The fundamental problems associated with the interactive display, manipulation, and editing of three-dimensional (3-D) objects obtained from medical imaging systems such as CT, PET, and MRI are addressed. Software, ha...
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The fundamental problems associated with the interactive display, manipulation, and editing of three-dimensional (3-D) objects obtained from medical imaging systems such as CT, PET, and MRI are addressed. Software, hardware, and firmware techniques for shaded graphics display of medical objects are described and evaluated in terms of flexibility and performance. A special purpose multiprocessor architecture (the Voxel Processor architecture) developed specifically for medical research, clinical diagnosis, and surgical planning is presented. The Voxel Processor implements a shaded graphics display system with rotation, scaling, translation, slice planes and tone scale transformations on gray-scale data in true real time. The high-speed image generation algorithms exploit the ability to partition object space and require only simple arithmetic and logical operations. Minimal preprocessing steps are required to prepare object data for the Voxel Processor, and the data are always readily accessible for analysis or editing. The architecture is highly structured and is ideally suited for VLSI implementation.
In Fourier optics, the Fourier transformation is performed on the amplitude of the electromagnetic wave, whereas in the computational method the transformation is usually applied to the grayness of its image which is ...
In Fourier optics, the Fourier transformation is performed on the amplitude of the electromagnetic wave, whereas in the computational method the transformation is usually applied to the grayness of its image which is proportional to the intensity of the electromagnetic signal.
Most of the investigations into direct methods for power system stability analysis have been limited to lower order simplified models as Lyapunov functions are readily constructed for conservative systems. This paper ...
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Most of the investigations into direct methods for power system stability analysis have been limited to lower order simplified models as Lyapunov functions are readily constructed for conservative systems. This paper presents recent results on extending direct methods to more realistic multi-machine models. The results are based on the general concept of constant total system energy. It can be shown that the post-disturbance Newton’s second law equation for each rotating machine multiplied by its transient speed, and integrated over time, results in energy terms that added with kinetic energy terms must equal an arbitrary constant when evaluated along a trajectory that satisfies the post-disturbance equations. This constant energy or Hamiltonian formulation is then used in conjunction with the potential energy boundary surface method to estimate power system stability. The method is illustrated on a simple system with a high order machine model and associated voltage control.
This paper presents an approach, illustrated through a case study, to designing a multivariable control system for large process models. The case study involves the development of a preliminary multivariable control d...
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This paper presents an approach, illustrated through a case study, to designing a multivariable control system for large process models. The case study involves the development of a preliminary multivariable control design for load following and frequency regulation on an Advanced Boiling Water Reactor (ABWR). The design procedure is based on the suboptimal output feedback regulator problem solved by use of projective controls. The procedure is applicable to design of controls for any power plant. In designing static controllers the selection of the projective control is based on eigenvalue sensitivity criteria developed to single out eigenvalues in the reference system most sensitive to perturbations in the control. These eignevalues are then retained by the use of projective controls, and the gains are adjusted, if necessary, to meet additional criteria, such as bumpless transfer in this particular case study.
Large-scale power systems commonly have weak connections which can be exploited to decompose the system into slowly coherent areas. The mathematical theory is based on time-scale separation when the dynamic model is p...
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Large-scale power systems commonly have weak connections which can be exploited to decompose the system into slowly coherent areas. The mathematical theory is based on time-scale separation when the dynamic model is put in a singularly perturbed form. In this paper we assume an area separation and construct expressions for energies associated with the areas, and the energies of machines within an area. We show that these time-scale models are adequate for use of direct methods of stability analysis. Attention is focused on the mode of instability for a particular fault and the nature of the slow energy and the fast energy for this particular fault. A three-machine example is used to illustrate modes of instability.
This paper concerns the damping controller design of systems with lightly damped modes, such as power systems and large space structures. Four state space pole-placement methods are studied. A frequency response techn...
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This paper concerns the damping controller design of systems with lightly damped modes, such as power systems and large space structures. Four state space pole-placement methods are studied. A frequency response technique shows that to provide the same amount of damping improvement, the space state designed controllers have similar gain and phase at the oscillatory mode frequency, provided no resonance conditions occur. In addition, the frequency response technique can be used to evaluate the impact of the controllers on the stability of unmodeled dynamics and the damping improvement when the system operating condition changes. Insights obtained from such a frequency response analysis are useful for the design of robust controllers. To make the illustrations practical, a power system stabilizer design example is used.
Sensitivity functions are used in many model parameter identification methods and adaptive control algorithms. Since one sensitivity model has to be used for each parameter, the computation requirement is large when m...
Sensitivity functions are used in many model parameter identification methods and adaptive control algorithms. Since one sensitivity model has to be used for each parameter, the computation requirement is large when many parameters have to be identified or adapted. This paper proposes a method to reduce the computation requirement by using one sensitivity model suitable for the generation of sensitivity functions for all parameters. Instead of using modal transformations and eigenvector sensitivities as previously proposed, this paper uses an input-output transfer function approach. Several sufficient conditions in terms of controllability are given for the implementation of the method.
This paper proposes a near-optimum control algorithm for a highly nonlinear robot manipulator model via a parameter sensitivity method. The method uses Pontrvagin's maximum principle and the Riccati formulation of...
This paper proposes a near-optimum control algorithm for a highly nonlinear robot manipulator model via a parameter sensitivity method. The method uses Pontrvagin's maximum principle and the Riccati formulation of the linear state regulator problem. The effectiveness of the proposed method is verified by simulation results for a two-link planar robot.
The robotic manipulator control performance database has been expanded by experimental evaluation of a joint space model-reference adaptive control technique. The trajectory tracking accuracy of the evaluated Model-Re...
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The robotic manipulator control performance database has been expanded by experimental evaluation of a joint space model-reference adaptive control technique. The trajectory tracking accuracy of the evaluated Model-Reference Adaptive Control technique was insufficient for gross motion control of a six degree of freedom PUMA manipulator. The adaption mechanism did not force the manipulator joints to track the reference model output. The Model-Referenced Adaptive Controller demonstrated efficacy inferior to dynamics based control techniques. Velocity reference input and friction compensation have been identified as essential components of any adaptive PUMA controller. Evaluation results provide valuable insight into further development of adaptive manipulator control methods.
A multicriteria quality control model for acceptance sampling is developed which defines several conflicting and non-commensurate objectives. The following objectives are proposed and quantified in this model: (1) to ...
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