scholarly journals An approximate derivate-based controller for regulating gene expression

2019 ◽  
Author(s):  
Saurabh Modi ◽  
Supravat Dey ◽  
Abhyudai Singh
Keyword(s):  
Biological Networks ◽  
Noise Suppression ◽  
External Disturbance ◽  
Open Loop ◽  
Loop System ◽  
Noise Sources ◽  
Output Fluctuations ◽  
Molecular Noise ◽  
Static Sensitivity ◽  
Stochastic Controller

AbstractInside individual cells, protein population counts are subject to molecular noise due to low copy numbers and the inherent probabilistic nature of biochemical processes. Such random fluctuations in the level of a protein critically impact functioning of intracellular biological networks, and not surprisingly, cells encode diverse regulatory mechanisms to buffer noise. We investigate the effectiveness of proportional and derivative-based feedback controllers to suppress protein count fluctuations originating from two noise sources: bursty expression of the protein, and external disturbance in protein synthesis. Designs of biochemical reactions that function as proportional and derivative controllers are discussed, and the corresponding closed-loop system is analyzed for stochastic controller realizations. Our results show that proportional controllers are effective in buffering protein copy number fluctuations from both noise sources, but this noise suppression comes at the cost of reduced static sensitivity of the output to the input signal. Next, we discuss the design of a coupled feedforward-feedback biochemical circuit that approximately functions as a derivate controller. Analysis using both analytical methods and Monte Carlo simulations reveals that this derivative controller effectively buffers output fluctuations from bursty stochastic expression, while maintaining the static input-output sensitivity of the open-loop system. As expected, the derivative controller performs poorly in terms of rejecting external disturbances. In summary, this study provides a systematic stochastic analysis of biochemical controllers, and paves the way for their synthetic design and implementation to minimize deleterious fluctuations in gene product levels.

scholarly journals Noise suppression in stochastic genetic circuits using PID controllers

2021 ◽  
Vol 17 (7) ◽  
pp. e1009249
Author(s):  
Saurabh Modi ◽  
Supravat Dey ◽  
Abhyudai Singh
Keyword(s):  
Noise Suppression ◽  
External Disturbance ◽  
Open Loop ◽  
Loop System ◽  
Pid Controllers ◽  
Noise Sources ◽  
External Disturbances ◽  
Stochastic Expression ◽  
Integral Feedback ◽  
The Impact

Inside individual cells, protein population counts are subject to molecular noise due to low copy numbers and the inherent probabilistic nature of biochemical processes. We investigate the effectiveness of proportional, integral and derivative (PID) based feedback controllers to suppress protein count fluctuations originating from two noise sources: bursty expression of the protein, and external disturbance in protein synthesis. Designs of biochemical reactions that function as PID controllers are discussed, with particular focus on individual controllers separately, and the corresponding closed-loop system is analyzed for stochastic controller realizations. Our results show that proportional controllers are effective in buffering protein copy number fluctuations from both noise sources, but this noise suppression comes at the cost of reduced static sensitivity of the output to the input signal. In contrast, integral feedback has no effect on the protein noise level from stochastic expression, but significantly minimizes the impact of external disturbances, particularly when the disturbance comes at low frequencies. Counter-intuitively, integral feedback is found to amplify external disturbances at intermediate frequencies. Next, we discuss the design of a coupled feedforward-feedback biochemical circuit that approximately functions as a derivate controller. Analysis using both analytical methods and Monte Carlo simulations reveals that this derivative controller effectively buffers output fluctuations from bursty stochastic expression, while maintaining the static input-output sensitivity of the open-loop system. In summary, this study provides a systematic stochastic analysis of biochemical controllers, and paves the way for their synthetic design and implementation to minimize deleterious fluctuations in gene product levels.

Enhanced Active Constrained Layer Damping Treatment for Broadband Vibration Suppression

2002 ◽  
Vol 8 (6) ◽  
pp. 777-803 ◽  
Author(s):  
Y. Liu ◽  
K. W. Wang
Keyword(s):  
Closed Loop ◽  
Noise Suppression ◽  
Vibration Suppression ◽  
Wide Frequency Range ◽  
Open Loop ◽  
Loop System ◽  
Constrained Layer Damping ◽  
Edge Elements ◽  
Modal Damping ◽  
Active Constrained Layer

