Services_quiz - How do I use rospy.Rate to move BB8 in perfect square?

Course Support ROS Basics In 5 Days (Python)
1

I received a 6 on the quiz. How should I edit my code so that the movement is more square-like?

server code

scrubbed :grimacing:

client code

scrubbed :grimacing:

2

Hi @linsu.han,
You should use smaller values for the velocities.

self.msg.angular.z = .05

and

self.msg.linear.x = 0.3

The bot has inertia, so expecially with spinning, it becomes very inaccurate for faster turning speeds.

And using rate.sleep() is kind of weird. Try something like this instead:

def move_straight(self, side):
        self.msg.linear.x = 0.3
        self.msg.angular.z = 0
        while self.pub.get_num_connections() < 1:
            # wait for a connection to publisher
            rospy.sleep(0.01)
        self.pub.publish(self.msg)
        rospy.sleep(side)
1 Like
3

I don’t know what magic you used to find those numbers, but it worked. Thank you!

1 Like
4

faced the same problem :wink:

5

Is it okay to put the self.pub.get_num_connections check in the handler?

def handler(self, request):
    while self.pub.get_num_connections() < 1:
        # wait for a connection to publisher
        rospy.sleep(0.01)
    try:
        print(request)
        for i in range(request.repetitions):
            for i in range(4):
                self.move_straight(request.side)
                self.turn_90_deg()