A Survey on Tactile Displays For Visually Impaired People.

Traditional paper documents with Braille characters and tangible graphics have obvious defects to disseminate knowledge in the information age. Information accessibility is an urgent challenge for blind individuals. Although many types of tactile displays were created for different applications, we especially focus on the tactile display for visually impaired people, which can dynamically generate tangible graphics and Braille characters, to help the blind obtain information conveniently. In this article, we present the state-of-the-art of graphic tactile displays (GTDs) and refreshable Braille displays (RBDs), then discuss their common kernel technologies about actuators and latch structures. This article summarizes the performance of typical actuators of tactile displays and analyzes the working principles of some latch structures. This article systematically summarizes latch structures of GTDs and RBDs, for the first time. Several comments in this paper will be useful to develop high-performance tactile displays for visually impaired people.

An Intelligent Multi-Sensor Variable Spray System with Chaotic Optimization and Adaptive Fuzzy Control.

During the variable spray process, the micro-flow control is often held back by such problems as low initial sensitivity, large inertia, large hysteresis, nonlinearity as well as the inevitable difficulties in controlling the size of the variable spray droplets. In this paper, a novel intelligent double closed-loop control with chaotic optimization and adaptive fuzzy logic is developed for a multi-sensor based variable spray system, where a Bang-Bang relay controller is used to speed up the system operation, and adaptive fuzzy nonlinear PID is employed to improve the accuracy and stability of the system. With the chaotic optimization of controller parameters, the system is globally optimized in the whole solution space. By applying the proposed double closed-loop control, the variable pressure control system includes the pressure system as the inner closed-loop and the spray volume system as the outer closed-loop. Thus, the maximum amount of spray droplets deposited on the plant surface may be achieved with the minimum medicine usage for plants. Multiple sensors (for example: three pressure sensors and two flow rate sensors) are employed to measure the system states. Simulation results show that the chaotic optimized controller has a rise time of 0.9 s, along with an adjustment time of 1.5 s and a maximum overshoot of 2.67% (in comparison using PID, the rise time is 2.2 s, the adjustment time is 5 s, and the maximum overshoot is 6.0%). The optimized controller parameters are programmed into the hardware to control the established variable spray system. The experimental results show that the optimal spray pressure of the spray system is approximately 0.3 MPa, and the flow rate is approximately 0.08 m3/h. The effective droplet rate is 89.4%, in comparison to 81.3% using the conventional PID control. The proposed chaotically optimized composite controller significantly improved the dynamic performance of the control system, and satisfactory control results are achieved.