RU226640U1 - SPACE MECHANISM WITH A CIRCULAR GUIDE WITH SIX DEGREES OF FREEDOM - Google Patents

Abstract

The utility model relates to robotics, namely to spatial manipulation mechanisms of robots for performing spatial movements. The spatial mechanism contains a base made in the form of a circular guide, an output link made in the form of a platform, three kinematic chains between the base and the output link, located along the perimeter of the base. Each of the kinematic chains contains a drive carriage equipped with a rotational drive and a non-drive carriage, which are installed on the base and connected to each other by a cross kinematic chain consisting of two links connected by a linear drive. In this case, the cross kinematic chain is connected to the drive carriage using a spherical joint, and to the non-drive carriage using a Hooke joint. The creation of a mechanism without redundant connections is ensured. 3 ill.

Description

The utility model relates to mechanical engineering, in particular to robotics, namely to spatial manipulation mechanisms of robots for performing spatial movements.

The spatial mechanism with six degrees of freedom that is closest in technical essence was chosen as a prototype (utility model application No. 2021114247, 05.20.2021). This spatial mechanism (Fig. 1) contains a base made in the form of a circular guide, an output link made in the form of a platform, three kinematic chains between the base and the output link, located along the perimeter of the base. Each of the kinematic chains includes a drive carriage equipped with a drive and one non-drive carriage, which are installed on the base and connected to each other by a cross kinematic chain consisting of two links connected by a linear drive, and the cross chain itself is connected to the carriages using rotational pairs . The drive and non-drive carriages are connected through spherical pairs by means of intermediate links with rotational pairs of the intermediate kinematic unit. This unit is connected to the output link by means of a dual kinematic pair and a rotational kinematic pair attached to it, the axes of which are mutually perpendicular. The output link has six degrees of freedom.

The disadvantage of this device is the presence of redundant connections in the cross kinematic chains of the mechanism.

The analysis shows that the redundant connections are due to the presence of two rotational joints in each cross kinematic chain (Fig. 1).

According to the Somov-Malyshev formula, the number of degrees of freedom for the mechanism is determined as:

where n is the number of moving parts of the mechanism; P ₅ , P ₄ , P ₃ , P ₂ , P ₁ - the number of one, two, three, four and five movable kinematic pairs in the mechanism.

The number of degrees of freedom of the prototype mechanism (Fig. 1) according to (1) will be equal to:

W _prototype = 6n - 5Р ₅ - 3Р ₃ = 6 ⋅ 25 - 5 ⋅ 27 - 3 ⋅ 6 = 150 - 135 - 18 = -3,

where n = 25, P ₅ = 27, P ₃ = 6.

The obtained result indicates that there are redundant connections in the prototype mechanism, although the mechanism has six degrees of freedom.

The prototype mechanism has nine redundant connections [1]:

q _izb.sv = W _{mech.without izb.} - W _prototype = 6 - ( -3) = 9,

where q _redundant = 9 the number of redundant connections in the prototype mechanism,

W _{mech.without.isn} = 6 number of degrees of freedom of the mechanism without redundant connections,

W _prototype = -3 number of degrees of freedom of the prototype.

When assembling a mechanism, the presence of redundant connections introduces additional increased requirements for the accuracy of manufacturing parts of the mechanism, otherwise the assembly of the mechanism is associated with elastic and plastic deformations of the mechanism parts [1]. The purpose of creating a new mechanism is to synthesize a structural diagram of the mechanism without redundant connections.

This goal is achieved by proposing a spatial mechanism with six degrees of freedom with a new design of cross chains.

The technical result is achieved by installing a spherical joint and a Hooke's joint into the design of each cross kinematic chain, which provides the output link of the mechanism with six degrees of freedom without redundant connections.

