ES2351499T3 - PARALLEL KINEMATIC MECHANISM WITH CONCENTRIC SPHERICAL ARTICULATION. - Google Patents

Abstract

A mechanism for positioning and orienting a final component in space with at least five degrees of freedom, the mechanism comprising: a base (1); a first actuating limb (A1) comprising at least one platform (11) connected to said base (1) by an angular joint (10) allowing a degree of rotational freedom around a central axis (1a), a first limb element (13) mobilely connected to said platform with a single degree of freedom actuated in relation to said platform, an actuator (101) for actuating said first end element in relation to said platform, and a second end element (15) mobile connected to said first limb element, said second limb element having at least three degrees of freedom relative to said base, in which at least one of said degrees of freedom of said second limb element is operable in relation to to that base; at least one second, third, fourth and fifth actuator limb (A2, A3, A4, A5), each of the actuator limbs comprising at least one actuator arm (3) rotatably connected to said base by means of an actuated angular joint ( 2) which allows the rotation around a respective actuator shaft (1a, 2a, 2b), an actuator to drive said actuator arm relative to said base, each of the second, third, fourth and fifth actuator limbs also comprising a forearm (5) movably connected to said actuator arm of the respective actuator limb, wherein said forearm has at least three degrees of freedom relative to said actuator arm including a degree of free rotating freedom around a respective forearm axis ( 5a); a first articulation body (20, 24, 25), wherein said second limb element is rotatably connected to said first articulation body and allows rotation relative to said first articulation body about a first axis of articulation (20a, 24a, 25a), and in which each of the forearms of said second and third actuator limb is rotatably connected to said first articulation body and allows the rotation relative to said first articulation body around a respective second and third axis of articulation (20b, 24b, 24c, 7a, 7b) that is not parallel to said forearm axis of the respective actuator limb; a second articulation body (30, 26), in which each of the forearms of said fourth and fifth actuator limb is rotatably connected to said second articulation body and allows rotation relative to said second articulation body around of a respective fourth and fifth articulation axis (30b, 7d, 7c) that is not parallel to said forearm axis of the respective actuator limb; and the mechanism also comprising said final component (40, 40a, 40b) mobilely connected to each of said first and second articulation body, the final component having at least two degrees of freedom rotating relative to said first and second body of articulation such that said final component can move with at least five degrees of freedom relative to said base.

Description

one

BACKGROUND

The present invention relates generally to an apparatus with multiple limbs to position and orient a final component in the space and joints to join the

limbs of said apparatus.

There is a need for effective and simple parallel kinematic mechanisms. Kinematic mechanisms are used in mechanical engineering applications for machining,

10 robotics, positioning devices, coordinate measurement, mechanisms, etc. In general, the mechanisms can be classified as serial or parallel. Serial kinematic mechanisms are widely used and dominate the market today.

15 A series kinematic mechanism has a series of cantilever beams that are mobilely connected together in an end-to-end way by means of spherical or angular, prismatic joints, forming an open loop. The closer an item is to a

The base of the mechanism within the series structure, the greater the load on that element. Additionally, the further a base element is, the greater its deflection with respect to the base element. When a serial kinematic mechanism is under load, the position of the furthest element,

25 that is, the terminal element is subjected to the accumulated deflections of all the elements in series. This results in large positioning errors in the terminal element. Being constructed of cantilevers, a series mechanism has a stiffness ratio to the poor mass, making these structures with a bulky design.

Serial kinematic mechanisms allow a quick and simple calculation of the position of the terminal element given the position or status of all actuators. In general, this calculation is known as direct kinematics of a mechanism. However, determining the position or status of all actuators given the position of the terminal element, also known as inverse kinematics, is generally difficult.

In relation to serial kinematic mechanisms, parallel kinematic mechanisms usually have an improved mass stiffness ratio, better accuracy, superior dynamic properties and can move at higher speeds and accelerations. A parallel kinematic mechanism has a plurality of joints that form one or more closed loops, whereby the joints share the load on the terminal element. Joints of said mechanism usually experience only compressive or tensile forces that allow the use of cheaper material and simpler joint designs. In addition, actuator positioning errors are usually divided, resulting in high precision of the terminal element. A well-known parallel kinematic mechanism is the Stewart-Gough platform that was introduced in 1965 and has since been subject to extensive study and analysis. A Stewart-Gough platform mechanism usually includes a movable platform that is connected to a base by six controllable joints. For example, U.S. Patent No. 5,179,525 describes an overview of mechanisms that are based or derived from the Stewart-Gough platform.

While parallel kinematic mechanisms can provide improved accuracy, rigidity, and the ability to carry high loads, they also suffer from significant control drawbacks. Most parallel kinematic mechanisms have very difficult direct kinematics. The solutions of direct kinematics have the form of polynomial equations of great order, which do not allow closed form solutions to calculate the position of the terminal element. Intensive calculation methods such as numerical approximations should be applied to calculate multiple solutions and select the correct one. For example, it has been shown that the general form of the Stewart-Gough platform has fourteen feasible solutions. For some special forms of the Stewart-Gough platform, closed-form solutions of direct kinematics exist. In these special, even and triple forms of spherical joints that connect the joints to the base and the platform are concentric. However, the difficulty of manufacturing such joints is well recognized in the art.

Stewart-Gough type mechanisms usually allow the positioning and orientation of the movable platform with six degrees of freedom. In general, the position and orientation of the platform are coupled which complicates the controls. In addition, due to the singularities in the workspace and the restricted working range of the joints and actuators, the translation and in particular the range of rotational movement of the platform is significantly limited. However, many applications, such as machining or assembly operations, require a drive around an axis with multiple

or infinite rotations, which is usually carried out by additional motors or shafts mounted on the terminal element. This means that one of the drives of these mechanisms is redundant. In addition, many applications, such as flexible assembly operations or 5-axis machining, require a large capacity of orientation of the terminal element.

Therefore, alternative parallel kinematics mechanisms have been proposed. For example, US Patent No. 4,776,749 describes a robotic device with only five positioning elements actuated to position and orient a work tool in space. The device uses two concentric ball joints, the first of which connects three and the second of which connects the two remaining actuated positioning elements at a respective first and second common point. Therefore, the device forms a bi-tetrahedral configuration that decouples the positioning and orientation of the work tool. While this configuration facilitates structural rigidity and a closed-form solution of direct kinematics, the concentric joint design significantly limits the rotational freedom of each positioning element. In addition, such joints limit the degree of orientation of the work tool and are difficult to manufacture in a precise way and at an effective cost.

To carry out a rigid bi-tetrahedral structure of the mechanism and a simple direct kinematics, alternative articulations have been proposed to connect three or more limbs with spherical movement around a common point. For example, US Patent No. 5,657,584 describes a joint that uses a large number of elements and pins to produce spherical movement of the joined limbs, resulting in a complex and expensive structure. Such a joint is not capable of carrying large loads and only offers limited spherical movement to its extremities.

