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This paper proposes an out-of-sample extension framework for a global manifold learning algorithm (Isomap) that uses temporal information in out-of-sample points in order to make the embedding more robust to noise and artifacts. Given a set of noise-free training data and its embedding, the proposed framework extends the embedding for a noisy time series. This is achieved by adding a spatio-temporal...
For intelligent robots to solve real-world tasks, they need to manipulate multiple objects, and perform diverse manipulation actions apart from rigid transfers, such as pushing and sliding. Planning these tasks requires discrete changes between actions, and continuous, collision-free paths that fulfill action-specific constraints. In this work, we propose a multi-modal path planner, named MOPL, which...
Recent studies revealed that hand gesture-based interfaces can complement therapies for individuals with upper motor impairments and reduce the need of traditional rehabilitation sessions through hospital visits. Unfortunately, existing gesture-based interfaces have been developed without considering the physical limitations of users with motor impairments. An analytic approach was presented in our...
This work presents a method for deriving a gain scheduled balance controller to stabilize the gate of a three legged under-actuated robotic platform called THALeR (Tri-Pedal Hyper Altitudinal Legged Robot). The scheduler adapts the controller gains in real time based upon the system's instantaneous potential energy in order to create a smooth, stable gait. The final controller is simulated with white...
To deal with redundancy and high-dimensionality that are typical of movement data, we propose to decompose action matrices in two decoupled steps: first, we discover a set of key postures, that is, vectors corresponding to key relationships among degrees of freedom (like angles between body parts) which we call spatial basis (SB) and second, we impose a parametric model to the spatio-temporal (ST)...
In this paper, a nonlinear continuous-time dynamics with input-delay is considered. Assuming the existence of a continuous-time stabilizing strategy in the delay free case, it is shown how the problem can be reformulated in the sampled-data context as an Immersion and Invariance I&I stabilizing one.
In this paper, we show that the existence of centrally synergistic potential functions on the n-dimensional sphere, denoted by Sn, is a sufficient condition for the global asymptotic stabilization of a point in Sn. Additionally, if these functions decrease exponentially fast during flows and are bounded from above and from below by some polynomial function of the tracking error, then the reference...
We consider the problem of integrability by quadratures of normal Hamiltonian system in sub-Riemannian problem on the groups of motions of hyperbolic plane or pseudo Euclidean plane which form the Lie group SH(2). The first step towards proof of integrability is to calculate the local representation of the Lie group SH(2) in canonical coordinates of second kind. Wei-Norman transformation is applied...
Current research methods directed towards measuring the influence of specific agents on the dynamics of a large-scale multi-agent system (MAS) rely largely on the notion of controllability of the full-order system, or on the comparison of agent dynamics via a user-defined macroscopic system property. However, it is known that several large-scale multi-agent systems tend to self-organize, and their...
This paper presents an Adaptive Variable Structure Control (AVSC) methodology to autonomously control an UAV platform known as the Vectored Thrust Aerial Vehicle (VTAV). The proposed control algorithm eliminates chattering present in Sliding Mode Control (SMC), and improves the settling time of the VTAV system by driving the error states in a parabolic trajectory towards the origin of error space...
Geometric controllers for mechanical system have been well-developed in past research work. Although geometric controllers possess the advantages of being coordinate-free and compact, these controllers don't take into account constraints such as safety-critical collision constraints or input saturations. In this paper, we utilize the concepts of control Lyapunov function(CLF) and control Barrier function(CBF)...
Sliding mode control (SMC) is one of the few controller design methodologies that can be applied to highly nonlinear and uncertain systems. In most mechanical applications, a smoothed version of SMC that we call “sliding control” is employed to keep the system trajectories close to but not necessarily on a stable differential/difference manifold. In this paper, we propose an extension to the sliding...
A geometric extension of Directed Guidance to more general manifolds is presented. In addition, we show that the inclusion of a relative torsional steering term provides increased flexibility in the 3-dimensional design framework. Stability arguments and a time-varying vector field guidance example are provided.
The paper deals with the sampled-data implementation of controllers designed by means of Immersion and Invariance stabilization techniques for a special class of dynamics. A multi-rate digital control law is derived to preserve at the sampling instants manifold attractivity. The immersion condition is guaranteed under sampling and invariance on the manifold is recovered asymptotically by the multi-rate...
A contraction based stabilization problem of systems with approximate strict feedback form is considered here. A high gain feedback is used to force the system into singularly perturbed form. Contraction theory based recursive controller design and singular perturbation analysis is used to design a stabilizing controller for the whole system. It is shown that, explicit error bounds between trajectories...
Power systems subjected to large disturbances may become transiently unstable, which can lead to uncontrolled system separation and cascading outages. An important goal of developing the smart grids is to maintain high-level system stability. Controlled islanding is a corrective measure that can efficiently attenuate the detrimental impact of large disturbances by splitting the system into self-healing...
This paper proposes a new framework for online detection of spontaneous emotions from low-resolution depth sequences of the upper part of the body. To face the challenges of this scenario, depth videos are decomposed into subsequences, each modeled as a linear subspace, which in turn is represented as a point on a Grassmann manifold. Modeling the temporal evolution of distances between subsequences...
We present a randomized kinodynamic planner that solves rearrangement planning problems. We embed a physics model into the planner to allow reasoning about interaction with objects in the environment. By carefully selecting this model, we are able to reduce our state and action space, gaining tractability in the search. The result is a planner capable of generating trajectories for full arm manipulation...
Drawing inspiration from flight behavior in biological settings (e.g. territorial battles in dragonflies, and flocking in starlings), this paper demonstrates two strategies for coverage and flocking. Using earlier theoretical studies on mutual motion camouflage, an appropriate steering control law for area coverage has been implemented in a laboratory test-bed equipped with wheeled mobile robots and...
We introduce a novel notion for lowering the dimensionality of motion planning problems: Irreducibility. Irreducibility of a configuration space trajectory τ means: We cannot find another configuration space trajectory τ′, such that the swept volume of τ′ is included in the swept volume of τ. The main contribution of our work is twofold: First, we show that motion planning in the space of irreducible...
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