阅读说明：本技术 一种基于形状记忆合金的汽车结构变刚度装置及其控制方法 (Shape memory alloy-based automobile structure rigidity changing device and control method thereof ) 是由 沈传亮 郑成峰 高振海 胡艺博 杜英辰 张山 徐孝东 石博文 安孝文 于 2019-10-18 设计创作，主要内容包括：本发明公开一种基于形状记忆合金的汽车结构变刚度装置,包括：车身振动信号采集器,其分布在汽车的车身结构板件上；以及汽车速度信号采集器,其安装在汽车的车辆变速器中；数据处理前端,其与所述车身振动信号采集器和所述汽车速度信号采集器相连接；中央控制单元,其包括输入端和输出端,所述输入端与所述数据处理前端相连接；功率输出单元,其与所述中央控制单元的输出端相连接；形状记忆合金丝,其与所述功率输出单元相连接,并且所述形状记忆合金丝安装在汽车的车身结构板件上。本发明还提供一种基于形状记忆合金的汽车结构变刚度装置的控制方法,能够根据不同的路况确定车辆的共振频率,更准确的避免车辆发生共振的可能。(The invention discloses a shape memory alloy-based automobile structure rigidity changing device, which comprises: the vehicle body vibration signal collector is distributed on a vehicle body structure plate of the automobile; and a vehicle speed signal collector installed in a vehicle transmission of the vehicle; the data processing front end is connected with the vehicle body vibration signal collector and the vehicle speed signal collector; the central control unit comprises an input end and an output end, and the input end is connected with the data processing front end; the power output unit is connected with the output end of the central control unit; a shape memory alloy wire connected with the power output unit and mounted on a body structure panel of an automobile. The invention also provides a control method of the automobile structure variable stiffness device based on the shape memory alloy, which can determine the resonance frequency of the automobile according to different road conditions and more accurately avoid the possibility of the resonance of the automobile.)

1. A shape memory alloy-based automobile structure rigidity changing device is characterized by comprising:

the vehicle body vibration signal collector is distributed on a vehicle body structure plate of the vehicle and is used for monitoring the vibration frequency of the vehicle in real time; and

the automobile speed signal collector is arranged in a vehicle transmission of an automobile and used for monitoring the running speed and the running acceleration of the automobile;

the engine speed signal collector is arranged on an internal flywheel of an engine of the automobile and is used for monitoring the engine speed of the automobile and the angle position of a crankshaft of the automobile;

the data processing front end is a processing unit with the capacity of signal mode-electricity conversion and is connected with the vehicle body vibration signal collector, the automobile speed signal collector and the engine rotating speed signal collector;

the central control unit comprises an input end and an output end, and the input end is connected with the data processing front end;

a power output unit connected with the output end;

a shape memory alloy wire connected with the power output unit and mounted on a body structure panel of an automobile.

2. The shape memory alloy-based automotive structural stiffening device of claim 1, wherein the shape memory alloy wire is connected to the automotive body structure panel by means of an insulated joint.

3. The shape memory alloy-based structural stiffening apparatus for automobiles according to claim 2 wherein said structural panel of the automobile body is a thin-walled panel structure of the automobile body and a beam structure of the automobile body.

4. The shape memory alloy-based automotive structural stiffening device of claim 3, wherein the length of the shape memory alloy wire is no more than half the maximum length of each side of the body structure panel to which it is attached.

5. The shape memory alloy-based automotive structural stiffening device of claim 4, wherein the shape memory alloy material is one or more of a NiTi shape memory alloy wire, a copper-based shape memory alloy wire, and an iron-based shape memory alloy wire.

