CN112388658B

CN112388658B - Flexible tongs based on liquid metal

Info

Publication number: CN112388658B
Application number: CN202011281394.4A
Authority: CN
Inventors: 张世武; 张亚龙; 金虎; 孙帅帅
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2020-11-16
Filing date: 2020-11-16
Publication date: 2022-05-13
Anticipated expiration: 2040-11-16
Also published as: CN112388658A

Abstract

The invention discloses a flexible gripper based on liquid metal, which comprises: the misclid of electro-magnet, electro-magnet mount, gasbag upper cover, gasbag, liquid metal and iron powder, wherein: the electromagnet fixing frame is mainly used for fixing the electromagnet at the upper end and is connected with the upper top cover of the middle air bag by four screws, the upper top cover of the air bag is covered by the air bag at the bottom, the mixed fluid of liquid metal and iron powder is filled in the air bag, and the electromagnet is connected with a power supply through an electric lead. The rigidity of the magnetic mixed fluid of the liquid metal and the iron is changed by the action of an external magnetic field to grab a real object, and the flexible gripper has the capability of grabbing objects in various shapes. The invention applies the physical property of liquid metal in a magnetic field, and the obtained flexible gripper greatly expands the application range.

Description

Flexible tongs based on liquid metal

Technical Field

The invention belongs to the field of intelligent machinery, and particularly relates to a flexible gripper based on liquid metal.

Background

Liquid metals (eutectic gallium indium and gallium indium tin alloys of 37-39, etc.) have become important flexible alpha soft metals. Such soft metals have a number of natural advantages: the resistance is extremely small, the fluidity is good, and the deformation is easy. Compared with another liquid metal (mercury Hg), the mercury-free mercury solution has the great advantage of low toxicity and low harm. It can also exhibit different morphologies under different ambient conditions and exhibit more physical properties when different other substances are mixed into the liquid metal.

Many original mechanical structures are abandoned by the flexible grip, and deformable materials such as rubber, silica gel and resin are adopted. These holders usually have one or two air bags in the lower part, which are filled with granular material or liquid mixture, and the filled material is controlled by interference phenomena to passively adapt to the object to be held, after the object is gripped, the part originally filled with granular material becomes a vacuum state. The interference clamp holder can theoretically clamp objects in any shapes, mechanical joints are abandoned, the dependence on electronic control components such as sensors, actuators and controllers is gradually reduced, however, deformable materials filled in the prior art are limited, and the prior new filling materials are to be developed, so that better control and grabbing performance is realized.

Disclosure of Invention

In order to overcome the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a flexible grip based on liquid metal, which is a new design of flexible grip, a derivative of the properties and applications of liquid metal, and a transition from materials science to engineering.

The technical scheme adopted by the invention is as follows: the utility model provides a flexible tongs based on liquid metal which characterized in that: comprises an electromagnet, an electromagnet fixing frame, an air bag upper top cover, an air bag, and a magnetic mixed fluid of liquid metal and iron powder; wherein:

the electromagnet fixing frame adopts a circular ring structure and is used for fixing the electromagnet;

the electromagnet fixing frame and the air bag upper top cover are coaxial and are connected through a connecting part by using a screw;

the air bag is arranged in the air bag upper top cover, the lower part of the air bag is hemispherical and is used for grabbing objects, the air bag comprises an upper part and a lower part, and the air bag upper top cover is embedded between the upper part and the lower part;

the magnetic mixed fluid of the liquid metal and the iron powder is filled in the air bag.

Furthermore, after the liquid metal and the iron powder are mixed by hydrochloric acid, objects with certain shapes and sizes are grabbed by using the change of the physical state of the liquid metal and the iron powder in a magnetic field.

Furthermore, the pouring models of the electromagnet fixing frame, the air bag upper top cover and the air bag are manufactured by a 3D printing technology.

Furthermore, the air bag is fixed on the upper top cover of the air bag in a bidirectional pouring mode, so that the air bag plays a role in fixing and supporting on one hand, and has a sealing effect on the other hand.

Furthermore, the middle part of the upper top cover of the air bag is also provided with a middle part, the middle part of the middle part is a circular sheet, the middle part of the circular sheet is provided with an opening which is coaxial with a small hole at the top of the air bag, and the small hole is used for not only pouring the magnetic mixed fluid of the liquid metal and the iron powder into the air bag, but also discharging the air inside when grabbing objects; four bulges are arranged around the circular sheet, and four fan-shaped gaps are formed by the circular sheet and the inner wall of the upper top cover of the air bag.

Furthermore, the top of the air bag is provided with a notch communicated with the upper top cover of the air bag and the small hole at the top of the air bag, and the notch is used for exhausting or sucking air when an object is grabbed or released.

