how to clear local cost map?

edit

I use sonar-layer in my local cost map, but I cant clear the layer.

local_costmap:
  global_frame: /odom
  robot_base_frame: /base_footprint
  update_frequency: 10.0
  publish_frequency: 0.5
  static_map: false
  rolling_window: true
  width: 3.5
  height: 3.5
  resolution: 0.05
  transform_tolerance: 1.0

  plugins:
    - {name: static_map,      type: "costmap_2d::StaticLayer"}
#- {name: obstacles,       type: "costmap_2d::ObstacleLayer"}
    - {name: sonar,           type: "range_sensor_layer::RangeSensorLayer"}
    - {name: inflation_layer, type: "costmap_2d::InflationLayer"}
  sonar:
    topics: ['/sonar_0', '/sonar_1','/sonar_2', '/sonar_3', '/sonar_4', '/sonar_6', '/sonar_7', '/sonar_8', '/sonar_9', '/sonar_10', '/sonar_11']  
    no_readings_timeout: 0.0
    clear_threshold: 0.0
  inflation_layer:
    inflation_radius: 0.10

when obstacle , sonar-layer cant clear the obstacle. My robot cant move.