The second derivative input signals modify which of the following? Which of the following statements is correct for any closed loop system? Which of the following statements is correct for a system with gain margin close to unity or a phase margin close to zero?
Due to which of the following reasons excessive bond width in control systems should be avoided? In a stable control system backlash can cause which of the following? In an automatic control system which of the following elements is not used? In a control system the output of the controller is given to a final control element b amplifier c comparator d sensor e none of the above Ans: a. A controller, essentially, is a a sensor b clipper c comparator d amplifier Ans: c.
Which of the following is the input to a controller? The capacitance, in force-current analogy, is analogous to a momentum b velocity c displacement d mass Ans: d. The temperature, under thermal and electrical system analogy, is considered analogous to a voltage b current c capacitance d charge e none of the above Ans: a. In electrical-pneumatic system analogy the current is considered analogous to a velocity b pressure c air flow d air flow rate Ans: d. In liquid level and electrical system analogy, voltage is considered analogous to a head b liquid flow c liquid flow rate d none of the above Ans: a.
The viscous friction co-efficient, in force-voltage analogy, is analogous to a charge b resistance c reciprocal of inductance d reciprocal of conductance e none of the above Ans: b. In force-voltage analogy, velocity is analogous to a current b charge c inductance d capacitance Ans: a. In thermal-electrical analogy charge is considered analogous to a heat flow b reciprocal of heat flow c reciprocal of temperature d temperature e none of the above Ans: d.
Mass, in force-voltage analogy, is analogous to a charge b current c inductance d resistance Ans: c. The transient response of a system is mainly due to a inertia forces b internal forces c stored energy d friction Ans: c.
A signal other than the reference input that tends to affect the value of controlled variable is known as a disturbance b command c control element d reference input Ans: a.
The transfer function is applicable to which of the following? From which of the following transfer function can be obtained? The term backlash is associated with a servomotors b induction relays c gear trains d any of the above Ans:. By which of the following the system response can be tested better?
In a system zero initial condition means that a The system is at rest and no energy is stored in any of its components b The system is working with zero stored energy c The system is working with zero reference signal Ans: a. In a system low friction co-efficient facilitates a reduced velocity lag error b increased velocity lag error c increased speed of response d reduced time constant of the system Ans: a.
Hydraulic torque transmission system is analog of a amplidyneset b resistance-capacitance parallel circuit c motor-generator set d any of the above Ans:.
Spring constant in force-voltage analogy is analogous to a capacitance b reciprocal of capacitance c current d resistance Ans: b. The frequency and time domain are related through which of the following?
An increase in gain, in most systems, leads to a smaller damping ratio b larger damping ratio c constant damping ratio d none of the above Ans: a. A conditionally stable system exhibits poor stability at a low frequencies b reduced values of open loop gain c increased values of open loop gain d none of the above Ans: b.
The position and velocity errors of a type-2 system are a constant, constant b constant, infinity c zero, constant d zero, zero Ans: c. In case of type-1 system steady state acceleration is a unity b infinity c zero d 10 Ans: b. If a step function is applied to the input of a system and the output remains below a certain level for all the time, the system is a not necessarily stable b stable c unstable d always unstable e any of the above Ans: a.
Which of the following is the best method for determining the stability and transient response? Phase margin of a system is used to specify which of the following?
Addition of zeros in transfer function causes which of the following? In order to increase the damping of a badly underdamped system which of following compensators may be used? In a stable control system saturation can cause which of the following?
Which of the following can be measured by the use of a tachogenerator? Which of the following is the definition of proportional band of a controller? In pneumatic control systems the control valve used as final control element converts a pressure signal to electric signal b pressure signal to position change c electric signal to pressure signal d position change to pressure signal e none of the above Ans: b.
Franklin J. Davis Powell Abbas F. Feedback control fundamentals with context, case studies, and a focus on design Feedback Control of Dynamic Systems, 8th Edition, covers the material that every engineer needs to know about feedback control—including concepts like stability, tracking, and robustness. Preface Preface is available for download in PDF format. An emphasis on design , beginning in Chapter 4, builds confidence in solving design problems from the start.
Examples compare and contrast the design techniques afforded by the different design methods and complex real-world design problems are attacked using all the methods in a unified way.
