scholarly journals Design of Ship Course-Keeping Autopilot using a Sine Function-Based Nonlinear Feedback Technique

2015 ◽  
Vol 69 (2) ◽  
pp. 246-256 ◽  
Author(s):  
Xian-ku Zhang ◽  
Guo-qing Zhang
Keyword(s):  
Control Strategies ◽  
Feedback Signal ◽  
Sine Function ◽  
Nonlinear Feedback ◽  
Control Effect ◽  
Control Error ◽  
Closed Loop Systems ◽  
Automatic Navigation ◽  
Feedback Scheme ◽  
Control Scheme

Course keeping for ships is the core of automatic navigation in sea transportation. Much work has concentrated on developing novel control strategies for closed loop systems. We have turned our attention the other way to improve the control performance of marine autopilots in this work by “modulating” the control error using a sine function while the construction of the controller is not changed. The nonlinear feedback signal thus obtained is sent to the controller to replace the control error itself, which used to be the deviation between the output response and the reference input of the system. Such a control scheme is called “nonlinear feedback control” hereafter. Theoretical analysis by using a describing function and robust control theory shows that the same control quality is guaranteed with minor control actions for the nonlinear feedback scheme. Simulation experiments were carried out for the ship Yulong of Dalian Maritime University. It is shown that the method postulated in this paper has advantages of safety and energy saving in navigation; the maximum initial rudder angle is reduced by 31·2% with satisfactory control effect.

scholarly journals Pressure Control of Insulation Space for Liquefied Natural Gas Carrier with Nonlinear Feedback Technique

2018 ◽  
Vol 6 (4) ◽  
pp. 133
Author(s):  
Jinghua Cao ◽  
Xianku Zhang ◽  
Xiang Zou
Keyword(s):  
Natural Gas ◽  
Control Strategy ◽  
Control Strategies ◽  
Nonlinear Function ◽  
Pressure Control ◽  
Feedback Signal ◽  
Control Input ◽  
Nonlinear Feedback ◽  
Pressure Control System ◽  
Liquid Natural Gas

This paper introduces a novel control strategy into the insulation space for liquid natural gas carriers. The control strategy proposed can improve the effects of control for differential pressure and reduce the energy consumption of nitrogen. The method combines a nonlinear feedback technique with a closed-loop gain shaping algorithm (CGSA). It is designed for the pressure control system which is vital for liquid natural gas carriers (LNGCs) in marine transportation. The control error is modulated using nonlinear function. The deviation signal is replaced with a nonlinear feedback signal. Comparison experiments are conducted under different conditions to prove the effectiveness of this strategy. This paper compares three control strategies: a control strategy with nonlinear feedback based on CGSA, a control strategy without nonlinear feedback based on CGSA, and a two-degree-of-freedom (DOF) control strategy. The simulation results show that this control strategy with nonlinear feedback performs better than the other two. The average reduction of control input is about 38.8%. The effect of pressure control is satisfactory.

Dynamic Nonlinear Feedback Control Applied to Improve Butanol Production by Clostridium acetobutylicum

2017 ◽  
Vol 15 (6) ◽  
Author(s):  
H. I Velázquez-Sánchez ◽  
G. Lara-Cisneros ◽  
R. Femat ◽  
R. Aguilar-López
Keyword(s):  
Clostridium Acetobutylicum ◽  
Numerical Experiments ◽  
Closed Loop ◽  
Open Loop ◽  
Feedback Signal ◽  
Butanol Production ◽  
Nonlinear Feedback ◽  
Operational Conditions ◽  
Continuous Bioreactor ◽  
Control Scheme

Abstract The goal of this work is to present a closed-loop operational strategy in order to improve the butanol production in an anaerobic continuous bioreactor for the called Acetone-Butanol-Ethanol (ABE) process. The proposed control scheme considers a class of feedback signal which includes a nonlinear bounded function of the regulation error. The control scheme is applied to a phenomenological unstructured kinetic model obtained from an experimental and metabolic study of butanol production by Clostridium acetobutylicum, which allows the proposed structure to predict several operational conditions from batch and continuous regimes. Numerical experiments using the proposed model considering continuous operation were performed in order to find a feasible operating region for maximum butanol production at open-loop regime. The proposed methodology is applied to regulate the product concentration, manipulating the dilution rate to lead to a higher butanol productivity. The closed-loop behaviour of the bioreactor is analysed, finding that the proposed controller minimizes the response time of the system and allows it to achieve a productivity gain of 55 % over open-loop operation. Further numerical experiments show the satisfactory closed-loop performance of the proposed methodology in comparison with a PI controller.

