Active air suspension system control method and device

Abstract

The present invention relates to a control method and device for an active air suspension system, and belongs to the field of vehicle control technology. The control method includes the following damping control steps: obtaining the road surface height at the preview point; calculating the virtual road surface height at the front axle based on the road surface height at the preview point and the first preview state equation relative to the front axle; obtaining the virtual road surface height at the rear axle based on the road surface height at the preview point and the second preview state equation relative to the rear axle; inputting the road surface height at the preview point, the virtual road surface height at the front axle, and the virtual road surface height at the rear axle into the control force model to obtain the optimal damping force of the front and rear wheels; and controlling the front and rear wheel continuously variable damping shock absorbers based on the optimal damping force of the front and rear wheels. The present invention obtains the road surface information at the preview point in advance, obtains the optimal damping force when the vehicle travels to the preview point, and then controls the damping force to improve the control effect and ride comfort.

Description

Technical Field

[0001] The present invention relates to a control method and device for an active air suspension system, belonging to the technical field of vehicle control. Background Art

[0002] Traditional suspension systems are passive, with neither damping nor height adjustment. A stiffer suspension system provides excellent handling, especially at high speeds, and helps maintain vehicle stability. However, this compromises comfort on rough roads. A softer suspension setting, while providing improved comfort, also compromises handling, with noticeable head lift during acceleration and head nodding during braking.

[0003] With the advancement of vehicle control technology, passive suspension can no longer meet existing needs. Therefore, a master-controlled air suspension system has been proposed. The master-controlled air suspension system's damping and vehicle height change with changes in driving conditions such as load, road conditions, vehicle speed, longitudinal acceleration, lateral acceleration, and vertical acceleration, as well as the driver's individual preferences, greatly improving ride comfort.

[0004] The height and damping control of existing main control air suspension systems generally perform active suspension control based on the current vehicle operating conditions and the current vibration acceleration. Since the vehicle is always in motion, if the damping is controlled using the current operating conditions, the vehicle operating conditions may have changed when the control results are obtained, which will cause control delays and fail to match the current operating conditions well, resulting in poor suspension control effects. Summary of the Invention

[0005] The purpose of this application is to provide a control method for an active air suspension system to solve the problem of control delay in existing suspension systems.

[0006] To achieve the above objectives, the present application proposes a technical solution for a control method of an active air suspension system, comprising the following control steps:

[0007] 1) Obtain the road surface height at the preview point;

[0008] 2) The virtual road height at the front axle is calculated based on the road height at the preview point and a first preview state equation relative to the front axle; the virtual road height at the rear axle is calculated based on the road height at the preview point and a second preview state equation relative to the rear axle; the virtual road height at the front axle is the virtual road height at the front axle at each moment in the process of the vehicle moving to the preview point; the virtual road height at the rear axle is the virtual road height at the rear axle at each moment in the process of the vehicle moving to the preview point;

[0009] 3) The road surface height at the preview point, the virtual road surface height at the front axle, and the virtual road surface height at the rear axle are input into a control force model to obtain the optimal preview control force; the control force model is obtained based on the vehicle vertical vibration equation, the first preview state equation relative to the front axle, and the second preview state equation relative to the rear axle:

[0010] U p =K p [x η] T ;

[0011] η=[η 1f η 2f η 1r η 2r ] T ;

[0012] U p =[U df U dr ] T ;

[0013]

[0014] Among them, U p is the optimal preview control force matrix; U df is the optimal damping force of the front wheel; U dr is the optimal damping force of the rear wheel; K p is the optimal control gain matrix; x is the system state variable matrix; Z f is the virtual road height at the front axle; Z r is the virtual road height at the rear axle; w is the road height at the preview point; a 1f is the second coefficient of the first preview state equation, which is obtained based on the time required for the front axle to move to the preview point; a 1r is the second coefficient of the second preview state equation, which is obtained according to the time required for the rear axle to move to the preview point;

[0015] 4) Control the operation of the front wheel continuously variable damping shock absorber according to the optimal damping force of the front wheel; control the operation of the rear wheel continuously variable damping shock absorber according to the optimal damping force of the rear wheel.

[0016] In addition, the present application proposes a technical solution for a control device of an active air suspension system, including a processor, a memory, and a computer program stored in the memory and runnable on the processor, and the processor implements a technical solution for a control method of an active air suspension system when executing the computer program.

