Vehicle posture and vehicle body height adjusting method

Abstract

The invention relates to the field of vehicle air suspension control, and discloses a vehicle posture and vehicle body height adjusting method. And determining a target mass center vertical displacement, a target pitch angle and a target roll angle of the vehicle as target data. And determining the mass center vertical displacement, the pitch angle and the roll angle of the vehicle after the previous round of adjustment as current data according to each round of adjustment of the vehicle attitude and the vehicle body height of the vehicle. And inputting the target data and the current data into a model prediction control module to obtain a target pressure parameter of the vehicle output by the model prediction control module. And inputting the target pressure parameter into a control feedback module to obtain an opening value of an air spring inflation and deflation valve port output by the control feedback module. And determining the vertical force of the air spring according to the opening value and the effective area of the air spring. And vertical force is applied to the air spring of the vehicle, so that the vehicle posture and the vehicle body height of the vehicle are adjusted, and the purpose of accurately adjusting the vehicle posture and the vehicle body height is achieved.

Description

Technical Field

[0001] This specification relates to the field of vehicle air suspension control, and particularly to a method for adjusting vehicle attitude and body height. Background Art

[0002] The dynamic control of vehicle attitude and body height is a core element of vehicle driving safety and comprehensive performance, which plays a decisive role in vehicle safety, comfort, and handling stability.

[0003] In terms of safety, during driving, if the body height and vehicle attitude cannot be effectively controlled, many safety hazards will occur. For example, during emergency braking, if the vehicle pitch angle is unreasonable, it will cause the load distribution imbalance between the front and rear axles of the vehicle, extend the braking distance, reduce the braking efficiency, and increase the risk of accidents such as rear-end collisions. In addition, an inappropriate vehicle height will also affect the passability of the vehicle. When encountering bumpy roads or obstacles, it may cause the vehicle chassis to scrape and damage vehicle components, further endangering driving safety.

[0004] In terms of comfort, the instability of vehicle attitude and body height will greatly affect the passenger experience. Frequent pitching and rolling during vehicle driving will make passengers feel carsick. Being in this state for a long time will make passengers feel uncomfortable and fatigued. Moreover, an unstable driving attitude will also cause the items in the vehicle to shake and even fall, bringing inconvenience to passengers.

[0005] Handling stability is also affected by vehicle attitude and body height. The handling performance of a vehicle depends on the good contact between the tires and the ground. If the vehicle attitude and body height are not well controlled, it will make the tire ground pressure uneven, affect the tire grip, and then reduce the vehicle's handling response speed and accuracy. This effect is more significant during high-speed driving or in complex road conditions, seriously restricting the vehicle's handling stability.

[0006] In order to effectively adjust the vehicle attitude and body height, the air suspension system with significant advantages such as variable stiffness, height adjustable, and natural frequency adjustable has stood out from many vehicle suspension systems and become the mainstream configuration of today's vehicles, especially new energy intelligent networked vehicles.

[0007] On a vehicle equipped with an air suspension system, the vehicle height and attitude control method is to fit the air spring force-displacement curve based on vehicle test data, and then adjust the air spring height in the Electronic-Controlled Air Suspension (ECAS) height control system through algorithms such as Sliding Mode Control (SMC) and Linear Quadratic Regulator (LQR). However, in this way, SMC has a chattering problem, which affects the control accuracy and the service life of components. LQR is sensitive to parameter changes, and the parameters vary during the actual operation of the vehicle, resulting in unsatisfactory control effects. Moreover, the cost of test-fitted curves is high, the time consumption is long, and it is easily interfered with.

[0008] Therefore, this specification provides a method for adjusting vehicle attitude and body height. Summary of the Invention

[0009] This specification provides a method for adjusting vehicle attitude and body height to partially solve the above problems existing in the prior art.

[0010] This specification adopts the following technical solutions: This specification provides a method for adjusting vehicle attitude and body height, including: Determine the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle as target data; For each round of adjustment of the vehicle attitude and body height of the vehicle, determine the vertical displacement of the center of mass, the pitch angle, and the roll angle of the vehicle after the previous round of adjustment as current data; Input the target data and the current data into the model predictive control module to obtain the target pressure parameter of the air spring of the vehicle output by the model predictive control module; Input the target pressure parameter into the control feedback module to obtain the opening value of the air spring charging and discharging valve port output by the control feedback module; Determine the vertical force of the air spring according to the opening value and the effective area of the air spring; Apply the vertical force to the air spring of the vehicle to achieve the adjustment of the vehicle attitude and body height of the vehicle.

[0011] According to the above technical means, the filling and discharging valve opening value and target pressure of the vehicle air spring are determined through the model prediction control module and the control feedback module, and the vertical force applied to the air spring can be accurately calculated, so as to adjust the height of the vehicle suspension and achieve the purpose of accurately adjusting the vehicle posture and body height, ensuring that the vehicle maintains a stable posture and improving the driving experience. In addition, through the model prediction control module and the control feedback module, the vibration and parameter sensitivity caused by the use of SMC and LQR are avoided, and the accuracy and stability of the vehicle posture and body height adjustment are improved.

