the basic damping coefficient satisfies the following relationship: In the formula, Based on the basic damping coefficient, The preset foundation damping value for highway working conditions. It is a frequency domain characteristic index. For pressure volatility, It is a natural constant. This is the damping coefficient under field conditions.

[0012] This invention establishes a basic comfort damping coefficient that includes frequency domain characteristic indices and pressure changes. It can dynamically adjust the weight distribution of the basic damping value for highway conditions and the damping gain for field conditions according to changes in road conditions, thus achieving an adaptive and smooth transition of suspension characteristics. At the same time, by utilizing pressure changes, it can quickly suppress the magnitude of the basic comfort damping coefficient when drastic fluctuations in cylinder pressure are detected. By sacrificing some comfort in exchange for the basic stability of the system under abnormal conditions, a dynamic balance between comfort and safety is achieved.

[0013] Preferably, the method for obtaining the pre-recorded mechanical center point data includes: during the initialization phase of the suspension control system, controlling the suspension cylinder to move to the upper dead point and lower dead point of the physical stroke respectively; recording the maximum and minimum readings of the displacement sensor, and taking the average of the maximum and minimum readings as the mechanical center point data.

[0014] Preferably, the protective factor satisfies the following relationship: In the formula, As a protective factor, For pure stretching displacement data, For mechanical midpoint data, This represents the maximum permissible one-way stroke of the suspension cylinder. The instantaneous velocity of the piston. It is a linear rectification function.

[0015] This invention constructs a protection factor based on the deviation distance and piston motion state, so that when the piston is within the safe stroke range, the protection factor has a negligible impact on the system, while when the piston approaches the limit stroke and moves away from the center position at high speed, the protection factor increases exponentially and rapidly, thereby driving the system to output a large damping force for emergency braking. This achieves a soft limit protection function that intervenes only at dangerous moments, avoiding interference of the protection strategy with normal driving comfort.

[0016] Preferably, obtaining the target damping control value based on the basic damping coefficient and the protection factor includes: using the product of the basic damping coefficient and the protection factor as the target damping control value.

[0017] This invention uses the product of the basic damping coefficient and the protection factor as the target damping control value. By utilizing the characteristic that the safety protection factor approaches a unit value in non-dangerous areas, the system can execute a comfort damping strategy based on road surface recognition without damage within the normal travel range. When a risk of piston impact limit is detected, the safety protection factor is directly applied to the basic damping with a sharp increase, forcibly increasing the overall damping force of the system. This achieves a smooth and powerful transient switch of suspension control from comfort-first mode to safety protection mode, effectively solving the control conflict between comfort adjustment and safety limit.

[0018] Preferably, the step of generating the final control command based on the target damping control value includes: calling a pre-calibrated current-damping characteristic mapping table and using the current-damping characteristic mapping table to convert the target damping control value into the target drive current of the proportional solenoid valve in the front suspension hydraulic control valve group.

[0019] Preferably, the step of generating the final control command based on the target damping control value further includes: performing PID closed-loop correction on the target drive current in conjunction with the current feedback signal, and adjusting the flow rate of hydraulic oil entering and exiting the accumulator and the pressure of the suspension cylinder by the drive front suspension hydraulic control valve group.

