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Author = Middleton, R.H.;
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Displaying Results 1 - 11 of 11 on page 1 of 1
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Channel Signal-to-Noise Ratio Constrained Feedback Control: Performance and Robustness
(2009)
Rojas, A.J.; Braslavsky, J.H.; Middleton, R.H.
Channel Signal-to-Noise Ratio Constrained Feedback Control: Performance and Robustness
(2009)
Rojas, A.J.; Braslavsky, J.H.; Middleton, R.H.
Abstract:
The limitations in performance and robustness imposed by explicitly considering a communication channel in a control loop have received increased attention in recent years. Previous results in the literature have stated these limitations in terms of a minimal transmission data rate necessary for stabilisation. In this paper a signal-to-noise ratio (SNR) approach is used to study two specific cases: (i) performance in terms of model matching and (ii) robustness against a multiplicative uncertainty in the plant model. The analysis performed leads to closed-form expressions that allow the quantification of the extra SNR required in both cases.
http://mural.maynoothuniversity.ie/1880/
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Feedback control performance over a noisy communication channel.
(2008)
Freudenberg, J.S.; Middleton, R.H.
Feedback control performance over a noisy communication channel.
(2008)
Freudenberg, J.S.; Middleton, R.H.
Abstract:
We consider the problem of minimizing the variance in the output of a plant that is driven by a Gaussian disturbance using measurements of the plant output obtained from a Gaussian channel. For the special case in which only the variance at the terminal time is penalized, we derive an optimal linear timevarying communication and control strategy, and argue that nonlinear strategies cannot achieve better performance.
http://mural.maynoothuniversity.ie/1753/
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Fundamental Limitations in Control over a Communication Channel
(2008)
Rojas, A.J.; Braslavsky, J.H.; Middleton, R.H.
Fundamental Limitations in Control over a Communication Channel
(2008)
Rojas, A.J.; Braslavsky, J.H.; Middleton, R.H.
Abstract:
Fundamental limitations in feedback control is a well established area of research. In recent years it has been extended to the study of limitations imposed by the consideration of a communication channel in the control loop. Previous results characterised these limitations in terms of a minimal data transmission rate necessary for stabilisation. In this paper a signal-to-noise ratio (SNR) approach is used to obtain a tight condition for the linear time invariant output feedback stabilisation of a continuous-time, unstable, non minimum phase (NMP) plant with time-delay over an additive Gaussian coloured noise communication channel. By working on a linear setting the infimal SNR for stabilisability is defined as the infimal achievable H2 norm between the channel noise input and the channel signal input. The result gives a guideline in estimating the severity of the fundamental SNR limitation imposed by the plant unstable poles, NMP zeros, time-delay as well as the channel NMP zeros, ...
http://mural.maynoothuniversity.ie/3522/
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Fundamental Limitations in Self-Sensing Magnetic Bearings when Modeled as Linear Periodic Systems.
(2006)
Peterson, K.S.; Middleton, R.H.; Freudenberg, J.S.
Fundamental Limitations in Self-Sensing Magnetic Bearings when Modeled as Linear Periodic Systems.
(2006)
Peterson, K.S.; Middleton, R.H.; Freudenberg, J.S.
Abstract:
In "Magnetic Bearing Measurement Configurations and Associated Robustness and Performance Limitations", Thibeault and Smith demonstrate that self-sensing magnetic bearings are impractical due to fundamental limitations in the achievable closed-loop robustness. Due to experimental data which appeared to contradict these results, Maslen, Montie, and Iwasaki showed that significantly better robustness is achievable in "Robustness limitations in selfsensing magnetic bearings" if the magnetic bearing is modeled as a linear periodic (LP) system rather than the linear time invariant (LTI) system used by Thibeault and Smith. The present paper explores why modeling the self-sensing magnetic bearing as a LP system improves the achievable robustness. This is accomplished by utilizing lifting to analyze the LP model as a MIMO discrete LTI system.
http://mural.maynoothuniversity.ie/1782/
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Input Disturbance Rejection in Channel Signal-to-Noise Ratio Constrained Feedback Control
(2008)
Rojas, A.J.; Middleton, R.H.; Freudenberg, J.S.; Braslavsky, J.H.
Input Disturbance Rejection in Channel Signal-to-Noise Ratio Constrained Feedback Control
(2008)
Rojas, A.J.; Middleton, R.H.; Freudenberg, J.S.; Braslavsky, J.H.
Abstract:
Communication channels impose a number of obstacles to feedback control. One recent line of work considers the problem of feedback stabilisation subject to a constraint on the channel signal-to-noise ratio (SNR). It has been shown for continuous-time systems that the optimal control problem of achieving the infimal SNR can be formulated as a linear quadratic Gaussian (LQG) control problem with weights chosen as in the loop transfer recovery (LTR) technique. The present paper extends this formulation to: discretetime systems; communications over channels with memory; and input disturbance rejection. By using this formulation, we derive exact expressions for the linear time invariant (LTI) controller that achieves the infimal SNR under the effect of time-delay and additive coloured noise. We then quantify the infimal SNR required for both stabilisation and input disturbance rejection for a relative degree one, minimum phase plant and a memoryless Gaussian channel.
http://mural.maynoothuniversity.ie/2245/
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Minimum Variance Control over a Gaussian Communication Channel
(2008)
Freudenberg, J.S.; Middleton, R.H.; Braslavsky, J.H.
