Posts Tagged ‘pneumatic manipulator’

2004 – OctArm – Christopher Rahn et al (American)

Penn State Research Team Develops OctArm Soft Robot Manipulator
Recent interest in expanding the capabilities of robot manipulators has led to significant research in continuum manipulators. The idea behind these robots is to replace the serial chain of rigid links in conventional manipulators with smooth, continuous, and flexible links. Unlike traditional rigid-linked robots, continuum robot manipulators can conform to their surroundings, navigate through unstructured environments, and grasp objects using whole arm manipulation. Soft continuum manipulators can be designed with a large number of actuators to provide hyper-redundant operation that enables dexterous movement and manipulation with robust performance. This improved functionality leads to many applications in industrial, space, and defense robotics.
Previous continuum robots used cable-tendon and pressurized tube actuators with limited performance. Cable-tendons must be tensioned or the cables become snarled or fall off drive pulleys, limiting the robot speed. Pneumatic bellows have low shear stiffness, limiting load capacity. Thus, there exists a need for a highly dexterous, fast, and strong soft robot manipulators.
Dr. Christopher Rahn, Professor of Mechanical Engineering at Penn State along with his students Dustin Dienno and Mike Pritts, and assisted by Dr. Michael Grissom developed the OctArm manipulator using air muscle actuators. These actuators are constructed by covering latex tubing with a double helical weave, plastic mesh sheath to provide the large strength to weight ratio and strain required for soft robot manipulators.
OctArm is divided into three sections. Each section is capable of two axis bending and extension which allows nine degrees of freedom. The manipulators are actuated with pressurized air (Maximum pressure = 120 psi) pressure control valves and polyurethane connective tubing.
The air muscle actuators are optimized to provide the desired wrap angles and workspace. The distal section of each OctArm is designed to have a minimum wrap diameter of 10 cm. The length of each section is chosen so that the manipulator can provide a range of 360 degrees wrap angles to accommodate a wide range of objects sizes. To provide the desired dexterity, OctArm is constructed with high strain extensor actuators extend up to 80%.
To provide two-axis bending and extension, three control channels are used. selected. Six actuators are used in sections one and two and three actuators are used in section three. The six sections have two actuators for each control channel and results in actuators located at a larger radius, corresponding to higher stiffness and load capacity. Secondary layers of mesh sleeving are used to group individual actuators in control channels. Three closely-spaced actuators provide high curvature
for the distal sections. The third, visible, mesh layer or fabric skin is designed to
protect the manipulator from abrasion and wear.
For the field tests, OctArm was mounted to the second link of a Foster-Miller TALON platform. The control valves and two air tanks provided nine channels of controlled pneumatic pressure. Clemson University provided the control electronics and operation interface for these tests. The OctArm /Talon system underwent extensive field trials in the spring of 2005 at the Southwest Research Institute (SwRI) in San Antonio, Texas.
Initial tasks included stacking and unstacking traffic cones. The ability of the system to grasp objects such as spheres and cylinders over a wide range of scales was recorded. The system was also operated in water. The OctArm was submerged in water, while attempting to grasp various payloads and to maintain grasps under turbulent flow. The system was also operated in rubble piles. The trials described demonstrate that OctArm continuum robots are a feasible and attractive alternative to conventional robot manipulators in unstructured environments, and also that there is room for improvement.
To further test the robot in real-world conditions, Dr. Rahn and his post-doc, Mike Grissom, took the Talon to the Radio Park Elementary School for demonstrations in three classrooms. First, the robot was teleoperated by Dr. Grissom while Dr. Rahn introduced the students to the vehicle and the electrical, mechanical, and computer engineering required to build it. The robot “responded” to audio commands (it has a microphone). Eventually, the fifth graders guessed that the robot was teleoperated after it answered some tough true/false questions. The third graders (and some of the teachers) initially thought it was just an extremely intelligent robot. The kindergarteners treated it like a pet dog – Robbie the Robot. The students were extremely excited about the visit and even wrote thank-you letters. Many said “I want to be an engineer!”


See selected pdfs here, here, here, and here.


See other Pneumatic, Fluidic, and Inflatable robots here.


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1995 – KSI Tentacle Manipulator – Immega and Antonelli (American)

Kinetic Sciences Inc. (1995) developed a tentacular robot, powered by a hybrid system of pneumatic bellows and electric motors. It can extend, contract and bend in 6 dof by using tendons threaded through cable guides.

