## 2 Related Work  
Integrated Vehicle Health Management (IVHM), as described in [10], has remained a key approach in optimizing maintenance of the aircraft and its vital systems. It is realized by generating a mechanism to analyze the data obtained from field operations through sensors and subsequently build efficient techniques for diagnostics and prognostics to assess the health of aircraft systems and structures in the real time. Although holistic in nature, the IVHM approach is not time- and resource-efficient,Application of IVHM in an EBS environment can be, however, made beneficial with the development and assimilation of rapid evaluation methods within IVHM.  
With respect to optimizing the digital modelling approach for braking systems, a number of models have been developed and simulated using the MATLAB/Simulink environment with a variety of results obtained under different specific conditions. For example, in [11], an anti-skid braking system (ABS) is integrated onto the model to assesses the performance of the system under different landing conditions. Similarly, an experimental model in [12], built for an EMA, is integrated into EBS and subjected to different asphalt conditions for investigating system behavioral response. Another digital model for the braking system in [13] employs a controller to stabilize the slip value and evaluate the system behaviour, thereby enhancing the performance evaluation capability of the model.  
Looking further, the EMA modelling approach, presented in [14], shows how an EMA can best be represented by a mathematical model using the MATLAB/Simulink environment. The model, when integrated with the aircraft electric braking system model, helps evaluate the reduction in the angular wheel speed against the aircraft speed, and gives a better picture of the systems' overall performance.  
In another study in [15], an ABS control for EBS employs an EMA model to evaluate the behaviour of the force applied to ABS braking system. The model helps make valuable assessments on the wheel and vehicle speed reduction responses. However, it lacks the consideration for adding some key factors such as motor angular velocity, force, and motor voltage as well as current to the model, that could provide a more holistic evaluation of the braking system reliability.  
Recently, the interaction of a physical and digital machine, termed as digital twin (DT), with connectivity and data flow in both directions (as shown in Figure 1), is being actively pursued to increase the safety and reliability of aircraft and its systems through near-realistic predictive analysis [7]. It implies ensuring optimal fidelity level in order to attain an accurate assessment of system condition, as well as providing a viable prognosis as an integral part of the overall health management regime. This can be, however, further augmented with techniques such as those presented in this paper--the qualitative validation.  
The aforementioned approaches, aimed at optimizing the health management (including CBM) of electromechanical actuators and the aircraft electrical braking and anti-skid braking systems they serve, are limited to building models, factoring in different mechanical and electrical parameters, and then assessing their performance and reliability. On the one hand, the IVHM approach relies on the data acquired through multiple sensors and their analysis to maintain the integrity and ensure  
Figure 1: The interaction between physical and digital objects depicting the difference between a “digital model” and “digital twin”.  
the availability of systems/sub-systems; digital models, on the other hand, provide efficient means of leveraging that data and constructing system performance and reliability profiles to help strategize associated maintenance activities. Our qualitative validation approach is a step further to augment and provide these approaches with more efficient and effective health management and condition-based maintenance regime for EMAs.