A torque sensor

Abstract

The application discloses a torque sensor, comprising: a middle shaft; a shaft sleeve assembly fixed to the outer periphery of the middle shaft; the shaft sleeve assembly comprises a shaft sleeve body, a first control board and a first coil, the first control board and the first coil are both mounted on the shaft sleeve body; a disc claw assembly is sleeved on the periphery of the middle shaft and is in transmission connection with the middle shaft, the disc claw assembly comprises a strain gauge, a second control board and a second coil; wherein the second control board is configured to generate a pulse position modulation signal after digitally encoding the voltage signal output by the strain gauge; the duty cycle of each symbol in the pulse position modulation signal is not greater than 1 / 3; the first control board is configured to receive the pulse position modulation signal and output torque information after decoding. The torque sensor has low cost and high precision. In addition, the disc claw assembly and the shaft sleeve assembly can be arbitrarily matched, thereby improving the manufacturability and maintainability.

Description

Technical Field

[0001] This invention relates to the technical field of motion parameter acquisition, and specifically to a torque sensor for data acquisition. Background Technology

[0002] To address the fatigue associated with traditional bicycle riding and the poor riding experience of electric bicycles when the battery is dead, the electric-assist bicycle was developed. An electric-assist bicycle is essentially a bicycle with an added power assistance system. The biggest difference between an electric-assist bicycle and a regular electric bicycle is that it lacks a control valve (a standard accelerator lever). Instead, it automatically completes the acceleration and assistance process through the collaboration of a bottom bracket sensor and a motor controller. In other words, the electric-assist bicycle uses sensors to collect riding parameters (primarily the rider's pedaling torque) to determine whether the rider needs motor assistance and how much assistance is required. Because the bottom bracket sensor is attached to a rotating mechanism, it cannot be powered or transmit signals via wires; therefore, power supply and reverse signal transmission must be achieved wirelessly.

[0003] Currently, the common technical solution is to communicate between signal processing and signal detection through optocoupler or VF conversion, which results in high communication costs and low acquisition accuracy.

[0004] In summary, there is a need to design a torque sensor to solve the aforementioned problems in the existing technology. Summary of the Invention

[0005] This invention provides a torque sensor that solves the technical problem of low accuracy in acquiring cycling parameters in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A torque sensor, comprising:

[0008] The central axle is detachably connected to the frame at both ends via support bearings.

[0009] A bushing assembly is fixed to the outer periphery of the central shaft; the bushing assembly includes a bushing body, a first control plate, and a first coil, wherein the first control plate and the first coil are both mounted on the bushing body;

[0010] A claw assembly is sleeved around the central shaft and drivenly connected to the central shaft. The claw assembly includes a strain gauge, a second control plate, and a second coil.

[0011] The second control board is configured to digitally encode the voltage signal output by the strain gauge to generate a pulse position modulation signal;

[0012] The duty cycle of the high level of each symbol in the pulse position modulation signal is less than the duty cycle of the low level;

[0013] The first control board is configured to receive the pulse position modulation signal, decode it, and output torque information.

[0014] In some embodiments of the present invention

[0015] The first control board is configured to output a pulse width modulation signal, which is then amplified via push-pull to power the claw assembly; the frequency of the pulse width modulation signal corresponds one-to-one with the frequency of the pulse position modulation signal.

[0016] The second control board is configured to control the modulation of the variable load using the pulse position modulation signal.

[0017] In some embodiments of the present invention

[0018] The first control board is also provided with a detection circuit, which includes a current sampler, an envelope detector, and a signal processing circuit. The current sampler converts the change in load current into a change in voltage, and after passing through the envelope detector, an envelope signal is obtained. The signal processing circuit amplifies and shapes the envelope signal to restore the pulse position modulation signal.

[0019] In some embodiments of the present invention

[0020] The second control board is also configured to store calibration data of the jaw assembly; when the torque sensor is powered on for the first time, the second control board is used to send the calibration data to the first control board; the calibration data includes the model, serial number, zero point and slope of the linear relationship between the torque and the voltage signal of the jaw assembly.