[0012] Furthermore, the method further comprises: Determine the vertical displacement of the unsprung mass at four suspensions of the air spring of the vehicle after the wheel is adjusted, the vertical displacement of the center of mass of the vehicle body, and the pitch angle and roll angle of the vehicle, and construct a seven-degree-of-freedom vehicle dynamics model of the vehicle; Determining a dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model; Determining a state space equation of the vehicle according to the dynamic equation; The state space equation is solved to obtain current data input into the model predictive control module during the next round of adjustment.

[0013] According to the above technical means, by constructing a seven-degree-of-freedom vehicle dynamics model that includes the vertical displacement of the unsprung mass at the four suspensions, the vertical displacement of the center of mass of the vehicle body, the pitch angle and the roll angle, the dynamic behavior of the vehicle under different driving conditions can be captured more accurately. This makes the dynamic equations and state-space equations obtained based on this model closer to the actual vehicle behavior, thereby improving the accuracy of posture and vehicle height adjustment. Based on the solved state-space equations, the current data for each round of adjustment is determined and input into the model predictive control module, which can make the control strategy more optimized. This method not only takes into account the immediate adjustment needs, but also predicts the system behavior in the future, thereby achieving a smoother and more effective adjustment process.

[0014] Furthermore, the seven-degree-of-freedom vehicle dynamics model includes a sixteen-dimensional column vector and a fourteen-dimensional column vector, and the sixteen-dimensional column vector and the fourteen-dimensional column vector are expressed as:

[0015]

[0016] in, represent the vertical displacements of the four unsprung masses of the air spring of the vehicle, for The corresponding vertical displacement of the sprung mass is for The vertical displacement of the unsprung mass corresponding thereto, is The vertical displacement of the unsprung mass corresponding thereto, is The vertical displacement of the unsprung mass corresponding thereto, respectively correspond to the vertical velocity, is the vertical displacement of the vehicle's center of mass, are the pitch angle and roll angle of the vehicle, is the vertical velocity of the center of mass, is the pitch angular velocity, is the roll angular velocity.

[0017] Furthermore, before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: Constructing a transformation relation between the vertical displacement of each unsprung mass and the vertical displacement of the vehicle's center of mass, the pitch angle and roll angle of the vehicle; Determining a conversion relation between the sixteen-dimensional column vector and the fourteen-dimensional column vector according to the transformation relation.

[0018] Furthermore, the transformation relation and the conversion relation are:

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] Wherein, in the seven-degree-of-freedom vehicle dynamics model, a is the vertical distance from the vehicle's center of mass to the vehicle's front axle, b is the vertical distance from the vehicle's center of mass to the vehicle's rear axle, and are respectively the lengths of the vehicle's front axle and the vehicle's rear axle, is a block matrix, and are both sub-matrices of eight rows and seven columns.

[0026] Furthermore, before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: For each suspension of the air spring of the vehicle, according to the vertical displacement of the unsprung mass and the vertical displacement of the sprung mass corresponding to that suspension, determine the combined force at the position of that suspension.

[0027] According to the above technical means, by precisely controlling the combined force of the vehicle air spring suspension system in this way, it can not only significantly improve the vehicle's ride experience and handling performance, but also help protect the vehicle structure, extend its service life, and ensure driving safety.

[0028] Furthermore, the combined force at the position of each suspension is obtained through the following formula:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Wherein, are respectively the combined forces of the spring force and the damping force corresponding to the positions of the four suspensions of the air spring of the vehicle, respectively represent the forces generated by the air springs at the positions of the four suspensions, respectively represent the damping parameters of the four suspensions, is the damping coefficient matrix of the shock absorber in parallel with the air spring of the vehicle, is the stiffness matrix of the air spring of the vehicle, is the effective action area matrix of the air spring of the vehicle, h is the height of the air spring of the vehicle, and n is the internal pressure of the air spring of the vehicle, is the total suspension combined force, represents the diagonal matrix composed of damping coefficients, is the matrix related to the suspension force, and d is a constant term.

[0035] Furthermore, before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: For each suspension of the air spring of the vehicle, according to the stiffness coefficient, damping coefficient, and target vertical displacement of the tire corresponding to that suspension, determine the tire force of the tire corresponding to that suspension; Determine the comprehensive tire force of the vehicle according to the tire forces corresponding to the positions of the suspensions of the air springs of the vehicle.

[0036] According to the above technical means, by accurately calculating the forces of each tire, the stability and controllability of the vehicle under various driving conditions can be better maintained.

