I am placing this in the general forum as i have not recieved any responces on the Motion forum, maybe I didn't ask the question right.

I have an assembly (basicly a 4 bar linkage) to flip an object. it is hydraulicly opperated and I would like to evaluate it with Motion and then use those results in Simulation. Unfortunately I am not sure how to replicate the hydralic cylinder.

I have attempted to use a spring in the place of the cylinder as well as a force vector but I wasn;t able to get the force vector acting in the direction I wanted. I have been thinking about using a motor at the location where the linkage arm the cylinder mounts to is pinned but am not sure that is correct. I only found one tutorial for motion is SW and it left as many questions as answers.

Does anyone have any suggestions as to how to approach this? I have SW Professional ( or Premium, which ever is the top level with full blown motion and simulation) and am using 2012.

Lacking suggestions, does anyone know of better tutorials or a good book dealing with motion and simulation? i am not opposed to working for the solution, i just want an idea where to start.

Thank you

Jim S

Jim, Happy New Year!!! I'm back from vacation and I have attached the model which has the hydraulic motor defined (See simple assembly a new MP5-3755.sldasm). These are the steps I followed:

a. Added a suppressed linear motor between the piston and cylinder. (LinearMotor1)

The idea behind suppressing is that we are going to use this as a sensor. There is a hidden functionality in Motion where you can still get displacement and velocity infomation from these suppressed motors. So in our case we are going to track the velocity of this motor so that the force we apply in a later step to mimic a hydraulic motor can adjust it's force input to honor a set velocity.

b. Created a result plot to track the linear velocity in x-direction (local) for the suppressed motor. (Plot1

The idea here is to use this in the force definition to create our hydrualic motor definition.

c. Create an action reaction force (action on the face of the piston and reaction on the face of the cylinder) using the following expression. (Force1)

30000*IF(STEP(TIME,0,0,.2,4)-{Linear Velocity1}:-1,0,1)*(STEP(ABS(STEP(TIME,0,0,.2,4)-{Linear Velocity1}),0,0,0.1,1))

30000 - This is the maximum force the hydraulic cylinder can generate

{Linear Velocity1} - That is the plot created from step b.

in the STEP function, 0.2 (used in two places) is the time it takes for the hydraulic cylinder to go from zero force to maximum force.

In the STEP function, 4 (used in two places) is the maximum speed the hydraulic cylinder needs to reach. In our example it is 4 inch./second. Feel free to change this to suit the speed of your mechanism.

So in a nutshell this function is going from 0 to 30000 lbs or less in 0.2 seconds until it tries to meet the 4 in/sec speed. After 0.2 seconds it is going to track the velocity of the piston and cylinder and try to adjust the force (+ or -ve) to keep the 4 in/sec. The last part of the STEP function ....Velocity1}),0,0,0.1,1)) tells the software to add or subract force within 0.1 seconds.

d. I created two other motion features Gravity and Force2 just to test a few things and it is not important for the problem you are trying to solve.

I have attached the 2012 files and let me know if this makes sense. If you haven't used motion result dependent functions, then also look at the the motion help for IF function to get an idea on how it works. Basically the IF function evaluates a number and can take three arguements; arguement 1 if the number is -ve, arguement 2 if the number is equal to zero, arguement 3 if the number is +ve).

Apologies if I cannot answer everthing more clearly. Feel free to post your questions here for further clarification.

Regards, Hari