Unlike a typical sailing ship, which is pushed along by the wind, a solar sail uses highly reflective sunlight to push it along. It is much easier to do that than it is to do it correctly. The sun can head up one side of the sail and cause it to spin. Disasters can befall any mission using this technology. There is a way to account for those situations. Control theory is common in system design, and now researchers at the university have come up with a control scheme that they think could help reduce the risk to solar sails.
Control systems are easily understood. In the case of a solar sail, the solar force pushing on it from the Sun could be one of the inputs. The distance from that object and the angle the solar sail is facing will be outputs the system designer wants to control.
The control system is a set of mathematical equations that take the inputs to the system and then determine how to manipulate other internal variables to make the outputs get to a desired value. If we know solar radiation is pushing on the solar sail with a force of 1000 N, we can calculate what adjustments we need to make for the probe to maintain its position.
These types of controls are especially useful in the space program. It's not the first time someone has thought of applying a control system to a solar sail system. There are several drawbacks to the ones that have been developed so far.
It is better to understand the specific type of control methodology used in the new paper first. Fuzzy logic is a different type of logic that computers use. Fuzzy logic can use any number between 0 and 1 as both an input and an output.
A lot of training is required for controllers that use fuzzy logic when using more varied numbers. Neural networks are a type of artificial intelligence architecture. Not many of the solar sail systems have taken flight yet and there isn't much data available. Any system that can lower the training threshold would be a huge advancement.
A system operator could model the system using known parameters instead of giving training data to the fuzzy logic controller. Operators would be able to develop new control schemes on the fly with the equivalent of a digital twin. This type of modeling is not helpful for attitude control. They came up with something else.
Their solution is known as an intelligent fuzzy logic controller designer. A fuzzy logic controller would be generated by the system. Operators would be able to control the attitude of their solar sail system.
The authors created a model of a solar sail with four separate components, a box for the controller, a frame, and the solar sail itself. After testing their intelligent controller design on this model, they found significant improvements in the accuracy of the controller, which is important in control systems, at the cost of a bit slow reaction time. Hopefully, the solar sail designers of the future will take the ideas from the paper to heart, because it sounds like an elegant solution to a specific problem.
You can learn more.
The Beijing Institute of Technology Press asked how a scientist came up with an intelligent fuzzy logical control.
The Intelligent Fuzzy Control in Stabilizing Solar Sail has individual controllable elements.
There is a new kind of solar sail that could allow us to explore difficult places in the solar system.
UT, what is a solar sail?
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