Speed source

Forces the flange to follow the input speed, filtered by a critical frequency.

signal
rotational
Modelica Standard Library
2 ports
1 parameter

BlockSpeed sourceKindspeedSourceLibraryRotational

Description

Forces the flange to follow a reference speed, supplying whatever torque that takes. The reference is passed through a first-order filter with critical frequency f_crit, so a step in w_ref gives a finite acceleration.

Example

Clutch, backlash, and rotational sources A clutch that locks, gear backlash, a spring-damper coupling, and a load that steps its torque.

100 rad/s at 0.1 sDriveClose at 0.5 sClutchDriven 1 kg·m²Driven speedω ref 10 sin 2πtSpeed sourceBacklash 0.1 radInertia 0.01Speed behind backlash0.5 N·mTorque sourceCouplingInertia 0.02, damping 0.05Coupled speed0.4 N·mShaft loadLoad speed

In Gradara, select a Speed source block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:Constant Mechanical load Step Inertia & load Speed sensor Sine wave Spring-damper Backlash Inertia (ideal)Clutch Torque source Constant torque Speed sensor (ideal)

Ports

Inputs 1

ωw_refsignal · rad/s

Reference angular velocity, in rad/s.

Conserving terminals 1

shaftflangerotational

Driven flange.

Parameters

Filter frequencyf_crit50 Hz

≥ 0

Corner frequency of the reference filter, in Hz. Must be positive; at 0 the speed never changes.

Equations

Modelica

ω = d(flange.phi)/dt
dω/dt = 2π · f_crit · (w_ref − ω)
Initial: flange.phi = 0, ω = w_ref

Implementation

Modelica Standard Library 4.1.0Modelica.Mechanics.Rotational.Sources.Speed

MSL documentation

Assumptions and limitations

The initial angle is fixed at 0 and the initial speed at w_ref; do not also fix the initial state of an inertia rigidly attached to the flange.
Torque is unlimited: the source is ideal.

Tips

Raise f_crit for closer tracking; a very high value makes the model stiff.