CN118054630A - Nonlinear vibration energy collecting system capable of jumping in energy level in full hysteresis range - Google Patents
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Abstract
The invention discloses a nonlinear vibration energy collecting system capable of jumping at the energy level in a full hysteresis range, which belongs to the field of vibration energy collection and comprises the following components: a nonlinear electromagnetic vibration energy collector and an electric energy conversion device; the nonlinear electromagnetic vibration energy collector is used for collecting energy in the environment; the energy conversion device forcedly changes the energy level by means of smoothly modulating the viscous damping and stiffness coefficient of the mechanical system when the energy collector works at a low energy level, so that the energy collector continuously works at the highest energy level. The nonlinear vibration energy collecting system capable of jumping in the energy level in the full hysteresis range can continuously and stably work in a high-energy-level output state. Compared with the traditional linear vibration energy collecting system, the system has higher output power and bandwidth. In addition, the system of the invention has high integration level, can independently operate, and can be applied to various vibration environments.
Description
Technical Field
The invention belongs to the field of vibration energy collection, and particularly relates to a nonlinear vibration energy collection system capable of jumping in the energy level of a full hysteresis range.
Background
The vibration energy collection technology aims at utilizing vibration energy widely existing in the environment to generate electric energy and supplying power for the low-power consumption wireless sensor network so as to reduce or even replace the use of a traditional battery and reduce the maintenance cost of the wireless sensor network. The current vibration energy collection methods mainly comprise electromagnetic type, piezoelectric type, electrostatic type and the like. The electromagnetic vibration energy collection method is a vibration energy collection method with high power density and high reliability, and the electromagnetic vibration energy collection method converts vibration energy into electric energy by means of relative motion of the magnet and the coil.
The Nonlinear Vibration Energy Harvester (NVEH) serves as one type of electromagnetic vibration energy harvesting, and can improve the working bandwidth of the vibration energy harvester. NVEH have nonlinear spring restoring forces such as attractive or repulsive forces, nonlinear tensile forces, and nonlinear forces resulting from asymmetric geometries, etc. The nonlinear restoring force causes the vibrator to exhibit multiple stable responses in certain frequency bands, thereby producing multiple output tracks with different energy levels. And the specific track on which the vibrator is operating is completely determined by its initial conditions. If the vibrator is operating on a low energy track exactly, the output power will be greatly reduced. Therefore, the premise of using the nonlinear restoring force characteristic to improve the energy collection bandwidth is to ensure that the vibrator can continuously and stably operate on a high-energy track. That is, when the vibrator is just operating in a low energy state, an energy jump technique is required to force NVEH to transfer from the low energy track to the stable highest energy track.
Several energy level jump techniques have been proposed, such as using high voltage source stimulation, stiffness modulation, deflection modulation, etc. However, when the vibrator approaches the highest vibration state, the currently existing method still cannot achieve reliable energy level jump, that is, the currently existing method cannot achieve reliable energy level jump within the full hysteresis range. In addition, the existing method needs to be connected with a high-voltage power supply, needs manual operation or needs auxiliary equipment such as a laser displacement sensor, so that the existing low-power NVEH system cannot operate independently.
Disclosure of Invention
Aiming at the defects and improvement demands of the prior art, the invention provides a nonlinear vibration energy collecting system capable of jumping energy levels in a full hysteresis range, and aims to enable the nonlinear vibration energy collecting system to realize energy level jumping in the full hysteresis range and independently operate without manual operation and auxiliary equipment.
To achieve the above object, according to a first aspect of the present invention, there is provided a nonlinear vibration energy harvesting system for energy level jump in a full hysteresis range, comprising: a nonlinear electromagnetic vibration energy collector and an electric energy conversion device;
The nonlinear electromagnetic vibration energy collector comprises a main coil and an auxiliary coil; the auxiliary coil is overlapped and wound on the surface of the main coil;
the electric energy conversion device comprises an H-bridge AC-DC circuit, a reference signal operation circuit, a PWM generating circuit, a viscous damping coefficient and a rigidity coefficient control module;
the main coil is connected with the H-bridge AC-DC circuit so as to charge a load;
The reference signal operation circuit is used for respectively performing proportional operation and integral operation on the output voltage of the auxiliary coil so as to obtain a voltage reference signal v ref of the H-bridge AC-DC circuit;
The PWM generation circuit is used for generating a PWM signal according to the voltage reference signal v ref to control the H-bridge AC-DC circuit so as to enable the output voltage of the H-bridge AC-DC circuit to be consistent with the voltage reference signal v ref;
The viscous damping coefficient and stiffness coefficient control module is used for adjusting the gain of the proportional operation and the gain of the integral operation so as to correspondingly change the viscous damping coefficient c and the linear stiffness coefficient k 1 of the nonlinear electromagnetic vibration energy collector, thereby realizing energy level jump or energy collection in a full hysteresis range.
