Integral Feedback Research Articles

A novel cutterhead off-stuck strategy for tunnel boring machine based on electro-hydraulic hybrid driving

The cutterhead driving system of a tunnel boring machine may easily get jammed in fault zones driven by electro-motors of low torque capacity. To improve the geological adaptability, this work presents a novel electro-hydraulic hybrid cutterhead driving system to control high-torque hydro-motors as followers under the torque master–slave strategy together with electro-motors. Specific half closed-type pump–motor system is designed, the work pressure of the hydro-motor is regulated by proportional overflow valve to track the torque of the main electro-motor, and a variable displacement pump is controlled to track the expected speed of the main electro-motor with stable overflow via the proportional overflow valve. Feed-forward control principles are derived via the inner mechanism analyses of the proportional overflow valve and variable displacement pump, and proportional and integral separated feedbacks are also introduced to build compound controllers for the tracking of pressure and pump displacement, respectively. The hybrid driving experiments on a Φ2.5 m tunnel boring machine rig indicate that the hydro-motor could track 1.5 times the main electro-motor torque with error within ±15.2 N m against load change and system oscillation, and the error ratios of hydro-motor and slave electro-motor are similar at normal load and fixed speed. Furthermore, jammed cutterhead could be restarted with each hydro-motor supplying double torque of the main electro-motor, and the required assembly power is only 25% of alternative electro-motors.

Control system design for tokamak remote maintenance operations using assisted virtual reality and haptic feedback

To meet the future electricity demands, tokamak based nuclear fusion machine is an attractive option for the researchers. The availability and reliability of these machines over a reasonable time span will be largely dependent on the planning of the remote maintenance scheme. The efficiency of the remote maintenance operations can be effectively increased by designing specialized remote handling control systems with high precision and accuracy. Huge efforts are needed to equip the RH operators with the advanced technologies that provide the real knowledge and interactions with the operating environment without being physically present. This can be achieved by using virtual reality techniques for tele-presence that may be extremely beneficial for the offline training as well as in assisting during the online RH operations. This paper outlines a concept with prototype experiments for an interactive control system using virtual reality integration and haptic feedback. Virtual 3D models of the complete work-cell have been developed and are updated synchronously for the monitoring and controlling of the robotic equipment. Force reflection servo type control strategy has been employed for the master-slave control. The proposed control system architecture and results from various test cases have been summarized here.

Stem cell homeostasis by integral feedback through the niche

Hematopoiesis is a paradigm for tissue development and renewal from stem cells. Experiments show that the maintenance of hematopoietic stem cells (HSCs) relies on signals from niche cells. However, it is not known how the size of the HSC compartment is set. Competition by HSCs for niche access has been suggested, yet niche cells in the bone marrow outnumber HSCs. Here we propose a cooperative model of HSC homeostasis in which stem and niche cells mutually interact such that niche cells function as negative feedback regulators of HSC proliferation. This model explains puzzling experimental findings, including homeostatic recovery of the HSC compartment after irradiation versus apparent lack of recovery after HSC ablation. We show that bidirectional niche-stem cell regulation has properties of a proportional-integral feedback controller. Moreover, we predict that the outflux of differentiated cells from HSCs can be regulated by the affinity of HSCs for niche cells. Much effort has been devoted to elucidating niche cell signaling to stem cells; our theoretical insights indicate that studying the effect of stem cells on the niche may be equally important for understanding stem cell homeostasis.

Evolutionary design of regulatory control. I. A robust control theory analysis of tradeoffs

The evolutionary design of regulatory control balances various tradeoffs in performance. Fast reaction to environmental change tends to favor plastic responsiveness at the expense of greater sensitivity to perturbations that degrade homeostatic control. Greater homeostatic stability against unpredictable disturbances tends to reduce performance in tracking environmental change. This article applies the classic principles of engineering control theory to the evolutionary design of regulatory systems. The engineering theory clarifies the conceptual aspects of evolutionary tradeoffs and provides analytic methods for developing specific predictions. On the conceptual side, this article clarifies the meanings of integral control, feedback, and design, concepts that have been discussed in a confusing way within the biological literature. On the analytic side, this article presents extensive methods and examples to study error-correcting feedback, which is perhaps the single greatest principle of design in both human-engineered and naturally designed systems. The broad framework and associated software code provide a comprehensive how-to guide for making models that focus on functional aspects of regulatory control and for making comparative predictions about regulatory design in response to various kinds of environmental challenge. The second article in this series analyzes how alternative regulatory designs influence the relative levels of genetic variability, stochasticity of trait expression, and heritability of disease.

