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14 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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AUTOCART

Team 1 (Team Code Name One)

Design Review Fall 2012

Andrew
Senetar

Shi
Jia

Yixin

Wang

Tommy Pollard

Presentation Outline


Project overview


Project
-
specific success criteria


Block diagram


Component selection rationale


Packaging design


Theory of operation and schematics


PCB
layouts


Software design/development status


Project completion timeline


Questions / discussion


Project Overview


Construct an electric go
-
kart able to drive itself


Pre
-
existing chassis



To Do:


BLDC Motor Controller


Electrically Controlled Braking/Steering


Battery Management


Safety Management


Autonomous Navigation


Project Specific Success Criteria

1.
An
ability to send vehicle telemetry data and receive remote
signals via wireless
communication


2.
An
ability to maintain a closed loop control of the drive motor
speed


3.
An
ability to adjust the heading of the cart through control of the
existing vehicle steering
system


4.
An
ability to follow a “road” using image and GPS
data


5.
An
ability to detect potential obstacles and take an appropriate
response



BLOCK DIAGRAM

Block
Diagram Overview

Block
Diagram


Power & Safety

Block
Diagram


Braking & Steering

Block
Diagram


Motor Controller

Block
Diagram


Control System

COMPONENT SELECTION

Microprocessor Selection Rationale


MCU Requirements


CAN Bus


Minimum 2 channel 10
-
bit ADC


Minimum 12 GPIO Pins


On
-
chip oscillator preferred


Minimum 2 SPI Modules


Minimum 2 UART


Atom board to USB to MCU


GPS to MCU


DSP libraries are a plus


BLDC Motor
-
enabling features for motor controller board




dsPIC33EP
MCU Family


28 Pins on TSSOP


1x ECAN


2x UART


DMA


Pin Remapping


10
-
bit/12
-
bit ADC


1.1
Msps

or 500
Ksps


Dedicated PWM on
MC series


BLDC Specific


3 PWM Channels


ECAN Network

Fully CAN 2.0B
Compliant.

Provides reliable inter
-
MCU communications in
electrically noisy
environments.

DC
-
DC Converter Selection Rationale


Power Requirements


67V to 97V supply, nominally 72V


12V for Atom motherboard


3.3V for dsPIC33 MCUs



Motherboard Selection Rationale


Motherboard
Requirements


Processing Power


Cost
-
effective


USB interfaces


Modern peripheral
interfaces


High Power Components


Motor Controller
switching device



High power connectors



Misc

Selection Rationale


Wireless communication


Xbee

vs

standard
Wifi


Tradeoffs between ease of use and range



Brake Actuator


Already a linear motion with position feedback


Linear actuator has quick movement and “off state” holding ability



Steering Actuator


Direct / Indirect steering shaft drive had a lot of mechanical work


Linear actuator method easier to implement


Only downside


pure drive by wire


PACKAGING DESIGN

Packaging Design System Layout

Multiple Enclosure Reasoning


Enables high modularity


Allows for better isolation between high voltage / current
and low voltage items


Some components require heat sinking and heat
dissipation


Some systems need to be mounted in physically separate
locations


Easier disconnect of individual component from system.

Atom / Daughter Board Enclosure

Enclosure

Location for Daughter Board

Other Enclosures


Aluminum and acrylic construction


High heat dissipation through use of aluminum plate and fins


Acrylic allows protection for indicators while allowing for high
visibility


Acrylic is non conductive and is structurally supportive in thicker
sheets

Battery Enclosure


THEORY OF OPERATION
AND SCHEMATICS

Power Supply Theory of Operation


72V battery supply

to drive motor


72V to 12V switching converter


Powers Atom board and distributed to other boards for further step
down


12V to 3.3V switching converters


Located on almost every board


Fuses between all boards
and power connections

12V to 3.3V Switching Converter

CAN Bus
Board Theory of Operation


Controller Area Network


Serial


Differential


Standardized automotive protocol


Device IDs act as priority indicators


No host required for arbitration


Requires isolated power supply


Devices on the bus will be connected in a star network

CAN Bus Board

Daughter
Board Theory of Operation


Provides interface between Atom board and CAN bus


USB to UART converter


dsPIC33 reads GPS sensor data


CAN transceiver


GPS receiver

Daughter Board

Motor Control Board Theory of Operation


dsPIC33 provides PWM signals to 3 phase gate driver


IBGT gates off
-
board


Hall Effect sensors built into motor


Current sensors


Communicates on CAN bus through transceiver

Motor Control Board

Braking/Steering Board


Both circuits drive a single linear actuator


Controlled by dsPIC33


CAN bus


H
-
Bridge driver


Potentiometer off
-
board to measure position



Braking/Steering Board

Safety Board Theory of Operation


Controls high voltage contactor


Displays current operating state via LEDs


dsPIC33 interfaced with LED drivers


CAN bus


Sensor inputs from all over the cart

Safety Board

Capacitor Board Theory of Operation


Ensures there is enough/stable current


One FET to safely charge/discharge caps through resistor


One FET for normal operation


Optically isolated


Controlled by Motor Control Board

DC
-
bus current without DC
-
bus capacitance

DC
-
bus current with 1mF DC
-
bus capacitance

Source: C. Mi, M.A.
Masrur

and D.W.
Gao
,
Hybrid Electric Vehicles: Principles and Applications with Practical Perspectives,
1st ed. John Wiley & Sons, Ltd., 2011.

Capacitor Board

PCB LAYOUTS

Daughter Board

Daughter Board


Top

Daughter Board


Bottom

Capacitor Board

Capacitor Board


Top

Capacitor Board


Bottom

Safety Board

Safety Board


Top

Safety Board


Bottom

Braking/Steering Board

Braking/Steering Board


Top

Braking/Steering Board


Bottom

CAN Bus Board

CAN Bus Board


Top

CAN Bus Board


Bottom

Motor Control Board

Motor Control Board


Top

Motor Control Board


Bottom

SOFTWARE DESIGN AND
DEVELOPEMENT

Software Development Status


CAN bus driver libraries finished


FIFO RX Buffer


Manually triggered TX


DMA
-
driven RX/TX


On
-
chip peripheral configuration in progress

MCU Programming Model

Synchronous Function Loop

While True:


Check Flags


Do Stuff












Interrupt Driven I/O

On CN Interrupt:


Set/Unset Flags


Return
f
rom Interrupt


On UART/ECAN Interrupt
(Masked):


Automatic DMA Transfer to SRAM
Region


Raise DMA Interrupt


Service DMA Interrupt


Project Completion Timeline

1.
10/19


Submit PCBs for manufacturing

2.
11/02


Receive PCBs and begin assembly

3.
11/14


Finish PCB assembly

4.
11/15


All MCU and navigation software functional

5.
11/20


All MCU software “fully” debugged

6.
11/20
-
11/30


Navigation testing

7.
11/30
-
12/05


Final tests and adjustments


QUESTIONS?