Automobile brake oscillation analysis method based on system response transient state

Abstract

The invention provides an automobile brake oscillation analysis method based on a system response transient state, and relates to the field of automobile safe driving, and the method is technically characterized in that S1, impulse response models of different states of automobile brake are constructed, and kn and an in the formula are to-be-identified parameters; according to the built impulse response model, an automobile brake switching model is built, and the input and output relation is analyzed; segmenting the input and output relation according to the gear switching moments T1, T2,..., Tn, and connecting the gear responses through a step function; and S3, the output transient state and the output steady state before braking are separated, and the transient oscillation process after automobile braking is analyzed. According to the automobile braking transient analysis method based on the system response transient state, the relation between the historical process and the automobile braking transient state is studied on the basis of the system response characteristics, the automobile braking transient relation is established in combination with the automobile braking initial state, and a new scheme is provided for an optimal control strategy on the premise that automobile safety braking is ensured; and the safety and the riding comfort are both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive safe driving, and particularly relates to a method for analyzing automotive braking oscillation based on the transient state of system response. Background Art

[0002] In the field of automotive autonomous driving, how to avoid obstacles safely and comfortably is an important research content. Automotive braking is a process where the input of the vehicle switches from one state to another. Without exception, for any system input switch in engineering, due to the memory characteristic of the system response, its output has a transient oscillation process.

[0003] On the one hand, automotive braking oscillation will reduce the riding comfort, degrade the vehicle performance, and exacerbate vehicle wear. When the oscillation amplitude exceeds a certain range, it even affects safe driving.

[0004] Combined with control theory, automotive braking oscillation is caused by the memory characteristic of the historical state due to the system response, and an oscillation process is generated under the combined action of the historical process and the current input. Only by combining the system response characteristics and the dynamic process can the oscillation process of automotive braking be analyzed. On this basis, a braking strategy can be designed to optimize the riding comfort of automotive braking on the premise of safety. Summary of the Invention

[0005] The purpose of the present invention is to solve the safety problem caused by the oscillation during automotive braking switching in the prior art. Starting from the braking response characteristics of the vehicle, the present application establishes a transient equation for automotive braking, studies the relationship between the switching output of the vehicle and the historical process and braking input, and establishes a method for analyzing automotive braking oscillation.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for analyzing automotive braking oscillation based on the transient state of system response, comprising the following steps:

[0008] S1: Construct an impulse response model for different states of automotive braking:

[0009] The impulse response function corresponding to different gears of the vehicle is:

[0010]

[0011] In the above formula, k n and a n are parameters to be identified;

[0012] S2: According to the impulse response model constructed in S1, establish an automotive braking switching model and analyze the input-output relationship;

[0013] According to the gear switching times T1, T2,..., T nSegment the input-output relationship and connect the responses of each gear through a step function;

[0014] S3: Separate the transient and steady states of the output before braking, and analyze the transient oscillation process after the vehicle brakes.

[0015] Preferably, after constructing the impulse response functions corresponding to different gears of the vehicle in S1, use the Legendre transform to convert the convolution model in the formula into an algebraic model, and identify the position parameters k n and a n .

[0016] Preferably, in S2, first establish the input-output relationship before the system brakes. If the system is in the k-th gear before braking, the input-output relationship can be obtained:

[0017] s(t) = h k (t) * f(t);

[0018] Then record the vehicle braking switching moment as T s , and the gear after switching is the n-th gear. The input-output relationship after switching can be obtained:

[0019] s(t) = h n (t) * f(t) (t > Ts).

[0020] According to the method for analyzing vehicle braking oscillation based on the transient state of system response described in claim 3, it is characterized in that: a step function is introduced in S2:

[0021]

[0022] After introducing the step function, assume that the gears from the initial moment are sequentially recorded as 1, 2, 3,..., n, and the switching moments at each gear are T1, T2,..., T n , and establish the following input-output equation

[0023] s(t) =

[0024] f(t) * [h1(t)(u(t) - u(t - T1))] + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))] +... + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))].

[0025] Preferably, the steps in S3 are as follows:

[0026] S3-1: Utilize the convolution property to separate the steady state and transient state of the system output:

[0027] S3-2: Establish the braking moment T of the vehicle according to the separation result n Initial state displacement s(T n ):

[0028] S3-3: Establish the relationship between the displacement after braking of the vehicle and the initial state displacement s(T n Initial state displacement s(T n ) and the transient process:

[0029] S3-4: According to the memory property of the system, intercept a certain length of historical dynamics to analyze the transient process of vehicle braking.

