Vehicle vibration energy collection device based on piezoelectric effect and nonlinear magnetic coupling and design method

Abstract

The invention provides a vehicle vibration energy collection device based on piezoelectric effect and nonlinear magnetic coupling and a design method, and belongs to the technical field of vibration energy recovery and automobile energy conservation. The device comprises a shell, a suspension spiral spring, a plurality of cantilever beams, a first permanent magnet and a second permanent magnet, the roots of the cantilever beams are fixed to the inner wall of the shell, the first permanent magnet and the second permanent magnet are fixed to the free ends of the cantilever beams and the suspension spiral spring respectively, and a gap is reserved between the first permanent magnet and the second permanent magnet; and a piezoelectric ceramic piece is arranged on the cantilever beam. The inherent frequency of the energy collection system is effectively reduced through magnetic coupling and mass block loading, efficient matching with the low-frequency vibration environment of the vehicle suspension is achieved, the initial horizontal gap between the first permanent magnet set and the second permanent magnet set is accurately set, the energy recovery efficiency is remarkably improved, and the energy recovery efficiency is improved. And power can be supplied to low-power-consumption vehicle-mounted electronic equipment.

Description

A vehicle vibration energy harvesting device and design method based on piezoelectric effect and nonlinear magnetic coupling Technical Field

[0001] This invention relates to the field of vehicle vibration energy recovery technology, and in particular to a vehicle vibration energy harvesting device and design method based on piezoelectric effect and nonlinear magnetic coupling. Background Technology

[0002] With the rapid development of the automotive industry, especially new energy vehicles, improving energy efficiency has become a key research topic. During vehicle operation, road surface unevenness generates continuous vibrations through the suspension system. This mechanical energy is typically dissipated as heat through the shock absorbers, resulting in energy waste. Recovering this energy is crucial for extending the driving range of electric vehicles and powering low-power in-vehicle electronic devices.

[0003] IN202511095479A discloses a device for recovering energy from a vehicle suspension system. It includes suspension links, a motion conversion assembly, an electromagnetic generator, an energy storage module, and control circuitry. The motion conversion assembly uses a rack and pinion mechanism to convert vertical vibrations into rotational motion. The electromagnetic generator includes a rotor and stator designed for high conversion efficiency. The converted rotational motion drives a generator to produce electricity. The generated power is stored and regulated for use by the vehicle's electrical system.

[0004] Piezoelectric energy harvesting technology is considered an effective way to recover vehicle vibration energy due to its advantages such as simple structure, high power density, and ease of integration. IN202541095891A provides a smart suspension system that integrates a traditional spring damper mechanism with modern technologies such as piezoelectric discs, sensors, and Arduino-based microcontrollers. When the vehicle encounters vibration, the piezoelectric element converts this mechanical energy into electrical energy, which is then stored in a battery or supercapacitor. This not only suppresses vibration but also collects and reuses energy that would otherwise be wasted in conventional setups.

[0005] However, existing technologies have many problems. The key parameters of magnetic coupling excitation lack accurate modeling and analysis, making it difficult to guarantee stable system operation. Current research relies heavily on empirical formulas for force analysis between permanent magnets, resulting in insufficient accuracy. Furthermore, the cantilever beam mechanical model does not fully consider the coordinated deformation of the composite layer structure, leading to deviations in the calculation of elastic restoring force and thus affecting the feasibility verification of the excitation mechanism. By employing precise finite element modeling and mathematical modeling, combined with system feasibility analysis, the optimal structural parameters are determined. Summary of the Invention

[0006] To improve the stability and efficiency of energy harvesting in vehicle vibration energy harvesting devices, this invention provides a vehicle vibration energy harvesting device and design method based on piezoelectric effect and nonlinear magnetic coupling, used to recover energy during vehicle vibration. Through finite element modeling of permanent magnets, mathematical modeling of cantilever beams, and targeted feasibility analysis, the key technical challenges of low-frequency vibration energy harvesting in vehicles are overcome, the optimal structural parameters are determined, and the system is ensured to operate efficiently and stably.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling is characterized by comprising a shell, a suspension coil spring, multiple cantilever beams, a first permanent magnet, and a second permanent magnet. The shell is disposed outside the suspension coil spring and connected to the vehicle body. The root of each cantilever beam is fixed to the inner wall of the shell, and the free end of each cantilever beam is fixed with a first permanent magnet. The second permanent magnet is fixed on the suspension coil spring at a position corresponding to the first permanent magnet, with a gap between them, forming a nonlinear magnetic coupling. Piezoelectric ceramic sheets are disposed on the cantilever beams.