[0020] The beneficial effects of this invention are as follows: This invention analyzes the energy distribution differences of road excitation signals in the frequency domain, enabling it to penetrate the interference of complex mechanical noise. This allows the suspension system to automatically and precisely switch between a flexible mode adapting to field undulations and a rigid mode adapting to highway driving without human intervention, ensuring both smooth tillage and stable handling during transport. Addressing the constraint of the limited stroke of the hydraulic cylinder, this invention monitors the piston's movement speed and position deviation in real time. At critical moments when the piston is about to impact the cylinder bottom or cylinder head, it utilizes nonlinearly increased damping force to achieve virtual soft limiting, eliminating the impact of hard mechanical impacts on the cab and effectively preventing fatigue damage to suspension components due to long-term overload collisions, thus extending the overall service life of the machine. Furthermore, by incorporating the pressure fluctuation state of the hydraulic circuit into the damping decision-making process, this invention establishes operational safety as a priority over ride comfort. When unstable hydraulic system pressure is detected, it automatically limits the execution amplitude of the low-damping strategy, preventing suspension loss of control due to lag in actuator response or pressure imbalance. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the active suspension control method for tractor cab based on road condition identification in this invention; Figure 2 This is a schematic diagram illustrating the frequency domain characteristic exponential fluctuation in this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] This invention discloses an active suspension control method for a tractor cab based on road condition recognition, referring to... Figure 1 This includes steps S1 to S5: S1. Real-time motion status data of the suspension system is obtained through sensors located on the front axle and frame.

[0025] It should be noted that in field operations, in addition to the low-frequency vibrations caused by uneven road surfaces, the tractor's structure is inevitably affected by the high-frequency vibrations generated by the high-power diesel engine and the mechanical coupling noise generated when the implements are attached. These non-road surface noise signals are mixed in with the raw sensor data. If input directly into the control algorithm without processing, the system may mistakenly identify the engine's high-frequency vibrations as characteristics of a gravel road surface, leading to erroneous responses from the actuators. Therefore, this invention uses noise reduction and bandpass filtering to retain only the effective frequency band data reflecting the road surface excitation characteristics, providing a clean data foundation for subsequent accurate operating condition identification.

[0026] Specifically, an accelerometer installed at the front axle axle head of the tractor collects vertical acceleration data of the front axle, a displacement sensor installed at the front of the frame collects real-time telescopic displacement data of the hydraulic suspension cylinder, and a pressure sensor in the hydraulic circuit reads real-time pressure data of the rodless and rod-side chambers of the suspension cylinder. The collected data undergoes noise reduction and bandpass filtering to obtain clean vertical acceleration data, clean telescopic displacement data, and clean pressure data.

[0027] S2. Based on the frequency domain energy distribution characteristics of the pure vertical acceleration data, obtain the frequency domain characteristic index of the road surface condition.

[0028] It should be noted that, under normal circumstances, the road conditions encountered by tractors exhibit significant differences in the frequency domain. Field furrows or deep tillage primarily exhibit large-amplitude low-frequency undulations, while hard roads or gravel surfaces mainly exhibit small-amplitude, dense high-frequency bumps. Simply relying on the vibration amplitude in the time domain is insufficient to distinguish between these two fundamentally different conditions, causing the control system to be unable to determine whether to loosen the suspension to accommodate large travel undulations or tighten it to maintain stability at high speeds. Therefore, this invention uses Fast Fourier Transform to convert the time-domain signal into a frequency-domain power spectrum, utilizing the ratio of low-frequency energy to high-frequency energy to digitally analyze road surface types, thereby defining the two typical working conditions: field operations and road transportation.

[0029] Specifically, a Fast Fourier Transform (FFT) is performed on the clean vertical acceleration data to convert the time-domain signal into a frequency-domain power spectral density function. The spectral energy integral values ​​within a preset low-frequency band are calculated to obtain the low-frequency energy value; similarly, the spectral energy integral values ​​within a preset high-frequency band are calculated to obtain the high-frequency energy value. The root mean square (RMS) value of the clean vertical acceleration data is used as the vibration intensity value. Based on the low-frequency energy value, high-frequency energy value, and vibration intensity value, the frequency-domain characteristic index of the road surface condition is obtained.

[0030] For example, the preset low frequency band is 0.5-3Hz, corresponding to undulating fields; the preset high frequency band is 3-10Hz, corresponding to road surface gravel or texture.

[0031] Specifically, the frequency domain characteristic index satisfies the following relationship: ; In the formula, For the frequency domain characteristic index of road surface conditions, Low-frequency energy value, This is a high-frequency energy value. This represents the root mean square value of the pure vertical acceleration data. It is a linear normalization function.

