Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2002-09-25
2003-05-27
Shah, Kamini (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
Reexamination Certificate
active
06571194
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a position detection data generating method and apparatus for use in a position detection system which generates a first A.C. output signal having an electrical phase angle shifted in a phase-advancing or positive direction in accordance with a position of an object of detection and a second A.C. output signal having an electrical phase angle shifted in a phase-retreating or negative direction. More particularly, the present invention relates to a technique intended to improve detection performance with respect to dynamic characteristics of an object of detection (i.e., detecting characteristics when the object of detection is changing in position with time); for example, the present invention concerns a technique of detecting a rotational or linear position of an object of detection, such as a rotational position detector like a resolver or synchro or a linear position detector based on a position detecting principle similar to that of the rotational position detector.
Induction-type rotational position detector apparatus of the type which produces two-phase outputs (i.e., outputs of sine and cosine phases) in response to a single-phase exciting input are commonly known as “resolvers”, and induction-type rotational position detector apparatus of the type which produces three-phase outputs (i.e., outputs of three phases shifted from each other by 120°) in response to a single-phase exciting input are commonly known as “synchros”. In the resolvers of the most traditional type, a stator includes two-pole (sine and cosine poles) secondary windings that intersect each other at a 90° mechanical angle, and a rotor includes a primary winding (the relationship between the primary and secondary windings may be reversed). The resolvers of this type are not satisfactory in that they need a brush to electrically contact the primary winding of the rotor. There have also been known brush-less resolvers that require no such brush; that is, these brush-less resolvers include, on the rotor side, a rotary transformer in place of the brush. The assignee of the instant application has recently developed an apparatus which, using a variable-reluctance-type detector having windings provided only on the stator (or the rotor), generates two-phase outputs (sine-phase and cosine-phase outputs) in response to a single-phase exciting input. The position detector apparatus which produce two-phase outputs (i.e., outputs of sine and cosine phases) in response to a single-phase exciting input as mentioned above have been proposed not only for the rotary position detection but also for the linear position detection.
The assignee of the instant application also proposed, in U.S. Pat. No. 5,710,509 (corresponding to Japanese Patent Laid-open Publication No. HEI-9-126809), a novel phase difference detection technique suitably applicable to the so-called resolver-type position detector apparatus producing two-phase outputs in response to a single-phase exciting input. This proposed phase difference detection technique gives a solution to the problem that A.C. signals induced in secondary windings would vary subtly in electric phase, in response to an ambient temperature change, to cause a detection error because the windings (coils) of the position detector apparatus vary in their impedance due to the ambient temperature change. The proposed phase difference detection technique generally comprises the following steps.
[Step 1] In response to a single-phase exciting input, the resolver-type position detector apparatus produces two A.C. output signals sin &thgr; sin &ohgr;t and cos &thgr; sin &ohgr;t having been amplitude-modulated by a sine function sin &thgr; and cosine function cos &thgr;, respectively, corresponding to a phase angle &thgr; of a position of an object to be detected (hereinafter, also referred to as a “position-to-be-detected”). These A.C. output signals sin &thgr; sin &ohgr;t and cos &thgr;sin &ohgr;t are processed electrically to generate a first A.C. output signal sin(&ohgr;t+&thgr;) having an electric phase angle (+&thgr;) shifted in the phase-advancing or positive direction in accordance with the position-to-be-detected and a second A.C. output signal sin(&ohgr;t−&thgr;) having an electric phase angle (−&thgr;) shifted in the phase-retreating or negative direction in accordance with the position-to-be-detected. If a phase error component caused by a winding impedance variation due to an ambient temperature change is represented by “±d”, then the above-mentioned A.C. output signals can be expressed by sin(&ohgr;t±d+&thgr;) and sin(&ohgr;t±d−&thgr;), respectively.
[Step 2] Phase differences (±d+&thgr; and ±d−&thgr;) of the A.C. output signals from a predetermined reference phase (e.g., zero phase of sin &ohgr;t) are detected, using a known digital phase difference measuring technique such as the “zero cross latch” scheme, to thereby obtain respective phase detection data.
[Step 3] Arithmetic operation of “{(±d+&thgr;)+(±d−&thgr;)}÷2=±d” is performed using the thus-obtained phase detection data, to thereby calculate error data ±d.
[Step 4] Error-free phase detection data &thgr; is obtained by subtracting the error data ±d from one of the phase detection data (e.g., ±d+&thgr;).
When the position-to-be-detected varies over time, the phase angle &thgr; corresponding thereto would also vary over time, although no significant problem occurs when the position-to-be-detected is not moving. In such a case, the phase difference amount &thgr; of the A.C. output signals sin(&ohgr;±d+&thgr;) and sin(&ohgr;t±d−&thgr;) would present, rather than a constant value, dynamic characteristics time-varying in correspondence with a moving speed of the object of detection. If the time-varying dynamic characteristics are represented collectively by &thgr;(t), then the A.C. output signals can be expressed by sin{&ohgr;t±d+&thgr;(t)} and sin{&ohgr;t±d−&thgr;(t)}, respectively. Namely, by the well-known Doppler effect, the leading-phase A.C. output signal shifts to a higher frequency in accordance with the dynamic characteristics +&thgr;(t), while the trailing-phase A.C. output signal shifts to a lower frequency in accordance with the dynamic characteristics −&thgr;(t). Namely, with the dynamic characteristics, the cycles of the two A.C. output signals sequentially shift in the opposite directions per cycle of the reference signal sin &ohgr;t, which would make it difficult to accurately calculate the phase variation error ±d by only performing the arithmetic operation of Step 3 above.
Thus, to provide a good solution to such an inconvenience, the above-discussed prior phase difference detection technique is arranged to detect when there occurs a coincidence in zero cross between the two A.C. output signals sin{&ohgr;t±d+&thgr;(t)} and sin{&ohgr;t±d−&thgr;(t)}. More specifically, each time such a coincidence in zero cross between the two A.C. output signals is detected, the phase detection data of either one of the A.C. output signals sin{&ohgr;t±d+&thgr;(t)} and sin{&ohgr;t±d−&thgr;(t)} relative to the predetermined reference A.C. signal sin &ohgr;t is held as the error data ±d, and then the position detection data is modified at Step 4 above using the thus-held error data.
However, because the phase detection data can be obtained only when the zero crosses of the A.C. output signals sin(&ohgr;t+&thgr;) sin(&ohgr;t−&thgr;) coincide with each other, the above-discussed prior phase difference detection technique faces the serious problem that the timewise detecting resolution of the phase detection data is limited to just one cyclic period of the A.C. signals and thus
Akatsu Nobuyuki
Goto Atsutoshi
Sakamoto Kazuya
Cherry Stephen J.
Goto Atsutoshi
Morrison & Foerster / LLP
Shah Kamini
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