Jane Medium ：

key word ： Optical flow sensor , Output range

§01 light Flow sensor

One 、 Background introduction

   stay Preliminary test of optical flow sensor ：GL9306 The optical flow sensor is preliminarily tested . There is a question ：  Whether the sensor output is linear with the relative speed ？  Is there an upper limit on the maximum measurement speed ？

Two 、 measuring method

1、 The test method

   In order to test the above characteristics of optical flow sensor ,  Use a DC motor to drive a rotary table to rotate .  Put it on the optical flow sensor to generate relative motion .

2、 DC motor

   DC motor interface ,  With magnetic encoder output .  Here are 6PIN Interface function definition .

  
   Apply different DC voltages to the motor ,  The motor will rotate at different speeds function .  This is the output waveform of the magnetic encoder after clicking .  The frequency of speed pulse can be measured by multimeter .

  
   Next, first measure the relationship between the motor voltage and the magnetic encoder .  This is the measurement result ,  It can be seen that the relationship between voltage and speed is basically linear .  After linear fitting , This linear relationship is ：f=200*v-74.3

3、 ... and 、 Measure relative motion

   Place the optical flow sensor in front of the rotating red heat insulation cotton ,  Distance about 5 Centimeter .  application MicroPython The experimental board reads the output of the optical flow sensor .  Program to display the output of optical flow sensor x,y The speed of movement in the direction .  Because the rotary table is in circular motion ,  You can see x,y The component of motion in both directions .

  
   Adjust the distance between the optical flow sensor and the rotating disc , You can see the change of the output value of the optical flow sensor .  Although the rotating speed of the rotary table has not changed , But the change of distance changes the relative speed .

  
   Increase the motor supply voltage , Increase the rotating speed of the turntable , You can see , The maximum output value of optical flow sensor shall not exceed 28. Especially when the speed is very high , The output value of the optical flow sensor obviously jumps .

※ total junction ※

One 、 Measurement procedures and data

   Check the output numerical characteristics of the optical flow sensor through experiments .  You can see that its output has the maximum value display ,  No more than 25,  Because the speed of DC motor is   It cannot be controlled accurately at low speed ,  Therefore, the output linear relationship has not been further verified .

1、 Measure the motor speed and pulse frequency

#!/usr/local/bin/python
# -*- coding: gbk -*-
#============================================================
# TEST1.PY -- by Dr. ZhuoQing 2022-07-15
#
# Note:
#============================================================

from headm import *
from tsmodule.tsvisa        import *
from tsmodule.tsstm32       import *


vdim = linspace(2, 7, 50)
fdim = []


for v in vdim:
dh1766volt(v)
time.sleep(2)
meter = meterval()

fdim.append(meter[0])
printff(v, meter)

tspsave('measure', vdim=vdim, fdim=fdim)


dh1766volt(0)

plt.plot(vdim, fdim)

plt.xlabel("Voltage(V)")
plt.ylabel("Frequency(Hz)")
plt.grid(True)
plt.tight_layout()
plt.show()


#------------------------------------------------------------
# END OF FILE : TEST1.PY
#============================================================

2、 Fit the linear relationship between motor and frequency

#!/usr/local/bin/python
# -*- coding: gbk -*-
#============================================================
# DRAW1.PY -- by Dr. ZhuoQing 2022-07-15
#
# Note:
#============================================================

from headm import *
from scipy.optimize        import curve_fit

vdim, fdim = tspload('measure', 'vdim', 'fdim')

def linefun(x, a, b):
return a*x + b

param = (1, 0)
param, conv = curve_fit(linefun, vdim, fdim, p0=param)
printf(param)


plt.plot(vdim, fdim)

plt.xlabel("Voltage(V)")
plt.ylabel("Frequency(Hz)")
plt.grid(True)
plt.tight_layout()
plt.show()




#------------------------------------------------------------
# END OF FILE : DRAW1.PY
#============================================================

3、 Motor voltage and frequency measurement data

4、Python Program

from machine                import Pin,UART
import time

uart = UART(1, baudrate=19200)
print(uart)

inbuf = bytes([0]*7)
recebuf = b''
mx = 0
my = 0
squal = 0

printcount = 0

while True:
if uart.any() > 0:
inb = uart.read(uart.any())
recebuf = recebuf + inb

buflen = len(recebuf)
delflag = 1
if buflen > 0:
id = 0
for b in recebuf:
if b == 0xfe:
if buflen >= id+9:
mx = recebuf[id+3]
mx = mx*256 + recebuf[id+2]
my = recebuf[id+5]
my = my*256 + recebuf[id+4]
squal = recebuf[id+7]

else:
recebuf = recebuf[id:]
delflag = 0
break

id += 1

if delflag > 0: recebuf = b''

time.sleep_ms(10)

printcount += 1
if printcount >= 10:
printcount = 0
print(mx, my, squal)

■ Links to related literature :

• Preliminary test of optical flow sensor ：GL9306