Longitudinal response of parallel hoisting system with time-varying rope length

The longitudinal vibration model of parallel hoisting system with tension auto balance device (TABD) attached to the ends of all hoisting ropes is established, and the governing equations of the model are derived based on Hamilton’s principle. Galerkin’s effort is applied to discretize the infinite-dimensional partial differential equations into a set of finite-dimensional ordinary differential equations, so that the model can be solved with numerical solutions. Subsequently, an ADAMS simulation is carried out, and the simulation result has verified the validity of the numerical solution. Consequently, in order to investigate the longitudinal responses of the two hoisting ropes, the model is calculated numerically with different coefficients and excitations. The results of the numerical solution have shown that: For the parallel hoisting system with TABD attached to the ends of all hoisting ropes, the conveyance will be the main excitation that affects the longitudinal vibration of the ropes, and the system acceleration will also cause a relatively large longitudinal vibration in the ropes

Finite element analysis of coupled vibration for hoisting cable with time-varying length

The coupled axial-torsional responses of the hoisting cable with time-varying length are investigated in order to predict the longitudinal vibration more accurately. The equations of motion are formulated by Hamilton’s principle and the finite element method (FEM), in which a variable-length cable element is introduced. In order to validate this theoretical model, an ADAMS simulation model is established in the framework of the multi-body system dynamic. The result shows that the numerical solution is in reasonably good agreement with the ADAMS simulation. The frequencies of the cables with the coupling considered and neglected are analyzed by varying the excitation frequency, which indicates that the coupling effect reduces the natural frequency of the cable and the maximum amplitude shifts from the resonance region to the deceleration stage as the coupling coefficient increases

Using Digital Hydraulics in Secondary Control of Motor Drive

Due to the increased focus on pollution and global warming, there is a demand for energy efficient systems. This also applies to the offshore oil and gas industry. Normally used hydraulic systems tend to suffer from low energy efficiency, especially when operating with part loads. In the last decades, a new pump and motor technology has experienced increased interest due to the potential of high energy efficiency in a wide range of operation conditions. This new technology is called digital displacement machine technology. Nowadays, there is a desire from the offshore oil and gas industry to use this digital displacement machine technology to design highly efficient hydraulic winch drive systems. The main objectives of the work presented in this thesis are to design a controller for a digital displacement winch drive system and evaluate its control performance. The design of a controller is one part of the work needed to realizing a winch drive system with digital displacement machines. A winch with a lifting capacity of 20000 kg and a drum capacity of 3600 m of wire rope is used as a case study. Digital displacement machines have strict requirements for the on/off valves used to control each cylinder chamber. It is important to activate the valves at optimal times to ensure operation with high energy efficiency and low pressure and flow peaks. Only a small mistiming of the valves will affect the performance of the digital displacement machine significantly. One of the first contributions presented in this thesis is a method for defining how early or late the valves can be timed without reducing the energy efficiency significantly. The control of digital displacement machines is complicated and non-conventional. Each cylinder can be controlled individually and multiple displacement strategies can be used to achieve the same displacement. Each displacement strategy has its dynamic response characteristics and energy efficiency characteristics. The dynamic response characteristics of the drive system are highly relevant when designing control systems. Therefore, in addition to the conventional classical controller, also a suitable displacement strategy must be designed. Designing controllers for digital displacement machines are therefore more complex than designing controllers for conventional hydraulic machines. One of the main focuses of this project has been to analyze the transient and steady state response characteristics of different displacement strategies. In all, three displacement strategies are examined: full stroke displacement strategy, partial stroke displacement strategy and sequential partial stroke displacement strategy. Also, during this work, a new version of the partial stroke displacement strategy has been developed and included in the dynamic response analysis. The dynamic response analysis is a simulation study, where the simulation model is experimentally validated. The experimental work is conducted on a prototype of a single cylinder digital displacement machine. The prototype consists of a five cylinder radial piston motor where one cylinder is modified to operate with the digital displacement technology. The rest of the cylinders are not changed and not used. In addition to validating the simulation model, the prototype is used to test all of the analyzed displacement strategies in low speed operation. The results from the dynamic response analysis are used to select the displacement strategy that is most suited for use in a winch drive system. Then, controllers for the digital displacement winch drive system are developed. The main focus in the control design phase is not to design a new type of controller but to examine already developed controllers and fit them to a winch system driven by digital displacement machines. In the end, the simulation results of the designed controllers are shown and the results are discussed. The simulation results show that digital displacement machines can be used in winch drive systems and achieve both high motion control performance and wire tension control performance.publishedVersio