[0037] Further, the tire forces corresponding to the positions of each suspension and the comprehensive tire force of the vehicle are obtained through the following formula:

[0038]

[0039] where respectively represent the tire forces corresponding to the tires at the positions of the four suspensions, respectively represent the stiffness coefficients of the tires corresponding to the positions of the four suspensions, respectively represent the damping coefficients of the tires corresponding to the positions of the four suspensions, respectively represent the target vertical displacements of the contact points between the tires corresponding to the positions of the four suspensions and the ground; [~]q is related to the target vertical displacement and is a zero matrix; and are respectively diagonal matrices composed of the negative values of the stiffness coefficient and the damping coefficient.

[0040] Further, the dynamic equation of the vehicle and the state space equation of the vehicle are:

[0041]

[0042]

[0043] where represents the vertical accelerations respectively corresponding to the four unsprung masses of the air springs of the vehicle, are the unsprung masses respectively corresponding to the four unsprung masses of the air springs of the vehicle, represents the vertical acceleration of the center of mass of the vehicle body, represents the pitch angular acceleration of the vehicle, represents the roll angular acceleration of the vehicle, m is the body mass, is the moment of inertia of the body about the pitch axis, is the moment of inertia of the body about the roll axis; I is the identity matrix, and the subscript 4 is its dimension; is ; is the state space equation of the vehicle.

[0044] The above at least one technical solution adopted in this specification can achieve the following beneficial effects: For the vehicle attitude and body height adjustment method provided in this specification, first, the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle are determined as target data. For each round of adjustment of the vehicle attitude and body height of the vehicle, the vertical displacement of the center of mass, the pitch angle, and the roll angle of the vehicle after the previous round of adjustment are determined as the current data. The target data and the current data are input into the model predictive control module to obtain the target pressure parameters of the vehicle output by the model predictive control module. The target pressure parameters are input into the control feedback module to obtain the opening value of the air spring charging and discharging valve port output by the control feedback module. According to the opening value and the effective area of the air spring, the vertical force of the air spring is determined. The vertical force is applied to the air spring of the vehicle to realize the adjustment of the vehicle attitude and body height.

[0045] Through the model predictive control module and the control feedback module, the opening value of the air spring charging and discharging valve port and the target pressure of the vehicle are determined, and the vertical force applied to the air spring can be accurately calculated, so as to realize the adjustment of the height of the vehicle suspension, achieve the purpose of precise adjustment of the vehicle attitude and body height, ensure that the vehicle maintains a stable attitude, and improve the vehicle use experience. Moreover, through the model predictive control module and the control feedback module, the chattering and parameter sensitivity problems caused by using SMC and LQR are avoided, and the accuracy and stability of the vehicle attitude and body height adjustment are improved. Description of the Drawings

[0046] The drawings described herein are used to provide a further understanding of this specification and constitute a part of this specification. The schematic embodiments of this specification and their descriptions are used to explain this specification and do not constitute an improper limitation of this specification. In the drawings: Figure 1 is a schematic flow chart of a vehicle attitude and body height adjustment method provided by an embodiment of this specification; Figure 2 is a schematic diagram of a seven-degree-of-freedom vehicle dynamics model provided by this specification; Figure 3 is a schematic flow chart of a cyclic adjustment of vehicle attitude and body height provided by this specification. Detailed Embodiments

[0047] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this specification will be clearly and completely described below in conjunction with specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this specification without creative efforts belong to the scope protected by this application.

[0048] The following will, with reference to the drawings, elaborate on the technical solutions provided by each embodiment of this specification.

[0049] Figure 1 The following is a schematic flowchart of a method for adjusting vehicle attitude and body height provided by an embodiment of this specification, including the following steps: S100: Determine the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle as target data.

[0050] S102: For each round of adjustment of the vehicle's attitude and body height, determine the vertical displacement of the vehicle's center of mass, the pitch angle, and the roll angle after the previous round of adjustment as current data.

[0051] In the process of determining the adjustment of the vehicle's attitude and body height in this specification, a device with computing capabilities such as a server or a computer can execute the process of determining the vertical force that the air spring should exert for adjusting the vehicle's attitude and body height. Of course, this specification does not limit which device implements the process of determining the vertical force that the air spring should exert for adjusting the vehicle's attitude and body height. Devices such as personal computers and mobile terminals can also be used. For the sake of convenience of description, the server will be used as the execution entity for illustration below.

[0052] In one or more embodiments of this specification, the server can obtain and determine the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle as target data. This target data is the vertical displacement of the center of mass, the pitch angle, and the roll angle in the state of stable vehicle attitude, representing the ideal data for stable vehicle attitude. Therefore, the vertical displacement of the center of mass, the pitch angle, and the roll angle can be used as data or parameters representing the vehicle's attitude and body height.

