Monitored control system includes an action device and a monitoring device for monitoring the operation of the action device. The action device includes actuator modules, a sensor module and a control module to command the actuator modules to perform a predefined task using the sensor data. The monitoring device receive monitored data from the action device and compute an action device operation indicator indicative of a correct or abnormal operation of the action device on the basis of the monitored data. The action device operation indicator is computed on the basis of a learned value of an adjustable monitoring parameter. The learned value is determined from a set of labelled data generated from trial datasets recorded by the action device during an iterative learning procedure.