Compass Programming with Vex Prototype- Matt Mannino

I have mounted the Arduino and the sensors onto the Vex prototype to start working on a main program.  I interfaced the Vex motors to the Arduino and added a 7.2V NiMH battery for power to the Arduino and the Vex Motors.  We started on a program that will face the robot in the correct heading based on what values it is given.  It works fine for headings up to 359 degrees.  It has trouble pointing North because it is on the threshold of 359 to 0 degrees and cannot compensate for that.  I have been trying to work on it so that it can work with that threshold of values.

Compass Program

#include <Wire.h>
#include <LSM303.h>
#include <Servo.h>

LSM303 compass;
Servo LeftMotor;
Servo RightMotor;
Servo BallMotor;

int stopp = 100;
int forward = 70;
int backward = 130;

void setup()
{
  Serial.begin(9600);
  Wire.begin();
  compass.init();
  compass.enableDefault();
  LeftMotor.attach(3);
  RightMotor.attach(2);
  BallMotor.attach(4);
 
  compass.m_min = (LSM303::vector<int16_t>){-32767, -32767, -32767};
  compass.m_max = (LSM303::vector<int16_t>){+32767, +32767, +32767};
}

void loop()
{
  int dir = compass.heading();
  Serial.println(dir);
 
  face(180);
}

void face (int val)
{
  int dir = 0;
 
  while(true)
  {
    compass.read();
    dir = compass.heading();
   
    Serial.println(dir);
   
     if(dir > (val+5))
     {
       turnleft();
     }
     else if(dir < (val-5))
     {
       turnright();
     }
     else
     {
       nospeed();
       delay(50);
       break;
     }
   }
 }

//motor movement functions
void goforward()
{
  RightMotor.write(backward);
  LeftMotor.write(forward);
  delay(1);
}

void gobackward()
{
  RightMotor.write(forward);
  LeftMotor.write(backward);
  delay (1);
}

void nospeed()
{
  RightMotor.write(stopp);
  LeftMotor.write(stopp);
  delay (1);
 
}

void turnleft()
{
  RightMotor.write(backward);
  LeftMotor.write(backward);
  delay (1);
}

void turnright()
{
  RightMotor.write(forward);
  LeftMotor.write(forward);
  delay(1);
}

void ballmotor()
{
  BallMotor.write(forward);
  delay(1);

}

Chassis Rail Machining - Andrew Baden

Today I worked with Dr. Bronakowski on machining the side chassis rails using the CNC machine to allow the motor mounts to be adjustable.  We would like these motor mounts to be adjustable so that we can minimize the amount of slack in the chains used for the drive system.

Slot in chassis rail for motor mounts

Here are pictures of the motor mount attached to one of the chassis rails:

Top view

Front view

The motor mount is not fully attached in these pictures because I just wanted to do a test fit with the motor mounts to see if they fit correctly with the fasteners that we are using.  Later I will need to machine a similar but larger slot for the motor's shaft to go through.