Prototype Verification System Research Articles

Parameters collaborative optimization design and innovation verification approach for fuel cell distributed drive electric tractor

Fuel cell distributed drive electric tractors (FCDET) are one of the necessary means to achieve truly green agriculture. However, low traction efficiency, poor control coordination, and excessive energy consumption are the main reasons hindering the industrialization of FCDET. This paper proposed a parametric collaborative optimization design method and innovative verification system that considers the drive system and energy system. Based on the tractor plowing operating conditions, a 7-DOF coupled dynamics model of the distributed drive system and a tire-soil interaction model were established, and the key component selection and parameter matching were completed. On the drive system optimization level, the front and rear wheelside transmission ratios are optimized based on a multi-island genetic algorithm (MIGA). On the energy system optimization level, the globally optimal power distribution ratio is found based on the dynamic programming algorithm (DP). A complete experimental prototype verification system is constructed based on the MATLAB/Simulink-NI PXI joint simulation platform, physical prototype test bench, and real vehicle multi-index test platform. The results show that the average efficiencies of the optimized drive and energy system are increased by 0.38 % and 3.82 %, the total energy consumption (total hydrogen consumption) is reduced by 25.40 % and 15.39 %, respectively. The maximum fault-free operating time is 5.5h, the average traction power is 21.07 kW, and the average traction force is 10610 N in the all-wheel drive mode. The experimental results fully demonstrate that the electric tractor with the fuel cell distributed drive system as the core can meet the verification of multiple indicators. This study can provide a new theoretical basis and technical verification method for the optimal design and system control of fuel cell distributed drive electric tractors.

Digital twin-driven parameter change propagation path optimization for production line variant design

ABSTRACT Current mass individualization requires that production lines for processing products be able to quickly vary to adapt to product changes. The variation and propagation of parameters have a central role in the variation process of a flexible production line, which increases the complexity of the design due to the non-unique propagation path of the variation. Obtaining the optimal variant design scheme has become a major challenge for designers. This paper aims to develop a method to determine optimal paths of change propagation. The digital twin-driven framework of parameter correlation path instantiation is presented. The high-fidelity simulation capability of digital twinning will contribute to the fast variant design of flexible production lines at low cost of trial and error. Then, a parameter variation search algorithm based on multi-fork tree has been proposed. The optimal variation design scheme has been achieved for the optimal propagation path of parameter variation from the perspectives of cost, time and complexity. A prototype verification system of production line design based on digital twin is developed to support the instantiation design of parameter change propagation path. An example of mobile phone welding assembly lines was taken to verify the effectiveness of the method.

Computer Vision-Aided Reconfigurable Intelligent Surface-Based Beam Tracking: Prototyping and Experimental Results

In this paper, we propose a novel computer vision-based approach to aid reconfigurable intelligent surface (RIS) for dynamic beam tracking and implement the corresponding prototype verification system. A camera is attached at the RIS to obtain the visual information about the surroundings, with which RIS identifies the incident beam direction and the desired reflected beam direction, and then adjusts the reflection coefficients according to the pre-designed codebooks. We build a 20-by-20 RIS running at 5.4 GHz and develop a high-speed control board to ensure the real-time refresh of the reflection coefficients. Meanwhile we implement an independent peer-to-peer communications system to simulate the physical link between the base station and the user equipment. The vision-aided RIS prototype system is tested in two mobile scenarios: RIS works in near-field conditions as a passive array antenna of the base station; RIS works in far-field conditions to assist the communication between the base station and the user equipment. The experimental results show that RIS can quickly adjust the reflection coefficients for dynamic beam tracking with the help of visual information.

Co-simulation and Formal Verification of Co-operative Drone Control With Logic-Based Specifications

AbstractUnmanned aerial vehicle (UAV) co-operative systems are complex cyber-physical systems that integrate a high-level control algorithm with pre-existing closed implementations of lower-level vehicle kinematics. In model-driven development, simulation is one of the techniques that are usually applied, together with testing, in the analysis of system behaviours. This work proposes a method and tools to validate the design of UAV co-operative systems based on co-simulation and formal verification. The method uses the Prototype Verification System, an interactive theorem prover based on a higher-order logic language, and the Functional Mock-up Interface, a widely accepted standard for co-simulation. In this paper, results on the co-simulation and proofs of safety requirements of a representative co-ordination algorithm are shown and discussed in a scenario where quadcopters are deployed and perform space-coverage operations.