Further, the viscous damping coefficient and stiffness coefficient control module realizes energy level jump in a full hysteresis range, and specifically includes:
Adjusting the proportional operation Gain Gain P_EH and the integral operation Gain Gain I_EH of the nonlinear electromagnetic vibration energy collector to correspondingly change the viscous damping coefficient c and the linear stiffness coefficient k 1, and taking the critical rising frequency omega u of the nonlinear electromagnetic vibration energy collector as a target that the critical rising frequency omega is larger than or smaller than the environmental vibration frequency omega, so as to obtain the adjusted corresponding gains Gain P_OJ and Gain I_OJ; if the cubic stiffness coefficient k 3 of the nonlinear electromagnetic vibration energy collector is greater than 0, ω u is greater than ω, otherwise ω u＜ω;GainP_EH and Gain I_EH are respectively proportional operation Gain and integral operation Gain corresponding to the nonlinear electromagnetic vibration energy collector working in a low energy level state and in an energy collection mode;
The adjusted gains Gain P_OJ and Gain I_OJ are correspondingly smoothed back to Gain P_EH and Gain I_EH to transition the nonlinear electromagnetic vibration energy harvester to a highest energy state.
Further, in the smoothing callback process, the gain adjusted in each step is as follows:
The Gain P_n is the Gain adjusted in each step in the process of smoothly returning the Gain P_OJ to the Gain P_EH; gain I_n is the Gain adjusted at each step in the process of smoothing Gain I_OJ back to Gain I_EH; n represents the number of steps of smoothing callback gain, n=0, 1,2 … …, and T is a coefficient measuring the degree of smoothing.
Further, the calculation process of Gain I_OJ includes:
If k 3 is more than 0, solving an inequality omega u is more than omega, and obtaining a critical value of a linear stiffness coefficient k 1' after gain adjustment according to a functional relation among a critical rising frequency omega u, an environment vibration frequency omega and the linear stiffness coefficient k 1;
According to the formula Calculating to obtain a critical value Gain I_ Critical of of the integral operation Gain, and then Gain I_OJ＜GainI_ Critical of ; wherein, R c represents the resistance of the main coil, and θ m and θ a are the electromechanical coupling coefficients of the main coil and the auxiliary coil respectively;
If k 3 is less than 0, solving an inequality omega u less than omega, and obtaining a critical value of a linear stiffness coefficient k 1' after gain adjustment according to a functional relation among a critical rising frequency omega u, an environmental vibration frequency omega and the linear stiffness coefficient k 1;
According to the formula Calculating to obtain a critical value Gain I_ Critical of of the integral operation Gain, and then Gain I_OJ＞GainI_ Critical of ;
gain P_OJ is set as: gain P_OJ＝θm/θa.
Further, when the nonlinear electromagnetic vibration energy collector works in the energy collection mode, the calculation modes of the proportional operation Gain P_EH and the integral operation Gain I_EH are as follows:
And taking the main coil output power P EH as a constraint, and according to the relation satisfied among the main coil output power P EH, the proportional operation Gain and the integral operation Gain, blending the proportional operation Gain P_EH and the integral operation Gain I_EH.
Further, when the nonlinear electromagnetic vibration energy collector works in an energy collection mode with equivalent impedance being a pure resistor, the integral operation Gain I_EH =0;
The calculation mode of the proportional operation Gain P_EH is as follows:
Wherein, R load is a preset system equivalent resistance, R c represents a main coil resistance, and θ m and θ a are electromechanical coupling coefficients of the main coil and the auxiliary coil respectively.
Further, the nonlinear electromagnetic vibration energy harvester further comprises: a housing, a nonlinear planar spring, and a magnet;
The nonlinear plane springs are fixed at two ends of the shell, two ends of the magnet are fixed on the nonlinear plane springs through connecting pieces, and the main coil surrounds the upper surface and the lower surface of the magnet and is wound in grooves of the shell.
Further, two upper pipes of the H-bridge AC-DC circuit adopt Pmos pipes, and two lower pipes adopt two Nmos pipes.
Further, the viscous damping coefficient and rigidity coefficient control module is mounted on the intermittently-operated singlechip.