In this paper, the Enhanced Active Constrained Layer (EACL) treatment is investigated for broadband damping augmentations on beam structures. The EACL concept was originally proposed to improve the damping performance of the Active Constrained Layer (ACL) by introducing edge elements at the treatment boundaries. It has been recognized that the edge elements can increase ACL performance by enhancing the direct active authority of the piezoelectric constraining layer. It has also been demonstrated that the edge element stiffness and the host structure strain field have significant influence on the overall closed-loop system damping and its various components: the active damping, the closed-loop passive damping, and the open-loop passive (fail-safe property - without any active action) damping. Through utilizing this finding, the present study explores how the EACL performance can be synthesized for multiple mode broadband applications using symmetric configurations. Although the edge elements will tend to reduce the maximum possible open-loop damping of one (or a few) vibration mode, open-loop damping of the other higher order modes could actually be increased. Moreover, the modal damping reduction in the open-loop system can generally be compensated by the significant increase of the closed-loop damping. In other words, the closed-loop EACL system damping over a wide frequency range can be significant, which makes it attractive for broadband vibration and noise suppression.

scholarly journals Assessment of adaptive capacity to sea level rise using open-loop system, case study: Cirebon and Pangandaran

2021 ◽  
Vol 708 (1) ◽  
pp. 012104
Author(s):  
I Fauzi ◽  
I M Radjawane ◽  
H Latief ◽  
Randy F Ritonga ◽  
H Y Faizin
Keyword(s):  
Sea Level Rise ◽  
Adaptive Capacity ◽  
Sea Level ◽  
Open Loop ◽  
Loop System ◽  
Open Loop System

Model-Matching Controller Design With Input-Output Data—A Numerical Approach for Redundantly Actuated Systems

1994 ◽  
Vol 116 (4) ◽  
pp. 800-805
Author(s):  
Jenq-Tzong H. Chan
Keyword(s):  
Explicit Knowledge ◽  
Controller Design ◽  
Numerical Technique ◽  
Open Loop ◽  
Loop System ◽  
Synthesis Process ◽  
Model Matching ◽  
Input Output ◽  
Output Data ◽  
Redundantly Actuated

A numerical technique for control system synthesis based on input-output data is presented. The method is applicable when the system is open-loop stable and redundantly actuated. The major merits of the method are as follows. First, the closed-loop system equation may be arbitrarily assigned. Second, explicit knowledge of an open-loop system model is not needed for controller synthesis. Third, the stability of the synthesized system may be verified during the synthesis process; hence, the workability of the controller is ensured.

Multi-Stage System Identification of a Gas Turbine

2017 ◽  
Author(s):  
Amit Pandey ◽  
Maurício de Oliveira ◽  
Chad M. Holcomb
Keyword(s):  
Gas Turbine ◽  
Closed Loop ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop Control ◽  
Input Output ◽  
Open Loop System ◽  
Loop Control ◽  
Multi Stage ◽  
Identification Techniques

Several techniques have recently been proposed to identify open-loop system models from input-output data obtained while the plant is operating under closed-loop control. So called multi-stage identification techniques are particularly useful in industrial applications where obtaining input-output information in the absence of closed-loop control is often difficult. These open-loop system models can then be employed in the design of more sophisticated closed-loop controllers. This paper introduces a methodology to identify linear open-loop models of gas turbine engines using a multi-stage identification procedure. The procedure utilizes closed-loop data to identify a closed-loop sensitivity function in the first stage and extracts the open-loop plant model in the second stage. The closed-loop data can be obtained by any sufficiently informative experiment from a plant in operation or simulation. We present simulation results here. This is the logical process to follow since using experimentation is often prohibitively expensive and unpractical. Both identification stages use standard open-loop identification techniques. We then propose a series of techniques to validate the accuracy of the identified models against first principles simulations in both the time and frequency domains. Finally, the potential to use these models for control design is discussed.

Decentralized MRAC for Large-Scale Interconnected Systems With State and Input Delays by Integrators Inclusion

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Seyed Hamid Hashemipour ◽  
Nastaran Vasegh ◽  
Ali Khaki Sedigh
Keyword(s):  
Large Scale ◽  
Practical Method ◽  
Open Loop ◽  
Loop System ◽  
Input Delay ◽  
Time Varying ◽  
Delay Compensation ◽  
State And Input Delays ◽  
Input Delays ◽  
Model Reference Adaptive

This paper investigates the problem of decentralized model reference adaptive control (MRAC) for a class of large-scale systems with time-varying delays in the interconnected terms and state and input delays. The upper bounds of interconnection terms with time-varying delays and external disturbances are assumed to be completely unknown. By integrators inclusion, a dynamic input delay compensator is established for input delay compensation and it is used as a practical method for state calculation x(t + R). Also, a method is presented for a class of decentralized feedback controllers, which can evolve the closed-loop system error uniformly bounded stable. As a numerical example, the proposed technique is applied to an unstable open-loop system to show the feasibility and effectiveness of the method.

