XROVER CDR

Critical Design ReviewFebruary 2, 2011

Filip MaksimovicViliam KleinPeter ZhangCorrina GibsonBrandon BenjaminVicki HsuElliott RichersonTyson WolachJohn Jakes

Aerospace Advisor: Scott Palo

Introduction

• JPL funded project with the Aerospace department• Goals are to explore feasibility of using multi-rover configurations for extraterrestrial exploration• Our system architecture has one mother rover and two deployable child rovers• Continuation of a project started two years ago

Objectives

Objective Description

The system maintains former capabilities from REMUS and R3

• CRs can deploy and dock from MR.• CRs can drive to LOI and capture

images that are transmitted back to the GS.

Relaying between MR and CRs for data transfer

• Mission CR will explore behind locations where maintaining communication with MR will be through relay.

MR and CR can traverse defined terrain

• CRs will maintain communication with MR at various orientations and altitudes.

• CRs will deploy and dock on flat terrain.

Terrain Definition

• 20 degree slopes (CR only)• 1 inch rises/discontinuities• 2 inch depth pea gravel surface

(slipping assumed)

Mother Rover (MR)Mother Rover (MR)

Location of Interest (LOI)

Identified

Relay Ability Confirmed

Rover Mission Sent to MR

CR Status and Data Evaluated

Commands Sent to CRs

Relay CRRelay CR

Ground Station Mother Rover C&DH Child Rovers Relay Area Terrain Location of Interest

dock &

undock

MR to deployment location

Concept of Operations

Mother Rover (MR)Mother Rover (MR)

C&DHC&DHRelay Relay

WaypointWaypoint

Location of Interest (LOI)

Identified

Relay Ability Confirmed

Rover Mission Sent to MR

CR Status and Data Evaluated

Commands Sent to CRs

Relay CRRelay CR

Ground Station Mother Rover C&DH Child Rovers Relay Area Terrain Location of Interest

Relay CR and MR Communication

dock &

undock

Concept of Operations

Mother Rover (MR)Mother Rover (MR)

C&DHC&DH

Mission CRMission CR

Relay Relay WaypointWaypoint

Location of Interest (LOI)

Identified

Relay Ability Confirmed

Rover Mission Sent to MR

CR Status and Data Evaluated

Commands Sent to CRs

Relay CRRelay CR

Ground Station Mother Rover C&DH Child Rovers Relay Area Terrain Location of Interest

Relay CR and MR Communication

dock &

undock

Concept of Operations

Mother Rover (MR)Mother Rover (MR)

C&DHC&DH

TerrainTerrain

Mission CRMission CR

LOILOI

Relay Relay WaypointWaypoint

Location of Interest (LOI)

Identified

Relay Ability Confirmed

Rover Mission Sent to MR

CR Status and Data Evaluated

Commands Sent to CRs

Mission CR and Relay CR Comm.

Relay CRRelay CR

Ground Station Mother Rover C&DH Child Rovers Relay Area Terrain Location of Interest

Relay CR and MR Communication

Image Obtained by Mission CR

Mission CR Position

Evaluated

dock &

undock

isolatedtravel

boundary of communication

Concept of Operations

Electronics Functional Block Diagram

Ground Station Mother Rover

Child Rover Child Rover

Power

Power

GUI Computer Wireless Router

Use

r Inp

ut

Wireless Router

Wireless Router

Wireless Router

MR Drive

CR Drive

CDH

CDH

Navigation

User inputs ‘waypoints’ to control child rovers

Power

CR Drive

CDH

Navigation

Desired Location

Desired Location

Mot

or C

ontr

ol,

Inte

rrup

t

Mot

or C

ontr

ol,

Inte

rrup

t

Position Position

PowerUSB

RS232Wireless Network

Child Rover Functional Block Diagram

Child Rover

Power

Wireless Router

CR Drive

CDH

Sensors

PowerData

5V

5V/12V

5V

Inte

rrup

t, Re

ques

t Dat

a

Navigation Data

RS232 Motor Drive

Desired Location

Child Rover Drive Subsystem

Module Child Rover Drive

Inputs • 5V @ 50mA from power system• 12V @ 2A max from power system• OneRS232 drive signal from CDH board

Outputs • Child Rover movement

Functionality This drive subsystem receives an RS232 motor control command. The motor controllers have convert the serial command to rotate the 12V motors.

