CN114609406B - A method for measuring the number and speed of moving objects based on Hall bars - Google Patents

Abstract

The invention discloses a Hall bar-based moving object quantity and speed measuring method. The system comprises a sensor module, an STDP composite algorithm module, a Hall strip, a state reading module and a calculating module; the sensor module comprises two fixed sensors at a certain distance, when a moving object passes through the sensor module, pulse signals are transmitted to the STDP composite algorithm module, the STDP composite algorithm module applies corresponding positive or negative pulse signals to the input end of the Hall strip according to the time difference of the front pulse signal and the back pulse signal, the state reading module reads the Hall resistance value of the Hall strip, and then the quantity, the moving speed and the moving direction of the moving object are obtained according to the change of the Hall resistance value through the calculation module, so that the measurement is completed. The Hall resistor can be continuously changed under the drive of pulse current, and has the advantages of non-volatility and the like. The invention provides a counting and object movement speed measuring system with low cost and low power consumption based on the characteristics of Hall strips.

Description

A method for measuring the number and speed of moving objects based on Hall bars

Technical Field

The invention belongs to the technical field of speed measurement and metering, and relates to a measurement method using a novel electronic device, and in particular to a counting and object movement speed measurement method based on a Hall bar.

Background Art

The existing technology uses high-precision laser sensors to measure the speed of moving objects, which has the advantage of accurate measurement. In practical applications, due to the influence of environmental factors, the performance of the sensor will decline and the life span will also be reduced, so the system cost is relatively high.

The Hall bar is a spin electronic device that achieves non-volatile changes in anomalous Hall resistance by flipping the magnetic domain inside the device through spin-orbit torque. Specifically, the anomalous Hall resistance of the Hall bar can change continuously under pulse current drive and remain unchanged in other states. Therefore, the Hall bar has the characteristics of non-volatile programming, long life, and simple preparation. It is usually used in the storage field, using Hall resistance to perform information storage functions. In addition, the Hall bar can also realize computing functions to achieve the goal of storage and computing integration.

Based on the above characteristics, using Hall bars to design a measurement system can improve the stability and reliability of the system and reduce costs.

Summary of the invention

In view of the shortcomings of the prior art, the present invention proposes a method for measuring the number and speed of moving objects based on Hall bars, which specifically includes the following steps:

Step 1: Prepare a moving object quantity and speed measurement device based on Hall bars, which includes a sensor module, a STDP (Spike Timing Dependent Plasticity) composite algorithm module, a Hall bar, a state reading module and a calculation module.

Step 2: Apply a pulse modulation signal with a fixed period and an amplitude greater than the critical current of the Hall bar to the input end of the Hall bar to change the Hall resistance value of the Hall bar, and record the law of the change of the Hall resistance value with the number of pulses and store it in the calculation module.

Step 3: According to the variation rule obtained in step 2, the variation rule of the Hall resistance value along with the pulse duty cycle is statistically analyzed and stored in the calculation module.

Step 4: Fix the sensor module at two points with known distances. When a moving object is detected passing by, the sensor module outputs a sensor signal to the STDP composite algorithm module.

Step 5: The STDP composite algorithm module applies a pulse signal with a corresponding duty cycle to the input end of the Hall bar according to the time difference of the sensor signals from different positions.

Step 6: The state reading module reads the Hall resistance value of the Hall bar at different times and inputs it into the calculation module. The calculation module calculates the number, speed and direction of the moving objects according to the change of the Hall resistance value and the change rules of the statistics in steps 2 and 3.

Preferably, it also includes a display module and a storage module, which are respectively used to display and store the calculation results of the calculation module.

Preferably, the sensor is a photoelectric sensor or a Hall sensor.

