Fuzzy Logic Sliding Mode Control for DC-DC Converter Stability
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Solution Overview
Problem
Existing control strategies for variable voltage converters in electrified vehicles rely on linear conventional digital control, which fails to maintain global stability under large load variations, leading to inefficient voltage regulation.
Innovation Solution
Implementing a sliding mode control using fuzzy logic rules, where the control signal is adjusted based on the distance from a sliding surface defined by the inductor current and DC bus voltage errors, to achieve stable operation and improve dynamic response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear conventional digital control is used for voltage regulation, then the control system is simple to implement, but it fails to maintain global stability under large load variations
Solution Approach 1:
The patent implements sliding mode control with fuzzy logic that dynamically adjusts the control signal based on the distance from the sliding surface. The control gain varies dynamically according to the system state, allowing the controller to adapt to large load variations and maintain global stability, resolving the contradiction between reliability under varying conditions and control system simplicity.
Solution Approach 2:
The patent changes the control parameter from fixed linear gain to variable fuzzy logic-based gain. By using fuzzy membership functions and sliding mode control parameters that adapt to system conditions, the controller maintains stability under large load variations while managing complexity through structured fuzzy rules rather than purely adaptive algorithms.
2Productivity
If sliding mode control with fuzzy logic is implemented, then dynamic response and stability are improved, but the control algorithm becomes more complex
Solution Approach 1:
The patent segments the control algorithm into distinct modules: sliding mode control calculation, fuzzy membership function evaluation, and control signal generation. This segmentation allows the complex fuzzy logic control to be implemented systematically, improving dynamic response while managing algorithmic complexity through modular structure that can be efficiently programmed and executed.
3Measurement precision
If the control signal is continuously adjusted based on fuzzy logic rules, then voltage regulation precision is improved, but computational load increases
Solution Approach 1:
The patent pre-defines fuzzy membership functions and control rules offline, storing them in lookup tables or pre-computed structures. During real-time operation, the controller only needs to evaluate the current state against these pre-established rules, significantly reducing computational load while maintaining precise voltage regulation. This preliminary preparation resolves the contradiction between precision and processing time.
Data Source
AI summary
A DC-DC converter for a vehicle includes a controller programmed to, in response to changes in an output voltage of the converter, adjust a control signal that controls an output voltage of the DC-DC converter to drive a ratio of a first error between a reference current and a current through the inductor to a second error between a voltage reference and the output voltage to a predetermined value.