Gripper with fingertip sensitivity

Article of 23 April 2015 

KoSiF research project | Image: Festo, Würth Elektronik, IMS Chips

Researchers in the funded  project, KoSiF (German for “Complex systems in foil”) are developing a "sensory organ" for machine grippers. For this purpose, flexible electronic components are embedded in a thin foil. Previously such sensors were rigid and could therefore only be fastened to curved surfaces with difficulty.

The new system, on the other hand, can also be attached to flexible, bendable objects. With the aid of this intelligent sensor system, gripping forces up to the form fit of the gripper are expected to be evaluated and the size of the gripped object detected. A gripper is thus given "fingertip sensitivity" and is able to grip different items more deliberately and assess them using sensor technology.

Demonstrator with adaptive gripper developed

Festo has been involved in this project with several research and industrial partners since the start of 2013. In the first project phase, the researchers developed an application demonstrator called “Smart Skin 1”. This was based on the adaptive gripper, which was also used in the Festo Bionic Handling Assistant. It consists of three flexible gripper fingers with Fin Ray Effect®, which can adapt to the widest variety of objects. “The aim of the first demonstrator is to equip the grippers with a thin foil with integrated strain sensors based on ultra-thin silicon chips. These adapt to the change of shape of the gripper fingers when gripping,” explains Stefan Saller, who manages the research project at Festo.

Three complex foil systems

In the second part of the project, another demonstrator is being set up. It consists of three functionally separated foil systems. The first foil, SmartSense, is made up of four ultra-thin chips for measuring strain. "As the gripper is adaptive, it deflects during the gripping process. A strain is thereby induced, which is recorded by the intelligent measuring system and measured with a high degree of precision. At the same time, the system provides further functions such as analogue signal processing and digital operations," says Stefan Saller. The second sensor foil, SmartInkSense, is based on printed strain gauges; the third foil, called SmartView, sports a flexible display.

Information such as the radio signal strength, battery charging status and gripping status can be read on this. All three systems feature a wireless interface, via which measurement and configuration data is exchanged between the sensor foils and the base station. An ultra-thin control chip, which is present in all three systems, controls the respective functions. There is also an SPI interface, via which the configuration data can be exchanged.

The planned conclusion of the project sponsored by the Federal Ministry of Education and Research is the middle of 2016. One possible application field of the gripper is the food sector. For example, it can harvest field crops safely using controlled, adaptive gripping. Yet there is also a wide range of applications in the industrial environment, which can benefit from the particular properties of an adaptive gripper such as this.

The following video shows how the gripping process is monitored (source: Festo, Würth Elektronik, IMS Chips):

Cover picture, top: Festo, Würth Elektronik, IMS Chips