6. A method for controlling a shape memory alloy based variable stiffness device for an automobile structure, which uses the shape memory alloy based variable stiffness device for an automobile structure according to any one of claims 1 to 5, and is characterized by comprising the following steps:

step one, acquiring real-time vibration frequency of an automobile, real-time speed of the automobile and real-time engine rotating speed of the automobile in the driving process of the automobile;

step two, when the difference value of the real-time vibration frequency of the automobile and the threshold value of the resonance frequency is larger than 5% of the threshold value of the resonance frequency, when the difference value of the real-time speed of the automobile and the threshold value of the speed of the automobile is larger than 5% of the threshold value of the speed of the automobile and when the difference value of the real-time engine speed of the automobile and the threshold value of the engine speed of the automobile is larger than 5% of the engine speed, judging that the automobile cannot resonate under the current working;

when the difference value of the real-time vibration frequency and the threshold value of the resonance frequency reaches 3% -5% of the threshold value of the resonance frequency, the difference value of the real-time speed of the automobile and the threshold value of the speed of the automobile reaches 3% -5% of the threshold value of the speed of the automobile, and the difference value of the real-time engine speed of the automobile and the threshold value of the engine speed reaches 3% -5% of the threshold value of the engine speed, the automobile is judged to be in resonance under the current working condition;

and step three, judging that the automobile resonates under the current working condition, starting the power output unit by the central control unit, electrifying the shape memory alloy wire, and further controlling the integral rigidity and the inherent frequency of the automobile structure.

7. The method for controlling a variable stiffness device of a vehicle structure based on shape memory alloy according to claim 6, wherein in the second step, the vehicle speed threshold is a vehicle speed at which resonance occurs during driving measured by simulating the vehicle;

the engine speed threshold value is used for measuring the engine speed which generates resonance in the running process through the simulated automobile.

8. The method for controlling the variable rigidity device of the automobile structure based on the shape memory alloy as claimed in claim 7, wherein in the second step, the resonant frequency threshold of the automobile is satisfied under the road condition:

in the formula (f)_w1Is the resonant frequency threshold of the automobile under the road condition, M is the mass of the automobile, g is the gravity acceleration, K is the balance coefficient of the resonant frequency, v_pSpeed of the vehicle for resonance, n_tThe engine speed is the resonance of the automobile, s is the length of the automobile body, d is the width of the automobile body, and h is the height of the automobile body.

9. The method for controlling a variable stiffness device of an automobile structure based on shape memory alloy according to claim 8, wherein in the second step, the resonant frequency threshold of the automobile is satisfied under off-road conditions:

in the formula (f)_w2Is the resonant frequency threshold of the automobile under the cross-country road condition, beta is the toe angle in the front wheel of the automobile tire, xi is the road gradient, j_cIs the rolling resistance of the vehicle tire.

10. The method for controlling a variable stiffness device of an automobile structure based on shape memory alloy according to claim 9, wherein the road surface gradient satisfies the following conditions:

wherein tau is the included angle between the running road surface of the vehicle and the horizontal plane.

Technical Field

The invention relates to the technical field of automobile riding comfort, in particular to an automobile structure variable stiffness device based on shape memory alloy and a control method thereof.

Background

With the improvement of living standard of people, the automobile keeping quantity is higher and higher, and the riding comfort of drivers and passengers of the automobiles is more important. In the driving process of an automobile, in order to ensure riding comfort, the resonance of an automobile body structure and external input vibration is required to be avoided as much as possible.

Vibration is an important problem commonly existing in engineering, and in the driving process of an automobile, different vibrations can be generated by parts such as a crankshaft flywheel set in an engine and wheels and jolts in driving caused by uneven road surfaces. Frequency is one of the important indicators describing the vibration characteristics, and if a device is excited and the excitation frequency is close to the natural frequency of the device, the amplitude of the device reaches a large value, which is called resonance. The factors influencing the magnitude of the natural frequency of the structure are the mass and the rigidity of the structure, and when the mass of a structure is not changed or the change of the mass is negligible, the change of the rigidity can directly influence the change of the natural frequency of the structure.

As a typical intelligent material, the shape memory alloy has properties such as shape memory characteristics, superelasticity, good fatigue resistance, and the like, and is widely applied to many fields. Because of the shape memory property, when the shape memory alloy wire is heated and the heating temperature exceeds a certain value, the shape memory alloy wire can generate large restoring force, thereby changing the rigidity property of the structure.