[0021] In some embodiments of the present invention

[0022] The central shaft is also surrounded by a multi-stage magnet. The first control board is equipped with a Hall sensor electrically connected to it. The Hall sensor is radially corresponding to and coaxially arranged with the multi-stage magnet. When the central shaft rotates, the relative position of the Hall sensor and the multi-stage magnet changes and outputs two pulse signals with a phase difference. The first control board outputs rotation speed information according to the pulse signals.

[0023] In some embodiments of the present invention

[0024] The multi-level magnet includes a first magnet and a second magnet, which are semi-circular magnets and together form a multi-level magnetic ring.

[0025] In some embodiments of the present invention

[0026] The first coil and the second coil are coaxially arranged to form a transformer coupling. A wire groove is provided on the central shaft, and the second coil is connected to the second control board through the wire groove.

[0027] In some embodiments of the present invention

[0028] The claw assembly also includes a claw body, which is assembled perpendicularly to the central axis. The claw body is symmetrically provided with mounting slots. There are two strain gauges, which are fixed in the symmetrically provided mounting slots respectively. The strain gauges are communicatively connected to the second control board.

[0029] In some embodiments of the present invention

[0030] The two strain gauges form a bridge circuit, which outputs a voltage signal under torque. The voltage signal is then transmitted to the second control board after passing through an amplification circuit and an AD conversion circuit.

[0031] In some embodiments of the present invention

[0032] The claw assembly also includes an upper claw shell and a lower claw shell located on both sides of the claw body; the upper claw shell and the lower claw shell are fixedly connected to form a mounting cavity for fixing the second control board.

[0033] The technical solution of the present invention has the following technical effects compared with the prior art:

[0034] This invention proposes a torque sensor comprising a jaw assembly and a bushing assembly, capable of measuring torque and rotational speed. Wireless power supply is achieved through transformer-coupled resonance, while digital transmission of the torque signal is realized by applying a pulse position modulation signal to the power supply circuit. This provides a low-cost, high-precision torque sensor. Furthermore, this invention outlines a calibration and communication process for the torque sensor, allowing for arbitrary interoperability between the jaw assembly and the bushing assembly, improving manufacturability and maintainability. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the torque sensor structure shown in the embodiment of this utility model.

[0037] Figure 2This is an exploded view of the torque sensor structure shown in the embodiment of this utility model.

[0038] Figure 3 This is a schematic diagram of the structure of the main body of the disk claw shown in the embodiment of this utility model.

[0039] Figure 4 This is a schematic diagram of the signal transmission of the torque sensor shown in the embodiment of this utility model.

[0040] Figure 5 This is a waveform diagram of the PPM modulation shown in the embodiment of this utility model.

[0041] Figure 6 The waveform diagram of the pulse position modulation signal shown in the embodiment of this utility model is shown.

[0042] Figure 7 This is a schematic diagram illustrating the calibration process of the torque sensor in the embodiments described in this utility model.

[0043] Figure 8 The image shows the rotational speed detection waveform of the embodiment described in this utility model.

[0044] Figure label:

[0045] 100-Central shaft; 110-Support bearing; 200-Sleeve assembly; 210-Sleeve body; 220-First control board; 230-First coil; 310-Strain gauge; 320-Second control board; 330-Second coil; 340-Claw body; 350-Claw upper shell; 360-Claw lower shell; 400-Multi-stage magnet; 500-Hall sensor. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0048] Example 1, Reference Figure 1 and Figure 4 As shown, a torque sensor includes:

[0049] The central axle 100 is detachably connected to the frame at both ends via support bearings 110.

[0050] A bushing assembly 200 is fixed to the outer periphery of the central shaft 100; the bushing assembly 200 includes a bushing body 210, a first control plate 220 and a first coil 230, the first control plate 220 and the first coil 230 are both mounted on the bushing body 210.

[0051] The claw assembly is sleeved around the central shaft 100 and is connected to the central shaft 100 in a transmission manner. The claw assembly includes a strain gauge 310, a second control plate 320, and a second coil 330.

[0052] The second control board 320 is configured to digitally encode the voltage signal output by the strain gauge 310 to generate a pulse position modulation signal.

[0053] The duty cycle of the high level of each symbol in the pulse position modulation signal is less than the duty cycle of the low level;

[0054] The first control board 220 is configured to receive the pulse position modulation signal, decode it, and output torque information.

