vehicle control not work correctly in manual_control.py

[inflameRuRu]

Hello,
i have tried to add a simple logic in the _Radar_callback method, that if the velocity larger than 54km/h, then the vehicle apply the brake.
here is my code added:

    vec = self._parent.get_velocity()
    vehicle_control_brake =  carla.VehicleControl(throttle=0.0,brake=1.0)
    velocity = math.sqrt(vec.x**2 + vec.y**2 + vec.z**2)
    #print (velocity)
    if velocity > 15.0:
        self._parent.apply_control(vehicle_control_brake)
        #time.sleep(0.05)
    control = self._parent.get_control()
    print (control.brake)

---

and for the output, I only get the correct value '1' in some cycle when the velocity >15m/s.
output:
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

could someone tell me where is the problem?
thanks a lot!