Anti-sway Control for Cranes

Design and Implementation Using MATLAB

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• Publisher: De Gruyter
• Year: 2017
• Print ISBN: 9783110519365
• eBook ISBN: 9783110519433
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Automatisation en ingénierie

The book introduces anti-sway control approaches for double-pendulum overhead cranes, including control methods, theoretical analyses, simulation results and source codes of each control design. All methods are analyzed and verified by MATLAB. Passivity-based, sliding-mode-based and Fuzzy-logic-based control methods are massively discussed. This book is suitable for both academic researchers and industrial R&D engineers.

1Introduction

Abstract: This chapter provides some necessary background information about cranes, which are the controlled plant in the book, and consequently, an introduction about the types of cranes is also discussed. Then, a brief historical overview of crane control since 2000 is considered. The history and the state-of-the-art research of both single-pendulum-type crane control and double-pendulum-type crane control are reviewed and presented. The chapter then proceeds with some insights for bottleneck issues of control and future research directions.

Keywords: crane type, crane control, single-pendulum dynamics, double-pendulum dynamics

1.1Cranes: An Overview

A crane is a machine or device used by humans to move loads, or better known as payload, from one point to another. It is typically equipped with a hoist or wire rope drum, wire ropes or chains, and sheaves that can be used to lift or lower the load or move the load horizontally. The machine can help humans to move loads beyond their capability.

The crane was invented by the Ancient Greeks and Romans for lifting heavy loads; see Figure 1.1 [1]. Such an early crane was operated by human or animal power. The Ancient Greeks were believed to have utilized the machine for constructing tall buildings. Larger cranes were developed later by employing human treadwheels; these cranes aided the lifting of heavier loads. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability.

Early cranes were constructed from wood. However, with the coming of the Industrial Revolution, cast iron, iron, and steel took over [2]. As far as crane power is concerned, ancient cranes were supplied by the physical exertion of men or animals. In the eighteenth or nineteenth century, steam engines were introduced to power cranes, which remained in use till the late twentieth century. From then on, modern cranes usually use internal combustion engines, electric motors, or hydraulic systems to provide a better lifting capability [3].

Today, millions of cranes serve around the world. Owing to their ability to handle hefty objects, they are widely used in many different environments, such as construction sites, warehouses, and harbors. Cranes exist in an enormous variety of forms. Every crane is tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing tall buildings. Mini cranes are also used for constructing tall buildings in order to facilitate constructions by reaching tight spaces [4].

Figure 1.1: Schematic diagram of an ancient Roman crane

In theory, cranes can be regarded as a class of underactuated Lagrangian systems [5]. First, crane systems are underactuated because they have fewer independent control actuators than degrees of freedom (DOF) to be controlled. For example, in a two-dimensional gantry crane system, both cart position on the girder and payload sway are controlled by a single motor. Second, cranes are classified as Lagrangian systems because their equations of motion can be obtained based on the formulation of Lagrangian mechanics like robotic manipulators. Basically, a crane system consists of a support mechanism, which is a part of its structure, and a hoisting mechanism. The hoisting mechanism of a crane often exhibits an oscillatory behavior due to the under-actuation of the system. For this reason, it is important for a crane operation to meet stringent safety requirement.

The oscillatory behavior of cranes originates from the physical structure that all cranes use vertical suspension cables to support the payload. Such a structure thereby creates the possibility of pendulum-like payload oscillation. According to the primary dynamic properties of cranes, the location of the suspension cable connection point can be described by different coordinate systems. Accordingly, cranes can roughly be categorized into three types: overhead cranes, boom cranes, and tower cranes [6].

1.2Overhead Cranes

The first category is overhead cranes, also named bridge cranes. Displayed in Figure 1.2, such an overhead crane operates in Cartesian space. The trolley moves along a bridge suggested by its name. The motion of the payload is perpendicular to that of the trolley. Overhead cranes that can also travel on a mobile base are often called gantry cranes. Overhead cranes are commonly found in industrial environments such as factories (Figure 1.3(a)) and warehouses (Figure 1.3(b)).

Figure 1.2: Schematic of overhead cranes

Figure 1.3: Real applications of overhead cranes in China: (a) application in a Chinese factory and (b) application in a Chinese warehouse

1.3Boom Cranes

The second category is boom cranes. A boom crane is distinguished from other cranes by its use of a single boom which pivots and rotates on a base at one end. The payload is hoisted from the other. Displayed in Figure 1.4, such a boom crane operates in spherical coordinates. In the coordinates, the boom rotates around axes both perpendicular and parallel to the ground. In Figure 1.4, 8 is the rotation around the vertical Z-axis, and θ is the rotation around the horizontal Y-axis. The payload is supported by a suspension cable at the end of the boom. The platform can be stationary (Figure 1.5(a)) or mobile (Figure 1.5(b)).

Figure 1.4: Schematic of boom cranes

Figure 1.5: Real applications of boom cranes in China: (a) stationary platform and (b) mobile platform

Boom cranes are commonly found at building construction sites. Their compact nature also lends well to being mounted on a mobile base. Boom cranes are often mounted on trucks, tracked vehicles, and ships.

1.4Tower Cranes

The third category is tower cranes. For convenience, the tower crane illustrated in Figure 1.6 can be described by cylindrical coordinates. In the coordinates, the horizontal jib arm can rotate around a vertical tower. The payload is supported by a cable from the trolley and the trolley moves along the jib arm in the radial direction. In Figure 1.6, ! and β are the rotational angles around the horizontal plane, θ is the rotation around the vertical Z-axis, and r is the distance between the trolley and the tower.

Tower cranes often give the best combination of height and lifting capacity. They are commonly found in the construction of tall buildings (Figure 1.7) because the type of cranes has the merit of having a small footprint-to-workspace ratio.

1.5Control Problems

A common characteristic among all cranes is that the payload is supported via an overhead suspension cable. The characteristic results in the same problem of ineffi-ciency caused by payload oscillations. Such payload oscillations make it difficult to manipulate payloads quickly, accurately, and safely. While this provides the basic functionality of cranes, it also presents several challenges, the primary of which is payload oscillation. Motion of cranes will often translate to large payload oscillations. These payload oscillations have many detrimental effects, including the degradation of payload positioning accuracy, increased task completion time, and decreased safety. Significant research effort has been made into reducing oscillations [7].

Figure 1.6: Schematic of tower cranes

Figure 1.7: Real applications of tower cranes in China

To date, the primary method utilized to limit this motion-induced vibration has been to train a skilled operator and to move slowly because the skilled operator could eliminate much of the sway by moving cranes in very small increments. While this does serve to reduce payload oscillations and, thereby, increase safety, it does not provide the most efficient operating condition. Taking safety and positioning accuracy into consideration, payload oscillations have adverse effects...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Preface
• Contents
• Acknowledgments
• 1. Introduction
• 2. Crane Dynamics
• 3. Passivity-Based Anti-sway Control
• 4. Sliding-Mode-Based Anti-sway Control
• 5. Output Feedback-Based Anti-sway Control
• 6. Fuzzy-Logic-Based Anti-sway Control
• 7. Input-Shaping-Based Anti-sway Control
• 8. Conclusions
• Appendix Software Program of Anti-sway Control Against Double-Pendulum Motions
• Index