[0032] in, This represents the frequency component tendency of pavement excitation. A larger value indicates that the vibration energy is mainly concentrated in the low-frequency part, which is more likely to correspond to field conditions, leading to the frequency domain characteristic index of pavement conditions. The larger the value, the more likely the suspension control system will switch to a long-stroke soft suspension mode; the smaller the value, the more likely the vibration energy is concentrated in the high-frequency part, which is more likely to correspond to highway conditions, resulting in a higher frequency domain characteristic index. The smaller the value, the more stable the suspension control system will be in a hard suspension mode. It reflects the overall intensity of road surface excitation. The larger the value, the more severe the current road surface bumps, thus enhancing the system's response sensitivity to operating condition identification; the smaller the value, the more static or slightly vibrating the current road surface, thus suppressing misjudgment switching caused by signal noise.

[0033] For example, Figure 2 This is a schematic diagram of the frequency domain characteristic index fluctuation in this invention. As can be seen from the figure, the frequency domain characteristic index of the road surface condition can show good condition differentiation. It remains at a low level under highway conditions, but responds quickly and maintains a high level after entering the field conditions. This achieves accurate definition of the working scenario, so that the comfort of field operations and the safety of highway driving can be taken into account in the subsequent suspension control process.

[0034] S3. Based on the frequency domain characteristic index of the road surface and the pressure state of the suspension cylinder, obtain the basic damping coefficient of the suspension system.

[0035] It should be noted that to ensure the tractor's anti-roll capability and handling stability at high speeds on highways, the suspension system must have a large basic damping to suppress vehicle sway. However, when encountering deep pits or ridges during low-speed field operations, the suspension system requires extremely low damping to maximize the absorption of impact energy using the accumulator's floating characteristics. A fixed damping setting cannot simultaneously meet these two conflicting needs, and the stability of pressure fluctuations within the hydraulic system directly determines whether the accumulator can function properly. Therefore, this invention dynamically adjusts the weighting of the damping coefficient using a frequency domain characteristic index and attenuates and corrects the soft suspension strategy in the field when the cylinder pressure fluctuates drastically, preventing safety hazards caused by forcibly implementing soft characteristic control under unstable hydraulic system conditions.

[0036] Specifically, a preset basic damping value for highway conditions is established. The absolute value of the difference between the pure pressure data and the preset equilibrium pressure value is obtained. The ratio of this absolute value of the difference to the preset equilibrium pressure value is calculated to obtain the pressure fluctuation rate. The basic damping coefficient of the suspension system is calculated based on the frequency domain characteristic index of the pavement condition, the pressure fluctuation rate, and the basic damping value for highway conditions.

[0037] For example, the basic damping value for highway operating conditions is the reference damping coefficient required for the tractor to maintain vehicle body stability under standard highway operating conditions. In this embodiment, the basic damping value for highway operating conditions is 4500 N·s / m. The preset balance pressure value is the standard working pressure of the suspension system under static load conditions. In this embodiment, the preset balance pressure value is 8.5 MPa. The implementer can determine the value of the balance pressure value according to the actual situation. For example, when the front counterweight of the tractor is increased or the load on the front axle is increased due to the suspension of a large front-mounted implement, the basic damping value for highway operating conditions needs to be appropriately increased in order to suppress brake dive or cornering tilt. When the tractor is performing light-load transportation operations, the basic damping value for highway operating conditions can be appropriately decreased in order to improve the driver's riding comfort.

