Abstract
In a previous paper, we reported a new system of artificial light radiation, in which static control of light intensity and spectral composition was made possible in the wavelength range from 350 nm to 800 nm.
Present paper deals with a system of automatic control of light for plant growth and development in a growth cabinet. Feedback control of light intensity and feedforward control of spectral composition were adopted with an online digital computer, and the variable-value control of light intensity and spectral composition was achieved. By this system, it was made possible to radiate plants with time series of both light intensity and spectral composition. Performances were as follows:
1) In a step response in light intensity control, the delay time was remarkably small, and the settling time was 5 min, where the proportional band, reset time and rate time were set at 85%, 1 min, and 0 min, respectively. 2) The fluctuation in the light intensity was made smaller in the feedback control than that in uncontrol. 3) In the feed-forward control, the response time was remarkably small. 4) The combined feedback and feed-forward control system made it possible to change the spectral composition in time series under keeping the optional light intensity constant. In this system, the integrated net area of spectral irradiance successfully conformed to the desired value of light intensity within the deviation of 0.5%.
