Experimental and Numerical Comparison Between Two Nonlinear Control Logics

2016 ◽  
Vol 08 (05) ◽  
pp. 1650061 ◽  
Author(s):  
Francesco Ripamonti ◽  
Egidio Leo ◽  
Ferruccio Resta
Keyword(s):  
Nonlinear Control ◽  
Sliding Mode ◽  
Nonlinear Behavior ◽  
Operating Conditions ◽  
System Stability ◽  
Flexible Manipulator ◽  
Engineering Practice ◽  
Numerical Comparison ◽  
System A ◽  
Nonlinear Form

Nonlinear behavior is present in the operating conditions of many mechanical systems, especially if nonsmall oscillations are considered. In these cases, in order to improve vibration control performance, a common engineering practice is to design the control system on a set of linearized models, for given operating conditions. The well-known gain-scheduling technique allows the parameters of the control law to be changed according to the current working condition, also increasing system stability. However, more recently new control logics directly applicable to the systems in nonlinear form have been developed. The aim of this paper is to study, both numerically and experimentally, the dynamic of a mechanical system (a 3-link flexible manipulator) comparing the performance of a fully nonlinear control (the sliding-mode control) and a standard linearized approach.

A Nonlinear Sliding Surface in Sliding Mode Control to Reduce Vibrations of a Three-Link Flexible Manipulator

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Francesco Ripamonti ◽  
Lorenzo Orsini ◽  
Ferruccio Resta
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Mechanical Systems ◽  
Operating Conditions ◽  
Nonlinear Observer ◽  
Flexible Manipulator ◽  
Engineering Practice ◽  
Sliding Surface ◽  
Mode Control ◽  
Highly Nonlinear

Many mechanical systems often show nonlinear behavior related to particular operating conditions or to the nonlinear characteristic of the elements (springs, dampers, etc.) making up the system. In these cases, common engineering practice is to linearize the equation of motion around a particular operating point and to design a linear controller. Although this approach is simple, its main disadvantage is that stability properties and validity of the controller are only local. For these reasons, over the last decades, nonlinear control techniques have been investigated more and more in order to improve control performance. In particular, in this paper, sliding mode control (SMC) technique, which is based on the model of the system (model-based), is considered because of its easy implementation, especially on simple mechanical systems, and the considerable robustness of the controller even under significant model uncertainties. This technique is analyzed numerically with respect to the pendulum system to better understand the influence of the control action on the system dynamics. A nonlinear sliding surface is also considered, recalling the terminal sliding mode (TSM) control already analyzed in the scientific literature. This sliding surface is characterized for the numerical system, and then it is applied experimentally in order to control a highly nonlinear system, consisting of a three-link flexible manipulator. For this system, a nonlinear modal model is developed, and a nonlinear observer is designed. Finally, results of experimental tests on the manipulator are reported, in order to compare the performances of the linear embedded control and the sliding mode controllers with the linear and nonlinear sliding surface.

Nonlinear Control Techniques for a SMA Active Ankle Foot Orthosis

2007 ◽  
Author(s):  
Ehsan Tarkesh ◽  
Mohammad Elahinia
Keyword(s):  
Nonlinear Control ◽  
Sliding Mode ◽  
Nonlinear Behavior ◽  
Good Alternative ◽  
Switching Control ◽  
Experimental Result ◽  
Ankle Foot Orthosis ◽  
Control Techniques ◽  
Slow Walking ◽  
Foot Orthosis

This paper is aimed toward the development and evaluation of a novel active ankle foot orthosis (AAFO) based on shape memory alloy (SMA) actuators. This device intends to fill the gap in the existing research aimed at helping patients with drop foot muscle deficiencies as well as rehabilitation activities. To check the feasibility of this idea, a brief study is done on the dynamic behavior of ankle joint and then an SMA manipulator with a similar biological concept is used for experiment. Nonlinear behavior of SMA wires requires nonlinear control techniques such as Sliding Mode Controller (SMC) for tracking the desired ankle angle. Simulation results of three different techniques are compared (PID, SMC and SMC-PID) and finally the experimental result of a SMC-PID switching control is provided. This results shows that a switching control between simple PID and Sliding Mode Control can be a good alternative to follow the desired trajectory in slow walking cycles.