According to a second aspect of the present invention there is provided a method of energy level jump over a full hysteresis range using the non-linear vibration energy harvesting system of any of the first aspects for energy level jump over a full hysteresis range.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
(1) According to the nonlinear vibration energy collecting system capable of jumping at the energy level in the full hysteresis range, the main coil of the nonlinear electromagnetic vibration energy collector is connected with the H-bridge AC-DC circuit so as to charge a load, and power supply of the whole system is provided; the method comprises the steps of overlapping and winding an auxiliary coil on the surface of a main coil of a nonlinear electromagnetic vibration energy collector so as to enable the phases of induced electromotive forces of the main coil and the auxiliary coil to be consistent, respectively carrying out proportional operation and integral operation on the electromotive force information (auxiliary coil output voltage) of the main coil collected by the auxiliary coil, generating reference voltages of an H-bridge AC-DC circuit, and generating corresponding PWM signals to control the H-bridge AC-DC circuit so as to enable the output voltages of the H-bridge AC-DC circuit to be consistent with the voltage reference signals v ref; in the control process, the magnitude and the direction of the output current of the nonlinear electromagnetic vibration energy collector can be controlled by adjusting the proportional gain and the integral gain, so that the viscous damping coefficient and the stiffness coefficient of the energy collector are changed, and the energy collector can be in an outward output power state (energy collection state) or in an energy level jump state. According to the method, the corresponding viscous damping coefficient and the linear stiffness coefficient are independently adjusted through the proportional gain and the integral gain, namely, the viscous damping coefficient is adjusted through the proportional gain, and the linear stiffness coefficient is adjusted through the integral gain, so that the viscous damping coefficient and the linear stiffness coefficient can be randomly adjusted within a certain range, and energy level jump or energy collection within a full hysteresis range can be conveniently realized. In addition, the system of the invention can realize independent operation without manual operation or additional auxiliary equipment.
(2) Further, when the nonlinear electromagnetic vibration energy collector works at a low energy level, the viscous damping coefficient and stiffness coefficient control module designed by the invention adjusts the proportional operation Gain and the integral operation Gain to Gain P_OJ and Gain I_OJ so as to enable the nonlinear electromagnetic vibration energy collector to work to a monostable high energy level state, and the energy level is forcedly changed by smoothly modulating the viscous damping coefficient and stiffness coefficient of the mechanical system, so that the energy collector continuously works at the highest energy level state, and the energy level jump of the full hysteresis range is realized.
(3) Further, the invention designs a specific Gain P_n and Gain I_n which are smoothly adjusted in each step, and by adopting the smoothly adjusted Gain steps, gain smooth callback can be realized so as to enable the nonlinear electromagnetic vibration energy collector to transition to the highest energy level state.
(4) Preferably, two upper tubes of the H-bridge AC-DC circuit adopt Pmos tubes, and two lower tubes adopt two Nmos tubes, so that isolation driving is avoided, and circuit control power consumption is reduced. Meanwhile, the H-bridge AC-DC circuit is connected with the main coil of the nonlinear electromagnetic vibration energy collector, so that the H-bridge AC-DC circuit can utilize self-inductance of the main coil without an additional inductance element.
(5) Preferably, the singlechip is used for controlling the gain of integration and proportional operation, and the singlechip is in a dormant state for most of the time, so that the circuit power consumption can be reduced.
In summary, the nonlinear vibration energy harvesting system of the present invention, which hops across the full hysteresis range, can continue to operate stably in a high level output state. The system of the present invention has a higher output power and bandwidth than conventional linear vibration energy harvesting systems. In addition, the system of the invention has high integration level, can independently operate, and can be applied to various vibration environments.
Drawings
FIG. 1 is a cross-sectional view of a nonlinear electromagnetic vibration energy harvester in accordance with an embodiment of the invention;
FIG. 2 is a graph of the steady-state amplitude-frequency response of nonlinear and linear vibration energy harvesters in an embodiment of the present invention;
FIG. 3 is a block diagram of a dual-purpose energy conversion device for energy level jump and energy harvesting in an embodiment of the present invention;
FIG. 4 is a diagram of the topology of an H-bridge AC-DC circuit in an embodiment of the invention;
fig. 5 is a diagram of a triangular wave generation circuit and PWM generation circuit in an embodiment of the present invention;
FIG. 6 shows the values of the parameter Gain I_OJ under different resistive loads according to an embodiment of the present invention;
FIG. 7 shows the values of the parameter T under different resistance loads according to the embodiment of the present invention;
Fig. 8 is a phase trajectory diagram of a successful implementation of energy level jump at a 53.3Hz vibration frequency in an embodiment of the invention.
