FOC requires precise position knowledge of rotor magnetic field to create appropriate stator magnetic field， oriented to produce maximum torque. 1. Costly sensor （encoder/resolver） - Mechanical alignment - Not necessarily magnetic unless “absolute” 2. Complex software algorithms （model observers） + Lower cost and no repair or replacement + Can be used where sensors can’t be - Not appropriate for FOC with position control TI’s new FAST software sensor is Superior + Works with synchronous & asynchronous motors 5 + Model relies on fewer motor parameters + Optional start-up parameter ID tool + Optional run-time parameter tracking + Observer requires no tuning + More accurate， more dynamically robust + Stable at and through zero speed + Stall recovery + Better at start-up under load + Parameters used to set FOC current controllers + Highest fidelity feedback signals - / + Proprietary technique， no source given