The invention involves a device for control of a spherical movement of a body connected with a frame through a spherical joint arranged on a shank connecting the body with the frame, where the shank is sectional and the spherical joint with at least two rotational degrees of freedom is arranged between the first part of the shank, which is firmly fixed to the frame, and the second part of the shank, which is firmly fixed to the body, and by means of actuating arms with linear actuators arranged on the frame.

State-of-the-art

The controlled spherical motion of a body is important in many applications, for example for tilting heads of machining devices or adjusting positions of telescopes and antennas. Such a movement is performed today either through mechanisms with a series kinematic structure, mostly based on gimbal, or mechanisms with a parallel kinematic structure. Mechanisms with a series kinematic structure have a large moveability, thereupon a range of 180 degrees in two rotations, but they are mass, their dynamic capabilities are low and they do not allow a continuous movement from one position to another in all positions. On the other hand, mechanisms with a parallel kinematic structure have a limited moveability, thereupon a range less than 90° in two rotations usually, but they feature substantially lower weight, have higher dynamic capabilities and they enable a continuous movement from all positions to all the subsequent positions.

Tilting heads of machining devices were successfully solved with the help of parallel kinematic structures in PCT WO 00/25976 and EP1123175B1 patents for Sprint Z3 tilting head made by DS Technologie company (called EcoSpeed), where the ability to move continuously between all positions with higher dynamics was achieved. Singular positions do not allow a larger angle range in these mechanisms. The improvement of this state-of-the-art can be achieved through application of redundant (excessive) number of arms with actuators, the number of which is higher than the number of degrees of freedom. Such a mechanism with a parallel kinematic structure for a spherical motion is described in an article by 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 there are 4 parallel arms used for a motion of a platform fixed to a frame through a spherical joint on a shank extended from the frame. This solution enables to increase a range of achievable angle positions substantially but it does not allow reaching a range of 90° and more, in addition, there is a lowered manipulability near extreme positions. This limitation emerges by two reasons. Both there are collisions occurring between the platform and the shank extending from the frame in extreme positions near 90° and the excessive number of 4 parallel arms is inadequate for a sufficient distance from singular positions within all the working area. Therefore a solution was proposed in CZ 302911 patent, removing the previous imperfections and reaching the motion range more than 90 degrees. However, this solution (called HexaSphere) needs four and more actuators, usually six actuators.

An alternative mechanism with a parallel kinematic structure, which enables to reach a platform tilting angles range up to 90° is Octapod (Valasek, M., Sika, Z., Bauma, V., Vampola, T.: The Innovative Potential of Redundantly Actuated PKM, In: Neugebauer, R.: Proc. of Parallel Kinematice Seminar 2004, IWU FhG, Chemnitz 2004, pp. 365- 384) and Metrom (Schwaar, M., Jaehnert, T., Hilenfeldt, S.: Mechatronic Design, Experimental Properte Analysis and Machining Strategie for a 5-Strut-PKM, In: Neugebauer, R.: Proc. of Parallel Kinematice Seminar 2002, IWU FhG, Chemnitz 2002, pp. 671-681). A disadvantage of Octapod is that arms are positioned all around the platform. A disadvantage of Metrom is lowered manipulability near extreme positions.

The aim of this invention is a device for a controlled spherical motion of bodies on the basis of mechanisms with a parallel kinematic structure, which would achieve a moveability consonant to mechanisms with a series kinematic structure, thereupon a range up to 200° in two rotations while preserving all advantages of mechanisms with a parallel kinematic structure, whereas requiring a lower number of actuators in comparison with similar mechanisms. Another goal of this invention is to achieve, at the same time, higher accuracy of adjusting of a body's positions. Subject Matter of the Invention

The subject matter of the device for control of a spherical motion of a body connected to a frame through a spherical joint arranged on a shank connecting the body with the frame, where the shank is sectional and the spherical joint with at least two rotational degrees of freedom is arranged between the first part of the shank, which is firmly fixed to the frame, and the second part of the shank, which is firmly fixed to the body, and by means of actuating arms with linear actuators arranged on the frame, consists in a fact that the number of parallel arms with linear actuators is three and at least one arm is connected to the linear actuator through a rotational joint, whereas other arm/s is/are connected to the linear actuator/s through a spherical joint. The parallel arms are connected to the linear actuators through spherical joints with at least two rotational degrees of freedom. A length of the first part of the shank attached to the frame is longer than the distance of the body's edge from the point of connection of the second part of the shank to the body. Axes of the linear actuators are parallel.

