Specified Motion of Piezoelectrically Actuated Structures

The problem considered is that of solving for the control input that generates partly specified motion of a deformable structure with distributed piezoelectric actuation. The motion constraint, called the program constraint, is specified as a desired relation on the motion of selected material points of the structure. The solution is based on a projection method applicable to a class of finite-dimensional dynamical systems which includes many common vibration models. For a nonlinear model with a nonlinear program constraint, the procedure in general results in a set of differential algebraic equations. It is shown that for linear models with linear periodic program constraints, the system is reduced to a set of algebraic equations. Application examples are presented for a Euler-Bernoulli beam to demonstrate the usefulness of the procedure.

Dynamics of a Thin Plate With Partly Specified Motion

The problem considered here is that of determining the precise forcing function that produces specified motion of a deformable structure. While fundamental in nature, the problem is practically important for evaluating actuation requirements for active structures. Our approach to this problem is to apply an existing solution method for finite-dimensional mechanical systems. We evaluate the direct application of this method to the spatially discretized, small strain equations of a thin plate. Several example cases are considered in which the program forces are determined, and then applied in finite element analysis software for verification of the program constraint.

THE INVERSE SIMULATION STUDY OF AIRCRAFT FLIGHT PATH RECONSTRUCTION

This paper presents a uniform approach to the modelling and simulation of aircraft prescribed trajectory flight. The aircraft motion is specified by a trajectory in space, a condition on airframe attitude with respect to the trajectory, and a desired flight velocity variation. For an aircraft controlled by aileron, elevator and rudder deflections and thrust changes a tangent realization of trajectory constraints arises which yields two additional constraints on the airframe attitude with respect to the trajectory. Combining the program constraint conditions and aircraft dynamic equations the governing equations of programmed motion are developed in the form of differential-algebraic equations. A method for solving the equations is proposed. The solution consists of time variations of the aircraft state variables and the demanded control that ensures the programmed motion realization.

On Realization of Program Constraints: Part I—Theory

The problem of realization of program constraints is considered. The classical theory approach based on replacing the constriant reactions by adequate control forces has been generalized to the case when the control forces are not collinear with program constraint vectors or, in the extreme, when the control forces do not project in these directions at all (control forces are tangent to constraint manifolds). A classification of possible ways of program constraint realization is proposed and a general solution of the problem is presented.

On Realization of Program Constraints: Part II—Practical Implications

Practical implications of a general mathematical model of realization of program constraints are investigated. Illustrative examples of different types of this realization are demonstrated and discussed. Some general conclusions concerning the problem of program constraint realization are drawn.

Reorientation in Primary Health Care Implementation: An Educational Intervention

The study was designed as a three-phase approach to reorient Community Health Officers working in Odukpani (one of the first model PHC Centers in Nigeria) toward Primary Health Care: 1) knowledge, attitude, and practice determination; 2) a PHC-based training module; and 3) teacher-learner evaluation. The results strongly suggest that this type of deliberate intervention to remove an identified program constraint, is crucial to the anticipated role of PHC workers as agents of change. The implications of the results for PHC system development in Nigeria are highlighted.