Rotation speed measuring method based on multiple trigger points of sinusoidal signals of double Hall sensors

Abstract

The invention discloses a rotating speed measuring method based on multiple triggering points of sinusoidal signals of double Hall sensors, and the method comprises the following steps: S1, providing a rotating member and a plurality of magnetic poles which are uniformly distributed along the circumferential direction of the rotating member, and enabling the magnetic poles to form periodic magnetic field changes when the rotating member rotates; s2, a first Hall sensor and a second Hall sensor are arranged at the positions, spaced by 90 degrees, in the circumferential direction of the rotating component and used for collecting the magnetic field change signals and outputting a first sinusoidal signal and a second sinusoidal signal, and the two sinusoidal signals have a 90-degree phase difference. On the premise that the number of magnetic poles and hardware cost are not increased, Hall signal frequency multiplication output is achieved by introducing a multi-trigger-point mechanism, and the sampling precision of rotation speed measurement and the system response speed are remarkably improved.

Description

Technical Field

[0001] The present invention relates to a speed measurement method, and more particularly to a rotational speed measurement method based on multiple trigger points of sine signals of dual Hall sensors. Background Art

[0002] With the wide application of electric assist bicycles (E-bikes) and other transportation vehicles based on hybrid human and electric drive, the system's demand for real-time and accurate perception of pedal frequency is increasing day by day to achieve rapid recognition and response to the intentions of riders, thereby realizing smooth switching of motor power and enhancing the overall vehicle usage experience. In such application scenarios, Hall effect sensors, as the core devices for detecting rotational angle or rotational speed, are widely used in pedal frequency sensing systems due to their advantages such as low cost, fast response, and compact structure.

[0003] Currently, the more common rotational detection schemes mostly use two Hall sensors arranged with a 90-degree phase difference to respectively collect orthogonal magnetic field signals. These signals form sine waves as they change with the rotation period. The system detects the zero-crossing points of the sine signals to achieve the flipping of the output level, thereby obtaining a periodic square wave signal, which can be sampled by a microcontroller to calculate the rotational angular velocity and rotational direction. However, in this technical solution, since there are only two effective zero-crossing points in a complete sine period, the frequency of the output square wave signal is limited, which in turn limits the sampling accuracy and response speed of the rotational speed.

[0004] To increase the single-turn output signal frequency, some technical solutions attempt to expand the effective trigger points per turn by increasing the number of magnetic poles, thereby improving the sampling frequency. However, increasing the number of magnetic poles not only poses higher precision requirements for the arrangement of the magnetic ring and Hall sensors, but also significantly increases the hardware manufacturing cost and system debugging difficulty, and does not have good compatibility in the existing E-bike system architecture. Therefore, this type of method is difficult to be popularized and applied in the market with cost constraints and high requirements for module standardization.

[0005] In summary, the existing rotational measurement technology based on dual Hall sensors has the following deficiencies: (1) The frequency of the output square wave signal is low, and the sampling rate is limited; (2) Increasing the resolution by increasing the number of magnetic poles will lead to an increase in hardware cost; (3) It is difficult for the existing technology to improve the measurement accuracy without changing the hardware structure. Summary of the Invention

[0006] To solve the above problems, the present invention provides a rotational speed measurement method based on multiple trigger points of sine signals of dual Hall sensors, which can, without increasing the number of magnetic poles, realize a rotational speed measurement method with frequency doubling output of square wave signals by optimizing signal sampling and processing methods, thereby effectively improving the sampling frequency and measurement accuracy.

