Equivalent stiffness and damping measurement method and device of piezoelectric energy feedback suspension

Abstract

The application provides a piezoelectric energy feedback suspension equivalent stiffness and damping measurement method and device, and relates to the technical field of suspension stiffness and damping measurement. The method comprises the following steps: building a test platform; simulating the motion process of the excitation gear and the piezoelectric cantilever beam when the piezoelectric energy feedback suspension vibrates, obtaining the vibration displacement of the free end of the piezoelectric cantilever beam, and measuring the voltage signal generated by the piezoelectric cantilever beam during the vibration process; obtaining the speed change curve of the free end of the piezoelectric cantilever beam based on the change of the vibration displacement with time; drawing the voltage change curve of the piezoelectric cantilever beam during the vibration process according to the voltage signal; obtaining the continuous stiffness of the piezoelectric cantilever beam, so as to obtain the equivalent stiffness and equivalent damping of the piezoelectric energy feedback suspension. The application can measure the equivalent stiffness and damping of the piezoelectric energy feedback suspension, and provides a theoretical basis for the dynamic characteristic analysis and real vehicle application of the piezoelectric energy feedback suspension.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of suspension stiffness and damping measurement, and particularly relates to an equivalent stiffness and damping measurement method and device for a piezoelectric energy feedback suspension. BACKGROUND

[0002] The laminated cantilever piezoelectric energy feedback suspension is composed of an excitation gear and a laminated piezoelectric cantilever beam (formed by laminating a plurality of piezoelectric cantilever beams) (for specific structures, refer to Chinese patent applications CN110504865A and CN112937241A). The laminated cantilever piezoelectric energy feedback suspension can replace the traditional suspension to provide the required stiffness and damping for the vehicle, and can recover the vibration energy of the suspension during vehicle driving.

[0003] Currently, there is no method to measure the stiffness and damping of the piezoelectric energy feedback suspension. Compared with the currently designed hydraulic suspension and electromagnetic suspension, the stiffness and damping provided by the piezoelectric energy feedback suspension during vehicle driving are discontinuous and nonlinear, which is not conducive to the analysis of the dynamic characteristics and increases the difficulty of real vehicle application. Therefore, it is necessary to theoretically equivalent the stiffness and damping of the piezoelectric energy feedback suspension to continuous and linear. SUMMARY

[0004] The present application aims to provide an equivalent stiffness and damping measurement method and device for a piezoelectric energy feedback suspension, which can solve the problems in the prior art, such as the inability to measure the stiffness and damping of the piezoelectric energy feedback suspension, the difficulty in real vehicle application, and the like, and can measure the equivalent stiffness and damping of the piezoelectric energy feedback suspension, thereby providing a theoretical basis for the dynamic characteristic analysis and real vehicle application of the piezoelectric energy feedback suspension.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides an equivalent stiffness and damping measurement method for a piezoelectric energy feedback suspension, comprising:

[0006] Building a test platform, the test platform comprising an excitation gear and a laminated piezoelectric cantilever beam, the upper and lower piezoelectric layers of the piezoelectric cantilever beam being respectively connected to both ends of a fixed resistor;

[0007] Simulating the movement process of the excitation gear and the piezoelectric cantilever beam when the piezoelectric energy feedback suspension vibrates through the test platform, obtaining the vibration displacement of the free end of the piezoelectric cantilever beam, and measuring the voltage signal generated by the piezoelectric cantilever beam during the vibration process;

[0008] Obtaining the speed change curve of the free end of the piezoelectric cantilever beam based on the change of the vibration displacement with time;

[0009] Drawing the voltage change curve of the piezoelectric cantilever beam during the vibration process according to the voltage signal;

[0010] obtaining continuous stiffness of the piezoelectric cantilever, and obtaining equivalent stiffness of the piezoelectric energy feedback suspension based on the continuous stiffness and a velocity variation curve;

[0011] obtaining equivalent damping of the piezoelectric energy feedback suspension based on the continuous stiffness and a voltage variation curve.

[0012] According to the piezoelectric energy feedback suspension equivalent stiffness and damping measurement method provided by the application, the movement process of the excitation gear and the piezoelectric cantilever is as follows:

[0013] One tooth of the excitation gear contacts the piezoelectric cantilever and presses the piezoelectric cantilever to bend; the piezoelectric cantilever bends to a limit position; the excitation gear is separated from the piezoelectric cantilever, and the piezoelectric cantilever performs high-frequency free vibration; the piezoelectric cantilever high-frequency hits the next adjacent tooth of the excitation gear.

