藤原 大悟

<p>Flight control system with position compensation applicable to trajectory tracking of agile maneuvers that require an attitude rotation and a reverse of main rotor thrust of single-rotor helicopters is proposed. The outer loop position compensator calculates the desired attitude and rotor thrust which reduce position tracking error by utilizing a kinematics equation established near the reference trajectory. The desired attitude is set using the magnitude of the rotor thrust in the reference trajectory, which enables continuous position feedback compensation based on the fact that the relationship between rotational and translational motion becomes independent as the rotor thrust decrease. To achieve high-bandwidth control of lateral-longitudinal angular rates in the inner loop, two-degree-of-freedom servo system is designed using a linear model with blade flapping motion dynamics. The control system is applied to autonomous control of flip maneuvers which include transition between upright and inverted hovering. The reference trajectory of a flip maneuver is generated as a parameterized simple equation which can be adjusted to the helicopter ability. Simulation and outdoor flight tests of the autonomous flip maneuvers demonstrated the capability of position feedback compensation that reduces position tracking error during out-of-trimmed flight state. This control technique can be extended to various agile flights for quick execution of flight tasks or recovery maneuvers from dangerous state.</p>

<p>Aiming at the realization of agile autonomous flight for the extension of the flying range of single-rotor helicopters in the limited flight time, the flight control system design and the control performance verification for the high-speed turn flight are conducted. To achieve the reference following control for large attitude angles and the rotor thrust, the control system is composed of the main-rotor thrust and body torque centralized controller based on the MIMO (Multiple-Input, Multiple-Output) helicopter model including the blade motion dynamics, rotor speed proportional-integral controller, the attitude controller designed via the backstepping method based on the quaternion attitude model, and the guidance controller based on translational motion model. Simulation results show that the hovering and 10-m/s straight cruise flight followed by over 45-degree bank turn is feasible by using the proposed control system. In addition, flight tests have been conducted using the experimental small unmanned electric helicopter equipped with the flight control computer, and the high speed turn agile autonomous flight was successful in the real environment.</p>

This paper describes considerations of the effectiveness about the recovery control of the yaw rate motion of single-rotor helicopters by using both motors (engines) and main-rotor brakes in autorotation flight under tail-rotor damage conditions. First, the newly-developed main rotor brake unit for the experimental small helicopter is introduced. Flight test results show the yaw rate controllability by using the proposed brake and motor. Next, the yaw rate control system with a dead-zone estimator/compensator is designed to improve the control performance considering dead zones of input command signals of the brake or the motor. New method of dead-zone estimation when disturbances are applied to helicopters is proposed in this paper. This method is based on the nonlinear extended Kalman filter which enables simultaneous estimantion of dead zones and a yaw moment external disturbance by using a rotational speed of a main rotor in addition to a yaw rate for measurement updates of the estimator, which is designed based on the helicopter motion dynamics model including a clutch and a brake with motor dynamics. Estimation and control performances of the proposed system are validated through several simulation and flight test results.

This paper describes the leader-follower formation control using two different approaches which are the PID leader-follower formation control (PID-LFFC) and Sliding Mode Control leader-follower formation control (SMC-LFFC). The strategy used in this paper is to apply the control algorithm for conducting a circular motion. This task is known to be important since a trajectory is a combination of movement. This movement can be divided into straight or curve lines. Curves lines or circular motion is essential for obstacle avoidance and also for turning movement. The curves lines or circular motion gives lower trajectory distance than only using straight or angled lines. Based on the experimental result, it is seen that the performance of the algorithm is reliable. When using SMC-LFFC over the PID-LFFC, the leader to follower distance error is 30% smaller and has a high 70% occurrence at 0 errors. Additionally, this research is known to be the first conducted in Japan.

In this paper, we present an Inverse Kinematics (IK) algorithm based on the nonlinear least-squares method for redundant manipulators. The Newton- Raphson (NR) method is a commonmethod for IK calculation of redundant manipulators. The NR method, however, causes many problems in terms of joint angle limits, singularity, and solvability. Severalmethods have therefore been proposed to solve these problems. Most, however, focus only on IK calculation performance when a desired trajectory moves outside of the workspace. A manipulator is required to move continuously, even after a desired trajectory moves outside of the workspace. It is thus also necessary to implement the IK calculation method for bringing a desired trajectory back into the workspace. In this study, we propose a user-friendly method for robotic manipulation that is capable of implementing accurate IK calculation when a desired trajectorymust be returned to the workspace.

In this paper, we design a feed-forward trajectory following controller by using optimal preview control theory for a helicopter, based on its transition model and an LQI position controller derived from previous work. In order to apply optimal preview control theory to trajectory following control at any given yaw angle, we propose a correction method for eliminating disturbances due to attitude perturbations on the magnetic direction sensor. We show the axis transform of position and velocity has a problem and as a result it can not be applied to optimal preview control at any given yaw angle. To solve it, we propose alternative axis transform method. Finally, the performance of the designed preview controller and the proposed axis transform were verified by"circular"and"S character"trajectory following experiments.