Furthermore, top cap is provided with the border on the gasbag to guarantee that the magnetic mixing fluid of liquid metal in the gasbag and iron powder can not overflow when snatching the real object, can snatch the object better.

Furthermore, the height of the electromagnet fixing frame and the preset height of the top cover on the air bag reach 1/6-1/3, namely 5cm-10cm, of the height of the electromagnet.

Furthermore, the electromagnet controls the existence of a magnetic field through the on-off of current, and controls the state of the magnetic mixed fluid of the liquid metal and the iron powder, so as to grab or release an object.

Further, the magnetic mixed fluid of the liquid metal and the iron powder is treated by dilute hydrochloric acid, so that oxides in the mixture are reduced, and the liquid metal and the iron powder are mixed more fully.

Further, the magnetic mixed fluid of the liquid metal and the iron powder is obtained by blending the liquid metal and 50-micron superfine iron powder with 6-8% of diluted hydrochloric acid.

Further, the mass ratio of the liquid metal to the superfine iron powder in the magnetic mixed fluid of the liquid metal and the iron powder is 3.2:1, and the deformation effect of the magnetic mixed fluid of the liquid metal and the iron powder under a magnetic field is the best at the ratio.

Furthermore, the proportion of the magnetic mixed fluid of the liquid metal and the iron powder in the air bag is not more than 60%, so that the overflow amount of the flexible hand grip when gripping an object is reduced, and the economic cost is reduced.

Furthermore, the small holes of the top cover of the air bag are sealed by a 50-mesh PE film covered on the small holes, and the 50-mesh PE film can only pass through air but not through the magnetic mixed fluid of the liquid metal and the iron powder, so that the magnetic mixed fluid of the liquid metal and the iron powder can be preserved.

Further, the gasbag pour the model and make through the gasbag, the model is pour to the gasbag includes that inner shell, left shell, right shell realize interference fit through unsmooth interface.

Has the advantages that:

compared with the prior art, the flexible gripper based on the liquid metal can show good gripping and releasing functions by utilizing the on-off of an external power supply. The magnetic mixed fluid of liquid metal and iron powder is utilized, the feasibility of designing the flexible gripper by utilizing the liquid metal and the potential of the liquid metal as a novel material are fully proved, and the magnetic mixed fluid has positive influence on the research of a soft robot and the flexible gripper.

Drawings

FIG. 1(a) is an overall view of a flexible grip;

FIG. 1(b) is a cross-sectional view of the interior of a flexible grip bladder;

FIG. 2 is a diagram of a casting model of the air bag;

FIG. 3 is a left shell of the air bag casting model;

FIG. 4 is a right shell of the air bag casting model;

FIG. 5 shows an inner shell of the air bag casting model;

FIG. 6 is an upper cover of the airbag;

FIG. 7 illustrates an electromagnet mount;

FIG. 8(a) is a bottom view of the upper cover of the airbag;

FIG. 8(b) is a top view of the upper cover of the airbag;

FIG. 9 is a schematic view of bladder casting;

fig. 10 is a schematic view of a flexible grip grasping an object.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The working principle of the flexible gripper based on liquid metal driving is as follows: the magnetic mixed fluid of the liquid metal and the iron powder is in a liquid state at normal temperature, after a magnetic field is applied, the molecular distance is reduced, the physical state is changed into a solid-like state, the rigidity is increased, and the rigidity can provide certain force for the embedded grabbed object. When the external magnetic field disappears, the magnetic mixed fluid of the liquid metal and the iron powder has small molecular distance, the physical state is restored to liquid state, the rigidity is reduced, and the object is released. And the existence of the magnetic field can be controlled by the current on-off of the electromagnet.

According to an embodiment of the invention, a flexible gripper based on liquid metal is proposed, comprising: the device comprises an electromagnet 1, an electromagnet fixing frame 2, an air bag upper top cover 3, an air bag 4 and a magnetic mixed fluid 5 of liquid metal and iron powder; FIG. 1(a) is an overall view of the flexible grip; FIG. 1(b) is a cross-sectional view of the interior of a flexible grip bladder;

fig. 7 is a schematic view of an electromagnet fixing frame 2, and the electromagnet fixing frame 2 is mainly used for fixing the electromagnet 1 on an airbag upper top cover 3 to prevent the electromagnet 1 from shaking left and right in the experiment process and even dropping. The appearance of the main body of the air bag is an annular cylinder, and the outer diameter of the annular cylinder is consistent with that of the upper top cover 3 of the lower air bag. Four connecting parts are derived around the excircle and are used for butting with the upper top cover 3 of the lower air bag by screws. In order to reduce the weight, the height of the annular cylinder only needs to reach 1/6-1/3 of the height of the electromagnet, namely 5cm-10cm, so as to achieve the function of the electromagnet. Because the magnetic field intensity of the magnetic field generated by the electromagnet is attenuated quickly, the magnetic field is supported only by the Ecoflex rubber block with the solidified bottom, and a supporting part is not suitable to be added on the bottom of the cylinder.