[0017] The beneficial effect of the technical solution of the control method and device of the active air suspension system of the present invention is as follows: the present invention plans the virtual road height at the front axle and the virtual road height at the rear axle corresponding to each moment when the vehicle travels to the preview point through the road height at the preview point, and then obtains the optimal damping force of the front and rear wheels based on the road height at the preview point, the virtual road height, and the vehicle vertical vibration equation, the first preview state equation relative to the front axle, and the second preview state equation relative to the rear axle, thereby gradually controlling the continuously variable damping shock absorbers of the front and rear wheels. The present invention plans the virtual road height at each moment in the process of the vehicle traveling to the preview point in advance to obtain the optimal damping force, and then gradually controls the damping force of the front and rear wheels at each moment during the driving process, thereby achieving a stable transition at the preview point and improving ride comfort.

[0018] Furthermore, in the control method and device of the above-mentioned active air suspension system, in step 4), the corresponding control current is obtained by looking up a table based on the optimal damping force of the front wheel and the optimal damping force of the rear wheel, and the front and rear wheel continuously variable damping shock absorbers are controlled according to the obtained control current.

[0019] Furthermore, in the control method and device for the active air suspension system, the road surface height at the preview point is obtained by a binocular camera.

[0020] Furthermore, in the control method and device for the active air suspension system, the first preview state equation relative to the front axle is:

[0021]

[0022]

[0023] Where w is the road surface height at the preview point; a 0f is the first coefficient of the first preview state equation.

[0024] Furthermore, in the control method and device for the active air suspension system, the second preview state equation relative to the rear axle is:

[0025]

[0026]

[0027] Where w is the road surface height at the preview point; a 0r is the first coefficient of the second preview state equation.

[0028] Furthermore, the control method and device for the active air suspension system further includes the step of controlling the vehicle height by controlling the opening of the height valve:

[0029] When the current vehicle speed is less than the second set vehicle speed V2, the vehicle height is controlled to be the high height H+;

[0030] When the current vehicle speed is greater than the third set speed V3 and the current height is the high height H+, the vehicle height is controlled to be the normal height H0;

[0031] When the current vehicle speed is greater than the fourth set vehicle speed V4 and the current height is the normal height H0, the vehicle height is controlled to the low height H-;

[0032] When the current vehicle speed is less than the first set vehicle speed V1, the vehicle height is controlled to be the normal height H0;

[0033] The first set vehicle speed V1 is less than the second set vehicle speed V2 and less than the third set vehicle speed V3 and less than the fourth set vehicle speed V4; and the high level height H+ is greater than the normal level height H0 and greater than the low level height H−.

[0034] Furthermore, in the control method and device of the above-mentioned active air suspension system, when the vehicle height is controlled to be a high height H+, the height of the vehicle's front axle is determined according to the high height H+ and the virtual road height at the front axle, and the height of the vehicle's rear axle is determined according to the high height H+ and the virtual road height at the rear axle; when the vehicle height is controlled to be a normal height H0, the height of the vehicle's front axle is determined according to the normal height H0 and the virtual road height at the front axle, and the height of the vehicle's rear axle is determined according to the normal height H0 and the virtual road height at the rear axle; when the vehicle height is controlled to be a low height H-, the height of the vehicle's front axle is determined according to the low height H- and the virtual road height at the front axle, and the height of the vehicle's rear axle is determined according to the low height H- and the virtual road height at the rear axle. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of damping control in the control method of the active air suspension system of the present invention;

[0036] Figure 2 Schematic diagram of damping and height control in the control method of the active air suspension system of the present invention;

[0037] Figure 3 1 is a schematic diagram of height control in the control method of the active air suspension system of the present invention;

[0038] Figure 4 is a high-level control flow chart of the control method of the active air suspension system of the present invention;

[0039] Figure 5 It is a structural diagram of the control device of the active air suspension system of the present invention. DETAILED DESCRIPTION

[0040] Active air suspension system control method embodiment:

[0041] The main idea of ​​the present invention is that, when controlling the damping, the virtual road surface height at the front axle and the virtual road surface height at the rear axle are planned by obtaining the road surface height of the preview point of the road ahead, and then the optimal damping force at each moment when the vehicle moves to the preview point is obtained according to the control force model, and then the continuously variable damping shock absorber is controlled to achieve a smooth transition of the damping force. By smoothly passing the preview point, the optimal damping force is calculated in advance, and the damping can be adjusted in time to improve ride comfort.

[0042] Specifically, the active air suspension system of the present invention can achieve damping and height control. When performing height control, it is necessary to open the height valve between the air spring and the air source.

[0043] Specifically, the optimal damping control process of the suspension is as follows: Figure 1 and Figure 2 As shown, the following steps are included:

[0044] 1) Obtain the road surface height at the preview point, and calculate the virtual road surface height at the front axle and the virtual road surface height at the rear axle based on the road surface height at the preview point.

