Penrose Cofie

Real-time random delay compensation with prediction-based digital redesign.

Todays technological demands require challenging control solutions such as real-time applications of Networked Control System (NCS). However, due to communication protocol and shared data bus, NCS experiences uncertain and unpredictable time delays in both input and output channels. These delays cause asynchronization between the controller and the plant thereby degrading the performance of closed-loop control systems. To address this problem, this paper proposes to utilize digital redesign technique to provide real-time random delay compensation.

A New Facility for Measurements of Three-Dimensional, Local Subcooled Flow Boiling Heat Flux and Related Critical Heat Flux for PFCs

Abstract In the development of plasma-facing components for fusion reactors and high-heat-flux heat sinks (or components) for electronic applications, the components are usually subjected to a peripherally nonuniform heat flux. Even if the applied heat flux is uniform in the axial direction (which is unlikely), both intuition and recent investigations have clearly shown that both the local heat flux and the eventual critical heat flux (CHF) in this three-dimensional (3-D) case will differ significantly from similar quantities found in the voluminous body of data for uniformly heated flow channels. Although this latter case has been used in the past as an estimate for the former case, more study has become necessary to examine the 3-D temperature and heat flux distributions and related CHF. Work thus far has shown that the nonuniform peripheral heat flux condition enhances CHF in some cases. To avoid the excess costs associated with using electron or ion beams to produce the nonuniform heat flux, a new facility was developed that will allow 3-D conjugate heat transfer measurements and two-dimensional, local subcooled flow boiling heat flux and related CHF measurements. The configurations under study for this work consist of (a) a nonuniformly heated cylinder-like test section with a circular coolant channel bored through the center and (b) a monoblock that is a square cross-section parallelepiped with a circular drilled flow channel along the channel centerline. The theoretical or ideal cylinder-like test section would be a circular cylinder with half (-90 to 90 deg) of its outside boundary subjected to a uniform heat flux and the remaining half insulated. For the monoblock, a uniform heat flux is applied to one of the outside surfaces, and the remaining surfaces are insulated. The outside diameter of the cylinder-like test section is 30.0 mm, and its length is 200.0 mm. The monoblock square is 30.0 mm long. The inside diameter of the flow channel for both types of test sections is 10.0 mm. Water is the coolant. The inlet water temperature can be set at any level in the range from 26.0 to 130.0°C, and the exit pressure can be set at any level in the range from 0.4 to 4.0 MPa. Thermocouples were placed at 48 locations inside the solid cylinder-like or monoblock test section to obtain 3-D wall temperature variations and related local heat flux. Finally, the mass velocity can be set at any level in the range from 0.4 to 10.0 Mg/m2·s for the 10.0-mm-diam channel.

Conjugate heat transfer measurements in a non-uniformly heated circular flow channel under flow boiling conditions

Abstract Plasma-facing components (PFCs) for fusion reactors and high heat flux heat sinks for electronic applications, are usually subjected to a peripherally non-uniform heat flux. The configuration under study is related to these applications and consists of a single-side heated circular-like cross-section test section (TS) with a circular coolant channel bored through the center. The TS has a heated length of 180.0 mm and has 10.0 and 30.0 mm inside and outside diameters, respectively. It was subjected to a constant heat flux on one side only, and the remaining half of the circumferential surface is not exposed to a heat flux. The inlet channel water temperature was held constant at 26.0 °C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59 Mg / m 2 s . The results consist of three-dimensional TS wall temperature distributions and a clear display of both CHF and post-CHF for this single-side heated configuration. These results are very encouraging in that they are among the first full set of truly three-dimensional TS wall temperature measurements for a one-side heated (OSH) flow channel which contains the effect of conjugate heat transfer for turbulent, subcooled flow boiling.

High heat flux removal using water subcooled flow boiling in a single-side heated circular channel

Abstract High heat flux removal from plasma-facing components and electronic heat sinks involves conjugate heat transfer analysis of the applicable substrate and flowing fluid. For the present case of subcooled flow boiling inside a single-side heated circular channel, the dimensional results show the significant radial, circumferential and axial variations in all thermal quantities for the present radial aspect ratio ( R o =outside radius to inside radius) of 3.0. A unified, dimensionless representation of the two-dimensional inside wall heat flux, and the dimensional inside wall heat flux ( q i ( φ , z )) and temperature ( T i ( φ , z )) data was found and used to collapse the data for all circumferential locations. Finally, 2-D boiling curves are presented and are among the first full set of 2-D boiling data presented for a single-side heated circular configuration.