[0038] Specifically, the foundation damping coefficient satisfies the following relationship: ; In the formula, Based on the basic damping coefficient, The preset foundation damping value for highway working conditions. It is a frequency domain characteristic index. For pressure volatility, It is a natural constant. The damping coefficient under field conditions is used in this embodiment. With a maximum strength of 2000 Ns / m, when the work site consists of extremely loose soil that has been deeply tilled, the road impact is mainly a large-amplitude, low-frequency wave. In this case, the strength can be appropriately increased. This allows the suspension to utilize its full travel for floating; when the work site is uncultivated, hard stubble land, the size can be appropriately reduced. To retain a certain amount of damping force to prevent excessive body sway.

[0039] in, This is the pressure stability factor of the hydraulic system. A larger value indicates that the real-time pressure of the suspension cylinder is closer to the preset equilibrium pressure, and the hydraulic system is in a steady state. At this point, the factor approaches 1, allowing for a higher frequency domain characteristic index of the road surface conditions. The more it participates in damping adjustment, the more accurately the system can respond to field road conditions; the smaller this value, the more severe the pressure fluctuations in the suspension cylinder or the abnormal sudden changes, indicating that the hydraulic system is in an unsteady state. At this time, the factor approaches 0, playing a suppressive role and forcibly shielding the frequency domain characteristic index. The ability to adjust damping prevents the implementation of a soft suspension strategy when the system becomes unstable.

[0040] This represents the flexible adjustment weight after pressure state correction. A larger weight value indicates that the system simultaneously identifies significant low-frequency field conditions while the hydraulic pressure remains stable, leading to a higher base damping coefficient. Preset foundation damping values ​​for highway working conditions The proportion decreased, while the field condition damping An increased weighting drives the suspension system to switch to a soft mode for long-stroke energy absorption; a smaller weighting value indicates a higher likelihood of identifying high-frequency highway conditions, or abnormal fluctuations in hydraulic pressure even in field conditions, causing the basic damping coefficient to be forcibly regressed and locked to the basic damping value for highway conditions. The location is nearby, thus prioritizing the rigid support of the vehicle body posture and driving safety.

[0041] S4. Obtain the protection factor based on the real-time stroke position of the suspension cylinder and the piston movement speed.

[0042] It should be noted that the physical stroke of the hydraulic suspension cylinder of the tractor front axle is limited. When the system is in a low-damping comfort mode and encounters severe bumps exceeding its designed stroke, the piston is highly susceptible to high-speed impact with the cylinder end cap or mechanical limit block. This mechanical impact not only completely destroys the comfort of the cab, but long-term effects can also lead to hydraulic cylinder seal failure or even mechanical suspension structure breakage. To prevent mechanical impact while maintaining comfort, this invention constructs a protection factor based on deviation distance and movement speed. When the piston approaches its stroke limit and continues to move rapidly away from the center position, it forcibly and significantly increases the system stiffness, achieving soft limit protection for the suspension stroke.

[0043] Specifically, during the power-on initialization phase of the suspension control system, the suspension cylinders are controlled to move to the top and bottom dead centers of their physical strokes, respectively. The maximum and minimum readings of the displacement sensors are recorded, and the average of the maximum and minimum readings is taken as the mechanical neutral point data. The absolute value of the difference between the pure telescopic displacement data and the mechanical neutral point data is obtained to determine the deviation distance. The pure telescopic displacement data is differentiated to obtain the instantaneous velocity of the piston. The protection factor is calculated using the magnitude of the pure telescopic displacement data relative to the mechanical neutral point, combined with the instantaneous velocity and the deviation distance.

[0044] Specifically, the protective factors satisfy the following relationship: ; In the formula, As a protective factor, For pure stretching displacement data, For mechanical midpoint data, This represents the maximum permissible one-way stroke of the suspension cylinder. The instantaneous velocity of the piston. It is a linear rectification function.

