A solenoid-based brake force adjustment method

Abstract

The application discloses a brake force adjusting method based on an electromagnetic valve and belongs to the field of automobile braking, and comprises the following steps: S1, comprehensively considering electromagnetic characteristics, hydraulic characteristics and mechanical movement characteristics of the electromagnetic valve, establishing a dynamic model of multi-physical field coupling containing electromagnetic force, valve core movement and hydraulic force, so as to describe a dynamic relationship between a valve core position of the electromagnetic valve and brake force; S2, obtaining optimal structure parameters of the electromagnetic valve through a finite element simulation method; S3, based on the optimal structure parameters of the electromagnetic valve and the dynamic model of multi-physical field coupling, generating a PWM signal by adopting a fractional order sliding mode variable structure control algorithm; and S4, controlling an electromagnetic coil current through the PWM signal. By adopting the brake force adjusting method based on the electromagnetic valve, high-precision, fast-response and strong-robustness adjustment of brake force is realized.

Description

Technical Field

[0001] This invention relates to the field of automotive braking technology, and in particular to a method for adjusting braking force based on an electromagnetic valve. Background Technology

[0002] In fields such as automotive braking and industrial machinery transmission, solenoid valves serve as core actuators, and their braking force regulation accuracy and response speed directly affect system safety and energy efficiency. With the development of intelligent driving technology, higher requirements are being placed on the dynamic performance of solenoid valves under complex operating conditions (such as anti-interference capability, nonlinear compensation, and energy loss control).

[0003] Existing technologies mainly focus on the structural design of solenoid valves, drive control algorithms, and hydraulic system matching, without fully considering the dynamic interaction of electromagnetic, mechanical, and hydraulic fields, resulting in large deviations between the model and actual working conditions. Furthermore, traditional linear control algorithms (such as PID) are unable to cope with the strong nonlinear characteristics of solenoid valves (such as magnetic saturation and reluctance nonlinearity caused by air gap changes), and have weak anti-interference capabilities. Summary of the Invention

[0004] The purpose of this invention is to provide a braking force adjustment method based on a solenoid valve to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides a braking force adjustment method based on a solenoid valve, comprising the following steps:

[0006] S1. Taking into account the electromagnetic, hydraulic and mechanical motion characteristics of the solenoid valve, a dynamic model with multi-physics coupling including electromagnetic force, valve core motion and hydraulic force is established to describe the dynamic relationship between the valve core position and braking force of the solenoid valve.

[0007] S2. Obtain the optimal structural parameters of the solenoid valve through finite element simulation.

[0008] S3. Based on the optimal structural parameters of the solenoid valve and the dynamic model of multi-physics coupling, a fractional sliding mode variable structure control algorithm is adopted to generate PWM signals;

[0009] S4. Braking force is adjusted by controlling the current of the electromagnetic coil through a PWM signal.

[0010] Preferably, step S1 specifically includes the following steps:

[0011] S11. Based on Maxwell's stress theory, establish an electromagnetic force model:

[0012]

[0013] In the formula, F m Represents electromagnetic force; ψ represents magnetic flux linkage, and R m1 represents the working air gap reluctance, R m2 represents the secondary air gap reluctance, n represents the number of turns of the electromagnetic coil, e represents the secondary air gap length, R represents the spool radius, l s represents the secondary air gap width; μ0 represents the vacuum permeability; S0 represents the pole area; i represents the electromagnetic coil current; z ev represents the real position of the electromagnetic valve spool;

[0014] S12, considering the electromagnetic force F m , the spring force F k , the hydraulic force F s , and the viscous friction force, a mechanical balance equation of the spool is established:

[0015]

[0016] wherein,

[0017] F k =F0+K k ·z ev (3);

[0018]

