Electrical Power Working Group report

The status of and need for power technologies for Spacecraft 2000 were assessed and development programs required to establish an achievable and competitive technology base for spacecraft of the 21st century were identified. The results are summarized, including the recommendations and the underlying rationale

Human-Like Impedance and Minimum Effort Control for Natural and Efficient Manipulation

Humans incorporate and switch between learnt neuromotor strategies while performing complex tasks. Towards this purpose, kinematic redundancy is exploited in order to achieve optimized performance. Inspired by the superior motor skills of humans, in this paper, we investigate a combined free motion and interaction controller in a certain class of robotic manipulation. In this bimodal controller, kinematic degrees of redundancy are adapted according to task-suitable dynamic costs. The proposed algorithm attributes high priority to minimum-effort controller while performing point to point free space movements. Once the robot comes in contact with the environment, the Tele-Impedance, common mode and configuration dependent stiffness (CMS-CDS) controller will replicate the human’s estimated endpoint stiffness and measured equilibrium position profiles in the slave robotic arm, in real-time. Results of the proposed controller in contact with the environment are compared with the ones derived from Tele-Impedance implemented using torque based classical Cartesian stiffness control. The minimum-effort and interaction performance achieved highlights the possibility of adopting human-like and sophisticated strategies in humanoid robots or the ones with adequate degrees of redundancy, in order to accomplish tasks in a certain class of robotic manipulatio

Development of Urban Electric Bus Drivetrain

The development of the drivetrain for a new series of urban electric buses is presented in the paper. The traction and design properties of several drive variants are compared. The efficiency of the drive was tested using simulation calculations of the vehicle rides based on data from real bus lines in Prague. The results of the design work and simulation calculations are presented in the paper

Immunotronics - novel finite-state-machine architectures with built-in self-test using self-nonself differentiation

A novel approach to hardware fault tolerance is demonstrated that takes inspiration from the human immune system as a method of fault detection. The human immune system is a remarkable system of interacting cells and organs that protect the body from invasion and maintains reliable operation even in the presence of invading bacteria or viruses. This paper seeks to address the field of electronic hardware fault tolerance from an immunological perspective with the aim of showing how novel methods based upon the operation of the immune system can both complement and create new approaches to the development of fault detection mechanisms for reliable hardware systems. In particular, it is shown that by use of partial matching, as prevalent in biological systems, high fault coverage can be achieved with the added advantage of reducing memory requirements. The development of a generic finite-state-machine immunization procedure is discussed that allows any system that can be represented in such a manner to be "immunized" against the occurrence of faulty operation. This is demonstrated by the creation of an immunized decade counter that can detect the presence of faults in real tim

State-preserving container orchestration in failover scenarios

Containers have been widely adopted for deployment of high availability applications and services. This adoption is in part due to the native support of fault tolerance mechanisms in container orchestration frameworks such as Kubernetes. While Kubernetes provides service replication as a fault tolerance mechanism for stateless applications, service replication does not satisfy requirements for stateful applications. Currently this shortcoming is addressed by data replication in databases. This requires a tight coupling and modification of the stateful application to support high availability. Thus, this thesis proposes a new Checkpoint/Restore (C/R) Kubernetes operator to achieve fault tolerance for stateful applications without any modification of the application. The operator takes a checkpoint in a configurable interval. In case of a fault a new application container is created automatically from the most recent checkpoint. We compare the proposed approach with a more conventional approach in which we pull and restore the application state from the application through an API. We measure the overhead of both methods, the service interruption and the recovery time in case of faults. We find the C/R Operator has similar performance in recovery time as the traditional approach, but does not need any application modification. The results signify C/R as a promising technology for a fault tolerance mechanism for stateful applications

A Logically Centralized Approach for Control and Management of Large Computer Networks

Management of large enterprise and Internet Service Provider networks is a complex, error-prone, and costly challenge. It is widely accepted that the key contributors to this complexity are the bundling of control and data forwarding in traditional routers and the use of fully distributed protocols for network control. To address these limitations, the networking research community has been pursuing the vision of simplifying the functional role of a router to its primary task of packet forwarding. This enables centralizing network control at a decision plane where network-wide state can be maintained, and network control can be centrally and consistently enforced. However, scalability and fault-tolerance concerns with physical centralization motivate the need for a more flexible and customizable approach. This dissertation is an attempt at bridging the gap between the extremes of distribution and centralization of network control. We present a logically centralized approach for the design of network decision plane that can be realized by using a set of physically distributed controllers in a network. This approach is aimed at giving network designers the ability to customize the level of control and management centralization according to the scalability, fault-tolerance, and responsiveness requirements of their networks. Our thesis is that logical centralization provides a robust, reliable, and efficient paradigm for management of large networks and we present several contributions to prove this thesis. For network planning, we describe techniques for optimizing the placement of network controllers and provide guidance on the physical design of logically centralized networks. For network operation, algorithms for maintaining dynamic associations between the decision plane and network devices are presented, along with a protocol that allows a set of network controllers to coordinate their decisions, and present a unified interface to the managed network devices. Furthermore, we study the trade-offs in decision plane application design and provide guidance on application state and logic distribution. Finally, we present results of extensive numerical and simulative analysis of the feasibility and performance of our approach. The results show that logical centralization can provide better scalability and fault-tolerance while maintaining performance similarity with traditional distributed approach

Control-Quality Optimization for Distributed Embedded Systems with Adaptive Fault Tolerance

In this paper, we propose a design framework for distributed embedded control systems that ensures reliable execution and high quality of control even if some computation nodes fail. When a node fails, the configuration of the underlying distributed system changes and the system must adapt to this new situation by activating tasks at operational nodes. The task mapping as well as schedules and control laws that are customized for the new configuration influence the control quality and must, therefore, be optimized. The number of possible configurations due to faults is exponential in the number of nodes in the system. This design-space complexity leads to unaffordable design time and large memory requirements to store information related to mappings, schedules, and controllers. We demonstrate that it is sufficient to synthesize solutions for a small number of base and minimal configurations to achieve fault tolerance with an inherent minimum level of control quality. We also propose an algorithm to further improve control quality with a priority-based search of the set of configurations and trade-offs between task migration and replication