Relationships used in design and throughout the book are collected inside the back cover for easy reference. Updated - New examples, updates, and additions keep the material relevant and up-to-date. New - Over 60 of the problems in this edition are either new or revised from the previous edition. New to This Edition. New examples, updates, and additions keep the material relevant and up-to-date. Table of Contents 1. Laplace Transforms Appendix B. Solutions to the Review Questions Appendix C.
Matlab Commands. Share a link to All Resources. Instructor Resources. Previous editions. Feedback Control of Dynamic Systems, 7th Edition. Relevant Courses. Sign In We're sorry! Username Password Forgot your username or password? It enables an identification of actions to be taken to alter systemic attributes and the nature of inter-systemic relationships, in order to establish an optimal goodness of fit between person and situation, or between the client system and its milieu.
This means altering direct- ionaltendencies, such as perception, decision-making, role performance; and external linkages, such as definitions of one's life situation. One then can choose from alternative objectives, levels, strategies, and tac- tics of intervention to formulate an interventive plan. Because an ecological approach to intervention is multi-factorial and is addressed to systemic attributes and intersystem relationships, social workers have been encouraged to develop and utilize a strong and varied repertoire of assessment instruments and helping interventions.
Ile now make use of a wide range of strategies, roles, and techniques, through which to work with a person, a family, a work situation, a neighborhood organization, a welfare service system. We are less apt now to select cases or program tasks, or to define problems, so as to suit narrow methods or techniques.
It is in accord with the requirements of an ecological systems model of practice that new forms of service and manpower patterns have appeared. Comprehensive, systemic approaches to programs and cases need social work and inter-disciplinary teams with many different kinds of knowledge and skills.
As Carol Meyer has pointed out, "A systems perspective per- mits the argument that imaginative use and deployment of manpower teams The framework makes possible imaginative uses of all levels of manpower There also is an increas- ing emphasis on an enriched use of volunteers, and on the development of, and assistance to, self-help and natural support groups.
Systems analysts assume that all systems are similar, but actually there are important differences between a person and a work organization, between the design of aerospace hardware and of a social service pro- gram, between mediating a national labor dispute and a marital conflict.
As Robert Leighninger observes, systems theorists "do not have a ter- ribly impressive track record," considering such examples as the War in Vietnam, or the Pentagon's cost-benefit planning for military equipment.
We can note here a tendency on the part of systems theorists to over- estimate the rationality of human beings and particularly of decision- making and problem-solving in organizational behavior. Thus, there is an effort to impose an unrealistic kind of rational image upon organiza- tional life. There is increasing evidence that our communities and our bureaucracies, including the universities and the military services, actually are "organized anarchies.
The pretense to rational administration is associated with a use of systems models, particularly in industry, that has operated to exacer- bate certain establishment tendencies. One pernicious trend has been the increase in bureaucratic, centralized control, with power placed in the hands of "systems-experts" rather than managers, with escalated costs due to overstaffing of non-productive personnel and to reams of paperwork.
Another difficulty posed by the systems model is the assumption that systemic components are so interdependent that impactful intervention at some crucial point should affect other' elements,. We do not have many more points of entry and levels of intervention into systems, with individuals, dyads, families, groups, organizations, communities, etc.
Also, we do not know how to control the con- sequences so that they consistently follow predictions and have positive, constructive results, in the immediate, as well as in the long-term, future. Unintended and negative consequences are a common result of planned systemic change programs, as in the classic example of how street gangs were weaned from gang warfare against each other, yet wound up addicted to drugs.
One result has been the use of systems theory to justify a generalist kind of social work practice, and for practi- tioners to believe that they need to be, and to be equally expert as, social planners, family therapists, community organizers, psychothera- pists, etc.
The result of such grandiose pretensions has been an increasing disenchantment of service agencies and of the public with the insubstantial rhetoric and lack of competence in the effective provision of basic social services that is exhibited by many mental health and social service practitioners. A more recent reaction has been the scaling down of claims for a generalist practice, and a recogni- tion of valued specializations and of individual talents to be confirmed within service teams.
