This paper covers the basic physics of solar sailing and then explores practical guidance techniques for controlling solar sailing spacecraft on the earth-moon halo orbit entry manifolds expected to be used by NASA...
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ISBN:
(数字)9781624105951
ISBN:
(纸本)9781624105951
This paper covers the basic physics of solar sailing and then explores practical guidance techniques for controlling solar sailing spacecraft on the earth-moon halo orbit entry manifolds expected to be used by NASA's Lunar Gateway. A four body (Sun, Earth, Moon, spacecraft) simulation is utilized to generate the resultant trajectory performance. Biases to the reference manifold trajectories are derived to center spacecraft acceleration capability within the limited solar sailing acceleration envelope, and improvements in performance are demonstrated.
Orbital debris in Earth orbit poses a threat to the future of spaceflight. To combat this issue, the rigid capture of these non-cooperative orbital targets is enabled through the use of dexterous robotic manipulators....
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ISBN:
(数字)9781624105951
ISBN:
(纸本)9781624105951
Orbital debris in Earth orbit poses a threat to the future of spaceflight. To combat this issue, the rigid capture of these non-cooperative orbital targets is enabled through the use of dexterous robotic manipulators. This paper proposes a novel robotic mechanism for capture and active servicing missions on non-cooperative targets;specifically, a tendon-driven manipulator is developed in this work. The capture mechanism is a prototype symmetric two-link gripper driven by an open-ended cable-sheath transmission mechanism. Since the cable-sheath transmission mechanism is a non-linear time varying hysteretic system, two separate adaptive control strategies were compared against the open-loop and proportional-integral-derivative controlled performance of the closed-loop gripper. Specifically, an indirect control method and a direct L-1 controller are proposed. Experimental results demonstrate that the adaptive controllers show better tracking performance of a joint trajectory over the proportional-integral-derivative and uncontrolled cases, while the L-1 controller performs best under dynamic conditions, and the indirect controller performs best in steady state.
In this paper, constant switching frequency current control of a three-phase boost rectifier is presented and implemented on a hardware-in-the-loop platform. The applied algorithm is capable of minimizing the harmonic...
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ISBN:
(纸本)9781665487788
In this paper, constant switching frequency current control of a three-phase boost rectifier is presented and implemented on a hardware-in-the-loop platform. The applied algorithm is capable of minimizing the harmonic content in both grid-side currents and output voltage, even under significant unbalance in supply voltages and input impedances. The constant switching frequency facilitates filtering of grid-side currents, thereby reducing the volume and cost of the filter components. While control algorithms similar to this one have been tested in simulations, no experimental verification has been offered so far. The hardware-in-the-loop implementation presented in this paper is a valuable in bridging the gap between simulation and the experiment. The control algorithm is implemented on an actual FPGA-based controller board, whereas all power components are simulated in real time on the hardware-in-the-loop platform. Various operating modes are analyzed to demonstrate the excellent performance of the algorithm regardless of the grid-side conditions.
Active-control algorithms such as optimal control or impulse control methods generally achieve satisfactory control effectiveness, but it often fails to control dynamic systems with time-delay effectively. In view of ...
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ISBN:
(纸本)9783037853115
Active-control algorithms such as optimal control or impulse control methods generally achieve satisfactory control effectiveness, but it often fails to control dynamic systems with time-delay effectively. In view of this reason, a novel active controller using Genetic algorithm (GA) is proposed in this paper, which is based on discrete motion equation of multi-freedom degree system with time delay. It can solve such subsistent problems as effective control for a seismically excited structure with an explicit time delay. Meanwhile it is also prone to achieve a desired vibration state in accordance with different control objectives. Finally in order to verify its validity, the GA controller are applied to a three-storey and a eight-storey structures excited by different seismic forces, numerical examples of which are given to prove it capable of providing satisfactory control effect with time delay.
Shearer and hydraulic support are matching equipments. To increase the operating speed of the shearer, the following speed of hydraulic support must be increased. This means increasing the volume of flow from emulsion...
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Shearer and hydraulic support are matching equipments. To increase the operating speed of the shearer, the following speed of hydraulic support must be increased. This means increasing the volume of flow from emulsion power station. Analyzing the operating characteristics of hydraulic supports, the number of simultaneously operating supports is obtained by means of pressure parameter and time history at a certain time, which is a theory base for development of control system to multi-pump emulsion power station.
作者：
Phan, Van Hieu
No. 1 Dai Co Viet Street Hanoi100000 Viet Nam
Currently, Quadcopter appears everywhere, such as environmental, agricultural, or transportation inspection;some works require more researches to clarify the effective results. The filtering performance used in popula...
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The performance of assistive and augmentative lower-limb exoskeletons has been tested in laboratory settings and can achieve goals of improved walking economy and metabolic cost reduction. However, it has been shown t...
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The performance of assistive and augmentative lower-limb exoskeletons has been tested in laboratory settings and can achieve goals of improved walking economy and metabolic cost reduction. However, it has been shown that even in controlled laboratory environments, exoskeletons may experience errors of improper torque assistance due to misalignments between the measured and actual state of the human-exoskeleton system. If the torque assistance repeatedly hinders a user's actions due to errors, the user may begin to anticipate errors and resist the exoskeleton. In order for exoskeletons to be adopted for everyday use, it is important to understand the immediate and long-term effects of exoskeleton errors on user motion and trust in the system, as errors are likely to occur in operational settings with complex, changing environments. It is also necessary to understand the strategies that people utilize when interacting with exoskeletons to design control methods to support collaboration between humans and exoskeletons. This work used the Dephy bilateral powered ankle exoskeleton, which applied an assistive plantarflexion torque during push-off to minimize energy expenditure during walking. The main aims of this thesis are to characterize the (1) immediate effects and (2) residual effects of exoskeleton errors on human gait strategies, as well as (3) develop a co-adaptive exoskeleton controller to support collaboration between the user and exoskeleton. In Chapter 2, immediate compensatory hip behavior was identified in response to pseudo-random exoskeleton errors (loss of exoskeleton assistance) as users maintained acceptable task performance on a targeted stepping task. Quantitative measures of human-exoskeleton fluency---the alignment of the user and exoskeleton's goals---were developed using joint kinematics and muscle activity metrics. Emergent gait strategies were identified in Chapter 3 using k-means clustering as users walked with imperfect exoskeleton algorithms
This study was conducted to investigate the application of a magnetorheological (MR) damper in the semi-active control of bridge response. A series of cyclic loading tests was carried out on a MR damper under various ...
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ISBN:
(纸本)0819440167
This study was conducted to investigate the application of a magnetorheological (MR) damper in the semi-active control of bridge response. A series of cyclic loading tests was carried out on a MR damper under various loading frequencies. loading amplitudes. and current levels. The damping force of the MR damper was idealized by the model composed of friction and viscous elements in parallel. Two algorithms to change damping force according to displacement or velocity were investigated. It is found that the commanded damping force can be realized by the MR damper. However, discrepancy of damping force is observed, especially when the rate of change of the damping force is high. The shaking table test was conducted on a model bridge with the MR damper to investigate the effectiveness of the control algorithms.
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