Rigidity control method of three-cavity air spring system

Abstract

According to the rigidity control method of the three-cavity air spring system, the three-cavity air spring system comprises an air spring body and air chamber change-over valves located in the air spring body, and a first air chamber change-over valve and a second air chamber change-over valve are arranged in the air spring body; the first air chamber change-over valve and the second air chamber change-over valve divide the air spring main body into a first air chamber, a second air chamber and a third air chamber which are separated from each other; the rigidity control method of the three-cavity air spring system comprises the step of calculating rigidity coefficients adopted in different driving modes according to a kinetic equation of the Newton's law three-cavity air spring system, a state equation of the three-cavity air spring system, an optimal control theory and a quadratic objective function. According to different driving modes and vehicle speeds, different rigidity adjustments are carried out, and the driving state and the control performance of the whole vehicle can be better fused.

Description

Technical Field

[0001] The invention relates to the technical field of air springs, and in particular to a stiffness control method for a three-chamber air spring system. Background Art

[0002] At present, most of the air springs installed in domestic passenger cars are single-chamber air springs. The stiffness of single-chamber air springs is fixed, which has certain limitations on the comfort and safety of car driving. A small number of high-end cars are equipped with double-chamber air springs, which can only achieve two different stiffness adjustments. Only a few foreign luxury cars are equipped with three-chamber air springs. The control system and control method of three-chamber air springs are a relatively new field. A good control system and control method have a great effect on improving the comfort and safety of the car. However, the current three-chamber air spring system cannot select the appropriate stiffness according to the car driving mode, and lacks a suitable method, and the user experience is very poor. Summary of the invention

[0003] In order to solve the above problems, the purpose of the invention is to provide a stiffness control method for a three-chamber air spring system.

[0004] To achieve the above-mentioned purpose, the technical solution of the invention is: a stiffness control method of a three-chamber air spring system, the three-chamber air spring system includes an air spring body and an air chamber conversion valve located in the air spring body, a first air chamber conversion valve and a second air chamber conversion valve are arranged in the air spring body, and the first air chamber conversion valve and the second air chamber conversion valve divide the air spring body into a first air chamber, a second air chamber and a third air chamber separated from each other;

[0005] Open the first air chamber conversion valve and the second air chamber conversion valve to connect the first air chamber, the second air chamber and the third air chamber. In this state, the stiffness of the air spring is stiffness one;

[0006] The first air chamber conversion valve is closed, and the second air chamber conversion valve is opened to connect the first air chamber with the third air chamber. In this state, the stiffness of the air spring is stiffness 2;

[0007] The first air chamber conversion valve is opened and the second air chamber conversion valve is closed to connect the first air chamber with the second air chamber. In this state, the stiffness of the air spring is stiffness three;

[0008] Close the first air chamber conversion valve and the second air chamber conversion valve to connect the first air chamber. In this state, the stiffness of the air spring is stiffness 4;

[0009] The stiffness control method of the three-chamber air spring system is: the stiffness coefficients used in different driving modes are calculated based on the dynamic equation of the three-chamber air spring system according to Newton's law, the state equation of the three-chamber air spring system, the optimal control theory and the quadratic objective function.

[0010] Furthermore, the specific steps of the stiffness control method of the three-chamber air spring system are as follows:

[0011] Step 1: According to Newton's law, the dynamic equation of the three-chamber air spring system is:

[0012]

[0013] S=F u / δ

[0014] In the formula, m s is the sprung mass, m w is the unsprung mass, F u is the control force generated by the air spring, S w is the stiffness of the tire, z w 、z s are the vertical displacement coordinates of the wheel axle and the vehicle body at their respective equilibrium positions, q is the displacement function of the road surface roughness, and δ is the deformation of the air spring due to the force;

[0015] Select the suspension air spring dynamic deflection z sw =z s -z w , body vertical speed Tire dynamic deformation qw =qz w , wheel axle vertical speed is the system state variable;

[0016] Step 2: The state equation of the three-chamber air spring system is:

