## 3 Experimental Setup  
The experimental setup is shown in Figure 2. A data acquisition system with 16-bit resolution and 1 MHz maximum repeat rate (IOtech WaveBook 516) is used to collect data and a laser displacement sensor with 0.6 \(\upmu\)m repeatability, 150 mm reference distance and \(\pm\)40 mm measurement range (Keyence LK-G155H) is used to record the displacement of the primary cantilever beam. A vibration exciting motor with an unbalanced mass (WS-25 GA370R) is used to generate a harmonic excitation on the end of the cantilever beam. The sampling frequency is set to 1000 Hz. The higher modes of vibration of the controlled structure will reduce quickly due to the higher damping ratio in higher modes. Therefore, the dominant vibration mode of the cantilever beam will be the first vibration mode. Therefore, the detuned characteristics under the first natural frequency are only considered in this paper. The fundamental frequency of the primary cantilever beam can be adjusted by changing the placement of a lumped mass (0.4 kg) on the cantilever beam, as shown in Figure 3. The primary cantilever beam is shown in Figure 3. When the movable lumped mass is set in  
Figure 1: A cantilever beam controlled by an eddy current tuned mass damper (ECTMD). Figure 2: Experimental setup for robustness study. the middle of the cantilever beam, the fundamental frequency of the beam is 3.53 Hz. When the weight is placed at the free end of the primary cantilever beam, the fundamental frequency of the cantilever beam is 3.05 Hz, and when it is moved close to the fixed end, the fundamental frequency is 4.06 Hz. An electric motor with an unbalanced mass, which is used as a vibration exciter, is installed at the free end of the primary cantilever beam, as shown in Figure 3. The parameters of the primary cantilever beam are listed in Table 1.  
The vibration suppression of the damper is much more effective when the damper is installed at the location where the maximum mode displacement happens [45]. In this study, the maximum mode displacement of the cantilever beam happens at the free end, and therefore the ECTMD or TMD is fixed at the free end. The configuration of the designed ECTMD is shown in Figure 4. The ECTMD consists of a small cantilever beam, a copper plate and a cube of acrylic glass embedded with a disk magnet. One end of the small cantilever beam is fixed on the controlled cantilever beam, and the other end is attached to the cube acrylic glass. The copper plate is fixed on the primary cantilever beam. The gap between the magnet and the copper plate is 3 mm. When the copper plate is removed from the cantilever beam, the ECTMD becomes a TMD. Since the mass of the thin copper plate is relatively small, the fundamental frequency of the cantilever beam will not be affected. Some parameters of the small cantilever beam, the copper plate and the cylindrical magnet are listed in Tables 2-4. When the fundamental frequency of the cantilever beam is changed from 3.06 Hz to 4.05 Hz, dynamic properties of the ECTMD and TMD, such as the frequency, remain at a constant value, equal to 3.53 Hz. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Material & Stainless steel 304 \\ Length & 750 mm \\ Width & 40 mm \\ Thickness & 5 mm \\ Adjustable frequency range & 3.06 Hz\(\rightarrow\)4.05 Hz \\ \hline \end{tabular}
\end{table} 
Table 1: Parameters of the primary cantilever beam. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Material & Stainless steel 304 \\ Length & 180 mm \\ Width & 30 mm \\ Thickness & 0.3 mm \\ \hline \end{tabular}
\end{table} 
Table 2: Parameters of the small cantilever beam. Figure 3: A moveable lumped weight installed on the cantilever beam.