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^Gerard meditating about what sensors we should use

Preliminary list of Sensors/brain dump (all these discussed down below in more detail):

1. IMUs (4)

   1. 1 on each upright and the other on the trailing arm.

   2. One on frame

2. Linear Potentiometers (3)

   1. 1 on each shock.

3. Rotational Potentiometers (2)

   1. 1 per pedal.

   2. more of an ergo thing and pedal board

4. Hall Effects (?)

   1. 1 for steering?

   2. Wheel Speed? (low priority)

NOTES FROM Dynamics and Data Acq/Electrical Meeting (7/26/25):

• Right now most sensors for next gen

• can discuss which ones to put on daybreak if we do actually get drive days happening (to talk about in our next meeting)

• Can talk more about putting sensors on daybreak for collecting data on a working car

  • would entail enclosures and powering them…etc.

  • table below was things kept in mind for choosing our sensors

  • red bolded sensors are axed/ignored

  • green bolded sensors are the ones we agreed upon

  • orange bolded is stuff that for sure will be discussed in our next meeting

    • WILL schedule 2nd meeting to come back to some of this stuff

• Last couple of things:

  • How useful is reading real-time data for dynamics/being displayed real time on photon?

  • This ones would be good for checking stuff in real-time

    • brake pressure, tire pressure

  • the rest will be saved real-time data but just not displayed

    • most plots will be vs time

    • brake pressure vs acceleration vs deacceleration

    • for brakes for example displayed a bar that goes up or down

    • will bring up in our 2nd meeting if something comes to mind on the dynamics side

      • future smaller meeting(s)

        • to go over mounting, sizing, design freeze, etc.

        • next meeting will be Unsprung focused; next Sat (4pm CT):

        • can schedule Steering/Suspension sensor meeting after Unsprung meeting

        • sensors to discuss:

          • 3 IMUs (not including the trailing arm sensor b/c t-arm is not finalized yet)

          • brake pressure sensor

          • tire pressure sensor

          • Goal of meeting is to make sure mechanical and electrical are on the same page

          • > mounting, sizing, etc.

Below table is the finalized list of sensors from the meeting (axed/ignored/low priority sensors not included):

bolded parts below are the parts discussed during the meeting:

Unsprung:

• Hall effect per wheel (2)

  • entails one board per upright and one magnet per hub

    • multiple magnets needed perhaps bc we cant mount the magnet in the axle itself

  • usage: lets us check the speed of the front two wheels vs the rear for speed. also lets us check for toe, if the speeds are significantly different then we can adjust toe to make them the same speed (ish)

  • new member project: measuring toe

  • would make sure our toe is good beforehand and then collect data

  • confounding variables to consider → differences in tire

  • more magnets would give more accurate reading is the idea

    • is the sweet spot 2 or a different number?

      • will need to figure out a reason for the # of magnets chosen

      • how to secure magnet to the wheel hub

      • EV just epoxied to their center lock; they machined slots into their centerlock for the magnets

      • Electrical: will talk about best # of sensors

      • Dynamics: will talk best way to mount; either include in our manufacturing plan or epoxy onto hub

• Actual Dynamics BoardarchivedPreview ← link to current dynamics IMU board with idea of how hall effect sensors would be mounted on wheel hub/unsprung assembly

• in-line brake pressure sensors (2)

  • one pressure sensor per banjo-bolt connection

  • would be on the calipers on themselves

  • usage: lets us check for brake failure real-time, also to check pressure within system and tune brake bias

  • what about knowing pressure loss over length in brake lines thru 2 sensors?

    • could look into more into it; might be more useful than comparing left to right

    • originally this was the plan → was integrated into pedal board originally

    • would let us know if there is a brake line leaking if there is a significant pressure difference

    • can check in code the brake pressure and display an error; can check pedal displacement vs how much you are actually braking to see if something is wrong

    • 1st purpose for sensor: to see if brake line leaking

      • though can eyeball this technically and the driver can feel the difference

    • 2nd purpose for sensor: would help determine if we are getting the brake bias we want and adjust from there

      • Dynamics too look into/double check if our understanding of how to adjust brake bias is correct

    • 2 sensors total: one on one of the front wheel; one on the back wheel

      • don’t need one on each front wheel b/c if one changes pressure in the front then the other front one will also change

      • the sensor has to be part of the brake lining itself; will be part of the caliper itself

• IMU on each upright / tarm and the frame (4)

  • usage: imu’s on upright let us see the real bump forces that unsprung experiences whereas one on frame lets us see bump force on frame, can prolly work out like some suspension/shock stuff from differences in forces from wheels to frame

  • see the way the inner vs outer wheels angle changes when turning to evaluate ackerman

  • would be a main thing to do evaluate our sus and mostly for next next gen

  • frame one would be validating sus kinematics

  • IMU on the frame to help see this; yaw and roll rate; can then adjust sus characteristics to get closer to our goal kinematics

  • IMU would allow to see acceleration in x,y,z directions

  • current dynamics board also includes gyroscope so IMU on frame would work

    • IMU for the car itself

    • would help to determine what slope/angle the car is on

    • could be on the bellypan/frame itself

    • can help us tell what incline we are on and see how we can optimize

    • know what current max incline the car can get over; would be a next next gen thing to optimize and get over a steeper incline ---> could make a FBD

    • this IMU can be the same as above described IMU (the one that would help us with roll,yaw, and spring rates)

    • 3 on wheels (2 upright; 1 on trailing arm); 1 on frame/bellypan

    • this sensor would help us with pose of the car

      • this could be very useful for knowing where you are at physically → for helping know stuff on the electrical side

      • IMU on the frame would help us determine forces on the frame itself vs bump force at the wheels

      • could also help us determine ride/natural frequency of the frame

      • wheels move independently of the frame hence reason for wanting an additional IMU on the frame

• real-time wheel pressure (3) AND temp sensor (3)

  • screws into valves for rims

  • usage: lets us check for flats and ensures we are operating within pressures

  • Would these be wireless? Otherwise, it could get interesting.