[0019] In the formula, m represents the mass of the spool; Cu represents the viscous damping coefficient of the electromagnetic valve spool movement; and respectively represent the first-order derivative and the second-order derivative of the real position of the electromagnetic valve spool; F0 represents the spring pre-tightening force; K k represents the spring stiffness; P m represents the master cylinder pressure; P w represents the wheel cylinder pressure; c d represents the flow coefficient; c1 represents the pressure distribution compensation coefficient; A t represents the orifice area; A ev represents the valve outlet area; α represents the valve seat cone angle half angle; A tw represents the conical surface area; ζ represents the energy loss coefficient;

[0020] S13, considering the coil inductance and the counter electromotive force generated by the spool movement, a coil circuit equation is established:

[0021]

[0022] In the formula, u i represents the electromagnetic coil voltage; r represents the electromagnetic coil resistance; represents the first-order derivative of the electromagnetic coil current.

[0023] Preferably, step S2 specifically comprises the following steps:

[0024] S21, an electromagnetic valve model is established by using ANSYS Electronics, and influences of different guide sleeve thicknesses and outer magnetic pole thicknesses on static electromagnetic force are simulated, and formula (1) is obtained by simplifying under initial constraint conditions:

[0025]

[0026] In formula, F δ represents initial electromagnetic force, and F δ > 15 N; B δ represents air gap magnetic induction intensity; d a1 represents armature effective diameter; and δ1 represents a sum of working air gap and limit sheet length.

[0027] S22, optimal structure parameters of the electromagnetic valve are determined by orthogonal test in combination with response speed and electromagnetic force requirements: guide sleeve thickness d g = 0.5 mm, outer magnetic pole thickness d p = 6 mm, armature length l a = 12.1 mm, and magnetic isolation angle θ m = 45°.

[0028] Preferably, under the initial constraint conditions in step S21, initial valve core position z ev0 = 0.1 mm, initial current i0 of the electromagnetic coil = 0.12 A, and electromagnetic coil turns n = 1000.

[0029] Preferably, step S3 specifically includes the following steps.

[0030] S31, the electromagnetic valve valve core position is estimated based on square root volume Kalman filtering In formula, the state equation is as follows:

[0031]

[0032] In formula, A and B are both state variables, and ΔP represents a difference between the master cylinder pressure and the wheel cylinder pressure.

[0033] S32, a fractional order sliding mode surface s is designed

[0034]

[0035] In formula, z nom , and respectively represent a target position of the electromagnetic valve valve core, a first order derivative of the target position, and a second order derivative of the target position; k x and k z both represent weight coefficients; γ and μ both represent fractional order orders, and 0 < γ, μ < 2. A first derivative of an electromagnetic valve spool estimated position;

[0036] S34, design the following control law:

[0037]

[0038] wherein,

[0039]

[0040] wherein, ε represents a sliding mode robust gain coefficient; k s represents a sliding mode surface damping coefficient, and 0<k s <10;

[0041] S34, convert the current target value into PWM duty ratio D by a PID algorithm pwm :

[0042]

[0043] wherein,

[0044] Δi e = i nom - i (13) ;

[0045] wherein, K p-duty , K i-duty and K d-duty respectively represent proportional, integral, and differential gain coefficients of a PID controller; Δi e (t) and Δi e (t-1) represent current deviations at t time and t-1 time; i nom represents a target electromagnetic coil current; and Δt represents a sampling interval.

[0046] Preferably, in step S33, γ is adjusted according to a disturbance frequency, and μ is adjusted according to a system overshoot, so as to improve robustness from error convergence, disturbance suppression, and chattering relief.

[0047] Therefore, the brake force adjusting method based on the electromagnetic valve has the beneficial effects that:

[0048] 1. Multi-physical field coupling modeling improves dynamic control precision: a coupling model is established by comprehensively considering electromagnetic, mechanical, and hydraulic characteristics, the dynamic relationship between the spool position and the brake force is accurately described, the problem of large deviation of traditional single physical field modeling is solved, and a reliable theoretical basis is provided for the control algorithm;

