Friday, May 11, 2012

Team A - Team JABS

1. Main Design Concept

Team JABS designed our shingling robot to be able to attach shingles to all sides and corners of the roof and to fit inside of a 2x2 square as detailed in the specifications given.  Our robot contained four primary subsystems: drive system, vision system, shingle manipulator, and peeling.  As seen in the complete CAD Model in Figure 1, the motors, batteries and electronics were all contained on the robot to ensure the robot was fully autonomous and not tethered.   Each of the components was designed to be inside of the robot and were laser cut for easy mounting.  The electronics board, batteries and laptop had parts made to mount it directly to the robot.  Each of the sensors had a mount that would allow for easy attachment – the digital IR sensors had tight fit made for that sensor and the limit switches were mounted with 4-40 screws.  The nail gun – by far the biggest element of our robot – was mounted in the dead center of the robot to drive over the shingle when it was placed and nail in the correct spot given.  

Figure 1 - Photo of Team JABS' Shingling Robot

We also based a lot of our design concepts on budget constraints.  Our custom-made motor controllers were based on a 5 dollar part and a CNC machined PCB , and could still handle the high current motors we were using.   Many of our motors were found in RoboClub in order to “reuse” parts.  We also found additional motor controllers in scrap bins and repaired them to decrease the cost of this robot.  The batteries were taken from the nail gun and scavenged from RoboClub. We also attempted to keep everything simple and fast to manufacture.  All the gears and structural components were cut from acrylic on the laser cutter for cost constraints.  Each of the components were created in CAD to ensure they all fit together properly.  The robot was then assembled using machine screws to ensure that everything would fit together nicely.

2. Team Member Responsibilities

  • Jon Boerner was primarily responsible for the shingler’s vision systems and code.  Jon also assisted with fabrication and CAD, as necessary.
  • Andrew Burks was primarily responsible for mechanical design; he also created the working CAD model of the robot and performed significant assembly work.
  • Ben Streeter was primarily responsible for mechanical design, took lead on fabrication, and assisted with assembly.
  • Samantha Tan was primarily responsible for the electrical hardware systems on the robot and the assorted sensing mechanisms.  

3. Labeled pictures of the overall system with description

Figure 2 below shows the primary subsystems of our robot: the two peeler wheels, one of the two elevators, the nail gun, and the drive modules.  At the top of the robot, the peeler wheels remove a single shingle from the top of the shingle stack and slide it into an elevated side roller.  The side rollers, moved by rack and pinion in a vertical slot, are controlled by limit switches – they can either be in the elevated or lowered position.  Once the side roller is in the lowered position, the robot drives forward and the side roller slides the shingle under the drive wheels simultaneously.  Once the robot is at the correct position on the roof, the nail gun delivers a nail, the robot drives farther forward, and the nail gun delivers a second nail.  The operation then starts over again.  The block diagram in Figure 4 highlights how these systems work together. 

Figure 2 - Photograph with Significant Subsystems

Figure 3 - CAD Rendering

Figure 4 - Functional Block Diagram

4. Pictures and descriptions of the subsystems

Drive System

The drive subsystem will move the entire robot about the roof. Figure 5 shows an image of the CAD model of this subsystem. Items of importance in this subsystem are the caster wheels that allow the robot to rotate while maintaining balance, the drive wheel that is another Roomba drive wheel, and the last caster wheel which prevents the robot from falling off the roof when it is hanging over the edge. The caster wheels are designed in such a way that the drive wheel always maintains contact with the roof regardless of some caster wheels being on a shingle while others are not.

Figure 5 - Drive Subsystem

Vision System

Figure 6 shows the results of the vision system used on our robot. The system is capable of finding the side edge of an already placed shingle, the side edge of a shingle being placed, the top edge of a shingle being placed, and the red line where the shingles should be placed. The side edges are used by the system to detect when the shingle being placed is in position horizontally. The top edge is used to orient and position the shingle correctly with respect to the red line. With one webcam on each side of the system, the robot is able to shingle in either direction.
Figure 6 - Results of the Vision System Used for the Robot


The peeler subsystem is at the very top of the robot, and is shown in Figure 7.  It consists of two Roomba wheel modules rigidly attached to a vertical slider.  The wheels push the top shingle on the shingle stack to one side of the robot or the other.  Once a shingle has been pushed off of the stack, gravity kicks in and pulls the Roomba wheels down onto the next shingle.

Figure 7 - CAD of the Peeler Subsystem


There are two degrees of freedom in the elevator subsystem, shown in Figure 8.  The first degree of freedom allows the entire system to slide up and down the side of the robot.  This is accomplished by gearing a DC gearmotor to a pair of pinion gears nested between a pair of rack gears.  The rack gears are fixed to the robots frame, so when the counter-rotating set of pinions begins to turn they force the elevator up and down the robot.

The second degree of freedom on the side elevators are a set of rubber rollers.  A small DC gearmotor connected to an encoder is geared to a pair of rubber rollers.  These rollers grip the shingle and pull it out the side of the robot.  The encoders are used to determine how much of the shingle is in the rollers.  An IR sensor is used to detect the initial presence of a shingle and zero the encoders.
Figure 8 - Diagram of the Rollers and Elevator

5. Video of the system in action

Included below is a link to our team's summary video:

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