Interface

class RoboPid

setGains(Kp, Ki, Kd)

sets the gains:

Kp - proportional gain

Ki - integral gain

Kd - derivative gain

Param: Kp - proportional gain
Param: Ki - integral gain
Param: Kd - derivative gain
Returns: None

getGains()

get the currently set gains

Kp - proprotional gain
Ki - integral gain
Kd - derivative gain

Returns: (Kp, Ki, Kd)
Return type: tuple

setKp(Kp)

sets the proportional gain Kp

Param: Kp - the proportional gain

getKp()

get the current proportional gain Kp

Returns: Kp
Return type: float

setKi(Ki)

sets the integral gain Ki

Param: Ki - the integral gain

getKi()

get the current integral gain Ki

Returns: Ki
Return type: float

setKd(Kd):

sets the derivative gain Kd

Param: Kd - the derivative gain

getKd()

get the current derivative gain Kd

Returns: Kd
Return type: float

setIntegrateModeOn()

Turns integrative mode on

In integrative mode, the timestep integrations are calculated inside the controller and the output from the PID controller for the current timestep is used directly or with modifications and sent to the device or process plant as the current input signal. The integrations are cumulative across all timesteps until the PID controller is restarted with reset() or resetAll()

Param: None
Returns: None

setIterateModeOn()

Turns iteration mode on

In iterative mode, the PID timestep integrations are manually calculated and updated outside the controller in the algorithm that calls the PID controller for the output of the PID at the current timestep. The output of the PID is localized to this timestep and not cumulative across all calls for the PID output since the start or restart of the controller by calling reset() or resetAll(). The accumulative effect of the PID is handled by the functional algorithm that is using the PID controller and then sent to the device or process plant as an input signal.

Param: None
Returns: None

inIntegrateMode()

check if using integrative mode for PID evaluation

Returns: True if in integrative mode and False if not
Return type: Bool

inIterateMode()

check if using iterative mode for PID evaluation

Returns: True if in iterative mode and False if not
Return type: Bool

setTimeinc(time_inc)

Sets the discrete timestep increment value used in integrative calculations. time_inc can be any positive value. Set the time_inc unit of measurement to be the same unit as the sample rate of current signal. This value can be changed dynamically while the controller is running to adjust to changes in the frequency of the input signal if necessary.

Param: time_inc
Returns: None

getTimeinc()

returns the current discrete timestep increment value

Param: None
Returns: time_inc

getPid(signal_ref, signal)

Returns the results of the PID equation evaluation since the last call to this function. It is usually called at each timestep interval that is synced to the measured signal that samples at the same timestep interval frequency. Calculation, accumulative and persistent values depend on the mode setting.

Param: signal_ref - reference signal value
Param: signal - current measured signal value returned by process
Returns: result of PID equation eval
Return type: float

getPidTuple(signal_ref, signal)

Returns tuple form of the components of the PID equation since last evaluation that was initiated by calling getPid(…) or an equivalent.

param

signal_ref - reference signal value

param

signal - current measured signal value returned by process

return

components of PID equation evaluation (Kp P, Ki, I, Kd, D)

Kp - proprotional gain

P - result of proportional term evaluation

Ki - integral gain

I - result of integral term evaluation

Kd - derivative gain

D - result of derivative term evaluation

Return type: tuple

pid(signal_ref, signal): short form for getPid(…)

get(signal_ref, signal): short form for getPid(…)

reset()

Resets the controller for a new run. Clears out integration results but keeps the currently set gains and mode parameters intact.

Param: None
Returns: None

resetAll()

Resets all runtime variables to the the object instance initialization state. Gains and timestep increment values are also set to default values. Previous integration results are cleared.

Param: None
Returns: None