AME 3623: Project 4

• All components of the project are due by Tuesday, March 23rd at 5 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,
• use a high-level program to test the functionality of the DC motor control interface, and
• implement a Finite State Machine in code.

Component 1: Micro-controller Circuit

Option 1: Dual H-Bridge Board

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

• You have a cable that connects to your battery with two exposed wires on the other end (DO NOT CONNECT THIS CABLE TO YOUR BATTERY UNTIL THE WIRING OF YOUR CIRCUIT IS COMPLETE). You will need to use wire cutters to cut down the diameter of the exposed ends of the wires.

• Connect GND and VIN (right side of the board) directly to these thick power cables (not to your 5V power supply provided by the Teensy board!!!). Make sure you do this without the battery 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.

• Your kit contains one DC motor and a cable that connects to this motor. This cable also has exposed wires opposite from the connector. Connect this cable to the OUT A/B screw terminals. Because these are brushed motors, the choice of which wire connects to which of A or B is arbitrary (only torque direction is affected).

H-Bridge Control Connections

• Connect GND and GND to your Teensy's ground
• Connect +5V to the Teensy +5V supply
• Connect PWM to a Teensy pin that generates PWM output. Possible pins are: 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, 20, 21, 22, 23, 29, 30, 35, 36, 37, 38
• INa and INb: connect the H-Bridge to a pair of Teensy pins on the same digital I/O port (different H-Bridges can use different ports).
  • A pattern of INa/b of "0 1" will result in torque being generated in one direction
  • A pattern of "1 0" will result in torque being generated in the other direction

• Your choice of PWM/INa/INb must be on the opposite side of the board from the A/B motor connector.

Option 2: Single H-Bridge Board

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

• The same warnings apply as in option 1.

• Connect GND and VIN (right side of the board) directly to these thick power cables (not to your 5V power supply provided by the Teensy board!!!). Make sure you do this without the battery 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.

• Your kit contains one DC motor and a cable that connects to this motor. This cable also has exposed wires opposite from the connector. Connect this cable to the OUT A/B screw terminals. Because these are brushed motors, the choice of which wire connects to which of A or B is arbitrary (only torque direction is affected).

H-Bridge Control Connections

• Connect GND to your Teensy's ground
• Connect +5V to the Teensy +5V supply
• Connect PWM to a Teensy pin that generates PWM output. Possible pins are: 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, 20, 21, 22, 23, 29, 30, 35, 36, 37, 38
• INa and INb: connect the H-Bridge to a pair of Teensy pins on the same digital I/O port.
  • A pattern of INa/b of "0 1" will result in torque being generated in one direction
  • A pattern of "1 0" will result in torque being generated in the other direction

Component 2

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

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 bound(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_motor(float val) that sets the thrust magnitude and direction for your motor.
  • This function must ensure that the value falls within the range of -64... 64. The value does not, then the offending value should be bounded to this range. This value corresponds to a duty cycle of 25%.

  • A positive value corresponds to counter-clockwise travel; a negative value corresponds to clockwise travel.

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 motor up to a duty cycle of 25%
  • Slowly ramp the motor down to a duty cycle of -25%
  • Slowly ramp the motor up to a duty cycle of 0%

• 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 delay() calls inside of it. In cases where you need a measured amount of time, introduce a counter variable inside of fsm_step() and rely on the fact that this function is called at regular intervals.

• 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: Submit your ino project file to the project4 area on Gradescope by the deadline. This program must be properly documented, as discussed in the project 1 specification.

• Demonstration/Code Review: All group members must be present. This review must be completed within five days of the deadline. However, it is better to complete these reviews as early as possible.

Grading

• A properly configured circuit
  • H-bridge installed correctly
  • Switch installed correctly

• Properly written software
  • Function that sets the motor direction and magnitude
  • Finite State Machine implementation

• Properly documented code
  • Project-level documentation at the top of the ino file: name and group number, date and project number
  • Function-level documentation above the function definition. Include an abstract description of what the function does; a list of the names, types and units associated with each parameter and return value; and the effects that the function has on the processor or connected components.
  • In-line documentation inside of functions: individual lines or small groups of lines have an English description that describes logically what the code is doing

andrewhfagg -- gmail.com

Last modified: Mon Mar 22 23:47:05 2021