Sikander M. Mirza

Cartesian path generation of robot manipulators using continuous genetic algorithms

Abstract In this paper, the authors describe a novel technique based on continuous genetic algorithms (CGAs) to solve the path generation problem for robot manipulators. We consider the following scenario: given the desired Cartesian path of the end-effector of the manipulator in a free-of-obstacles workspace, off-line smooth geometric paths in the joint space of the manipulator are obtained. The inverse kinematics problem is formulated as an optimization problem based on the concept of the minimization of the accumulative path deviation and is then solved using CGAs where smooth curves are used for representing the required geometric paths in the joint space through out the evolution process. In general, CGA uses smooth operators and avoids sharp jumps in the parameter values. This novel approach possesses several distinct advantages: first, it can be applied to any general serial manipulator with positional degrees of freedom that might not have any derived closed-form solution for its inverse kinematics. Second, to the authors’ knowledge, it is the first singularity-free path generation algorithm that can be applied at the path update rate of the manipulator. Third, extremely high accuracy can be achieved along the generated path almost similar to analytical solutions, if available. Fourth, the proposed approach can be adopted to any general serial manipulator including both nonredundant and redundant systems. Fifth, when applied on parallel computers, the real time implementation is possible due to the implicit parallel nature of genetic algorithms. The generality and efficiency of the proposed algorithm are demonstrated through simulations that include 2R and 3R planar manipulators, PUMA manipulator, and a general 6R serial manipulator.

Sensitivity of reactivity insertion limits with respect to safety parameters in a typical MTR

Abstract The sensitivity of various safety parameters, affecting the reactivity insertion limits imposed by clad melting temperature for a typical pool type research reactor, have been investigated in this work. The analysis was done for low enriched uranium (LEU) core with scram disabled conditions. The temperature coefficients of fuel and coolant, void/density coefficient and β eff were individually varied and the reactor behavior for different ramp reactivity transients was studied. In this work ramp reactivity insertions from 1.6 to 2

Study of the void coefficients of reactivity in a typical pool type research reactor

/0.5 s were selected and peak power, maximum fuel, clad and coolant temperatures were determined. Results show that peak power decreases with an increase in the Doppler coefficient of reactivity. However, it rises with an increase in the reactivity insertion. Core remains insensitive to the coolant temperature coefficient of reactivity for ramps in the range of 1.6–1.9/0.5 s. Peak power decreases with an increase in the void coefficient of reactivity (0.1

Fitness Function Evaluation for Image Reconstruction using Binary Genetic Algorithm for Parallel Ray Transmission Tomography

/%void to 0.8

Computer simulation of corrosion product activity in primary coolants of a typical PWR under flow rate transients and linearly accelerating corrosion

/%void). With a decrease in the void coefficient of reactivity, the maximum fuel and clad temperatures show a non-linear rise. Power and temperature peaks in the transient are sensitive to the values of β eff . Finally, it can be concluded that LEU is a safe core due to its smaller β eff , larger Doppler coefficient and void coefficient of reactivity. It is inferred through this work that reactivity insertion limits of LEU core are quite insensitive to β eff , the Doppler coefficient and the coolant temperature coefficient of reactivity. They are highly sensitive to the change of the void coefficient of reactivity in the core.

Object Tracking using Correlation, Kalman Filter and Fast Means Shift Algorithms

The spatial dependence of the void coefficient of reactivity in a low-enriched-uranium (LEU) material test reactor (MTR) core with central flux trap configuration has been determined experimentally. The voids were simulated by using Teflon and aluminium. In these measurements, the void coefficient of reactivity was found to be positive for the central flux trap region and negative for the rest of the core. The overall void coefficient of reactivity for the entire core is negative. Detailed theoretical calculations have been performed using diffusion-theory three-dimensional modelling of the core. The results of the calculations (C) show agreement with the corresponding experimental values (E) in regions where the core has small flux gradients, while deviations in the CE ratio from unity are found elsewhere. In the central flux trap region, the induced reactivity increases when the void volume is increased from 117 to 468 cm3.

