In an ultra-modern factory in the heart of Stuttgart, a group of ‘free radical’ biologists and engineers have joined forces to find ways of learning from nature. Whether it’s a flexible gripper inspired by a chameleon’s tongue, or cooperative behaviour based on ants, their open-source work is changing the means by which products and systems are being created.
The researchers inspired by plants and animals are part of the Bionic Learning Network, which initially had its roots within industrial group Festo. Nowadays, the network pulls together open-minded thinkers from around the world, all of whom are keen to consider how natural phenomena might underpin the automation technology and production systems of the future.
“Nature is about evolution, without wastage, and we are very keen to learn from it,” says Dr Heinrich Frontzek, vice-president of future concepts at Festo, the German controls and automation company that leads the Bionic Learning Network. “If you look closely at nature, maybe you will find some answers. So the network brings together designers and engineers, biologists, and control specialists from around the world. It’s not about big budgets, it’s about big ideas. And everybody is invited to take part.”
The fruits of their labour are demonstrated at Festo’s main production facility in Stuttgart. Swarms of mechatronic butterflies dance through the air in a central atrium using realtime-optimised communication to avoid collision. Meanwhile, a flexible gripper with a silicone cap, based on a chameleon’s tongue, is used to gently pick up a host of objects. “All this work might feed into factory automation, logistics and guidance supervision,” says Frontzek. “The Bionic Learning Network is about not having any fear, and it’s about having fun. And that freedom allows people to think beyond the horizon.”
The network has delivered dozens of nature-inspired projects, some of which are moving towards the creation of commercial products. Most notable is the FlexShape Gripper, which owes its existence to the chameleon’s tongue. The unique combination of force and form demonstrated by the tongue can be observed when the chameleon is on the hunt for insects. Once the animal has identified its victim, its tongue shoots out like a rubber band. Just before the tip of the tongue reaches the insect, it retracts in the middle, while the edges continue to move forwards. This allows the tongue to adapt to the shape and size of the prey and firmly enclose it.
For the Bionic Learning Network interpretation, the FlexShape Gripper consists of a double-acting cylinder, of which one chamber is filled with compressed air while the second one is permanently filled with water. The second chamber is fitted with elastic silicone moulding, which equates to the chameleon’s tongue. The volume of the two chambers is designed so that the deformation of the silicone part is compensated. A piston, which closely separates the two chambers from each other, is fastened with a thin rod on the inside of the silicone cap.
A handling system guides the gripper across the object so that it touches the article with its silicone cap. The top pressurised chamber is then vented. The piston moves up by means of a spring support and the water-filled silicone part pulls itself inwards. Simultaneously, the handling system guides the gripper further across the object. In doing so, the silicone cap wraps itself around the object to be gripped, which can be of any shape, resulting in a tight form fit. The elastic silicone allows a precise adaptation to a range of different geometries.
Friction holds firm
The high static friction of the material generates a strong holding force. Both the holding and the release mechanism are triggered pneumatically. No additional energy is necessary for the holding process. The yielding quality of the compressible compressed air simplifies the coordination between the handling system and gripper during the grip stage. The force and the deformation of the silicone part can be set very precisely with the aid of a proportional valve. This allows several parts to be gripped at once.
“The revolutionary feature of the FlexShape Gripper is that it can grasp, pick up and place objects of diverse shapes in a single process – without the need for manual conversion,” says Frontzek. In future, it could be used in any facility where multiple objects with a range of different shapes are handled at the same time, he says, either in a factory handling small components, or perhaps in a food production plant delicately picking fruits or vegetables. Frontzek says that Festo is talking to industrial partners to commercialise the research.
Another intriguing nature-inspired area of work at the Bionic Learning Network is a means of highly integrated movement based on the delicate anatomy of an ant. For the first time, the cooperative behaviour of the creatures has been transferred to the world of technology using complex control algorithms. “Like their natural role models, the Bionic Ants work together under clear rules,” explains Frontzek.
