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A set of algorithms are developed to estimate the air velocity of the quadrotors by fusing the plant model of the three-dimensional aerodynamic force and the IMU (inertial measurement unit) measurement. The main ideas are to compute out the air velocity of the quadrotors at first with the measured load acceleration and the model of the aerodynamic force, and then to smooth the computed results with the extended Kalman filtering against the model uncertainties. The developed algorithms are verified in the closed-loop flight control system. The simulation results demonstrate that the air velocity of the quadrotors are estimated well in the large airspeed and the resulting closed-loop system with the estimated air velocity can achieve almost the same flight performances as that with the real air velocity.

In this paper, a novel motion planning approach is proposed for high-speed flight of Micro Air Vehicles (MAVs) in unknown cluttered environment using a stereo camera as unique sensor. The proposed motion planning works directly on a depth map which represents partial surrounding environment due to limited field of view (FOV) of the stereo camera. The depth map updates at each sampling time. An optimal local target is selected from a set of local targets to which line-of-sight paths are collision-free. Then an optimal collision-free trajectory satisfying kinematic constraints is generated. The simulation results demonstrate the effectiveness of the proposed motion planning approach.

A hierarchical composite nonlinear feedback (HCNF) control technique is proposed in which the auxiliary integrators are introduced to remove the steady-state bias due to the disturbances. The main idea of HCNF is to separate the control design of the auxiliary integrators and the composite nonlinear feedback (CNF) control design. The auxiliary integrators are applied only to remove the steady-state bias by automatically adjusting the commands to be tracked by the CNF control law in which the CNF control design does not involve with the auxiliary integrators. The HCNF control technique is applied to design the attitude control law of a maneuvering flight control law for a quadrotor. The resulting closed-loop system is verified in simulation successfully to complete the maneuvering flight.

A comprehensive model of a quadrotor is built for the maneuvering flight control design in which the nonlinearities of the quadrotor become dominant. The modeling is based on the components of the quadrotors such as the propellers by ignoring the weak coupling among the four propellers. The property of the propellers is tested in the wind tunnel in presence of the relative air flow and in each scheduled condition. The comprehensive model of the quadrotor is derived with the Newton's laws by integrating the property of the propellers. The built model is verified with the wind tunnel test data and The verification results show that the output of the propeller model is matched well with the test data. The built model is useful to the maneuvering flight control design of the quadrotors in high speed and large acceleration as the kinematical and aerodynamic nonlinearities are formulated in the model.

The nonlinear flight control design with the hierarchical dynamic inversion (HDI) and recursive control (RC) approaches is presented based on the comprehensive model of a quadrotor to implement the maneuvering flight in high speed and large acceleration. The flight control design comprises the kinematical control, command generation and dynamic control design. The command generation is to convert the required acceleration from the kinematical control into the flight commands of the roll, pitch angles and the heave load acceleration that the dynamic control laws can easily track. The designed nonlinear flight control laws are verified in simulation based on the comprehensive model of the quadrotor. The simulation results demonstrate that the resulting closed-loop system can successfully implement the maneuvering flight in high speed and large acceleration as well as its robustness against the model uncertainties is well. The introduction of the derivative commands of the roll and pitch angles yields a novel flight mode in which the quadrotor head points to a designated direction while the quadrotor conducts the maneuvering flight.

A nonlinear model of a flapping-wing micro aerial vehicle (MAV) is built in which the load acceleration and equivalent moment are formulated linearly in the body frame. The aerodynamic force and moment are not considered directly because the mass and moment of inertia of the flapping-wing MAV are too tiny. The visual measurement system (VMS) is taken to measure the flight data such as the position and Euler angles of the plant because there is no onboard sensor. The nonlinear optimization is applied to identify the parameters in the nonlinear model. Based on the built model, the under-actuated control laws are designed with the hierarchical dynamic inversion (HDI). The designed under-actuated control laws are verified in simulation. The simulation results demonstrate that the resulting closed-loop system is capable of asymptotically tracking the references in which the yaw angle is free. The modeling and control analysis are useful to development of the flapping-wing MAVs.

This paper present the Composite Nonlinear Feedback Control and Proportional Integral Sliding Mode Control (CNF-PISMC). The advantages of Composite Nonlinear Feedback Control are reducing overshoot; improve transient performance and fast response. The advantages of PISMC are to overcome uncertainties and steady state error in the system. The used of a boundary layer solution in the control law of CNF-PISMC is to reduce the chattering problem. The result of the boundary layer thickness is representing the ability of the CNF-PISMC controller in MacPherson strut active suspension system. The value of boundary thickness is tuned by using Evolutionary Strategy (ES) to provide the two values of boundary layer thickness. The multi-body dynamics system software so called CarSim is used for validation purposes.