[0014] According to the piezoelectric energy feedback suspension equivalent stiffness and damping measurement method provided by the application, the continuous stiffness of the piezoelectric cantilever is obtained, and includes:

[0015] A weight is hung at the free end of the piezoelectric cantilever, and the displacement increment at the free end is measured; the hung weight mass is changed, and M times of measurement are performed, and the continuous stiffness of the piezoelectric cantilever is calculated as follows:

[0016]

[0017] Wherein, k i =m i g / s i ;

[0018] In the formula, m i is the weight mass of the i-th measurement, s i is the free end displacement increment of the i-th measurement, k es is the continuous stiffness of the piezoelectric cantilever, and g is the acceleration of gravity.

[0019] According to the piezoelectric energy feedback suspension equivalent stiffness and damping measurement method provided by the application, the equivalent stiffness of the piezoelectric energy feedback suspension is obtained based on the continuous stiffness and a velocity variation curve, and includes:

[0020] According to the velocity variation curve, the impact force of each impact of the piezoelectric cantilever, the pressing time of the piezoelectric cantilever, the excitation period, the action time of the piezoelectric cantilever for each impact of the excitation gear are obtained, and the equivalent stiffness of the piezoelectric cantilever, that is, the equivalent stiffness of the piezoelectric energy feedback suspension, is calculated.

[0021] According to the piezoelectric energy feedback suspension equivalent stiffness and damping measurement method provided by the application, the impact force of the i-th impact of the piezoelectric cantilever is:

[0022]

[0023] is the equivalent mass of the piezoelectric cantilever, is the speed variation of the i th impact, is the action time of the piezoelectric cantilever to stimulate the gear each time.

[0024] According to the application, an equivalent stiffness and damping measurement method of a piezoelectric energy feedback suspension is provided, and the equivalent stiffness of the piezoelectric cantilever is:

[0025]

[0026] In the formula, T s is the pressing time of the piezoelectric cantilever, T 1 is the stimulation period, d is the gear pitch of the stimulation gear, and n is the number of impacts of the piezoelectric cantilever in the stimulation period of the piezoelectric cantilever.

[0027] According to the application, an equivalent stiffness and damping measurement method of a piezoelectric energy feedback suspension is provided, and the equivalent damping of the piezoelectric energy feedback suspension is obtained based on the continuous stiffness and voltage variation curve, which comprises:

[0028] According to the voltage variation curve, the electric energy generated when the piezoelectric cantilever impacts is obtained;

[0029] Based on the continuous stiffness, the potential energy of the piezoelectric cantilever is obtained;

[0030] Thus, the total energy of the piezoelectric cantilever is obtained;

[0031] The vibration of the piezoelectric cantilever is regarded as a simple harmonic vibration, and the equivalent damping of the piezoelectric cantilever, i.e. the equivalent damping of the piezoelectric energy feedback suspension, is obtained.

[0032] According to the application, an equivalent stiffness and damping measurement method of a piezoelectric energy feedback suspension is provided, and the electric energy generated when the i th impact of the piezoelectric cantilever occurs is:

[0033]

[0034] In the formula, U i is the voltage variation before and after the i th impact of the piezoelectric cantilever, and R is the resistance value of the fixed resistor;

[0035] The potential energy of the piezoelectric cantilever is: E s = 0.5 × k es × d 2 ;

[0036] The total energy of the piezoelectric cantilever is: W sum = E p + Es .

[0037] According to the application, an equivalent stiffness and damping measurement method of a piezoelectric energy feedback suspension is provided, and the equivalent damping of the piezoelectric cantilever beam is:

[0038]

[0039] In the formula, N is the number of layers of the piezoelectric cantilever beam, is the vibration frequency, T0 is the total time experienced by the piezoelectric cantilever beam, and Y0 is the bending distance of the piezoelectric cantilever beam.

[0040] In a second aspect, the application provides an equivalent stiffness and damping measurement device of a piezoelectric energy feedback suspension, comprising:

[0041] A building unit is configured to build a test platform, and the test platform comprises an excitation gear and a piezoelectric cantilever beam arranged in layers, and the upper and lower piezoelectric layers of the piezoelectric cantilever beam are respectively connected to both ends of a fixed resistor.

