RU2818704C1 - Parallel spherical manipulator of asymmetric type with three degrees of freedom - Google Patents

Abstract

FIELD: robotics.

SUBSTANCE: invention can be used in multi-position machining centers, assembly lines, multifunctional process plants, medical rehabilitation. Manipulator comprises three lower arched support arms, each of which is made in the form of a kinematic link with an arched rod, one end rotatable is fixed on one axis of rotation with upper arched support arms and a mobile platform arranged inside upper support arched arms. At that, other ends of lower arched support arms are arranged with possibility of rotation on base axis arranged on base of robot, by means of rotation drive providing rotation of at least one of lower arched support arms installed on common axis and at least two conjugated upper arched support arms.

EFFECT: wide angle of deviation of the mobile platform is provided.

8 cl, 2 dwg

Description

TECHNICAL FIELD

The invention relates to the field of robotics, more precisely to spatial manipulation mechanisms of a parallel structure with 3 rotational degrees of freedom and can find application in multi-position machining centers, assembly lines, multifunctional technological installations, and medical rehabilitation.

BACKGROUND ART

Similar devices are known from the prior art, for example, the bionic shoulder joint (see CN101301755A, published November 12, 2008), which has a displacement output and spherical surfaces with three degrees of freedom, which are located in parallel. The bionic shoulder joint is characterized in that the center line of the lower hinge support rod of the central spherical surface is pushed through the center of the fixed platform of the mechanism parallel to the spherical surface with three degrees of freedom; in addition, the outer end of the lower support rod of the hinge of the central spherical surface is rigidly connected to the fixed platform of the mechanism parallel to the spherical surface with three degrees of freedom; the fixed platform is rigidly connected to the fixed ring through three evenly distributed connecting posts; The center line of the straight output rod of the central spherical surface hinge or the center line of the straight output rod of the circular prism is pushed through the center of the movable platform of the three-degree parallel mechanism with spherical surfaces; In addition, the outer end of the straight output rod of the central spherical surface parallelism mechanism is fixedly connected to the movable platform.

The bionic shoulder joint has such advantages as high static rigidity and a large working space, but the space for moving the mobile platform of the proposed analogue is not enough.

Also known from the prior art is a bionic shoulder joint with five degrees of freedom (see CN104908060A, published September 16, 2015). A parallel mechanism with two degrees of freedom consists of a bionic strut, an intermediate movable platform, an S-shaped connecting rod between the bionic strut and the intermediate movable platform and two movable branches of the same design, with each movable branch of the chain sequentially consisting of a movable pair of linear guides, a leading slider , hook connection, driven rod and spherical pair; a spherical parallel mechanism with three degrees of freedom, containing an intermediate movable platform, three rotating branches and a tail movable platform; a spherical joint with a large working space contains a support rod, a two-ear bracket, a ball head, a U-shaped stirrer, an intermediate support roller, a hollow output rod and a pin; The bias output block contains an output pin and a bias output pin. According to the bionic shoulder joint, the output displacement rod can move in five degrees of freedom, and the bionic shoulder joint is as close as possible to the real state of the human shoulder joint in terms of structure, movement and function.

The closest analogue, according to the applicant, is the robot's shoulder joint (see CN100544901, published 09.30.2009). The shoulder joint servo motor is installed on the base, and one end of the drive rod is rigidly connected to the rotation shaft of the servo motor through the mounting hole. The other end of the driving rod is connected to one end of the driven rod through the first rotary joint, and the other end of the driven rod is connected to the movable platform, the axes of the rotation shafts of the three servo motors in the three branches of motion are perpendicular to each other in space, and the three driven arms are connected to the movable platform by three seconds of revolution The axes of the secondary hinge shafts are perpendicular to each other in space. The moving platform can be connected to a mechanical arm, and the three-dimensional rotation of the moving platform can be realized by correspondingly driving the corresponding drive rods through three servo motors. The invention has the advantages of simple structure, high load-bearing capacity, high response speed, good manufacturability, etc., and is suitable for use as a shoulder joint of a humanoid robot.

SUMMARY OF THE INVENTION

This invention is aimed at solving a technical problem associated with the creation of a parallel spherical manipulator of an asymmetric type with three degrees of freedom with a wide angle of deviation of the mobile platform.

The technical result of the invention is to increase the angle of deviation of the mobile platform.

The technical result is achieved by means of a parallel spherical manipulator of an asymmetrical type with three degrees of freedom, containing three lower arcuate support arms, each of which is made in the form of a kinematic link with an arcuate rod at one end with the possibility of rotation fixed on the same axis of rotation with the upper arcuate support arms and placed inside upper supporting arched shoulders with a mobile platform.

