Jonas Biteus

Distributed Diagnosis Using a Condensed Representation of Diagnoses With Application to an Automotive Vehicle

In fault detection and isolation, diagnostic test results are commonly used to compute a set of diagnoses, where each diagnosis points at a set of components which might behave abnormally. In distributed systems consisting of multiple control units, the test results in each unit can be used to compute local diagnoses while all test results in the complete system give the global diagnoses. It is an advantage for both repair and fault-tolerant control to have access to the global diagnoses in each unit since these diagnoses represent all test results in all units. However, when the diagnoses, for example, are to be used to repair a unit, only the components that are used by the unit are of interest. The reason for this is that it is only these components that could have caused the abnormal behavior. However, the global diagnoses might include components from the complete system and therefore often include components that are superfluous for the unit. Motivated by this observation, a new type of diagnosis is proposed, namely, the condensed diagnosis. Each unit has a unique set of condensed diagnoses which represents the global diagnoses. The benefit of the condensed diagnoses is that they only include components used by the unit while still representing the global diagnoses. The proposed method is applied to an automotive vehicle, and the results from the application study show the benefit of using condensed diagnoses compared to global diagnoses.

An algorithm for computing the diagnoses with minimal cardinality in a distributed system

In fault diagnosis, the set of minimal diagnoses is commonly calculated. However, due to for example limited computation resources, the search for the set of minimal diagnoses is in some applications focused on to the smaller set of diagnoses with minimal cardinality. The key contribution in this paper is an algorithm that calculates the diagnoses with minimal cardinality in a distributed system. The algorithm is constructed such that the computationally intensive tasks are distributed to the different units in the distributed system, and thereby reduces the need for a powerful central diagnostic unit.

DISTRIBUTED DIAGNOSIS FOR EMBEDDED SYSTEMS IN AUTOMOTIVE VEHICLES

Abstract Fault diagnosis is important for automotive vehicles, due to economic reasons such as efficient repair and fault prevention, and legislations which mainly deals with safety and pollution. In embedded systems with dozens of electronic control units that states local diagnoses, it can be arbitrary difficult to find which combination of local diagnoses that points at the correct faulty components. An algorithm is presented that both finds the diagnoses that in themselves are complete and chooses only those diagnoses that are more likely to be correct, this restriction is wanted due to the limitations in processing power, memory, and network capacity. The embedded system in a Scania heavy duty vehicle has been used as a case study to find realistic requirements on the algorithm.

Determining the fault status of a component and its readiness, with a distributed automotive application

In systems using only single-component tests, the fault status of a component is ready if a test only supervising the component has been evaluated. However, if plausibility tests that supervise multiple components are used, then a component can be ready before all tests supervising the component have been evaluated. Based on test results, this paper contributes with conditions on when a component is ready. The conditions on readiness are given for both centralized and distributed systems and are here applied to the distributed diagnostic system in an automotive vehicle.

A SYSTEMATIC INCLUSION OF DIAGNOSIS PERFORMANCE IN FAULT TREE ANALYSIS

Safety is of major concern in many applications such as in automotive systems and aerospace. In these applications it is standard to use fault trees, and a natural question in many modern systems that include sub-systems like diagnosis, fault tolerant control and autonomous functions, is how to include the performance of these algorithms in a fault tree analysis for safety. Many possibilities exist but here a systematic way is proposed. It is shown both how safety can be analyzed and how the interplay between algorithm design in terms of missed detection rate and false alarm rate is included in the fault tree analysis. Examples illustrate analysis of diagnosis system requirement specification and algorithm tuning.

Residual Generators for DAE Systems Utilizing Minimal Subsets of Model Equations

Abstract A common approach to design diagnostic systems is to use residual generators. These generators are usually constructed considering all the model equations. However, there are several advantages of instead consider small subsets of model equations, so called minimal structurally singular (MSS) sets of equations. This paper presents a new method for finding residual generators for MSS sets. A special property of the MSS set, namely that it is minimally over determined, is utilized. Two approaches are considered, one which is based on the use of a dynamic numerical equation solver, and another which uses a static numerical equation solver. The approaches are demonstrated on a non-linear point-mass satellite system.

Guided Integrated Remote and Workshop Troubleshooting of Heavy Trucks

When a truck or bus suffers from a breakdown it is important that the vehicle comes back on the road as soon as possible. In this paper we present a prototype diagnostic decision support system cap ...

Determining a component's fault status and the status' readiness

Abstract A diagnosis points at a set of components whose abnormal behavior could explain why a system does not function as intended, and a set of diagnoses points at different such sets of components. It would be an advantage for repair technicians if it, as a complement to the diagnoses, was possible to exactly state which components that certainly are faulty, which that are only suspected to be faulty, and which that are normal, i.e. to state the components’ fault statuses. There would also be an advantage if the technicians could get an indication when a components fault status cannot be changed by evaluating additional diagnostic tests, and the fault status is in that case said to be ready. The key contributions in the present paper are conditions that can be used to decide a components fault status and the fault status’ readiness. Conditions are stated for both centralized and distributed systems.