Cable array robot for material handling

Details Cable array robot for material handling Cable array robot for material handling

2003-03-14

2004-11-30

Black, Thomas G. (Department: 3661)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Robot control

C700S246000, C700S254000, C700S258000, C700S260000, C700S261000, C700S264000, C318S566000, C318S568220, C405S191000, C901S022000, C901S023000

Reexamination Certificate

active

06826452

ABSTRACT:

REFERENCE TO A MICROFICHE APPENDIX
Not applicable
BACKGROUND OF THE INVENTION
One of the least expensive ways to move freight is by ship, and, indeed, cargo ships cross the oceans of the world hauling products from port to port, country to country. There are in particular container ships that carry cargo in large, uniform containers, such as standard, ISO 20-foot containers that meet the requirements of an international standards organization for size and configuration. The cargo containers are stacked on the large flat deck of a container ship and in its hold. Once in port, the containers are offloaded typically with an assortment of cargo handling cranes. Unloading these ships is, of course, a time-consuming task and requires a crew to assure that the right containers are removed safely and efficiently. Efficient loading and unloading are important in getting good utilization from a container ship and in meeting delivery schedules.
Once off-loaded from the ship, these containers may be loaded directly onto a truck frame with a set of wheels for hauling by tractor truck overland to a next destination. Alternatively, the cargo containers may be placed onto a smaller ship, called a lighter, for transport to a dock, a shallow water port or onto the beach in logistics-over-the-shore military operations.
Not every port or other commercial location has the large assortment of cargo handling cranes needed for off-loading large sea-going container ships. Present day fixed and mobile cranes or bridge cranes are often not practical because of cost, operating and maintenance constraints, and the time required to erect and deploy them. Furthermore, gantry cranes have relatively small workspaces within which they operate before the entire massive crane has to be moved down a permanent track on which vehicles and other objects may have inadvertently become obstacles. Even when the path is clear, the mobility limitation requires stopping the crane's operation, stowing the boom and outriggers, moving, and redeploying the boom and outriggers before operations can resume. Large rail cranes are also physically limited. Current ship-carried systems can sometimes compensate for limited port facilities, but because of the large pedestal size needed to support a rotating crane that can cover the ship deck, this is generally achieved at the expense of considerable cargo space or by requiring a separate crane ship to load and unload a cargo ship. In no case can they operate outside of well-protected port facilities where sea state three or higher conditions occur most of the time.
Loading and unloading containers using overhead or gantry cranes, in addition to their limited range of motion, have another problem. These types of cranes have X-Y actuation mechanisms from which a cable hangs like a pendulum. The pendulous nature of the gantry crane makes it less suitable for certain purposes, namely unloading ships, because it is so difficult to have the carried payload follow a trajectory without swinging. The motion of the sea results in an additional instability that translates into large swings in the payload. High wind and foul weather even further impede—or stall altogether—the process of loading and unloading these ships. When wind is blowing, the containers have to be restrained by crewmembers using ropes. This is a dangerous task. When the crane is on a ship and the sea is rough, the ship will roll and pitch, creating the same effect as high wind, namely, increased oscillation of the cargo container. Likewise, if the lifting mechanism is on a dock and the container is on the pitching, rolling deck of a ship, moving the container that is on the ship using the crane is a slow and difficult process. If the sea is too rough, such as sea state three or higher, unloading must be halted. Unfortunately, around the world, sea state three is common. There is a seventy percent chance that a ship will encounter sea state three or higher at any moment anywhere in the world.
In addition to their physical problems, traditional single boom shipboard crane systems are expensive, involve considerable maintenance, and require highly skilled operators. Dockside gantry cranes are also quite expensive to acquire, operate and maintain.
The field of robotics has developed rapidly over the past twenty years as electronic components that control robotic movements have gotten smaller and more robust. Robotic welding machines play a substantial role in manufacturing automobiles, for example. The concept of a robotic device is easy to grasp in general but hard to define with any specificity because of the large number of forms robotics devices may take. For example, robotic devices may be electrical, mechanical or electromechanical and may range from simple manipulators to vehicles for exploration of the surface of the moon, the planets or the ocean floor. Generally, however, the robotic device may be defined as a device that is capable of manipulating an object in a work place.
There is a particular type of robotic device, to which this patent lays claim, based on use of an array of cables attached to a lifting device. This “cable array robot” is defined as a robot that uses multiple cables connected together either directly or through an end-effector to manipulate an object in a workspace. A description of cable array robots is set forth by the inventor's team in
The Cable Array Robot: Theory and Experiment
, by Gorman, Jablakow and Cannon, 2001, Proceedings of the IEEE International Conference on Robotics and Automation, incorporated herein in its entirety by reference.
Three-cable and four cable systems can be used to move loads within a workspace, and computers can be programmed to control this movement. Equations of motion for a multi-cable crane system, for example, are developed using Lagrange's equations and certain assumed modes of operation. Then the resulting equations for four-cable arrays, which are kinematically redundant due to fewer degrees of freedom than the number of cables, are solved by first using a non-linear transformation to reduce the number of variables. An optimal-force distribution method can be applied to solve the transformed equations to yield a set of cable tensions needed to track a desired trajectory. The mathematical treatment of this subject is found in
Optimal Force Distribution Applied to a Robotic Crane with Flexible Cables
, by Shiang, Cannon, and Gorman, 2000, Proceedings of the IEEE Conference on Robotics and Automation, and
Dynamic Analysis of the Cable Array Robotic Crane
, by Shiang, Cannon and Gorman, 1999, Proceedings of the IEEE Conference on Robotics and Automation, both of which are incorporated herein in their entirety by reference.
The study of robotics may suggest the use of robots in the movement of cargo containers, but the complexities of real-world application, particularly in ship-to-ship movement of containers in sea state three conditions impose significant challenges. Nonetheless, there remains a need for a better way to move cargo containers than traditional cranes, particularly in loading and unloading ships during all weather conditions and in related tasks such as underway cargo replenishment, at-sea missile replenishment and mobile offshore basing. Other applications for the cable array robot cross a full range including hazardous waste remediation (e.g. radioactive waste drum handling in open fields), painting or de-icing vehicles (e.g. airplane servicing when they taxi into the workspace), open-pit mining (e.g. truck loading at the mine surface to avoid building and traveling miles of pit roads), and overhead pallet handling in manufacturing (e.g. to move pallets loaded with workpieces from one workcell to the next). The invention also envisions a new class of the world's largest robots including array robots with workspaces of nearly unlimited size including construction sites between tall buildings and stockyards or port areas engulfing whole valleys or fjords between nearby mountains on which the system's mast structures ar

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