08-11-2016, 10:38 AM
1466517276-ProposalPresentation1.pptx (Size: 4.69 MB / Downloads: 19)
Body
Deciding factors for the body design
Light weight
Aerodynamic
Six square meters of Solar Array space
Size requirements for race
High strength
Proposed Design
Monocoque Construction
Construction technique that utilizes the exterior of the body as the load bearing
Proposed Design
Designed using SolidWorks
Aerodynamic
Flow analysis using CAD model
Carbon Fiber
Light weight
Very strong
Shaped using wood molds
High cost
Proposed Design
Steering
Proposed Design
Rack and Pinion Steering System
Converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
It provides a gear reduction, making it easier to turn the wheels.
Statement of Work
Work with engineers designing body, and suspension of front two wheels.
Steering system will be designed in respect to body’s dimension and design.
Analysis of key components:
Rack and Tie Rod dimensions
Ackerman angle for steering, steering bar location,
Kingpin axis, Steering Knuckle location
Steering Stops
Geometry and dimensions of the system.
Statement of Work
Determine steering ratio
Analyze design using SolidWorks and working model to test linkage
Order parts needed for assembling the system
Verify steering system can complete all required tests in order to compete in race
Braking System
Proposed design
Two disc brake systems on front two wheels
Manual parking brake
Statement of Work
Braking forces for each front tire will be calculated using an estimated total vehicle weight
Analysis and sizing of components
Pedals
Master cylinders
Brake calipers
Disc
Statement of Work
Race regulations
Brake pad must have a contact area with the brake disc greater than 6.0 cm^2.
Solar cars must be able to repeatedly stop from speeds of 50 km/h or greater, with an average deceleration, on level wetted pavement, exceeding 4.72 m/s^2.
Suspension
Suspension
The job of a car suspension
Maximize the friction between the tires and the road surface
Provide steering stability with good handling
Ensure the comfort of the passengers
Approach
Work with the engineers designing the body, braking and steering systems, and motor
Independent Suspension
Isolates vehicle by its points of contact from the road
Eliminates disadvantages of beam axle
Loss of friction by the wheels
Small maximum spring deflection
No steering system control
Over-steer
Front Suspension
Objective
Design a double wishbone suspension for the front wheels
Choose the right shock size
Shock size will depend on total weight of the car
Double Wishbone
2 wishbone shaped links
Provide a strong member to overcome forces from braking and acceleration
Fixed to the frame and upper and lower ball joints
Spring and damper between the 2 wishbones
Double Wishbone Advantages
Kinematics easily tuned and optimized
More control over camber angle (degree to which the wheels tilt in and out)
Minimize body roll and sway
More consistent steering feel
Roll and Camber Angle
Body Roll
Camber Angle
Rear Suspension
Objective
Design a trailing-arm suspension for the rear wheel
Choose the right shock size
Shock size will depend on total weight of the car
Motor will be mounted on rear wheel
Trailing Arm
Arm joined at the front to the chassis
Allows the rear to swing up and down
No side-to-side scrubbing
Only allows the wheel to move up and down
Suspension Design
System will be designed in SolidWorks
Custom parts include
Trailing arm
Wishbone arm links
Hub
Knuckle
Fork-shaped link
Shocks will be bought according to calculated specifications
Suspension Testing
Individual then as a whole
Structural testing in SolidWorks
Finite Element Analysis
Fatigue and stress points
MSC Adams/Car to analyze and predict
Roll and vertical forces
Static loads
Steering characteristics
Wheel travel
Adjust camber angle, caster angle, toe pattern, roll center height, scrub radius, and scuff
Smoother and more comfortable ride
CAD Testing Examples
Positioning
Finite Element Analysis
Power Generation
Power Generation
Cell, Module, Array
Solar Power
Performance:
Insolation
Semiconductor (Si, GaAs)
Temperature
Position of sun
Weather
Solar Cell
Single Junction Silicon
Cheap
Efficiency = 14 -16 %
Fill Factor > 0.4
Voc, Isc
Not-Flexible
Easily Broken
Not Waterproof
Amorphous Multi-junction Silicon
Expensive
Efficiency = 10-12 %
Fill Factor = 0.67-0.75
Voc, Isc
Flexible
Durable
Waterproof
Solar Module
32 - 36 Cells (series) / module
Encapsulate
Electrical parameters (Isc – Voc)
Mismatch effect
Bypass diode
2 Bypass diodes/ 36-cell module
Bypass Diode, Blocking Diode
Solar Array
Series/Parallel module = Solar array
1 Blocking diode per module
Minimize cell temperature
PV Array Voltage > Battery Voltage
Max array power = 750 W
MPPT
Maximum Peak Power Tracker
DCC Converter
92-97% efficiency
Optimizes power output from panel while providing maximum amps into system
1 MPPT per solar panel
Winter, cloudy, hazy
Overcharge, reverse current protection
Regenerative Braking
Brake -> Motor -> Motor controller
Kinetic energy to electrical energy
Motor becomes generator
Charge stored in battery
60 – 70 % Efficiency (commercial E-V)
Friction + Regenerative Braking = Total Braking Output
Control System
Overview
Integration of control subsystems
Dashboard interface for driver input
Provides driver with telemetry and car systems status information
Master Control Unit
Microcontroller Based
I/O lines
Serial Ports
Relays/Switches
Servo control
LCD Output
Communicates with and manages control subsystems
Dashboard
Current Features
Speedometer
Throttle Gauges
Control Enable Switch
Air Gap Adjustment
Pre-charge Switch
Dashboard
New Features
State of Charge Meter
LCD Display
Video Display
Light Switches
Automated Startup
Automated Gap Control
Management system
Overview
Protection Circuit
Keep batteries in safe operating range
Send signal to Battery Management System (BMS)
Will require use of the microcontroller
Battery Management System(BMS)
Designed for electric car use
Four signal inputs
Slowly powers down the system
Voltage Protection
Cell Modules will be used for voltage protection:
Already connected to each cell
Big series signal from BMS
Break signal circuit if outside operational voltage
Current Protection
Current Transformer
Will send information to microcontroller
This information will also be used for SOC
Temperature Protection
PTC Thermistor
Positive temperature coefficient
Ideally hooked up directly through BMS
Cut off temperature, drastic increase in resistance
State of Charge (SOC)
The state of charge will display information for the driver about battery levels
Voltage Display
Current Display
Temperature Display
Battery Fuel Gauge (purchased device)
Will attempt to use information obtained from protection circuitry
Power Control
Creation of a power bus
Voltage regulation (batteries/solar)
Regenerative braking
Pre-charge circuit for motor controller
Electronic relay for shutdown
Budget & Schedule
Budget
Budget estimate to date: $38,168
Budget from University: $5,000
Deficit: $33,168
Donations
Hexcel
SolidWorks