HW Integration Meetings

Owned by Jonathan Xie
Last updated: Nov 18, 2023 by Mitchell Langdon Ostler
19 min read

Vehicle Fault States - Non Battery

Pedal

Fault

Condition

Action

Fault

Condition

Action

Stuck Pedal

No way to detect it

N/A

Lose communication in pedal node

No pedal data

Set throttle to 0 upon missed transmission

MCI

Fault

Condition

Action

Fault

Condition

Action

CAN Fault

Error status from WS22

Error indication on console, immediately auto-clear

Maybe limit torque for overcurrent

Steering

  • No detectible errors

Power Distribution

Fault

Condition

Action

Fault

Condition

Action

Output over current

Isc reading at full scale

  • Disable load switch

If BMS fault

  • BPS Fault

Else

  • Display error code if possible (if not CC fault), pull over if needed

Aux Fault

AUX Valid GPIO low

  • Error code, pull over

DCDC Fault

DCDC Valid GPIO low PA15 or PB5

  • Error code pull over, leave everything on

    • Not allowed to drive on AUX

Aux low

AUX ADC voltage low PB3 or PB4

  • Indicator light turns on

    • Might need to add

  • Make determination on where to stop

AUX/DCDC Overcurrent

Current greater than x value (can be 8A for now)

  • Indicate, pull over/manually turn off car

AUX/DCDC Overtemp

Temp greater than 60C (can change)

  • Indicate, pull over/manually turn off car

AUX not valid on startup

AUX Valid GPIO low on startup

  • Will never get detected, car won’t turn on

DCDC Fault signal

Signal high from DCDC PA6

  • Nothing, display warning light

Solar Sense

Fault

Condition

Action

Fault

Condition

Action

No current

No current in one or more strings when relay closed

  • Display error code

Dead

No response over CAN

  • Display error code

 

Timelining

Complete

Pending

Optional

Complete

Pending

Optional

Controller Board

MSXV PD

  • Dec 2

Solar

  • Jan

Center Console

Pedal

  • Nov 11

 

MCI

Carrier

  • Nov 25

 

MSXIV PD

Current Sense

  • Nov 25

 

Steering

 

 

MSXIV AFEs + LTC6820

 

 

Mockup creation: Feb - Mar/Apr

Functional Testing: Apr - May

Vehicle Fault States

Battery

Parameter

Source

Condition

Action

Parameter

Source

Condition

Action

Cell Voltage

BMS AFE - LTC6811

One cell group falls under: 2.5V

  • BPS Fault Minor

 

 

One cell group rises above: 4.25V

  • BPS Fault Major

 

 

One cell group is imbalanced by greater than 0.5V

  • BPS Fault Major

Pack Current

BMS Current Sense - MAX17261

Pack current rises above 58.2A

  • BPS Fault Minor

 

 

Pack current falls below -27.08A

  • BPS Fault Minor

Cell Temperature

BMS AFE - LTC6811 (cell + ambient)

BMS Current Sense - MAX17261 (cell)

Ambient temperature rises above xxC

  • BPS Fault Major

 

 

Cell temperature rises above xxC

  • BPS Fault Major

Pre-charge time

BMS Carrier CB

Pre-charge takes too long

  • Failure to complete state transition, err code on display

Lose BMS

Power Distribution

BMS hard fault

  • 30 second timer, Shut down BMS AUX power to cut relays, keep BMS DCDC power on for fans

Lose AFE

BMS Carrier CB

AFE does not respond

  • BPS Fault Minor

Lose current sense

BMS Carrier CB

Current sense does not respond

  • BPS Fault Minor

BPS Fault:

  • Relays open (one IO per relay):

    • Main relay pos

    • Main relay neg

    • Pre-charge relay

    • Solar relay

  • BPS Strobe External

  • BPS Indicator Center Console

  • Cut MCI

    • Send message to PD to disable MCI LS, in the event that regen was commanded to prevent it from keeping the HV bus energized

  • Display error code on centre console

PVDR Battery Test Plan Review

Solar Testing

Coulomb counting

  • Decided to go with on-vehicle SoC calc with max17261.pdf on current sense

    • CC by itself is not sufficient due to drift, algo needs to integrate vsense to anchor CC mesurements

    • Developing in-house SoC algo is difficult and unsure of what accuracy will be

  • Eric’s notes: https://uwmidsun.atlassian.net/l/cp/oPkT0eia

Solar Irradiance

  • Has theoretical power of one array using pysolar

  • Next steps:

    • Model all panels + effects of aero curvature

    • Obtain power for a given route

    • Add weather effects

    • Account for system efficiency over varying loads

Coulomb counting

  • Found fuel guage IC that we might be able to use for main pack, a lot of FW complexity

  • Strategy algo progress basically 0

    • On-vehicle calc limits model complexity → lower accuracy

    • Unsure of resource usage on micro

  • Decision to be made next Tuesday on which method to pursue, to consider

    • FW effort of writing I2C driver for IC vs building in-house CC algo

    • Accuracy of OTS vs in-house

  • Forest to build 36x1 pack this weekend to support testing of CC + AFE

Telemetry

  • RF implementation is complex and involves dealing with FW drivers, regulations, and interference

    • Was initially proposed as a simpler alternative to dealing with networking protocols, but that doesn’t seem like it’s the case

  • From strat, we only need accurate SOC every 5 mins for their model, possible to do over radio

    • What accuracy is needed?

  • Baseline is no live data, will be a task but not on the critical path

    • Critical assumption made is that we will be able to get accurate SOC calculation entirely on the vehicle, which is possible especially with OTS ICs

Battery box board mounting

  • Started mounts, mostly done with carrier

  • To focus on AFEs since they are most complete

    • Backup is to use MSXIV AFEs, design mounts for those

  • To get current sense as close as possible to carrier

  • Figure out HV harnessing and where to place current sense

    • Should be on low side (connecting to neg pack terminal)

    • It is allowed to be before the main contactors as per regs section 8.6.A.4. Relays only need to disconnect HV wires exiting the pack.