MechDesigner Reference & User Interface > 2.2 Mechanism-Editor: > Modelling Function-Blocks

Why should I use a Polynomial-Fit FB?

With Inverse-Kinematics, your motion-design (that you design with MotionDesigner) is defined for a Tool/End-Effector. Then, typically, you add more parts, which you join to the Tool-Part, to create a more complex kinematic-chain. Finally, you use a servo-motor to drive a part that in the kinematic-chain, that has a different motion to the Tool-Part.

To plot the motion for the servo-motor you can use a Measurement FB, add a Graph FB, and then export a list of positional data-points for the servo-controller.

While this is often satisfactory, it is often preferable to give the servo-controller a series of polynomials rather than a list of data-points.

The output from the Polynomial Fit FB is the best-fit motion to the data at its input-connector, but defined as a series of 5th order Polynomials.

You can export the Polynomials directly to MotionDesigner. In MotionDesigner, you can further manipulate the Polynomials, as required.

Add Polynomial-Fit FB

What to do :

STEP 1:Add a Polynomial-Fit FB to the graphic-area

1.Click Add menu > Add Polynomial-Fit FB

1.Click Modeling FB toolbar > Add Polynomial-Fit FB

Then:

2.Click the graphic-area

The Polynomial-Fit FB is now in the graphic-area

MD-GA-PolyFitFB

STEP 2:Connect a wire to its input-connector.

1.Drag a wire from a different FB to the input-connector of the Polynomial-Fit FB

A wire is now connected to the input-connector of the Polynomial-Fit FB.

STEP 3.Open the Polynomial-Fit dialog:

1.Double-click a Polynomial-Fit FB in the graphic-area

1.See How to Open a dialog

The Polynomial-Fit dialog is now open.

STEP 4:See Polynomial Fit dialog

Notes:

Wires that connect Function-Blocks have 3 Data-Channels (in most cases).

The three(3) Data-Channels are usually:

•Position, Velocity, and Acceleration, or

•Total Force, Force X, and Force Y

See Data-Channels for more information.