Manufacturing system under I4.0 workshop based on blockchain: Research on architecture, operation mechanism and key technologies

With the further intelligent upgrading of industry 4.0, the intelligent manufacturing ecosystem based on CPS is realized in the form of Intelligent unit, Intelligent system and System of system. Under the open workshop architecture, intelligent workshop, as an important part of intelligent system, has acute problems such as safe sharing of manufacturing data and opaque monitoring of manufacturing process. This paper proposes the architecture of I4.0 workshop reference manufacturing system based on blockchain. Combined with I4.0 component and blockchain technology, this paper focuses on the mechanism and key implementation technologies of workshop manufacturing chain from three aspects: standardized information modeling, distributed control and trusted autonomous execution. By studying the autonomous trusted trigger mechanism of smart contract and the distributed storage method of manufacturing data in workshop manufacturing system, integrating workshop service system, a system operation mechanism of manufacturing data security and manufacturing process trusted trigger is established. In addition, based on the standardized modeling method of I4.0 components, the Asset Administration Shell-Blockchain process data verification model is designed, and the standardized blockchain verification model is established from the equipment layer to support the system architecture. Finally, the implementation of the prototype verification system is analyzed by selecting representative verification sources.

A Logic Theory Pattern for Linearized Control Systems

This paper describes a procedure that system developers can follow to translate typical mathematical representations of linearized control systems into logic theories. These theories are then used to verify system requirements and find constraints on design parameters, with the support of computer-assisted theorem proving. This method contributes to the integration of formal verification methods into the standard model-driven development processes for control systems. The theories obtained through its application comprise a set of assumptions that the system equations must satisfy, and a translation of the equations into the logic language of the Prototype Verification System theorem-proving environment. The method is illustrated with a standard case study from control theory.

Use of the PVS formal logic system in the method of formal proof of security in the construction of information security systems

The object of research is the information and telecommunication system (ITS) and ensuring the protection of information stored, processed and circulating in it. One of the most problematic areas in the creation of secure ITS is the logical inconsistency and incompleteness of the information security policy. That is, a set of laws, rules, restrictions, recommendations, etc., which regulate the procedure for processing information and are aimed at protecting information from a certain set of threats. The reason for such problems is usually the absence of pre-design modeling of the information security system as a component of the information and telecommunications system, which in the end causes the latter to be vulnerable. An important prerequisite for the creation of a secure ITS is the construction of a subject-object model of the system, which makes it possible to determine the connections between objects, their features, to model information flows and types of access to information and infrastructure resources. According to the existing clear, complete and consistent subject-object model of the ITS, it becomes possible to apply mathematical methods to modeling the processes of its functioning, including for solving the problem of formal proof of security. The paper considers the main idea of the method of formal proof of security, which can be used when building information security systems or assessing the security of the created information and telecommunications system. It is shown that for its implementation it is possible to use the methodology of automatic theorem proving. One of the ways to solve this problem, which is proposed in the work, is the use of the PVS (Prototype Verification System) formal logic system, which is widely used for writing specifications and constructing proofs. The main components of this system are considered, as well as the possibilities of its use for automatic proof of statements about the impossibility of unauthorized access under the conditions of a certain security policy. An example of the use of the PVS system for the formal proof of the security of the system in the framework of the Bella-LaPadula security policy is given.

Teaching Interactive Proofs to Mathematicians

This work discusses an approach to teach to mathematicians the importance and effectiveness of the application of Interactive Theorem Proving tools in their specific fields of interest. The approach aims to motivate the use of such tools through short courses. In particular, it is discussed how, using as case-of-study algebraic notions and properties, the use of the proof assistant Prototype Verification System PVS is promoted to interest mathematicians in the development of their mechanized proofs.

Formal analysis of the compact positionreporting algorithm

Abstract The Automatic Dependent Surveillance-Broadcast (ADS-B) system allows aircraft to communicate current state information, including position and velocity messages, to other aircraft in their vicinity and to ground stations. The Compact Position Reporting (CPR) algorithm is the ADS-B protocol responsible for the encoding and decoding of aircraft positions. CPR is sensitive to computer arithmetic since it relies on functions that are intrinsically unstable such as floor and modulus. In this paper, a formal verification of the CPR algorithm is presented. In contrast to previous work, the algorithm presented here encompasses the entire range of message types supported by ADS-B. The paper also presents two implementations of the CPR algorithm, one in double-precision floating-point and one in 32-bit unsigned integers, which are both formally verified against the real-number algorithm. The verification proceeds in three steps. For each implementation, a version of CPR, which is simplified and manipulated to reduce numerical instability and leverage features of the datatypes, is proposed. Then, the Prototype Verification System (PVS) is used to formally prove real conformance properties, which assert that the ideal real-number counterpart of the improved algorithm is mathematically equivalent to the standard CPR definition. Finally, the static analyzer Frama-C is used to verify software conformance properties, which say that the software implementation of the improved algorithm is correct with respect to its idealized real-number counterpart. In concert, the two properties guarantee that the implementation meets the original specification. The two implementations will be included in the revised version of the ADS-B standards document as the reference implementation of the CPR algorithm.

