This paper presents the design and implementation of leaping control methods for replicating highspeed dolphin leaping behavior. With full consideration of both mechanical configuration and propulsive principle of a p...
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This paper presents the design and implementation of leaping control methods for replicating highspeed dolphin leaping behavior. With full consideration of both mechanical configuration and propulsive principle of a physical robot comprising one neck joint, two propulsive joints, and a pair of two-degrees-of-freedom (2-DOF) mechanical flippers, closed-loop pitch, roll, yaw, and depth control methods are integrated to accomplish precise attitude control. Specifically, two pitch control strategies are proposed to separately satisfy small and large pitch requirements based on the real-time feedback of the pitch angle, while the roll controller is further implemented as a proportional-integral-derivative (PID) loop. A combination of pitch and roll control is utilized to regulate the desired pitch maneuvers. Finally, a parameterized five-phase leaping control algorithm instead of Weihs's three-phase porpoising model is implemented on the self-contained real robot, enabling the examination of biological leaping phenomena which are hard to observe or measure. Latest experimental results reveal that besides high speeds exceeding the minimum exit speeds, the pitch control closely related to pitch angle and submersion depth is another critical factor contributing to effective dolphin leaping.
The fact that the linear estimators using the rank-based Wilcoxon approach in linear regression problems are usually insensitive to outliers is known in statistics. Outliers are the data points that differ greatly fro...
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The fact that the linear estimators using the rank-based Wilcoxon approach in linear regression problems are usually insensitive to outliers is known in statistics. Outliers are the data points that differ greatly from the pattern set by the bulk of the data. Inspired by this fact, Hsieh et al. introduced the Wilcoxon approach into the area of machine learning. They investigated four new learning machines, such as Wilcoxon neural network (WNN), and developed four gradient descent based backpropagation algorithms to train these learning machines. The performances of these machines are better than ordinary nonrobust neural networks in outliers exist tasks. However, it is hard to balance the learning speed and the stability of these algorithms which is inherently the drawback of gradient descent based algorithms. In this paper, a new algorithm is used to train the output weights of single-layer feedforward neural networks (SLFN) with input weights and biases being randomly chosen. This algorithm is called Wilcoxon-norm based robust extreme learning machine or WRELM for short. (C) 2016 Elsevier B.V. All rights reserved.
Precision management of agricultural systems, aiming at optimizing profitability, productivity and sustainability, comprises a set of technologies including sensors, information systems, and informed management, etc. ...
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Image matching based on local features is a challenging task because it is difficult to build a robust local descriptor which is invariant to large variations in scale, viewpoints, illumination and rotation. To addres...
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Image matching based on local features is a challenging task because it is difficult to build a robust local descriptor which is invariant to large variations in scale, viewpoints, illumination and rotation. To address these issues, Scale Invariant Feature Transform (SIFT) descriptor has been proposed to build a robust and distinctive local descriptor. However, it is not fully affine invariant. In this letter, we propose a novel robust descriptor: Sampling based Local Descriptor (SLD) to perform reliable image matching under large variations in scale, viewpoints, illumination and rotation. We build the descriptor based on elliptical sampling which samples image pixels according to the elliptic equations. The main advantage of elliptical sampling is that two controllable parameters of elliptical sampling can generate descriptors with different viewpoints and rotations. Besides, the descriptor has two notable properties: 1) it is fully invariant to affine changes;2) it enables fast matching process because we only need to search two controllable parameters for elliptical sampling, which is more efficient than other affine invariant descriptors. We test the proposed descriptor on standard benchmark for evaluation. Experimental results show the robustness of the proposed method under large variations in illumination, viewpoints and scale.
We present a novel off-axis XR concentrator design that enables a high efficiency energy collection while avoiding the shadowing problem encountered in the designs of symmetry XR type concentrator. Combining with a 1 ...
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We present a novel off-axis XR concentrator design that enables a high efficiency energy collection while avoiding the shadowing problem encountered in the designs of symmetry XR type concentrator. Combining with a 1 cm(2) multi-junction solar cell, the off-axis XR concentrator is able to achieve high optical efficiency of the photovoltaic system. The concentrator design is performed based on the non-imaging optic principle, with one reflective mirror (X) and one refractive lens (R). Both surfaces of the reflective and refractive element are of freeform shapes and fitted as freeform expression in the design analysis. The concentrator has concentration ratio greater than 500x and acceptance angle greater than 2 degrees. A square homogenizing irradiance distribution on the cell is achieved with the help of a suitable rob. The tolerance of the system is analyzed. The results show that the high concentration ratio and greater acceptance angle relax all optical and mechanical tolerances reduce the production and operation cost. (C) 2013 Elsevier GmbH. All rights reserved.
