cis32 homework #2

sklar/spring-2006

The homework is due BY EMAIL on Friday March 24.

Send the homework to: sklar@sci.brooklyn.cuny.edu as PLAIN TEXT or PDF.

This homework is worth 6 points in total. The distribution of points is indicated below.

All of the questions here refer to the robot which is described in lecture #3:

Here you will get to write a line-following program for this robot in two ways: (1) as a production system and (2) using a neural network.

clarification added: You can assume that there are no breaks in the line.

and the questions are...

(2 points) The robot (represented by the @ symbol in the figures below) has 4 sensors (one in the front, one in the back and one on each side):
```
front
  1 
 4@2
  3
 back
```
If there is a line under a sensor, the sensor returns 1; otherwise it returns 0. For example:
```
 | 
 @
 |
```
returns 1010. If the robot is in the middle of a crossroads, e.g.:
```
 | 
-@-
 |
```
the sensors return 1111.
1a. How many possible states are there? Enumerate them. For convenience in completing the next two steps, label each state (e.g., x₁, x₂, etc.).
1b. revised and clarified description:
First, define the possible actions for the robot (hint: there are only four). For convenience in completing the next two steps, label each action (e.g., a₁, a₂, etc.).
Then, define one recommended action for each state.
For example, if the robot is in this state:
```
 | 
 @
 |
```
then the robot could either go forward or backward; since it is doing line-following, it won't make sense for it to go left or right (oops---I've just given away all of the possible actions...). You decide whether you prefer for the robot to go forward or backward when it encounters that state; then add that to your list of recommended actions.
Each state should have one recommended action.
(2 points) Define a production system (see lecture #3) that the robot can use for doing line-following.
(2 points) Define a series of TLU's (see lecture #11) that the robot can use for doing line-following.