scholarly journals Dynamic visual servoing with Kalman filter-based depth and velocity estimator

2021 ◽  
Vol 18 (3) ◽  
pp. 172988142110166
Author(s):  
Ting-Yu Chang ◽  
Wei-Che Chang ◽  
Ming-Yang Cheng ◽  
Shih-Sian Yang
Keyword(s):  
Kalman Filter ◽  
System Dynamics ◽  
Visual Servoing ◽  
Control Design ◽  
Torque Control ◽  
Depth Information ◽  
Calibration Error ◽  
Feature Points ◽  
Control Scheme ◽  
Account System

Camera calibration error, vision latency, nonlinear dynamics, and so on present a major challenge for designing the control scheme for a visual servoing system. Although many approaches on visual servoing have been proposed, surprisingly, only a few of them have taken into account system dynamics in the control design of a visual servoing system. In addition, the depth information of feature points is essential in the image-based visual servoing architecture. As a result, to cope with the aforementioned problems, this article proposes a Kalman filter-based depth and velocity estimator and a modified image-based dynamic visual servoing architecture that takes into consideration the system dynamics in its control design. In particular, the Kalman filter is exploited to deal with the problems caused by vision latency and image noise so as to facilitate the estimation of the joint velocity of the robot using image information only. Moreover, in the modified image-based dynamic visual servoing architecture, the computed torque control scheme is used to compensate for system dynamics and the Kalman filter is used to provide accurate depth information of the feature points. Results of visual servoing experiments conducted on a two-degree of freedom planar robot verify the effectiveness of the proposed approach.

scholarly journals Control design, implementation, and evaluation for an in-field 500 kW wind turbine with a fixed-displacement hydraulic drivetrain

2018 ◽  
Vol 3 (2) ◽  
pp. 615-638 ◽  
Author(s):  
Sebastiaan Paul Mulders ◽  
Niels Frederik Boudewijn Diepeveen ◽  
Jan-Willem van Wingerden
Keyword(s):  
Wind Turbine ◽  
Control Design ◽  
Business Case ◽  
Torque Control ◽  
Offshore Wind ◽  
Pelton Turbine ◽  
Torque Control Strategy ◽  
Control Scheme ◽  
Active Valve ◽  
Electrical Generator

Abstract. The business case for compact hydraulic wind turbine drivetrains is becoming ever stronger, as offshore wind turbines are getting larger in terms of size and power output. Hydraulic transmissions are generally employed in high-load systems and form an opportunity for application in multi-megawatt turbines. The Delft Offshore Turbine (DOT) is a hydraulic wind turbine concept replacing conventional drivetrain components with a single seawater pump. Pressurized seawater is directed to a combined Pelton turbine connected to an electrical generator on a central multi-megawatt electricity generation platform. This paper presents the control design, implementation, and evaluation for an intermediate version of the ideal DOT concept: an in-field 500 kW hydraulic wind turbine. It is shown that the overall drivetrain efficiency and controllability are increased by operating the rotor at maximum rotor torque in the below-rated region using a passive torque control strategy. An active valve control scheme is employed and evaluated in near-rated conditions.

A Switched Extend Kalman-Filter for Visual Servoing Applied in Nonholonomic Robot with the FOV Constraint

2015 ◽  
Vol 19 (2) ◽  
pp. 185-190
Author(s):  
Yuan Fang ◽  
◽  
Zhang Xiaoyong ◽  
Huang Zhiwu ◽  
Wentao Yu ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Visual Servoing ◽  
Field Of View ◽  
Feature Points ◽  
Extend Kalman Filter ◽  
The Real ◽  
Nonholonomic Robots ◽  
The Status ◽  
Real State

In this paper, a switched Kalmanfilter (KF) is used to predict the status of feature points leaving the field of view (FOV), which is one of the most common constraints in FOV. By using the prediction of status to compensate for the real state of feature points, nonholonomic robots conduct visual servoing tasks efficiently. Results of simulation and experiments verify the effectiveness of the proposed approach.

scholarly journals Control design, implementation and evaluation for an in-field 500 kW wind turbine with a fixed-displacement hydraulic drivetrain