This cooperative behaviour provides interesting approaches for the factory of tomorrow. Production systems will be founded on intelligent components, which adapt flexibly to different production scenarios and so take on tasks from a higher control level.
By pushing and pulling together, the artificial ants can move an object across a defined area. Thanks to this intelligent division of work, they are able to transport loads that a single ant could not move.
“They communicate with each other and coordinate their actions and movements,” says Frontzek. “Each ant makes its decisions autonomously, but in doing so is always subordinate to the common objective and thereby plays its part towards solving the task at hand.”
The Bionic Ants also come close to their natural role models in terms of design and constructional layout. The mouth instrument used for gripping objects is replicated in accurate detail. The pincer movement is provided by two piezo-ceramic bending transducers, which are built into the jaw as actuators. If a voltage is applied to the tiny plates, they deflect and pass on the direction of movement mechanically to the jaws.
The benefit of piezo technology has also been applied for the legs on the artificial ants. Piezo elements can be controlled very precisely and quickly. They require little energy, are almost wear-resistant and do not need much space. Three trimorphic piezo-ceramic bending transducers, which serve both as an actuator and a design element, are therefore fitted into each thigh. By deflecting the top bending transducer, the ant lifts its leg. With the pair underneath, each leg can be exactly deflected forwards and backwards. To increase the relatively low lift, the team developed a flexible hinge joint, which extends the ant’s step size significantly.
Highly complex control algorithms are used for the cooperative behaviour. With two rechargeable batteries on board, the ants can work for 40 minutes before they have to link up with a charging station via their feelers. All actions are based on a distributed set of rules, which have been worked out using mathematical modelling and simulations and are stored on every ant.
The control strategy provides for a multi-agent system in which participants are not hierarchically ordered. Instead, all the Bionic Ants contribute to the process of finding a solution together by means of distributed intelligence. The information exchange between the ants required for this takes place via the radio module in the torso.
Navigation aids
Cameras and floor sensors also work together. The ant uses the 3D stereo camera in its head to identify the object to be gripped as well as for self-localisation purposes using landmarks. The opto-electrical sensor in the abdomen uses the floor structure to tell how the ant is moving in relation to the ground. With both systems combined, each ant knows its position – even if its sight is temporarily impaired.
Frontzek says that, by implementing the special behaviour of ants by combining various technologies, the scientists and engineers have recreated a basic design principle for a highly integrated microsystem, which is also equipped with its own intelligence for acting at a local level. “So the ants illustrate possible production scenarios of tomorrow,” he says.
The Bionic Learning Network also took butterflies as the inspiration behind the creation of flying objects with collective behaviour. The eMotion Butterflies feature highly integrated on-board electronics, so they can activate their wings individually with precision for complex flight.
To enable the butterflies to make the different flying manoeuvres with process reliability and stability, permanent communication is necessary. The localisation of the individual flying objects is ensured by the radio and sensor technology on board in combination with the guidance and monitoring system.
An important part of the indoor GPS is a camera system, as could also be used in the factory of the future. Ten infrared cameras installed in the space record the butterflies using two active markers (infrared LEDs). The cameras transmit the position data to a central master computer, which acts like an air traffic controller and coordinates the butterflies from outside, providing clear behaviour patterns for collision-free movement, with no human pilot required.
Frontzek says that, with the eMotion Butterflies, the researchers have created an ultra-lightweight artificial insect with coordinated flight behaviour in a swarm. This illustrates complex topics from future production worlds such as functional integration, ultra-lightweight design and networked, realtime-optimised communication between individual systems.
“However, the eMotion Butterflies will not fly through the factory of the future; rather, they will suggest new approaches to a networked overall system or show us what industrial logistics applications could look like,” he says.
He concludes: “Where might this work go next? Maybe gesture and brain controls – these could be areas of the future. It’s an exciting time – and the work of the network gives us the chance to get to the hearts and minds of young people, and to get them interested in engineering. It’s a matter of motivation.”