System control of an autonomous planetary mobile spacecraft

The goal is to suggest the scheduling and control functions necessary for accomplishing mission objectives of a fairly autonomous interplanetary mobile spacecraft, while maximizing reliability. Goals are to provide an extensible, reliable system conservative in its use of on-board resources, while getting full value from subsystem autonomy, and avoiding the lure of ground micromanagement. A functional layout consisting of four basic elements is proposed: GROUND and SYSTEM EXECUTIVE system functions and RESOURCE CONTROL and ACTIVITY MANAGER subsystem functions. The system executive includes six subfunctions: SYSTEM MANAGER, SYSTEM FAULT PROTECTION, PLANNER, SCHEDULE ADAPTER, EVENT MONITOR and RESOURCE MONITOR. The full configuration is needed for autonomous operation on Moon or Mars, whereas a reduced version without the planning, schedule adaption and event monitoring functions could be appropriate for lower-autonomy use on the Moon. An implementation concept is suggested which is conservative in use of system resources and consists of modules combined with a network communications fabric. A language concept termed a scheduling calculus for rapidly performing essential on-board schedule adaption functions is introduced

Scheduling Techniques for Operating Systems for Medical and IoT Devices: A Review

Software and Hardware synthesis are the major subtasks in the implementation of hardware/software systems. Increasing trend is to build SoCs/NoC/Embedded System for Implantable Medical Devices (IMD) and Internet of Things (IoT) devices, which includes multiple Microprocessors and Signal Processors, allowing designing complex hardware and software systems, yet flexible with respect to the delivered performance and executed application. An important technique, which affect the macroscopic system implementation characteristics is the scheduling of hardware operations, program instructions and software processes. This paper presents a survey of the various scheduling strategies in process scheduling. Process Scheduling has to take into account the real-time constraints. Processes are characterized by their timing constraints, periodicity, precedence and data dependency, pre-emptivity, priority etc. The affect of these characteristics on scheduling decisions has been described in this paper

A Survey of Fault-Tolerance Techniques for Embedded Systems from the Perspective of Power, Energy, and Thermal Issues

The relentless technology scaling has provided a significant increase in processor performance, but on the other hand, it has led to adverse impacts on system reliability. In particular, technology scaling increases the processor susceptibility to radiation-induced transient faults. Moreover, technology scaling with the discontinuation of Dennard scaling increases the power densities, thereby temperatures, on the chip. High temperature, in turn, accelerates transistor aging mechanisms, which may ultimately lead to permanent faults on the chip. To assure a reliable system operation, despite these potential reliability concerns, fault-tolerance techniques have emerged. Specifically, fault-tolerance techniques employ some kind of redundancies to satisfy specific reliability requirements. However, the integration of fault-tolerance techniques into real-time embedded systems complicates preserving timing constraints. As a remedy, many task mapping/scheduling policies have been proposed to consider the integration of fault-tolerance techniques and enforce both timing and reliability guarantees for real-time embedded systems. More advanced techniques aim additionally at minimizing power and energy while at the same time satisfying timing and reliability constraints. Recently, some scheduling techniques have started to tackle a new challenge, which is the temperature increase induced by employing fault-tolerance techniques. These emerging techniques aim at satisfying temperature constraints besides timing and reliability constraints. This paper provides an in-depth survey of the emerging research efforts that exploit fault-tolerance techniques while considering timing, power/energy, and temperature from the real-time embedded systems’ design perspective. In particular, the task mapping/scheduling policies for fault-tolerance real-time embedded systems are reviewed and classified according to their considered goals and constraints. Moreover, the employed fault-tolerance techniques, application models, and hardware models are considered as additional dimensions of the presented classification. Lastly, this survey gives deep insights into the main achievements and shortcomings of the existing approaches and highlights the most promising ones