Another parallel kinematic mechanism without a sixth redundant actuator is described in DE 198 40 886 A1. Five joints with driven elbows are connected with separate universal joints on a movable platform that can be positioned and oriented in space. The movable platform serves as the central joint that connects all the elbow joints to form closed loops. The arrangement simplifies the design of the joint, but neither allows a closed-form solution of the direct kinematics or the decoupling of the position and orientation of the movable platform. The arrangement no longer forms a rigid bi-tetrahedral structure. Additionally, in comparison with the Stewart-Gough platform the mechanism is said to only slightly improve the orientation capacity of the movable platform.

Still another parallel kinematic mechanism with five driven joints is present in DE 101 53 854 C1. Similar to the aforementioned device, a simplified joint design is provided consisting of five pairs of single-axis joints with a common line of rotation that improves the manufacturing of the mechanism. However, the arrangement also does not allow a closed solution to the problem of direct kinematics or the decoupling of the position and orientation of the terminal element. In addition, structural rigidity is lost by deviating from a purely bi-tetrahedral structure.

It is well recognized in the art that parallel kinematic mechanisms and in particular devices based on the Stewart-Gough platform or any of the aforementioned descriptions suffer from a small ratio of work area to footprint. The terminal element usually has a limited range that is also reduced when high orientation capacity is required at any point in the workspace. The poor ratio of work area to footprint is generally considered a critical factor that prevents parallel kinematic mechanisms from entering or entering the market and competing successfully with kinematic mechanisms.

serially.

The disadvantage described is not only inherent in all the aforementioned descriptions but also in several parallel kinematic mechanisms that provide less than five or six degrees of freedom in the terminal element. For example, US Patent 4,790,718 describes a manipulator for positioning a flange with known orientation in space. By design, the manipulator is mounted on a beam to operate in an up-down manner, resulting in a large footprint similar in size to the projected volume of the work area. Another device for the movement and positioning of an element in space with three or four degrees of freedom is present in US Patent 4,976,582. Like the previously described manipulator, the device also lends itself to being actuated before a reinforcement beam on which it is mounted, giving rise to a work area ratio to a similar footprint.

To improve the ratio of work area to the footprint of parallel kinematic mechanisms, alternative designs have been proposed. For example, WO 02/22320 A1 describes a manipulator for moving an object in a space with at least three arms. Two arms are mounted on a central column and actuated to move in horizontal planes while the third arm is operated to operate in a vertical plane. Joints connect the arms to the terminal element that can move around this column in a cylindrical workspace with three degrees of freedom of translation. In one of the manipulators described, the third arm actuator is mounted and rotated by one of the other arms, causing additional inertia and asymmetric load loads for both arms. Whenever the terminal element is at a great distance or near the central commune, said arrangement places the third arm in an unfavorable asymmetrical position relative to the other two arms and causes asymmetric precision and stiffness characteristics.

In particular, WO 02/22320 A1 describes a mechanism for positioning and orienting an end component in place with four degrees of freedom, the mechanism comprising a base 1, a first actuating end C comprising at least one platform connected to the pivoting part. of a second actuator limb A, a first limb element 8a mobilely connected to said platform with a single degree of freedom actuated in relation to said platform, and a second limb element 18 movably connected to said first limb element, said second limb element having at least three degrees of freedom relative to said base, in which at least one of said degrees of freedom from said second limb element can be operated relative to said base; at least second and third actuator extremities A, B, each of the second and third actuator limbs comprising at least one actuator arm 6a, 7 rotatably connected to said base by an actuated angular joint allowing rotation around a respective actuator axis , each of said second and third actuator limbs comprising a forearm 14-17 mobilely connected to said actuator arm of the respective actuator limb, wherein said forearm has at least three degrees of freedom relative to said actuator arm including a degree of freedom with free rotation around a respective forearm axis; a first articulation body, in which said second limb elements is pivotally connected to said first articulation body and allows the rotation relative to said first articulation body about two axes, and in which each of the forearms of said second and third actuator extremities is pivotally connected to said first articulation body and is allowed to rotate relative to said first articulation body about three axes; the mechanism also comprising said final component 36, such that said final component can move with at least three degrees of freedom relative to said base.

WO 02/22320 A1 further describes a mechanism for positioning and orienting a final component in space with four degrees of freedom, the mechanism comprising: a base 1; a first actuating limb C comprising at least one platform connected to the pivoting part of a second actuating limb A, a first limb element 8a mobilely connected to said platform with a single degree of freedom actuated in relation to said platform, and a second limb element 18 movably connected to said first limb element, said second limb element having at least three degrees of freedom relative to said base, in which at least one of said degrees of freedom from said second limb element can act in relation to said base; at least second and third actuator extremities A, B, each of the second and third actuator limbs comprising at least one actuator arm 6a, 7 rotatably connected to said base by an actuated angular joint allowing rotation around a respective actuator axis , each of said second and third actuating limbs comprising an upper and lower forearm 1417 mobilely connected to said actuator arm of the respective actuating limb, wherein each of said upper and lower forearms has at least three degrees of freedom with relation to said actuator arm including a degree of freedom with free rotation around a respective upper and lower forearm axis; a first articulation body 2, in which said second limb elements is pivotally connected to said first articulation body allowing rotation about two axes, and in which each of the forearms of said second and third actuator limbs is pivotally connected to said first articulation body allowing rotation about three axes; said mechanism also comprising said final component 36 connected to said first articulation body, such that said final component can move with at least three degrees of freedom relative to said base.

WO 02/058895 A1 describes a similar manipulator that also includes a joint that connects the movements of the three arms such that the third arm always remains in the middle between the other two arms. This results in an improved work area ratio with a footprint that is comparable to that of serial kinematic mechanisms of the type known as SCARA (Selective Compliance Assembly Robot Arm) robots. However, the mechanisms of both descriptions do not provide an indicative capacity and only present three degrees of freedom of translation in the terminal element. If orientation capability is desired, dolls or other devices must be mounted in series on the terminal element, making the design complex and the mechanism heavy and slow. In addition, the use of ball joints at the junctions between the terminal element and the arms is preferred in the aforementioned descriptions but is undesirable in many applications. In addition, the mechanism requires a large number of degrees of freedom of the passive joints by degree of freedom provided in the terminal element, causing additional costs, slack and inaccuracies.

