“…Piezoelectric motors have attracted numerous attentions due to their superior merits over electromagnetic motors such as simple/compact structure, self-locking when power off, low speed with high torque, quick response, and quiet operation (Jian et al, 2017;Liu et al, 2018Liu et al, , 2019Lv et al, 2017). These advantages make them competitive candidates not only for conventional fields including micro-robot (Shen et al, 2017), medical instruments (Liang et al, 2018), and nanopositioning stages (Lee and Lee, 2015) but also for special field such as space exploration (He et al, 2014;Kubota et al, 2008) and weapon system (Diwiny et al, 2014;Tang et al, 2017).…”