The existing structural vibration suppression technology mostly adopts materials with large damping ratio to change the structural rigidity or redesigns the structure to achieve the purpose of suppressing the vibration, and the technical methods inevitably generate larger additional mass for an automobile device and need larger energy input, which is not in accordance with the aim of pursuing the lightweight of the automobile in modern automobile engineering. Compared with the prior art, the advantage of using the shape memory alloy to suppress vibration is that the mass of the shape memory alloy wire is small, the mass of the whole set of rigidity changing devices is small, and the whole set of rigidity changing devices can be acted only by inputting current to the shape memory alloy wire, so that the additional mass and the energy input generated to the automobile device are small.

Disclosure of Invention

The invention aims to design and develop a shape memory alloy-based automobile structure rigidity changing device, wherein a central control unit controls a power output unit to electrify a shape memory alloy wire to generate temperature load, the shape memory alloy wire is heated to generate restoring force, the rigidity characteristic of the automobile structure device is changed, and the inherent frequency of an automobile body structure is changed along with the rigidity change. Therefore, the integral natural frequency of the automobile avoids the original resonance area, and the aims of inhibiting the structural vibration and improving the riding comfort of a driver and passengers are fulfilled.

The invention also aims to design and develop a control method of the automobile structure variable stiffness device based on the shape memory alloy, which can accurately control the time for starting the device according to different road conditions, and better avoid the possibility of resonance of the automobile.

The technical scheme provided by the invention is as follows:

a shape memory alloy-based automotive structural variable stiffness device, comprising:

the vehicle body vibration signal collector is distributed on a vehicle body structure plate of the vehicle and is used for monitoring the vibration frequency of the vehicle in real time; and

the automobile speed signal collector is arranged in a vehicle transmission of an automobile and used for monitoring the running speed and the running acceleration of the automobile;

the engine speed signal collector is arranged on an internal flywheel of an engine of the automobile and is used for monitoring the engine speed of the automobile and the angle position of a crankshaft of the automobile;

the data processing front end is a processing unit with the capacity of signal mode-electricity conversion and is connected with the vehicle body vibration signal collector, the automobile speed signal collector and the engine rotating speed signal collector;

the central control unit comprises an input end and an output end, and the input end is connected with the data processing front end;

a power output unit connected with the output end;

a shape memory alloy wire connected with the power output unit and mounted on a body structure panel of an automobile.

Preferably, the shape memory alloy wire is connected to the body structure panel of the automobile by means of an insulation bond.

Preferably, the vehicle body structural panel is a vehicle body thin-wall panel structure and a vehicle body beam structure.

Preferably, the length of the shape memory alloy wire is no more than half the maximum length of each side of the vehicle body structure panel to which it is attached.

Preferably, the shape memory alloy material is one or more of a NiTi shape memory alloy wire, a copper-based shape memory alloy wire and an iron-based shape memory alloy wire.

A control method of an automobile structure variable stiffness device based on shape memory alloy comprises the following steps:

step one, acquiring real-time vibration frequency of an automobile, real-time speed of the automobile and real-time engine rotating speed of the automobile in the driving process of the automobile;

step two, when the difference value of the real-time vibration frequency of the automobile and the threshold value of the resonance frequency is larger than 5% of the threshold value of the resonance frequency, when the difference value of the real-time speed of the automobile and the threshold value of the speed of the automobile is larger than 5% of the threshold value of the speed of the automobile and when the difference value of the real-time engine speed of the automobile and the threshold value of the engine speed of the automobile is larger than 5% of the engine speed, judging that the automobile cannot resonate under the current working;

if the difference value between the real-time vibration frequency and the threshold value of the resonance frequency reaches 3% -5% of the threshold value of the resonance frequency, the difference value between the real-time speed of the automobile and the threshold value of the speed of the automobile reaches 3% -5% of the threshold value of the speed of the automobile, and the difference value between the real-time engine speed of the automobile and the threshold value of the engine speed reaches 3% -5% of the threshold value of the engine speed, the automobile is judged to be in resonance under the current working condition;

and step three, judging that the automobile resonates under the current working condition, starting the power output unit by the central control unit, electrifying the shape memory alloy wire, and further controlling the integral rigidity and the inherent frequency of the automobile structure.

