DG-4F¶

4-finger gripper with fingertip force/torque sensors. This gripper has 4 main fingers with 4 joints each, plus 2 inner joints for a total of 18 joints.

Specifications¶

Parameter	Value
Model ID	`0x4F02`
Fingers	4
Joints	18 (4 per finger + 2 inner joints)
F/T Sensor	Yes
GPIO	Yes (3 outputs, 1 input)

Packages¶

Package	Description
`dg4f_description`	URDF/xacro model, meshes, and RViz display launch files
`dg4f_driver`	ros2_control hardware driver, controller configs, and launch files
`dg4f_gz`	Gazebo simulation launch files
`dg4f_moveit_config`	MoveIt 2 configuration (SRDF, planners, mock hardware)

Joint Naming Convention¶

Each joint is named j_dg_F_J where:

F = finger number (1-4)
J = joint number within the finger (1 = base, 4 = tip)

Additionally, there are two inner joints: j_dg_1_inner and j_dg_4_inner.

Launch Files¶

Driver Launch Files (Hardware Connection)¶

Launch File	Controller Type	Description
`dg4f_driver.launch.py`	Joint Trajectory Controller	Default driver with JTC (position control with PID)
`dg4f_effort_controller.launch.py`	JointGroupEffortController	Direct effort (current) control

Visualization and Simulation¶

Launch File	Package	Description
`dg4f_display.launch.py`	`dg4f_description`	RViz visualization with joint sliders
`dg4f_gz.launch.py`	`dg4f_gz`	Gazebo simulation

Launch Arguments¶

All driver launch files accept these arguments:

Argument	Default	Description
`delto_ip`	`169.254.186.72`	IP address of the gripper
`delto_port`	`502`	TCP port of the gripper
`fingertip_sensor`	`false`	Enable reading F/T sensor data from the hardware
`ft_broadcaster`	`false`	Enable broadcasting F/T data as ROS 2 topics
`io`	`false`	Enable GPIO interfaces

Example:

ros2 launch dg4f_driver dg4f_driver.launch.py delto_ip:=192.168.1.100 fingertip_sensor:=true ft_broadcaster:=true

Controller Types¶

Joint Trajectory Controller (JTC) – Default¶

ros2 launch dg4f_driver dg4f_driver.launch.py

The JTC accepts trajectory goals and uses a PID loop to move joints to target positions.

Send a position command:

ros2 action send_goal /dg4f/dg4f_controller/follow_joint_trajectory control_msgs/action/FollowJointTrajectory "{
  trajectory: {
    joint_names: [j_dg_1_1, j_dg_1_2, j_dg_1_3, j_dg_1_4],
    points: [
      {positions: [0.5, 0.5, 0.5, 0.5], time_from_start: {sec: 2, nanosec: 0}}
    ]
  }
}"

Note

The DG-4F JTC supports allow_partial_joints_goal: true, so you can command a subset of joints without specifying all 18.

Config file: config/dg4f_controller.yaml

Key config values:

Update rate: 300 Hz
PID gains: p=1.5, i=0.0, d=0.0 (per joint)

Effort Controller (Direct Current)¶

ros2 launch dg4f_driver dg4f_effort_controller.launch.py

Send effort commands (18 values, one per joint):

ros2 topic pub /dg4f/effort_controller/commands std_msgs/msg/Float64MultiArray "{data: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]}" --once

Warning

The effort controller has no position feedback loop. Start with small values to avoid damage.

MoveIt Integration¶

The dg4f_moveit_config package provides MoveIt 2 motion planning for the DG-4F with mock hardware support.

Mock Hardware (No Device Required)¶

ros2 launch dg4f_moveit_config dg4f_moveit.launch.py use_mock:=true

Real Hardware with MoveIt¶

ros2 launch dg4f_moveit_config dg4f_moveit.launch.py use_mock:=false delto_ip:=169.254.186.72

Planning Groups¶

Group	Joints
`finger_1`	`j_dg_1_1` ~ `j_dg_1_4` + `j_dg_1_inner` (chain to `l_dg_1_tip`)
`finger_2`	`j_dg_2_1` ~ `j_dg_2_4` (chain to `l_dg_2_tip`)
`finger_3`	`j_dg_3_1` ~ `j_dg_3_4` (chain to `l_dg_3_tip`)
`finger_4`	`j_dg_4_1` ~ `j_dg_4_4` + `j_dg_4_inner` (chain to `l_dg_4_tip`)
`all_fingers`	All 18 joints

F/T Sensor Setup¶

The DG-4F has 4 fingertip F/T sensors. To enable them:

ros2 launch dg4f_driver dg4f_driver.launch.py fingertip_sensor:=true ft_broadcaster:=true

Check the F/T topics:

ros2 topic list | grep fingertip

/dg4f/fingertip_1_broadcaster/wrench
/dg4f/fingertip_2_broadcaster/wrench
/dg4f/fingertip_3_broadcaster/wrench
/dg4f/fingertip_4_broadcaster/wrench

Calibrate the sensors:

ros2 service call /dg4f/delto_hardware_interface_node/set_ft_sensor_offset std_srvs/srv/Trigger

Topics Published¶

Namespace: /dg4f/

Topic	Type	Description
`joint_states`	`sensor_msgs/msg/JointState`	Position, velocity, and effort for all 18 joints
`robot_description`	`std_msgs/msg/String`	URDF robot description
`dg4f_controller/state`	`control_msgs/msg/JointTrajectoryControllerState`	Controller state (JTC only)
`fingertip_N_broadcaster/wrench`	`geometry_msgs/msg/WrenchStamped`	F/T sensor data for finger N (if enabled)

Services¶

Replace <ns> with dg4f.

/<ns>/delto_hardware_interface_node/set_ft_sensor_offset: Type: std_srvs/srv/Trigger; Zero-calibrate all fingertip F/T sensors. Call when nothing is touching the fingertips.
/<ns>/set_gpio_output1: Type: std_srvs/srv/SetBool; Set GPIO output 1 (true = high, false = low)
/<ns>/set_gpio_output2: Type: std_srvs/srv/SetBool; Set GPIO output 2
/<ns>/set_gpio_output3: Type: std_srvs/srv/SetBool; Set GPIO output 3

Verifying the Connection¶

# Check hardware interfaces
ros2 control list_hardware_interfaces

# Check active controllers
ros2 control list_controllers

# Read joint states
ros2 topic echo /dg4f/joint_states --once

Note¶

DG-4F motor direction is always standard (no firmware version dependency). No special configuration is needed regardless of your firmware version.