Integral feedback control is at the core of task allocation and resilience of insect societies

Homeostatic self-regulation is a fundamental aspect of open dissipative systems. Integral feedback has been found to be important for homeostatic control on both the cellular and molecular levels of biological organization and in engineered systems. Analyzing the task allocation mechanisms of three insect societies, we identified a model of integral control residing at colony level. We characterized a general functional core mechanism, called the "common stomach," where a crucial shared substance for colony function self-regulates its own quantity via reallocating the colony's workforce, which collects and uses this substance. The central component in a redundant feedback network is the saturation level of this substance in the colony. An interaction network of positive and negative feedback loops ensures the homeostatic state of this substance and the workforce involved in processing this substance. Extensive sensitivity and stability analyses of the core model revealed that the system is very resilient against perturbations and compensates for specific types of stress that real colonies face in their ecosystems. The core regulation system is highly scalable, and due to its buffer function, it can filter noise and find a new equilibrium quickly after environmental (supply) or colony-state (demand) changes. The common stomach regulation system is an example of convergent evolution among the three different societies, and we predict that similar integral control regulation mechanisms have evolved frequently within natural complex systems.

PI boundary control of linear hyperbolic balance laws with stabilization of ARZ traffic flow models

This paper investigates the proportional–integral (PI) boundary feedback control for the linear hyperbolic systems of balance laws which control and output measures are located at the boundaries. We address the issue of feedback stabilization by means of PI boundary controllers. By constructing a new weighted Lyapunov function, the sufficient conditions in terms of matrix inequalities are developed for the exponential stability of closed-loop systems. These results are illustrated by the linearized Aw–Rascle–Zhang (ARZ) traffic flow model. We design a PI boundary controller to stabilize the oscillations of the traffic parameters of a freeway segment and evaluate the performance with numerical simulations.

Analysis of the impacts of homogeneous minor actinides loading in low void effect sodium fast reactor cores

Minor actinides transmutation is a solution to decrease the long-term radiotoxicity of nuclear waste and limit their short-term decay heat. In the homogenous approach, minor actinides are mixed in the fuel and loaded in the core in order to turn them into fission products. This leads to a neutron spectrum hardening in the core, which has a negative impact on the core integral feedback coefficients such as the Doppler Effect or the sodium void worth. Analysis of these impacts was used in the past to establish limit on maximal minor actinides loading in a reactor core. Low-void cores (CFV in French) have been recently developed by CEA to achieve negative sodium void worth by adding axial heterogeneities in the core layout in the form of an upper sodium plenum and an inner fertile blanket. In this paper, the impacts of minor actinides loading in such a core are analyzed and a comparison is carried out with earlier homogeneous core designs. In a first time, the impacts on integral feedbacks coefficients are evaluated, and in a second time, the perturbations of the core behavior during selected representative transients are analyzed. It is shown that even if the impacts on integral coefficients are similar between the two core designs, the low-void core behavior during loss-of-flow transient is not negatively impacted by minor actinides loading. For reactivity insertion transient, the two core designs behave similarly. It can be concluded that considering heterogeneous cores, the use of integral coefficients is insufficient to characterize the impact of minor actinides loading on the core for loss-of-flow transient. However, the impacts of minor actinides loading on the Doppler integral feedback coefficient can be used as reliable estimator for the modification of the core behavior during a reactivity insertion transient.

Development of a control system for the fourth-harmonic cavity of the HLS storage ring

Harmonic RF cavities are commonly used in storage rings to lengthen the bunches and thus suppress the beam’s instabilities and increase its Touschek lifetime. The voltage and phase of the electromagnetic fields in the harmonic cavity are of great importance for stretching the bunch. In the Hefei Light Source storage ring, a passive fourth-harmonic cavity is installed, and the cavity is monitored and controlled by an analog control module provided by its manufacturer. To vary and maintain the voltage of the harmonic cavity in a more effective way, a digital proportional, integral, and derivative feedback system based on the Experimental Physics and Industrial Control System is developed on top of the analog control module. This paper reports the details of the development of this voltage control system. Some test and operational results are also presented.

