| 1. |
- Merz, Mariann, et al.
(författare)
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Autonomous UAS-Based Agriculture Applications : General Overview and Relevant European Case Studies
- 2022
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Ingår i: DRONES. - : MDPI. - 2504-446X. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- Emerging precision agriculture techniques rely on the frequent collection of high-quality data which can be acquired efficiently by unmanned aerial systems (UAS). The main obstacle for wider adoption of this technology is related to UAS operational costs. The path forward requires a high degree of autonomy and integration of the UAS and other cyber physical systems on the farm into a common Farm Management System (FMS) to facilitate the use of big data and artificial intelligence (AI) techniques for decision support. Such a solution has been implemented in the EU project AFarCloud (Aggregated Farming in the Cloud). The regulation of UAS operations is another important factor that impacts the adoption rate of agricultural UAS. An analysis of the new European UAS regulations relevant for autonomous operation is included. Autonomous UAS operation through the AFarCloud FMS solution has been demonstrated at several test farms in multiple European countries. Novel applications have been developed, such as the retrieval of data from remote field sensors using UAS and in situ measurements using dedicated UAS payloads designed for physical contact with the environment. The main findings include that (1) autonomous UAS operation in the agricultural sector is feasible once the regulations allow this; (2) the UAS should be integrated with the FMS and include autonomous data processing and charging functionality to offer a practical solution; and (3) several applications beyond just asset monitoring are relevant for the UAS and will help to justify the cost of this equipment.
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| 2. |
- Bergenhem, Carl, et al.
(författare)
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A novel modelling pattern for establishing failure models and assisting architectural exploration in an automotive context
- 2012
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Ingår i: 31st International Conference on Computer Safety, Reliability, and Security, SAFECOMP 2012. - Berlin, Heidelberg : Springer Berlin Heidelberg. ; , s. 247-257
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Konferensbidrag (refereegranskat)abstract
- With the introduction of the automotive functional safety standard ISO 26262, several challenges related to the representation of dependability information has emerged. This paper addresses how safety requirements can be formalized; which is mandatory for high-integrity requirements. Particular focus is given to asymmetric failures. Such a failure can be caused by a communication fault, and implies that data in a distributed system will be inconsistent among system outputs or within the system (incorrect, corrupt or omitted, etc.). We investigate along two lines; 1) The EAST-ADL automotive architecture description language is extended with a capability to represent asymmetric faults and failures. 2) The Compute-Distribute Results (CDR) pattern is introduced to assist reasoning about distributed systems, in particular potential inconsistencies. We show how this can support architectural decisions regarding selection of communication topology and communication technology for a given distributed system. A brake-by-wire application and FlexRay bus are analysed to illustrate the concepts.
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| 3. |
- Bergenhem, Carl, et al.
(författare)
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A pipelined fiber-ribbon ring network with heterogeneous real-time support
- 2006
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Ingår i: ARTES - A network for Real-Time research and graduate Education in Sweden 1997-2006. - Uppsala : Uppsala university : Department of Information Technology. - 9150618598 ; , s. 23-
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Konferensbidrag (refereegranskat)abstract
- The paper presents results of simulations done with the CCR-EDF (Control Channel based Ring network with EDF scheduling) pipelined ring network together with a case study of system area networks for radar signal processing. The topology of the network is a pipelined unidirectional fibre-ribbon ring that supports several simultaneous transmissions in non-overlapping segments. Access to the network is divided into slots. In each slot the node that has the highest priority message is permitted to transmit. This feature of the medium access protocol gives the network the functionality for earliest deadline first scheduling. Different classes of traffic are supported for the user. These are guaranteed logical real-time channels (LRTC), best effort (BE) channels and non real-time (NRT) traffic. The case study used is from an airborne radar signal processing (RSP) application. Results of the simulations indicate that the CCR-EDF network works well with the RSP application studied.
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| 4. |
- Bergenhem, Carl, et al.
(författare)
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A Pipelined Ring Network - Heterogeneous Real-time in Radar Signal Processing
- 2003
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Ingår i: Applied Informatics. - : ACTA Press. - 0889863415 ; , s. 825-832
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Konferensbidrag (refereegranskat)abstract
- The paper presents results of simulations done with the CCR-EDF (Control Channel based Ring network with EDF scheduling) pipelined ring network together with a case study of system area networks for radar signal processing. The topology of the network is a pipelined unidirectional fibre-ribbon ring that supports several simultaneous transmissions in non-overlapping segments. Access to the network is divided into slots. In each slot the node that has the highest priority message is permitted to transmit. This feature of the medium access protocol gives the network the functionality for earliest deadline first scheduling. Different classes of traffic are supported for the user. These are guaranteed logical real-time channels (LRTC), best effort (BE) channels and non real-time (NRT) traffic. The case study used is from an airborne radar signal processing (RSP) application. Results of the simulations indicate that the CCR-EDF network works well with the RSP application studied.
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| 5. |
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| 6. |
- Bergenhem, Carl, 1975, et al.
