No description available.
Masoud, Ziyad Nayif
24 January 2001
Ship-mounted cranes are used to transfer cargo from large container ships to smaller lighters when deep-water ports are not available. The wave-induced motion of the crane ship produces large pendulations of hoisted cargo and causes operations to be suspended. In this work, we show that in boom type ship-mounted cranes, it is possible to reduce these pendulations significantly by controlling the slew and luff angles of the boom. Such a control can be achieved with the heavy equipment that is already part of the crane so that retrofitting existing cranes would require a small effort. Moreover, the control is superimposed on the commands of the operator transparently. The successful control strategy is based on delayed-position feedback of the cargo motion in-plane and out-of-plane of the boom and crane tower. Its effectiveness is demonstrated with a fully nonlinear three-dimensional computer simulation and with an experiment on a 1/24 scale model of a T-ACS (The Auxiliary Crane Ship) crane mounted on a platform moving with three degrees of freedom to simulate the ship roll, pitch, and heave motions of the crane ship. The results demonstrate that the pendulations can be significantly reduced, and therefore the range of sea conditions in which cargo-transfer operations could take place can be greatly expanded. Furthermore, the control strategy is applied experimentally to a scaled model of a tower crane. The effectiveness of the controller is demonstrated for both rotary and gantry modes of operation of the crane. This work was supported by the Office of Naval Research under Contract #N00014-96-1-1123. / Ph. D.
Henry, Ryan J.
14 July 1999
It is sometimes necessary to transfer cargo from a large ship to a smaller ship at sea. Specially designed craneships are used for this task, however the wave-induced motions of the ship can cause large pendulations of cargo being hoisted by a ship-mounted crane. This makes cargo transfer in rough seas extremely dangerous and therefore transfer operations normally cease when sea state 3 is reached. If the cargo pendulations could be reduced in higher sea states, transfer operations would be possible. By controlling the boom luff angle, one can reduce the cargo pendulations in the plane of the boom significantly. A two-dimensional pendulum with a rigid massless cable and massive point load is used to model the system. A control law using time-delayed position feedback is developed and the system is simulated on a computer using the full nonlinear equations of motion. A three-degree-of-freedom ship-motion simulation platform, capable of simulating heave, pitch, and roll motions, was built. The computer simulation results were experimentally verified by mounting a 1/24th scale model of a T-ACS crane on the ship-motion simulation platform. / Master of Science
Nayfeh, Nader Ali
30 December 2002
Cranes are increasingly used in transportation and construction. increasing demand and faster requirements necessitate better and more efficient controllers to guarantee fast turn-around time and to meet safety requirements. Container cranes are used extensively in ship-to-port and port-to-ship transfer operations. In this work, we will extend the recently developed delayed position feedback controller to container cranes. In contrast with traditional work, which models a crane as a simple pendulum consisting of a hoisting cable and a lumped mass at its end, we have modeled the crane as a four-bar mechanism. The actual configuration of the hoisting mechanism is significantly different from a simple pendulum. It consists typically of a set of four hoisting cables attached to four different points on the trolley and to four points on a spreader bar. The spreader bar is used to lift the containers. Therefore, the dynamics of hoisting assemblies of large container cranes are different from that of a simple pendulum. We found that a controller which treats the system as a four-bar mechanism has an improved response. We developed a controller to meet the following requirements: traverse an 80-ton payload 50 m in 21.5 s, including raising the payload 15 m at the beginning and lowering the payload 15 m at the end of motion, while reducing the sway to 50 mm within 5.0 s at the end of the transfer maneuver. The performance of the controller has been demonstrated theoretically using numerical simulation. Moreover, the performance of the controller has been demonstrated experimentally using a 1/10th scale model. For the 1/10th scale model, the requirements translate into: traverse an 80 kg payload 5 m in 6.8 s, including raising 1.5 m at the beginning and lowering 1.5 m at the end of motion, while reducing the sway to 5 mm in under 1.6 s. The experiments validated the controller. / Master of Science
Haneman, David S
Performance feedback has long been a popular strategy for organizational change (Fairbank & Prue, 1981). One of the primary advantages of performance feedback interventions is the relatively low cost of implementation for organizations when compared to other productivity-enhancement techniques, such as monetary incentives (Yukl, Wexley, & Seymore, 1972) like pay for performance (Lazear, 1995) or employee of the month programs with rewards associated with them (Daniels, 2000). Performance feedback is beneficial to ensure that employees are knowledgeable of the expectations, and what aspects of job performance need to be improved. Three studies (i.e., Betchel, McGee, Huitema, & Dickinson (2015); Alajadeff Abergel, Peterson, Wiskirchen, Hagen & Cole (2017) and Wine et. al. (2019)) have published research evaluating feedback presented prior to completion of a task; however, results varied. The current study evaluated whether feedback presented prior to a performance event improves performance when compared to a baseline condition where no feedback was presented. / Applied Behavioral Analysis