Another manipulator similar to that shown in WO 02/058895 A1 is described in US Patent No. 5,539,291. The manipulator employs three conductive mechanisms interposed between a base and a mobile element to move and orient the mobile element in a cylindrical workspace with three degrees of freedom. Mobile elements of two of the mechanisms operate in a transverse plane and determine the radial distance and orientation of the mobile element via a connecting rod and a position transmission element that maintains the mobile element with a constant attitude towards the transverse plane. The third conductive mechanism operates in a plane perpendicular to the transverse plane and influences the axial position of the mobile element in the cylindrical work space. Similar to the aforementioned descriptions, the manipulator only provides three degrees of freedom of translation and therefore has a lack of orientation capability of the mobile element. In addition, the preferred implementation of the transmission element such as two wheels and cables may be undesirable in terms of manufacturing costs, assembly, precision, clearance and rigidity of the manipulator.

A very important concern in many robotic applications is cable control. To connect various tools such as electricity, sensors, joint encoders, utility or electrical cables or pressure, they must be guided along the mobile structure of the mechanism, exposing such cables to significant stress and wear. To ensure functional reliability, custom or utility cables are required, causing an additional cost.

Another concern particularly with existing serial kinematic mechanisms, such as articulated robots or SCARA, is the lack of scalability and modularity. To vary the output parameters, such as the size or shape of the workspace, rigidity or precision characteristics, the entire series structure including the actuators usually needs to be redesigned and changed. Thus, offering a wide range of products does not allow economies of scale.

Therefore there is a need to provide a parallel kinematic mechanism that has practical and simple direct kinematics by allowing the solution of the position of the terminal element in closed form. There is also a need for a parallel kinematic mechanism with articulation structures that allows three or more limbs to interconnect and facilitate closed-form solutions of direct kinematics and decoupling of the position and orientation of the terminal element. Said joint structure should be compact and with an effective cost in the design, improve the range of spherical movement of the interconnected limbs, and should not limit the working space and the orientation range of the terminal element of the mechanism.

In addition, there is a need for a parallel kinematic mechanism that is precise and has a wide range of rotational movement and translation of the terminal element in combination with a high ratio of work area to footprint. This mechanism should have a rigid, bi-tetrahedral, robust, modular and scalable design without superfluous actuators and joints and an improved mass stiffness ratio. In addition, there is a need to provide a fast mechanism with high acceleration capabilities and improved dynamic properties. Ideally, the stiffness, precision and acceleration properties of the terminal element will remain similar within the range of motion of the terminal element. In addition, the mechanism should allow simple cable control and improved functional reliability with reduced costs.

DESCRIPTION OF THE INVENTION

The present invention provides a parallel kinematic mechanism that overcomes the difficulties envisaged in prior art devices by utilizing improved articulation structures and a new limb arrangement.

An object of the invention is to provide a mechanism

improved

for position Y guide a element in he

space.

A object plus concrete from the invention is

provide

saying mechanism that facilitates he calculation from

Simplified direct kinematics with a closed form solution. Advantageously, a kinematic mechanism having a design according to the present invention is such that the mathematics of direct kinematics is widely simplified. The design of the proposed mechanism reduces the calculations to the simple problem of finding the intersection point of three spheres, which makes trivial direct kinematics and has a closed form solution for the position of the terminal element or final component.

According to an embodiment of the invention, simplification in the solution has been achieved by means of a concentric spherical joint or joint assembly that allows three or more extremities to connect together with their longitudinal axes always intersecting at a common point, regardless of the orientations. . In an alternative embodiment, the articulation assembly has a symmetrical structure without end axes intersecting simplifying the design as well as allowing a closed-form solution. The joint provides advantages over the prior art, presenting an improved degree of spherical movement between its articulated limbs, fewer parts with an efficient cost, less wear and friction, improved stiffness and improved accuracy. It can also support tension loads, unlike some kneecaps. The proposed joint assembly according to an embodiment of the invention advantageously has a simple and robust design, which requires only a minimum number of angular joints per degree of freedom for a five-axis mechanism. In one embodiment, the symmetrical design of a mechanical construction according to the invention allows said minimum number of angular joints.

Another object of the invention is to provide a mechanism with an improved working area ratio at a fingerprint. In one embodiment of the invention, five driven elbow joints are arranged to rotate around a common central axis with a minimal footprint, allowing the positioning and orientation of a final component in a large cylindrical workspace with five or six degrees of freedom . The first three elbow joints are interconnected by a first joint assembly while the fourth and fifth elbow joints are joined by a second joint assembly, both joint assemblies being further connected to the final component. The proposed provision significantly improves the poor ratio of work area to footprint of prior art devices in the field of parallel kinematic mechanisms and is compared with serial devices of the SCARA type. Another advantage of the arrangement is the large volume of work space that can be achieved by a final component combined with a large capacity for symmetric orientation throughout this workspace. In another embodiment, two of the driven elbow joints are arranged to rotate around separate axes that are parallel and close to each other, and resulting in an increased work area ratio, increased stiffness and reduced manufacturing costs in comparison with prior art devices.

Still another object of the invention is to improve a mechanism that is capable of rapid movements and accelerations of the terminal element. According to one embodiment, the parallel driven extremities of the mechanism have an elbow joint design with an actuator arm and a forearm capable of moving small rotary drives of the actuator arm in large displacements of the terminal element. The dynamic and speed properties of the mechanism are further improved by a simple and lightweight design and the existence of a closed-form solution of direct kinematics.

It is another object of the invention to provide a mechanism with improved structural rigidity and accuracy. In one embodiment the invention uses two joint assemblies to connect five driven elbow joints such that the structure formed by the forearms of the elbow joints reassembles a bi-tetrahedral configuration, giving it a behavior like a beam. Generally, loads are distributed on the final component among all the actuators which, in return, compensate for positioning errors of the final component through its parallel arrangement. Therefore, the mechanism provides a high mass stiffness ratio and high accuracy. Since the joints that support the final component are mostly subjected to tensile or compressive forces, mechanisms with a design according to the invention can be constructed in a light and cost efficient manner, especially in comparison with serial kinematic devices . The proposed bi-tetrahedral arrangement also decouples the position and orientation of the final component, simplifying the controls of the mechanism.

Another advantage of the invention is that, in one embodiment, it provides a mechanism that has a modular and non-superfluous design that uses only five actuator limbs, four of which are identical, two types of articulation assemblies, a base, an actuator, and a work tool. The low number of parts and the use of mostly angular joints or simple kneecaps results in a precise positioning mechanism with an efficient cost that finds wide use in many areas.

In another embodiment, a parallel kinematics mechanism according to the present invention has five elbow joints actuated with actuator arms and forearms, the elbow joints being arranged to rotate about a common central axis. The mechanism also includes a joint that influences the position of a first elbow joint depending on the state of one or more of the other elbow joints. Advantageously, the actuator arms of a second and third elbow joint operate in the same plane perpendicular to the central axis while the first elbow joint operates in a plane parallel to the central axis. The first elbow joint is rotated by the actuator arms of the second and third elbow joint and forced to follow its movements to achieve symmetrical working space conditions and a favorable structural rigidity of the mechanism. Preferably, the first elbow joint remains midway between the second and third elbow joint.

