The dynamical behaviour of a parametrically excited Duffing-van der Pol oscillator under linear-plus-nonlinear state feedback control with a time delay is concerned. By means of the method of averaging together with t...The dynamical behaviour of a parametrically excited Duffing-van der Pol oscillator under linear-plus-nonlinear state feedback control with a time delay is concerned. By means of the method of averaging together with truncation of Taylor expansions, two slow-flow equations on the amplitude and phase of response were derived for the case of principal parametric resonance, it is shown that the stability condition for the trivial solution is only associated with the linear terms in the original systems besides the amplitude and frequency of parametric excitation. And the trivial solution can be stabilized by appreciate choice of gains and time delay in feedback control. Different from the case of the trivial solution, the stability condition for nontrivial solutions is also associated with nonlinear terms besides linear terms in the original system. It is demonstrated that nontrivial steady state responses may lose their stability by saddle-node （SN） or Hopf bifurcation （HB） as parameters vary. The simulations, obtained by numerically integrating the original system, are in good agreement with the analytical results.展开更多
The dynamical behavior of the extended Duffing-Van der Pol oscillator is investigated numerically in detail. With the aid of some numerical simulation tools such as bifurcation diagrams and Poinearé maps, the dif...The dynamical behavior of the extended Duffing-Van der Pol oscillator is investigated numerically in detail. With the aid of some numerical simulation tools such as bifurcation diagrams and Poinearé maps, the different routes to chaos and various shapes of strange attractors are observed. To characterize chaotic behavior of this oscillator system, the spectrum of Lyapunov exponent and Lyapunov dimension are also employed.展开更多
In this paper, a modified averaging scheme is presented for a class of time-delayed vibration systems with slow variables. The new scheme is a combination of the averaging techniques proposed by Hale and by Lehman and...In this paper, a modified averaging scheme is presented for a class of time-delayed vibration systems with slow variables. The new scheme is a combination of the averaging techniques proposed by Hale and by Lehman and Weibel, respectively. The averaged equation obtained from the modified scheme is simple enough but it retains the required information for the local nonlinear dynamics around an equilibrium. As an application of the present method, the delay value for which a secondary Hopf bifurcation occurs is successfully located for a delayed van der Pol oscillator.展开更多
This paper proposes an impulsive control scheme for chaotic systems consisting of Van der Pol oscillators coupled to linear oscillators （VDPL） based on their Takagi-Sugeno （T-S） fuzzy models. A T-S fuzzy model is ...This paper proposes an impulsive control scheme for chaotic systems consisting of Van der Pol oscillators coupled to linear oscillators （VDPL） based on their Takagi-Sugeno （T-S） fuzzy models. A T-S fuzzy model is utilized to represent the chaotic VDPL system. By using comparison method, a general asymptotical stability criterion by means of linear matrix inequality （LMI） is derived for the T-S fuzzy model of VDPL system with impulsive effects. The simulation results demonstrate the effectiveness of the proposed scheme.展开更多
In this paper, phase synchronization and the frequency of two synchronized van der Pol oscillators with delay coupling are studied. The dynamics of such a system are obtained using the describing function method, and ...In this paper, phase synchronization and the frequency of two synchronized van der Pol oscillators with delay coupling are studied. The dynamics of such a system are obtained using the describing function method, and the necessary conditions for phase synchronization are also achieved. Finding the vicinity of the synchronization frequency is the major advantage of the describing function method over other traditional methods. The equations obtained based on this method justify the phenomenon of the synchronization of coupled oscillators on a frequency either higher, between, or lower than the highest, in between, or lowest natural frequency of the aggregate oscillators. Several numerical examples simulate the different cases versus the various synchronization frequency delays.展开更多
