Basic Control Strategy Research Articles

Route adaptation of control strategies for a hybrid city bus

A series hybrid city bus with diesel engine and electric batteries is studied on a specified route. The study uses two different basic control strategies, “On/off” and “Continuous” strategy. These basic strategies are complemented in two ways. First, an “Adviser” strategy which filters the driver commands and gives driver support feedback based on the route data. Second, an “Adapter” strategy, which adapts and the control to the route, using different control depending on the vehicle present position. Simulation results are presented. They show that the adviser and adapter strategies improves both emissions and fuel consumption.

Limit cycle oscillation control and suppression

AbstractThe prediction and characterisation of the limit cycle oscillation (LCO) behaviour of non-linear aeroelastic systems has become of great interest recently. However, much of this work has concentrated on determining the existence of LCOs. This paper concentrates on LCO stability. By considering the energy present in different limit cycles, and also using the harmonic balance method, it is shown how the stability of limit cycles can be determined. The analysis is then extended to show that limit cycles can be controlled, or even suppressed, by the use of suitable excitation signals. A basic control scheme is developed to achieve this, and is demonstrated on a simple simulated non-linear aeroelastic system.

Simulation study of unified power flow controller

The increasing complexity of ac power networks requires a high-performance power flow control system in order to obtain the desired power flow and enhance static and dynamic stability. One of the most effective power electronic systems to satisfy these requirements is a UPFC (Unified Power Flow Controller) employing self-commutated converters. This paper presents basic control strategies and simulation results for the UPFC using the EMTP (Electromagnetic Transient Program). The simulations were carried out for start and stop operations, power flow change operations in normal system conditions, as well as operations during system fault conditions. Thyristor-based bypass switches are used for the protection of the series compensator of the UPFC from system fault currents, and satisfactory protection capability was confirmed. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 23–30, 1999

Vibration Control of Travelling Suspended Systems by Wave Control.

This paper describes the vibration control of suspended systems which travel from one position to another using a wave control method. Two types of suspended systems are considered: a multiple pendulum system and a rope-and-weight system. The basic control strategy is similar to the wave control method which has been presented formerly for a non-travelling multiple-pendulum system. Analysis shows that the formerly presented method can be successfully applied to the travelling suspended systems. In order to confirm the analytical results, experiments have been done both for a multiple-pendulum system and a rope-and-weight system. The suspended system is supported by a ball-screw and a nut which is driven by a DC servomotor. The control system has a computer which calculates the vibration control signal based on the signal of the rotary encoder attached to the uppermost pendulum in order to measure its deflection. The travelling command and vibration control signals are combined to form the input to the servomotor driver.

An active piezoelectric probe for precision measurement on a CMM

The use of coordinate measuring machines (CMMs) for post-process inspection has increased as their speed and accuracy of measurement have improved; however, current passive CMM probes are still limited with respect to these criteria. The implementation of a piezoelectric (PZT) actuator as an active probe for use on CMMs is investigated. PZT actuators provide machines with a higher bandwidth response, enabling a CMM to measure more accurately at faster speeds. The development and control of the PZT probe are detailed. Upon development of the probe's experimental setup, validation of its performance is achieved by the implementation of a basic (proportional) control scheme. The goal of the probe's controller is to maintain a constant contact force between the probe and workpiece, following (while measuring) the profile of the workpiece at highly precise levels. Experimental results of the PZT based active probe are compared with results from a passive probe to quantify its relative advantages. The PZT based probe performs better than the passive probe in two areas. First, it is more effective at maintaining a constant contact force. Secondly, it more accurately measures the size of the workpiece.

Achieving a balanced quality portfolio: The relative costs of quality control and enhancement schemes

This article points out that there are costs associated with schemes for ensuring quality in higher education, and the more elaborate the scheme the higher the cost. Further, the marginal quality returns decrease as the measures become more involved and more expensive. There are also differing relationships between cost and quality return for quality control and quality enhancement schemes. In the former, improvement in quality tends towards a plateau as teaching and courses reach some minimum acceptable standard. There may even be a decrease in quality if schemes become excessively time consuming or inquisitorial. Quality enhancement schemes show smaller reductions in marginal quality returns as investment increases. Workshop‐type schemes tend to peter out as the level of offering increases, but project‐type approaches continue to show returns unless the investment becomes very high. These relative cost structures are used as an argument for evaluating quality measures themselves, for simplifying quality control measures where necessary, and for a shift towards quality enhancement. It is suggested that institutions need a balanced portfolio of quality measures, with basic quality control schemes to ensure minimum standards, workshops up to the level of market demand, and remaining resources allocated for quality enhancement initiatives through schemes such as grants for educational development projects.

