EE4701 Preliminary Design Presentation

Ben MaderazoJustin Smith

Presentation Goals

Present our own requirements analysis and design decisions for critiqueDefend our decisions and explain why our design will perform better than othersProve that we are ready to begin assembling and testing our robot for competition

Team Goals

Apply KISS principle in hardware implementation to save timeSpend more time on algorithm development and application than hardwareWin competition

Competition Rules

Each robot must fit within a twelve inch cube

Each match will be the best of three rounds with each round lasting no longer than fifteen minutes

The ball may be captured, pushed, or kicked into the goal

Robot and ball position will be monitored by an overhead camera

To enter into the competition, each robot must pass preliminary qualification tests

Preliminary Qualifications

Robot must travel from one goal to other and back in less than two minutesThe robot must capture a ball and return it to the home goal in under five minutesThe robot must retrieve three balls, one at a time, and return them to its home goal in fifteen minutes while avoiding an immobile obstruction

Robot Subsystems

Information processingObstacle detectionLocomotionRF receptionBall capturePower

Information Processing Subsystem

Must take data from other subsystems, process it, and issue commands.

Analysis

Speed

Must be done 10x per second

Mathematical Computation Addition, subtraction, and absolute value Arc tangent

Function # of Times Instructions

Calculate relative distance 5 10

Check current score 1 15

Check if target ball has moved 1 10

Check if robot is at destination 1 2

Misc. 1 65

Total ~150

Requirements3 input ports for switches2 A/D converter ports for IR sensors.2 PWM output ports for H-Bridge.Ability to send and receive 4 serial transmissions.Ability to compute basic math and binary operations.Ability to compute the arc tan function.Ability to use interrupts.

OOPIC

Advantages Virtual Circuits Interrupts Object Oriented Programming Predefined objects Unlimited serial ports

Disadvantages Slower than the PIC

Math Coprocessor

PAK-II Features

Communicates Serially 20Mhz Performs sin, cos, tan, inverse functions,

square roots, powers, and many other functions

Schematics

Obstacle Detection Subsystem

The robot will need to detect objects in its path to pass the second round of qualifying.

It is not certain if this will be used during the contest.

Analysis

Distance Requirements Robot travels at max 2 ft/s Estimate .5s for robot to stop after

detection .5s x 2 ft/s = .5 ft

IR Detector

Advantages Long Distance

~4” to 3’

Disadvantages Higher power

Ability to test at set times to save power

RF Reception

RF Reception will be used to receive data and instructions from the Vision System.

The part will be supplied by Bryan Audiffred and there will be little room for design in this subsystem.

Ball Capture

The robot will be required to capture a ball, know if the capture was successful, and secure it.

Requirements

Can only control one ball at a timeMust be able to effectively capture and release ballsMust be able to provide feedback of success or failure

Hardware choice

Construct a housing on the robot chassis that will encase the ballUse a generic servomotor to close a gate at the entrance of the housingInterior is lined with material to reduce inertia of the tennis ballIR emitter, receiver pair on sides of the housing to determine if ball captured

Locomotion Subsystem

Fetching a ball and returning that ball to a goal requires some type of locomotion.Locomotion involves steering, a propagation system, equipment to drive the propagation, and control circuitry to operate the equipment.

Minimum Requirements

Speed of at least 0.14 feet per second.Ability to alter the heading and direction of travel.Ability to stop.

Locomotion: Introduction to Steering

To compete well in the 6’ x 8’ area, robots will need a tight turning radius.The chassis configuration must also be taken into account when analyzing the problem of steering.

Locomotion: Steering Analysis

Robot must be able to rotate 360° without changing its positionRobot must be able to rotate a minimum of 3° at a time

Locomotion: Steering Hardware

Differential steering system2 Wheels driven by two separate motors and 2 casters for supportUse formula Vi / Rt = Vo / (Rt+D) and derivations to calculate velocities and turning radii

Steering Hardware Continued

Tires: ‘Lite Flite’ Foam tires have a 3” diameter and are made of a foam rubber compound

Chassis Schematics

Locomotion: Introduction to Motor

Drives the propagation and steering systemsA good balance of power and precision is desiredEfficiency considerations must be taken into account

Locomotion: Motor Requirements

To be competitive with other robots, we want our robot to travel an average of 1 foot/second.To achieve this speed with our 3” wheels, only around 100 rpms are needed. However, to account for friction, the motor can be geared down to increase the torque.

Locomotion: Motor Hardware

2 Mabuchi FA-130RA-2270 motors with Tamiya 70097 Dual Motor Gear boxThe gear box has ratios of 58:1 and 203:1The motor has an operating range of 1.5-3.0 voltsThe stall current is 2 amps

Motor Hardware Continued

At max efficiency, the speed is 6990 rpms. Using the 58:1 gear setting and 3” wheels, the projected speed is 1.6 feet per second. Our goal of 1 foot per second is easily accomplished with this motor and gearbox combo.

Motor Schematic

Locomotion: Introduction to Motor Driver

External circuitry is needed to interface the motors with the mcuThis circuitry helps the motors run efficiently and safelyAllows motor to operate at various RPMs as well as forward and reverse

Locomotion: Motor Drive Requirements

Drive two motors simultaneouslyMust be able to output from 1.5 to 3 voltsMust be able to output up to 2 amps per motor at stall torque

Locomotion: Motor Driver Hardware

Lynxmotion Dual H-bridgeAll that is needed is to hook up mcu input lines, motor output lines, motor power supply, and 5V Vcc

Power: Introduction

Power efficiency much more crucial in battery powered devicesBatteries can add significant weightRobot will need adequate voltage and amp outputNeed batteries to power MCU and motor

Power: Requirements

H-bridge we chose requires 6 volts to drive the motor and max of 4 amps if both motors stallMCU must have voltage regulated to 5 voltsRobot must compete in an undetermined number of matches so rechargeable or extra batteries may be needed

Power: Hardware

2 prepackaged Rechargeable Nickel Metal Hydride battery packsSmart charger9V battery with a voltage regulator for MCU

Power: Hardware continued

Maximum 30 amp discharge rate.As high as 3000mah capacity nickel

metal hydride.All cells are matched. No cell memory, you can recharge the pack without fully discharging

Voltage: 9.6 volts

Power: Hardware continued

2000ma constant output current for any voltage battery pack

Charging current will reduce to trickle charging at 50mah when battery pack close to full, then green LED will be on

For 3000 mAh battery pack, charging time is about 90 minutes

Battery Packs and Smart Charger

Budget

OOPIC IC $26.00

Pak-II$30.00

IR transmitter $1.00

IR receiver$1.00

GP2D12 IR Ranging Module$18.95

Twin Motor Gearbox Kit $15.95

Standard Futaba Servo $15.00

Ball Casters$8.95

3" Lite Flite Wheels$4.75

Chassis$30.00

Lynxmotion H-Bridge $25.00

Battery Pack$30.00

PCB Board $100.00

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Total Price $307.00

Main Process