Modelica.Magnetic.FluxTubes.Examples.MovingCoilActuator.Components

Information

Package Content

Name	Description
PermeanceActuator	Detailed actuator model for rough magnetic design of actuator and system simulation
ConstantActuator	Simple behavioural actuator model for system simulation

Modelica.Magnetic.FluxTubes.Examples.MovingCoilActuator.Components.PermeanceActuator

Information

In the ConstantActuator model the force F is strictly proportional to the current i as indicated by the converter constant c. However, there is an additional non-linear force component in such an actuator that is due to the dependency of the coil inductance L on the armature position x. The inductance increases as the armature moves into the stator. The total force is

        1  2 dL
    F = - i  --  + c i
        2    dx

Both force components are properly considered with a simple permeance model as shown in the figures below. Figure (a) illustrates the dimensions of the axisymmetric moving coil actuator that are needed in the permeance model. Figure (b) shows partitioning into flux tubes and the permanent magnetic field without current. G_ma and G_mb both are the permeances resulting from a series connection of the permanent magnet and air gap sections. The field plot of the coil-imposed mmf is shown in figure (c) without the permanent magnetic mmf (H_cB=0). The placement of the magnetic network components in figure (d) retains the geometric structure of the actuator. In figure (e), the permeance model is restructured and thus simplified.

Parameters

Name	Description
N	Number of turns
R	Coil resistance [Ohm]
r_core	Radius of ferromagnetic stator core [m]
l_PM	Radial thickness of permanent magnet ring [m]
t	Axial length of permanent magnet ring and air gap respectively [m]
l_air	Total radial length of armature air gap [m]
l_FeOut	Radial thickness of outer back iron (for estimation of leakage permeance) [m]
Material
material	Ferromagnetic material characteristics
Armature and stopper
m_a	Mass of armature [kg]
c	Spring stiffness between impact partners [N/m]
d	Damping coefficient between impact partners [N.s/m]
x_min	Position of stopper at minimum armature position [m]
x_max	Position of stopper at maximum armature position [m]

Connectors

Name	Description
p	Electrical connector
n	Electrical connector
flange	Flange of component

Modelica.Magnetic.FluxTubes.Examples.MovingCoilActuator.Components.ConstantActuator

Information

Similar to rotational DC-Motors, the electro-mechanical energy conversion of translatory electrodynamic actuators and generators of moving coil and moving magnet type can be described with the following two converter equations:

      F = c * i
    V_i = c * v

with electrodynamic or Lorentz force F, converter constant c, current i, induced back-emf V_i and armature velocity v. The model is very similar to the well-known behavioural model of a rotational one-phase DC-Machine, except that it is for translatory motion. For a moving coil actuator with a coil inside an air gap with flux density B and a total wire length l inside the magnetic field, the converter constant becomes

    c = B * l.

The converter constant c as well as coil resistance R and inductance L are assumed to be known, e.g., from measurements or catalogue data. Hence this model is well-suited for system simulation together with neighbouring subsystems, but not for actuator design, where the motor constant is to be found on base of the magnetic circuit's geometry, material properties and winding data. See PermeanceActuator for a more accurate model of this actuator that is based on a magnetic network. Due to identical connectors, both models can be used in system simulation, e.g. to simulate a stroke as demonstrated in ArmatureStroke.

Parameters

Name	Description
k	Converter constant [N/A]
R	Coil resistance [Ohm]
L	Coil inductance at mid-stroke [H]
Armature and stopper
m_a	Armature mass [kg]
c	Spring stiffness between impact partners [N/m]
d	Damping coefficient between impact partners [N.s/m]
x_min	Minimum armature position [m]
x_max	Maximum armature position [m]

Connectors

Name	Description
p	Electrical connector
n	Electrical connector
flange	Flange of component