arXiv subjects

Claudio Mandrioli

Publications and source records attributed to Claudio Mandrioli.

5 recordsLinked to original sources

arXiv2026

On the Time and Frequency Domain Representations of Signals for CPS Specification

Specification languages are instrumental to the Verification \& Validation of Cyber-Physical Systems (CPSs). Most state-of-the-art specification languages use the time-domain representation of signals, which is not always suitable for describing signal shapes and dynamic behaviours. Instead, fields like control and robotics use the frequency-domain representation to characterise these behaviours. Time-frequency representations combine the capabilities of both domains. We investigate the use of time-frequency representations to specify CPS requirements. We analyse existing taxonomies of CPS requirements to identify which requirement classes can benefit from time-frequency representations. We derive the desiderata for a specification language that uses time-frequency representations and propose Signal-Spectrum Temporal Logic (S2TL), a language enabling assertions over frequency intervals and relations between frequency components. We operationalise the S2TL semantics for monitoring CPS traces, and implement a monitor. We define specification templates for the identified requirement classes and compare time- and time-frequency-domain formulations in terms of applicability, expression fidelity, and noise tolerance of monitoring. We observe that, while time-domain specifications are applicable only to input traces containing step-like changes or using constant interpolation, time-frequency specifications extend their evaluation to traces generated through linear interpolation, and improve tolerance to offset and high-frequency noise, while achieving comparable fidelity to the intended system properties.

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arXiv2026

Comparing Controller Synthesis Methods with Deadline-Miss Awareness

This paper presents a comparative study of real-time controller design methods for dynamical control systems subject to deadline overruns. Numerous techniques have been proposed to handle missed deadlines, i.e., including models or information of possible deadline misses directly in the control design. These approaches substantially differ in their assumptions, supported execution semantics, required runtime information, and provided guarantees, making direct comparison challenging. We address this gap with a qualitative assessment of representative deadline-miss-aware control methods. We analyze the design space of such controllers and identify the critical assumptions on the real-time constraints, the control design criteria and implementation aspects. We expose how these different assumptions lead to the different trade-offs in applicability, and control performance and guarantees. We contribute a comparison tool enabling researchers to systematically benchmark new techniques against the state of the art. The study is supported by simulations on two case studies: a Furuta pendulum and an electric motor to illustrate the practical behavior of the different approaches under missed-deadline conditions.

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arXiv2025

Diagnosing Violations of State-based Specifications in iCFTL

As modern software systems grow in complexity and operate in dynamic environments, the need for runtime analysis techniques becomes a more critical part of the verification and validation process. Runtime verification monitors the runtime system behaviour by checking whether an execution trace - a sequence of recorded events - satisfies a given specification, yielding a Boolean or quantitative verdict. However, when a specification is violated, such a verdict is often insufficient to understand why the violation happened. To fill this gap, diagnostics approaches aim to produce more informative verdicts. In this paper, we address the problem of generating informative verdicts for violated Inter-procedural Control-Flow Temporal Logic (iCFTL) specifications that express constraints over program variable values. We propose a diagnostic approach based on backward data-flow analysis to statically determine the relevant statements contributing to the specification violation. Using this analysis, we instrument the program to produce enriched execution traces. Using the enriched execution traces, we perform the runtime analysis and identify the statements whose execution led to the specification violation. We implemented our approach in a prototype tool, iCFTL-Diagnostics, and evaluated it on 112 specifications across 10 software projects. Our tool achieves 90% precision in identifying relevant statements for 100 of the 112 specifications. It reduces the number of lines that have to be inspected for diagnosing a violation by at least 90%. In terms of computational cost, iCFTL-Diagnostics generates a diagnosis within 7 min, and requires no more than 25 MB of memory. The instrumentation required to support diagnostics incurs an execution time overhead of less than 30% and a memory overhead below 20%.

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arXiv2025

Testing CPS with Design Assumptions-Based Metamorphic Relations and Genetic Programming

Cyber-Physical Systems (CPSs) software is used to enforce desired behaviours on physical systems. To test the interaction between the CPS software and the system's physics, engineers provide traces of desired physical states and observe traces of the actual physical states. CPS requirements describe how closely the actual physical traces should track the desired traces. These requirements are typically defined for specific, simple input traces such as step or ramp sequences, and thus are not applicable to arbitrary inputs. This limits the availability of oracles for CPSs. Our recent work proposes an approach to testing CPS using control-theoretical design assumptions instead of requirements. This approach circumvents the oracle problem by leveraging the control-theoretical guarantees that are provided when the design assumptions are satisfied. To address the test case generation and oracle problems, researchers have proposed metamorphic testing, which is based on the study of relations across tests, i.e., metamorphic relations (MRs). In this work, we define MRs based on the design assumptions and explore combinations of these MRs using genetic programming to generate CPS test cases. This enables the generation of CPS input traces with potentially arbitrary shapes, together with associated expected output traces. We use the deviation from the expected output traces to guide the generation of input traces that falsify the MRs. Our experiment results show that the MR-falsification provides engineers with new information, helping them identify passed and failed test cases. Furthermore, we show that the generation of traces that falsify the MRs is a non-trivial problem, which is successfully addressed by our genetic search.

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arXiv2023

Stress Testing Control Loops in Cyber-Physical Systems

Cyber-Physical Systems (CPSs) are often safety-critical and deployed in uncertain environments. Identifying scenarios where CPSs do not comply with requirements is fundamental but difficult due to the multidisciplinary nature of CPSs. We investigate the testing of control-based CPSs, where control and software engineers develop the software collaboratively. Control engineers make design assumptions during system development to leverage control theory and obtain guarantees on CPS behaviour. In the implemented system, however, such assumptions are not always satisfied, and their falsification can lead to loss of guarantees. We define stress testing of control-based CPSs as generating tests to falsify such design assumptions. We highlight different types of assumptions, focusing on the use of linearised physics models. To generate stress tests falsifying such assumptions, we leverage control theory to qualitatively characterise the input space of a control-based CPS. We propose a novel test parametrisation for control-based CPSs and use it with the input space characterisation to develop a stress testing approach. We evaluate our approach on three case study systems, including a drone, a continuous-current motor (in five configurations), and an aircraft.Our results show the effectiveness of the proposed testing approach in falsifying the design assumptions and highlighting the causes of assumption violations.

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