[0009] Furthermore, the number of cantilever beams is eight, which are fixed to the inner wall of the outer shell in a spiral array.

[0010] Furthermore, piezoelectric ceramic sheets are provided on both the upper and lower sides of the cantilever beam.

[0011] Furthermore, the gap between the second permanent magnet and the first permanent magnet is 8mm.

[0012] Furthermore, the cantilever beam uses an elastic steel substrate with a Young's modulus of 200 GPa, and the piezoelectric ceramic sheet is a PZT-5H piezoelectric ceramic sheet with a Young's modulus of 60 GPa.

[0013] Furthermore, both the first and second permanent magnets are NdFeB N40 grade cylindrical permanent magnets with a diameter of 10mm and a height of 4mm.

[0014] The design method for the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling is characterized by the following steps:

[0015] S1: Structural design of the energy harvesting device;

[0016] S2: Simulate the magnetic coupling between the first permanent magnet and the second permanent magnet, and determine the gap size between them;

[0017] S2.1 Finite element modeling of permanent magnets: Based on the COMSOL Multiphysics platform, a finite element model of the permanent magnets is constructed, which includes two symmetrically arranged permanent magnets and the surrounding air domain. The two permanent magnets are the same size, which are NdFeBN40 grade cylindrical permanent magnets with a diameter of 10mm and a height of 4mm. The initial horizontal gap between the two permanent magnets is defined as s.

[0018] S2.2 sets boundary conditions: the left permanent magnet is fixed and constrained, and the right permanent magnet is subjected to displacement excitation along the z-axis to simulate the relative motion of the magnets caused by vehicle suspension vibration; the outer air domain is included to simulate the magnetic field distribution.

[0019] S2.3: The magnetic flux density contour distribution in the outer air domain is obtained through simulation, and the variation of the magnetic attraction between the two permanent magnets is calculated when the right permanent magnet moves along the z-axis under different initial horizontal gaps;

[0020] S2.4 Mathematical Modeling of Cantilever Beams: Based on the classical beam theory in mechanics of materials, a systematic modeling and analysis of the flexural behavior of cantilever beams subjected to concentrated loads at their free ends was conducted.

[0021]

[0022] According to the deflection solution of a cantilever beam under a concentrated force F at its free end, the relationship between the free end deflection and the applied load is expressed as follows:

[0023]

[0024] Equivalently, the required force is:

[0025]

[0026] In the formula, For the equivalent stiffness of the cantilever beam, Let Ieq be the perpendicular distance between the centroid of the PZT layer section and the centroid of the overall section of the laminated beam, Ieq be the equivalent bending stiffness, A be the area of ​​the PZT layer, and L be the length of the beam. Here, represents the Young's modulus of the PZT layer, and Esteeel represents the Young's modulus of the elastic steel. For free end deflection, A force applied to the free end by external forces;

[0027] S2.5 Extract magnetic attraction data under different initial horizontal gaps from the finite element model of permanent magnet, extract elastic restoring force data corresponding to deflection of 1~8mm from the mathematical model of cantilever beam and conduct comparative analysis to select the most suitable initial horizontal gap.

[0028] S3 Vehicle Suspension Vibration Response and Excitation Input Modeling:

[0029] First-order filtered white noise is used to generate random road surface excitation that meets band-limited characteristics. Its mathematical model is shown in equation (5):

[0030]

[0031] In equation (1), Indicates the next cutoff frequency; This represents a random road surface excitation signal; Indicates the road surface roughness coefficient;

[0032] According to Newton's second law of motion, the differential equation of motion for a quarter-vehicle model with a two-degree-of-freedom suspension is as follows:

[0033]

[0034]

[0035] in, Indicates the vertical velocity of the wheel. Indicates the vertical speed of the vehicle body. This indicates the vertical acceleration of the vehicle body. Indicates the mass of the wheel. Indicates vehicle body mass. For the equivalent stiffness of the wheel, Let be the equivalent stiffness of the suspension, c be the equivalent damping coefficient of the suspension, and q be the road excitation. This represents the vertical displacement of the wheel. This refers to the vertical displacement of the vehicle body. For active control;

[0036] Under the influence of road surface excitation, time-domain response simulation analysis of suspension dynamic travel was conducted for different road surface grades (A to D) and various vehicle speed conditions to obtain the random road surface excitation signal, i.e., the vehicle vibration displacement z utilized by the energy harvesting device.

