Thoughts on crank angle sensing

[Peter Wales]

>I've been thinking about high resolution crank angle sensors lately..what does
>anyone think about the following ideas?
>
>First, I want to get away from doing all the work in the CPU (reducing load
>on the CPU)..but, I still want a measurement of maximum torque angle, position,
>and overall velocity.
>
>Position is simple..the usual missing pulse detector will pick it out. And
>then position itself can be handled by cleaning up a high resolution crank
>angle sensor (200+ teeth) and sending the pulse train to a counter..the
>missing pulse detector triggers the reset. This provides an instantaneous
>angle position by simply reading the counter.

Yes, if you can get a 200 tooth wheel.

>
>To get to velocity, I think a better way to go is to feed the pulse train
>into a simple phase locked loop circuit, which will calculate the derivative
>AND have the advantage of cleaning noise off the signal by altering the
>characteristics of the loop filter. This will also give average torque by
>assuming the engine mass is constant.

How about using a counter reset by every tooth. Then read the number and you
have a count proportional to velocity.

>
>As for instantaneous acceleration, 

Subtract this reading from the last and get acceleration

Phase lock loops are difficult to make reliable and keeping it digital keeps
it simple.

Peter Wales
President Superchips Inc
Chairman Superchips Ltd        "Timing is everything"
Superchips home page with all the answers http://www.superchips.com