[0042] An analog unit is configured to simulate the movement process of the excitation gear and the piezoelectric cantilever beam when the piezoelectric energy feedback suspension vibrates, obtain the vibration displacement of the free end of the piezoelectric cantilever beam, and measure the voltage signal generated by the piezoelectric cantilever beam during the vibration process.

[0043] A first processing unit is configured to obtain the speed change curve of the free end of the piezoelectric cantilever beam based on the change of the vibration displacement with time.

[0044] A second processing unit is configured to draw the voltage change curve of the piezoelectric cantilever beam during the vibration process according to the voltage signal.

[0045] A stiffness calculation unit is configured to obtain the continuous stiffness of the piezoelectric cantilever beam, and obtain the equivalent stiffness of the piezoelectric energy feedback suspension based on the continuous stiffness and the speed change curve.

[0046] A damping calculation unit is configured to obtain the equivalent damping of the piezoelectric energy feedback suspension based on the continuous stiffness and the voltage change curve.

[0047] The technical scheme of the application at least has the following technical effects:

[0048] This invention provides a method and apparatus for measuring the equivalent stiffness and damping of a piezoelectric energy-powered suspension. The method includes: constructing a test platform; simulating the motion of the gears and piezoelectric cantilever beam during vibration of the piezoelectric energy-powered suspension using the test platform, acquiring the vibration displacement of the free end of the piezoelectric cantilever beam, and measuring the voltage signal generated by the piezoelectric cantilever beam during vibration; obtaining the velocity change curve of the free end of the piezoelectric cantilever beam based on the change in vibration displacement over time; plotting the voltage change curve of the piezoelectric cantilever beam during vibration based on the voltage signal; obtaining the continuous stiffness of the piezoelectric cantilever beam; obtaining the equivalent stiffness of the piezoelectric energy-powered suspension based on the continuous stiffness and velocity change curve; and obtaining the equivalent damping of the piezoelectric energy-powered suspension based on the continuous stiffness and voltage change curve. This invention can measure the equivalent stiffness and damping of a piezoelectric energy-powered suspension, providing a theoretical basis for the dynamic characteristic analysis and practical application of piezoelectric energy-powered suspensions. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0050] In the attached diagram:

[0051] Figure 1 This is a schematic diagram of the motion process of the piezoelectric cantilever beam inside the piezoelectric energy-feeding suspension of the present invention;

[0052] Figure 2 This is a flowchart of the equivalent stiffness and damping measurement method for the piezoelectric energy-fed suspension of the present invention;

[0053] Figure 3 A line graph of measurement data from M measurements performed to change the mass of the suspended weights in this invention;

[0054] Figure 4 This is a schematic diagram showing the vibration displacement change of the free end of the piezoelectric cantilever beam during the excitation cycle of the present invention.

[0055] Figure 5 The diagram shows the displacement and velocity curves of the free end of the piezoelectric cantilever beam of this invention.

[0056] Figure 6 This is a voltage curve diagram of the piezoelectric cantilever beam of the present invention. Detailed Implementation

[0057] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0058] Some embodiments of the present application will be described in detail below with reference to the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0059] Please refer to Figure 1 , the piezoelectric energy feedback suspension comprises an excitation gear and a plurality of piezoelectric cantilever beams arranged in layers, Figure 1 only a single piezoelectric cantilever beam is shown in the figure, when the piezoelectric energy feedback suspension vibrates, the excitation gear rotates continuously, thereby repeating the following processes:

[0060] 1. The tooth A of the excitation gear is in contact with the piezoelectric cantilever beam, and the piezoelectric cantilever beam is bent by being pressed down by the excitation gear;

[0061] 2. The piezoelectric cantilever beam is bent to the limit position;

[0062] 3. The excitation gear is separated from the piezoelectric cantilever beam, and the piezoelectric cantilever beam performs high-frequency free vibration;

[0063] 4. The piezoelectric cantilever beam impacts the tooth B of the excitation gear at a high frequency, and the tooth B is adjacent to the tooth A.

[0064] In processes 1 and 2, the excitation gear presses down the piezoelectric cantilever beam to bend it, and the piezoelectric cantilever beam provides a support force (stiffness effect) by relying on its own stiffness, while absorbing and converting the vibration energy of the piezoelectric energy feedback suspension into elastic potential energy of the piezoelectric cantilever beam (damping effect).