[0045] in, This represents the risk level of the piston position approaching the mechanical limit. A higher value indicates that the piston is closer to the end of its stroke, leading to... A sharp increase in this value enhances the stiffness of the suspension control system to resist impacts; a smaller value indicates that the piston is closer to the safe neutral zone, causing the protection factor to approach 1, thus not interfering with basic comfort control. This represents the weighted value of the piston's movement direction on the risk. A larger value indicates that the piston is more likely to be moving rapidly away from the center position and heading towards the limit point, causing the protection factor to activate and strengthen immediately, thus implementing emergency braking; a smaller value indicates that the piston is falling back towards the center position, causing the protection factor to fail, thus avoiding obstructing the self-resetting process of the suspension system. Used to obtain The sign of plus or minus, for example, hour =1, hour = 1, thus obtaining The positive and negative aspects, The use of this technology enables the activation of protection when facing danger and the release of intervention when safely resetting. This is achieved when the piston moves at high speed away from the midpoint and towards the physical limit. When the value is positive, the protection factor is activated and amplified, causing the system to forcibly apply a large damping force for emergency braking, implementing soft limiting to avoid mechanical hard impact; when the piston is in the safe self-resetting phase, falling back towards the midpoint, A value of 0 disables the entire protection factor add-on.

[0046] S5. Generate the final control command based on the basic damping coefficient and protection factor to drive the front suspension hydraulic control valve group to operate.

[0047] It should be noted that the final vibration reduction effect depends on the precise regulation of hydraulic oil flow and pressure by the solenoid valve. However, comfort adjustment and safety protection may conflict at certain extreme moments. To enable a smooth transition between comfort and safety modes in suspension control, this invention integrates basic comfort damping with protection factors and uses a PID closed-loop algorithm to precisely map the target damping into a pulse width modulation signal that drives the proportional solenoid valve. This ensures that the suspension system maximizes driver comfort within absolutely safe travel boundaries.

[0048] Specifically, the current-damping characteristic mapping table, pre-calibrated on the hydraulic test bench and stored in the controller, is retrieved. The product of the basic damping coefficient and the protection factor is used as the target damping control value. Using the current-damping characteristic mapping table, the target damping control value is converted into the target drive current of the proportional solenoid valve in the front suspension hydraulic control valve group. Combined with the current feedback signal, a PID closed-loop correction is performed on the target drive current, driving the control valve group to adjust the flow rate of hydraulic oil in and out of the accumulator and the pressure of the cylinder, thereby achieving suspension control.

[0049] A larger target damping control value indicates that the suspension travel is close to its limit or the speed is too high, causing the target damping control value to be magnified multiple times from the base damping coefficient, thus forcibly increasing the system damping to prevent mechanical impact. A smaller target damping control value indicates that the suspension system is within a safe travel range, causing the target damping control value to approach the base damping coefficient, thus allowing the system control to be completely returned to the road condition recognition algorithm to maximize driving comfort. The base damping coefficient represents the basic damping requirement based on road characteristics. A larger value indicates that highway conditions or stable cylinder pressure has been identified, resulting in a higher baseline value for the target damping control value, thus ensuring driving stability. A smaller value indicates that field conditions have been identified and the pressure is normal, resulting in a smaller target damping control value, thus providing a flexible vibration reduction effect.

[0050] In one embodiment, the method for obtaining the current-damping characteristic mapping table includes: installing the front suspension hydraulic control valve group to be calibrated on a standard hydraulic test bench and connecting a constant current source driver and a high-precision flow and pressure sensor; controlling the drive current to perform reciprocating scanning between 0mA and the maximum saturation current with a preset step size; recording the hydraulic damping force and piston movement speed at each current node in real time to calculate the actual damping coefficient; taking the average damping coefficient of the upward stroke and the downward stroke as the calibration value; and constructing a mapping table containing the target damping coefficient index and the corresponding drive current value, for example, with a preset step size of 20mA and a maximum saturation current of 1200mA.