[0053] In one or more embodiments of this specification, during the vehicle's travel, there may be multiple rounds of adjustment of the vehicle's attitude and body height. The vehicle's attitude and body height are continuously adjusted to ensure the vehicle's stable travel. Therefore, for each round of adjustment of the vehicle's attitude and body height, the server can determine the current vertical displacement of the vehicle's center of mass, the pitch angle, and the roll angle after the previous round of adjustment of the vehicle's attitude and body height, and use them as current data.

[0054] It should be noted that for the vehicle that adjusts the vehicle attitude and body height as described above, it can be an actual vehicle during driving, or a vehicle that tests the adjustment of the vehicle attitude and body height on a test site. Of course, it can also be a vehicle model constructed in a server, and the vehicle attitude and body height are continuously adjusted on the vehicle model to test the feasibility and accuracy of the test plan. Therefore, in the following description, the vehicle model is taken as an example to execute the vehicle attitude and body height adjustment method.

[0055] S104: Input the target data and the current data into the model predictive control module to obtain the target pressure parameter of the air spring of the vehicle output by the model predictive control module.

[0056] In one or more embodiments of this specification, the server inputs the target data and the current data into the Model Predictive Control (MPC) module to obtain the target pressure parameter of the vehicle output by the MPC module.

[0057] Specifically, the server converts the vertical displacement of the center of mass, the pitch angle, and the roll angle in the target data and the current data into a time-domain step signal, and inputs the time-domain step signal into the MPC module. Among them, the vertical displacement of the center of mass, the pitch angle, and the roll angle in the target data, that is, the target vertical displacement of the center of mass, the target pitch angle, and the target roll angle, are used as the reference values in the MPC module after being converted into a time-sequence step signal. 。

[0058] After that, the server performs quadratic programming (QP) solution on the target data and the current data input into the MPC module to determine the target pressure parameter.

[0059] It should be noted that in the MPC module, parameter definitions and related matrix definitions are carried out, including: Prediction time domain , indicating the prediction range for predicting the future vehicle state. For example, it can be set to 。

[0060] Control time domain , indicating the prediction range of the adjustable vehicle state. For example, it can be set to 。

[0061] Output dimension , indicating the dimension of the result output by the MPC module. For example, it can be set to , Control input dimension , indicating the input dimension of the MPC module. For example, it can be set to 。

[0062] Upper and lower limits of the result output by the MPC module: upper limit , lower limit , which can be set .

[0063] Prediction matrix :

[0064] Control matrix :

[0065] Weight matrix :

[0066] Among them correspond to the weight values of the vertical displacement of the centroid, the pitch angle, and the roll angle respectively. The weight matrix can be set to , and it is extended to a diagonal matrix with dimension .

[0067] Control weight matrix :

[0068] Among them, is the control weight coefficient, is the identity matrix with dimension , is the dimension of the control input. The control weight matrix can be set to .

[0069] In the process of calculating the target pressure parameter through the MPC module, the MPC module will calculate the predicted value of the future state of the vehicle and the future reference value , and obtain the error . The involved expressions are as follows:

[0070]

[0071]

[0072] Among them, repmat is a matlab function.

[0073] Furthermore, the MPC module constructs the objective function of the quadratic programming problem, and its expressions H and its constraint expression f are as follows:

[0074]

[0075] Further, the MPC module solves the objective function of the quadratic programming problem.

[0076]

[0077]

[0078] Among them, the upper and lower limits are encapsulated as a matrix of dimension , corresponding to the above and respectively.

[0079] After solving, the optimal control sequence within the future control time domain of the vehicle can be obtained , and the first control quantity in this sequence is selected as the output at the current moment, that is, the target pressure parameter u of the air spring.

[0080] S106: Input the target pressure parameter into the control feedback module to obtain the opening value of the air spring charging and discharging valve port output by the control feedback module.

[0081] In one or more embodiments of this specification, the server inputs the target pressure parameter into the control feedback module, and this control feedback module is a Proportional Integral Derivative (PID) module. After that, the PID module can determine the opening value of the air spring charging and discharging valve port according to the target pressure parameter and the actual pressure parameter of the air spring. Among them, the expression for calculating the opening value is as follows:

[0082] Among them, is the output of the PID module at time t, representing the opening value, is the difference between the target pressure parameter and the actual pressure parameter of the air spring, that is , the target pressure parameter is output by the MPC module, and the actual pressure parameter is the air spring pressure fed back by the vehicle model. , and are the proportional, integral, and differential control gain coefficients respectively, is the cumulative error calculated from time 0 to t.

[0083] Through the adjustment of PID, the opening degree of the air spring charging and discharging valve port is precisely controlled to achieve precise adjustment of the air spring pressure. This not only ensures the stability of the vehicle body height and vehicle attitude, but also improves the driving comfort and handling performance of the vehicle. In addition, the parameters included in the PID module can be adjusted according to the specific requirements and working conditions of the vehicle to achieve the best control effect.