[0065] In processes 3 and 4, the piezoelectric cantilever beam will continuously impact the excitation gear, and the impact force generated in the impact process is used to support the vehicle body, which can be regarded as an extremely large instantaneous stiffness existing in the impact moment. And at the impact moment, a part of the vibration energy of the piezoelectric energy feedback suspension is also absorbed and converted into electrical energy.

[0066] In order to measure the stiffness and damping of the piezoelectric energy feedback suspension, as shown in Figure 2 , the present application provides an equivalent stiffness and damping measurement method for a piezoelectric energy feedback suspension, comprising the following steps:

[0067] Step 1: Build a vibration test platform, which comprises an excitation gear and a plurality of piezoelectric cantilever beams arranged in layers, and the upper and lower piezoelectric layers of the piezoelectric cantilever beam are respectively connected to both ends of a fixed resistor.

[0068] Step 2, simulate the vibration of the piezoelectric energy feedback suspension through the test platform, and obtain the vibration displacement of the free end of the piezoelectric cantilever beam and the voltage signal generated by the piezoelectric cantilever beam during the vibration process;

[0069] Specifically, the displacement sensor, such as a laser displacement sensor, is used to measure the vibration displacement of the free end of the piezoelectric cantilever beam, and the laser sensing head is placed above the piezoelectric cantilever beam. The voltage signal generated by the piezoelectric cantilever beam during the vibration process is measured through a data acquisition card, such as a NI (National Instruments) acquisition card.

[0070] Step 3, obtain the speed change curve of the free end of the piezoelectric cantilever beam based on the change of the vibration displacement with time;

[0071] Step 4, draw the voltage change curve of the piezoelectric cantilever beam during the vibration process according to the voltage signal;

[0072] Step 5, obtain the continuous stiffness of the piezoelectric cantilever beam, and obtain the equivalent stiffness of the piezoelectric energy feedback suspension based on the continuous stiffness and the speed change curve;

[0073] Step 6, obtain the equivalent damping of the piezoelectric energy feedback suspension based on the continuous stiffness and the voltage change curve.

[0074] Specifically, the displacement signal and the voltage signal are input into a computer, such as a PC.

[0075] In this embodiment, the stiffness and damping of the suspension are measured by taking a single piezoelectric cantilever beam as an example.

[0076] Specifically, the continuous stiffness of the piezoelectric cantilever beam is obtained, including:

[0077] A weight is hung at the free end of the piezoelectric cantilever beam, and a displacement sensor is used to measure the displacement increment at the free end. As shown in Figure 3 , the mass of the hung weight is changed, and M measurements are performed to calculate the continuous stiffness of the piezoelectric cantilever beam as:

[0078]

[0079] Where k i = m i g / s i ;

[0080] In the formula, m i is the mass of the weight measured for the i-th time, s i is the free end displacement increment measured for the i-th time, k es is the continuous stiffness of the piezoelectric cantilever beam, and g is the acceleration of gravity.

[0081] It should be noted that the tooth of the excitation gear presses the piezoelectric cantilever beam at the balance position, and the excitation gear stops rotating when the next tooth reaches the balance position again, that is, one excitation cycle. The displacement sensor is used to collect the vibration displacement change data of the free end of the piezoelectric cantilever beam from the moment when the tooth is separated from the piezoelectric cantilever beam to the moment when the piezoelectric cantilever beam stops vibrating, as shown in Figure 4 ; and the voltage signal generated by the piezoelectric cantilever beam during vibration is measured. Then, by means of matlab software, the displacement and velocity change curves of the free end of the piezoelectric cantilever beam are calculated, as shown in Figure 5 ; and the voltage change curve of the piezoelectric cantilever beam during vibration is drawn, as shown in Figure 6 .

[0082] From the perspective of impulse, the size of the impact force can be calculated. The calculation method of the impact force of the i-th impact is as follows:

[0083]

[0084] In the formula, is the velocity change of the i-th impact, is the action time of the piezoelectric cantilever beam on the excitation gear each time.

