Technology

Summary

The gripping challenge

Nowadays, robot are often charged with monotonous tasks – but they are not well equipped to be flexible and adapt to unknown environments. Robot grippers rely on computer vision to locate, identify and handle objects. In addition, grippers struggle to handle fragile objects because vision inadequately feeds back information about applied gripping forces.

The solution is tactile sensing

Our solution is a gripping tool equipped with an advanced set of sensors:

  • We are adding tactile feedback to enable the sense of touch to robots.
  • Additionally, we are adding distance sensing to speed up object handling
  • Also, we aim to detect object slippage as a unique feature
  • Hereby, objects are better and faster handled, without causing damage, bruising or dropping of objects

What is tactile sensing?

  • When a robotic end-effector engages with an object, a human operator or other parts of the surrounding environment, it is crucially important to apply sensing techniques. Not only is operator safety of essence, but also avoiding any bruising, dropping or other means of damaging and object  is valuable. 
  • In modern, state-of-the-art pick-and-place applications, a camera and image processor is the main sensing devices to locate objects and avoid obstacles. Computer vision using cameras and processor work well in many cases, however can also be hindered by obstructing objects, impairment from poor lighting or having to navigate through a dynamically changing environment. Further improving computer vision as input to robot application can be costly, either increasing pixel resolution and processing power or even using stereo cameras and advanced image processing.  
  • Instead of seeking improved performance through more advanced camera sensing, we promote tactile sensing as an augmented sensing technique to camera sensing. Tactile sensing captures any forces applied  to an end-effector like a robot gripping tool. Sensors are placed on the “fingers” of the robot gripper, meaning right at the location of interaction.  

What is the advantage of using tactile sensing in robotics?

  • Tactile sensing enables robot manipulators to better handle challenging objects. Fragile objects can be challenging, irregular objects can be challenging, slippery objects can be challenging. However random objects meaning any combination of aforementioned objects are probably more challenging to robot manipulators than anything else. 
  • Fragile objects are, for instance, found in applications like food harvesting, processing and packaging. Our tactile grippers ensure that excessive forces are not applied to the food object, hence any bruising or damaging is avoided
    •Irregular objects can be difficult to pick up. Using arrays of tactile sensors, Graspian tactile grippers detect object surface curvature, edges and ensures good and stable contact between object and manipulator. 
  • Slippery objects can be tricky to handle. Slippage arises, for instance, when the gravity force exceeds the friction force. Friction is reduced by objects with low surface roughness, and when objects are coated by lubrication other similar oily-type liquids. There are several options for ensuring that objects aren’t dropped when slippage is detected. Either additional gripping force can be applied, or the object can be rotated to hinder orientation towards the ground.

Step-by-step pick-and-place procedure

 

1. Object locationing

  • Apply computer vision to identify and locate an object, or use a priori knowledge about its location
  • Move the robot arm towards the object

2. Object picking

  • As the manipulator fingers approach the object, use tactile sensing to classify object compliance and ensure a good grip. A good grip is defined as one with sufficient force applied, even distribution of force from each robot finger, and avoiding to pick up an object close to edges and other irregular object features

3. Object lifting

  • When object is raised from it’s resting position, any unexpected motion caused by a poor grip or by slippage is being detected. If the motion happens instantly upon lift-off, then the procedure can be aborted by releasing the object.

4. Object moving

  • Other mission abortion techniques must be applied if the slippage or risk of droppage is detected when the object has been raised further from its resting position. Also, collision with the surrounding environment is detected by tactile sensors and abortion strategies can be put to practice.

5. Object placing

  • As the object approaches it’s destination, sensing of initial base contact is detected and a signal can be sent to the manipulator to release the object.
  • Alternatively, a human operator can tell a cobot (collaborative robot) to release an object, e.g. by pulling the object upwards. This will tell the robot system that the operator is taking over the picking control of the object.
     
     

Applications of tactile grasping

Midsection,of,workers,slicing,fishes,at,table

Avoiding bruising and damages in agriculture

Midsection,of,workers,slicing,fishes,at,table

Carry out laboratory tasks in a sterile or toxic environment

Saving manual labour in facility management services

Midsection,of,workers,slicing,fishes,at,table

Pick and place tiny and fragile objects in assembly

Midsection,of,workers,slicing,fishes,at,table

Reducing intensive manual labour in food processing

Tactile grasping for your application
 

Graspian tactile gripper

  • Object force detection from a few grams to many kilograms 
  • Object slippage detection at sub-millimeter motion 
  • Customisable mechanical design, where sensors and finger dimensions can be optimised for specific gripping challenges 
  • Tell us about your gripping challenge. We are here to help…

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