[0084] S108: Determine the vertical force of the air spring according to the opening value and the effective area of the air spring.

[0085] In one or more embodiments of this specification, after the server determines the opening value of the air spring charging and discharging valve port, it can then determine the effective area of the air spring. According to the opening value of the air spring charging and discharging valve port and the effective area of the air spring, determine the vertical force of the air spring.

[0086] It should be particularly noted that in this specification, a physical model of the air spring can be built through Amesim software. This physical model includes components such as airbags, orifice plates, and control valves. Key parameters such as the effective area, initial pressure, and stiffness coefficient of the air spring can also be defined. The specific parameter definition can be adjusted according to the vehicle model. After that, the pressure and vertical force of the air spring can be calculated based on this physical model.

[0087] The calculation method of the change in the internal pressure of the air spring is as follows:

[0088] Among them, is the pressure change value, is the valve port flow coefficient, D is the opening value.

[0089] According to the pressure change value and the air spring characteristics, the vertical force generated by the air spring can be expressed as:

[0090] Among them, F is the vertical force of the air spring, is the effective area of the air spring, which is simplified to a constant in the embodiments of the present invention, P is the initial pressure of the air spring, is the atmospheric pressure.

[0091] S110: Apply the vertical force to the air spring of the vehicle to achieve the adjustment of the vehicle attitude and body height of the vehicle.

[0092] In one or more embodiments of the present specification, after determining the vertical force of the air spring of the vehicle, the vertical force can be applied to the air spring of the vehicle (or vehicle model) according to the vertical force, so as to adjust the vehicle attitude and body height of the vehicle (or vehicle model).

[0093] Based on Figure 1 The provided vehicle attitude and body height adjustment method first determines the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle as target data. For each round of adjustment of the vehicle attitude and body height of the vehicle, the vertical displacement of the center of mass, the pitch angle, and the roll angle of the vehicle after the previous round of adjustment are determined as the current data. The target data and the current data are input into the model predictive control module to obtain the target pressure parameter of the vehicle output by the model predictive control module. The target pressure parameter is input into the control feedback module to obtain the opening value of the air spring charging and discharging valve port output by the control feedback module. According to the opening value and the effective area of the air spring, the vertical force of the air spring is determined. The vertical force is applied to the air spring of the vehicle to realize the adjustment of the vehicle attitude and body height of the vehicle.

[0094] Through the model predictive control module and the control feedback module, the opening value of the air spring charging and discharging valve port and the target pressure of the vehicle air spring are determined, and the vertical force applied to the air spring can be accurately calculated, so as to realize the adjustment of the height of the vehicle suspension, achieve the purpose of precise adjustment of the vehicle attitude and body height, ensure that the vehicle maintains a stable attitude, and improve the vehicle use experience. Moreover, through the model predictive control module and the control feedback module, the chattering and parameter sensitivity problems caused by using SMC and LQR are avoided, and the accuracy and stability of the vehicle attitude and body height adjustment are improved.

[0095] In addition, in one or more embodiments of the present specification, the server can determine the vertical displacement of the unsprung mass at the four suspensions of the vehicle's air spring, the vertical displacement of the vehicle body center of mass, the pitch angle, and the roll angle of the vehicle after this round of adjustment, and construct a seven-degree-of-freedom vehicle dynamics model of the vehicle (i.e., the above-mentioned vehicle model). Then, according to the seven-degree-of-freedom vehicle dynamics model, the dynamic equation of the vehicle is determined. According to the dynamic equation, the state space equation of the vehicle is determined. Finally, by solving the state space equation, the current data input into the model predictive control module for the next round of adjustment can be obtained.

[0096] Figure 2 It is a schematic diagram of a seven-degree-of-freedom vehicle dynamics model provided in the present specification.

[0097] Specifically, for the constructed seven-degree-of-freedom vehicle dynamics model, the seven-degree-of-freedom vehicle dynamics model includes a sixteen-dimensional column vector and a fourteen-dimensional column vector The sixteen-dimensional column vector and the fourteen-dimensional column vector are respectively represented as:

[0098]

[0099] wherein, with reference to Figure 2 , respectively represent the vertical displacements of the four unsprung masses of the air springs of the vehicle, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, respectively correspond to the vertical velocities, is the vertical displacement of the vehicle body center of mass, is the pitch angle and roll angle of the vehicle, is the vertical velocity of the center of mass, is the pitch angular velocity, is the roll angular velocity.

[0100] In one or more embodiments of the present specification, the server can construct transformation relationships between the vertical displacements of the sprung masses and the vertical displacement of the vehicle body center of mass, the pitch angle and roll angle of the vehicle. And according to the transformation relationships, determine the conversion relationship between the sixteen-dimensional column vector and the fourteen-dimensional column vector.

