Which variables are integral variables?

I. The law of integral regulation and its characteristics Integration refers to the accumulation over time. Integral control refers to the integral action on the deviation DV, △MV=1/TI, where TI is known as the integration time ； 1/TI is referred to as the integral velocity. The integral action depends on whether a deviation exists; as long as there is a deviation, no matter how small it may be, and as long as it persists for a sufficient length of time, the regulator’s output will be large. When the deviation is 0, the output stops changing, and thus the integral action can eliminate residual errors. The greater the deviation, the faster the output changes. The integration time TI indicates the magnitude of the integrating effect. As TI decreases, the integrating effect increases. Characteristics of integral action: 1. The change in output is proportional to the integral of the error. 2. It can eliminate residual errors: as long as DV exists, ΔMV increases over time until DV becomes 0. 3. Its regulatory effect is slower than that of proportional control; therefore, integral action is not used alone but in combination with proportional action.

It should be the integral variable! Given a function f(x), if there exists a function F(x) such that F'(x) = f(x) on the interval (a, b), then F(x) is called an antiderivative of f(x) on the interval (a, b). Since \(=F'(x)\), if an antiderivative of \(f(x)\) exists, there are infinitely many of them, and they differ from one another by at most a constant; therefore, all the antiderivatives of \(f(x)\) can be expressed as \(F(x)+C\). The set of all antiderivatives of f(x) is called the indefinite integral of f(x), denoted as ∫f(x)dx, where ∫ denotes the integral sign ； x is called the integration variable ； f(x) is called the integrand ； f(x)dx is called the integrand.