Master-slave controller

In this configuration, the outer portions of IPMC serve as one sector (Sector 1) and are driven by input i(0> while the middle portion serves as a second sector (Sector 2) and is driven by input U2(t). Thus, toe IPMC comprises two controllable sectors. To control the performance of the sectored IPMC, toe feedforward architecture in Fig. 15 can be used. In this diagram, Ci(s) and C2 s) are the controllers and Gi(5) and G2(s) are their respective transfer functions associated with Sector 1 and Sector 2, respectively. Tstructure represents an open loop version of the master-slave control system. The advantage of the open... 

In principle the setpoints of the controllers that are now in place, eould be used for master-slave control. These are Tj, Fair,sp, and Pr,sp- It may be expected that the setpoint of the reactor pressure controller Pr,sp will not have much impact on the proeess variables that still have to be controlled, i.e. it is expected that the power of control of Pr sp will be very small This leaves us with the remaining three setpoints that can be used for eontrol. Tte situation is given in Table 35.5, in which... 

In control situations with more then one measured variable but only one manipulated variable, it is advantageous to use control loops for each measured variable in a master-slave relationship. In this, the output of the primary controller is usually used as a set point for the slave or secondary loop. 

With this arrangement, the output of one controller is used to adjust the set point of another. Cascade control can give smoother control in situations where direct control of the variable would lead to unstable operation. The slave controller can be used to compensate for any short-term variations in, say, a service stream flow, which would upset the controlled variable the primary (master) controller controlling long-term variations. Typical examples are shown in Figure 5.22c (see p. 235) and 5.23 (see p. 235). 

One of the most useful concepts in advanced control is cascade control. A cascade control structure has two feedback controllers with the output of the primary (or master) controller changing the setpoint of the secondary (or slave) controller. The output of the secondary goes to the valve, as shown in Fig. 8.2n. 

Figu re 9.14 Principles of a cascade controller. The master controller controls the reactor temperature (Tr) the slave controls the cooling system temperature (Tc). 

HPLC systems operate on a master-slave arrangement in setting up for automation. One module sets the timing and initiates the process, and the remaining modules accept a signal and follow the leader. In a gradient HPLC system, the master module can be a microprocessor-based controller, a computer software-based controller, an autosampler, or an integrator. 

Cascade control. The actuator of the slave controller (electric heater) maintains the temperature of the jacket water controlled in a value set by the master controller. 

Cascade loops consist of two or more controllers in series and have only a single, independently adjustable set point, that of the primary (master) controller. The main value of having secondary (slave) controllers is that they act as the first line of defense against disturbances, preventing these upsets from entering and upsetting the primary process, because the cascade slave... 

Providing external reset for the cascade master from the slave measurement is always recommended. This guarantees bumpless transfer when the operator switches the loop from slave control to cascade control (Figure 2.45). The internal logic of the master controller algorithm is such that as long as its output signal (m) does not equal its external reset (ER), the value of m is set to be the sum of the ER and the proportional correction (Kc(e)) only. 

In heat exchanger applications, cascade loops are configured so that the master detects the process temperature and the slave detects a variable, such as steam pressure, that may upset the process temperature. The cascade loop, responds immediately and corrects for the effect of the upset before it can influence the process temperature. The cascade master adjusts the set point of the slave controller to assist in achieving this. Therefore, the slave must be much faster than the master. A rule of thumb is that the time constant of the primary controller should be ten times that of the secondary, or the period of oscillation of the primary should be three times that of the secondary. One of the quickest (and therefore best) cascade slaves is the simple and inexpensive pressure regulator. 

In handling a radioactive material, it is basically important not to hold a radiation source directly with the hand. Handle it by remote operation as much as possible. Use forceps, tongs or similar devices. In handling radioactive materials of curie level or higher, remote controlling devices such as a master-slave type manipulator must be used. 

Cascade control significantly reduces the effect of certain types of disturbances by applying two control loops in tandem, i.e., the output of one controller is the setpoint for the other controller. The secondary or slave controller receives its setpoint from the primary or master controller and operates on a much faster cycle time than the primary. As a result, the secondary controller can eliminate certain disturbances before they are able to affect the primary control loop. 

In tuning a cascade control system, the slave controller is tuned first with the master controller in manual. Often only a proportional controller is needed for the slave loop, since offset in that loop can be treated by using proportional plus integral action in the master loop. When the slave controller is transferred to automatic, it can be tuned using the techniques described earlier in this section. Seborg et al. (1988) and Stephanopoulos (1984) provide further analysis of cascade control systems. 

Basically, a cascade control system has a master controller and a slave controller. The slave controller detects and corrects minor changes in the system, allowing the master controller to keep the primary variable constant. 

Hoshimiya, N. and Handa,Y., A master-slave type multichannel functional electrical stimulation (FES) system for the control of the paralyzed upper extremities, Automedica 11 209-220,1989. 

Actuator network The IE actuator netwoik is based on a master/slave protocol and uses many of the NERVIA network components. It is dedicated to safety actuator control needed for example for the Engineered Safety Features,... 

The tray temperature controller is the secondary (slave) controller. It is set up in exactly the same way as we did in the previous section. It looks at tray temperature (Stage 9) and manipulates reboiler heat input. However, its SP is not fixed. The SP signal is the output signal of the composition controller, which is the primary (master) controller. 

Meanwhile, in the area of remote manipulation, electrohydraulic, or electromechanical, bilateral master-slave systems were developed for the nuclear power industry to reduce the mental burden placed on the operator by providing force reflection. Aircraft controls for large planes and some high-performance military aircraft, building on work from the field of teleoperation or remote manipulation, have done away with the direct physical interconnection of the pilot and flight surfaces and now use fly-by-wire systems. 

Surgeon controls the robot in real-time through the haptic interface. Robot faithfully replicates the surgeon s motions with the interface. Master-slave surgeon gets real-time feedback from surgical scene via the camera and the force feedback from the instruments. 

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