How to modify move_base minimum velocities?

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I am using navigation stack in order to navigate my robot. I know that after giving a goal, move_pase constructs global and local plans. Using local plan, move_base publisher to /cmd_vel topic in order to move my robot.

I have written yaml file to set the parameters for the local plan like this: ecovery_behavior_enabled: true clearing_rotation_allowed: true

TrajectoryPLannerROS:
  acc_lim_x: 1
  acc_lim_y: 0 # as we have a differential robot
  acc_lim_theta: 1.6
  max_vel_x: 1.6 # configure, was 0.2
  min_vel_x: 0.8 # was 0.1
  max_vel_y: 0.0  # zero for a differential drive robot
  min_vel_y: 0.0
  max_vel_theta: 1.0 # 0.35
  min_vel_theta: 0.0 #-0.35
  min_in_place_vel_theta: 0.4 #0.25
  min_rot_vel: 0.1
  escape_vel: 0.0

  holonomic_robot: false

  meter_scoring: true

  xy_goal_tolerance: 0.3 # 0.15, 0.3->about 20 cm
  yaw_goal_tolerance: 0.20 # 0.25, about 11 degrees
  latch_xy_goal_tolerance: true  #false

  sim_time: 4 # <2 values not enough time for path planning and can't go through narrow
  sim_granularity: 0.05 # How frquent should the points on trajectory be examined
  angular_sim_granularity: 0.025
  vx_samples: 5
  vy_samples: 0 # 0 for differential robots
  vtheta_samples: 5
  controller_frequency: 15

  pdist_scale: 0.8
  gdist_scale: 0.4
  occdist_scale: 0.01
  oscillation_reset_dist: 0.2
  heading_scoring: false
  heading_lookahead: 0.1 # how far to look ahead in meters
  heading_scoring_timestep: 0.8
  dwa: true
  publish_cost_grid_pc: false
  global_frame_id: odom
  simple_attractor: false

  reset_distance: 4

  prune_plan: true

As you can see, I specifically said that the minimum x vel is 0.8 because from my motor speed calculations:

def callback(self, msg):
    transVelocity = msg.linear.x
    rotVelocity = msg.angular.z
    velDiff = (self.wheelSep * rotVelocity) / 2.0
    leftPower = (transVelocity + velDiff) / self.wheelRadius
    rightPower = (transVelocity - velDiff) / self.wheelRadius
    self.pwm_left.ChangeDutyCycle(leftPower)
    self.pwm_right.ChangeDutyCycle(rightPower)

When the x.linear velocity is small my wheels do not spin as it has not enough power. However, after setting a goal and listening to /cmd_vel topic I get this message:

linear: 
  x: 0.55
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -0.368421052632

Why is linar X is below 0.8? having those values, from my callback formula it will only deliver 20% of duty cycle and it is not enough.

My move_base launch file:

 <!-- Launch move_base -->
   <node pkg="move_base" type="move_base" name="move_base" output="screen"> 
     <!--param name="base_global_planner" value="simple_planner/SimplePlanner"/-->
   <rosparam file="$(find map)/config/costmap_common_params.yaml" command="load" ns="global_costmap" />
   <rosparam file="$(find map)/config/costmap_common_params.yaml" command="load" ns="local_costmap" />
   <rosparam file="$(find map)/config/local_costmap_params.yaml" command="load"/>
   <rosparam file="$(find map)/config/global_costmap_params.yaml" command="load"/>
   <rosparam file="$(find map)/config/trajectory_planner.yaml" command="load"/>
   <rosparam file="$(find map)/config/move_base_params.yaml" command="load"/>
   <rosparam file="$(find map)/config/global_planner_params.yaml" command="load"/>
   </node>