C. M. Bailey, E. Fyfe, A. Burns, and A. J. Wellings, The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation. University of York, Department of Computer Science, 1993.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....system. Its organization follows the proposed modus operandi as shown in Fig. 6.1. The Attitude and Orbital Control System (AOCS) of the communication satellite Olympus exemplifies an application with tight timing requirements. Its real time properties have been analyzed by Burns et al. BWBF93] in a similar case study. Showing a HRT HOOD [BW95b] specification of the AOCS, deadline monotonic schedulability analysis has been used to prove the timelineness of an Ada implementation on a Motorola 68020 board. Real time analysis requires that processing times of the application itself, ....

A. Burns, A. Wellings, C. Bailey, and E. Fyfe. The Olympus attitude and orbital control system: A case study in hard real--time system design and implementation. In Ada sans frontiers, Proc. of the 12th Ada--Europe Conf., Lecture Notes in Computer Science, pages 19--35. Springer--Verlag, 1993. 89

....hold, and the analysis can remain unchanged. However, there are additional computational overheads with this approach which must be bounded; this can be done in a similar way to that of the token bus protocol. 8. EXTENDING THE MODEL VARIABLE LENGTH PACKETS In a typical aerospace application [6] data messages tend to be small (perhaps one or two words) and therefore a large packet size would entail wasted bandwidth 13 . Conversely, in multi media applications the messages tend to be large, amortising overhead costs across several packets. In a mixed environment, where there may be ....

Burns, A., Wellings, A. J., Bailey, C. M., and Fyfe, E., "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation," YCS 190, Department of Computer Science, University of York (1993).

....O i J i after the start of the transaction, and may not re arrive until a further e i transaction invocations have taken place. It is clear, therefore, that task i inherits a period of e i T t . The motivation for including e i comes from control applications in the aerospace field [5] where data is gathered periodically, and then every n periods some extra processing is performed on the collected data and output. The response time of a task i is the time between the arrival task i (at time O i after the arrival of the transaction) and the completion of the computation of task ....

Burns, A., Wellings, A.J., C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation," YCS 190, Department of Computer Science, University of York (1993).

....the requirements discussed in this section are realistic. This statement is supported by the case study presented in Chapter 7. There are also a number of other examples that have similar types of requirements to the ones discussed, including the Olympus Attitude and Orbital Control System [28] and the mine pump system [29] There are four principal categories of timing requirements considered; those associated with tasks (i.e. existing on only one processor) those involving messages which transfer data between processors (i.e. existing on the databus) those associated with ....

....response time is expressed as: R i = R n 1 i J i (3.6) 3.1.5 Deadline Monotonic Priority Ordering A limitation with rate monotonic scheduling is the fact there is no mechanism for dealing with criticality. This can cause problems when tasks with long periods need a high priority. Burns et al. [28] provides a real example for a satellite telemetry system, where the software to transfer data to and from the ground station is only needed once a day. The execution of the software within a tight window of opportunity is critical to the system s effectiveness. With the rate monotonic policy the ....

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A. Burns, A. J. Wellings, C. Bailey, and E. Fyfe, "The olympus attitude and orbital control system, a case study in hard real-time system design and implementation," pp. 240--248, Springer Verlag, 1993.

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A. Burns, A. J. Wellings, C. M. Bailey and E. Fyfe, `The Olympus attitude and orbital control system: a case study in hard real-time system design and implementation', in Ada sans frontieres, Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science, Springer-Verlag, 1993.

....# Sporadic tasks, # Hard real time tasks, Soft real time tasks, # Background tasks, # Communication over a bus. Currently, the operational software is coded in 9989 assembler and scheduled by a cyclic scheduler. Software Design The software redesign of the AOCS has been presented elsewhere[10, 11]. 5.2. Summary of Results and Experiences The case study consisted of 3155 lines of Ada source code, corresponding to 62 HRT HOOD objects. The object code sizes are (in bytes) 116,312 (code) 2,976 (initialised data) and 6,948 (uninitialised data) Note that all these figures are unoptimised; ....