In this paper, a class of n coupled van der Pol oscillator model with delays is considered. By employing an analysis approach, some sufficient conditions to guarantee the existence of stability and oscillations for th...In this paper, a class of n coupled van der Pol oscillator model with delays is considered. By employing an analysis approach, some sufficient conditions to guarantee the existence of stability and oscillations for themodel are obtained. Examples are provided to demonstrate the results.展开更多
In this paper, a powerful analytical method, called He’s homotopy perturbation method is applied to obtaining the approximate periodic solutions for some nonlinear differential equations in mathematical physics via V...In this paper, a powerful analytical method, called He’s homotopy perturbation method is applied to obtaining the approximate periodic solutions for some nonlinear differential equations in mathematical physics via Van der Pol damped non-linear oscillators and heat transfer. Illustrative examples reveal that this method is very effective and convenient for solving nonlinear differential equations. Comparison of the obtained results with those of the exact solution, reveals that homotopy perturbation method leads to accurate solutions.展开更多
This paper proposes a Van der Pol (VDP) oscillator screening for peripheral arterial disease (PAD) in patients with diabetes mellitus. The long-term elevated blood sugar levels produce a high risk of peripheral neurop...This paper proposes a Van der Pol (VDP) oscillator screening for peripheral arterial disease (PAD) in patients with diabetes mellitus. The long-term elevated blood sugar levels produce a high risk of peripheral neuropathy and peripheral vascular disease, especially in the foot of a diabetic. Early detection is important, in order to prevent foot problems for diabetic patients with PAD. Photoplethysmography (PPG) is a non-invasive method for the detection of blood volume changes in peripheral arteries. Because of changes in the resistance-compliance, the rise time and transit time for the PPG signals increase and change in their shape are highly correlated with PAD severity. In this study, the Burg autoregressive (AR) method is used to determine the characteristic frequencies of the right-and left-side PPG signals. For bilateral frequency spectra, the VDP oscillator uses asynchronous signals. This produces damped sinusoidal responses and the oscillation overshoot (OS) is an approximating function only of the damped factor. This index is used to estimate the degree of PAD, including normal the condition and diabetic patients with PAD. The results show that the proposed method is efficient and more accurate in the estimation of PAD.展开更多
The collective behavior of a ring of coupled identical van der Pol oscillators is numerically studied in this work. Constant, gaussian and random distributions of the coupling parameter along the ring are considered. ...The collective behavior of a ring of coupled identical van der Pol oscillators is numerically studied in this work. Constant, gaussian and random distributions of the coupling parameter along the ring are considered. Three values of the oscillators constant are assumed in order to cover from quasilinear to nonlinear dynamic performance. Single and multiple coupled frequencies are obtained using power spectra of the long term time series. Phase portraits are obtained from numerical simulations, and the coupled behavior is analyzed, compared and discussed.展开更多
This paper discusses a novel technique and implementation to perform nonlinear control for two different forced model state oscillators and actuators. The paper starts by discussing the Duffing oscillator which featur...This paper discusses a novel technique and implementation to perform nonlinear control for two different forced model state oscillators and actuators. The paper starts by discussing the Duffing oscillator which features a second order non-linear differential equation describing complex motion whereas the second model is the Van der Pol oscillator with non-linear damping. A first order actuator is added to both models to expand on the chaotic behavior of the oscillators. In order to control the system without comprising linearization, Lyapunov non-linear control was used. A control Lyapunov function was tailored to the system. This led to improved maneuverability of the controller and the performance of the overall system. The controller was found to be highly efficient in system tracking and had swift response time. Simulations were performed on both the uncontrolled and controlled cases. Both simulation results ultimately confirmed the effectiveness of the proposed controller.展开更多
