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

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.

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)

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.

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.

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.

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)