While grippers for industrial automation have so far been designed primarily for robustness, durability and performance, the focus with gripper hands is on the aspect of flexibility of movement. The closer humans and robots work together, the greater the relevance of humanoid 5-finger hands. "In the extreme, humans and service robots will share one and the same workplace, including all tools and aids," Dr. Martin May, Head of Research/Advanced Technologies at Schunk, is convinced. This is precisely why the company had the SVH 5-finger hand certified for collaborative operation by the DGUV (German Social Accident Insurance) as the world's first gripper back in 2017. With the help of a total of nine drives, its five fingers can perform a wide variety of gripping operations. In addition, numerous gestures can be displayed, which facilitates visual communication between humans and service robots and can also increase acceptance for use in a human environment.

Different variants

Schunk has different gripping hands in its portfolio to suit the respective application, ranging from a 2-finger hand for service robotics, which is reduced to the basic functions of gripping, to the industrial 3-finger hand SDH and the complex SVH 5-finger hand. The latest model, the SIH, also has five human-like fingers, but differs fundamentally from the SVH in terms of drive and kinematics. While the SVH, which is driven by nine motors, fulfills the typical aspects of a precisely working robotic hand, the SIH, which is equipped with five motors and operated by cable pulls, is much more closely based on its human model with its tendons and muscles: three of its fingers can be moved independently of each other, while the two smallest can be moved together as a team. This means that the SIH can be used more flexibly than other gripping hands with cable pull mechanisms on the market, and it is also more robust and attractively priced. According to Martin May, the latter aspect in particular was a key requirement in the research project, as service robotics applications in the domestic environment in particular require strict cost management if they are to be successful on the market.

In order to achieve the goal of an affordable, flexible and easy-to-use 5-finger hand, Schunk uses experience from bionics as well as modern motor and electronics concepts. With the help of an intelligent gripper control system, a wide range of gripping processes can be implemented via an easy-to-use interface without having to program them precisely.

Autonomous gripping

With the SIH, the gripper specialist is expanding its portfolio with a robust and attractively priced gripper hand. © Schunk

In its Smart Labs, the gripper specialist goes even further: in addition to the gripping component, the company is focusing on the gripping process as a whole and looking for ways to complete handling tasks autonomously. The complex programming of the robot, which has so far been carried out manually by the user or integrator, is to be replaced in future by a learning, autonomous component network. Instead of defining positions, speeds and gripping forces step by step, intelligent gripping systems will in future detect their target objects via cameras and take over the gripping planning independently. Based on data sets and algorithms, gripping systems will be able to recognize regularities and derive appropriate reactions. Schunk researchers are also working on algorithms to classify different geometries and arrangements and to develop optimal gripping strategies. The aim is to enable gripping systems to handle parts independently and to continue to refine the underlying gripping processes.

Independent evaluation of the gripping quality

In this application, the Schunk SVH 5-finger hand autonomously grips any object that has been placed anywhere. © Schunk

The greater the variance of the parts to be gripped and the more complex the task, the more likely it is that gripper hands will be used. Using appropriate sensors in the gripper fingers, the motor current and intelligence integrated into the gripper hand, it should be possible to record and evaluate the quality of a grip and readjust it if necessary. In addition, object characteristics such as geometry, size or flexibility can be recorded via the gripper alone and transmitted to higher-level systems or upstream or downstream stations.

Dr. Martin May, Head of Research Advanced Technology at Schunk in Lauffen/Neckar. © Schunk

"With the help of artificial intelligence methods, it will also be possible to train service and assistance robots intuitively and to create and enrich individual libraries for gripping planning," Martin May is convinced. "Flexible gripping hands in particular will no longer be used only for repetitive tasks, but will be able to continuously adapt to new objects and contexts and constantly optimize their gripping strategies."

Prof. Dr.-Ing. Markus Glück, Managing Director Research & Development, CINO, Schunk / ag