[0030] Preferably, in the above S3-1, according to the convolution operation, the length of the output signal is the sum of the length of the input signal and the length of the impulse response.

[0031] Assume that the gear shift occurs at time T n of the system, and separate the output before braking into the steady state and the transient state one by one:

[0032] f(t)*[h1(t)(u(t)-u(t-T1))] = {f(t)*[h1(t)(u(t)-u(t-T1))]}(u(t)-u(t-T n )) + {f(t)*[h1(t)(u(t)-u(t-T1))]}(u(t-T n ))

[0033] f(t)*[h2(t)(u(t-T1)-u(t-T2))] = {f(t)*[h2(t)(u(t-T1)-u(t-T2))]}(u(t-T1)-u(t-T n )) + {f(t)*[h2(t)(u(t-T1)-u(t-T2))}(u(t-T n ))

[0034] ……

[0035] f(t)*[h n (t)(u(t-T n-1 )-u(t-T n ))] =

[0036] {f(t)*[h n (t)(u(t-T n-1 )-u(t-T n ))]}(u(t-T n-1 )-u(t-T n )) + {f(t)*[hn (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n ))

[0037] Preferably, in the said S2

[0038] s(T n ) =

[0039] {f(t) * [h1(t)(u(t) - u(t - T1))] + f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))] + … + f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))]}(u(t) - u(t - T n ))

[0040] Preferably, the displacement of the vehicle after braking in 3 - 2:

[0041] s(t) =

[0042] s(T n ) + {f(t) * [h1(t)(u(t) - u(t - T1))]}(u(t - T n )) + {f(t) * [h2(t)(u(t - T1) - u(t - T2))]}(u(t - T n )) + … + {f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n ))

[0043] Preferably, in S3 - 4, combining the attenuation characteristics of the vehicle braking impulse response, a certain length of T f of the historical process is intercepted to analyze the transient process. Assuming T n - T i+1 < T f < T N - T i , the displacement estimation equation of the vehicle after braking can be obtained:

[0044] s(t) =

[0045] s(T n ) + {f(t) * [h i (t)(u(t - Ti ) - u(t - T i+1 ))]}(u(t - T n )) + {f(t) * [h i+1 (t)(u(t - T i+1 ) - u(t - T i+2 ))]}(u(t - T n )) + … + {f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n ))

[0046] The right - hand side part in the above formula is the transient estimation of vehicle braking. Based on this transient estimation, the safe braking distance of the vehicle can be optimized; within the range of the safe braking distance, the optimal braking strategy is designed to improve the riding comfort of the vehicle.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] 1. The present invention proposes a method for analyzing the transient state of vehicle braking based on the transient state of system response. Based on the system response characteristics, this method studies the relationship between the historical process and the transient state of vehicle braking, and combines the initial state of vehicle braking to establish the transient state relationship of vehicle braking, providing a new solution for the optimal control strategy under the premise of ensuring safe vehicle braking, taking into account both safety and riding comfort.

[0049] 2. The present invention uses the input - output response characteristics to establish the impulse response model of each braking gear of the vehicle, and uses the equivalent simplified model of the complex model for modeling, which not only simplifies the model but also reduces the difficulty of model parameter identification, and only two parameters need to be identified.

[0050] 3. According to the system attenuation characteristics, the present invention intercepts a certain length of dynamic information for transient analysis, considering the influence of different vehicle response characteristics and historical dynamics on the braking transient state, and also intercepts a certain length for analysis in combination with the attenuation characteristics, reducing the analysis complexity and comprehensively considering the algorithm complexity and vehicle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the vehicle braking process in the prior art;

[0052] Figure 2 It is a flowchart of a method for analyzing the transient state of vehicle braking based on the transient state of system response in an embodiment of the present invention;

[0053] Figure 3Flow chart for modeling impulse response models of different states in S1 of an automotive braking transient analysis method based on system response transients in one embodiment of the present invention;

[0054] Figure 4 Flow chart for constructing an automotive braking model in S2 of an automotive braking transient analysis method based on system response transients in one embodiment of the present invention;

[0055] Figure 5 Flow chart for automotive braking transient analysis in S3 of an automotive braking transient analysis method based on system response transients in one embodiment of the present invention;

[0056] Figure 6 Automotive braking transient simulation diagram in Example 1 of the present invention;

[0057] Figure 7 Automotive braking transient simulation diagram in Example 2 of the present invention. Detailed implementation manners

[0058] The present invention will be further described in detail below with reference to specific embodiments.

