Engee documentation

Variable Translational Spring

Tension-compression spring with variable stiffness.

variable translational spring

Description

The Variable Translational Spring block represents a tensile-compression spring with variable stiffness. The value of the variable spring stiffness coefficient is input to the K input port. The spring stiffness value is equal to the product of the value at port K and the value of the relative linear displacement between the two non-directional ports. A minimum spring stiffness value prevents unphysical values from occurring.

The spring force value satisfies the following expression:

where

  • - is the force transmitted through the spring between the two non-directional ports;

  • - spring stiffness coefficient;

  • - minimum permissible spring stiffness coefficient;

  • - the relative displacement between the two non-directional ports, defined as ;

  • - initial spring deformation;

  • - absolute displacement of the non-directional port R;

  • - absolute displacement of the non-directional port C.

The block applies equal opposite spring forces to the two non-directional ports. The sign of the spring force acting on port R is equal to the sign of the relative linear displacement between the two ports. A positive translational velocity corresponds to a positive force acting on port R and a negative force of the same magnitude acting on port C.

Assumptions and limitations

The value of the spring stiffness coefficient must be greater than zero.

Ports

Conserving

# R — slave port
translational mechanics

Details

A non-directional progressive mechanical port connected to the positive end of a spring. The positive direction is from port R to port C.

Program usage name

rod_flange

# C — base port
translational mechanics

Details

A non-directional progressive mechanical port connected to the negative end of a spring. The positive direction is from port R to port C.

Program usage name

case_flange

Input

# K — variable spring stiffness
scalar

Details

Variable coefficient of spring stiffness.

Data types

Float64.
Complex numbers support

No

Parameters

Parameters

# Minimum spring rate — minimum spring stiffness factor
N/m | lbf/ft | lbf/in

Details

The minimum permissible spring stiffness coefficient. If the stiffness value at port K is less than this value, it is equated to it. The value of this parameter must be greater than zero.

Units

N/m | lbf/ft | lbf/in
Default value

1.0 N/m
Program usage name

k_min
Evaluatable

Yes