joint_state_controller loaded but failed to start

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Dear all, i am having a situation where I have managed to load the joint_state_controller as well as the velocity controllers for the 4 joints of my robot, but, while spawning them i get:

[INFO] [1583148364.122978, 0.000000]: Loading controller: joint_state_controller
[INFO] [1583148364.137343, 27.471000]: Loading controller: FRJ_velocity_controller
[INFO] [1583148364.224540, 27.544000]: Loading controller: FLJ_velocity_controller
[INFO] [1583148364.282939, 27.590000]: Loading controller: BLJ_velocity_controller
[INFO] [1583148364.347087, 27.639000]: Loading controller: BRJ_velocity_controller
[INFO] [1583148364.423555, 27.701000]: Controller Spawner: Loaded controllers: joint_state_controller, FRJ_velocity_controller, FLJ_velocity_controller, BLJ_velocity_controller, BRJ_velocity_controller
[ERROR] [1583148364.426532, 27.703000]: Failed to start controllers: joint_state_controller, FRJ_velocity_controller, FLJ_velocity_controller, BLJ_velocity_controller, BRJ_velocity_controller

Please note that if I replace velocity with position controllers, I am able to load joint_state_controller as well as postion controllers for my 4 joints.

My robot_control launch is:

<launch>

   <param name="robot_description" textfile="$(find robot)/urdf/robot.urdf" />
   <arg name="gui" default="False" />
   <param name="use_gui" value="$(arg gui)"/>
   <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" ></node>
   <node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher" />


<!-- Show in Rviz-->
<node name="rviz" pkg="rviz" type="rviz" args="-d $(find robot)/urdf.rviz"/>


  <!-- Load joint controller configurations from YAML file to parameter server -->
  <rosparam file="$(find robot_control)/config/robot_control.yaml" command="load"/>

  <!-- convert joint states to TF transforms for rviz, etc -->
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"
    respawn="false" output="screen" ns="/robot">
    <remap from="/joint_states" to="/robot/joint_states" />
  </node>

<!-- load the controllers -->
  <node name="controller_spawner" pkg="controller_manager" type="spawner" respawn="false"
    output="screen" ns="/robot" args="joint_state_controller FRJ_velocity_controller FLJ_velocity_controller BLJ_velocity_controller BRJ_velocity_controller"/>

</launch>

My robot_control.yaml is:

robot:  
  # Publish all joint states -----------------------------------
  joint_state_controller:
    type: joint_state_controller/JointStateController
    publish_rate: 20  

  # # Position Controllers ---------------------------------------
  # FLJ_position_controller:
  #   type: effort_controllers/JointPositionController
  #   joint: FLJ
  #   pid: {p: 1.0, i: 1.0, d: 0.0}
  # FRJ_position_controller:
  #   type: effort_controllers/JointPositionController
  #   joint: FRJ
  #   pid: {p: 1.0, i: 1.0, d: 0.0}

  # BLJ_position_controller:
  #   type: effort_controllers/JointPositionController
  #   joint: BLJ
  #   pid: {p: 1.0, i: 1.0, d: 0.0}

  # BRJ_position_controller:
  #   type: effort_controllers/JointPositionController
  #   joint: BRJ
  #   pid: {p: 1.0, i: 1.0, d: 0.0}


   #Velocity Controllers ---------------------------------------
  FRJ_velocity_controller:
    type: effort_controllers/JointVelocityController
    joint: FRJ
    pid: {p: 1.0, i: 1.0, d: 0.0}

  FLJ_velocity_controller:
    type: effort_controllers/JointVelocityController
    joint: FRJ
    pid: {p: 1.0, i: 1.0, d: 0.0}

  BRJ_velocity_controller:
    type: effort_controllers/JointVelocityController
    joint: BRJ
    pid: {p: 1.0, i: 1.0, d: 0.0}

  BLJ_velocity_controller:
    type: effort_controllers/JointVelocityController
    joint: BLJ
    pid: {p: 1.0, i: 1.0, d: 0.0}

The URDF for the model is:

<?xml version="1.0" ?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from robot.xacro                    | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot name="robot" xmlns:xacro="http://www.ros.org/wiki/xacro">
  <!--This URDF was automatically created by SolidWorks to URDF Exporter! Originally created by Stephen Brawner (brawner@gmail.com) 
     Commit Version: 1.5.1-0-g916b5db  Build Version: 1.5.7152.31018
     For ...