A CDC semi-active suspension control method considering solenoid valve driving capability

Abstract

A CDC semi-active suspension control method that considers the solenoid valve drive capability relates to a vehicle semi-active suspension control method. Based on the test characteristic data of the CDC damper, a three-segment model is established, which includes the damping force, suspension extension and contraction velocity, and solenoid valve drive current. Combined with the dynamic model of the semi-active suspension system, a switching nonlinear state-space model of the semi-active suspension system is obtained. Nonlinear terms are selected as antecedent variables and converted into a switching T-S model of the semi-active suspension system. A controller for the solenoid valve drive current is designed to provide the desired control current. Taking into account the nonlinear characteristics of the damper, a controller design is proposed to effectively suppress vehicle vibration within the feasible region of the drive current.

Description

Technical Field

[0001] The present invention relates to a vehicle semi-active suspension control method, in particular to a CDC semi-active suspension control method considering the driving capability of a solenoid valve, and belongs to the technical field of vehicle vibration reduction control. Background Art

[0002] The increasing popularity of SUVs and the advent of autonomous driving technology are prompting automakers to focus on optimizing the balance between ride comfort and handling performance. To achieve this goal, semi-active suspension systems have emerged. These systems utilize sensors to dynamically adjust suspension characteristics based on driving conditions. Compared to traditional passive suspension systems, semi-active suspension has demonstrated significant potential for enhancing vehicle performance. Furthermore, if the semi-active suspension fails for any reason, the system will continue to function as a passive suspension, maintaining system stability. Due to its superior ability to reduce vibration transmission, nearly comparable to active suspension without the high cost and complexity, development in this area is particularly active and remains a hot topic in academia and industry.

[0003] On the one hand, the nonlinear dynamic characteristics of CDC dampers pose challenges in the design of semi-active suspension control algorithms, such as over-linearization or complex nonlinear controllers. For example, the commonly used "shearing" strategy uses the damping force as an intermediate control variable, designs the desired damping force based on a linear model, then converts it to current using an inverse damper model, and then uses forced saturation as the final control variable. This approach inevitably results in a loss of desired performance. Directly considering the nonlinear characteristics without linearization often results in a more complex controller, complicating control system implementation. Furthermore, although the input current supplied to the shock absorber is actually limited, current semi-active suspension controller design often overlooks the constraints on the actual system control variables, resulting in suboptimal performance.

[0004] Therefore, designing and developing a control algorithm that targets the nonlinear characteristics of the semi-active suspension and fully ensures that the control current is within the executable range of the damper is of great significance for improving the comfort and handling of the vehicle. Summary of the Invention

[0005] To address the above-mentioned deficiencies, the present invention provides a CDC semi-active suspension control method that takes into account the solenoid valve driving capability. It takes into account the nonlinear characteristics of the damper and provides a controller design that effectively suppresses vehicle vibration within the feasible domain of the driving current.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a CDC semi-active suspension control method considering the driving capability of the solenoid valve, comprising the following steps:

[0007] Step 1: Based on the test characteristic data of the CDC damper and the expansion and contraction velocity signal, a CDC damper model including the damping force, suspension expansion and contraction velocity, and solenoid valve drive current is established using a three-segment modeling approach.

[0008] Step 2: Shift the CDC damper model to the left by I0, i.e. The model of the CDC damper after translation is obtained:

[0009]

[0010] in,

[0011]

[0012] Where, F CDC It represents the damping force generated by the CDC damper, I represents the solenoid valve driving current, and represents the solenoid valve driving current polynomial, represents the suspension extension and contraction speed, θ i Indicates the suspension extension and contraction speed range, i represents the partition where the suspension extension and contraction speed is located, All are constant values;

[0013] Step 3: Combined with the dynamic model of the semi-active suspension system, the switching nonlinear state space model of the semi-active suspension system is obtained:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] The state quantity of the semi-active suspension system is taken as Where M b is the sprung mass, M t is the unsprung mass, x b is the sprung mass vibration displacement, x t is the vibration displacement of the unsprung mass, x bt is the suspension extension displacement, x tr is the telescopic displacement of the unsprung mass, k s is the spring stiffness, k t is the vertical stiffness of the tire, c p is the equivalent passive damping, is the current value of the system response after translation, is the desired solenoid valve driving current, β is the response time constant of the damper, u is the control variable of the semi-active suspension system, w is the disturbance of the semi-active suspension system, x r is the road height, z is the performance output of the semi-active suspension system, and is the weight parameter;

[0020] Step 4: Select the nonlinear term in the switching nonlinear state space model of the semi-active suspension system as the antecedent variable, and convert the switching nonlinear state space model of the semi-active suspension system into the switching TS model of the semi-active suspension system:

[0021]

[0022]

[0023] Where j represents the jth TS sub-model in the current partition, u ij is the control quantity of the jth TS sub-model in the i partition, U i (x) is the partition switching signal, h j (Z) is the weight of the TS sub-model;

