How to move specific joint only using MoveIt?

edit

As mentioned above, one solution is to read the current joint values, build a dictionary of "joint names" vs "current joint angles", modify the ones you need, then send to moveit for planning and execution, here a python example of how to do it (for our robot):

#!/usr/bin/env python3

'''
example on how to control specific arm joints with moveit
'''

import sys
import rospy
import moveit_commander

rospy.init_node('move_joints_test', anonymous=False)

try:
    rospy.loginfo('waiting for move_group action server')
    moveit_commander.roscpp_initialize(sys.argv)
    robot = moveit_commander.RobotCommander()
    # robot.arm.set_planning_time(20.0)
    # robot.arm.set_goal_tolerance(0.01)
    rospy.loginfo('found move_group action server')
except RuntimeError:
    # moveit_commander.roscpp_initialize overwrites the signal handler,
    # so if a RuntimeError occurs here, we have to manually call
    # signal_shutdown() in order for the node to properly exit.
    rospy.logfatal('could not connect to Moveit in time, exiting! \n')
    rospy.signal_shutdown('fatal error')

# to test if arm and moveit work
#arm_posture_name = 'observe100cm_right'
#robot.arm.set_named_target(arm_posture_name)
#robot.arm.go()

# give only the arm joints that we want to affect, NOTE: for some reason this does not work!
#arm_dic = {'mobipick/ur5_shoulder_pan_joint':-1.25, 'mobipick/ur5_elbow_joint':1.8}

# get current joint angles
joint_states = robot.arm.get_current_state().joint_state

arm_joints_dic = {}

joints_of_interest = ['mobipick/ur5_shoulder_pan_joint', 'mobipick/ur5_shoulder_lift_joint', 'mobipick/ur5_elbow_joint', 'mobipick/ur5_wrist_1_joint', 'mobipick/ur5_wrist_2_joint', 'mobipick/ur5_wrist_3_joint']
for joint_of_interest in joints_of_interest:
    # find index
    for i, joint_name in enumerate(joint_states.name):
        if joint_of_interest == joint_name:
            # print(f'{joint_of_interest}:{joint_states.position[i]}') # uncomment for debug purposes
            arm_joints_dic[joint_of_interest] = joint_states.position[i]

# rospy.logwarn(f'current arm state: {robot.arm.get_current_state().joint_state}')

# modify required joints
arm_joints_dic['mobipick/ur5_shoulder_pan_joint'] = -1.25
arm_joints_dic['mobipick/ur5_elbow_joint'] = 1.8

robot.arm.set_joint_value_target(arm_joints_dic)
robot.arm.go()

rospy.spin()

MoveIt! added a method for this recently. Cool.

bool setJointValueTarget (const std::string &joint_name, double value)

You can setup JointModelGroups (planning groups) for each single joint in your srdf to plan with these joints only.

How to actuate these trajectories on your robot arm depends on the concrete hardware driver. I've not worked with Yumi up to now, so I can't help you there.