Mobile manipulation skills¶

This page lists system skills (ie, installed by default) related to 🦾 Manipulation. You can directly use these skills in your tasks and mission controller.

`hand_grasp`¶

Interface: /skill/hand_grasp
Message type: manipulation_skills/action/HandGrasp

Controls a robotic hand or gripper to either close (grasp) or open (release). This skill sends a goal to the specified end-effector (left, right, or default) with an optional precision setting for the closing position.

Once invoked, the robot will:

Target the desired hand/gripper.
Perform the requested action (close/open).
Report back feedback and a result message indicating success or failure.

Typical uses include closing a gripper to get hold of an object, releasing an object, or partially closing the gripper to a specific position for delicate handling.

Input parameters¶

hand string, default: ""
Which hand or end-effector to use. Supported values:
- left: Use the left hand.
- right: Use the right hand.
- default (empty string): Use the default hand (the right in case of 2 arms).
Any other value will be rejected and the default will be used.
action integer, default: 0
The gripper action to perform:
- 0: Close the gripper (grasp).
- 1: Open the gripper (release).
Values outside [0, 1] will be clamped to the closest integer.
closing_position float, default: 0.0

Defines how far to close the gripper. Range: [0.0, 1.0] (0.0 = fully closed, 1.0 = fully open). Values outside the range will be replaced with the default (0.0).

This allows partial grasps for delicate objects.
meta.priority integer, default: 128

Between 0 and 255. Higher means this skill request will be prioritized.

Output fields¶

result.error_msg string

A string describing the execution outcome.
Examples:
- Grasp Executed!: Successful grasp/release.
- Problems during execution.: Action failed.
feedback object
Live updates while the action runs. Can contain:
- data_str: Text feedback (e.g., which hand, action, position).
- data_bool: True if action succeeded, False otherwise.

Quick snippets¶

Call the skill from the command-line¶

$ ros2 action send_goal /skill/hand_grasp manipulation_skills/action/HandGrasp # then press Tab to complete the message prototype

How to use in your code¶

See code samples for the corresponding /skill/hand_grasp: code samples

You can call this skill from QML using the following code snippet. See Building a touchscreen interface via ROS and QML to learn more.

import Ros 2.0

// ...
HandGraspSkill {
    id: mySkill

    onResult: {
        console.log("Skill result: " + result);
    }
    onFeedback: {
        console.log("Skill feedback: " + feedback);
    }
}

// Call the skill
mySkill.hand_grasp();