A hierarchical-distributed methodology (HDM) is presented to implement the autonomous mission execution for multiple unmanned aerial vehicles (UAVs). The main idea of HDM is to divide the event control law into the group and individual event control laws. The group event control law is focused on the mission events. The individual event control laws are focused on the task events and motion events. Such division is reasonable as it emphasizes the task management and dynamic control of the single UAV and simplifies the mission management of the multiple UAVs. The simulation results demonstrate that the closed-loop system designed with the ideas of HDM autonomously completes the designated mission of the formation flight.

In this paper, we present a vision-based relative sensing system for UAVs to realize leader-follower formation flight without inter-vehicle communication. A monocular camera is mounted on the follower to detected the leader and measure the relative distance by using the geometry information of the leader without artificial markers. The measured relative distance is utilized to estimate the velocity and acceleration of the leader under the quasi-steady states assumption. Experimental results show that the proposed sensing system is capable of achieving the vision-based leader-follower formation flight.

The composite nonlinear feedback (CNF) control technique is successfully applied to design the controller based on control law for an active suspension system. The CNF control law is composed of a linear control law and a nonlinear feedback part. The main idea of CNF is to design the linear control law with a low damping-ratio to achieve fast rising time and to design the nonlinear feedback part to result in a high damping-ratio to remove the overshoot caused by the linear control law when the system controlled output approached the reference. Such the CNF control laws can improve the tracking and regulating performances of the resulting closed-loop systems. The active suspension system is hierarchically divided into two subsystems with the system transformation based on the system structural properties at first and then the CNF control laws are designed for the two subsystems each One of the CNF control laws is designed for tracking control and the other is designed against the mismatching disturbance. The complete control law is made by combining the two CNF control laws and the system transformation. The simulation results show that CNF controller is better than LQR controller and passive model. The computer simulation is done to prove the CNF control performance.

The purposes or functions of the commercial car suspension system are to take care on the car body weight, to isolate the car body from road profiles disturbance and to maintain the grip force between the wheel and road profiles. The Composite Nonlinear Feedback (CNF) control law is proposed in this comparative study between conventional linear model and Macpherson model. The control performance consists of velocity of car body, suspension deflection, wheel deflection and velocity of a car wheel. The main measurement in this study is the acceleration of the car body. The Linear Quadratic Regulator (LQR) and passive model are involved in this control performance is for comparison purposes. The mathematical model of linear model and MacPherson model are focused on the quarter car model active suspension system. The simulation work is done by using MATLAB and SIMULINK to see the control performance on the quarter car active suspension model. In this paper we can conclude that the CNF achieved the main objective of active suspension which is the ride comfort and road handling.

This paper proposes LMI-based design procedures for two classes of unknown input observers (UIOs) for the purpose of fault detection and isolation (FDI). The design procedures for the first class of UIOs can not only relax the restrictions on the rank of output and noise, but also take into account both robustness and sensitivity to UIOs. Several tuning techniques are also provided. For the second class of UIOs, an alternative structure is recommended to reduce the design complexity in multiple-fault cases. We analyze the advantages and weaknesses of the proposed approaches, and utilize a linearized model of fixed-wing unmanned aerial vehicle (UAV) with disturbance as the design platform to illustrate their performance.

Hierarchical dynamic inversion (HDI) is proposed together with newly developed variant-factor and recursive control techniques to design autonomous flight control (AFC) laws for fixed-wing aircraft. HDI is applicable to control design of some non-affine nonlinear systems to which dynamic inversion is not applicable. The AFC law designed with HDI at the nominal flight condition is applicable to other flight conditions in a wide flight envelope so that workload can be reduced significantly in AFC design compared to gain scheduling. The simulation results demonstrate that with the AFC law designed with HDI, the aircraft successfully completes the pre-scheduled maneuvering flight in a subsonic flight envelope.

In this paper, we present an enhancement scheme for global positioning system (GPS) signals received on an unmanned aerial-vehicle (UAV) helicopter system. Because of the limitation of the hardware units and the GPS system, parts of the signals are discontinuous and have huge jumps from time to time. Such a problem degrades a great deal the overall performance of the automatic flight control system of our UAV helicopter. We employ in this work an Kalman filter technique together with a complementary filter to regenerate smooth and accurate signals that can be used for the implementation of automatic flight control systems. Our simulation and implementation results show that the proposed scheme is very effective and yields a good improvement on the performance of the overall flight control system of our UAV helicopter.

