Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 93-99).

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2007. / William Singhose, Committee Chair ; Steven Danyluk, Committee Member ; Donna Llewellyn, Committee Member ; Nader Sadegh, Committee Member ; Neil Singer, Committee Member.

Cranes are an indispensable aid to the construction industry, and much responsibility with regard to performance has been placed in the hands of the operator. The problem of controlling sway of the load due to crane motion, or wind effects must be solved dynamically by the operator to increase productivity and maintain safety. At the hands of inexperienced operators safety is sometimes sacrificed in order to expedite the required task. In an effort to minimize the loss of life and equipment, and to maximize productivity a system for actively damping the crane load has been developed. This paper discusses an active damping system using state feedback control for a crane load modeled as a two-dimensional pendulum. Mathematical analysis indicates that the control theory used to damp the sway in the pendulum may be extended linearly into three dimensions. Thus, two control algorithms, operating independently, can be used to damp sway in two horizontal dimensions. The designed system responds to sensed displacements of the load from equilibrium. It employs a control arm positioned a small distance below the boom tip that applies a force to the cable to damp the sway of the load. This system is intended to allow less experienced operators to work more efficiently and safely, decreasing training time and increasing overall productivity. / Master of Science

Cranes, which comprise a significant class of material handling equipment, are basically designed to lift and lower loads. In addition to dynamic loading, cranes are exposed to loads which may be environment specific. Many crane accidents are due to uncontrolled swaying of the payload resulting in collisions with construction workers or objects. At present, it is left to the operator to apply his/her skills in controlling this uncontrolled swaying. If the controlling is automated and computer controlled, the effect of human errors and limitations can be minimized. The control of this sway will thus greatly improve safety and significantly enhance productivity. The control strategy in the present thesis is based on applying appropriate, periodic balancing forces and moments to the crane cable to dampen the oscillation. The present thesis presents a discussion on the experimental methods attempted before the development of an automated control. / Master of Science

The nonlinear differential equations describing the motion of a crawler crane in a plane are formulated by applying Lagrange's equation to the system kinetic energy, potential energy and virtual work. The transient response of the crane system due to the vertical drop of the suspended load is simulated by numerically integrating the equations of motion. The crane model includes the vertical translation and rotation of the crane body, the rotation of the boom, the stretch and pendulation of the load line, and two discrete boom displacements. The model includes the effects of tilting of the crane tracks, shortening of the boom length, and loss of tension in the elastic cables. The model has been carefully developed to include the important effects which influence the crane system motion without loosing the simplicity which allows auxiliary control systems to be added with relative ease. A hydraulic valve-controlled piston actuator is adapted to the crawler crane pendent line to reduce the boom-tip excursions which excite the motion of the suspended load. Three proportional feedback compensation techniques, which detect the error between the desired crane state and the actual crane state, are used to describe the pendent actuator's valve position. The transient response of the system generalized coordinates for both the uncompensated crane and the compensated crane is presented subject to three sets of initial conditions and crane configurations. One controller which measures the deflection at a single point in the crane boom is able to attenuate the entire crane system response due to a 7.6 cm vertical drop of the 13,600 Kg load with only 13 Kw of hydraulic source power. / Master of Science

Aerial lifts are used to elevate people and material to high heights. There are many different types of aerial lifts which have vastly different dynamics characteristics. Thus, a new categorization for aerial lifts was created and organizes them by their kinematics. Many accidents occur while using aerial lifts. Hazards of aerial lifts and current solutions to those hazards were reviewed to understand the causes of the accidents. Some major accidents are due to the complex dynamics and flexibility of aerial lifts, such as oscillations and tip-overs. Oscillations of full-size aerial lifts were experimentally tested to determine frequencies in different configurations. Machine-motion induced oscillations of an articulating aerial lift were simulated and analyzed for both non-overcenter and overcenter configurations. Input shaping was used to achieve reduction in machine-motion induced oscillations. Tip-over stability margin was used to simulate and analyze the stability of both non-overcenter and overcenter configurations. The effect of increased platform mass on tip-over stability margin was also analyzed. The results in this thesis are a categorization of aerial lifts including their hazards and methods of reducing those hazards, an experimental verification of the dynamic response of full-size aerial lifts, a fully dynamic tip-over prediction model of double-boom articulating aerial lift by applying flexibility in the joints and realistic velocity profiles, and a detailed study of the dynamics of a double-boom articulating aerial lift.