Another object of the invention is to provide a mechanism for positioning a final component in space with at least three degrees of freedom of translation and fixed orientation. The mechanism includes only three operated elbow joints, a first of which comprises a first limb element and a second actuated limb element, a second and third of which comprise an actuator arm and two forearms. A first joint assembly joins the second end element of the first elbow joint with a forearm of the second and third elbow joint, while a second joint assembly interconnects the remaining forearm of the second and third elbow joint. The two articulation assemblies jointly support a final component and a work tool in space. Preferably, the actuator arms of the second and third elbow joints operate in the same plane, while the first elbow joints operate in a direction perpendicular to that plane.

Work tools, such as cutting tools or robot clamps, can be mounted on the final component of mechanisms that have a design according to the invention. In one embodiment, the work tool is powered by a motor or actuator that is fixed on the base and transmits its rotation or movement on the work tool through a telescopic shaft-keyway assembly. In another embodiment, transmission is achieved via an elbow joint. Both designs allow moments that act around the longitudinal axis of the work tool to transfer directly to the base, relieving the entire structure of the positioning and orientation mechanism. In another embodiment, the work tool is powered by a motor or actuator that is fixed in the final component.

In yet another embodiment, a mechanism having a design according to the invention allows extremely simple cable control by integrating all actuators into or near the fixed base. Therefore, most cables and other utility lines do not need to move or flex during operation and always remain in a fixed position relative to the base. In addition, the integrated drive in the base combined with a lightweight and economical forearm structure significantly improves the scalability of mechanisms provided by this invention. Varying the output parameters requires only the replacement of the economic forearm structure while expensive base structures and actuators can be reused. This allows a standard design to be used in many applications with minimal modifications to the customer's location.

Mechanisms according to an embodiment of the invention can be useful in machining and robotics. In particular, the mechanism can be used for free-form milling, assembly operations, collection and placement tasks, coordinate measurement, or any other type of operation that requires an element to be positioned and oriented in space.

Additional features and advantages of the present invention are described, and will be apparent, from the detailed description of the preferred embodiments and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The following is a description, by way of example only, of different embodiments of the mechanism, its variations, derivations and reductions.

Figure 1 is a perspective view of a bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having five actuator limbs with an elbow joint design arranged to rotate about a central axis to position and orient a final component in space with five degrees of freedom.

Figure 2 is a perspective and detailed view of the final component and a first and second joint assembly, joining the five actuator extremities of the mechanism shown in the embodiment of Figure 1.

Figure 3 is a perspective view of the bi-tetrahedral parallel kinematics mechanism shown in the embodiment of Figure 1, the final component of the mechanism having a different orientation and position.

Figure 4 is a perspective and detailed view of an alternative articulation arrangement with three single-axis angular joints in series that can replace the ball joints in the elbow joints of the mechanism shown in the embodiment of Figure 1.

Figure 5 is a perspective and detailed view of an alternative design of the first articulation assembly seen in the embodiment of Figure 2.

Figure 6 is a perspective and detailed view of the bi-tetrahedral parallel kinematics mechanism seen in the embodiment of Figure 1, the mechanism having an additional actuator mounted on the final component to rotatably drive a work tool with Six degrees of freedom.

Figure 7 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having an additional actuator mounted on a fixed frame or base and which rotatably drives a work tool via an assembly. of axis-telescopic keyway, having the tool work six degrees of freedom.

Figure 8 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having an additional actuator for orienting a work tool via an elbow joint, the work tool being mounted in a manner mobile in the final component and having six degrees of freedom.

Figure 9 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having five actuator limbs with an elbow joint design, three of which are connected with an additional outer joint to influence in the radial orientation of one of them.

Figure 10 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having five actuator limbs with an elbow joint design, three of which are connected with an additional inner joint for influence the radial orientation of one of them.

Figure 11 is a perspective and detailed view of an alternative joint that can be used in conjunction with the embodiments of Figures 9 and 10.

Figure 12 is a perspective and detailed view of another alternative joint that can be used in conjunction with the embodiments of Figures 9 and 10.

Figure 13 is a perspective and detailed view of an alternative articulation arrangement that can be used in the joint shown in the embodiment of Figure 10.

Figure 14 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having five actuator limbs with an elbow joint design, three of which are connected to another outer joint to influence in the radial orientation of one of them.

Figure 15 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having five actuator limbs with an elbow joint design, three of which are arranged to rotate about an axis central, and two of which have individual and separate axes of rotation, the mechanism positioning and guiding a final component in space with five degrees of freedom.

Figure 16 is a perspective view of another bi-tetrahedral parallel kinematics mechanism constructed in accordance with the invention, the mechanism having three actuator limbs with an elbow joint design arranged to rotate about a central axis and position a final component in space with three degrees of freedom and fixed orientation.

Figure 17 is a perspective and detailed view of an alternative design of the first and second joint assembly seen in the embodiment of Figure 2.

Fig. 18 is a detailed perspective view of an alternative design of the first and second articulation assembly seen in the embodiment of Fig. 16.

Figure 19 is a perspective and detailed view of an alternative articulation arrangement that can replace the ball joints in the elbow joints of the mechanism shown in the embodiment of Figure 16. DETAILED DESCRIPTION OF THE CURRENTLY PREFERRED EMBODIMENTS

Now referring to the drawings, in which equal numbers indicate equal components, Figure 1 shows a five-axis parallel kinematics mechanism 100 constructed in accordance with the indications of the present invention. The mechanism 100 includes a fixed base 1 and is operative to position and orient a final component 40 in the space in relation to the base 1 with five degrees of freedom. The position and orientation of the final component 40 are determined by five actuator ends A1, A2, A3, A4 and A5 which will be described.

As illustrated in Figure 1, the mechanism 100 includes a first tetrahedral structure formed by first, second and third actuator limbs A1, A2, A3. The actuating extremity A1 is an actuated elbow joint device comprising a platform 11, a first extremity element 13, and a second extremity element 15. The platform 11 is movably mounted on the base 1 by an angular joint 10 , allowing the free rotation of the platform 11 in relation to the base 1 around a central axis 1a. In addition, an actuated angular joint 12 connects the platform 11 to the first end member 13, allowing the first end member 13 to rotate around a main shaft 12a after actuation. Preferably, the main axis 12a is perpendicular to the central axis 1a. As illustrated in the embodiment, the driven angular joint 12 is driven by an actuator 101 mounted on the platform 11. It will be understood that the driven angular joint 12 could alternatively be driven by an actuator fixed to the base 1 and a transmission gear . The limb element 15 is movably connected to the first limb element 13 by an angular joint 14 allowing the second limb element 15 to rotate relative to the first limb element 13 about a secondary axis 14a. Preferably, the secondary axis 14a remains parallel to the main axis 12a for all positions of the mechanism 100.