[0101] The transformation relationships and the conversion relationship are respectively:

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] wherein, with reference to Figure 2 , in the seven-degree-of-freedom vehicle dynamics model, a is the vertical distance from the vehicle center of mass to the vehicle front axle, and b is the vertical distance from the vehicle center of mass to the vehicle rear axle, and are the lengths of the front axle and the rear axle of the vehicle respectively, is a block matrix, and are both sub-matrices with eight rows and seven columns.

[0109] In one or more embodiments of this specification, the server can also, for each suspension of the air spring of the vehicle, determine the comprehensive force at the position of the suspension according to the vertical displacement of the unsprung mass and the vertical displacement of the sprung mass corresponding to that suspension.

[0110] Thus, the comprehensive force at the position of each suspension can be obtained through the following formula:

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] where are the comprehensive forces of the spring force and the damping force corresponding to the positions of the four suspensions of the air spring of the vehicle respectively, respectively represent the forces generated by the air springs at the positions of the four suspensions, refer to Figure 2 , respectively represent the damping parameters of the four suspensions, is the damping coefficient matrix of the shock absorber in parallel with the air spring of the vehicle, is the stiffness matrix of the air spring of the vehicle, is the effective action area matrix of the air spring of the vehicle, h is the height of the air spring of the vehicle, and n is the internal pressure of the air spring of the vehicle, is the total suspension comprehensive force, represents the diagonal matrix composed of damping coefficients, is the matrix related to the suspension force, and d is a constant term.

[0117] In one or more embodiments of this specification, the server can, for each suspension of the air spring of the vehicle, determine the tire force of the tire corresponding to the position of the suspension according to the stiffness coefficient, damping coefficient, and target vertical displacement of the tire corresponding to the position of the suspension. Then, according to the tire forces of the tires corresponding to the positions of the suspensions of the air spring of the vehicle, determine the comprehensive tire force of the vehicle.

[0118] Thus, the tire forces corresponding to the positions of each suspension and the combined tire forces of the vehicle are obtained through the following formula:

[0119]

[0120] Wherein, respectively represent the tire forces corresponding to the tires at the positions of the four suspensions, respectively represent the stiffness coefficients corresponding to the tires at the positions of the four suspensions, respectively represent the damping coefficients corresponding to the tires at the positions of the four suspensions, respectively represent the target vertical displacements of the contact points between the tires corresponding to the positions of the four suspensions and the ground; [~]q is related to the target vertical displacement and is a zero matrix; and are respectively diagonal matrices composed of the negative values of the stiffness coefficients and damping coefficients.

[0121] In one or more embodiments of the present specification, the dynamic equation of the vehicle and the state space equation of the vehicle are:

[0122]

[0123]

[0124] Wherein, represents the vertical accelerations respectively corresponding to the four unsprung masses of the air springs of the vehicle, are the unsprung masses respectively corresponding to the four unsprung masses of the air springs of the vehicle, represents the vertical acceleration of the vehicle body mass center, represents the pitch angular acceleration of the vehicle, represents the roll angular acceleration of the vehicle, m is the vehicle body mass, is the moment of inertia of the vehicle body about the pitch axis, is the moment of inertia of the vehicle body about the roll axis, referring to Figure 2 , the pitch axis is the axis parallel to the front and rear axles of the vehicle, and the roll axis is the axis perpendicular to the front and rear axles of the vehicle; I is the identity matrix, and the subscript 4 is its dimension; is ; is the state space equation of the vehicle.

[0125] It should be noted that in the present specification, forces or related parameters similar to , etc. that can be represented by the relevant parts corresponding to the positions of the four suspensions can respectively act on , are represented as follows. In this specification , etc. are matrices of 4 rows and 16 columns. Each row (i.e., , etc.) corresponds to the force or relevant parameter represented by the relevant part corresponding to the position of a suspension.

[0126] In this specification, without considering the constant term and the height of the air spring , only making the control quantity be the target pressure parameter, that is . Through the discretized state - space model (which can be represented by the matrices , and ), predict the future state of the vehicle and calculate the control quantity corresponding to the optimal target pressure parameter of the air spring . The state - space equation is as follows:

[0127] wherein, ,

[0128] Figure 3 is a schematic flow chart of a process for cyclically adjusting the vehicle attitude and body height provided in this specification. As Figure 3 shown, after the server obtains and determines the target data, input the target data into the MPC module. Through the MPC module, using the target data and the current data determined in the previous round of adjustment, obtain the target pressure parameter of the air spring and input it into the PID module. The PID module calculates the opening value of the air - spring charging and discharging valve port according to the target pressure parameter and the actual pressure parameter of the air spring fed back by the air - spring model. According to this opening value, determine the vertical force of the air spring, and thus adjust the seven - degree - of - freedom vehicle model according to the vertical force to achieve the adjustment of the vehicle attitude and body height. After the adjustment is completed, continue to calculate the current data required for the next round of adjustment according to the state equation and input it into the MPC module.

