Robot Design Report

Robot Design Report

Team 2B:

Christian Schneider

Megan Ketchum

Jeff Monahan

Alex Companioni

EML4320L -- MAE Design and Manufacturing Laboratory

Instructor: Mike Braddock

Fall 2004

October 19, 2004

Introduction

We have been assigned to design and build a robot capable of entering an arena, sorting golf balls from tennis balls, and then leaving the arena with the golf balls. The ten golf balls are mixed with 10 tennis balls and then evenly divided between 2 buckets. Extra points are awarded for leaving the tennis balls in the bucket.

Problem Statement

The area will be a 10 x 20 ft enclosed space bordered by 2 x 4’s which are standing on edge. The entry will be a box 3 x 6 x 3 feet and this entry way must be passed through both at the beginning and the completion of the mission. The balls will be 5 golf balls, and 5 tennis balls in each bucket. The robot must enter the arena, retrieve the golf balls, but not the bucket or the tennis balls, and then leave the arena.

Background Information

While researching ideas for our robot’s design, we referred to the class website (www.mae.ufl.edu/designlab/main.htm) and the posted pictures and results of previous classes (Summer of 2004 and Spring of 2004) to get an idea of what could be done with the parts being provided. The underlying theme of all of the previous projects we studied was efficiency: since time management was a priority of past competitors, most of them decided to accomplish both required tasks (removing the golf balls and replacing the tennis balls inside the bucket) at the same time. This research, however, was not the only work done prior to our design’s conception. After determining what the best way of retrieving the balls would be, we moved on to how best to implement these ideas. Knowing that the balls needed to be retrieved directly from the buckets we brainstormed different ideas and came up with our design one. Additional research was completed on what kind of motors would be needed. This was done both with theoretical calculations and real world, hands on testing. Information was gathered and brainstormed from many different sources.

Conceptual Design Generation

In the first design, the robot moves to the bucket and pushes it onto the tray. The tray will be stabilized by balancing it between the robot and one of the walls, trapping it between the two, and allowing the robot to grab onto it. The upper catch will be high enough for the bucket to get onto the tray but low enough not allowing the bucket room to move. When the bucket has been successfully captured, the entire capture mechanism will lift the bucket from the vertical to horizontal position. When this occurs, the balls will filter through the top catch. The catch’s bars are just far enough apart to allow the golf balls to flow through but not far enough apart to allow the tennis balls to pass too. When the filtering step has been completed, the robot will replace the bucket on the ground and move to the next bucket. The design for the capture mechanism has many options, this is one. Another option involves hooking the lip of the bucket with half-circular arms. The main challenge of this current design is removing the bucket from the tray after retrieval of the golf balls is completed. This design drawing is labeled as Figure 1.

In the second design, the robot uses a filtering device to sort all of the balls and then return the balls to the bucket. The robot uses a hook, which is on the front of the robot, to tip the bucket onto the front tray. Any balls that do not make it onto the tray or which roll off will be collected at a later time. The robot then lifts the tray so that the center section is horizontal. The bars are just far enough apart to allow the golf balls to flow through but not far enough apart to allow the tennis balls to pass as well. While lifting to the horizontal position, the front tray will lift the bucket back into the standing position. When the sorting process is finished, the robot will tilt the tray past the horizontal position. This in turn will activate a flap on the rear side allowing the balls to drain back into the bucket. This design drawing is labeled as Figure 2.

In the third design, the robot uses a wedge on its back portion to tip the buckets over and spill the golf and tennis balls on the floor. Then, dustpans which are on both arms will close under the balls and scoop them up. A chute built into the front of the robot which is only large enough for golf balls to pass through leads to a retention area inside the robot. Here, the robot will store the golf balls and exit the arena. Two motors are placed on the robots exterior; one is attached to a system of rods which control the opening and closing of the dustpans and the other is attached to the side, where a rod parallel to the arm is attached to an L-bracket. The motor rotates the L-bracket bringing the dustpans up to the chute so the golf balls can be deposited. This design drawing is labeled as Figure 3.

Selection of Design Concept

We have come to the conclusion that our best design is design two. We used many criteria to weigh in on which design we liked best for this competition such as size, speed, reliability, simplicity, manufacturability, appearance, and cost. We then ranked each design by which one had the best overall rating and it came down to design two.

Criteria / Weight / Design One / Value / Rating / Design Two / Value / Rating / Design Three / Value / Rating
Size / 10% / Middle / 6 / 0.6 / Middle / 6 / 0.6 / Large / 4 / 0.4
Speed / 15% / Fast / 8 / 1.2 / Slow / 2 / 0.3 / Slow / 2 / 0.3
Reliability / 20% / Middle / 7 / 1.4 / Middle / 7 / 1.4 / Low / 5 / 1
Simplicity / 10% / Very / 9 / 0.9 / Very / 9 / 0.9 / Least / 4 / 0.4
Manufacture / 20% / Easy / 8 / 1.6 / Easy / 8 / 1.6 / Hard / 4 / 0.8
Appearance / 5% / Good / 5 / 0.25 / Good / 5 / 0.25 / Best / 8 / 0.4
Cost / 20% / Cheap / 8 / 1.6 / Cheap / 8 / 1.6 / Expensive / 4 / 0.8
Total / Best / 7.55 / Middle / 6.65 / Worst / 4.1

Detailed Design Description

In this design the robot uses a filtering device to sort all of the balls and the return the balls to the bucket. The robot uses a v-shaped flange to grab the lip around the bucket. When the robot drives up to the bucket this connection is made and the entire lifter, filtering mesh, and bucket will be lifted. When the angle has reached approximately 80 degrees the balls will roll against the mesh. This mesh has been designed to allow the golf balls to pass but retain the tennis balls in the bucket. After the filtering process has been completed the lifter assembly will be returned to the ground and then the robot can back away from the bucket.

The robot will be driven by a permanent magnet right angle gear motor. One motor will be attached at each front wheel for a total of two motors. We chose these motors because of their orientation on the robot, that, when assembled, will be more advantageous than motor 5-993. We will be using the smaller wheel, dimensions 6 x 1.375 in, along with one castor wheel mounted to a bracket on the rear of the robot. We believe this will add more maneuverability within the enclosed space of the competition area. This will also allow the robot body to be parallel with the ground. If the castor were mounted on the undercarriage, the robot would either be tilted at a high angle or the drive wheels would have to be increased in size. If this were to happen the lifter would have to be mounted uncomfortably low to be able to reach the bucket and also be horizontal. For the filtering mechanism we will be using the globe motors. These motors, from preliminary testing, will provide the most torque, approximately 125 in-lbs according to specifications, needed to lift the filtering device when the bucket and balls are placed on the tray. Until we can test certain parts needed for our robot and until the robot is assembled and can analyze our work, we will be unable to provide exact analysis on the robot's performance. Currently our design requires only the wire mesh for the filtering device. This mesh can either be built from existing materials in the lab. All other materials may be purchased from the lab. No other materials will have to be purchased from an outside source, except possibly the mesh if existing materials can not be found.

Project Schedule

Date Task (Group member responsible)

October 19 Begin mobile platform and Lifter assembly

(Jeff and Christian)

Begin filtering mechanism and bucket actuator (Megan and Alex)

October 26 Complete mobile platform and filter assembly

Complete filtering mechanism and

Begin robot assembly (time permitting)

November 2 Complete robot assembly (all group members)

Time permitting; begin preliminary testing (all group members)

November 9 Complete preliminary testing and make any necessary design changes (all group members)

Time permitting; begin final testing (all group members)

November 16 Complete final testing and complete all adjustments and final modifications to the robot (all group members)

5

Group 2B