Proof Learning in PVS With Utility Pattern Mining

Interactive theorem provers (ITPs) are software tools that allow human users to write and verify formal proofs. In recent years, an emerging research area in ITPs is proof mining, which consists of identifying interesting proof patterns that can be used to guide the interactive proof process in ITPs. In previous studies, some data mining techniques, such as frequent pattern mining, have been used to analyze proofs to find frequent proof steps. Though useful, such models ignore the facts that not all proof steps are equally important. To address this issue, this paper proposes a novel proof mining approach based on finding not only frequent patterns but also high utility patterns to find proof steps of high importance (utility). A proof process learning approach is proposed based on high utility itemset mining (HUIM) for the PVS (Prototype Verification System) proof assistant. Proofs in PVS theories are first abstracted to a computer-processable corpus, where each line represents a proof sequence and proof commands in proof sequences are associated with utilities representing their weightage (importance). HUIM techniques are then applied on the corpus to discover frequent proof steps/high utility patterns and their relationships with each other. Experimental results suggest that combining frequent pattern mining techniques, such as sequential pattern mining and high utility itemset mining, with proof assistants, such as PVS, is useful to learn and guide the proof development process.

An Integrated Development Environment for the Prototype Verification System

The steep learning curve of formal technologies is a well-known barrier to the adoption of formal verification tools in industry. This paper presents VSCode-PVS, a modern integrated development environment for the Prototype Verification System (PVS). This new environment integrates the editing and proof management functionalities of PVS in Visual Studio Code, a popular code editor widely used by software developers. VSCode-PVS provides functionalities that developers expect to find in modern verification tools, but are not available in the standard Emacs front-end of PVS, such as auto-completion, point-and-click navigation of definitions, live diagnostics for errors, and literate programming. The main features and architecture of the environment are presented, along with a comparison with other similar tools.

Quality of service in IoT protocol as designs and its verification in PVS

AbstractReliable data transmission during communication in Internet of things (IoT)–based systems has gained much interest in last few years due to the current growth and huge investment in such systems. Message Queue Telemetry Transport (MQTT) is an open publish/subscribe–based messaging protocol that is widely used for device communication in IoT. For data transmission between devices, different levels of quality of service (QoS) are used in MQTT. In this paper, we provide a formal model for MQTT protocol under the Unifying Theories of Programming (UTP) semantic framework, where QoS levels in MQTT are modeled as designs in UTP. Refinement and equivalence relations between QoS levels can be established naturally via implication between predicates. Moreover, Prototype Verification System (PVS) is used to encode the UTP design models and some important properties as well as the refinement relation between QoS levels is proved with the PVS proof assistant.

Verification Templates for the Analysis of User Interface Software Design

The paper describes templates for model-based analysis of usability and safety aspects of user interface software design. The templates crystallize general usability principles commonly addressed in user-centred safety requirements, such as the ability to undo user actions, the visibility of operational modes, and the predictability of user interface behavior. These requirements have standard forms across different application domains, and can be instantiated as properties of specific devices. The modeling and analysis process is carried out using the Prototype Verification System (PVS), and is further facilitated by structuring the specification of the device using a format that is designed to be generic across interactive systems. A concrete case study based on a commercial infusion pump is used to illustrate the approach. A detailed presentation of the automated verification process using PVS shows how failed proof attempts provide precise information about problematic user interface software features.

A PVS-Simulink Integrated Environment for Model-Based Analysis of Cyber-Physical Systems

This paper presents a methodology, with supporting tool, for formal modeling and analysis of software components in cyber-physical systems. Using our approach, developers can integrate a simulation of logic-based specifications of software components and Simulink models of continuous processes. The integrated simulation is useful to validate the characteristics of discrete system components early in the development process. The same logic-based specifications can also be formally verified using the Prototype Verification System (PVS), to gain additional confidence that the software design complies with specific safety requirements. Modeling patterns are defined for generating the logic-based specifications from the more familiar automata-based formalism. The ultimate aim of this work is to facilitate the introduction of formal verification technologies in the software development process of cyber-physical systems, which typically requires the integrated use of different formalisms and tools. A case study from the medical domain is used to illustrate the approach. A PVS model of a pacemaker is interfaced with a Simulink model of the human heart. The overall cyber-physical system is co-simulated to validate design requirements through exploration of relevant test scenarios. Formal verification with the PVS theorem prover is demonstrated for the pacemaker model for specific safety aspects of the pacemaker design.

A Decision Procedure for Univariate Polynomial Systems Based on Root Counting and Interval Subdivision.

