Engineering and Technology

Universal robotised hand on the basis of loose materials is developed

  The universal manipulator on the basis of loose materials in operation . Above: subjects of the different form which are lifted successfully by the manipulator. Below: its principle of action. Having fallen on a subject, the sack with a loose material accepts its form; after pumping out of air the material sharply hardens without form change, as allows to keep a body on weight. The image from discussed article

The American researchers have created exclusively simple manipulator, capable to seize and lift subjects of absolutely different form. A working element in it are loose materials which pressure at change are capable to be switched between fluid and rigid conditions.

One of key problems robotics — creation of the effective robotised hands-manipulators, capable to take subjects and to manipulate them. The set of researchers works on this problem; separate monographies (see, for example, recent book Robot grippers) are devoted it. In an ideal such hand should be: 

• Universal — it should be able seize and move subjects of the most different form reliably,

• "Intellectual" — it should not waste time on preliminary "cognizance" of the form of a subject by palpation,

• Safe for easily deformable and fragile subjects,

• Reliable.
The modern robotised manipulators solve these problems far not completely. The majority of such hands consists of two and more fingers which lift a subject, seizing it for ledges or squeezing it. That such scheme was effective, it is required to create, first, fingers with several independent joints so , to use exact enough electromecanics. Secondly, it is necessary to organise feedback — as visual, so by means of pressure sensor controls on "finger-tips". Thirdly, access to powerful enough computing resources for processing (in real time is necessary!) The arriving information, calculation of mechanics of process and formation of commands for each separate joint on each finger. Basically , all it can be carried out, but exclusive complexity of realisation looks to absolutely disproportionate initial problem simply to take a subject. Besides, such scheme does not solve the second point from the list: after all before "taking" a subject with unknown mechanical properties (that is to apply certain force to certain points), the robot will need to feel in the beginning it.

In article arXiv:1009.4444, appeared one of these days in archive of electronic pre-prints, the collective of the American researchers has offered and realised new and exclusively simple scheme of the universal robotised hand. Its action is based on unique features of behaviour of loose substances: depending on conditions, they can flow, as if liquids, and can and hold pressure, as firm bodies (Dynamics of loose materials — a new word in the physicist see a popular note).

The device of this «hvatalki» is shown in drawing. It consists only from latex a sack in the size some centimetres, filled under an outset a loose material ( ground coffee particularly in this case was used). The tubule is brought To tightly closed sack from the pump which if necessary pumps out air from free space between coffee parts. In a normal state ground coffee is very pliable (in what everyone can be convinced at home on kitchen) so the sack is easily deformed at the slightest influence. If the manipulator lowers such sack from above on a subject lying on a table it it will be simple to envelop all ledges of a subject, accepting its form.

However if now to pump out from a sack air it will sharply harden: external atmospheric pressure squeezes coffee, and because of a friction the friend about the friend of a part any more can be displaced so easily from each other. From the point of view of physics in loose substance at pressure increase there comes phase transition — a jam (jamming), sharp transition from a pliability mode in an elasticity mode. (Besides, houses on kitchen it is possible to observe return process personally: when you pierce a new pack of ground coffee, the briquette sharply loses hardness.) The most important here that sharp hardening comes practically without change of the form of a sack. Thus, the subject suddenly appears in such "vice" of the suitable form which strongly keep a subject, almost without squeezing it. Now does not make any problems to lift a subject. Authors of work result the list of objects which they successfully lifted by means of this device: small bulbs incandescent, sweets M&M 's, light-emitting diodes, covers from bottles, batteries, a various stationery and etc . However, authors admit that the device could not seize flat disks and soft wadded balls.

Strengths of the new manipulator are evident at once. It is universal (in reasonable limits) and can lift subjects even the most intricate form (drawing see). It does not need preliminary "acquaintance" to a subject as the loose material in a pliable condition automatically accepts the demanded form. It is safe enough for fragile subjects; moreover, it can even lift the subjects literally collapsing on a part, and to transfer them, without changing relative position of parts. And certainly, its main advantage — exclusive simplicity. The manipulator does not demand difficult and exact electromecanics (and in general an electricity!) Neither high-quality materials, nor a file of sensor controls, computing capacities for mechanics calculations in real time. It also is very simple in circulation, and in case of its damage for certain it will be possible to repair and in field conditions. And all it became possible because the given manipulator is not active as the usual robotised hand, and passive — that is thanks to it we do not put active actions for subject maintenance, and simply we allow the nature to make all for us.

Authors of work were not limited to only one demonstration of the working manipulator, but also investigated its mechanical properties. They have found out that keeping of subjects is carried out at the expense of co-operative action at once three different forces. First, it is simply mechanical support because the sack has got rigidity. Secondly, it is force of a friction about латексную a surface. And at last, it is additional «effect of a sucker» which works on enough smooth surface: when the membrane site between several parts of substance is involved inside, it pulls behind itself(himself) and a subject. Thanks to this mechanism there is no necessity to clasp a subject from different directions , and it is enough to take of it only on the one hand; and force of deduction, in comparison with expectations on the basis of the simple geometrical analysis, can grow several times. Experiences have shown that the sack in radius of 4 sm is capable to keep on weight cargoes in some kg.

Basically, already now described device is ready for application in practice. However authors plan and to study further mechanics of such universal hand, in particular at a difficult manipulation a subject. After all one business — to lift a stick from the earth, and another — to learn safely it to wave. So it is not excluded that simple household robots of the future will not compress subjects metal claws, and to stick into them with sacks with loose substance.