Tentacle-like manipulators with adjustable tension lines by Guy Immega

Patent number: 5317952
Filing date: Dec 14, 1992
Issue date: Jun 7, 1994

A tentacle-like manipulator has a resiliently longitudinally extensible, laterally bendable elongate member, e.g. an inflatable bellows or a helical compression spring-like member, with an end effector mounting on one end thereof. Tendon-like tension members extend along said elongate member and are spaced apart from one another around said elongate member, one end of each of said tension members being to said elongate member at said one end thereof. Guides spaced apart along and secured to said elongate member and slidably engage said tension members for guiding said tension members relative to said elongate member. Further tension members extend along only a portion of the length of the elongate member and are secured to the elongate member at a location intermediate the ends of the elongate member. Winches are used to wind and unwind the tension members to correspondingly control the length and the bending of the elongate member.

See full patent details here.

Kinetic Sciences Inc. – Immega and Antonelli

See my related Immega Pneumatic Bellows article here.


See other Pneumatic, Fluidic, and Inflatable robots here.


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1990 – Inflatable Robot Arm – Yoram Koren (Israeli/American)

A world’s-first robot that he built had inflatable arm linkages for deployment in hostile and confined spaces. The inflatable robot is a low-volume and low-weight alternative to rigid arms. The inflatable robot arms can achieve the required load-bearing capacity and rigidity through the appropriate selection of size and pressure. The links of the robot are made of thin film material and are inflatable by air or other gas. The robot can achieve the required load-bearing capacity and rigidity through the appropriate selection of materials, size and pressure. This robot might be useful for surveillance and resource operations, or in areas difficult to access in buildings.

An inflatable structure, particularly adapted for use in outer space, employs one or more inflatable links which are connected at a base of the structure. A distal end of an outer most link is provided with a gripper assembly which can be remote controlled, and suitable encoders are included to indicate the angular position of each of the links. The motors for driving the at least one link is situated at the base to thereby reduce the mass of the at least one link and correspondingly reduce moments of inertia during operation.

Inflatable structure Yoram Koren and Yechiel Weinstein    
Patent number: 5065640
Filing date: Jul 9, 1990
Issue date: Nov 19, 1991

See here for full patent details.

Although Yoran is Israeli, he invented this arm whilst working at the University of Michigan.


See other Pneumatic, Fluidic, and Inflatable robots here.


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1984 – Bellows Robotic Arm/Trunk – James Wilson (American)

 


Reference:  Science News – March 26, 1988
The Muscular Machinery of Tentacles, Trunks and Tongues

Scientists discover a new way for muscles to work By STEFI WEISBURD

An arm without bones could not bend. A person who tried to bend such an arm would instead end up with a short, fat bulge of biceps. This might score big points at a Mr. Universe contest, but would be fairly useless otherwise. In order to move effectively, muscles — which shorten but cannot lengthen on their own accord — need bones to work against.

Not all animals have bones, however. In insects and other arthropods, for example, muscles instead pull against an external skeleton. And in other invertebrates, including many worm-like animals and polyps such as the sea anemone, muscles work against cavities filled with incompressible fluids.

But what of squids, octopi, chambered nautiluses and other cephalopods, which have neither hardened skeletons nor hydrostatic cavities? "According to everything we're taught, these animals shouldn't be able to function," says biologist William M. Kier at the University of North Carolina in Chapel Hill.

Kier and Kathleen K. Smith, an anatomist at Duke University in Durham, N.C., have solved this muscular mystery by working out the biomechanical principle behind cephalopod movement. Moreover, they've found that the same biomechanics can explain how elephant trunks and human and lizard tongues — none of which possess skeletons or hydrostatic cavities — are able to move so deftly. According to Kier, scientists had remarked on the similarities between the musculature of elephant trunks, tongues and cephalopods in the last century. But until now, no one had attempted to explain how all these muscles work, he says. "It was just waiting for us."

Kier and Smith's discovery of this important but previously unrecognized kind of muscular action is adding a new dimension to the well-studied field of muscles. It is prompting biologists to hunt for other animals possessing cephalopod-like muscular arrangements, which may have been overlooked in the past, and it has already changed how physiologists view the beating of the human heart.