The same reference numbers are used throughout the drawings to reference like elements or structures, wherein:
1-nonlinear plane spring, 2-main coil, 3-magnet, 4-auxiliary coil, 5-connecting piece, 6-shell.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The nonlinear vibration energy collecting system capable of jumping in the energy level in the full hysteresis range mainly comprises: a nonlinear electromagnetic vibration energy collector, an energy level jump and energy collection dual-purpose electric energy conversion device;
In particular, as shown in FIG. 1, a nonlinear electromagnetic vibration energy harvester (NVEH) is used to harvest energy in an environment; mainly comprises the following steps: a housing 6, a nonlinear planar spring 1, a magnet 3, a main coil 2 and an auxiliary coil 4; the nonlinear plane spring 1 is fixed at two ends of the shell 6, two ends of the magnet 3 are fixed on the nonlinear plane spring 1 through the connecting piece 5, and vibration is carried out under the drive of the nonlinear plane spring 1; the main coil 2 is wound in the grooves of the shell 6 around the upper surface and the lower surface of the magnet 3, and the auxiliary coil 4 is wound on the surface of the main coil 2 in a overlapping mode, so that the output voltage phases of the main coil 2 and the auxiliary coil 4 are consistent, and the auxiliary coil 4 can acquire the electromotive force information of the main coil 2. The external vibration drives the nonlinear plane spring 1 to vibrate, so that the magnet 3 and the coil generate relative displacement, and electric energy is induced in the coil; the coils are a main coil and an auxiliary coil.
The nonlinear vibration energy harvester of the present invention has a variety of steady states, and if it can continue to operate at the highest output power, will have a greater output power and bandwidth than the linear energy harvester.
In the embodiment of the invention, the housing 6 is made of plastic material and provides support and fixation for the device. The magnet 3 is a cylindrical magnet.
In the embodiment of the invention, the nonlinear planar spring 1 is made of planar metal by cutting, and four corners are fixed by screws, so that the beam of the spring can be bent and stretched when the magnet moves. It can be demonstrated that the spring restoring force due to beam bending is proportional to the first power of displacement; the restoring force due to the stretching of the beam is proportional to the third power of displacement. Therefore, the restoring force of the nonlinear flat spring 1 can be written as:
Fsp＝k1z+k3z3 (1)
Where k 1 and k 3 are the linear and cubic stiffness coefficients, respectively, of the nonlinear planar spring 1, and z is the relative displacement between the magnet and the coil.
Correspondingly, the motion equation of the nonlinear vibration energy collector is:
Wherein m is the mass of the vibrator formed by the magnet and the nonlinear plane spring; c is the viscous damping coefficient of the ambient medium; ω is the ambient vibration frequency; y is the displacement amplitude of the substrate, i.e. the displacement amplitude of the vibrator fixing member.
The working environment of the energy collector is generally not vibrated too much, nor is the relative displacement of the vibrator (relative displacement z between magnet and coil) excessive. Thus, the nonlinear energy collector can be modeled as a typical weak nonlinear dafen system. Further write equation (2) as a standard form:
Where x is the amplitude ratio, ω n is the natural frequency of the system, ζ is the damping ratio, ε is a cubic factor. Their specific definitions are as follows:
In a weakly nonlinear system, ε is a small parameter. Thus, the response of NVEH systems can be considered to be close to that of linear systems. Thus, the main resonance response of equation (3) can be written as:
x＝acos(ωt-β) (5)
Where a and β are the amplitude and phase of the forced vibrational response.
By classical averaging, the forced response of the weak nonlinear dafen system can be obtained as:
Where ω u represents a critical rising frequency and ω d represents a critical falling frequency.
FIG. 2 shows a steady-state amplitude-frequency response curve obtained by solving the above equation. For comparison, the response curves of the same energy harvester under a linear condition of k 3 =0 are also plotted. It can be seen that the frequency response has a stiffening effect, with hysteresis between ω u and ω d. These two critical frequencies can be determined by letting dω/da=0 in equation (6). Under the premise of weak damping, two critical frequencies can be solved as follows:
It is apparent from fig. 2 that NVEH, if able to operate on a high-level track at all times, will have a higher bandwidth and output power than in the linear case. In fig. 2, the half power bandwidth in the nonlinear case is 205% in the linear case.
Specifically, as shown in fig. 3, the energy level jump and energy collection dual-purpose electric energy conversion device includes: an H-bridge AC-DC circuit and an auxiliary coil-based viscous damping and stiffness coefficient control circuit; wherein, the viscous damping and rigidity coefficient control circuit based on the auxiliary coil includes: the device comprises a reference signal operation circuit, a triangular wave generation circuit, a PWM generation circuit, a viscous damping coefficient and a rigidity coefficient control module;
NVEH is connected to an H-bridge AC-DC circuit to charge the load; specifically, a main coil of NVEH is connected with the midpoints of two bridge arms of the H-bridge AC-DC circuit; in the embodiment of the invention, the load is a super capacitor. The super capacitor is stabilized by the voltage stabilizing circuit and then supplies power for the whole system.