[0017]

[0018] The output equation of the active suspension air spring system is:

[0019]

[0020] The standard form of the state equation and output equation of the active suspension air spring system is

[0021]

[0022] Y=CX+DU

[0023] In the formula, U=F u ,

[0024] Step 3: According to the optimal control theory:

[0025] U=-KX

[0026] Where K = [k1, k2, k3, k4], called the optimal feedback (gain) matrix, U = F u ,

[0027] The performance objective function of the active suspension air spring system is:

[0028]

[0029] In the formula, q1, q2, q3, and q4 are weight coefficients of the corresponding physical quantities. Different driving modes have different weight coefficients.

[0030] Step 4: The quadratic objective function is:

[0031]

[0032] In the formula,

[0033] Taking the control law U=-KX can satisfy the minimum system performance index under given conditions. The matrix P is obtained by the Riccati equation:

[0034]

[0035] Furthermore, the three-chamber air spring system monitors the driving status of the vehicle. The driving modes are divided into off-road mode, standard mode, sports mode, and comfort mode. Different driving modes use different stiffness coefficients.

[0036] Furthermore, the opening and closing states of the first air chamber conversion valve and the second air chamber conversion valve are input to the stiffness control system through feedback signals, and the stiffness control system monitors the fault states of the first air chamber conversion valve and the second air chamber conversion valve in real time; the three-chamber air spring system determines the sudden braking state through the opening and closing of the brake pedal and the acceleration signal collected by the acceleration sensor, and determines the sudden acceleration state through the opening and closing of the accelerator pedal and the acceleration collected by the acceleration sensor.

[0037] Furthermore, during sudden braking, the three-chamber air spring system on the front axle switches to stiffness four; during sudden acceleration, the three-chamber air spring system on the rear axle switches to stiffness four; during high-speed cornering, the three-chamber air spring system on the outer wheel switches to stiffness four, and the three-chamber air spring system on the inner wheel switches to stiffness three.

[0038] Through the above settings, the present invention adopts a three-chamber air spring, which is combined with three different air chambers. The air spring can achieve four different stiffnesses. Compared with the two stiffnesses of the double-chamber air springs currently on the market, it has a better stiffness control effect. Compared with the current three-chamber air spring, the stiffness coefficients used in different driving modes are calculated according to the dynamic equation of the three-chamber air spring system based on Newton's law, the state equation of the three-chamber air spring system, the optimal control theory and the quadratic objective function; the present invention performs optimal selection calculations through the opening and closing of the brake pedal and the acceleration signal collected by the acceleration sensor to judge the emergency braking state, and performs optimal selection calculations through the opening and closing of the accelerator pedal and the acceleration collected by the acceleration sensor to judge the emergency acceleration state. Compared with the current market that only uses the brake pedal and the accelerator pedal to judge the emergency braking and emergency acceleration states, it has higher accuracy and better safety; different stiffness adjustments are made according to different driving modes and vehicle speeds, which can be better integrated into the driving state and handling performance of the whole vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention will now be further described with reference to the accompanying drawings.

[0040] Figure 1 It is a schematic diagram of the cross-sectional structure of the air spring body of the present invention;

[0041] Figure 2 It is the overall technical flow chart of the control method of the present invention. DETAILED DESCRIPTION

[0042] like Figure 1-2 As shown, a stiffness control method of a three-chamber air spring system, the three-chamber air spring system includes an air spring body and an air chamber conversion valve located in the air spring body, a first air chamber conversion valve 1 and a second air chamber conversion valve 2 are arranged in the air spring body, and the first air chamber conversion valve 1 and the second air chamber conversion valve 2 divide the air spring body into a first air chamber 3, a second air chamber 4 and a third air chamber 5 which are separated;

[0043] Open the first air chamber conversion valve 1 and the second air chamber conversion valve 2 to connect the first air chamber 3, the second air chamber 4 and the third air chamber 5. In this state, the stiffness of the air spring is stiffness 1;