[0037]

[0038] Where z2 is the vertical displacement of the vehicle body, and the suspension support rod is connected to the tire, and its vertical displacement is z1;

[0039] S4 Experimental Verification and Performance Evaluation;

[0040] S4.1 Install the cantilever beam and the first permanent magnet on the inner wall of the outer shell according to the structure designed in S1 and the gap determined in S2, to ensure that all components are firmly connected;

[0041] S4.2: Construct an experimental platform including an exciter, power amplifier, function generator, oscilloscope, and laser displacement sensor.

[0042] S4.3: Fix the shell containing the cantilever beam and the first permanent magnet onto the vibratory table of the exciter, connect the piezoelectric ceramic sheet to the load circuit, set the exciter frequency and amplitude according to the actual road surface grade and vehicle speed to simulate road surface grades A to D, record the output voltage of the piezoelectric ceramic sheet with an oscilloscope, and evaluate the energy harvesting effect.

[0043] Furthermore, in step S2.3, the initial gap between the first permanent magnet and the second permanent magnet is set to 7~9mm;

[0044] Furthermore, the load circuit in S3.3 adopts an adjustable resistor circuit with a resistance adjustment range of 8~12kΩ and an optimal matching resistor of 10kΩ, which is used to stably receive the output power of the piezoelectric element and adapt to different working conditions.

[0045] Further, in S3, considering the actual driving conditions of the vehicle, the first four levels A, B, C, and D are selected, where the road power spectral densities of levels A, B, C, and D are 16, 64, 256, and 1024, respectively. The core structure of the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling described in this invention consists of multiple cantilever beams and permanent magnets, all encapsulated within a cylindrical shell rigidly connected to the vehicle body. The root of each cantilever beam is fixed to the inner wall of the shell, and its free end integrates a first permanent magnet mass block. A corresponding second permanent magnet is mounted on the coil spring of the suspension system, forming a nonlinear magnetic attraction coupling with the first permanent magnet mass block at the end of the cantilever beam. The first permanent magnet mass block is attached to the free end of the cantilever beam to adjust its natural frequency, and a piezoelectric ceramic sheet is attached to the surface of the cantilever beam. When stationary, the two permanent magnets are horizontally aligned. When the suspension vibrates during vehicle movement, causing the cantilever beam to vibrate, the second permanent magnet, which corresponds to the first permanent magnet at the end of the cantilever beam, moves with the vibration of the suspension spring. At this time, the magnetic force between the two permanent magnets causes the beam to bend repeatedly. This mechanical deformation directly causes the piezoelectric ceramic sheet attached to the cantilever beam to produce strain. The piezoelectric ceramic sheet then converts the mechanical strain into charge output through the positive piezoelectric effect.

[0046] The design method of the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling described in this invention focuses on achieving efficient capture of low-frequency vibration energy through finite element modeling of permanent magnets, mathematical modeling of cantilever beams, and feasibility analysis.

[0047] Beneficial effects of the present invention

[0048] 1. Frequency Tuning and Nonlinear Excitation: By adding permanent magnet mass blocks to the free end of the cantilever beam, the natural frequency of the system is effectively reduced. More importantly, by utilizing the nonlinear magnetic coupling between the permanent magnets, non-contact and efficient excitation of low-frequency, large-amplitude vibrations of the suspension is achieved, fundamentally solving the frequency mismatch problem between traditional piezoelectric data acquisition devices and the vehicle vibration environment.

[0049] 2. High-efficiency energy conversion: Experimental results show that a single cantilever beam can achieve a peak voltage of 9.59V and a power of 7.67mW under resonant conditions. The overall device composed of 8 cantilever beams can achieve an output power of 414.37mW under simulated Class D road conditions and a driving speed of 90km / h, demonstrating great potential for practical applications.

