ECU structure strengthening method of electric power steering system

Abstract

The invention discloses an ECU (Electronic Control Unit) structure strengthening method of an electric power steering system. The method comprises the following steps: S1, analyzing a vibration transmission path of whole vehicle impact transmitted to an inductor of an ECU; s2, data of real-time impact force on the auxiliary frame cross beam in the vehicle road test are collected; s3, building a simulation model according to the vibration transmission path; s4, calculating the stress value of the inductance welding point of the ECU through the simulation model according to the data of the real-time impact force and the installation position of the sensor for extracting the impact force by utilizing the simulation model; and S5, according to the stress value, calculating the glue coating amount of glue for fixing the inductor of the ECU in the ECU shell. According to the method, the gluing amount of the glue, fixed in the ECU shell, of the inductor of the ECU is determined through simulation analysis, external vibration transmission is blocked, and the reliability of the power-assisted steering system under the special abuse working condition is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power steering, and particularly relates to a method for strengthening the ECU structure of an electric power steering system. Background Art

[0002] In recent years, automotive autonomous driving technology has been increasingly emphasized by more and more automobile manufacturers. The reliability, safety, etc. of intelligent driving of the steering system face new challenges. How to achieve autonomous driving in a complex road condition environment and ensure the reliability of the steering system has become an important development direction for future electric power steering systems. Redundant design needs to be carried out for the electronic control system, and dual redundant design is required for the motor ECU and sensors to ensure the reliability of autonomous driving.

[0003] With the increasing demand for driving in special abusive working conditions for off-road vehicles, the requirements for the driving road condition environment are improved.

[0004] Most current automobiles are family cars driving on public roads and in urban working conditions, and there are no very strict requirements for the vibration and impact of the steering gear. Only 10% of the vehicle's life cycle is on mountain roads, and 90% is in urban working conditions. Automobile manufacturers pay more attention to driving comfort. However, with the increasing demand for driving in special abusive working conditions by some people, such as 80% mountain roads and 20% river beach roads, when driving in these special abusive working conditions, the vehicle chassis may be subjected to extremely large load impacts from road stones or curbs. Therefore, how to improve the structural strength of the ECU of the electric power steering system and greatly reduce the risk of strength failure of the ECU under special abusive working conditions is the current technical problem. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method for strengthening the ECU structure of an electric power steering system, including:

[0006] Step S1, analyzing the vibration transmission path from the vehicle's overall impact to the inductor of the ECU;

[0007] Step S2, collecting the data of the real-time impact force on the subframe crossbeam during vehicle road tests;

[0008] Step S3, building a simulation model according to the vibration transmission path;

[0009] Step S4, using the simulation model, according to the data of the real-time impact force and the installation position of the sensor for extracting the impact force, calculating the stress value of the inductor welding point of the ECU through the simulation model;

[0010] Step S5, calculating the glue application amount for fixing the inductor of the ECU in the ECU housing according to the stress value.

[0011] Preferably, in the step S1, the vibration transfer path from the vehicle's overall impact to the inductor of the ECU is analyzed by building a test bench, knocking the ECU test sample, and measuring the acceleration at the inductor.

[0012] Preferably, in the step S1, the vibration transfer path from the vehicle's overall impact to the inductor of the ECU is analyzed by analyzing the road spectrum and the acceleration data of sensors at different positions collected during the overall impact vibration process to obtain the transfer function of the actual working condition.

[0013] Preferably, the vibration transfer path includes: from the tire - suspension - tie rod - rack - turbine - motor - the inductor welding point of the ECU, and from the tire - suspension - subframe - steering gear mounting point - the inductor welding point of the ECU.

[0014] Preferably, in the step S4, the method for the simulation model to calculate the stress value of the inductor welding point of the ECU is as follows:

[0015] Step S41, constructing the dynamic equations of the subframe and the electric power steering system;

[0016] Step S42, obtaining the acceleration frequency response function of the inductor welding point of the ECU by transforming according to the dynamic equations;

[0017] Step S43, calculating the stress value of the inductor welding point according to the acceleration frequency response function.

[0018] Preferably, in the step S5, the method for calculating the glue application amount for fixing the inductor of the ECU in the ECU housing according to the stress value is: m*σ = F*H*ρ, where m is the glue amount, σ is the stress value, ρ is the glue density, F is the known force acting on the glue, and H is the thickness of the glue.