Shared planning and control for mobile robots with integral haptic feedback

This paper presents a novel bilateral shared framework for online trajectory generation for mobile robots. The robot navigates along a dynamic path, represented as a B-spline, whose parameters are jointly controlled by a human supervisor and an autonomous algorithm. The human steers the reference (ideal) path by acting on the path parameters that are also affected, at the same time, by the autonomous algorithm to ensure: (i) collision avoidance, (ii) path regularity, and (iii) proximity to some points of interest. These goals are achieved by combining a gradient descent-like control action with an automatic algorithm that re-initializes the traveled path (replanning) in cluttered environments to mitigate the effects of local minima. The control actions of both the human and the autonomous algorithm are fused via a filter that preserves a set of local geometrical properties of the path to ease the tracking task of the mobile robot. The bilateral component of the interaction is implemented via a force feedback that accounts for both human and autonomous control actions along the whole path, thus providing information about the mismatch between the reference and traveled path in an integral sense. The proposed framework is validated by means of realistic simulations and actual experiments deploying a quadrotor unmanned aerial vehicle (UAV) supervised by a human operator acting via a force-feedback haptic interface. Finally, a user study is presented to validate the effectiveness of the proposed framework and the usefulness of the provided force cues.

Teachers Mentoring Teachers in the Billion Oyster Project and Curriculum and Community Enterprise for the Restoration of New York Harbor with New York City Public Schools (BOP-CCERS) Fellowship

The Billion Oyster Project and Curriculum and Community Enterprise for the Restoration of New York Harbor withNew York City Public Schools (BOP-CCERS)(NSF DRL 1440869/PI Lauren Birney) program is a National ScienceFoundation (NSF) supported initiative through collaboration by multiple institutions and organizations led by PaceUniversity. Partners on this initiatitve include Columbia Lamont Doherty, the New York Aquairum, the New YorkHarbor Foundation, the New York Academy of Sciences, the River Project, Good Shepher Services, SmartstartEvaluation and Research, the University Maryland Center for Environmental Science and Fearless Solutions. Inthis study, teachers from one cohort were paired with teachers from a succeeding cohort in order to facilitate amentoring process between the two cohorts. This allows for teacher ambassardors to have a support structurethroughout the program, seek integral feedback, modify teaching techniques, integrate project research and establishlong term partnerships within the project team.

Spacecraft Attitude Fractional Feedback Control Using Rotation Matrices and Exponential Coordinates

Two fractional proportional–integral–derivative controllers are proposed for rigid spacecraft rotational dynamics. In the first strategy, the controller is developed on the tangent bundle of SO(3), which is the Lie group of rigid-body rotational motion, using states consisting of a rotation matrix and an angular velocity vector in the fractional-order derivative and integral feedback terms. In the second strategy, the exponential coordinates are used to design the controller. The fractional derivative and integral feedback terms have adjustable orders that can be used to tune the closed-loop response. The performances of the controllers are studied numerically for different values of the derivative and integral fractional orders in terms of control effort, steady-state response characteristics, and robustness to unmodeled disturbances; and the results are compared with those of an integer-order controller. It is shown that the inclusion of fractional orders in the controllers allows for a desired shape and spectrum of the controlled response to be obtained by tuning the fractional derivative and integral orders. For instance, the settling time and control effort may be simultaneously reduced, in contrast to the case of integer feedback control in which a tradeoff exists between these competing design specifications. The proposed fractional feedback attitude control strategies thus allow for a greater degree of flexibility over their integer-order analogs.

Outcome of special vibration controller techniques linked to a cracked beam

• Analytical solution and numerical simulation of non-linear differential equations. • Multiple scale perturbation technique is used to obtained the first order approximation. • PPF, IRC and NIPPF controllers to reduce the vibration. • Stability study subjected to external excitation. • Effect of different parameters in the system. This paper presents a comparison between three different controller methods added to a cracked beam under the action of a harmonic excitation. Those three controllers are Positive Position Feedback (PPF), Integral Resonant Control (IRC) and Nonlinear Integral Positive Position Feedback (NIPPF) which be added to the measured system. The multiple scales method (MSM) is applied for getting the approximate solution on behalf of measured design. This method is effective to solve the major equations of measured system. Stability and effect of different coefficients of the system are demonstrated. The approximate solution response is established via numerical simulation outcome. NIPPF controller is the best one gives better results compared to the other two controllers in decreasing the high amplitude of the system. Comparison between mathematical solution and numerical simulation are considered. Relationship of formerly available papers is considered.