Fig. 6 shows the airbag upper top cover 3, the main body of the airbag upper top cover 3 is also a cylinder, the outer diameter of the main body is the same as that of the electromagnet fixing frame 2, and four connecting parts are derived from the upper part of the airbag upper top cover. The upper part and the lower part of the upper cover 3 of the airbag are respectively provided with a cylindrical groove with different inner diameters, as shown in fig. 8(a) and 8(b), and the inner diameter of the upper part 3 of the upper cover of the airbag is smaller than that of the lower part. The circular groove of the upper part is mainly used for pouring Ecoflex rubber, and four fan-shaped gaps 9 are reserved to be connected with the bottom air bag (the shape and the size of the gaps are perfectly matched with the air bag poured from the lower part). The lower part of the upper top cover 3 of the air bag is designed into a cylindrical groove with the height of 15cm so that the flexible hand grip can better wrap the object after being embedded into the object to be gripped, and the liquid metal is not dispersed too much so that the contact area with the object to be gripped is too small to influence the gripping effect. The middle of the upper top cover 3 of the air bag is also provided with a middle part, the middle part is a circular sheet, the middle part is provided with an opening, and the middle opening is used for filling a mixed fluid 5 of liquid metal and iron powder; four bulges are arranged around the circular sheet, and four fan-shaped gaps 9 are formed between the circular sheet and the inner wall of the upper top cover 3 of the air bag;

according to another embodiment of the invention, in order to be able to better pour and fix the Ecoflex sack-like airbag 4, the invention utilizes the property that the already solidified Ecoflex and the liquid freshly formulated Ecoflex mix can still be fused together well and with almost no gaps, using a two-way pouring method.

Fig. 2 is a diagram of an air bag casting model, fig. 3 is a left shell of the air bag casting model, and fig. 4 is a right shell of the air bag casting model; FIG. 5 shows an inner shell of the air bag casting model;

firstly, the invention designs a mould for pouring the lower half part of the bag-shaped air bag. The set of mould comprises three parts: a left outer shell 7, a right outer shell 8 and an inner shell 6. According to the shape of the air bag, the left shell 7 and the right shell 8 are assembled into a shell; the outer shell and the inner shell are respectively composed of a lower hemisphere and an upper cylinder. When the left outer shell 7, the right outer shell 8 and the inner shell 6 are assembled, a cavity with the thickness of 1.8mm can be reserved, and the invention only needs to pour the prepared Ecoflex fluid into the cavity. And because the Ecoflex fluid has certain buoyancy, and the inner shell is lighter, a heavy object needs to be pressed on the inner shell. The reason why the housing is not designed as one piece but divided into two halves is to better remove the lower half of the already solidified airbag.

Due to the design of the mold, four protrusions appear at the top of the lower half of the cast airbag. The four protruding parts are fully utilized in the design of the upper top cover 3 of the air bag, namely the four fan-shaped gaps 9 are reserved on the upper top cover of the air bag, so that the protruding parts can be embedded perfectly.

After the lower half of the air bag is solidified, the left outer shell 7, the right outer shell 8 and the inner shell 6 are removed and are embedded through four fan-shaped gaps of the upper top cover 3 of the air bag. The small holes of the top cover 3 of the air bag are sealed by adhesive tapes. Finding a disc, firstly laying a layer of preservative film, laying a layer of Ecoflex rubber on the preservative film, inverting the lower half part of the air bag on the preservative film, slowly pouring the Ecoflex rubber (figure 9) along the outer edge of the air bag, and standing. After solidification, a small hole communicated with the notch 10 of the upper top cover of the air bag is formed at the top of the air bag.

Each standing of Ecoflex rubber requires at least four hours and in order to better extract the cured Ecoflex bladder, a layer of petrolatum is applied to the mold at the very beginning of the pour.

After solidification, the tape is torn off, and then a magnetic mixed fluid 5 of liquid metal and iron powder is prepared.

It is first necessary to dilute the concentrated hydrochloric acid to concentrated hydrochloric acid. Pouring 36-38% concentrated hydrochloric acid into a beaker, slowly pouring water along the wall of the beaker while stirring, and obtaining dilute hydrochloric acid with the concentration of 6-8% after 2 min.