A spatial mechanism with six degrees of freedom is proposed in a general view (Fig. 1), including:

base made in the form of a circular guide;

output link, made in the form of a platform;

three kinematic chains between the base and the output link, located along the perimeter of the base, each of which includes a drive carriage equipped with a rotational drive and a non-drive carriage, which are mounted on a circular guide, and which are connected to each other by a cross kinematic chain consisting of two links, connected by a linear drive, and the cross kinematic chain is connected to the drive carriage using a spherical hinge and connected to the non-drive carriage using a Hooke's hinge;

an intermediate kinematic link that includes radially mounted four rotational kinematic pairs, of which two pairs form a dual kinematic pair with a common axis of rotation, and the other two are rotational kinematic pairs placed coaxially opposite each other and perpendicular to the mentioned dual kinematic pair;

two links in the form of rods, one of which, using a rotational kinematic pair, connects the intermediate link with the drive carriage using a spherical pair, and the second link, using a rotational kinematic pair, connects the intermediate link with the non-drive carriage, also using a spherical pair;

output link, which is connected to the intermediate link using a rotational kinematic pair in the form of a T-shaped link, the axis of which is perpendicular to the axis of the dual rotational kinematic pair.

The technical result achieved by the utility model is the elimination of redundant connections, reducing the requirements for the precision of manufacturing parts and simplifying the assembly of the mechanism.

The utility model is illustrated by a drawing (Fig. 2), which shows a block diagram of a spatial mechanism with six degrees of freedom. A spatial mechanism with six degrees of freedom contains: an output link 1, made in the form of a platform, a base 2, three identical kinematic chains I, II and III between the base 2 and the output link 1. Each of the three kinematic chains (Fig. 3) includes a drive carriage 3 and a non-drive carriage 4, connected to each other by a cross kinematic chain consisting of links 5 and 6 connected by a linear drive 7. The cross kinematic chain is connected to the drive carriage 3 via a spherical pair 8, and the other end of the cross chain is connected to the non-drive carriage 4 using a Hooke's hinge 9. The kinematic chain also includes an intermediate link 10, on which two coaxially located rotational kinematic pairs 11 and dual rotational kinematic pairs 12 are installed. On the one hand, the intermediate link 10 is connected to the carriages 3 and 4 using links 13 and 14 via spherical hinges 15 and rotary hinges 11. In addition, the intermediate link 10 is movably connected to the output link 1 using a T-shaped link 16 by means of a double rotary pair 12 and a rotary pair 17.

The mechanism works as follows (Fig. 3).

The output link 1 performs spatial movement, communicated by the drive carriages 3 and linear drives 7 (using non-drive carriages 4) through their corresponding kinematic chains. During operation, the drive carriages 3 and non-drive carriages 4 move along the circular guides of the base 2, and the links 13 and 14 cause complex spatial movement of the intermediate link 10. Next, with the help of the intermediate link 10 and the T-shaped link 16, the movement is transmitted to the output link 1.

For the resulting structural diagram of the spatial mechanism, in which there are no redundant connections, according to formula (1), the number of degrees of freedom will be equal to:

W _{mechanical without.isn} = 6 ⋅ 25 - 5 ⋅ 3 ⋅ 7 - 4 ⋅ 3 ⋅ 1 - 3 ⋅ 3 ⋅ 3 = 150 - 105 - 12- 27 = 6,

where n=25 is the number of moving parts of the mechanism; P ₅ = 21, P ₄ = 3, P ₃ = 9 - the number of single-moving (rotational joint), double-moving (Hooke's joint) and three-moving (spherical joint) kinematic pairs in the three kinematic chains of the mechanism.

Thus, a spatial mechanism with six degrees of freedom and without redundant connections was synthesized.

Bibliography

1. Artobolevsky I.I. Theory of mechanisms and machines / Textbook for universities // 4th ed., revised. and additional M.: Science. 1988. 640 p.

Claims (1)

A spatial mechanism with six degrees of freedom, containing a base made in the form of a circular guide, an output link made in the form of a platform, three kinematic chains between the base and the output link, located along the perimeter of the base, each of which includes a drive carriage equipped with a rotational drive , and a non-drive carriage mounted on a circular guide and connected to each other by a cross kinematic chain consisting of two links connected by a translational drive pair, characterized in that the cross kinematic chain is connected to the drive carriage using a spherical hinge, and to the non-drive carriage - with using a Hooke's hinge.