Improved Concise Backstepping Control of Course Keeping for Ships Using Nonlinear Feedback Technique

2017 ◽  
Vol 70 (6) ◽  
pp. 1401-1414 ◽  
Author(s):  
XianKu Zhang ◽  
Guangping Yang ◽  
Qiang Zhang ◽  
Guoqing Zhang ◽  
Yuqi Zhang
Keyword(s):  
Controller Design ◽  
Nonlinear Function ◽  
Backstepping Control ◽  
Energy Output ◽  
Nonlinear Feedback ◽  
Nonlinear Controller ◽  
Control Effect ◽  
Automatic Navigation ◽  
One Step ◽  
The Mathematical Model

Course keeping for ships is vital for automatic navigation in marine transportation. To improve the control effect and reduce the energy output of the controller, this article proposes an improved concise backstepping controller based on a Lyapunov candidate function by introducing a nonlinear function of course error to replace the course error itself in the feedback loop. The procedure of nonlinear controller design has been reduced from two steps to one step using information from controlled plant to construct the Lyapunov candidate function. Compared with the pure backstepping control, the proposed improved algorithm reserves the nonlinear item of the system, and possesses a strong disturbance rejection ability and robustness to the mathematical model uncertainty. The algorithm given here has advantages of simplified construction method, satisfactory control effect, robustness and energy saving.

Closed-Loop Control Vortex-Airfoil Interaction Noise

2006 ◽  
Author(s):  
M. M. Zhang ◽  
L. Cheng ◽  
Y. Zhou
Keyword(s):  
Closed Loop ◽  
Leading Edge ◽  
Fast Response ◽  
Vortical Flow ◽  
Feedback Signal ◽  
Closed Loop Control ◽  
Vortex Interaction ◽  
Control Effect ◽  
Loop Control ◽  
Control Scheme

Closed-loop controlled interactions between an airfoil and impinging vortices were experimentally investigated. This work aims to minimize the fluctuating flow pressure (p) at the leading edge of the airfoil, which is a major source of the blade-vortex interaction noises commonly seen in rotorcrafts. Piezo-ceramic actuators were used to create a local surface perturbation near the leading edge of the airfoil in order to alter the airfoil-vortex interaction. Two closed-loop control schemes were investigated, which deployed p and the streamwise fluctuating flow velocity (u) as the feedback signal, respectively. While the control effect on p was measured using a fast response pressure transducer, the oncoming vortical flow was monitored using a particle image velocimetry and a hot wire. It was found that the control scheme based on the feedback signal u led to a pronounced impairment in the strength of oncoming vortices and meanwhile a maximum reduction in p by 39%, outperforming the control scheme based on the feedback signal p. Physics behind the observations is discussed.

Continuous Finite-Time Torque Control for Flexible Assistance Exoskeleton with Delay Variation Input

Robotica ◽  
2020 ◽  
pp. 1-26
Author(s):  
Tao Xue ◽  
ZiWei Wang ◽  
Tao Zhang ◽  
Ou Bai ◽  
Meng Zhang ◽  
...  
Keyword(s):  
Finite Time ◽  
Disturbance Rejection ◽  
High Performance ◽  
Control Strategies ◽  
Fractional Power ◽  
Critical Issue ◽  
Human Robot Interaction ◽  
Torque Control ◽  
Finite Time Stability ◽  
Control Scheme

SUMMARY Accurate torque control is a critical issue in the compliant human–robot interaction scenario, which is, however, challenging due to the ever-changing human intentions, input delay, and various disturbances. Even worse, the performances of existing control strategies are limited on account of the compromise between precision and stability. To this end, this paper presents a novel high-performance torque control scheme without compromise. In this scheme, a new nonlinear disturbance observer incorporated with equivalent control concept is proposed, where the faster convergence and stronger anti-noise capability can be obtained simultaneously. Meanwhile, a continuous fractional power control law is designed with an iteration method to address the matched/unmatched disturbance rejection and global finite-time convergence. Moreover, the finite-time stability proof and prescribed control performance are guaranteed using constructed Lyapunov function with adding power integrator technique. Both the simulation and experiments demonstrate enhanced control accuracy, faster convergence rate, perfect disturbance rejection capability, and stronger robustness of the proposed control scheme. Furthermore, the evaluated assistance effects present improved gait patterns and reduced muscle efforts during walking and upstair activity.

Robust fault-tolerant tracking control for a class of nonlinear systems based on position measurements only

2016 ◽  
Vol 230 (6) ◽  
pp. 486-497 ◽  
Author(s):  
Gang Shen ◽  
Zhen-Cai Zhu ◽  
Xiang Li ◽  
Qiang Meng ◽  
Yu Tang ◽  
...  
Keyword(s):  
Nonlinear Systems ◽  
Fault Tolerant ◽  
Tracking System ◽  
High Quality ◽  
Differential Signal ◽  
Time Dynamic ◽  
Closed Loop Systems ◽  
Controlled Systems ◽  
Attitude Tracking ◽  
Control Scheme

The problem of trajectory tracking for a class of nonlinear systems in the presence of un-modeled dynamics, parameter variations and even the actuator faults is investigated in this paper. A novel fault-tolerant control scheme is proposed by combining the nominal model-based controller and time-delay controller, which are adopted to achieve the real-time dynamic compensation and guarantee the robust stability of the controlled systems, respectively. Moreover, high-quality differential signals are unavailable in the presence of disturbances and measurement noise, which limit the performance of closed-loop systems in practice. Therefore, an extended state observer (ESO) is introduced to obtain high-quality differential signal estimations based on position measurements only. Furthermore, the effectiveness of the proposed novel control scheme is verified by testing in the spacecraft attitude tracking system.