In addition, as illustrated in Figure 1, each of the actuator limbs A2 and A3 is an elbow joint device having a respective actuator arm 3 and a forearm 5. The actuator arm 3 is connected to the base 1 by an actuated angular joint 2 that allows the actuator arm 3 to pivot after actuation around an actuator shaft which, as illustrated in the embodiment, coincides with the central axis 1a. Each of the actuator extremities A2 and A3 further comprises a kneecap 4 that connects the actuator arm 3 to the forearm 5. The kneecap allows the forearm 5 three rotational degrees of freedom relative to the actuator arm 3, including a degree of rotational freedom around an axis of the forearm 5a. Ideally, as shown in the embodiment, the pivot points or connection points of the ball joints 4 of both actuator ends A2 and A3 move in the same plane that is perpendicular to the central axis 1a.

Included in the concept of the invention is that the patella 4 in the mechanism 100, and other mechanisms described in the memory, can be replaced by any articulation arrangement that allows three degrees of rotational freedom. In particular, as shown in Figure 4, a triple-axis articulation assembly consisting of three angular joints in series can be used to connect the actuator arm 3 to the forearm 5. Particularly in this embodiment, a first fork 70 is rigidly coupled to the actuator arm 3 and mobilely connected to a cross 71 by a first angular joint 72 with a rotation axis 72a. The cross 71 is also movably mounted to a second fork 74 by a second angular joint 73 with a rotation axis 73a. The two forks 70, 74 and the cross 71 together are compared to a universal joint. A third angular joint 75 movably connects the second fork 74 to the forearm 5 allowing the rotation around an axis 75a that preferably coincides with the axis of the forearm 5a. Ideally, the three axes of rotation 72a, 73a and 75a intersect at a connection point P3 to facilitate a closed solution of the direct kinematics of the mechanism 100. In addition, the connection points P3 of the triple articulation assemblies axis of both actuator extremities A2 and A3 preferably move in the same plane perpendicular to the central axis 1a. It will be recognized by those skilled in the art that the order of the three angular joints 72, 73 and 75 can be changed without affecting the operation of the mechanism.

Referring again to Figure 1, the actuator ends A1, A2 and A3 are joined together by a first joint assembly J1. More specifically, as illustrated in greater detail in Figure 2, the second end member 15 of the actuator end A1 has a rigidly coupled fork 16 that is movably connected to an articulation body 20 by an angular joint 17 allowing the fork 16 rotates around a first articulation shaft 20a. Ideally, the first articulation axis 20a remains parallel to the main axis 12a and the secondary axis 14a of the mechanism 100. The angular joint 17, like all other angular joints of the mechanism 100 and other mechanisms described herein, can include two bearings individual as shown in the embodiment. The forearms 5 of the actuator extremities A2 and A3 are rigidly coupled to respective forks 6 which are rotatably connected to the articulation body 20 by respective angular joints 7. The angular joints 7 allow each of the forks 6 to rotate independently around a respective second and third articulation, which can coincide with a first axis of articulation body 20b as shown in the embodiment. Ideally, the first axis of the articulation body 20b is perpendicular to the first axis of articulation 20a. The articulation body 20 generally has a cross shape as used in the universal joints, but allows three or four, instead of two, forks to be connected to each other. The first articulation axis 20a, the first axis of the articulation body 20b and the axes of the forearm 5a of the actuator extremities A2 and A3 can intersect or cross a first common point P1, as shown in the embodiment. Preferably, the first axis of the articulation body 20b is perpendicular to the axes of the forearm 5a of both actuator extremities A2 and A3.

As shown in Figure 1, the first articulation assembly J1 interconnects the three actuator limbs A1, A2, A3 with a geometry that facilitates in the long term a closed-form solution of the direct kinematics of the mechanism 100. In addition, it forces the angular position of the first actuator limb A1, which can generally rotate around the central axis 1a due to the angular joint

10. Given the state of the actuated angular joints of the actuator limbs A2 and A3, the angular position of the actuator arms 3 and the location of the ball joints 4 relative to the base 1 can be derived. With the ball joints 4 being in known positions in space, the location of the first joint assembly J1 or, more particularly, the first common point P1 is limited to being placed in a circle. The circle corresponds to the intersection of two spheres, having a radius equal to the length of the forearms 5 and centered on the respective kneecaps 4. The actuating limb A1 adds an additional restriction, which completely forces the location of the first articulation assembly J1 in relation to the base.

As a result of the preferred perpendicular configuration of the main axis 12a and the central axis 1a, a plane of symmetry can be defined for mechanism 100 and other mechanisms described herein. The plane of symmetry is perpendicular to the main axis 12a and contains or crosses the central axis 1a. Ideally, this plane also contains the first common point P1. Furthermore, due to the preferred parallel configuration of the main axis 12a, the secondary axis 14a and the first articulation axis 20a, the first end element 13 and the second end element 15 are linked to move in this plane of symmetry and of this way they define the angular position of the platform 11 and the actuator end A1. Given the state of the driven angular joint 12 and the orientation of the platform 11, the angular position of the first end member 13 and the location of the angular joint 14 are determined. This allows the calculation of the first common point P1 by geometrically finding the intersection point of the circle created by the intersection of two spheres as described above and an arc drawn by the fork 16 when it is allowed to rotate around the secondary axis 14a. Given the preferred symmetrical design of the mechanism 100 as illustrated in the embodiment of Figure 1, the actuator limb A1 will always be oriented midway between the two actuator arms 3 of the actuator limbs A2, A3.

As will be recognized by those skilled in the art, there are generally two solutions for locating the first common point P1, the first being inside the three actuator limbs A1, A2 and A3, the second being outside. However, with the previous position of the mechanism 100 known or based on the mounted configuration, the correct solution can be selected. As shown in the embodiments of Figures 1 and 2, the actuator ends A1, A2 and A3 not only oblige the position of the articulation body 20 of the first articulation assembly J1 but also its orientation. Since it is preferred that the first articulation axis 20a is parallel to the main axis 12a and therefore perpendicular to said plane of symmetry, the first axis of the joint body 20b is ligated to be coplanar with said plane of symmetry and perpendicular to both 5a forearm axes of the actuator extremities A2 and A3.

Referring again to FIG. 2, the first articulation assembly J1 is attached to the final component 40. More particularly, a fork 21 is mounted on the articulation body 20 by a first angular joint 22 allowing rotation around a first angular axis which, as illustrated in the embodiment, preferably coincides with the first articulation axis 20a. The first angular axis 22, like all other angular joints of mechanism 100 and other mechanisms described in the memory, may include two individual bearings as shown in the embodiment. The fork 21 is further connected to the final component 40 by a second angular joint 23 in series with the first angular joint 22, allowing rotation around a second angular axis 23a. Ideally, the second angular axis 23a is generally perpendicular to the first angular axis and the first articulation axis 20a and also crosses the first common point P1. It will be understood that the first and second angular axis can have any position and orientation in relation to the articulation body 20 as long as they are not parallel. With the first and second angular articulation 22 and 23 being in series, the final component 40 has two rotational degrees of freedom relative to the articulation body 20.

