11 Replies Latest reply on Jan 20, 2013 6:38 PM by Hari Padmanabhan

    replicate a Hydraulic cylinder in motion

    Jim Steinmeyer

      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

        • Re: replicate a Hydraulic cylinder in motion
          Jerry Steiger

          Jim,

           

          Bummer that you haven't gotten any help yet. About all I know is that you've got SW Premium.

           

          Have you tried the SW Tutorials under Help/SW Tutorials/Design Analysis/SolidWorks Motion?

           

          It seems like putting a linear motor between the hydraulic cylinder and rod would be the right thing to do.

           

          You might try searching in SW Help for "linear motor".

           

          Jerry S.

          • Re: replicate a Hydraulic cylinder in motion
            Gregory Goetsch

            Jim,

             

            Found a relevant tutorial on YouTube, you should be able to figure it out from the visual information.

             

            http://www.youtube.com/watch?v=_MQnfGDpqpY

             

            Greg

            • Re: replicate a Hydraulic cylinder in motion
              Hari Padmanabhan

              Hello Jim,

              I briefly looked at your model and try to add a motion and some parts were not behaving properly. One of the first things I do when you use flexible sub-assemblies is to make sure no part in the flexible sub-assembly is connected to ground (any planes like Front Plane, etc.).  The new mates were created between the parts they connect. That way if one part moves the other will follow and not be tied to the ground.

               

              I made the following corrections and I was able to create a simple motion using the linear motion function. I'm using windows 8 and I'm not able to add file or video I made to this post. Will try to add it when I can.

               

              mates.png

               

              To get a more realistic behavior like the hydraulic cylinder you need to create a force using a result dependent function. What is the maximum hydraulic force you think this actuator can generate?

               

              Once I have this information, I will send you a file with some instructions.

               

              Hari

                • Re: replicate a Hydraulic cylinder in motion
                  Jim Steinmeyer

                  Hari,

                  Thank you, the cylinder is 4" with a 1.25" shaft and will be using 3000psi hydraulics so the projected force would be 34,000 pounds force in the retract direction. There is a small segment on the bottom side of the beam being flipped that I was goind to place a 1250 pound force down on to simulate the weight of the weldment. I am now going through the you tube video mentioned above. It will be interesting to see if I can replicate your results when I am finished.

                   

                  Thank you

                   

                  edit, ok the language barror (sp) is a little difficult but I think I see what I need to do.

                    • Re: replicate a Hydraulic cylinder in motion
                      Jim Steinmeyer

                      Humm,

                      I see from the picture, and then opening my zip folder that not all of the assembly survived the pack-n-go. I wonder why that is?

                       

                      I will have to get everything back together andimbed a movie once I have it working.

                      • Re: replicate a Hydraulic cylinder in motion
                        Hari Padmanabhan

                        Hello Jim,

                        Thanks for the hydraulic pressure data. One last input I need is what is the maximum velocity you want to achieve. Or in how much time should it go from say one position to the final position.

                        Thanks.

                        Hari

                          • Re: replicate a Hydraulic cylinder in motion
                            Jim Steinmeyer

                            Hari,

                            I think the operative word here is slow. While i am sure things can go a lot faster safely, I think the end users will be more comfortable if the cycle takes from 10 to 15 seconds or longer. That is something else I need to learn how to control is the velocity of the motion. Are you aware of any good training books for motion?

                             

                            Thank you

                              • Re: replicate a Hydraulic cylinder in motion
                                Hari Padmanabhan

                                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

                                  • Re: replicate a Hydraulic cylinder in motion
                                    Jim Steinmeyer

                                    Hari,

                                    Many thanks for the time and effort you have done on this project. I have been busy on other tasks and am just getting back to this. I will attempt to learn how this is done following what you did. As I am an independant contractor working part time going to classes is out of the question for me. would it be possible to purchase the SolidWorks training manuals and files without attending the classes? Also my ultimate goal would be to use Simmulation to size the pins and linkages in this system. Would both Motion and Simmulation be covered in the same training material? I do have FEA background from school and using Algor but have used nothing for a few years and need to learn the new software.

                                     

                                    Again many thanks for your assistance.