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This paper presents a smooth command (SC) input shaper for suppressing payload oscillations in rest-to-rest simultaneous radial and tangential motions of a tower crane. The radial and tangential acceleration profiles of the compound motions are represented by multi-sine wave functions with independent and variable maneuvering time. The proposed SC is designed using a nonlinear mathematical model of the tower crane while the parameters of the acceleration profiles and maneuvering times were optimized using a particle swarm algorithm (PSO). The simulated results were verified experimentally on a laboratory scale tower crane. The results confirm that the proposed SC input effectively canceled residual vibrations of the payload compound motions with a time length comparable to zero vibrations (ZV) shaper. Moreover, sensitivity analysis to variations in cable length reveals that the proposed command input is robust over a wide range of cable lengths. [ABSTRACT FROM AUTHOR]

Cables are used in civil and mining engineering applications, such as in cable stays for suspension bridges, elevators, construction cranes, mining shovels and draglines. Such cables are mainly used for supporting or hoisting and can be considered to be either stationary or running cables. In supporting functions, cables are subjected to cyclic tension, with the primary mode of failure due to fretting fatigue of individual wires that make up the cables as they abrade against each other. Stationary cables subjected to cyclic tension (tension–tension) fatigue are the focus of this work, and although other researchers have investigated the fatigue life of such cables, there remains much of the cyclic tensile behavior that needs further investigation. The stress condition of several cables such as 19-, 91- and 92-wire strands; independent wire rope core; and the 6 × 19 Seale–independent wire rope core wire ropes was investigated using finite element modeling techniques. A stress-based approach was used with the results of finite element modeling to obtain the fatigue life for these cables. In practice, it would be challenging for a finite element analysis to be carried out each time the fatigue life of a cable is needed, so in a preventive maintenance stance, regression coefficients have been proposed for use with a fatigue life prediction model. [ABSTRACT FROM AUTHOR]

A new solution is presented to the problem of controlling the motion of a crane’s suspended load through arbitrarily complex, 3D paths through the crane’s manoeuvre space. A generalized boom crane arrangement is considered, so that gantry and luffing arrangements are included as particular cases. Thus the crane’s boom slews about a central, vertical (tower) axis. This boom is either a horizontal gantry with a trolley moving radially along it, from which the load can be winched, or a jib, which can rotate in the vertical plane, with the hoisting cable passing over a pulley attached at its end point. In either case, there are three directly controlled motion variables, the effects of which on the suspended payload’s motion are strongly cross-coupled. The challenge is to enable the payload to follow the desired 3D path as closely as possible during the manoeuvre, and come to rest rapidly at target, by directly controlling these three actuating motions. Thus the controller must achieve position control combined with active swing suppression throughout the manoeuvre and on arrival at the desired end point. A model is developed of the generalized crane for both gantry and luffing crane types. The proposed control strategy is then applied and tested on this model. The controller is based on mechanical wave concepts. When applied to the model, it is shown to be very effective. It is accurate, robust to system changes and actuator limitations, very stable, requires sensing only at the trolley (and not at payload), and is easy to implement. [ABSTRACT FROM AUTHOR]

This paper presents an output-based command shaping (OCS) technique for an effective payload sway control of a 3D crane with hoisting. A crane is a challenging and time-varying system, as the cable length changes during the operation. The OCS technique is designed based on output signals of an actual system and reference model, does not require the natural frequency and damping ratio of the system, and thus can be utilized to minimize the hoisting effects on the payload sway. The shaper was designed by using the derived non-linear model of a 3D crane. To test the effectiveness of the controller, simulations using a non-linear 3D crane model and experiments on a lab-scale 3D crane were performed and compared with a zero vibration derivative (ZVD) shaper and a ZVD shaper designed using an average travel length (ATL) technique. In both the simulations and the experiments, the OCS technique was shown to be superior in reducing the payload sway with reductions of more than 56% and 33% in both of the transient and residual sways that were achieved when compared with both the ZVD and the ATL shapers, respectively. In addition, the OCS technique provided the fastest time response during the hoisting. It is envisaged that the method can be very useful in reducing the complexity of closed-loop controllers for both tracking and sway control. [ABSTRACT FROM AUTHOR]

Classical input shaping is based on convolving a general input signal with a sequence of timed impulses. These impulses are chosen to match certain modal parameters of the system under control to eliminate residual vibrations in rest-to-rest maneuvers. This type of input shaping is strongly dependent on the system period. In this work, an adjustable maneuvering time wave form command shaper is presented. The equation of motion of a simple pendulum model of a crane is derived and solved in order to eliminate residual vibrations at the end of motion. Several cases are simulated numerically and validated experimentally on an experimental model of an overhead crane. Results show that the proposed command shaper is capable of eliminating residual vibrations effectively with a single continuous wave form command. The work is extended to include the effect of hoisting on the shaper performance. Several functions are used to simulate hoisting. To overcome the added complexity of hoisting on the system, an approximation technique is used to determine initial shaped command parameters, which are later used in a genetic algorithm optimization scheme. Numerical and experimental results prove that the proposed command shaper can effectively eliminate residual vibrations in rest-to-rest maneuvers. [ABSTRACT FROM AUTHOR]

The behavior of many mechanical systems, such as overhead cranes, can be predicted through intuitive observation of their motion under various forces. Mathematical modeling of an overhead crane shows that it is highly coupled. Nonetheless, it is surprisingly easy for an experienced crane operator to drive payloads to target positions with minimal cable swing. This observation naturally promotes the use of fuzzy logic to control overhead cranes. Traditionally, fuzzy logic controllers of overhead cranes were presented for specific crane system/motion parameters. This work presents a novel approach for automatically creating anti-swing fuzzy logic controllers for overhead cranes with hoisting. The model of the crane includes the distributed mass of the cable. The presented approach uses the inverse dynamics of the overhead crane and the desired motion parameters to determine the ranges of the variables of the controllers. The control action is distributed among three fuzzy logic controllers (FLCs): The travel controller, hoist controller, and anti-swing controller. Simulation examples show that the proposed controller can successfully drive overhead cranes under various operating conditions. [ABSTRACT FROM AUTHOR]

This work considers the control problem of overhead cranes with flexible cable and load hoisting or lowering during crane travel. The objective is to drive the overhead crane to its final desired position while suppressing the payload swing. The proposed control strategy is based on three fuzzy logic controllers where the control action is based on expert knowledge. These controllers are a trolley motion controller, payload hoist controller and payload anti-swing controller. Numerical simulations are provided to show the effectiveness of the proposed fuzzy control scheme. [ABSTRACT FROM AUTHOR]