[0085] is the equivalent mass of the piezoelectric cantilever beam, and its calculation method is as follows:

[0086] Let the maximum deflection of the free end of the piezoelectric cantilever beam be delta m . Therefore, the static deflection of the piezoelectric cantilever beam with a length of l m at a distance of x from the origin is:

[0087]

[0088] According to the kinetic energy theorem, the kinetic energy of the whole beam can be written as:

[0089]

[0090] In the formula, rho and m are the linear density and mass of the piezoelectric cantilever beam, respectively. Then the equivalent mass of the piezoelectric cantilever beam during vibration is:

[0091]

[0092] Then the instantaneous stiffness k m of the piezoelectric cantilever beam is:

[0093]

[0094] Δd irepresents the rotation distance of the excitation gear before the ith impact.

[0095] However, experiments show that the stiffness variation characteristics of the piezoelectric energy feedback suspension are nonlinear variation in a single excitation period T1, and the continuous stiffness can be regarded as linear variation. The instantaneous stiffness can be equivalent to the continuous stiffness because the piezoelectric cantilever beam is high-frequency vibration, and the instantaneous stiffness gradually decreases with the attenuation of vibration and the impact force of the excitation gear gradually decreases, so the instantaneous stiffness can also be regarded as linear variation. Therefore, the nonlinear stiffness of the piezoelectric energy feedback suspension can be equivalent to the continuous linear stiffness, and the equivalent stiffness of the piezoelectric cantilever beam is:

[0096]

[0097] In the formula, T s is the compression time of the piezoelectric cantilever beam, d is the tooth pitch of the excitation gear, and n is the number of impacts of the piezoelectric cantilever beam in the excitation period of the piezoelectric cantilever beam.

[0098] It can be seen that when the size parameters and material properties of the excitation gear and the piezoelectric cantilever beam are fixed, the equivalent stiffness k e is affected by the excitation period T1.

[0099] It should be noted that the damping reflects the ability of the suspension to consume energy. Therefore, the damping characteristics of the piezoelectric energy feedback suspension can be tested from the energy point of view.

[0100] In a single excitation period T1, the vibration energy in the piezoelectric energy feedback suspension is first stored by the excitation gear compressing the piezoelectric cantilever beam to convert the vibration energy into the elastic potential energy of the piezoelectric cantilever beam. The bending distance Y0 of the piezoelectric cantilever beam depends on the tooth pitch d of the excitation gear. If the bending of the piezoelectric cantilever beam is regarded as approximately linear variation, then the stored energy, i.e. the potential energy of the piezoelectric cantilever beam, is:

[0101] E s =0.5× k es ×d 2 .

[0102] The upper and lower piezoelectric layers of the piezoelectric cantilever beam are connected to both ends of a fixed resistor through wires. The NI acquisition card is used to measure the voltage across the fixed resistor, and the voltage acquisition program is built in labVIEW on the PC side to measure the output voltage data. The output voltage data of the piezoelectric cantilever beam can be measured at the same time as the vibration displacement is measured, as shown in Figure 5 and Figure 6 .

[0103] The voltage data shows that when the piezoelectric cantilever beam impacts the excitation gear, it instantly increases the amplitude of the output voltage. Therefore, the electrical energy Ep generated during the impact can be calculated:

[0104]

[0105] In the formula, U i R represents the voltage change of the piezoelectric cantilever beam before and after the i-th impact, and R is the resistance of the fixed resistor.

[0106] Based on the total energy W consumed by the piezoelectrically powered suspension during a single excitation cycle T1 sum = E p +E s It can be seen that its damping characteristics are discontinuous. Considering that the piezoelectric cantilever beam vibrates at high frequencies, the discontinuous damping can be equivalent to continuous damping. Furthermore, treating the vibration of the piezoelectric cantilever beam as simple harmonic motion, the equivalent damping of the piezoelectric cantilever beam is derived as follows:

[0107]

[0108] In the formula, N is the number of layers of the piezoelectric cantilever beam. Let be the vibration frequency, T0 be the total time experienced by the piezoelectric cantilever beam during impact, and Y0 be the distance the piezoelectric cantilever beam bends. In this embodiment, Y0 = d.

[0109] It can be seen that when the size parameters and material properties of the piezoelectric cantilever beam are determined, the excitation period T1 will also affect the equivalent damping.

[0110] Based on the same inventive concept, another embodiment of the present invention provides an equivalent stiffness and damping measurement device for a piezoelectrically powered suspension. This device corresponds to the method of the aforementioned embodiment and includes:

[0111] The assembly unit is used to build a test platform, which includes an excitation gear and a stacked piezoelectric cantilever beam. The upper and lower piezoelectric layers of the piezoelectric cantilever beam are respectively connected to the two ends of a fixed resistor.