Claims

1. A tractor cab active suspension control method based on road condition recognition, characterized in that, include: The vertical acceleration data of the tractor front axle, the telescopic displacement data of the suspension cylinder, and the pressure data of the suspension cylinder are acquired. The vertical acceleration data, telescopic displacement data, and pressure data are denoised and bandpass filtered to obtain clean vertical acceleration data, clean telescopic displacement data, and clean pressure data. Frequency domain analysis is performed on the clean vertical acceleration data. Based on the spectral energy integral values ​​in the preset low-frequency band and the preset high-frequency band, as well as the root mean square value of the clean vertical acceleration data, the frequency domain characteristic index of the road surface condition is obtained. The pressure fluctuation rate is obtained based on the difference between the pure pressure data and the preset equilibrium pressure value. The basic damping coefficient of the suspension system is obtained based on the frequency domain characteristic index of the road surface condition, the pressure fluctuation rate, and the preset basic damping value of the highway condition. The instantaneous movement speed of the suspension cylinder piston is obtained by performing differential calculation on the pure telescopic displacement data. The protection factor is obtained based on the deviation distance of the pure telescopic displacement data from the pre-recorded mechanical midpoint data, combined with the instantaneous movement speed and movement direction of the suspension cylinder piston. The target damping control value is obtained based on the basic damping coefficient and the protection factor. The final control command is generated based on the target damping control value.

2. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The acquisition of vertical acceleration data of the tractor front axle, extension and retraction displacement data of the suspension cylinder, and pressure data of the suspension cylinder includes: acquiring vertical acceleration data of the front axle through an acceleration sensor installed at the axle head of the tractor front axle; acquiring real-time extension and retraction displacement data of the suspension cylinder through a displacement sensor installed at the front end of the frame; and reading real-time pressure data of the rodless chamber and rod chamber of the suspension cylinder through a pressure sensor in the hydraulic circuit.

3. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The frequency domain analysis of the pure vertical acceleration data includes: performing a fast Fourier transform on the pure vertical acceleration data to convert the time domain signal into a frequency domain power spectral density function, and presetting low-frequency and high-frequency bands.

4. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The frequency domain characteristic index satisfies the following relationship: ； In the formula, For the frequency domain characteristic index of road surface conditions, Low-frequency energy value, This is a high-frequency energy value. This represents the root mean square value of the pure vertical acceleration data. It is a linear normalization function.

5. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The basic damping coefficient satisfies the following relationship: ； In the formula, Based on the basic damping coefficient, The preset foundation damping value for highway working conditions. It is a frequency domain characteristic index. For pressure volatility, It is a natural constant. This is the damping coefficient under field conditions.

6. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The method for obtaining the pre-recorded mechanical midpoint data includes: during the initialization phase of the suspension control system, controlling the suspension cylinder to move to the upper and lower dead points of the physical stroke respectively; recording the maximum and minimum readings of the displacement sensor, and using the average of the maximum and minimum readings as the mechanical midpoint data.

7. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The protective factors satisfy the following relationship: ； In the formula, As a protective factor, For pure stretching displacement data, For mechanical midpoint data, This represents the maximum permissible one-way stroke of the suspension cylinder. The instantaneous velocity of the piston. It is a linear rectification function.

8. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The step of obtaining the target damping control value based on the basic damping coefficient and the protection factor includes: using the product of the basic damping coefficient and the protection factor as the target damping control value.

9. The tractor cab active suspension control method based on road condition recognition according to claim 1, characterized in that, The step of generating the final control command based on the target damping control value includes: calling a pre-calibrated current-damping characteristic mapping table and using the current-damping characteristic mapping table to convert the target damping control value into the target drive current of the proportional solenoid valve in the front suspension hydraulic control valve group.

10. The tractor cab active suspension control method based on road condition recognition according to claim 9, characterized in that, The step of generating the final control command based on the target damping control value also includes: performing PID closed-loop correction on the target drive current in conjunction with the current feedback signal, and adjusting the flow rate of hydraulic oil entering and exiting the accumulator and the pressure of the suspension cylinder by the drive front suspension hydraulic control valve group.

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