The momentum turbine: a gravitational energy system

This paper presents a complete review of the work done by this author during the past decade on a new scheme for generating electricity using gravitational energy. The system is called a “momentum turbine”, and it uses a set of massive underground spinning wheels, each wheel being fitted with a mechanism to receive and transmit gravitational torque pulses from a passing vehicle to keep the wheels in motion. Each wheel, in combination with an appropriate gear system, then acts as the prime mover of an alternator which will produce the electricity. Both open-loop and closed-loop operations of the energy system are considered in this paper. In the open-loop operation using the basic scheme, an oscillating mode is found to appear in the turbine wheel speed. However, it is observed that the amplitude of these oscillations decreases with a decrease in wheel damping or with an increase in the value of wheel inertia or the associated momentum. For closed-loop operation of the turbine, on the other hand, it is shown that the desired wheel speed can never be attained following a load change unless the basic (proportional) control scheme used in the turbine is augmented by an integral mode of control. It is suggested that, in practice, this can be easily achieved through use of a standard hydraulic valve-ram component. The proposed energy concept is then examined in the light of existing thermodynamic principles. While the Second Law of Thermodynamics is not applied to the proposed scheme, application of the First Law is found useful in computation of the available mechanical energy developed at the shaft of each underground wheel. It is shown that as much as 9.4 Megawatts of mechanical power can be easily generated with a reasonable design of the momentum turbine.

自励式位相調整器の瞬時値解析による検討

The increasing complexity of ac power networks requires a high-performance power flow control system in order to obtain the desired power flow and enhance static and dynamic stability. One of the most effective power electronic systems to satisfy these requirements is a UPFC (Unified Power Flow Controller) employing self-commutated converters. This paper presents basic control strategies and simulation results for the UPFC using the EMTP (Electromagnetic Transient Program). The simulations were carried out for start and stop operations, power flow change operations in normal system conditions, as well as operations during system fault conditions. Thyristor-based bypass switches are used for the protection of the series compensator of the UPFC from system fault currents, and satisfactory protection capability was confirmed. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 23–30, 1999

Nonlinear controllers for vibration suppression in a large flexible structure

This paper deals with the problem of active vibration suppression in a laboratory model of a large flexible space structure, using nonlinear control laws. The basic control strategy is first presented in the simplified case of a one-degree-of-freedom mechanical oscillator; the results of this analysis are then used for the synthesis of two different controllers for the truss structure, one employing on-off air jet thrusters and the other employing piezoelectric active members as actuators. Experimental results obtained with the first controller are also given.

Developments in Centrifugal Compressor Surge Control—A Technology Assessment

There are a number of surge control schemes in current use for centrifugal compressors employed in natural gas transmission systems. Basically, these schemes consist of a set of detection devices that either anticipate surge or detect it at its inception, and a set of control devices that act to prevent surge from occurring. A patent search was conducted in an attempt to assess the level and direction of technology development over the last 20 years and to define the focus for future R&D activities. In addition, the paper presents the current state of technology in three areas: surge control, surge detection, and surge suppression. Patent data obtained from on-line databases showed that most of the emphasis has been on surge control rather than on detection and control and that the current trend in surge control will likely continue toward incremental improvement of a basic or conventional surge control strategy. Various surge suppression techniques can be grouped in two categories: (i) those that are focused on better compressor interior design, and (ii) others that attempt to suppress surge by external and operational means.

A new electromagnetic levitation system for rapid transit and high speed transportation

A Maglev system using permanent and electromagnet is described. Such a system offers the advantages of high lift force to magnet weight ratio and nearly zero ohmic loss of its control winding. However, it is more difficult to control. Also, unlike the conventional electromagnetic levitation system, the control current is always maintained at zero value even with load variations. Analysis shows that the size and weight of this system are smaller by a factor of three compared to the conventional Maglev system. Basic design criteria and control strategy using variable structure control method are given, together with experimental results of a small model to verify its feasibility and good dynamic response. >

Dynamic and static fusion gait of a quadruped walking vehicle on a winding path

A quadruped walking vehicle has the potential both to walk, conserving the conditions of smoothness and static stability, and to run, where the ride will be bumpy but fast and dynamically stable. The authors have already proposed the concept of 'dynamic and static fusion gait control' and discussed a basic control scheme for the purpose of adaptive selection of these gaits during continuous walking. This paper extends the concept to walking at variable speeds along a winding path. The motion scheme is discussed on the basis of a generalized trot gait and incorporating stability control based on feedforward and feedback control; trajectory modification is based on the concept of zero moment point. The validity of the motion schemes was verified in walking experiments using the quadruped walking vehicles TITAN IV and TITAN VI.