[0050] 3. Compact structure and high reliability: The entire device is encapsulated in a cylindrical shell, allowing for direct installation near the suspension without altering the original suspension structure, resulting in minimal impact on vehicle dynamics. Non-contact excitation avoids mechanical wear, improving the device's long-term reliability. Attached Figure Description

[0051] Figure 1 is a design flowchart of the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to the present invention.

[0052] Figure 2 is a structural diagram of the preliminary design of the vehicle vibration energy harvesting device.

[0053] Figure 3 is a schematic diagram of the energy harvesting principle of the vehicle vibration energy harvesting device.

[0054] In Figure 4, (a), (b), (c), and (d) represent the first, second, third, and fourth vibration modes of the cantilever beam, respectively.

[0055] Figure 5 shows the first, second, third, and fourth vibration modes of the cantilever beam with the first permanent magnet fixed in (a), (b), (c), and (d), respectively.

[0056] Figure 6(a) shows the three-dimensional mesh model of the magnet system, and Figure 2(b) shows the mesh division of the axial section of the magnet.

[0057] Figure 7 shows the geometric configuration of the two cylindrical magnets under axial and lateral relative displacement.

[0058] Figure 8 is a comparison of the magnetic force variation between the theoretical model and the finite element model constructed in this invention.

[0059] Figure 9 shows the relationship between the elastic restoring force of the cantilever beam and the attractive force of the magnet.

[0060] Figure 10 shows a 1 / 4 scale model of the vehicle suspension structure.

[0061] Figure 11 shows the output power of the energy harvesting device under different road surface grades and vehicle speeds.

[0062] Explanation of reference numerals in the attached figures:

[0063] 1. Outer shell, 2. Suspension coil spring, 3. Cantilever beam, 4. Piezoelectric sheet, 5. First permanent magnet, 6. Second permanent magnet. Detailed Implementation

[0064] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0065] The flowchart of the design method of the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling described in this invention is shown in Figure 1.

[0066] Step 1: Preliminary design of a vehicle vibration energy harvesting device, the structure of which is shown in Figure 2.

[0067] The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling includes a housing, a suspension coil spring, eight cantilever beams, eight first permanent magnets, and eight second permanent magnets, all encapsulated within a cylindrical housing rigidly connected to the vehicle body. The housing is located outside the suspension coil springs and connected to the vehicle body. The root of each cantilever beam is fixed to the inner wall of the housing, and a first permanent magnet is fixed to its free end. Second permanent magnets are fixed to positions on the suspension coil springs corresponding to the positions of the first permanent magnets, with gaps between them, forming nonlinear magnetic coupling. Piezoelectric ceramic plates are disposed on the cantilever beams.

[0068] Rigid housing: The housing is fixed to the vehicle body, is cylindrical in shape, and is used to enclose the internal components of the device;

[0069] Cantilever beam array: The cantilever beam array is set inside the shell and is spirally and uniformly arranged along the z-axis. The root of each cantilever beam is fixed to the inner wall of the shell, and the free end is suspended. The dimensions of the cantilever beam are 20mm×80mm×0.2mm, and its equivalent natural frequency is tuned to 16.75Hz.

[0070] Piezoelectric ceramic sheet: A PZT-5H piezoelectric ceramic sheet is attached to the upper surface of each cantilever beam, and the size of the piezoelectric ceramic sheet is 20mm×60mm×0.2mm;

[0071] First permanent magnet: Each cantilever beam has a permanent magnet fixed at its free end, forming a first permanent magnet group of 8;

[0072] Second permanent magnet: The second permanent magnet is fixed on the vehicle suspension coil spring, and the second permanent magnet is set in a one-to-one correspondence with the first permanent magnet; the first permanent magnet and the second permanent magnet are both cylindrical magnets made of NdFeB N40 material, with a diameter of 10mm and a height of 4mm. A horizontal gap is left between the two sets of permanent magnets to form a nonlinear magnetic attraction coupling.

[0073] Load circuit: The load circuit is electrically connected to the piezoelectric element and has a resistance of 10kΩ. It is used to receive the electrical energy output by the piezoelectric element.

