The performance of an electromechanical system not only depends on its controller design, but also on the design of its mechanical structure. In order to achieve the excellent performance of the four-bar-link mechanism by employing the simple PD control, we redesign the structure of the four-bar-link mechanism by a mass-redistribution scheme to simplify the dynamic model. Theoretically, we analyze the stability of the closed-loop system consisting of the PD controller and several kinds of four-bar-link mechanisms, and discuss the relations between the performance of the PD controller and its gains and the mechanical design. The obtained results show that the performance of the PD controller may be significantly improved by using the methodology of Design For Control (DFC). The effectiveness of the proposed methodology has also been verified by some simulation studies.

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Enterprise is a mini social-technical-ecological system in that it consists of humans, equipment and machines, and it has a location or site. Its structure follows the substanceinfrastructure (S-I) framework (Zhang and Wang 2016; Zhang and van Luttervelt 2011). There are two types of the S-I framework: the substance drives the infrastructure (Type I) and the infrastructure drives the substance (Type II). The enterprise system belongs to Type II. For instance, to a manufacturing system, the substance refers to goods made of materials, and the infrastructure refers to humans and machines, which produce and deliver goods to customers in response to their demands. To a service system (Wang et al. 2014), the substance refers to data (knowledge and information) (Zhang 1994) or signals or humans, and the infrastructure refers to humans and machines, which generate data, produce signals, or offer services to customers in accordance with their demands. Enterprise is a dynamic system, and it changes in its state and/or structure with respect to time, location, and/or event, and both the substance and infrastructure may change. A change on the part of the structure and/or state, say A, always has a reason or reasons, and this change is further associated with the change of another part of the structure and/or state of the system, say B; B is an independent variable and A is a dependent variable in this case (Zhang et al. 2005). The knowledge that governs the relation of A and B is called principle (Zhang et al. 2005; Zhang and Wang 2016). For instance, B is the force (F) applied on a block and A is the acceleration (a) of the block system, and the knowledge that governs the relation of A and B, in this case, is the Newton's second law, that is, F = ma, where m is the mass of the block system. A care must be taken that the principle (knowledge) may be hidden or unfolded in data or big data but a correspondence relation of A and B can be built using various machine learning methods, e.g., Artificial Neural Network (ANN) (Zhao and Zhang 2017), various deep learning methods (Zhang et al. 2018), etc. The independent variable is a function of time, location, and/or event, so is the dependable variable, and thus the whole system changes with respect to time, location, and/or event. Design of an enterprise system means to determine its structure (infrastructure and substance) in response to a need or demand in a context (Zhang and Wang 2016). For instance, in response to the need of charging to electric vehicles, a new enterprise idea, the electric charge station enterprise, emerges. To this new enterprise, one needs to determine the charging equipment, number of workers, and so on, which makes sense to the design of an enterprise (Zhang and Wang 2016). Construction of an enterprise follows its design. Design and construction are processes, so it makes sense to say about their management. A good practice of the management of design and construction thus results in a good structure.