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Multisegment Spring |
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The spring allows you to connect two parts together using a standard damped spring that you can find described in any physics textbook. The mathematical description for this system is shown in equation 1.
K is the stiffness of the spring. Delta x is the displacement of the spring from its resting length. B is the damping coefficient, and v is the velocity of the mass. So the spring exerts a force that is proportional to the amount it is stretched or compressed. The damper produces forces proportional to how fast the mass is moving. So the faster the block tries to move, the harder the dashpot pushes back on it to resist that movement. The spring connects to other parts using attachments. The main difference between this spring and the regular spring is that this one allows you to connect the spring along multiple attachment points. This lets you simulate things like wire and rope to connect parts. You can change the stiffness and damping to emulate the properties of different types of connectors. You can also specify what type of forces the spring is to apply. The available types are compression, extension, and both. A good example of using these properties to simulate types of connectors is using rope. If you connect rope to something and pull on it a pulling force will be transfered to the connected object, but if you push on the rope then it will slacken and no pushing forces will be applied. You can set the stiffness and damping to the values of your rope and then use extension only forces. If you connect the parts using a stiff spring or a rod then both types of forces will be generated. You can do this using a large stiffness with both types of forces. Springs can be enabled or disabled. You can set this feature directly using the Enable property. You can also do it by applying an enabler stimulus to enable and disable the spring for specific periods of time. Another way to control whether a spring is enabled is by using neural control. The default input into a spring controls whether it is enabled. Any input into a spring above 0 will cause the setting of the enabled property to be flipped. So if the spring is initially set to be disabled and you have a positive input go into the spring it will enable it while that positive input is maintained. If Enabled is initially set to true then any input into the spring will disable the spring while the input is maintained. Another difference between the multisegmented spring and the standard one is in stability. The standard spring is an integrated part in the vortex physics engine. This spring is one that I wrote myself. Both of these provide good matches to the equations of motion predicted by the physics, but the vortex spring is simply more stable. It can operate at a faster time step than this one. I am not totally sure why this happens, but I believe it is because within a given time step vortex can dynamically change its step sizes to subdivide a time slice into smaller parts if the equations become stiff. This would let it slow down when it needed to without having to always use a slow time step. So you need to keep this in mind when choosing which of these two springs you want to use.>/p> For more information on how the spring works please see the spring page of the mechanical tests section and watch the video tutorial. Spring Properties
The color of the line drawn for this spring between the attachment points. This is only visible once attachment points have been selected. Default value: Beige Acceptable range: Any Color Damping The damping coefficient of the spring. This is B in equation 1 above. Default value: 1 Kg/s Acceptable range: 0 or greater Enabled Determines if this spring is enabled or not. If it is disabled then it is as if the spring does not exist in the simulation. Default value: True Acceptable range: True/False Force Type Determines what types of forces this spring can apply. If you select extension then it will only produce forces when the spring is extended from its natural length. When you compress it there will be no opposing forces. You can use this to simulate different properties of connectors. A good example of this is rope. If you connect rope to something and pull on it a pulling force will be transfered to the connected object, but if you push on the rope then it will slacken and no pushing forces will be applied. If you connect the parts using a stiff spring then both types of forces will be generated. Default value: Both Acceptable range: Both, Compression, Extension Maximum Tension The maximum tension that this spring can apply. Default value: 100 N Acceptable range: Any value greater than 0. Name The name of this spring. Default value: Blank Acceptable range: Any string Natural Length The natural length of the spring. When the spring is stretched or compressed away from this length a force is produce that is proportional to the spring constant. Default value: 1 m Acceptable range: Any value greater than 0. Spring Attachments This displays the attachments dialog. You can specify the order of the attachments that you want to use for the spring. The spring is attached to those points in the order in which you specify them, so if you order them badly you can get weird loops. To add a new attachment select it in the drop down and hit the add button. This will add it to the list on the right. To remove an attachment from the list select it and hit the remove button. To change the order of the items select an item and hit the up/down arrow buttons to move it.
Spring Length A read-only property that tells you how long the spring is between the two set attachment points. You can use this to determine the natural length of the spring. Stiffness The stiffness coefficient of the spring. This is K in equation 1 above. Default value: 50 kN Acceptable range: Any value greater than 0. Visible Determines if the spring is visible in the simulation or not. Default value: True Acceptable range: True/False |
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