Symplectic Partitioned Runge‐Kutta Methods for High‐Order Approximation in Linear‐Quadratic Optimal Control of Hamiltonian Systems

Symplectic partitioned Runge-Kutta (SPRK) methods are known to be a good choice in forward simulations of Hamiltonian systems due to their structure-preserving properties. Recent works study the application of SPRK methods to nonlinear and linear-quadratic optimal control problems howing various advantages of these methods compared to standard non-symplectic integration schemes. Now, our focus is on extending the comparison to SPRK and RK methods of higher orders. For linear-quadratic optimal control problems, we consider the discrete-time Riccati feedback as well as the feedforward control implementation. For applications in which computational power or computation time is limited, low sampling rates are of particular interest. Hence we study this case for the n-fold harmonic oscillator

Robust Model Predictive Longitudinal Position Tracking Control for an Autonomous Vehicle Based on Multiple Models

The aim of this work is to control the longitudinal position of an autonomous vehicle with an internal combustion engine. The powertrain has an inherent dead-time characteristic and constraints on physical states apply since the vehicle is neither able to accelerate arbitrarily strong, nor to drive arbitrarily fast. A model predictive controller (MPC) is able to cope with both of the aforementioned system properties. MPC heavily relies on a model and therefore a strategy on how to obtain multiple linear state space prediction models of the nonlinear system via input/output data system identification from acceleration data is given. The models are identified in different regions of the vehicle dynamics in order to obtain more accurate predictions. The still remaining plant-model mismatch can be expressed as an additive disturbance which can be handled through robust control theory. Therefore modifications to the models for applying robust MPC tracking control theory are described. Then a controller which guarantees robust constraint satisfaction and recursive feasibility is designed. As a next step, modifications to apply the controller on multiple models are discussed. In this context, a model switching strategy is provided and theoretical and computational limitations are pointed out. Lastly, simulation results are presented and discussed, including computational load when switching between systems.Comment: Accepted for 2020 IEEE Symposium Series on Computational Intelligence (IEEE SSCI

Hormone-Sensitive Lipase Serine Phosphorylation and Glycerol Exchange Across Skeletal Muscle in Lean and Obese Subjects : Effect of β-Adrenergic Stimulation

OBJECTIVE—Increased intramuscular triacylglycerol (IMTG) storage is a characteristic of the obese insulin-resistant state. We aimed to investigate whether a blunted fasting or β-adrenergically mediated lipolysis contributes to this increased IMTG storage in obesity