Simulation of over-power transients in tank-in-pool type research reactors

Various fitness functions have been evaluated for image reconstruction using binary genetic algorithm (BGA) based parallel ray transmission tomography. The population initialization is carried out using the filtered backprojection (FBP) technique. Various fitness functions used for image reconstruction include: root mean squared error (RMSE), mean squared error (MSE), mean absolute error (MAE), relative squared error (RSE), root relative squared error (RRSE) and relative absolute error (RAE). RMSE and MAE outperformed for small as well as large size images with different shape complexities. Mixed selection scheme with two variations of crossover operators, namely image-row and block crossover operators have been used for crossover. Binary mutation operator has been used for creating diversity in local search scope. For 64 times 64 head and lung phantoms, BGA has resulted in PSNR values with RMSE 19.26 and 16.49 respectively and 27.20 and 29.65 dB with MAE

Effect of flow rate and power perturbations on dose rates due to coolant activity in low-power research reactors

Computer simulation of behavior of coolant activation due to corrosion products have been investigated in a typical pressurized water reactor (PWR) under flow rate perturbations for linearly accelerating corrosion. The computer program CPAIR-P (Deeba et al., 1999) has been modified to accommodate for time dependent corrosion. Results for 24Na, 56Mn, 59Fe, 60Co and 99Mo show that the specific activity in primary loop approaches equilibrium value under normal operating conditions fairly rapidly. During reactor operation, predominant corrosion product activity is due to 56Mn and after shutdown cobalt activity dominates. These simulations suggest that the effect of flow rate perturbations on specific activity in the form of a depression in the activity curve can be smeared by a linearly rising corrosion. Such a dip can only be seen in activity when corrosion rate approaches to an equilibrium value well before the initiation of the transient. The time period to reach minimum coolant activity during transient is a function of the slope of flow rate perturbation parameter, g(t). The new saturation value for activity depends on changes in flow rate (Δw) and equilibrium value (Cs) for the corrosion rate. For linearly accelerated corrosion and a pump coastdown condition, the activity does not show an initial drop when flow starts decreasing. It monotonically rises and follows the slope of corrosion rate. If the slope is greater than 9×10−6 μg/s2, then the activity crosses the normal saturation value of 0.22 μCi/cm3 before the reactor scram occurs. These results also indicate that the pump coastdown does produce a coolant activity spike before the reactor scram; however it can only be observed when the corrosion acceleration is fast.

Kinetic study of fission product activity released inside containment under loss of coolant transients in a typical MTR system.

Object detection in videos involves verifying the presence of an object in image sequences and possibly locating it precisely for recognition. Object tracking is to monitor an objects spatial and temporal changes during a video sequence, including its presence, position, size, shape, etc. This is done by solving the temporal correspondence problem, the problem of matching the target region in successive frames of a sequence of images taken at closely-spaced time intervals. These two processes are closely related because tracking usually starts with detecting objects, while detecting an object repeatedly in subsequent image sequence is often necessary to help and verify tracking. In this paper, a novel approach is being presented for object tracking. It includes combination of 2D normalized correlation, Kalman filter and fast mean shift algorithm

Biologically inspired computing framework for solving two-point boundary value problems using differential evolution

Abstract A tank-in-pool type Research Reactor Simulator (TPR2) has been developed which models the core neutronics using the point kinetics equations along with the Doppler and moderator reactivity feedbacks. For thermal-hydraulic calculations, it uses a lumped parameters, multizone model based correlation which has been verified by physical mockup of the reactor assembly. The coupled set of dynamics equations has been solved by the semi-implicit method utilizing Richardsons extrapolation scheme. The computer implementation includes adaptive time step control which enables the simulations to be carried out in real-time and even faster. The predictions of the TPR2 simulator have been compared with the experimental data obtained for transient over power (TOP) tests carried out at the Pakistan Research Reactor-2 (PARR-2). The TPR2 computed values of the reactor power and the coolant temperatures at the core outlet were found in good agreement with the corresponding experimental data throughout various positive reactivity induced transients.