But without a value system that can give it constructive direction and purpose, it will lack meaning, will not motivate its members productively, and therefore will follow an entropic course into stagnation and decline. The popularity of systems theory has been associated with a prevailing adversary, competitive culture and a dominant value system that features prominently a narcissistic hedonism, individualistic autonomy and freedom, and materialistic achievement.
This kind of personalist, hedonistic value system - that gives primacy to self-actualization, autonomy, and present gratification - is also accepted and endorsed by many social workers. It appears to underlie certain harmful aspects of social work practice, a fact that now is being openly discussed and criticized. Glasser and Glasser, for example, charge that social system theory, as applied in social work, has focused on family functions for the good of individual members with a neglect of the needs of the society and of a proper balance between them.
The Dialectic of Stability and Change The criticism of systems theory as reinforcing the maintenance of the status-quo is at variance with the use bf systems theory by radicals and reformists, who characteristically proclaim the need to reform and ,,change the whole system.
He spoke of the "capitalist system," and apparently did use a systems analytic model as a basis for developing his theory of historical materialism, and for his view of the key subsystem of economic produc- tion. This is well argued by McQuarie and Maburgey, who also find that Marx conceived of the key system elements as the economic forces and social relations of production, and the political-cultural superstruc- tures and forms of consciousness in a society which are derived from them.
Social change was viewed by Marx as taking place as a result of the dialectical process concerning these inherent contra- dictions and resultant class conflicts.
In addition, Marx and Engels were committed to what we now call an ecological systems conception of man in relation to fellow man and to nature, as is well demonstrated by Howard Parsons.
They viewed and affirmed man in dialectical relations with nature, whereby each reciprocally creates and transforms the other. Their vision of a comunistic society encompassed a "socialist ecology," to use Parsons' phrase, in which there would be "real human freedom" in a harmony between man and nature.
As a result, there. In addition to ance, and of adaptive change, for individuals and social systems. The dialectical life which negates and affirms. The ecological model thus can subsume structural-functionalist synergistic relationships and productive tlansactions.
As Marx and Engels said of this process, rrin revolutionary interventive forns, so that these were and are integrati-ve, meliorating, activity the changing of oneself coincides l4rith the changing of protective and controlling, as well as consciousness-raising and opposi- circumstances.
Its societal tasks call upon the social worker to be One inportant function of social work, essential to the dialectical a social conscience, a noral and educative agent' an advocate and social process, is to aid people with their difficulties around liaison for the dependent and deviant, a caretaker and social reformer. It represents a potentiation of essential tendencies for de- bility and change, toward a jult, pluralistic and integrated, peaceful, velopment and change, and thus a potentiation and anplification as well comnunal society.
In mediating deviance- control processes in our society, social workers are concerned to help people achieve constructive outcornes. They are norn-senders and rule enforcers as well as notm-changers and value stretchers. In addition to a characteristic person-in-situation perspective, social.
By its very nature, then, social work practice is a Draxis, a union of practical, instruzmental theory and practice, through which social workers act and intervene to help people consciously shape their life conditions and history, to change both their consciousness and their reality.
As Marx and Engels said of this process, "in revolutionary activity the changing of oneself coincides with the changing of circumstances. It aims to effect change in person and situation and in their trans- actional relationships for an optimal and equitable exchange balance, as well as to help people "achieve at one and the same time their own and society's betterment. Its societal tasks call upon the social worker to be a social conscience, a moral and educative agent, an advocate and liaison for the dependent and deviant, a caretaker and social reformer.
To be influential and effective in accomplishing them, and to have public legitimation and support, social authority and resourcesf social workers need to be highly credible, unified, and competent. They are required to provide efficient and beneficial social services, and to present expertly organized and persuasive evidence of unmet needs and for requisite changes in social welfare policies and programs.
Social workers therefore need to understand and to utilize both control and reform types of strategies, principles, and procedures, as they are appropriate in helping situations. Social work practice needs both conservative and radical contributions.
We note, however, that the contributions of the establishment-practice approaches have for a long time been extensive and predominant. Part of the appeal of establishment- oriented psychoanalytic and behaviorist approaches has been the opera- tional, technical, and thereby useable, nature of their practice theories and procedures. These approaches and procedures actually are as capable of application for social reformist purposes, and they merit such a development.
