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In dynamics, the Van der Pol oscillator is a non-conservative oscillator with non-linear damping. It evolves in time according to the second-order differential equation:
where x is the position coordinate—which is a function of the time t, and μ is a scalar parameter indicating the nonlinearity and the strength of the damping.
The Van der Pol oscillator was originally proposed by the Dutch electrical engineer and physicist Balthasar van der Pol while he was working at Philips.^{[1]} Van der Pol found stable oscillations, which he called relaxation-oscillations^{[2]} and are now known as limit cycles, in electrical circuits employing vacuum tubes. When these circuits were driven near the limit cycle they become entrained, i.e. the driving signal pulls the current along with it. Van der Pol and his colleague, van der Mark, reported in the September 1927 issue of Nature ^{[3]} that at certain drive frequencies an irregular noise was heard. This irregular noise was always heard near the natural entrainment frequencies. This was one of the first discovered instances of deterministic chaos.^{[4]}
The Van der Pol equation has a long history of being used in both the physical and biological sciences. For instance, in biology, Fitzhugh^{[5]} and Nagumo^{[6]} extended the equation in a planar field as a model for action potentials of neurons. The equation has also been utilised in seismology to model the two plates in a geological fault,^{[7]} and in studies of phonation to model the right and left vocal fold oscillators.^{[8]}
Liénard's theorem can be used to prove that the system has a limit cycle. Applying the Liénard transformation y = x - x^3/3 - \dot x/\mu, where the dot indicates the time derivative, the Van der Pol oscillator can be written in its two-dimensional form:^{[9]}
Another commonly used form based on the transformation y = \dot x is leading to
Two interesting regimes for the characteristics of the unforced oscillator are:^{[10]}
The forced, or driven, Van der Pol oscillator takes the 'original' function and adds a driving function Asin(ωt) to give a differential equation of the form:
where A is the amplitude, or displacement, of the wave function and ω is its angular velocity.
Author James Gleick described a vacuum-tube Van der Pol oscillator in his book Chaos: Making a New Science.^{[12]} According to a New York Times article,^{[13]} Gleick received a modern electronic Van der Pol oscillator from a reader in 1988.
Mathematics, Physics, Meteorology, Biology, Economics
Simple pendulum, Van der Pol oscillator, Phase plane, Potential energy, Dynamical system
Chaos theory, Mathematics, Orbit, Van der Pol oscillator, Fractal
Netherlands, IEEE Medal of Honor, Physics, Valdemar Poulsen Gold Medal, England
Classical mechanics, Mathematics, Physics, Parameter, Quantum mechanics