We present in this paper a flight control system design for the yaw channel of a UAV helicopter using a newly developed composite nonlinear feedback (CNF) control technique. From the actual flight tests on our UAV helicopter, it has been found that the commonly used yaw dynamical model for the UAV helicopter proposed in the literatures is very rough and inaccurate. This motivates us to first obtain a comprehensive model for the yaw channel of our UAV helicopter. The CNF control method is then utilized to design an efficient control law, which gives excellent overall performance. In particular, our design has achieved a level 1 performance according to the standards set for military rotorcraft. The results are verified through actual flight tests.

We present in this paper a linearized hovering model of a UAV helicopter obtained using the in-flight data generated through a perturbation method. The UAV helicopter is constructed from a radio-controlled helicopter by integrating an onboard system, which includes a data processing unit, a data acquisition system, a wireless communications and all necessary sensors. A flight control law is then designed using a newly developed nonlinear control technique, i.e. the composite nonlinear feedback control. Actual flight testing shows that the design is successful.

The modeling of yaw dynamics of a UAV helicopter is focused on together with its control system design. From the flight tests on our actual UAV helicopter, it has been found that the yaw dynamical model for the UAV helicopter proposed in the literatures is very rough and inaccurate, which might cause the helicopter to shake severely in certain flight conditions. A complete examination is carried out to identify a perfect model of the yaw channel in the UAV helicopter. It would be found that the assumption in the old model is not appropriate. Some advanced control schemes will then be adopted to solve the shaking problem observed in the yaw channel.

This paper presents a discrete-time robust non-linear control method to achieve fast and accurate set-point tracking for servo systems subject to actuator saturation and disturbances. The idea here is to use a combination of composite nonlinear feedback (CNF) control and disturbance estimation cum compensation. The CNF control is responsible for superior transient performance, i.e. to guarantee a fast response with low overshoot, while the disturbance estimator/compensator is used to remove the steady state bias that would otherwise be existent due to disturbances. Practical application in a micro hard disk drive servo system will be given to demonstrate the effectiveness of this control method.

A generalized composite nonlinear feedback (CNF) control technique will be presented to track non-step references. A reference generator will be adopted to supplement the CNF control technique so as to track the non-step references. The reference generator can be designed to produce a desired reference. The generalized CNF control law comprises the reference generator and a modified enhanced CNF control law. The proposed method will be applied to design control laws for an XY-table. Simulation and implementation results will verify that the generalized CNF control law is indeed capable of tracking the non-step references.

This paper deals with compensation of torque disturbances in a hard disk drive (HDD) to improve its head positioning performance. The torque disturbances from the data flex cable and friction in the actuator rotary pivot bearing yield a significant bias and large residual error, which deteriorate performance of the overall system. Reducing effect of these torque disturbances has been one of challenges in designing head positioning servo systems. In this paper, a comprehension physical model of the voice coil motor (VCM) will be derived through analysis of physical effects and the parameters will be determined with the Monte Carlo method to match those responses measured in the perturbation method. A modified integral is added into a linear control law to reduce the disturbances and improve performance of head positioning servo systems. The simulation and experimental results show significant improvement on performance of the head positioning servo systems.

This paper is to analyze effect of the data flex cable and friction in the actuator rotary pivot bearing on performance of head positioning servo systems in micro hard disk drives (HDD). The micro HDD is one of trends in the disk drive industry, which can be used by portable devices such as digital cameras. A nonlinear model of the micro HDD will be established, where its configuration of nonlinearities will be identified with analysis of physical effects and its parameters will be determined with the Monte Carlo method. A control law will be designed to analyze effect of these torque disturbances on performance of head positioning servo systems through simulations and experiments.

The strictly decreasing relationship between the sample approximation error and the number of hidden units in a three layer artificial feedforward neural network (AFNN) is proven in the sample space. The relationship is a powerful tool in determining the number of hidden units needed. A hybrid optimization algorithm is proposed on the relationship for simultaneously determining the number of hidden units and weight coefficients in the AFNN. The algorithm is the synthesis of golden section, evolutionary programming and gradient based algorithm which is effective in determining the number of hidden units and weight coefficients in the neural network.