    • HAS to be wireless basically

  • right now have wireless wheel pressure sensors

    • need to check the current model selected doesn’t interfere with unsprung assembly

    • model might not exist but data sheet and in person exist

    • current TPMS sensor doesn’t have proof of concept yet so this could change

    • temp sensor helps us find where our contact patch is + could help us determine ideal steering characteristics

      • could do a temp camera on drive days

      • multiple temp sensors on wheel would be hard on the electrical side

        • this can be lower priority sensor for now

• Strain Sensors in CAs and TA?

  • would also validate our hand calcs and see deflection

  • mounting on the upright, etc. ?

  • EV has strain gauge on pushrod → can determine how much force and displacement we are experiencing

    • this would be complex and would need multiple strain gauges

    • also would need to validate if strain gauge is accurate

    • could just put CA on instrom and test there

    • this even if not on the car would still need a board

  • overall don’t really need this sensor; more helpful for next next gen; would only want it on one wheel to validate forces going into one CA; would need strain gauge for all rods

    • wouldn’t really help us change anything on the current car; no need to make high priority

    • for these reasons; place this as low priority (way down the line; axe it/ignore for now)

Steering:

• Wheel angle sensor (rotary pot?) (maybe a rot encoder) (1)

  • Measures rotation of steering column during cornering

  • Helps with evaluating driver inputs and steering characteristics such as over/understeer by combining with throttle and brake traces

  • can determine whether oversteer is induced by too much throttle or if its bc of weight shift or smth

  • measure rack travel for relevant shock travel - for measuring bump steer

  • potential for checking our Ackermann

  • Pablo looked into this a while ago and someone else; Pablo was looking into using a hall effect sensor instead

    • Pablo found a paper about this a while ago –> can send in chat later

      • could instead use a rot pot instead of hall effect sensors; might be easier; electrical will look into more

    • How would hall effect sensor work in this case?

      • Pablo presented this a while ago and mentioned hard to find an elegant solution for this

      • will come back to this in our follow up meeting

    • what position/units does dynamics want?

      • degrees; ideal precision would be 1 deg

      • can measure rack travel from this sensor too

    • 2nd Sensor Idea from Cesar (more of a thing that could be helpful for next next gen design)

      • some angular displacement sensor to measure the angular twist of the CF steering shaft; if we have the CF shaft properties from rockwest (might be hard since might not be super accurate); then we can use this strain to measure the torsion and typical torque the steering wheel/shafts are experiencing

Suspension:

• Shock travel (3 - one for each wheel) (lin pots)

  • Measure how much travel we actually use

  • Can validate ride frequency and also useful for fatigue failure calcs

  • If we have coil shocks, calculate force on each wheel along with load transfer

  • Dynamics will have to design mounting for this sensor

  • EV has lin pots on their shocks

    • could 3D print mounts for sensors like IC and EV did

    • would size lin pot depending on length of compressed shock; how much we fully compress → not sure if its possible for lin pot to be both shorter than shortest shock travel and longer than longest shock travel

      • if that’s the case would have to pivot to strain gauges on the pushrod

        • would give force on pushrod and therefore the shock but bell crank involved

        • would give us a force reading

        • Dynamics would have to characterize our shocks (if we go with air)

          • shock travel, strain gauges → on the instrom to characterize

        • Dynamics:

          • have max compression and extension of shock

          • knowing our max travel would be ideal

          • not sure if bump stops are in CAD yet

          • bump stops in CAD would be good → would allow final chosen length of lin pot, etc.

          • we need to finalize actual shock selection

• Force sensors (if we run air shocks)(idk if these exist lowk)

  • To calculate load transfer in braking and turning, validates vehicle calcs and helps

  • both of these would help validate hand calcs and our goal sus kinematics

  • consider where we would mount these

  • maybe bit more of a next next gen thing that would help

  • not super super high priority but would be nice to have; especially helpful for next next gen design

  • would not need this if we use coil shocks; otherwise implementation might be weird

  • IMU sensors discussed above could help a little bit but not a lot b/c would give location of upright but not more than that

• Electrical might want a ride height sensor (1)

  • this would let them know if the car is on jacks

  • would let them do a software limiter

  • nice thing to have as well

  • ride height for us would also be nice – would help us validate sus kinematics and tuning

  • probably ultrasonic

  • would measure distance of bottom of car to the ground

  • would be easier to just have this versus finding the difference from the IMUs on the electrical side

  • would allow electrical to know when on the jacks; etc.

    • really easy way to determine in code: just see if wheel is spinning a lot then probably on jacks

  • could use this to find load transfer front and back perhaps on the dynamics side?

    • IMUs can do this for us

    • otherwise we can validate we pass regs for ride height

    • but we can just use a measuring tape for this lol