5.3.2.3.1. Implementation issues common to all methods

5.3.2.3.1.1. API of qei_sync

Each of the back-emf synchronization methods has been designed to meet the following API for all methods:

• The generated code is located in the qei_sync module

• Dependencies of the qei_sync module

  • It may depend on the startup and qei modules
  • There are no dependencies on the system_state or commutation modules
  • It does not access any HAL functions directly

• State data of the qei_sync module

  • is located in motor.estimator.qei.sync
  • has type MCAF_QEI_SYNC_T
  • motor.estimator.qei.sync.complete is a flag that denotes whether back-emf synchronization is complete. To re-run the synchronization, set this flag to false using the real-time diagnostic software.

• Methods

  • MCAF_EstimatorQeiSyncInit() — initialization function, runs once

  • MCAF_EstimatorQeiSyncStep() — update function, runs in control ISR, returns action flags to influence startup behavior in certain states. These action flags are only valid in startup states with a status code of MSST_ALIGN or MSST_SPIN. The return value can contain any of the following bit flags:

    • MESACT_DELAY — startup state machine will be delayed, and remain in its current state
    • MESACT_SET_CURRENT `` --- ``MCAF_EstimatorQeiSyncOverrideCurrent() will be called
    • MESACT_SET_ANGLE — MCAF_EstimatorQeiSyncOverrideAngle() will be called
    • MESACT_SET_FREQUENCY  – ``MCAF_EstimatorQeiSyncOverrideFrequency() will be called

  • MCAF_EstimatorQeiSyncIsComplete() — returns whether synchronization is complete

  • MCAF_EstimatorQeiSyncGetCommutationOffset() — returns commutation offset computed by the qei_sync module. This result is only required to be valid if synchronization is complete (otherwise this function’s return value should be considered invalid)

• Override handlers

  The handler functions listed below are special methods that get called during appropriate stages of the startup sequence. A pointer to specific data is provided by the caller. This facilitates modularity by eliminating coupling between the startup and qei_sync modules; intercommunication is performed in the commutation module.

  Each handler has the option to change data or not, and is generally declared inline static so that an empty handler function would be optimized out.

  Method	Applicable state	Behavior
  MCAF_EstimatorQeiSyncOverrideCurrent()	MSST_SPIN	Can set current
  MCAF_EstimatorQeiSyncOverrideAngle()	MSST_ALIGN	Can set the applied electrical angle
  MCAF_EstimatorQeiSyncOverrideFrequency()	MSST_ALIGN	Can set the applied electrical frequency

5.3.2.3.1.2. Important data elements

The following data members are available, regardless of which qei_sync method is used:

• motor.estimator.qei.position.commutationOffset — controls commutation offset, which is the angle added to the raw electrical angle from the encoder before it is used for commutation. This can be modified using a real-time diagnostic tool to adjust the commutation offset while the motor is running. Any such changes should be slow: maximum recommended step size is 11 electrical degrees (2000 counts). Step changes larger than this may cause the control loops in FOC to lose synchronism.
• motor.estimator.qei.position.commutationOffsetFromIndex — this is a convenience calculation provided at the end of back-emf synchronization, and it measures the commutation offset relative to the index position within one electrical cycle. When using a motor with an encoder that has an index pulse, the values of commutationOffsetFromIndex will be fairly consistent, independent of the starting position of the motor when the QEI peripheral is enabled.