[0112] The simulation unit is used to simulate the motion process of the gear and piezoelectric cantilever beam when the piezoelectric-powered suspension vibrates through the test platform, obtain the vibration displacement of the free end of the piezoelectric cantilever beam, and measure the voltage signal generated by the piezoelectric cantilever beam during the vibration process.

[0113] The first processing unit is used to obtain the velocity variation curve of the free end of the piezoelectric cantilever beam based on the change of vibration displacement over time.

[0114] The second processing unit is used to plot the voltage change curve of the piezoelectric cantilever beam during the vibration process based on the voltage signal.

[0115] A rigidity calculation unit is configured to obtain continuous rigidity of the piezoelectric cantilever beam, and to obtain equivalent rigidity of the piezoelectric energy feedback suspension based on the continuous rigidity and a velocity change curve.

[0116] A damping calculation unit is configured to obtain equivalent damping of the piezoelectric energy feedback suspension based on the continuous rigidity and a voltage change curve.

[0117] The following is a specific embodiment of the present application.

[0118] In the embodiment, M measurements are performed in total, and the weight of the suspended weight in the i-th measurement is m i The corresponding free end displacement is s i The continuous rigidity of the i-th measurement can be calculated as k i =m i g / s i The average value is obtained, and the continuous rigidity when the excitation gear is pressed is:

[0119]

[0120] The actual data is substituted, and k es =0.03109 N / mm.

[0121] The pitch d of the excitation gear is 7 mm.

[0122] According to the vibration displacement curve, it can be determined that:

[0123] The vibration period T2 of the piezoelectric cantilever beam is about 24 ms, that is, the vibration frequency is about 263.9 rad / s or 42 Hz. The action time Δt of the piezoelectric cantilever beam impacting the excitation gear is about 3 ms each time, the effective impact number is about 6 times, and after the sixth impact, the impact is weak, so the total time T0 of the piezoelectric cantilever beam impacting is about 6*T2=144 ms.

[0124] The mass m of the selected piezoelectric cantilever beam is 10 g, and according to the equivalent mass calculation of the cantilever beam, the equivalent mass of the piezoelectric cantilever beam is 2.36 g. With the help of matlab software, the vibration velocity curve is calculated, the velocity of the free end before and after the impact can be determined, and the formula

[0125]

[0126] The impact force each time can be calculated, and the six impact forces are 1.53 N, 1.28 N, 1.04 N, 0.85 N, 0.67 N, and 0.49 N.

[0127] Assuming the vibration speed of the piezoelectric cantilever beam is 20 mm / s, the entire excitation cycle length T1=350 ms is calculated, subtracting the vibration time, the down time T s =210 ms, the equivalent stiffness k e is calculated as 0.0258 N / mm.

[0128]

[0129] The potential energy of the piezoelectric cantilever beam can be calculated as E s =0.5×k es ×d 2 =0.000762 J, combined with the voltage curve, the resistance R of the fixed resistor is selected as 5 kΩ, according to the formula

[0130]

[0131] The electrical energy generated after each impact can be calculated as: 3.49×10 -4 J, 1.97×10 -4 J, 1.04×10 - 4 J, 5.6×10 -5 J, 2×10 -5 J, 1.6×10 -5 J, and the total electrical energy is 7.42×10 -4 J.

[0132] The total energy W sum consumed is calculated as 0.001504 J, considering the vibration of the piezoelectric cantilever beam as a simple harmonic vibration, the equivalent damping calculation formula can be simplified as follows:

[0133]

[0134] Wherein, the number of piezoelectric cantilever beams N=1, the vibration frequency =263.9 rad / s, the total time T0=144 ms experienced by the piezoelectric cantilever beam, and the distance Y0=d=7 mm of the piezoelectric cantilever beam bending. The equivalent damping c e is calculated as 0.00162 Ns / mm.