[0074] Figure 3 illustrates the principle of the energy harvesting device, which involves the coordinated action of the electrical and structural domains. The core of the structural domain is a cantilever beam with a first permanent magnet mass attached to its free end to adjust its natural frequency. The electrical domain consists of PZT-5H piezoelectric ceramic sheets attached to the upper surface of the cantilever beam. The natural vibration frequencies of the cantilever beam are shown in Figure 4 and Table 1.

[0075] Table 1. Natural vibration frequencies of the piezoelectric cantilever beam without permanent magnets in each mode.

[0076] Modal frequencies (Hz): 1.5623, 0.9328, 3.4865, 2.4 surface

[0077] The core working principle of the vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling lies in the electromechanical coupling effect. When stationary, the two permanent magnets are horizontally aligned. When the suspension vibrates during vehicle movement, external excitation induces beam vibration. The second permanent magnet, corresponding to the first permanent magnet at the end of the cantilever beam, moves with the vibration of the suspension spring. At this time, the magnetic force generated by the two permanent magnets causes the cantilever beam to repeatedly bend and deform. This mechanical deformation directly causes strain in the PZT-5H attached to the cantilever beam. The PZT-5H then converts the mechanical strain into charge output through the positive piezoelectric effect. Figure 5 and Table 1 show the natural vibration frequencies of the piezoelectric cantilever beam carrying permanent magnets, respectively.

[0078] Table 2 Natural vibration frequencies of the piezoelectric cantilever beam carrying permanent magnets in each mode.

[0079] Modal frequencies (Hz): 16.75, 170.31, 245.75, 70.99 surface

[0080] Step 2: Simulate the magnetic coupling excitation mechanism and determine the gap size between the two.

[0081] In the designed vibration energy harvesting device, the nonlinear magnetic coupling force between the cylindrical first permanent magnet integrated at the end of the cantilever beam and the second permanent magnet on the suspension helical spring constitutes the core excitation mechanism. The initial horizontal gap distance is a key design parameter for this mechanism. When the initial gap distance is too large, the coupling strength between the magnets significantly decreases, resulting in suppression of the cantilever beam's vibration amplitude under external excitation along the z-axis, thus drastically reducing the electrical power output of the piezoelectric conversion layer. Conversely, if the initial gap distance is too small, the attractive force generated between the magnets will far exceed the elastic restoring force threshold of the cantilever beam. This mechanical imbalance would cause the energy harvester to completely lose its function.

[0082] To investigate the relationship between the interaction force and the gap distance between cylindrical permanent magnets, a finite element model was constructed based on the COMSOL Multiphysics platform. The model consists of two identical NdFeB N40 grade cylindrical magnets, each with a diameter of 10 mm and a height of 4 mm, and an surrounding air domain. The initial gap distance is defined as s. The left magnet is set as a fixed constraint, while the right magnet is subjected to displacement excitation along the z-axis. The result for a specific gap distance s is shown in Figure 6.

[0083] To verify the accuracy of the constructed finite element model, among various analytical schemes for calculating the interaction force between permanent magnets, the expressions for the axial and lateral forces between cylindrical magnets were derived by Avvari et al. using integral form. Figure 7 shows the geometric configuration of two cylindrical magnets under axial and lateral relative displacements. The derived analytical formula for the lateral force between identical magnets is expressed as follows:

[0084]

[0085] In the equations above, s represents the axial distance between the magnets; J is the first-order Bessel function of the first kind; μ0 is the free permeability; ε is +1 for attraction and −1 for repulsion; q is a dimensionless parameter reflecting the shape function and magnetic vector potential characteristics of the cylindrical magnet in Fourier space; M is the magnetization; R is the radius; t is the thickness of the magnet; r is the lateral distance between the magnets; and s is the axial distance between the magnets. The data obtained from the constructed finite element model are compared with the model constructed by Avvari et al., and the results are shown in Figure 8, demonstrating the accuracy and reliability of the magnetic field model constructed in this invention.

[0086] To further investigate the mechanical response characteristics of cantilever beams under external loads, particularly the quantitative relationship between load and displacement at their free ends, a systematic modeling and analysis of the flexural behavior of cantilever beams subjected to concentrated loads at their free ends was conducted. The research object is a composite layer cantilever beam structure composed of piezoelectric ceramic (PZT-5H) and an elastic steel substrate, whose equivalent bending stiffness is determined by the geometric and physical properties of each component material.