[0049] 2. The structural parameter optimization significantly improves the electromagnetic force response: through finite element simulation and orthogonal test, the parameters such as the thickness of the guide sleeve (0.5mm) and the thickness of the outer magnetic pole (6mm) are optimized, and the initial electromagnetic force is improved by 40% by combining the design of 45° magnetic isolation angle, the response time is shortened to 1.5ms, the eddy current loss is reduced, and the bottleneck of slow response and high energy consumption of traditional electromagnetic valves is broken through;

[0050] 3. Fractional order sliding mode control enhances system robustness: the fractional order γ and μ are introduced, the error convergence rate and phase characteristics are adjusted, the suppression ability of electromagnetic valve nonlinearity (such as magnetic saturation, liquid dynamic force coupling) and multi-frequency interference (high-frequency current ripple, low-frequency pressure fluctuation) is improved, the control error is reduced by 30% compared with traditional PID, and the anti-interference ability is improved by 40%;

[0051] 4. Square root cubage Kalman filter (SRCKF) realizes accurate estimation of implicit state: based on the coupling model, the SRCKF algorithm is designed, the valve core position is indirectly estimated through measurable variables (current, pressure), the direct measurement cost is avoided, the estimation error is controlled within 5μm, and real-time and high-precision feedback is provided for closed-loop control.

[0052] The technical solutions of the present application will be further described in detail below with the help of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 A flowchart of a brake force regulation method based on an electromagnetic valve according to the present application. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be further described in detail below with the help of the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present application and not to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. The examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout.

[0055] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or server including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0056] The embodiments of the present application will be described in detail below with the help of the accompanying drawings.

[0057] As Figure 1 shown, a brake force adjustment method based on a solenoid valve includes the following steps:

[0058] S1, considering the electromagnetic characteristics, hydraulic characteristics and mechanical motion characteristics of the solenoid valve, a dynamic model of multi-physical field coupling including electromagnetic force, valve core motion and hydraulic force is established to describe the dynamic relationship between the solenoid valve core position and the brake force;

[0059] Step S1 specifically includes the following steps:

[0060] S11, according to Maxwell stress theory, an electromagnetic force model is established:

[0061]

[0062] In the formula, F m represents the electromagnetic force; ψ represents the magnetic flux linkage, and R m1 represents the working air gap reluctance, R m2 represents the secondary air gap reluctance, n represents the number of turns of the electromagnetic coil, e represents the secondary air gap length, R represents the valve core radius, l s represents the secondary air gap width; μ0 represents the vacuum permeability; S0 represents the magnetic pole area; i represents the electromagnetic coil current; z ev represents the actual position of the solenoid valve core;

[0063] S12, considering the electromagnetic force F m , spring force F k , hydraulic force F s and viscous friction force, a valve core mechanical equilibrium equation is established:

[0064]

[0065] Wherein,

[0066] F k = F0+K k ·z ev (3);

[0067]

[0068] In the formula, m represents the mass of the valve core; Cu represents the viscous damping coefficient of the solenoid valve core motion; and respectively represent the first order derivative and the second order derivative of the actual position of the solenoid valve core; F0 represents the spring pre-tightening force; K k represents the spring stiffness; P m represents the master cylinder pressure; P wrepresents the wheel cylinder pressure; c d represents the flow coefficient; c1 represents the pressure distribution compensation coefficient; A t represents the throttle opening area; A ev represents the valve outlet area; a represents the valve seat cone angle half angle; A tw represents the conical surface area; z represents the energy loss coefficient;

[0069] S13, considering the coil inductance and the counter electromotive force generated by the spool movement, a coil circuit equation is established:

[0070]

[0071] In the formula, u i represents the electromagnetic coil voltage; r represents the electromagnetic coil resistance; represents the first derivative of the electromagnetic coil current.