[0135] In summary, the present application combines the internal structure characteristics of piezoelectric energy feedback suspension, considers the stiffness and damping characteristics from the aspects of vibration analysis stress and energy conversion, and proposes a measurement method for the stiffness and damping characteristics of the piezoelectric energy feedback suspension. The stiffness and damping characteristics of the piezoelectric energy feedback suspension are nonlinear and discontinuous, and the dynamics characteristics of such suspension are difficult to analyze, which brings difficulties for real vehicle application. According to the high-frequency vibration characteristics of the internal piezoelectric cantilever beam, the present application combines the measured results, proposes an equivalent continuous linear stiffness and damping model, and provides a theoretical basis for the dynamics characteristic analysis and real vehicle application of the piezoelectric energy feedback suspension.

[0136] According to the internal structure and movement process of the suspension, the present application measures the stiffness and damping of the piezoelectric energy feedback suspension, and combines the suspension characteristics to equivalently the nonlinear stiffness and discontinuous damping. The present application has the following advantages:

[0137] 1. By studying the internal structure characteristics of the piezoelectric suspension, based on the action characteristics of the vehicle stiffness and damping, a measurement method for the stiffness and damping of the piezoelectric energy feedback suspension is proposed.

[0138] 2. Based on the high-frequency vibration characteristics of the piezoelectric cantilever beam, the nonlinear stiffness and discontinuous damping of the piezoelectric energy feedback suspension are equivalently converted into continuous linear stiffness and continuous damping for subsequent suspension dynamics characteristic analysis.

[0139] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

Claims

1. A method for measuring the equivalent stiffness and damping of a piezoelectrically powered suspension, characterized in that, include: A test platform is constructed, which includes an excitation gear and a stacked piezoelectric cantilever beam, wherein the upper and lower piezoelectric layers of the piezoelectric cantilever beam are respectively connected to the two ends of a fixed resistor; The test platform simulates the motion of the excitation gear and piezoelectric cantilever beam during the vibration of the piezoelectric-powered suspension, obtains the vibration displacement of the free end of the piezoelectric cantilever beam, and measures the voltage signal generated by the piezoelectric cantilever beam during the vibration process. The velocity variation curve of the free end of the piezoelectric cantilever beam was obtained based on the change of vibration displacement over time. The voltage change curve of the piezoelectric cantilever beam during vibration was plotted based on the voltage signal. The continuous stiffness of the piezoelectric cantilever beam is obtained, and the equivalent stiffness of the piezoelectric energy-feeding suspension is obtained based on the continuous stiffness and velocity variation curve. The equivalent damping of the piezoelectrically fed suspension is obtained based on the continuous stiffness and voltage variation curves. The motion process of the excitation gear and the piezoelectric cantilever beam is a repetition of the following process: One tooth of the excitation gear contacts the piezoelectric cantilever beam and presses it down, causing it to bend; the piezoelectric cantilever beam bends to its limit position; the excitation gear separates from the piezoelectric cantilever beam, and the piezoelectric cantilever beam undergoes high-frequency free vibration; The piezoelectric cantilever beam high-frequency impact excites the next adjacent tooth of the gear; The process of obtaining the continuous stiffness of the piezoelectric cantilever beam includes: A weight is suspended at the free end of a piezoelectric cantilever beam, and the displacement increment at the free end is measured. The mass of the suspended weight is changed, and M measurements are performed. The continuous stiffness of the piezoelectric cantilever beam is calculated as follows: Where, k i =m i g / s i ; In the formula, m i Let s be the mass of the weight in the i-th measurement. i Let i be the free end displacement increment of the i-th measurement. k es denoted as , where is the continuous stiffness of the piezoelectric cantilever beam, and g is the acceleration due to gravity.

2. The method for measuring the equivalent stiffness and damping of a piezoelectrically powered suspension according to claim 1, characterized in that, The process of obtaining the equivalent stiffness of the piezoelectrically fed suspension based on the continuous stiffness and velocity variation curve includes: Based on the velocity change curve, the impact force of each impact of the piezoelectric cantilever beam, the pressing time of the piezoelectric cantilever beam, the excitation cycle, and the action time of the excitation gear for each impact of the piezoelectric cantilever beam are obtained. Then, the equivalent stiffness of the piezoelectric cantilever beam, i.e., the equivalent stiffness of the piezoelectric energy-feeding suspension, is calculated.

3. The method for measuring the equivalent stiffness and damping of a piezoelectrically fed suspension according to claim 2, characterized in that, The impact force of the i-th impact of the piezoelectric cantilever beam is: For the equivalent mass of the piezoelectric cantilever beam, Let be the velocity change during the i-th impact. The duration of each impact of the piezoelectric cantilever beam on the excitation gear.

