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With the model-based approaches gaining popularity in the development of complex systems, formal approaches for functional modeling have attracted a lot of attention. However, existing approaches for functional modeling do not involve structural states of a system, which often makes the functional models of such systems ambiguous and incomplete. To address this issue, research on a state-integrated approach for generalized functional modeling has been conducted. First, the State-Bahvior-Function model for components is proposed, which can represent the structural states, behaviors, and functions of a component. Thereafter, an approach for generalized functional modeling of systems is proposed, which can represent different structural states of a system, as well as the functions corresponding to the states of the system. Finally, the functional modeling process of a peeler centrifuge is provided as an example, which demonstrates that the state-integrated approach for generalized functional modeling can enable engineers to establish explicit and complete functional models of systems.

Functional design is an extremely important part in the design and development of complex systems. It is necessary to establish a forward development method to ensure the correctness and completeness of functional design. Therefore, taking the flight control system of civil aircraft as an example, a forward development method for functional design is proposed. First, system modeling language is used to establish the functional requirements relationship model from aircraft level to system level and then to item level. Then, the functional requirements are combined with the safety requirements in SAE ARP4754A aircraft development guide to construct the functional knowledge set of the flight control system. Finally, the functional model of the flight control system is established based on functional unit block diagram and functional integration block diagram. This method can be used as a reference for the functional design of complex systems.

The performance of reciprocating friction pairs in low-speed marine diesel engines has an important impact on the economy, stability, and safety of the ship operation, which deserves special attention. However, the available research is very limited. In this article, a new tribodynamics modeling method and an online measurement method for friction force are proposed. The friction force is simulated and verified by experiments. Based on the principle of multibody dynamics and mixed lubrication theory, a tribodynamic model coupling the reciprocating friction pairs (piston assembly–cylinder liner, piston rod–stuffing box, and crosshead slipper–guide) is first established. The friction force and dynamics are theoretically analyzed. Then a friction measurement method, which can measure the friction force of reciprocating friction pairs under engine firing conditions, is developed and used to verify the simulation. By comparison, it is found that the simulated friction is in good agreement with the experimental one. The results show that the crosshead slipper and piston assembly have obvious secondary motion, which will affect the vibration and noise of the engine. The friction force of the piston assembly is much higher than that of other reciprocating friction pairs. Improving the lubrication state near the top dead center of the piston assembly is of great significance to reduce the friction loss of the low-speed marine engines. [ABSTRACT FROM AUTHOR]

Optimal conceptual design synthesis is the very starting and key phase in the product design. Its result is the optimal alternative in the solution space, and will be further completed and improved into the final product design scheme in the next detailed design works. With the progress of the Internet technology, a large number of design resources actually construct an increasingly growing distributed resource environment. If these rich resources can be fully introduced into the optimal conceptual design synthesis, the design efficiency and product innovation will be promoted largely. Therefore, a computational approach was proposed for the optimal conceptual design synthesis based on the distributed resource environment. In this approach, the distributed resource environment is modelled as a set of numerous functional units (FUs), and the optimal conceptual design synthesis is concluded into a process of generating the optimal objective FU chain. Here, the main workload is completed by a proposed computer algorithm. To prove the feasibility of this approach, a computer programme called Optimal Conceptual Design Synthesis System (OCDSS) was established. A garbage-powered lighting system was designed with OCDSS as an illustration. [ABSTRACT FROM PUBLISHER]

Conceptual design of mechanisms has attracted a number of research efforts in recent years due to its significance in product development. However, existing approaches for automated conceptual design of mechanisms are either prone to a loss of optimal solutions or inextensible to achieve conceptual design of complex mechanisms. This paper is devoted to developing a comprehensive and extensible methodology for automated conceptual design of mechanisms utilizing a design prototype synthesis methodology. To support automated mechanism synthesis effectively, the traditional morphological matrix is improved as a motional function matrix (MFM). In addition, a mechanism prototype knowledge base is developed to provide systematic knowledge support for conceptual design decision-making. Based on the integrated MFM, an exhaustive mechanism synthesis algorithm is developed to yield as many solutions as possible to desired functions to facilitate the discovery of novel and optimal combinatorial solutions. To curb the possible combinatorial explosion from the exhaustive search, a performance constraint verification approach is proposed to help designers .filter out combinatorial solutions violating performance constraints, .followed by a satisfaction degree-based approach for evaluating the total performances of combinatorial solutions according to the performances of their subsolutions. An automated mechanism conceptual design prototype system is developed and a design case is presented to illustrate the feasibility and practicality of the proposed methodology. Keywords: conceptual design, morphological matrix, mechanism synthesis, constraint verification, combinatorial evaluation, design catalogue

The stuffing box-piston rod system is widely used in the low-speed marine diesel engines to scrape oil and ensure sealing. Its friction power loss and wear rate are great, but the studies about the system are very limited. In this study, based on the special structure and working conditions of the stuffing box, the analytical model for the tribological properties of the stuffing box-piston rod system is developed considering the oil starvation and relative ring location effects. The minimum oil film thickness, friction, oil transportation, and asperity contact are calculated for the stuffing box. The analysis results show that compared with the fully flooded lubrication, the minimum oil film thicknesses of the rings reduce significantly in the middle of the strokes under the starved lubrication condition, but the friction losses of the rings are influenced by the comprehensive effects of the oil film thickness reduction and lubricating area reduction under the starved lubrication condition, which is related to the specific profiles of the rings. In addition, compared with the engine piston ring pack, the relative ring location effect is more obvious in the stuffing box ring pack because there are more rings and the ring intervals are larger. The relative ring location effect makes the minimum oil film thicknesses, friction forces, and asperity contacts of the rings have oscillations after bottom dead center and top dead center. [ABSTRACT FROM AUTHOR]