It is only now that radical, social-provision, and reformist social workers are beginning to translate ideological rhetoric into the develop- ment of specific, realistic, operational theory, principles and pro- cedures. The lessons and advances of what was effective social work practice during earlier social reform eras are valuable but as yet neglected resources. It is from current perspectives that Leonard declares, "viewing social structures in terms of systems is not necessarily a means of justifying them," and he urges the use of systems theory to understand and change existing institutions.
We need here to recognize that many truly radical social work programs are developed and implemented without a "radical" label, such as a number of effective systems-based projects that have been realized in public welfare, industrial, health, and other institutional organiza- tions and settings. An intellectual and attitudinal openitess is needed to clarify and resolve what are presently confused and controversial matters: for example, about what are appropriate and effective moral and political roles consistent with the social work profession's social contract and mission, and with the professional, agency.
Conclusions In this analysis of ecological systems theory, of its advantages and disadvantages, it is evident that these refer to their usages and applications, much more than to the inherent nature of the theory or model itself. We observed that the ecological systems model has advanced the evolution of systems theory and therefore of basic social work practice theory. It is meeting social work perspectives and purposes and its present contributions outweigh its limitations.
Social work is a societal instrument that serves people in their efforts to maintain, restore and enhance their individual and col- lective social functioning and that mediates dialectical social con- trol and deviance-change processes. Ecological systems theory is such a general meta-theory, one that provides for the many, and at times contradictory, purposes and activities of social workers.
It constitutes an essential element of the generic core of social work knowledge, of its common person-in- situation and dialectical perspective, and of its basic helping approach. It supports the social work assessment and interventive focus on people transacting with others in their situational milieu, utilizing inner and external resources to develop and to function well.
From this base, social work practice has developed and adapted a variety of specialized helping models and approaches. The ecological model itself is not a helping approach per se, although in recent years it has been conceptualized at less abstract and more operational levels, and we have identified certain behavior and practice principles that have emerged. However, ecological systems theory will continue to be used primarily as a framework for a complex and changing set of theories and models needed for the ever-evolving nature of social work practice.
The current awareness of the sharp conflict in the social work value system - between individualistic, self-fulfillment orientations and the socially responsible, altruistic orientations - should help us arrive at new balances and syntheses of ethical and value positions, more in keeping with current reality needs.
Social workers then can be of better help to clients with such value dilemmas and conflicts. The ecological systems model, by implication, gives priority to certain values: social integration and constructive conflict; a harmonious interdependence of parts that includes apparent contradictions or com- petition for resources; a goodness of fit between sub-system needs and competencies; a balanced complementarity of resource exchange that makes for reciprocity, mutual aid, and mutual need-meeting.
Ecological systems theory can provide support for the mediating func- tion of social work in regard to the dialectical forces of social stability-control and social deviance-change, and in furthering the processes of social evolution.
The predominant use of systems theory has seemed to favor the control-care responsibilities of practice, although the social-provision, radical, and reformist responsibilities have recently and currently been given more attention. Social work needs both control and reform types of strategies, principles, and procedures, including from conservative and Marxist persuasions.
Ecological systems theory not only expresses a traditional social work orientation to man and nature, but it now can support a conception of social work practice as a praxis, as an instrumental theory and practice to help people shape their history and life conditions, and to change both their consciousness and their reality.
Such a conception of social work practice makes use of the ecological system as a metaphor and symbol for a social work utopian vision of good people in a right, just, democratic society. It is such a symbol that is needed at present in social work to help us resolve current value and ideological conflicts, and to advance the effectiveness of social work practice. It can enable social work as a profession to regain its esteemed and central place in society's effort to enhance the quality of individual and social welfare.
References: 1. For historical accounts, see: Robert D. Leighninger, Jr. Jesse F. Bernard, ed. Steiner, op. Burgess, "The Social Survey," American Journal of Sociology, , , present the influence of the social survey movement on the development of sociological "human ecology.
Mary E. It is noteworthy that prior to Richmond experimented with drawings of a family and its milieu, what are now called "ecomaps. Ada E. Florence Hollis, Casework, 2d ed. Francis J. This older practice model is well described by Harriett M. Werner A.
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