Adaptive fuzzy observer based hierarchical sliding mode control for uncertain 2D overhead cranes

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. This paper proposes a new approach to robustly control a 2D under-actuated overhead crane system, where a payload is effectively transported to a destination in real time with small sway angles, given its inherent uncertainties such as actuator nonlinearities and external disturbances. The control law is proposed to be developed by the use of the robust hierarchical sliding mode control (HSMC) structure in which a second-level sliding surface is formulated by two first-level sliding surfaces drawn on both actuated and under-actuated outputs of the crane. The unknown and uncertain parameters of the proposed control scheme are then adaptively estimated by the fuzzy observer (FO), where the adaptation mechanism is derived from the Lyapunov theory. More importantly, stability of the proposed strategy is theoretically proved. Effectiveness of the proposed adaptive FO-based HSMC approach was extensively validated by implementing the algorithm in both synthetic simulations and real-life experiments, where the results obtained by our method are highly promising

Dynamic analysis of hook block for polar crane in nuclear power plant

A systematic method to analyze the trajectory of hook block for polar crane in nuclear power plant (NPP) is proposed, in which dynamic equations of the system and the compatibility conditions for drum parameters are presented. Properties and formulations of the variables involved in these equations are studied in detail. A method to describe the rope-pulley system is given and a numerical method is derived to solve the positions and velocities of the common tangents that consistent with the reeving ropes between spatial pulleys. Based on these displacements and velocities, the angular speeds of pulleys are given to solve the difficulty to confirm the rotating directions of pulleys in some rope-pulley systems. A numerical example contrasting the dynamic model with corresponding static model is demonstrated to validate the systematic method. The proposed method is largely universal and can be a reference for designing and analyzing of polar cranes in NPP

Input shaping-based control schemes for a three dimensional gantry crane

The motion induced sway of oscillatory systems such as gantry cranes may decrease the efficiency of production lines. In this thesis, modelling and development of input shaping-based control schemes for a three dimensional (3D) lab-scaled gantry crane are proposed. Several input shaping schemes are investigated in open and closed-loop systems. The controller performances are investigated in terms of trolley position and sway responses of the 3D crane. Firstly, a new distributed Delay Zero Vibration (DZV) shaper is implemented and compared with Zero Vibration (ZV) shaper and Zero Vibration Derivative (ZVD) shaper. Simulation and experimental results show that all the shapers are able to reduce payload sway significantly while maintaining desired position response specifications. Robustness tests with ±20% error in natural frequency show that DZV shaper exhibits asymmetric robustness behaviour as compared to ZV and ZVD shapers. Secondly, as analytical technique could only provide good performance for linear systems, meta-heuristic based input shaper is proposed to reduce sway of a gantry crane which is a nonlinear system. The results show that designing meta-heuristic-based input shapers provides 30% to 50% improvement as compared to the analytical-based shapers. Subsequently, a particle swarm optimization based optimal performance control scheme is developed in closed-loop system. Simulation and experimental results demonstrate that the controller gives zero overshoot with 60% and 20% improvements in settling time and integrated absolute error value of position response respectively, as compared to a specific designed PID-PID anti swing controller for the lab-scaled gantry crane. It is found that crane control with changing cable length is still a problem to be solved. An adaptive input shaping control scheme that can adapt to variation of cable’s length is developed. Simulation with real crane dimensions and experimental results verify that the controller provides 50% reduction in payload sway for different operational commands with hoisting as compared to the average travel length approach

Advanced Discrete-Time Control Methods for Industrial Applications

This thesis focuses on developing advanced control methods for two industrial systems in discrete-time aiming to enhance their performance in delivering the control objectives as well as considering the practical aspects. The first part addresses wind power dispatch into the electricity network using a battery energy storage system (BESS). To manage the amount of energy sold to the electricity market, a novel control scheme is developed based on discrete-time model predictive control (MPC) to ensure the optimal operation of the BESS in the presence of practical constraints. The control scheme follows a decision policy to sell more energy at peak demand times and store it at off-peaks in compliance with the Australian National Electricity Market rules. The performance of the control system is assessed under different scenarios using actual wind farm and electricity price data in simulation environment. The second part considers the control of overhead crane systems for automatic operation. To achieve high-speed load transportation with high-precision and minimum load swings, a new modeling approach is developed based on independent joint control strategy which considers actuators as the main plant. The nonlinearities of overhead crane dynamics are treated as disturbances acting on each actuator. The resulting model enables us to estimate the unknown parameters of the system including coulomb friction constants. A novel load swing control is also designed based on passivity-based control to suppress load swings. Two discrete-time controllers are then developed based on MPC and state feedback control to track reference trajectories along with a feedforward control to compensate for disturbances using computed torque control and a novel disturbance observer. The practical results on an experimental overhead crane setup demonstrate the high performance of the designed control systems.Comment: PhD Thesis, 230 page

The dynamics of mine hoist catenaries.