And the explanation turned out to be surprisingly simple, Kier notes. Muscles are made up primarily of water, an incompressible fluid. This means that regardless of the motion, a muscle's volume remains constant: A muscle that contracts in length gets fatter in width. When a squid shoots out its tentacles to ensnare prey, for example, the muscles that are aligned at right angles to each tentacle's long axis contract and the resultant fattened parts push against one another to extend the tentacle along its length.

Thus, the squid's muscles not only power motion but also serve as the skeletal support, says Kier, and their particular arrangement enables the animal to lengthen, shorten, bend and twist its appendages with ease. In a paper recently submitted to the JOURNAL OF ZOOLOGY, he extends his previous studies of these muscle structures, which he calls "muscular hydrostats," to the fins of cuttlefish and squid.

"We'd gotten complacent about our understanding of muscle," comments biologist Stephen Wainwright at Duke University. "Bill and Kathleen have shown… a totally new mechanism for the useful action of muscle. It means that all muscular systems should now be looked at again to see where we might have overlooked this mechanism before."

In particular, Wainwright and his students suspect that muscular hydrostats power sharks, eels and dolphins when they swim. And he notes that the muscular hydrostat idea has already reshaped physiologists' thinking about how the human heart expands after contraction. The traditional view, he says, has been that blood pressure in the veins re-inflates the heart, even though scores of physiology students know that when a dissected frog's heart is disconnected from its blood flow and is taken out of the body, it keeps on beating. Now scientists have found that the fattening of some contracting heart muscles is responsible for the heart's re-expansion.

In recent work, Kier has also discovered that the muscle arrangement in squid tentacles, which can snatch prey in an impressive 30 milliseconds, is similar to that in the slower-moving squid arms, which bend to manipulate the food during eating. "This was a little surprising because they're doing such different things," he says. "In vertebrates, two muscle masses serving different functions are usually arranged differently." But using an electron microscope, Kier discovered that tentacle muscles instead contain especially fast-contracting muscle fibers never before seen in cephalopods. "Here, then, is a case in which the arrangement is the same but the muscle itself has evolved for a special function."

As important as muscular hydrostats can be, they have their disadvantages. Squids, for example, are not as good burrowers as animals with cavities; nor would they be impressive runners or jumpers on land like skeleton-containing animals. They also require unusually complex nerve circuitry to control movement — for instance, there are three times as many neurons in the nerve chord of an octopus' arm as in its brain, according to Kier. This suggests that considerable peripheral nervous processing is going on in the arms.

Nonetheless, Kier notes that squids and related animals have many capabilities that are unavailable to animals with other types of muscle-skeleton systems. "In general, they're capable of much finer control, more precise bending and manipulative movements," he says. Without being constrained to bend only where there are joints, for example, an octopus is able to scratch its right "elbow" with its right "hand," says Wainwright.

This kind of flexibility has caught the eye of Duke University's James F. Wilson and his colleagues, who have recently built a pneumatically driven robot arm. The arm, reminiscent of an elephant's trunk, is made of partly corrugated polyurethane tubes that work as half-bellows, expanding and bending when air is pumped into them. Guided in part by nature's muscular hydrostat examples, Wilson expects that such complaint robot arms will be more robust and will be able to operate in tighter, more awkward work spaces than their conventional, rigidlimbed counterparts.

Kier believes that many more innovative designs and concepts would arise if biologists and engineers were less shy about muscling in on one another's traditional territories. "The wonderful thing we see as zoologists is the incredible diversity ~of nature|. Many things have been tried and have been successful over the course of millions of years. Natural selection has a real power and creativity that could provide a lot of interesting ideas for engineering. That sort of interaction would be a really neat thing to foster."

Photo[missing]: Even though the squid doesn't have bones or any other of the usual kinds of skeletal supports, it's no slouch. With its arrangement of muscles, the squid's tentacles can snap up a shrimp in 30 miliseconds, and its graceful arms can then maneuver its prey with great dexterity.

Photo[missing]: If elephants can do it, why not robots? This pneumatic arm is based on similar muscular principles. This photograph, taken with a strobe light, captures a sequence in which the arm grabs an object from the table and then puts it on the shelf above, all in less than five seconds.


See pdf's on James Wilson's Pneumatic Robot Arms here and here.


1981 – Robot Arm with Pneumatic Gripper – Nikolai Teleshev (Russian)

Inventor Nikolai Teleshev watching the operation of an integral robot designed by him.

Any further information on this inventor and robot gripper most welcomed.


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