2018 ◽  
Author(s):  
Sebastiaan Paul Mulders ◽  
Niels Frederik Boudewijn Diepeveen ◽  
Jan-Willem van Wingerden
Keyword(s):  
Wind Turbine ◽  
Control Design ◽  
Business Case ◽  
Torque Control ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Torque Control Strategy ◽  
Control Scheme ◽  
Active Valve ◽  
Valve Control

Abstract. The business case for compact hydraulic wind turbine drivetrains is becoming ever stronger, as offshore wind turbines are getting larger in terms of size and power output. Hydraulic transmissions are generally employed in high load systems, and form an opportunity for application in multi-megawatt turbines. The Delft Offshore Turbine (DOT) is a hydraulic wind turbine concept replacing conventional drivetrain components with a single seawater pump. Pressurized seawater is directed to a combined Pelton-generator combination on a central multi-megawatt electricity generation platform. This paper presents the control design, implementation and evaluation for an intermediate version of the ideal DOT concept: an in-field 500 kW hydraulic wind turbine. It is shown that the overall drivetrain efficiency and controllability is increased by operating the rotor at maximum rotor torque in the below-rated region using a passive torque control strategy. An active valve control scheme is employed and evaluated in near-rated conditions.

scholarly journals Three-Step Epipolar-Based Visual Servoing for Nonholonomic Robot with FOV Constraint

2014 ◽  
Vol 2014 ◽  
pp. 1-14
Author(s):  
Yang Xu ◽  
Jun Peng ◽  
Wentao Yu ◽  
Yuan Fang ◽  
Weirong Liu
Keyword(s):  
Output Feedback ◽  
Visual Servoing ◽  
Feature Points ◽  
Efficient Technology ◽  
Nonholonomic Mobile Robots ◽  
Current Configuration ◽  
Control Scheme ◽  
Simulation Results ◽  
The Difference ◽  
Configuration Simulation

Image-based visual servoing for nonholonomic mobile robots using epipolar geometry is an efficient technology for visual servoing problem. An improved visual servoing strategy, namely, three-step epipolar-based visual servoing, is developed for the nonholonomic robot in this paper. The proposed strategy can keep the robot meeting FOV constraint without any 3D reconstruction. Moreover, the trajectory planned by this strategy is shorter than the existing strategies. The mobile robot can reach the desired configuration with exponential converge. The control scheme in this paper is divided into three steps. Firstly, by using the difference of epipoles as feedback, the robot rotates to make the current configuration and desired configuration in the same orientation. Then, by using a linear input-output feedback, the epipoles are zeroed so as to align the robot with the goal. Finally, by using the difference of feature points, the robot reaches the desired configuration. Simulation results and experimental results are given to illustrate the effectiveness of the proposed control scheme.

Robust Control for Heave Compensator With the Use of Kalman Filter-Based Disturbances Estimator

2017 ◽  
Author(s):  
William H. Cuellar ◽  
Tassio Melo Linhares ◽  
Jose Oniram de A. Limaverde Filho ◽  
Jose A. R. Vargas ◽  
Eugenio Fortaleza
Keyword(s):  
Kalman Filter ◽  
Robust Control ◽  
Smooth Function ◽  
Control Design ◽  
Governing Equations ◽  
External Disturbances ◽  
Practical Applications ◽  
Backstepping Approach ◽  
Control Scheme ◽  
Disturbance Estimator

This paper presents a backstepping approach for an active heave compensator actuated by a double acting cylinder. For practical applications, is desired to stabilize the system around the equilibrium point when subjected to unknown external disturbances. Knowing the governing equations, a robust backstepping control design is proposed by introducing a well-defined smooth function and using a Nussbaum function together with a Kalman filter-based disturbance estimator. The efficiency of the proposed control scheme is demonstrated through numerical simulations and compared with related works.

scholarly journals Motion Estimation Using Region-Level Segmentation and Extended Kalman Filter for Autonomous Driving

2021 ◽  
Vol 13 (9) ◽  
pp. 1828
Author(s):  
Hongjian Wei ◽  
Yingping Huang ◽  
Fuzhi Hu ◽  
Baigan Zhao ◽  
Zhiyang Guo ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Motion Estimation ◽  
Optical Flow ◽  
Extended Kalman Filter ◽  
Conditional Random Field ◽  
Autonomous Driving ◽  
Parameter Estimate ◽  
Depth Information ◽  
Parameter Estimates ◽  
Feature Points

