COMP322/S2000/L281 Task Planning Three types of planning: l Gross Motion Planning concerns objects...
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Transcript of COMP322/S2000/L281 Task Planning Three types of planning: l Gross Motion Planning concerns objects...
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COMP322/S2000/L28 1
Task Planning
Three types of planning: Gross Motion Planning concerns objects being moved from
point A to point B without problems, i.e. movement of manipulator without collision with obstacles
Grasping Planning concerns where to grasp the object so that no collision will occur the grasp configurations so that object will not fall off the gripper duri
ng transportation Fine Motion Planning concerns the motions of the robot wh
en it is approaching a surface, i.e. guarded motion; and in contact with a surface, i.e. compliant motion
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COMP322/S2000/L28 2
Gross Motion Planning Concerns objects moving from Point A to Point B without col
lision ==> obstacle avoidance problem Gross in the sense that there is no contact of the robot with an
y parts Objective is to plan a path to move a part from an initial pos
ition and orientation to a final position and orientationnin the presence of obstacle without colliding with the obstacls.
The planned path should be optimal, e.g. the shortest one. In general, path planning is a search in the 6-Dimension spac
e (3 translational and 3 rotational). However, the no. of degrees of freedom is usually less than 6. Why?
Configuration space is needed before an optimal path can be defined.
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COMP322/S2000/L28 3
Gross Motion Planning (cont’d)
Configuration space defines the positions and orientations of the part (both initial and final) and the obstacles.
Path Planning is to define the explicit free space in the configuration space for the object to move from the intitial location to the final location.
One possible approach: Shapes and sizes of part (to be moved) and obstacles (station
ary) are known To define the configuration space, the moving part is “shrink
ed” to a reference point (e.g. centroid) while the obstacles are “grown” to compensate the lost.
Once the configuration is defined, the optimal path can be found.
Example (Given in class)
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COMP322/S2000/L28 4
Grasping Planning
Concerns where to grasp the object so that no collision will occur and the object will not fall off during transportation.Three main considerations: Safety - collision free, contact free; Reachability - able to reach initial configuration, with object
in the gripper, move in a collision free path to the final destination; and
Stability - the grasp should be stable in the presence of forces exerted on the object while in motion.
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COMP322/S2000/L28 5
Grasping Planning (cont’d)
Three main goals: must identify a single configuration, i.e. position and orientat
ion of the gripper; must consider the detailed interaction of the gripper‘s shape,
surfaces of contact; and must deal with the interaction of the choice of grasp consider
ation and the constraints imposed by the sequence of operations
Most approaches consist of three steps: choose a set of potential grasp configurations; Prune those that are not reachable by the robot or may lead to
collision; and choose the optimal from the remaining ones.
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COMP322/S2000/L28 6
Grasping Planning (cont’d)
Note: These approaches assume the configurations of objects are kn
own With the help of sensors, e.g. vision, configurations of object
s can be computed Touch sensors are often used to achieve the actual grasping o
f the objects.
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COMP322/S2000/L28 7
Fine Motion Planning
Concerns the motions of the robot when it is approaching a surface ==> guarded motion in contact with a surface ==> compliant motion
Force and tactile sensors are usually used
Guarded Motion Movement along a specific direction until certain event occur
rs
Compliant Motion After contact, the type of motion must comply with the const
raints imposed by the surface Motion is usually continuous and guided by contact with the
surfaceExample (given in class)