scholarly journals LPV robust servo control of aircraft active side-sticks

2020 ◽  
Vol 92 (4) ◽  
pp. 599-609
Author(s):  
Guang Rui Zhou ◽  
Shi Qian Liu ◽  
Yuan Jun Sang ◽  
Xu Dong Wang ◽  
Xiao Peng Jia ◽  
...  
Keyword(s):  
Control Method ◽  
Linear Time ◽  
External Disturbance ◽  
Servo System ◽  
Slip Angle ◽  
Content Type ◽  
Civil Aircraft ◽  
Non Linear ◽  
Lpv Control ◽  
The Impact

Purpose This paper aims to focus on the variable stick force-displacement (SFD) gradience in the active side stick (ASS) servo system for the civil aircraft. Design/methodology/approach The problem of variable SFD gradience was introduced first, followed by the analysis of its impact on the ASS servo system. To solve this problem, a linear-parameter-varying (LPV) control approach was suggested to process the variable gradience of the SFD. A H∞ robust control method was proposed to deal with the external disturbance. Findings To validate the algorithm performance, a linear time-variant system was calculated to be used to worst cases and the SFD gradience was set to linear and non-linear variation to test the algorithm, and some typical examples of pitch angle and side-slip angle tracking control for a large civil aircraft were also used to verify the algorithm. The results showed that the LPV control method had less settling time and less steady tracking errors than H∞ control, even in the variable SFD case. Practical implications This paper presented an ASS servo system using the LPV control method to solve the problem caused by the variable SFD gradience. The motor torque command was calculated by pressure and position feedback without additional hardware support. It was more useful for the electronic hydraulic servo actuator. Originality/value This was the research paper that analyzed the impact of the variable SFD gradience in the ASS servo system and presented an LPV control method to solve it. It was applicable for the SFD gradience changing in the linear and non-linear cases.

Visual servoing of dynamic wheeled mobile robots with anti-interference finite-time controllers

2018 ◽  
Vol 38 (5) ◽  
pp. 558-567 ◽  
Author(s):  
Hua Chen ◽  
Lei Chen ◽  
Qian Zhang ◽  
Fei Tong
Keyword(s):  
Mobile Robots ◽  
Finite Time ◽  
Visual Servoing ◽  
Control Method ◽  
External Disturbance ◽  
Nonholonomic Systems ◽  
Stability Control ◽  
Interference Control ◽  
Wheeled Mobile Robots ◽  
Content Type

Purpose The finite-time visual servoing control problem is considered for dynamic wheeled mobile robots (WMRs) with unknown control direction and external disturbance. Design/methodology/approach By using finite-time control method and switching design technique. Findings First, the visual servoing kinematic WMR model is developed, which can be converted to the dynamic chained-form systems by using a state and input feedback transformation. Then, for two decoupled subsystems of the chained-form systems, according to the finite-time stability control theory, a discontinuous three-step switching control strategy is proposed in the presence of uncertain control coefficients and external disturbance. Originality/value A class of discontinuous anti-interference control method has been presented for the dynamic nonholonomic systems.

Stability control for end effect of mobile manipulator in uneven terrain based on active disturbance rejection control

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chuang Cheng ◽  
Hui Zhang ◽  
Hui Peng ◽  
Zhiqian Zhou ◽  
Bailiang Chen ◽  
...  
Keyword(s):  
Disturbance Rejection ◽  
Control Method ◽  
External Disturbance ◽  
Stability Control ◽  
Mobile Manipulator ◽  
Active Disturbance Rejection Control ◽  
End Effector ◽  
Content Type ◽  
Active Disturbance Rejection ◽  
Disturbance Rejection Control

Purpose When the mobile manipulator is traveling on an unconstructed terrain, the external disturbance is generated. The load on the end of the mobile manipulator will be affected strictly by the disturbance. The purpose of this paper is to reject the disturbance and keep the end effector in a stable pose all the time, a control method is proposed for the onboard manipulator. Design/methodology/approach In this paper, the kinematics and dynamics models of the end pose stability control system for the tracked robot are built. Through the guidance of this model information, the control framework based on active disturbance rejection control (ADRC) is designed, which keeps the attitude of the end of the manipulator stable in the pitch, roll and yaw direction. Meanwhile, the control algorithm is operated with cloud computing because the research object, the rescue robot, aims to be lightweight and execute work with remote manipulation. Findings The challenging simulation experiments demonstrate that the methodology can achieve valid stability control performance in the challenging terrain road in terms of robustness and real-time. Originality/value This research facilitates the stable posture control of the end-effector of the mobile manipulator and maintains it in a suitable stable operating environment. The entire system can normally work even in dynamic disturbance scenarios and uncertain nonlinear modeling. Furthermore, an example is given to guide the parameter tuning of ADRC by using model information and estimate the unknown internal modeling uncertainty, which is difficult to be modeled or identified.

