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FSAE BPSD Design

Posted: Tue Jun 14, 2022 7:38 am
by NormanAlphaspeed
Hey guys, I'm sponsoring a few FSAE teams and I'm thinking about helping them with the BPSD (Brake System Plausibility Device), a device with NO PROGRAMMABLE CIRCUITS that can detect some rules which I will state up next. Since that could be an actual safety product to be sold to more teams with proper documentation.

First off, there's something called a BSE, Brake System Encoder, which is a fancy acronym for a brake pressure or brake pedal position sensor. This must be fed to the control unit that controls throttle (through Analog or CAN, in our case it'll be CAN since the 4chan is already out of analog inputs), but it must also go the BPSD

The rules are as follows:
The BSPD must monitor for the following conditions:
a. Both of the following for more than one second:
• Hard braking (for example >0.8 g deceleration but without locking the wheels)
• Throttle greater than 10% open
b. Loss of signal from the braking sensor(s) for more than 100 msec
c. Loss of signal from the throttle sensor(s) for more than 100 msec
d. Removal of power from the BSPD circuit
IC.4.8.4 When any of the above conditions exist, the BSPD must Open the Shutdown Circuit IC.9.2.2
IC.4.8.5 The BSPD must only be reset by cycling the Primary Master Switch IC.9.3 OFF and ON

A, B, and C are somewhat easy. I already have a basic design which I'm pretty sure will work, using a few comparators (for "hard braking" and TPS), an AND and two OR's, which should take care for A, B and C.

To tackle D, the device needs to boot up the output when it turns on (and all conditions are OK), and power it off when unpowered, which I'm not too sure on how to do (not an electrical engineer here)

IC 4.8.4 is handled by the main output so that's fine

My big conundrum is with IC4.8.5, having the output NOT change when conditions are back to normal, only on power down. I assume that would need a flip flop on the output, but I have basically forgotten everything I ever learned about flip flops lol, so

What do? I have attached a base design which I'm basing myself off (this design is for an Electric FSAE, which can reset on it's own and the timing is different on the shutdowns [500msec instead of 100msec, but that's just recalculating the RC circuit which I already did]), but I have no idea how to latch the output to stay off until power down while ignoring any change in state of the inputs. Halp pls
FSAE Electric BPSD
FSAE Electric BPSD
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My BPSD for IC
My BPSD for IC
image.png (90.83 KiB) Viewed 11531 times

Re: FSAE BPSD Design

Posted: Fri Jul 01, 2022 7:18 am
by NormanAlphaspeed
https://www.fsaeonline.com/cdsweb/rqa/ViewFAQ.aspx?faqnum=106

Here's a question that might/might not have to do witha quesiton asked previous about using FPGA's

Also,
GR.2.5 Violations on Intent
The violation of the intent of a rule will be considered a violation of the rule itself.

I think this one covers using an FPGA or anything that isn't a simple electrical circuit.

I just wonder if using pots passes as "programmable"

Re: FSAE BPSD Design

Posted: Mon Jul 25, 2022 8:57 am
by rubmack
Hi Norman,
this is an interesting idea. Attached you will find a design, that i did for FSAE 2017. It passed inspection and worked pretty well, i think. Maybe it can provide some ideas for your design.

image.png
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image.png
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Regarding the pots. This device used potentiometers as well and it was no problem during inspection. But that does not prove the compliance.

I think i had to modifiy the inputs of the RS-Flip Flop a little bit, but i dont remember the modification.

The idea behind the counter as the timing device (and not a RC curcuit) was, that i wanted the device to fully reset immediately after the error disappears.

Best regards
Marcel

Re: FSAE BPSD Design

Posted: Wed Jul 27, 2022 7:46 pm
by NormanAlphaspeed
Thanks a ton for your input!

My only question about what you said about using a counter, is that I think the BPSD has to stay latched if an error occurs,
image.png
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as IC4.8.5 states. Besides that everything else is a great help!

Re: FSAE BPSD Design

Posted: Sat Jan 21, 2023 2:49 am
by m8r
I think our design for this year's FSAE is pretty clever. Also, I think we may be the only team using microRusEFI. It would be cool for the last few years of IC if more FSAE teams started using it instead of the other locked-down/expensive engine management solutions that exist.
image.png
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hasn't passed inspection yet, but it fulfills all the rules requirements, and even the latching requirement.

Re: FSAE BPSD Design

Posted: Sat Jan 21, 2023 3:02 am
by AndreyB
m8r wrote:
Sat Jan 21, 2023 2:49 am
I think we may be the only team using microRusEFI.
Please please please provide way more details in a separate thread :)