Minimum Variance Control over a Gaussian Communication Channel
(2008)
Freudenberg, J.S.; Middleton, R.H.; Braslavsky, J.H.
Abstract:
We consider the problem of minimizing the response of a plant output to a stochastic disturbance using a control law that relies on the output of a noisy communication channel. We discuss a lower bound on the performance achievable at a specified terminal time using nonlinear timevarying communication and control strategies, and show that this bound may be achieved using strategies that are linear.
http://mural.maynoothuniversity.ie/2244/
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Optimal Signal to Noise Ratio in Feedback over Communication Channels with Memory
(2006)
Rojas, A.J.; Freudenberg, J.S.; Braslavsky, J.H.; Middleton, R.H.
Optimal Signal to Noise Ratio in Feedback over Communication Channels with Memory
(2006)
Rojas, A.J.; Freudenberg, J.S.; Braslavsky, J.H.; Middleton, R.H.
Abstract:
Communication channels impose a number of obstacles to feedback control, such as delay, noise, and constraints in communication data-rate. One alternate line of recent work considers the problem of feedback stabilization subject to a constraint in the signal-to-noise ratio (SNR). It has been shown for continuous-time systems that the optimal control problem arising in achieving minimal SNR can be formulated as a linear quadratic Gaussian (LQG) control problem with weights chosen as in the loop transfer recovery (LTR) technique. The present paper extends such LQG/LTR formulation to discretetime systems with feedback over channels with memory. By using such formulation, we derive exact expressions for the LTI controller and loop sensitivity functions that achieve minimal SNR under the effect of time-delay, non minimum phase zeros and colored additive noise. For the minimum-phase case with white noise and no time delay, we show that the optimal feedback loop obtained after applying LTR...
http://mural.maynoothuniversity.ie/1789/
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Piezoelectric power scavenging of mechanical vibration energy
(2007)
Singh, U.K.; Middleton, R.H.
Piezoelectric power scavenging of mechanical vibration energy
(2007)
Singh, U.K.; Middleton, R.H.
Abstract:
The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. With piezoceramic materials, it is possible to harvest power from vibrating structures. It has been proven that micro-to milliwatts of power can be generated from vibrating systems. The project targets the transformation of mechanical vibration into electrical energy using piezoelectric material. In some mining applications, eg water jet drilling; large high frequency vibrations may be present. If successfully harvested, this energy could be used to eliminate batteries in wireless sensors. This article presents a model of a piezoelectric transducer, a mechanical vibration spectrum, the simulation of the model, prototype of the power scavenging circuit, experimental results and its future perspectives.
http://mural.maynoothuniversity.ie/1694/
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Reducing computational time via order reduction of a class of reaction–diffusion systems
(2012)
Lopez-Caamal, F.; García, M.R.; Middleton, R.H.
Reducing computational time via order reduction of a class of reaction–diffusion systems
(2012)
Lopez-Caamal, F.; García, M.R.; Middleton, R.H.
Abstract:
In this paper, we consider a class of reaction– diffusion PDEs. For this class, a suitable state transformation allows conversion to a heat equation together with a lower order PDE set. By giving an explicit solution to the heat equation we are able to obtain a complete solution to the original PDE. By focusing on the computational load, we give a comparison of the pure numerical, analytical/numerical, analytical/approximated, and approximated methods of solving the PDE. In some examples, we note an almost order of magnitude improvement in computational load.
http://mural.maynoothuniversity.ie/3627/
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Stabilization and Performance over a Gaussian Communication Channel for a Plant with Time Delay
(2009)
Freudenberg, J.S.; Middleton, R.H.
Stabilization and Performance over a Gaussian Communication Channel for a Plant with Time Delay
(2009)
Freudenberg, J.S.; Middleton, R.H.
Abstract:
Two problems that have received much attention are those of finding the minimum channel signal to noise ratio compatible with closed loop stability, and of finding the optimal performance, in terms of disturbance attenuation, for a channel with specified signal to noise ratio. In this paper, we study these problems for the case in which the plant has relative degree greater than one, and thus introduces a delay greater than one time step. We show that, unlike the relative degree one case, for the problem of stabilization linear time varying control and communication strategies may have advantages over linear time invariant strategies. We derive a lower bound on optimal disturbance response at a fixed terminal time. If the encoder has access to the state of the plant, then this bound is achievable using linear time varying communication and control.
http://mural.maynoothuniversity.ie/1643/
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Stabilization with Disturbance Attenuation over a Gaussian Channel
(2007)
Freudenberg, J.S.; Middleton, R.H.; Braslavsky, J.H.
Stabilization with Disturbance Attenuation over a Gaussian Channel
(2007)
Freudenberg, J.S.; Middleton, R.H.; Braslavsky, J.H.
Abstract:
We propose a linear control and communication scheme for the purposes of stabilization and disturbance attenuation when a discrete Gaussian channel is present in the feedback loop. Specifically, the channel input is amplified by a constant gain before transmission and the channel output is processed through a linear time invariant filter to produce the control signal. We show how the gain and filter may be chosen to minimize the variance of the plant output. For an order one plant, our scheme achieves the theoretical minimum taken over a much broader class of compensators.
http://mural.maynoothuniversity.ie/1722/
Displaying Results 1 - 11 of 11 on page 1 of 1
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