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A fixed-time sliding mode control scheme is designed in this paper for the high-order linear systems in the pure-feedback form with system uncertainties. A recursive procedure is utilized where a set of switching manifolds have been resorted to realize the fixed-time stability. The initial conditions of the system variables are confined in a particular region so as to avoid the singularity problem...
The predefined-time stabilization of second-order systems, i.e. the fixed-time stabilization with settling time as a function of the controller parameters, is revisited in this paper. The proposed controller is a time-based switched controller which first drive the system trajectories to a linear manifold in predefined time and then uses a nested second-order controller. The application of the results...
A sliding mode control approach is proposed to synchronize a class of delayed neural networks in a finite time, where the mismatched parameters and neuron activation functions are taken into account. In the controller design, a sliding mode manifold is directly defined by the synchronization error, which greatly reduces the synchronization time. Its concise design process and its ability to synchronize...
This paper considers the multi-camera motion segmentation problem using unsynchronized videos: given two video clips containing several moving objects, captured by unregistered, unsynchronized cameras with different viewpoints, our goal is to assign features to moving objects in the scene. This problem challenges existing methods, due to the lack of registration information and correspondences across...
In this paper, we study the problem of facial expression recognition using a novel space-time geometric representation. We describe the temporal evolution of facial landmarks as parametrized trajectories on the Riemannian manifold of positive semidefinite matrices of fixed-rank. Our representation has the advantage to bring naturally a second desirable quantity when comparing shapes – the spatial...
Analyzing data representing multifarious trajectories is central to the many fields in Science and Engineering; for example, trajectories representing a tennis serve, a gymnast’s parallel bar routine, progression/remission of disease and so on. We present a novel geometric algorithm for performing statistical analysis of trajectories with distinct number of samples representing longitudinal (or temporal)...
This paper presents a path following controller for quadrotors to follow splines in the output space. The control pipeline includes utilization of a cascaded control architecture, generation of paths using quintic spline interpolation, transformation of coordinates using Frenet-Serret (FS) frames, and decoupling controllers for the transversal and tangential sub-systems. The result is a time-invariant...
For robotics navigation, artificial potential functions are commonly utilized. Among these functions, control Lyapunov functions (CLFs) guarantee stability of nonlinear autonomous systems. Particularly, a vehicle such as a two-wheeled mobile robot is a major application for a navigation problem. However, it is difficult to stabilize due to the its nonholonomic constraint. This paper presents a controller...
Due to the relative position invariance of L2 Libration point in the Earth-moon system, Halo orbits around LL2 adapt to the best mission trajectory for Lunar Relay Satellite, which can offer relay communication for space missions such as deep-space exploration and Moon outpost construction. In order to improve the payload launch capacity of Lunar Relay Satellite, the electric thrusters which have...
The standard output regulation theorem is utilized to construct a nonlinear flight tracking controller for a hypersonic vehicle in presence of non-minimum phase dynamic in the paper. When the elevator is chosen as the only control surface, the hypersonic vehicle model exhibits unstable hyperbolic zero-dynamics, preventing the application of standard inversion-based control technique. The standard...
In this paper we present a review of gait analysis methods used for medical applications. First of all, we introduce a system of real-time gait acquisition. Next, three ways of gait data representation: trajectories, Euler angles and medical angles are described along with the most promising methods of gait analysis based on those representations like gait indices, Dynamic Time Warping, manifold methods...
For radio-based indoor localization, the approaches founded on the radio fingerprint concept are efficient duo to low cost and the ability to handle occlusion effects. However, the approaches require a lot of human labor to label training data for radio map (fingerprint) construction. To address this issue, in this paper, we proposed an unsupervised framework to learn a Wi-Fi radio map in an indoor...
This paper considers a nonsingular terminal sliding mode control problem for the attitude tracking of a quadrotor. To solve the chattering problem of sliding mode control, a novel terminal sliding mode controller based on a second-order sliding mode algorithm known as super-twisting algorithm is proposed. With the help of the proposed terminal sliding mode controller, the pitch, roll and yaw angles...
In this study we introduce a new approach to train a fully recurrent artificial neural network by solving a constraint satisfaction problem using the quotient gradient method. The quotient gradient method is a trajectory based methodology for global optimization that does not suffer from the problem of local minima encountered in Newton based methods. Simulation results show that the network trained...
During the optimal design process of low-thrust transfer trajectory to translunar Libration point, the governing variable such as pitching and yaw angle of satellite were considered. However, the consideration is not enough because the selection of initial orbit after satellite-rocket separation and the inlet point of invariant manifolds are also of great importance to the transition time and the...
A causality method based on predictions in reconstructed state spaces is presented and tested in relation to the ability to detect coupling and synchronization of interconnected dynamical systems. The method is demonstrated on a test example of two uni-directionally coupled chaotic systems of Rössler type. The results show that the predictability of the driven system can be improved by incorporating...
State space reconstruction is usually the first step of nonlinear time series analysis. Among many state space reconstruction approaches, the method of delays (MOD) has been a popular method in noise-free situations. Unfortunately, many real-world time series are usually noisy so that the reconstruction performance can be of low quality. In this paper, we propose an autoencoder-based approach that...
Trajectory reversing is a method commonly used for estimating the region of attraction of stabilized equilibria. Using a discrete set of points obtained by trajectory reversing, this paper presents an algorithm for estimation and mathematical representation of the region of attraction using convex hulls. Several two-dimensional examples are presented to illustrate the usefulness of the algorithm....
In this paper, a finite-time trajectory tracking control approach is proposed for an unmanned surface vehicle (USV) with unknown dead-zones and unknown disturbances. External disturbances can be observed exactly by a robust homogeneous differentiator with finite-time convergence. Based on the information of the bounds of the dead-zone slopes as well as treating the time-varying inputs coefficients...
We introduce the concept of trajectory-specific sensory manifolds. They are the unique multidimensional and time-varying combinations of afferent signals that obligatorily emerge during a limb movement. We use the example of muscle spindles (i.e., the muscle's proprioceptors for length and velocity) that arise during movements of an arm (a planar 2-DOF 6-muscle model) during the production of straight,...
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