# A Robust Generator-Harvester for Independent Sensor Systems +
## 4 Experiments  
Considering the previously published approaches referred to above, especially in the introduction, an experimental concept of a generator with a renewable form of energy and a linear displacement-driven generator (compressed gas [38]), we proposed the specific arrangement shown in Figure 2. The renewable form of energy in compressed gas is considered in car-based transportation systems that perform braking via compressing air into a container, the air being subsequently used as \"renewable energy\", or, by a more exact definition, extracted from the energy during braking, engine starting, and other relevant action. The concept employs two piston units (Figure 5b,c) driven by CO2 or N2, which are adapted from a CO2 engine (Figure 5a). The power unit and the link to the electromagnetic generator are schematically represented in Figure 5b. The theoretical properties of the magnetic flux transition from the moving to the fixed part of the magnetic circuit through air (Figure 4) were utilized in the design of the experimental embodiment (Figure 5d) of the  
Figure 4: Examples of pole attachment geometry FEM solutions, single- or double-acting models: (**a**) the magnetic flux modulus \(B\), and (**b**) the fluxlines 1 in the detailed design of a magnetic flux converter.  
generator concept, comprising both the single-acting and the double-acting embodiments (Figures 3 and 4, respectively). Figure 6 shows the single-segment setup for the experimental verification concept of the single-acting generator design (Figure 2). Figure 5c then details the full setup of the experimental fixture with four segments, in the single-acting design (Figure 2), and the setup for the load mode test \(Z_{1,\text{Re}}=150\)\(\Omega\), \(Z_{2,\text{Re}}=1000\)\(\Omega\), and \(Z_{3}=\alpha\)\(\Omega\).  
Figure 5: The linear generator drive unit: (**a**) CO\({}_{2}\) engine, (**b**) unit arrangement, (**c**) experimental arrangement, (**d**) detail of the pole adapter—flux converter of segment I (the concept from Figure 2).  
Figure 6: The experimental part (one segment) of the verification of the single-acting variant of the harvester, type I, type II.  
The windings of the coils with turn \(N_{1}\), \(N_{2}\), \(\ldots\), \(N_{4}\) of the experimental generator are connected in series with, in one sense, polarity of the output voltage on the coil. In segment I, the number of the coil turns was \(N_{1}=1000\), and the linear motion speed equaled \(v=4\) m/s. The unit was driven by compressed gas N\({}_{2}\) at a pressure of \(p=10\) bar (Figure 7), and \(m_{\text{m}}=150\) g according to Equations (14)-(16). A comparison of the measurements for one module of concepts I to III (Figures 1-3) is shown in Table 2. The measuring tasks in Table 2 were performed with an oscilloscope in real time, and the mean value of the quantity was subtracted from the preset steady values. The amount of the measurements was greater than \(n=30\). The type A uncertainty is attached. Below (Figure 8), we show the concept of a periodic arrangement of the harvester from segments with expected parameters that meet the desired power (in the band \(P=10\)-\(10\),\(000\) W) while maintaining the resistance and lifetime prerequisites, meaning a robust approach and device.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Measurement HV@\(n=30\)** & * **Type I** & \(n_{\text{A,I}}\) & **Type II** & \(n_{\text{A,II}}\) & *** **Type III** & \(n_{\text{A,III}}\) \\ \hline \(U_