ClosedLoop module

Implements a PID algorithm, with integral saturation limits

Allows for a different time period to be used each update, so the algorithm does not have to run with constant timing.

class ClosedLoop.ClosedLoop(Kp, Ki, Kd, lowerSatLimit, upperSatLimit)

Bases: object

PID Controller with changeable setpoint and gains.

Does not need to run at a set frequency, adjust gains based on user-input time deltas.

Parameters:

  • Kp (float) – value of proportional gain

  • Ki (float) – value of integral gain

  • Kd (float) – value of derivative gain

  • lowerSatLimit (int or long) – Lower saturation limit for I path.

  • upperSatLimit (int ot long) – Upper saturation limit for I path.

calculateEfforts(currentValue, msTimePassed)

Calculates P, I, D efforts

Saturated according to set saturation bounds. Use this in an interrupt routiene that is called at the same period according to samplePeriod.

Parameters:

  • currentValue (float) – Current “actual” value used to calculate error.

  • msTimePassed (float) – Time passed in ms since function last called. Used to calculate I and D efforts.

Returns:

[P effort, I effort, D effort]. The effort itself is not saturated.

Return type:

list of float

clearIntegral()

Sets integrated error to 0 but does not turn I path off

To disable the I path, use SetKi to change the I gain to 0

getError()

Returns list of errors used to caluclate P, I, and D efforts.

Returns:

[currentError, integratedError, rateOfError] list of errors according to each path.

Return type:

list of floats

getTarget()

Returns target value in-use by PID

Returns:

Target value

Return type:

float

setKd(Kd)

Sets D gain.

Parameters:

Kd (float) – D gain.

setKi(Ki)

Sets I gain.

Does not affect integrated error.

Parameters:

Ki (float) – I gain.

setKp(Kp)

Sets P gain

Parameters:

Kp (float) – P gain

setSatLower(lowerSatLimit)

Sets the lower saturation limit

Parameters:

lowerSatLimit (float) – lower saturation limit for integral error. Not a limit on the magnitude of the I effort.

setSatUpper(upperSatLimit)

Sets the upper saturation limit

Parameters:

upperSatLimit (float) – upper saturation limit for integral error. Not a limit on the magnitude of the I effort.

setTarget(target)

Changes target value.

Does not change I path.