[0045] The virtual road surface height at the front axle here is the virtual road surface height corresponding to each moment at the front axle during the process of the vehicle moving to the preview point. The virtual road surface height at the rear axle is the virtual road surface height corresponding to each moment at the rear axle during the process of the vehicle moving to the preview point. The virtual road surface height is the virtually planned road surface height, not the actual road surface height. Subsequent calculations are performed based on the planned road surface height.

[0046] A binocular camera is used to collect road surface image information at a preview point 30 meters in front of the vehicle, and then the road surface height at the preview point is obtained based on the image information. Then, a road surface roughness recognition algorithm is used to obtain the virtual road surface height at the front axle and the virtual road surface height at the rear axle.

[0047] The road roughness recognition algorithm includes a first preview state equation relative to the front axle and a second preview state equation relative to the rear axle. The preview point is a point at a set distance in front of the vehicle, set as needed, and the binocular camera collects data in real time. The derivation of the first preview state equation relative to the front axle is as follows:

[0048] The road height at the preview point is w, and the virtual road height at the front axle is Z f , w and Z f The Laplace function expression is:

[0049]

[0050] Where s is the Laplace operator; τ fThe time required for the front axis to move to the preview point, L f is the distance between the front axle and the preview point, and V is the vehicle speed.

[0051] The transfer function between the front axle road surface input and the preview point road surface input is:

[0052]

[0053] After finishing, we can get:

[0054] [Z f (s)-w(s)][a 0f +a 1f s+a 2f s 2 ]=-2a 1f sw(s);

[0055] In this embodiment, the second-order Pade approximation is used for calculation: The Pade approximate calculation expression is:

[0056]

[0057] Get a 0f =8 / τ f 2 , a 1f =4 / τ f , a 2f =1.

[0058] Define the state variable η 1f =Z f -w, The first preview state equation relative to the front axis is:

[0059]

[0060] in, It can be seen that a 0f is the first coefficient of the first preview state equation; a 1f is the second coefficient of the first preview state equation, a 0f and a 1f Obtained based on the time required for the front axle to move to the preview point.

[0061] Similarly, the derivation process of the second preview state equation relative to the rear axis is as follows:

[0062] The road height at the preview point is w, and the road height at the rear axle is Z r , w and Z r The Laplace function expression is:

[0063]

[0064] Where s is the Laplace operator; τ r The time required for the rear axle to move to the preview point, L r is the distance between the rear axle and the preview point; V is the vehicle speed.

[0065] The transfer function between the rear axle road surface input and the preview point road surface input is:

[0066]

[0067] After finishing, we can get:

[0068] [Z r (s)-w(s)][a 0r +a 1r s+a 2r s 2 ]=-2a 1r sw(s);

[0069] In this embodiment, the second-order Pade approximation is used for calculation: The Pade approximate calculation expression is:

[0070]

[0071] Get a 0r =8 / τ r 2 , a 1r =4 / τ r , a 2r =1.

[0072] Define the state variable η 1r =Z r -w, The second preview state equation relative to the rear axis:

[0073]

[0074] in, It can be seen that a 0r is the first coefficient of the second preview state equation; a 1r is the second coefficient of the second preview state equation, a 0r and a 1r It is obtained based on the time required for the rear axle to move to the preview point.

[0075] 2) The road surface height at the preview point, the virtual road surface height at the front axle, and the virtual road surface height at the rear axle are input into a pre-established control force model to obtain the optimal preview control force.

[0076] The control force model is obtained according to the vehicle vertical vibration equation, the first preview state equation relative to the front axle, and the second preview state equation relative to the rear axle.

[0077] The first preview state equation relative to the front axis and the second preview state equation relative to the rear axis are obtained together:

[0078]

[0079] in,

[0080] The vertical vibration equation of the vehicle is:

[0081] Where, is the system state variable, where Z bf is the displacement on the front spring, Z br is the displacement on the rear spring, Z uf is the displacement under the front spring, Z ur is the rear unsprung displacement, is the speed on the front spring, is the speed on the rear spring, is the front unsprung speed, is the rear unsprung speed, is the sprung mass center velocity, is the pitch angular velocity; W=[Z f Z r ] T , Z f =η 1f +w、Z r =η 1r +w is the virtual road height at the front and rear axles, U=[U f U r ] T is the control input force matrix, U f is the front wheel damping force; U r is the rear wheel damping force, A, B and F are coefficient matrices.

[0082] Substituting the combined state equations into the vehicle vertical vibration equation, we obtain the vehicle vertical vibration equation that includes the preview road surface information:

[0083]

[0084] in, is the coefficient matrix.

