China
Africa
Explore chapters and articles related to this topic
Controls
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
With proportional control, the output of a controller is proportional to the difference between the process value and the set point. Assume the LT covered earlier to produce the process value. In this case, the controller will be used for level control. Also assume that the level control valve is reverse acting. An increase in controller output will close the valve. When the water level in the tank increases, the control signal decreases. To make the system work, any increase in process value should result in an increase in output to close the valve. Now look at the ratio totalizer to see how to connect the process variable. The output bellows pushes up on the right side of the beam. Any increase in output will tend to rotate the beam around the pivot in a counterclockwise direction. It is a pressure balance system. The process variable has to create a tendency to rotate the beam in the opposite direction to balance the forces.
Programmable-logic controllers and operation
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
In applications requiring fine continuous control, closed-loop or negative feedback is provided where the sensed variable is compared to a user setpoint to determine an error. The PLC corrective output signal may be 4–20mA, 0–5Vdc, or another signal whose value is relative to the amount of error, and the correction is applied in a manner to eliminate the error. To provide sufficient actuation forces, the 4–20mA or 0–5Vdc output signal is often converted to a 3–15 psi or a 0–30 psi pneumatic signal to position a valve actuator or a power cylinder. The current-to-pneumatic converter is referred to as an I/P converter, which is essentially a signal amplifier. Proportional-only control leaves offset, or a deviation from the setpoint after a process disturbance has taken place, because the corrective signal is generated only after observing that a deviation exists. If the system can tolerate some level variations and the response speed is satisfactory, then proportional-only control is adequate. To reduce offset, the gain or sensitivity of the proportional control can be increased. Gain is the amplification of the output-signal relative to the input-signal. Gain can only be increased within limits constrained by the system dynamics, and controls that are too sensitive result in instability or hunting. PID mathematical instructions can be programmed into the PLC to improve the control. The integral and derivative functions add behavior that removes offset and speeds the response. This topic is discussed in Chapter 2 on “Control Terminology and Theory.”
HVAC Control Systems
Published in T. Agami Reddy, Jan F. Kreider, Peter S. Curtiss, Ari Rabl, Heating and Cooling of Buildings, 2016
T. Agami Reddy, Jan F. Kreider, Peter S. Curtiss, Ari Rabl
Proportional control corrects the controlled variable in proportion to the difference between the controlled variable and the setpoint. For example, a proportional controller would make a 10% increase in the coil heat output rate in Figure 21.2 if a 10% decrease in the coil outlet air temperature were sensed. The proportionality constant between the error and the controller output is called the gain Kp. A proportional controller can be modeled as follows: V=Vo+Kpe
Random forest-based simultaneous and proportional myoelectric control system for finger movements
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Khairul Anam, Dwiretno Istiyadi Swasono, Agus Triono, Aris Z. Muttaqin, Faruq S. Hanggara
The implementation of random forests in MCS is mainly dominated by the classification scheme (Gijsberts et al. 2014; Abdullah et al. 2017; Pancholi and Joshi 2018), although it limits one class of movement activated at a time, contrary to body movement. A recent trend for MCS is predicting kinematics hand to get more movements not limited by just a few movement classes. This type of control system is called a simultaneous and proportional control system (Cho et al. 2020). The application of machine learning is changed from classification to regression mode. To the best of our knowledge, the random forest is less evaluated for predicting the kinematic joint of the fingers. Therefore, we propose an estimator for simultaneous and proportional MCS using the random forest by predicting the angle of 22 finger joints from an electromyography signal. Our main contribution lies in using the random forest for regression in simultaneous and proportional MCS implemented on an angle estimation of finger joints.
Proportional-integral-proportional control and compensation design for low-speed motions of permanent magnet synchronous motor driven servomechanism with position-dependent disturbance
Published in Journal of the Chinese Institute of Engineers, 2022
The position-dependent disturbance can be effectively suppressed by a PMSM driving control and by modifying the hardware structure. However, these cannot be applied to commercialized PMSM servomotor packs, which are low cost and have well-designed hardware. To suppress the position-dependent disturbance using commercialized PMSM servomotor packs, it is important to consider the complexity of the control law and limited computational capability of the PMSM driver. The proportional-integral-proportional (PIP) feedback control generally used in commercialized PMSM drivers is a type of cascade control that has inner and outer feedback loops for speed and position controls, respectively; the PI represents the proportional-integral control of the speed feedback loop, and the P represents the proportional control of the position feedback loop. The objective of this study was to develop a PIP control and compensation design that suppresses the adverse effects induced by position-dependent disturbance to improve the low-speed motions of the PMSM-driven servomechanism; moreover, it should be possible to implement it on commercialized PMSM drivers without excessively increasing the computational burden on the commercialized PMSM drivers and without hardware modifications to the commercialized PMSM servomotor packs.
Tracking control of soft dielectric elastomer actuator based on nonlinear PID controller
Published in International Journal of Control, 2022
Peng Huang, Jundong Wu, Chun-Yi Su, Yawu Wang
The reasons for the above settings are as follows. For the proportional control, the function produces a high output when the error is small, which is beneficial to improve the rapidity of the closed-loop control system and facilitates to mitigate the phase-delay caused by the hysteresis nonlinearity of the SDEA. On the other hand, the function produces a low output when the error is large, which is conductive to prevent the high frequency chattering of the SDEA caused by the excessive output. For the integral control and differential control, the function has similar effects. Besides, for the integral control, the function is beneficial to handle the integral windup problem encountered in practical experiments (Gao et al., 2001). More importantly, for the differential control, the function facilitates to produce the favourable differential action in practical experiments of the SDEA. Under the regulation of the differential control, the NEFC can predict the trend of the error and provide the phase-lead compensation to reduce the phase-delay of the SDEA.