[0044] Close the first air chamber conversion valve 1 and open the second air chamber conversion valve 2 to connect the first air chamber 3 with the third air chamber 5. In this state, the stiffness of the air spring is stiffness 2;

[0045] Open the first air chamber conversion valve 1 and close the second air chamber conversion valve 2 to connect the first air chamber 3 with the second air chamber 4. In this state, the stiffness of the air spring is stiffness three;

[0046] Close the first air chamber conversion valve 1 and the second air chamber conversion valve 2 to connect the first air chamber 3. In this state, the stiffness of the air spring is stiffness 4;

[0047] The stiffness control method of the three-chamber air spring system is as follows: the stiffness coefficients used in different driving modes are calculated based on the dynamic equation of the three-chamber air spring system according to Newton's law, the state equation of the three-chamber air spring system, the optimal control theory and the quadratic objective function. The specific steps of the stiffness control method of the three-chamber air spring system are as follows:

[0048] Step 1: According to Newton's law, the dynamic equation of the three-chamber air spring system is:

[0049]

[0050] S=F u / δ

[0051] In the formula, m s is the sprung mass, m w is the unsprung mass, F u is the control force generated by the air spring, S w is the stiffness of the tire, z w 、z s are the vertical displacement coordinates of the wheel axle and the vehicle body at their respective equilibrium positions, q is the displacement function of the road surface roughness, and δ is the deformation of the air spring due to the force;

[0052] Select the suspension air spring dynamic deflection z sw =z s -z w , body vertical speed Tire dynamic deformation qw =qz w , wheel axle vertical speed is the system state variable;

[0053] Step 2: The state equation of the three-chamber air spring system is:

[0054]

[0055] The output equation of the active suspension air spring system is:

[0056]

[0057] The standard form of the state equation and output equation of the active suspension air spring system is

[0058]

[0059] Y=CX+DU

[0060] In the formula, U=F u ,

[0061] Step 3: According to the optimal control theory:

[0062] U=-KX

[0063] Where K = [k1, k2, k3, k4], called the optimal feedback (gain) matrix, U = F u ,

[0064] The performance objective function of the active suspension air spring system is:

[0065]

[0066] In the formula, q1, q2, q3, and q4 are weight coefficients of the corresponding physical quantities. Different driving modes have different weight coefficients.

[0067] Step 4: The quadratic objective function is:

[0068]

[0069] In the formula,

[0070] Taking the control law U=-KX can satisfy the minimum system performance index under given conditions. The matrix P is obtained by the Riccati equation:

[0071]

[0072] Through the above steps, the three-chamber air spring system can accurately determine the driving state of the car. For example, the driving mode is divided into off-road mode, standard mode, sports mode, and comfort mode. Different driving modes use different stiffness coefficients. The opening and closing states of the first air chamber conversion valve 1 and the second air chamber conversion valve 2 are input to the stiffness control system through feedback signals. The stiffness control system monitors the fault state of the first air chamber conversion valve 1 and the second air chamber conversion valve 2 in real time. The three-chamber air spring system determines the emergency braking state through the opening and closing of the brake pedal and the acceleration signal collected by the acceleration sensor, and determines the emergency acceleration state through the opening and closing of the accelerator pedal and the acceleration collected by the acceleration sensor. For example, when braking suddenly, the three-chamber air spring system of the front axle switches to stiffness four; when accelerating suddenly, the three-chamber air spring system of the rear axle switches to stiffness four; when turning at high speed, the three-chamber air spring system of the outer wheel switches to stiffness four, and the three-chamber air spring system of the inner wheel switches to stiffness three.

[0073] The above description is only an illustrative embodiment of the invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the invention shall fall within the scope of protection of the invention.