CDM Based Servo State Feedback Controller with Feedback Linearization for Magnetic Levitation Ball System

This paper explains the design of Servo State Feedback Controller and Feedback Linearization for Magnetic Levitation Ball System (MLBS). The system uses feedback linearization to change the nonlinear model of magnetic levitation ball system to the linear system. Servo state feedback controller controls the position of the ball. An integrator eliminates the steady state error in servo state feedback controller. The parameter of integral gain and state feedback gains is achieved from the concept of Coefficient Diagram Method (CDM). The CDM requires the controllable canonical form, because of that Matrix Transformation is needed. Hence, feedback linearization is applied first to the MLBS then converted to a controllable form by a transformation matrix. The simulation shows the system can follow the desired position and robust from the position disturbance. The uncertainty parameter of mass, inductance, and resistance of MLBS also being investigated in the simulation. Comparing CDM with another method such as Linear Quadratic Regulator (LQR) and Pole Placement, CDM can give better response, that is no overshoot but a quite fast response. The main advantage of CDM is it has a standard parameter to obtain controller’s parameter hence it can avoid trial and error.

Study on reducing the charge delay of the no-insulation HTS coil after solder impregnation

A new kind of Impregnation method using conductive material, solder, was proposed recently. Experimental results showed that the solder impregnation (SIM) method was a feasible method for fixing no-insulation (NI) coils. However, the charge delay of the solder impregnated coil is too long which is one of the shortcomings of this method. Therefore, this paper focuses on using the proportional and integral (PI) feedback control of the power supply to reduce the charge time of the SIM coil. Comparing the charge delay of the SIM coil without and with the PI control, the time to reach the target magnetic could be reduced from about 350 s to about 20 s and the relative overshoot could be limited within 4%. The test results show that the charge delay of the SIM coil can be well addressed. Moreover, for comparison, an insulation coil and a NI coil were both fabricated and tested.

Antithetic proportional-integral feedback for reduced variance and improved control performance of stochastic reaction networks.

The ability of a cell to regulate and adapt its internal state in response to unpredictable environmental changes is called homeostasis and this ability is crucial for the cell's survival and proper functioning. Understanding how cells can achieve homeostasis, despite the intrinsic noise or randomness in their dynamics, is fundamentally important for both systems and synthetic biology. In this context, a significant development is the proposed antithetic integral feedback (AIF) motif, which is found in natural systems, and is known to ensure robust perfect adaptation for the mean dynamics of a given molecular species involved in a complex stochastic biomolecular reaction network. From the standpoint of applications, one drawback of this motif is that it often leads to an increased cell-to-cell heterogeneity or variance when compared to a constitutive (i.e. open-loop) control strategy. Our goal in this paper is to show that this performance deterioration can be countered by combining the AIF motif and a negative feedback strategy. Using a tailored moment closure method, we derive approximate expressions for the stationary variance for the controlled network that demonstrate that increasing the strength of the negative feedback can indeed decrease the variance, sometimes even below its constitutive level. Numerical results verify the accuracy of these results and we illustrate them by considering three biomolecular networks with two types of negative feedback strategies. Our computational analysis indicates that there is a trade-off between the speed of the settling-time of the mean trajectories and the stationary variance of the controlled species; i.e. smaller variance is associated with larger settling-time.

Estimation of plasmid concentration in batch culture of Escherichia coli DH5α via simple state observer

The aim of this paper is to present an alternative state observer structure for online estimation purposes of the key dynamical variables in a class of batch culture for plasmid production; the latter has been extremely attractive to be used as DNA vaccines or gene therapy. A mathematical model for culture of Escherichia coli DH5α-harboring plasmid was considered a benchmark system for the application of the proposed estimation methodology. Local observability analysis revealed that the system is partially observable for plasmid concentration considering only the biomass concentration in the batch culture as the measured variable. The proposed observer is designed with a simple proportional–integral feedback of the measured biomass concentration, where under the proposed design, the observer gain´s array can compensate the main nonlinearities of the estimation error dynamics. The convergence of estimated variables to the real ones is mathematically analyzed, reaching an asymptotic behavior. Numerical experiments were performed, where a comparison with a standard extended Luenberger observer was done and the proposed estimation methodology revealed a satisfactory performance.

Speed-constrained three-axes attitude control using kinematic steering

Spacecraft attitude control solutions typically are torque-level algorithms that simultaneously control both the attitude and angular velocity tracking errors. In contrast, robotic control solutions are kinematic steering commands where rates are treated as the control variable, and a servo-tracking control subsystem is present to achieve the desired control rates. In this paper kinematic attitude steering controls are developed where an outer control loop establishes a desired angular response history to a tracking error, and an inner control loop tracks the commanded body angular rates. The overall stability relies on the separation principle of the inner and outer control loops which must have sufficiently different response time scales. The benefit is that the outer steering law response can be readily shaped to a desired behavior, such as limiting the approach angular velocity when a large tracking error is corrected. A Modified Rodrigues Parameters implementation is presented that smoothly saturates the speed response. A robust nonlinear body rate servo loop is developed which includes integral feedback. This approach provides a convenient modular framework that makes it simple to interchange outer and inner control loops to readily setup new control implementations. Numerical simulations illustrate the expected performance for an aggressive reorientation maneuver subject to an unknown external torque.

