Critical Design Reviewseaairland.psu.edu/.../Critical-Design-Review-Example.docx · Web viewThe robot will be programmed to run autonomously with a four-wheel motor. The robot will

1

Critical Design ReviewExample Provided Courtesy of

Kiski Area Engineering Club

2

Table of Contents

1.0 Introduction 31.2 Purpose 41.3 Scope 51.4 Definitions and Acronyms 61.5 References 72.1 Overall Description 82.2 Product Perspective 92.3 Product Functions 122.4 User Characteristics 172.5 Constraints 182.6 Assumptions & Dependencies 193.0 Specific Requirements 214.0 Test Plan 22

3

1.0 Introduction

The purpose of this document is to define the exact design of the (name of robot/challenge) Robot submitted by the (name of school/team name). This document is to be used as a communication tool with the customer, which in this case is the Electro-Optic Center (EOC) team, so that every complexity of the (name of robot) robot is understood by both parties. In addition, this document outlines the overall description of the robot, including details regarding the product perspective, product functions, user characteristics, constraints, and assumptions and dependencies. Specific requirements that were assigned by the EOC team are also listed.

4

1.2 Purpose

The purpose of the design is to complete the challenge proposed by the EOC. (Team Name) was challenged to build a robot that can autonomously complete an obstacle course, knock down five targets located in unknown positions, navigate unspecified course obstacles, and determine when the course is completed, all in a shorter length of time compared to the other contestants. The challenge defined by the customer has many tasks and complexities that will have to be overcome.

5


1.3 Scope

The robot will be programmed to run autonomously with a four-wheel motor. The robot will navigate the course using three line trackers, a motion detector, and a bumper switch. The robot will travel continuously forward unless it encounters a break in the law, a turn, or a tick mark. If the robot encounters a break in the line, it will use the motion detector to continue traveling through the course. The robot will have to differentiate a 90 degree angel in the line between sensing a turn or tick mark. If the robot recognizes it as a turn, it will change direction. If the robot recognizes as a tick mark, it will know that a target is located directly across from where the tick mark is located. When the robot encounters the tick mark, the program will tell the robot to move backwards slightly and to extend its arm and knock over the target. If the arm extends more than seven inches to hit a target, the robot will know to retract the arm and move on. If the arm does not extend past the wall seven inches, then the robot will move backwards and forwards, trying again at each new stop, until the target is hit. All parts and operations will comply with the $500 budget.

6


1.4 Definitions and Acronyms

Critical Design Review - (CDR) The CDR is this document.

EasyC V4 Software - (EasyC) This is the software that was issued by the customer to program Kiski’s autonomous

robot. The software license number issued was 628F-D4RU-CSNV-0240.

Electro-Optic Center - (EOC) The EOC sponsors the Land Challenge.

Global Positioning System - (GPS) GPS is used in the description of the targets.

Kiski Land Challenge Team - (KLCT) KLCT evolved from Kiski Area High School’s Engineering Club. This is the team put together to accomplish the challenge of building a robot for the EOC Land Competition.

Preliminary Design Review - (PDR) The CDR is an updated version of the PDR.

7


1.5 References

People:

Francis DeSantis: Mr. DeSantis is the sponsor of the Kiski Area Engineering Club and has advised the students on the team regarding the designs and programming of the robot. His past experience as an electrical engineer has

aided his ability to advise the students.

Christine Palmiero: Ms. Palmiero is the sponsor of the KLCT. She has dedicated her time to advise and assist the

students with the design of the robot, and she has also aided them in the writing of their PDR and CDR.

Jeff Searle: Mr. Searle, a software engineer, met with the KLCT to introduce the competition and better explain the specific challenges that the robot will have to overcome.

Jason Mizgorski: Mr. Mizgorski, the Technical Lead of Specialty Sciences and Engineering, responded to e-mails

from the team and set-up the Google Docs page for the KLCT to access.

Lori Harvey: Mrs. Harvey, the Senior Program Coordinator, has provided answers to weekly questions proposed by the KLCT via e-mail.

Websites:

VEX: (www .vexr obotics.com ) The KLCT utilized this website to learn more about the products they were

considering to purchase for the robot. Note: The website was only used for research purposes, the KLCT did not buy any parts. This was done so the team could be absolutely sure about the products they wanted to include in

the CDR.

Intelitek: (www .intelitek.com ) The KLCT referred to this website for programming tutorials in EasyC.

8


2.1 Overall Description

This part of the document contains the description of the product perspective, product functions, user characteristics, constraints, and assumptions and dependencies.

9


2.2 Product Perspective

For this project, the KLCT chose to utilize VEX products. The KLCT plans to construct a robot that is 9.5 inches in width and 9 inches in length. Width is defined by the distance from wheel to wheel across the robot, while length is defined by distance from front wheel to back wheel. The robot will have an arm that uses a motor to knock over the targets, three line trackers, a motion detector powered by a servo motor, and a bumper sensor.

