Reliability Analysis of Safety Grade Programmable Logic Controller
This paper focuses on the random hardware failures necessary for the safety assessment of the reactor protection system (RPS). A prediction method of the hardware failure rate for safety assessment is suggested, and applied to the safety grade programmable logic controller (PLC) to identify design weak points from a safety point of view
Overlay Architecture for Field Computing Systems
Conventional production systems have mainly focused on production practices. Future production system is required to have more flexibility to deal with various problems for production auxiliary tasks in addition to production practices. In order to solve these problems, the use of field data from devices on the factory floor is required in many cases. For using the field data more effectively for auxiliary tasks, an approach to add functions to field devices is increasingly required. However, for building a computing environment that achieves this approach, it is necessary to solve the following two issues. (1) Provide field devices with the common computing environment independent of the device type. However, this environment should not adversely affect the original device functions for production practices. (2) Allow multiple persons in charge of auxiliary tasks to use the common computing environment concurrently. In other words, persons in charge can select necessary devices and build distributed applications on top of them without interfering with other activities. This paper presents FOA (field overlay architecture) that allows building the computing environment on top of the production system to deal with various problems for production auxiliary tasks, and also describes a new operating model of FOA-based production system
Static task-scheduling algorithms for battery-powered DVS systems
Battery lifetime enhancement is a critical design parameter for mobile computing devices. Maximizing the battery lifetime is a particularly difficult problem due to the nonlinearity of the battery behavior and its dependence on the characteristics of the discharge profile. In this paper, we address the problem of task scheduling with voltage scaling in a battery-powered single and multiprocessor system such that the residual charge or the battery voltage (the parameters for evaluating battery performance) is maximized. We propose an efficient heuristic algorithm using a charge-based cost function derived from the analytical battery model. Our algorithm first creates a task sequence that ensures battery survival, and then distributes the available delay slack so that the cost function is maximized. The effectiveness of the algorithm has been verified using DUALFOIL, a low-level Li-ion battery simulator. The algorithm has been validated on synthetic examples created from applications running on Compaq's handheld computing research platform, ITSY