Velocity controllers and missing P gain

I am using the `VelocityJointController` from `velocity_controllers` to control a robot loaded in Gazebo simulation. I specify PID gains in a .yaml file. However when I launch the simulation, the error pops out [ERROR] [1546601044.601198350, 0.165000000]: No p gain specified for pid. Namespace: /robot/gazebo_ros_control/pid_gains/joint_rear_left_wheel And no metter what PID gains I set, the robot behaves always the same. The PID gains set in .yaml configuration file has no effect on the simulation. my transmission: transmission_interface/SimpleTransmissionhardware_interface/VelocityJointInterfacehardware_interface/VelocityJointInterface1 control yaml imow: # Publish all joint states ----------------------------------- joint_state_controller: type: joint_state_controller/JointStateController publish_rate: 50 # Velocity Controllers ----------------------------------------- joint_rear_left_wheel_controller: type: velocity_controllers/JointVelocityController joint: joint_rear_left_wheel pid: {p: 1, i: 1, d: 1} What is happening?