Device and Method for Measuring Angular Speed

Field of the Invention:

The present subject matter in general, relates to "Device and Method for Measuring Angular Speed" and more particularly for identification of angular position of the Dating object at any time during rotation event.

Background of the Invention:

There have been several methods to find the angular speed of rotating objects which ave been used in the past. Some of these methods use slotted disc or toothed gear 1 combination with a sensor to detect change in reluctance of the magnetic path, uch as a variable reluctance sensor.

To find the angular position of the rotating object during rotation, some of the methods include a missing tooth on toothed gear or missing slot in the slotted disc as a reference point and then counting the teeth or slots encountered. When such methods are used, the controller should always check for the missing element and ignoring one such element could lead to several errors in system performance.

Therefore the present invention tries to overcome the above problem by providing a solution to find the speed, and angular position of rotating object at any time during the rotation event.

Summary of the Invention:

The present invention has been devised in view of the above difficulty and it is therefore an object of the present invention to provide a device and method for measuring angular position of the rotating object at any time during rotation event.

Another object of the present invention is to provide a device and method for measuring angular speed including a rotary disk.

Another object of the present invention is to provide a device for measuring angular speed including a rotary disk mounted to the rotational element, which will provide the speed of rotating element at any time during rotation.

Another object of the present invention is to provide an angular speed detection device which is easy to manufacture.

Yet another object of the present invention is to provide a device for detection of angular speed of a rotating object which is cost effective.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief description of the Drawings:

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

FIG. 1 is a conventional motorcycle.

FIG. 2 shows the rotary disk having progressively varying teeth according to the present invention embodiments.

Detailed Description of the Drawings:

The present invention now will be described more fully hereinafter with different embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather those embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the invention to those skilled in the art. The subject matter of present invention relates to a device which is used to measure the angular speed of the rotating element and more particularly for any rotating element of a two wheeled vehicle.

For purpose of illustration a motorcycle is described in general, which can have the invention incorporated in it. With reference to figure 1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (201) of the vehicle frame, a front wheel (103) attached to these front forks (102), a handle bar (104) connected to the front forks (102), a fuel tank (105) attached so as to straddle an upper part of the vehicle frame, a seat (106) attached to the upper rear portion of the vehicle frame, an engine unit (107) attached to the lower front section of the vehicle frame, a swing arm (108) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown) from the vehicle frame and a rear wheel attached to a rear end of swing arm (108). The intake system of the engine comprises of a fuel air metering device such as a carburetor (109), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (110) for covering an upper part of the front wheel (103), and a rear fender (111) for covering an upper part of the rear wheel (112).

The drive from the engine (107) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

According to the present invention and referring to figure 2, the rotational speed and angular position detection is done with the help of a sensor (201), a rotary disk (202) having teeth and an electronic controller to process the signals. The electronic controller can be a microcontroller based system with necessary circuits or discrete element circuit with ability to process analogue and digital signals.

The said sensor (201) can be any sensor which gives output signal corresponding to the change in magnetic field through the sensor. Apart from the variable reluctance sensor, other types of sensors can be magneto resistive, basic Hall Effect based sensor or like sensors. Signal output type for variable reluctance sensor and Hall Effect sensor type is voltage, while magneto resistive sensor has change in resistance, which can be converted to voltage with a small circuit and can be integrated with sensor element.

When the sensor is used in combination with a rotary disk having teeth (202) , the expected output is an oscillating voltage signal. When the sensing face of the said sensor (201) is in close proximity of the toothed rotary disk (202), the said sensor faces metal (202 a) and slot (202 b) alternatively. Assuming, the fixed air gap between metal edge (202 a) and the sensor face to be ga1 and ds to be the depth of recess on the toothed rotary disk (202), then the total air gap ds + ga will contribute to high reluctance path and ga contributes to low reluctance path of distinguishable reluctances which contribute to change in flux through the sensor element (201) such that a detectable voltage is induced across the sensor coil.

Increasing air gap ga shall have effect on the amplitude alone of the output signal but not on the frequency, mainly because the number of flux change events per second remains same and only the amount of flux change varies.

