RO128018B1 - Parallel mechanism with six mobility degrees for robot construction - Google Patents

Abstract

The invention relates to a spatial parallel mechanism with six degrees of mobility for the construction of robots intended for handling or processing operations. According to the invention, the mechanism comprises two hexagonal platforms (1 and 9), namely a fixed lower platform and a mobile upper platform, linked by six kinematic chains articulated at the two extremities to the two hexagonal platforms (1 and 9), where to the upper mobile platform (9) a clamping mechanism can be attached, each of the kinematic chains consisting of two elements articulated to each other by some ball joints (4), the first element consisting of an assembly (2-3) of variable length and the second element being a bar (5) of a fixed length, through the assembly (2-3), at the lower end, the kinematic chains forming a translation couple and at the upper end, the bars (5) being coupled to the mobile platform (9) by some cardan joints (6-7-8), the parallel mechanism being driven, by means of the six translation couples, by some rotary electric motors (12) which thereby control the lengths of the kinematic chains, an inclination angle ( λ) of the translation couples being variable in the plane normal to the lower fixed platform, placed in parallel, at a preset distance from the homologous side of the hexagon, by the inclination of a support (10) rotating about a cylindrical hinge (11), the inclination angle of the support (10) being fixed, by means of a screw (13), by a support (14) integral with the fixed platform (1), the mobile platform (9) having six degrees of mobility being able to move at high speeds and accelerations, and having high rigidity which confers it the capacity to perform high precision motion.

Description

The invention relates to a parallel spatial mechanism, with six degrees of mobility, usable for the construction of parallel robots, intended for handling or processing operations.

As is known, the parallel mechanisms are driven by motors disposed on the rod in the parallel, which has the effect of reducing the mass of the moving mechanism, and increasing its rigidity, which gives it the ability to perform high-precision, high-speed and high accelerations. The main disadvantage of the parallel mechanisms is the limited working space.

In order to build parallel robots, several spatial mechanisms are known with 9 hinged bars, which have up to six degrees of mobility.

Such a mechanism is described in US Patent 5333514, which consists of an 11 fixed platform, three kinematic chains articulated at the base, at a predetermined distance around the center of the fixed platform, and a mobile platform, of which the three chains are articulated. kinematic, and on which a fastening system is mounted. Each kinematic chain is driven by a pair of rotary motors, mounted in open spaces in the fixed platform. The kinematic chains consist of two pairs of bars articulated between them. The disadvantage of this mechanism is that it has a small workspace.

Also known from GB 2311149 is a parallel programmable positioning mechanism, having a base plate, a movable plate and six linear actuating elements, with six degrees of freedom, and extending between the two plates by means of actuators. . The linear actuating elements are connected by the two plates through single-jointed verses 21. The ends of the actuators are paired in a fashion! triangular to each plate, and the actuators do not pass each other. Thus, two actuators with one end associated with the motherboard each have an opposite end associated with another actuator from the moving plate. The actuators are screw units for changing the length of each actuator in a programmable way. The actuators can also be mechanically coupled to reduce the degrees of freedom and the number of motors and controls required.

Also known is the document US 2010/0122602 Al, which refers to an apparatus for 29 positioning during the assembly operation, having a base plate, a movable plate and six linear actuating elements, with six degrees of freedom, elements that are extend between the two plates by means of actuators. The linear drive elements are connected by the two plates through universal joints.

The technical problem solved by the invention consists in the realization of a mechanism of spatial parallel, with multiple degrees of mobility, which ensures a larger working space and has a simple structure.

The parallel mechanism with six degrees of freedom, for the construction of the robots according to the invention, removes the disadvantages of the mechanisms known by the fact that the variable-length assembly is connected, by a spherical joint, bars connected by cardan joint to the mobile platform, and the rotary electric motor it is mounted under the fixed hexagonal platform, for each variable length assembly.

The parallel mechanism according to the invention has the following advantages:

- has a simple cinematic structure;

- has a larger workspace than the existing parallel mechanisms, which can be modeled by different inclines of the kinematic chains of motors;

- it has high rigidity, because the engines are fixed to the base, which gives it the ability to perform high precision movements;

- has a low weight, which contributes to the reduction of energy consumption during operation, and of manufacturing costs;

- can execute displacements with high speeds and accelerations.