[0024] Step 5: Design the controller of the solenoid valve drive current. Since the control quantity of each TS sub-model is constrained to be I0≤u ij ≤I max +I0, defines the expression of the desired solenoid valve drive current:

[0025]

[0026] Among them, K ij is the TS sub-model gain,

[0027] Controller gain By solving the following questions:

[0028] maxη

[0029]

[0030] LMI(I):

[0031]

[0032] LMI (II):

[0033]

[0034] Step 6: For the CDC damper model in step 1, the expected control current expression given by the controller is:

[0035]

[0036] Compared with the prior art, the beneficial effects of the present invention are: the present invention takes into account the constraints of the actual damper driving current and provides a design of a damper driving current controller. Compared with the controller that uses the damping force as the control quantity, it avoids the current "shearing" caused by the need to use the damper inverse model, thereby ensuring the full realization of the expected performance. In addition, the control method provided by the present invention can significantly improve the comfort and controllability of the vehicle on uneven roads under the premise of a relatively smooth control quantity, which is conducive to implementation in embedded electronic control systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a segmented schematic diagram of the establishment of the CDC damper model in the method of the present invention;

[0038] Figure 2 is a schematic diagram of a dynamic model of a semi-active suspension system in the method of the present invention;

[0039] Figure 3 is an output curve diagram of the controller designed in the embodiment;

[0040] Figure 4 2 is a comparison diagram of the response of the vehicle body vibration acceleration in the embodiment. DETAILED DESCRIPTION

[0041] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] A CDC semi-active suspension control method considering solenoid valve driving capability includes the following steps:

[0043] Step 1: Reference Figure 1 As shown in the figure, based on the test characteristic data of the CDC damper and the expansion and contraction velocity signal, a CDC damper model including the damping force, suspension expansion and contraction velocity, and solenoid valve drive current is established using three-segment modeling as follows:

[0044]

[0045] Where, F CDC It represents the damping force generated by the CDC damper, I represents the solenoid valve driving current, and represents the solenoid valve driving current polynomial, represents the suspension extension and contraction speed, θ i Indicates the suspension extension and contraction speed range, i represents the partition where the suspension extension and contraction speed is located;

[0046] Step 2: Shift the CDC damper model to the left by I0 (I0>0), that is, The model of the CDC damper after translation is as follows:

[0047]

[0048] in,

[0049]

[0050] Where, All are constant values;

[0051] Step 3: Reference Figure 2 As shown in Figure 2, the dynamic model of the semi-active suspension system is as follows:

[0052]

[0053]

[0054]

[0055] Where M b is the sprung mass, M t is the unsprung mass, x b is the sprung mass vibration displacement, x t is the vibration displacement of the unsprung mass, x bt is the suspension extension displacement, x tr is the telescopic displacement of the unsprung mass, k s is the spring stiffness, k t is the vertical stiffness of the tire, c p is the equivalent passive damping, is the current value of the system response after translation, is the desired solenoid valve drive current, and β is the response time constant of the damper.

[0056] It is worth noting that when the control current given by the controller meets the actuator constraints, the current value responded by the underlying layer must also be within the constraint range. This information will be used in the design of subsequent controllers.

[0057] The state quantity of the semi-active suspension system is taken as The switching nonlinear state space model of the semi-active suspension system is obtained as follows:

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] Where u is the control variable of the semi-active suspension system, w is the disturbance of the semi-active suspension system, x r is the road height, z is the performance output of the semi-active suspension system, and is the weight parameter;

[0064] Step 4: Select the nonlinear term in the switching nonlinear state space model of the semi-active suspension system as the antecedent variable, that is, take the antecedent variable Since the driving current is bounded, the two antecedent variables are bounded,

[0065] Using the idea of "sector nonlinearity", and It can be expressed as:

[0066]

[0067] Where, and is the membership function of the antecedent variable at its extreme value, defined as:

[0068]

[0069] Therefore, when the semi-active suspension system is in partition i, the relationship between the antecedent variables and the fuzzy rules can be expressed as follows:

[0070]

[0071] z=C i1 x+δ i

[0072]

[0073] z=C i2 x+δ i

[0074]

[0075] z=C i3 x+δ i

[0076]

[0077] z=C i4 x+δ i

[0078] Then the switching nonlinear state space model of the semi-active suspension system is converted into the switching TS model of the semi-active suspension system:

[0079]

[0080]

[0081] Where j represents the jth TS sub-model in the current partition, u ij is the control quantity of the jth TS sub-model in the i partition, v i (x) is the partition switching signal, h j (Z) is the weight of the TS sub-model,

[0082] Step 5: Design the controller of the solenoid valve drive current. Since the control quantity of each TS sub-model is constrained to be I0≤u ij ≤I max +I0, defines the expression of the desired solenoid valve drive current as:

[0083]

[0084] Among them, K ij is the TS sub-model gain,

[0085]

[0086] Define the Lyapunov function of the semi-active suspension system If the closed-loop system is stable under road disturbance input and the L2 gain from the disturbance to the performance output is γ, the following conditions must be met:

[0087]

[0088] For the partition containing the origin, since Therefore, the response Therefore, the domain of the semi-active suspension system in the current partition is described by the following ellipse: _2 :={||E _2 x+f _2||≤1}, i=2, where f i =-(2I0+I max ) / I max ,

[0089] For the partition that does not contain the origin, the domain of the semi-active suspension system in the front partition is described by the following ellipse: _i :={||E i x+f i ||≤1}, i=1,3, where c=[0 0 1 -1 0].

