Cyber Physical Systems (CPS) defines how a physical system integrates sensor, communication, computing, and control in a large scale cyber infrastructure. Digital Twin system has multiple definitions and each has a different perspective. From product designer perspective, product life cycle management (PLM) is the key platform to use product design model to monitor, test, control, and service the products in the field. From a user perspective, the design model often is not available. Users will use data from the usage to model the purpose (quality, efficiency, maintenance, etc). They will own the data and domain knowledge which often designers might not have or lacking. From a system integrator perspective, many different products will be used so the data analytics will be conducted through another platform which designers and users might not have. In summary, CPS is system thinking from networked products and operations. Digital twin is a engineering system that drive new abilities to design, operate, maintain, and create new services to maximize its value.
A cyber physical system and a digital twin of a system are somewhat the same thing but the same is not available for CPS or DT of a product.
For a product again there are categories, a machine tool as a product may have both CPS and DT i.e. bot visible and invisible twin but for a consumer product it might not be feasible.
So on one hand the CPS which is the visible one is inline with DT which is the invisible one. Where as for many product categories the vice versa is not necessarily true.
Thus in conclusion I think the two have overlapping vision in cases where the product is running in its life cycle with those smart sensor systms onboard whereas for products that render it difficult for onboard systems in their life cycle it will be a difficult trade.
Thanks for the inputs and insights. Digital Twin is a living system that can continuously update its relationship between the original model and the behavioral model for augmented decision making. CPS is a system methodology which provides a fundamental for designing an interactive system within an integrated communication, computing, and control environment.
To understand the similarities and differences between Digital Twin and CPPS, I would suggest the following description:
Cyber-Physical Systems are an integration of digital data and cyber methods with physical processes. Embedded computers and networks monitor and control the physical processes, usually with feedback loops, where physical processes affect computations and vice versa. The Digital Twin is a virtual representation of a physical asset in a Cyber-Physical Production System (CPPS), capable of mirroring its static and dynamic characteristics. It contains and maps various models of a physical asset, of which some are executable,called simulation models.But not all models are executable, therefore the Digital Twinis more than just a simulation of a physical asset. Within this context, an asset can be an entity that already exists in the real world or can be a representation of a future entity that will be constructed.
Cyber Physical Systems (CPS) focus on how a physical system integrates into the cyber system augmented with identification, connection and interaction capabilities, such as autonomous automobile systems and self-organizing/autonomous manufacturing systems. The idea of digital twin originates from the stream of Product Lifecycle Management (PLM), but nowadays, digital twin has evolved into a broader concept that refers to an equivalent digital representation of an object, a process or a system with a real-time update as the physical counterpart changes. For exploring the application of digital twin in the industry, several questions need to be discussed first for better understanding its capabilities and potential benefits. Firstly, for digital twin, it should serve a specific purpose. Secondly, an appropriate set of information should be contained in the digital representation of the physical entity for the purpose. Finally, the digital entity should keep synchronization with the physical entity with appropriate frequency to the purpose. In a recent paper (https://doi.org/10.1016/j.rcim.2019.101917), we explored the application of digital twin in fixed-position assembly with three levels (digital twin of manufacturing object at object level, digital twin of the assembly process of the product at product level and digital twin of the production system at system level), and the paper is attached for your reference.
In my understanding, CPS are the base fot the construction of Digital Twin Models. The basic idea of a CPS is to understand the basic connection of virtual and real environments passing by the communication protocols and even data conversion. Is a mix between control theory and simulation models. DT, on the other hand is related with data integration from the entire lifecycle and on the idea of using this data to understand products evolution and conditions over its life. In the begging of the use of DT concept in industry there was an intersection between CPS and DT. Now, DT depends on CPS to gather and process information.
Attempting to make an abstract delimitation between CPS and DT, I have come to the following conclusion:
Cyber-Physical Systems have: physical components, connectivity and information processing abilities. This enables them to act intelligently, utilizing their models. Here the comparison to DT comes into play. The more broadly defined CPS concept gets partially refined by the DT concept, by having multi-disciplinary models, some of which should be simulation models (i.e. executable models). The DT also has the capabilitiy of synchronization based on dynamically acquired data in order to have an up-to date representation along the entire CPS life-cycle.
As a follow-up to the differences between CPS and DTnoted by Behrang Ashtari, let me add the following.
CPS can exist without DT and even without a model of a physical object (the original), as, for example, in automatic control systems. DT is also possible without CPS. This happens at the stage of the DT prototype when the original does not yet exist in "physics".
But where a model appears in the control loop the most important function of DT is implemented – to be in a "hot" mode relative to the original, especially where the synchronization of the twin and the original should take place at a pace close to the pace of object controling.