AME 3623: Project 8: Proportional-Derivative Control

• All components of the project are due by Thursday, April 21st at 9:00 am
• Groups are the same as for project 1.
• Discussion within groups is fine.
• Discussion across groups may not be about the specifics of the solution (general programming/circuit issues are fine to discuss).

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

• tune PD-control parameters so as to achieve near critically-damped behavior of the hovercraft.

Component 1: Hardware

• If you have removed the switch from your circuit, please add it back.

• Balance your craft so that when the chamber is pressurized, the craft does not drift substantially (note that it will likely rotate).

Component 2: Software

Implement the following function:

• void position_derivative_control(int16_t forward_thrust, int16_t error, int16_t rotation_rate) synthesizes your previous position_control() and derivative_control() implementations, adding an additional signal for net forward thrust. The implementation will be along the lines of:

         int16_t thrust = Kp * error - Kv * rotation_rate;  // Your exact implementation may vary
         set_side_motor_magnitudes(forward_thrust - thrust, forward_thrust + thrust);
         

Structure your main() function as follows:

1. Initialize and read current heading to use as the goal.

2. Wait for the switch to be pressed. While waiting, read both the gyro and compass, displaying both rotation rate and rotation error using the LEDs.

3. Ramp up middle fan thrust until the craft begins to rotate.

4. Wait for the switch to be pressed again. While waiting, execute the following control loop:
   • Read the sensors
   • Display rotation rate and rotation error
   • Generate control signals to maintain heading goal (with forward_thrust = 0)
   • Remember to use flag_timing to ensure that your control loop executes at a reliable rate.

5. Turn off lateral fans.

6. Ramp middle fan down.

7. Enter infinite while() loop.

Component 3: Testing

• At the end of the previous project, you should have a reasonable choice of Kp. This should cause your craft to be relatively aggressive about moving toward the heading goal, though it will likely oscillate around the goal (perhaps damped, perhaps not).

• Slowly increase Kd until most of the oscillation has been removed.

• After tuning, the craft should be able to recover from disturbances from the heading goal. In addition, as the heading error approaches and then crosses 180 degree error, the thrust fans should flip polarity (e.g., shifting from hard right to hard left).

• Remember that fprintf() is an expensive operation in terms of time. Although useful for debugging, it can cause problems when used inside of a control loop.

What to Hand In

• Demonstration/Code Review: All group members must be present. Given time, this can be done during class. The demonstration must be completed by Monday, April 25th.

• Check in the following to your project 8 area of your subversion tree:
  • Documented code: See the project 1 specification for detailed documentation requirements.

• Personal report: There is no personal report due for this project.

Grading

• Each person must accumulate at least three personal programming credits over the course of the semester. This project offers one.

• To receive credit, you must be the primary designer, implementer and debugger of the component. This does not mean that your other group members should not be looking over your shoulder. But: you must do the "driving."

• 35%: Project implementation
• 30%: Demonstration of working project (to either of the TA or the instructor)
• 35%: Documentation

Group Grading Rubric

Grades for individuals will be based on the group grade, but weighted by the assessed contributions of the group members to the non-personal programming items.

References

• OUlib documentation

andrewhfagg -- gmail.com

Last modified: Wed Apr 20 22:49:37 2016