26-11-2012, 05:42 PM
Development of a Robotic Bridge Maintenance System
Development of a Robotic.PDF (Size: 3.55 MB / Downloads: 311)
Abstract
This paper will expand on the Rrobotic
Bridge Maintenance Ssystem (RBMS) developed by
the Construction Automation and Robotics
Laboratory (CARL) at North Carolina State
University (NCSU). The system consists of a 4-
degree-of-freedom robot designed and built at NCSU
mounted on the end of a truck mounted peeper crane.
Additionally, a containment system is mounted in
front of the robot to contain the toxic waste created
by the removal of the lead-based paint from the
bridge beams and trusses.
Introduction
Robotic systems for construction
applications have advanced dramatically over the
past few years. Automated systems were initially
developed to reduce labor requirements, shorten
construction time, reduce costs, and improve quality.
Currently, benefits such as moving workers out of the
dangerous work areas and conformance to agency
standards such as those set by the Environmental
Protection Agency (EPA), the Toxic Substance
Control Act (TSCA), and the Occupational Safety
and Health Administration (OSHA) have improved
the workers' environments and improved worker
morale.
Overview of System
The robotic bridge maintenance system has
four main capabilities: remote inspection, spray
washing, paint removal, and painting. The original
prototype of the system was developed and
successfully tested as a robotic bridge paint removal
system August of 1994. The basic goals of the
system were to eliminate the need for a human to be
involved directly in the removal process and to
contain the lead-based paint. (A schematic of the
original system is shown in Figure 1 and a picture of
the system in action is shown in Figure 2.)
Control of the System
The control of the system can be divided
into two parts : control of the crane and control of the
robot. It is possible to control the crane and the robot
individually or at the same time.
Crane Control
Since the bridge maintenance process has
been robotized in an attempt to improve safety and
health conditions, automation of the crane is desired.
Because of the highly unstructured nature of the
environment, it is desirable to use a tele-robotic mode
of control instead of a fully automated mode. The
control of the crane is based on a graphic path
planner which creates the manipulator path from a
starting position to a desired destination in a CAD
environment. [2] The path planning supports a
graphic overlay control which allows for a telerobotic
mode of operation.
Off-line path planning provides a basis for
on-line crane control in the tele-robotic mode.
Predetermining the crane path generates the required
control data for the deployment of the crane under
the bridge.
Robot Control
The robot control is a closed loop system
with feedback from the robot's actuators back to the
computer. The rotary and linear actuators have
positional feedback, from the actuator-mounted
potentiometers, routed through Cyclon STC's (signal
tracking controllers) with PID adjustments. The
proportional valves operating the actuators allow the
mechanical means of implementing the PID functions
needed for smooth movement. Opto brain and bus
boards were used to communicate between the STC's
and the host computer, a Pentium 90 running Win95.
These analog/digital and digitalIanalog converters
allow the PC bus board to properly address the
signals for communication between the Opto
equipment and the PC. The control equipment
needed to be together in a single location due to the
need for parallel communcation. For this reason, a
common containment box was built to hold all
equipment including power supplies, controllers,
etc.(as shown in Figure 6.)
Conclusion
This paper has describe the development of
the Robotic Bridge Maintenance System jointly
developed by the NCDOT and CARL at NCSU. The
system allows an operator to be removed from the
dangerous environment under the bridge and allows
him/her to tele-operate the entire bridge maintenance
procedure.
One of the major advantages that this system
has over others is that it has been designed as a
relatively simple modification to existing equipment.
The gantry table and robot mount to the peeper crane
with four bolts and four quick connect lines. This
also has the advantage of making the system easy to
transport.
Another advantage is the use of a robot to
do the bridge maintenance procedure. By using a
robot and a universal gripper, virtually any type of
blasting method can be used. Additionally the robot
can be used for other types of applications in which a
tool needs to be manipulated and it is desirable to
place the worker at a safe distance.