[0087] In such laminated structures, due to the coordinated deformation between different material layers, an equivalent bending stiffness needs to be introduced to characterize the overall bending resistance. The expression for this equivalent stiffness takes into account the stiffness of both the piezoelectric ceramic layer and the steel substrate, and the formula is as follows:

[0088]

[0089] According to the deflection solution of a cantilever beam under a concentrated force F at its free end, the relationship between the free end deflection and the applied load is expressed as follows:

[0090]

[0091] Equivalently, the required force can be solved as follows:

[0092]

[0093] In the formula, For the equivalent stiffness of the cantilever beam, Ieq is the perpendicular distance between the centroid of the PZT layer section and the centroid of the overall section of the laminated beam; A is the equivalent bending stiffness; L is the area of ​​the PZT layer; EPZT is the Young's modulus of the PZT layer; and Esteeel is the Young's modulus of the elastic steel. For free end deflection, A force applied to the free end by external forces.

[0094] Based on the above theoretical model, the concentrated load required to be applied when the deflection at the free end of the cantilever beam varies within the range of 1 to 8 mm was further calculated. To further evaluate the excitation feasibility of this cantilever beam system, the calculated elastic restoring force was compared and analyzed with the magnetic attraction force between permanent magnets under different horizontal gaps, as shown in Figure 9.

[0095] In summary, based on a comprehensive trade-off between excitation efficiency and structural integrity, an optimal design parameter of 8 mm is determined for the horizontal gap between the end magnet of the cantilever beam and the fixed magnet on the suspension helical spring. This configuration ensures sufficient excitation for the cantilever beam while effectively preventing structural failure or fatigue damage due to excessive deformation, thereby significantly enhancing the operational stability and long-term reliability of the entire energy harvesting device.

[0096] Step 3: Modeling the vibration response and excitation input of the vehicle suspension;

[0097] Vibration during vehicle operation mainly originates from excitation introduced by road surface unevenness. A vibration energy harvester is placed in the suspension system, and the road excitation is transmitted to this device through the suspension, driving it to generate an electromechanical converter. First-order filtered white noise is used to generate random road excitation that conforms to band-limited characteristics; its mathematical model is shown in equation (5).

[0098]

[0099] In equation (5), Indicates the next cutoff frequency; This represents a random road surface excitation signal; The road surface roughness coefficient is represented by the first four levels, taking into account the actual driving conditions of vehicles. The road surface power spectral density is shown in Table 3.

[0100] Table 3 Road surface power spectral density

[0101] Road surface grades ABCD 16642561024 surface

[0102] According to Newton's second law of motion, the differential equation of motion for a quarter-vehicle model with a two-degree-of-freedom suspension is as follows:

[0103]

[0104]

[0105] in, Indicates the vertical velocity of the wheel. Indicates the vertical speed of the vehicle body. This indicates the vertical acceleration of the vehicle body. Indicates the mass of the wheel. Indicates vehicle body mass. For the equivalent stiffness of the wheel, Let be the equivalent stiffness of the suspension, c be the equivalent damping coefficient of the suspension, and q be the road excitation. This represents the vertical displacement of the wheel. This refers to the vertical displacement of the vehicle body. This is for active control. The simulation parameters of the suspension structure are shown in Table 4.

[0106] Table 4 Simulation parameters of suspension structure

[0107] Symbolic parameter name Numerical unit Wheel weight 40Kg Vehicle weight 480Kg Wheel equivalent stiffness 150000 N / m The equivalent stiffness of the suspension is 16000 N / m. The equivalent damping of the suspension is 1200 N·s / m. surface

[0108] Under the influence of road surface excitation, time-domain response simulation analysis of the suspension dynamic travel was conducted for different road surface grades (A to D) and various vehicle speed conditions, obtaining random road surface excitation signals. As shown in Figure 10, the vertical displacement of the vehicle body is z2, and the vertical displacement of the suspension support rods connected to the tires is z1. Therefore, the vehicle vibration displacement z utilized by the energy harvesting device is:

[0109] .

