CZ2018705A3 - Device for controlling the spherical movement of a body - Google Patents

Abstract

Device for controlling the spherical movement of the body (1) connected to the frame (5) by means of a spherical joint (2) arranged on a shank connecting the body (1) to the frame (5) and by means of the control arms (3). The shank is a three-part and a spherical joint (2) with at least two rotational degrees of freedom is arranged between the first shank part (7) which is fixedly attached to the frame (5) and the second shank part (8) that is fixedly attached to the body ( 1). The second part (8) is connected to the first part (7) by the intermediate part (13) by spherical joints (2, 12). The shank portions (7, 8, 13) have a non-zero length. The number of constant-length control arms (3) provided with rotary joints (6) connected by the rotary arm (16) to the spherical joint (10) and connected to the frame (5) by means of rotary drives (15), and / or variable length provided with a slide drive (4) ) or a telescopic drive (14) and connected to the frame (5) by means of rotary joints (6), there are three. The arms (3) are connected to the body (1) by spherical joints (10).

Description

Device for controlling the spherical motion of a body

Field of technology

The invention relates to a device for spherically moving a body connected to a frame by means of a spherical joint arranged on a shank connecting the body to the frame, the shank being in three parts and a spherical joint with at least two rotational degrees of freedom being arranged between a first shank part fixed to the frame and a second. part of the shank which is firmly attached to the body and by means of control arms pivotally connected to the frame and to the body.

Prior art

Controlled spherical movement of the body is important in many applications, for example for tilting heads of machine tools or for adjusting the position of telescopes and antennas. Such a movement is now realized either by mechanisms with a serial kinematic structure, mostly based on a Cardan hinge, or by mechanisms with a parallel kinematic structure. Mechanisms with a serial kinematic structure have great mobility, ie in two rotations a range of 180 degrees, but they are material, their dynamic capabilities are small and not in all positions allow continuous movement from one position to another. In contrast, mechanisms with a parallel kinematic structure have limited mobility, i.e. in two rotations the range is usually less than 90 degrees, but they have a significantly lower weight, have greater dynamic capabilities and allow continuous movement from all positions to subsequent positions.

The tilting heads of machine tools have been successfully solved using parallel kinematic structures in PCT WO 00/25976 and in EP 1123175 (B1) for the Sprint Z3 tilting head by DS Technologie (called EcoSpeed), where the ability to move continuously between all positions with increased dynamics was achieved. . Singular positions do not allow these mechanisms a wider range of angles. An improvement of this state can be achieved by using a redundant number of arms with drives, the number of which is greater than the number of degrees of freedom. Such a mechanism with a parallel kinematic structure for spherical motion is described in Kurtz, R., Hayward, V .: Multiple-Goal Kinematic Optimization of a Parallel Spherical Mechanism with Actuator Redundancy, IEEE Transactions on Robotics and Automation, 8 (1992), 5 , pp. 644-651, where 4 parallel arms are used to move the platform attached to the frame by a spherical joint on a shank extending from the frame. This solution makes it possible to considerably increase the range of achievable angle positions, but does not make it possible to reach a range of 90 or more degrees, moreover, with a deterioration in the manipulability around the extreme positions. This restriction arises for two reasons. On the one hand, collisions occur between the platform and the shank coming out of the frame at extreme positions approaching 90 degrees, and on the other hand, the excessive number of 4 parallel arms is insufficient in its arrangement for sufficient distance from singular positions in the entire working space. Therefore, a solution was proposed in the patent CZ 302911, which eliminates the previous shortcomings and achieves a range of motion of over 90 degrees. However, this solution (called HexaSphere) requires four or more drives, usually six drives.

Another mechanism with a parallel kinematic structure that allows to reach a range of 90 degree platform tilt angles is the Octapod (Valášek, M., Sika, Z., Bauma, V., Vampola, T .: The Innovative Potential of Redundantly Actuated PKM, In: Neugebauer , R .: Proc, of Parallel Kinematics Seminar 2004, IWU FhG, Chemnitz 2004, pp. 365-384) and Metrom (Schwaar, M., Jaehnert, T., Ihlenfeldt, S .: Mechatronic Design, Experimental Proper Analysis and Machining Strategies for a 5-Strut-PKM, In: Neugebauer, R .: Proc, of Parallel Kinematics Seminar 2002, IWU FhG, Chemnitz 2002, pp. 671-681). The disadvantage of the Octapod is that the arms are placed around the platform from all sides. The disadvantage of Metrom is the deterioration of manipulability in the vicinity of extreme positions.