A computational model for how cells choose temporal or spatial sensing during chemotaxis.

Cell size is thought to play an important role in choosing between temporal and spatial sensing in chemotaxis. Large cells are thought to use spatial sensing due to large chemical difference at its ends whereas small cells are incapable of spatial sensing due to rapid homogenization of proteins within the cell. However, small cells have been found to polarize and large cells like sperm cells undergo temporal sensing. Thus, it remains an open question what exactly governs spatial versus temporal sensing. Here, we identify the factors that determines sensing choices through mathematical modeling of chemotactic circuits. Comprehensive computational search of three-node signaling circuits has identified the negative integral feedback (NFB) and incoherent feedforward (IFF) circuits as capable of adaptation, an important property for chemotaxis. Cells are modeled as one-dimensional circular system consisting of diffusible activator, inactivator and output proteins, traveling across a chemical gradient. From our simulations, we find that sensing outcomes are similar for NFB or IFF circuits. Rather than cell size, the relevant parameters are the 1) ratio of cell speed to the product of cell diameter and rate of signaling, 2) diffusivity of the output protein and 3) ratio of the diffusivities of the activator to inactivator protein. Spatial sensing is favored when all three parameters are low. This corresponds to a cell moving slower than the time it takes for signaling to propagate across the cell diameter, has an output protein that is polarizable and has a local-excitation global-inhibition system to amplify the chemical gradient. Temporal sensing is favored otherwise. We also find that temporal sensing is more robust to noise. By performing extensive literature search, we find that our prediction agrees with observation in a wide range of species and cell types ranging from E. coli to human Fibroblast cells and propose that our result is universally applicable.

Adaptive Proportional–Integral Clock Synchronization in Wireless Sensor Networks

In this paper, we present a novel control-theoretic time synchronization algorithm, named PISync for synchronizing sensor nodes in wireless sensor networks (WSNs). The PISync algorithm is based on an adaptive proportional–integral controller. It applies a proportional feedback (P) and an integral feedback (I) on the local measured synchronization errors to compensate the differences between the clock offsets and the clock speeds. We present practical flooding-based and fully distributed protocol implementations of the PISync algorithm, and we provide theoretical analysis to highlight the benefits of this approach in terms of improved steady-state error and scalability as compared with existing synchronization algorithms. We show through theoretical analysis, real-world experiments, and simulations that PISync protocols have better or comparable performance over existing protocols in the WSN literature in terms of rate of convergence and steady-state error with the additional advantages of requiring minimal CPU overhead, memory allocation, and code footprint independent of network size and topology, and of employing blind communication.

A Systematic Controller Design for a Grid-Connected Inverter with LCL Filter Using a Discrete-Time Integral State Feedback Control and State Observer

Inductive-capacitive-inductive (LCL)-type filters are currently preferred as a replacement for L-type filters in distributed generation (DG) power systems, due to their superior harmonic attenuation capability. However, the third-order dynamics introduced by LCL filters pose a challenge to design a satisfactory controller for such a system. Conventionally, an LCL-filtered grid-connected inverter can be effectively controlled by using a full-state feedback control. However, this control approach requires the measurement of all system state variables, which brings about more complexity for the inverter system. To address this issue, this paper presents a systematic procedure to design an observer-based integral state feedback control for a LCL-filtered grid-connected inverter in the discrete-time domain. The proposed control scheme consists of an integral state feedback controller and a full-state observer which uses the control input, grid-side currents, and grid voltages to predict all the system state variables. Therefore, only the grid-side current sensors and grid voltage sensors are required to implement the proposed control scheme. Due to the discrete-time integrator incorporated in the state feedback controller, the proposed control scheme ensures both the reference tracking and disturbance rejection performance of the inverter system in a practical and simple way. As a result, superior control performance can be achieved by using the reduced number of sensors, which significantly reduces the cost and complexity of the LCL-filtered grid-connected inverter system in DG applications. To verify the practical usefulness of the proposed control scheme, a 2 kW three-phase prototype grid-connected inverter has been constructed, and the proposed control system has been implemented based on 32-bit floating-point digital signal processor (DSP) TMS320F28335. The effectiveness of the proposed scheme is demonstrated through the comprehensive simulation and experimental results.