Value-based scheduling in real-time systems

A real-time system must execute functionally correct computations in a timely manner. Most of the current real-time systems are static in nature. However in recent years, the growing need for building complex real-time applications coupled with advancements in information technology drives the need for dynamic real-time systems. Dynamic real-time systems need to be designed not only to deal with expected load scenarios, but also to handle overloads by allowing graceful degradation in system performance. Value-based scheduling is a means by which graceful degradation can be achieved by executing critical tasks that offer high values/benefits/rewards to the functioning of the system. This thesis identifies the following two issues in dynamic real-time scheduling: (i) maintaining high system reliability without affecting its schedulability and (ii) providing graceful degradation to the system during overload and maintaining high schedulability during underloads or near full loads. Further, we use value-based scheduling techniques to address these issues. The first contribution of this thesis is a reliability-aware value-based scheduler capable of maintaining high system reliability and schedulability. We use a performance index (PI) based value function for scheduling, which can capture the tradeoff between schedulability and reliability. The proposed scheduler selects a suitable redundancy level for each task so as to increase the performance index of the system. We show through our simulation studies that proposed scheduler maintains a high system value (PI). The second contribution of this thesis is an adaptive value-based scheduler that can change its scheduling behavior from deadline-based scheduling to value-based scheduling based on the system workload, so that it can maintain a high system value with fewer deadline misses. Further, the scheduler is extended to heterogeneous computing (HC) systems, wherein the computing capabilities of processors/machines are different, and propose two adaptive schedulers (Basic and Integrated) for HC systems. The performance of the proposed scheduling algorithms is studied through extensive simulation studies for both homogeneous and heterogeneous computing systems. We have concluded that the proposed adaptive scheduling scheme maintains a high system value with fewer deadlines misses for all range workloads. Amongst the schedulers for HC systems, we conclude that the Basic scheduler, which has a lesser run-time complexity, performs better for most of the workloads. The last contribution of this thesis is the design and implementation of the proposed adaptive value-based scheduler for homogeneous computing systems in a real-time Linux operating system, RT-Linux. We compare the performance of the implementation with EDF and Highest Value-Density First (HVDF) schedulers for various ranges of workloads and show that the proposed scheduler performs better in maintaining a high system value with fewer deadline misses

Product Platform Concepts Applied to Small Satellites: A New Multipurpose Radio Concept by AeroAstro Inc.

AeroAstro Inc., with the development of their new multipurpose radio platform, has solved many of the communication problems faced by spacecraft system designers. With each new satellite application, engineering teams repeatedly address several communication requirements that are common to all satellite application. As part of a U.S. Air Force sponsored effort, AeroAstro’s Space Frame initiative is implementing product platform concepts to develop a family of radios that are modular, based on standard interfaces, and use an open architecture. The new multipurpose radio uses standard core modules that can be configured to meet a wide range of spacecraft radio applications. For example, modules for a receiver, a transmitter, a baseband processor and a power amplifier will be designed. Some of these modules will have differentiators, or selectable parameters. Once the design of these modules is mature, the design of a particular satellite radio is simply a matter of selecting the correct modules with the right parameters and interconnecting them. The new multipurpose radio reduces the time and cost required to meet the communication requirements of multiple spacecraft applications. This paper describes the new product platform approach and some of the subsystem functions imbedded in this multipurpose radio

Distribution System Voltage Management and Optimization for Integration of Renewables and Electric Vehicles: Research Gap Analysis

California is striving to achieve 33% renewable penetration by 2020 in accordance with the state’s Renewable Portfolio Standard (RPS). The behavior of renewable resources and electric vehicles in distribution systems is creating constraints on the penetration of these resources into the distribution system. One such constraint is the ability of present-­‐‑day voltage management methodologies to maintain proper distribution system voltage profiles in the face of higher penetrations of PV and electric vehicle technologies. This white paper describes the research gaps that have been identified in current Volt/VAR Optimization and Control (VVOC) technologies, the emerging technologies which are becoming available for use in VVOC, and the research gaps which exist and must be overcome in order to realize the full promise of these emerging technologies

Preliminary design of an auxiliary power unit for the space shuttle. Volume 4: Selected system supporting studies

Selected system supporting analyses in conjunction with the preliminary design of an auxiliary power unit (APU) for the space shuttle are presented. Both steady state and transient auxiliary power unit performance, based on digital computer programs, were examined. The selected APU provides up to 400 horsepower out of the gearbox, weighs 227 pounds, and requires 2 pounds per shaft horsepower hour of propellants