## 1 Introduction
The electrodes of piezoelectric materials are switched on/off at the voltage extrema of the piezoelectric patch in every vibration cycle. Consequently, the voltage and the structural velocity are always in near opposite direction, providing a (nonlinear) force that hinders vibration of the host structure. It has been well demonstrated that SSD has many advantages in comparison with the passive strategies [26; 27], such as an improved multi-modal damping performance and insensitive with the variation of modal frequencies. Several variants of SSD techniques have been defined, depending on the subsequent electric components, such as SSDS [24] (S for 'on short-circuited'), SSDI [25] (I for 'on inductance'), SSDV [26] (V for 'on voltage source') and SSDNC [27] (NC for 'on negative capacitance'). A large number of experimental studies have been carried out, however most of the host structures are beams [24; 25; 26; 27]. Recently, researchers have started to study the feasibility of applying SSD to bladed disks [28; 29; 30; 31; 32]. Numerical tools are developed for analyzing the steady-state vibration of bladed disks with SSD, based on multi-harmonic balance method [28], nonlinear modal synthesis method [29] and linearization approach [30]. A comparative study between SSDNC and dry friction dampers are conducted [31], and results show both dampers have similar single-mode performance but SSDNC has better multi-mode and multi-engine-order performance. Detailed experimental results on blades and bladed disks can be found in the work of [PERSON] [32]. In these studies, one SSD circuit is required for each blade, therefore the overall number of SSD circuits equals to the overall number of blades (whichcan vary from 20 to 40 in reality). Note that each SSD circuit constitutes a few electric components and requires external power (despite can be very low), thus conventional local SSD configuration may face implement difficulty in reality. In this paper, we propose a new configuration of SSDI strategy for bladed disk, where two blade sectors are interconnected by a shared SSDI circuit thus termed the 'dual-connected SSDI' (Figure 1). In this way, the switching action of SSDI is triggered by the relative displacement between two blade sectors. Note that the idea of interconnected shunt circuits has been explored by various authors for different purposes, for example to enhance the damping performance of passive circuits on bladed disks [11; 12; 13; 14; 15; 16] and to improve the control of wave propagation [33; 34; 35; 36]. The conducted numerical and experimental work concentrate on the application of vibration control of bladed disks. In what follows, we will first show the feasibility of the dual-connected SSDI by numerical studies on a 2-DOF (degree-of-freedom) mechanical system (Section 2). The main findings will be experimentally validated on beam systems with a low-power implementation of the switching circuit (Section 3). Eventually, we conduct numerical simulation on the mistuned bladed disk to highlight the advantages of the proposed configuration (Section 4). Figure 1: The schematic plots of (**a**) the conventional synchronized switching damping inductance (SSDI), (**b**) the dual-connected SSDI with PP (positive-to-positive) connection and (**c**) the dual-connected SSDI with PN (positive-to-negative) connection.