[0085] The optimal objective of this equation is:

[0086]

[0087] in, Q, R and N are the optimal solution coefficient matrices.

[0088] Then we can get the optimal preview control force:

[0089] U p =K p [x η] T ;

[0090] η=[η 1f η 2f η 1r η 2r ] T

[0091] U p =[U df U dr ] T ;

[0092] Among them, U p is the optimal preview control force matrix; U df is the optimal damping force of the front wheel; U dr is the optimal damping force of the rear wheel; K p is the optimal control gain matrix; x is the system state variable matrix.

[0093] 3) Obtain the optimal damping force U of the front wheel df , optimal damping force of rear wheel U dr After that, the corresponding control current is obtained by looking up the table, and then the front and rear suspension CDC shock absorbers (i.e. front and rear wheel continuously variable damping shock absorbers) are controlled respectively.

[0094] The diagram of controlling the vehicle height by controlling the opening of the height valve is as follows Figure 3 、 Figure 4 As shown, the following steps are included:

[0095] When the vehicle passes through a horizontal road, the basic height control is: when the current vehicle speed is less than the second set speed V2, the vehicle height is controlled to be the high height H+; when the current vehicle speed is greater than the third set speed V3 and the current height is the high height H+, the vehicle height is controlled to be the normal height H0; when the current vehicle speed is greater than the fourth set speed V4 and the current height is the normal height H0, the vehicle height is controlled to be the low height H-; when the current vehicle speed is less than the first set speed V1 (it can also last for about 2s), the vehicle height is controlled to be the normal height H0; among which, the first set speed V1 is less than the second set speed V2 is less than the third set speed V3 is less than the fourth set speed V4; and the high height H+ is greater than the normal height H0 and is greater than the low height H-.

[0096] When the vehicle passes through an uneven road, when the vehicle height is controlled at the high height H+, the final control height of the vehicle's front axle is determined according to the high height H+ and the virtual road height at the front axle, and the final control height of the vehicle's rear axle is determined according to the high height H+ and the virtual road height at the rear axle; when the vehicle height is controlled at the normal height H0, the final control height of the vehicle's front axle is determined according to the normal height H0 and the virtual road height at the front axle, and the final control height of the vehicle's rear axle is determined according to the normal height H0 and the virtual road height at the rear axle; when the vehicle height is controlled at the low height H-, the final control height of the vehicle's front axle is determined according to the low height H- and the virtual road height at the front axle, and the final control height of the vehicle's rear axle is determined according to the low height H- and the virtual road height at the rear axle.

[0097] For example, when the initial height of the vehicle is controlled to be the normal height H0, the virtual road height at the front axle is calculated by obtaining the road height w at the preview point and calculating it as Z. f and the virtual road height Z at the rear axle r , then the final height change of the front axle of the controlled vehicle is H0+Z f , the final change of the rear axle height is H0+Z r .

[0098] The present invention realizes the control of the damping and height of the main control air suspension system, and the control of the suspension height and damping is achieved by obtaining road surface information at a preview location in advance, thereby obtaining the height and damping control of the vehicle at the preview location, thereby improving the control effect and riding comfort.

[0099] Example of a control device for an active air suspension system:

[0100] Active air suspension system controls, such as Figure 5 As shown, the system includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the control method of the active air suspension system is implemented.

[0101] The specific implementation process and effects of the control method of the active air suspension system are introduced in the above-mentioned control method embodiment of the active air suspension system, and will not be repeated here.

[0102] That is, it should be understood that the method described in the above embodiments of the active air suspension system control method can be implemented by computer program instructions. These computer program instructions can be provided to a processor (such as a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device), so that the processor executes these instructions to implement the functions specified in the above method flow.

[0103] The processor referred to in this embodiment refers to a processing device such as a microprocessor MCU or a programmable logic device FPGA;

[0104] The memory referred to in this embodiment is used to store computer program instructions generated to implement the control method for the active air suspension system, and includes physical devices for storing information, typically digitizing the information and then storing it in media utilizing electrical, magnetic, or optical means. Examples include various types of memory that use electrical energy to store information, such as RAM and ROM; various types of memory that use magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, bubble memories, and USB flash drives; and various types of memory that use optical means to store information, such as CDs and DVDs. Of course, other types of memory exist, such as quantum memory and graphene memory.

[0105] The control device of the active air suspension system is composed of the memory and processor that store the computer program instructions formed by the control method for implementing the active air suspension system. The control method is implemented by the processor in the computer executing the corresponding program instructions. The computer can use the Windows operating system, Linux system, or other systems, such as Android and iOS system programming languages, to implement it on a smart terminal, and can also be implemented based on the processing logic of a quantum computer.