[0007] The present invention is realized through the following technical solutions: A rotational speed measurement method based on multiple trigger points of sine signals of dual Hall sensors, the method comprising the following steps: S1. Provide a rotating member and a plurality of magnetic poles evenly distributed along its circumference, and the magnetic poles form a periodic magnetic field change when the rotating member rotates; S2. Respectively arrange a first Hall sensor and a second Hall sensor at positions 90 degrees apart in the circumferential direction of the rotating member for collecting the magnetic field change signals and outputting a first sine signal and a second sine signal, and there is a 90-degree phase difference between the two sine signals; S3. Respectively perform zero-crossing detection on the first sine signal and the second sine signal, and when any sine signal passes through zero, generate a level flip trigger signal once; S4. Compare the amplitudes of the first sine signal and the second sine signal, and when the absolute values of their amplitudes are equal or close, generate another group of level flip trigger signals; S5. Combine the level flip trigger signals into an output sampling square wave signal, and the sampling signal contains multiple level flip points within each sine period for improving the rotational speed sampling frequency; S6. Transmit the sampling square wave signal to a microcontroller, and the microcontroller calculates the rotational speed of the rotating member according to the number of flips within a unit time.

[0008] As a preferred technical solution, the generation of the level flip trigger signal is based on continuous comparison of the amplitudes of sine signals, and a threshold is set to determine whether the voltage difference between the first sine signal and the second sine signal is less than a preset threshold, so as to determine that they are equal or close.

[0009] As a preferred technical solution, the magnetic poles include a magnetic ring composed of alternately arranged N poles and S poles, forming a continuously changing magnetic field signal.

[0010] As a preferred technical solution, the first Hall sensor and the second Hall sensor are arranged at a fixed angle through a printed circuit board, and the 90-degree relative position is achieved by accurately aligning the magnetic pole arrangement.

[0011] As a preferred technical solution, the level flip trigger signal is a TTL level signal with a voltage amplitude of 0V to 5V, suitable for edge trigger interrupt sampling of a single-chip microcomputer.

[0012] As a preferred technical solution, the sampled square wave signal includes eight level inversion points within each complete sine signal period, doubling the output frequency compared to the method based only on zero-crossing points.

[0013] As a preferred technical solution, the first sine signal and the second sine signal respectively pass through an analog amplifier circuit and a low-pass filter circuit before being input into the microcontroller to reduce signal interference and improve detection accuracy.

[0014] As a preferred technical solution, the microcontroller performs timed sampling based on the high and low level inversion edges of the sampled square wave signal, and determines the rotational speed by calculating the number of edges within a unit time. The determination result is used to control the motor power output of the electric assist bicycle.

[0015] As a preferred technical solution, it further includes: judging the rotation direction of the rotating member according to the relative phase of the first sine signal and the second sine signal.

[0016] The beneficial effects of the present invention are as follows: based on the output of orthogonal sine signals by two Hall sensors, the present invention designs trigger points with "zero-crossing points" and "points with equal absolute values", realizing the output of multiple level inversion signals within each sine period, effectively doubling the frequency of the traditional square wave signal triggered by zero-crossing points, improving the sampling density, thereby enhancing the detection accuracy of the rotational speed and the system response speed; Based on the existing hardware, the present invention optimizes the processing algorithm of Hall signals, excavates the unused information points in the dual Hall sensors, realizes frequency doubling sampling output, without increasing the number of magnetic poles or replacing the sensor model, avoiding the problems of cost increase and structural complexity caused by hardware changes; The present invention does not need to modify the physical structure of the traditional cadence sensor. Only by adding a multi-trigger point recognition mechanism to the signal processing logic, it can be compatible with the existing cadence control system of electric assist bicycles, having good system adaptability and popularization and application value; The present invention adopts a standard Hall element and a magnetic ring structure, and can complete signal acquisition through standard PCB layout and angle design, maintaining the simplicity of the system design while improving performance, and reducing the debugging and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic diagram of the hardware layout of the dual Hall sensors of the present invention; Figure 2 Schematic diagram of the inversion point of the output signal inversion point of the present invention; Figure 3 Simulation diagram of the output signal of the present invention Specific implementation manners

[0019] All features disclosed in this specification, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any manner.

[0020] Any feature disclosed in this specification (including any additional claims, abstract, and drawings), unless specifically recited, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically recited, each feature is only an example of a series of equivalent or similar features.