A Simple Switching Control for Linear Systems to Assure Nonovershooting Step Responses

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Bo Zhu ◽  
Kai-Yuan Cai
Keyword(s):  
Switching Control ◽  
Linear Feedback ◽  
Linear Feedback Control ◽  
Time Intervals ◽  
Closed Loop Systems ◽  
State Dependent ◽  
Control Scheme ◽  
Performance Limitation ◽  
The Common ◽  
Step Responses

In the paper, we show that for a class of linear plants, although the common linear control can be used to stabilize them, the step responses of the resulting closed-loop systems must have overshoot; however, a simple switching between them may avoid the overshoot. This indicates that switching control may overcome the performance limitation of linear feedback control in the overshoot-avoidance respect. A simple switching control scheme with such a quality is exploited and the conditions for its existence are presented. In the scheme, two common controllers are needed and they are only required to guarantee no overshoot on the time intervals [0, ts) and [ts, ∞), respectively, where ts denotes the switching time. For actual implementation, a state-dependent version of the switching control law is developed. Two examples are presented to show its effectiveness.

Real-Time Planning and Nonlinear Control for Quadrupedal Locomotion With Articulated Tails

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Randall T. Fawcett ◽  
Abhishek Pandala ◽  
Jeeseop Kim ◽  
Kaveh Akbari Hamed
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Center Of Mass ◽  
Hierarchical Control ◽  
Nonlinear Feedback ◽  
Nonlinear Controller ◽  
External Disturbances ◽  
Quadrupedal Locomotion ◽  
Control Scheme ◽  
High Level

Abstract The primary goal of this paper is to develop a formal foundation to design nonlinear feedback control algorithms that intrinsically couple legged robots with bio-inspired tails for robust locomotion in the presence of external disturbances. We present a hierarchical control scheme in which a high-level and real-time path planner, based on an event-based model predictive control (MPC), computes the optimal motion of the center of mass (COM) and tail trajectories. The MPC framework is developed for an innovative reduced-order linear inverted pendulum (LIP) model that is augmented with the tail dynamics. At the lower level of the control scheme, a nonlinear controller is implemented through the use of quadratic programming (QP) and virtual constraints to force the full-order dynamical model to track the prescribed optimal trajectories of the COM and tail while maintaining feasible ground reaction forces at the leg ends. The potential of the analytical results is numerically verified on a full-order simulation model of a quadrupedal robot augmented with a tail with a total of 20 degrees-of-freedom. The numerical studies demonstrate that the proposed control scheme coupled with the tail dynamics can significantly reduce the effect of external disturbances during quadrupedal locomotion.

Cyber Physical Control Systems

2015 ◽  
pp. 263-285
Keyword(s):  
Artificial Intelligence ◽  
Control Systems ◽  
Intelligent Systems ◽  
Control Strategies ◽  
Case Based Reasoning ◽  
Physical Control ◽  
Closed Loop Systems ◽  
Intelligence Models ◽  
Algorithmic Design ◽  
Case Based

The focus of algorithmic design is to solve composite problems. Intelligent systems use intellectual concepts like evolutionary computation, artificial neural networks, fuzzy systems, and swarm intelligence to process natural intelligence models. Artificial intelligence is used as a part of intelligent systems to perform logic- and case-based reasoning. Systems like mechanical and electrical support systems are operated by utilizing Supervisory Control and Data Acquisition (SCADA) systems. These systems cannot accomplish their purpose, provided the control system deals with the reliability of it. In CPSs, dimensions of physical processes are taken by sensors and are processed in cyber subsystems to drive the actuators that affect the physical processors. CPSs are closed-loop systems. The adaptation and the prediction are the properties to be followed by the control strategies that are implemented in cyber subsystems. This chapter explores cyber physical control systems.

scholarly journals Adaptive Decentralized Control Scheme for a Stochastic Interconnected System

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiaoli Jiang ◽  
Siqi Liu ◽  
Mingyue Liu ◽  
Li Yang ◽  
Lina Liu
Keyword(s):  
State Feedback ◽  
Closed Loop ◽  
Reference Signal ◽  
Network Control ◽  
Neural Network Control ◽  
Neural Structure ◽  
Interconnected System ◽  
Feedback Scheme ◽  
Control Scheme ◽  
Adaptive Decentralized Control

This work investigates a decentralized state feedback scheme of neural network control for an interconnected system. The completely unknown associated terms are estimated directly by the neural structure. A modified approach is proposed to deal with the state feedback format. By combining the Lyapunov function and backstepping technology together, an adaptive decentralized controller is established, and we can construct the boundedness of all signals in the closed-loop structure through the controller, which can drive the formation of a given reference signal. In the end, the effectiveness of the presented strategy is referred to a simulation example.

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