[ROS] publishing /joint_command velocity message does't change the /joint_state's velocity

[chr0430]

I published the /joint_command with prismatic_x_joint velocity change
but /joint_states velocity elements remain as 0.0.
(position change control works but velocity change control does not work)

#!/usr/bin/env python

# Copyright (c) 2021-2022, NVIDIA CORPORATION.  All rights reserved.
#
# NVIDIA CORPORATION and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto.  Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA CORPORATION is strictly prohibited.

import rospy
from sensor_msgs.msg import JointState
import numpy as np
import time

rospy.init_node("test_rosbridge", anonymous=True)

pub = rospy.Publisher("/joint_command", JointState, queue_size=10)
joint_state = JointState()


joint_state.name = [
    "dummy_base_prismatic_x_joint",
    "dummy_base_prismatic_y_joint",
    "dummy_base_revolute_z_joint",
    "iiwa_joint_1",
    "iiwa_joint_2",
    "iiwa_joint_3",
    "iiwa_joint_4",
    "iiwa_joint_5",
    "iiwa_joint_6",
    "iiwa_joint_7",
]

num_joints = len(joint_state.name)

# Initialize velocities for each joint
joint_state.velocity = [0.0] * num_joints

# Control the velocity of prismatic_joint_x
prismatic_x_index = joint_state.name.index("dummy_base_prismatic_x_joint")

# Set the desired velocity for prismatic_joint_x
desired_velocity = 0.2  # Adjust the desired velocity as needed

# position control the robot to wiggle around each joint
time_start = time.time()
rate = rospy.Rate(20)

while not rospy.is_shutdown():
    # Control prismatic_joint_x velocity
    joint_state.velocity[prismatic_x_index] = desired_velocity
    
    print(joint_state.velocity)
    pub.publish(joint_state)
    rate.sleep()

(c.f. action graph)

[chr0430]

Figured out that I had to set damping to zero. Thank you.