OpenVSP Linear Links

Introduction

Linear parameter linking in OpenVSP is establishing a linear relationship between any two parameters according to a scale and offset by B = A*Scale + Offset where B is the dependent variable and A is the independent or driving variable. Setting up a linear link is relatively simple. Users may choose parameters from the dropdown menus or drag-and-drop a parameter onto the Parm A or Parm B variable selections and then click the Add Link button. All linear links will be displayed under the Parm Link List header. Note that you should use Links when specific linear relationships, including equality, are needed in your model but should avoid linking every parameter by default. As with many features in OpenVSP, less is often more.

Creating or Modifying Links

Creating a linear link is very straightforward. Open the Model > Link menu and choose your A and B parameters to be linked. Recall that Parm B is the driven or dependent variable in the relationship. You may choose to set a Scale and/or Offset at the creation of the Link as well as any constraints on Parm B. Click Add Link to create the link and update the model. To modify a Link, click on the Link in the Parm Link List and then alter the relationship using the activation buttons or entry fields.

Deactivating the Scale and Offset button flags has the same effect as setting Scale = 1.0 and Offset = 0.0. You may also set upper and lower limits to the B variable from the Link window by activating the Lower and/or Upper buttons and then setting the value.

Parametric Clones

Parametric clones are essentially when components are made to be identical to another component by linking all of the Design group parameters. This can be done quite easily by choosing Groups for two matching components and clicking Link All. However, in order for this process to work, each component must have the same number and type of Groups so that the links relate directly to the parameters of the parent. This tutorial demonstrates creating clones with a Pod; a very simple example in which only the Design group parameters need to be linked to create a clone. A wing, on the other hand, requires that each component has the same number of sections, the same cross-section types, etc.

In some cases, users may wish to only link all of a certain group of parameters and allow others to remain free. In such a case, you may either pick and choose individual parameters one at a time or Link All for the chosen Group.