AME 3623: Project 4

All components of the project are due by Thursday, March 23rd at 8:55 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:

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 new hardware for this project includes:

Two Dual H-Bridge boards
Three motor power cables (red connector) for lateral fans
One motor power cable (black connector for the middle fan
Also: pick up a second trickle charger for your kit

The current amplifier board is composed of two full H-Bridge circuits. We will be using one full H-Bridge to control each of the four fans on board your hovercraft.

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

Add wires to connect the motor control board to the fans and to the batteries (6 screw terminal connectors on the right side of the board):

Connect GND and VIN 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 H-Bridge. Make sure you do this without the batteries plugged in, and have someone else check your connections before you apply power.
Note: you will 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.
Connect each of the fans to their corresponding OUT A/B screw terminals.

H-Bridge Control Connections

Connect the H-Bridge boards to your Teensy chip (the 15 pin connector on the left side of the board):

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:
- Lateral fans: connect to a pair of Teensy pins on the same digital I/O port
- Central fan: connect one pin to GND and one pin to +5V (the latter through a 10K-ohm resistor). Make your choices are such that the middle fan will push air into the chamber when the motor is turned on.

Component 2

Create the function interface that will generate the direction and PWM signals for each of the inputs to the motor control board.

Implement the following functions:

int16_t clip(int16_t value, int16_t min_value, int16_t 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_lift_motor_magnitude(int16_t magnitude) that sets the thrust magnitude for the lift fan. This function must ensure that magnitude falls within the range of 0... 255 (which correspond to 0% ... 100% duty cycle). If the value does not fit within the range, then it should be clipped to this range.
void set_lateral_motor_magnitudes(int16_t 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 magnitudes fall within the range of -255... 255. If any do not, then the offending value should be clipped to this range. Note that -255 corresponds to a 100% duty cycle with the fan moving backwards and 255 corresponds to 100% duty cycle with the fan moving forwards.

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

analogWrite(pin, duty);

where pin is an Arduino pin index and duty is a value in the range 0 ... 255.

Component 3

Implement the following in your loop() function:

If your switch is pressed:
- Slowly ramp the lift fan thrust upwards until 25% duty cycle
- Wait until the switch is released
- Slowly ramp the lift fan thrust downwards until zero
If your switch is not pressed:
- 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 right, then back fan
Note: use your LEDs or Serial.printf() to indicate which phase of the program that you are in.

Note: it is okay in this case for you to have one or more loops within your loop() function.

What to Hand In

Code: Check your documented code into your group subversion tree for project 4. This is due by Thursday, March 23rd at 8:55 am.
Demonstration/Code Review: All group members must be present. This must be completed by Tuesday, March 28th.
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: Thu Mar 9 03:11:07 2017