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Conspicuous physicochemical vertical stratification in the deep sea is one of the main forces driving microbial diversity in the oceans. Oxygen and sunlight availability are key factors promoting microbial diversity throughout the water column. Ocean currents also play a major role in the physicochemical stratification, carrying oxygen down to deeper zones as well as moving deeper water masses up...
This paper presents a new strategy for task space control in the cooperative manipulation framework. We extend the cooperative dual task-space (CDTS)—which uses dual quaternions to represent the bimanual manipulation—to explicitly regard self-motion dynamics that arise from redundant kinematics. In this sense, we propose a flexible task execution criterion that enriches the Jacobian null space with...
This paper presents a robot-assisted approach for automatic steering of flexible beveled needles in percutaneous procedures. The method uses duty-cycled rotation of the needle to perform insertion with arcs of adjustable curvature, and combines closed-loop imaging feedback with an intraoperative motion replanning strategy to compensate for system uncertainties and disturbances. Differently from previous...
This paper addresses the H∞ robust control problem for robot manipulators using unit dual quaternion representation, which allows an utter description of the end-effector transformation without decoupling rotational and translational dynamics. We propose three different H∞ control criteria that ensure asymptotic convergence, whereas reducing the influence of disturbances upon the system stability...
In this paper, a robust stability criterion is proposed for NCSs liable to model uncertainties and time-varying delays. The analysis concerns the establishment of a maximum allowable delay bound for continous time NCSs under parameter uncertainties. The new proposed criterion is based on the solution of a set of linear matrix inequalities (LMIs). Numerical examples are given to validate the theoretical...
This paper presents an extended Kalman filter for discrete-time nonlinear systems subject to uncertainties. The proposed filter considers that the linearization of the nonlinear functions are unknown, but within a known set. The nonlinear functions are assumed to belong to a conic region. This condition is characterized as a Lipschitz condition on the system state, control signal and the noise residuals...
This paper presents a new application in the field of rehabilitation robotics. It is part of a research project which consists of the development of a robotic leg prosthesis for above knee amputees. This application aims at providing real-time estimates of the prosthesis foot orientation with respect to ground. An Extended Kalman Filter (EKF) is used in order to estimate the foot orientation based...
This paper presents a new path planning algorithm that uses adaptive random walks to incrementally construct a roadmap in the robot's free configuration space. This algorithm, named Incremental Adaptive Random Walks (iARW), uses a modified version of the ARW algorithm proposed by Carpin and Pillonetto for exploring the configuration space and storing the discovered path in a roadmap. Thus, the main...
In this paper, the kinematic model of a quadruped robot is derived. The model is equivalent to that of a parallel manipulator, in that each leg can be seen as a manipulator. However, the model is extended to consider that in one gait cycle some legs are in contact with the ground and others are not. In order to obtain the inverse kinematics model, this paper presents as contribution the use of the...
This paper presents a myoelectric knee joint angle estimation algorithm for control of active transfemoral prostheses, based on feature extraction and pattern classification. The feature extraction stage uses a combination of time domain and frequency domain methods (entropy of myoelectric signals and cepstral coefficients, respectively). Additionally, the methods are fused with data from proprioceptive...
This paper presents a novel two-step approach for modeling forward and backward network delays in networked control systems (NCS). The first step is to build a colored Petri net (CPN) structural model for the simulation of Ethernet based networked control systems. The modular model captures the most important features of industrial networked control systems, such as client/server input/output scanning...
This paper presents a robust filter for discrete-time nonlinear systems subject to uncertainties. The nonlinear functions are assumed to be uncertain but belonging to a conic region. This condition is characterized as a Lipschitz condition on the system state and control signal residuals. The proposed design also allows dynamic and measurement noises to have unknown time-varying expected values, covariances...
This work presents the design and evaluation of knee joint controllers for an above-knee prosthesis. The prototype is a three degree of freedom prosthesis which is planned to be controlled in part by EMG thigh signals, in part by a predictive trajectory generator based on multisensorial data such that the foot can be correctly positioned with respect the floor. There is described a simplified non-linear...
This work presents the nonlinear modeling of a small-scale helicopter and the identification of its thirty two parameters using prediction error minimization methods. The proposed model intends to be simple enough to be used in classical control design and accurate enough to represent rotorcraft dynamics in several different non acrobatic flight modes, to the contrary of the best-known models that...
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