scholarly journals Forecasting stock price movement: new evidence from a novel hybrid deep learning model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yang Zhao ◽  
Zhonglu Chen
Keyword(s):  
Time Series ◽  
Deep Learning ◽  
Hybrid Model ◽  
Stock Price ◽  
Linear Time ◽  
Price Movement ◽  
Content Type ◽  
Non Linear ◽  
New Evidence ◽  
Deep Learning Model

PurposeThis study explores whether a new machine learning method can more accurately predict the movement of stock prices.Design/methodology/approachThis study presents a novel hybrid deep learning model, Residual-CNN-Seq2Seq (RCSNet), to predict the trend of stock price movement. RCSNet integrates the autoregressive integrated moving average (ARIMA) model, convolutional neural network (CNN) and the sequence-to-sequence (Seq2Seq) long–short-term memory (LSTM) model.FindingsThe hybrid model is able to forecast both linear and non-linear time-series component of stock dataset. CNN and Seq2Seq LSTMs can be effectively combined for dynamic modeling of short- and long-term-dependent patterns in non-linear time series forecast. Experimental results show that the proposed model outperforms baseline models on S&P 500 index stock dataset from January 2000 to August 2016.Originality/valueThis study develops the RCSNet hybrid model to tackle the challenge by combining both linear and non-linear models. New evidence has been obtained in predicting the movement of stock market prices.

Design of H_/H∞ fault detection observer for closed-loop nonlinear system with disturbance

2020 ◽  
Vol 40 (4) ◽  
pp. 589-599
Author(s):  
Zhengquan Chen ◽  
Lu Han ◽  
Yandong Hou
Keyword(s):  
Fault Detection ◽  
Closed Loop ◽  
External Disturbance ◽  
Adaptive Threshold ◽  
Linear Matrix ◽  
Content Type ◽  
Non Linear ◽  
Runge Kutta ◽  
Non Linear System ◽  
Residual Generator

Purpose This paper proposes a novel method of fault detection, which is based on H_/H∞ Runge–Kutta observer and an adaptive threshold for a class of closed-loop non-linear systems. The purpose of this paper is to improve the rapidity and accuracy of fault detection. Design/methodology/approach First, the authors design the H_/H∞ Runge–Kutta fault detection observer, which is used as a residual generator to decouple the residual from the input. The H_ performance index metric in the specified frequency domain is used to describe how sensitive the residual to the fault. The H∞ norm is used to describe the residual robustness to the external disturbance of the systems. The residual generator is designed to achieve the best tradeoff between robustness against unknown disturbances but sensitivity to faults, thus realizing the accurate detection of the fault by suppressing the influence of noise and disturbance on the residual. Next, the design of the H_/H∞ fault detection observer is transformed into a convex optimization problem and solved by linear matrix inequality. Then, a new adaptive threshold is designed to improve the accuracy of fault detection. Findings The effectiveness and correctness of the method are tested in simulation experiments. Originality/value This paper presents a novel approach to improve the accuracy and rapidity of fault detection for closed-loop non-linear system with disturbances and noise.

Evaluation of Impact Loads on Offshore Jacket Platform During Float-Over Mating Operation

2019 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Mahesh B. Addala ◽  
Gudimella G. S. Achary ◽  
Subramanyam V. R. Sripada
Keyword(s):  
Time Domain ◽  
Linear Time ◽  
Random Wave ◽  
Impact Loads ◽  
Transient Effects ◽  
Seed Selection ◽  
Mooring Lines ◽  
Contact Points ◽  
Non Linear ◽  
The Impact

