Indirect and Direct Force Control of a Two-Phase Tubular Permanent Magnet Machine

Vector control and direct torque control are employed extensively in variable-speed ac drive systems, particularly for induction machine drives. This paper describes the application of both control techniques to a two-phase tubular permanent magnet machine supplied from a full H-bridge inverter, with space vector modulation being employed to derive variable-amplitude, variable-frequency, two-phase sinusoidal voltages. The direct force control (DFC) strategy controls the flux and thrust force by means of an active and reactive force estimator, utilizing the concept of active and reactive power. It is demonstrated that compared to vector control, DFC is more effective in compensating for the influence of the cogging force