Electricity: motive power systems – Positional servo systems – Digital or numerical systems
Reexamination Certificate
1999-09-11
2001-07-03
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
Digital or numerical systems
C318S609000, C318S621000, C318S632000
Reexamination Certificate
active
06255794
ABSTRACT:
The invention relates to a procedure for the digital evaluation of analogue output signals from a resolver.
A resolver is a device which permits the acquisition of the angular position of a rotor with respect to a stator, as well as the angular velocity of the turning rotor. It is usual for the stator to have at least two stator windings, which are arranged perpendicular to each other if only two windings are provided. The rotor carries at least one rotor winding. Initially a sinusoidal excitation signal is fed to the rotor, which results in an equally sinusoidal signal to be induced in one of the stator windings, and a cosine-shaped signal in the other stator winding, on account of the relative position of the two stator windings with respect to each other. By application of the inverse tangential function it then becomes possible to determine from the two signals both the relative angle between the stator and the rotor and the angular velocity of the rotor.
With the aid of the invention a procedure is to be established which will enable a purely digital evaluation of the signals derived from the stator windings, whereby the signals representing the required angular value and the required angular velocity should be as free of interference as possible and become available without any otherwise inherent delay.
According to one aspect of the invention, for the digital evaluation of the analogue output signals from a resolver with at least two stator windings arranged perpendicular with respect to each other on one stator, and at least one rotor winding on a rotor which can turn with respect to the stator, the following steps are to be implemented:
A) a sinusoidal excitation signal is fed to the rotor winding;
B) sinusoidal and cosine-shaped signals, respectively, depending on the angular position of the stator in relation to the rotor, are derived from the stator windings and, after oversampling, are converted into digital signals;
C) for the purpose of bandwidth limiting, the digital signals are fed through an FIR bandpass filter;
D) the filtered signals are then subjected to decimation using the factor applied to the previous oversampling process;
E) by computation of the inverse tangential function, an angular value for the relative angular position between the rotor and the stator, affected by a propagation delay error due to the preceding process, is derived from the signals subjected to the decimation process;
F) the computed angular value is applied to the input of a control loop, in which
a) the computed angular value is compared with an assumed delay-time affected angular value,
b) the deviation between the computed angular value and the assumed angular value is applied to a PI regulator as regulation deviation value,
c) from the applied regulation deviation, the PI regulator generates an output signal corresponding to the angular velocity of the rotor without propagation delay,
d) the output signal is subjected to IIR filtering,
e) the assumed angular value, not affected by delay time, is obtained from the filtered output signal by integration,
f) the assumed angular value is delayed by the propagation time value and fed to the unit which compares it with the computed angular value,
G) the assumed angular value and the angular velocity without propagation time delay become available as the output signals of the resolver.
The process steps involved in the procedure according to the invention are steps of a nature that can be implemented as pure digital process steps. This makes it possible to have all these steps executed by a digital signal processor, which is specially programmed for the execution of these steps. An essential factor for the generation of the delay-free angular value between rotor and stator is the inclusion of a control loop which makes it possible to counteract the delay times inherent in the digital processing sequence, so that the required angular value and the required angular velocity become available without being affected by time delay.
REFERENCES:
patent: 4529922 (1985-07-01), Ono
patent: 4594540 (1986-06-01), Currie et al.
patent: 4795954 (1989-01-01), Sakurai et al.
patent: 4972186 (1990-11-01), Morris
patent: 5134397 (1992-07-01), Eyerly et al.
patent: 6084376 (2000-07-01), Piedl et al.
Kempler William B.
Ro Bentsu
Telecky , Jr. Frederick J.
Texas Instruments Deutschland GmbH
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