22 May 2012
Today, except for mathematical operations, our brain functions much faster and more efficient than any supercomputer. It is precisely this form of information processing in neural networks that inspires researchers to create systems that mimic the brain’s information processing capabilities. In this thesis we propose a novel approach to implement these alternative computer architectures, based on delayed feedback. We show that one single nonlinear node with delayed feedback can replace a large network of nonlinear nodes. First we numerically investigate the architecture and performance of delayed feedback systems as information processing units. Then we elaborate on electronic and opto-electronic implementations of the concept. Next to evaluating their performance for standard benchmarks, we also study task independent properties of the system, extracting information on how to further improve the initial scheme. Finally, some simple modifications are suggested, yielding improvements in terms of speed or performance.
Omar, Hanafy M.
27 January 2003
The main objective of this work is to design robust, fast, and practical controllers for gantry and tower cranes. The controllers are designed to transfer the load from point to point as fast as possible and, at the same time, the load swing is kept small during the transfer process and completely vanishes at the load destination. Moreover, variations of the system parameters, such as the cable length and the load weight, are also included. Practical considerations, such as the control action power, and the maximum acceleration and velocity, are taken into account. In addition, friction effects are included in the design using a friction-compensation technique. The designed controllers are based on two approaches. In the first approach, a gain-scheduling feedback controller is designed to move the load from point to point within one oscillation cycle without inducing large swings. The settling time of the system is taken to be equal to the period of oscillation of the load. This criterion enables calculation of the controller feedback gains for varying load weight and cable length. The position references for this controller are step functions. Moreover, the position and swing controllers are treated in a unified way. In the second approach, the transfer process and the swing control are separated in the controller design. This approach requires designing two controllers independently: an anti-swing controller and a tracking controller. The objective of the anti-swing controller is to reduce the load swing. The tracking controller is responsible for making the trolley follow a reference position trajectory. We use a PD-controller for tracking, while the anti-swing controller is designed using three different methods: (a) a classical PD controller, (b) two controllers based on a delayed-feedback technique, and (c) a fuzzy logic controller that maps the delayed-feedback controller performance. To validate the designed controllers, an experimental setup was built. Although the designed controllers work perfectly in the computer simulations, the experimental results are unacceptable due to the high friction in the system. This friction deteriorates the system response by introducing time delay, high steady-state error in the trolley and tower positions, and high residual load swings. To overcome friction in the tower-crane model, we estimate the friction, then we apply an opposite control action to cancel it. To estimate the friction force, we assume a mathematical model and estimate the model coefficients using an off-line identification technique using the method of least squares. With friction compensation, the experimental results are in good agreement with the computer simulations. The gain-scheduling controllers transfer the load smoothly without inducing an overshoot in the trolley position. Moreover, the load can be transferred in a time near to the optimal time with small swing angles during the transfer process. With full-state feedback, the crane can reach any position in the working environment without exceeding the system power capability by controlling the forward gain in the feedback loop. For large distances, we have to decrease this gain, which in turn slows the transfer process. Therefore, this approach is more suitable for short distances. The tracking-anti-swing control approach is usually associated with overshoots in the translational and rotational motions. These overshoots increase with an increase in the maximum acceleration of the trajectories . The transfer time is longer than that obtained with the first approach. However, the crane can follow any trajectory, which makes the controller cope with obstacles in the working environment. Also, we do not need to recalculate the feedback gains for each transfer distance as in the gain-scheduling feedback controller. / Ph. D.
