AME 3623: Project 4

• All components of the project are due by Friday, March 15th at 11:59 pm.
• 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:

• through low-level functions, control the speed and direction of DC motors through an H-bridge circuit, and
• use a high-level program to test the functionality of the DC motor control interface.

Component 1: Microcontroller Circuit

The detailed documentation for the motor control board can be found on the Pololu Web site. Below is a picture of the H-Bridge board:

Motor/Power Connections

• Connect GND and VIN (right side of the board) directly to the thick power cables (not to your 5V power supply provided by the Teensy board!!!). There is one pair of black/red cables for each board. Make sure you do this without the batteries plugged in, and have someone else check your connections before you apply power.

  Note: you may need to use a wire stripper to remove the insulation from these power wires. Remove 1/4 inch of insulation and twist the strands of the wire together. Insert the cables into the screw terminal on the side and tighten the corresponding screw. Once you are done, you must have no exposed wire; if it is necessary, trim down the length of your exposed wire and re-connect.

• Each ducted fan has a pair of wires routed to the upper deck. Connect each of the fans to their corresponding OUT A/B screw terminals. Because these are brushed motors, the choice of which wire connects to which of A or B is arbitrary.

H-Bridge Control Connections

• Connect GND and GND to your Teensy's ground
• Connect +5V to the hovercraft +5V supply
• Connect PWM to a Teensy pin that generates PWM output
• INa and INb: connect each H-Bridge to a pair of Teensy pins on the same digital I/O port (different H-Bridges can use different ports)

Component 2

// Promise that we will implement this function later
void fsm_step();

// Create a task that will be executed once per 50 ms
PeriodicAction fsm_task(50, fsm_step);

// Gains to be used for reverse thrust
const float FAN_GAIN[] = {1.0, 1.0, 1.0}

Implement your loop() function in this way:

void loop()
{
  // Check to see if it is time to execute the fsm_task
  fsm_task.step();
}

With this implementation, you will ensure that the function fsm_task() is called once every 50ms

Component 3

Implement the following functions:

• float clip(float value, float min_value, float max_value) that returns
  • min_value if value is smaller than min_value
  • max_value if value is larger than max_value
  • value otherwise

• void set_lateral_fan_magnitudes(float magnitudes[3]) that sets the thrust magnitude for the lateral fans (the order in the array is LEFT, RIGHT and BACK).
  • This function must ensure that each of the input magnitudes fall within the range of -127... 127. If any do not, then the offending value should be clipped to this range. These values correspond to a duty cycle of 50%.

  • Positive values must correspond to pushing air through the duct in the "correct" direction; negative values correspond to pulling air through the duct in the atypical direction.

  • If a negative value is specified for fan i, then the magnitude should be multiplied by FAN_GAIN[i]. Adjust the values of FAN_GAIN to achieve approximately the same thrust in the positive and negative directions (this will be hard to assess for this project, so take your best guess and we will readjust later).

PWM Interface

Use the following Arduino function to set the duty cycle of a PWM pin:

analogWrite(pin, duty);

Component 4

Implement a Finite State Machine in fsm_step() that does the following:

• If your switch is pressed, initiate the following sequence:
  • Slowly ramp the left fan up to a duty cycle of 25%
  • Slowly ramp the left fan down to a duty cycle of -25%
  • Slowly ramp the left fan back to zero
  • Repeat for the back, then right fan

• Once complete, then your FSM should return to waiting for the switched to be pressed.

Finite State Machine notes:

• The logic of your FSM must be implemented inside of your fsm_step() function.

• Your fsm_step() function must not have any while or for loops or sleep() calls inside of it.

• Declare a State enumerated data type in your project.h file to represent the different possible states of the FSM:

  typedef enum {
     STATE_START,
     #LIST YOUR OTHER STATES HERE#
  } State;
  

• You will have two types of events:
  • Switch is pressed/unpressed
  • Counter reaches a certain value

• You can use your LEDs or Serial.printf() to indicate which state of the program that you are in.

What to Hand In

• Code: Check your documented code into your group subversion tree for project 4. This is due by Friday, March 15th at 11:59pm.

• Demonstration/Code Review: All group members must be present. This must be completed by Tuesday, March 26th.

• Personal report: there is no personal report for this project.

Grading

• Personal programming credit: this project offers one programming credit.

• Group grade distribution:
  • 35%: Project implementation
  • 30%: Demonstration of working project (to either of the TA or the instructor)
  • 35%: Code 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.

andrewhfagg -- gmail.com

Last modified: Wed Mar 27 10:55:58 2019