Air gap ga can be increased to such a value where voltage induced in the sensor coil due to the ga and ga + ds air gap variation at the lowest speed of rotor ( or rotating element) to be observed is detectable. Lower limit on the ga is only because of component dimension tolerances and can go to as low as 0.

At a given fixed speed of the rotor (or rotating element), if the air gap ga is continuously varied within the limits as mentioned above along the circumference, the resulting signal at the sensor coil shall be of constant frequency with varying magnitudes. On close observation, this data reveals that the average value of the amplitude variations correspond to the average air gap and lowest air gap produces largest amplitude and vice versa.

A toothed rotary disk (202) when attached to a rotating element wherein the toothed rotary disk (202) is having varying tooth height (203) and a sensor (201) is being arranged in proximity of the said toothed rotary disk (202) such that the average air gap between metal tooth and sensor face is gs, and maximum and minimum air gaps being gs+Ags and gs-Ags, the output signal magnitude for a fixed rotational speed varies between those values corresponding to air gaps gs+Ags and gs-Ags with same frequency as that of rotation and the profile of the signal amplitude is dependent on the way in which the amplitude of the teeth on the toothed gear varies gradually. This dependence may be defined as a function in terms of the profiling of the heights of the teeth around the circumference of the toothed gear.

Once the signals from the sensor are obtained, from the frequency measurement of the signal, it is possible to detect the rotational speed of the rotor.

An electronic signal processing circuit such as a microcontroller based circuit is used to calculate the rotational speed from the frequency of the pulses. Or equivalents a simple frequency to voltage converter circuit may also be used to obtain the value equivalent to the rotational speed of the rotor.

A table is pre-compiled and made available to the angular speed and position detection system which has maximum and minimum values of voltages occurring at predefined set of speeds within a range of lowest and highest speeds possible for the rotating element. If the distance of the sensor from the centre of toothed gear changes, table values need to be changed. This may be achieved by a self-calibration mechanism in which the electronic controller of the system observes the maximum and minimum signal peak profile for a constant rotational speed for predefined time duration, and then correspondingly scales all the table values to match the present signal amplitudes. Alternatively a manual calibration method is also possible in which a calibrate command is given to the electronic controller which holds the table data and the rotor is rotated at fixed speed.

The table data is compiled such that peak values for any speed possible within the limits of the table data can be obtained with any known interpolation methods from the speed and peak values mentioned in the table.

In one of the embodiments of the present invention, the toothed rotary disk (202) with varying heights of teeth (203) can be constructed such that it is elliptical in shape, and one of the focal points being considered as centre of the toothed rotary disk. When connected with the rotating element, the toothed rotary disk (202) rotates about this focal point. The lengths of major axis and minor axis can be selected to suit the application based on the maximum and minimum air gaps permitted for teeth from the sensor element.

According to another embodiment of the present invention, the toothed rotary disk (202) can be constructed by overlapping two virtual circles with their centres offset. In this method of construction, a disc with sufficient thickness to be used as a toothed rotary disk (202) is used to obtain a primary toothed rotary disk whose teeth are at least as long as the longest of the teeth in the final toothed rotary disk. Using standard cutting mechanisms, a circular part of the primary toothed rotary disk is cut out such that the cut portion has its centre offset from the centre of the primary toothed rotary disk. The offset of the cut circle can be selected to suit application based on the maximum and the minimum air gaps permitted for teeth from the sensor element.

Based on the inputs from sensors and microcontroller different look up table can be made for different required purpose.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.

We Claim:

1. A device for measuring angular speed and position of a rotating element comprising:

a toothed rotary disk mounted to a rotational element;

a sensor placed in proximity to the toothed rotary disk; and

a controller electrically connected to said sensor and to calculate angular position and speed of rotating element;

wherein the said toothed rotary disk is having progressively varying teeth height on its periphery.

2. The device as claimed in claim 1, wherein the said sensor is any sensor which gives output signal corresponding to the change in magnetic field.

3. The device as claimed in claim 1, wherein the said controller processes the analog and digital signal.

4. A method for measuring angular speed and position of a rotating element, comprising the following steps:

Generating rotation of toothed rotary disk to produce a detecting signal;

Sensing said detecting signal;

Applying said detection signal to controller; and

Performing on said signal thus processed