A parallel spherical manipulator of an asymmetrical type with three degrees of freedom is characterized by the fact that the rotation axes are located in the same plane at a distance of 120° from each other, the other ends of the lower arcuate support arms are rotatably placed on the base axis located on the base of the robot, by means of a rotation drive, providing rotation of at least one of the lower arcuate support arms installed on a common axis, and at least two associated upper arcuate support arms.

In a preferred embodiment, the mobile platform has three rotational degrees of freedom ranging from -90 to 90 degrees.

In a preferred embodiment, the upper arc support arms have the shape of circular arcs.

In a preferred embodiment, the lower arc support arms have the shape of circular arcs.

In a preferred embodiment, the lower arc support arms have the shape of a rounded right angle.

In a preferred embodiment, the rotation axes of the lower and upper arcuate support arms and the mobile platform are connected to the lower support arms through an active joint, including a drive that ensures rotation of the upper arcuate support arms.

In a preferred embodiment, the base axis is connected to an active base joint, including a rotation drive of the lower arcuate support arms.

In a preferred embodiment, the rotation drive is designed as a motor with a hollow shaft.

In a preferred embodiment, the rotation drive of one of the cylindrical bushings of the lower arcuate support arms installed on a common axis contains a shaft, the length of which is not less than the total length of the three cylindrical bushings of the lower arcuate support arms and is coupled with one of them using a key or similar connection.

BRIEF DESCRIPTION OF DRAWINGS

The essence of the invention is illustrated by drawings, in which:

In fig. Figure 1 shows a parallel spherical manipulator of an asymmetric type with three degrees of freedom;

Figure 2 shows a diagram of the coordinate systems of a parallel spherical manipulator; mathematical approximation (2A) real model (2B).

The positions in figure 1 indicate the following:

1 - robot base;

2 - active base joint;

3 - base axis;

4, 5, 6 - lower arched support shoulders;

7, 8, 9 - active joints;

10, 11, 12 - upper arched support shoulders;

13 - mobile platform.

OPTION FOR IMPLEMENTATION OF THE INVENTION

The claimed parallel spherical manipulator of an asymmetrical type with three degrees of freedom, as shown in Fig. 1, has lower arcuate support arms 4, 5, 6. Arms 4, 5, 6 are kinematic links with an arcuate rod. One end of each lower arcuate support arm 4, 5, 6 is fixed for rotation on the same axis of rotation, respectively, with the upper arcuate support arms 10, 11, 12 and the mobile platform 13 located inside the upper arcuate support arms. The upper arcuate support arms 10, 11, 12 may take the form of circular arcs. The lower arc support arms 4, 5, 6 can have the shape of circular arcs or the shape of a rounded right angle. The rotation axes are located in the same plane at a distance of 120° from each other, the other ends of the lower arcuate support arms 4, 5, 6 are placed with the possibility of rotation on the base axis 3, located on the base of the robot 1, by means of a rotation drive. The drive rotates one or more lower arcuate support arms 4, 5, 6 mounted on a common axis, which in turn drive both upper arcuate support arms 10, 11, 12 associated with each of the lower arms 4, 5, 6.

The rotation axes of the lower 4, 5, 6, upper arcuate support arms 10, 11, 12 and the mobile platform 13 are connected to the lower support arms through an active joint 7, 8, 9, including a drive that ensures rotation of the upper arcuate support arms 10, 11, 12 The base axis 3 is connected to the active base joint 7, 8, 9, which includes a rotation drive of the lower arcuate support arms 4, 5, 6. The rotation drive is made in the form of a motor with a hollow shaft.

The rotation drive of one of the cylindrical bushings of the lower arcuate support arms installed on a common axis contains a shaft, the length of which is not less than the total length of the three cylindrical bushings of the lower arcuate support arms and is coupled with one of them by a key or similar connection.

In fig. 2A and FIG. Figure 2B shows the coordinate system of the proposed parallel spherical manipulator.

The following designations are used in the figures of the proposed invention: movable kinematic connections - 1. The center of rotation of the robot is located at point O, this is the point of contact of the vertices of the two pyramids. Set of corners defines the mechanical properties of a given robot and does not change for configuration, these parameters are called robot operating parameters. Angles And determine the position of the center of rotation and the angle of attachment of the legs to the base and mobile platforms, respectively, and the angles And determine the lengths of the arcs of the supporting arms that make up each robot leg.

In Fig. 2A, b and e indicate the coordinate systems of the base and moving platforms, they are common to all legs. And the coordinate systems u, w and v belong to the joints in each leg. Moreover, the z- component of the coordinate systems is directed along the axis of rotation of each joint. We will denote the angles at the joints of each leg as a vector . The legs are located on the upper and lower platforms with an angle , where i is the leg number:

(1)

The position of the robot's moving platform can be described using the XYZ parametrization of Euler angles [4-6].

