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