The reference signal operation circuit is used for respectively performing proportional operation and integral operation on the output voltage of the auxiliary coil 4 so as to obtain a voltage reference signal v ref of the H-bridge AC-DC circuit;
After the voltage reference signal v ref is compared with the triangular wave signal v tri generated by the triangular wave generating circuit, the voltage reference signal v ref is used as the input of the PWM generating circuit, and four paths of PWM signals are generated by the PWM generating circuit to control a switching tube in the H-bridge AC-DC circuit so that the output voltage of the H-bridge AC-DC circuit is consistent with the voltage reference signal v ref;
The viscous damping coefficient and stiffness coefficient control unit is used for adjusting the Gain P of the proportional operation so as to change the viscous damping coefficient c of NVEH; and adjusting the integrated Gain I to change the linear stiffness coefficient k 1 of NVEH to achieve energy level jump or energy harvesting within the full hysteresis range.
Specifically, as shown in fig. 4, two upper tubes of the H-bridge AC-DC circuit are Pmos tubes, and two lower tubes are Nmos tubes, so that isolation driving is avoided, and circuit control power consumption is reduced. Meanwhile, the H-bridge AC-DC circuit is connected with the main coil of the nonlinear electromagnetic vibration energy collector, so that the H-bridge AC-DC circuit can utilize self-inductance of the main coil without an additional inductance element. Specifically, in the embodiment of the present invention, as shown in fig. 5, the triangle wave generating circuit and the PWM generating circuit use a unipolar frequency doubling mode, and can generate a PWM signal twice the triangle wave frequency.
In the embodiment of the invention, the viscous damping coefficient and stiffness coefficient control module is carried on a singlechip for realizing. The gain control of the proportional and integral circuits is realized through the communication of a digital potentiometer and a Serial Peripheral Interface (SPI) of the singlechip. Meanwhile, the singlechip also performs frequency sampling. The singlechip adopts an intermittent working mode, and is in a dormant state most of the time so as to reduce the power consumption of the circuit.
Specifically, the mechanism of the electric energy conversion device of the present invention for damping and stiffness adjustment is as follows.
The output voltage of the auxiliary coil can be written as:
Where θ m and θ a are the electromechanical coupling coefficients of the main coil and the auxiliary coil, respectively. v EMF is the main coil electromotive force, in phase with the relative velocity, and can be written as:
In the embodiment of the present invention, the output voltage v EH (the output voltage of the main coil) of NVEH is equal to the reference voltage v ref generated by the reference signal operation circuit, and there are:
vEH＝GainPva+GainI∫vadt (10)
Combining equation (8) and equation (9), v EH can be further written as:
the output current i EH of NVEH satisfies:
Where R c represents the main coil resistance and L c represents the main coil inductance.
From this, it can be seen that by controlling the magnitude of the two gains, the magnitude and direction of the NVEH output current can be controlled, and in a typical small-sized vibration energy collector, the main coil reactance ωl c is far smaller than the main coil resistance R c, and can be ignored. Thus, the output power P EH of NVEH can be expressed as:
The two gains are properly configured so that when the NVEH output power P EH is greater than 0, the H-bridge AC-DC circuit will operate in the energy harvesting mode and NVEH will charge the storage capacitor (load). If it is desired that the system operate in an energy harvesting mode with an equivalent impedance of pure resistance, gain I is set to 0. At this time, the equivalent resistance R load of the system is:
gain P is calculated by equation (14), and Gain P is adjusted such that the output power P EH of NVEH is greater than 0, and such that the output power P EH of NVEH is greater than 0.
On the other hand, when the gains Gain P and Gain I are properly adjusted so that the output power P EH of NVEH is less than 0, the super capacitor will provide energy to NVEH through the H-bridge AC-DC circuit to excite the motion of the vibrator. This excitation is essentially achieved by the ampere force generated by the coil current.
The ampere force F A generated by the main coil current is:
It can be seen that the ampere force can be decomposed into two components in phase with the relative velocity and relative displacement, which will have an effect on the viscous damping and linear stiffness, respectively, and that, at this time, after adjusting Gain P and Gain I, the corresponding new viscous damping coefficient c 'and linear stiffness coefficient k 1' can be written as:
Therefore, the energy level jump and energy collection dual-purpose electric energy conversion device can accurately and independently adjust the viscous damping coefficient and the linear stiffness to new values by adjusting two gains. At a particular damping coefficient and linear stiffness coefficient, the converter will operate in an energy harvesting state and achieve maximum power extraction. Meanwhile, the purpose of exciting the vibrator to move can be achieved by adjusting the damping coefficient and the linear stiffness coefficient, even if the converter works in an energy level jump state.
