Tethered capture of space debris is a promising method of active debris removal (ADR), but has numerous well-known challenges in the post-capture phase. control of the system in this phase is complicated by nonlinear ...
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ISBN:
(数字)9781624107115
ISBN:
(纸本)9781624107115
Tethered capture of space debris is a promising method of active debris removal (ADR), but has numerous well-known challenges in the post-capture phase. control of the system in this phase is complicated by nonlinear dynamics with the potential of chaotic motion, unknown debris parameters, and debris tumbling. The inherent uncertainty present in the system and the need for control often necessitate the estimation of debris states and parameters such that the post-capture system can remain controlled. To this end, a relative distance ProportionalIntegral-Derivative (PID) control and an Unscented Kalman Filter (UKF) are implemented during the post-capture phase of an ADR mission. It is assumed that some debris (target) states and properties are unknown to the chaser, requiring the estimation of the attitude, angular rates, and principal moments of inertia of the target. For estimating these states, the UKF uses measurements of the tether tension magnitude and pixel coordinates of feature points on the target provided by a camera mounted on the chaser. Both estimation and control are done simultaneously, simulating online estimation and control of an ADR mission. The PID control was found to maintain safe conditions when using the estimated states in two separate Monte-Carlo simulations, differing in the measurement frequency of the pixel coordinates, while the estimation of the principal moments of inertia of the debris was satisfactory.
Because of the communication distance, the more nodes, the requirements of high real-time, LED lighting control system for railway vehicle carriage chooses controller Area Network (CAN) as the communication mode to ac...
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ISBN:
(纸本)9783037857649
Because of the communication distance, the more nodes, the requirements of high real-time, LED lighting control system for railway vehicle carriage chooses controller Area Network (CAN) as the communication mode to achieve centralized control in all carriages. Illuminance gathered from multi-sensors which were installed on the surface of the carriages was feed back to the Industrial Personal Computer (IPC). And then, through the incremental PID control algorithm, the IPC achieve the brightness of the lighting system intelligent control for vehicle consulting brightness intensity which according to the external environment. Experiment shows that this method is practical and effective.
New lasers, special digital signal processing electronics, algorithms and new materials for optics enabled development of new absolute distance measurement methods. The phenomenon of the mode-lock of the femtosecond p...
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ISBN:
(纸本)9781538656839
New lasers, special digital signal processing electronics, algorithms and new materials for optics enabled development of new absolute distance measurement methods. The phenomenon of the mode-lock of the femtosecond pulse laser increased a number of potential applications with distance surveying where a stable generator of very short and periodically repeated coherent pulses can be used. The aim of the work is a presentation of our unique control algorithm for measuring the length of unknown distance with direct traceability to a time standard. The principle is based on a passive optical cavity with mirrors keeping distance to be measured. Time spacing of short femtosecond pulses generated by femtosecond laser is optically phase locked to the cavity free spectral range. A value of the repetition frequency of the laser determines the measured distance in that case.
In order to eliminate oscillation arisen from AIMD window control strategy in TCP, an adaptive PI rate controller (PI-RCA) was proposed to smooth the traffic and to prevent network from congestion. Theoretical analysi...
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ISBN:
(纸本)9781424423835
In order to eliminate oscillation arisen from AIMD window control strategy in TCP, an adaptive PI rate controller (PI-RCA) was proposed to smooth the traffic and to prevent network from congestion. Theoretical analysis and simulation evaluation showed that PI-RCA can make flow control system achieve stability robustness and adapt to sudden changes in network environment, thus providing the network with good transient behaviors. In this paper, we present an implemental evaluation of PI-RCA. We first implemented PI-RCA in the Linux kernel and solved various system issues. Second, we conducted some experiments to validate the previous simulation results. Compared with TCP, the experimental results show that the PI-RCA is much more easily to maximize link/per-flow utilization, to achieve fairness and nearly zero packet drops rate.
The paper discusses the conditions for diagnosis of combustion process using additional signals from non-invasive optical methods. This approach allows to obtain additional information about the ongoing process in an ...
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ISBN:
(纸本)9781138031630
The paper discusses the conditions for diagnosis of combustion process using additional signals from non-invasive optical methods. This approach allows to obtain additional information about the ongoing process in an non-invasive way. The radiation emitted by the flame is a reflection of the chemical and physical reactions, occurring in the combustion process. The changes of the flame position in space results in shape fluctuations that can be interpreted as disruption of the balance results. The authors assumed that under certain conditions the shape of the flame can be an important indicator. Considering adequate emission flame spectrum, it is possible to determine the content appropriate process parameters. The optical methods based control seems to be particularly important for effective combustion and co-combustion, considering both economical and ecological factors in sense of industrial ecology.
