A set of three orthogonally aligned torque rods wired up so they can generate a magnetic dipole field of either sign (i.e. flip the North and South. Magnetic Torquers. These devices interact with the Earth’s magnetic field and create control torque, which can be adjusted to the required value. Combined with. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the.

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Archived from the original pdf on Post as a guest Name. That field is controlled by switching current flow through the coils on or off, usually under computerized feedback control.

This page was last edited on 2 Decemberat Magnetorquers are essentially sets of electromagnets which are laid out to yield a rotationally asymmetric anisotropic magnetic field over an extended area.

However, there are different ways to obtain the coil, thus according to the construction strategy it is possible to find three type of magnetorquer, apparently very different from each other but based on the same concept [1]:. Torque rods are used to desaturate these effectors which accumulate momentum due to disturbance torques like atmospheric drag, and to de-spin manetic e.

In Earth orbit, sunlight is one such practically inexhaustible energy source, using solar panels.

Home Questions Tags Users Unanswered. Without resistance, it will overshoot the pole, making it difficult to exactly line up on an axis. The dependence on the highly variable intensity of Earth’s magnetic field is also problematic because then the attitude control problem becomes highly nonlinear. Sign up or log in Sign up using Google.

## Magnetorquer

Typically three coils are used, although reduced configurations of two or even one magnet can suffice where full attitude control torquets not needed or external forces like asymmetric drag allow underactuated control. Math is very frequently helpful in spaceflight. A set of three orthogonally aligned torque rods wired up so they can generate a magnetic dipole field of either sign i.

That said, the field is weak, so the actual torque produced by torque rods is very small.

### artificial satellite – What is the math behind Magnetorquers? – Space Exploration Stack Exchange

The full analysis will be easier to apply by measuring one magnetorquer at a time, but I’m going to assume that their torque lines up with the rotational vectors reasonably well, allowing for all of them to be handled. This makes it possible to freely pivot the craft around in a known local gradient of the magnetic field by only using electrical energy.

Views Read Edit View history. A further advantage over momentum wheels and control moment gyroscopes is the absence of moving parts and therefore significantly higher reliability. If you are lined up perfectly with the magnetic field, you cannot control your rotation about the field. Basically, most magnetorquers function something like bar magnets that can be dialed to select how powerful, and what direction, they pull in. Any spinning satellite made of a conductive material will lose rotational momentum in Earth’s magnetic field due to generation of eddy currents in its body and the corresponding braking force proportional to its spin rate.

Mathematically, the torque is provided in the direction of: I have magnetorquers on the satellite of a known strength, and I’m trying to determine how much control authority I have in various directions. Over time active control can produce very fast spinning even here, but for accurate attitude control and stabilization the torques provided often aren’t enough.

How much control authority do I have, given a magnetic field in body coordinates, and 3 equal strength magnetorquers in orthogonal vectors lined up with the body axis?

Equating the control torque with the rigid-body rotational equations of motion:. This is not always possible within the energy constraints of the vessel. The magnetjc dipole generated by the magnetorquer is expressed by the formula:.

The math behind them turns out to be really simple. This means as the spacecraft orbits the Earth it encounters a diversity of Earth magnetic field orientations and in general the time-averaged effect of this field diversity enables full 3-axis control. Sign up using Facebook. It’s completely unsuitable for agile spacecraft e. By using this site, you agree to the Terms magneetic Use and Privacy Policy.