Qarhan Salt Lake is rich in mineral resources, such as sodium chloride, potassium, and magnesium [1].At present, liquid mine exploiting is the main exploitation form for the Qarhan Salt Lake. Salt mining ships with mi...
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Qarhan Salt Lake is rich in mineral resources, such as sodium chloride, potassium, and magnesium [1].At present, liquid mine exploiting is the main exploitation form for the Qarhan Salt Lake. Salt mining ships with mining equipments are widely used to exploit carnallite which is located at the bottom of pools. Conventionally, workmen utilize rude ferric sampler to collect carnallite samples
In this paper, a novel learning optimal control scheme is established to design the robust controller of a class of uncertain nonlinear systems. The robust control problem is transformed into the optimal control probl...
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ISBN:
(纸本)9781479900305
In this paper, a novel learning optimal control scheme is established to design the robust controller of a class of uncertain nonlinear systems. The robust control problem is transformed into the optimal control problem by properly choosing a cost function that reflects the uncertainty, regulation, and control. Then, the online policy iteration algorithm is presented to solve the Hamilton-Jacobi-Bellman （HJB） equation by introducing a critic neural network. The approximate expression of the optimal control policy can be derived directly. Moreover, the closed-loop system is proved to be uniformly ultimately bounded. The equivalence of the neural-network-based HJB solution of the optimal control problem and the solution of the robust control problem is developed as well. Finally, an example is provided to verify the effectiveness of the constructed approach.
This paper develops a novel neural-network-based direct adaptive control scheme for a class of multi-input-multioutput uncertain nonlinear discrete-time(DT) systems in the presence of unknown bounded *** employing fee...
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ISBN:
(纸本)9781479900305
This paper develops a novel neural-network-based direct adaptive control scheme for a class of multi-input-multioutput uncertain nonlinear discrete-time(DT) systems in the presence of unknown bounded *** employing feedback linearization methods,neural network(NN) approximation can cancel the nonlinearity of the DT ***,the weights of NNs are directly updated online instead of preliminary offline *** addition,unlike most literatures,the condition for persistent excitation is *** on Lyapunov's direct method,both tracking errors and weight estimates are guaranteed to be uniformly ultimately bounded,while keeping the closed-loop system ***,an example is provided to demonstrate the effectiveness of the proposed approach.
This paper presents a concrete and practical hydrodynamic analysis for a hybrid gliding robotic *** order to obtain the accurate hydrodynamic performance of both dolphin-like swimming and gliding motion,a Computationa...
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ISBN:
(纸本)9781509009107
This paper presents a concrete and practical hydrodynamic analysis for a hybrid gliding robotic *** order to obtain the accurate hydrodynamic performance of both dolphin-like swimming and gliding motion,a Computational Fluid Dynamics(CFD) method is ***,based on the F1 UENT dynamic mesh interface,a novel dynamic mesh and user-defined function(UDF) are developed to describe the dorsoventral oscillations of the ***,the corresponding turbulent model and SIMPLE algorithm suited to dolphin-like swimming are also meticulously selected for great accuracy and high ***,the FLUENT simulation results reveal the pressure distribution and velocity field distribution around the robotic ***,some important hydrodynamic coefficients including lift coefficients and drag coefficients at different frequencies are also *** simulation results illustrate an expected hydrodynamic performance of the gliding robotic dolphin.
This paper presents a novel approach for a visual system of robotic fish to reduce the instability of camera image caused by the inherent periodic yawing of the fish *** order to acquire the stable image from the came...
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ISBN:
(纸本)9781509009107
This paper presents a novel approach for a visual system of robotic fish to reduce the instability of camera image caused by the inherent periodic yawing of the fish *** order to acquire the stable image from the camera located inside of the fish head,a camera stabilizer for the visual system is ***,an Inertial Measurement Unit(IMU) with nine degrees-of-freedom(DoFs) is employed to maintain the attitude of the camera stable with respect to the inertial *** accurately describe the stabilizer system characteristics,a simple and effective system model is ***,a feedbackfeedforward controller is proposed to mitigate the periodic swing effect and obtain stable and clear camera image when the robotic fish is ***,the simulation and experiments both verified the effectiveness of the mechanism design for camera stabilizer and the corresponding feedback-feedforward control approach for enhancing the stability of images.
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