A comparison of Sliding Mode approaches to a nanometre position control application

A vacuum air bearing based linear drive is presented that is capable of precision positioning with a relative accuracy of a few nanometres. Three different control systems embodying sliding mode control (SMC) are compared by simulation and experiment regarding their individual positioning performance. The three control designs investigated are high gain SMC, a first order and a second order version of outer loop SMC where the inner loop consists of a forced dynamic control law (FDC, a special form of state space controller) applied to the linear drive to be positioned.