Abstract In the mating phase of float-over operation, the topsides deck load from the vessel is transferred onto the jacket either by ballasting the vessel or by the combination of ballasting and hydraulic jacking system. During this phase of operation, the topsides and jacket experience impact loads through the contact points in a short duration of time. To evaluate the impact loads and to capture the transient effects precisely, a non-linear time domain hydrodynamic analysis is required. To obtain the design loads, generally the numerical jacking simulation is initiated at the time instant of maximum wave height when the jacking system is used. However, the conservative response may also depend on the relative velocity between the jacket and topsides legs. In this paper, a series of non-linear time domain as well as linear frequency domain hydrodynamic analyses are performed to evaluate the impact loads between 9000 tonne integrated topsides deck and a 4-legged jacket in a water depth of 50 m during float-over mating operation. The simulations are performed using MOSES software. The float-over hardware such as LMUs (leg mating unit), DSUs (deck support unit), Jacks, Fenders and Mooring lines are modelled as appropriate linear / nonlinear springs. The principle of the mating operation is considered through a combination of vessel ballasting and jacking operation. This paper discusses about random wave seed selection, effect of vessel response and wave headings on the impact loads of LMUs and Jacks/DSUs.

scholarly journals The yin and yang nature of coopetition activities: non-linear effects and the moderating role of competitive intensity for internationalised firms

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
James M. Crick ◽  
Dave Crick
Keyword(s):  
Chinese Philosophy ◽  
Market Performance ◽  
Company Performance ◽  
Competitive Intensity ◽  
Content Type ◽  
Non Linear ◽  
Yin And Yang ◽  
The Impact ◽  
Moderating Role

PurposeThis paper draws upon the Yin and Yang concept of Chinese philosophy within a Western context to examine coopetition, namely, the interplay between cooperation and competition. Although coopetition activities should positively affect company performance, earlier research involving this relationship has typically been linear in nature and without moderating factors. Consequently, underpinned by resource-based theory and the relational view, the purpose of this investigation is to examine the non-linear (inverted U-shaped) link between coopetition and company performance under the moderating role of competitive intensity.Design/methodology/approachCollection of survey data involved a sample of 101 internationalising wine producers in New Zealand. Following a check of the statistical data for all major assessments of reliability and validity (together with common method variance), testing the research hypotheses and control paths took place through hierarchical regression. Furthermore, 20 semi-structured interviews helped explain the underlying mechanisms behind the quantitative results.FindingsCoopetition had a non-linear (inverted U-shaped) relationship with market performance. Surprisingly, competitive intensity yielded a negative moderation effect. The mixed methods results highlighted that firms must strike an effective balance between the paradoxical forces of cooperativeness and competitiveness across their product-market strategies.Originality/valueThis investigation contributes to the existing literature by developing and testing a conceptual framework examining the nature of the relationship between coopetition activities and market performance – using non-linear (inverted U-shaped) and moderating effects. It addresses a debate between two schools-of-thought concerning the impact of competitive intensity on the coopetition paradox. Additionally, this study helps to explain the coopetition construct through the Yin and Yang concept to highlight how the paradoxical forces of cooperativeness and competitiveness can create harmful outcomes for organisations if they do not manage them effectively (across domestic and international markets).

Application Research on H∞ Optimization Control of Permanent Magnet Linear Servo System Based on Adaptive Fuzzy Control Strategy

2013 ◽  
Vol 694-697 ◽  
pp. 2185-2189
Author(s):  
Xiao Ping Zhu ◽  
Xiu Ping Wang ◽  
Chun Yu Qu ◽  
Jun You Zhao
Keyword(s):  
Fuzzy Control ◽  
Control Strategy ◽  
Control Method ◽  
Fuzzy Controller ◽  
External Disturbance ◽  
Adaptive Fuzzy Control ◽  
Servo System ◽  
Robust Controller ◽  
Adaptive Fuzzy Controller ◽  
Adaptive Fuzzy

In order to against the uncertain disturbance of AC linear servo system, an H mixed sensitivity control method based on adaptive fuzzy control was putted forward in the paper. The controller is comprised of an adaptive fuzzy controller and a H robust controller, the adaptive fuzzy controller is used to approximate this ideal control law, H robust controller is designed for attenuating the approximation errors and the influence of the external disturbance. The experimental results show that this control strategy not only has a strong robustness to uncertainties of the linear system, but also has a good tracking performance, furthermore the control greatly improves the robust tracking precision of the direct drive linear servo system.

