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Lyapunov-Based Adaptive Control Using Deep Residual Neural Networks (ResNets) for Uncertain Nonlinear Systems


Kernkonzepte
This paper provides the first result on Lyapunov-derived adaptation laws for the weights of each layer of a ResNet-based adaptive controller to compensate for unstructured uncertainties in nonlinear dynamical systems.
Zusammenfassung

The paper presents a Lyapunov-based approach to derive weight adaptation laws for a deep residual neural network (ResNet)-based adaptive controller. The key highlights are:

  1. Motivation: Deep neural network (DNN)-based controllers can compensate for unstructured uncertainties, but existing methods either use static DNN models or require offline training of inner-layer weights. This motivates the need for a ResNet-based adaptive controller with real-time weight adaptation.

  2. Approach: The ResNet is expressed as a composition of building blocks involving a shortcut connection across a fully-connected DNN. A constructive Lyapunov-based approach is provided to derive weight adaptation laws for the ResNet using the gradient of each DNN building block.

  3. Novelty: This is the first result on Lyapunov-derived adaptation laws for ResNets, which pose additional mathematical challenges compared to fully-connected DNNs due to the shortcut connections.

  4. Analysis: A nonsmooth Lyapunov-based analysis is provided to guarantee asymptotic tracking error convergence. The analysis ensures the system state remains within a compact domain where the universal function approximation property of the ResNet holds.

  5. Simulations: Comparative Monte Carlo simulations demonstrate that the ResNet-based adaptive controller provides a 64% improvement in tracking and function approximation performance compared to an equivalent fully-connected DNN-based adaptive controller.

  6. Key Advantages: The ResNet architecture overcomes the vanishing gradient problem present in fully-connected DNNs, enabling faster weight adaptation and better compensation of system uncertainties.

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Statistiken
The tracking error norm ∥e∥is reduced by 63.93% using the ResNet-based adaptive controller compared to the fully-connected DNN-based controller. The function approximation error norm ˜ f is reduced by 64.77% using the ResNet-based adaptive controller compared to the fully-connected DNN-based controller.
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Tiefere Fragen

How can the ResNet-based adaptive control framework be extended to handle uncertainties with long-term temporal dependencies

To extend the ResNet-based adaptive control framework to handle uncertainties with long-term temporal dependencies, incorporating a Long Short-Term Memory (LSTM) component can be a viable approach. LSTM networks are well-suited for capturing long-term dependencies in sequential data due to their ability to retain information over extended time intervals. By integrating LSTM units within the ResNet architecture, the model can effectively learn and adapt to uncertainties that exhibit long-term temporal patterns. The LSTM component can be utilized to process and store information over multiple time steps, allowing the adaptive controller to consider historical data and trends when making control decisions. This can enhance the system's ability to predict and respond to uncertainties with long-term dependencies, leading to improved tracking and control performance in dynamic environments.

What are the potential benefits and challenges of incorporating a long short-term memory (LSTM) component within the ResNet architecture for adaptive control applications

Incorporating a Long Short-Term Memory (LSTM) component within the ResNet architecture for adaptive control applications offers several potential benefits and challenges: Potential Benefits: Long-Term Dependency Handling: LSTM networks excel at capturing long-term dependencies in sequential data, enabling the adaptive control system to effectively model uncertainties with extended temporal patterns. Memory Retention: LSTM units can retain information over multiple time steps, allowing the controller to make decisions based on historical data and trends. Improved Prediction Accuracy: The LSTM component can enhance the system's predictive capabilities, leading to more accurate and reliable control actions. Enhanced Adaptability: By incorporating LSTM, the adaptive controller can adapt to changing dynamics and uncertainties more effectively, improving overall system performance. Challenges: Complexity: Adding LSTM units increases the complexity of the ResNet architecture, requiring careful design and optimization to ensure efficient training and inference. Training Data Requirements: LSTM networks may require larger amounts of training data to effectively learn long-term dependencies, which can be challenging to obtain in some applications. Hyperparameter Tuning: Configuring the LSTM component, such as the number of memory cells and layers, requires thorough hyperparameter tuning to achieve optimal performance. Computational Resources: LSTM networks are computationally intensive, potentially requiring more resources for training and inference compared to standard ResNet architectures.

Can the proposed Lyapunov-based design be combined with other robust modification techniques, such as sigma modification or e-modification, to obtain a uniformly ultimately bounded tracking result without requiring knowledge of the uncertainty bounds

The proposed Lyapunov-based design can be combined with robust modification techniques like sigma modification or e-modification to achieve a uniformly ultimately bounded tracking result without requiring precise knowledge of uncertainty bounds. By integrating these robust modification methods with the Lyapunov-based adaptive control framework, the system can exhibit enhanced stability and robustness in the presence of uncertainties. Benefits of Combining with Robust Modification Techniques: Robustness: Sigma modification and e-modification techniques can enhance the robustness of the adaptive control system against uncertainties and disturbances. Improved Performance: By incorporating robust modifications, the system can achieve better tracking performance and disturbance rejection capabilities. Simplified Implementation: These techniques offer a straightforward way to introduce robustness without the need for detailed knowledge of uncertainty bounds. Stability Guarantees: The combination of Lyapunov-based design and robust modifications can provide formal stability guarantees for the adaptive control system. Challenges: Parameter Tuning: Proper tuning of the parameters in the robust modification techniques is crucial to ensure effective performance without compromising stability. Complexity: Integrating multiple control strategies can increase the complexity of the system, requiring careful implementation and testing. Trade-offs: Balancing the benefits of robustness with potential trade-offs in control performance and responsiveness needs to be carefully considered. Computational Overhead: Robust modification techniques may introduce additional computational overhead, impacting real-time control applications.
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