Referring again to Figure 1, the mechanism 100 includes a second tetrahedral structure formed by a fourth and fifth actuator limb A4, A5 and the final component 40. Similar to the actuator limbs A2 and A3, each of the actuator limbs A4 and A5 is an elbow joint device having a respective actuator arm 3 and forearm 5. The actuator arm 3 is connected to the base 1 by an actuated angular joint 2 which allows the actuator arm 3 to rotate after driving around an axis. actuator which, as illustrated in the embodiment, coincides with the central axis 1a. Each of the actuator extremities A2 and A3 further comprises a kneecap 4 that connects the actuator arm 3 to the forearm 5. The kneecap 4 allows the forearm 5 three rotational degrees of freedom relative to the actuator arm 3, including a degree of rotational freedom around of a forearm axis 5a. Ideally, as shown in the embodiment, the central points or connection points of the ball joints 4 of both actuator ends A4 and A5 remain in the same plane that is perpendicular to the central axis 1a independent of the

state

from the respective joints angular 2

powered.

Be will understand that the ball joint 4 may be

replaced

by any joint that allow three

degrees

from freedom swivel, such how be he has described

previously in conjunction with the actuator extremities A2 and A3.

The actuator ends A4 and A5 are joined together by a second joint assembly J2. More particularly, as illustrated in greater detail in Figure 2, the forearms 5 of the actuator ends A4 and A5 are rigidly coupled to the respective forks 6 which are rotatably connected to an articulation body 30 by respective angular joints 7 The angular joints 7 allow each of the forks 6 to rotate independently around a respective fourth and fifth axis of articulation, which can coincide with a second axis of the articulation body 30b shown in the embodiment. The articulation body 30 generally has the shape of a cross as is commonly used in universal joints, but allows three, rather two, forks that connect to each other. As previously described with respect to the first articulation assembly J1, the fourth and fifth articulation axis, the second axis of the articulation body 30b and the forearm axes 5a of the respective actuator limbs A4 and A5 can intersect or cross a second common point P2. Preferably, the second axis of the articulation body 30b is perpendicular to the forearm axes 5a of both actuator limbs A4 and A5.

As shown in Fig. 2, the second articulation assembly J2 is further attached to the final component 40. More particularly, a fork 31 is mounted on the articulation body 30 by a third angular joint 32 which allows rotation around a third angular axis 30a. The third angular joint 32, like all other angular joints of mechanism 100 and other mechanisms described herein, may include two individual bearings. The fork 31 is further connected to the final component 40 by a fourth angular joint 33 in series with the third angular joint 32, allowing the rotation around a fourth angular axis 33a. Preferably, as illustrated in the embodiment, the third angular axis 30a is generally perpendicular to the fourth and fifth articulation axis and the second axis of the articulation body 30b and crosses the second common point P2. Similarly, the fourth angular axis 33a is ideally perpendicular to the third angular axis 30a and also crosses the second common point P2. It will be understood that the third and fourth angular axis could generally have any position and orientation in relation to the articulation body 30 as long as they are not parallel. With the third and fourth angular articulation 32 and 33 in series, the final component 40 has two rotational degrees of freedom relative to the articulation body

30

Referring again to Figure 1, mechanism 100 is generally a bi-tetrahedral structure. The first tetrahedral structure is formed by the actuator limbs A1, A2 and A3 or, more particularly, by the second limb element 15 and the respective forearms 5 of the actuator limbs A2 and A3. Together, they define the first common point P1. The second tetrahedral structure is formed by the actuator limbs A4 and A5 or, more particularly, by the respective forearms 5 of the actuator limbs A4, A5 and the final component 40. Together, they determine the position of the second common point P2. In addition, the first and second common point P1 and P2 define the position and orientation of the final component 40 which therefore has three degrees of freedom of translation driven and two rotary driven relative to the base 1. In the illustrated embodiment, the axes of the actuator of the actuated angular joints 2 of the respective actuator ends A2, A3, A4 and A5 coincide with the central axis 1a. In said configuration, it is possible to rotate the final component 40 around the central axis 1a completely 360 degrees or multiple 360 degrees in a rigid body shape without having any relative movement between the actuator limbs A1, A2, A3, A4, A5. This results in a large cylindrical workspace and a footprint work area ratio similar to that of serial mechanisms such as SCARA robots.

As shown in Figure 1, the final component 40 can support a terminal element or work tool 41, such as a clamp, a grabber, welding device, drilling or milling device, cutting tool, pressure element, detector or any type of terminal element. In addition, as shown in greater detail in Figure 6, a sixth degree of freedom can be added to the mechanism 100 and other mechanisms described herein by a motor or actuator 42 that is mounted on the final component 40. In the embodiment the Actuator 42 rotatably drives an actuator shaft 43 about an axis 43a. The actuator shaft 43 carries a terminal element or work tool 44 to perform a desired operation or manipulation. The work tool 44 therefore presents three degrees of freedom of translation driven and three rotary driven relative to base 1.

In addition, it will be understood that the mechanism 100 shown in Figure 1, and other mechanisms described herein, can be controlled with one or more computers (not shown). The computer is operative to move the mechanism in a controlled manner, and the computer can order the actuator limbs to move in a desired manner. In a generally known manner, the computer receives various return inputs indicating the position and state of the mechanism, such as signals transmitted from detectors located in the respective actuators. From this information on the position of the actuator, the computer can calculate the position and orientation of the terminal element or work tool, which is generally known in the art. This type of calculation is generally known as direct kinematics. The advantageous design of the articulation assemblies described herein facilitates a closed solution to this calculation of direct kinematics, as will be recognized by those skilled in the memory. This allows enormously simplified mathematics and a faster computer process.

Included in the concept of the invention is that the actuation of the four actuated angular joints 2 of the actuator ends A2, A3, A4, A5 in the mechanism 100, and other mechanisms described herein, can be achieved by direct drive, such transmissions such as gearboxes, hollow shafts or any other type of transmission configuration constructed or mounted on the fixed base 1 and connected to the driven angular joints 2. Said integrated drive configuration in the base facilitates simple and cost-effective cable control since utility lines or cables remain stationary. In addition, it improves the modulability and therefore the scalability of the mechanisms constructed in accordance with the invention. For example, the size of the workspace can easily be controlled by varying the lengths of the forearms 5 and the actuator arms 3.