[0055] Specifically, the claw assembly is mainly used to collect the deformation of the claw, obtain a torque signal, and transmit the torque signal to the bushing assembly 200. After receiving the torque signal sent by the claw assembly, the bushing assembly 200 converts it into the output quantity of the torque sensor, i.e., torque information.

[0056] The transmission process between the two is as follows: the second control board 320 acquires the deformation signal and encoding of the strain gauge 310, and transmits the torque signal to the bushing assembly 200 by controlling the load change of the power supply circuit, using pulse position modulation. Then, the first control board 220 uses the pulse input capture function to obtain the high and low level times of the modulated signal, thus achieving decoding.

[0057] In some embodiments of the present invention

[0058] Continue to refer to Figure 4 As shown, the first control board 220 is configured to output a pulse width modulation signal, which is then amplified by push-pull to power the claw assembly;

[0059] Specifically, the first control board 220 outputs a high-frequency pulse width modulation signal with a 50% duty cycle, referring to... Figure 1As shown, the first coil 230 and the second coil 330 are coaxially arranged, and each coil is wound using a close-wound method. The first coil 230 and the second coil 330 are coupled by a transformer, and their output voltage is determined by the turns ratio. Depending on factors such as the diameter of the shaft and the width of the air gap, the turns ratio is generally between 1:1.5 and 1:4. After extensive experimental analysis, within a power supply range of 3.3V to 5V, the number of turns of the outer coil is 20 to 30T, and the number of turns of the second coil 330 is 30 to 120T. The first coil 230 is fixed to the bushing body 210; the second coil 330 is fixed to the central shaft 100 and rotates with the central shaft 100.

[0060] Furthermore, the central shaft 100 is made of steel and functions similarly to the iron core of a transformer, which can improve the coil coupling coefficient; the first coil 230 has 26 turns and is wound in 1 layer, and the second coil 330 has 75 turns and is wound in 3 layers.

[0061] A high-frequency pulse width modulation signal with a duty cycle of 50% and a frequency of 888kHz is amplified by a push-pull mechanism to drive a second coil 330, which in turn powers the claw assembly. Additionally, a wire groove is provided on the central shaft 100, through which the second coil 330 is connected to the second control board 320. The AC voltage across the second coil 330 is rectified and regulated to power the claw assembly, specifically the second control board 320.

[0062] In some embodiments of the present invention, reference is made to... Figure 2 and Figure 3 As shown, the claw assembly also includes a claw body 340, a claw upper shell 350, and a claw lower shell 360, wherein the claw upper shell 350 and the claw lower shell 360 are located on both sides of the claw body 340 and are fixedly connected to form a mounting cavity for fixing the second control plate 320.

[0063] The claw assembly is perpendicularly mounted to the central shaft 100. The claw body 340 is symmetrically provided with mounting slots. Two strain gauges 310 are fixed in the symmetrically arranged mounting slots. The purpose of the mounting slots is to improve the linearity and sensitivity of the output signal of the strain gauges 310 while ensuring the overall structural strength of the claw. The strain gauges 310 are communicatively connected to the second control board 320.

[0064] Two strain gauges 310 form a bridge circuit. Under torque, the bridge outputs a voltage signal. This voltage signal is then amplified and converted by an AD converter before being transmitted to the second control board 320. The second control board 320 digitally encodes the obtained data to generate the pulse position modulation signal. This pulse position modulation signal controls the switching on and off of the transistor, achieving load modulation. The frequency of the pulse position modulation signal corresponds one-to-one with the frequency of the pulse width modulation signal.

[0065] The encoding format proposed in this embodiment includes four code elements: a start bit, a sign bit (logic "0"), a sign bit (logic "1"), and a stop bit. Each code element consists of a high-level pulse and a low-level pulse, differing only in the duration of the high and low levels. (Refer to...) Figure 5 As shown.

[0066] As described above, the pulse position modulation signal controls the state of the variable load, i.e., a high level corresponds to a high load state, and a low level corresponds to a low load state. Since the modulation results in a specific change in the load current, in order to ensure that there is no voltage drop or excessive power consumption due to excessive load current, the duty cycle of each symbol should not be greater than 1 / 3, i.e., TxH < 2 * TxL, where TxH is the high-level duty cycle and TxL is the low-level duty cycle.

