55,438 research outputs found
Control systems with network delay
In this paper motion control systems with delay in measurement and control channels are discussed and a new structure of the observer-predictor is proposed. The feature of the proposed system is enforcement of the convergence in both the estimation and the prediction of the plant output in the presence of the variable, unknown delay in both measurement and in the control channels. The estimation is based on the available data – undelayed control input, the delayed
measurement of position or velocity and the nominal parameters of the plant and it does not require apriori knowledge of the delay. The stability and convergence is proven and selection of observer and the controller parameters is discussed. Experimental results are shown to illustrate the theoretical prediction
Time-Varying Input and State Delay Compensation for Uncertain Nonlinear Systems
A robust controller is developed for uncertain, second-order nonlinear
systems subject to simultaneous unknown, time-varying state delays and known,
time-varying input delays in addition to additive, sufficiently smooth
disturbances. An integral term composed of previous control values facilitates
a delay-free open-loop error system and the development of the feedback control
structure. A stability analysis based on Lyapunov-Krasovskii (LK) functionals
guarantees uniformly ultimately bounded tracking under the assumption that the
delays are bounded and slowly varying
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
Novel observers for compensation of communication delay in bilateral control systems
The problem of communication delay in bilateral or
teleoperation systems is even more emphasized with the use of the
internet for communication, which may give rise to loss of
transparency and even instability. To address the problem,
numerous methods have been proposed. This study is among the
few recent studies taking a disturbance observer approach to the
problem of time delay, and introduces a novel sliding-mode
observer to overcome specifically the effects of communication
delay in the feedback loop. The observer operates in combination
with a PD+ controller which controls the system dynamics, while
also compensating load torque uncertainties on the slave side. To
this aim, an EKF based load estimation algorithm is performed on
the slave side. The performance of this approach is tested with
computer simulations for the teleoperation of a 1-DOF robotic
arm. The simulations reveal an acceptable amount of accuracy
and transparency between the estimated slave and actual slave
position under both constant and random measurement delay and
variable and step-type load variations on the slave side,
motivating the use of the approach for internet-based bilateral
control systems
Predictive Control of Autonomous Kites in Tow Test Experiments
In this paper we present a model-based control approach for autonomous flight
of kites for wind power generation. Predictive models are considered to
compensate for delay in the kite dynamics. We apply Model Predictive Control
(MPC), with the objective of guiding the kite to follow a figure-of-eight
trajectory, in the outer loop of a two level control cascade. The tracking
capabilities of the inner-loop controller depend on the operating conditions
and are assessed via a frequency domain robustness analysis. We take the
limitations of the inner tracking controller into account by encoding them as
optimisation constraints in the outer MPC. The method is validated on a kite
system in tow test experiments.Comment: The paper has been accepted for publication in the IEEE Control
Systems Letters and is subject to IEEE Control Systems Society copyright.
Upon publication, the copy of record will be available at
http://ieeexplore.ieee.or
Effects of Transport Delays of Manual Control System Performance
Throughput or transport delays in manual control systems can cause degraded performance and lead to potentially unstable operation. With the expanding use of digital processors, throughput delays can occur in manual control systems in a variety of ways such as in digital flight control systems in real aircraft, and in equation of motion computers and computer generated images in simulators. Research has shown the degrading effect of throughput delays on subjective opinion and system performance and dynamic response. A generic manual control system model is used to provide a relatively simple analysis of and explanation for the effects of various types of delays. The consequence of throughput delays of some simple system architectures is also discussed
Analysis and equalization of data-dependent jitter
Data-dependent jitter limits the bit-error rate (BER) performance of broadband communication systems and aggravates synchronization in phase- and delay-locked loops used for data recovery. A method for calculating the data-dependent jitter in broadband systems from the pulse response is discussed. The impact of jitter on conventional clock and data recovery circuits is studied in the time and frequency domain. The deterministic nature of data-dependent jitter suggests equalization techniques suitable for high-speed circuits. Two equalizer circuit implementations are presented. The first is a SiGe clock and data recovery circuit modified to incorporate a deterministic jitter equalizer. This circuit demonstrates the reduction of jitter in the recovered clock. The second circuit is a MOS implementation of a jitter equalizer with independent control of the rising and falling edge timing. This equalizer demonstrates improvement of the timing margins that achieve 10/sup -12/ BER from 30 to 52 ps at 10 Gb/s
Compensation of distributed delays in integrated communication and control systems
The concept, analysis, implementation, and verification of a method for compensating delays that are distributed between the sensors, controller, and actuators within a control loop are discussed. With the objective of mitigating the detrimental effects of these network induced delays, a predictor-controller algorithm was formulated and analyzed. Robustness of the delay compensation algorithm was investigated relative to parametric uncertainties in plant modeling. The delay compensator was experimentally verified on an IEEE 802.4 network testbed for velocity control of a DC servomotor
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