4. The method for measuring the equivalent stiffness and damping of a piezoelectrically fed suspension according to claim 3, characterized in that, The equivalent stiffness of the piezoelectric cantilever beam is: In the formula, T s The pressing time of the piezoelectric cantilever beam. T 1 represents the excitation period, d represents the tooth pitch of the excitation gear, and n represents the number of impacts of the piezoelectric cantilever beam within the excitation period.

5. The method for measuring the equivalent stiffness and damping of a piezoelectrically fed suspension according to claim 4, characterized in that, The equivalent damping of the piezoelectrically fed suspension, obtained based on the continuous stiffness and voltage variation curves, includes: The electrical energy generated during the impact of the piezoelectric cantilever beam is obtained from the voltage change curve. The potential energy of the piezoelectric cantilever beam is obtained based on the continuous stiffness. Thus, the total energy of the piezoelectric cantilever beam can be obtained; By treating the vibration of the piezoelectric cantilever beam as simple harmonic motion, the equivalent damping of the piezoelectric cantilever beam is derived, which is the equivalent damping of the piezoelectric energy-feeding suspension.

6. The method for measuring the equivalent stiffness and damping of a piezoelectrically fed suspension according to claim 5, characterized in that, The electrical energy generated by the piezoelectric cantilever beam during the i-th impact is: In the formula, U i R represents the voltage change of the piezoelectric cantilever beam before and after the i-th impact, and R is the resistance of the fixed resistor. The potential energy of the piezoelectric cantilever beam is: E s =0.5× k es ×d 2 ; The total energy of the piezoelectric cantilever beam is: W sum = E p +E s .

7. The method for measuring the equivalent stiffness and damping of a piezoelectrically fed suspension according to claim 6, characterized in that, The equivalent damping of the piezoelectric cantilever beam is: In the formula, N is the number of layers of the piezoelectric cantilever beam. Where is the vibration frequency, T0 is the total time experienced by the piezoelectric cantilever beam during impact, and Y0 is the distance the piezoelectric cantilever beam bends.

8. A device for measuring the equivalent stiffness and damping of a piezoelectrically powered suspension, characterized in that, include: A construction unit is used to construct a test platform, which includes an excitation gear and a stacked piezoelectric cantilever beam. The upper and lower piezoelectric layers of the piezoelectric cantilever beam are respectively connected to the two ends of a fixed resistor. The simulation unit is used to simulate the motion process of the gear and piezoelectric cantilever beam when the piezoelectric-powered suspension vibrates through the test platform, obtain the vibration displacement of the free end of the piezoelectric cantilever beam, and measure the voltage signal generated by the piezoelectric cantilever beam during the vibration process. The first processing unit is used to obtain the velocity variation curve of the free end of the piezoelectric cantilever beam based on the change of vibration displacement over time. The second processing unit is used to plot the voltage change curve of the piezoelectric cantilever beam during the vibration process based on the voltage signal. The stiffness calculation unit is used to obtain the continuous stiffness of the piezoelectric cantilever beam, and to obtain the equivalent stiffness of the piezoelectric energy-feeding suspension based on the continuous stiffness and the velocity variation curve. A damping calculation unit is used to obtain the equivalent damping of the piezoelectrically fed suspension based on the continuous stiffness and voltage change curves. The motion process of the excitation gear and the piezoelectric cantilever beam is a repetition of the following process: One tooth of the excitation gear contacts the piezoelectric cantilever beam and presses it down, causing it to bend; the piezoelectric cantilever beam bends to its limit position; the excitation gear separates from the piezoelectric cantilever beam, and the piezoelectric cantilever beam undergoes high-frequency free vibration; The piezoelectric cantilever beam high-frequency impact excites the next adjacent tooth of the gear; The process of obtaining the continuous stiffness of the piezoelectric cantilever beam includes: A weight is suspended at the free end of a piezoelectric cantilever beam, and the displacement increment at the free end is measured. The mass of the suspended weight is changed, and M measurements are performed. The continuous stiffness of the piezoelectric cantilever beam is calculated as follows: Where, k i =m i g / s i ; In the formula, m i Let s be the mass of the weight in the i-th measurement. i Let i be the free end displacement increment of the i-th measurement. k es denoted as , where is the continuous stiffness of the piezoelectric cantilever beam, and g is the acceleration due to gravity.

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