Choosing kinematics software?

[EdDanzer]

We are doing more product design utilizing hydraulic cylinders to drive structures that must be light weight and robust. I have used Working Model and COSMOSMotion both, neither have a way to input acceleration rate, deceleration rate, maximum velocity and force into one element to simulate a simple linear actuator.
What is the best software to do this type of kinematics with so the pin forces and direction can be accurately be input in to the FEA model?

 

[rb1957]

I don't use it myself, but I've heard good things about ADAMS (an MSC product, I think)

 

[GregLocock]

I think you may be expecting too much. I could do what you describe in ADAMS, but would use more than one component, by choice. Similarly, I could do it in in WM3D, and again, I'd use more than one element.

It might be possible to abstract the performance of the actuator down to one equation, but I'd rather try and model the processes that cause the non linearities.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GBor]

EdDanzer,

Are you saying that within your complex model of multiple lines, plates etc, that you are trying to apply the accelerations/decelerations, velocities, etc. to a single element? If so, although I don't use the programs you mentioned, I would think they would still be able to do it...you may just have to be a little creative. It wouldn't be a purely kinematic analysis...more like an event simulation, but I'm not sure I understand your real question.

The accelerations, decelerations, and velocities would be determined by a single input curve as either a displacement vs. time curve using prescribed displacements or some derivation of this curve using other input types.

I'm not sure what you are doing with the "Force"...are you trying to drive the cylinder using the forces but still apply the velocities and accelerations?

Sounds like an interesting problem...at least what I understand of it.

 

[GregLocock]

Just tinking about it you can do it in working model, but it is a bit ugly.

I can't remember the syntax for the arguments, but basically if you want to do it in a single component you need to build a single line expression for the force output of the actuator.

Here's what I would do in Working Model: simple force actuator, in parallel with a damper, to give your friction and speed limits, all in series with a mass, to govern your acceleration. If deceleration is via a different mechanism then just put in a whole second block similar to the above, in parallel.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[EdDanzer]

Greg,
I have not looked at Working Model since 2002. At that time the acceleration rate was relative to the force value of the actuator. A low input force gave a low acceleration rate and a large force gave a high acceleration rate.
I used a 4” bore cylinder at 1000 psi, and at 15,000 psi in one example. At 15,000 psi the acceleration rate used required over 1000 hp. This gave bogus pin and contact forces so it took many steps and some hand calculations to have meaningful data.

GBor,
I’m not trying to do complex simulations. Any simulation should represent real world features. To simulate movement of a linear or rotary actuator and see the results of its interaction with the components it interacts with it is mandatory to provide a maximum acceleration rate, acceleration force, maximum velocity, maximum force available, deceleration rate and deceleration force. Many times these values are relative to the power available to drive the system and simple to define.
Hydraulic cylinders driving arms on an excavator are one example. The lift or dig force is relative to boom position and working pressure. The speed is flow driven, and the acceleration is engine power driven.

Has anyone used SimHydraulics™?

 

[cbrn]

Hi,
I seem to remember that you can do that with CosmosMotion by using ADAMS' arguments & functions in the "motion generator" (CM's kernel is the simplification of ADAMS', but it accepts the same "language"). Btw, the latest versions of CM have probably improved a lot under this point of view. I can't be more specific because the last version of CW I saw was 2004...

Regards

 

[gfbotha]

My vote goes for Working Model. But, it is not going to be a straight forward task, as Greg pointed out. (Most of my experience lies in WM2D - quick and it allows me to evaluate conceptual layouts even before 3D CAD details exist - granted that 3D effects are not important).

It is likely that you will have to scratch your head and enter formulas/expressions and not simply values when defining your actuators. To handle limits you could make use of conditional formulas or make use of the "if" statement. There is also an "Active when..." option when specifying actuators.

But, of course, having sorted this out once, it will be easier for subsequent simulations.

