Slovakia

Offset-free action of model predictive control (MPC) for nonlinear systems with the number of measured outputs greater than controlled outputs is a nontrivial problem. Motivated by investigating the possible application of MPC for the control system of magnetic levitation (Maglev) vehicles -- tracking only the gap while measuring the gap, acceleration, and current -- for higher speeds than hitherto travelled, different possible offset-free nonlinear MPC strategies are reviewed and discussed.

Moreover, a novel approach based on a two-stage observer is introduced, requiring less effort to design an offset-free MPC. The different strategies are applied and analyzed in detail for a realistic model of the control system of the latest Transrapid vehicle, called TR09. Unlike usual offset-free MPC studies, the controller performance is also studied in a typical dynamic scenario, revealing the conflict and trade-off between the requirements for speed of command response and the robustness of closed-loop stability.

Nonlinear Model Predictive Control Conference 2021

Offset-free Nonlinear Model Predictive Control by the Example of Maglev Vehicles

The IFAC Conference on Nonlinear Model Predictive Control (NMPC 2021) aims to bring together researchers interested in and work in the MPC field from both academia and industry. This allows us to reflect and establish the current state-of-the-art and focus on the future development of the MPC field towards relevant directions.

Model predictive control (MPC) is indisputably one of the advanced control techniques that have significantly affected control engineering practice with thousands of controllers implemented in various fields, spanning from the process industry to automotive and robotics. This is due to its unique ability to handle constraints, take preview information about disturbances and setpoint changes into account, and optimize performance. Furthermore, MPC allows the consideration of various types of dynamics, from linear to nonlinear, discrete to continuous, as well as an online adaptation of models and parameters. The research community on MPC is very active, with hundreds of papers published every year. Over the past decades, many theoretical, as well as implementation results, have been achieved.

### **All content presented at NMPC2021, including videos, papers and slides will be available only to registered (regular/student) participants. The content can be accessed until August 31st, 2021.**



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The IFAC Conference on Nonlinear Model Predictive Control (NMPC 2021) aims to bring together researchers interested in and work in the MPC field from both academia and industry. This allows us to reflect and establish the current state-of-the-art and focus on the future development of the MPC field towards relevant directions.

keynote

Stochastic Model Predictive Control (MPC) has established itself as a simple method to approximate stochastically disturbed optimal control problems, yet it comes with significant computational effort. In particular, taking into account all information of stochastic disturbances—if at all possible—can be expensive. However, due to the continuous re- optimization, MPC schemes also have a certain inherent robustness. Hence, we ask the question, which part of the perturbation is absorbed by the MPC-inherent robustness, and which needs to be explicitly taken into account in the optimization.

Does the Effort of Monte Carlo Pay Off? a Case Study on Stochastic MPC

In this paper, we propose an efficient zero-order algorithm that can be used to compute an approximate solution to robust optimal control problems (OCP) and robustified nonconvex programs in general. In particular, we focus on robustified OCPs that make use of ellipsoidal uncertainty sets and show that, with the proposed zero-order method, we can efficiently obtain suboptimal, but robustly feasible solutions. The main idea lies in leveraging an inexact sequential quadratic programming (SQP) algorithm in which an advantageous sparsity structure is enforced. The obtained sparsity allows one to eliminate the variables associated

Zero-Order Robust Nonlinear Model Predictive Control with Ellipsoidal Uncertainty Sets

We consider the control of constrained, uncertain systems over wireless communication networks with varying capabilities. We focus on the case that a radio resource manager, which manages the wireless network, provides guaranteed minimum communication at fixed time instants while offering more frequent communication depending on the current load of the shared network, available network capacity or other conditions. To exploit the additionally available

Robust MPC for Networks with Varying Communication Capabilities

We present a feedback-optimizing model predictive

Feedback-Optimizing Model Predictive Control for Constrained Linear Systems

During the last 20 years there has been increased interest in estimating the INTENT of the Human motion (as part of human action) during the man-machine interaction. The main motivation has been to prepare the robot to act safely and being as helpful as possible during their interaction with the Human.

While the Control community has had predictive control formulation (the literature on this topic is quite rich, see references 16-18) unfortunately this formulation is based on the assumption that one has the knowledge of the dynamics of the system. This of course is not the case for human. As we all know humans are many times unpredictable. However during the last 20 years thanks to brain imaging techniques, such as MRI.FMRI,EEG and more ,the neuroscientists, the psychologists, cognitive scientists have identified unconscious signals in the cortex that are precursors to humans in their motion planning. We have reviewed a selected list of those articles and in our full talk will give the essence of these papers 1-15. One fundamental observation we can already make is that while during 20th century the prevalent modus operandi both for behavioral psychologists and roboticists was the stimulus-response, perception-action cycle, the 21st century hypothesis is combination of feedforward and feedback, action –perception, hence the anticipatory behavior in addition reactive behavior.

Anticipating and Predictive Behavior

We discuss state-of-the-art in mixed-integer nonlinear optimization (MINLP) solver software and the current state of research in the field. We hope to spark a conversation about the connections to NMPC.

Numerical approaches to mixed-integer nonlinear optimization

In this talk, we propose a suboptimal moving horizon estimator for nonlinear systems. For the stability analysis we transfer the “feasibility-implies-stability/robustness” paradigm from model predictive control to the context of moving horizon estimation in the following sense: Using a suitably defined, feasible candidate solution based on the trajectory of an auxiliary observer, robust stability of the proposed suboptimal estimator is inherited independently of the horizon length and even if no optimization is performed.

Robust Stability of Suboptimal Moving Horizon Estimation Using an Observer-Based Candidate Solution

In this presentation, I cover the basic concepts used in our paper which enables real-time MPC for large scale system. To this end, the contraint selection/removal procedure is detailed and the requirements for recursive feasbility and constraint satisfaction are explained. Last, a simulation study is presented to visualize the ca-MPC scheme.

Constraint-Adaptive MPC for Large-Scale Systems: Satisfying State Constraints without Imposing Them

This talk presents recently developed methods for non-standard NMPC problems which cannot directly be formulated and solved in the form of smooth nonlinear programs (NLP).

NMPC with state dependent discontinuities, and homotopy based active set solution methods tailored to mathematical programs with complementarity constraints (MPCC). NMPC with state dependent jumps, and their reformulation to case 1) via “time freezing”. NMPC with discrete actuators, and a Gauss-Newton inspired heuristic. Throughout the talk, the focus will be on the exploitation of convex structure in these strongly non-convex problems The algorithms and methods will be illustrated by tutorial and some real-world examples.

The talk presents joint work with Armin Nurkanovic, Sebastian Albrecht, Jonas Hall, Florian Messerer, Sebastian Sager, Clemens Zeile, and Adrian Bürger.

Related Papers:
• [Time-Freezing for State Dependent Jumps](https://syscop.de/files/users/Moritz.diehl/Nurkanovic2021Freezing.pdf)

• [LCQP Algorithm for Quadratic Programs with Complementarity Contstraints](https://syscop.de/files/users/Moritz.diehl/Hall2022LCQP.pdf)

• [Survey of Sequential Convex Programming (SCP) and GGN](https://syscop.de/files/users/Moritz.diehl/Messerer2022-SCP-GGN.pdf)

• [Software pycombina for CIA MILP arising in MIOCP](https://cdn.syscop.de/publications/Buerger2020a.pdf)

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Next from Nonlinear Model Predictive Control Conference 2021

Does the Effort of Monte Carlo Pay Off? a Case Study on Stochastic MPC

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Robust MPC for Networks with Varying Communication Capabilities

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PRESENTATIONS

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