# A Novel Ropes-Driven Wideband Piezoelectric Vibration Energy Harvester
## 3 Device Configuration and Experimental Setup  
A vertical view of the experimental system is illustrated in Figure 4. As shown in Figure 4a, AB-VEH is composed of a three-beam array with piezoelectric material, PZT (Sinoceramics, Ins., Shanghai, China). The beams array comprises a brass supporting base attached with a PZT (5 mm \(\times\) 14 mm \(\times\) 0.15 mm) layer and copper proof mass attached to the top of beams. The resonant frequencies of these three beams are 58.8, 64.4, and 69.8 Hz, respectively, and the detailed geometry is shown in Table 1. In addition, the three piezoelectric beams of the array have the same optimal load resistance of 250 k\(\Omega\), and are connected in parallel and series to measure the maximum output power with optimal load resistance. The characteristics of output power are compared with the proposed VEH system to verify the novel system's superior output performance with the increasing number of beams. The novel VEH system has a configuration similar to the AB-VEH system, but the novel VEH system is composed of one HFGB, besides three brass beams array as LFDBs, as shown in Figure 4b. The HFGB comprises a brass supporting base (39.2 mm \(\times\) 14 mm \(\times\) 0.5 mm) attached with a PZT layer (20 mm \(\times\) 14 mm \(\times\) 0.15 mm) without inertial mass, and the resonant frequency is 206.8 Hz. Three LFDBs have similar dimensions and configuration with that of the beams array of the AB-VEH system, but without a piezoelectric layer, and the resonant frequencies are 64.4, 69.8, and 75.6 Hz, respectively, and the detailed geometry is shown in Table 1. Meanwhile, the dacron-ropes are used to connect the HFGB with LFDBs with the same predetermined rope margins of 0.8 mm. When the vibration amplitude of LFDBs is larger than the rope margin, the HFGB is triggered by the ropes into a high-frequency self-oscillation, and the electric current is generated once the PZT layer on HFGB deforms. The characteristic of output power is measured under optimal load resistance with the increasing number of LFDBs. Figure 4: Experimental geometric construction of AB-VEH (**a**) and novel VEH (**b**) systems. Figure 5 shows the detail experimental setup of the novel PVEH system. To experimentally study the output power, wide bandwidth, and adjustable performance of the novel PVEH system, a precise adjustment system was used to finely adjust the rope margins between the HFGB and LFGB. As shown in Figure 5a, the precise adjustment system comprises a micro-stage, a micrometer, and a circular support. The HFGB is fixed on the micro-stage and then fixed to the circular support, the LFDBs array is fixed on the support directly under the HFGB, such that the relative position of the HFGB and LFDBs can be adjusted accurately by the micrometer with a precision of 0.01 mm in the \(z\)-direction. The entire precise adjustment system and the accelerometer are mounted on a vibration shaker as shown in Figure 5b. The vibration frequency and amplitude of the shaker are controlled by a signal generator through a power amplifier. The HFGB is connected with the resistance box, which is as the resistance load, and the voltage of the load is recorded by the DAQ (data acquisition); meanwhile, the acceleration of the system amplified by the charge amplifier is also recorded by DAQ. The AB-VEH system has a similar vibration testing setup which only needs the piezoelectric beams array fixed on the support. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Beam 1** & **Beam 2/LFDB1** & **Beam 3/LFDB2** & **LFDB3** & **HFGB** \\ \hline Length (mm) & 50.3 & 46.8 & 48.3 & 48.3 & 39.2 \\ Width (mm) & 15.0 & 15.0 & 15.0 & 15.0 & 14.0 \\ Thickness (mm) & 0.4 & 0.3 & 0.4 & 0.4 & 0.5 \\ Hypotense length (mm) & 17.8 & 19.8 & 19.9 & 19.0 & - \\ Proof mass (g) & 2.2 & 1.2 & 2.2 & 2.2 & - \\ Frequency (Hz) & 58.8 & 64.4 & 69.8 & 75.6 & 206.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The parameters of AB-VEH and novel VEH systems.