Functional Decomposition

Child Rover Drive Subsystem Block Diagram

RS2325V/12V

Motor voltages

Child Rover Drive Subsystem

Further Functional DecompositionModule Motor Controller (Pololu qik2s9v1)

Inputs • 5V @ 50mA from power system• 12V @ 2A max from power system• One RS232 drive signal from CDH board

Outputs • Motor Voltages @ 1A max each

Functionality Two controllers can control two motors each. They can be daisy-chained along the same RS232 line and commands are issued to each motor individually. The motor voltages determine speed.

Module DC Motor (Pololu 19:1 Metal Gearmotor)

Inputs • Motor Voltages @ 1A each

Outputs • Child Rover movement

Functionality The DC motor receives a voltage and spins. The stall current is 5A, but the controller has a current limiter to prevent excessive draw.

Sensors Functional Decomposition

Module Child Rover Navigation Sensors

Inputs • 5V from battery• The world

Outputs • 4x quadrature from encoders• 2x indexed quadrature from encoders• 3-axis accelerometer ±18g (IMU)• Triaxial digital gyroscope ±75 o/sec (IMU)• 3-axis magnetometer (cheating)• Range from 2 ultrasonic crickets

Functionality The child rover sensors provide data to the CDH for processing to determine the CR’s position and orientation.

Further Sensor Functional Decomposition

Module Analog Devices IMUInputs • 5V from Power system

• Configuration settings from CDHOutputs • 3-axis accelerometer, gyro, and magnetometer (unused)

• All available on an SPI line (depending on configuration settings)Functionality The IMU provides highly accurate angular and linear acceleration experienced by

the child rover. Downsides are thermal noise and (usually) linear gyro drift

Module US Digital 100CPR Free Wheel EncoderInputs • 5V from Power systemOutputs • Indexed quadrature related to the distance that one of the two free wheels has

travelledFunctionality These optical encoders spin when the wheels move. Based on this movement, the

output is a quadrature line that can easily be converted to a count. These encoders also include an index line which goes high for one cycle when the encoder detects one revolution.

Module Pololu 64CPR 19:1 Encoder (comes with motor)Inputs • 5V from Power systemOutputs • Quadrature related to the distance that one of the corner wheels has travelledFunctionality These encoders spin when the wheels move. Based on this movement, the output

is a quadrature line that can easily be converted to a count. Because of the gear ratio, these encoders spin 19 times faster that the motor shafts.

Quadrature

TimeGen Demo

TimeGen Demo 1 2 3 4 5 6 7 8 9 10

TimeGen Demo TimeGen Demo

T

imeG

en D

emo

Tim

eG

en

De

mo

T

imeG

en D

emo

TimeGen Demo

TimeGen Demo TimeGen Demo

TimeG

en Dem

o

Tim

eG

en

De

mo

TimeG

en Dem

o

TimeGen Demo

TimeGen Lite

A

B

Index

• Quadrature encoders have an A line and a B line 90o out of phase• Phase lead/lag is used to determine whether shaft is rotating clockwise or counter-clockwise• Frequency of signals can be used to determine rotation rate• If encoder spins too quickly, sometimes counter will miss a count resulting in erroneous reading• Index line signals whenever one revolution has completed and can be used to “zero out” the encoder count to remedy the missed-counts problem

Rangefinding Crickets

Power System Functional Decomposition

Module Child Rover Power

Inputs • 14.4V from Li-ion battery• 4x1.5V from AAA batteries

Outputs • 5V to motor controllers• 5V to logic, sensors (separate)• 12V to motors

Functionality The power system must provide regulated voltages to all of the electronic components on the child rover. It must also keep the motor lines voltages separate from the logic and sensor voltages

Power System Block Diagram

14.4V Li-ion

6V AAA

Pico PSU Motor Controllers

5V

12V

OnboardOptoisolator

Gumstix

Crickets, Webcam

Linear Regulator I/O Expander

Sensors

Electronic Isolation

5V

5V

5V

5V

CDH Functional Decomposition

Module Child Rover CDH

Inputs • Desired waypoint from user (via wifi)• IMU, encoder, and cricket data• Webcam picture• 5V from power system

Outputs • RS232 motor commands to controllers• Webcam picture to GS via wifi• CR position measurement

Functionality The CDH acts as the brain of the child rover. It closes the navigation loop by providing a PID controller that moves the CR based on user input.