Lemley, Duane C.
19 December 2005
(has links) (PDF)
Although there is general agreement that feedback plays an important role in student performance, the majority of the studies found in the research literature explore the impact of different types of feedback in a traditional and university-level setting. In order to explore the impact of different feedback types in a non-traditional distance learning setting, 352 high school students enrolled in courses offered through BYU's Independent Study (IS) department received either delayed feedback or immediate feedback generated by Speedback™, BYU's automated grading and feedback program, depending on whether they had opted to submit end of unit assignments by mail or computer. Results of a comparison of final exam scores indicated that those students receiving immediate feedback performed significantly better on course final exams, but surprisingly those who received delayed feedback completed course in significantly less time.
The Utility of Immediate and Delayed Feedback within the Math to Mastery Intervention Package in a School SettingMiller, Marylyn Woods 13 December 2014 (has links)
The purpose of this study was to use a single subject research design to examine the effects of immediate feedback and delayed feedback within the Math to Mastery Intervention Package. The participants were 6 elementary school students who were performing approximately 1 year below grade level in math. A combined simple phase change design was used for the study. 3 of the students experienced the design in the A/B/A/C order, while the other 3 students experienced the design in a reversed order for B and C. During this study, ‘A’ represented the baseline phase and the return to baseline phase, ‘B’ represented the immediate feedback intervention phase, and ‘C’ represented the delayed feedback intervention phase. Each feedback phase was implemented separately for up to 4 weeks for each student. The final phase of intervention for each student included use of the most effective intervention condition after the student was exposed to both intervention feedback conditions. 2 weeks after the best intervention, follow-ups were conducted to determine if the students were able to maintain the skills that they were taught during the intervention. Results revealed that both intervention conditions were successful for addressing deficits in math academic performance. Improvement was seen for all 6 students with increases in digits correct per minute on single skill math worksheets, single skill math progress worksheets, and multiple skill math progress worksheets. Implications for school leadership within school settings are provided.
The Effect Of Immediate Feedback And After Action Reviews (AARS) On Learning, Retention And TransferSanders, Michael 01 January 2005 (has links)
An After Action Review (AAR) is the Army training system's performance feedback mechanism. The purpose of the AAR is to improve team (unit) and individual performance in order to increase organizational readiness. While a large body of knowledge exists that discusses instructional strategies, feedback and training systems, neither the AAR process nor the AAR systems have been examined in terms of learning effectiveness and efficiency for embedded trainers as part of a holistic training system. In this thesis, different feedback methods for embedded training are evaluated based on the timing and type of feedback used during and after training exercises. Those feedback methodologies include: providing Immediate Directive Feedback (IDF) only, the IDF Only feedback condition group; using Immediate Direct Feedback and delayed feedback with open ended prompts to elicit self-elaboration during the AAR, the IDF with AAR feedback condition group; and delaying feedback using opened ended prompts without any IDF, the AAR Only feedback condition group. The results of the experiment support the hypothesis that feedback timing and type do effect skill acquisition, retention and transfer in different ways. Immediate directive feedback has a significant effect in reducing the number of errors committed while acquiring new procedural skills during training. Delayed feedback, in the form of an AAR, has a significant effect on the acquisition, retention and transfer of higher order conceptual knowledge as well as procedural knowledge about a task. The combination of Immediate Directive Feedback with an After Action Review demonstrated the greatest degree of transfer on a transfer task.
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