Figure 3 illustrates the same mechanism 100 as seen in the embodiment of Figure 1. However, the final component 40 and the work tool 41 are shown in another position and orientation relative to the base

1. More particularly, the first limb element 13 of the first actuator limb A1 has been rotated within the volume enclosed by the five actuator limbs A1, A2, A3, A4 and A5, causing the final component 40 to move down . In addition, the actuator arms 3 of the second and third actuator limbs A2 and A3 have been turned clockwise, moving the first articulation assembly J1 to the left and influencing or correcting the radial orientation of the first actuator limb A1 accordingly. Platform 11 has inherently rotated such that the first end member 13 remains at an equal angular distance from the actuator arms 3 of the second and third actuator end A2 and A3. Actuator arms 3 of the fourth and fifth actuator limbs A4 and A5 have also been turned clockwise, however the amount of rotation is less than that of actuator extremities A2 and A3, causing the second assembly of articulation J2 deviate to the left in an amount smaller than the first assembly of articulation J1. As illustrated in the embodiment, this causes the final component 40 to tip sideways. Not shown in the embodiment is a greater radial displacement of the final component 40 that can be achieved by rotating the actuator arms 3 of the actuator ends A2, A3 and A4, A5 relative to each other. For example, reducing the angular distance between respective pairs of opposing actuator arms 3 would urge the final component to move away from the central axis 1a in a radial direction.

Figure 5 shows an alternative design of a joint assembly that can replace the first joint assembly J1 in mechanism 100 and other mechanisms described herein. The articulation assembly J3 is generally similar to the first articulation assembly J1 except that in the articulation assembly J3 the second articulation axis and the third articulation axis do not coincide. More particularly, the second end member 15 of the actuator end A1 has a rigidly joined fork 16 that is movably connected to an articulation body 24 by an angular joint 17 allowing the fork 16 to rotate around a first axis of 24a joint. The forearms 5 of the actuator extremities A2 and A3 are rigidly connected to the respective elbows 8 that are movably connected to the articulation body 24 by respective angular joints 9 which allow each of the elbows 8 to rotate around respective second and third articulation shaft 24b and 24c. The first, second and third articulation axis 24a, 24b, 24c and the forearm axes 5a intersect or cross a common point P4. The articulation assembly J3 further connects the final component 40 in a manner previously described in conjunction with the first articulation assembly J1. It will be understood that the second and third articulation axis that intersect but not coincident 24b and 24c illustrated in Figure 5 can also be used for the second joint assembly J2 of mechanism 100 and other mechanisms described herein.

Referring now to Figure 17, another embodiment is shown with an alternative design of the first and second joint assembly J1 and J2 used in mechanism 100 and other mechanisms described herein. The first joint assembly J4 is generally similar to the first joint assembly J1 except that the second joint axis and the third joint axis are parallel and offset from each other. More particularly, the fork 6 of the actuator end A1 and the forks 6 of the actuator ends A2 and A3 are connected to an articulation body 25 via respective angular joints 17 and 7 allowing the fork 16 to rotate around the respective second axis of articulation 7a and third axis of articulation 7b. Preferably, the second and third articulation axis 7a and 7b are perpendicular to the first articulation axis 25a and symmetrically displaced with respect to the symmetric plane which is ideally perpendicular to the first articulation axis 25a and crosses the central axis 1a of the mechanism 100 and others. mechanisms described in this report. Not shown in the embodiment is that the second and third articulation axis 7a and 7b may be displaced from each other but intersect with the articulation axis 25a. Also, the second and third axis of articulation 7a and 7b could coincide and be placed in the plane of symmetry but be displaced from the first axis of articulation 25a. It will be emphasized that any of the displaced axis configurations described allow a closed form solution of the direct kinematics of mechanism 100 and can also be combined with any other mechanism described herein. Within the concept of this invention is that the forks 16, 6 and 21 shown in the embodiment of Figure 17 could be replaced by hinges.

In addition, the second joint assembly J5 is generally similar to the second joint assembly J2 except that the fourth joint axis and the fifth joint axis are parallel and offset from each other. More particularly, the forks 6 of the actuator limbs A4 and A5 are connected to an articulation body 26 via respective angular joints 7 which allow the forks 6 to rotate around the respective fourth axis of articulation 7c and fifth axis of articulation 7d. The articulation body 26 is further connected to the fork 31 by a third angular joint 32 allowing the rotation around an angular axis 26a. Preferably, the fourth and fifth articulation axis 7c and 7d are perpendicular to the angular axis 26a. Not shown in the embodiment is that the fourth and fifth articulation axis 7c and 7d may be offset from each other but intersect with the angular axis 26a.

Also, the fourth and fifth axis of articulation 7c and 7d could coincide with one another and be displaced from the second common point P2.

Returning to Figure 7, another mechanism 200, constructed in accordance with the indications of the present invention, is shown to position and orient a work tool in space with six degrees of freedom. The mechanism 200 is similar to the embodiment of Figure 1, except that the mechanism 200 is equipped with an additional motor or actuator 45 mounted on a fixed frame to rotatably drive a terminal element or work tool 49. Therefore, The mechanism 200 provides six degrees of freedom to the working tool 49 in relation to the base 1. As shown in Figure 7, the actuator 45 is rigidly mounted on the base 1b which is fixed in the space and cannot move in relation to the base 1. The actuator 45 rotates an axis 46 that transmits the rotation to an axis 47 via a shaft-keyway assembly S1. The shaft 46 is connected to a first universal joint 80. The first universal joint 80 drives elements of a male and female keyway shaft 81a and 81b that fit together depending on the position and orientation of the working tool 49 in relation to the base 1b. A second universal joint 82 connects the male keyway shaft element 81b to the shaft 47 which is movably mounted on a final component 40a. The final component 40a is connected to the first and second articulation assembly J1 and J2 in the same manner as described for the final component 40 together with Figure 1. As illustrated in the embodiment, the shaft 47 transmits the rotation to the work tool 49 via a gear 48. It will be understood that the work tool 49 could be connected directly to the shaft 47. In addition, the work tool 49 could be replaced by tweezers, pick-up tool, welding device, cutting tool, element clamp, detector or any other type of terminal element. It is further understood that the keyway shaft assembly S1 could be replaced by any other configuration that is capable of transmitting a torque to the work tool

49.

Figure 8 shows another mechanism 300 for positioning and orienting a work tool in space with six degrees of freedom. The mechanism 300 is similar to the embodiment of Figure 1, except that the mechanism 300 is equipped with an additional motor or actuator that guides a terminal element or work tool 50 relative to a final component 40b via an orientative joint O1. More particularly, as illustrated in the embodiment, the final component 40b is mounted on the first and second articulation assembly J1 and J2 in the same manner as previously described for the final component 40 in the embodiment of Figure 1. The final component 40 is further connected to the work tool 50 by an angular joint 51 that allows the rotation around a work tool axis 51a which, as shown in the embodiment, can pass through the first and second common point of the first and second joint assembly J1 and J2. The work tool 50 has a rigidly connected lever 52 which is actuated by an orientation joint O1.

