From Theory to Practice: Incremental Nonlinear Control

A special issue of Actuators (ISSN 2076-0825). This special issue belongs to the section "Control Systems".

Deadline for manuscript submissions: 31 January 2025 | Viewed by 9979

Special Issue Editors


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Guest Editor
Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
Interests: non-linear control; aerial robotics; aeroservoelasticity; morphing; reinforcement learning
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Guest Editor
Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
Interests: nonlinear control; interval analysis; global nonlinear optimization; knowledge-based control

Special Issue Information

Dear Colleagues,

Nonlinear incremental control is a branch of control methods that utilize a data-driven incremental model. It exploits sensor measurements online and can simultaneously reduce controller model dependency and robustness. The word incremental means the controllers are designed considering the variations of state, control, and control derivatives in one incremental time step. The first invented and most well-known incremental control method is the incremental nonlinear dynamic inversion (INDI). Both theoretical and practical research has shown superior robustness and easier implementation of INDI compared to its nonlinear dynamic inversion counterpart. Originating from INDI, various nonlinear incremental control methods have been developed in the past decade, including incremental backstepping, adaptive incremental control, incremental adaptive dynamic programming, etc. These nonlinear incremental control methods have also found their broad applications in various practical fields including, aerospace, robotics, and mechanical systems.

This Special Issue aims to welcome contributions to the theoretical and practical perspectives of incremental control, including but not limited to the following:

  • Stability analysis;
  • Robustness analysis;
  • Novel controller design based on an incremental model;
  • Novel applications of nonlinear incremental control.

Dr. Xuerui Wang
Dr. Erik-Jan Van Kampen
Guest Editors

Manuscript Submission Information

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Keywords

  • nonlinear control
  • incremental
  • robustness
  • data-driven

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Published Papers (6 papers)

