Engee documentation

Variable Rotational Spring

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Pivoting spring with variable stiffness.

variable rotational spring

Description

The Variable Rotational Spring block is a rotational spring with a variable stiffness coefficient. The value of the variable stiffness ratio of the spring is input to the K input port. The spring torque value is equal to the product of the value at port K and the value of the relative angular displacement between the two non-directional rotation ports. A minimum spring stiffness value prevents unphysical values from occurring.

The spring torque satisfies the following expression:

where

  • - is the torque transmitted through the spring;

  • - spring stiffness coefficient;

  • - minimum permissible spring stiffness coefficient;

  • - is the relative angular displacement measured between two non-directional ports of rotation as follows: ;

  • - initial angular strain between two non-directional ports of rotation;

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

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

The unit applies equal opposite spring torques to the two ports of rotation. The sign of the spring torque acting on the R port is equal to the sign of the relative angular velocity. A positive relative angular velocity corresponds to a positive damping torque acting on port R and a negative damping torque 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 — rotation port
`rotational mechanics

Details

Non-directional port of rotation.

Program usage name

rod_flange

# C — rotation port
`rotational mechanics

Details

Non-directional port of rotation.

Program usage name

case_flange

Input

# K — spring stiffness
scalar

Details

The coefficient of stiffness of a spring.

Data types

Float64.
Complex numbers support

No

Parameters

Parameters

# Minimum spring rate — minimum spring stiffness factor
HP_DIN/rpm | N*m/rad | W*s/rad | m*mN/rad | HP_DIN*s/rad | ft*lbf/rad

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.

Values

HP_DIN/rpm | N*m/rad | W*s/rad | m*mN/rad | HP_DIN*s/rad | ft*lbf/rad
Default value

0.01 N*m/rad
Program usage name

k_min
Evaluatable

Yes