[0106] As another embodiment, the control device of the active air suspension system may further include other processing hardware, such as a database or multi-level cache, a GPU, etc. The present invention does not specifically limit the structure of the control device of the active air suspension system.

Claims

1. A control method for an active air suspension system, characterized in that: The control steps of damping include the following: 1) Obtain the road surface height at the preview point; 2) The virtual road height at the front axle is calculated based on the road height at the preview point and a first preview state equation relative to the front axle; the virtual road height at the rear axle is calculated based on the road height at the preview point and a second preview state equation relative to the rear axle; the virtual road height at the front axle is the virtual road height at the front axle at each moment in the process of the vehicle moving to the preview point; the virtual road height at the rear axle is the virtual road height at the rear axle at each moment in the process of the vehicle moving to the preview point; 3) The road surface height at the preview point, the virtual road surface height at the front axle, and the virtual road surface height at the rear axle are input into a control force model to obtain the optimal preview control force; the control force model is obtained based on the vehicle vertical vibration equation, the first preview state equation relative to the front axle, and the second preview state equation relative to the rear axle; the control force model is: U p =K p [x n] T ; the=[the 1f or 2f or 1r or 2r ] T ; IN p =[U df IN dr ] T ; η 1f =Z f -In, η 1r =Z r -In, Among them, U p is the optimal preview control force matrix; U df is the optimal damping force of the front wheel; U dr is the optimal damping force of the rear wheel; K p is the optimal control gain matrix; x is the system state variable matrix; Z f is the virtual road height at the front axle; Z r is the virtual road height at the rear axle; w is the road height at the preview point; a 1f is the second coefficient of the first preview state equation, which is obtained based on the time required for the front axle to move to the preview point; a 1r is the second coefficient of the second preview state equation, which is obtained according to the time required for the rear axle to move to the preview point; 4) Control the front wheel continuously variable damping shock absorber according to the optimal damping force of the front wheel; control the operation of the rear wheel continuously variable damping shock absorber according to the optimal damping force of the rear wheel.

2. The control method of the active air suspension system according to claim 1, characterized in that: In the step 4), based on the optimal damping force of the front wheel and the optimal damping force of the rear wheel, the corresponding control current is obtained by looking up the table, and the front and rear wheel continuously variable damping shock absorbers are controlled according to the obtained control current.

3. The control method of the active air suspension system according to claim 1, characterized in that: The road surface height at the preview point is obtained through the binocular camera.

4. The control method of the active air suspension system according to claim 1, characterized in that: The first preview state equation relative to the front axis is: Among them, a 0f is the first coefficient of the first preview state equation.

5. The control method of the active air suspension system according to claim 1, characterized in that: The second preview state equation relative to the rear axis is: Where w is the road surface height at the preview point; a 0r is the first coefficient of the second preview state equation.

6. The control method of the active air suspension system according to claim 1 or 2, characterized in that: The method further includes the steps of controlling the vehicle height by controlling the opening of the height valve: When the current vehicle speed is less than the second set vehicle speed V2, the vehicle height is controlled to be the high height H+; When the current vehicle speed is greater than the third set speed V3 and the current height is the high height H+, the vehicle height is controlled to be the normal height H0; When the current vehicle speed is greater than the fourth set vehicle speed V4 and the current height is the normal height H0, the vehicle height is controlled to the low height H-; When the current vehicle speed is less than the first set vehicle speed V1, the vehicle height is controlled to be the normal height H0; Wherein, the first set vehicle speed V1 is less than the second set vehicle speed V2 and the third set vehicle speed V3 is less than the fourth set vehicle speed V4; and High height H+>normal height H0>low height H-.

7. The control method of the active air suspension system according to claim 6, characterized in that: When the vehicle height is controlled at the high height H+, the height of the front axle of the vehicle is determined according to the high height H+ and the virtual road height at the front axle, and the height of the rear axle of the vehicle is determined according to the high height H+ and the virtual road height at the rear axle; when the vehicle height is controlled at the normal height H0, the height of the front axle of the vehicle is determined according to the normal height H0 and the virtual road height at the front axle, and the height of the rear axle of the vehicle is determined according to the normal height H0 and the virtual road height at the rear axle; when the vehicle height is controlled at the low height H-, the height of the front axle of the vehicle is determined according to the low height H- and the virtual road height at the front axle, and the height of the rear axle of the vehicle is determined according to the low height H- and the virtual road height at the rear axle.

8. A control device for an active air suspension system, characterized in that: The invention comprises a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the control method of the active air suspension system according to any one of claims 1 to 7 when executing the computer program.

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