(författare)
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A Process Group Membership Service for Active Safety Systems Using TT/ET Communication Scheduling
- 2007
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Ingår i: Proceedings of PRDC 2007 IEEE 13th Pacific Rim International Symposium on Dependable Computing, Dec 17-19, 2007, Melbourne, Australia. - 0769530540 ; , s. 282-289
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Konferensbidrag (refereegranskat)abstract
- This paper describes a process group membership protocol for distributed real-time systems, that use a communication network which supports both timetriggered (TT) and event-triggered (ET) communication. The protocol allows a group of cooperating real-time processes to establish a consistent view of each other's operational status, i.e. working correctly or not. The aim is to provide an application independent membership service in systems where several distributed real-time tasks share processing nodes. We assume that each such task consists of several processes executing on different nodes and that each node can execute processes belonging to different tasks. The protocol is applicable to any application domain, but has been developed for automotive active safety systems. Here, typical distributed real-time tasks include anti-lock braking, stability control and collision mitigation. In such systems, a membership service provides invaluable support for implementing fault-tolerance and graceful degradation.
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| 7. |
- Bergenhem, Carl, 1975, et al.
(författare)
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A Process Health Status Service for Safety Related Systems Using TT/ET Communication Scheduling
- 2008
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Ingår i: Proc. IEEE 14th Pacific Rim International Symposium on Dependable Computing (PRDC 2008). - 9780769534480 ; , s. 122-131
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Konferensbidrag (refereegranskat)abstract
- This paper describes a health status protocol fordistributed real-time systems that use TTCAN, Flexray,or other networks which support both time-triggeredand event-triggered communication. The protocolallows a group of co-operating processes to establish aconsistent view of each other’s health status over time. Itextends the instantaneous view, of operational status ofeach process, provided by a process group membershipprotocol. The health status and membership protocolsare intended for systems where processes (not nodes)are considered the smallest unit of failure, and whereprocess failures can be detected and recovered locallyby the host node. Such systems require a decisionfunction that determines whether a process failure istemporary (the process is being recovered by the hostnode) or permanent (local recovery is not possible orwas unsuccessful). Our protocol ensures that suchdecisions are made consistently among correct nodesdespite symmetrical and asymmetrical omission failures.
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| 8. |
- Bergenhem, Carl, 1975, et al.
(författare)
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A Process Membership Service for Active Safety Systems
- 2007
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Ingår i: SAE 2007 World Congress & Exhibition, April 16-19, Detroit, Michigan, USA. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0768016339 ; 2007
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Konferensbidrag (refereegranskat)abstract
- This paper describes a process membership protocol for distributed real-time systems that use both time-triggered and event-triggered message passing for communication between its processing nodes (ECUs). TTCAN and FlexRay are examples of communication networks that support such systems. The membership protocol supports redundancy management in architectures where distributed applications such as braking, stability control, and collision mitigation share a common set of processing nodes. We assume that each such application consists of several processes executing on different nodes and that each node executes processes belonging to different applications. The protocol allows a group of cooperating processes to establish a consistent view of each other's operational status, i.e., whether they function correctly or not.
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| 9. |
- Bergenhem, Carl
(författare)
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A status protocol for system-operation in a fault-tolerant system : Verification and testing with SPIN
- 2012
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA. - 9781467347372
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Konferensbidrag (refereegranskat)abstract
- This paper presents a status protocol for a fault-tolerant distributed real-time system. The protocol aims to give all nodes a consistent view of the status of processing operations during one communication cycle; despite the occurrence of asymmetric omission failures. The system consists of nodes interconnected with a time-triggered network. A part of the protocol is performed only on-demand i.e. when failure is detected and can thus make use of event-triggered messages in e.g. FlexRay. The protocol is studied in several configurations of nodes and processes. Model checking with SPIN shows that it is not possible to guarantee a consistent decision when more than one failure occurs. SPIN is then used to enumerate the success-ratio (at least 90%) of the protocol in failure scenarios for a number of configurations of the protocol.
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| 10. |
- Bergenhem, Carl, et al.
(författare)
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A System Model for Distributed Real-time Systems
- 2012
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Rapport (refereegranskat)abstract
- This report presents a system model for a class of distributed real-time systems. The goal is to assist the design of fault tolerance protocols such as membership agreement. The system model contains a description of the node, network, processing in respective sub-models. It also contains a failure model that describes the failures that can plausibly occur in the system. These failures can then be addressed by the fault tolerance protocol. The report contributes with a taxonomy by which failures can be described. The resulting failure model is affected by the model of the system and by the model of how processing is done in the system. The class of system is assumed to be strongly partitioned which provides a high degree of error containment for real-time processes executed in the same node and also for processes executed on different nodes. The smallest unit of failure is therefore the process. The system model uses a broadcast communication network similar to Flexray, i.e. it supports both time-triggered and event-triggered communication. The class of system is chosen based on the requirements of safety-critical applications such as x-by-wire. The processing model for the system is presented in which operation is divided into sequentially executed primitive operations, called CDR-operations (Compute and Distribute Result operations). A CDR-operation involves a producer process which computes a result and distributes the result via broadcast communication to consumer processes. Failures of CDR-operations are characterised by four aspects: type, symmetry, detectability and persistence; depending on which system component that is faulty. We compare our definitions of failure types with communication errors according to IEC 61784-3.
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