This paper presents a formally verified decision procedure for determinining the satisfiability of a system of univariate polynomial relations over the real line. The procedure combines a root counting function, based on Sturm's theorem, with an interval subdivision algorithm. Given a system of polynomial relations over the same variable, the decision procedure progressively subdivides the real interval into smaller intervals. The subdivision continues until the satisfiability of the system can be determined on each subinterval using Sturm's theorem on a subset of the system's polynomials. The decision procedure has been formally verified in the Prototype Verification System (PVS). In PVS, the decision procedure is specified as a computable boolean function on a deep embedding of polynomial relations. This function is used to define a proof producing strategy for automatically proving existential and universal statements on polynomial systems. The soundness of the strategy solely depends on the internal logic of PVS.

Confluence of Orthogonal Term Rewriting Systems in the Prototype Verification System

Orthogonality is a discipline of programming which syntactically guarantees determinism of functional specifications. Essentially, orthogonality avoids critical forks in term rewriting systems (TRSs) twofold: avoiding overlappings between left-hand sides of the rules (non-ambiguity) prohibiting rules in the definitions of functions that may apply simultaneously and forbidding repetitions of variables in the left-hand side of the rules (left-linearity) that may produce forks. In the theory of term rewriting systems, determinism is captured by the well-known property of confluence that is a consequence of orthogonality. This work describes a complete formalization in PVS of the theorem of confluence of orthogonal term rewriting systems. The formalization includes definitions and results on parallel reduction, in particular Rosen’s Parallel Moves Lemma. It is made available as a PVS theoryorthogonality inside the directory TRS of the NASA Langley PVS Library. Like all of TRS, orthogonality is intended to stay close to textbook proofs. The present proof uses the Parallel Moves Lemma at dominating positions of a parallel context. In this manner, all parallel forks filling the holes of the context are joined and, as result, a term of joinability for the whole fork is constructed.

Formalising Confluence in PVS

Confluence is a critical property of computational systems which is related with determinism and non ambiguity and thus with other relevant computational attributes of functional specifications and rewriting system as termination and completion. Several criteria have been explored that guarantee confluence and their formalisations provide further interesting information. This work discusses topics and presents personal positions and views related with the formalisation of confluence properties in the Prototype Verification System PVS developed at our research group.

Verifying safety properties of a nonlinear control by interactive theorem proving with the Prototype Verification System

Interactive, or computer-assisted, theorem proving is the verification of statements in a formal system, where the proof is developed by a logician who chooses the appropriate inference steps, in turn executed by an automatic theorem prover. In this paper, interactive theorem proving is used to verify safety properties of a nonlinear (hybrid) control system.

Formalization in PVS of Balancing Properties Necessary for Proving Security of the Dolev-Yao Cascade Protocol Model

In this work, we present an algebraic approach for modeling the two-party cascade protocol of Dolev-Yao and for fully formalizing its security in the specification language of the Prototype Verification System PVS. Although cascade protocols could be argued to be a very limited model, it should be stressed here that they are the basis of more sophisticated protocols of great applicability, such as those which allow treatment of multiparty, tuples, nonces, name-stamps, signatures, etc. In the current algebraic approach, steps of the protocol are modeled in a monoid freely generated by the cryptographic operators. Words in this monoid are specified as finite sequences and the whole protocol as a finite sequence of protocol steps, that are functions from pairs of users to sequences of cryptographic operators. In a previous work, assuming that for balanced protocols admissible words produced by a potential intruder should be balanced, a formalization of the characterization of security of this kind of protocols was given in PVS. In this work, the previously assumed property is also formalized, obtaining in this way a complete formalization which mathematically guarantees the security of these protocols. Despite such property being relatively easy to specify, obtaining a complete formalization requires a great amount of effort, because several algebraic properties, that are related to the preservation of the balancing property of the admissible language of the intruder, should be formalized in the granularity of the underlying data structure (of finite sequences used in the specification). Among these properties, the most complex are related to the notion of linkage property, which allows for a systematic analysis of words of the admissible language of a potential saboteur, showing how he/she is unable to isolate private keys of other users under the assumption of balanced protocols. The difficulties that arose in conducting this formalization are also presented in this work.

Verification of Dependable Architecture Based on Prototype Verification System

The electronic power system can be viewed as a system composed of a set of concurrently interacting subsystems to generate, transmit, and distribute electric power. The complex interaction among sub-systems makes the design of electronic power system complicated. Furthermore, in order to guarantee the safe generation and distribution of electronic power, the fault tolerant mechanisms are incorporated in the system design to satisfy high reliability requirements. As a result, the incorporation makes the design of such system more complicated. We propose a dependable electronic power system architecture, which can provide a generic framework to guide the development of electronic power system to ease the development complexity. In order to provide common idioms and patterns to the system designers, we formally model the electronic power system architecture by using the PVS formal language. Based on the PVS model of this system architecture, we formally verify the fault tolerant properties of the system architecture by using the PVS theorem prover, which can guarantee that the system architecture can satisfy high reliability requirements.