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1

Effective nonlinear predictive and CTC-PID control of rigid manipulators

Tatjewski Piotr

Journal of Automation Mobile Robotics and Intelligent Systems

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2024

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Vol. 18, No. 2

1--16

EN

Effective nonlinear control of manipulators with dynamically coupled arms, like those with direct drives, is the subject of the paper. Model-based predictive control (MPC) algorithms with nonlinear state-space models and most recent disturbance attenuation technique are proposed. This technique makes controller design and online calculations simpler, avoiding necessity of dynamic modeling of disturbances or resorting to additional techniques like SMC. The core of the paper are computationally effective MPC-NPL (Nonlinear Prediction and Linearization) algorithms, where computations at every sample are divided into two parts: prediction of initial trajectories using nonlinear model, then optimization using simplified linearized model. For a comparison, a known CTC-PID algorithm, which is also model-based, is considered. It is applied in standard form and also proposed in more advanced CTC-PID2dof version. For all algorithms a comprehensive comparative simulation study is performed, for a direct drive manipulator under disturbances. Additional contribution of the paper is investigation of influence of sampling period and of computational delay time on performance of the algorithms, which is practically important when using model-based algorithms with fast sampling.

2

Nieliniowe sterowanie predykcyjne ramion manipulatorów

Tatjewski Piotr

Pomiary Automatyka Robotyka

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2023

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R. 27, nr 2

47--58

PL

Przedmiotem artykułu są algorytmy sterowania predykcyjnego (typu MPC - Model Predictive Control) ramion manipulatorów sztywnych. Zastosowano MPC z modelem w przestrzeni stanów i wykorzystano najnowszą technikę tłumienia zakłóceń i błędów modelowania, pozwalającą uniknąć dynamicznego modelowania zakłóceń lub uciekania się do dodatkowych technik ich eliminowania, takich jak SMC. Rozważane są przede wszystkim najbardziej efektywne obliczeniowo algorytmy MPC-NPL (NPL - Nonlinear Prediction and Linearization), w dwóch wersjach: z optymalizacją QP (Quadratic Programming) z ograniczeniami i z jawną optymalizacją bez ograniczeń i spełnieniem ograniczeń nierównościowych a posteriori. Dla wszystkich rozważanych algorytmów przeprowadzono kompleksową analizę symulacyjną sterowania manipulatorem z napędem bezpośrednim, przy dwóch rodzajach zakłócenia: zewnętrznym i parametrycznym. Wyniki porównano z uzyskanymi dla znanego algorytmu CTC-PID (CTC - Computer Torque Control), uzyskując lepszą jakość regulacji algorytmami MPC. Zbadano wpływ długości okresu próbkowania i obliczeniowego opóźnienia sterowania na jakość regulacji, co jest istotne dla algorytmów z szybkim próbkowaniem opartych na modelach.

EN

The subject of the article are predictive control algorithms (of MPC type - Model Predictive Control) for rigid manipulator arms. MPC with a state-space model and with the latest disturbance and modeling error suppression technique was applied, which avoids dynamic disturbance modeling or resorting to additional disturbance cancellation techniques, such as SMC. First of all, the most computationally efficient MPC-NPL (Nonlinear Prediction and Linearization) algorithms are considered, in two versions: the first with constrained QP (Quadratic Programming) optimization and the second with explicit (analytical) optimization without constraints and satisfying a posteriori inequality constraints. For all considered algorithms, a comprehensive simulation analysis was carried out for a direct drive manipulator, with two kinds of disturbances: external and parametric. The obtained results were compared with those for the well-known CTC-PID algorithm (CTC - Computer Torque Control), showing better control quality with MPC algorithms. In addition, the influence of the length of the sampling period and of the computational delay on control quality was investigated, which is important for model-based algorithms with fast sampling.

3

Effectiveness of Dynamic Matrix Control algorithm with Laguerre functions

Tatjewski Piotr

Archives of Control Sciences

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2021

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Vol. 31, No. 4

795--814

EN

The paper is concerned with the presentation and analysis of the Dynamic Matrix Control (DMC) model predictive control algorithm with the representation of the process input trajectories by parametrised sums of Laguerre functions. First the formulation of the DMCL (DMC with Laguerre functions) algorithm is presented. The algorithm differs from the standard DMC one in the formulation of the decision variables of the optimization problem - coefficients of approximations by the Laguerre functions instead of control input values are these variables. Then the DMCL algorithm is applied to two multivariable benchmark problems to investigate properties of the algorithm and to provide a concise comparison with the standard DMC one. The problems with difficult dynamics are selected, which usually leads to longer prediction and control horizons. Benefits from using Laguerre functions were shown, especially evident for smaller sampling intervals.