The team started with a basic VEX Cortex Controller. This was loaned to the KLCT by the EOC. Then, KLCT

continued with the VEX theme and chose to use the VEX Clawbot Kit. The Clawbot Kit included:

• (3) 2-wire motors

• (1) claw kit assembly (includes motor)

• (21) shaft collars

• (4) shaft coupler

• (8) 3 inch long shafts

• (18) bearing flats

• (2) 12-tooth spur gears



• (4) 4” wheels

• (2) 20 hole bars

• (2) 20 hole chassis bumpers

• (4) 16 hole chassis rales

• (2) 1x2x1x15 hole c- channels

• (1) 1x2x1x20 hole c- channels

• (2) 29 motor controllers

• (1) 2 pack battery strap

• (32) 8-32 x 1/4” long screws

• (14) 8-32 x 1/2” long screws

• (2) 8-32 x 1 1/2” long screws

• (6) 6-32 x 1/4” long locking screws

• (6) 6-32 x 1/2” long locking screws

• (42) 8-32 keps nuts

• (6) 4.6mm shaft spacers

• (50) 4” tie wraps

• (32) Bearing Pop- Rivets

• (2) 5/64” Allen Wrenches

• (2) 3/32” Allen Wrenches

• (2) VEX Open-Ended Wrenches

• (1) Clawbot Quick Start Guide

Rationale: The team needs the Clawbot as a base kit to start building their robot. This kit contains all the basic parts to start with the initial construction of the robot.

10


To meet the arm design requirements, the KLCT chose the VEX made Linear Motion Kit. This kit included:

• (2) 12 inch long linear slide tracks

• (2) 17.5 in long linear slide tracks

• (2) rack brackets

• (4) inner delrin slide tracks

• (1) outer derlin slide

Rationale: These parts enable the team to design an arm that can extend and knock over the targets.

Along with the Linear Motion Kit, the team also chose the Advanced Gear Kit, which

includes:

• (8) 19-tooth rack gears

• (2) 12-tooth pinion gears

• (4) worm gears

• (4) worm wheels

• (1) differential frame

• (7) 24-tooth bevel gears

• (16) 6-32 by 1/4 inch button head screws

Rationale: This kit is needed to because the gears of the other kits are not the sizes that the KLCT wishes to use in the construction of the the robot.

Also, the KLCT chose the VEX Limit Switch 2-Pack, which includes:

• (2) Limit Switch Sensors

• (4) 5-32 3/8” Screws

• (4) Keps Nut• (1) Inventor’s Guide Insert

Rationale: The limit switches will be used in addition to the arm as a way to know when the target has been knocked over.

11


Next, the KLCT chose the Sensor Kit, which includes:

• (1) Line Tracking Kit• (1) Ultra Sonic Range

Finder

• (1) Light Sensor

• (2) Optical Shaft Encoders• (2) Potentiometers

Rationale: All of these sensors will be used in the construction of the robot. Specific details on each of these sensors can be found in the Product Functions

of the CDR.

Lastly, the KLCT chose two 3-Wire Servo Motors. This kit includes:

• (1) VEX Servo Motor• (1) VEX Servo Motor

Gear Set (4 total gears, 1 replacement for each gear inside)

• (2) 6-32 x 1/4”

Screws

• (2) 6-32 x 1/2”

Screws• (1) Clutch

• (1) Clutch Post

Rationale: The servo motors will be used in conjunction with the motion detector. One will be needed as a spare.

12


2.3 Product Functions

The KLCT’s robot will autonomously complete the course designed by the EOC, knock over five targets successfully, navigate effectively, know when the course is completed, all while trying to obtain the fastest time among all the other competitors. The following is a list with detailed descriptions regarding each aspect of the robot that will allow the previous statement to occur.

1. Arm: Objects will be knocked over by an arm that moves in a linear motion. Each end of the arm will have a hinge with a limit switch attached. The hinge will prohibit the switches from going towards the robot, but will allow them to move upwards 90 degrees (See Figure Below). When the arm is extended, the limit switches will change state by hitting either the targets or the wall. The switch position and the arm linear motion detector (rotary encoder) determines whether the switch has hit something past seven inches away from its starting position. If this occurs, it has hit a target, and it is free to move to the next target. If the switch hits the wall, which will be only seven inches away, it will be programmed to move backward or forward in order to hit the target.

Preliminary Drawing of Arm:

13


2. Sensors: There are two types of sensors used in the navigation of KLCT’s robot. First, the primary navigation

input is the line trackers. The backup navigation input is the motion detector. There is one type of sensor used in the extension of the arm, which is called the rotary encoder.