Preferably, in the second step, the vehicle speed threshold is a vehicle speed at which resonance occurs during driving, which is measured by simulating the automobile;

the engine speed threshold value is used for measuring the engine speed which generates resonance in the running process through the simulated automobile.

Preferably, in step two, the resonant frequency threshold of the vehicle meets the following requirements under the road condition:

in the formula (f)_w1Is the resonant frequency threshold of the automobile under the road condition, M is the mass of the automobile, g is the gravity acceleration, K is the balance coefficient of the resonant frequency, v_pSpeed of the vehicle for resonance, n_tThe engine speed is the resonance of the automobile, s is the length of the automobile body, d is the width of the automobile body, and h is the height of the automobile body.

Preferably, in step two, the resonant frequency threshold of the vehicle is satisfied under off-road conditions:

in the formula (f)_w2Is the resonant frequency threshold of the automobile under the cross-country road condition, beta is the toe angle in the front wheel of the automobile tire, xi is the road gradient, j_cIs the rolling resistance of a vehicle tire;

preferably, the road surface gradient satisfies:

wherein tau is the included angle between the running road surface of the vehicle and the horizontal plane.

The invention has the following beneficial effects:

(1) the invention provides an automobile structure variable stiffness device based on shape memory alloy, which is an automobile structure intelligent device based on shape memory alloy. The advantage is novel technique, and the device additional mass that produces and input energy are less and can effectively avoid the car in-process to take place resonance phenomenon, improve and take the travelling comfort.

(2) The control method of the automobile structure variable stiffness device based on the shape memory alloy can determine the resonance frequency, the speed and the engine speed of the automobile according to the specific road condition, and more accurately prevent the possibility of the resonance of the automobile.

Drawings

FIG. 1 is a schematic structural diagram of a shape memory alloy-based automobile structural rigidity changing device according to the present invention.

FIG. 2 is a schematic diagram of the starting process of the shape memory alloy-based automobile structure rigidity changing device.

FIG. 3 is a schematic view of a connection structure of the shape memory alloy wire and a vehicle body structural panel according to the present invention.

FIG. 4 is a schematic view of another connection structure of the shape memory alloy wire and a vehicle body structural panel according to the present invention.

FIG. 5 is a schematic view of an arrangement of shape memory alloy wires according to the present invention.

FIG. 6 is a schematic view of another arrangement of shape memory alloy wires according to the present invention.

Fig. 7 is a schematic diagram of modal analysis according to the present invention.

Fig. 8 is a schematic structural view of the shape memory alloy wire installed according to modal analysis according to the present invention.

Detailed Description

The present invention is described in further detail below in order to enable those skilled in the art to practice the invention with reference to the description.

The invention provides a shape memory alloy-based automobile structure rigidity changing device, which is characterized in that a shape memory alloy wire arranged on a structural plate of an automobile body is electrified and heated to generate restoring force, so that the structural rigidity and the natural frequency of the automobile body are changed, resonance is avoided in the driving process, and the purpose of inhibiting structural vibration is achieved.

As shown in fig. 1, the overall structural schematic diagram of the shape memory alloy-based automobile structural rigidity changing device of the present invention includes: the automobile body structure comprises a body structure plate 110, a shape memory alloy wire 120, a data processing front end 130, a central control unit 140, a power output unit 150, a body vibration signal collector 160, an automobile speed signal collector 170, an engine rotating speed signal collector 180 and a lead wire 190.