In this study, homotopy perturbation method and parameter expanding method are applied to the motion equations of two nonlinear oscillators. Our results show that both the (HPM) and (PEM) yield the same results for th...In this study, homotopy perturbation method and parameter expanding method are applied to the motion equations of two nonlinear oscillators. Our results show that both the (HPM) and (PEM) yield the same results for the nonlinear problems. In comparison with the exact solution, the results show that these methods are very convenient for solving nonlinear equations and also can be used for strong nonlinear oscillators.展开更多
The principal resonance of Van der Pol-Duffing oscillator to combined deterministic and random parametric excitations is investigated. The method of multiple scales was used to determine the equations of modulation of...The principal resonance of Van der Pol-Duffing oscillator to combined deterministic and random parametric excitations is investigated. The method of multiple scales was used to determine the equations of modulation of amplitude and phase. The behavior, stability and bifurcation of steady state response were studied. Jumps were shown to occur under some conditions. The effects of damping, detuning, bandwidth, and magnitudes of deterministic and random excitations are analyzed. The theoretical analysis were verified by numerical results.展开更多
通过多尺度法对Duffing-van der Pol系统的幅频响应特性进行研究,多频激励改变了单频激励条件下系统的振动状态。与Duffing系统相比,Duffing-van der Pol系统不但使系统主共振曲线发生了偏移,而且系统的振幅也发生了变化。经过分析得出...通过多尺度法对Duffing-van der Pol系统的幅频响应特性进行研究,多频激励改变了单频激励条件下系统的振动状态。与Duffing系统相比,Duffing-van der Pol系统不但使系统主共振曲线发生了偏移,而且系统的振幅也发生了变化。经过分析得出了Duffing-van der Pol系统主共振幅频特性曲线的偏移和振幅的改变与加入的多频激励的幅度和频率有关。利用Matlab对Duffing-van der Pol进行了数值仿真,仿真结果得出多频外激励改变了原有单频激励的振动状态,并且随着多频激励的幅值和频率的改变,系统的振动状态出现了一定规律的变化。对比研究了解析分析与数值仿真结果,得出的结论比较一致。展开更多
研究了Duffing-van der Pol振子在一类时滞反馈控制下零解的稳定性问题以及极限环的振幅和稳定性问题。依平均法和对时滞反馈控制项泰劳展开的截断得到的平均方程表明,零解的稳定性除与原方程中线性项的系数有关外,只与线性反馈有关,与...研究了Duffing-van der Pol振子在一类时滞反馈控制下零解的稳定性问题以及极限环的振幅和稳定性问题。依平均法和对时滞反馈控制项泰劳展开的截断得到的平均方程表明,零解的稳定性除与原方程中线性项的系数有关外,只与线性反馈有关,与非线性反馈无关。通过调整线性反馈的增益和时滞,可以使不稳定的零解变得稳定。零解发生Hopf分岔导致的周期解的振幅除与原方程中非线性项的系数有关外,与线性反馈和非线性反馈均有关。通过调整反馈增益和时滞,不仅可以控制极限环的振幅,还可以抑制极限环的产生。此外,根据平均方程还容易发现反馈时滞对系统动力学行为的影响具有周期性。数值仿真的结果验证了理论分析的正确性。展开更多
研究了含有两个分岔参数的多频激励下Duffing-van der Pol系统的分岔特性.分3种情况进行了讨论:情形1,将λ1看成分岔参数;情形2,将λ2看成分岔参数;情形3,将λ1和λ2都看成分岔参数.根据转迁集的定义,不同的情况下,整个参数空间都被分...研究了含有两个分岔参数的多频激励下Duffing-van der Pol系统的分岔特性.分3种情况进行了讨论:情形1,将λ1看成分岔参数;情形2,将λ2看成分岔参数;情形3,将λ1和λ2都看成分岔参数.根据转迁集的定义,不同的情况下,整个参数空间都被分成了若干个不同的区域,得到了各个参数空间上系统的分岔图,从而为该类系统的参数优化控制奠定了基础.展开更多
基金Project supported by the Scientific Research Foundation for Returned Overseas Chinese Scholar of Ministry of Eduction, China (No.2006-331)
文摘The dynamical behaviour of a parametrically excited Duffing-van der Pol oscillator under linear-plus-nonlinear state feedback control with a time delay is concerned. By means of the method of averaging together with truncation of Taylor expansions, two slow-flow equations on the amplitude and phase of response were derived for the case of principal parametric resonance, it is shown that the stability condition for the trivial solution is only associated with the linear terms in the original systems besides the amplitude and frequency of parametric excitation. And the trivial solution can be stabilized by appreciate choice of gains and time delay in feedback control. Different from the case of the trivial solution, the stability condition for nontrivial solutions is also associated with nonlinear terms besides linear terms in the original system. It is demonstrated that nontrivial steady state responses may lose their stability by saddle-node （SN） or Hopf bifurcation （HB） as parameters vary. The simulations, obtained by numerically integrating the original system, are in good agreement with the analytical results.