Camera

I/O Expander

Gumstix Computer

Mesh Router

CDH Block Diagram

Request Picture

Image

Interrupt, Motor Command Sensor Data

CR Position, Image

Requested Position, Mission Info

Crickets

InterruptRange

IMU DataEncoder Data

USB

SPI Bus

I/O Expander Schematic (rev.1)

I/O Expander Block Diagram

Encoder Counter

Encoder Counter

Encoder Counter

Encoder Counter

Encoder Counter

Encoder Counter

Atmega128

Aux PSU

SPI

RS232

To Gumstix

I/O Expander PCB Layout

Revision 2 plans:• Fix reset pin circuit• Add VCC, GND pins for all encoder and motor headers• Wire the USB properly• Change LED circuit so that they are off when line is high• Move USB and IMU connectors to same side of board

TimeGen Demo

TimeGen Demo

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

TimeGen Demo TimeGen Demo

T

imeG

en D

emo

Tim

eG

en

De

mo

T

imeG

en D

emo

TimeGen Demo

TimeGen Demo TimeGen Demo

TimeG

en Dem

o

Tim

eG

en

De

mo

TimeG

en Dem

o

TimeGen Demo

TimeGen Lite

Clock

SS_Encoder

SS_IMU

MISO

SPI Timing Diagram

• Both encoders and IMU have continuous data modes where they will release data while the SS line is held low• Each encoder has 4 bytes of data, and the IMU can provide 39 bytes of status registers and data

Additional IMU Timing Information

• Maximum SPI clock is 1MHz• Minimum stall time is 9 clock cycles (9 µs)• 600 µs delay between sync timer and data ready when specific data is requested

Encoder Counter Circuit

Free/Powered Wheel Encoder

Encoder to Counter Converter

LS366R 32bit Counter

ATMega128

SPI Protocol

Aux Battery

Each component is powered by

regulated 5V from the AUX battery

PID Control Simulation

• PID simulation run in Mathematica to determine effectiveness of controller in following waypoints• Input to simulation is actual CR position

GUI

Software – Finite State Machine LogicDocked

Wait

mission started

Switch COMM

Interface Rotate to LOI

Imaging

Rotate to Next Waypoint

Mission Complete

Conn?

Conn?

no

yes

yes

noSafe

Undock waypoint

?Calibrate

File Update

Final waypoint

no

yes

Drive

Waypoint Reached

DEFCON1

Relay rover?

Wait for Mission CR

yes

no Returning?

Returning?

Reverse Waypoints

yes

Returning?

nono

returning = true

no

no

yes

yes yes

Rotate to Next Waypoint

Software – How to determine position

The Black Box

x’’, y’’, z’’ θ‘, ψ’, φ’

r (crickets)V, r (encoders)

x, y, z, θ, ψ, φ

Wireless Communication

• Must provide communication between GS, MR, and CRs• Also must provide relay communication to a hidden CR• Solution is an ad-hoc mesh network to maximize throughput and minimize packet loss• These from Alfa Corporation are wireless mesh routers• They also come with nice software showing packet transfer and were free

Budget

Source Confirmed? [Y/N] Total AmountJPL Funding Y $5000EEF N $2000

Item Name / Description Unit Price Quantity Total Amount

ASUS Eee PC 1015T-MU17-BK Black AMD V Series V105 (1.20GHz)

$350 1 $350

MR Body Materials (aluminum, screws, nuts, bolts, bearings, etc.)

$800 1 $800

CR Body Materials (aluminum, wheels, tires, screws, etc.)

$800 2 $1600

S5 Optical Shaft Encoders $85 4 $340Polulu Qik 2s9v1 Dual Serial Motor Controller

$25 3 $75

LFLS7366R-S 32-bit Quadrature Counter with Serial Interface

$6 6 $36

100:1 Metal Gear Motor 37Dx57Lmm with 64 CPR Encoder

$40 8 $320

Atmega128A-AU-ND $10 2 $20PCB $80 2 $160Analog Devices IMU ADIS16360 $750 1 $750Cabling and Miscellaneous Adapters

$200 1 $200

Test Bed Materials (wood, gravel, screws, etc.)

$300 1 $300

Shipping Costs - - $200Printing (fall and spring final reports) $250 2 $500Margin 30% - $1670

Total $ $7321

Manufacturing Schedule

Milestone 1 Milestone 2

Verification and Testing Schedule

Milestone 1 Milestone 2

Milestone Goals

Milestone 1 Milestone 2• 2nd revision of board ordered and populated• Display functional interrupt-driven communication between Gumstix and I/O expander• Drive (not navigate) a child rover• Confirm reception of data by Gumstix from IMU, encoders, and crickets• Demonstrate wireless packet transfer over mesh network through intermediary node

• Drive child rover with use input through GUI• Determination of absolute position within 10cm with sensor data and navigation algorithm• Complete all physical construction of electronics and mechanical hardware