CEB 3D Printer

Concept (Illustrated Below): This idea is to develop an automated brick-laying system that can build homes from the ground up, literally. Using a combination of the CEB Press, a conveyor belt, gripper, and a common machine configuration (TBD), the machine acts like a large 3D printer which picks and places compressed bricks robotically.

Two video animations, originally made as Java applets, illustrate two such designs:

Animation (Gantry Design)

http://img.youtube.com/vi/Il1stSJcZTU/0.jpg

Animation (Cable Design)

http://img.youtube.com/vi/0HDd9J_Cc14/0.jpg

High-Level Actuator Architecture:

High-Level Feedback Architecture:

Sample Source Code:

Pseudo Code

Arduino Code

DECLARE VARIABLES & FUNCTIONS Initialize Output Channels // Tell microcontroller which pins are output Initialize Input Channels  // Tell microcontroller which pins are input MAIN LOOP   For Motors 1 to 4:       Read Encoder Values       Calculate Motor Output to Achieve Desired Position       Write to Motor Output Channel       // Note: the motor signal is sent to a speed controller      // to be amplified   END FOR LOOP   END MAIN LOOP

void setup() {   pinMode(2, OUTPUT); // to Base motor 1   pinMode(3, OUTPUT); // to Base motor 2   pinMode(4, OUTPUT); // to Base motor 3   pinMode(5, OUTPUT); // to Base motor 4   pinMode(6, INPUT); // from digital Encoder 1   pinMode(7, INPUT); // from digital Encoder 2   pinMode(8, INPUT); // from digital Encoder 3   pinMode(9, INPUT); // from digital Encoder 4 } void loop() {   for (int motorIndex = 0; motorIndex < 3; motorIndex++)   {     read_encoders();         pid();     write_to_motors();   }  }

Read Encoders Function: Read digital encoders. This function will need to be written after testing is done, but I can provide skeleton code soon.

Calculate Length Function: Now that desire gripper position & all 4 current lengths are known, desired length for each cable can be calculated.

float px, py, pz; // p (x,y,z) is the current position of the gripper
float dpx, dpy, dpz; // p (x,y,z) is the desired position of the gripper

float Bheight = 12.0, Blength = 18.0, Bwidth = 12.0; // Base dimensions at 12'x18'x12'

float B1x = 0.0,     B1y = 0.0,       B1z = Bheight; // top point of base rod 1
float B2x = 0.0,     B2y = Blength,   B2z = Bheight; // top point of base rod 2
float B3x = Bwidth,  B3y = Blength,   B3z = Bheight; // top point of base rod 3
float B4x = Bwidth,  B4y = Blength,   B4z = Bheight; // top point of base rod 4

float L1,L2,L3,L4, dL1,dL2,dL3,dL4; // Current and desired length variables

// This function calculates the length that each of the cables
// must be in order to attain the desired gripper position.
void get_lengths() 
{
  
  // Lengths are determined from top of base rod to gripper,
  // so this does not include length from motor to pulley 
  // at the top of the rod.
  
  L1 = dist3d(B1x, B1y, B1z, px,py,pz);  // Length of cable 1 in feet
  L2 = dist3d(B2x, B2y, B2z, px,py,pz);  // Length of cable 2 in feet
  L3 = dist3d(B3x, B3y, B3z, px,py,pz);  // Length of cable 3 in feet
  L4 = dist3d(B4x, B4y, B4z, px,py,pz);  // Length of cable 4 in feet
  
  // Desired lengths calculated the same way.
  
  dL1 = dist3d(B1x, B1y, B1z, dpx,dpy,dpz); // Desired length of cable 1
  dL2 = dist3d(B2x, B2y, B2z, dpx,dpy,dpz); // Desired length of cable 2
  dL3 = dist3d(B3x, B3y, B3z, dpx,dpy,dpz); // Desired length of cable 3
  dL4 = dist3d(B4x, B4y, B4z, dpx,dpy,dpz); // Desired length of cable 4
  
}

//____________CALCULATE_THE_3-D_DISTANCE_(L-3_NORM)________________//
float dist3d(float p1x, float p1y, float p1z, float p2x, float p2y, float p2z)
{
  float dist3 = sqrt((p2x-p1x)*(p2x-p1x) + (p2y-p1y)*(p2y-p1y) + (p2z-p1z)*(p2z-p1z));
  return dist3;
}

PID Function: Now that desired length and current length are known, motor output and direction for each motor can be calculated.

float[] err = new float[4];  // error array
float[] dir = new float[4];  // direction array
float[] out = new float[4];  // output array

float kp = 500;  // this gain is arbitrary, but must be positive
float Prop;      // Variable used for proportional gain.
float max_output = 100; // Saturate the output at 100, also arbitrary

//___________________PID_FUNCTION______________________//
void pid() // Actually just P for simplicity's sake
{
  
  Prop = kp*err[motorIndex]; // P = const*(desired_length - current_length)
  out[motorIndex] = Prop;    // output = P;
 
  if (out[motorIndex] > 0)  dir[motorIndex] = 1; // Get direction either 1
  else dir[motorIndex] = 0;                      // or 0
  
  constrain(out[motorIndex], -max_output, max_output); // saturate output
  out[motorIndex] = abs(out[motorIndex]); // now that we know direction, we
                                          // just need the absolute output
}

Write to Motors Function: Digital write to speed controllers (output is amplified using the higher current & voltage power source from 12V batteries. This function, just like the encoders will need to be written after/while testing is done, but I can provide skeleton code soon.

IRC Online Meeting Schedule: This is temporary section I'm experimenting with which doesn't quite belong here.

IRC Experimental Meeting Test Chart: This chart is used to display group meeting times on the OSE Internet Relay Chat (IRC) http://opensourceecology.org/wiki/Irc where groups can discuss project ideas and progress with realtime feedback. Group member names, IRC chat usernames, and status of sub-projects are listed.

This chart will be used as a temporary example.

Group Name

Group Manager

Meeting Time: 8PM-10PM EST

Task	Name/Pseudonym	IRC Username	Status of Project	Extra
Motor Testing	vc_nepo	vc_nepo	10 %	Link
Encoder	User B	userBonIRC	20 %
Material Spec	User C	userConIRC	Complete