• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.531-536
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• 2003

In this paper, a redesigned guidance and control system for a lunar lander is presented. In past studies, the authors developed a trajectory and attitude control system which achieves the vertical soft landing on the lunar surface. It is confirmed that the system has a good tracking ability to a predefined profile and good robustness against a thruster failure mode where a partial failure of clustered engines was assumed. However, under the previous control laws, the landing point tends to be shifted, in response to the system parameter values, from a target point. Also, an unbalanced moment due to a thruster failure mode was not considered in the simulation. Therefore, in this study, the downrange control is added to the system to enable the vehicle to land at a pre-assigned target point accurately. Furthermore, inhibiting the effect of the unbalanced moment is attempted thorough redesigning the attitude control system. A numerical simulation was performed to confirm the ability of the proposed system with regard to the above problems. Moreover, in the past simulations, a low initial altitude was assumed as an initial condition: in this study, however, the performance of the proposed system is examined over the whole trajectory from an initial altitude of 10 [km] to the lunar surface.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.11
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• pp.1004-1010
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• 2013

In this paper, a simple design of a DOB (Disturbance Observer) for attitude control of a quad-rotor system is presented. A modified DOB structure from the conventional DOB is introduced to eliminate time-delay in the calculation. The proposed simple modification in the DOB configuration provides an efficiency in the calculation of the disturbance term such that the delayed calculation is not required. The performance of the modified DOB is evaluated through simulation studies. To confirm the simulation results, experimental studies of the attitude control of a quad-rotor system are conducted.

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.230-236
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• 2007

In this study, a tail rotor system for an agricultural RF controlled helicopter was developed and tested. This study concluded the mechanical development of the 'Agro-heli' by completing the tail rotor system and its radio console. The RF control system was closely related with the tail system for the control of flying attitude. The thrust of the tail system balance off the reaction torque, created by the main rotor. Lifting tests with and without the tail system were compared for estimating the consumption of power. The tail system would use $4{\sim}5%$ of the total power which was in an acceptable range. Flying performance and attitude was visually inspected. It showed reliable and safe control during the distance flying trials and could be adapted for utilization in aerial applications. Aerial application using an RF controlled agricultural helicopter may make precise and timely spraying possible.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.107-122
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• 2002

Multi-body spacecraft attitude and configuration control formulations based on the use of collaborative control theory are considered. The control formulations are based on two-player, nonzero-sum, differential game theory applied using a Nash strategy. It is desired that the control laws allow different components of the multi-body system to perform different tasks. For example, it may be desired that one body points toward a fixed star while another body in the system slews to track another satellite. Although similar to the linear quadratic regulator formulation, the collaborative control formulation contains a number of additional design parameters because the problem is formulated as two control problems coupled together. The use of the freedom of the partitioning of the total problem into two coupled control problems and the selection of the elements of the cross-coupling matrices are specific problems ad-dressed in this paper. Examples are used to show that significant improvement in performance, as measured by realistic criteria, of collaborative control over conventional linear quadratic regulator control can be achieved by using proposed design guidelines.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.307-317
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• 2008

Relaxed static stability(RSS) concept has been applied to improve aerodynamic performance of modem version supersonic jet fighter aircraft. Therefore, flight control system are necessary to stabilize an unstable aircraft and provides adequate handling qualities. Also, flight control systems of modem version aircraft employ a safety system to support emergency situations such as a pilot unknown attitude flight conditions of an aircraft in night flight-testing. This situation is dangerous because the aircraft can lose if the pilot not take recognizance of situation. Therefore, automatic recovery system is necessary. The system called the "Pilot Activated Recovery System" or PARS, provided a pilot initiated automatic maneuver capable of an aircraft recoveries in situations of unusual attitudes. This paper addresses the concept of PARS and designed using nonlinear control law design process based on model of supersonic jet trainer. And, this control law is verified by nonlinear analysis and real-time pilot evaluation using in-house software. The result of evaluation reveals that the PARS support recovery of an aircraft unusual attitude and improve a safety of an aircraft.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.9
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• pp.881-885
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• 2008

To calculate the attitude in ARS(Attitude Reference System) using 3 gyros and 3 accelerometers, gyro drift must be compensated with accelerometer to avoid divergence of attitude error. Kalman filter is most popular method to integrate those two sensor outputs. In this paper, new Kalman filtering method is proposed for roll and pitch attitude estimation. New states are defined to make linear equation and algorithm for changing Kalman filter parameters is proposed to ignore disturbances of acceleration. This algorithm can be easily applied to low cost ARS.

• Journal of Biosystems Engineering
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• v.18 no.3
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• pp.199-208
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• 1993

This study was attempted to develop the eletronic-hydraulic hitch system for controlling the attitude of tractor implements and to investigate control performance of the system through experiments. Main components of the system developed in this study were reference inputs panel, inclination angle detecter, electronic controller consisted of IBM-AT PC and interfaces, electro-hydraulic directional valves and other hydraulic components and three-point hitch linkage. Experiments were carried out to investigate the response of the system to the step and sine inputs. The effects of hydraulic flow rate and dead band on control performance were analized. Attitude of the implement was controlled within 2.4-5.1 degrees to the setting attitude when the hydraulic flow rate was in the range of $0.25-1.5{\ell}/min$. And implement was controlled without rapid amplitude attenuation and phase angle change in the frequency range of 0.02-0.2Hz when the hydraulic flow rate was in the range of $0.25-1.5{\ell}/min$. Control performance of the system can be expected to be improved if the inclination angle detecter show rapid and stable output as the implement moves.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1599-1603
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• 2004

Based on the idea that nonlinear PWM controller design can be directly applied to the attitude tracking problem of thruster-controlled spacecraft because it constitutes a sub-class of nonlinear PWM controlled system, nonlinear and output error feedback PWM controlled system is considered to describe the behavior of thruster-controlled spacecraft, and to determine actual thruster on-time which guarantees system stability. A differential geometric approach is utilized to show an asymptotical stability of average PWM system, which finally guarantees the stability of closed loop PWM controlled system. Simulation results show that the motions of PWM controlled system occurs very closely around those of the average model of PWM controlled system.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.459-475
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• 2018

In the field of aerospace engineering, accurate control of a spacecraft's orientation is often very important to mission success. Therefore, attitude control is a technically plentiful and extensively studied subject in controls literature during recent decades. This investigation of spacecraft attitude control is assumed to address two important aspects of the problem solutions. One sliding mode anti-disturbance control for utilization of faulty actuator components and another one disturbance observer based control to improve the pointing accuracy in the absence of anti-vibration equipment for the elastic appendages like a solar panel. Simultaneous occurrence of vibration due to flexible appendages and reaction degradation due to failure in attitude actuators complicates this case. The advantage of this method is acquisition proper control by the combination of disturbance observer and sliding mode compensation that form a fault tolerant control for the concerned satellite attitude control system. Furthermore, the proposed composite method indicates that occurrence the failure in actuators and even elastic solar panel vibration effect may be handled directly without reconfiguring the control components or providing piezoelectric devices. It's noteworthy, attitude quaternion and angular velocity commands are robustly tracked via controllers to become inclined to zero.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.1
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• pp.69-78
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• 1999

The attitude determination system is indispensable for navigation, guidance and control tasks. In order to construct this system some special products that use dual frequencies or have on receiver engine with multiple antennas are used. But they are so expensive. Thus there are still strong requirements for the conventional low cost single frequency off-the-shelf receiver. This paper will propose a new technique to resolve integer ambiguity with single frequency GPS receiver and will show the problems of the attitude applications in which low cost receiver are being used. Also, based on this new technique precise attitude determination is presented.