01 example of literature presentation

1. Planning and visualization
for automated robotic crane
erection processes
in construction
Automation in Construction 15 (2006) 398 – 414
Authors /
ShihChung Kang
Eduardo Miranda
Presenter /
Ray Wen

2. Introduction & Motivation
• An efficient crane operation has great
influence on the schedule, cost, and safety of
a construction project.

3. PREVIOUS RESEARCH

4. Crane-related research
• Crane-related research
(1) Crane selection
(2) Optimum placement of tower cranes and
supply location of erection materials
(3) Estimation of erection schedule
(4) Usage and coordination of multiple cranes
(5) Simulation and visualization of operations

5. Crane-related research
• Many researchers have developed methods to
determine the time for transporting the
structural elements from the supply location
to the final destination.

6. Construction automation research
• Two directions:
– Degree of automation
• reduce the repetitive manual procedures by using
computational methods
– Degree of reality
• move the abstract model toward the virtual world and
the real world.

8. • To achieve fully automatic level, motion
planning is important.
• The main goal of motion planning methods is
to find continuous, collision-free paths by
giving the initial and target positions.

9. MOTION PLANNING OF A SINGLE
CRANE

10. Crane model and its configure space
• Denavit-Hartenberg notation is used to model
a crane and the crane is treated as a 4DOF
robot.
• Transformation matrices were created to
represent links (joints) between neighboring
bodies of a robot crane.
• By multiplying all the transformation matrices
together, a global matrix, or a direct
kinematics of manipulators, is obtained.

12. The purpose of developing these manipulators is to transfer the model
between the real world space and the configure space(C-space).

13. Finding a collision-free erection path is simplified to a problem of finding a path
not going through the C-obstacle
Obstacles from the real-world are also
converted to the C-space and are called
C-obstacles.

14. Path-planning and motion-planning
methods
• Find a collision-free path
• Refine the path
• QuickLink
– most inexpensive, lowest success rate
• RandomGuess
– most expensive, highest success rate
• QuickGuess
– intermediate approach of the three.

15. links the two trees if the guessed
random point can see both of
them.
keeps adding new points randomly to each tree
and use QuickLink to check if the two trees can
be linked without any collision.
adds random points above two end points,
then check those points from the roots
whether it’s collision-free.

16. Path refining methods
• Optimize the path and make it more realistic.
• Three steps:
– Remove redundant nodes
• but the remaining path is not necessarily the optimal
path.
– Soften sharp angles
• making a smoother route for the object to move.
– Make the path easier for crane operations.
• by taking into account how cranes move.

17. removes the redundant nodes between the
examined node and the farthest node
picks a random point within a line segment
between two nodes, connect them, and
replace the old path if the new path is
collision-free.
replace the line with a curve.

18. Collision-detecting method
• ApproxCheck
– detects the collisions and the distance between
the object and the obstacles.
• Boundary of objects
– Using cuboids (rectangular boxes) reduces the
computation cost.

19. Collision-detecting method
• Collision status determined in 3 levels
– Rough check: uses the longest length of cuboid
– Fine check: uses the second longest length
– Finest check: uses the shortest length
• Errors when applied on a construction site
– Rough check: 100 cm ~ 300 cm
– Fine check: 15 cm ~ 50 cm
– Finest check: 5 cm ~ 15 cm

20. Collision-detecting
method
• SeeEachOther
– detecting collisions from both ends in the C-space
of a crane
– storing the distance between the end point and
the nearest obstacle if the end point is collision-
free, and move the end point toward the other by
that distance.
– repeat the same process from the other end
– if the sum of the two free distances > distance
between two ends, the path is collision-free.

21. MOTION PLANNING OF MULTIPLE
CRANES

22. • Crane-operating areas often overlap, resulting
in spatial conflicts.
• Some tower cranes use sensors that force the
cranes to stop when too close to each
other.(Passive)
• Centralized planning method
• Decoupled planning method.

23. Centralized Planning
• Considers all the robots as a single one by
encoding their degree of freedoms in a single
composite C-space.
• The number of the dimension of C is equal to
the total number of degree of freedoms of all
the cranes.
• A path found in the composite C-space
describes the individual path of each robot
and how the robots are to be coordinated.

24. Decoupled Planning
• Two-phase approach
– First phase: generating a collision-free path for
each crane by ignoring other cranes
– Second phase: velocity tuning, the relative
velocities of the robots along their respective path
are selected to avoid collision among them.

26. Decoupled Planning
• searches lower dimensional spaces more than
centralized planning, reducing the
computation cost.
• A decoupled planner based on global
coordination is less incomplete than one
based on pair-wise coordination.

27. Incremental decoupled method
• Cranes need to avoid collision with all
structural elements that have previously been
erected.
• Planning the motions for an individual crane
during a certain amount of time.
• The time interval is usually the average time
needed to erect 3 or 4 elements.

28. IMPLEMENTATION AND RESULTS

29. 5.1. Implementation of iCrane
(1) generating erection sequence;
(2) finding collision-free erection paths of each
structural element;
(3) planning the motions of construction crane(s)
to follow the calculated erection paths; and
(4) coordinating the motions between multiple
cranes.

31. OpenGL
• Graphical language broadly used in computer
graphics
• Be developed in the Microsoft.Net platform
• Allows users to control the view angles and
play speed of the animation.
• Users are able to shift the view points

32. 5.2. Comparison with previous research

35. • In the analysis, we found that some structural
elements lead to large differences in erection
time between iCrane and Zhang’s model.
Approximately 5% of the structural elements
have more than 200% difference; and
approximately 38% of the structural elements
have at least a 150% difference.

36. Benefits of iCrane
(1) Engineers can revise the engineering model and
repeatedly run.
(2) Project planners can use the system to test
different erection processes to obtain an
optimal schedule.
(3) This system can produce precise and detailed
planning and scheduling before real
construction to eliminate potential risky and
inefficient activities.
(4) Avoid the crane having to wait for the material
to arrive to the site or to minimize storage on
site.

37. (5) iCrane used the algorithms developed in the
research to find a collision-free and
operational-optimal path for erecting each
structural element.
(6) While applied iCrane in construction practice,
iCrane system can broadly benefit crane
operators and construction management to
perform their work more efficiently.

38. (6)The computer-aided planning method can also
increase the accuracy and efficiency of project
management to support larger, more complex,
safer and faster projects in the future.
(7)iCrane can be executed in most personal
computers and enables users to simulate
construction processes virtually as many times as
necessary before a real construction project
begins.