The present invention has the following beneficial effects:

The Hall bar has the advantages of long service life and simple preparation. This method uses a moving object number and speed measurement device based on the Hall bar to give full play to the high stability of the Hall bar, realize the measurement of the number and speed of moving objects, and provide a low-cost, low-power, and high-reliability measurement method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for measuring the number and speed of moving objects based on Hall bars;

FIG2 is a device for measuring the number and speed of moving objects based on Hall bars used in the embodiment;

FIG3 is a graph showing the relationship between the Hall resistance of the Hall bar and the pulse current in the embodiment;

FIG4 is a curve showing the variation of the Hall resistance value with the number of forward pulses in the embodiment;

FIG5 is a curve showing the variation of the Hall resistance value with the number of negative pulses in the embodiment;

FIG6 is a curve showing the fitting of the Hall resistance value versus the effective time of the forward pulse in the embodiment;

FIG7 is a curve showing the fitting of the Hall resistance value versus the negative pulse effective time in the embodiment;

FIG. 8 is a curve showing the variation of the object movement speed with the Hall resistance value measured in the embodiment.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is further described in detail below in conjunction with the drawings in the examples of the present invention. Naturally, the specific embodiments described here are part of the invention, not all embodiments. The detailed description of the drawings of the following embodiments is only used to illustrate the specific embodiments of the present invention, and does not limit the scope of protection claimed by the present invention. Based on the embodiments of the present invention, ordinary technicians in this field make non-creative modifications to the technical solutions recorded in the embodiments, or make equivalent replacements for some of the technical features therein, which all fall within the scope of protection of the present invention.

This embodiment applies a method for measuring the number and speed of moving objects based on Hall bars to the measurement of 50-meter sprint results in a physical fitness test, and can automatically calculate the number of students taking the test and the scores of each student. As shown in FIG1 , the method specifically includes the following steps:

Step 1: Prepare a moving object quantity and speed measurement device based on Hall bars, as shown in FIG2 , the device includes sensor 1, sensor 2, STDP (Spike Timing Dependent Plasticity) composite algorithm module, Hall bars, state reading module, calculation module, display module and storage module.

Step 2, place the Hall bar on the electrical measurement platform, and apply an in-plane auxiliary magnetic field parallel to the input end of the Hall bar. Use a program-controlled 6221 current source to provide a pulse modulation signal with a duty cycle of 30us, a period of 1ms, and an amplitude greater than the critical current to the two ends of the Hall bar input to change the Hall resistance value. Then the input end of the Hall bar is connected in series with a 10kΩ power resistor, and a sinusoidal voltage signal with an amplitude of 5V and a frequency of 317Hz is provided to the Hall bar and the resistor through the SR830 digital phase-locked amplifier, which is equivalent to inputting a sinusoidal current signal with an amplitude of 0.5mA and a frequency of 317Hz to the input end of the Hall bar. The Hall resistance value of the Hall bar can be obtained by comparing the output voltage of the Hall bar with Ohm's law.

As shown in Figure 3, a positive pulse signal with a continuous period of 1ms, an amplitude of ﹢10mA, and a duty cycle of 30us is applied to the input end of the Hall bar, and the Hall resistance value at the corresponding moment is calculated. The law of the Hall resistance value decreasing with the number of positive pulses x is statistically analyzed, as shown in Figure 4, and obtained through Matlab fitting:

R_H _down (x)＝0.1385*exp(-0.246x)+0.3876*exp(-0.0006048x)

A negative pulse current signal with a continuous period of 1ms, an amplitude of -10mA, and a duty cycle of 30us is applied to the input end of the Hall bar, and the Hall resistance value at the corresponding moment is calculated. The law of the increase of the Hall resistance value with the number of negative pulses y is statistically analyzed, as shown in Figure 5, and obtained through Matlab fitting:

R_H _up (y)＝0.622*exp(0.001568y)-0.09067*exp(-0.2667y)

The above curve equation is stored in the calculation module.

Step 3, as shown in FIG6 , the duty cycle of the forward pulse signal is taken as the effective duration t of the signal, and according to the curve in FIG4 , a curve in which the Hall resistance value decreases as the effective duration of the forward pulse signal increases is fitted by Matlab:

R_H _{down_t} (t)＝0.1385*exp(-0.0082t)+0.3876*exp(-0.00002016t)

As shown in FIG7 , the duty cycle of the negative pulse signal is taken as the effective duration k of the signal. According to the curve in FIG5 , a curve showing that the Hall resistance value increases with the increase of the effective duration of the negative pulse signal is fitted by Matlab:

R_H _{up_t} (k)＝0.622*exp(0.00005226k)-0.09067*exp(-0.008889k)

The above curve equation is also stored in the calculation module.