In this paper, we propose a model-based control system design for autonomous flight and guidance control of a small-scale unmanned helicopter. Small-scale unmanned helicopters have been studied by way of fuzzy and neural network theory, but control that is not based on a model fails to yield good stabilization performance. For this reason, we design a mathematical model and a model-based controller for a small-scale unmanned helicopter system. In order to realize a fully autonomous small-scale unmanned helicopter, we have designed a MIMO attitude controller and a trajectory controller equipped with a Kalman filter-based LQI for a small-scale unmanned helicopter. The design of the trajectory controller takes into consideration the characteristics of attitude closed-loop dynamics. Simulations and experiments have shown that the proposed scheme for attitude control and position control is very useful.

Accurate positioning of an unmanned aerial vehicle is quite important for stable and safety flight. A GPS is very useful to get correct position and velocity of an movable body. But it can not always get accurate data because of varying measurement environment of the GPS signal from satellites. This paper discribes the GPS aided inertial navigation system (INS/GPS) for small-scale unmanned helicopter. We designed simple INS/GPS based on the steady state kalman filter to obtain more accurate positioning and apply this to control system of helicopter which we have been developed. And we prove experimentally that the usefulness of the INS/GPS.

Even though in our recent research we have developed autonomous hovering control, trajectory tracking control etc. successfully, the movements of the helicopter had to be limited only for slow maneuvers. So in this research we develop a method to achieve aggressive autonomous flights for our helicopter. We achieve high speed forward velocity control with a high acceleration by switching between velocity feed back control and feed forward attitude reference based attitude control. Then the 360 degree roll maneuver, using a complete feed forward sequence control method learned from the acrobatic flight test data of expert pilots. Finally we achieved a complete 360 degree roll maneuver starting form hover to the end of the maneuver autonomously by combining the above two methods.

In this paper, we propose a method of autonomous take-off and landing of small unmanned helicopter in time of peace or emergency. On a concrete target, the algorithm which can perform take-off and landing safety in time of peace, is built on basis of velocity control of helicopter. On the other hand, the flight called autorotation landing as a landing means in emergencies, such as an engine trouble, is automated. Autorotation is a flight method of getting energy from air and obtaining a thrust by falling. And we verified the validity of the method by performing experiment.

In this paper, we propose the model based control system design for autonomous flight and guidance control of a small-scale unmanned helicopter. A small-scale unmanned helicopter has been studied with fuzzy and neural network theory, but it is not so good performance for unmodel based control to stabilize it. For this reason, we design a mathmetical model (Mettler's model) and a model based controller for a small-scale unmanned helicopter system. In order to realize a full autonomous small-scale unmanned helicopter, we have designed the attitude controller and trajectory controller with kalman filter based LQI for a small-scale unmanned helicopter. The characteristic of the attitude closed loop dynamics is taken into consideration to design a trajectory controller. By way of the simulations and experiments, it has been clarified that the proposed scheme for attitude control and guidance control is very useful.

This paper describes hovering and horizontal guidance control with H_∞ controller and performance verification through flight experiments for the hobby-class small-scale unmanned helicopter. Simple system identification method was applied to acquire single-input/single-output models. Cross-validation results have shown that those models were reflected in the actual dynamics very well. Attitude control has been constructed by proportional-integral feedback loop with derivative feed-forward compensator for improvement of reference following performance. H_∞ control theory was applied for horizontal velocity control. Four closed-loop transfer functions were shaped according to the design specifications given in the frequency domain. Also, horizontal position control has been designed as proportional-derivative feedback. In the flight experiment, good performance of hovering and reference following has been shown through 15 m square point-to-point traveling guidance control, and this also showed high accuracy of the models.

We developed a small autonomous hobby-class unmanned helicopter that weighs about 9 kg, focusing on attitude and velocity models and controller design. Singe Input Single Output (SISO) transfer function models are derived from brief kinematical analysis and system identification for each of the helicopter dynamics of pitch, roll, yaw, and three direction velocities. We designed six separate controllers based on derived models using LQG and LQI control theory. The models and control structure are verified by experimental results. Accurate position control, namely, hover control and trajectory-following control, is achieved by a simple control algorithm using a designed attitude and velocity control structure. Robustness of the controller against wind was confirmed in a windy-day experiment. To'verify robustness against the perturbation of physical helicopter parameters, the controller is applied to a larger helicopter.

小型無人ヘリコプタは、ホバリング飛行や垂直離着陸といったフレキシブルな飛行形態を持つ事から高所危険作業に広く用いられている。本研究では、そういった小型無人ヘリコプタのモデルベース制御に用いるためのモデルをシステム同定ソフトCIFERを用いて求めることを目的とする。