2.1. Line Trackers: The KLCT chose to use line trackers because the description of the challenge states that a high contrast line will be placed in the center of the track. Therefore, the team will be able to utilize the line tracker sensor output to navigate the course. Tick marks, which signal the location of a target, will protrude from the high contrast line. The KCLT’s line trackers will sense these tick marks to locate where the targets are.

Also, using line trackers can prevent mistakes associated with the overextension of the high contrast line at a turning point. There will be three line trackers strategically placed on the underside of the robot. They will be placed in the center of the robot, from front to back, and be in a row, similar to the figure to the left. They will be placed so that the line can be seen at all times by one of the trackers. If only the center line sensor sees the line, the robot is on track and will continue moving forward. If only the left or right senses the line, the robot will be programmed to veer in the opposite direction until it is back on track. If none of the sensors pick up the line, the motion detector will be used to get the robot back on track. The line trackers will sense the line drawn in the center of the course. The line trackers will also be used to recognize the difference between a tick mark (meaning a target is directly across from it) or a turn

in the line. In order to differentiate between a turn and a target, a motion detector will be used in conjunction with the line sensors. If the motion detector sees a wall seven inches away in front of the robot, the robot will know that it has come to a turn and will proceed to make a left or right turn. To make a right turn, the right and center sensor will sense the line, and when this happens in the program, the robot will make a 90 degree right turn. The turn will be exactly 90 degrees because each wheel will turn at the same speed. To make a left turn, the left and center sensor will sense the line, and when this happens in the program, the robot will make a 90 degree left turn. These three sensors will be the main navigation of the robot through the course.

2.2. Motion Detector: The team chose to use a motion detector in order to differentiate between turns and targets. Also, there exists a possibility of breaks in the high contrast line. If there is

a break in the line, the motion detector will rapidly rotate using a servo motor to keep the robot in the center of the course. It will do this by knowing that the center of the robot needs to stay 7 inches away from either wall at all times. The motion detector will sense if the robot is getting too close to a wall, and it will be able to tell the robot to center itself back onto the line. Also, the motion detector will be used to determine when the course is over. The KLCT was assured that that the course finish line is when the robot detects no walls to either the right or

14

left side. The motion detector will monitor the distance to the closest wall, and if it is greater than14 inches, the robot will stop. Overall, the motion detector will be used to keep the robot on track during the

15


course. The motion detector will also be used as a back up if the line trackers were to malfunction. The motion detector will be assembled near the top of the robot and be run by a servo motor. The rationale behind choosing the servo motor is that it is less programming, inexpensive, and equally efficient compared to using multiple stationary motion detectors.

2.3. Rotary Encoder: The KLCT chose the rotary encoder to supplement the motor attached to the arm.

The rotary encoder stores the number of revolutions as a variable so that the revolution number can be used in a program to determine arm position. This way, the programming

can prompt the motor to run until the desired number of rotations is reached. The revolution number will also be useful in telling the robot how far the arm extends before

the limit switch is activated.

3. Switches and Other Input Devices

3.1. Limit Switch: The KLCT decided to use limit switches to determine when the targets have been hit.

Limit switches were chosen because they require less force to activate, and they will allowthe team to know when the target has been hit. Each end of the arm will have a hingewith a limit switch attached. The hinge will prohibit the switches from moving towards the robot, but will allow them to move upwards 90 degrees. When the arm is extended, the limit switches will change state by hitting either the targets or the wall. The switch positions along with the arm linear motion detector (rotary encoder) determines whether the switch has hit something past seven inches away from it’s starting position. If this occurs, it has hit a target and it is free to move to the nexttarget. If the switch hits the wall, which will be only seven inches away, it will be programmed to move backward or forward in order to hit the target.

3.2. Bumper Switch: The KLCT decided to use a bumper switch as safety precaution. Depending on the speed the robot is traveling, the robot could easily miss a turn. For instance, if the robot missed a turn in the line and ran into the wall, the bumper switch, located on the front of the robot, would be hit and therefore would activate a loop in the program that would tell the robot to back up and turn. This action will be programmed as a precaution to keep the robot on track. The bumper switch will also be used as a safety net to the line trackers malfunctioning.

3.3. Jumper Switch: The course will have a high-contrast line for the robot to follow. However, it was not specified whether this would be a dark line on a light surface or a light line on a dark surface. Therefore, the KLCT decided to use a jumper switch to easily adjust the program for either situation.

16


3.4. Potentiometer: In addition to determining the contrast, the KLCT decided a potentiometer will be needed to adjust the threshold between light and dark. Because the intensity of the high contrast line was not clarified by the customer, the potentiometer will allow the KCLT to make last minute adjustments to the program, enabling the vehicle to pick up any line intensity.

