“…Many methods have been proposed to detect displacement or clearance over the last few decades (e.g., capacitive sensors [ 12 ], magnetic sensors [ 13 , 14 , 15 ], microwave sensors [ 16 ], optical sensors [ 17 ], and inductive sensors [ 18 , 19 , 20 ]). Compared with other methods, capacitive sensors have the advantages of high resolution and good dynamic performance [ 21 , 22 , 23 , 24 , 25 ].…”