[0129] Of course, in addition to the software implementation method, this specification does not exclude other implementation methods, such as logical devices or the combination of software and hardware, etc. That is to say, the execution subject of the following processing flow is not limited to each logical unit, and can also be hardware or logical devices.

[0130] In the 1990s, it was quite obvious to distinguish whether an improvement to a technology was a hardware improvement (e.g., improvement to circuit structures such as diodes, transistors, switches, etc.) or a software improvement (improvement to method flows). However, with the development of technology, many method flow improvements today can be regarded as direct improvements to hardware circuit structures. Almost all designers obtain the corresponding hardware circuit structures by programming the improved method flows into the hardware circuits. Therefore, it cannot be said that an improvement to a method flow cannot be implemented with hardware entity modules. For example, a Programmable Logic Device (PLD) (such as a Field Programmable Gate Array (FPGA)) is such an integrated circuit whose logical function is determined by the user programming the device. Designers can program on their own to "integrate" a digital system onto a single PLD, without having to ask a chip manufacturer to design and fabricate a dedicated integrated circuit chip. Moreover, nowadays, instead of manually fabricating integrated circuit chips, this programming is mostly implemented using "logic compiler" software, which is similar to the software compilers used in program development and writing. The original code before compilation also has to be written in a specific programming language, which is called a Hardware Description Language (HDL). There is not only one type of HDL, but many types, such as ABEL (Advanced Boolean Expression Language), AHDL (Altera Hardware Description Language), Confluence, CUPL (Cornell University Programming Language), HDCal, JHDL (Java Hardware Description Language), Lava, Lola, MyHDL, PALASM, RHDL (Ruby Hardware Description Language), etc. Currently, the most commonly used are VHDL (Very-High-Speed Integrated Circuit Hardware Description Language) and Verilog. Those skilled in the art should also be aware that as long as the method flow is slightly logically programmed with the above-mentioned several hardware description languages and programmed into the integrated circuit, it is easy to obtain the hardware circuit that implements the logical method flow.

[0131] The controller can be implemented in any suitable manner. For example, the controller can take the form of, for example, a microprocessor or a processor and a computer-readable medium storing computer-readable program code (such as software or firmware) executable by the (micro)processor, logic gates, switches, an application specific integrated circuit (ASIC), a programmable logic controller, and an embedded microcontroller. Examples of the controller include, but are not limited to, the following microcontrollers: ARC 625D, Atmel AT91SAM, Microchip PIC18F26K20, and Silicone Labs C8051F320. The memory controller can also be implemented as part of the control logic of the memory. Those skilled in the art also know that, in addition to implementing the controller in the form of pure computer-readable program code, it is entirely possible to make the controller implement the same function in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, such a controller can be considered a hardware component, and the devices included therein for implementing various functions can also be regarded as the structures within the hardware component. Or even, the devices for implementing various functions can be regarded as either software modules for implementing the method or the structures within the hardware component.

[0132] The systems, devices, modules, or units illustrated in the above embodiments can be specifically implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0133] For the convenience of description, the above devices are described by dividing them into various units according to their functions. Of course, when implementing this specification, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0134] Those skilled in the art should understand that the embodiments of this specification can be provided as a method, a system, or a computer program product. Therefore, this specification can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, this specification can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program code.

[0135] This specification is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the specification. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general purpose computers, special purpose computers, embedded processors, or other programmable data processing devices to produce a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 one or more of the blocks for implementing the specified functions.

[0136] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable memory produce a manufacture including instruction means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 one or more of the blocks.

[0137] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 one or more of the blocks.

[0138] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0139] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM), and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. The memory is an example of computer-readable media.

[0140] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0141] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0142] It should be understood by those skilled in the art that the embodiments of this specification may be provided as methods, systems or computer program products. Therefore, this specification may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, this specification may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0143] This specification may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. This specification may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0144] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for the relevant parts, reference can be made to the corresponding description in the method embodiment.

[0145] The above description is only for the embodiments of this specification and is not intended to limit this specification. For those skilled in the art, various changes and modifications can be made to this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included within the scope of the claims of this specification.

Claims

1. A vehicle attitude and body height adjustment method, characterized in that, Including: Determine the target vertical displacement of the vehicle's center of mass, the target pitch angle, and the target roll angle as target data; For each round of adjustment of the vehicle's attitude and body height, determine the vertical displacement of the vehicle's center of mass, the pitch angle, and the roll angle after the previous round of adjustment as the current data; Input the target data and the current data into the model predictive control module to obtain the target pressure parameter of the air spring of the vehicle output by the model predictive control module; Input the target pressure parameter into the control feedback module to obtain the opening value of the air spring charging and discharging valve port output by the control feedback module; Determine the vertical force of the air spring according to the opening value and the effective area of the air spring; Apply the vertical force to the air spring of the vehicle to adjust the vehicle's attitude and body height.

