Elec <> Strategy

Recurring meetings weekly Thursday at 11ET

Solar Power

• Strategy has model for sun intensity

• To sync with what inputs/outputs are

• Input lat/long + time of day

• Get out solar irradiance

Array Size

• 256 cells * 153cm2 = 3.9168m2

• 1000W/m2: 3.62W

Solar Cell configuration

• @Former user (Deleted) to give cell normal angle for each array

  • Later forest to give angle for each cell

• @Ryan Lam @Rodrigo Tiscareno Look at legacy code and see what translates over

Optimal speed model @Rodrigo Tiscareno @Ryan Lam

• Inputs: Cd, A, wind speed, air density, weight, rolling resistance, system (mostly motor) efficiency curve (not constant for all loads)

  • Information that tells you how much energy you will need to move the car

  • @Former user (Deleted) to provide vehicle parameters

• Priority 1: Make sure we can get to EOD checkpoint in time

• Priority 2: Drive at speed at which the least energy is spent to move a given distance (Wh/km)

• General info

  • rolling resistance is mostly constant per given distance

  • air resistance is proportional to velocity squared

  • wind direction and speed will influence air resistance

  • road material/condition will influence rolling resistance (can be a lot)

  • looking for point at which derivative of speed with respect to power = 0

Motor Max Power Model

• What is the steepest grade in the route

• On that steepest grade in varying wind conditions what is the motor power required to maintain our most optimal speed

Vehicle Passing Model

• What is the power and energy consumption we would need to pass another car

  • How do we pass cars efficiently

  • Passing cars means going fater than our optimal speed and also requiring the system to privide a large burst load of power

    • This causes efficiency losses

    • If we succeed in passing how much extra power did that use compared to if that car wasn’t there

    • If we fail or succeed in passing how much do we gain compared to just staying behind that car at a slightly less optimal speed

Notes from strategy sync, 6/26
Overall goal: make telemetry as simple as possible

Comms:

• Wifi

  • Low range, especially with ESP32 (30m? have we tested it? we will be outside where there are no walls etc.)

  • High data rate (multiple MBps)

  • Lost packets are resent, no missing data (unless connection completely drops)

• RF

  • Very long range (1km?)

  • Can interface directly with Arduino with minimal code

  • Arduino supports CAN, reads bus, stores in json and sends as bytes to the transmitted

  • Another Arduino receives the messages on the chase car, sends it to computer over serial

  • Make sure antenna is omnidirectional

  • Loses packets

• leaning towards RF due to range advantage, need to implement systems to account for data loss

  • Add checksum to verify integrity, and just interpolate if data is bad?

  • How will the receiver know if a byte was missed completely? @Mitchell Ostler

  • Maybe we can add a rolling counter?

  • Can we implement our own retransmission thing where if checksum doesn't match or counter is not sequential byte gets resent

  • Receiver can send ack to signify successful reception

  • If data transmission can't be guaranteed, coulomb counting has to be done on the car itself

• To look into exactly what hardware to use @Mitchell Ostler

Project Responsibility:

• Largely a strategy owned project, with fw/hw support

• FW

  • Provide background information

  • Define system requirements, including packet format

  • Assist in hw setup

• Strategy

  • HW purchases

  • System implementation

  • Integration with database and models

  • Testing and validation

Timelining:

• Likely to start more seriously in the fall

  • Currently lacking onsite members capable of independently taking this on

  • Can be alleviated by providing detailed system requirements and resources

• FW to assign someone on-site to support

Elec Data Points:

• Primarily interested in battery metrics

  • State of charge (SOC)

  • Power usage

  • Power generation

• Overall health of systems (whether they are online or not)

• Everything that occurs on the CAN bus will be broadcasted over telemetry

Telemetry Power

• Will be powered off aux batt, need only to supply 5v

• Aux batt can be recharged/swapped without penalty at least once a day

  • Maybe more often with penalty? Don't know, @Yanshen Zhou can you take a look?

Strategy General Update:

• Building out their microservices

  • Correct me if I'm wrong but the goal is to process a bunch of data to feed into a live loop decision model

• This lets us determine if our car has enough energy to take optional loops, increasing our distance travelled (race is distance based not time)

  • Largely developing models for external facing data

  • Weather API integration

  • Route elevation

  • Solar irradiance

• Primarily missing internal metrics due to lack of system definition

  • How SOC plays into the model

  • Correlating solar irradiance with power generation

    • Using datasheet?

  • Power budget and typical vehicle consumption

    • Previous power budget https://github.com/uw-midsun/strategy/tree/master/auxloss

    • @Forest Zhou to work on this https://docs.google.com/spreadsheets/d/1p7sRoQ8vFM0XcknKR91l4tNxka4DDQgWxOqwXCTtDZc/edit?usp=sharing

• To look into range sensitivities for mass and non-motive power consumption @Rodrigo Tiscareno