Gripper Close

SUMMARY

Close Gripper commands a parallel gripper to close its fingers to 0 mm and grasp an object.

This skill is used to pick an object after the robot has positioned the gripper around it.

UNITS

speed / force in the configured speed and force units (default percent for Robotiq; OnRobot ignores speed and uses N for force).

The Skill

status = gripper.close(speed=100.0, force=100.0, asynchronous=False)

The Code

Safety first!

A real robot will faithfully do whatever you ask of it - so please take a moment to clear the workspace, keep an E-Stop within reach, and be ready to disconnect.

Operating real hardware is at your own risk.

Real

"""
Demonstrates closing a parallel gripper.

Supports OnRobot and Robotiq grippers, and Isaac Sim.

Usage:
    python close.py --ip <GRIPPER_IP>
    python close.py --prim_path <PRIM_PATH>

Note:
    Experimental gripper support for Isaac Sim:  Robotiq 2F85 (USD-based simulation only); Schunk EGP and
    PZN+ are.
"""

import argparse
from loguru import logger

from telekinesis.synapse.tools.parallel_grippers import onrobot


def main(ip: str | None,
         protocol: str,
         prim_path: str | None) -> None:
    """Closes an OnRobot gripper fully at 50 N force."""

    #===================== Create Gripper ======================================
    gripper = onrobot.OnRobotRG6()

    try:
        #===================== Connect Gripper =================================
        if prim_path:
            gripper.connect(simulation_prim_path=prim_path)
        else:
            gripper.connect(ip=ip, protocol=protocol)

        # ==================== Run Skill ====================================
        status = gripper.close(force=50.0,
                               asynchronous=False)
        logger.success(f"close() status: {status}, "
                       f"position: {gripper.get_current_position():.2f}")
    except (ConnectionError, OSError) as e:
        logger.error(f"Error occurred: {e}")
    finally:
        gripper.disconnect()


if __name__ == "__main__":
    p = argparse.ArgumentParser(description="OnRobot gripper close")
    p.add_argument("--protocol",
                   choices=["MODBUS_TCP"],
                   default="MODBUS_TCP")
    p.add_argument("--ip", default=None, help="IP for OnRobot Gripper")
    p.add_argument("--prim_path", type=str, default=None,
                   help='Isaac Sim gripper prim path, e.g. "/World/onrobot_rg6"')
    args = p.parse_args()

    main(ip=args.ip,
         protocol=args.protocol,
         prim_path=args.prim_path)

Running the Example

Real

python close.py --ip 192.168.1.100

Isaac Sim

python close.py --prim_path /World/onrobot_rg6

For all options:

python close.py --help

Parameter Configuration

Robotiq 2F-85

Parameter	Type	Default	Description
speed	float	100.0	Motion speed in percent (0-100). Pass -1.0 to use the session default.
force	float	100.0	Gripping force in percent (0-100). Pass -1.0 to use the session default.
asynchronous	bool	False	If True, returns "MOVING" immediately without waiting.

OnRobot RG2 / RG6

Parameter	Type	Default	Description
force	float	-	Gripping force in Newtons, clamped to the model's max force.
asynchronous	bool	False	If True, returns "MOVING" immediately without waiting.

Returns

Status	Description
"MOVING"	Returned when asynchronous=True
"AT_DEST"	Fingers reached fully closed - no object detected
"STOPPED_OUTER_OBJECT"	Robotiq only - stopped against an external object (grasp detected). OnRobot hardware cannot distinguish inner from outer grip, so this value is never returned by OnRobot.
"STOPPED_INNER_OBJECT"	Robotiq: stopped by internal contact (grasp detected). OnRobot: any detected grasp (the hardware does not distinguish inner from outer).
"UNKNOWN_STATUS_<code>"	Unexpected hardware status

Raises

Robotiq 2F-85

Exception	Condition
TypeError	asynchronous is not a bool
ValueError	The configured connection protocol is not supported
RuntimeError	The gripper is not connected

OnRobot RG2 / RG6

Exception	Condition
TypeError	An argument's value does not match its expected type
RuntimeError	The gripper is not connected, or the underlying Modbus command fails

How to Tune the Parameters

Check the return value after closing. "STOPPED_OUTER_OBJECT" or "STOPPED_INNER_OBJECT" confirms a successful grasp before transporting the object.

Where to Use the Skill

• Pick operations - Close after the robot is positioned at the pick target
• Grasp verification - Check the return status to confirm a successful grasp before transporting
• Re-grasp - Open and close again if the initial grasp is unsuccessful

When Not to Use the Skill

Do not use Close Gripper when:

• A specific intermediate position is required - use Tool Move to close to a defined width
• The gripper is not connected - always call connect before issuing motion commands