In this paper, in view of the advantages of widely used Proportional-Integral-Derivative (PID) controller and gain scheduling control strategy in aerospace and industrial applications, a control strategy by using gain scheduling based PID controller is proposed for fault tolerant control (FTC) of a quad-rotor Unmanned Aerial Vehicle (UAV). The nonlinear dynamic equations of motion of the quad-rotor UAV are firstly derived based on the Newton's second law. PID controllers under fault-free and several different fault situations are then designed and tuned to control the quad-rotor UAV model under normal and different faults flight conditions. Each PID controller uses the speed and the orientation of each propeller for stabilizing and hovering motion of the quad-rotor UAV. Based on a decision variable (used as scheduling variable in this case) associated with a fault detection and isolation module, switching of each pre-tuned PID controller can be made in real-time and on-line. Simulation results under different fault scenarios have shown the effectiveness of the proposed approach for a six-degree-of-freedom nonlinear quad-rotor UAV model. Nomenclature M = mass of the vehicle x, y, z = x, y, and z position of the vehicle, respectively φ ,θ , ψ = roll, pitch, and yaw angle of the vehicle, respectively 1
This paper proposes an electrochemical etching technique to fabricate tungsten tips. Tips combining well-defined conical shape, a length as large as 2 mm, and sharpness with a radius of curvature of around 20 nm are fabricated using the proposed technique. These tips are needed in a variety of applications including multipoint contact measurements and nanomanipulation. The technique consists of three steps: the first is static etching, which creates a neck-in phenomenon on the wire; the second is dynamic etching, where the wire is oscillated up and down in the solution to form a long conical shape; finally, static etching is applied again to break the wire, and thus, sharp tips are produced. The best operating conditions of the process were experimentally obtained. These factors include the position of the cathode, the length of the immersed wire, and the applied voltage. The effects of these factors on the etching current and tip fidelity were also examined based on the measured etching current. In particular, the position of the cathode determines the strength of the electrical field near the air/solution interface; the immersed wire depth determines mainly the equivalent resistance of the process and thus controls the etching current; and the applied voltage defines the etching rate of the wire.
Controller Area Network (CAN) is the most prevalent communication protocol used in the automotive industry. This in-vehicle network provides a means communication between Electronic Control Units (ECUs) and components within the vehicle. The recent rapid development of connected, electric, and autonomous vehicles expands the complexity and information exchange within CAN and demands an increase in the reliability of the network. Efficient system-level diagnosis functions need to be integrated over the network to ensure for reliability and enhance the ease of troubleshooting. This paper presents a method to identify physical CAN faults such as loss of electrical connections and shorted wires. Fault signatures of predefined physical CAN faults are used to detect and identify the failure modes. The method can identify both permanent and intermittent faults caused by, for instance, damaged connectors and vibrations, respectively. Diagnosis tasks are implemented on in-vehicle module by measuring and processing physical layer voltages of all CAN buses. A real-time data buffer of a predefined size is utilized to calculate health indicators from the physical layer CAN voltages. The health indicators are then compared to predefined thresholds to determine the presence and type of the fault. Compared to ground truth data, the results show that the presented method can identify with high accuracy physical CAN faults including open electrical connection and shorted wires.
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