The body structure panel 110 of the automobile is a thin-wall body structure and a body beam structure which are easy to cause vibration, the body structure panel 110 is a body manufacturing steel plate, and preferably, the body structure panel 110 is a composite material panel; the vehicle body vibration signal collector 160 is distributed in each easily-vibrated area of the vehicle body, the vehicle body vibration signal collector 160 can collect real-time vehicle vibration signals, and the vehicle body vibration signal collector 160 is connected with the data processing front end 130 through a wire 150, preferably, the vehicle body vibration signal collector 160 is a patch type vibration sensor; the automobile speed signal collector 170 is a sensor capable of testing data such as automobile running speed, acceleration and the like, and the automobile speed signal collector 170 is connected with the data processing front end 130; in this embodiment, the automobile speed signal collector 170 and the engine speed signal collector 180 are existing sensors in the existing automobile circuit structure, preferably, the automobile speed signal collector 170 is a doppler speed sensor, and the engine speed signal collector 180 is a hall sensor; the data processing front end 130 is a processing unit capable of performing mode-to-electricity conversion on a vibration signal; the central control unit 140 includes an input end and an output end, the input end is connected to the data processing front end 130, and the output end is connected to the regulated dc power output unit 150 with power output function through a wire 190, so as to transmit electric signals and current; the voltage-stabilizing direct-current power output unit is connected with the shape memory alloy wire 120 through a conducting wire 190, the shape memory alloy wire 120 is connected with a specific position on the vehicle body structure plate 110 in an insulation joint mode, and the connection point is arranged at the position, most prone to vibration, of each area of the vehicle body structure plate 110.

The shape memory alloy wire 120 is made of NiTi shape memory alloy wire or copper-based shape memory alloy wire or iron-based shape memory alloy wire, the shape memory alloy wire 120 is made of one or a combination of multiple materials, and multiple layers of materials can be stacked according to actual needs.

The diameter of the shape memory alloy wire can be 0.5MM, 0.75MM, 1.0MM and the like, and the shape memory alloy wire with the corresponding diameter can be selected according to actual needs.

The shape memory alloy wire 120 should be in a state that each part has no temperature difference, no stress action and certain pre-strain, and the pre-strain cannot exceed the maximum recoverable strain of the used shape memory alloy wire 120, so that the pre-strain is set to be 3% -5% and not more than 8%.

In the present embodiment, as shown in fig. 3, the shape memory alloy wire 120 is connected to the vehicle body structure panel 110 through a nylon guide post 121, the nylon guide post 121 has high temperature resistance and insulation properties, and can prevent the shape memory alloy wire 120 from deforming due to electricity and heat generation, when the nylon guide post 121 is used, the nylon guide post 121 is connected to the vehicle body structure panel 110, and the shape memory alloy wire 120 is connected to the nylon guide post 121 in a fastening manner of a plastic screw 122, and preferably, can be fixed by welding, because the shape memory alloy wire 120 generates a large restoring force when it changes phase, at least two ends and a midpoint of the shape memory alloy wire should be completely constrained on the nylon guide post 121.

In another embodiment, as shown in fig. 4, which is a schematic structural view of the shape memory alloy wire 120 being connected to the vehicle body structure panel 110 by the adhesive 210, the shape memory alloy wire 120 is adhered to the vehicle body structure panel 110 at the selected mounting point by using a special adhesive 210, so that the shape memory alloy wire 120 is fixed to the vehicle body structure panel 110, and at least two ends and the middle point of the shape memory alloy wire 120 should be completely restrained because the shape memory alloy wire 120 generates a large restoring force when it is transformed into a phase.

In the present embodiment, as shown in fig. 5, which is a schematic diagram of an arrangement manner of the shape memory alloy wires 120, when a multi-wire arrangement manner is used, the arrangement manner of the shape memory alloy wires 120 may be that the wires are arranged in parallel, and the shape memory alloy wires are connected in series, so that a good stiffness changing effect can be obtained, and the working efficiency of the power output unit can also be improved.

