Changes

[[File:Equation5.png|frame|center]]

Magnetic torquer is a current carrying insulated loop which can be mounted on satellite body. The outer space has magnetic field due to the earth. In presence of this field, torquer can exert torque on the satellite when current is passed through it. Since magnetic field doesn’t vary over the length scale of dimension of torquer, it can be assumed to be uniform and above formula is applicable.

== Modeling of Torquer ==

The actuator is a part of control system which implements the control law on our plant. In case of satellite, the required control torque is determined by control law. This torque is generated by passing the electric current determined by the above equation, through torquer. But it should be noted that microcontroller can provide voltage signal. Thus it is necessary to study the relation between voltage applied to torquer and current generated in it. <br \>

The torquer coil has some specific resistance R. Since it forms a loop it will also have inductance L. Thus torquer can be modelled as series L-R circuit.<br \>

== Effect of the ferromagnetic core ==

The magnetorquers in shape of coil take too much space and have larger mass. In order to generate larger moment with stringent mass and size constraints, ferromagnetic core torquers can be used. <br \>

These are called torque rods. It is a solenoid of length ‘l’ and radius ‘r’ with ferromagnetic core of relative permeability ‘µ_r’. The magnetic moment for cored solenoid in steady state is given by: <ref>http://www.aerospades.com/uploads/3/7/3/2/37325123/cadre_torquers.pdf </ref>