The amount of liquid metal and iron powder mixture is formulated according to 40% -60% of the designed flexible grip lower bag-like air bag volume. By calculation, liquid metal (gallium indium tin) and iron powder (diameter about 50 microns) were mixed in a mass ratio of 3.2:1, pouring into a beaker, slowly pouring the prepared diluted hydrochloric acid, and stirring while pouring until the upper part of the beaker becomes transparent and clear. And after standing for a period of time, pouring the waste liquid out to obtain the magnetic mixed fluid 5 of the liquid metal and the iron powder required by the invention.

And finally, pouring the magnetic mixed fluid 5 of the liquid metal and the iron powder into the air bag through a small hole in the middle of the upper top cover 3 of the air bag, packaging the air bag through a 50-mesh PE film, and fixing the air bag with an electromagnet fixing frame (fixedly connected) through screws. The present invention has been completed.

Fig. 10 is a schematic view of a gripper gripping an object, the object with a preset shape is placed on a plane and is gripped by the flexible gripper of the invention, the object is wrapped by the magnetic mixed fluid 5 of liquid metal and iron powder in the flexible gripper, then the electromagnet is electrified, and the magnetic mixed fluid 5 becomes solid, so that the object can be gripped.

Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.

Claims

1. The utility model provides a flexible tongs based on liquid metal which characterized in that: comprises an electromagnet (1), an electromagnet fixing frame (2), an air bag upper top cover (3), an air bag (4) and a magnetic mixed fluid (5) of liquid metal and iron powder; wherein:

the electromagnet fixing frame (2) adopts a circular ring structure and is used for fixing the electromagnet, and the electromagnet is connected with a power supply through an electric lead;

the electromagnet fixing frame (2) and the air bag upper top cover (3) are coaxial, and the connecting part is connected through a screw;

the air bag (4) is arranged in the air bag upper top cover (3), the lower part of the air bag (4) is hemispherical and is used for grabbing objects, the air bag (4) comprises an upper part and a lower part, and the air bag upper top cover (3) is embedded between the upper part and the lower part;

the magnetic mixed fluid (5) of the liquid metal and the iron powder is filled in the air bag (4);

the middle part of the upper top cover (3) of the air bag is also provided with a middle part which is a circular sheet, the middle part of the circular sheet is provided with an opening which is coaxial with a small hole at the top of the air bag (4), and the small hole is used for not only pouring the magnetic mixed fluid (5) of the liquid metal and the iron powder into the air bag (4) but also discharging the air inside when grabbing objects; four bulges are arranged around the circular sheet, and four fan-shaped gaps (9) are formed by the surrounding of the circular sheet and the inner wall of the upper top cover (3) of the air bag;

the magnetic mixed fluid (5) of the liquid metal and the iron powder is obtained by blending the liquid metal and the superfine iron powder with the diameter of 50 microns under the blending of dilute hydrochloric acid with the concentration of 6-8 percent, so that the liquid metal and the iron powder are fully mixed; the mass ratio of the liquid metal in the magnetic mixed fluid (5) of the liquid metal and the iron powder to the superfine iron powder with the diameter of 50 microns is 3.2:1, and an object with a certain shape and size is grabbed by utilizing the change of the physical state of the magnetic mixed fluid (5) of the liquid metal and the iron powder in a magnetic field;

the top cover (3) of the air bag is provided with an edge to ensure that the magnetic mixed fluid (5) of the liquid metal and the iron powder in the air bag (4) cannot overflow when the object is grabbed.

2. Flexible grip according to claim 1, characterized in that said bladder (4) is fixed to the upper cover (3) of the bladder by means of two-way casting, on the one hand for the fixing support and on the other hand for the sealing effect.

3. Flexible grip on the basis of liquid metal according to claim 1, characterized in that the top of the upper cover (3) of the bladder is provided with notches (10) communicating with small holes at the top of the bladder (4) for the evacuation or suction of air when gripping or releasing objects.

4. Flexible grip according to claim 1, characterized in that said magnetically mixed fluid (5) of liquid metal and iron powder is not more than 60% in the bladder (4).

5. Flexible grip according to claim 1, characterized in that the opening of the intermediate element is closed by a 50 mesh PE film applied thereto, said 50 mesh PE film being capable of preserving the magnetic mixed fluid (5) of liquid metal and iron powder only by air and not by the magnetic mixed fluid (5) of liquid metal and iron powder.

6. The flexible liquid metal-based gripper according to claim 1, wherein the air bag is made of an air bag casting model, the air bag casting model comprises an inner shell (6), a left outer shell (7) and a right outer shell (8), and the inner shell (6), the left outer shell (7) and the right outer shell (8) are in interference fit through concave-convex interfaces.