Regards

 

[GregLocock]

I haven't used ADAMS/Hydraulics, but I really find it hard to believe it does not cover this in exhaustive detail. A quick look at the Help file reveals the following topics

Connecting Hydraulic Ports
Creating Components
Accumulator
Cartridge Valve3p
Valve2
Check Valve3p
Check Valve4p
Counter Balance Valve4p
Cylinder1
Cylinder1f
Cylinder2
Cylinder2ff
Directional Control Valve2w2
Directional Control Valve3w2
Directional Control Valve4w3
Flow Control Valve2
Flow Source
Fluid
Force Source
Generic Pump/Motor2
Generic Junction2
Generic Junction3
Generic Junction4
Laminar Orifice
Mass1
Orifice
Pipe 1
Pipe 2ff
Pipe 2pf
Pipe 2pp
Pressure-Reducing Valve3
Pressure Relief Valve2
Pressure Source
Pump/Motor3
Reservoir2
Restrictor Valve2
Servovalve4w3
Shuttlevalve3
Spline Orifice
Sum of Flows
Sum of Flows2
Sum of Flows3
Sum of Flows4
Tank
Disconnecting all Hydraulic Ports
Disconnecting a Single Port
Hydraulics Copy
Hydraulics Default Set
Hydraulics Delete
Hydraulics Rename
Hydraulics Reorient
Modifying Components
Accumulator
Cartridge Valve3p
Check Valve2
Check Valve3p
Check Valve4p
Counter Balance Valve4p
Cylinder1
Cylinder1f
Cylinder2
Cylinder2ff
Directional Control Valve2w2
Directional Control Valve3w2
Directional Control Valve4w3
Flow Control Valve2
Flow Source
Fluid
Force Source
Generic Pump/Motor2
Generic Junction2
Generic Junction3
Generic Junction4
Laminar Orifice
Mass1
Orifice
Pipe 1
Pipe 2ff
Pipe 2pf
Pipe 2pp
Pressure-Reducing Valve3
Pressure Relief Valve2
Pressure Source
Pump/Motor3
Reservoir2
Restrictor Valve2
Servovalve4w3
Shuttlevalve3
Spline Orifice
Sum of Flows
Sum of Flows2
Sum of Flows3
Sum of Flows4
Tank




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[EdDanzer]

Adams/Hydraulics is not in COSMOSMotion. They do not have any accurate way to define a linear actuator. The only force options are a Springs, Dampers, Bushings, Action Only and Action/Reaction.

 

[GBor]

Can you use a thermal expansion to cause the force?

 

[EdDanzer]

The concern with thermal expansion would be rate and distance. Some cylinders move at 3ft/1m per second but most move less than 60ft/18.3m per minute. Strokes go up to 40ft/12m or more.

 

[GregLocock]

OK, so what are you going to do? It sounds like the problem is solvable in the right software, but not necessarily in COSMOSMotion.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[EdDanzer]

I have sent some information to Algor and am waiting for a response. I’m waiting for a call from Mathworks about a demo. Mathworks stuff is less money than Algor but can do other things. Mathworks does not tie into CosmosWorks so data will have to be manually input so the results won’t be as good as Algor.
I have contacted CosmosWorks again about a time line commitment for a simple solution but no answer.

Today it Sucks to be me!

 

[fkmeyers]

Have you looked at FEDEM?

 

[GBor]

Ed,

Who did you contact at Algor?

Garland

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[EdDanzer]

Fkmeyers,
I will look at FEDEM since I’m not familiar with it.

GBor,
The sales guy is Ed Simmons, and I can’t remember the technical guys name.

 

[GregLocock]

Had a play in WM. I built a system that would do what you asked, more or less.

Link a pair of coords by a rigid joint on a slot. join them with a linear actuator. Change it to a force type. Enter your raw force expression. Add a mass to the moving end, to limit the max accel. Add a spring between the same two coords. 0 the k part, change the damping element to limit the max speed.

It would be easy to build a pump block to create a pressure vs flow rate source, and use that pressure to drive the force actuator.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[cbrn]

Hi,
it seems like a great solution, GregLocock.
I don't have understood very well if the O.P. is already using something of the CosmosWorks family, since the very same solution you describe can be very easily done in CosmosMotion, if he needs.

Regards

 

[GregLocock]

I also added a pure friction term... and discovered why you never do that.

The seal/ring friction in a shock absorber is of the order of 300N, so I added a force actuator which supplied a force of

300*(1-2*(shock.v.x<0))

As you can imagine it never stops moving, it just jitters around the equilibrium position. Real systems don't do that, I need to think of a better way of modeling friction. Funny though.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.