A. Burns, A.J. Wellings, C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation", YCS 190, Department of Computer Science, University of York (1993).

....# Sporadic tasks, # Hard real time tasks, Soft real time tasks, # Background tasks, # Communication over a bus. Currently, the operational software is coded in 9989 assembler and scheduled by a cyclic scheduler. Software Design The software redesign of the AOCS has been presented elsewhere[10, 11]. 5.2. Summary of Results and Experiences The case study consisted of 3155 lines of Ada source code, corresponding to 62 HRT HOOD objects. The object code sizes are (in bytes) 116,312 (code) 2,976 (initialised data) and 6,948 (uninitialised data) Note that all these figures are unoptimised; ....

A. Burns, A.J. Wellings, C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation", pp. 19-35 in Ada sans frontieres Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science 688, Springer-Verlag (1993).

....property that no simple algorithm (such as rate or deadline monotonic) gives the optimal priority ordering. In this section, a theorem and algorithm for assigning priorities in arbitrary situations is given. The theorem considers the behaviour of the lowest priority thread (Audsley, Tindell and Burns, 1993). Theorem If thread is assigned the lowest priority and is feasible then, if a feasible priority ordering exists for the complete thread set, an ordering exists with assigned the lowest priority. The proof of this theorem comes from considering the schedulability equations for example, ....

....occasions. Cyclic executives (static scheduling) for example, explicitly use offsets to order executions and obtain feasible schedules. Without offsets, priority based systems are often too pessimistic; with offsets, equivalent behaviour to cyclic executives can be obtained (Audsley, Tindell and Burns, 1993). For example, a case study (Burns et al. 1993) Burns, Wellings, Forsyth and Bailey, 1995) of the Olympus satellite AOCS (Attitude and Orbital Control System) containing some 30 threads, was deemed unschedulable by the standard response time test modified to include kernel overheads. On ....

[Article contains additional citation context not shown here]

Burns, A., Wellings, A. J., Bailey, C. and Fyfe, E. (1993). The olympus attitude and orbital control system: A case study in hard real-time system design and implementation, Ada sans frontieres Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science 688, SpringerVerlag, pp. 19--35.

....Cache size (Kbytes) k 8 4 16 Linesize Cache block size (words) r 1 1 4 Assoc Cache associativity degree m 80 20 150 MIPS MIPS b 40 20 60 Readtime Memory read time (nS) a 2 1 4 Acctime Memory access time (cycles) 6. 2 Workload model Real examples of real time workloads can be found in [17] 16][4]. However, the workload used in this paper is inspired on the application level synthetic benchmark Hartstone [24] The workload used in the experiment is a set of periodic and independent tasks. The task periods and task loads are configured as a function of a variety of factors (see Table II) ....

A. Burns, A. Wellings, C. Bailey and E. Fyfe."The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation". Ada sans frontieres Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science 688, pages 19-35, 1993.

....goal of placing the satellite in a standard attitude. Thrusters rather than reaction wheels are used to control the spacecraft orientation. A full description of the Requirements of the AOCS is given by Bailey[Bailey1992] 4.3. Software Design We have presented the design of the AOCS elsewhere [Burns1993b, Burns1993c ] The software for the two modes consists of 10 cyclic objects, 3 sporadic objects, 14 protected objects, and 16 passive objects. Overall over 3,000 lines of Ada code was produced. 5. Performance Evaluation Although the schedulability analysis techniques allow the response time of each task to ....

A. Burns, A.J. Wellings, C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation", pp. 19-35 in Ada sans frontieres Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science 688, Springer-Verlag (1993).

....goal of placing the satellite in a standard attitude. Thrusters rather than reaction wheels are used to control the spacecraft orientation. A full description of the Requirements of the AOCS is given by Bailey[Bailey1992] 4.3. Software Design We have presented the design of the AOCS elsewhere [Burns1993b, Burns1993c ] The software for the two modes consists of 10 cyclic objects, 3 sporadic objects, 14 protected objects, and 16 passive objects. Overall over 3,000 lines of Ada code was produced. 5. Performance Evaluation Although the schedulability analysis techniques allow the response time of each task to ....