In addition, since the modulation ratio cannot exceed 1, i.e., the output voltage V EH of NVEH cannot exceed the output voltage V out of the H-bridge AC-DC circuit, two gains are to be satisfied:
where Z is the magnitude of Z.
Based on the nonlinear vibration energy collecting system capable of jumping in the energy level of the full hysteresis range, the method for jumping in the energy level of the full hysteresis range in the embodiment of the invention comprises the following steps:
the proportional operation gain and the integral operation gain are adjusted, so that the nonlinear electromagnetic vibration energy collector originally working at a low energy level works to a monostable high energy level state; the viscous damping coefficient and linear stiffness coefficient are then smoothly adjusted back so that the system returns to the high energy level energy harvesting state.
Specifically, the method comprises the following steps:
(1) Setting a proportional operation Gain P and an integral operation Gain I of the vibrator in a low-energy-level state and in an energy collection mode to be Gain P_EH,GainI_EH respectively;
(2) Gain P,GainI is adjusted to enable critical rising frequency omega u of the nonlinear electromagnetic vibration energy collector after Gain adjustment to be larger than environmental vibration frequency omega; transitioning the vibrator from a low energy state to a unique high energy steady state solution state; that is, at this point equation (6) will have only a single high-level steady state solution, so the vibrator will be forced to a high-level state. The adjusted gains are respectively and correspondingly marked as Gain P_OJ,GainI_OJ, and the calculation method of the adjusted Gain P_OJ,GainI_OJ is as follows:
If k 3 is more than 0, according to the formula (7), obtaining a critical value of a linear stiffness coefficient k 1' of the nonlinear electromagnetic vibration energy collector after gain adjustment from the critical frequency omega u being larger than the environmental vibration frequency omega; substituting the formula (16) to obtain the critical value Gain I_ Critical of ,GainI_OJ of the integral operation Gain after adjustment, which is smaller than the critical value Gain I_ Critical of , so as to ensure enough margin. Although ω u is independent of the damping coefficient, a proper reduction in damping helps to speed up the response and reduce the power loss in the process. In the practice of the invention, gain P_OJ may be set to θ m/θa to zero electromagnetic damping. Specifically, the Gain I_OJ values for different resistive loads are shown in fig. 6.
If the vibration energy harvester is a soft nonlinear system (i.e., k 3 < 0), then the threshold Gain I_ Critical of ,GainI_OJ for the adjusted integral Gain is greater than the threshold Gain I_ Critical of based on ω u < ω.
(3) Gain P_OJ,GainI_OJ is correspondingly smoothly ramped back to Gain P_EH,GainI_EH to transition the nonlinear electromagnetic vibration energy harvester to the highest energy state. Otherwise an excessive step size will cause the vibrator to fall back into the low level track. In order to implement smooth callback, in the embodiment of the present invention, the gain adjusted in each step is defined as:
The Gain P_n is the Gain adjusted in each step in the process of smoothly returning the Gain P_OJ to the Gain P_EH; gain I_n is the Gain adjusted at each step in the process of smoothing Gain I_OJ back to Gain I_EH; n=0, 1,2 … …, n represents the number of steps of smoothing the callback gain; t is a coefficient for measuring the smoothness, the viscous damping coefficient and the stiffness coefficient of each step can be calculated according to the formula (18) and the formula (6) to calculate the corresponding phase track, and then a critical value which can be successfully jumped is obtained, and T is larger than the critical value to leave enough margin. It is apparent that the larger T, the smoother the callback. Fig. 7 shows the value of T that ensures successful energy level jump under different resistive loads. The curve of t=0 indicates that direct removal of the excitation is successful; in practice T may take a very small value and cannot be completely zero.
For non-constant or random vibrations, the minimum Gain I_OJ and maximum T in fig. 6 and 7 should be chosen to ensure the success of the track jump. This is done at the cost of inevitably increasing power consumption. Fig. 8 shows a phase trajectory diagram for successful energy level jump at a 53.3Hz vibration frequency. It can be seen that after multiple adjustments of damping and stiffness, the vibrator successfully approximates a new high amplitude stabilization point. The smooth callback scheme ensures that the vibrator cannot fall to a low-energy-level state in the callback process, and has high reliability and stability.
