Multivariable Robust Control for a Red–Green–Blue LED Lighting System

This paper proposes a novel control structure for a red-green-blue (RGB) LED lighting system, and applies multivariable robust control techniques to regulate the color and luminous intensity outputs. RGB LED is the next-generational illuminant for general lighting or liquid crystal display backlighting. The most important feature for a polychromatic illuminant is color adjustability; however, for lighting applications using RGB LEDs, color is sensitive to temperature variations. Therefore, suitable control techniques are required to stabilize both luminous intensity and chromaticity coordinates. In this paper, a robust control system was proposed for achieving luminous intensity and color consistency for RGB LED lighting in a three-step process. First, a multivariable electrical-thermal model was used to obtain RGB LED luminous intensity, in which a lookup table served as a feedforward compensator for temperature and power variations. Second, robust control algorithms were applied for feedback control design. Finally, the designed robust controllers were implemented to control the luminous and chromatic outputs of the system. From the experimental results, the proposed multivariable robust control was deemed effective in providing steady luminous intensity and color for RGB LED lighting.