[0067] In other words, since this implementation uses coil coupling for power supply, and since coil coupling has limited efficiency and is not an ideal transformer, adjusting the ratio of high and low levels of each symbol to no more than 1:2 can control the load current from being too large, thus preventing voltage drops or unnecessary power losses.

[0068] Specifically, the encoded data is transmitted in the form of data frames, with each frame taking approximately 7.7 milliseconds to transmit, resulting in a communication rate of approximately 130 frames per second. Each frame consists of 4 bytes of data: a 1-byte status word, 2 bytes of data, and a 1-byte checksum. The checksum is the result of a bitwise XOR operation between the high and low bytes of the data word. A complete frame waveform is shown below. Figure 6 As shown.

[0069] In some embodiments of the present invention, after receiving the pulse position modulation signal sent by the second control board 320, the first control board 220 performs decoding, with a decoding fault tolerance rate set to 30%. Taking the reception of logic 0 as an example, if the captured pulse period range is 67~124us and the pulse width range is 22~42us, then the current bit is determined to be 0. After a complete frame of data is received, the first control board 220 converts it into the corresponding output quantity, namely the torque information of the torque sensor.

[0070] In some embodiments of the present invention, reference continues to be made to... Figure 4As shown, the first control board 220 is also provided with a detection circuit, which includes a current sampler, an envelope detector, and a signal processing circuit. The current sampler converts the change in load current into a change in voltage, and after passing through the envelope detector, an envelope signal is obtained. The signal processing circuit amplifies and shapes the envelope signal to restore the pulse position modulation signal.

[0071] To improve the timing accuracy of waveform detection, falling edge capture is required. Therefore, the output signal at this time is out of phase with the original pulse position modulation signal. The output signal of the detection circuit is sent to the first control board 220, which obtains the symbol information of each data bit based on the captured pulse period and pulse width, ultimately obtaining the entire data frame.

[0072] In some embodiments of the present invention, in order to achieve arbitrary adaptation between the bushing assembly 200 and the claw assembly, the conversion process of the output quantity needs to be calculated based on the calibration data of the claw assembly.

[0073] Specifically, the torque sensor needs to be calibrated for its zero point and slope parameters during production. The second control board 320 is also configured to store the calibration data of the claw assembly; see reference... Figure 7 As shown, when the torque sensor is powered on for the first time, the second control board 320 sends the calibration data to the first control board 220; after obtaining the torque data, the first control board 220 calculates the torque based on the calibration data, performs D / A conversion, and outputs the torque signal, or outputs the torque data through the serial port.

[0074] The calibration data includes the model and series number of the jaw assembly, and the zero point and slope in the linear relationship between torque and voltage signal. Since the torque magnitude is linearly related to the sampled data of the jaw, only the zero point and slope (or full-scale change) are needed to complete the calculation.

[0075] In some embodiments of the present invention, the rotational speed measurement function is implemented by a multipole magnet 400 and a Hall sensor 500 disposed on the central shaft 100.

[0076] Specifically, refer to Figure 1 As shown, a multi-stage magnet 400 is also sleeved around the central shaft 100. A Hall sensor 500 electrically connected to the central shaft 100 is provided on the first control board 220. The Hall sensor 500 is radially corresponding to and coaxially arranged with the multi-stage magnet 400. When the central shaft 100 rotates, the relative position of the Hall sensor 500 and the multi-stage magnet 400 changes and outputs two pulse signals with a phase difference. The first control board 220 outputs rotation speed information according to the pulse signals.

[0077] In some embodiments of the present invention, the multi-level magnet 400 includes a first magnet and a second magnet, both of which are semi-circular magnets with an even number of magnetic poles, one end being the N pole and the other end being the S pole. This allows the two magnets to attract each other during installation, forming a complete multi-level magnetic ring, which is easier to assemble than a pre-formed ring magnet.

[0078] During the use of the torque sensor, the rotation of the central shaft 100 causes the Hall sensor 500, fixed on the bushing assembly 200, to sense the alternating changes in magnetic poles and generate two high- and low-level pulses with a phase difference of ±90°. These two pulse signals are acquired by the first control board 220. The first control board 220 determines the forward or reverse rotation based on the phase relationship of the two signals. During forward rotation, the first control board 220 multiplies the frequency of the two input pulses to generate a pulse output corresponding to the number of magnetic poles. During reverse rotation, the current output level remains unchanged. Figure 8 As shown.