Another mechanism is proposed in the patent CZ 305471, which eliminates the previous drawbacks a

- 1 CZ 2018 - 705 A3 reaches a range of motion of over 90 degrees and has only three drives. However, this solution (called EcoSphere) does not achieve as good handling as HexaSphere.

Furthermore, a mechanism (called TetraSphere) was proposed in patent CZ 306555, which reaches a range of motion over 90 degrees and has only four drives with special control, thus achieving better maneuverability than EcoSphere, but not as good as HexaSphere.

All of these solutions either have four or more drives or do not achieve as good maneuverability as HexaSphere.

Finally, a mechanism (called DoubleSphere) was proposed in CZ 306965, which achieves a range of motion of over 90 degrees and has only three drives, thus achieving better maneuverability than EcoSphere, but not as good as HexaSphere. Its disadvantage is that the construction space of this mechanism is larger in the case of a drive realized by sliding on the frame.

The object of the present invention is a device for controlled spherical motion of bodies based on mechanisms with a parallel kinematic structure, which would achieve mobility identical to mechanisms with a serial kinematic structure, i.e. in two rotations range up to 200 degrees while maintaining all the advantages of mechanisms with a parallel kinematic structure. required a lower number of drives compared to similar mechanisms and achieved similar maneuverability and needed less construction space. Another object of the present invention is to simultaneously achieve higher accuracy in adjusting the positions of the body.

The essence of the invention

The device comprises a device for controlling the spherical movement of a body connected to a frame by means of a spherical joint arranged on a shank connecting the body to the frame, the shank being in three parts and a spherical joint with at least two rotational degrees of freedom being arranged between a first shank part fixed to the frame; part of the shank which is firmly attached to the body, and the second part of the shank is connected to the first part of the shank by an inserted part of the shank by spherical joints, and by means of control arms connected to the frame and the body, the number of control arms constant lengths provided with rotary joints connected by a rotary arm with a spherical joint and connected to the frame by means of rotary drives and / or variable lengths provided with a sliding drive or a telescopic pull-out drive and connected to the frame by means of m of rotary joints are three, the control arms are connected to the body via spherical joints. The rotary joints and / or rotary drives, by means of which the three control arms are connected to the frame, form an angle of 120 ° about the axis of the shank in projection. The first part of the shank may have a variable length by means of a sliding drive with which the first part of the shank is provided.

Explanation of drawings

The attached figures schematically show a device for spherical movement of a body, where Fig. 1 shows schematically one of the possible embodiments Fig. 2 shows a vertical projection of the device according to Fig. 1 Fig. 3 shows another variant of the embodiment according to Fig. 1 Fig. 4 shows another variant embodiment according to FIG. 1

-2EN 2018 - 705 A3 Fig. 5 shows an arm of a device provided with a rotary joint Fig. 6 shows another variant of the embodiment according to Fig. 1 with a variable shank length

Examples of embodiments of the invention

Fig. 1 schematically shows a variant of the solution according to the invention. As can be seen in Fig. 1, the platform-body 1 is connected to the frame 5 by means of three shank parts 7, 8, 13, the first shank part 7 being firmly connected to the frame 5 at one end and connected to the insert by a spherical joint 2 at the other end. a shank part 13, which is connected at one end to the first shank part 7 and at the other end is connected by a spherical joint 12 to a second shank part 8, which is firmly connected to the body L. The platform-body 1 carries a machining tool 120 whose axis is perpendicular to the platform -body 1 and passes through its center. One end of the first shank part 7 may optionally form one part with the frame and one end of the second shank part 8 may form one part with the body L. The two parts 7, 8 are connected together via the shank insert part 13 by spherical joints 2 and 12, allowing the body to move. 1 with respect to the frame 5. All three parts 7, 8, 13 of the shank have a non-zero length. The body 1 and the frame 5 are further interconnected in three different ways. These three methods are shown in Figs. 1, 3 and 4. The variant in Fig. 1 uses three parallel control arms 3, which are connected to the frame 5 by rotary joints 6, provided with telescopic retractable drives 14 for controlled change of the control arms 3 and connected. to the platform-body 1 by spherical joints 10 on the end shanks 9. By changing the length of the arms 3 by means of drives 14 a controlled spherical movement of the body L is achieved. or pneumatic cylinders. The spherical joints 2, 12, 10 are formed by joints with at least two rotational degrees of freedom. The number of parallel arms 3 with drives 4 is three and is redundant, which means that the number of drives of parallel control arms 3 is three and is greater than the number of degrees of freedom of body 1 given by two rotations to set body direction 1 in two degrees of freedom 120. This eliminates singular positions in the working space of the spherical movement of the body 1.

