Buck converters, or step down converters, put out less power than they receive, and the tracking signals in the output can get stuck. This results in a small but harmful frequency fluctuation, or 'chatter', which is said to lead to worn hardware, temperature changes in the circuits, and to make the system difficult to accurately control.
"In order to suppress the chattering, a high order sliding mode control technique was previously proposed, and was established as the most successful chattering avoidance method," said Delft University Professor Hassan HosseinNia.
The purpose of the sliding mode control for the buck converter is to control the output voltage. The technique is said to sample the system, creating a representative sample of the system's typical behaviour.
However, according to the researchers, the control method becomes less reliable and robust if other unknown variables come into play. Since the output is known, the researchers need to control the other variables to meet the desired output.
To eliminate the chatter and better control the system, the scientists designed what they call a second order sliding mode controller via twisting algorithm.
"The adaptive sliding mode control method for controlling the buck converter voltage leads to a more effective performance against disturbances and system uncertainties than the sliding mode control method; the only difference is that in this method the parameter in the sliding line is not constant," HosseinNia explained.
By allowing flexibility in the sliding line parameter, the researchers claim they can clear the chatter while retaining robustness of the system at the output.