TacLINK: an artificial skin made to measure for collaborative robots

One of the biggest problems of cobots , increasingly widely used in the era of the so-called "Industry 4.0", lies in security. In fact, cobots collaborate with humans and operate in the same environments in which humans also work. Therefore, the need arises to guarantee a certain level of reliability to operators who find themselves having to carry out activities in collaboration with them . Almost all of the protection systems against accidental encounters that can arise between humans and robots is currently based on the use of sensors of various types.

They make the machine "endowed" with a good perception capacity able to avoid dangerous contacts with the people around it. By now the most advanced robots, especially used in the industrial field, are capable of perceiving many of our canonical five senses. There are two, however, on which the challenges of research in the near future are oriented: taste and touch. Now, things seem to have changed with TacLink, the first prototype of artificial skin for robots.

The idea of ​​an artificial leather

It is precisely in this direction that in the laboratories of the Japan Advanced Institute of Science and Technology , prof. Van Anh Ho and his collaborators made an artificial skin for robots. The prototype, named TacLINK , is built on a tubular structure covered with a silicone membrane equipped with a wide range of sensors capable of providing the robot wearing it not only with tactile feedback, but also the ability to pick up micro- deformations to which the membrane is subject when it comes into contact with an external body.

TacLINK acts as an artificial skin for robots, behaving like humans.
TacLINK acts as an artificial skin for robots, behaving like humans.

How TacLINK is made, the artificial skin for robots

The artificial haptic system developed by the researchers includes two 640 × 480 px cameras, each with 30 fps, and a series of high-intensity LEDs. LEDs also use a polarizing filter to generate uniform light while minimizing reflected light. At the center of the tube-shaped structure there is also a layer of black material in order to block the light produced by the LEDs which, otherwise, would impact the sensors of the rooms. The artificial leather, only 3.5 mm thick, has a sensitive area of ​​about 500 square centimeters in total consisting of a mesh of small holes, called “markers”, capable of receiving tactile feedback.

The image processing at the basis of tactile feedback

The operating principle of the TacLINK tactile feedback is based on the use of the two coaxial chambers placed at the two ends of the tubular structure. Together, they form a stereo camera thanks to which it is possible to know moment by moment the positions of all the markers placed on the silicone membrane. An i mage processing algorithm reconstructs the 3D model of the membrane starting from the displacements of the detected markers . In doing so, it is able to model the deformations suffered by the skin, simply by analyzing the distribution of the forces exerted on it. This is also possible thanks to the Finite Element Model (FEM) of the membrane previously built and used to estimate the structural rigidity of the skin.

TacLINK, the artificial skin for robots. Source: Japan Advanced Institute of Science and Technology
TacLINK, the artificial skin for robots. Source: Japan Advanced Institute of Science and Technology

By combining the data coming from the chambers and the results obtained from the FEM analysis, the processor reconstructs the contact geometry with high precision and extreme speed. Tests conducted on artificial skin showed that the tactile feedback system takes about 35 milliseconds to completely rebuild the haptic response . Although the presence of reflections or occluded regions can prevent the correct processing of the images and the developed system requires a high capacity of real-time calculation, prof. Ho was quite confident about a rapid commercialization of the prototype made:

" The artificial skin used in our studio can be easily manufactured with the casting method and also used on other parts of robots, such as fingers, legs, chest and head and even to make smart prostheses for humans, allowing a person disabled to be able to have the same perceptions of a healthy person. "

Prof. Van Anh Ho

3D reconstruction of the deformation of the skin. Source: Japan Advanced Institute of Science and Technology
3D reconstruction of the deformation of the skin. Source: Japan Advanced Institute of Science and Technology

Solutions of this type open the way to new frontiers in the development of wearable robotic systems. They will be able to receive tactile feedback that can be useful not only in industry, but also in medicine, creating prostheses that can correctly perceive external stimuli.

Article by Augusto Bozza

The article TacLINK: an artificial skin made to measure for collaborative robots comes from Tech CuE | Close-up Engineering .