As shown in fig. 6, which is another schematic diagram of the arrangement of the shape memory alloy wires 120, when a plurality of wires are used for arrangement, if the vibration characteristics of a certain vibration region of the body structure panel 110 of the automobile are special, the arrangement of the shape memory alloy wires 120 can be optimized according to the specific vibration condition of the region.

When the shape memory alloy wires 120 are installed, modal analysis is firstly carried out on the region, and the shape memory alloy wires 120 can be used for connecting two closest peak points in each order of modes during installation, so that a better vibration suppression effect can be obtained under the condition that the same number of shape memory alloy wires 120 are used.

In another embodiment, as shown in fig. 7, the structural plate 110 in the hood region of the automobile is selected and subjected to modal analysis to obtain modal shapes of each order: the first-order mode peak point 210, the two peak points 220 of the second-order mode and the two peak points 230 of the third-order mode should be connected to the peak points of the respective order mode when the shape memory alloy wire 120 is arranged, and the specific arrangement manner of the shape memory alloy wire 120 is shown in fig. 8.

As shown in fig. 2, the invention further provides a method for controlling the shape memory alloy-based automobile structure variable stiffness device, and the method using the shape memory alloy-based automobile structure variable stiffness device comprises the following steps:

the method comprises the following steps: under experimental conditions, carrying out automobile running simulation working condition test on an automobile simplified automobile model automobile to obtain a speed threshold value of the automobile when the vibration frequency is at a peak value and an engine speed threshold value of the automobile when the vibration frequency is at the peak value, and obtaining a resonance frequency threshold value of the automobile, and inputting the speed threshold value, the engine speed threshold value and the resonance frequency threshold value into a central control unit;

step two: in the driving process of the automobile, acquiring the real-time vibration frequency of the automobile, the real-time speed of the automobile and the real-time engine rotating speed of the automobile and inputting the real-time vibration frequency, the real-time speed and the real-time engine rotating speed of the automobile into a data processing front end, wherein the data processing front end transmits signals to the central control unit and compares the signals with the resonant frequency threshold rate, the speed threshold and the engine rotating speed threshold of the automobile:

when the difference value between the real-time vibration frequency of the automobile and the threshold value of the resonant frequency is greater than 5% of the threshold value of the resonant frequency, when the difference value between the real-time speed of the automobile and the threshold value of the speed of the automobile is greater than 5% of the threshold value of the speed of the automobile and when the difference value between the real-time engine speed of the automobile and the threshold value of the engine speed of the automobile is greater than 5% of the engine speed, judging that the automobile does not resonate under the current;

if the difference value between the real-time vibration frequency and the threshold value of the resonance frequency reaches 3% -5% of the threshold value of the resonance frequency, the difference value between the real-time speed of the automobile and the threshold value of the speed of the automobile reaches 3% -5% of the threshold value of the speed of the automobile, and the difference value between the real-time engine speed of the automobile and the threshold value of the engine speed reaches 3% -5% of the threshold value of the engine speed, the automobile is judged to be in resonance under the current working condition;

step three: and judging that the automobile resonates under the current working condition, starting the power output unit by the central control unit, electrifying the shape memory alloy wire, and further controlling the integral rigidity and the inherent frequency of the automobile structure.

In the second step, the real-time vibration condition of the automobile is detected through an automobile body vibration signal collector which is distributed in an area where the automobile body structure is easy to vibrate to obtain the vibration characteristic of the automobile body, particularly the vibration frequency,

in the second step, a decoder arranged in the data processing front end inputs the vibration signal into the central control unit through digital signal after analog-to-digital conversion, and the central control unit monitors and processes the vibration signal after receiving the signal by using the built-in vibration test software, and continuously compares the vibration signal with the previously input natural frequency value of the automobile body structure of the automobile to judge whether to start the device.

In the second step, the vehicle speed threshold is the vehicle speed which is measured by the simulated automobile and generates resonance in the driving process; the engine speed threshold value is used for measuring the engine speed which generates resonance in the running process through the simulated automobile.