FEA-based tracking control of flexible body switching dynamic structure

Robotica ◽  
2021 ◽  
pp. 1-20
Author(s):  
M. R. Homaeinezhad ◽  
F. FotoohiNia
Keyword(s):  
Continuum Mechanics ◽  
Tracking Control ◽  
Sliding Mode ◽  
Equations Of Motion ◽  
Operating Conditions ◽  
System Stability ◽  
Control Input ◽  
Element Analysis ◽  
Control Effort ◽  
Modeling Uncertainties

Abstract In dynamically switched systems with unknown switching signal, the control system is conventionally designed based on the worst switching scenario to ensure system stability. Such conservative design demands excessive control effort in less critical switching configurations. In the case of continuum mechanics systems, such excessive control inputs result in increased structural deformations and resultant modeling uncertainties. These deformations alter differential equations of motion which cripple the task of control. In this paper, a new approach for tracking control of uncertain continuum mechanics multivariable systems undergoing switching dynamics and unknown time delay has been proposed. Control algorithm is constructed based on the mathematical rigid model of the plant and a Common Lyapunov Function (CLF) is proposed upon sliding hyperplane regarding all switching configurations. Considering the model-based nature of sliding mode control (SMC) and inevitable uncertainties induced from modeling simplifications of continuum system or parameter evaluation errors, Finite Element Analysis (FEA) is utilized to approximate total model uncertainties. To obtain robust stability, instead of conventional switching functions in the construction of control law, the control inputs are selected such that system dynamics reside within stability bounds which are calculated based on the Lyapunov asymptotic stability criterion. Therefore, the unwanted chattering issue caused by continuous switching is not observed in control input signals. Eventually, the accuracy of the proposed method has been verified through the student version of ANSYS® mechanical APDL-based simulations and its effectiveness has been demonstrated in multiple operating conditions.

Research on a New Azimuth Control Method for Stratospheric Balloon-Borne Gondola System

2012 ◽  
Vol 190-191 ◽  
pp. 1033-1039
Author(s):  
Hong Hui Wang ◽  
Zhao Hui Yuan ◽  
Juan Wu
Keyword(s):  
Control Method ◽  
Sliding Mode ◽  
Tracking Error ◽  
System Stability ◽  
Control Input ◽  
Tracking Accuracy ◽  
Cmac Neural Network ◽  
System A ◽  
Stratospheric Balloon ◽  
Robust Adaptive

For a class of non-matching uncertain nonlinear system such as stratospheric balloon-borne gondola azimuth control system, a new robust adaptive multiple sliding mode controller is proposed. In this control method, the virtual and the practical control variables are obtained by designing the multiple sliding modes step-by-step. For avoiding the chattering problem generated by discontinuous input, the traditional sign function is replaced by hyperbolic tangent function. Meanwhile, the CMAC neural network is used to approximate the system uncertainties and the derivative of virtual control input online, which can reduce the conservation of controller parameters design. The system stability analyses show that the control method can guarantee that the output tracking error and slide modes asymptotically convergent to boundary layer. The simulation results show that the controller has higher tracking accuracy, and stronger robust to nonlinear and uncertainty of system, and it also can be applied to other similar non-matching uncertain nonlinear systems.

scholarly journals Auto-tuning of PV controllers to improve the speed response and stability of the P&O algorithm

2015 ◽  
Vol 35 (1Sup) ◽  
pp. 5-12 ◽  
Author(s):  
Paula Andrea Ortiz Valencia ◽  
Carlos Andrés Ramos Paja
Keyword(s):  
Control System ◽  
Sliding Mode ◽  
Fast Response ◽  
Operating Conditions ◽  
System Stability ◽  
Pv System ◽  
Adaptive Law ◽  
Current Controller ◽  
Auto Tuning ◽  
Power Point

<span>This paper proposes an auto-tuning control system to ensure a fast response of the photovoltaic (PV) voltage by reducing the <span>perturbation time of a P&amp;O algorithm. This solution accelerates the tracking of the maximum power point and, at the same time, <span>guarantees the system stability, which increases the amount of energy produced by the PV system. The control system consists of three <span>cascaded controllers: a P&amp;O algorithm dynamically parameterized by the adaptive law in order to guarantee stability; an adaptive <span>PI controller whose parameters are modified by the adaptive law, depending on the operating conditions, to reduce the settling <span>time of the system as much as possible; and a sliding mode current controller to mitigate environmental and load perturbations and <span>ensure global stability. The design of the new control structure is supported by mathematical analyses and validated with simulations <span>performed in PSIM in order to demonstrate the robustness of the proposed solution.</span></span></span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span>

scholarly journals Stability Improvement of VSC-HVDC based Multi Machine Power System using Optimized Super Twisting Sliding Mode Controller

