SLVAFF1 January   2023 DRV8452 , DRV8462

PRODUCTION DATA  

  1.   Abstract
  2.   Trademarks
  3. 1Power Efficiency of Stepper Motor Drivers
  4. 2Auto-Torque
    1. 2.1 Auto-Torque: Learning Principle
      1. 2.1.1 Configuring Auto-Torque Learning Routine
    2. 2.2 Current Control
      1. 2.2.1 Setting Current Control Parameters
    3. 2.3 PD Control Loop
    4. 2.4 Impact of Auto-Torque Tuning Parameters
      1. 2.4.1 Impact of Learning Parameters on Load Transient Response
      2. 2.4.2 Impact of ATQ_UL, ATQ_LL Hysteresis
      3. 2.4.3 Impact of Load Profile on Power Saving
      4. 2.4.4 Adaptive ATQ_UL, ATQ_LL
      5. 2.4.5 PD Parameter Dependency Curves
        1. 2.4.5.1 Dependency on KP
        2. 2.4.5.2 Dependency on KD and ATQ_D_THR
        3. 2.4.5.3 Dependency on ATQ_FRZ and ATQ_AVG
        4. 2.4.5.4 Dependency on ATQ_ERROR_TRUNCATE
      6. 2.4.6 ATQ_CNT at Different Motor Speeds
      7. 2.4.7 ATQ_CNT at Different Supply Voltages
      8. 2.4.8 Motor Temperature Estimation
    5. 2.5 Efficiency Improvement With Auto-Torque
  5. 3Case Studies
    1. 3.1 Application 1: ATM Machines
      1. 3.1.1 ATM Motor Operating Conditions
      2. 3.1.2 ATM Motor With Auto-Torque
    2. 3.2 Application 2: Textile Machines
      1. 3.2.1 Textile Motor Operating Conditions
      2. 3.2.2 Textile Motor With Auto-Torque
    3. 3.3 Application 3: Printer
      1. 3.3.1 Printer Motor With Auto-Torque
  6. 4Summary
  7. 5References

2.2.1 Setting Current Control Parameters

The following methodology explains how you select the values of the current control parameters:

ATQ_TRQ_MIN is the minimum motor current needed to support the minimum load torque applied to the motor.

  1. To find this parameter:
    1. Load the motor with minimum load torque (TMIN) and drive the motor with full-scale current (IFS).
    2. Set ATQ_UL and ATQ_LL to zero and set KP as 1.
    3. Reduce current till the motor stalls.
    4. Note the current (IA) at which the motor stalls.
    5. Set ATQ_TRQ_MIN = 1.1 x IA.
  2. To find ATQ_TRQ_MAX:
    1. With the motor current at IA, load the motor with maximum load torque (TMAX) and the motor will stall.
    2. Start increasing the motor current. Note the current (IB) at which the motor restarts from stall.
    3. Set ATQ_TRQ_MAX = 1.1 x IB. Note the ATQ_CNT (AMAX) with current at ATQ_TRQ_MAX and load torque at TMAX.
  3. For the ATQ_UL:
    1. Set an initial value of 0.5 x AMAX.
    2. Apply the load profile (peak load and idle load) specific to the application.
      1. If the motor stalls, decrease the value ATQ_UL until the motor is no longer stalled.
      2. If the motor does not stall after applying the load profile, ATQ_UL can be increased until the motor stalls.
    3. Higher value of ATQ_UL saves more power at peak load, but in case of a fast load transient, the motor can stall.
    4. Lower value of ATQ_UL reduces the power saving at peak load, but also reduces the chances of motor stall and step loss.
  4. For most applications, a difference of 2 between ATQ_UL and ATQ_LL is a good starting point.
  5. VM_SCALE bit should be made 1b only after ATQ_UL and ATQ_LL have been set by the user.

The flowchart for selecting ATQ_UL, ATQ_LL, ATQ_TRQ_MAX and ATQ_TRQ_MIN parameters is shown in Figure 2-6.

Figure 2-6 Selecting ATQ_TRQ_MIN, ATQ_TRQ_MAX, ATQ_UL, ATQ_LL