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Research

16 pages, 2656 KiB  
Article
Ground Motion Modeling and Adaptive Joint Control for Large-Scale UAVs
by Bo Wang, Wensheng Wang, Xiaodan Cui and Xiaoxiong Liu
Actuators 2025, 14(1), 6; https://doi.org/10.3390/act14010006 - 27 Dec 2024
Viewed by 322
Abstract
Aiming at the problem of lateral deviation of large-scale long-endurance solar-powered UAVs relative to the runway during takeoff or landing, a UAV ground motion control structure based on the combination of engine differential and rudder was proposed. According to the structural characteristics of [...] Read more.
Aiming at the problem of lateral deviation of large-scale long-endurance solar-powered UAVs relative to the runway during takeoff or landing, a UAV ground motion control structure based on the combination of engine differential and rudder was proposed. According to the structural characteristics of large-scale long-endurance solar-powered UAVs, a ground motion model of a three-point layout UAV including landing gear was established, and the ground rolling dynamics and modal characteristics were analyzed. In order to accurately correct the trajectory error, the outer loop designs a trajectory correction control law and gives the inner loop desired control instructions. In order to solve the problem of environmental disturbance and small heading damping, the inner loop adopts the adaptive back-stepping control method. The disturbance signal is estimated through the adaptive law and compensated into the control system to achieve balanced control of speed and rolling correction. Finally, medium-speed and high-speed sliding tests were designed to verify the rationality of the proposed control scheme and control structure, as well as the efficiency of the control law design method adopted. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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20 pages, 3401 KiB  
Article
Incremental Nonlinear Dynamics Inversion and Incremental Backstepping: Experimental Attitude Control of a Tail-Sitter UAV
by Alexandre Athayde, Alexandra Moutinho and José Raul Azinheira
Actuators 2024, 13(6), 225; https://doi.org/10.3390/act13060225 - 17 Jun 2024
Viewed by 1023
Abstract
Incremental control strategies such as Incremental Nonlinear Dynamics Inversion (INDI) and Incremental Backstepping (IBKS) provide undeniable advantages for controlling Uncrewed Aerial Vehicles (UAVs) due to their reduced model dependency and accurate tracking capacities, which is of particular relevance for tail-sitters as these perform [...] Read more.
Incremental control strategies such as Incremental Nonlinear Dynamics Inversion (INDI) and Incremental Backstepping (IBKS) provide undeniable advantages for controlling Uncrewed Aerial Vehicles (UAVs) due to their reduced model dependency and accurate tracking capacities, which is of particular relevance for tail-sitters as these perform complex, hard to model manoeuvres when transitioning to and from aerodynamic flight. In this research article, a quaternion-based form of IBKS is originally deduced and applied to the stabilization of a tail-sitter in vertical flight, which is then implemented in a flight controller and validated in a Hardware-in-the-Loop simulation, which is also made for the INDI controller. Experimental validation with indoor flight tests of both INDI and IBKS controllers follows, evaluating their performance in stabilizing the tail-sitter prototype in vertical flight. Lastly, the tracking results obtained from the experimental trials are analysed, allowing an objective comparison to be drawn between these controllers, evaluating their respective advantages and limitations. From the successfully conducted flight tests, it was found that both incremental solutions are suited to control a tail-sitter in vertical flight, providing accurate tracking capabilities with smooth actuation, and only requiring the actuation model. Furthermore, it was found that the IBKS is significantly more computationally demanding than the INDI, although having a global proof of stability that is of interest in aircraft control. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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18 pages, 8899 KiB  
Article
A Sparse Neural Network-Based Control Method for Saturated Nonlinear Affine Systems
by Jing Zhang, Baoqun Yin, Jianwen Huo, Hongliang Guo and Zhan Li
Actuators 2024, 13(6), 204; https://doi.org/10.3390/act13060204 - 29 May 2024
Viewed by 808
Abstract
Saturated nonlinear affine systems are widely encountered in many engineering fields. Currently, most control methods on saturated nonlinear affine systems are not specifically designed based on sparsity-based control methodologies, and they might require sparse identification at the beginning stage and applying tracking control [...] Read more.
Saturated nonlinear affine systems are widely encountered in many engineering fields. Currently, most control methods on saturated nonlinear affine systems are not specifically designed based on sparsity-based control methodologies, and they might require sparse identification at the beginning stage and applying tracking control afterwards. In this paper, a sparse neural network (SNN)-based control method from an lp-norm (1p<2) optimization perspective is proposed for saturated nonlinear affine systems by taking advantage of the nice properties of primal dual neural networks for optimization. In particular, when p=1, a new alternative controller based on SNN is derived, encountering computational difficulties distinct from those of another solution set in the basic dual neural network. The convergence properties of such SNN-based controllers are investigated and analyzed to find a control solution. Five illustrative examples further are shown to demonstrate the efficiency of the proposed SNN-based control method for tracking the desired references of saturated nonlinear affine systems. In the practical application scenario involving the UR5 robot control, the trajectory’s average errors are consistently confined to a minimal magnitude of 10−4 m. These findings substantiate the efficacy of the SNN-based control approach proposed for precise tracking control in saturated nonlinear affine systems. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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16 pages, 1811 KiB  
Article
A Novel Extended Unscented Kalman Filter Is Designed Using the Higher-Order Statistical Property of the Approximate Error of the System Model
by Chengyi Li and Chenglin Wen
Actuators 2024, 13(5), 169; https://doi.org/10.3390/act13050169 - 1 May 2024
Cited by 1 | Viewed by 1320
Abstract
In the actual working environment, most equipment models present nonlinear characteristics. For nonlinear system filtering, filtering methods such as the Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), and Cubature Kalman Filter (CKF) have been developed successively, all of which show good results. [...] Read more.