The actuating parallel arms are connected to the body through a spherical joint with at least two degrees of freedom connected to the external shank firmly fixed to the body, whereas the arms may be possibly bow-shaped.

A connecting line of the spherical joint centre and the centre of the spherical joint on the arm with the rotational joint is perpendicular to the rotational joint axis.

A plane perpendicular to the rotational joint axis and passing through the centre of the spherical joint on the arm with the rotational joint passes possibly off the spherical joint centre.

On the body there is an attached tool, an axis of which is parallel with the plane perpendicular to the rotational joint axis and passing through the centre of the spherical joint on the arm with the rotational joint, whereas it is perpendicular to the connecting line of the shank spherical joint centre and the centre of the spherical joint on the arm with the rotational joint.

Alternatively, the first part of the shank is fitted with an actuator for a modification of the spherical joint position. The advantage of this device consists in creation of the sectional shank which enables rotating the body by 90° and more without collisions with the shank and in application of a low number of arms with actuators, in spite of their low number enabling to remove an occurrence of singular positions and to provide a sufficient distance from them within all the working area of the body.

Survey of Figures in Drawings

The device for a body's spherical motion is schematically depicted in the attached Figures, where

Fig. 1 represents a scheme of a basic arrangement of the body connected to the frame by a spherical joint and performing a controlled spherical motion with a help of linear actuators in parallel arms,

Fig. 2 represents a vertical projection of the body as depicted in Fig. 1,

Fig. 3 represents a vertical projection of the arrangement of the body with offset arms,

Fig. 4 represents a vertical projection of the arrangement of the body with arms of various lengths,

Fig. 5 represents a scheme of a basic arrangement of the body with out-of-parallel axes of the linear actuators,

Fig. 6 represents an arrangement of a tool on the body,

Fig. 7 represents a possible alternative arrangement of a tool on the body,

Fig. 8 represents a scheme of an alternative arrangement of a parallel arm shape,

Fig. 9 represents a scheme of the basic arrangement of the body with the linear actuator at the shank with a spherical joint

Examples of the Embodiments of the Invention

As it is evident in Fig. 1, platform-body 1 is connected to frame 5 through a shank, the first part 7 of which is firmly fixed to frame 5 and its second part 8 is firmly fixed to body I. The first part 7 of the shank can possibly form one component together with frame 5 and the second part 8 may form one component with body 1. Both parts 7, 8 of the shank are connected together to spherical joint 2 which enables the body's I motion towards frame 5 _. Body I and frame 5 are connected to one another through parallel actuating arms 3, which are fitted with linear actuators 4 for draw-out movement of actuating arms 3. These parallel arms 3 have constant lengths. They are connected to body 1 through spherical joints 10 on shanks 9. Shanks 9 prevent a collision between arms 3 and body I when moving. One of arms 3 is connected to linear actuator 4 through rotational joint 6. The other two arms 3 are connected to linear actuators 4 through spherical joints 1L A controlled spherical motion of body 1 is achieved by a change in positions of linear actuators 4 in the guides on frame 5, leading to a change in positions of joints 11 and 6 of arms 3. The spherical motion of body 1 originates from a change in two tarnings of body I, which can be described by an azimuth and elevation. Linear actuators 4 can be e.g. realized as trolleys on a linear guide attached to frame 5 with a linear actuator consisting of a ball screw or a linear electric actuator. Spherical joints 2, 10, 11 consist of joints with at least two rotational degrees of freedom. The number of parallel arms 3 with drives 4 is redundant, which means that the number of parallel actuating arms 3 is three and is higher than the number of degrees of freedom of body determined by two turnings. By this, singular positions are excluded from the working area of the spherical motion of body 1.

The use of the sectional shank composed of the first and the second part 7 and 8 enables to turn body 1 by more than 90°. To achieve such a turn, the length of the first part 7 of the shank fixed to frame 5 should be longer than a distance of the edge of body 1 from a point where the second part 8 of the shank is fixed to body 1. Adapting the length of the second part of shank 8, a varied angle range of rotation over 90° of body 1 can be achieved. Shanks 9 have a similar function to prevent a collision of platform-body I and arms 3 during their relative motion.

