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# CS344 : Introduction to Artificial Intelligence - PowerPoint PPT Presentation

CS344 : Introduction to Artificial Intelligence. Pushpak Bhattacharyya CSE Dept., IIT Bombay Lecture 17- Robotic Planning mainly discussed the search issues. Example : Blocks World. STRIPS : A planning system – Has rules with precondition deletion list and addition list . Robot hand.

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### CS344 : Introduction to Artificial Intelligence

Pushpak BhattacharyyaCSE Dept., IIT Bombay

Lecture 17- Robotic Planning mainly discussed the search issues

• STRIPS : A planning system – Has rules with precondition deletion list and addition list

Robot hand

Robot hand

A

C

B

A

B

C

START

GOAL

Sequence of actions :

Grab C

Pickup C

Place on table C

Grab B

Pickup B

6. Stack B on C

• Grab A

• Pickup A

• Stack A on B

• STRIPS : A planning system – Has rules with precondition deletion list and addition list

Robot hand

Robot hand

A

C

B

A

B

C

START

GOAL

on(B, table)

on(A, table)

on(C, A)

hand empty

clear(C)

clear(B)

on(C, table)

on(B, C)

on(A, B)

hand empty

clear(A)

• R1 : pickup(x)

Precondition & Deletion List : handempty, on(x,table), clear(x)

• R2 : putdown(x)

• Precondition & Deletion List : holding(x)

• Add List : handempty, on(x,table), clear(x)

• R3 : stack(x,y)

Precondition & Deletion List :holding(x), clear(y) Add List : on(x,y), clear(x), handempty

• R4 : unstack(x,y)

• Precondition & Deletion List : on(x,y), clear(x),handempty

• Add List : holding(x), clear(y)

• For the given problem, Start  Goal can be achieved by the following sequence :

• Unstack(C,A)

• Putdown(C)

• Pickup(B)

• Stack(B,C)

• Pickup(A)

• Stack(A,B)

• Execution of a plan: achieved through a data structure called Triangular Table.

on(C,A)

1

clear(C)

unstack(C,A)

hand empty

holding(C)

putdown(C)

2

on(B,table)

hand empty

pickup(B)

3

clear(C)

holding(B)

stack(B,C)

4

on(A,table)

clear(A)

hand empty

pickup(A)

5

6

clear(B)

holding(A)

stack(A,B)

on(C,table)

on(B,C)

on(A,B)

7

clear(A)

0

3

6

1

2

4

5

• For n operations in the plan, there are :

• (n+1) rows : 1  n+1

• (n+1) columns : 0  n

• At the end of the ith row, place the ith component of the plan.

• The row entries for the ith step contain the pre-conditions for the ith operation.

• The column entries for the jth column contain the add list for the rule on the top.

• The <i,j> th cell (where 1 ≤ i ≤ n+1 and 0≤ j ≤ n) contain the pre-conditions for the ith operation that are added by the jth operation.

• The first column indicates the starting state and the last row indicates the goal state.

### Connection between triangular matrix and state space search

Kernel 0 = S0 (starting state)

on(C,A)

1

clear(C)

hand empty

2

on(B,table)

3

4

on(A,table)

5

6

7

0

unstack(C,A)

holding(C)

2

on(B,table)

3

4

on(A,table)

clear(A)

5

6

7

0

1

Start

Pickup(B)

Unstack(C,A)

• Ex: Blocks world

• to some amount of fault-tolerance in the robot

S1

S2

NOT ALLOWED

A

C

C

C

B

A

B

A

B

START

WRONG MOVE

• After a wrong operation, can the robot come back to the right path ?

• i.e. after performing a wrong operation, if the system again goes towards the goal, then it has resilience w.r.t. that operation