In the actual working environment, most equipment models present nonlinear characteristics. For nonlinear system filtering, filtering methods such as the Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), and Cubature Kalman Filter (CKF) have been developed successively, all of which show good results. However, in the process of nonlinear system filtering, the performance of EKF decreases with an increase in the truncation error and even diverges. With improvement of the system dimension, the sampling points of UKF are relatively few and unrepresentative. In this paper, a novel high-order extended Unscented Kalman Filter (HUKF) based on an Unscented Kalman Filter is designed using the higher-order statistical properties of the approximate error. In addition, a method for calculating the approximate error of the multi-level approximation of the original function under the condition that the measurement is not rank-satisfied is proposed. The effectiveness of the filter is verified using digital simulation experiments. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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33 pages, 6190 KiB  
Article
Practical System Identification and Incremental Control Design for a Subscale Fixed-Wing Aircraft
by Rasmus Steffensen, Kilian Ginnell and Florian Holzapfel
Actuators 2024, 13(4), 130; https://doi.org/10.3390/act13040130 - 4 Apr 2024
Cited by 2 | Viewed by 2055
Abstract
An incremental differential proportional integral (iDPI) control law using eigenstructure assignment gain design is tested in flight on a subscale platform to validate its suitability for fixed-wing flight control. A kinematic relation for the aerodynamic side-slip angle rate is developed to apply a [...] Read more.
An incremental differential proportional integral (iDPI) control law using eigenstructure assignment gain design is tested in flight on a subscale platform to validate its suitability for fixed-wing flight control. A kinematic relation for the aerodynamic side-slip angle rate is developed to apply a pseudo full state feedback. In order to perform the gain design and assessment, a plant model is estimated using flight test data from gyro, accelerometer, airspeed and surface deflection measurements during sine-sweep excitations. Transfer function models for the actuators and surface deflections are identified both in-flight and on the ground for several different actuators and control surfaces using hall sensor surface deflection measurements. The analysis reveals a large variation in bandwidth between the different types of servo motors. Flight test results are presented which demonstrates that the plant model estimates based on tests with good frequency excitation, high bandwidth actuators and surface deflection measurements can be used to reasonably predict the closed-loop dynamic behavior of the aircraft. The closed-loop flight test results of the iDPi control law show good performance and lays the groundwork for further development. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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16 pages, 2115 KiB  
Article
Incremental Nonlinear Control for Aeroelastic Wing Load Alleviation and Flutter Suppression
by Roderick Schildkamp, Jing Chang, Jurij Sodja, Roeland De Breuker and Xuerui Wang
Actuators 2023, 12(7), 280; https://doi.org/10.3390/act12070280 - 9 Jul 2023
Cited by 2 | Viewed by 3008
Abstract
This paper proposes an incremental nonlinear control method for an aeroelastic system’s gust load alleviation and active flutter suppression. These two control objectives can be achieved without modifying the control architecture or the control parameters. The proposed method has guaranteed stability in the [...] Read more.
This paper proposes an incremental nonlinear control method for an aeroelastic system’s gust load alleviation and active flutter suppression. These two control objectives can be achieved without modifying the control architecture or the control parameters. The proposed method has guaranteed stability in the Lyapunov sense and also has robustness against external disturbances and model mismatches. The effectiveness of this control method is validated by wind tunnel tests of an active aeroelastic parametric wing apparatus, which is a typical wing section containing heave, pitch, flap, and spoiler degrees of freedom. Wind tunnel experiment results show that the proposed nonlinear incremental control can reduce the maximum gust loads by up to 46.7% and the root mean square of gust loads by up to 72.9%, while expanding the flutter margin by up to 15.9%. Full article
(This article belongs to the Special Issue From Theory to Practice: Incremental Nonlinear Control)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Innovative Design Optimization of Electromagnetic Soft Actuators Using Advanced Nonlinear Methods
Authors: Hussein Zolfaghari1, Nafiseh Ebrahimi2, Xaq Pitkow3, Mohammadreza Davoodi1*
Affiliation: 1 Department of Electrical and Computer Engineering, The University of Memphis, Memphis, TN 38111, USA 2 Department of Applied Engineering Technology, Virginia State University, Petersburg, VA 23806, USA 3 Neuroscience Institute and Department of Machine Learning, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Abstract: The rising interest in soft robotics stems from their unique ability to perform tasks beyond the capabilities of rigid robots, with soft actuators at the core of this innovation. Among these, Electromagnetic Soft Actuators (ESAs) excel for their fast response, simple control mechanisms, and compact design. Compact actuators are essential for ensuring user comfort, mobility, efficient force application, and seamless integration into wearable or minimally invasive devices. Both analytical and experimental studies indicate that smaller ESAs improve the force-to-cross-section area (F/CSA) ratio. This paper introduces an innovative nonlinear optimization framework for refining the design parameters of an ESA with a permanent magnet core, aimed at maximizing force output with enhanced efficiency. Unlike earlier approaches that optimized ESA design by adjusting key parameters—such as ESA length, permanent magnet diameter, and number of turns—sequentially, this study optimizes all these parameters simultaneously and comprehensively to achieve a more effective and efficient design. This study utilizes a nonlinear optimization framework that incorporates key parameters of the ESA to maximize the F/CSA ratio, while accounting for various constraints. The results validate the effectiveness of simultaneous optimization for complex ESA systems, offering promising advancements in soft robotics applications.

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