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+--- Thread: angular servo motor can't keep up with angle inputs (/thread-8865.html)
angular servo motor can't keep up with angle inputs - taher50 - Mar-10-2018
I am working on a piece of code that uses OpenCV in my python code. I am using python 2.7.4 with the OpenCV 3.4.0.
In my code, i have built a tracking program to track certain colours in my case its red. I also have a servo motor sitting on top of the servo motor. The centre point of the targeted object is retrieved and printed.
I have verified that the servo motor works fine on its own. when inputting angle from the user, but in my code, i have the servo motor changing angles depending on the position of the red object. In my for loop the angle is retrieved and the duty cycle is sent to the motor.
The problem I am having is that the angle is being retrieved from the code and sent to the servo motor and it can't process it because the next angle has already been sent. This process is happening to fast and my servo motor can't keep up.
I have narrowed the problem down to here. In this for loop i have got the contour information and i just plot bounding boxes around my red objected. I also get the distance from an ultrasonic sensor.
for c in contours: x1, y1, w1, h1 = cv2.boundingRect(c) cv2.rectangle(image, (x1,y1), (x1+w1,y1+h1), (0,255,0), 2) rect = cv2.minAreaRect(c) box = cv2.boxPoints(rect) box = np.int0(box) cv2.drawContours(image, [box], 0, (0, 0, 255), 2) # finally, get the min enclosing circle (x, y), radius = cv2.minEnclosingCircle(c) # convert all values to int center = (int(x), int(y)) radius = int(radius) x_cor = int(x) y_cor = int(y) image = cv2.circle(image, center, 1, (255, 0, 0), 2) Ob_Distance = int(distance()) print "Distance = %d cm Centre point x = %d y = %d" %(Ob_Distance, x_cor, y_cor) if x_cor < XAxisCentre and ServoPosition >= 5: ServoPosition = ServoPosition - 2 elif x_cor > XAxisCentre and ServoPosition <= 175: ServoPosition = ServoPosition + 2 #end if else print "servo position = " + str(ServoPosition) UpdateServoPositions(pwmObject, ServoPosition) #time.sleep(0.0001) #end for
angular servo motor can't keep up with angle inputs - taher50 - Mar-10-2018
Hi this is my entire code.
#OpenCV_Original.py
# this program tracks a red objects
#Later we will try and move the webcam to track the red object
import cv2
import numpy as np
import os
import RPi.GPIO as GPIO
import time
def main():
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO_TRIG = 18
GPIO_ECHO = 24
servo_gpio_pin = 23
pwmFreq = 100
IntialDutyCycle = 13
GPIO.setup(GPIO_TRIG, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)
GPIO.setup(servo_gpio_pin, GPIO.OUT)
pwmObject = GPIO.PWM(servo_gpio_pin, pwmFreq)
lowerBound = np.array([0,135,135]) # Ranges for filtering when light is reflecting of red
lowerBound1 = np.array([18,255,255])
upperBound = np.array([165,135,135])
upperBound1 = np.array([179,255,255])
lowerBound2 = np.array([169,100,100])
upperBound2 = np.array([189,255,255])
kernelOpen = np.ones((5,5))
kernelClose = np.ones((20,20))
font = cv2.FONT_HERSHEY_SIMPLEX
cam = cv2.VideoCapture(0)
if cam.isOpened() == False:
print "\nerror: Webcam not accessed successfully\n"
os.system("pause")
return
