Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
2000-02-25
2003-07-29
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
C702S150000, C702S146000, C702S145000, C073S510000
Reexamination Certificate
active
06601011
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for measuring an angular velocity variation rate (viz., angular acceleration) of a rotary axle applicable to, for example, an apparatus for detecting a torque of an oscillation-type chassis dynamometer and applicable to cases where an electric inertia simulation is carried out without use of a mechanical variable inertia device and where velocity fluctuations are suppressed in an electric motor having many load variations.
2. Description of the Related Art
An angular velocity variation rate (i.e. angular acceleration or deceleration) is an important control parameter when electric inertia control is carried out in a chassis dynamometer.
Japanese Patent Application First Publication No. Heisei 5-322,924 published on Dec. 7, 1993 (now Japanese Patent No. 2,500,565) exemplifies an analog-type angular velocity variation rate measuring apparatus.
In the analog-type angular velocity variation rate measuring apparatus disclosed in the above-described Japanese Patent First Publication, a pair of pulse pick-ups are disposed concentrically around an inductor attached onto the rotary axle on a virtual line passing a center of the rotary axle with one of the pulse (magnetic) pick-ups disposed in a positional phase difference of 180° to the other. A frequency (a repetition rate) of a revolution velocity pulse train proportional to a revolution velocity of the rotary axle generated by means of each pulse pick-up, is then converted into an analog velocity indicative signal to derive an average value by means of a frequency-to-voltage converter. Each analog velocity indicative signal is averaged and the averaged analog velocity indicative signal is differentiated by means of a differentiator to provide an angular velocity variation rate indicative signal. Since the pair of the pulse pickups are disposed around the inductor at a pulse interval of 180°, a measurement error due to an eccentricity of the inductor to the rotary axle can be cancelled.
SUMMARY OF THE INVENTION
However, in the frequency-to-voltage converter used in the analog angular velocity variation rate measuring apparatus, the linearity of the conversion of the frequency to the voltage is reduced in a relatively low frequency range.
In addition, in an electrical inertia control such as carried out in the chassis dynamometer, a rated angular acceleration measurement range is extremely small and a zero point stability is degraded. For example, in a chassis dynamometer having rollers each roller having a diameter on which vehicular road wheels are mounted, a normal rated velocity is about 160 Km/h (=44.4 m/s and the roller revolution speed is 11.67s
−1
) and a rated angular velocity variation rate measurement range is about ±5 m/s
2
.
That is to say, it takes eight seconds or longer to accelerate the roller up to the rated velocity.
A differentiator, provided in the above-described analog type velocity variation rate measuring apparatus, to calculate the angular acceleration from the angular velocity is constituted by a first capacitor interposed between an angular velocity input and a first resistor , a second resistor connected across a first operational amplifier, a second capacitor connected across the first operational amplifier, a third resistor, a variable resistor connected to the first operational amplifier, and a second operational amplifier across which the variable resistor is connected and which outputs the angular velocity variation rate. If a differentiation time is obtained within a time on the basis of which the above-described velocity variation rate is derived, the first capacitor indicates approximately 4 &mgr;F and the first resistor indicates approximately 250 kilo-ohms.
Although the measurement accuracy is reduced if a film capacitor having a small leakage resistance is not used as the first capacitor, an actual mounting limit of 4 &mgr;F is present in terms of dimension of the first capacitor. If the angular velocity signal voltage inputted into the differentiator is 10 V at 160 Km/h, a voltage variation rate at the differentiator indicates ±1.2 V/s. An input current to the differentiator is 1.2×4×10
−6
=about 0.005 mA. This current value is relatively small as compared with about 0, 2 mA which is the input current at the rated velocity to prevent a variation due to a temperature variation and an external noise interference in a normally available analog controller. Consequently, a stability at a zero point becomes worsened.
The differentiator requires insertions of the second capacitor and the second resistor in order to prevent the detrimental effect of external noise and to prevent self oscillation from occurring.
Consequently, the response rate is degraded. An experimental result indicated that a maximum limit of 30 ms was placed at a response time percentage of 63%.
The analog-type angular velocity variation rate measuring apparatus described above under the heading of “related art” suffers from a number of drawbacks. In order to improve the measuring accuracy of the angular velocity variation rate with the above-described problems eliminated, a digital type angular velocity variation rate measuring apparatus has been proposed.
This previously proposed digital angular acceleration (angular velocity variation rate) measuring apparatus includes: an inductor of a toothed gear type attached concentrically onto the rotary axle; the pair of same pulse pick-ups whose disposed positions are the same as described in the case of the analog type velocity variation rate measuring apparatus; a pair of pulse shapers, each shaper shaping the corresponding velocity pulse signal from the corresponding pick-up of the first pair; a pair of velocity pulse counters counting the shaped velocity pulse signal from the pair of pulse shapers; a pair of period measuring counters, each period measuring counter receiving a velocity pulse from the corresponding pulse pick-up to count the velocity pulse signal; a memory to store a result of measurement corresponding to a predetermined number of times upon a receipt of the velocity pulse counters and the period measuring counters; an angular velocity calculator to calculate an average angular velocity upon receipt of the output of the memory; a controller to control the memory and the angular velocity calculator; a pair of digital-to-analog converters to convert the angular velocity and the angular acceleration calculated into digital signal. The digital-to-analog converter converts the angular velocity and the angular velocity variation rate into the digital signal. A first angular velocity variation rate calculating section is constituted by each circuit subsequent to the pair of pulse shapers.
As described above, each pulse pick-up generates magnetically the velocity pulse in synchronization with a revolution of the inductor. After the velocity pulse is shaped by means of the pair of pulse shapers, the number of velocity pulses is counted by means of each velocity pulse counter and is stored into an output register storing the accumulated number of velocity pulses.
Whenever the velocity pulses are inputted, the contents of the output register are updated. Each period measuring counts the number of clock pulses and is stored into the output register storing the number of accumulated clock pulses. Whenever the velocity pulse is inputted, the count of the output register is updated.
The controller, whenever the period measuring clock is inputted, issues a read command to the memory to store a latest measurement value stored into each output register of the corresponding counter, viz., the accumulated clock pulse number. Thereafter, the controller issues a calculation command to the angular velocity calculating section to read the latest accumulated velocity pulse number from the memory. The controller, thus, calculates the latest average angular velocity from the previously measured corresponding data, outputs the latest average angular
Miyamoto Teruo
Suzuki Yorikatsu
Barlow John
Cherry Stephen J.
Foley & Lardner
Kabushiki Kaisha Meidensha
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