The application is a divisional application with the filing date of 2020, 6/18, application number 2020105620650, entitled method for measuring the rotation speed and angle of a micro-shaft.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a brand-new system for measuring the rotating speed and the angle of a micro shaft.
In order to solve the technical problems, the invention adopts the following technical scheme:
a system for measuring the rotation speed and angle of miniature shaft is composed of a sensor unit consisting of a stator with circular and straight tube-shaped cross section, a rotor in the stator and able to rotate freely around its central line, an ultrasonic sensor fixed to the end of rotor, and multiple grid bars uniformly distributed around the stator, and an information acquisition unit consisting of ultrasonic sensor and grid bars, multiple information acquisition units on stator and rotor, and a signal processing unit, one group of information acquisition units in the plurality of groups is provided with one grid bar, and two groups of grid bars of two adjacent groups of information acquisition units in other groups of information acquisition units are distributed in a relative staggered manner.
During measurement, the detected shaft and the rotor are coaxially fixed, or the detected shaft is directly adopted to replace the rotor, the rotation transmission part is used for driving the detected shaft to rotate around the axis direction of the rotation transmission part, and the signal processing part carries out signal analysis on detection information obtained by the sensor part so as to obtain measurement information.
Preferably, be formed with from the inside sunken mounting groove in surface on the circumference side of the supersound echo detection zone that the rotor corresponds, the information acquisition unit has three groups, and three group's grid strip sets up side by side at the stator inner wall, and three ultrasonic sensor and grid strip one-to-one just are side by side in the mounting groove, and wherein the grid strip quantity of first row and second row equals to be N, and has 180 degrees/N's angular deviation between the grid strip of first row and second row, the third row grid strip quantity is 1. Through the synchronous motion of the information acquisition units of multiple groups and the acquisition of information, namely multi-bit gray coding, namely an absolute encoder, the number of bits of the gray coding is improved by increasing the number of rows of the grid strips and the number of the ultrasonic sensors, so that the resolution of the encoder is improved, and the detection result is more accurate.
Furthermore, an angular deviation of 180 °/N is also provided between the grid bars of the second and third rows.
Preferably, during measurement, signal acquisition of ultrasonic echo is performed under synchronous rotation of the detected shaft and the ultrasonic sensor, wherein when an emitting surface of the ultrasonic sensor is parallel to a tangent line of each grating strip, a reflected echo signal is strongest and is Amax, when the emitting surface of the ultrasonic sensor is over against the middle position of two adjacent grating strips, the reflected echo signal is weakest and is Amin, and when the emitting surface of the ultrasonic sensor is at other positions, the reflected echo signal is between Amax and Amin.
According to a specific implementation and preferred aspect of the invention, the stator is arranged close to the end of the grid bars, and during measurement, the ultrasonic echo detection area is filled with an ultrasonic transmission medium. Therefore, after the end part of the stator is closed, a transmission medium, such as water, a saline water mixture and other media can be filled in the ultrasonic echo detection area formed by the stator, and the ultrasonic can be smoothly transmitted between the ultrasonic sensor and the grating strip, and between the ultrasonic sensor and the inner wall of the stator.
Preferably, the detected shaft is the rotor and has a diameter greater than or equal to 0.3 mm; the inner diameter of the stator is more than or equal to 0.4mm, and the outer diameter of the stator is more than or equal to 0.5 mm. Thus, in this example, the rotation speed and rotation angle of the upper shaft having a diameter of 0.3mm or more can be detected.
According to a further embodiment and preferred aspect of the invention, the grid bars are embedded, etched or evaporated on the inner wall of the stator. Of course, the outer wall also works, and the advantage of the grille strips arranged on the inner wall is that: the ultrasonic echo can be reflected more accurately, and the detection precision is improved.
Preferably, the stator has a notch formed in an inner wall thereof, and the grill bars are formed in the notch.
Specifically, the side of the grid bar facing the rotor is flush with the inner wall surface of the stator. Therefore, the forming of the grid bars is very convenient, the ultrasonic echo detection is more accurately realized, and the appearance is more attractive.
Preferably, the grid bars are made of metal sheets or metal wires, and the stator is made of plastic. The echo intensity formed between the metal and the plastic is greatly different, so that the acquisition of a detection signal is facilitated, namely, the echo signal formed by the grating bars is stronger than the echo signal formed by the side wall of the stator.
Furthermore, a rotary connection is provided between the rotor and the stator. Certainly, the rotating connecting piece is not arranged and is not influenced, and after the rotating connecting piece is arranged, the rotor rotates more stably relative to the stator.
Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:
the invention uses the ultrasonic sensor to form the rotation of the ultrasonic echo detection area in a plurality of grid bars and form echo signals with different strengths to be fed back to the signal processing part for analysis processing, thereby obtaining the detection result, meanwhile, the accurate detection ultrasonic detection can be implemented even if the outer diameter of the detected shaft is 0.3mm or more, compared with the other parts, the invention has the following advantages that the transmission of the ultrasonic has no requirements on light, electromagnetism and the like, is not easily influenced by external conditions, and is suitable for the detection of lightproof materials.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise explicitly specified or limited, a first feature "on" or "under" a second feature may be directly contacted with the first and second features, or indirectly contacted with the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.
As shown in FIG. 1, the present embodiment discloses a system for measuring the rotational speed and angle of a miniature shaft, which uses an ultrasonic rotary encoder for detection.
Specifically, the ultrasonic rotary encoder comprises a sensor part 1, a rotation transmission part 2 (which can be a slip ring, a rotary transformer, a rotary capacitor, a rotary optical fiber coupler, etc.), and a signal processing part 3, wherein the rotation transmission part 2 comprises a rotating part 20 for driving a detected shaft to rotate around the axis direction of the rotation transmission part, and an information transmission part 21 communicated with the sensor part 1 and the signal processing part 3, detection information obtained by the sensor part 1 is transmitted to the signal processing part 3 by the information transmission part 21, and the signal processing part 3 performs signal analysis to obtain measurement information.
The sensor section 1 includes a stator 10 having a circular cross section and a straight tube shape, a rotor 11 rotatably provided inside the stator 10 around the center line direction of the stator 10, an ultrasonic sensor 12 fixedly provided at an end of the rotor 11 extending into the stator 10, and a plurality of grid bars 13 uniformly distributed around the circumference of the stator 10.
In this example, the outer diameter of the stator 10 is 1.0mm, the inner diameter of the stator is 0.8-0.9mm, and the outer diameter of the rotor 11 is 0.6 mm.
The detected shaft is the rotor 11, and the rotor 11 and the stator 10 are coaxially and rotationally connected through a rotational connecting piece 14.
In this example, each of the grating bars 13 is a tungsten wire disposed on the inner wall of the stator 10, and the ultrasonic sensor 12 is located in an ultrasonic echo detection region formed by the plurality of grating bars 13.
Referring to fig. 2, a notch 100 is formed in the inner wall of the stator 10, a grid bar 13 is formed in the notch 100, and the side surface of the grid bar 13 facing the rotor 11 is flush with the inner wall surface of the stator 10. The forming of grid bars is very convenient, and the ultrasonic echo detection is more accurately realized.
Simultaneously, the material of stator 10 is plastics, and the closed setting of tip that stator 10 is close to grid strip 13, so, after the closed of stator 10 tip, can be full of transmission medium in the supersound echo detection zone that stator 10 formed, medium such as water, salt water mixture, and then guarantee that the ultrasonic wave can be smooth propagate between ultrasonic sensor and grid strip, ultrasonic sensor and stator inner wall.
An inwardly recessed mounting groove 110 is formed on a circumferential side surface of the rotor 11 that protrudes into an end portion of the stator 10, and the ultrasonic sensor 12 is disposed in the mounting groove 110.
The mounting groove 110 extends along the length direction of the rotor 11, and the ultrasonic sensor 12 and the corresponding grating strip 13 constitute a set of information acquisition units H.
The rotor 11 is provided hollow inside, and the sensor portion 1 further includes a cable 15 located inside the rotor 11 and capable of communicating the ultrasonic sensor 12 with the rotation transmission portion 2. Of course, the ultrasonic sensor 12 may feed back the obtained information to the information transmission unit 21 by wireless, and the information is forwarded to the signal processing unit 3 by the information transmission unit 21.
In this example, the length, width, and height of the ultrasonic sensor 12 are 0.4mm 0.5mm 0.3 mm.
In conjunction with fig. 3, during the rotation of the ultrasonic sensor 12, according to the principle of acoustic reflection, when the emitting surface of the ultrasonic sensor 12 is parallel to the tangent of each grating strip 13, the reflected echo intensity is maximum Amax, and at the middle position between two adjacent grating strips 13, the reflected echo intensity is weakest Amin, and when at other positions, the reflected echo intensity is between Amax and Amin.
Referring to fig. 4, three sets of information acquiring units H are formed on the stator 10 and the rotor 11, three ultrasonic sensors 12 are arranged in the mounting groove 110 side by side, three sets of grid bars 13 are arranged on the inner wall of the stator 10 side by side, wherein the number of the grid bars 13 in the first row and the second row is equal to N, an angle deviation of 180 °/N is formed between the grid bars 13 in the first row and the second row, and the number of the grid bars 13 in the third row is 1.