[0072] S2, the optimal structure parameters of the electromagnetic valve are obtained by a finite element simulation method;

[0073] Step S2 specifically includes the following steps:

[0074] S21, an electromagnetic valve model is established by ANSYS Electronics, the influence of different guide sleeve thicknesses and outer magnetic pole thicknesses on static electromagnetic force is simulated, and the formula (1) is obtained under initial constraint conditions:

[0075]

[0076] In the formula, F δ represents the initial electromagnetic force, and F δ > 15 N; B δ represents the air gap magnetic induction intensity; d a1 represents the armature effective diameter; d1 represents the sum of the working air gap and the length of the limit piece;

[0077] S22, the optimal structure parameters of the electromagnetic valve are determined by an orthogonal test in combination with the response speed and electromagnetic force requirements: the guide sleeve thickness d g = 0.5 mm, the outer magnetic pole thickness d p = 6 mm, the armature length l a = 12.1 mm, and the magnetic isolation angle Q m = 45°.

[0078] Preferably, under the initial constraint conditions in step S21, the initial spool position z ev0 = 0.1 mm, the initial current i0 of the electromagnetic coil is 0.12 A, and the number of turns n of the electromagnetic coil is 1000.

[0079] S3, based on the optimal structure parameters of the electromagnetic valve and the dynamic model of multi-physical field coupling, a fractional order sliding mode variable structure control algorithm is adopted to generate a PWM signal;

[0080] Step S3 specifically comprises the following steps:

[0081] S31, based on the square root cubage Kalman filter to estimate the electromagnetic valve spool position The state equation is as follows:

[0082]

[0083] In the formula, A and B are state variables, and ΔP represents the difference between the master cylinder pressure and the wheel cylinder pressure;

[0084] S32, design a fractional order sliding surface s:

[0085]

[0086] In the formula, z nom , and respectively represent the target position of the electromagnetic valve spool, the first derivative of the target position, and the second derivative of the target position; k x and k z both represent weight coefficients; γ and μ both represent fractional order, and 0<γ, μ<2; represents the first derivative of the estimated position of the electromagnetic valve spool;

[0087] S34, design the following control law:

[0088]

[0089] In the formula,

[0090]

[0091] In the formula, ε represents the sliding mode robustness gain coefficient; k s represents the sliding mode surface damping coefficient, and 0<k s <10;

[0092] In step S33, γ is adjusted according to the disturbance frequency, and μ is adjusted according to the system overshoot, to realize the improvement of robustness from error convergence, disturbance suppression, and chattering relief. Specifically, when the high-frequency disturbance is taken, take γ=1.5, and when the low-frequency disturbance is taken, take γ=0.8; when the overshoot is large, μ=0.5, and when the overshoot is small, μ=1.2.

[0093] S34, convert the current target value into PWM duty cycle D pwm by PID algorithm:

[0094] wherein,

[0095] Δi e = i nom - i(13) ;

[0096] wherein, K p-duty , K i-duty and K d-duty represent the gain coefficients of the proportional, integral and derivative of the PID controller respectively; Δi e (t) and Δi e (t-1) represent the current deviation at time t and time t-1; i nom represents the target electromagnetic coil current; Δt represents the sampling interval.

[0097] S4, controlling the electromagnetic coil current through the PWM signal to realize the brake force adjustment.