Thus, the invention establishes a complete nonlinear electromagnetic vibration energy collection system capable of running autonomously, and can realize reliable energy level jump in a full hysteresis range. The system will have a higher output power and operating bandwidth than conventional linear vibration energy harvesting systems.
According to the nonlinear vibration energy collecting system capable of jumping at the energy level in the full hysteresis range, the main coil of the nonlinear electromagnetic vibration energy collector is connected with the H-bridge AC-DC circuit so as to charge a load, and power supply of the whole system is provided; the method comprises the steps of overlapping and winding an auxiliary coil on the surface of a main coil of a nonlinear electromagnetic vibration energy collector so as to enable the phases of induced electromotive forces of the main coil and the auxiliary coil to be consistent, respectively carrying out proportional operation and integral operation on the electromotive force information (auxiliary coil output voltage) of the main coil collected by the auxiliary coil, generating reference voltages of an H-bridge AC-DC circuit, and generating corresponding PWM signals to control the H-bridge AC-DC circuit so as to enable the output voltages of the H-bridge AC-DC circuit to be consistent with the voltage reference signals v ref; in the control process, the magnitude and the direction of the output current of the nonlinear electromagnetic vibration energy collector can be controlled by adjusting the proportional Gain P and the integral Gain I, so that the viscous damping coefficient and the stiffness coefficient of the energy collector are changed, and the energy collector can be in an outward output power state (energy collection state) or in an energy level jump state. According to the method, the corresponding viscous damping coefficient and the linear stiffness coefficient are independently adjusted through the proportional Gain P and the integral Gain I, namely, the viscous damping coefficient is adjusted through the proportional Gain P, the linear stiffness coefficient is adjusted through the integral Gain I, the viscous damping coefficient and the linear stiffness coefficient can be randomly adjusted within a certain range, and energy level jump or energy collection within a full hysteresis range is facilitated. In addition, the system of the invention can realize independent operation without manual operation or additional auxiliary equipment.
According to the method for realizing the full hysteresis range energy level jump, when the nonlinear electromagnetic vibration energy collector works at a low energy level, the proportional operation gain and the integral operation gain are adjusted to enable the nonlinear electromagnetic vibration energy collector to work to a monostable high energy level state, and the energy collector is enabled to continuously work at the highest energy level state through the forced change energy level of the viscous damping coefficient and the stiffness coefficient of the smooth modulation mechanical system, so that the full hysteresis range energy level jump is realized.
The invention provides a nonlinear electromagnetic vibration energy collecting system capable of realizing energy level jump in a full hysteresis range by depending on the output characteristics of a nonlinear vibration energy collector and defining the basic principle of energy level jump.
Example 2
The invention also provides a method for jumping the energy level in the full hysteresis range, which adopts the nonlinear vibration energy collecting system for jumping the energy level in the full hysteresis range in the embodiment 1 to realize the energy level jumping in the full hysteresis range; for specific implementation manner, refer to embodiment 1, and are not described herein.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. A nonlinear vibration energy harvesting system that hops at a full hysteresis range energy level, comprising: a nonlinear electromagnetic vibration energy collector and an electric energy conversion device;
The nonlinear electromagnetic vibration energy collector comprises a main coil and an auxiliary coil; the auxiliary coil is overlapped and wound on the surface of the main coil;
the electric energy conversion device comprises an H-bridge AC-DC circuit, a reference signal operation circuit, a PWM generating circuit, a viscous damping coefficient and a rigidity coefficient control module;
the main coil is connected with the H-bridge AC-DC circuit so as to charge a load;
The reference signal operation circuit is used for respectively performing proportional operation and integral operation on the output voltage of the auxiliary coil so as to obtain a voltage reference signal v ref of the H-bridge AC-DC circuit;
The PWM generation circuit is used for generating a PWM signal according to the voltage reference signal v ref to control the H-bridge AC-DC circuit so as to enable the output voltage of the H-bridge AC-DC circuit to be consistent with the voltage reference signal v ref;
The viscous damping coefficient and stiffness coefficient control module is used for adjusting the gain of the proportional operation and the gain of the integral operation so as to correspondingly change the viscous damping coefficient c and the linear stiffness coefficient k 1 of the nonlinear electromagnetic vibration energy collector, thereby realizing energy level jump or energy collection in a full hysteresis range.
