The motion of a charged particle in an electrodynamic chamber under feedback control

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Abstract

The motion of a charged particle in an electrodynamic chamber under feedback control was calculated and measured. The measuring system is based on photodiode array (PDA) shadowgraphy. A 128 linear PDA is used to measure the shadow of the particle. The PDA trace is transferred by an analog to digital (A/D) converter to a 386-microprocessor (25 or 33 MHz) computer that determines the position of the particle and uses a proportional-integral-derivative (PID) algorithm to calculate a value related to the deviation of the particle from the center position. This value is fed back by a D/A converter that generates a direct current (DC) voltage which is added to the DC voltage between the chamber electrodes. The sampling rate of the system is 500–800 Hz. Calculations of the particle motion under feedback control were carried out by adding a PID term into the equation of motion of the particle. The position of particle was calculated to yield one-to-one fit with the experimental measurements. It is shown that the characteristic time for relaxation (after experiencing a perturbation) is insensitive to the particle size, and was found to be 100–150 ms. The feed-back control system was demonstrated by measuring the adsorption of CO2by a char particle.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalAerosol Science and Technology
Volume15
Issue number1
DOIs
StatePublished - 1 Jan 1991

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