Motion estimation is crucial to predict where other traffic participants will be at a certain period of time, and accordingly plan the route of the ego-vehicle. This paper presents a novel approach to estimate the motion state by using region-level instance segmentation and extended Kalman filter (EKF). Motion estimation involves three stages of object detection, tracking and parameter estimate. We first use a region-level segmentation to accurately locate the object region for the latter two stages. The region-level segmentation combines color, temporal (optical flow), and spatial (depth) information as the basis for segmentation by using super-pixels and Conditional Random Field. The optical flow is then employed to track the feature points within the object area. In the stage of parameter estimate, we develop a relative motion model of the ego-vehicle and the object, and accordingly establish an EKF model for point tracking and parameter estimate. The EKF model integrates the ego-motion, optical flow, and disparity to generate optimized motion parameters. During tracking and parameter estimate, we apply edge point constraint and consistency constraint to eliminate outliers of tracking points so that the feature points used for tracking are ensured within the object body and the parameter estimates are refined by inner points. Experiments have been conducted on the KITTI dataset, and the results demonstrate that our method presents excellent performance and outperforms the other state-of-the-art methods either in object segmentation and parameter estimate.

scholarly journals A Study on Vision-Based Backstepping Control for a Target Tracking System

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 105
Author(s):  
Thinh Huynh ◽  
Minh-Thien Tran ◽  
Dong-Hun Lee ◽  
Soumayya Chakir ◽  
Young-Bok Kim
Keyword(s):  
Control System ◽  
Visual Servoing ◽  
Tracking System ◽  
Experimental Studies ◽  
Imaging Geometry ◽  
Control Scheme ◽  
Decoupled Control ◽  
Control Configuration ◽  
A New Technique ◽  
Pointing Control

This paper proposes a new method to control the pose of a camera mounted on a two-axis gimbal system for visual servoing applications. In these applications, the camera should be stable while its line-of-sight points at a target located within the camera’s field of view. One of the most challenging aspects of these systems is the coupling in the gimbal kinematics as well as the imaging geometry. Such factors must be considered in the control system design process to achieve better control performances. The novelty of this study is that the couplings in both mechanism’s kinematics and imaging geometry are decoupled simultaneously by a new technique, so popular control methods can be easily implemented, and good tracking performances are obtained. The proposed control configuration includes a calculation of the gimbal’s desired motion taking into account the coupling influence, and a control law derived by the backstepping procedure. Simulation and experimental studies were conducted, and their results validate the efficiency of the proposed control system. Moreover, comparison studies are conducted between the proposed control scheme, the image-based pointing control, and the decoupled control. This proves the superiority of the proposed approach that requires fewer measurements and results in smoother transient responses.

scholarly journals Pose Measurement for Unmanned Aerial Vehicle Based on Rigid Skeleton

2021 ◽  
Vol 11 (4) ◽  
pp. 1373
Author(s):  
Jingyu Zhang ◽  
Zhen Liu ◽  
Guangjun Zhang
Keyword(s):  
Measurement Errors ◽  
Structural Characteristics ◽  
Geometric Model ◽  
Formation Flight ◽  
Depth Information ◽  
Feature Points ◽  
Feature Point Extraction ◽  
Aerial Vehicle ◽  
Uav Navigation ◽  
Rigid Skeleton

Pose measurement is a necessary technology for UAV navigation. Accurate pose measurement is the most important guarantee for a UAV stable flight. UAV pose measurement methods mostly use image matching with aircraft models or 2D points corresponding with 3D points. These methods will lead to pose measurement errors due to inaccurate contour and key feature point extraction. In order to solve these problems, a pose measurement method based on the structural characteristics of aircraft rigid skeleton is proposed in this paper. The depth information is introduced to guide and label the 2D feature points to eliminate the feature mismatch and segment the region. The space points obtained from the marked feature points fit the space linear equation of the rigid skeleton, and the UAV attitude is calculated by combining with the geometric model. This method does not need cooperative identification of the aircraft model, and can stably measure the position and attitude of short-range UAV in various environments. The effectiveness and reliability of the proposed method are verified by experiments on a visual simulation platform. The method proposed can prevent aircraft collision and ensure the safety of UAV navigation in autonomous refueling or formation flight.

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.

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