93 research outputs found
A Fault Tolerant Adaptive Control for Robot Manipulators
No full textA Fault Tolerant adaptive control for a robotic
manipulator with fault affecting the joint actuators is presented.
First, in order to achieve a proper detection and isolation of the
fault, an observer based scheme for fault diagnosis is developed.
Then, an inverse dynamics robust controller is reconfigured in
such a way to include an adaptive term, depending on the
isolated fault. The model uncertainties are explicitly taken into
account and estimated via an off-line-trained Support Vector
Machine. Finally, simulation results are presented in order to
prove the effectiveness of the approach
Discrete-Time Framework for Fault Diagnosis in Robotic Manipulators
No full textIn this paper, a discrete-time framework forbreak diagnosis of faults of joint sensors, wrist-mounted force/torque sensors, and actuators of robotic manipulators is devised. It is assumed that redundant joint sensor measurements are available. Sensor measurements, together with the estimates computed by two isolation observers, are processed by a decision-making system, providing detection and isolation of the faults of the joint sensors as well as healthy measurements. Then, healthy measurements are used to feed a bank of diagnostic observers aimed at detecting, isolating, and identifying faults of joint actuators and force/torque sensors. The framework is experimentally tested on a cooperative industrial setup, composed of two industrial robots with six degrees of freedom performing a cooperative task
Distributed cooperative object parameter estimation and manipulation without explicit communication
No full textThe paper presents a two stages distributed algorithm for cooperative manipulating an unknown object rigidly grasped by mobile manipulators, in the absence of both a central unit and any explicit information exchange among robots. In the first stage, robots cooperatively estimate the object kinematic and dynamic parameters by properly moving the object or applying specific contact wrenches. In the second stage, the estimated parameters are used in a distributed cooperative algorithm aimed at controlling the object pose while limiting both the squeezing wrenches exerted by the manipulators and the wrench exerted by the environment on the object. Numerical simulations demonstrate the feasibility of the approach
Aerobic oxidation of trivalent phosphorus and arsenic compounds in the presence of 3-methylbutanal and metal catalyst
No full textThe oxidation of alkyl and aryl phosphines, tryphenylphosphite and triphenylarsine was achieved using oxygen or air as the oxidant in the presence of excess 3-methylbutanal and catalytic amount Co(acac)2. Tests carried out with a heterogeneous analogue of Co(acac)2 revealed that the supported cobalt polymer acts as an active and reusable catalyst in the oxidation of triphenylphosphine
Comparative analysis of different methods to evaluate the thermal conductivity of homogenous materials
No full textThermal conductivity of materials for structural elements and thermal insulation represents a fundamental parameter in the assessment of the energy need of buildings. In this paper, two different systems for thermal conductivity measurement are compared, based respectively on the calibrated hot box and on the guarded hot plate methods. The study is specifically aimed at assessing the range of thermal transmittance where the hot box system is suitable and verifying the strengths and the weaknesses of the system.
The comparison between measurements on specimens with different thermal conductivity and thickness showed that the two methods are substantially equivalent in the considered range of thermal conductivity, but are not completely interchangeable. In particular, the measurement campaign confirmed the expectation that the hot box system gives more accurate results with low thermal resistance samples
Grasp force and object impedance control for arm/hand systems
No full textThis paper deals with fine contact force control in
robotic grasping. The main objective is to achieve tracking of
the planned trajectory for a grasped object and, at the same
time, ensure suitable grasp quality. Interaction of the grasped
object with the external environment is considered as well. To
this aim, an impedance control law is adopted to enforce a
compliant behavior of the object when comes in contact with the
environment. A simulation case study is developed to confirm
the effectiveness of the proposed control scheme
An adaptive hierarchical control for aerial manipulators
No full textThis paper addresses the trajectory tracking control problem for a quadrotor aerial vehicle, equipped with a robotic manipulator (aerial manipulator). The controller is organized in two layers: in the top layer, an inverse kinematics algorithm computes the motion references for the actuated variables; in the bottom layer, a motion control algorithm is in charge of tracking the motion references computed by the upper layer. To the purpose, a model-based control scheme is adopted, where modelling uncertainties are compensated through an adaptive term. The stability of the proposed scheme is proven by resorting to Lyapunov arguments. Finally, a simulation case study is proposed to prove the effectiveness of the approach
A hand/arm controller that simultaneously regulates internal grasp forces and the impedance of contacts with the environment
No full textThis paper presents a control framework for arm/hand systems aimed at controlling internal forces exchanged between the fingers and the grasped object, and enforcing a compliant behavior in presence of environmental interactions. A dynamic planner computes the motion references for the fingers by using the feedback of the contact forces, while an impedance control, in which dynamic effects exerted by the hand on the wrist are explicitly taken into account, is designed for the arm. The approach is experimentally validated on a 7-DOFs Barrett WAM with a Barrett Hand280
Cooperative impedance control for multiple UAVs with a robotic arm
No full textIn this paper, an impedance control scheme for cooperative quadrotors with robotic arms is proposed in order to limit both the contact forces, due to the object/environment interaction, and the internal forces, due to the manipulators/ object interaction. To this aim, two impedance filters are used to determine the reference trajectories for manipulator end effectors: the first is aimed at conferring a compliant behavior at the object level (external impedance), while the second filter, is aimed at avoiding large internal loading of the object (internal impedance). Such trajectories are fed to a motion controller including an inverse kinematics algorithm and a PD controller with gravity compensation. The effectiveness of the proposed approach is then verified in simulation
Control of Quadrotor Aerial Vehicles Equipped with a Robotic Arm
No full textIn this paper a novel hierarchical motion control scheme for quadrotor aerial vehicles equipped with a manipulator is proposed. The controller is organized into two layers:
in the top layer, an inverse kinematics algorithm computes the motion references for the actuated variables; in the bottom layer, a motion control algorithm is in charge of tracking the motion references computed by the top layer. A simulation case study is developed to demonstrate the effectiveness of the approach in the presence of disturbances and unmodeled dynamics
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