🤖 Pick Node

See the source code for implementation details.

The Pick Node controls the MyCobot arm and gripper to pick up objects once the robot reaches the target location.
It integrates directly with the Mission Manager Node and executes a predefined pick sequence.

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🔗 MyCobot Integration

The Pick Node communicates with the MyCobot arm over:

• ROS2 topics/services (if using mycobot_ros2 driver)
• TCP/Wi-Fi API (if using direct API control)

Typical integration flow:

1. Receive trigger from Mission Manager (/pick_trigger or action call)
2. Calculate pick position (from /target_pose or pre-defined offset)
3. Move arm to pre-grasp position (safe above object)
4. Lower arm to grasp position
5. Close gripper to grab object
6. Lift to transport pose
7. Send completion flag back to Mission Manager

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✋ Gripper Control Mechanisms

The gripper can be controlled in two ways:

1. Position Command:

• Send "open" or "close" angles directly
• Example: gripper.publish(servo_angle)

2. Service Call:

• Use dedicated service: /gripper_control with commands open or close

Example (pseudo-ROS2 code):

def close_gripper():
    self.gripper_pub.publish(Int16(100))  # Fully closed

def open_gripper():
    self.gripper_pub.publish(Int16(0))    # Fully open

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🛡 Error Handling Procedures

Error Case	Action Taken
Arm fails to reach pose	Retry up to N times, log warning
Gripper fails to close/open	Retry with adjusted force, log error
Timeout on pick sequence	Abort pick, return failure to Mission Manager
Object slips after pick	Trigger re-grasp attempt if enabled

Safety First

Always implement a maximum number of retries to avoid damaging the arm or gripper.

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🧪 Testing & Verification

Before live tests:

1. Simulation: Test pick sequence in MoveIt2 or Gazebo without real hardware
2. Dry Run: Run arm sequence in the air (no object) to verify poses
3. Slow Speed: Run live test at reduced joint speeds for safety

Verification checklist:

• ✅ Arm moves to correct pre-grasp pose
• ✅ Arm descends vertically to grasp pose
• ✅ Gripper closes fully and holds object
• ✅ Arm lifts without collision

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🛠 Troubleshooting Common Issues

Symptom	Possible Cause	Solution
Arm stops mid-motion	Power or connection issue	Check MyCobot power & network
Gripper does not respond	Wrong topic/service name	Verify correct ROS2 topic/service
Pick position is off	Wrong transform or pose offset	Calibrate TF frames, adjust offsets
Object slips during lift	Low grip force or wrong gripper pose	Increase grip force or close fully
Node crashes when triggered	Missing parameter or bad message	Validate inputs before starting

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📚 Learn More

• MyCobot ROS2 Docs
• ROS2 Services & Actions
• MoveIt2 Manipulation

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🎯 Next Steps

• Drop Node
• Mission Manager Node
• Manipulation Basics