Actuator systems

The key parts of the positioner/actuator system, shown in Fig. 8-74 7, are (1) an input-conversion network, (2) a stem-position feedback network, (3) a summing junction, (4) an amplifier network, and (5) an actuator. 

Sequence valves control the sequence of operation between two branches in a hydraulic circuit. In other words, they enable one component within the system to automatically set another component into motion. An example of the use of a sequence valve is in an aircraft landing gear actuating system. 

Mitigation measures can also be passive safeguards, meaning that they require no human intervention and no engineered sensing and actuation system to work. Examples of passive mitigation measures are secondary containment systems, blast-resistant and fire-resistant structures, insulated or low-heat-capacity spill surfaces to reduce the rate of evaporation, and an increased distance between the hazardous materials and energies and the sensitive receptors. 

The use of automatically actuated systems involves an increased cost of initial installation (e.g., because of the control unit), as well as additional maintenance costs throughout the life of the automatic systems. 

The relative contribution of heat release from the pulsed fuel injection provides another explanation. Because the same actuator system was utilized in all... 

The ISFET-based integrated coulometric sensor-actuator system was introduced in 1985 [154] in order to facilitate in situ calibration of ISFETs. The essential components of a prototype sensor based on this operational principle are shown in Fig. 4.20.B. The system was built by integrating a large noble-metal actuator electrode and a counter-electrode in a piece of silicon. A window in the actuator electrode was etched to receive the gate of the ISFET, which functioned as a pH indicator. The flow-through cell was constructed by sealing a silicon cover with an etched cavity of the chip. The system operation resembles that of a conventional coulometric titration system very closely. The sample was first injected into the cavity and the... 

In order to reduce radionuclide transportation from the primary to the secondary cooling system, containment isolation valves should be installed. These valves will be automatically closed by the signal detecting the heat transfer tube rupture of IHX. Meanwhile, the current engineered safety features actuating system is not designed to detect the rupture since the scenario did not impact on the reactor safety of the original HTTR. Therefore, a detection method of heat transfer tube rupture of IHX should be established. 

The strategy of detection method establishment is to apply the simple and reliable method since it would comprise the engineered safety featured actuation system. 

The DLC market is expected to grow rapidly to reach the billion dollar size. Hundreds of millions of small size DLCs (IF, 5V) are used in the consumer electronic market for more than 20 years. Millions of larger size DLCs (350F, 2.5 V) have already been installed in industrial applications, like wind turbine pitch systems, since 2002. Today DLCs are already used in the car industry, as for example in the breaking actuator system of the Toyota Prius hybrid car, and in the aircraft industry, as for example in the door opening system of the Airbus A380. 

FIG. 12 Basic elements of the coulometric sensor-actuator system based on an ISFET with gate-covering porous actuator electrode. The thickness of the porous actuator is about 100 /pore size is about I /mi. 

To avoid the need for coordination in breathing and actuation of the inhaler, a breath-actuated system has been devised. Patients who inhaled at 50 L/min did not experience significantly greater bronchodilation using a breath-actuated device than those using a conventional MDI [173], The Autohaler, shown in... 

Natural polymers remain an inspiration and provide considerable stimulation for researchers of artificial intelligent materials and systems. For example, antibodies and enzymes provide the molecular recognition capabilities used so magnificently by nature. Macromolecules are also the basis of that most useful of actuator systems muscles. Furthermore, it is the generation and transmission of electrical signals that regulate the processes behind the formation and operation of these biosystems. 

To apply control to a process, one measures the controlled variable and compares it to the setpoint and, based on this comparison, typically uses the actuator to make adjustments to the flow rate of the manipulated variable. The industrial practice of process control is highly dependent upon the performance of the actuator system (final control element) and the sensor system as well as the controller. If either the final control element or the sensor is not performing satisfactorily, it can drastically affect control performance regardless of controller action. Each of these systems (i.e., the actuator, sensor, and controller) is made up of several separate components therefore, the improper design or application of these components, or an electrical or mechanical failure of one of them, can seriously affect the resulting performance of the entire control loop. The present description of these devices focuses on their control-relevant aspects. Later, troubleshooting approaches and control loop component failure modes are discussed. 

FIGURE 15.13 Schematic of the CST thermal mixer showing the actuator system, sensor system, controller, and the process. 

The actuator system for a process control system in the CPI is typically composed of the control valve, the valve actuator, the I/P transmitter, and the instrument air system. The actuator system is known industrially as the final control element. In addition, a variety of optional equipment is designed to enhance the performance of the actuator system, such as valve stem positioners and instrument air boosters. 

The key to effective troubleshooting is expressed in the old adage, divide and conquer. It is important to locate the portion of the control loop hardware that is causing the poor performance the hnal control element, the sensor system, the controller, or the process. The place to start is to test each system separately to determine whether that portion of the control loop is operating properly. The hnal control element can be evalnated by applying a series of input step tests. That is, the input to the hnal control element, which is normally set by the controller, can be manually adjusted. The test allows the determination of the dynamic response and deadband of the actuator system. If the performance in these two areas is satisfactory, there is no need to evaluate the actuator system further. 

Even if the manipulated variable seems to follow the controller ontput, there could be a problem with the actuator. Estimates of the actuator deadband and dynamic response are required to determine if the actuator system is performing properly (both of which can be determined by a block sine wave test). This test is shown in Figure 15.21. A block sine wave is a series of eqnally sized step changes that approximate a sine wave. For the test shown in the figure, the amplitude... 

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