Fig. 2 shows a vertical projection of the device according to Fig. 1 in the direction of the shank axis 7. The rotary joints usually lie on the surface of a cylinder or on a circle around the shank axis 7. In this embodiment, the rotary joints 6 are arranged symmetrically by 120 degrees. The position of the device is shown here, where all parts 7, 8, 13 of the shank are in one axis. There is a clear condition of the arrangement according to Fig. 1, where the rotary joints 6 of the arms 3 are arranged symmetrically around the spherical joint 2, which means that the projections of the rotary joints 6 and the arms 3 form angles of 120 degrees and that the rotary joints 6 in Fig. 2 lie on a circle around the projection of the spherical joint 2. The arms 3 are connected to the body by spherical joints 10 on the end shanks 9, which are arranged on the platform-body 1 with a circular shape symmetrically by 120 degrees.

The axis of the tool 120 passes through the center of this circle and is perpendicular to the plane formed by the centers of the spherical joints 10. The end shanks 9 favorably prevent a collision between the arms 3 and the body 1 during movement, but are not necessary for the solution. The parallel control arms 3 are connected to the sliding drives 4 by rotary joints 6. By changing the position of the sliding drives 4 in the guides on the frame 5 and thus by changing the position of the rotary joints 6 of the arms 3 a controlled spherical movement of the body 1 is achieved.

The spherical movement of the body 1 is formed by changing three rotations of the body 1, which can be described by azimuth, elevation and self-rotation, or setting the direction of the body 1 is formed by changing only two rotations of the body 1 which can be described by azimuth and elevation. The azimuth is the rotation of the body 1 about the tool axis 120, the elevation is the change in inclination of the tool axis 120 (usually relative to the axis of the first shank part 7) and the actual rotation is the rotation of the body 1 about the tool axis 120 in the final position given by the previous azimuth and elevation rotation. However, all these rotations are performed simultaneously. For the function of this device, it is often sufficient only to turn the axis of the tool 120 in the desired direction, which is given by the use of only the first ones

-3 CZ 2018 - 705 A3 two rotations by azimuth and elevation.

In general, however, the control arms 3 can be arranged asymmetrically, which would mean that in Fig. 2 the projections of the arms 3 form different angles from 120 degrees or that the rotary joints 6 do not lie on a circle around the projection projection of the spherical joint 2 or that the rotary joints 6 do not lie on a cylindrical surface with an axis formed by the axis of the first part 7 of the shank. Also the machining tool 120 is mounted on the platform-body 1 asymmetrically.

A great advantage of the described arrangement is that it is possible to move the platform-body 1 in two rotations with a range of up to 200 degrees of elevation while maintaining all the advantages of mechanisms with a parallel kinematic structure with only three drives. The achieved mobility is large and a sufficient distance from the singular positions in the whole working space is achieved, which also leads to a favorable transmission of forces between the tool 120 and drives 4 and to an increase in positioning accuracy of the tool 120. This is a great progress compared to previous solutions where either five to six drives or movement was not possible on such a large scale even with four drives or was very limited with three drives.

The use of a divided shank composed of three parts 7, 8, 13 allows the rotation of the body 1 by more than 90 °. To achieve such a rotation, the length of the first part 7 of the shank attached to the frame 5 is greater than the distance of the edge of the body 1 from the point of attachment of the second part 8 of the shank to the body. with parts 7, 13 of the stem. The end shanks 9 have a similar function for preventing collisions during the mutual movement of the platform body J. and the arms 3. The advantage of non-zeroing the length of the shank parts is to limit the deflection of the body 1 from the axis of the shank part 7.

It is possible to add drives, thereby increasing drive redundancy while improving maneuverability. The advantage of the solutions described here is that, compared to previous solutions, a smaller degree of drive redundancy is required to achieve a certain level of maneuverability, i.e. how many more drives than degrees of freedom.

The advantage of the described device over the patent CZ 306965 is that the construction space is limited by a plane formed by the centers of the rotary joints 6, below which the arm drives 3 do not move as in CZ 306965. The construction space of the described device is limited only to the cylinder given by the centers of the rotary joints 6. shank 7, by the plane of the rotary joints 6 and by a parallel plane passing through the spherical joint 2.

