Patent ID: 7366633

Claim:
A process for monitoring the rotation of a body revolving around an axis of rotation and having a periphery, wherein over said periphery, at least a first circular track centered on the axis of rotation comprises marks spaced regularly from one another, in which each track of said marks is associated with a sensor which is stationary relative to the revolving body and disposed facing said track and influenced by the marks of said each track which travel past said sensor and producing, as an output signal, a periodic signal, in which extraction is performed of at least one variable associated with said periodic signal having a frequency at most equal to a predetermined maximum frequency and including a possible continuous component, a sinusoidal fundamental component and possible harmonics, the process comprising the steps of: performing a preliminary operation to establish a dynamic system model defined by an instantaneous state vector having a plurality of components and by a state transition matrix, a first of said plural components being representative of an instantaneous amplitude of the sinusoidal fundamental component of the periodic signal, a second of said plural components being representative of the instantaneous amplitude of the sinusoidal fundamental component of the periodic signal out of phase by 90 degrees, a third of said plural components being representative of the amplitude of the continuous component, and a fourth of said plural components being representative of a pulsation or frequency of the fundamental component; performing an iterative measurement to produce, at a frequency at least equal to twice the predetermined maximum frequency, numerical samples each of which is representative of the measured instantaneous amplitude of the periodic signal; performing an iterative prediction to calculate a predicted instantaneous amplitude of the periodic signal at each current instant by applying the state transition matrix to the state vector associated with an instant preceding the current instant, said prediction resulting in a predicted state vector for the current instant, and by applying to the predicted state vector an observation matrix interpreting the measured instantaneous amplitude of the periodic signal as an at least partial manifestation of the instantaneous state vector of the dynamic system; performing an iterative correction to quantify a difference between the measured instantaneous amplitude and the predicted instantaneous amplitude of the periodic signal at the current instant; performing an iterative update of the instantaneous state vector of the dynamic system, associated with the current instant, as a function of the quantified difference and the predicted state vector of the dynamic system which is associated with the instant preceding the current instant; and performing an iterative presentation of a result to deduce at each instant said at least one variable of at least one of said plural components of the instantaneous state vector associated with said instant.