13 : omni-directional robot design review
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13 : Omni-Directional Robot Design Review. Ben Wolf Brent Cornelius Ed Cramer John Grabner James Grabner Advisor & Client: Dr. Nicola Elia. Introduction. What is an Omni-Directional Robot - PowerPoint PPT PresentationTRANSCRIPT
13 : Omni-Directional RobotDesign Review
Ben WolfBrent CorneliusEd CramerJohn GrabnerJames Grabner
Advisor & Client:Dr. Nicola Elia
Introduction
• What is an Omni-Directional Robot– A robot that is able to move any direction in the
X/Y plane without changing it’s orientation. As well as being able to move in a single direction while freely rotating 360⁰
• In 2010, a team designed a new robot platform but did not complete it, our goal is complete the assembly of the robot and implement any missing features
Problem statement:
• Current design needs the following:– Analog I/O board– A working IMU– Battery protection and monitoring
• Other features to be worked on– Operating system– Assembly documentation– Chassis reorganization
Functional Requirements• I/O board:
– Needs to have at least 4 inputs– 12 bit resolution at 1kHz
• IMU:– Assess purchased Pololu CHR-6d– Find alternatives if necessary– IMU must be mounted on robot and functioning
• Operating System:– Must boot in 30 seconds or less– Must be tolerant of unexpected power loss– Must be compatible with existing hardware
Functional Requirements• Chassis:
– Must have outer shell for use with visualization system– Undercarriage wiring must be organized– Use PCBs where possible to simplify manufacture and
assembly of robot
• Battery protection:– Must have automatic disconnect to prevent battery
module damage– Battery voltages must be available to OS/AI
Non-Functional Requirements
• Maintain function of “legacy” system
• Provide documentation for robot assembly
• Characterize robot performance
Design (8 slides)
Operating System
• Korebot series robots used Familiar Linux• The previous team used Ubuntu 10.10 to get
started quickly• A more efficient replacement was needed
– Reduce boot time– Stored on compact flash memory– Read-only file system to prevent corruption and
unintentional modifications
Operating System
• Researched a variety of embedded and portable systems– MicroCore Linux, Linux From Scratch– Emdebian Linux
• We needed a quick start as well– Custom kernel and Debian 6 installed on the robot– Gather information about the hardware– Start testing other components like the I/O board
Analog I/O Board
• PCI boards were too expensive• Inadequate resources to develop our own• Chose WinSystems PCM-MIO-G
– Linux supported out of the box– Less expensive than other models– Software available for testing before purchase
• Issues with Stack Configuration
Battery Protection and Monitoring(BPAM)
• BPAM requirements– Must shut off pack when one or more cells reached 3.2-3 volts– Must be able to report cell voltages over a serial line– Must be able to work with 2 or 3 cell batteries
• We decided to not use commercially available BPAM– Had overvoltage protection, but no under-voltage protection– Only protected a fixed number of cells– Most did not meet all the requirements
• Decided to design and implement our own microcontroller based battery protection system that would shut off power to a robot when cells reached 3.2 volts, be able to be used with 2 or 3 cell battery packs, and would be able to communicate cell voltages over a serial line.
BPAM Schematic
BPAM Design• PIC16F688 microcontroller
– Has 8 channel 10 bit ADC, we need three to read cell voltage– Output pins can be used to turn on/off power MOSFET and
sense amplifier– Has USART for serial communication
• TL084 JFET Quad Op Amp– Input Impedance > 1Tohm– Can drive resistor dividers on sense lines
• MC78LC00 Regulator– Provides the microcontroller with 3V for power– Low quiescent current
Chassis Organization
• System before our additions– Two Layer System– Needs Switches, Indicator Lights, and Top Shell – Lower chassis wiring needs to be redone
Chassis Organization
• When adding I/O board Stack configuration will need to be altered– Computer is PC-104/+ Form factor – Mesa board is PCI-104– I/O is PC-104– Solution:
• Adapter Board
Adapter board
• Pass through PCI Bus• Offset ISA Bus
Adapter Board
• Secondary function – Chassis ReorganizationThe empty board space was not wasted:
• Motor drivers• Voltage regulators• Motor connectors• Motor controller interface• New motor current sense circuits• Switches
IMPLEMENTATIONTESTINGEVALUATION
Operating System
• There are several versions of the OS today:– Development OS (eris-00.04)– Veisha OS (eris-00.03)– Debian Live (generic)
• Fastest boot time is 38 seconds– 18 seconds consumed by POST– CF slot much faster than USB with GRUB
• More robust file systems are necessary– Compressed and/or ramdisk is ideal– Move to journaling file system
I/O Board: Accuracy and Sample Rate
0 500 1000 1500 2000 2500
-5
-4
-3
-2
-1
0
1
2
3
4
5
PCM-MIO-G High Speed Sampling1KHz 9Vpp Sine Input (~56 KHz)
Elapsed Time (uS)
Volts
HP 34401A PCM-MIO-G4.2045 V 4.2027 V8.4119 V 8.4117 V2.6406 V 2.6401 V
•A simple how-to program was written for future users
• Maximum observed sample rate was 71,428 Hz
I/O Board: Sensor Manager
230 235 240 245 250 255 260 2650
5000
10000
15000
20000
25000
30000
Sensor Manager Data Logging200Hz sinusoidal input
Time (ms)
Sen
sor M
agni
tude
(16-
bit,
0-5V
rang
e)
0 10 20 30 40 50 60 700
5000
10000
15000
20000
25000
30000
Sensor Manager Data Logging200Hz sinusoidal Input (~2300Hz)
Sample #
Sam
ple
Mag
nitu
de
BPAM• gEDA used to create schematics and PCB
layout– Considerations for making PCB by ourselves
• Microcontroller Programming – MPLAB IDE v8.76 with Hi Tech C Compiler– PICkit 2– Main Functions of the Program
BPAM Pictures
BPAM Testing
• Microcontroller Functionality• Linearity and Accuracy • Static Load Test• Complex Load Test• Testing with a Robot
Chassis Reorganization
• Power Switches• Bumper Guards• Adapter Board
Adapter board
• gEDA was once again used to create schematics and PCB layout
• Schematic to PCB tool • Board was ordered through Advanced Circuits
– Assembly is nearly complete, connectors arriving later today
Adapter Board Pictures
Conclusion
• BPAM – Primary Goal Accomplished (batteries are
protected)– Do not foresee any major obstacles to complete
remaining requirements• Operating System
– Boots quickly and is in a usable state
Conclusion
• I/O Board– Integrated on robot and performs adequately
• Chassis Successfully reorganized– Requires a permanent lid assembly
Lessons Learned
• Just because it seems simple doesn’t mean that it will be done quickly (BPAM)
• The best robot is useless without proper documentation
• Don’t let a project intimidate you, start working and ask for help if you get stuck
Questions