This paper considers the application of the finite element method for the analysis of translating or rotating plates, based on Mindlin plate theory and the von Kármán strain expression, in the ...context of linear thermoelasticity. The existence of convective terms generates gyroscopic terms, unstabilizing effects in the stiffness matrix, and radial in-plane tension. Homogenization theory, applicable to not only determining the global material properties for composite materials like laminate or fiber-reinforced matrix, but also computing microscopic stress levels, was applied to obtain orthotropic material properties. The quasi-static stretching assumption was used to simplify the governing equations. A second order implicit time-integration scheme, applicable for both the linear and non-linear governing equations, was presented, which allows a time increment sufficiently large (without numerical stability problems) based on the accuracy needed. This paper (Part I) presents the problem formulation and solution methods, while a companion paper (Part II) presents and discusses results for specially orthotropic rotating disks.
High-performance position control algorithms for multi-axis servo-systems, due to presence of asymmetric dynamics and disturbance, do not guarantee high-precision contouring. Cross-Coupling Control ...(CCC) conventionally uses a static Contour Error Estimate (CEE) to reduce the shortest distance between the reference map and actual position, known as contour error. However, reliability of the static CEE deteriorates for high-speed reference feeds and also for sharp corners and deep curves. We propose a dynamic CEE using a Newton-based update law to obtain a precise CEE for fast and highly-curved contours. The Newton-based algorithm uses an estimate of the contour error curvature in order to eliminate the convergence dependence on the contour shape. The proposed CCC design includes one PID controller per axis, and combines the proposed Newton-based CEE with Integral Sliding Mode Control (ISMC) which is well-known for its capability in dealing with parameter uncertainty and external disturbances. The proposed ISMC performance is enhanced with an adaptive disturbance estimate. The proposed CCC algorithm reduces the time-averaged contour error (TACE) at least by an order of magnitude in comparison to conventional CCC algorithms. Various simulation results are presented to highlight the significant improvement achieved by the proposed algorithm.
A new approach for designing control systems which possess the property of component swapping modularity is presented. The system is assumed to consist of several "smart" components, which can ...perform computations, and communicate via bidirectional communication networks. Compared to a previous 3-step design method, the new method proposed here is to design the optimal distributed controllers directly, rather than first designing a centralized controller and then distributing it to the components. To illustrate the approach, an application to optimal controller design for throttle actuator swapping modularity in the automotive idle speed control (ISC) problem is considered. The advantages of the new direct method are twofold. First, the direct method can provide swapping modularity in cases where the 3-step method fails. Second, the direct method can allow one to tradeoff system performance against swapping modularity. The direct method leads to a two-stage optimization problem, which is solved numerically.
Monitoring and control of machining systems has been shown to dramatically improve operation productivity and part quality; however, very little attention has been given to the coordination of ...multiple complex machining modules. The current practice is to design the module coordination and to debug the resulting computer code in an
ad hoc manner. In this paper, the concept of supervisory machining control, in the context of machining module regulation, is presented. The structure of, and elements contained in, a supervisory controller are detailed, and a systematic design procedure for constructing these controllers is presented. The design procedure is utilized to construct a supervisory machining controller which is experimentally implemented in a face milling operation.
This paper addresses the coupling between the plant and control optimization problems for a suspension comprising both passive and active components. Suspension dynamics are modeled using a two ...degree-of-freedom, linear and time-invariant quarter-car model whose ability to capture the influence of the passive stiffness on rattle space depends on the ground disturbance's spectral density. Nested optimization, a strategy that guarantees system optimality, is presented and used to find the optimal suspension system design. The design exhibits superior performance compared to its passive, active and sequentially optimized passive/active counterparts because it accounts for the coupling between the passive and active suspension optimization problems.
Increased availability of electronics at much lower costs have helped to create a new breed of control system components; so called "smart" components, which can perform control responsibilities in ...the actuator and sensor components as well as in the controller. "Smart" components can communicate bi-directionally in networked control systems. Our results show that an "ideal" system with bidirectional communications is equivalent to a single loop control system in terms of performance. However, performance improvements are possible in "non-ideal" cases. Using bi-directional communications can also improve the control system design process since it facilitates the configuration and re-configuration. Building cost effective modular control systems using bi-directional controls appears increasingly attractive.
Examines plant and controller optimization problems. One can solve these problems sequentially, iteratively, using a nested (or bi-level) strategy, or simultaneously. Unlike the nested and ...simultaneous strategies, the sequential and iterative strategies fail to guarantee system-level optimality. This is because the plant and controller optimization problems are coupled. This coupling is introduced using a simple experiment. To prove it theoretically, the necessary conditions for combined plant and controller optimality are derived. These combined optimality conditions differ from the individual sets of necessary conditions for plant and controller optimality by a coupling term that reflects the plant design's influence on the plant dynamics and control input constraints.
A design method for time-delayed vision-based DC motor control is presented and experimentally validated. Both proportional-velocity (PV) and proportional-integral-velocity (PIV) feedback controllers ...are considered. When vision is used to measure the angular displacement of the motor shaft time delays arise due to image processing. Such delays must be considered in the controller design or can lead to poor performance and even instability. In this research we use rightmost eigenvalue assignment, based on the Lambert W function method, to design PV and PIV controllers. Experimental results validate previous theoretical and simulation studies 19, 20.
This paper analyzes the effect of control architectures and communication networks on a manufacturing system's performance in terms of part precision and productivity; the network bandwidth ...requirement for a distributed control system is also included. The objective is to design the system such that the control and communications (both hardware and software) would not be the limiting factors in system performance. For simplicity we analyze the performance of a machining center control system. The base-line for comparison is a conventional computerized numerical controlled (CNC) with discrete event management/adaptive system.
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