[0059] The vehicle achieves braking through gear shifting, and its braking process is as Figure 1 shown. Different gears of the vehicle have different corresponding characteristics, and it is necessary to establish impulse response models for different gears.

[0060] Based on this, please refer to Figure 2 , this application provides an automotive braking oscillation analysis method based on system response transients, including the following steps:

[0061] S1: Construct impulse response models for different states of automotive braking:

[0062] In one embodiment, as Figure 3 shown, S1 specifically includes the following steps:

[0063] S1-1: Fix the automotive braking system in the first gear and establish a model for the vehicle power input and body output response:

[0064] s(t) = h n (t) * f(t) (1)

[0065] In the above formula, s(t) represents the body displacement, f(t) represents the power, and h n (t) represents the impulse response of the vehicle in the nth gear.

[0066] S1-2: Establish an equivalent simplified expression for h n (t)

[0067] The impulse response of any system can always be expressed in the form: However, due to the complex structure of the vehicle, it is almost impossible to establish a model based on complex mechanisms. By using input-output data for modeling, the larger the M, the higher the modeling accuracy. However, as M increases, the identification of unknown parameters increases, making parameter identification difficult. Using the equivalent model relationship, the following equivalent simplified model is established:

[0068]

[0069] In the above formula, k n and a n are parameters to be identified. Only these two unknown parameters need to be identified.

[0070] S1-3: Use the Legendre transform to convert the convolution model in formula (1) into an algebraic model.

[0071] S1-4: Construct a cost function, and combine the gradient algorithm and the particle swarm optimization search algorithm to identify the position parameters k n and a n .

[0072] S1-5: Establish the impulse response functions of all gears of the vehicle according to the above steps 1-1 to 1-4.

[0073] S2: Establish a vehicle braking switching model and analyze the input-output relationship:

[0074] Please refer to Figure 4 , and the specific steps of S2 are as follows:

[0075] S2-1: According to the impulse response model constructed in S1, establish the input-output relationship before the system brakes. If the system is in the k-th gear before braking, the input-output relationship can be obtained:

[0076] s(t) = h k (t) * f(t) (3)

[0077] S2-2: Denote the vehicle braking switching moment as T s , and the gear after switching is the n-th gear. The input-output relationship after switching can be obtained:

[0078] s(t) = h n (t) * f(t) (t > T S ) (4)

[0079] S2-3: Introduce the step function:

[0080]

[0081] S2-4: Connect the input-output of each gear according to time slices:

[0082] Assume that the gears from the initial moment are sequentially denoted as 1, 2, 3, …, n, and the switching moments of each gear are T1, T2, …, T n , establish the following input-output equation s(t) =

[0083] f(t) * [h1(t)(u(t) - u(y) - T1))] + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))] + … + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))] (6)

[0084] S3: Separate the output transient state and steady state before braking, and analyze the transient oscillation process after the vehicle brakes:

[0085] Please refer to Figure 5 , and the specific steps of S3 are as follows:

[0086] S3-1: Use the convolution property to separate the steady state and transient state of the system output:

[0087] According to the convolution operation, the length of the output signal is the sum of the length of the input signal and the length of the impulse response. As long as the length of the system impulse response is not 0 (the length of the impulse response of all systems in nature is not 0), the length of the output signal is always greater than the length of the input signal. When the input stops, the output does not stop and there is still a transient state.

[0088] Assume that the system has a gear shift at time T n , and separate the output before braking into steady state and transient state one by one:

[0089] f(t) * [h1(t)(u(t) - u(t - T1))] = {f(t) * [h1(t)(u(t) - u(t - T1))]}(u(t) - u(t - T n )) + {f(t) * [h1(t)(u(t) - u(t - T1))]}(u(t - T n ))

[0090] f(t) * [h2(t)(u(t - T1) - u(t - T2))] = {f(t) * [h2(t)(u(t - T1) - u(t - T2))]}(u(t - T1) - u(t - T n )) + {f(t) * [h2(t)(u(t - T1) - u(t - T2))]}(u(t - T n ))

[0091] ……

[0092] f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))] =

[0093] {f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))]}(u(t - T n-1 ) - u(t - T n )) + f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n )) (7)

[0094] S3 - 2: Establish the vehicle braking moment T according to the separation result n Initial displacement s(T n ):

[0095] s(T n ) =

[0096] {f(t)*[h1(t)(u(t) - u(t - T1))] + f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))] + … + f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))]}(u(t) - u(t - T n )) (8)

