Fluidic muscle: from bionic robots to driving and flight simulators

How can automated movement be made even more efficient and productive with the help of bionics¹? Festo is once more demonstrating innovative drive concepts from the Bionic Learning Network. The test objects make use of state-of-the-art technology from Festo. Integrated mechatronic² designs that allow remote maintenance and diagnosis are just as much part of this concept as are the latest piezo valves and electric drive mechanisms. The fluidic muscle from Festo, already long established in production, repeatedly proves its worth as an all-round talent in astonishing applications. These complex forms of motion take phenomena in air and water, but above all the human being, as their sources of inspiration.

Dissimilar twins: Aqua_ray and Air_ray
Analysis of various types of movement through water has established that rays are perfectionists in submarine "flight" and gliding. The up-and-down motion of their flanks in water closely resembles the flapping of a bird's wings in the air. This wavelike movement perfectly combines maximum propulsion with minimum energy consumption. The streamlined form lends graceful movement to the manta ray, in particular, and makes it a veritable submarine acrobat.

Aqua_ray is a remote-controlled fish with a water-hydraulic drive unit; its form and kinematics are modelled on the movement patterns of the manta ray.

Bionic fluidic muscles from Festo serve as actuators. These largely consist of hollow elastomer tubes with integrated woven aramide fibres. When the fluidic muscle is filled with air or water, its diameter increases and it contracts longitudinally, giving rise to smoothly flowing elastic movement.

The fluidic muscle from Festo, in combination with the Fin Ray Effect®, constitutes Aqua_ray's central propulsion and control unit. The Fin Ray Effect® is a construction that is derived from the functional anatomy of a fish's fin and imitates almost perfectly the mode of propulsion executed by the natural model.

It is entirely due to the mechanics of the fin rays - bony rods that constitute the fin's supporting structure – that the wing can be arched to ensure even distribution of forces. The smoothly flowing muscular movements are transformed into the dynamic flapping of a wing, which propels the artificial manta ray though the water.

Like a heart, Aqua_ray's water-driven central vane cell pump generates the propulsion energy, which is conveyed in the form of pressure via specially developed valves to three antagonistically acting pairs of muscles. Their force of contraction is transferred by artificial tendons of high-strength Dyneema® cord via spools and sheaths to the wings and the tail, which in turn transform the tendon travel of 55 mm into a vertical wing amplitude of more than 550 mm.

Through the use of new elastic materials for all moving components and for the 3D-deformable skin, and by matching the elasticity and self-adaptive characteristics of the internal wing and tail structures to the hydrodynamic forces, it has been possible to reproduce the kinematics of nature's marine model. Water is essential to Aqua_ray's function, since entirely authentic movement can only be attained in combination with this medium and its special characteristics.

Aqua_ray can be excellently manoeuvred and can be operated either as a hydrostatic glider or with actively flapping wings. This makes for considerable energy savings. Thanks to its form and its mode of propulsion, Aqua_ray is suitable for application in diverse fields of marine research without disturbance to the natural environment.

Air_ray, likewise modelled on the manta ray, is a remote-controlled hybrid construction comprising a helium-filled ballonet and a flapping-wing drive mechanism. Its extremely light design enables it to almost hover in the air by means of the buoyant force of the helium ballonet, floating through a sea of air just as the manta ray does in water.

The propulsion is effected by a flapping-wing mechanism. The wing module, which can be moved up and down by a servo drive unit, has a structure that makes use of the Fin Ray Effect® described above. This structure consists of two alternating pressure and tension flanks flexibly connected by ribs. When one flank is subjected to pressure, the geometrical structure automatically bends in the direction opposed to the force applied. A servo drive unit pulls on the two flanks longitudinally in alternation, thus moving the wing module up and down.

The structure is supplemented by a torsionally resistant central spar developed by Rainer Mugrauer. Mounted to its exterior end is a servo drive unit that enables the flapping wing to rotate about its transverse axis, so that Air_ray can fly backwards. The pitch elevator is also designed as a Fin Ray structure driven by a servo unit.

The Fin Ray Effect® is now also being used for the first time in automation: with the bionic material gate from Festo, seven different components can be simultaneously sorted in one single operation.

Airic’s_arm
How can technology be used to contrive a movement device which comes as close as possible to the human model in terms of overall concept, technical design and bionics?

Airic’s_arm was inspired by nature. Its combination of mechatronics and bionics opens up new opportunities for shaping the future of automated movement.

Airic’s_arm is a robot arm with artificial bones and muscles. A total of 30 muscles move the bone structure which, as with our own arms, consists of ulna and radius, metacarpal and finger bones, a shoulder joint and a shoulder bone - joints that are otherwise not encountered in this form in the world of technology. Airic's bones have not grown of their own accord, nor do they automatically heal following a fracture. They were designed on computer and are grown in a three-dimensional polyamide structure using a state-of-the-art laser sintering process.

The muscles, a product of Festo, are already widely found in industrial application under the name of fluidic muscles. These are elastomer tubes with integrated woven aramide fibres. When a fluidic muscle is filled with compressed air, its diameter increases and it is simultaneously shortened. This artificial muscle has immense starting power, and its dynamic behaviour is similar to that of a human muscle. Its greatest advantage over its human counterpart is that when contracted, it requires no further supply of energy. A weight once lifted can thus be held in any position indefinitely by Airic’s_arm. With this technology, the forces applied and the muscle's rigidity can be precisely metered. This is effected with very small, highly innovative proportional valves from Festo based on piezo technology. The tensile forces and the contraction of the individual muscles are measured by pressure and length sensors. A mechatronic unit developed by Festo then regulates the pressure distribution within the system, allowing movements that closely approach the action of human muscles in terms of kinematics, rapidity, force, but also refinement.

Coordinating all these actuators is only possible using the most up-to-date mechatronic systems and software available. Movements which we humans carry out subconsciously, or even in a reflex action, still require a great amount of effort using computer-supported control and regulation. Extending the sensory range of Airic’s_arm, e.g. by means of cameras or tactile perception elements, would be conceivable in the future along with further developments in designing a back, hip, neck etc.

All these characteristics are of great interest to the future of robotics; they will enable more and more dangerous and hazardous tasks to be handled by technology.

Pure mechatronics: Sky_liner and Airmotion_ride
Flying a kite calls for a great deal of skill. With the Sky_liner project, Festo is demonstrating for the first time that a kite can be controlled fully automatically by means of mechatronics, and is thereby forging a link to its key field of competence: automation by means of flowing air.

Sky_liner comprises a configuration of two dual-line kites, each controlled by a mechatronic unit. These kites are thus no longer flown by hand, but automatically operated from indoors with servo motors and artificial wind. Each line is coupled to a DMSP pneumatic muscle from Festo, which contracts and thus "shortens" the line to counteract this movement of the kite.

The bionic construction Airmotion_ride enables highly diverse driving and flight simulations to be realised in combination with mechatronic systems. A parallel-kinetic hexapod structure with six fluidic muscles from Festo creates a realistic impression of driving and flying. As the leading supplier of pneumatic technology, Festo is demonstrating with this project an exciting, cost-efficient alternative to intricate hydraulic constructions.

Source: Festo AG & Co. KG

Bionics: (also known as biomimetics, biognosis, biomimicry, or bionical creativity engineering) is the application of methods and systems found in nature to the study and design of engineering systems and modern technology.

Mechatronics: is the synergistic combination of mechanical engineering, electronic engineering and software engineering. The purpose of this interdisciplinary engineering field is the study of automata from an engineering perspective and serves the purposes of controlling advanced hybrid systems. The word itself is a portmanteau of 'Mechanics' and 'Electronics'.