28,048 research outputs found
Network Representation and Passivity of Delayed Teleoperation Systems
The paper proposes a general network based
analysis and design guidelines for teleoperation systems. The
electrical domain is appealing because it enjoys proficient analysis
and design tools and allows a one step higher abstraction
element, the network. Thus, in order to analyze the system by
means of network elements the mechanical system must be first
modeled as an electric circuit. Only then power ports become
apparent and networks can be defined. This kind of analysis
has been previously performed in systems with well defined
causalities, specially in the communication channel. Indeed,
a communication channel exchanging flow-like and effort-like
signals, as for instance velocity and computed force, has a
well defined causality and can thus be directly mapped as a
two-port electrical network. However, this is only one of the
many possible system architectures. This paper investigates how
other architectures, including those with ambiguous causalities,
can be modeled by means of networks, even in the lack of
flow or effort being transmitted, and how they can be made
passive for any communication channel characteristic (delay,
package-loss and jitter). The methods are exposed in the form
of design guidelines sustained with an example and validated
with experimental results
Passive Compliance Control of Aerial Manipulators
This paper presents a passive compliance control for aerial manipulators to
achieve stable environmental interactions. The main challenge is the absence of
actuation along body-planar directions of the aerial vehicle which might be
required during the interaction to preserve passivity. The controller proposed
in this paper guarantees passivity of the manipulator through a proper choice
of end-effector coordinates, and that of vehicle fuselage is guaranteed by
exploiting time domain passivity technique. Simulation studies validate the
proposed approach.Comment: IEEE/RSJ International Conference on Intelligent Robots and Systems
(IROS) 201
A family of asymptotically stable control laws for flexible robots based on a passivity approach
A general family of asymptotically stabilizing control laws is introduced for a class of nonlinear Hamiltonian systems. The inherent passivity property of this class of systems and the Passivity Theorem are used to show the closed-loop input/output stability which is then related to the internal state space stability through the stabilizability and detectability condition. Applications of these results include fully actuated robots, flexible joint robots, and robots with link flexibility
Passivity Enforcement via Perturbation of Hamiltonian Matrices
This paper presents a new technique for the passivity enforcement of linear time-invariant multiport systems in statespace form. This technique is based on a study of the spectral properties of related Hamiltonian matrices. The formulation is applicable in case the system input-output transfer function is in admittance, impedance, hybrid, or scattering form. A standard test for passivity is first performed by checking the existence of imaginary eigenvalues of the associated Hamiltonian matrix. In the presence of imaginary eigenvalues the system is not passive. In such a case, a new result based on first-order perturbation theory is presented for the precise characterization of the frequency bands where passivity violations occur. This characterization is then used for the design of an iterative perturbation scheme of the state matrices, aimed at the displacement of the imaginary eigenvalues of the Hamiltonian matrix. The result is an effective algorithm leading to the compensation of the passivity violations. This procedure is very efficient when the passivity violations are small, so that first-order perturbation is applicable. Several examples illustrate and validate the procedure
Relaminarisation of Re_τ=100 channel flow with globally stabilising linear feedback control
The problems of nonlinearity and high dimension have so far prevented a complete solution of the control of turbulent flow. Addressing the problem of nonlinearity, we propose a flow control strategy which ensures that the energy of any perturbation to the target profile decays monotonically. The controller’s estimate of the flow state is similarly guaranteed to converge to the true value. We present a one-time off-line synthesis procedure, which generalises to accommodate more restrictive actuation and sensing arrangements, with conditions for existence for the controller given in this case. The control is tested in turbulent channel flow (Re_τ = 100) using full-domain sensing and actuation on the wall-normal velocity. Concentrated at the point of maximum inflection in the mean profile, the control directly counters the supply of turbulence energy arising from the interaction of the wall-normal perturbations with the flow shear. It is found that the control is only required for the larger-scale motions, specifically those above the scale of the mean streak spacing. Minimal control effort is required once laminar flow is achieved. The response of the near-wall flow is examined in detail, with particular emphasis on the pressure and wall-normal velocity fields, in the context of Landahl’s theory of sheared turbulence
Relaminarisation of Re_{\tau} = 100 channel flow with globally stabilising linear feedback control
The problems of nonlinearity and high dimension have so far prevented a
complete solution of the control of turbulent flow. Addressing the problem of
nonlinearity, we propose a flow control strategy which ensures that the energy
of any perturbation to the target profile decays monotonically. The
controller's estimate of the flow state is similarly guaranteed to converge to
the true value. We present a one-time off-line synthesis procedure, which
generalises to accommodate more restrictive actuation and sensing arrangements,
with conditions for existence for the controller given in this case. The
control is tested in turbulent channel flow () using full-domain
sensing and actuation on the wall-normal velocity. Concentrated at the point of
maximum inflection in the mean profile, the control directly counters the
supply of turbulence energy arising from the interaction of the wall-normal
perturbations with the flow shear. It is found that the control is only
required for the larger-scale motions, specifically those above the scale of
the mean streak spacing. Minimal control effort is required once laminar flow
is achieved. The response of the near-wall flow is examined in detail, with
particular emphasis on the pressure and wall-normal velocity fields, in the
context of Landahl's theory of sheared turbulence
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