Machine vibration leads to lower precision, efficiency, and safety. As a result, large sums of money and innumerable man-hours are spent in efforts to reduce vibration in machinery. A subclass of machinery that is widely used in industry is two-mode flexible systems. Cranes with double-pendulum dynamics and two-link flexible robotic arms are representative examples of two-mode flexible systems. In order to thoroughly understand these types of systems, a detailed study of double-pendulum cranes is preformed. The crane payload is considered to be a distributed mass. The parameters of the payload and the crane has important effects on the dynamic response. the effects are studied as a function of the parameters so that effective control methods can be developed. This thesis develops a technique for improving the control of two-mode flexible systems called input shaping. Input shaping is a control strategy that uses a series of impulses to modify the reference command to suppress unwanted vibration in a system. This thesis reviews several types of input shapers and presents a method for optimizing a robust input shaper called Specified Insensitivity input shapers using knowledge of amplitude contributions of each mode to the overall response. Simulations and experiments are presented to verify the new algorithm. Two human operator studies are presented to demonstrate the effectiveness of input shaping when used in conjunction with distributed crane payloads, such as cargo containers. One study investigates the improvement in efficiency when using input shaping and the differences in efficiency between input shapers. The other study investigates operator learning when moving a payload with unshaped and shaped commands.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Singhose, William; Committee Member: Costello, Mark; Committee Member: Whiteman, Wayne

Thesis (M.S.)--Mississippi State University. Department of Industrial and Systems Engineering. / Title from title screen. Includes bibliographical references.

Bridge and gantry cranes are crucially important elements in the industrial complex; they are used in many areas such as shipping, building construction, steel mills, and nuclear facilities, just to name a few. These types of systems tend to be highly flexible in nature, generally responding to commanded motion with oscillations of the payload and hook. The response of these systems to external disturbances, such as wind, is also oscillatory in nature. Often, the oscillations of the hook and payload have undesirable consequences. For instance, precise manipulation of payloads is difficult when cable sway is present. Oscillation of the hook can also present a safety hazard. For these reasons, the ability to successfully negate these detrimental dynamics can result in improved positioning, quicker settling time, and improved safety. This thesis addresses the dynamic properties of bridge and gantry cranes in an effort to develop a control scheme that enables strides to be made in these areas of positioning, efficiency, and safety. The fundamental advancement arising from this thesis is the development of a control scheme that enables precise positioning of the payload while motion and disturbance-induced oscillations are eliminated. A command generation technique uniquely suited for reducing oscillation in low-frequency flexible systems is examined and utilized in the control. The control scheme is implemented on a 10-ton bridge crane for validation purposes.

Millions of cranes are used around the world. Because of their wide-spread use in construction industries, boom cranes are an important class of cranes whose performance should be optimized. One limitation of most boom cranes is they are usually attached to a stationary base or a mobile base that is only used for initial positioning and not during operation. This limits the workspace of the boom crane significantly. If a boom crane was attached to a mobile base that could be safely used during lifting operations, then the boom crane workspace could be extended significantly. The problem with using cranes, and in particular mobile cranes, is the large oscillations of the payload that are typically induced when moving the crane. One control strategy that has been used to control oscillation on other types of cranes is called Input Shaping, a command filtering technique that reduces motion-induced vibration in oscillatory systems. This thesis develops a dynamics model for a mobile boom crane and analyzes the difficulty of controlling payload oscillation on a boom crane. Input shaping will shown to be effective for controlling oscillation on boom cranes. A new method for operating a boom crane in Cartesian coordinates will also be shown. This thesis will also detail the design of a small-scale mobile boom crane for experimental and research purposes. A substantial part of this thesis will also focus on the development of new input-shaping methods for nonlinear drive systems commonly found on boom and other types of cranes. An example application of a control system featuring input shaping for an industrial bridge crane will also be discussed.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007. / Research on cranes and crane support structures has been completed at Stellenbosch University’s Structural Division. In order to link the research already completed with that which is practically relevant, an industry related expert survey was proposed. Consequently, the research title is “Best Practice of Crane Support Structures Design – An Expert Survey”. The primary objective of the study is to complete research, which can be used at a later stage to compile a “best practice” guideline for support structures design. The expert survey allows practical experience and opinion to be gathered from experts. The primary drawback being the uncertainty involved in such opinionated research material. For this reason an attempt is made in the thesis to apply a scientific approach, in order to attain rationally defendable results. The survey was conducted using interviews with experienced crane support structure designers and crane manufacturers in South Africa. The experts were then rated according to their answers to seeded questions, the number of colleague recommendations they each received and the years of experience each expert has. The expert opinion was subsequently combined using the expert ratings as weights. To further improve the scientific rationale behind the results, several of the topics mentioned by the experts were verified using related literature - thereby validating the use of the combined expert opinion for this research. The results obtained from the survey and verification process are regarded as useful to the objectives of the study. Information concerning pre-design specifications, loads and actions, structural analysis, design, design details and fatigue was compiled. The direct results are tabulated in an appendix and commentary, based on the expert opinions, is provided. A failure investigation was also completed with less success than initially intended. This was due, in part, to confidentiality issues and a lack of failure information easily accessible to the experts. For this reason the results of the failure investigation focuses more on various failure mechanisms. The success of the survey indicates that expert opinion is a useful tool for research. Furthermore, the minor differences in expert opinion, when compared to information obtained from crane support structure literature, indicates that the expertise in the South African crane support structure design is at an international standard.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007. / In structural engineering practice the actions imposed by overhead travelling cranes onto the supporting structure are defined as static forces amplified by dynamic coefficients and applied as pseudo-static forces without taking the interaction between crane and supporting structure into account. To investigate the validity of this approach, the forces generated at the wheels of an experimental crane are measured, as the crane traverses on the supporting structure. The interaction at the wheels of the crane is also visually recorded. These wheel load results will also be used by other researchers, to calibrate a numerical model of the experimental system. A full-scale 5 ton electric overhead travelling crane (EOTC) running on top of rails and a supporting structure, was designed and erected for research purposes. The crane has a span of 8.3 m and wheel spacing of 4 m, which can be modified. The supporting structure consists of three simply supported mono-symmetric plate girders on each side, with a total length of 13.8 m. This is supported by columns with a height of about 3.5 m. This paper describes the calibration of this system for measurement purposes. A data acquisition system was implemented to capture forces, strains, deflections and accelerations at various points on the crane and the supporting structure as well as to measure the velocity of the crane. The forces at the crane wheels are measured through strain gauges on the end carriage load measuring system. The calibrated facility is used to investigate the behaviour of the crane and the supporting structure under regular and exceptional wheel loads, which are classified as follows: - Regular wheel loads occur during normal payload hoisting and lowering, longitudinal crane travel with payload and lateral crab travel with payload. - Exceptional wheel loads occur during eccentric payload hoisting (payload outside normal operational area), impact forces on end-stops, maximum hoisting of the payload, failure of a longitudinal drive mechanism of the crane, misalignment of the supporting structure and skewing of the crane. The maximum values of these experimentally determined wheel loads and the dynamic response of the system is used to help describe the behaviour of the electric overhead travelling crane and its supporting structure.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

Includes bibliographical references (p. 46-48).

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 524-542).