Power Quality and Reliability of University Campus Equipment – Industry and Academic Partnership Program

One area where universities and industry can partner is in the area of power systems reliability and quality curriculum development. Industry can provide the necessary industrial experiences and the academia can offer the theory to support the industrial practices. The purpose of the program was to develop a curriculum in reliability of electrical facilities at Prairie View A&M University through academic-industrial partnership. A new course in reliability analysis of electrical facilities was introduced and taught. Topics that were covered in the course include: reliability and probabilistic theory, Monte Carlo simulations, preventive and predictive maintenance management systems, power generation, transmission and distribution networks, power quality, and field study. The course included demonstrations, inspections and testing of equipment in four buildings at Prairie View A&M University campus. Instructors from Prairie View A&M University and University of Texas at Arlington collaborated with engineers at electrical protection and control to complete this work

Design of a speed controller using Extended Kalman Filter for PMSM

A novel design of a proportional-integral-differential equivalent controller using state observer based Extended Kalman Filter (EKF) for a Permanent Magnet Synchronous Motor (PMSM) is proposed. The EKF is constructed to achieve a precise estimation of the speed and current from the noisy measurement. Linear Quadratic Regulator (LQR) technique is used to construct a proportional integral derivative (PID) controller to achieve the speed command tracking performance. The proposed method greatly enhances the speed control performance. The simulation results for the speed response and variation of the states when the PMSM is subjected to the load disturbance are presented. The results verify the effectiveness of the proposed method.

Digital controller design for analog MIMO systems with multiple I/O delays

This paper proposes a discretization scheme and an optimal digital cascaded plus state-feedback controller for Multiple-Input-Multiple-Output (MIMO) continuous-time systems with multiple time delays in both inputs and outputs. Firstly, an equivalent discrete-time model is obtained from the MIMO analog time-delayed system. The equivalent discrete-time model and a partially predetermined digital cascaded controller are formulated as an augmented discrete-time state-space system for state-feed forward and state-feedback Linear Quadratic Regulator (LQR) design. As a result, the parameters of the cascaded controller and its associated state-feedback controller can be determined by tuning the weighting matrices in the LQR optimal design. Then a discrete-time optimal observer for the MIMO analog time-delayed system is constructed for the implementation of the designed state-feedback digital controller. The proposed methodology has been verified through both simulation and experiment on the induction motor drive system.

Real-time network induced delay compensation with digital redesign technique

Our technological demands today require extremely challenging control solutions such as real-time applications of Networked Control System (NCS). However, due to communication protocol and shared data bus, NCS always experiences uncertain and unpredictable time delays in both input and output channels. These delays cause asynchronization between controller and plant thereby degrading the performance of closed-loop control systems. To address the concern of stability improvement in real-time, this paper proposes to utilize digital redesign technique to compensate for these network induced delays.

Single-Side Heated Monoblock, High Heat Flux Removal Using Water Subcooled Turbulent Flow Boiling

Plasma-facing components for fusion reactors and other high heat flux heat sinks are subjected to a peripherally nonuniform heat flux. The monoblock test section under study is a single-side heated square cross-section heat sink with a circular coolant channel bored through the center. The heated length of the test section is 180 mm. The inside diameter and outside square sides are 10 mm and 30 mm, respectively. It was subjected to a constant heat flux on one side of the outside surfaces, and the remaining portion was not heated. The exit water subcooling varied from 55 to 101°C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59 Mg/m 2 s

Multidimensional Heat Transfer and Flow Boiling Curve Measurements in Single-Side-Heated Flow Channels

Abstract In order to accommodate high thermal loading of single-side-heated (SSH) components, robust thermal management and high-heat-flux-removal approaches are essential to prevent thermal instability, thermal runaway, or a thermal spiral toward component failure. This paper presents multidimensional steady-state heat transfer measurements for a high-strength-copper SSH monoblock (heat sink) coolant flow channel with a helical wire insert (HI) and thermally developing internal laminar and turbulent water (coolant) flow. In the present case, the term “monoblock” refers to a solid parallelepiped with a central coolant flow channel along the axial centerline. In addition to producing local two-dimensional (axial and circumferential) flow boiling curves, multidimensional monoblock wall temperature distribution comparisons were made between flow channels with and without a HI. Further, flow boiling curves were measured up to ∼4.0 MW/m2 at the inside flow channel wall. For the same inside flow channel temperature, the HI enhanced (1) the incident heat flux by >70% when compared with the flow channel without the insert and (2) the inside flow channel wall heat flux by up to a factor of 5 near the monoblock heated side and at all axial locations. These results can be used for validation of computational fluid dynamics codes.