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Quadrotors have been applied to collect information for traffic, weather monitoring, surveillance and aerial photography. In order to accomplish their mission, quadrotors have to follow specific trajectories. This paper presents proportional-integral-derivative (PID) cascade control of a quadrotor for path tracking problem when velocity and acceleration are small. It is based on near hover controller for small attitude angles. The integral of time-weighted absolute error (ITAE) criterion is used to determine the PID gains as a function of quadrotor modeling parameters. The controller is evaluated in three-dimensional environment in Simulink. Overall, the tracking performance is found to be excellent for small velocity condition. IntroductionRecently, a growing interest in unmanned aerial vehicles (UAVs) has been shown among the research community. Quadcopters are flying vehicles that can be equipped with cameras and sensors to perform many complex tasks. Due to their high maneuverability and small size, quadrotors have been widely used. Their potential applications include search-and-rescue, homeland security, military surveillance, and earth sciences [1][2][3]. In general, quadrotors are naturally unstable, under-actuated, under damped, coupled and nonlinear systems that need to be controlled. Several control techniques can be utilized to control a quadrotor including proportional-integral-derivative (PID) [4,5], linear quadratic regulator (LQR) [6], and backstepping and sliding mode control [7,8]. Because of its simple structure and good stability, PID plays an important role in quadrotor control.In this study, a PID controller is used for attitude and position control. Assuming small acceleration and small attitude angles, the corresponding control laws are derived. A Simulink model is developed where the performance of the controller is tested for different path-tracking cases.

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In this paper, we have used the differential evolution to optimize the design of a Micro Air Launch Vehicle and its launch trajectory. Since trajectory design of a launch vehicle requires prior knowledge of the masses and propulsion performance parameters of the Micro Air Launch Vehicle, whereas the vehicle design requires prior knowledge of the required velocity V to insert the required payload into the target orbit, a two step optimization cycle was adopted. A Micro Air Launch Vehicle was designed to launch a 20 kg payload into a 00 km circular polar orbit. The preliminary design of the Micro Air Launch Vehicle was conducted given the required V, which was obtained from trajectory optimization, and then applied in mission analysis to obtain the initial masses. These initial masses were used in the vehicle design to get the performance and geometry parameters. The objective function of the Micro Air Launch Vehicle design optimization is to minimize the initial mass under speci ed constraints on the insertion orbit. The objective of trajectory optimization is to maximize the payload mass under constraints on orbit speci cations and design variables. For the 20 kg payload mass, the optimal initial mass is 1267.8 kg and optimal payload is 20.6 kg, which slightly exceeds the mission requirements.