V.V. Balashov et al. Tools for monitoring of data exchange in real-time avionics systems

Tools for monitoring of data exchange
in real-time avionics systems

V.V. Balashov, V.A. Balakhanov, A.G. Bakhmurov, M.V. Chistolinov,
P.E. Shestov, R.L. Smeliansky, N.V. Youshchenko

Lomonosov Moscow State University, Dept. of Computational Mathematics and Cybernetics,
Laboratory of Computer Systems

e-mail: {hbd,baldis,bahmurov,mike,osmin,smel,yoush}@lvk.cs.msu.su

Abstract

In this paper we present a toolset for monitoring of data exchange through onboard channels of real-time avionics (RTA) systems. The toolset is applicable to different stages of RTA system development, from purely-software simulation to field testing. Checking correctness of data exchange schedule and correctness of transferred data is supported. The toolset uses project database as the source of information on data exchange schedule and on messages structure. It is applied on practice to development and testing of aircraft RTA systems.

1. Introduction

Modern real-time avionics (RTA) systems contain dozens of data exchange channels connecting multiple devices. Data sets transferred through these channels must have correct values and timings. Data exchange, real or simulated, takes place on following phases of simulation-based development of RTA systems [1]:

1. purely-software simulation;

2. hardware-in-the-loop (HITL) simulation and integration;

3. prototype evaluation;

4. field testing.

On phase 1 of development process proposed in [1], data exchange is performed via software models of data exchange channels, in particular MIL STD-1553B and ARINC 429. These channel models simulate data exchange transactions between attached onboard device models, with correct transfer timings. Device model can include source code of target RTA device’s application and system software, which enables simulation-based software development. Realistic simulation of channel operation along with using real software for data exchange control enable full-featured data exchange workout and verification. This activity requires monitoring of simulated data exchange and analysis of monitoring results.

On phase 2 step-by-step integration and verification of RTA system is performed, with gradual replacement of software models by hardware units, up to a fully integrated RTA system or its subsystem. During this phase, data exchange takes place both on simulated channels and real hardware channels. It is necessary to verify both correctness of data exchange between subscribers of hardware channels and matching of data exchange characteristics for simulated channels and real channels which replace them. Absence of such matching might mean that transition from simulation models to real devices introduced a problem, or that the models were incorrect. To perform a smooth transition from simulation models to real devices, it is necessary to monitor and analyze data exchange for real and simulated channels in a uniform way. Furthermore, a uniform representation of data exchange for different channel types is necessary, for example, to check if data received by one type of channel and sent farther by a different type of channel have coherent values.

On phase 3, a complete RTA system (or its subsystem) is evaluated and verified. This includes full-scale testing of RTA devices operation, including monitoring and verification of data exchange. This phase includes iterative upgrades of RTA devices software, and may coexist with phase 4.

Both phases 2 and 3 typically involve an integration/testing bench which includes computers responsible for channel monitoring. Full-scale monitoring and verification of data exchange requires simultaneous monitoring of most channels, so multiple computers are necessary for monitoring of data exchange. Computers with multiple onboard interface adapters, responsible for generation of test data traffic, are attached to channels in the testbench, and it makes a benefit to use monitoring features of these adapters (if present) instead of installing separate computers and adapters solely for monitoring purposes.

On phase 4, a real RTA system installed on a (prototype of) controlled system, e.g. an aircraft, is tested. A mobile monitoring solution is necessary to examine the data exchange. Such examination is essential as no technological software stubs are allowed to provide extra information on what is going on inside the RTA devices. Such solution can be farther used during field operation phase in case the controlled system does not have tight constraints on mass and size of “extra” load; for instance, it is acceptable to take a compact mobile monitoring device onboard a ship or a heavy transport aircraft. As RTA system developers are not typically available on-site during field operation, it is necessary to support long-lasting monitoring process (for several days at minimum).

On all phases of RTA system development process mentioned above, data exchange specifications (message formats, schedules etc) are taken from a project database.

A single solution is necessary to support data exchange monitoring and analysis on all four phases of the process. Requirements to this solution are as follows:

1. support for monitoring of different types of channels present in RTA system, with uniform representation of monitoring results and unified capabilities for analysis of these results;

2. support for monitoring of both real and simulated channels;

3. integration with project database as a source of data exchange specifications;

4. support for following configurations:

• software only installation for working with a purely software simulation model of RTA system on early development phases;

• stationary multi-computer system (a part of testbench) controlled from a single workstation; sharing of channel adapters with test traffic generating computers is a favorable feature;

• compact mobile platform (e.g. a rugged notebook) for use during field testing and field operation.

This paper presents a software toolset for data exchange monitoring which suits all the requirements listed above and provides a wide range of features to support data exchange monitoring and analysis. This toolset is developed in the Computer Systems Laboratory (CS Lab) of Computational Mathematics and Cybernetics department of the Moscow State University.

