Instruments and meters: 【Question of the Week】Week 19, 2011: What conditions must be met for something to constitute an automatically regulated object?

This post was last edited by denghl on 2012-12-21 at 20:56. An automatic control system consists of three components: (1) The measuring unit (transmitter), which is used to determine the value of the quantity being controlled, and converts the original physical quantities (such as pressure, water level, temperature, flow rate, etc.) into measurement signals that are proportional to those quantities and suitable for transmission over long distances. (2) The operation unit (adjustment unit) can receive the signal of the quantity to be adjusted from the measuring component, compare it with a specified value, and when there is a discrepancy between the quantity to be adjusted and the measured value, it emits a signal indicating the direction and magnitude of that discrepancy. At the same time, this signal is processed according to pre-set rules (proportion, integration, differentiation, clipping, or non-linearity), and a series of signals are generated based on the results of these processing steps. (3) Actuator: An actuating mechanism that operates based on the direction and magnitude of the signal sent by the computing unit.

1. The parameters to be regulated in the control object can be measured continuously. 2. There are disturbance factors within the system being regulated that affect the parameter under control, causing it to deviate from the set value. 3. Among the parameters to be regulated, at least one quantity can be adjusted (controlled). By adjusting this quantity, the impact of external disturbances on the parameter being regulated can be compensated for, thereby keeping that parameter constant. This quantity is what is known as the control parameter.

This post was last edited by denghl on 2012-12-21 at 20:57. 1. The parameters to be adjusted in the control object can be measured continuously. 2. There are interfering factors within the system being regulated that affect the parameter in question, causing it to deviate from the set value. 3. Among the variables to be regulated, at least one quantity can be adjusted (i.e., it is controllable). By adjusting this quantity, the impact of external disturbances on the parameter being regulated can be compensated for, thereby keeping that parameter constant. This quantity is what is known as the control parameter.

IV. Composition of the automatic control system: First, the general-purpose controller, which includes sensors, transmitters, and setpoints; second, the controlled object

This post was last edited by denghl on 2012-12-21 at 20:58. A simple control system typically refers to a single-loop control system composed of a sensing element, a transmitter, a controller, a control valve, and a process variable; it is therefore also known as a single-loop control system. When constructing an automatic control system, the selection of the controlled variable is extremely important; it determines whether the system can achieve stable operation, increase production, improve quality, enhance working conditions, and ensure safety, and it is crucial to the success or failure of the control scheme. The selection of the controlled variables is closely related to the production process. There are many factors that affect the proper operation of a production process, but not all of these factors need to be automatically controlled. Therefore, it is necessary to go deep into reality, conduct investigations and research, analyze the processes, and identify the key variables that affect production as the controlled variables. In automatic control systems, the variable used to counteract the effects of disturbances on the controlled variable and thereby achieve control is called a control variable; the most common control variable is the flow rate of the medium. Generally, there are often several rather than just one external input that affects the dependent variable; among these inputs, some are controllable (can be adjusted) while others are uncontrollable. In principle, among the various inputs that affect the controlled variable, one input that has a significant impact on it and is easy to control is selected as the manipulative variable, while all other unselected inputs are considered to be disturbances to the system. Generally, control variables are selected based on the following principles: 1. The control variable should be controllable, that is, a variable that can be adjusted in the manufacturing process. 2. The control variable should generally be more sensitive to the effects of other disturbances on the controlled variable. To this end, by reasonably selecting the control variables, it is necessary to ensure that the amplification factor of the control loop is sufficiently high, the time constant is sufficiently low (but not too low, as this can lead to oscillations), and the pure lag time is as small as possible. To reduce the impact of other disturbances on the controlled variable, the amplification factor of the disturbance channels should be as small as possible, and their time constants should be as large as possible. 3. When selecting control variables, in addition to considering automation aspects, the rationality of the process and the economic efficiency of production must also be taken into account. Generally speaking, it is not advisable to use production load as a control variable, as it is directly related to the output volume of products and should not fluctuate frequently. Furthermore, from an economic perspective, material and energy consumption should be reduced as much as possible

This post was last edited by denghl on 2012-12-21 at 20:59. 1. The parameters to be adjusted in the control object can be measured continuously. 2. There are disturbance factors within the system being regulated that affect the parameter under control, causing it to deviate from the set value. 3. Among the variables to be regulated, at least one quantity can be adjusted (i.e., it is controllable). By adjusting this quantity, the impact of external disturbances on the parameter being regulated can be compensated for, thereby keeping that parameter constant. This quantity is what is known as the control parameter.

This post was last edited by denghl on 2012-12-21 at 21:00. It must meet the following conditions: 1. The parameters to be adjusted within the system under consideration must be adjustable continuously. 2. There are interfering factors within the system being regulated that affect the parameters to be adjusted. 3. There must be a variable that can be adjusted among the objects to be regulated.

This post was last edited by denghl on 2012-12-21 at 21:02. The automatic control device consists of the following three parts: (1) The measuring section (transmitter), which is used to determine the value of the quantity being controlled, and converts the original physical quantities (such as pressure, water level, temperature, flow rate, etc.) into measurement signals that are proportional to those quantities and suitable for transmission over long distances. (2) The operation unit (adjustment unit) can receive the signal of the quantity to be adjusted from the measuring component, compare it with a specified value, and when there is a discrepancy between the quantity to be adjusted and the measured value, it emits a signal indicating the direction and magnitude of that discrepancy. At the same time, this signal is processed according to pre-set rules (proportion, integration, differentiation, clipping, or non-linearity), and a series of signals are generated based on the results of these processing steps. (3) Actuator: An actuating mechanism that operates based on the direction and magnitude of the signal sent by the computing unit.

This post was last edited by denghl on 2012-12-21 at 21:03: 1. The actuator outputs effective control over the variable being regulated; 2. The variable being regulated participates in the regulation process; 3. The regulation parameters can be modified (by changing the weight of the ball or the length of the pendulum)

The last edit to this post was made by denghl on 2012-12-21 at 21:05; these are the process variables that play a decisive role in ensuring stable production, as well as in maintaining product quality and output, while also guaranteeing economic benefits and safe production