The purpose of this project was to first learn how to use then determine the usefulness of a virtual prototypeing software called Working Model 3D. The software itself was purchased by Grand Valley State University and was used by myself at an off site location for evaluation.
Learning the Software:
I started by running through the different tutorials that came with the software. This gave me a basic feel for what the interface was like. Haveing worked with Working Model 2D I was somewhat familiar with what the software was ment to do however the way in which it was done was quite different. All commands are carried out through the toolbar or the menu bar. The tool bar holds all of the basic tools needed to create objects, join them together and change the "camera" or view angle of the simulation. Below is the same simulation as above viewed from a different angle:
It took several days to learn how to create a system that would work
together to simulate what was desired.
The hardest part about createing a simulation was in the joining of the different elements. They are done useing the "create cord" command. The cord is used to create places where joints can be created. I found it quite difficult to place them onto an object in a way that would allow easy joining. I found that the easiest way was to create the entire simulation from a world coordinate stand point and simply key in the cooridantes for the cords to assure that they would be placed in the appropriate places. An alternative to creating the simulation in Working Model was to create it in a third party solids modeler and then inport the geometries into Working Model. This feature will be disucussed further at a later point.
I also found the the orientation of the objects themselves to be somewhat cumbersome. However, again using the world coordiante system it made this task much easier.
Most everything that was created operates much the same way as working model 2D, and was otherwise fairly easy to put together.
The hardest part I found on building the simulations was in orienting the simulation in such a way that the object being created was placed in the appropriate possition relative to the other objects in the simulation. As can be seen from the two images below that depending on your perspective the simulation changes.
This difficulty was best remidied by using the world coordate system
and keying in the desired placement.
For this project I simulated a material handleing system, that can be seen below. This was accomplished by extrudeing several cylinders lineing them up in a row and attatching motors with a constant velocity to the ends. This served as a type of converyor system to move the material along a linear path and up inclines. For any motion required in the downward direction I used incline polygons with low coeficients of friction to simulate gravity conveyors.
One of the biggest advantages of Working Model 3D is it's ablilty to use 3 dimensional space:
Due to the nature of the simulations even a simple simulation can take a very long time. The above simulation was performed on a 233MHz Pentium with 64 meg of RAM and it still took over an hour and a half to run completely. It is for this reason that a video export function was built into Working Model 3D. This allows the simulation to be exported in an avi format for viewing with an external video viewer. The advantage is that in a presentation or demonstration of a simulation it simply take too much time to effectively demostrate what the simulation is designed to do. However, if the simulation is ran previously and saved to as a video file it can be shown in real time to demonstrate the functionality of the simulation. Here is the AVI file for the simulation, if it is played you can see that the simulation takes a matter of seconds to run rather than a matter of hours as the simulation requires.
Just as in Working Model 2D forces on all the bodies as well as torques, velocities and possitions can be measured at any point on the body. The nice part about Working Model 3D is that a particular area can be zoomed in on so a very small element of a body can be measure for force analysis. For instance if a particular stress consentration has been determined to exist at a certain point, that point can be singled out and the stress can be measure.
Prototype of Geometry
This can be a very important feature of Working Model 3D. I found it to be usefull in the simulation that is shown above, especially in the area where the box moves up the incline. I found that with too steep an incline the boxes would simply not have enough friction to be moved up the incline. Even after I reduced the angle of the incline the box had a hard time moveing up as well. I then reduced the spaceing between the rollers to afford additional points of contact to increase friction. Below is an image of the simulation.
The biggest disadvantage of the software I found was the processing requirments for simulations of any size. For the material handeling system described above I was useing a 233MHz Pentium II with 64 megs of RAM, and to run the simulation through from the begining to the start of the incline rollers took approximately 1.5 hours, and the reason I only ran it to the begining of the incline was that the simulation crashed. An error said the reason was that the it was out of memory. I never was able to run the simulation through completely from begining to end. My hopes were to have it run several times in a loop, but due to the lack of computeing powere I was unable to do this. It's my understanding that this is also a problem with other virtual prototypeing packages such as Pro-
Solid Modeling Import
Although being able to import from a solidis modeling package does help in the creating of the solids, they don't aid much in the actual building of the system. Once a set of solids is inported they must be joined one at a time which is time consumeing and requires the orientation of the solids to be broken up.
As stated above the simulations are dependent on processeing power, a subset of this then is the complexity of simulations that can be achieved with Working Model 3D. Simulaitons must be kept relatively small, less than 100 entities, and moveing entities must also be kept to a minimum as well. A good alternative would be to divide a simulation up into component parts and run smaller more simple simualtions than one single large simulation.
Overall Working Model 3D was relatively easy to use and can be quickly learned, and as any other software package the more it's used the easier it is to use. It's interface aided in the speed of construction and allowed easy navigation around the 3 dimensional space of the simulation.
It's usefulness is self evident in that it can greatly reduce the amount of time to prototype a new system as well is the amount of money due to the fact that the system can be prototyped virtually before it is actually built.
The single largest downfall that I experienced was that if this software were to be used within a company where "time is money" a very high end machine would have to be purchased along with the software and with a ticket price of approximately $5,000 for the software purchaseing may not be real excited about dropping another $3,500 on a computer.