fix: Initialize encoder_ticks_ in hw interface

Initialize values in encoder_ticks_ member array of hardware interface
to zero because receiving meaningfultick values from the microcontroller
might take some time. Alleviates problems in #30

diffbot_base/include/diffbot_base/diffbot_hw_interface.h

@@ -181,4 +181,4 @@ namespace diffbot_base
 
 }  // namespace
 
-#endif // DIFFBOT_HW_INTERFACE_H
+#endif // DIFFBOT_HW_INTERFACE_H

diffbot_base/src/diffbot_hw_interface.cpp

@@ -79,6 +79,10 @@ namespace diffbot_base
 
             joint_velocity_commands_[i] = 0.0;
 
+	    // Initialize encoder_ticks_ to zero because receiving meaningful
+	    // tick values from the microcontroller might take some time
+	    encoder_ticks_[i] = 0.0;
+
             // Initialize the pid controllers for the motors using the robot namespace
             std::string pid_namespace = "pid/" + motor_names[i];
             ROS_INFO_STREAM("pid namespace: " << pid_namespace);
@@ -311,4 +315,4 @@ namespace diffbot_base
         return angle * wheel_diameter_ / 2.0;
     }
 
-};
+};