Gripper

Mechanical grippers are the most common type, using two or more rigid fingers or jaws that close to apply a clamping force. They are actuated by pneumatic, electric, or hydraulic systems.

• Parallel Jaw: Fingers move in parallel, ideal for prismatic objects (e.g., boxes, blocks).
• Angular Jaw: Fingers pivot, useful for gripping objects with tapered or irregular shapes.
• 2-Finger vs. 3-Finger: Two-finger designs are simpler; three-finger designs can achieve form closure on cylindrical objects.

Key Applications: Industrial assembly, machine tending, and pick-and-place operations where objects are rigid and graspable from the sides.

Vacuum grippers use negative pressure (a vacuum) to adhere to an object's surface. They consist of one or multiple suction cups connected to a vacuum generator.

• Passive Vacuum: Uses a venturi or vacuum pump to evacuate air.
• Active Vacuum: Includes a blowing function for positive release.
• Benefits: Excellent for flat, smooth, non-porous surfaces (e.g., glass, metal sheets, cardboard). They enable top-down grasping without needing to wrap around an object, making them ideal for bin picking.

Limitations: Performance degrades on porous, rough, or curved surfaces and requires a continuous power source to maintain the seal.

Magnetic grippers use magnetic force, either permanent or electromagnetic, to lift and hold ferromagnetic objects.

• Permanent Magnets: Simple, no power required, but require a mechanical stripper to release the object.
• Electromagnets: Can be turned on/off electronically, allowing for precise control and release. They often include backup batteries to prevent drops during power failure.

Key Applications: Highly efficient in metalworking, stamping, and logistics for handling steel plates, parts, and containers. They are not suitable for non-ferrous materials like aluminum, plastic, or wood.

Soft grippers are constructed from compliant, deformable materials like silicone or rubber and are actuated by pneumatic pressure. They conform to an object's shape upon contact.

• Operating Principle: Internal chambers inflate, causing the gripper structure to bend or envelop an object. This provides a gentle, distributed contact force.
• Key Advantages: Exceptional for fragile, delicate, or highly variable objects (e.g., fruit, eggs, irregularly shaped consumer goods). Their compliance offers inherent safety for human-robot interaction (HRI).
• Considerations: Generally lower grip force than mechanical grippers and can be slower to actuate.

Dexterous hands are multi-fingered, articulated end-effectors designed to mimic the kinematics and functionality of the human hand, enabling dexterous manipulation.

• Actuation: Often uses numerous tendons or embedded actuators, leading to complex control challenges.
• Capabilities: Enable in-hand reorientation, regrasping, and fine manipulation of tools and objects, going beyond simple pick-and-place.
• Applications: Research platforms, prosthetics, and advanced tasks in unstructured environments where a robot must use human tools. They are often paired with advanced tactile sensing arrays for feedback.

This category includes grippers designed for unique challenges, often incorporating multiple principles or adaptive mechanisms.

• Needle Grippers: Use arrays of thin, penetrating pins to grip porous or fibrous materials like foam, fabric, or insulation.
• Electrostatic Grippers: Use electrostatic adhesion for handling very thin, smooth materials (e.g., semiconductor wafers, glass panels).
• Gecko-Inspired Grippers: Use van der Waals forces via micro-structured surfaces to grip smooth surfaces without suction or residue.
• Underactuated & Adaptive Grippers: Use clever mechanical linkages (e.g., pulley systems, differential mechanisms) so that a single actuator can drive multiple fingers, allowing them to passively conform to object shapes, simplifying control.

The most common industrial gripper, featuring two opposing fingers that move in parallel to clamp an object. Their simplicity and robustness make them ideal for high-speed, repetitive tasks.

• Key Components: Actuator (pneumatic, electric, or hydraulic), jaws, and a linkage mechanism.
• Industrial Use: Machine tending, packaging, and assembly lines for handling rigid, well-defined parts like metal blocks, electronic components, or packaged goods.
• Considerations: Provide high grip force but require precise object positioning. Often lack compliance for delicate or irregular items.

Grippers with fingers that pivot from a central point (angular) or use three radially symmetric fingers. They excel at grasping cylindrical objects or applying centering force.

• Angular Grippers: Fingers open and close in an arc, useful for accessing objects in confined spaces.
• Three-Finger Grippers: Provide enveloping grasps for spheres, tubes, or irregular shapes. Common in machining for handling raw bar stock or finished pipes.
• Application Example: CNC machine tending for metal rods, where a centered, secure hold is critical during transfer.

These grippers use negative pressure (vacuum) to adhere to smooth, non-porous surfaces. They are the dominant solution for handling flat, fragile, or large-panel items.