Control systems in dissonance: The computer as an ink blot

This study focuses on the choice that organizations have to make between two basic control strategies when they are facing increasing complexity and uncertainty. Firstly, organizations may choose to invest in vertical information systems and secondly, they may try to reduce organizational complexity and foster self-contained tasks. However, it is expected that dissonance will occur when vertical information systems are introduced in so-called “self-renewing organizations”. The study is based on a comparative case analysis of five engineering workshops of a large Dutch multinational. The study indicates that the impact of computerized production control systems on the organization is heavily dependent on the actual use of those systems. Organizations tend to maintain consonance of their control style by making a selective use of the system.

Gaze controls cooperating through prediction

Animate vision systems, biological or robotic, employ gaze control systems to acquire and stabilize objects on their retinae, and in some animals to foveate (centre) objects. Our goal is to guild robust gaze control behaviour from cooperating lower-level visual reflexes. Predictive control strategies can cope with time delayed, multi-rate and interacting controls. Solutions are explored through simulation incorporating ten primitive gaze control capabilities, more or less comparable to subsystems in primate gaze and head control. Versions of several of the subsystems have been implemented on a binocular robot. Smith prediction is the basic control strategy, using kinematic simulation of agent and optimal filtering to predict world state.

A control of a brownian storage system with two switcnover drifts

We consider a bounded storage system whose content level is bounded between two critical levels 0 and 1. In the absence of any control, the content level process fluctuates as a Brownian notion with drift μ and reflected barriers at 0 and 1. We assune that the purpose of any control scheme of the system is to decrease the chance that the process hits the critical levels and increase the proportion of tine it spends in a safe zone (a,b), 0<a<b<1, where a and b are chosen to mininize suitable cost functions. In this paper we consider a basic control scheme in which the controller is free to change (at any tine) the drift of the Brownian motion and use two drift values. We study several variations of this control scheme and derive suitable cost functions

Commutated relay switching system

A basic electronic control scheme which allows relays to be utilized at fast switching rates with long lifetimes and is applicable with standard microprocessor-based systems is described. The basic power-switching circuit consists of a commutating diode connected in parallel with the contacts of a single master relay, and this combination connected in series with a parallel combination of slave switching relays and associated loads. Timing and control is provided in such a way that the relays are switched at a high frequency but never with current flowing through the contacts. An actual range application with multiple loads is described, along with the necessary circuitry and logic. In addition, a diagnostic scheme is described which takes advantage of the commutated system to determine component failures in the power switching loads. >

Dynamic Modeling and Control of Mineral Processing Operations Based on the Forth Language

This paper presents a software product written in the FORTH language which is intended for dynamic modelling of mineral processing operations with or without control loops. To take the advantage of the FORTH language which is powerful for defining generic functions among other features the authors have developed a package of tools to generate basic models and control schemes available for single-as well as multi-component mass flows specific to mineral processing operations. The software package developed so far involves generators for complete mixers with or without backflow, pipes to simulate plug flow as well as reactions such that grinding, flotation and other process kinetics can be embraced. The system will also embody process indentification and adaptive control schemes which will enable quasi-automatic design and installation of control circuits.

Dependency of Service Time on Waiting Time in Switchng Systems--A Queueing Analysis with Aspects of Overload Control

Performance degradation of switching systems when the load increases above the engineered load can be caused by systemdependent and customer-dependent factors. In this paper the dependency of the service time and the call completion rate on the waiting time of a customer is investigated. The problem is modeled by means of a queueing system of type <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M^{[x]}/G/1</tex> , where state-dependent batch size distributions are considered. Two analysis methods, the continuous Markov chain approach and the regenerative method, are used for Markovian and generally distributed service phases, respectively. Numerical results are given for system characteristics, in particular the call completion rate of the system. Finally, a basic overload control scheme is investigated which increases the throughput of completed calls at higher traffic levels.

Analysis of Power System Stability Enhancement by Static VAR Compensators

The paper presents a fundamental analysis of the application of static VAr compensators (SVC) for stabilizing power systems. Basic SVC control strategies are examined in terms of enhancing the dynamic and transient stabilities, improving tieline transmission capacity and damping power oscillations. Synchronizing and damping torque contributions of the SVC are determined for different controls. The analysis is supplemented by digital simulations for a simple practical example. Deficiencies of available control policies are demonstrated and a new concept, based on optimal control, is developed.

The load-independent commutated voltage source inverter for induction heating

This paper presents a load-independent commutated voltage source inverter scheme for induction heating at the lower region of the medium frequency range. The basic control strategy for regulating the inverter output voltage, current and the load power factor is described. Preferred turn-off circuits for reliable and effective control of a force-commutated and a gate turn-off inverter main thyristors are identified. The factors affecting the inverter circuit component ratings and overall efficiency are discussed.