AME 3623: Project 2: Beacon Following I

Project Goals

• Microcontroller programming
• Writing programs that interface with the real world
• Design and implementation of finite state machines

Project Due Date

Robot Task

• Phase 1:
  • Move toward the beacon in front of the robot
  • Scan for another beacon to the left
  • When the beacon is found, turn toward it and begin phase 2.

• Phase 2:
  • Move toward the beacon in front of the robot
  • Scan for another beacon to the right
  • When the beacon is found, turn toward it and begin phase 1.

• Phase 1:
  • Rotate the turret to the right
  • If a beacon is found in the new direction (immediately), then the robot will turn toward it and continue with phase 2.
  • If no beacon is found, then turn the turret forward and stop moving.

• Phase 2:
  • Rotate the turret to the left
  • If a beacon is found in the new direction (immediately), then the robot will turn toward it and continue with phase 1.
  • If no beacon is found, then turn the turret forward and stop moving.

Test Courses

Design Process

1. Design
   • Identify the FSM states
   • Identify the FSM inputs (events). How do the FSM inputs relate to the sensory inputs?
   • Identify the FSM outputs. What are the actions that your robot must take?
   • Define the state transition function.
   • Define the output function. What does the robot do at each state transition?

2. Implementation
   • Design and assemble a circuit based on an Atmel Mega8 processor.
   • Implement your FSM design in C.
   • Burn your program onto your processor.
   • Get it to work (do not underestimate the amount of time that this step will take).

Hints

• See the Atmel HOWTO for details about circuits and programming.

• Remember that events are instantaneous (e.g., a change in a sensory input) and that states are about maintaining a memory of the situation between events.

• Think about what control actions that your program must issue between events.

• Implement and debug your program incrementally. As with many embedded systems, you only understand the complete problem once you begin to work with the hardware. So - expect your design to evolve over the next few weeks. Here is a list of practical steps that you might consider taking before implementation of your FSM:
  1. Build the test circuit described in the Atmel HOWTO. Compile and download the test program. (and make sure that the lights blink as you expect)
  2. Design and implement the connections to the beacons receivers (the 8 bits), the robot control lines (3 bits), and the turret control lines (2 bits). Write several interface routines that are responsible for reading from or writing to the appropriate port bits (this is where the bit masking comes in!). A good way to handle the beacon receiver reading is for this interface routine to fill in an array of length 4 (one for each receiver) in which each element of the array can take on a value between 0 and 3.
  3. Write simple test routines that generate a robot/turret movement, followed by a delay, followed by a "stop" (in the case of the robot).
  4. Design and implement a routine that takes the receiver state and generates a robot motor command that steers the robot toward the beacon in front of it (a coded version of your lab 1). This routine should make a single movement decision & then return (we will call it repeatedly from the next level up).
  5. Design and implement a routine that effectively turns away from the beacon in front of the robot and toward a beacon to either the left or right. This routine should return once the rotation is complete.
  6. Finally, design and implement your FSM, using the pieces that you have developed above. Get your FSM to work first without the exception handling (just transition to a HALT state if you lose sight of the beacon). Then - add the exceptions.

• LED's on extra output pins can be used by your program to communicate debugging information to you.

• You may construct paper shields for your infrared sensors. This will allow you to better control the angular sensitivity of these sensors.

• Sensor filtering: as you discovered in lab 1, despite preprocessing, the infrared sensors can be somewhat noisy. This problem becomes more significant as we add more beacons to our environment. One way to deal with this is to filter these signals. A simple filtering mechanism is to sample the beacon receiver bits multiple times (e.g., separated by 1 msec intervals), and to sum the results. This will tend to give you more reliable sensor readings.

Robot Interface

What to Hand In

Project Report

• The names of the group members

• Describe the details of your FSM design (the components listed in the design section).

• A diagram of your circuit.

• A copy of your documented program (this may be handed in as a separate file).

Personal Reports

• Your name

• An estimate of your contribution to the project in terms of percentage of effort.

• An estimate of the contribution of each of your fellow group members.

fagg at ou.edu

Last modified: Mon Mar 28 19:04:13 2005