2019 ◽  
Vol 9 (1) ◽  
pp. 4871-4879
Keyword(s):  
Power System ◽  
Dynamic Stability ◽  
Sliding Mode ◽  
Pi Controller ◽  
Operating Conditions ◽  
System Stability ◽  
Flower Pollination Algorithm ◽  
Sliding Mode Controller ◽  
Multi Objective ◽  
Flower Pollination

This article presents application of an optimized robust and nonlinear controller approach for dynamic stability of a multi machine power system integrated with VSC-HVDC transmission. To improve dynamic stability of the system, a super twisting Sliding Mode Control approach, whose gains are optimized by multi objective flower pollination algorithm is designed to enhance the system stability over a various operating conditions, such as three phase fault, dc link fault, converter and inverter parameter change, increase of the mechanical input of the generator and change of active and reactive power. The super twisting sliding mode controller is designed for its superiority in robustness and chattering free actions over conventional siding mode controller in which a hyperbolic tangent function is chosen for the sliding surface. A multi objective flower pollination algorithm is applied to find optimized gains of the super twisting Sliding mode controller, in order to improve the capacity of the controller and the dynamic stability of the system. The results are compared with STSMC and conventional PI controller. It is shown from the result that the proposed controller is more capable in settling the system in steady state from any abnormal condition quickly than SMC and PI controller

scholarly journals Complex dynamical behaviors of a novel exponential hyper–chaotic system and its application in fast synchronization and color image encryption

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042110033
Author(s):  
Javad Mostafaee ◽  
Saleh Mobayen ◽  
Behrouz Vaseghi ◽  
Mohammad Vahedi ◽  
Afef Fekih
Keyword(s):  
Image Encryption ◽  
Chaotic System ◽  
Sliding Mode ◽  
Color Image ◽  
Equilibrium Points ◽  
Lyapunov Stability Theory ◽  
System Stability ◽  
Color Image Encryption ◽  
Terminal Sliding Mode ◽  
Finite Time Stability

This paper proposes a novel exponential hyper–chaotic system with complex dynamic behaviors. It also analyzes the chaotic attractor, bifurcation diagram, equilibrium points, Poincare map, Kaplan–Yorke dimension, and Lyapunov exponent behaviors. A fast terminal sliding mode control scheme is then designed to ensure the fast synchronization and stability of the new exponential hyper–chaotic system. Stability analysis was performed using the Lyapunov stability theory. One of the main features of the proposed controller is the finite time stability of the terminal sliding surface designed with high–order power function of error and derivative of error. The approach was implemented for image cryptosystem. Color image encryption was carried out to confirm the performance of the new hyper–chaotic system. For image encryption, the DNA encryption-based RGB algorithm was used. Performance assessment of the proposed approach confirmed the ability of the proposed hyper–chaotic system to increase the security of image encryption.

scholarly journals Research on predictive sliding mode control strategy for horizontal vibration of ultra-high-speed elevator car system based on adaptive fuzzy

2021 ◽  
Vol 54 (3-4) ◽  
pp. 360-373
Author(s):  
Hong Wang ◽  
Mingqin Zhang ◽  
Ruijun Zhang ◽  
Lixin Liu
Keyword(s):  
Sliding Mode Control ◽  
High Speed ◽  
Sliding Mode ◽  
Mode Switching ◽  
Parameter Uncertainties ◽  
Horizontal Vibration ◽  
Adaptive Fuzzy ◽  
Mode Control ◽  
System A ◽  
Ultra High Speed

In order to effectively suppress horizontal vibration of the ultra-high-speed elevator car system. Firstly, considering the nonlinearity of guide shoe, parameter uncertainties, and uncertain external disturbances of the elevator car system, a more practical active control model for horizontal vibration of the 4-DOF ultra-high-speed elevator car system is constructed and the rationality of the established model is verified by real elevator experiment. Secondly, a predictive sliding mode controller based on adaptive fuzzy (PSMC-AF) is proposed to reduce the horizontal vibration of the car system, the predictive sliding mode control law is achieved by optimizing the predictive sliding mode performance index. Simultaneously, in order to decrease the influence of uncertainty of the car system, a fuzzy logic system (FLS) is designed to approximate the compound uncertain disturbance term (CUDT) on-line. Furthermore, the continuous smooth hyperbolic tangent function (HTF) is introduced into the sliding mode switching term to compensate the fuzzy approximation error. The adaptive laws are designed to estimate the error gain and slope parameter, so as to increase the robustness of the system. Finally, numerical simulations are conducted on some representative guide rail excitations and the results are compared to the existing solution and passive system. The analysis has confirmed the effectiveness and robustness of the proposed control method.

Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

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