2. The system for nonlinear vibration energy harvesting energy hopped over a full hysteresis range of claim 1, wherein the viscous damping coefficient and stiffness coefficient control module implements energy hopping over a full hysteresis range, comprising:
Adjusting the proportional operation Gain Gain P_EH and the integral operation Gain Gain I_EH of the nonlinear electromagnetic vibration energy collector to correspondingly change the viscous damping coefficient c and the linear stiffness coefficient k 1, and taking the critical rising frequency omega u of the nonlinear electromagnetic vibration energy collector as a target that the critical rising frequency omega is larger than or smaller than the environmental vibration frequency omega, so as to obtain the adjusted corresponding gains Gain P_OJ and Gain I_OJ; if the cubic stiffness coefficient k 3 of the nonlinear electromagnetic vibration energy collector is greater than 0, ω u is greater than ω, otherwise ω u＜ω;GainP_EH and Gain I_EH are respectively proportional operation Gain and integral operation Gain corresponding to the nonlinear electromagnetic vibration energy collector working in a low energy level state and in an energy collection mode;
The adjusted gains Gain P_OJ and Gain I_OJ are correspondingly smoothed back to Gain P_EH and Gain I_EH to transition the nonlinear electromagnetic vibration energy harvester to a highest energy state.
3. The system for nonlinear vibration energy harvesting energy in full hysteresis range energy level jump of claim 2, wherein the gain adjusted at each step during the smoothing callback is:
The Gain P_n is the Gain adjusted in each step in the process of smoothly returning the Gain P_OJ to the Gain P_EH; gain I_n is the Gain adjusted at each step in the process of smoothing Gain I_OJ back to Gain I_EH; n represents the number of steps of smoothing callback gain, n=0, 1,2 … …, and T is a coefficient measuring the degree of smoothing.
4. A nonlinear vibration energy harvesting system according to claim 2 or 3, wherein the Gain I_OJ calculation process comprises:
If k 3 is more than 0, solving an inequality omega u is more than omega, and obtaining a critical value of a linear stiffness coefficient k 1' after gain adjustment according to a functional relation among a critical rising frequency omega u, an environment vibration frequency omega and the linear stiffness coefficient k 1;
According to the formula Calculating to obtain a critical value Gain I_ Critical of of the integral operation Gain, and then Gain I_OJ＜GainI_ Critical of ; wherein, R c represents the resistance of the main coil, and θ m and θ a are the electromechanical coupling coefficients of the main coil and the auxiliary coil respectively;
If k 3 is less than 0, solving an inequality omega u less than omega, and obtaining a critical value of a linear stiffness coefficient k 1' after gain adjustment according to a functional relation among a critical rising frequency omega u, an environmental vibration frequency omega and the linear stiffness coefficient k 1;
According to the formula Calculating to obtain a critical value Gain I_ Critical of of the integral operation Gain, and then Gain I_OJ＞GainI_ Critical of ;
gain P_OJ is set as: gain P_OJ＝θm/θa.
5. A system for harvesting nonlinear vibration energy in full hysteresis range energy level jump according to claim 2 or 3 wherein the proportional Gain P_EH and the integral Gain I_EH are calculated by:
And taking the main coil output power P EH as a constraint, and according to the relation satisfied among the main coil output power P EH, the proportional operation Gain and the integral operation Gain, blending the proportional operation Gain P_EH and the integral operation Gain I_EH.
6. A system for harvesting nonlinear vibration energy in full hysteresis range energy level jump according to claim 2 or 3, wherein said integral Gain I_EH = 0 when said nonlinear electromagnetic vibration energy harvester is operated in an energy harvesting mode with equivalent impedance as a pure resistor;
The calculation mode of the proportional operation Gain P_EH is as follows:
Wherein, R load is a preset system equivalent resistance, R c represents a main coil resistance, and θ m and θ a are electromechanical coupling coefficients of the main coil and the auxiliary coil respectively.
7. The system for nonlinear vibration energy harvesting energy hopped at a full hysteresis range of claim 1, wherein the nonlinear electromagnetic vibration energy harvester further comprises: a housing, a nonlinear planar spring, and a magnet;
The nonlinear plane springs are fixed at two ends of the shell, two ends of the magnet are fixed on the nonlinear plane springs through connecting pieces, and the main coil surrounds the upper surface and the lower surface of the magnet and is wound in grooves of the shell.
8. The system for harvesting nonlinear vibration energy in full hysteresis range energy level jump of claim 1, wherein two upper tubes of said H-bridge AC-DC circuit employ Pmos tubes and two lower tubes employ two Nmos tubes.
9. The system for collecting nonlinear vibration energy in full hysteresis range energy level jump according to claim 1, wherein said viscous damping coefficient and stiffness coefficient control module is mounted on an intermittently operating single chip microcomputer.
10. A method of energy level jump in the full hysteresis range, characterized in that the energy level jump in the full hysteresis range is achieved with a nonlinear vibration energy harvesting system of any one of claims 1-9.
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