[0110] Table 5. Vertical relative displacement of AD-level road surface at different vehicle speeds

[0111] Class A, Class B, Class C, Class D: 30km / h: 1mm, 2mm, 4.02mm, 8.43mm; 60km / h: 1.36mm, 2.72mm, 5.8mm, 10.75mm; 90km / h: 1.62mm, 3.23mm, 7.04mm, 12.53mm surface

[0112] Step 4: Experimental verification and performance evaluation;

[0113] To investigate the impact of different road surface grades on the power generation performance of a vehicle vibration energy harvester, a complete experimental testing system was built. This system generates an adjustable frequency and amplitude electrical signal using a function signal generator, which drives the exciter via a power amplifier, thus simulating different road surface excitation conditions. The cantilever beam and the first permanent magnet are mounted on the inner wall of the outer casing according to the structure designed in S1 and the gap determined in S2, ensuring a secure connection between all components. Because the outer casing of the energy harvester is mounted on the vehicle body, and the permanent magnet corresponding to the end of the cantilever beam is mounted on the suspension, and the magnetic force between the two permanent magnets can excite the cantilever beam to vibrate, the amplitude of the cantilever beam vibration is the vehicle vibration displacement z used in step three, i.e., the relative displacement in Table 5. During the experiment, the outer casing containing the cantilever beam and the first permanent magnet is fixed to the vibration table of the exciter, and its vibration amplitude is monitored in real time by a displacement sensor. The voltage and power are recorded under the condition of vehicle vibration displacement z. The open-circuit voltage output by the harvester is recorded using a high-precision oscilloscope, and the output power is calculated accordingly. By comparing and analyzing the output voltage and power of the device under different operating conditions, its power generation capacity can be evaluated. The output power of the AD-level road surface at different vehicle speeds is shown in Figure 11 and Table 6.

[0114] Table 6 Output power of Class A and D road surfaces at different vehicle speeds

[0115] Class A, Class B, Class C, Class D; 30km / h: 2.64mW, 10.56mW, 42.65mW, 93.78mW; 60km / h: 4.88mW, 19.52mW, 88.76mW, 152.49mW; 90km / h: 6.92mW, 27.53mW, 130.77mW, 414.37mW surface

[0116] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling, characterized in that, The device includes a housing, a suspension coil spring, multiple cantilever beams, a first permanent magnet, and a second permanent magnet. The housing is disposed outside the suspension coil spring and connected to the vehicle body. The root of the cantilever beam is fixed to the inner wall of the housing, and the free end of the cantilever beam is fixed with the first permanent magnet. The second permanent magnet is fixed on the suspension coil spring at a position corresponding to the position of the first permanent magnet, with a gap between them, forming a nonlinear magnetic coupling with the first permanent magnet. Piezoelectric ceramic sheets are disposed on the cantilever beams.

2. The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 1, characterized in that, The number of cantilever beams is eight, which are fixed to the inner wall of the outer shell in a spiral array.

3. The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 1, characterized in that, Piezoelectric ceramic sheets are provided on both the upper and lower sides of the cantilever beam.

4. The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 1, characterized in that, The gap between the second permanent magnet and the first permanent magnet is 8mm.

5. The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 1, characterized in that, The cantilever beam uses an elastic steel substrate with a Young's modulus of 200 GPa, and the piezoelectric ceramic sheet is a PZT-5H piezoelectric ceramic sheet with a Young's modulus of 60 GPa.

6. The vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 1, characterized in that, Both the first and second permanent magnets are cylindrical NdFeB N40 grade permanent magnets with a diameter of 10mm and a height of 4mm.

