SLVAFF1 January 2023 DRV8452 , DRV8462
PRODUCTION DATA
This section explains how the internal PD control loop smoothens the response to sudden load torque transients while minimizing the error.
Table 2-3 describes the major parameters associated with the PD control loop -
Parameter | Description |
---|---|
KP[7:0], KD[3:0] | Proportional and differential gain parameters for the PD control loop. |
ATQ_AVG[2:0] | The
ATQ_CNT parameter is a moving average of ATQ_AVG number of half-cycles. Therefore, a
high value for ATQ_AVG slows down the loop response time to a sudden peak load
demand, but ensures smooth jerk-free transition to higher torque output. A low value
causes the loop to respond immediately to a sudden load demand.
|
ATQ_FRZ[2:0] | Delay in
electrical half-cycles after which current is changed in response to the PD loop. A
small value increases the current quickly to meet peak load demand. This parameter
has a range of 1 to 7. 001b - Fastest response time, but the loop can become unstable 111b - Slowest response, but the loop will be stable |
ATQ_D_THR[7:0] | If error
change is less then ATQ_D_THR, then KD does not contribute to correction. KD
contributes only when error change is greater than ATQ_D_THR. For example: if ATQ_D_THR = 10, If error change is 9, u(t) = KP * e(t) If error change is 12, then u(t) = KP * e(t) + KD * de(t)/dt |
ATQ_ERROR_TRUNCATE[3:0] | Number of LSB bits truncated from error before used in PD loop equations. A high value reduces any oscillation in the current waveform. |
The PD control algorithm is expressed as -
where,
KP and KD = PD loop constants
Guidelines to tune the PD loop parameters are as follows:
Figure 2-7 is the flowchart for selecting PD control loop parameters.