Model-based design is a common methodology in the development of embedded complex control systems. Control system engineers typically prefer to use MATLAB® Simulink® and suitable automatic code generators for the development and deployment of software. Embedded systems are subject to random hardware faults; bit-flips, for example, may affect random access memory (RAM) cells and central processing unit (CPU) registers and cause data errors that may propagate to critical system outputs and result in system failures.
From a dependability perspective, the design space of control systems includes the selection of a suitable (reliable) implementation of a control algorithm. Such algorithm can be implemented with model-based software development frameworks, such as Simulink using different, but functionally equivalent implementations. However, these functional equivalents may exhibit completely different reliability properties. This thesis proposes an analytical method for the evaluation of the reliability properties of control systems that are designed with Simulink models. The method is based on a transformation of the assembly code, which is generated from the Simulink model,
into a formal stochastic error propagation model as well as its quantification through underlying Markov chain models and state-of-the-art probabilistic model-checking techniques. The application of the method to the functionally equivalent implementations can determine which one is less vulnerable to data errors due to random hardware faults.
Fault tolerance is significant to dependable system design. Control systems can be protected with fault tolerance mechanisms to increase the reliability. Redundancy is the key underlying concept for achieving fault tolerance that is usually implemented at the hardware or software level. In the case of model-based development, redundancy mechanisms are preferable for direct application at the model level (Simulink model level). This thesis introduces a systematic classification of fault-tolerant design patterns. Such patterns can be applied to the Simulink model to tolerate random hardware faults, and taken into account during the control system design. In addition, it is more transparent and convenient for control system engineers to directly protect vulnerable parts with fault tolerance mechanisms at the model level.
The rigorous reliability assessment of the embedded control systems must be conducted at the assembly level based on the modeling of data errors that occurred in RAM and CPU. However, the scalability of the assembly-level assessment method is challenging and even problematic in view of the state space explosion (SSE) problem of the underlying Markov chain models. The computational complexity may increase exponentially as the assembly code size increases. Moreover, the transformation from the Simulink models to the assembly code is a complicated procedure. It is also more convenient for control engineers to already be able to estimate reliability properties and implement possible reliability improvements at the model level in the early design phase, when the model-based design is actually applied. Therefore, this thesis proposes a model-level reliability evaluation of Simulink models to address the aforementioned problems. The efficiency of the proposed modellevel evaluation is verified by a comparison of the reliability properties that are assessed at the assembly and model levels.:1. Introduction
2. Preliminaries
3. Reliability evaluation of control algorithm implementations at the assembly level
4. Fault-tolerant design patterns
5. MORE: MOdel-based REdundancy for Simulink models
6. Model-level assessment of Simulink models
7. Conclusion
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:75390 |
| Date | 08 July 2021 |
| Creators | Ding, Kai |
| Contributors | Janschek, Klaus, Rauzy, Antoine |
| Publisher | Technische Universitaet Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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