7. A design method for a vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling, characterized in that, Includes the following steps: S1: Structural design of the energy harvesting device; S2: Simulate the magnetic coupling between the first permanent magnet and the second permanent magnet, and determine the gap size between them; S2.1 Finite element modeling of permanent magnets: Based on the COMSOL Multiphysics platform, a finite element model of the permanent magnets is constructed, which includes two symmetrically arranged permanent magnets and the surrounding air domain. The two permanent magnets are the same size, which are NdFeB N40 grade cylindrical permanent magnets with a diameter of 10mm and a height of 4mm. The initial horizontal gap between the two permanent magnets is defined as s. S2.2 Set boundary conditions: the left permanent magnet is fixed and constrained, and the right permanent magnet is subjected to displacement excitation along the z-axis to simulate the relative motion of the magnets caused by vehicle suspension vibration; the outer air domain is included to simulate the magnetic field distribution; S2.3: The magnetic flux density contour distribution in the outer air domain is obtained through simulation, and the variation law of the magnetic attraction between the two permanent magnets is calculated when the right permanent magnet moves along the z-axis under different initial horizontal gaps; S2.4 Mathematical modeling of cantilever beam: Based on the classical beam theory in mechanics of materials, the deflection behavior of a cantilever beam subjected to concentrated load at its free end is systematically modeled and analyzed; According to the deflection solution of a cantilever beam under a concentrated force F at its free end, the relationship between the free end deflection and the applied load is expressed as follows: Equivalently, the required force is: In the formula, For the equivalent stiffness of the cantilever beam, Let Ieq be the perpendicular distance between the centroid of the PZT layer section and the centroid of the overall section of the laminated beam, Ieq be the equivalent bending stiffness, A be the area of ​​the PZT layer, and L be the length of the beam. Here, represents the Young's modulus of the PZT layer, and Esteeel represents the Young's modulus of the elastic steel. For free end deflection, Force applied to the free end from the outside; S2.5 Extract magnetic attraction data under different initial horizontal gaps from the finite element model of the permanent magnet, extract elastic restoring force data corresponding to deflection of 1~8mm from the mathematical model of the cantilever beam and conduct comparative analysis to select the most suitable initial horizontal gap; S3 Modeling of vehicle suspension vibration response and excitation input: First-order filtered white noise is used to generate random road excitation that conforms to band-limited characteristics, and its mathematical model is shown in equation (5): In equation (1), Indicates the next cutoff frequency; This represents a random road surface excitation signal; This represents the road surface roughness coefficient; according to Newton's second law of motion, the differential equation of motion for a quarter-vehicle model with a two-degree-of-freedom suspension is: ； ;in, Indicates the vertical velocity of the wheel. Indicates the vertical speed of the vehicle body. This indicates the vertical acceleration of the vehicle body. Indicates the mass of the wheel. Indicates vehicle body mass. For the equivalent stiffness of the wheel, Let be the equivalent stiffness of the suspension, c be the equivalent damping coefficient of the suspension, and q be the road excitation. This represents the vertical displacement of the wheel. This refers to the vertical displacement of the vehicle body. To provide active control, under the action of road excitation, time-domain response simulation analysis of suspension dynamic travel was conducted for different road surface grades (A to D) and various vehicle speed conditions. This yielded the random road excitation signal, i.e., the vehicle vibration displacement z utilized by the energy harvesting device. Where z2 is the vertical displacement of the vehicle body, and the suspension support rod is connected to the tire, with its vertical displacement being z1; S4 Experimental verification and performance evaluation; S4.1 Install the cantilever beam and the first permanent magnet on the inner wall of the outer shell according to the structure designed in S1 and the gap determined in S2, ensuring that all components are firmly connected; S4.2: Build an experimental platform including a vibrator, power amplifier, function signal generator, oscilloscope, and laser displacement sensor; S4.3: Fix the outer shell containing the cantilever beam and the first permanent magnet on the vibrator vibration table, connect the piezoelectric ceramic sheet to the load circuit, set the vibrator frequency and amplitude according to the actual road surface grade and vehicle speed to simulate road surfaces of grades A to D, record the output voltage of the piezoelectric ceramic sheet through the oscilloscope, and evaluate the energy harvesting effect.

8. The design method for a vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 7, characterized in that, In S2.3, the initial gap between the first permanent magnet and the second permanent magnet is set to 7~9mm.

9. The design method for a vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 7, characterized in that, The load circuit in S4.3 adopts an adjustable resistor circuit with a resistance adjustment range of 8~12kΩ and an optimal matching resistor of 10kΩ, which is used to stably receive the output power of the piezoelectric element and adapt to different working conditions.

10. The design method for a vehicle vibration energy harvesting device based on piezoelectric effect and nonlinear magnetic coupling according to claim 7, characterized in that, In S3, considering the actual driving conditions of the vehicle, the first four levels A, B, C, and D are taken, with the road power spectral densities of levels A, B, C, and D being 16, 64, 256, and 1024, respectively.

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