Both RGB and YCrCb color space are often used in video image processing, along with the wide application of FPGA in the field of video image processing, RGB to YCrCb color space conversion is frequently needed on FPGA. This paper analyzes the process of RGB to YCrCb color space conversion on FPGA, and proposes a fast conversion method using look-up table and pipeline technology. Firstly, on the premise of holding accuracy, floating point numbers are expanded to integer which is convenient for FPGA processing. Secondly, aimed at the speed limitation of multiplication in conversion, multiplications are transformed to look-up tables and additions. Finally, in the course of numerous addition operations, pipeline technology is fully utilized to further improve the operation speed. The proposed method which is implemented on XC4VLX15 chip for color space conversion, obtains maximum operating frequency of 358MHz, 3.5 times faster than that of direct method. Experimental results demonstrate that the proposed method can effectively improve the speed of RGB to YCrCb color space conversion when compared with existing method.
Wind energy as a renewable energy source is easily available and widely distributed in cities. However, current wind-energy harvesters are inadequate at capturing energy from low-speed winds in urban areas, thereby limiting their application in distributed self-powered sensor networks. A triboelectric–electromagnetic hybrid harvester with a low startup wind speed (LSWS-TEH) is proposed that also provides output power within a wide range of wind speeds. An engineering-implementable propeller design method is developed to reduce the startup wind speed of the harvester. A mechanical analysis of the aerodynamics of the rotating propeller is performed, and optimal propeller parameter settings are found that greatly improved its aerodynamic torque. By combining the high-voltage output of the triboelectric nanogenerator under low-speed winds with the high-power output of the electromagnetic generator under high-speed winds, the harvester can maintain direct current output over a wide wind-speed range after rectification. Experiments show that the harvester activates at wind speeds as low as 1.2 m/s, powers a sensor with multiple integrated components in 1.7 m/s wind speeds, and drives a Bluetooth temperature and humidity sensor in 2.7 m/s wind speeds. The proposed small, effective, inexpensive hybrid energy harvester provides a promising way for self-powered requirements in smart city settings.
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