Stability and Control of Biomolecular Circuits through Structure

Due to omnipresent uncertainties and environmental disturbances, natural and engineered biological organisms face the challenging control problem of achieving robust performance using unreliable parts. The key to overcoming this challenge rests in identifying structures of biomolecular circuits that are largely invariant despite uncertainties, and building feedback control through such structures. In this work, we develop the tool of log derivatives to capture structures in how the production and degradation rates of molecules depend on concentrations of reactants. We show that log derivatives could establish stability of fixed points based on structure, despite large variations in rates and functional forms of models. Furthermore, we demonstrate how control objectives, such as robust perfect adaptation (i.e. step disturbance rejection), could be implemented through the structures captured. Due to the method’s simplicity, structural properties for analysis and design of biomolecular circuits can often be determined by a glance at the equations.

A Novel Moth-Flame Algorithm for PID-Controlled Processes With Time Delay

This chapter proposes a classical controller to control the industrial processes with time delay. A new population-based metaheuristic technique, called moth flame optimization (MFO) algorithm, is employed to tune the parameters of the classical proportional-integral-derivative (PID) controller for achieving the desired set point and load disturbance response. MFO-based PID controller may deal with wide ranges of processes, which includes integrating and inverse response as well as it may control the processes of any order with time delay. The transient step response profile obtained from the proposed MFO-based PID controller is juxtaposed with those obtained from other methods for optimizing the gains of the PID controller to control the processes with time delay. The proposed controller is analyzed by implementing step disturbance in the process at a specific simulation time. For few time delay processes, reference models are employed for better transient response as well as to analyze the controller for controlling the overall system with reference model.

No-Load Stability Analysis of Pump Turbine at Startup-Grid Integration Process

This paper focuses on no-load stability during startup-grid integration process. First, no-load operating dynamic character under startup-grid integration process is studied by bifurcation diagram, based on a classical pumped storage plant model. Second, the no-load stability of pump turbine was analyzed by introducing step disturbance and slopes. Finally, the results indicate that the no-load operating point is easy to be disturbed and some factors, such as different disturbance intensity and slopes, have different influence on no-load stability. These methods and results will supply theoretical basis for operating the pumped storage plant steadily.

A Disturbance Adaptive Control Scheme Based on Order Identification

Using a order identification method based on wavelet transform to detect the positions of step disturbances, a adaptive control scheme of disturbance based on the order identification method is designed. The simulation shows that the controller can not only track the set point accurately, but also suppress the step disturbance appeared in different position timely. This control scheme is simple, effective and useful in engineering application.

The Measuring Method of Static Delay Rate Based on the Frequency Step Disturbance

This article introduces the definition of delay rate in turbine electro-hydraulic control system and its significance in practical applications, and builds the simulation model to measure it. By introducing and analyzing the principal of current domestic delay rate measuring method that uses uplink and downlink ramp signal, it can be found that this kind of determination is affected by the speed largely, and simulation experiments show its validity. Aiming at solving problems of this method, a measuring method of static delay rate based on the frequency step disturbance has been put forward and simulated.

Synchronous Control of Multi-Integrated System of Electro-Hydraulic with Mechanic Based on Virtual Axis Model

The article gives a solution to the precise synchronous control of multi-hydraulic cylinders which exist in the large-sized pressure and flattening machine by the virtual axis method. To fulfill the job, the scheme introduces the acceleration feedback to the virtual control model to make the model practical. According to the Newton’s mechanical law and fluid mechanic, the article set up the model mentioned above. The control system presented is investigated through simulation of Matlab under step disturbance and productive practice which successfully demonstrate the effectiveness of the proposed control model.

A Design Method for Modified Smith Predictors for Non-Minimum-Phase Time-Delay Plants with Multiple Feedback-Connected Time-Delays

In this paper, we examine a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays. The Smith predictor is proposed by Smith to overcome time-delay and known as an effective time-delay compensator for a plant with large time-delay. The Smith predictor by Smith cannot be used for plants having an integral mode, because a step disturbance will result in a steady state error. Several papers considered the problem to design modified Smith predictors for unstable plants. However, no paper examines a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays. In this paper, we examine a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays.