Project 2: Serial Communication and Control

All components of the project are due by Thursday, March 29th at 5:00pm. Note that between now and the due date, you have a midterm exam in the class and Spring break. Please start early (this is not a single-session project).
Groups will be composed of 4-5 students

Project Goals

At the end of this project, you should be able to:

Create simple microcontroller-based circuits,
Implement in code serial communication protocols for reading sensors and commanding actuators,
Write a proportional-derivative controller that connects sensing to actuation.

Hardware Overview

Our "helicopters" are 4-rotor X-UFOs that are equipped with their own, on-board microcontroller circuit that allows you to command the helicopter remotely and to query the state of a compass (both through a serial interface). The helis have four dimensions of control: throttle, roll, pitch, and yaw.

We will have a total of three complete heli systems available for this project. In addition, there will be two "test systems" that consist of the on-board microcontroller only. These latter units will allow you to test your own system's ability to request a compass reading and to read the response over the serial interface.

Project Overview

For this project, you will be creating a microcontroller circuit and the associated program to maintain the orientation of helicopter at a specified compass direction (i.e., you will be doing yaw control). In brief, your craft must:

Bring the throttle to a level sufficient for hovering. This is easy to do in "open-loop" (without sensing) because of the cables that dangle from the bottom of the craft
Hover for one minute
During the hover, the craft must orient to and maintain a heading that is specified at the time time of your demonstration (you may recompile and redownload your code to input the desired heading).
After the minute of hovering, the throttle must be reduced slowly so as to bring the craft to a soft landing.

Project Components

All components are required to receive full credit for the project. Although the final demonstration will focus on part 5, you should be prepared to show the functionality of the other components (this could be as simple as making a quick change to your code so that a different function is called).

Part 1: Microcontroller Circuit

Create a mega8-based circuit on a solderless breadboard.

See the bottom of the Atmel HOWTO for a circuit starting point. This contains everything that you need to create a programmable mega8
Connect pin 2 of the mega8 (the "serial receive pin") to the orange serial line; connect pin 3 (the "serial transmit pin") to the purple serial line.
A set of LEDs that will be used to display the current heading of the craft.

Part 2: Serial Interface

Create a software interface to the craft. Implement the following functions. See the OU-XUFO hardware specification for details of the serial interface.

int16_t get_heading(void) will send the necessary command to request the current heading from the craft. This function will then wait for the serial response and return the heading as an integer.
void set_throttle(uint8_t) will send the necessary command to set the current throttle level (due to the dangling wire, this signal is a combination of acceleration and position command).
void set_yaw(uint8_t) will send the necessary command to set the current yaw level (this is essentially an acceleration command).

Part 3: Compass Test

show_heading(void) will repeatedly query the state of the compass and display the craft heading.
show_heading_change(void) will repeatedly query the state of the compass and display the rate of change in the heading.
show_heading_error(void) will repeatedly query the state of the compass and display the difference between the current heading and a specified "desired" heading. Note that you must handle the "wrap around" case: 5 degrees and 355 degrees are very near each other, but their numeric difference large.

Part 4: Throttle Test

Create a test function that will slowly ramp the throttle up to a given level and then slowly bring it down. The craft should lift gently into the air and (just as gently) return to the ground.

Part 5: Control

Create a proportional-derivative controller that will bring the craft's heading to a specified orientation. In essence, you will implement the following:

yaw_command = yaw_center + Kp * (theta_desired - theta_actual) - Kv * theta_derivative_actual

where Kp and Kv are gain parameters that you must select (start small!), and yaw_center is the yaw command that corresponds to "no yaw acceleration" (this latter parameter should be 128).

Note: if you are using different data types (e.g., int and float), you must take care to cast one in terms of the other before mixing them (see the AVR programming book on type casting)

References

What to Hand In

All components of the project are due by Thursday, March 29th at 5:00pm.

Demonstration/Presentation: All group members must be present.
- Demonstrate your final product.
- Present your design and implementation (5 minutes). The group is responsible for assembling a short presentation consisting of 3-4 slides (on computer or in printed form). Describe the design including: your general approach to solving the problem, the circuit, any key software algorithms (how the general problems are solved in code), and the software organization (describe how the software problem is split into different separable sub-problems, and how the different components interact).
Code: Turn in your documented code to the project 2 digital dropbox on D2L (text format). Only hand in one copy of the code per group.
Group report: Augment your presentation with any details that do not fit within the allotted time. You may use your presentation format (e.g., powerpoint) for this report. Turn in one copy per group.
Personal report: One submission per person to the project 2 digital dropbox. State the relative contribution of you and your group members (in terms of percentage of effort) (text format only!)

Grading

Group grade distribution:

40%: Project implementation
30%: Demonstration/presentation of working project (to either of the TAs or the instructor). This demonstration is due at the same time as the reports
30%: Code documentation and group report

Grades for individuals will be based on the group grade, but weighted by the assessed contributions of the group members.

fagg [[at]] ou.edu

Last modified: Wed Mar 7 10:55:33 2007