2. The method according to claim 1, wherein The method further includes: Determine the vertical displacements of the unsprung masses at the four suspensions of the vehicle's air spring, the vertical displacement of the vehicle body's center of mass, and the pitch angle and roll angle of the vehicle after this round of adjustment, and construct a seven-degree-of-freedom vehicle dynamics model of the vehicle; Determine the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model; Determine the state space equation of the vehicle according to the dynamic equation; Solve the state space equation to obtain the current data input into the model predictive control module for the next round of adjustment.

3. The method according to claim 2, wherein The seven-degree-of-freedom vehicle dynamics model includes a sixteen-dimensional column vector and a fourteen-dimensional column vector, and the sixteen-dimensional column vector and the fourteen-dimensional column vector are expressed as: Among them, respectively represent the vertical displacements of the four unsprung masses of the air springs of the vehicle, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, is the vertical displacement of the corresponding sprung mass, respectively correspond to the vertical velocities, is the vertical displacement of the vehicle body's center of mass, is the pitch angle and roll angle of the vehicle, is the vertical velocity of the center of mass, is the pitch angular velocity, is the roll angular velocity.

4. The method according to claim 3, wherein Before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: Construct a transformation relation between the vertical displacement of each sprung mass and the vertical displacement of the vehicle body's center of mass, the pitch angle, and the roll angle of the vehicle; Determine the conversion relation between the sixteen-dimensional column vector and the fourteen-dimensional column vector according to the transformation relation.

5. The method according to claim 4, wherein The transformation relation and the conversion relation are: Wherein, in the seven-degree-of-freedom vehicle dynamics model, a is the vertical distance from the vehicle's center of mass to the vehicle's front axle, and b is the vertical distance from the vehicle's center of mass to the vehicle's rear axle. and are the lengths of the vehicle's front axle and the vehicle's rear axle respectively. is a block matrix. and are both sub-matrices with eight rows and seven columns.

6. The method according to claim 5, wherein Before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: For each suspension of the vehicle's air spring, determine the combined force at the position of the suspension according to the vertical displacement of the unsprung mass and the vertical displacement of the sprung mass corresponding to the suspension; 7. The method according to claim 6, wherein The combined force at the position of each suspension is obtained through the following formula: Among them, They are respectively the combined acting forces of the spring forces and damping forces corresponding to the positions of the four suspensions of the air springs of the vehicle, They respectively represent the acting forces generated by the air springs at the positions of the four suspensions, They respectively represent the damping parameters of the four suspensions, is the damping coefficient matrix of the shock absorbers connected in parallel with the air springs of the vehicle, is the stiffness matrix of the air springs of the vehicle, is the effective acting area matrix of the air springs of the vehicle, h is the height of the air springs of the vehicle, and n is the internal pressure of the air springs of the vehicle, is the total suspension combined acting force, represents the diagonal matrix composed of damping coefficients, is the matrix related to the suspension acting force, and d is a constant term.

8. The method according to claim 7, wherein Before determining the dynamic equation of the vehicle according to the seven-degree-of-freedom vehicle dynamics model, the method further includes: For each suspension of the vehicle's air spring, determine the tire force at the position of the suspension according to the stiffness coefficient, damping coefficient, and target vertical displacement of the tire corresponding to the position of the suspension; Determine the combined tire force of the vehicle according to the tire forces of the tires corresponding to the positions of the suspensions of the vehicle's air spring.

9. The method according to claim 8, wherein The tire force at the position of each suspension corresponding to the tire and the combined tire force of the vehicle are obtained through the following formula: Among them, respectively represent the tire forces of the tires corresponding to the positions of the four suspensions, respectively represent the stiffness coefficients of the tires corresponding to the positions of the four suspensions, respectively represent the damping coefficients of the tires corresponding to the positions of the four suspensions, respectively represent the target vertical displacements of the contact points between the tires corresponding to the positions of the four suspensions and the ground; [~]q is related to the target vertical displacement and is a zero matrix; and are respectively diagonal matrices composed of the negative values of the stiffness coefficients and the damping coefficients.

10. The method according to claim 9, characterized in that, The dynamic equation of the vehicle and the state space equation of the vehicle are: Among them, represent the vertical accelerations respectively corresponding to the four unsprung masses of the air springs of the vehicle, are the unsprung masses respectively corresponding to the four unsprung masses of the air springs of the vehicle, represents the vertical acceleration of the vehicle body mass center, represents the pitch angular acceleration of the vehicle, represents the roll angular acceleration of the vehicle, m is the vehicle body mass, is the moment of inertia of the vehicle body about the pitch axis, is the moment of inertia of the vehicle body about the roll axis; I is the identity matrix, and the subscript 4 is its dimension; is ; is the state space equation of the vehicle.

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