At the same time, the same angular deviation (angle of 180 °/N) also exists between the grid bars 13 of the third row and the grid bars 13 of the second row.
Therefore, three sets of information acquisition units are set, namely 3-bit gray coding, namely absolute type coder.
Also, the number of gray-coded bits can be increased by increasing the number of scale lines and the number of ultrasonic sensors, thereby increasing the resolution of the encoder.
In addition, taking an ultrasonic probe with a center frequency of 50MHz as an example, the transverse resolution of the ultrasonic probe is about 200um, and the size of the resolution determines that the minimum scale interval of the grating bars on the stator cannot be smaller than the transverse resolution of the ultrasonic probe, so that the required strong and weak signals can be acquired
Assuming a lateral resolution of λ, the angular resolution of the encoder is up to 360 °/λ. We can improve the accuracy of the encoder by increasing the number of sensors.
In summary, in the embodiment, the sensor is designed by using the intensity of the reflected echoes of different reflectors when the ultrasonic waves encounter, and the rotation speed and the position of the rotating object are measured by using the principle of rotation coding.
Meanwhile, the ultrahigh frequency miniature ultrasonic sensor can be used for designing the structure of the encoder to be used for measuring the rotating speed and the position of a detected shaft with the diameter of more than 0.3mm, so that the ultrahigh frequency miniature ultrasonic sensor can be applied to the field of high-precision detection, such as in-vivo interventional medical imaging equipment, can effectively correct image distortion (NURD) and the like caused by rotational distortion, ensures the accuracy of images and has very good advantages.
The detection process of this embodiment is as follows:
1) replacing the rotor with the detected shaft, forming a mounting groove at the end part of the rotor, and correspondingly distributing the ultrasonic sensors in the mounting groove and correspondingly positioning the ultrasonic sensors in an ultrasonic echo detection area formed by a plurality of grid bars;
2) starting the rotary transmission part and the ultrasonic sensor, and acquiring signals of ultrasonic echoes under the synchronous rotation of a detected shaft and the ultrasonic sensor, wherein when the transmitting surface of the ultrasonic sensor is parallel to the tangent line of each grating strip, the intensity of the reflected echo is strongest and is Amax, when the transmitting surface of the ultrasonic sensor is over against the middle position of two adjacent grating strips, the intensity of the reflected echo is weakest and is Amin, and when the transmitting surface of the ultrasonic sensor is at other positions, the intensity of the reflected echo is between Amax and Amin;
3) and the ultrasonic sensor transmits the acquired reflected echo intensity to the signal processing part, and the signal processing part performs data analysis, wherein specific values of the rotating speed and the rotating angle of the detected shaft can be obtained according to the analysis result. .
Meanwhile, in order to further improve the resolution of the encoder, in step 1), three groups of information acquisition units may be arranged side by side to form a three-bit gray code, and of course, multiple groups of multi-bit gray codes may be used for detection, so that the motion data of the detected shaft can be acquired more accurately.
Specifically, in this example, the grid bars uniformly distributed on the circumference of the stator form n scales, so the angle between each reflection scale is θ =360 °/n, during the rotation of the ultrasonic sensor, the ultrasonic sensor continuously transmits and receives ultrasonic signals, and assuming that the number of transmitted signals per rotation is m, the value needs to be much larger than n (because if only n signals are received per rotation of the rotor, that is, each grid bar only receives one echo signal, so that data sampling is far insufficient, and therefore enough m transmitted signals exist, so that the amplitude of the received back signal can be guaranteed, and each position and the adjacent position are almost continuously changed).
The value of each received echo intensity of the sensor is set to Ai,
the strength values of the echoes received in each turn of the ultrasonic sensor are respectively as follows:
A1,A2,……Ai,……Am.
since the value of m set by the user is far greater than n, it can be assumed that the intensity of n scale reflected echoes is the maximum, the signal Amax, the intensity of n reflected echoes is the minimum, and the signal Amin are all assumed in each circle.
The signal processing section calculates the intensity Ai of the reflected signal and the echo intensity value Ai versus time t can be plotted as shown in fig. 5. The curve shown in fig. 6 can be obtained by processing of the signal processing part.
Similarly, if three sets of information acquiring units are used, wherein the angle deviation of θ/2 is formed between the scales formed by the first and second rows, and the scale of the third row has only one scale, the information obtained by each set of information acquiring units is transmitted to the signal processor, so as to obtain the curve shown in fig. 7.
The present invention has been described in detail in order to enable those skilled in the art to understand the invention and to practice it, and it is not intended to limit the scope of the invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the present invention.