Localization System For Visually Impaired People Based On Visible Light Communication

China is a country with the largest number of visually impaired people in the world.As the problem of aging accelerates,the number of visually impaired groups is also expanding.Action is the biggest problem facing the visually impaired.There are usually three ways to facilitate the visually impaired: the care worker,the guide dog,and the walking stick.The escorts are safe but time consuming and cannot guarantee companionship.The length of training for guide dogs is high and can be tolerated by non-ordinary families.The cane is not the first choice for travel because of the psychological impediment of the visually impaired.Visually impaired people are more inclined to use positioning equipment to help travel.The existing visually impaired people positioning system is mainly a GPS positioning system.The positioning system has obvious deficiencies.When the visually impaired people enter large supermarkets and shopping centers,because the environment is usually in the underground or high floors,the wall is occluded,and the signal is extremely extreme.Attenuation results in extremely low indoor positioning accuracy,generally only 5m,which does not meet the positioning requirements of the indoor environment.It is of far-reaching practical significance to develop a new type of visually impaired people to wear positioning equipment for indoor positioning.Based on the analysis of the current indoor positioning technology,this paper proposes and designs a positioning system for visually impaired people based on LED through the research and discussion of all relevant key technologies involved in the indoor positioning system.Designed for the visually impaired users,the device is made into a wearable form,and the miniaturized sheet is more suitable for wear.At the same time,because the user's vision is basically deprived,the interaction design is made from the sense of hearing and touch,and the human-computer interaction is mainly reflected in the display.The device can guide the visually impaired to operate through voice announcements or vibration feedback modes.Considering the current research status and enforceability of equipment,the design indicators are set as follows: positioning accuracy is 5cm,outer dimension are 10 cm and 5cm,positioning height is 160 cm.(1)Principle of visible light positioning.The optical signal is first transmitted,and the LEDs of different positions carry different position information through the optical signal frequency modulation module.The optical signal is then received by the photodetector,and the signal transmitted by the LED is received using a specific receiver(PD).Generally,when an optical signal is received,there is a photoelectric conversion process,and the optical signal is converted into an electrical signal for processing.The processed electrical signal is then processed by a positioning algorithm to calculate the position coordinates of the receiver.The location information is transmitted to the mobile phone through the Bluetooth device,and displayed in the mobile phone APP to achieve the purpose of long-distance communication.(2)Overall program design.Based on the products,the majority of the vulnerable groups are faced.When selecting components,it is necessary to select low-cost and high-precision equipment,and the cost and accuracy are the main reference factors for system design.The positioning system is divided into five modules: a light emitting module,a light receiving module,a signal processing module,a display module,and a communication module.It mainly includes the selection of positioning light source,the selection of photodetector,the design of positioning algorithm,the design of human-computer interaction warning function of display module and the design of mobile APP.(3)Analysis of main influencing factors of positioning accuracy.Through the analysis of the factors affecting the positioning accuracy involved in the system,including the error of the algorithm,measurement error,etc.,the real experiment can be avoided to improve the positioning accuracy.(4)The paper verified the correctness of the positioning method through experiments.The corner point correction is performed on the algorithm of the positioning system,so that the positioning error is greatly reduced.And the final experimental results show that the positioning error is within 5cm,which meets the design specifications.