[0019] Preferably, in the step S42, the displacement frequency response function of the inductor welding point of the ECU is also obtained by transforming according to the dynamic equations.

[0020] Preferably, in the step S43, the vibration amplitude of the inductor welding point is calculated according to the displacement frequency response function.

[0021] Compared with the prior art, the present invention determines the glue application amount for fixing the inductor of the ECU in the ECU housing through simulation analysis, realizes the blocking of external vibration transfer, and improves the reliability of the power steering system under special abusive working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following further describes the present invention in detail in conjunction with the drawings and specific embodiments:

[0023] Figure 1Schematic structural diagram of the electric power steering system of Embodiment 1;

[0024] Figure 2 Schematic diagram of the electric power steering system of Embodiment 1 assembled onto the crossbeam of the subframe;

[0025] Figure 3 Schematic structural diagram of the ECU of Embodiment 1;

[0026] Figure 4 Schematic diagram of the data collected from the knocking ECU test sample of Embodiment 1;

[0027] Figure 5 Schematic diagram of the inductor fixed inside the ECU housing in Embodiment 1. Detailed implementation manners

[0028] The following illustrates the implementation manners of the present invention through specific embodiments. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific implementation manners. The details in this specification can also be applied based on different viewpoints, and various modifications or changes can be made without departing from the overall design concept of the invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited only to the specific embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary specific embodiments to those skilled in the art.

[0029] Embodiment 1

[0030] As Figure 1 shown, the electric power steering system includes an ECU (electronic control unit) 1, a motor 2, a reduction mechanism 3, a steering gear 4, a left mounting point 5, and a right mounting point 6. As Figure 2 shown, the steering gear 4 is assembled onto the crossbeam 8 of the subframe through bolts 7.

[0031] An ECU structure strengthening method for an electric power steering system provided in this embodiment includes:

[0032] Step S1, analyzing the vibration transmission path of the vehicle's overall impact transmitted to the inductor of the ECU;

[0033] Step S2, collecting the data of the real-time impact force on the crossbeam of the subframe during the vehicle road test;

[0034] Step S3, building a simulation model according to the vibration transmission path;

[0035] Step S4: Using the simulation model, based on the data of the real-time impact force and the installation position of the sensor for extracting the impact force, calculate the stress value of the inductance welding point of the ECU through the simulation model;

[0036] Step S5: Calculate the glue application amount for fixing the inductance of the ECU in the ECU housing according to the stress value.

[0037] One way to obtain the vibration transmission path is:

[0038] In the said Step S1, by building a test bench, knocking on the ECU test sample, and measuring the acceleration at the inductance, analyze and obtain the vibration transmission path from the vehicle's overall impact transmitted to the inductance of the ECU. Specifically as follows:

[0039] Build a test bench, knock on the ECU test sample, and measure the acceleration transmission path at the inductance. Fix the steering gear 4 to the crossbeam 8 through 2 mounting bolts 7, fix the crossbeam 8 to the test bench, and simulate the use scenario of special abuse working conditions. As Figure 3 shown, stick acceleration sensors on the outer shell of the crossbeam 8 and the motor 2, the ECU housing 9 and the pin1 11 of the inductance welding part. Give an impact force input to the middle part of the crossbeam 8, collect the acceleration data of the outer shell of the crossbeam 8 and the motor 2, the ECU housing 9 and the pin1 11 of the inductance welding part. By knocking on 3 samples, ensure that the impact force on the crossbeam is equivalent each time. Analyze the vibration transmission path of the vehicle's overall impact vibration according to the acceleration data collected from various parts of the 3 samples for use in building a simulation model by CAE.

[0040] As Figure 4 shown, it can be obtained from the collected data that the acceleration gradually amplifies from the crossbeam to the motor, to the ECU housing, and then to the inductance part. Finally, the acceleration amplification multiple from the crossbeam to the inductance is 5 - 6 times. It is necessary to contain the amplified vibration transmission from the transmission path.

[0041] Another way to obtain the vibration transmission path is: In the said Step S1, by analyzing the road spectrum collected during the vehicle's overall impact vibration process and the acceleration data of sensors at different positions, analyze and obtain the vibration transmission path from the vehicle's overall impact transmitted to the inductance of the ECU by the method of obtaining the transfer function of the actual working condition. The road spectrum data can be collected during the vehicle road test.

