Point of view of dynamic theory, systems, which was firstthe complete rotor method may be regardedperspective of dynamic the harm evolution of proposed by Chelidze [31]. From the as a high-order method composed of a “fast time” scale plus a “slow time” scale. Its definition is as follows:xf x, g x, , t,t(7)In Equation (7), x Rn may be the “fast time” scale variable, which is usually measured directly.R m is the “slow time” scale variable, which can directly reflect the damageMachines 2021, 9,10 oftheory, the harm evolution with the complete rotor program is often regarded as a high-order technique composed of a “fast time” scale and a “slow time” scale. Its definition is as follows: x = f [ x,), t] . = g( x, , t).(7)In Equation (7), x Rn is the “fast time” scale variable, which may be measured directly. Rm would be the “slow time” scale variable, which can straight reflect the harm state in the entire system but can’t be measured directly. f ( and g( are the “fast time” and “slow time” scaling functions, respectively. is actually a function from the variable , t represents time, and (0 1) is usually a constant parameter that defines the harm price from the method. The response states on the bearing system in the initial time point t0 and after operating to get a specific period tp could be expressed as x0 = F [ x0 , 0), t0 ] xt = F x p , t), t p (eight)Suppose that the bearing system always maintains its initial state without having experiencing any change or harm, then the response from the bearing method might be 5-Methylcytidine manufacturer calculated making use of Equation (9). x R t p = F x p , 0), t p (9) Thus, with the initial operating state from the bearing method as the reference state, there’s t0 = t R . Then, the damage state of the bearing program (or harm tracking) may be expressed as follows: e = F x p , ( P), t p – F x p , ( R), t p (10)In Ref. [31], immediately after performing the Taylor expansion, the bearing system’s harm state is often finally expressed as e= F p – R O p p – R O(11)where O( represents higher-order infinitesimal. In this paper, the raw acceleration signal from the bearing is regarded as an observable “fast time” scale variable, whilst the harm state of the bearing method is regarded as a “slow time” scale variable. Generally, to calculate the damage state of the bearing, the phase space reconstruction theory according to the Takens embedding theorem would be introduced, and also the damage state on the bearing would be quantified on this basis. The phase space reconstruction is mathematically expressed as follows: y R (n) = [ x R (n), x R (n ), . . . , x R (n ( D – 1))]T n = 1, . . . , N ( D – 1) (12)exactly where y R R D could be the reference initial state from the phase space of the bearing program, n will be the number of vectors within the phase space, and N would be the total number of observation data points. and D represent the time delay and embedding dimension of the phase space, which can be calculated employing the mutual facts [32] process and Cao’s approach [33]. Theoretically, the unknown mapping involving the reconstruction vector y R (n) within the reference phase space and that of your next step y R (n 1) around the “slow time” scale–that is, under the reference state from the bearing R –can be expressed as y R ( n 1) = P [ y R ( n); R ] (13)Machines 2021, 9,11 ofIn engineering, linear regression is the most straightforward and generic model for Oprozomib manufacturer establishing the mapping among reconstruction vectors y R (n) and y R (n 1) inside the reference phase space, as shown by Equation (14). y R ( n 1) = A n y ( n) (14)exactly where An Rdd1) is.