In FIG. 3, the variant of FIG. 1 is adapted in such a way that the telescopic retractable drives 14 are replaced by sliding drives 4 of the arms 3. The sliding drives 4 can be realized, for example, as continuous drives with a nut with a moving screw or a rack with a rotary electric drive or a guide with linear electric drive.

In the variant according to Fig. 3, although the ends of the arms 3 will move below the plane formed by the rotary joints 6, the required construction space will be smaller than in the solution according to the patent CZ 306965.

In Fig. 4, the variant of Fig. 1 is modified so that the variable length arms 3 realized by the telescopic extension drives 14 are replaced by parallel control arms 3, which are provided with rotary drives 15 for rotational movement of the control arms 3. The parallel control arms 3 are rotary joint 6 and rotary arm 16 fixed to spherical joints 10 for connection to platform-body L. These parallel control arms 3 have a constant length and are three and are driven by rotation by rotary drives 15. Examples of rotary drives 15 are rotary electric drives.

A possible alternative to the solution of the variant according to FIG. 4 is the mutual exchange of rotary joints with a drive 15 and without a drive 6 on one or more control arms 3.

-4EN 2018 - 705 A3

Compared to the CZ 306965 patent, this solution has the advantage of a limited construction space above the plane of the rotary drives 15 with only three control arms with drives. The use of only three control arms is made possible by the use of rotary joints 6 between the control arm 3 and the rotary arm 16 and two spherical joints 2 and 12 in a divided shank. Again, the advantage of the solution with the end shanks 9 is the prevention of collisions during the mutual movement of the platform-body 1 and the rotating arms 16.

Fig. 5 shows in more detail the rotary drive 15 with the control arm 3 and the rotary arm 16 of Fig. 4. The rotary drive 15, usually formed by a rotary electric motor with angular position measuring and possibly with a gearbox, is mounted on a frame 5. which in FIG. 5 is fixedly attached to the shaft of the rotary drive 15 and is connected to the rotary arm 16 by a rotary joint 6. According to FIG. 4, the rotary arm 16 is then connected by a spherical joint 10 to the platform body 1 via an end shank 9.

Fig. 6 shows a variant according to Fig. 1, where the first shank part 7 has a variable length by means of a sliding drive 17 with which the first shank part 7 is provided. This allows, in addition to tilting, the extension of the tool 120 with the body 1.

The basic advantage of the described solution is the need for a smaller construction space for the implementation of a device for controlling the spherical movement of the body. The advantage of the non-zero length of the shank parts is the limitation of the deflection of the body 1 from the axis of the shank part 7. The mentioned solution variants can be combined with each other. In particular, the types of drives and the types of control arms can be interchanged. If parallelism or perpendicularity or the angle of axes or planes is stated, then this condition is realized by the production of the device and this production realization of the exact condition of parallelism or perpendicularity is always only fulfilled within the production tolerances. If the non-zero length is stated, then it is non-zero within a possible design. The described symmetry of the arrangement need not be performed. The number of drives can be increased. The spherical joints can be realized in various ways, for example by a ball joint or several connected rotary joints. End shanks 9 can be added or removed. The position of the drives is controlled by a computer.

Claims (3)

PATENT CLAIMS Device for controlling the spherical movement of a body (1) connected to a frame (5) by means of a spherical joint (2) arranged on a shank connecting the body (1) to the frame (5), the shank being three-part and the spherical joint (2) having at least two rotational degrees of freedom is arranged between the first shank part (7), which is firmly attached to the frame (5), and the second shank part (8), which is firmly attached to the body (1), and the second shank part (8) is connected with the first shank part (7) by means of the shank insert part (13) by spherical joints (2) and (12), and by means of control arms (3) connected to the frame (5) and to the body (1), characterized in that the parts (7) ), (8), (13) of the shanks have a non-zero length, a number of control arms (3) of constant length provided with rotary joints (6) connected by a rotary arm (16) with a spherical joint (10) and connected to the frame (5) by rotary drives (15), and / or variable d There are three elements provided with a sliding drive (4) or a telescopic pull-out drive (14) and connected to the frame (5) by means of rotary joints (6), the control arms (3) being connected to the body (1) by means of spherical joints (10). . Device for controlling the spherical movement of a body (1) according to claim 1, characterized in that the rotary joints (6) and / or the rotary drives (15), by means of which the three control arms (3) are connected to the frame (5), they make an angle of 120 ° around the axis of the shank (7). -5 CZ 2018 - 705 A3 Device for controlling the spherical movement of a body (1) according to claims 1 and 2, characterized in that the first shank part (7) has a variable length by means of a sliding drive (17) with which the first shank part (7) is provided.