[0098] S3 - 3: Establish the relationship between the displacement after vehicle braking and the initial displacement s(T n Initial displacement s(T n ) and the transient process:

[0099] Combining S2 - 4, S3 - 1 and S3 - 2, the displacement after vehicle braking can be obtained:

[0100] s(t) =

[0101] s(T n ) + {f(t)*[h1(t)(u(t) - u(t - T1))]}(u(t - T n )) + {f(t)*[h2(t)(u(t - T1) - u(t - T2))]}(u(t - T n))+…+{f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n )) (9)

[0102] S3 - 4: According to the system memory characteristics, intercept a certain length of historical dynamics to analyze the transient process of vehicle braking;

[0103] It is shown in S3 - 3 that the transient process of vehicle braking is related to all historical dynamic processes. However, it is impossible to combine all historical dynamics to analyze the transient process in engineering. But any impulse response of a gear is a function that decays with time, and the influence of historical dynamic information on the vehicle braking transient decays with time. Therefore, the historical information beyond a certain time scale range has a weak influence on vehicle braking and can be ignored. Therefore, combining the decay characteristics of the vehicle braking impulse response, intercept a certain length of T f of the historical process to analyze the transient process. Suppose T n -T i+1 <T f <T n -T i , the displacement estimation equation after vehicle braking can be obtained: s(t) =

[0104] s(T n ) + {f(t)*[h i (t)(u(t - T i ) - u(t - T i+1 ))]}(u(t - T n )) + {f(t)*[h i+1 (t)(u(t - T i+1 ) - u(t - T i+2 ))}(u(t - T n )) + … + {f(t)*[h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n )) (10)

[0106] The right - hand part of formula (10) is the transient estimation of vehicle braking. Based on this transient estimation, the safe braking distance of the vehicle can be optimized; within the safe braking distance range, design the optimal braking strategy to improve the riding comfort of the vehicle.

[0107] The above content is elaborated below in combination with specific application examples:

[0108] Example 1: Assume that the output torque of the automotive engine is 200 N·m. It experiences a gear shift impulse response of 0.001t^(-0.9) within 0 - 10 seconds, a gear shift impulse response of 0.001t^(-0.5) within 10 - 20 seconds, and after 20 seconds, the vehicle brakes with a braking gear shift impulse response of 0.001t^(0.05). The vehicle displacement curve is as Figure 6 shown.

[0109] Example 2: Assume that the output torque of the automotive engine is 200 N·m. It experiences a gear shift impulse response of 0.001t (-0.5) , a gear shift impulse response of 0.001t (-0.9) within 10 - 20 seconds, and after 20 seconds, the vehicle brakes with a braking gear shift impulse response of 0.001t (0.05) . The vehicle displacement curve is as Figure 7 shown.

[0110] A method for analyzing the transient state of automotive braking based on the transient state of system response proposed in this application studies the relationship between the historical process and the transient state of automotive braking based on the system response characteristics, and combines the automotive braking state to establish the transient state relationship of automotive braking, providing a new solution for the optimal control strategy under the premise of ensuring the safe braking of the vehicle, taking into account both safety and ride comfort.

[0111] In this application, the impulse response models of each braking gear of the vehicle are established by using the input-output response characteristics, and the equivalent simplified model of the complex model is used for modeling, which not only simplifies the model but also reduces the difficulty of model parameter identification, and only two parameters need to be identified.

[0112] According to the system attenuation characteristics, a certain length of dynamic information is intercepted for transient analysis in the present invention. The influence of different automotive response characteristics and historical dynamics on the braking transient state is considered, and a certain length is intercepted for analysis in combination with the attenuation characteristics, reducing the analysis complexity and comprehensively considering the algorithm complexity and automotive performance.

Claims

1. An analysis method for automotive braking oscillation based on the transient state of system response, characterized in that: It includes the following steps: S1: Construct an impulse response model for different states of vehicle braking: The impulse response functions corresponding to different gears of the vehicle are: k in the above formula n and a n are parameters to be identified; S2: Based on the impulse response model constructed in S1, establish a vehicle braking switching model and analyze the input-output relationship; According to the gear shift times T1, T2, …, T n Segment the input-output relationship and connect the responses of each gear through a step function; S3: Separate the pre-braking output into transient and steady states and analyze the transient oscillation process after vehicle braking.

