Page 65 - ASME DSCC 2015 Program

Technical Program

operator Testing on Dual-Hoist Cranes Moving Triangular Payloads dynamic Modeling of Torsional Impact and Its Stiffness Measurement
Contributed regular paper. DSCC2015-9882 for Impact Wrench
Caroline Rhee, Alex Miller, William Singhose, Georgia Institute of Invited session paper. DSCC2015-10000
Technology, Atlanta, GA, United States Shengli Zhang, Jiong Tang, University of Connecticut, Storrs Mansfield, CT,
United States
Certain heavy-lifting applications require the coordinated movement of
multiple cranes. Such tasks dramatically increase the complexity of crane Impact wrench is a popular hand tool whose mechanism is featured with
operation, especially when the payload has a non-uniform shape. There- impact characterized by short time duration and large contact torque. The
fore, controlling such a complex dynamic system requires skilled operators. nonlinear impact problem has drawn researchers’ interests for a long time
However, even with extensive operator training, manipulating a crane with and the investigation is still undergoing. Fully and accurately modeling
a large payload is difficult and presents serious safety hazards. This paper impact can facilitate the understanding and improving the performance of
studies the dynamic behavior of a dual-hoist bridge crane moving triangu- impact wrench. Under certain circumstance, not only coefficient of restitution
lar payloads. Test subjects used a wireless controller to move a dual-hoist is interested but also the whole impact process. Hence, discrete impact
crane with a triangular payload. They drove the payload through an obstacle model cannot fulfill these requirements and dynamic modeling is indispens-
course under various operating conditions. The time required to complete able. At the same time, sufficient knowledge about contact parameters such
the course and the operator effort were recorded. Test runs were complet- as contact stiffness is necessary for accurately impact modeling. But these
ed with and without input-shaping oscillation control. The result shows that parameters are usually not readily available. Moreover, researchers mainly
using input-shaping oscillation control significantly reduces not only the task focused on translational impact problem while rotational impact problem is
completion time but also the number of button pushes. ignored. In this paper, Hunt-Crossley nonlinear contact model is applied and
extended in torsional impact dynamic modeling. Based on this model, an
Three-dimensional Modeling and experimental Verification of
experimental method is developed to evaluate the distribution of inertias in
off-centered crane Lifts
lumped parameter models. Contact stiffness is measured based on spec-
Contributed regular paper. DSCC2015-9805
trum results. To obtain reliable experimental data, impact wrench is driven by
Anthony Jon Garcia, Virginia Tech, Blacksburg, VA, United States, a servo motor to generate a controllable torque impulse. Contact stiffness is
William Singhose, Aldo ferri, Georgia Institute of Technology, Atlanta, GA, acquired under different impact speed. Results show the nonlinear relation-
United States
ship between contact stiffness and impact speed.
When cranes lift heavy payloads off the ground, the payload may slide or
Task-Allocation and Control of a Ground Robots Collective for
swing sideways unexpectedly. This dangerous motion occurs when the
Warehouse Automation
payload is not directly beneath the overhead suspension point of the hoist
Contributed regular paper. DSCC2015-9938
cable. Given that cable suspension points are usually tens of feet, and
perhaps hundreds of feet above the payload, it is very difficult for crane Mehmet Ali Guney, Ioannis Raptis, University of Massachusetts Lowell,
operators to know if the hoist cable is perfectly vertical before they start Lowell, MA, United States
to lift the payload off the ground. Inevitably, some horizontal motion of the In the last years, there have been several attempts to deploy Autonomous
payload will occur at lift off. If an off-center lift creates substantial horizontal Guided Vehicles (AGVs) to automate the operation of warehouse envi-
motion, then it can create significant hazards for the human operators, the ronments. The implementation of AGVs has numerous advantages over
payload, and the surrounding environment. This paper develops a three- conventional warehouse automation systems in terms of cost and scalability.
dimensional dynamic model of off-centered lifts. The accuracy of the model In this work, we present the development of a test-bed platform for the
is experimentally investigated using a 10-ton bridge crane. utilization of AGV collectives to a warehouse automation system. The system
architecture has plug-and-play algorithmic design which makes it extremely
modular. In this system, robotic small-scale forklifts are used to transport
an arbitrary number of circular pallets to predefined locations. The forklift
robots are able to move in the arena without crashing each other due to the
implementation of a centralized collision avoidance algorithm. The devel-
oped task allocation algorithm prevents the forklift drives from getting caged
by a fence of pallets. The performance of the proposed system is validated
by both simulation and experimental results.

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