1,381 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
Control and measurement delay compensation in bilateral position control
The main aim of this study is the improvement of the previously presented disturbance observer based bilateral control approaches of the authors with a delay regulator and a model tracking control (MTC) that runs on the slave side. These improvements eliminate the problems related to variable time delay inherent to such systems and model mismatch, respectively, and, hence, addressing the control and measurement delay problems in bilateral control applications. The performance is evaluated experimentally on a single-link arm controlled over the internet. The results demonstrate a significant improvement over the previously presented results obtained under load uncertainties and randomly varying network delays both in the control and feedback loop
Scaled bilateral teleoperation using discrete-time sliding mode controller
In this paper, the design of a discrete-time slidingmode
controller based on Lyapunov theory is presented along
with a robust disturbance observer and is applied to a piezostage
for high-precision motion. A linear model of a piezostage was
used with nominal parameters to compensate the disturbance
acting on the system in order to achieve nanometer accuracy. The
effectiveness of the controller and disturbance observer is validated
in terms of closed-loop position performance for nanometer
references. The control structure has been applied to a scaled
bilateral structure for the custom-built telemicromanipulation
setup. A piezoresistive atomic force microscope cantilever with a
built-in Wheatstone bridge is utilized to achieve the nanonewtonlevel
interaction forces between the piezoresistive probe tip and
the environment. Experimental results are provided for the
nanonewton-range force sensing, and good agreement between
the experimental data and the theoretical estimates has been
demonstrated. Force/position tracking and transparency between
the master and the slave has been clearly demonstrated after
necessary scalin
Issues, concerns, and initial implementation results for space based telerobotic control
Telerobotic control for space based assembly and servicing tasks presents many problems in system design. Traditional force reflection teleoperation schemes are not well suited to this application, and the approaches to compliance control via computer algorithms have yet to see significant testing and comparison. These observations are discussed in detail, as well as the concerns they raise for imminent design and testing of space robotic systems. As an example of the detailed technical work yet to be done before such systems can be specified, a particular approach to providing manipulator compliance is examined experimentally and through modeling and analysis. This yields some initial insight into the limitations and design trade-offs for this class of manipulator control schemes. Implications of this investigation for space based telerobots are discussed in detail
An Analysis of Sampling Effect on the Absolute Stability of Discrete-time Bilateral Teleoperation Systems
Absolute stability of discrete-time teleoperation systems can be jeopardized
by choosing inappropriate sampling time architecture. A modified structure is
presented for the bilateral teleoperation system including continuous-time
slave robot, master robot, human operator, and the environment with
sampled-data PD-like + dissipation controllers which make the system absolute
stable in the presence of the time delay and sampling rates in the
communication network. The output position and force signals are quantized with
uniform sampling periods. Input-delay approach is used in this paper to convert
the sampled-data system to a continuous-time counterpart. The main contribution
of this paper is calculating a lower bound on the maximum sampling period as a
stability condition. Also, the presented method imposes upper bounds on the
damping of robots and notifies the sampling time importance on the transparency
and stability of the system. Both simulation and experimental results are
performed to show the validity of the proposed conditions and verify the
effectiveness of the sampling scheme
Sensors Allocation and Observer Design for Discrete Bilateral Teleoperation Systems with Multi-Rate Sampling
This study addresses sensor allocation by analyzing exponential stability for discrete-time teleoperation systems. Previous studies mostly concentrate on the continuous-time teleoperation
systems and neglect the management of significant practical phenomena, such as data-swap, the effect of sampling rates of samplers, and refresh rates of actuators on the system’s stability. A multi-rate sampling approach is proposed in this study, given the isolation of the master and slave robots in teleoperation systems which may have different hardware restrictions. This architecture collects data through numerous sensors with various sampling rates, assuming that a continuous-time controller stabilizes a linear teleoperation system. The aim is to assign each position and velocity signals to sensors with different sampling rates and divide the state vector between sensors to guarantee the stability of the resulting multi-rate sampled-data teleoperation system. Sufficient Krasovskii-based conditions will be provided to preserve the exponential stability of the system. This problem will be transformed into a mixed-integer program with LMIs (linear matrix inequalities). These conditions are also used to design the observers for the multi-rate teleoperation systems whose estimation errors converge exponentially to the origin. The results are validated by numerical simulations which are useful in designing sensor networks for teleoperation systems
- …