Automatic diagnosis and control of distributed solid state lighting systems

Abstract

This paper describes a new design concept of automatically diagnosing and compensating LED degradations in distributed solid state lighting (SSL) systems. A failed LED may significantly reduce the overall illumination level, and destroy the uniform illumination distribution achieved by a nominal system. To our knowledge, an automatic scheme to compensate LED degradations has not yet been seen in the literature, which requires a diagnostic step followed by control reconfigurations. The main challenge in diagnosing LED degradations lies in the usually unsatisfactory observability in a distributed SSL system, because the LED light output is usually not individually measured. In this work, we tackle this difficulty by using pulse width modulated (PWM) drive currents with a unique fundamental frequency assigned to each LED. Signal processing methods are applied in estimating the individual illumination flux of each LED. Statistical tests are developed to diagnose the degradation of LEDs. Duty cycle of the drive current signal to each LED is re-optimized once a fault is detected, in order to compensate the destruction of the uniform illumination pattern by the failed LED.

An Alternative Approach for High Uniformity Distribution of Indoor Lighting LED

“…LEDs tend to produce a circular pattern with high intensity at the center and low intensity at the edge of the illuminated area. To avoid the non-uniform radiation distribution of the LED lighting systems, there have been several improvement methods to redistribute the LED patterns [16]- [18]. Both outdoor and indoor lightings, the high uniform illuminances are required for friendly with human eyes which leads to improving cognitive performance.…”

Efficient distributed control of light-emitting diode array lighting systems

“…We can write the rendered spatial illumination pattern from an LED array compactly in matrix form as [2,5,6] y B · u;…”

“…The conditions to ensure that the equation, r B · u, has a unique solution are n ≥ m and also that B has a full column rank; i.e., B T B −1 exists. A regularized LS solution is then used by solving (see, e.g., [5]) Note that because reference r can change due to occupancy or varying daylight (as in the case of general lighting applications [2]), both r and u o are not fixed, but they need to be computed in real time.…”