[0079] The technical solution of the present invention has the following technical effects compared with the prior art:

[0080] This invention proposes a torque sensor comprising a jaw assembly and a bushing assembly, capable of measuring torque and rotational speed. Wireless power supply is achieved through transformer-coupled resonance, while digital transmission of the torque signal is realized by applying a pulse position modulation signal to the power supply circuit. This provides a low-cost, high-precision torque sensor. Furthermore, this invention outlines a calibration and communication process for the torque sensor, allowing for arbitrary interoperability between the jaw assembly and the bushing assembly, improving manufacturability and maintainability.

[0081] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0082] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A torque sensor, characterized in that, include: The central axle is detachably connected to the frame at both ends via support bearings. A bushing assembly is fixed to the outer periphery of the central shaft; the bushing assembly includes a bushing body, a first control plate, and a first coil, wherein the first control plate and the first coil are both mounted on the bushing body; A claw assembly is sleeved around the central shaft and drivenly connected to the central shaft. The claw assembly includes a strain gauge, a second control plate, and a second coil. The second control board is configured to digitally encode the voltage signal output by the strain gauge to generate a pulse position modulation signal; The duty cycle of the high level of each symbol in the pulse position modulation signal is less than the duty cycle of the low level; the ratio of the high level to the low level of each symbol is adjusted to no more than 1:2; The first control board is configured to receive the pulse position modulation signal, decode it, and output torque information; The second control board is also configured to store the calibration data of the disk claw assembly; When the torque sensor is powered on for the first time, the second control board sends the calibration data to the first control board. The calibration data includes the model and serial number of the claw assembly, the zero point and slope in the linear relationship between the torque and the voltage signal. After obtaining the torque data, the first control board calculates the torque based on the calibration data, performs D / A conversion, and outputs the torque signal, or outputs the torque data through the serial port.

2. A torque sensor according to claim 1, characterized in that, The first control board is configured to output a pulse width modulation signal, which is then amplified via push-pull to power the claw assembly; the frequency of the pulse width modulation signal corresponds one-to-one with the frequency of the pulse position modulation signal. The second control board is configured to control the modulation of the variable load using the pulse position modulation signal.

3. A torque sensor according to claim 1, characterized in that, The first control board is also provided with a detection circuit, which includes a current sampler, an envelope detector, and a signal processing circuit. The current sampler converts the change in load current into a change in voltage, and after passing through the envelope detector, an envelope signal is obtained. The signal processing circuit amplifies and shapes the envelope signal to restore the pulse position modulation signal.

4. A torque sensor according to claim 1, characterized in that, The central shaft is also surrounded by a multi-stage magnet. The first control board is equipped with a Hall sensor electrically connected to it. The Hall sensor is radially corresponding to and coaxially arranged with the multi-stage magnet. When the central shaft rotates, the relative position of the Hall sensor and the multi-stage magnet changes and outputs two pulse signals with a phase difference. The first control board outputs rotation speed information according to the pulse signals.

5. A torque sensor according to claim 4, characterized in that, The multi-level magnet includes a first magnet and a second magnet, which are semi-circular magnets and together form a multi-level magnetic ring.

6. A torque sensor according to claim 5, characterized in that, The first coil and the second coil are coaxially arranged to form a transformer coupling. A wire groove is provided on the central shaft, and the second coil is connected to the second control board through the wire groove.

7. A torque sensor according to claim 4, characterized in that, The claw assembly also includes a claw body, which is assembled perpendicularly to the central axis. The claw body is symmetrically provided with mounting slots. There are two strain gauges, which are fixed in the symmetrically provided mounting slots respectively. The strain gauges are communicatively connected to the second control board.

8. A torque sensor according to claim 7, characterized in that, The two strain gauges form a bridge circuit, which outputs a voltage signal under torque. The voltage signal is then transmitted to the second control board after passing through an amplification circuit and an AD conversion circuit.

9. A torque sensor according to claim 7, characterized in that, The claw assembly also includes an upper claw shell and a lower claw shell located on both sides of the claw body; the upper claw shell and the lower claw shell are fixedly connected to form a mounting cavity for fixing the second control board.

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