# Catia motion simulation with laws

#### podliy16

##### New member
Hi guys.

I have following mechanism:

It's rotating crank around fixed block. I'm trying add some "physics" to this simulation. My crank should speed up when it falling(1nd zone), and slow down when it's "climbing" up(2nd zone), due to the law of gravity. How I can implement this in catia v5? Right now I can implement only constant acceleration/deceleration, independent from crank position.

I did it like:
Angle of crank = AngleSpeed * Mechanism.1\KINTime
AngleSpeed(Custom parameter) = InitialSpeed + (AngleAcc * Mechanism.1\KINTime) / 1s
InitialSpeed = 10turn_mn
AngleAcc = -1turn_mn

And I got constantly decelerating crank. The main problem: I can't reference current crank angle in this computation, because I'm getting a cycle in formulas. Something like this:
Angle of crank = ... + Angle of crank + ...

One of possible solutions -- calculate current position via time of simulation, but it's very difficult(or I only think so?).

I can't find any good tutorials for this laws, so I totally upset. Maybe solution is close enough but I'm so tired and stupid so I can't find it.

Sorry for my English, thanks for any help.

#### bigbomber

##### New member
Hi
you've achieved 90% of what you want. the remain will be down by "knowledgeware/ knowledge Advisor".
Knowledge Advisor is a workbench of CATIA which you can Create laws and conditions (If.. then ...) for Parameters and relations.
you can use this workbench and via a condition determine when speed should be increased and when when decrease.