This function is used to control a discrete actuator in period modulation. The logic output is set at 1 following a period proportional to the command calculated by the PID and to the given period modulation. The cyclic ratio of this type of output is defined as being the output activity rate, meaning the time ratio when the output is active throughout the whole period. The cyclic ratio (expressed in %) of a PMW output is therefore equal to the command calculated by the loop controller (expressed in %).

(*) Hot/Cold or Split Range case

The function period must be chosen according to the characteristics of the actuator. Therefore it is logical that the function period is equal to the loop controller sampling period because the actuator would not be in a position to take faster account of a sampling command.

The time base used for modulation is the MAST task period or the FAST task period. In other words, the smallest available pulse lasts for the task period. However, the user is able to define a minimum pulse that is greater using the T_MINI parameter , so that the actuator constraints may be respected.

The larger the PMW resolution function, the more precise the command carried out will be. The resolution is defined by the relationship between: sampling period / task period. A minimum of 10 is recommended.

For example, if the sampling period = 2 s (chosen according to actuator characteristics), the task period must not exceed 200 ms.

The system indicates a processing error in the following cases:

In each case, the error is considered to be serious. The loop output is frozen, while errors are signaled in the status words.