Ziyad N. Masoud

Dynamics and Control of Cranes: A Review:

We review crane models available in the literature, classify them, and discuss their applications and limitations. A generalized formulation of the most widely used crane model is analyzed using the method of multiple scales. We also review crane control strategies in the literature, classify them, and discuss their applications and limitations. In conclusion, we recommend appropriate models and control criteria for various crane applications and suggest directions for further work.

Cargo Pendulation Reduction on Ship-Mounted Cranes Via Boom-Luff Angle Actuation

The wave-induced motions of a ship can cause large pendulations of cargo being hoisted by a ship-mounted crane. In this paper, the authors show that controlling the boom-luff angle can reduce these pendulations significantly. A planar pendulum with a rigid massless cable and massive point load is used to model the system. A control law using delayed position feedback is developed, and the controlled system is simulated on a computer using the full nonlinear equations of motion. The computer simulation results are verified experimentally using a three-degree-of-freedom ship-motion simulation platform and a 1/24th scale model of a T-ACS crane.

Sway Reduction on Quay-side Container Cranes Using Delayed Feedback Controller: Simulations and Experiments:

Traditionally, a container crane is modeled as a simple pendulum with either a flexible or a rigid hoisting cable, and a lumped mass at the end of the cable. However, in the case of quay-side container cranes, the actual configuration of the hoisting mechanism is significantly different; it consists typically of a set of four hoisting cables. The cables are hoisted from four different points on a trolley and are attached on the load side to four points on a spreader bar used to lift containers. A controller design based on the actual model will most likely result in a response superior to those based on simple pendulum models. In this paper, we develop a mathematical model of the actual quay-side container crane. A simplified model is then used to obtain the gain and time delay for a delayed feedback controller, which will be used for the control of payload sway oscillation. Performance of the controller is simulated on a 1/10th scale computer model of a 65 ton container crane using the full model. Simulation results are verified experimentally on a 1/10th scale model of the same container crane.

Delayed Position-Feedback Controller for the Reduction of Payload Pendulations of Rotary Cranes

In this paper, we show that, in rotary cranes, it is possible to reduce payload pendulations significantly by controlling the cranes translational and rotational degrees of freedom. Such a control can be achieved with the heavy equipment that is already part of the crane, so that retrofitting existing cranes with such a controller would require little effort. Moreover, the control is superimposed transparently on the commands of the operator. The successful control strategy is based on delayed position feedback of the payloads in-plane and out-of-plane motions. Its effectiveness is demonstrated with a fully nonlinear three-dimensional computer simulation and with an experiment on a scaled model of a rotary crane. The results demonstrate that the pendulations can be significantly reduced, and therefore the rate of operation can be greatly increased. The effectiveness of the controller is demonstrated for both rotary and gantry modes of operation.

A Graphical Approach to Input-Shaping Control Design for Container Cranes With Hoist

A traditional input-shaping technique is adapted to control transfer maneuvers on quay-side container cranes. The controller is developed using an accurate two-dimensional four-bar-mechanism model of a container crane and accounts for maneuvers that involve large hoisting operations. A graphical representation of the phase plane of the payload oscillations is used to derive mathematical constraints to compute the switching times of a double-step acceleration profile that results in minimal transient and residual oscillations. In contrast with single-step shaped acceleration profiles which are very sensitive to frequency approximations, the proposed double-step profile is less sensitive to small variations in the frequency even for large trolley accelerations

