PROJECT TIMOTHY

(Group 74 #1)

Caitlin Haisler, Jennifer Luebbers, Scheile Preston, Andrew Xu

APPROACH TO THE PROBLEM

The first objective of Project Timothy was to implement an A* pathfinding algorithm that guided the robot around any obstacles to the specified waypoints in the course. The A* algorithm is called for the first time when the robot is turned on, and the first waypoint is set as the robot's destination. When the robot comes within half a tile of its destination, the next waypoint is set as its new destination. The XY coordinates of the robot are constantly tracked by the Optitrack camera system. The robot uses its XY position as well as the LADAR sensor to mark obstacles in the course in a map character array. The robot used data from the LADAR in 10-degree increments to build an obstacle map that was highly accurate. If the robot encountered a new obstacle, it re-ran the A* algorithm to find an alternate route. The A* algorithm always guided the robot to its destination with the purpose of traveling as short a distance as possible.

The next goal for Timothy was to program the robot to locate and kill both pink and blue weeds strewn about the course. The weeds were supposed to be killed only once, and the robot had to keep track of the number and color of weeds killed. The first step in accomplishing this task was to establish an accurate HSV range for both the pink and blue weeds in the course using the provided HSV Matlab code. Next, the Colorvision code that processed the data received from the camera checked to see if there was an object (checking alternately for pink or blue) in the proper HSV range to be considered a weed and noted the number of pixels the object consisted of. The Colorvision file then sent the location of the centroid of the object on the LCD screen to the main C file.

With each loop through the main C file, the number of pixels of the pink or blue object was compared to the threshold value, determining if the object was large enough to be a weed. If it was large enough, Timothy paused from following its A* path, turned, and looked at the weed. It then determined the world XY location of the weed in the course by converting the centroid location of the weed from the camera coordinates to a distance in world coordinates. The robot used this distance and its own XY position and angle to calculate the XY position of the weed. If the robot had not already killed a weed within 1 tile in any direction of the weed it was looking at, it moved forward towards the weed using its centroid location rom the camera. When the weed was almost out of sight of the camera, the robot switched from following the weed to moving forward in a straight line blindly for a specified amount of time. After this, the robot would be sitting directly over the weed and stop for one second to kill the weed. The robot stored its current XY location in an array to keep track of the positions of the weeds already killed. With the location of the weed marked, the robot re-ran the A* algorithm to continue traveling to the next waypoint.

A case statement made up of five possible states determined the robot's "mission" or objective at any given moment. State 1 contained the instructions for the robot to continue following its current a* path. While in State 1, if the robot's camera picked up a blue or pink object that had above the established threshold of pixels, the robot set a flag marking which color weed it found and sent the robot into State 3, interrupting the instructions for the a* path.

While in State 3, the robot stopped moving forward and was allowed time to turn and look at the weed. It recorded the centroid location of the weed it was looking at and then calculated the location of the weed in the map to see if it had already killed it. If it had not yet killed the weed, the robot moved into State 4. If the weed had been killed, the robot moved into State 2, which updated the A* path to lead the robot onto the next waypoint.

While in State 4, the robot slowly moved directly towards the weed until it was a specified distance away. Once it reached this distance, the robot was sent into State 5. In State 5, the robot blindly moved forward for a given amount of time until it was positioned directly over the weed. (This time was determined by trial and error.) Once over the weed, the robot paused for one second, added its current XY position (also the location of the weed) to an array, and incremented the appropriate blue or pink weed count. Finally, it moved into State 2 where the A* path was recalculated to lead the robot to the next waypoint.

The above process was repeated until either 5 weeds were found or all the waypoints had been reached. If 5 weeds were found before all the waypoints were reached, Timothy would continue traveling to the waypoints without looking for any more weeds.

After all the waypoints had been reached, the robot moved outside the course to first the blue, and then the pink circles. It paused inside each circle and used a mounted servo motor to display the number of blue or pink weeds respectively it had killed in its completed run.

ROBOT PERFORMANCE VIDEOS

Course 1

Course 2

COURSE 2: 162.25 (time) – 100 (all 5 weeds found) – 60 (all 5 weeds killed) – 40 (no touch) FINAL SCORE = -37.25

LABVIEW FEATURES

Timothy includes five features in its companion LabVIEW program:

· Standard grid coordinate and wall drawing in the main display

· Main display traces the robot’s path, with a radius toggle to adjust size of robot’s circle

· Weed find indicator shows coordinates of found weeds, the color, and also plots in on the main display, with the dot correlating with its color

· Obstacles show up in the main display as green dots

· The next waypoint that the Robot heads to shows up in the main display as a red dot, and previous waypoints show up as brown dots.

OTHER USER FRIENDLY FEATURES ON TIMOTHY

Timothy utilizes the five LEDs that are arranged in a circle to indicate what state Timothy is in. This allows for quick diagnosing, as the LEDs are easier to see than the LCD screen in the back.

State 1 (following A* determined path) - LEDs flash counterclockwise

State 2 (Recalculating A*) – All LEDs on

State 3 (Camera sees color) – LED 2 on

State 4 (Robot goes towards color) – LED 3 on

State 5 (Robot is in open-loop mode) – LED 4 on

State 6 (Robot is in blue hexagon) – LED 5 on

State 7 (Robot is in pink hexagon and course is complete) – All LEDs flash at the same time.

Dials in the front of the robot show how many pink and blue weeds are killed. The dials are controlled using two servos and display once the robot reaches the pink or blue hexagon.

The LCD screen displays different information according to which mode it is in.

While the robot is running the course, the screen will display “Project Timothy” on the first line, and displays the current number of blue and pink weeds as well as X and Y coordinates on the second line.

When the robot gets to the blue hexagon, the screen will display “Blue Hexagon” on the first line and display the final number of blue weeds on the second line.

When the robot gets to the pink hexagon, the screen will first display “Pink Hexagon” on the first line and display the final number of pink weeds on the second line. After 3 seconds the screen will display “Maze Completed!” and display the number of blue, pink, and total weeds.

THE TEAM

(Left to Right) Caitlin Haisler, Scheile Preston, Jennifer Luebbers, Andrew Xu