SLLA665 April   2025 MCF8315A , MCF8315C , MCF8315C-Q1 , MCF8315D , MCF8316A , MCF8316C-Q1 , MCF8316D , MCF8329A , MCF8329A-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Open Loop and Handoff Stage
  5. 2EEPROM Configurations Affecting Open Loop to Closed Loop Handoff
  6. 3Open Loop to Closed Loop Handoff Tuning
    1. 3.1 Experimental Way to Tune Open Loop and Handoff Stage
      1. 3.1.1 Step-1: Initial Configuration
      2. 3.1.2 Step-2: Tuning of Parameters In Case Handoff is not Proper
        1. 3.1.2.1 Tuning of OL_ILIMIT
        2. 3.1.2.2 Tuning of Open Loop Acceleration Co-Efficient A1
        3. 3.1.2.3 Tuning of Handoff Thresholds
      3. 3.1.3 Step-3: Tuning of Handoff Configurations
  7. 4Optimum Handoff
    1. 4.1 Open Loop Time With the Recommended Settings
    2. 4.2 Open Loop Time by Following Optimum Handoff Steps
  8. 5Summary
  9. 6References

3.1.3 Step-3: Tuning of Handoff Configurations

After pass off to closed loop at a sufficient speed, there can be still some theta error, if the estimator is not fully aligned. The MCF83xx device brings down this theta error to zero, before transitioning to closed loop, at the rate of THETA_ERROR_RAMP_RATE. This state is referred as CLOSED_LOOP_UNALIGNED_STATE. The speed reference in this state follows CL_SLOW_ACC (suggested value is half of CL_ACC) .

Above parameters are to be tuned for a smoother phase current profile in handoff state, this depends on the how IQ_REF_CLOSED_LOOP varies post open loop state, which in turn depends on THETA_ERROR_RAMP_RATE, CL_SLOW_ACC, SPD_LOOP_KP and SPD_LOOP_KI.

The following are few captures to show how the THETA_ERROR_RAMP_RATE affects the IQ_REF_CLOSED_LOOP variations during handoff stage and thus current profile for a given CL_SLOW_ACC, SPD_LOOP_KP and SPD_LOOP_KI. IQ_REF_CLOSED_LOOP is brought out on the DACOUT1 pin of the device.

For THETA_ERROR_RAMP_RATE = 111b, the IQ_REF_CLOSED_LOOP is varying at faster rate, and we observe more oscillations in motor phase current

THETA_ERROR_RAMP_RATE = 111b Figure 3-6 THETA_ERROR_RAMP_RATE = 111b

For THETA_ERROR_RAMP_RATE = 000b, the IQ_REF_CLOSED_LOOP is varying at slower rate, and we observe oscillations getting damped out in motor phase current.

THETA_ERROR_RAMP_RATE = 000b Figure 3-7 THETA_ERROR_RAMP_RATE = 000b
Note: Recommended setting for THETA_ERROR_RAMP_RATE is 100b. Increase this setting for a faster IQ_REF_CLOSED_LOOP variation at handoff point and decrease this setting to slow down the IQ_REF_CLOSED_LOOP variation at handoff point.