what are benefits of using ROS-I and motoman_driver?

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Note: you can actually send a trajectory that you have computed yourself (so without using MoveIt) to motoman_driver. Just use the /follow_joint_trajectory action server for that.

MoveIt is not needed at all.

This would even work with single-point trajectories (actually: two-point trajectories (start, destination)). It would be joint interpolation though. But it is supported.

Note also: I'm not saying a pick-and-place application cannot be complex. What I'm saying is that depending on where the complexity comes from, the resources that an OEM controller has may not be sufficient to control more than just the robot itself. YRC1000 controllers are pretty OK machines, but you cannot run arbitrary programs on them, and even if you could, they would be seriously limited in CPU processing power and memory available to them.

To escape those limitations, external control makes sense.

@gvdhoorn Thank you for the great answer. As I want to use motoman_driver only for communication between PC and controller. because I found that using Motocom32 I can give related object pick,place position but it is not "free". so using motoman_driver can I give pick, place position using vision directly? but I do not understand "send a trajectory that you have computed yourself "? is it not done by robot controller?

No, you cannot just send positions. It's always a trajectory.

MotoCOM allows you to set registers, that is not what MotoROS is for.

If you have the option, you may want to take a look at the highspeed ethernet server.

Edit: if you have MotoPlus and are comfortable programming in C, you can definitely add getting and setting registers to MotoROS. See this fork for some inspiration.

oh, I understand wrong. I thought i will use motoman_driver, then sending POSE information to controller, Ik service and /follow_joint_trajectory I can do pick and place. so, I think then it is good to have Motocom32 as my programming experience is intermediate.

@gvdhoorn how can I calculate trajectory for given POSE if I want to use motoman_driver? I think then I have to use Moveit?

oh, I understand wrong. I thought i will use motoman_driver, then sending POSE information to controller, Ik service and /follow_joint_trajectory I can do pick and place

Things are not as black-and-white as you make them to be.

No, you cannot use MotoROS to send single poses (to registers) and use INFORM. Yes you can actually create a pick-and-place application with MotoROS.

But it all depends on where your focus is, and how much time you are willing to invest (and of course whether that time investment makes sense depends on what else you'd like to do).

@gvdhoorn how can I calculate trajectory for given POSE if I want to use motoman_driver? I think then I have to use Moveit?

a trajectory is nothing more than a sequence of joint space poses and associated time_from_start values (and velocity, if you don't want to stop at each point).

"calculating" is a strong word: you can just "make up" joint poses and append them to a trajectory_msgs/JointTrajectory. Set the joint_names field correctly, make sure to specify proper time_from_start values, wrap it in a FollowJointTrajectoryGoal and submit it to the /follow_joint_trajectory action server.