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Sensor Systems in Engineering
Published in Clarence W. de Silva, Sensor Systems, 2016
Better results can be obtained by measuring these disturbance inputs and using that information in generating the control action. This is feedforward control. Note that in the absence of feedforward control, any changes in the inputs w1, w2, and w3 in Figure 1.5 would be detected only through their effect on the feedback signal (i.e., room temperature). Hence, the subsequent corrective action can considerably lag behind the cause (i.e., changes in wi). This delay will lead to large errors and possible instability problems. With feedforward control, information on the disturbance input wi will be available to the controller immediately, and its effect on the system response can be anticipated, thereby speeding up the control action and also improving the response accuracy. Faster action and improved accuracy are two very desirable effects of feedforward control.
Demand Calibration in Multitask Environments: Interactions of Micro and Macrocognition
Published in Emily S. Patterson, Janet E. Miller, Macrocognition Metrics and Scenarios, 2018
Feedforward control uses the anticipated future state of the system to guide behavior. Feedforward control is critical for safe driving; it enables experienced drivers to detect hazards more reliably than inexperienced drivers (McKenna et al., 2006). Feedforward control can compensate for the limits of feedback control, but it suffers from other problems. Feedforward control requires an accurate internal model to anticipate the future state of the system and is vulnerable to unanticipated disturbances. The uncertainty associated with poor mental models of the roadway and the IVIS coupled with inherent variability limits the effectiveness of feedforward control to modulate attention between the road and the IVIS.
Measurement and Control in Food Processing
Published in Mohammed M. Farid, Mathematical Modeling of Food Processing, 2010
Feedforward control is often used in conjunction with feedback control to improve the performance of both. Feedforward control, adjusts for error in the input, while the feedback control adjusts for errors generated within the process measured at the output. Moriera et al.11 provide an example of feedforward control being used on a cooking extruder. They suggest that feedforward control can help to eliminate variation in the die pressure caused be varying feed rate and feed moisture content. Moriera et al.11 also suggest that for tight control, feedforward control of the extruder should be used with feedback control.
Tuning rules for feedforward control from measurable disturbances combined with PID control: a review
Published in International Journal of Control, 2021
A regulation control problem is classically known as the design of a feedback control law to reduce the disturbance effects on the process variable. In that problem, it is assumed that the load disturbance is unmeasurable and therefore no information is available about the disturbance signal. However, in many cases, disturbances can be measured and this information can be incorporated into the feedback loop to contribute to the disturbance rejection. This is the main idea of the feedforward control approach, as its name indicates. That is, the disturbance signal is measured and fed in advance (forward) into the loop before affecting the process output. Thus, feedforward control is proactive against load disturbances, while a feedback control scheme is a reactive since it acts once the process output has been modified by the disturbance signal (Liu et al., 2019).
Dynamic Control of Pressure Drop Oscillation in a Microchannel Cooling System
Published in Heat Transfer Engineering, 2021
Qi Jin, John T. Wen, Shankar Narayanan
This strategy involves using feedforward control for all the system inputs based on the chosen optimum operating conditions for the anticipated change in the evaporator heat load (Figure 7(a)). Applying the feedforward control is the fastest control method since the response of system inputs only depends on the response time of the individual components. Figure 7 shows that the system response for 9%, 9 Hz, and 400 W, which is the optimum operating condition for 300 W, when changes from 300 to 280 to 325 W. In this case, the PO is 15%, the ST is 4 s. With this controller, the evaporator wall temperature, Twe, cannot be maintained at the optimum condition listed in Table 2 since there is no error control for Twe. Hence, the system does not achieve the maximum possible performance.
Grid Synchronization and Islanding Detection Control Algorithm for Two-stage Three-phase SPV System
Published in IETE Journal of Research, 2023
Nikita Gupta, Rachana Garg, Parmod Kumar
To improve the dynamic response of the control algorithm, the feedforward controller is added in the control algorithm. The feedback controllers respond only after they detect a deviation in the value of the controlled output from its desired set point. On the other hand, a feedforward controller can detect the disturbance directly and takes an appropriate control action in order to eliminate its effect on the process output. Any controller in feedforward configuration would act according to the disturbance for which it is designed. Thus, the feedforward controller makes the SPV system adaptive to disturbances occurring in the overall system. Feedforward control loop estimates the feedforward current given by where is the power obtained from SPV array and is the amplitude of PCC voltage and can be estimated as, where vta, vtb, and vtc are the three-phase voltages at PCC. Feedforward control is used to estimate the SPV array contribution to the reference grid currents used for switching of the inverter. It is observed that the feedforward quantity calculated is directly dependent on SPV array power and inversely dependent on the voltage of the utility grid. SPV array power dependence helps track the changes in atmospheric conditions and utility grid voltage dependence tracks the grid side issues like voltage sag or swell, etc. The controller output is estimated from the IFF and ILoss components. The feedforward output is then subtracted from the DC-link voltage controller given by, The reference active component of supply current () is estimated from output of adaptive controller (IPI) and fundamental DC current component of load current. Further, the measured grid currents and the generated reference currents (isa*, isb*, isc*) signals are processed by Hysteresis Current Control (HCC) which generates the gating pulses for the VSC.