基金supported by the National Natural Science Foundation of China under Grant No.10875078the Natural Science Foundation of Zhejiang Province of China under Grant No.Y7080455
文摘The dynamical behavior of the extended Duffing-Van der Pol oscillator is investigated numerically in detail. With the aid of some numerical simulation tools such as bifurcation diagrams and Poinearé maps, the different routes to chaos and various shapes of strange attractors are observed. To characterize chaotic behavior of this oscillator system, the spectrum of Lyapunov exponent and Lyapunov dimension are also employed.
基金FANEDD of China (200430)the National Natural Science Foundation of China (10372116,10532050)
文摘In this paper, a modified averaging scheme is presented for a class of time-delayed vibration systems with slow variables. The new scheme is a combination of the averaging techniques proposed by Hale and by Lehman and Weibel, respectively. The averaged equation obtained from the modified scheme is simple enough but it retains the required information for the local nonlinear dynamics around an equilibrium. As an application of the present method, the delay value for which a secondary Hopf bifurcation occurs is successfully located for a delayed van der Pol oscillator.
文摘This paper proposes an impulsive control scheme for chaotic systems consisting of Van der Pol oscillators coupled to linear oscillators （VDPL） based on their Takagi-Sugeno （T-S） fuzzy models. A T-S fuzzy model is utilized to represent the chaotic VDPL system. By using comparison method, a general asymptotical stability criterion by means of linear matrix inequality （LMI） is derived for the T-S fuzzy model of VDPL system with impulsive effects. The simulation results demonstrate the effectiveness of the proposed scheme.
文摘In this paper, phase synchronization and the frequency of two synchronized van der Pol oscillators with delay coupling are studied. The dynamics of such a system are obtained using the describing function method, and the necessary conditions for phase synchronization are also achieved. Finding the vicinity of the synchronization frequency is the major advantage of the describing function method over other traditional methods. The equations obtained based on this method justify the phenomenon of the synchronization of coupled oscillators on a frequency either higher, between, or lower than the highest, in between, or lowest natural frequency of the aggregate oscillators. Several numerical examples simulate the different cases versus the various synchronization frequency delays.
文摘In this paper, a class of n coupled van der Pol oscillator model with delays is considered. By employing an analysis approach, some sufficient conditions to guarantee the existence of stability and oscillations for themodel are obtained. Examples are provided to demonstrate the results.
文摘In this paper, a powerful analytical method, called He’s homotopy perturbation method is applied to obtaining the approximate periodic solutions for some nonlinear differential equations in mathematical physics via Van der Pol damped non-linear oscillators and heat transfer. Illustrative examples reveal that this method is very effective and convenient for solving nonlinear differential equations. Comparison of the obtained results with those of the exact solution, reveals that homotopy perturbation method leads to accurate solutions.
文摘This paper proposes a Van der Pol (VDP) oscillator screening for peripheral arterial disease (PAD) in patients with diabetes mellitus. The long-term elevated blood sugar levels produce a high risk of peripheral neuropathy and peripheral vascular disease, especially in the foot of a diabetic. Early detection is important, in order to prevent foot problems for diabetic patients with PAD. Photoplethysmography (PPG) is a non-invasive method for the detection of blood volume changes in peripheral arteries. Because of changes in the resistance-compliance, the rise time and transit time for the PPG signals increase and change in their shape are highly correlated with PAD severity. In this study, the Burg autoregressive (AR) method is used to determine the characteristic frequencies of the right-and left-side PPG signals. For bilateral frequency spectra, the VDP oscillator uses asynchronous signals. This produces damped sinusoidal responses and the oscillation overshoot (OS) is an approximating function only of the damped factor. This index is used to estimate the degree of PAD, including normal the condition and diabetic patients with PAD. The results show that the proposed method is efficient and more accurate in the estimation of PAD.
