task_4

Robotics Task 4: Minesweeper

Subject Area:
Engineering and Technology

Age or Grade:
9th through 12th grade

Estimated Length:
6-7 class periods

Prerequisite knowledge/skills:
Simple Machines
Freshman physics and understanding of position, velocity and acceleration
Use of Microsoft Windows operating environment
Concepts learned in previous robotics tasks

Description of New Content:
Using the concepts used in the previous robotics tasks, students will build and program a robot to sweep 10 soda can "mines" out of a ring in as little time as possible.

Students will learn about:
a text-based programming structure
programming loop structures
conditional logic
flowcharts
linear and rotational motion control
Motor Outputs
use of feedback with sensors
logical and syntax errors
the need for sensor inputs
light color and intensity
detection algorithms
design of threshold values
how to apply their knowledge of the sensors in previous tasks to a new challenge

Materials Needed:
LEGO Mindstorm kit for every 2-3 students
Computer for every Mindstorm kit
Brix Command center software
At least 6 AA batteries per kit (rechargeable recommended)
4x4' white-board sheet
1/2" electrical tape
1-2 light sensors for each group
1-2 touch sensors for each group
10 empty soda cans or bottles
heavy mass ~6" diameter (coffee can filled with sand)

Procedure

Build minesweeper playing field. The center circle of electrical tape is simply to indicate that a can will not be placed within 1" of the center heavy object. This can also be used by the light sensors to keep the robot from running into the center object and getting stuck.

Opener:
(Not required, but may be fun for students) Find and show students a video on robots where robots perform activities that are too dangerous for humans. Possible examples could be the robotic arm on the space shuttle, deep sea diving robots, bomb detection and detonation, ...etc

Tell students that they are going to build and program their robots to sweep a simulation mine field where there are 10 cans (mines) randomly placed around the field with a heavy obstruction in the center of the field. They can think of the center heavy obstruction as being a small village being surrounded by the mines and the robot must move the mines a safe distance away from the field so that the villagers can safely farm.

The rules are that the robot can start outside the large circle, but may not exit the circle until all the mines have been removed from the within the circle. Since the villagers are starving and need to get to their crops, the robot has only 1 minute to remove the mines.

Development:
Tell students that they can remove and sense the mines any way that they wish using a light sensor and/or a touch sensor. For this task, the goal is for students to use the light sensor to locate the tape boundaries to stay in the circle and avoid the village, and use the touch sensor to sense the mines and count how many of the 10 have been removed.

Again, you can come up with a simple scoring system that will give points based on sweeping time up to 1 minute, fastest time, penalties for the robot leaving the track area/line and failure to remove each mine. This score can be used as an incentive as extra credit to the top-placing team or teams.

Evaluation:
Have students turn in a complete description of how their program works, any problems encountered, and the solutions to the problems. In addition, have the students turn in a copy of their programming code and a flowchart showing their programming algorithm.

Remind students that they are not graded on how successful they are, but how they demonstrate understanding of how a robot and program can be used to perform a specific task.

If students are simply able to program a robot to stay within the minefield boundary and/or count the number of mines knocked out, students have demonstrated understanding.