[0042] The vibration transmission path obtained through the above method includes: from the tire - suspension - tie rod - rack - turbine - motor - inductance welding point of the ECU, and from the tire - suspension - subframe - steering gear mounting point - inductance welding point of the ECU.

[0043] In the said Step S4, the method for the simulation model to calculate the stress value of the inductance welding point of the ECU is:

[0044] Step A1, construct the dynamic equations of the subframe and the electric power steering system;

[0045] Step A2, obtain the acceleration frequency response function of the inductance welding point of the ECU according to the transformation of the dynamic equations;

[0046] Step A3, calculate the stress value of the inductance welding point according to the acceleration frequency response function.

[0047] Alternatively, in the step S4, the method for the simulation model to calculate the stress value of the inductance welding point of the ECU is as follows:

[0048] Step B1, construct the dynamic equations of the subframe and the electric power steering system;

[0049] Step B2, obtain the displacement frequency response function of the inductance welding point of the ECU according to the transformation of the dynamic equations;

[0050] Step B3, calculate the stress value of the inductance welding point according to the displacement frequency response function.

[0051] The specific process is as follows:

[0052] According to the vehicle impact vibration transmission path, build a simulation model that can truly simulate the actual vehicle conditions, then extract the overall mass M, stiffness K, and damping C matrices, and construct the dynamic equations of the subframe and the electric power steering system. The dynamic equations of the multi-degree-of-freedom damped dynamic system of the electric power steering system with a subframe are expressed as follows:

[0053]

[0054] In the formula, M represents the mass matrix of the system, C represents the damping matrix of the system, and K represents the stiffness matrix of the system; x(t) represents the displacement matrix of the system, and f(t) represents the external force matrix of the system. After performing Fourier transform on the formula, we get:

[0055] (-ω 2 M + ωjC + K){X(ω)} = {F(ω)} (2)

[0056] In formula (2), X(ω) is the Fourier transform of the displacement x(t) matrix, and F(ω) is the Fourier transform of the external force matrix f(t); take

[0057] Z(ω) = (-ω 2 M + ωjC + K) (3)

[0058] Here, Z(ω) is defined as the dynamic stiffness matrix of the structure, and formula (2) can be rewritten as:

[0059] {Z(ω)}{X(ω)} = {F(ω)} (4)

[0060] Define the inverse matrix H(ω) of the dynamic stiffness matrix Z(ω) as the frequency response function matrix, then H(ω) can be expressed as

[0061] H(ω) = [-ω 2 M + ωjC + K] -1 (5)

[0062] After transforming Equation (4), the displacement response expression of the system is obtained as follows:

[0063] X(ω) = H(ω)F(ω) (6)

[0064] Applying the natural modes of the system, the system displacement function in modal coordinates can be expressed as:

[0065] X(ω) = [Φ]{q(ω)} (7)

[0066] Substitute Equation (6) into Equation (7) and pre-multiply both sides of the equation by [Φ] T , we can get:

[0067] [Φ] T (-ω 2 M + ωjC + K)[Φ]{q(ω)} = [Φ] T {F(ω)} (8)

[0068] After expanding Equation (8), according to modal orthogonality, we have:

[0069] [M R = [Φ] T MΦ (9)

[0070] [C R = [Φ] T CΦ (10)

[0071] [K R = [Φ] T KΦ (11)

[0072] In Equation (9), [M R and [K R are diagonal matrices, but [C R is not necessarily a diagonal matrix. Assume that the damping of the system is proportional damping, and the damping matrix C is a linear combination of the mass matrix M and the stiffness matrix K, i.e., C = αM + βK, then it is a diagonal matrix. Equation (8) can be rewritten as:

[0073] (-ω 2 [M R + ωj[C R + [K R)[Φ]{q(ω)}=[Φ] T {F(ω)} (12)

[0074] Taking the r-th order modal coordinate, from Equation (12), we get:

[0075]

[0076] In Equation (11), If only excited at point p and the excitations at other points are zero, then:

[0077] {F(ω)}=[0…F p (ω)…0] T (13)

[0078] Therefore, F r (ω) can be written as:

[0079]

[0080] Substituting F r (ω) into q r (ω), we can obtain:

[0081]

[0082] When excited at the above-mentioned point p, the response at any point l is:

[0083]

[0084] Thus, the displacement frequency response function between the excitation point and the measurement point (i.e., the displacement frequency response function of the inductance welding point of the ECU) is obtained as:

[0085]

[0086] The acceleration frequency response function (i.e., the acceleration frequency response function of the inductance welding point of the ECU) is:

[0087]

[0088] The frequency response function is essentially a relationship curve between frequency and response. This response can be amplitude (the vibration amplitude is displacement), acceleration, velocity, etc. When one of the amplitude, acceleration, and velocity is obtained, the other two can be deduced inversely.