Design of the Servo System for the Micro Milling Machine

2007 ◽  
Vol 364-366 ◽  
pp. 389-393
Author(s):  
Bo Wang ◽  
Ju Xiang Wang ◽  
Ying Chun Liang
Keyword(s):  
High Performance ◽  
Servo System ◽  
Micro Milling ◽  
Milling Machine ◽  
Tracking Accuracy ◽  
Non Linear ◽  
Micro Parts ◽  
Linear Encoder ◽  
Micro Structures ◽  
The Impact

To manufacture the micro parts or micro structures effectively and precisely, a high precision 3-axis micro milling machine is built. All the three axis are driven by linear piezoelectric ultrasonic motors and the slides are supported by cross-roller guide. Investigations are firstly made to analyze the impact of the non-linear characteristics in the servo mechanism on the performance of the servo system. To achieve the positioning and tracking accuracy at sub-micrometer and micrometer level respectively, on one hand, a optical linear encoder with the resolution of 50nm is applied to close the control loop and a high performance DSP based motion control card is used to carried out the reference command. On the other hand, sophisticated control and compensation strategies are also implemented to overcome the non-linear characteristics in the servo system. Positioning and tracking experiments show that, with this well-tuned control system, the positioning and tracking accuracy are ±0.5μm and ±2.4μm respectively. Using this machine, a micro part with 5μm thin-walled structure is machined successfully.

Robot compliant catching by Maxwell model based Cartesian admittance control

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Le Fu ◽  
Jie Zhao
Keyword(s):  
Control Method ◽  
Maxwell Model ◽  
Admittance Control ◽  
End Effector ◽  
Content Type ◽  
Model Based ◽  
Time Optimal ◽  
Voigt Model ◽  
Optimal Movement ◽  
The Impact

Purpose Admittance control is a typical complaint control methodology. Traditionally, admittance control systems are based on a dynamical relationship described by Voigt model. By contrast, after changing connection of spring and damper, Maxwell model produces different dynamics and has shown better impact absorption performance. This paper aims to design a novel compliant control method based on Maxwell model and implement it in a robot catching scenario. Design/methodology/approach To achieve this goal, this paper proposed a Maxwell model based admittance control scheme. Considering several motion stages involved in one catching attempt, the following approaches are adopted. First, Kalman filter is used to process the position data stream acquired from motion capture system and predict the subsequent object flying trajectory. Then, a linear segments with parabolic blends reaching motion is generated to achieve time-optimal movement under kinematic and joint inherent constraints. After robot reached the desired catching point, the proposed Maxwell model based admittance controller performs such as a cushion to moderate the impact between robot end-effector and flying object. Findings This paper has experimentally demonstrated the feasibility and effectiveness of the proposed method. Compared with typical Voigt model based compliant catching, less object bounding away from end-effector happens and the success rate of catching has been improved. Originality/value The authors proposed a novel Maxwell model based admittance control method and demonstrated its effectiveness in a robot catching scenario. The author’s approach may inspire other related researchers and has great potential of practical usage in a widespread of robot applications.

The impact of external debt on total factor productivity and growth in HIPCs: non-linear regression approaches

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sisay Demissew Beyene ◽  
Balázs Kotosz
Keyword(s):  
Total Factor Productivity ◽  
Threshold Model ◽  
External Debt ◽  
Seemingly Unrelated Regression ◽  
Complete Analysis ◽  
Threshold Values ◽  
Factor Productivity ◽  
Content Type ◽  
Non Linear ◽  
The Impact

Purpose The purpose of this study is to provide an empirical analysis of the impact of external debt on total factor productivity (TFP) and growth along with the TFP channel through which external debt affects the growth of heavily indebted poor countries (HIPCs). Design/methodology/approach This study uses panel data econometrics; basically, the seemingly unrelated regression (SUR) and alternative non-linear (panel threshold) models. For robustness check, it also uses panel-corrected standard errors, feasible generalized least squares and SUR (using alternative variables). Findings External debt significantly reduces both TFP and growth. Besides, it confirms that the relationship between external debt and TFP and gross domestic product growth is non-linear. Further external debt can affect the growth of HIPCs through the TFP channel. However, the threshold model result reveals weak evidence of threshold values although there are some threshold values of 67 and 54 for TFP and growth models, respectively. Originality/value To the best of the authors’ knowledge, this is the first study on most concerned countries (HIPCs) that shows a detailed and complete analysis of the TFP channel and the impact of external debt on growth. Thus, it provides appropriate and sound policies that consider the unique characteristics of the countries. Unlike most previous findings, this study does not support an inverted U-shape relationship between external debt and growth. Further, it provides insights into the relationships among TFP, external debt and growth. Moreover, it considers basic panel econometric tests like cross-sectional dependence, uses a non-linear simultaneous equations model along with the alternative non-linear model and is supported by different robustness checks.

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