A Thesis Submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, South Africa for the Degree of Doctor of Philosophy.The dynamic analysis of catenary vibration of mine hoist ropes on South African mines is examined. This research has been preceded by studies in the mining industry, which have laid the foundation fot the definition of design guidelines of hoist systems to avoid catenary vibrations or rope whip. These guidelines are based on a classical linear analysis of a taut string, and in essence rely on ensuring that the frequency of excitation at the winder drum due to the coilingmechanism, does not coincide with the linear transverse natural frequency of the taut catenary. Such an approach neglects the nonlinear coupling between the lateral catenary motion and the longitudinal systern response. Although previous research sug gested the possibility of autoparametric coupling between the catenary and vertical rope, this was not developed further on a theoretical level.. The possibility of such behaviour is defined by considering the equations of motion of the coupled system. A design methodology is developed for determining the parameters of a mine hoist systern so as to avoid rope whip. The methodology accounts for the nonlinear coupling between the catenary and longitudinal system. In order to implement the proposed methodology, two phases of the analysis are developed. In the first phase the stability of the linear steady state motion is examined in the context of the nonlinear equations of motion, by applying a harmonic balance method. The stability analysis defines regions of secondary resonance, where it is shown that such regions may arise at sum and difference combinations of the linear lateral and longitudinal natural frequencies due to autoparametric excitation. Prior to this research, this phenomenon had not been appreciated in the context of the mine hoist system. A laboratory experiment was conducted to confirm the existence of these regions experimentally. In reality, the system is non-stationary since the dynamic characteristics of the system change during the winding cycle, and hence the steady state stability analysis can only describe potential regions of nonlinear interaction on a qualitative basis. The second phase of the analysis deals with a non-linear numerical simulation of the hoist system, which accounts for the non-stationary nature of the systems dynamic characteristics, and includes transient excitations induced during the wind. The methodology developed is assessed by considering the Kloof mine rope system, where rope whip was observed. This study demonstrates that although an appreciation of the steady state system characteristics is useful, the stability analysis alone is not sufficient. It is necessary to account for the non-stationary aspects of the winding cycle if a realistic interpretation of the observed behavlcur is to be achieved. To compliment this study, a motion analysis system was developed to record catenary response on an existing mine hoist installation. Such data has not been recorded before. This data provides direct evidence of the autoparametric nature of the coupled catenary/vertical rope system.AC201

Computational dynamics and virtual dragline simulation for extended rope service life

The dragline machinery is one of the largest equipment for stripping overburden materials in surface mining operations. Its effectiveness requires rigorous kinematic and dynamic analyses. Current dragline research studies are limited in computational dynamic modeling because they eliminate important structural components from the front-end assembly. Thus, the derived kinematic, dynamic and stress intensity models fail to capture the true response of the dragline under full operating cycle conditions. This research study advances a new and robust computational dynamic model of the dragline front-end assembly using Kane\u27s method. The model is a 3-DOF dynamic model that describes the spatial kinematics and dynamics of the dragline front-end assembly during digging and swinging. A virtual simulator, for a Marion 7800 dragline, is built and used for analyzing the mass and inertia properties of the front-end components. The models accurately predict the kinematics, dynamics and stress intensity profiles of the front-end assembly. The results showed that the maximum drag force is 1.375 MN, which is within the maximum allowable load of the machine. The maximum cutting resistance of 412.31 KN occurs 5 seconds into digging and the maximum hoist torque of 917. 87 KN occurs 10 seconds into swinging. Stress analyses are carried out on wire ropes using ANSYS Workbench under static and dynamic loading. The FEA results showed that significant stresses develop in the contact areas between the wires, with a maximum von Mises stress equivalent to 7800 MPa. This research study is a pioneering effort toward developing a comprehensive multibody dynamic model of the dragline machinery. The main novelty is incorporating the boom point-sheave, drag-chain and sliding effect of the bucket, excluded from previous research studies, to obtain computationally dynamic efficient models for load predictions --Abstract, page iii