A. Burns, A.J. Wellings, C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation", YCS 190, Department of Computer Science, University of York (1993).

No context found.

Burns, A., et al . The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-Time System Design and Implementation. in Ada sans fontieres: Proceedings of the 12th Ada Europe Conference. 1993. Paris, France: Springer-Verlag.

No context found.

Burns, A., Wellings, A. J., Bailey, C. M., and Fyfe, E., "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation," YCS 190, Department of Computer Science, University of York (1993).

.... Cache size (Kbytes) k 8 4 16 Linesize Cache block size (words) r 1 1 4 Assoc Cache associativity degree m 80 20 150 MIPS MIPS b 40 20 60 Readtime Memory read time (nS) a 2 1 4 Acctime Memory access time (cycles) 7 Workload model Real examples of real time workloads can be found in [28] 25][8]. However, the workload used in this paper is inspired on the application level synthetic benchmark Hartstone [45] The workload used in the experiment is a set of periodic and independent tasks. The task periods and task loads are configured as a function of a variety of factors (see Table III) ....

A.Burns, A.Wellings, C.Bailey and E.Fyfe. "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation". Ada sans frontieres Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science 688, pages 19-35, 1993.

....0 18 14 tives (static scheduling) for example, explicitly use offsets to order executions and obtain feasible schedules. Without offsets, priority based systems are often too pessimistic; with offsets, equivalent behavior to cyclic executives can be obtained [8] For example, a recent case study [18, 19] of the Olympus satellite AOCS (Attitude and Orbital Control System) containing some 30 tasks, was deemed unschedulable by the standard deadline monotonic test (i.e. Equation (10.1) modified to include kernel overheads) On inspection it contained three tasks of identical period that could not ....

A. Burns, A.J. Wellings, C.M. Bailey, and E. Fyfe. The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-Time System Design and Implementation. In Ada sans frontieres, Proceedings of the 12th Ada-Europe Conference, Lecture Notes in Computer Science. Springer-Verlag, New York, 1993.

....0 18 14 tives (static scheduling) for example, explicitly use offsets to order executions and obtain feasible schedules. Without offsets, priority based systems are often too pessimistic; with offsets, equivalent behavior to cyclic executives can be obtained [8] For example, a recent case study [18, 19] of the Olympus satellite AOCS (Attitude and Orbital Control System) containing some 30 tasks, was deemed unschedulable by the standard deadline monotonic test (i.e. Equation (10.1) modified to include kernel overheads) On inspection it contained three tasks of identical period that could not ....

....and derived properties such as priority and response time. HRT HOOD is a structured method supporting a graphical representation and a textual equivalent syntactical form. It has been used, together with some of the scheduling analysis discussed in this chapter, on an extensive case study [18]. One of the interesting features of the HRT HOOD method is that it contains systematic mapping from the object system to Ada 9X. This indicates that the computational model is realizable in that language. 10.5 Slack Scheduling It is possible to compare scheduling approaches by considering the ....

A. Burns, A.J. Wellings, C.M. Bailey, and E. Fyfe. The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-Time System Design and Implementation. Technical Report YCS 190, Department of Computer Science, University of York, 1993.

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C. M. Bailey, E. Fyfe, A. Burns, and A. J. Wellings, The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation. University of York, Department of Computer Science, 1993.

No context found.

A. Burns, A. Wellings, C. Bailey, and E. Fyfe. The Olympus attitude and orbital control system: A case study in hard real-- time system design and implementation. In Ada sans frontiers, Proc. of the 12th Ada--Europe Conf., Lecture Notes in Computer Science, pages 19--35. Springer--Verlag, 1993.

No context found.

Burns, A., Wellings, A.J., C.M. Bailey and E. Fyfe, "The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-time System Design and Implementation," YCS 190, Department of Computer Science, University of York (1993).

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