The rest of the paper is organized as follows. Section 2 presents an overview of several existing monitoring solutions, including the presented toolset, and compares their feature sets. In particular the toolsets are checked for conformance to requirements 1-4. Section 3 describes structure of the presented toolset. Section 4 presents the workflow for application of the toolset. Section 5 contains two case studies. In the last section, future directions of work are proposed.

2. Related work

In this section we list several examples of monitoring toolsets provided by different vendors and assess their feature sets with special attention to support of requirements 1 – 4 from Section 1. The scope of analysis is limited to MIL STD-1553B and ARINC 429 channels as they are most widely used in today's military avionics [2].

The toolsets of interest are as follows:

• PBA.pro from AIM GmbH [3];

• CoPilot from Ballard Technology [4];

• DataSIMS from DDC [5];

• MIL-1553 Tester from Elcus [6];

• Flight Simulyzer from AIT [7];

• ADS2 from TechSAT GmbH [8];

• Luthier from Sital Technology [9];

• BusTools from General Electric [10];

• Exalt+ from Excalibur Systems [11];

• IMUX G2 from Wyle [12];

• MIL STD-1553B and ARINC 429 Analyzer, introduced in this paper.

Overview results are summarized in Table 1. Analysis of feature sets reveals following main features of monitoring tools, in addition to listed in Section 1:

• Unpacking parameters from recorded data blocks ("Par" column in Table 1);

• MIL STD-1553B terminal devices management, including setting/viewing subaddress data ("RT" column);

• MIL STD-1553B bus controller (and ARINC 429 sender) management, including exchange sequence specification and execution ("BC" column);

• Recording and display of data exchange traces ("Rec" column);

• Replay of registered exchange ("Rpl" column);

• Fault injection into channel ("FI" column);

• Recording start/stop on specified events during data exchange ("Ev" column).

Support for a mobile platform is typical for the reviewed tools (provided that the computer is powerful enough, and there are extension slots for adapter cards). If a monitoring toolset supports both MIL STD-1553B and ARINC 429, it usually represents monitoring results in a uniform way for both channel types. Considering this, specific features related to requirements 1-4 from Section 1 are as follows:

• support for monitoring of both real and simulated channels ("Sim" column); the latter implies support for software only configurations;

• integration with project database ("DB" column);

• support for a stationary multi-computer system (a part of testbench) controlled from a single workstation ("MCS" column);

• sharing of channel adapters with test traffic generating computers of a testbench ("SHR" column).

Table 1. Monitoring toolsets capabilities

Toolset name

Supported channel types

Par

RT

BC

Rec

Rpl

FI

Ev

Sim

DB

MCS

SHR

PBA.pro

M1553, A429, FC-AE, ADFX, CAN, Panavia

+

+/-

+

+

-

+

+

-

-

-

+/-

CoPilot

M1553, A429, AFDX, A708

+

+

+

+

+

+

-

-

-

-

-

DataSIMS

M1553, A429

+

+

+

+

+

+

+

-

-

-

-

MIL-1553 Tester

M1553

-

-

-

+

-

-

-

-

-

-

-

Flight Simulyzer

M1553, A429

-

+

+

+

-

+

-

-

-

+

-

ADS2

M1553, A429, AFDX, CAN, …

+

+

+

+

-

+

+

-

+

+

+/-

Luthier

M1553

-

+

+

+

-

-

-

-

-

-

-

BusTools

M1553, A429, AFDX

+

+

+

+

-

+

+

-

-

-

-

Exalt+

M1553, A429, A708,AFDX,...

+

+/-

+

+

-

+

+

-

-

-

-

IMUX G2

M1553, A429, A624, FC-AE, ...

+

-

-

+

-

-

-

-

+

+

+/-

MIL STD-1553B and ARINC 429 Analyzer

M1553, A429

*

+

+

+

-

-

-

+

*

+

+

Notes for Table 1.

• "+/-" for RT management feature means that only RT and subaddress status flags management is supported, but not setting up data for RT subaddresses;

• "+/-" for hardware adapter sharing between testing and monitoring tools means that this toolset supports both testing and monitoring functions, but it is unclear from available documentation whether adapter sharing is supported;

• "*" means that the feature implementation is on schedule.

The overview shows that the most full-featured toolsets like PBA.Pro, DataSIMS, ADS2 "as is" cannot support simulation-based development of RTA systems [1] on phases 1 and 2 which involve data exchange through simulated channels, and most toolsets do not support multiple computer configurations controlled from a single workstation. The proposed toolset lacks some of "common" features but is designed for full support of all four phases of the process [1] (see Section 1).

3. Monitoring toolset structure

Figure 1 show the structure of the presented monitoring toolset in multiple computer configuration.