4.0 Wheels: The KLCT assumed that the course obstacles listed in the requirements would consist mainly of terrain obstacles. Therefore, the team chose to focus on the wheels. The wheels chosen for the robot are four inches in diameter and have a sturdy tread. The wheels raise the robot approximately one and a half inches off the ground. This aspect of the design allows the robot to simply run over small terrain obstacles, such as pebbles or stones. Next, the wheels on the robot are big enough to handle any loose terrain, while still having good traction. However, they are also small enough to fit within the dimensions of the course. In addition, the center of mass of the robot has been designed so that if small inclines are encountered, the robot will be averse to tipping.

NOTE: We decided against the use of any type of GPS. This is because we believe that commercial GPSs can only register different points within a meter apart. Because the course is only 14” wide, it is illogical to use GPS tags.

CADD drawings of robot

17


:

18


2.4 User Characteristics

The robot designed for the competition will be autonomous and programmed using EasyC. The EasyC software allows the functions to be programmed faster and easier. Forward, backward, left turn, right turn, and stop functions

will be created. The robot will complete these simple directions by using the correct programming.

19


2.5 Constraints

1. The major constraint is that the KLCT cannot spend over $750. The following table is a breakdown of the cost of every part the KLCT chose to fulfill and build this design.

Product Price Quantity Cumulative Total

VEX Cortex Controller $0.00 1 $0.00

VEX Clawbot Kit $149.99 1 $149.99

VEX Linear Motion Kit $24.99 1 $174.98

Advanced Gear Kit $19.99 1 $194.97

Limit Switches $12.99 1 $207.96

Sensor Kit $99.99 1 $307.95

3-Wire Servo $19.99 2 $307.95

Total $347.93

2. The robot cannot be bigger than 9.5” by 9” so that the robot can make the 90 degree serpentine turns

3. Although we were given the option of a remote controlled robot, rather than the autonomously programmed robot, we chose the autonomous option because points will be deducted for remote controlled robots.

4. The battery pack capacity must supply power for the full duration of the course.

20


2.6 Assumptions & Dependen- cies

The following is a detailed list of assumptions and dependencies that have been either defined by the costumer or hypothesized by the KLCT.

1. Course Layout

1.1. The land course will be a serpentine, 90 degree turn layout.

1.2. The course walls will be 14” from inside to inside.

1.3. The targets will be no more than 10” from the center of the course.

1.4. The course will have 5 targets that will need to be knocked over. These targets will be located on both the left and right sides of the course.

1.5. The course will have terrain obstacles that the vehicle must be able to transverse.

1.6.The course will have a high contrast line painted down the center. The line will have a minimum width of 1/4” and a maximum width of 2”.

1.7. There are no restrictions on the size of the robot, other than it has to fit in the course.

2. Target Definition

2.1.There will be five targets that will be needed to be knocked over. These targets will be located on both

the left and right sides of the course.

2.2. There will not be targets on both sides at the same time.

2.3. The targets will be no more than 10” from the center of the course.

2.4. Targets will be located inside a break in the wall.

21


2.5. The targets will be perpendicular to a tick mark in the high contrast line.

2.6. Targets will have a GPS tag associated with them.

2.7. Targets will be found by using a mark in the high contrast line.

2.8. Turning points will be GPS tagged.

2.9. The targets will be lightweight.

3. Line Definition

3.1.There will be a high contrast line to follow.

3.2. The line will have a minimum width of 1/4” and a maximum width of 2”.

3.3. There will be breaks in the line.

3.4.There will be a high contrast tick mark directly across (perpendicular) from where the targets are located.

3.5. It is possible for the line to overextend past turns.

22


3.0 Specific Requirements

The following is a list of specific requirements requested by the customer.

1. Autonomously complete the course.

2. Successfully knock over all five targets.

3. Successfully navigate different types of course obstacles.

4. Be able to distinguish when course is over.

5. Complete the course in the faster than all of the other contestants.

NOTE: Users may control the robots remotely but will be deducted points.

23


4.0 Test Plan

In order to test the KLCT’s robot, the team will first set up an area to test the line trackers. They will tape white paper onto a lab bench. Then, they will use black electrical tape to make the line. This situation will create a high contrast line that will stimulate the one that will be at the competition. To test the motion detector, the team plans to set up cardboard walls around the high contrast line that they will create on the lab bench. Also, to test the wheels for terrain obstacles, the team will put pebbles or small stones on the homemade course. During the testing, the team will wear googles to protect their eyes. In addition, they will be careful with moving gears so that they do not hurt their fingers during the testing of the robot.

Documents

Critical Design Reviewseaairland.psu.edu/.../Critical-Design-Review-Example.docx · Web viewThe robot will be programmed to run autonomously with a four-wheel motor. The robot will