[0098] It should be noted that the above examples are only used to illustrate the technical solutions of the present application rather than limiting the same. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A solenoid-based brake force adjustment method, characterized by: The method comprises the following steps: S1, comprehensively considering the electromagnetic characteristics, hydraulic characteristics and mechanical motion characteristics of the electromagnetic valve, a dynamic model of multi-physical field coupling including electromagnetic force, valve core motion and hydraulic force is established to describe the dynamic relationship between the valve core position and the braking force of the electromagnetic valve; S2, obtaining the optimal structure parameters of the electromagnetic valve through a finite element simulation method; S3, based on the optimal structure parameters of the electromagnetic valve and the dynamic model of multi-physical field coupling, a fractional order sliding mode variable structure control algorithm is adopted to generate a PWM signal; S4, controlling the electromagnetic coil current through the PWM signal to realize the adjustment of the braking force; Step S1 specifically comprises the following steps: S11, according to the Maxwell stress theory, an electromagnetic force model is established: where F m represents the electromagnetic force; ψ represents the magnetic flux linkage, and R m1 represents the working air gap reluctance, R m2 represents the secondary air gap reluctance, n represents the number of turns of the electromagnetic coil, e represents the secondary air gap length, R represents the spool radius, l s represents the secondary air gap width; μ0 represents the vacuum permeability; S0 represents the pole area; i represents the electromagnetic coil current; z ev represents the actual position of the electromagnetic valve spool; S12, consider electromagnetic force F m , spring force F k , hydraulic force F s and viscous friction force, the valve core mechanical equilibrium equation is established: Wherein, F k = F0+ K k ·z ev (3); In the formula, m represents the mass of the valve core; Cu represents the viscous damping coefficient of the electromagnetic valve valve core movement; and respectively represent the first derivative and the second derivative of the real position of the electromagnetic valve valve core; F0 represents the spring pre-tightening force; K k represents the spring stiffness; P m represents the master cylinder pressure; P w represents the wheel cylinder pressure; c d represents the flow coefficient; C1 represents the pressure distribution compensation coefficient; A t represents the orifice area; A ev represents the valve outlet area; α represents the valve seat cone half-angle; A rw represents the conical surface area; ζ represents the energy loss coefficient; S13, considering the coil inductance and the counter electromotive force generated by the valve core motion, a coil circuit equation is established: wherein u i represents the electromagnetic coil voltage; r represents the electromagnetic coil resistance; represents the first derivative of the electromagnetic coil current; Step S2 specifically comprises the following steps: S21, an electromagnetic valve model is established by using ANSYS Electronics, the influence of different guide sleeve thickness and outer magnetic pole thickness on the static electromagnetic force is simulated, and formula (1) is simplified under the initial constraint condition to obtain: where F δ represents the initial electromagnetic force, and F δ > 15N; B δ represents the air gap magnetic induction; d a1 represents the armature effective diameter; δ1 represents the sum of the working air gap and the length of the limit piece; S22, comprehensive response speed and electromagnetic force demand, through orthogonal test to determine the optimal structure parameters of electromagnetic valve: guide sleeve thickness d g = 0.5mm, outer magnetic pole thickness d p = 6mm, armature length l a = 12.1mm, magnetic isolation angle θ m = 45°; Step S3 specifically comprises the following steps: S31, estimating the electromagnetic valve spool position based on square root cubature Kalman filter where the state equation is as follows: In the formula, A and B are state variables, and ΔP represents the difference between the master cylinder pressure and the wheel cylinder pressure; S32, a fractional order sliding mode surface s is designed: wherein z nom , and respectively represent the target position of the electromagnetic valve spool, the first derivative of the target position, and the second derivative of the target position; k x and k z both represent weight coefficients; γ and μ both represent fractional orders, and 0 < γ, μ < 2; represents the first derivative of the electromagnetic valve spool estimated position; S34, the following control law is designed: Wherein, where ε represents a sliding mode robust gain coefficient; k s represents a sliding mode surface damping coefficient, and 0 < k s <10; S34, convert the current target value to a PWM duty ratio D by a PID algorithm pwm : Wherein, Δi e = i nom - i (13); In the formula, K p-duty K i-duty and K d-duty These represent the proportional, integral, and derivative gain coefficients of the PID controller, respectively; Δi e (t) and Δi e (t-1) represents the current deviation between time t and time t-1; i nom Δt represents the target electromagnetic coil current; Δt represents the sampling interval.

2. A solenoid-based brake force regulation method according to claim 1, characterized in that: Under the initial constraint conditions described in step S21, the initial spool position Z zv0 = 0.1 mm, the initial current of the electromagnetic coil i0= 0.12 A, and the number of turns of the electromagnetic coil n = 1000.

3. The solenoid-based brake force regulation method of claim 1, wherein: In step S33, γ is adjusted according to the disturbance frequency, and μ is adjusted according to the system overshoot to realize the improvement of robustness from error convergence, disturbance suppression and chattering alleviation.

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