[0089] As Figure 5 shown, in the step S5, the method for calculating the glue application amount of the glue 16 for fixing the inductance 10 of the ECU in the ECU housing according to the stress value is: m*σ=F*H*ρ, where m is the glue amount, σ is the stress value, ρ is the glue density, F is the known force acting on the glue, and H is the thickness of the glue.

[0090] In a practical example, a simulation model is built through CAE to calculate the stress and amplitude at the inductor welding position. For the original ECU, the maximum stress at the solder joints of pin1 and pin2 is 8.80e-4 Mpa. After optimization, the maximum stress at the solder joints of pin3 and pin4 of the ECU is 5.56e-4 Mpa, and the stress is reduced by 36%. The amplification factor of the vibration transfer from the original ECU housing to Pin1 is 5.3. After optimization, the amplification factor of the vibration transfer from the 9ECU housing to pin3 is 3, and the amplification factor is reduced.

[0091] The present invention has been described in detail through specific implementation manners and embodiments above, but these do not constitute a limitation to the present invention. Without departing from the principle of the present invention, those skilled in the art can also make many deformations and improvements, which should also be regarded as the protection scope of the present invention.

Claims

1. An ECU structure strengthening method for an electric power steering system, characterized in that Including: Step S1: Analyze the vibration transmission path from the vehicle's overall impact to the inductor of the ECU. Step S2: Collect the data of the real-time impact force on the subframe crossbeam during vehicle road tests. Step S3: Build a simulation model according to the vibration transmission path. Step S4: Use the simulation model to calculate the stress value of the inductor welding point of the ECU based on the data of the real-time impact force and the installation position of the sensor for extracting the impact force. Step S5: Calculate the glue application amount for fixing the inductor of the ECU in the ECU housing according to the stress value.

2. The ECU structure strengthening method of the electric power steering system according to claim 1, characterized in that In the step S1, the vibration transmission path from the vehicle's overall impact to the inductor of the ECU is analyzed by building a test bench, knocking the ECU test sample, and measuring the acceleration at the inductor.

3. The ECU structure strengthening method of the electric power steering system according to claim 1, characterized in that, In the step S1, the vibration transmission path from the vehicle's overall impact to the inductor of the ECU is analyzed by analyzing the road spectrum collected during the vehicle's overall impact vibration process and the acceleration data of sensors at different positions to obtain the transfer function of the actual working condition.

4. The ECU structure strengthening method of the electric power steering system according to claim 2 or 3, characterized in that The vibration transmission path includes: from the tire - suspension - tie rod - rack - turbine - motor - inductor welding point of the ECU, and from the tire - suspension - subframe - steering gear installation point - inductor welding point of the ECU.

5. The ECU structure strengthening method of the electric power steering system according to claim 1, characterized in that In the step S4, the method for the simulation model to calculate the stress value of the inductor welding point of the ECU is as follows: Step A1: Construct the dynamic equations of the subframe and the electric power steering system. Step A2: Obtain the acceleration frequency response function of the inductor welding point of the ECU by transforming according to the dynamic equations. Step A3: Calculate the stress value of the inductor welding point according to the acceleration frequency response function.

6. The method for strengthening the ECU structure of the electric power steering system according to claim 1, characterized in that In the step S4, the method for the simulation model to calculate the stress value of the inductor welding point of the ECU is as follows: Step B1: Construct the dynamic equations of the subframe and the electric power steering system. Step B2: Obtain the displacement frequency response function of the inductor welding point of the ECU by transforming according to the dynamic equations. Step B3: Calculate the stress value of the inductor welding point according to the displacement frequency response function.

7. The ECU structure strengthening method of the electric power steering system according to claim 5 or 6, characterized in that, In the step S5, the method for calculating the glue application amount for fixing the inductor of the ECU in the ECU housing according to the stress value is: m*σ = F*H*ρ, where m is the amount of glue, σ is the stress value, ρ is the density of the glue, F is the known force acting on the glue, and H is the thickness of the glue.

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