Fretting Behavior of Coated and Treated Titanium Alloy Using an Open-Loop System

2005 ◽  
Author(s):  
G. R. Yantio Njankeu ◽  
J.-Y. Paris ◽  
J. Denape ◽  
L. Pichon ◽  
J.-P. Rivie`re
Keyword(s):  
Titanium Alloy ◽  
Relative Motion ◽  
High Frequency ◽  
Open Loop ◽  
Loop System ◽  
Test Apparatus ◽  
Open Loop System ◽  
Wear Rates ◽  
Low Wear

Titanium alloys are well known to present poor sliding behaviour and high wear values. Various coatings and treatments have been tested to prevent such an occurrence under fretting conditions at high frequency of displacement (100 Hz). An original test apparatus, using an open-loop system instead of a classical imposed displacement simulator, has been performed to directly display the phenomenon of seizure, defined as the stopping of the relative motion between the contacting elements. A classification of the tested coatings has been proposed on the basis of their capacity to maintain full or partial sliding conditions, to present low wear rates and to prevent seizure.

Application of Anytime Control to an Inherently Unstable Physical System

2015 ◽  
Author(s):  
Wayne Maxwell ◽  
Al Ferri ◽  
Bonnie Ferri
Keyword(s):  
Closed Loop ◽  
Initial Conditions ◽  
Transient Behavior ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Pendulum System ◽  
Inverted Pendulum System ◽  
Lqr Controller ◽  
Two Stages

This paper extends the use of closed-loop anytime control to systems that are inherently unstable in the open-loop. Previous work has shown that anytime control is very effective in compensating for occasional missed deadlines in the computer processor. When misses occur, the control law is truncated or partially executed. However, the previous work assumed that the open-loop system was stable. In this paper, the anytime strategy is applied to an inverted pendulum system. An LQR controller with estimated state feedback is designed and decomposed into two stages. Both stages are implemented most of the time, but in a small percentage of time, only the first stage is applied, with the resulting closed-loop system being unstable for short periods of time. The statistical performance of the closed-loop system is studied using Monte-Carlo simulations. It is seen that, on average, the closed-loop performance is very close to that of the full-order controller as long as the miss rate is relatively small. However, the variance of the response shows much higher dependence on the miss rate, suggesting that the response becomes more unpredictable. At a critical value of miss rate, the closed-loop system is unstable. The critical miss rate found through simulation is seen to correlate well with the results of a deterministic stability analysis. The statistics on the settling time are also studied, and shown to grow longer as the miss rate increases. The transient behavior of the system is studied for a range of initial conditions.

Active Control of Flexible Riser Vibration by Boundary Control Based on LQR Controller

2019 ◽  
Author(s):  
Jinxin Yu ◽  
Weimin Chen
Keyword(s):  
Boundary Control ◽  
Vibration Suppression ◽  
Lateral Displacement ◽  
Open Loop ◽  
Loop System ◽  
Ocean Current ◽  
Control Law ◽  
Flexible Riser ◽  
Linear Quadratic ◽  
Rotational Angle

Abstract The lateral displacement and the rotational angle of marine riser are likely to get larger as it is in stronger ocean current and, particularly, undergoes the consequences such as vortex-induced vibration or collisions between individual risers. The riser vibration with large amplitude value will lead to fatigue or coating damage of the structural body. In this study, the active vibration control, in terms of its angle and the displacement reductions, of a flexible riser under time-varying distributed load are considered using boundary control. The governing equations of the structural dynamics involving the control system of a flexible riser are built. The riser is modeled as an Euler-Bernoulli beam under the actions of ocean loads and the feedback controller. A torque actuator is introduced at the upper riser boundary, and the control law is employed to generate the required signal for riser angle control and displacement reduction. The feed-back control law is designed in state space, and the optimization of the control law is implemented based on the LQR approach. The linear quadratic regulator is used to determine the gain matrix, which can calculate the boundary control law by solving the Recatti equation. Based on the numerical simulations, the responses of the open-loop system and closed-loop system are presented and compared. The effectiveness of the vibration suppression of the flexible riser is examined.

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