#end if
print "Original Resolution = " + str(cam.get(cv2.CAP_PROP_FRAME_WIDTH)) + "x" + str(cam.get(cv2.CAP_PROP_FRAME_HEIGHT))
cam.set(cv2.CAP_PROP_FRAME_WIDTH, 320.0)
cam.set(cv2.CAP_PROP_FRAME_HEIGHT, 240.0)
print "Updated Resolution = " + str(cam.get(cv2.CAP_PROP_FRAME_WIDTH)) + "x" + str(cam.get(cv2.CAP_PROP_FRAME_HEIGHT))
XAxisCentre = int(float(cam.get(cv2.CAP_PROP_FRAME_WIDTH)) / 2.0)
YAxisCentre = int(float(cam.get(cv2.CAP_PROP_FRAME_HEIGHT)) / 2.0)
pwmObject.start(13)
ServoPosition = int(90)
#print "servo position = " + str(ServoPosition)
UpdateServoPositions(pwmObject, ServoPosition)
while cam.isOpened() == True and cv2.waitKey(1) != 27:
ret, image = cam.read()
if not ret or image is None:
print "\nerror: Frame not read from webcam\n\n"
os.system("pause")
break
# end if
imageHSV = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
imageLow = cv2.inRange(imageHSV,lowerBound,lowerBound1)
imageHigh = cv2.inRange(imageHSV,upperBound,upperBound1)
imageMed = cv2.inRange(imageHSV,lowerBound2,upperBound2)
imageMask = cv2.add(imageLow, imageHigh, imageMed)
imageMask = cv2.GaussianBlur(imageMask, (3, 3), 2)
#imageMask = cv2.dilate(imageMask,kernelOpen)
#imageMask = cv2.erode(imageMask,kernelOpen)
imageMask = cv2.morphologyEx(imageMask,cv2.MORPH_OPEN,kernelOpen)
imageMask = cv2.morphologyEx(imageMask,cv2.MORPH_CLOSE,kernelClose)
imageMask, contours, hier = cv2.findContours(imageMask,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
for c in contours:
x1, y1, w1, h1 = cv2.boundingRect(c)
cv2.rectangle(image, (x1,y1), (x1+w1,y1+h1), (0,255,0), 2)
rect = cv2.minAreaRect(c)
box = cv2.boxPoints(rect)
box = np.int0(box)
cv2.drawContours(image, [box], 0, (0, 0, 255), 2)
# finally, get the min enclosing circle
(x, y), radius = cv2.minEnclosingCircle(c)
# convert all values to int
center = (int(x), int(y))
radius = int(radius)
x_cor = int(x)
y_cor = int(y)
image = cv2.circle(image, center, 1, (255, 0, 0), 2)
Ob_Distance = int(distance())
print "Distance = %d cm Centre point x = %d y = %d" %(Ob_Distance, x_cor, y_cor)
if x_cor < XAxisCentre and ServoPosition >= 5:
ServoPosition = ServoPosition - 2
elif x_cor > XAxisCentre and ServoPosition <= 175:
ServoPosition = ServoPosition + 2
#end if else
print "servo position = " + str(ServoPosition)
UpdateServoPositions(pwmObject, ServoPosition)
#time.sleep(0.0001)
#end for
cv2.namedWindow("Webcam", cv2.WINDOW_AUTOSIZE)
cv2.namedWindow("imageMask", cv2.WINDOW_AUTOSIZE)
cv2.imshow("Webcam",image)
cv2.imshow("imageMask",imageMask)
# end while
cv2.destroyAllWindows()
return
def distance():
GPIO.setmode(GPIO.BCM)
GPIO_TRIG = 18
GPIO_ECHO = 24
pulse_start = 0
pulse_end = 0
pulse_duration = 0
distance = 0
GPIO.setup(GPIO_TRIG, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)
GPIO.output(GPIO_TRIG, True)
time.sleep(0.00001)
GPIO.output(GPIO_TRIG, False)
while GPIO.input(GPIO_ECHO) == 0:
pulse_start = time.time()
#end while
while GPIO.input(GPIO_ECHO) == 1:
pulse_end = time.time()
#end while
pulse_duration = pulse_end - pulse_start
distance = (pulse_duration * 34300) / 2
return distance
def UpdateServoPositions(pwmObject, ServoPosition):
dutyCycle = ((float(ServoPosition) * 0.01) + 0.45) * 10
pwmObject.ChangeDutyCycle(dutyCycle)
return
if __name__ == "__main__":
main()