The rapid movement of machines is a challenging control problem because it often results in high levels of vibration. As a result, flexible machines are typically moved relatively slowly to avoid such vibration. Therefore, motion-induced vibration limits the operational speed of the system. Input shaping is one method that eliminates motion-induced vibrations by intelligently designing the reference command such that system vibration is cancelled. It has been successfully implemented on a number of systems, including bridge and tower cranes. The implementation of input shaping on cranes provides a substantial increase in the operational efficiency. Unfortunately, most cranes, once erected, have limited or no base mobility. This limits their workspace. The addition of base mobility could help extend the operational effectiveness of cranes and may also expand crane functionality. Mobile cranes may also be better suited for use in harsh and/or distant environments. Teleoperation of oscillatory systems, such as cranes, then becomes another avenue for advancement of crane functionality. Base mobility in cranes presents both additional control challenges and operational opportunities. A crane with base mobility is redundantly actuated (overactuated), such that multiple combinations of actuators can be used to move a payload from one location to another. This opens the possibility for the selection of a combination of actuation that provides both rapid motion and limited system vibration. The extension of input shaping into this operational domain will provide a method to maximize effective actuation combinations. Toward addressing these issues, new multi-input shaping methods were developed and applied to a mobile, portable tower crane. During this development, a firm understanding of robust input shaping techniques and the compromises inherent to input shaper design was formed. In addition, input shaping was compared to other command generation techniques, namely lowpass and notch filtering, and proven to be superior for vibration reduction in mechanical systems. Another, new class of input shapers was also introduced that limit the input shaper induced overshoot in human operated systems. Finally, a series of crane operator studies investigated the application of input shaping techniques to teleoperated cranes. These studies suggested that input shaping is able to dramatically improve remote crane operator performance.

Cranes occupy a crucial role within the industry. They are used throughout the world in thousands of shipping yards, construction sites, and warehouses. However, payload oscillation inherent to all cranes makes it challenging for human operators to manipulate payloads quickly, accurately, and safely. Manipulation difficulty is also increased by non-intuitive crane control interfaces. Intuitiveness is characterized by ease of learning, simplicity, and predictability. This thesis addresses the issue of intuitive crane control in two parts: the design of the interface, and the design of the controller. Three novel types of crane control interface are presented. These interfaces allow an operator to drive a crane by moving his or her hand freely in space. These control interfaces are dependent on machine vision and radio-frequency-based technology. The design of the controller based on empirical means is also discussed. Various control architectures were explored. It was concluded that a controller with an input shaper within a Proportional Derivative feedback loop produced the desirable crane response. The design of this controller is complemented with a structured design methodology based on root locus analysis and computer numerical methods. The intuitive crane control systems were implemented on a 10-ton industrial bridge crane; simulation and experimental results are presented for validation purposes.

This thesis investigated a tip-over stability of mobile boom cranes with swinging payloads. Base and crane motion presents a tip-over problem. Attaching complex payloads further complicates the problem. They study began with a single-pendulum payload to analyze a tip-over stability characteristics under different conditions. A simple tip-over prediction model was developed with a goal of limiting a computational cost to a minimum. The stability was characterized by a tip-over stability margin method. The crane's tip-over stability was also represented by the maximum possible payload it can carry throughout the workspace. In a static stability analysis, mobile boom crane was assumed to be stationary, thus with no payload swing. The study provided basic understanding on the relationship between tip-over stability and boom configuration. In a pseudo-dynamic stability analysis, the method incorporated payload swing into the analysis by adding estimated maximum payload swing due to motions. To estimate the angles, differential equations of motions of payload swings were derived. The thesis extended the study to a double-pendulum payload. The maximum swing angles estimated in the single-pendulum case were directly applied to the double-pendulum case. To validate the analytical methods, a full dynamic multi-body simulation model of a mobile boom crane was developed. The predictions from the previous analysis were verified by the simulation results. The prediction model and the analytical methods in the thesis provide a significant tool for practical application of tip-over stability analysis on mobile boom cranes. The experimental results increase the confidence of the study's accuracy.

Boom cranes are one of the most dynamically complicated types of cranes because they possess rotational joints as opposed to the linear tracks of bridge and gantry cranes. In addition, if the boom crane is placed on a mobile base, additional complexity is added to the system. However, mobile boom cranes have huge potential benefits as they can be quickly transported from one location to another. Furthermore, if they utilize their mobile base during lifting operations, then they can have an extremely large workspace. All cranes share the same limiting weakness; the payload oscillates when the crane moves. A command-generation approach is taken to control the payload oscillation. Input shaping is one such command-generation technique that modifies the original reference command by convolving it with a series of impulses. The shaped command produced by the convolution can then move the crane without inducing payload oscillation. Input shaping can accommodate parameter uncertainties, nonlinearities, multiple modes of vibration, and has been shown to be compatible with human operators. This thesis focuses on three aspects of mobile boom cranes: 1) dynamic analysis, 2) input-shaping control, and 3) experimental testing. A majority of the thesis focuses on analyzing and describing the complicated dynamics of mobile boom cranes. Then, various input-shaping controllers are designed and tested, including two-mode shapers for double-pendulum dynamics. In order to experimentally verify the simulation results, a small-scale mobile boom crane has been constructed. The details of the mobile boom crane and its important features are presented and discussed. Details of the software used to control the crane are also presented. Then, several different experimental protocols are introduced and the results presented. In addition, a set of operator performance studies that analyze human operators maneuvering the mobile boom crane through an obstacle course is presented.