[0021] As Figures 1 - 3 shown, the present invention provides a rotational speed measurement method based on multiple trigger points of a sine signal of a dual Hall sensor, which is applicable to an e-assisted bicycle system that requires high-precision cadence detection or a similar control system based on rotational speed detection.

[0022] In this embodiment, without increasing the number of magnetic poles, the method realizes signal frequency doubling sampling by introducing multiple trigger point logics in the signal processing strategy, thereby improving the speed sampling rate and meeting the system's requirements for high real-time performance and high sensitivity.

[0023] Specifically, first, a plurality of magnetic poles are arranged in the circumferential direction of the rotating member. The magnetic poles are alternately arranged N poles and S poles, forming a closed-loop magnetic ring structure. When the rotating member rotates, the magnetic poles move accordingly, forming a stable periodic magnetic field change. The Hall sensor is used to sense this magnetic field change and then output a corresponding voltage signal.

[0024] To obtain sine signals with a 90-degree phase difference from each other, in this embodiment, two positions separated by 90 electrical degrees in the circumferential direction of the rotating member are respectively provided with a first Hall sensor and a second Hall sensor. To ensure the accuracy of the arrangement angle, the two Hall sensors are fixed on the same printed circuit board (PCB). The PCB is stably connected to the rotating member through a bracket. During the arrangement process, the relative position between it and the magnetic poles is precisely adjusted by using a positioning tooling, so that the two sensors can respectively output sine voltage signals with a 90-degree phase difference under ideal conditions.

[0025] As the magnetic ring rotates, two Hall sensors respectively output a first sine signal and a second sine signal. Before being processed, these signals are analog voltage signals. To improve the signal stability and recognition accuracy, before entering the signal processing module, the signals are first processed by an analog amplification circuit and a low-pass filter circuit to amplify the weak signal voltage and filter out high-frequency noise interference.

[0026] In the signal processing stage, zero-crossing detection is first performed on the two sine signals. Zero-crossing detection can be achieved through a level comparator. When the voltage of any Hall sine signal changes from positive to negative or from negative to positive and passes through a set threshold region, it is recognized as a valid zero-crossing, and a level flip trigger signal is output once. This trigger signal is usually TTL level (0V to 5V), which is suitable for the microcontroller to perform edge sampling through the external interrupt method.

[0027] In addition to the traditional zero-crossing trigger, the present invention introduces a second type of trigger point in the technical solution: the trigger point when the absolute values of the amplitudes of the two sine signals are equal or approximate.

[0028] To implement this function, a threshold comparison circuit is set up to continuously compare the voltage value difference between the two sine signals at any moment. When the absolute value of this voltage difference is less than the set threshold (for example, 10mV), it is considered that the amplitudes of the current two sine signals are equal or close, and thus it is determined as another valid trigger point, and a level flip signal is also output.

[0029] Through the above two types of trigger points, within each complete sine period, a total of eight valid level flip points can be obtained: four of them come from zero-crossing detection (two for each of the two sine waves), and the other four come from the detection of equal amplitude points; These trigger points are integrated by the signal integration module into a unified sampling square wave signal. Each period of this square wave signal contains eight level edge changes, and the frequency is twice that of the traditional method, effectively improving the time resolution of the signal.

[0030] The sampled square wave signal is transmitted to the microcontroller. The microcontroller is configured in the edge-triggered interrupt sampling mode to record in real time the number of level flips detected within a unit time, and calculate the instantaneous rotation speed of the rotating member accordingly.

[0031] For example, by setting a 1-second timing window, after counting the number of trigger signals within this time period and combining the number of cycles and structural parameters, the cadence or angular velocity is calculated through conversion. This rotation speed is used as an input parameter for the control logic and finally used to control the motor output power to achieve power response control that matches the rider's cadence intention.

[0032] In further optimization, the microcontroller can also determine the rotation direction by combining the relative phases of the two Hall signals. For example, if the first Hall signal leads the second Hall signal by a fixed phase, it is determined to be rotating clockwise; otherwise, it is rotating counterclockwise. This function is of great significance in systems involving the recognition of the movement direction.