A hybrid command-shaper for double-pendulum overhead cranes

A crane is generally modeled as a simple pendulum with a point mass attached to the end of a massless rigid link. Numerous control systems have been developed to reduce payload oscillations in order to improve safety and positioning accuracy of crane operations. However, large-size payloads may transform the crane model from a simple-pendulum system to a double-pendulum system. Control systems that consider only one mode of oscillations of a double pendulum may excite large oscillations in the other mode. In multi-degree-of-freedom systems, command-shaping controllers designed for the first mode may eliminate oscillations of higher modes provided that their frequencies are odd integer multiples of the first mode frequency. In this work, a hybrid command-shaper is designed to generate acceleration commands to suppress travel and residual oscillations of a double-pendulum overhead crane. The shaper consists of a primary double-step command-shaper complemented by a virtual feedback system. The primary command-shaper is designed to eliminate oscillations in a slightly modified version of the crane model with frequencies satisfying the odd integer multiple criterion. The virtual feedback loop is then used to modify the commands of the primary shaper to accommodate the difference between the modified and the original models of the crane. It is shown that the suggested hybrid command-shaper is capable of minimizing oscillations of both modes of a scaled experimental double-pendulum model of an overhead crane. Results show that the hybrid command-shaper produces a reduction of 95% in residual oscillations in both modes of the double pendulum over the time-optimal rigid-body commands.

A Novel Wave-Form Command-Shaping Control With Application on Overhead Cranes

In this work, a novel continuous command-shaping control strategy for a simple harmonic oscillator is proposed and implemented on an overhead crane model. A Wave-Form (WF) acceleration command profile is derived analytically, and its performance is validated numerically. To enhance the performance of the proposed command-shaping control strategy, a Modulated Wave-Form (MWF) acceleration command profile is derived. It was determined that the proposed Wave-Form and Modulated Wave-Form command profiles are capable of eliminating the travel and residual oscillations. Furthermore, unlike traditional impulse and step command-shaping, the proposed command profiles have smoother intermediate acceleration, velocity, and displacement profiles.Copyright

An Iterative Learning Control Technique for Point-to-Point Maneuvers Applied on an Overhead Crane

An iterative learning control (ILC) strategy is proposed, and implemented on simple pendulum and double pendulum models of an overhead crane undergoing simultaneous traveling and hoisting maneuvers. The approach is based on generating shaped commands using the full nonlinear equations of motion combined with the iterative learning control, to use as acceleration commands to the jib of the crane. These acceleration commands are tuned to eliminate residual oscillations in rest-to-rest maneuvers. The performance of the proposed strategy is tested using an experimental scaled model of an overhead crane with hoisting. The shaped command is derived analytically and validated experimentally. Results obtained showed that the proposed ILC control strategy is capable of eliminating travel and residual oscillations in simple and double pendulum models with hoisting. It is also shown, in all cases, that the proposed approach has a low sensitivity to the initial cable lengths.

A Hybrid Command-Shaping Control System for Highly Accelerated Double-Pendulum Gantry Cranes

A gantry cranes is generally modeled as a simple-pendulum with a point mass attached to the end of a massless rigid link. Numerous control systems have been developed to reduce payload oscillations in order to improve safety and positioning accuracy of crane operations. However, large-size payloads transforms the crane model from a simple-pendulum system to a double-pendulum system. Control systems that consider only one mode of oscillations of a double-pendulum may excite large oscillations in the other mode. In multi-degrees-of-freedom systems, command-shaping controllers designed for the first mode may eliminate oscillations of higher modes provided that their frequencies are odd integer multiples of the first mode frequency. In this work, a hybrid command-shaping controller is designed to generate acceleration commands to suppress travel and residual oscillations of a highly accelerated double-pendulum gantry crane. It is shown that the suggested hybrid command-shaper is capable of minimizing oscillations of both modes of a scaled experimental double-pendulum model of a gantry crane. Results show that the hybrid command-shaper produces a reduction of 95% in residual oscillations in both modes of the double-pendulum over the time-optimal rigid-body commands.© 2009 ASME

Oscillation Control of Quay-Side Container Cranes Using Cable-Length Manipulation

Cranes play a very important role in the shipping industry. As a result there is an increasing demand on faster and safer cranes. Inertial forces on crane payloads due to crane-commanded trajectories can cause payloads to experience large sway oscillations. Consequently, sway control on quay-side container cranes is becoming a requirement rather than a luxury. Some modern quay-side container cranes use independent front and rear hoisting cables. This degree of freedom can be utilized to control payload sway oscillations. In this work, a delayed feedback algorithm is used to produce a controlled differential change in the length of the front and rear hoisting cables of a typical quay-side container crane to reduce payload sway.