Step 4: Fix sensor 1 and sensor 2 at the starting point and the end point of the 50-meter sprint measurement route respectively. When a student is detected passing by, sensors 1 and 2 respectively output pulse signals to the STDP composite algorithm module.

Step 5: The STDP composite algorithm module applies a pulse signal of a corresponding duty cycle to the input end of the Hall bar according to the time difference between the signals received from sensors 1 and 2.

Step 6: The state reading module reads the Hall resistance values R_H ₀ , R_H ₁ , .. R_H _N of the Hall bar at different times and inputs them into the calculation module. The calculation module substitutes the changes in the Hall resistance values into the curve equations fitted in steps 2 and 3 to calculate the number, speed and direction of the moving objects.

(1) When R_H ₀ ＞R_H _N , the Hall resistance value decreases as the number of pulses and effective time increase. Substituting into the curve and R_H _{down_t} (t):

Wherein, n=1,2,3,...N, x0 and _xN represent the number of forward pulse currents corresponding to the Hall resistance values of R_H ₀ and R_H _N , respectively, t(n-1) and tn represent the effective action time of the forward pulse currents corresponding to the Hall resistance values of R_H _n-1 and R_H _n , respectively, the number of testers is xN-x0, and the speed of the n-1th tester is 50/(tn-t(n-1)), as shown in FIG8 .

(2) When R_H ₀ ＜R_H _N , the Hall resistance value increases with the number of pulses and the effective time. Substituting into the curves R_H _up (y) and R_H _{up_t} (k):

Wherein, y0 and yN represent the number of negative pulse currents corresponding to the Hall resistance values of R_H ₀ and R_H _N, respectively; k(n-1) and kn represent the effective action time of negative pulse currents corresponding to the Hall resistance values of R_H _n-1 and R_H _n , respectively; the number of testers is yN-y0, and the speed of the n-1th tester is 50/(kn-k(n-1)).

Step 7: The display module and the storage module receive, display and store the calculation results of the calculation module.

Claims (3)

1. The method for measuring the quantity and the speed of the moving objects based on the Hall strips is characterized by comprising the following steps of: the method specifically comprises the following steps:

Step 1, preparing a Hall strip-based moving object quantity and speed measuring device, wherein the device comprises a sensor module, an STDP composite algorithm module, a Hall strip, a state reading module and a calculating module;

Step 2, a pulse adjusting signal with the duty ratio of 30us, the period of 1ms and the amplitude of more than critical current is applied to the input end of the Hall strip so as to change the Hall resistance value of the Hall strip, a sinusoidal current signal with the amplitude of 0.5mA and the frequency of 317Hz is input to the input end of the Hall strip, the Hall voltage of the output end of the Hall strip is read, the Hall resistance value is calculated according to ohm law, the law that the Hall resistance value changes along with the number of pulses is recorded, and the rule is stored in a calculation module;

Step 3, counting the change rule of the Hall resistance value along with the pulse duty ratio according to the change rule obtained in the step 2, and storing the change rule into a calculation module;

Step 4, fixing the sensor module on two points with known distances, and outputting a sensor signal to the STDP composite algorithm module by the sensor module when the moving object is detected to pass through;

step 5, the STDP composite algorithm module applies a pulse signal with a corresponding duty ratio to the input end of the Hall strip according to the time difference of the sensor signals from different positions;

Step 6, the state reading module reads the Hall resistance values of the Hall strips at different moments and inputs the Hall resistance values into the calculating module; and (3) the calculation module calculates the quantity, the movement speed and the movement direction of the moving objects according to the change condition of the Hall resistance value and the change rule counted in the step (2) and the step (3).

2. The method for measuring the number and the speed of moving objects based on Hall strips according to claim 1, wherein the method comprises the following steps: the system also comprises a display module and a storage module which are respectively used for displaying and storing the calculation result of the calculation module.

3. The method for measuring the number and the speed of moving objects based on Hall strips according to claim 1, wherein the method comprises the following steps: the sensor is a photoelectric sensor or a Hall sensor.