[0033] Through the technical solution of the present invention, not only is the effective improvement of the detection accuracy of the rotation speed realized under the existing hardware architecture, but also the hardware upgrade problem caused by increasing the number of magnetic poles is avoided, making this method have good engineering feasibility and cost control advantages. In scenarios such as electric assist bicycles that require fast response and precise control, this technology has broad application prospects.

[0034] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of without creative labor should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.

Claims

1. A rotational speed measurement method based on multiple trigger points of sine signals of dual Hall sensors, characterized in that, Including the following steps: S1. Provide a rotating member and a plurality of magnetic poles evenly distributed along its circumference. When the rotating member rotates, a periodic magnetic field change is formed; S2. Respectively arrange a first Hall sensor and a second Hall sensor at positions 90 degrees apart in the circumferential direction of the rotating member, for collecting the magnetic field change signals, outputting a first sine signal and a second sine signal, and there is a 90-degree phase difference between the two sine signals; S3. Perform zero-crossing detection on the first sine signal and the second sine signal respectively. When any sine signal passes through zero, a level flip trigger signal is generated once; S4. Compare the amplitudes of the first sine signal and the second sine signal. When the absolute values of their amplitudes are equal or close, another group of level flip trigger signals is generated; S5. Combine the level flip trigger signals into an output sampling square wave signal. This sampling signal contains multiple level flip points within each sine period, for increasing the rotation speed sampling frequency; S6. Transmit the sampling square wave signal to a microcontroller, and the microcontroller calculates the rotation speed of the rotating member according to the number of flips within a unit time.

2. The rotational speed measurement method based on a multi-trigger point sine signal of a dual Hall sensor according to claim 1, characterized in that: The generation of the level flip trigger signal is based on continuous comparison of the amplitudes of the sine signals, and a threshold is set to judge whether the voltage difference between the first sine signal and the second sine signal is less than a preset threshold, so as to determine that they are equal or close.

3. The rotational speed measurement method based on a sine signal of a dual Hall sensor with multiple trigger points according to claim 1, characterized in that: The magnetic poles include a magnetic ring formed by alternating N poles and S poles, forming a continuously changing magnetic field signal.

4. The rotational speed measurement method based on a sine signal with multiple trigger points of a dual Hall sensor according to claim 1, characterized in that: The first Hall sensor and the second Hall sensor are arranged at a fixed angle through a printed circuit board, and the 90-degree relative position is achieved by accurately aligning the arrangement of the magnetic poles.

5. The rotational speed measurement method based on a multi-trigger point sine signal of a dual Hall sensor according to claim 1, characterized in that: The level flip trigger signal is a TTL level signal, with a voltage amplitude of 0V to 5V, suitable for edge-triggered interrupt sampling of a single-chip microcomputer.

6. The rotational speed measurement method based on multi-trigger points of sine signals of dual Hall sensors according to claim 1, wherein: The sampling square wave signal contains eight level flip points within each complete sine signal period, doubling the output frequency compared with the method based only on zero-crossing.

7. The rotational speed measurement method based on a multi-trigger point sine signal of a dual Hall sensor according to claim 1, characterized in that: Before the first sine signal and the second sine signal are input into the microcontroller, they respectively pass through an analog amplification circuit and a low-pass filter circuit to reduce signal interference and improve detection accuracy.

8. The rotational speed measurement method based on a multi-trigger point sine signal of a dual Hall sensor according to claim 1, characterized in that: The microcontroller performs timed sampling based on the high and low level flip edges of the sampling square wave signal, and judges the rotation speed by calculating the number of edges within a unit time. The judgment result is used to control the motor power output of an electric-assisted bicycle.

9. The rotational speed measurement method based on multiple trigger points of sine signals of dual Hall sensors according to claim 1, characterized in that: Also included: Judge the rotation direction of the rotating member according to the relative phase of the first sine signal and the second sine signal.

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