3-Finger Adaptive Gripper for Pipe Handling

Precision Grasping Technology Inspired by GelSight Svelte Hand

Our project features a specialized 3-finger adaptive gripper designed to handle PVC pipes with consistent force and high precision. This gripper is a key innovation in our automated coupling system, enabling secure handling of pipes throughout the water bath and molding process while adjusting to different pipe diameters.

Gripper Model

Our custom 3-finger adaptive gripper model developed in Gazebo simulation environment.

Gripper Reference

The GelSight Svelte Hand that served as inspiration for our gripper design.

Gripper Design & Capabilities

Our gripper design was implemented using the Gazebo simulation environment and draws inspiration from the GelSight Svelte Hand. The three-finger design provides exceptional versatility for grasping objects of different sizes and shapes, while maintaining a simple control mechanism requiring only 2 degrees of freedom.

Key Features of Our Adaptive Gripper

  • Three-Finger Configuration: Provides stable grasping with optimal force distribution
  • Adaptive Force Control: Maintains consistent force regardless of pipe diameter variations
  • Low Mechanical Complexity: Achieves multiple grasping modes with minimal actuators
  • Semi-Rigid Structure: Combines rigidity for strength with compliance for adaptive grasping
  • Optimized for Cylindrical Objects: Specialized for handling PVC pipes of different diameters

Multiple Grasping Modes

Like the GelSight Svelte Hand that inspired our design, our gripper supports three primary grasping modes:

Precision Grasp

Two-finger pinch grasp for precise handling of small objects and accurate positioning of pipes before insertion

Lateral Grasp

Intermediate grasp that provides both precision and strength, ideal for transporting pipes to the water bath

Power Grasp

Three-finger opposition grasp for maximum stability when handling heated pipes and placing them into molds

Simulation Implementation

We implemented our gripper in Gazebo, a robust physics simulation environment that allows us to test and refine the gripper's performance under various conditions. The simulation includes:

  • Physical modeling of finger joints, actuators, and contact surfaces
  • Force feedback simulation for adaptive grasping
  • Integration with the robotic arm kinematics
  • Testing of different grasping modes for various pipe diameters
  • Optimization of gripper parameters for consistent force application

Reference Design: GelSight Svelte Hand

Jialiang (Alan) Zhao and Edward H. Adelson, "GelSight Svelte Hand: A Three-finger, Two-DoF, Tactile-rich, Low-cost Robot Hand for Dexterous Manipulation," Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology.

Our gripper design was inspired by the GelSight Svelte Hand, a novel 3-finger 2-DoF tactile robotic hand developed at MIT. This innovative hand can perform precision grasps, power grasps, and intermediate grasps with just two actuators. Key features that influenced our design include:

  • Three-finger arrangement with one "thumb" opposing two other fingers
  • Simplified actuation mechanism requiring only two motors
  • Ability to perform multiple grasp types with a small number of actuators
  • Semi-rigid endoskeleton with compliant outer materials for both strength and adaptability

While our implementation does not include the tactile sensing capabilities of the original GelSight design, we've optimized our gripper specifically for the PVC pipe coupling task, focusing on consistent force application and reliable handling through the heating and placement process.

Adaptive Force Control

A key innovation in our gripper design is the adaptive force control mechanism that ensures consistent force application regardless of pipe diameter. This is achieved through:

  • Compliant Beam Mechanics: Using the principles detailed in the Advanced Mathematical Foundations section of our main report
  • Optimized Finger Geometry: Designed to maintain contact force within 3% variation across all pipe sizes
  • Torque-Controlled Actuation: Rather than position control, allowing adaptive response to different object sizes
  • Force Distribution: Even distribution of force across the three contact points to prevent deformation of heated pipes

Conclusion

Our 3-finger adaptive gripper represents a significant advancement in automated PVC pipe handling. By drawing inspiration from cutting-edge research like the GelSight Svelte Hand while focusing on our specific application requirements, we've developed a gripper that combines simplicity, reliability, and precision. The gripper's ability to maintain consistent force across varying pipe diameters while supporting multiple grasping modes makes it ideal for the challenging task of handling both rigid and heat-softened PVC pipes throughout the coupling process.