Speed controller design for a vector-controlled permanent magnet synchronous motor drive with parameter variations

When classical techniques are used for designing fixed-structure speed controllers for AC drives, the design is normally done around a nominal value of the controlled plant. Generally, a sensitivity analysis is subsequently done to ensure that the design specifications are met when the plant parameters change. An alternative is proposed where the parameter variations are included at the outset of the design task. The Nichols chart lends itself rather well to this application since it represents both magnitude and phase information on a single diagram. By using this alternative, it may be possible to reduce the overall time needed to complete the design. The particular technique, quantitative feedback theory (QFT), is used in conjunction with the Nichols chart. The basics of QFT are presented, and it is shown how it can be used for the design of fixed-structure controllers for parameter-sensitive plants. A design is presented and verified experimentally.<>