## 4 Experimental Setup  
The experimental setup for the 2 MM Flexible Drive System is illustrated in Figure 2. It includes two incremental encoders for measuring the motor and load speeds, as well as a current sensor for measuring the armature current. Real-time control is achieved using the dSPACE DS1401/1512/1513 MicroAutobox II controller, which interfaces with MATLAB/Simulink and Control-Desk.  
The system comprises an actuating motor on the left side, connected to an inertia disk, a flexible coupling, an encoder, and another inertia disk, forming the first mass. On the right side, there is the second mass, an inertia load connected to a load motor. The actuating motor used in this research is a Buhler DC Motor of model 1.13.075.214. High-resolution encoders with 40,000 PPR are used to measure the angular speeds of the masses. The inertias are supported by ball bearings and interconnected by a torsional shaft.  
To facilitate the identification process, an open-loop current controller with hysteresis current control was implemented in MATLAB/Simulink and later deployed to the dSPACE controller. The hysteresis current controller is sampled at a rate of 20 us, while the speed measurements are sampled every 1 ms. Figure 3 shows the overall system block diagram,  
Figure 2: The two-mass model (2 MM) experimental platform.  
including the hysteresis current controller implementation. In current control mode, the dynamic equation does not explicitly include electrical components like resistance \(R_{a}\) and inductance \(L_{a}\). The current controller effectively handles these parameters to account for their impact on system dynamics.  
The 2 MM system was excited by periodic chirp input current signals with frequencies ranging from \(f_{1}=1\) Hz to \(f_{2}=40\) Hz, an amplitude current of \(A=3\) A, and a time duration ranging from \(T_{0}=0\) s to \(T_{f}=3\) s. Previous research was conducted to identify the parameters of the system. These analyses involved identifying the inertias and stiffness of the system through frequency domain analysis, as well as determining the friction coefficients through time domain analysis [1; 2]. In the time domain identification, the friction coefficients for both the motor and load sides were estimated individually. The approach described in [62] was utilized, which involved using a ramp function as the torque input and performing numerical analysis on speed and torque data to estimate the viscous friction coefficient and Coulomb friction coefficient. For more detailed information on the identification techniques used, interested readers are encouraged to refer to the mentioned papers [1; 2; 62]. The parameters identified in our previous research serve as benchmarks for comparing the results obtained from the proposed methods. In this study, we normalized these parameters using the rated values of the DC motor provided in the datasheet. This normalization improves the interpretability, robustness, and consistency of the results, as well as the numerical stability of the simulation models. The identified benchmark parameters of the 2 MM system are presented in Table 1, both in their SI units and normalized units.