Beyond Human Hands Part 1

Comprising 27 bones, 27 joints, 34 muscles, and more than 100 ligaments and tendons, the hand is capable of an astonishing range of movements and tasks, from delicate, precise actions like threading a needle to powerful grips that can lift heavy objects. The coordination between sensory feedback and motor control allows the hand to perform these tasks effortlessly and intuitively. Our hands, a marvel of biological engineering, are capable of precision manipulation of virtually any object.

Not the real thing…yet

Although robotics continually strives to emulate the human hand, technology lags far behind biology. In time robot hands will match (or outmatch) our own. Until that time, most robotics companies will continue to provide special-purpose end-effectors, designed for specific use cases. Some examples include:

• Suction only. Uses a vacuum and suction cup.
• Suction cup array. Distributes the suction force across several points.
• Pinching. Mimics the human action of pinching, using two fingers to grasp objects.
• Bubble. Leverages one or more inflated surfaces, often in tandem with one or more rigid surfaces.
• Soft. Constructed from flexible materials that conform to the shape of the object being grasped.
• Fingers and suction. Uses fingers to position and stabilize an object while the suction cup provides a secure hold.

Each type of end effector has its strengths and weaknesses, and the choice of which to use depends on the specific requirements of the task at hand. For example, the suction-only approach is the simplest design, however it lacks the ability to manipulate large objects. The suction cup array is an excellent option for large objects, however might be susceptible to multi-picking smaller items, impacting order integrity. 

Design Considerations

Designing a robotic grasping device is a multifaceted challenge that demands a deep understanding of both the task at hand and the environment in which the robot will operate. The goal is to create an end effector that can reliably and efficiently perform the required tasks under varying conditions. Here are critical considerations for designing such devices:

• Application Specificity: Understanding the specific needs of the target industry is crucial, given the unique requirements of each. For example, the demands of e-commerce fulfillment differ significantly from those of manufacturing and assembly or food and agriculture.
• Object Characteristics: Considerations include the shapes, sizes, weights, fragility, and materials of the objects to be handled.
• Environmental Conditions: The operating conditions, such as humidity, dust, and temperature extremes, must be factored into the design.
• Suction Techniques: The method by which suction will be generated, such as Venturi or high vacuum.
• Sensing and Feedback: The necessity of tactile sensing and the ability to detect when an object is grasped are crucial for precision.
• Modularity and Adaptability: Whether the solution will use a single end-effector or multiple ones affects its flexibility.
• Actuation and Control: The number and type of actuators used in the end effector determine its dexterity and precision.
• Regulatory Compliance: Regulatory considerations, such as food handling or electrical standards.
• Design for manufacturability: A solution that is easy to manufacture and assemble reduces production costs and time.
• Design for robustness: Industrial environments can be harsh, with frequent impacts, vibrations, and exposure to various elements.
• Design for maintainability: An end effector that is easy to service and maintain is crucial for minimizing downtime and extending its operational life. 

Even the most well-designed robotic grasping solutions will encounter complex challenges in production settings. First, the end effector must successfully grasp the item, a task influenced by factors such as product packaging, material composition, and the item's location, orientation, and the dimensions of its container. Next, it must maintain order quality and integrity by picking up only one item at a time without causing damage. The solution must then reliably transport the item to its destination without dropping it. Finally, it must place the item accurately and safely in its designated spot, ensuring no damage occurs during the placement.

Case in point: A package of batteries. The hang tag can complicate the use of suction-based grasping by causing multiple items to be picked simultaneously, which disrupts order integrity. Additionally, the thin cardboard packaging is prone to damage under pressure, requiring delicate handling. Furthermore, the blister pack design does not allow for a stable suction seal, making it difficult to maintain a secure grasp. These factors necessitate a nuanced approach to designing robotic end-effectors capable of handling such packaging reliably and efficiently.

In the next edition of The Robotic Touch, we’ll discuss in more detail real-world grasping problems and solutions, featuring insights from experts at RightHand Robotics who are pushing the boundaries of what's possible.