In step two, the resonant frequency threshold of the vehicle is divided into two modes according to different road conditions: the first mode is a highway mode, and the vibration input caused by external environments such as uneven road surfaces is smaller than the vibration caused by the automobile in the driving process of the automobile, so that the driving speed of the automobile and the rotating speed of an engine are close to a set critical value firstly; the second mode is an off-road mode, for example, under extremely uneven road conditions, the vibration input from the outside will approach the set critical value first; therefore, the two starting modes are set to be in parallel connection, namely when any one of the running speed of the automobile, the rotating speed of the engine and the real-time vibration frequency of the automobile approaches to the set critical value, the automobile variable stiffness system is started.

In highway mode, the resonant frequency threshold of the car satisfies:

in the formula (f)_w1Is the resonant frequency threshold of the automobile under the road condition, M is the mass of the automobile, g is the gravity acceleration, K is the balance coefficient of the resonant frequency, v_pSpeed of the vehicle for resonance, n_tThe engine speed is the resonance of the automobile, s is the length of the automobile body, d is the width of the automobile body, and h is the height of the automobile body.

In the off-road mode, the resonant frequency threshold of the vehicle satisfies:

in the formula, beta is the toe angle in the front wheel of the automobile tire, xi is the road surface gradient, j_cIs the rolling resistance of the vehicle tire.

Wherein the road surface gradient satisfies:

wherein tau is the included angle between the running road surface of the vehicle and the horizontal plane.

In the automobile variable stiffness system, after the central control unit sends out the starting signal, the power output unit is started to electrify the shape memory alloy wire, the shape memory alloy wire generates resistance heat when electrified, and the shape memory effect and the restoring force are generated after the shape memory alloy wire is heated, so that the integral stiffness of the structure is changed, the resonance frequency of an automobile is increased, and the automobile is prevented from resonating.

In the automobile structure rigidity changing device, the heating temperature of the shape memory alloy wire is higher than the austenite complete phase transition temperature of the used shape memory alloy wire, so that the shape memory alloy wire generates enough restoring force and the effect of changing the structure rigidity is more obvious.

In another embodiment, a simplified model is made for a passenger vehicle, the model is subjected to a driving test under laboratory conditions, the driving speed of the vehicle which generates resonance is determined to be 150km/h, the rotating speed of an engine is determined to be 3000r/min, and the resonance frequency of the vehicle is obtained to be 7Hz in a highway mode; the automobile structure rigidity changing device is arranged on the passenger automobile, a NiTi-based shape memory alloy wire is selected, and the complete phase change temperature of the NiTi-based shape memory alloy wire is 90 degrees; the adopted power output unit is a constant current power supply, and the input current of the power output unit is 6A; when the variable stiffness device is started to work, the electrifying time of the shape memory alloy wire is 3-6S, and the complete phase transition temperature of the shape memory alloy wire is 90 degrees. In the running process of the vehicle, when the vehicle speed signal collector detects that the running speed of the vehicle reaches 143-.

The invention relates to a shape memory alloy-based automobile structure variable stiffness device, which is an automobile structure intelligent device based on shape memory alloy, wherein when an external excitation frequency is closer to the natural frequency of an automobile body structure or reaches a certain speed and engine speed, a power output unit is controlled by a central control unit to electrify a shape memory alloy wire to generate a temperature load, the shape memory alloy wire is heated to generate a restoring force, the stiffness characteristic of the intelligent structure device is changed, and the natural frequency of the automobile body structure is changed along with the change of the stiffness, so that the natural frequency of the whole automobile avoids the original resonance region, the aims of inhibiting the structural vibration and improving the riding comfort of a driver and passengers are fulfilled, and the additional mass and the input energy generated on the whole automobile are smaller.

The control method of the automobile structure variable stiffness device based on the shape memory alloy, which is designed and developed by the invention, can more accurately prevent the possibility of the automobile resonance by detecting the resonance frequency, the speed when the automobile resonates and the engine speed when the automobile resonates under different road conditions.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the embodiments shown and described without departing from the generic concept as defined by the claims and their equivalents.