Feedforward controller problem

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This post was last edited by lcgllsr on 2016-3-29 23:28. I would like to ask everyone: since a feedforward controller can only be used for one type of disturbance, how is this type of disturbance defined? For example, in the case of a heat exchanger, the main disturbances are the flow rate and inlet temperature of the process fluid. In my understanding, to implement a feedforward controller, two such controllers are needed: one to control the flow rate and another to control the inlet temperature. If that is the case, the book also states that the static feedforward control device in static feedforward control is a multi-input device capable of providing static compensation for the inlet temperature of the material, its flow rate, and the setpoint for the outlet temperature of the heat exchanger. This contradicts my previous understanding, as it seems that this static feedforward control device can handle both the flow rate of the process medium and its inlet temperature as sources of disturbance. Isn’t this a conflict? Should it be understood that: 1. One type of disturbance for which a feedforward controller can be used is the kind of disturbance originating from the process medium, and such disturbance can include multiple perturbation variables. 2. A static control device can include multiple feedforward controllers to compensate for multiple corresponding disturbances. Please give me some suggestions~ Thank you