RO 128018 Β1

The following is an example of the realization of the parallel mechanism, in relation to 1 fig, 1,. 3, which represents:

FIG. 1, image of the kinematic chain of the mechanism; 3

FIG. 2, section according to plan A-A, from fig. 3;

FIG. 3, section through the drive system of the kinematic chain. 5

The parallel mechanism for the construction of the robots, according to the invention (fig. 1), is formed by a fixed hexagonal platform 1, located at the base (bat), and a movable upper platform 9. 7

The two platforms are connected by six cinematic chains, articulated at the two ends of the two platforms. A clamping mechanism can be attached to the upper platform. 9 The mobile platform has six degrees of mobility.

The kinematic chains (fig. 1) are formed, each, by two elements articulated between them by 11 spherical joints 4. The first element is formed by the assembly 2, 3, of variable length, and the second element is the bar 5, of fixed length. Through the assembly 2, 3, at the lower end, the kinematic chains 13 form a translation couple. At the upper end, the bars 5 are coupled to the movable platform by pivot joints 6-7-8, which have the input shafts 6 fixed by threading 15 of the bars 5, and the output shafts 8 - fixed by threading the upper platform 9. The two shafts 6, 8 of the drive joint are cylindrically hinged by the drive shaft 7. 17

The parallel mechanism is actuated by means of the six translation couplings, with rotary electric motors 12, which, in this way, control the lengths of the kinematic chains. 19 The angle of inclination of the translation couples AND is variable in the normal plane to the fixed platform, located parallel to a predetermined distance from the homologous side of the hexagon, by the inclination of the support 10, which rotates about the cylindrical joint 11, with the angle with respect to parallel to the fixed platform at the base. The angle of inclination of the support 10 is fixed by the screw 13, 23 by the support 14, which is a common body with the fixed platform 1.

As shown in FIG. 2, the six kinematic chains are arranged on a hexagonal contour 25, on the fixed platform from the base 1.

The drive of the kinematic chain (fig. 3) is realized by the rotary electric motor 12, fixed 27 by the support 10 through the screws 15. The movement is transmitted from the motor 12 to the driving screw 21 through the elastic coupling 16, 18, fixed by the motor shaft and the driving screw. through 29 screws 17, 19. The lead screw 21 is mounted by tightening on the inner ring of the two-row ball bearing 28, which is fixed in the housing 22 by the elastic ring 27. 31

The rotation movement of the driving screw 21 is transformed into the rotation movement of the nut 20, which is fixed to 26, which translates into the linear channel of the housing 22, 33 fixed by the support 10 through the screws 29. On the housing 22 is fixed the cover 25, through the screws 24.

On the hole of the housing is mounted the felt ring 23. 35

The degree of mobility of the mechanism is calculated according to the following formula;

M = 6n-3C3-2C2-C1 = 6 7-3-6-2-6-6 = 42-36 = 6 37 where n = 6 + 6+ 1 = 13 is the number of movable elements 3, 5, 9; C3 = 6 is the number of spherical couples 4; C2 = 6 is the number of cardan couplings 6-7-8; and C1 = 6 is the number of prismatic couples 39 2-3.

Claims (2)

3 1. Parallel mechanism, with six degrees of freedom, for the construction of robots, consisting of a fixed platform (1) and a movable platform (9), joined together by a length assembly 5 variable (2, 3), driven by an electric motor (12), characterized in that the variable-length assembly (2, 3) are connected, by a spherical joint (4), some bars (5) 7 connected by cardan joint (6, 7, 8) to the movable platform (9), and the rotary electric motor (12) is mounted under the fixed hexagonal platform (1), for each variable length assembly 9 (2,3). 2. A parallel mechanism according to claim 1, characterized in that the linear drives 11 can be inclined in the normal plane to the fixed platform from the base, located parallel to a predetermined distance from the homologous side of the hexagon, with the angle AJ to the normal, which him 13 allows the configuration of a larger workspace.