Boots – shoes – and leggings
Patent
1985-08-16
1988-08-16
Lall, Parshotam S.
Boots, shoes, and leggings
364565, 364724, 180179, G01P 300
Patent
active
047648716
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for converting a sinus-shaped output signal of a rotational speed transducer, the amplitude and frequency of which are dependent on a rotational speed that is to be detected and are subject to distortion, into a low-distortion signal.
In anti-skid systems, also known as anti-lock systems, the wheel speed must be detected. To this end, conventional systems typically use an electromagnetic measuring transducer, which comprises a gear ring and a pole pin. The gear ring is secured on the wheel and rotates with it. The pole pin is secured to the axle. An alternating voltage is induced at the pole pin when the wheel rotates. The frequency of the alternating voltage is determined by the wheel speed and by the number of teeth on the gear ring. If a tooth of the gear ring is located facing the pole pin, then the voltage is positive, and conversely, if a tooth gap is facing the pole pin, then the voltage is negative. This characteristic is utilized by measuring the time between two successive zero passages in opposite directions. This time is proportional to the wheel speed.
For measuring the time between zero passages, the alternating voltage is amplified and sent through a limiter, which limits the voltage at the top and bottom. The amplification factor is selected to be quite large, so that a rectangular signal is produced. The zero passages are then signalled by voltage jumps. To keep distortion in the alternating voltage from affecting the measurement, the amplifier input is provided with a hysteresis.
The amplitude of the alternating voltage is dependent not only on the wheel speed but also on the gap between the pole pin and the gear ring. The amplitude of the alternating voltage increases with the wheel speed and decreases as the gap increases. The information contained in the alternating voltage signal is partially erased by voltage limitation in the amplifier. The tolerances with which the sensor parts are manufactured are a problem. Because of this, the distances between the teeth of the gear ring are not exactly equal, and at high speed there can be large jumps in the calculated wheel speed. Specialized logical decisions which take physical principles into account, limit these jumps and thus filter the wheel speed. Distortion which just exceeds the input threshold of the amplifier is also a problem. If the frequency of the distortion is high, but not high enough to be recognized as distortion during the logical monitoring, then this distortion is included in the wheel speed calculation, which can cause incorrect functioning of the anti-skid regulating system.
The present invention discloses a method with which these problems can be screened out, or at least diminished. To this end, a statistical observer, known as a Kalman filter, is used. The main components of the filter are the simulation of the dynamic wheel rotation and the simulation of the alternating voltage signal of the sensor. By simulating the wheel rotation, the filter thus automatically includes the principles of physics. The amplified signal is no longer limited, so that not only the frequency but also the information contained in the amplitude of the signal are now advantageously evaluated. A more accurate speed signal is obtained than was possible with the conventional measuring method. As a result, greater tolerances in manufacturing the sensor elements can be accommodated. Also, tooth shapes other than the conventional one with a rectangular cross section, as well as quite different sensors having signals which can readily be mathematically simulated, can be used.
Furthermore, the subsequent calculation of wheel acceleration can also be eliminated, because this variable is also estimated by the Kalman filter. The method according to the invention can be realized with both analog and digital switching means.
The invention will now be described in greater detail in terms of the exemplary embodiments illustrated in the drawings. Shown are:
FIG. 1, a first exemplary embodiment of the invention, based on a
REFERENCES:
patent: 4215412 (1980-07-01), Bernier et al.
patent: 4335432 (1982-06-01), Pue
patent: 4420814 (1983-12-01), Arikawa et al.
patent: 4467428 (1984-08-01), Caldwell
patent: 4489382 (1984-12-01), Jonner et al.
patent: 4569027 (1986-02-01), Nakano et al.
patent: 4577260 (1986-03-01), Sugano et al.
Black Thomas G.
Greigg Edwin E.
Lall Parshotam S.
Robert & Bosch GmbH
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