2. The automotive braking oscillation analysis method based on the system response transient according to claim 1, wherein: After constructing the impulse response functions corresponding to different gears of the vehicle in S1, use the Legendre transform to convert the convolution model in the formula into an algebraic model, and identify the position parameters k n and a n .

3. The method for analyzing vehicle braking oscillation based on the transient state of system response according to claim 1, wherein: In S2, first establish the input-output relationship before system braking. If the system is in the k-th gear before braking, the input-output relationship can be obtained: s(t) = h k (t) * f(t); Then record the vehicle braking switching moment as T s , and the gear after switching is the nth gear. The input-output relationship after switching can be obtained as follows: s(t) = h n (t) * f(t) (t > T_s).

4. The automotive braking oscillation analysis method based on the transient state of system response according to claim 3, wherein: In S2, introduce a step function: After introducing the step function, assuming that the gears at the initial moment are sequentially denoted as 1, 2, 3, …, n starting from the initial moment, and the switching moments at each gear are T1, T2, …, T n , the following input-output equation is established s(t) = f(t) * [h1(t)(u(t - u(t - T1)))] + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))] + … + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))].

5. A method for analyzing automotive braking oscillation based on the transient state of system response according to claim 1, characterized in that: The steps in S3 are as follows: S3-1: Utilize the convolution property to separate the steady state and transient state of the system output: S3-2: Establish the vehicle braking moment T according to the separation result n Initial state displacement s(T n ): S3-3: Establish the relationship between the displacement of the vehicle after braking and the braking moment T of the vehicle n Initial displacement s(T n ) and the transient process: S3-4: According to the system memory property, intercept a certain length of historical dynamics to analyze the vehicle braking transient process.

6. A method for analyzing vehicle braking oscillation based on the transient state of system response according to claim 5, characterized in that: In 3-1, according to the convolution operation, the length of the output signal is the sum of the lengths of the input signal and the impulse response. Assume that the system performs a gear shift at time T n When the gear shift occurs, separate the output before braking into steady-state and transient components one by one: f(t)*[h1(t)(u(t)-u(t-T1))] = f(t)*[h1(t)(u(t)-u(t-T1))]}(u(t)-u(t-T n ))+{f(t)*[h1(t)u(t)-u(t-T1))]}(u(t-T n )); f(t)*[h2(t)(u(t - T1)-u(t - T2))] = {f(t)*[h2(t)(u(t - T1)-u(t - T2))]}(u(t - T1)-u(t - T n )) + f(t)*[h2(t)(u(t - T1)-u(t - T2))]}(u(t - T n )); …… f(t)*[h n (t)(u(t - T n-1 )) - u(t - T n ))] = {f(t)*[h n (t)(u(t - T n-1 )) - u(t - T n ))]}(u(t - T n-1 )) - u(t - T n )) + f(t)*[h n (t)(u(t - T n-1 )) - u(t - T n ))]}T n-1 (u(t - T n ))。 7. A method for analyzing automotive braking oscillation based on system response transients according to claim 6, characterized in that: In S2 s(T n ) = {f(t) * [h1(t)(u(t) - u(t - T1))] + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))] + … + f(t) * [h n (t)(u(t - T n-1 )) - u(t - T n ))]}(u(t) - u(t - T n ))。 8. A method for analyzing vehicle braking oscillation based on the transient state of system response according to claim 7, characterized in that: The displacement after vehicle braking in 3-2: s(t) = s(T n ) + {f(t) * [h1(t)(u(t) - u(t - T1))]}(u(t - T n )) + {f(t) * [h2(t)(u(t - T1) - u(t - T2))]}(u(t - T n )) + … + {f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n ))。 9. A method for analyzing automotive braking oscillation based on the transient state of system response according to claim 1, characterized in that: In S3-4 Combined with the decay characteristics of the automotive braking impulse response, a certain length of T is intercepted f for the historical process analysis of the transient process; if T n -T i+1 <T f <T n -T i , the displacement estimation equation after automotive braking can be obtained: s(t) = s(T n ) + {f(t) * [h i (t)(u(t - T i ) - u(t - T i+1 ))]}(u(t - T n )) + {f(t) * [h i+1 (t)(u(t - T i+1 ) - u(t - T i+2 ))]}(u(t - T n )) +... + {f(t) * [h n (t)(u(t - T n-1 ) - u(t - T n ))]}T n-1 (u(t - T n )); The right part of the above formula is the transient estimation of vehicle braking. Based on this transient estimation, the safe braking distance of the vehicle can be optimized; within the safe braking distance range, design an optimal braking strategy to improve the riding comfort of the vehicle.

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