• Components: Vacuum pump or generator, suction cups (bellows or flat), and valves.
• Key Advantages: Can handle large surface areas with minimal point pressure, ideal for glass, sheet metal, cardboard, and food products.
• Industrial Dominance: Over 80% of packaging and palletizing applications use vacuum systems due to their speed and adaptability to box size variation.

Grippers that use magnetic force to lift and hold ferromagnetic materials. They offer rapid, non-contact acquisition and release.

• Permanent Magnets: Simple, energy-free holding. Require a mechanical striker or slide to break contact for release.
• Electromagnets: Allow programmable on/off control via an electrical current. Enable precise pick-and-place cycles.
• Primary Use Case: Metal fabrication and stamping for handling steel sheets, blanks, and finished parts. Essential in high-temperature environments where other grippers would fail.

Grippers made from compliant materials like silicone, rubber, or fabric that conform to an object's shape. They are inherently safe and can handle a wide variety of items without complex sensing.

• Operating Principles: Use pneumatic inflation (pneumatic networks), granular jamming, or tendon-driven deformation.
• Key Benefit: Passive adaptation to irregular geometries—from delicate fruits and vegetables to complex industrial castings—without precise pose estimation.
• Emerging Applications: Agriculture (fruit picking), logistics (unstructured bin picking), and electronics handling where marring must be avoided.

Complex, multi-fingered end-effectors that mimic the kinematics of a human hand. They are used for advanced, in-hand manipulation tasks requiring reorientation and fine motor skills.

• Capabilities: Dexterous manipulation such as rotating a screwdriver, regrasping a pen, or manipulating small assembly parts.
• Actuation: Typically uses numerous tendons or embedded actuators, making them mechanically complex and expensive.
• Current Deployment: Primarily in research (e.g., DLR Hand, Shadow Hand) and niche high-value assembly, not yet common in bulk industrial automation due to cost and control complexity.

An end-effector is the device mounted at the end of a robotic arm, of which a gripper is one common type. It is the terminal component that directly interacts with the environment to perform work.

• Types: Beyond grippers, end-effectors include tools like welders, drills, spray guns, and suction cups.
• Interface: It attaches via a mechanical or magnetic interface, often featuring standardized mounting plates (e.g., ISO 9409-1).
• Role: The end-effector defines the robot's task capability; swapping it can repurpose a single arm for different operations.

Force/torque (F/T) sensing is the measurement of multi-axis contact forces and moments, typically via a sensor mounted between the robot's wrist and the end-effector.

• Function: Enables compliant control strategies by providing real-time feedback on interaction forces.
• Applications: Critical for delicate assembly (peg-in-hole), polishing, and ensuring safe human-robot collaboration by detecting unexpected collisions.
• Integration: A gripper equipped with or operating in conjunction with an F/T sensor can perform guarded moves and measure grasp force to prevent object damage.

Grasp planning is the algorithmic process of determining optimal contact points and gripper pose to achieve a stable and task-functional grasp of a target object.

• Inputs: Uses a 3D model or perceived point cloud of the object, along with gripper geometry and task constraints (e.g., required orientation after pickup).
• Metrics: Evaluates potential grasps using criteria like form closure, resistance to disturbance, and accessibility without collisions.
• Output: Produces a gripper pose and finger configuration (for articulated grippers) for execution.

Dexterous manipulation refers to the skillful, in-hand movement of an object using a multi-fingered robotic hand or advanced gripper, beyond simple pick-and-place.

• Capabilities: Includes regrasping, finger gaiting, rolling, sliding, and using the object as a tool.
• Complexity: Requires high degrees of freedom, sophisticated tactile sensing, and advanced control policies, often leveraging reinforcement learning.
• Contrast: Differs from simple parallel-jaw gripping, aiming for human-like adaptability in unstructured environments.

Tactile sensing is the measurement of contact properties through sensors embedded in a gripper's fingers or pads, providing rich, localized data about the grasp.

• Measurands: Includes normal and shear pressure distribution, vibration, slip detection, temperature, and texture.
• Benefits: Enables blind grasping in occluded areas, real-time adjustment of grip force to prevent slip, and object identification by texture.
• Technologies: Implemented using piezoresistive arrays, capacitive sensors, optical waveguides, or barometric MEMS sensors.

Compliant assembly is a robotic strategy for precise part mating (e.g., inserting a shaft into a bearing) that accommodates positional uncertainty through controlled mechanical flexibility.

• Methods: Can be active (using force/torque feedback to guide the robot) or passive (using a mechanical Remote Center of Compliance (RCC) device between the gripper and wrist).
• Principle: Instead of relying on perfect positional accuracy, the system allows the gripper and part to "float" slightly, using contact forces to self-align components.
• Result: Dramatically reduces jamming and damage compared to rigid, position-only control.