The stability of temperature in the chamber of excimer laser has a great effect on working performance of the excimer especially for the energy stability and useful life. So it is very important to keep the chamber te...
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ISBN:
(纸本)9781479954582
The stability of temperature in the chamber of excimer laser has a great effect on working performance of the excimer especially for the energy stability and useful life. So it is very important to keep the chamber temperature constantly. Based on that, a high precision temperature control system of excimer laser and two improved PID control algorithms were designed. Experimental results indicate that the designed system runs reliably and has superior control precision which provides a favorable temperature environment for the laser's operation.
We present a new technology for real-time walking of a humanoid robot. A humanoid robot necessitates achieving stabilization for real time walking since it has basic problems such as structural stability. In this pape...
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ISBN:
(纸本)9788993215090
We present a new technology for real-time walking of a humanoid robot. A humanoid robot necessitates achieving stabilization for real time walking since it has basic problems such as structural stability. In this paper, a robust control algorithm for stable walking is proposed based the ground reaction forces, which are measured using force sensors during walking, and the environmental conditions are estimated from these situation. From this information the robot selects the proper motion and overcomes ground irregularities effectively. In order to generate the proper angel of the joint. The performance of the proposed algorithm is verified by simulation and experiments for a 20-DOFs humanoid robot.
Earthquake inflicts damage on bridges in various ways. In this research an experimental study was carried out to decrease the damage caused by the pounding of bridges as earthquake load was added. For the experiment, ...
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ISBN:
(纸本)9783037857960
Earthquake inflicts damage on bridges in various ways. In this research an experimental study was carried out to decrease the damage caused by the pounding of bridges as earthquake load was added. For the experiment, we designed a model of successive bridge composed of a reinforced concrete bridge top and I section steel. At each bridge pier was placed a rubber bearing which was frequently used for seismic isolation. As for damper, we ourselves designed and produced a MR damper of 30 KN. Five experimental conditions were given ranging from without damper, with damper but no electricity input, with damper and electricity input, each with two different algorithms. For the experiment, we inflicted a 50% reduced wave of Kobe earthquake horizontally on the model, and compared the displacements and power data under each condition. The result proved that the MR damper of our own design was effective to prevent the successive bridge model from colliding by exerting a sizable amount of influence on its displacement and power data.
In this paper, model predictive control (MPC) approaches are implemented to deal with spacecraft maneuvering problems for cargo carrying with an uncertain load for future in-space servicing and assembly missions. Firs...
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ISBN:
(数字)9781624107115
ISBN:
(纸本)9781624107115
In this paper, model predictive control (MPC) approaches are implemented to deal with spacecraft maneuvering problems for cargo carrying with an uncertain load for future in-space servicing and assembly missions. First, a tube-based robust MPC approach is tested using Astrobee robots onboard the International Space Station (ISS). Its performance and capability are demonstrated when an active Astrobee moves an inactive Astrobee as an unknown object to a desired position. Second, a decentralized MPC framework is exploited to transport an unknown object to a desired location using two active Astrobees. Based on a leader-follower strategy using a virtual leader and formation constraints, the two robots can maintain a specific formation and achieve multi-agent cooperative transportation tasks. Simulation and experimental results are compared to demonstrate the decentralized MPC approach's capability.
At present, because of the shortcomings of traditional visual servo control methods, such as slow convergence speed and camera calibration, an advanced visual servo control method is based on the combination of fuzzy ...
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ISBN:
(纸本)9798350334722
At present, because of the shortcomings of traditional visual servo control methods, such as slow convergence speed and camera calibration, an advanced visual servo control method is based on the combination of fuzzy logic and Kalman filter, which is proposed in the paper. In the control method, Kalman filter algorithm is used to estimate image Jacobian matrix online, and fuzzy logic control algorithm is used to design variable control coefficient instead of traditional fixed control coefficient, which not only reduces convergence time of visual servo control system, but also avoids complex phase machine calibration, saves a lot of time, and improves work efficiency. Finally, the effectiveness and superiority of the proposed control method are verified by experiment simulation.
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