文摘The collective behavior of a ring of coupled identical van der Pol oscillators is numerically studied in this work. Constant, gaussian and random distributions of the coupling parameter along the ring are considered. Three values of the oscillators constant are assumed in order to cover from quasilinear to nonlinear dynamic performance. Single and multiple coupled frequencies are obtained using power spectra of the long term time series. Phase portraits are obtained from numerical simulations, and the coupled behavior is analyzed, compared and discussed.
文摘This paper discusses a novel technique and implementation to perform nonlinear control for two different forced model state oscillators and actuators. The paper starts by discussing the Duffing oscillator which features a second order non-linear differential equation describing complex motion whereas the second model is the Van der Pol oscillator with non-linear damping. A first order actuator is added to both models to expand on the chaotic behavior of the oscillators. In order to control the system without comprising linearization, Lyapunov non-linear control was used. A control Lyapunov function was tailored to the system. This led to improved maneuverability of the controller and the performance of the overall system. The controller was found to be highly efficient in system tracking and had swift response time. Simulations were performed on both the uncontrolled and controlled cases. Both simulation results ultimately confirmed the effectiveness of the proposed controller.
文摘In this study, homotopy perturbation method and parameter expanding method are applied to the motion equations of two nonlinear oscillators. Our results show that both the (HPM) and (PEM) yield the same results for the nonlinear problems. In comparison with the exact solution, the results show that these methods are very convenient for solving nonlinear equations and also can be used for strong nonlinear oscillators.
文摘The principal resonance of Van der Pol-Duffing oscillator to combined deterministic and random parametric excitations is investigated. The method of multiple scales was used to determine the equations of modulation of amplitude and phase. The behavior, stability and bifurcation of steady state response were studied. Jumps were shown to occur under some conditions. The effects of damping, detuning, bandwidth, and magnitudes of deterministic and random excitations are analyzed. The theoretical analysis were verified by numerical results.
文摘通过多尺度法对Duffing-van der Pol系统的幅频响应特性进行研究,多频激励改变了单频激励条件下系统的振动状态。与Duffing系统相比,Duffing-van der Pol系统不但使系统主共振曲线发生了偏移,而且系统的振幅也发生了变化。经过分析得出了Duffing-van der Pol系统主共振幅频特性曲线的偏移和振幅的改变与加入的多频激励的幅度和频率有关。利用Matlab对Duffing-van der Pol进行了数值仿真,仿真结果得出多频外激励改变了原有单频激励的振动状态,并且随着多频激励的幅值和频率的改变,系统的振动状态出现了一定规律的变化。对比研究了解析分析与数值仿真结果,得出的结论比较一致。
文摘研究了Duffing-van der Pol振子在一类时滞反馈控制下零解的稳定性问题以及极限环的振幅和稳定性问题。依平均法和对时滞反馈控制项泰劳展开的截断得到的平均方程表明,零解的稳定性除与原方程中线性项的系数有关外,只与线性反馈有关,与非线性反馈无关。通过调整线性反馈的增益和时滞,可以使不稳定的零解变得稳定。零解发生Hopf分岔导致的周期解的振幅除与原方程中非线性项的系数有关外,与线性反馈和非线性反馈均有关。通过调整反馈增益和时滞,不仅可以控制极限环的振幅,还可以抑制极限环的产生。此外,根据平均方程还容易发现反馈时滞对系统动力学行为的影响具有周期性。数值仿真的结果验证了理论分析的正确性。
文摘研究了含有两个分岔参数的多频激励下Duffing-van der Pol系统的分岔特性.分3种情况进行了讨论:情形1,将λ1看成分岔参数;情形2,将λ2看成分岔参数;情形3,将λ1和λ2都看成分岔参数.根据转迁集的定义,不同的情况下,整个参数空间都被分成了若干个不同的区域,得到了各个参数空间上系统的分岔图,从而为该类系统的参数优化控制奠定了基础.