(2)

Since the robot has a parallel structure, the homogeneous transformation of each leg must converge at one point:

(3)

The robot has a set of active and passive joints. The movement of the robot is carried out due to active joints, which contain the source of movement. Passive joints regulate movement in a robot due to its morphological structure and most often passive joints contain bearings. This study compares classical and asymmetrical robot designs. In the classic design of the robot, the active joints are located at the junction of the legs with the base platform, which in the diagram corresponds to the u coordinate systems. Accordingly, a set of active and passive joints of a given design can be described by the following set of vectors:

(4)

The second is the asymmetric type, in which three active joints are located at the junction of the support arms of each robot leg, which corresponds to w coordinate systems and one of the motors is located at the base of the first leg, respectively, a set of active and passive joints can be described as:

(5)

To calculate the angles at the lower joints of the supporting arms, we need to use the scalar product for the z-vectors v and w of the coordinate systems in each of the legs. It is known that their scalar product must be equal to the cosine of the arc of the supporting arm between them:

(6)

In the last equation the following substitution can be made:

(7)

Accordingly, equation (1.6) is transformed into a simple quadratic equation:

(8)

What does it mean that the solution for there will be a solution to this quadratic equation and its further transformation through the arctangent:

(9)

To calculate the angles at the middle joints between the supporting arms in the leg, the following equation is used:

(10)

To calculate angles, the same set of operations is performed on equation (1.10) as was described in equations (1.7-9), only with respect to the angle .

The differential task of kinematics for this is to find the incremental transformation matrix between the increments of angles in the orientation of the mobile platform and the angles in the active joints [9, 10]. This transformation is called the Jacobian and for an individual leg (if we consider it from the point of view of a sequential manipulator) has the form:

(eleven)

The parallel spherical manipulator has a closed circuit structure and therefore has limitations described by the following system of equations:

(12)

This means that there is the following relationship between active and passive joints

(13)

Based on this, the increment of angles in passive joints depends on the active joints according to the following law:

(14)

The final form of the Jacobian for the classical execution of this type of manipulator:

(15)

And the final version of the Jacobian for asymmetric execution is:

(16)

The claimed kinematic model of a parallel spherical manipulator underlies a robotic hand joint simulator.

First of all, the direct and inverse kinematics problems for this type of robots were solved. The inverse problem was solved based on the geometric features of the robot, the direct problem was solved by solving a nonlinear optimization problem based on the idea that the robot can be a system of 3 robotic arms, the end effector of which always converges at one point.

The differential kinematics problem for this type of robot was calculated using the same basic concepts as in the direct kinematics problem, except that the final Jacobian matrix was calculated from one of the robot's legs.

After solving the basic problems of kinematics, a definition was given for the workspace of this type of robot, and a study of singular states was carried out and several types of internal collisions for the robot were considered. Based on these definitions, the problem of optimizing the robot parameters to maximize the workspace was formulated.

A comparison was made of two versions of the robot (classical and asymmetric) based on solutions to optimization problems, and the version with the maximum working space was selected.

As a result of the research, it was confirmed that the proposed asymmetric design of a parallel spherical manipulator is more advantageous in terms of useful working space than the classical design in a situation where the lower support arms converge along one axis. This statement was confirmed by mathematical analysis of the system.

Thus, for the described mathematical model for two versions of a parallel spherical manipulator, an analysis of its singular states and collision analysis was carried out and the problem of optimizing the work space was solved and the system indicators were identified for two versions of the robot, at which the maximum work space is achieved.

After that, motors were selected for this type of robot, suitable for the human hand according to the maximum permissible parameters regarding the moments of force for the hand.

Claims (8)

1. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom, containing three lower arcuate support arms, each of which is made in the form of a kinematic link with an arcuate rod, one end rotatably fixed on the same axis of rotation with the upper arcuate support arms and placed inside the upper supporting arcuate arms by a mobile platform, characterized in that the other ends of the lower arcuate support arms are placed for rotation on the base axis located on the base of the robot, by means of a rotation drive providing rotation of at least one of the lower arcuate support arms installed on a common axis and along at least two conjugate upper arcuate support arms. 2. A parallel spherical manipulator of an asymmetric type with three degrees of freedom according to claim 1, characterized in that the mobile platform has three rotational degrees of freedom ranging from -90 to 90 degrees. 3. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the upper arc support arms have the shape of circular arcs. 4. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the lower arc support arms have the shape of circular arcs. 5. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the lower arc support arms have the shape of a rounded right angle. 6. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the rotation axes of the lower, upper arcuate support arms and the mobile platform are connected to the lower support arms through an active joint, including a drive that ensures rotation of the upper arcuate support arms. 7. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the base axis is connected to an active base joint, including a rotation drive of the lower arcuate support arms. 8. A parallel spherical manipulator of an asymmetrical type with three degrees of freedom according to claim 1, characterized in that the rotation drive is made in the form of a motor with a hollow shaft.