Claims

1. A stiffness control method for a three-chamber air spring system, the three-chamber air spring system comprising an air spring body and an air chamber conversion valve located in the air spring body, characterized in that: A first air chamber conversion valve (1) and a second air chamber conversion valve (2) are arranged in the air spring body, and the first air chamber conversion valve (1) and the second air chamber conversion valve (2) divide the air spring body into a first air chamber (3), a second air chamber (4) and a third air chamber (5) which are separated from each other; Opening the first air chamber conversion valve (1) and the second air chamber conversion valve (2) to connect the first air chamber (3), the second air chamber (4) and the third air chamber (5), in which state the stiffness of the air spring is stiffness one; The first air chamber conversion valve (1) is closed, and the second air chamber conversion valve (2) is opened so that the first air chamber (3) is connected to the third air chamber (5). In this state, the stiffness of the air spring is stiffness 2; The first air chamber conversion valve (1) is opened and the second air chamber conversion valve (2) is closed so that the first air chamber (3) and the second air chamber (4) are connected. In this state, the stiffness of the air spring is stiffness three; The first air chamber conversion valve (1) and the second air chamber conversion valve (2) are closed to connect the first air chamber (3), and the stiffness of the air spring in this state is stiffness four; The stiffness control method of the three-chamber air spring system is: the stiffness coefficients used in different driving modes are calculated based on the dynamic equation of the three-chamber air spring system according to Newton's law, the state equation of the three-chamber air spring system, the optimal control theory and the quadratic objective function.

2. A stiffness control method for a three-chamber air spring system as claimed in claim 1, characterized in that: The specific steps of the stiffness control method of the three-chamber air spring system are as follows: Step 1: According to Newton's law, the dynamic equation of the three-chamber air spring system is: S=F u / d In the formula, m s is the sprung mass, m w is the unsprung mass, F u is the control force generated by the air spring, S w is the stiffness of the tire, z w 、z s are the vertical displacement coordinates of the wheel axle and the vehicle body at their respective equilibrium positions, q is the displacement function of the road surface roughness, and δ is the deformation of the air spring due to the force; Select the suspension air spring dynamic deflection z sw =z s -z w , body vertical speed Tire dynamic deformation qw =qz w , wheel axle vertical speed is the system state variable; Step 2: The state equation of the three-chamber air spring system is: The output equation of the active suspension air spring system is: The standard form of the state equation and output equation of the active suspension air spring system is Y=CX+DU In the formula, Step 3: According to the optimal control theory: U=-KX Where K = [k1, k2, k3, k4], called the optimal feedback (gain) matrix, U = F u , The performance objective function of the active suspension air spring system is: In the formula, q1, q2, q3, and q4 are weight coefficients of the corresponding physical quantities. Different driving modes have different weight coefficients. Step 4: The quadratic objective function is: In the formula, Taking the control law U=-KX can satisfy the minimum system performance index under given conditions. The matrix P is obtained by the Riccati equation:

3. The stiffness control method of a three-chamber air spring system according to claim 1, characterized in that: The three-chamber air spring system monitors the vehicle's driving status. The driving modes are divided into off-road mode, standard mode, sports mode, and comfort mode. Different driving modes use different stiffness coefficients.

4. The stiffness control method of a three-chamber air spring system according to claim 3, characterized in that: The opening and closing states of the first air chamber conversion valve (1) and the second air chamber conversion valve (2) are input into the stiffness control system via feedback signals, and the stiffness control system monitors the fault states of the first air chamber conversion valve (1) and the second air chamber conversion valve (2) in real time; the three-chamber air spring system determines the emergency braking state via the opening and closing of the brake pedal and the acceleration signal collected by the acceleration sensor, and determines the emergency acceleration state via the opening and closing of the accelerator pedal and the acceleration collected by the acceleration sensor.

5. The stiffness control method of a three-chamber air spring system according to claim 3, characterized in that: During sudden braking, the three-chamber air spring system on the front axle switches to stiffness four; during sudden acceleration, the three-chamber air spring system on the rear axle switches to stiffness four; during high-speed cornering, the three-chamber air spring system on the outer wheel switches to stiffness four, and the three-chamber air spring system on the inner wheel switches to stiffness three.

Images