Cao Guangzhong

On the LQG and LQG/LTR methodology

The paper considers the well-known linear quadratic Gaussian with loop transfer recovery (LQG/LTR) methodology as a special case of standard LQG methodology. In another words, problems solved using LQG/LTR methodology can equally be solved by the standard LQG methodology. In this way we can directly tackle the problem we want to solve. Proof is given to show how LQG/LTR methodology is related to LQG methodology.

Modeling of the rapid lifetime assessmentsystem with multiple stresses for LED devices using adaptive geneticalgorithm

The light-emitting diode (LED) is a promising candidate for the lighting, instrument reading, etc., due to its features of high efficiency, long lifetime, small size, fast response, anti vibration, low-voltage operation, and environmental protection, which is an emerging cold light source. This paper proposes a novel model of the rapid lifetime assessment system with multiple stresses for LED devices, to solve the problems of the complex environmental stresses imposed on the lifetime of LED devices, the model of accelerated life testing without consideration of multiple stresses, and the low-precision lifetime assessment model. This model is suitable for all types of LED devices. Taking the operating time to 30% of lumen depreciation as the lifetime of LED devices, the environmental temperature and humidity, and input current are the inputs of this model, and the lifetime of the LED device is the output of this model. The parameters of this model are determinated by using the designed adaptive genetic algorithm. A several number of sample data is first obtained through accelerated life testing under the condition of high temperature, humidity, and current. The parameters of this model are then identified with the obtained sample data. This model is further built by applying the identified parameters. Additionally, the lifetime evaluation is carried out via this model under the condition of normal temperature, humidity, and current. Research results demonstrate that the proposed model can evaluate the lifetime of LED devices fast with a comparatively high accuracy; the evaluated lifetime of the proposed model is close to the realizable life expectancy of the LED industry under the condition of normal temperature, humidity, and current; the practicability of the proposed model for lifetime reliability evaluation of LED devices is verified; the proposed model can be further developed with much more stresses.