[0090] Therefore, it can be deduced that the LMI that makes the semi-active suspension system asymptotically stable is:

[0091]

[0092] At the same time, the LMI that satisfies the control quantity constraint is deduced as:

[0093]

[0094] In summary, for the semi-active suspension system generated by step 2, the influence of road disturbance on vehicle body vibration acceleration, suspension expansion displacement and tire expansion displacement can be minimized, and the desired control quantity always satisfies the constraint [0 I max +I0] is equivalent to solving the following LMI inequality:

[0095] maxη

[0096]

[0097] LMI(I):

[0098]

[0099] LMI (II):

[0100]

[0101] The controller gain is

[0102] Step 6: For the CDC damper model in step 1, the expected control current expression given by the controller is:

[0103]

[0104] Example

[0105] In this embodiment, a test vehicle equipped with a CDC damper is used to verify the performance of the present invention. The test characteristic data of the CDC damper is referenced to Figure 1 As shown, the CDC damper controller runs the passive suspension control strategy (soft suspension, hard suspension), the shear control strategy and the strategy of the present invention respectively, and drives over the speed bump road at the same speed. The control output of the controller designed by the present invention is referenced Figure 3 As shown, the output control current is always within the executable range of the solenoid valve drive current, the control amount is smooth, and the response comparison of the vehicle body vibration acceleration is referenced. Figure 4 As shown, the performance is significantly better than that under the passive suspension control strategy and the shear control strategy.

[0106] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other configurations without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations coming within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0107] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A CDC semi-active suspension control method considering the solenoid valve driving capability, characterized by: The following steps are involved: Step 1: Based on the test characteristic data of the CDC damper and the expansion and contraction velocity signal, a CDC damper model including the damping force, suspension expansion and contraction velocity, and solenoid valve drive current is established using a three-segment modeling approach. Step 2: Shift the CDC damper model to the left by I0, i.e. The model of the CDC damper after translation is obtained: in, Where, F CDC It represents the damping force generated by the CDC damper, I represents the solenoid valve driving current, and represents the solenoid valve driving current polynomial, represents the suspension extension and contraction speed, θ i Indicates the suspension extension and contraction speed range, i represents the partition where the suspension extension and contraction speed is located, All are constant values; Step 3: Combined with the dynamic model of the semi-active suspension system, the switching nonlinear state space model of the semi-active suspension system is obtained: F＝[0 -1 0 0 0] T The state quantity of the semi-active suspension system is taken as Where M b is the sprung mass, M t is the unsprung mass, x b is the sprung mass vibration displacement, x t is the vibration displacement of the unsprung mass, x bt is the suspension extension displacement, x tr is the telescopic displacement of the unsprung mass, k s is the spring stiffness, k t is the vertical stiffness of the tire, c p is the equivalent passive damping, is the current value of the system response after translation, is the desired solenoid valve driving current, β is the response time constant of the damper, u is the control variable of the semi-active suspension system, w is the disturbance of the semi-active suspension system, x r is the road height, z is the performance output of the semi-active suspension system, and is the weight parameter; Step 4: Select the nonlinear term in the switching nonlinear state space model of the semi-active suspension system as the antecedent variable, and convert the switching nonlinear state space model of the semi-active suspension system into the switching TS model of the semi-active suspension system: Where j represents the jth TS sub-model in the current partition, u ij is the control quantity of the jth TS sub-model in the i partition, υ i (x) is the partition switching signal, h j (Z) is the weight of the TS sub-model; Step 5: Design the controller of the solenoid valve drive current. Since the control quantity of each TS sub-model is constrained to be I0≤u ij ≤I max +I0, defines the expression of the desired solenoid valve drive current: Among them, K ij is the TS sub-model gain, Controller gain By solving the following questions: LMI(I): LMI (II): Step 6: For the CDC damper model in step 1, the expected control current expression given by the controller is:

2. The CDC semi-active suspension control method considering the solenoid valve driving capability according to claim 1, characterized in that: The dynamic model of the semi-active suspension system in step 3 is as follows:

3. The CDC semi-active suspension control method considering the solenoid valve driving capability according to claim 1, characterized in that: In step 4, the antecedent variable is taken and Expressed as: Where, and is the membership function of the antecedent variable at its extreme value, defined as: Therefore, when the semi-active suspension system is in partition i, the relationship between the antecedent variables and the fuzzy rules is expressed as follows: z=C i1 x+δ i z=C i2 x+δ i z=C i3 x+δ i z=C i4 x+δ i 。 4. The CDC semi-active suspension control method considering the solenoid valve driving capability according to claim 3, characterized in that: The weight of the TS sub-model

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