# A Roadmap to Integrate Digital Twins for Small and Medium-Sized Enterprises
## 4 Discussion
### RQ2: Digitisation and Digital Transformation Strategy  
The purpose of the digitisation of physical assets into 3D models was two-fold. Firstly, the 3D model itself provided a visual representation of the physical asset, in essence the face of its DT, and precise mathematical representations of its behaviours. Secondly, it enabled predictive capabilities in the form of simulations and adjustments of variables. The digitisation process in this study was completed in two stages: (1) the systems model, and (2) the 3D model. The systems model was a process-oriented representation where each element consisted of a mathematical relationship of the inputs and outputs. It was used to map out the physics behind the physical asset, essentially dictating how the DT will behave. For the digitisation process, the platform of choice was important as DT development requires a program with high functionality and versatility [31]. The software would need to be an open platform such that it performs as programmed but gives the users versatility in adapting the software to their specific needs since DT is not a one-size-fits-all methodology. We used one of the enabling DT technologies, i.e., 3 DExperience (described in Section 1.3) for our model development. We started with the 3D model of the micro servo, which was designed in a simpler fashion with the focus on representing the rotational motion. The engineering connections (i.e., constraints) established when assembling the model were used to determine the kinematic motion of the 3D model. Then, we proceeded with the development of a system model. The system model was divided into three components that were deemed to be capable of modelling the behaviour of interest. The first component was designed to create the connection between temperature sensor data and driving input into the electric and logic circuits. Initially, there was a significant challenge of mapping temperature data from the RTD sensor and PLC unit into the 3 DExperience software that did not have readily available connectors. After examining the Modelica library, it was noted that utility functions related to file manipulation were available. After some research into Modelica coding, a block that called the Read File function was built and output it as a real variable to be used at the next stage. The second component contained the electrical circuit, logic components and a brake for driving the moving parts of the servo. The third component was the kinematics of the servo model. These were generated directly from the 3D model; however, it is possible to map out the kinematics directly from the Modelica library similar to Figure 3 in Section 2. The development of the systems model is dependent on the relevant parameters chosen by the SME or user. It is possible to build a comprehensive system model to measure the essential parameters for productivity evaluations. For example, in modelling a crankshaft, where the rotational variables are the topic of interest, the user may omit variables that are not of interest, such as vibration or temperature. This simplified model reduced time and costs, and potentially removed the need for someone with expertise in computer-aided engineering while achieving the same outcome. It is in this stage that predictive simulations can be achieved through adjusting variable values. For example, experimenting with brake variables such as maximum normal force exerted, running the simulation and observing the subsequent changes of the simulation. From the engineering design point of view, our simplified 3D modelling approach may trade off a degree of accuracy when compared to more complex models. However, using this approach, we managed to achieve a model that replicates the live state of the micro servo, can output predictive variable values of the parameters that are adjusted, and did not limit our team from creating an iterative process whereby further details could be added to the DT model in the future.