Fig. 2 represents a vertical projection of the device along the direction of axes of linear actuators 4 _^ where these axes are relatively parallel to each other. There is an obvious condition of the arrangement, where a connecting line of the centre of spherical joint 2 and the centre of spherical joint 10 on arm 3 with rotational joint 6 is perpendicular to the axis of rotational joint 6. This is also determined by that the axis of rotational joint 6 is perpendicular to the axis of linear actuator 4 for movement of rotational joint 6. This condition ensures that spherical joint 2 lies in a plane where the centre of spherical joint 10 moves on arm 3 with rotational joint 6. Then body 1 rotates both around the axis perpendicular to this plane (this rotary motion ensures a movement of linear actuator 4 with rotational joint 6) and around the axis formed by the connecting line of the centre of spherical joint 2 and the centre of spherical joint 10 on arm 3 with rotational joint 6. (This rotary motion is ensured by movements of linear actuators 4 with spherical joints Π.)

Fig. 3 represents a vertical projection of the device along the direction of axes of linear actuators 4, where these axes are relatively parallel to each other. There is an obvious condition of the arrangement, where a plane p perpendicular to the axis of rotational joint 6 and passing through the centre of spherical joint 10 on arm 3 with rotational joint 6 passes off the centre of spherical joint 2. This is an infringement of the condition depicted in Fig. 2. This arrangement may be advantageous for preventing collisions and for better moveability.

Fig. 4 represents a vertical projection of the device along the direction of axes of linear actuators 4, where these axes are relatively parallel to each other. There is an obvious condition of the arrangement, where a position of the centres of spherical joints 10 is not of the same distance from the centre of spherical joint 2, which is determined e.g. by the fact that the lengths of shanks 9 are different or platform-body i is not round-shaped. Further, there is an obvious condition of the arrangement, where lengths of particular arms 3 vary. This is an infringement of the conditions depicted in Fig. 2. The relevant lengths of arms 3 with spherical joints JJ _. are longer in Fig. 4 than for arm 3 with rotational joint 6. However, this may also be reversely and there can be all possible combinations of ratios of lengths. These arrangements may be advantageous for preventing collisions and for better moveability.

Fig. 5 represents a scheme of an arrangement with out-of-parallel axes of linear actuators 4. Actuators 4 move along the frame in various directions. These directions can be general or can exhibit also some other symmetry, for example a cone or a hyperboloid. This out-of- parallel arrangement may be advantageous for preventing collisions and for better moveability.

Fig. 6 and Fig. 7 schematically depict an arrangement of tool 12 on body 1. In Fig. 6 a condition is met that the axis of tool 12 carried on platform 1 is parallel to the plane perpendicular to the axis of rotational joint 6 passing through the centre of spherical joint 10 on arm 3 with rotational joint 6. And in Fig. 7 a condition is met that the axis of tool 12 carried on platform 1 is perpendicular to the connecting line of the centre of spherical joint 2 and the centre of spherical joint 10 on arm 3 with rotational joint 6. It is evident that generally the centre of the tool has not to pass through the centre of platform-tool 1. Fig. 8 represents an alternative arrangement of parallel arm 3, which is bow-shaped. In Figures described above the parallel arms 3 are rectilinear. However, these arms may be bow- shaped in order to prevent collisions, for example a collision with spherical joint 2, as evident in Fig. 8. A working area of the device can be enlarged this way.

Fig. 9 shows a possible additional actuator 13 of the shank of spherical joint 2 on the frame. The actuator is arranged that the first part 7 of the shank is fitted with actuator 13. for a change in a position of spherical joint 2. An example of such an actuator 13 can be a linear actuator, which, along with actuators 4^ enables to draw-out platform-body J_ from the guides determined by movements of actuators 4. However, these can also be more complicated actuators with more degrees of freedom, for example in all moving axes x, y, z.

A great advantage of the described arrangement is that a motion of platform-body 1 is possible within two rotations in a range up to 200 degrees, while preserving all advantages of mechanisms with a parallel kinematic structure using only three actuators. The achieved moveability is large and a satisfactory distance from singular positions in the entire working area is achieved, leading also to a favourable transmission of forces between tool 12 and actuators 4 and to an increase in accuracy of positioning of tool 12. This is a great progress in comparison with previous solutions, where five to six actuators were needed or a motion was not possible within such a large range even with four actuators or was very limited with three actuators.

The described solution variants may be combined with each other. If a parallelism or perpendicularity of axes or planes is given, then this condition is realized through the manufacture of the device and this manufacturing realization of the accurate condition of parallelism or perpendicularity is always met only within manufacturing tolerances. Spherical joints may be realized in various ways, for example as ball joints or more of connected rotational joints. The position of actuators is computer-controlled.