As shown in FIG. 8, the orientative joint O1 comprises an actuated angular joint 202 that is mounted on the base 1 and pivots an orientation arm 203. Preferably, the axis of rotation of the actuated angular joint 202 coincides with the central axis 1a which allows the mechanism 300 to swing completely around the central axis 1a of a rigid body shape. An orientation joint 205 joins the orientation arm 203 to the lever 52 via a first and second ball joint 204 and 206. It is understood that any of the ball joints could be replaced by a universal ball joint or that the ball joints could be replaced by any joint configuration that Allow three degrees of freedom.

After actuation of the driven angular joint 202, the orientative joint O1 causes the work tool 50 to rotate about the axis of the work tool 51a. As will be apparent to those skilled in the art, the axis of the work tool 51a can be mounted on the final component 51 in any position and orientation. For example, if the work tool 50 is a circular turret or tool magazine, the axis of the work tool 51a can be made parallel to the first articulation axis of the first articulation assembly J1 such that the tool magazine rotates around the axis of work tool 5a and selectively couple various tools.

Figure 9 illustrates another mechanism 400 for positioning and orienting a work tool in space with five degrees of freedom. The mechanism 400 is similar to the embodiment of Figure 1, except that the mechanism 400 further comprises influencing means or, more particularly, a joint L1. The joint L1 influences the radial orientation of the actuator limb A1 or the angular position of the platform 11 around the central axis 1a in relation to the angular position of the actuator arms 3 of the second and third actuator limbs A2 and A3 around the axis central 1st.

The joint L1 comprises two influence arms 92 that are connected to respective actuator arms 3 of the second and third actuator limbs A2 and A3 by first influence joints with two or three degrees of freedom. In the embodiment shown, a ball joint 91 is used for each connection. The influence arms 92 are also connected to a guide arm 94 by second influence joints with two or three degrees of freedom. This connection is achieved, as shown in Figure 9, by two ball joints 93 that could be replaced by any joint configuration that allows each influence arm 92 two or three degrees of freedom relative to the guide arm 94. For example , the two kneecaps could be concentric. It will be understood that any of the kneecaps 91 and 93 of a respective influence arm 92 could be replaced by a universal joint to limit the free rotation of the influence arms 92 around its longitudinal axes. Any of the kneecaps could be replaced by three single-axis angular joints. If desired, the guide arm 94 could be divided into two outer guiding joints that would transmit a torque around the central axis 1a not as a moment of bending but as pure tensile or understanding forces.

The guide arm 94 is further connected to a mounting arm 96 by an angular joint 95, the mounting arm 96 being rigidly coupled to the platform 11 of the first actuator end A1. When the angle between the two actuator arms 3 of the second and third actuator limbs A2 and A3 changes, the two influence arms 92 force the outer end of the guide arm 94 to rise or fall on an arc about the axis of rotation of the angular joint 95. Thus, the L1 joint is able to compensate for changes in the angular distance of the two actuator arms 3 of the second and third actuator assembly A2 and A3.

The joint L1 further forces the platform 11 to rotate around the central axis 1a depending on the position of the actuator arms 3 and the state of the actuated angular joints 2 of the second and third actuator limbs A2 and A3. Preferably, the joint L1 has a symmetrical design, that is, the length of the two influence arms 92 is the same, the position of the two ball joints 91 is equidistant from the central axis 1a, and the axis of rotation of the angular joint 95 is parallel to the main axis 12a and the secondary axis 14a. Given the symmetrical design, the joint L1 ensures that the horizontal extension of the first and second limb element 13 and 15 of the first actuator limb A1 is always placed halfway between the actuator arms 3 of the second and third actuator limbs A2 and A3 . In other words, the angular distances of the first and second limb element 13 and 15 measured from the actuator arms 3 of the second and third actuator limbs A2 and A3 are required to be substantially equal. The joint L1 thus provides a similar function as described in conjunction with the embodiment of Figure 1, that is, it supports the rotation of the actuator limb A1 around the central axis 1a when the position of the actuator limbs A2 and A3 changes. The joint L1 acts as a differential mechanism that avoids any angular difference between the first limb element 13 and the actuator arms 3 of the actuator limbs A2 and A3.

Turning now to Figure 10, another mechanism 500 for positioning and orienting a work tool in space with five degrees of freedom is illustrated. The mechanism 500 is similar to the embodiment of Figure 9, except that the mechanism 500 uses alternative means of influence or, more specifically, an alternative joint L2 that performs the same function as the union L1 previously described. More particularly, the joint L2 comprises two influence arms 98 and a guide arm 99. The two influence arms 98 are connected to the respective actuator arms 3 of the second and third actuator limbs A2 and A3 by first influence joints with At least two degrees of freedom. As shown in the embodiment, the two ball joints 91 are used for this connection. The inner end of the guide arm 99 is connected to the first end member 13 of the actuating end A1 by an angular joint 102, while the outer end of the guide arm 99 is connected to the two influence arms 98 by second articulations of influence, which are integrated and designed as a double hook joint 97 in Figure 10. The double hook joint comprises a cross and three forks, one of which is rotatably mounted to the second cross bar so that they revolve around the same axis. As an alternative to the double hook joint 97, concentric or separate ball joints can be used to connect the two influence arms 98 to the guide arm 99. Said concentric ball joint configuration 97a is shown in greater detail in Figure 13.

Preferably, the L2 joint has a symmetrical design as described previously for the L1 joint in conjunction with Figure 9. It will be understood that the joint configurations for connecting the guide arm and the respective influence arms in Figures 9 and 10 are interchangeable that is, the double hook joint 97 could also be used to connect the guide arm and the influence arms of the joint L1 while two separate ball joints 93 could be used to join the guide arm and the influence arms of the joint L2 In addition, the L1 and L2 junctions can be combined with other mechanisms described herein.

Since both joints L1 and L2 in Figures 9 and 10 ensure a guided rotation of the platform 11 as described above, they relieve the entire structure of the parallel kinematic mechanisms. More particularly, they reduce the bending moments in the first and second limb elements 13 and 15 and the tensile or compressive forces in the forearms 5 of the actuator extremities A2 and A3. The radial orientation of the first actuator limb A1 no longer has to be bound by the first and second limb elements 13 and 15 and the first articulation assembly J1. Therefore, as shown in Figure 11 in greater detail, it will be understood that the angular joint 14 could now be replaced by a universal joint 18 that allows the second end member 15 not only to rotate around the secondary axis 14a but also pivoting on both sides about a tertiary shaft 18a relative to the first end member 13. In addition to the universal joint 18, another degree of freedom (not shown) can be introduced between the second end member 15 and the articulation body 20 of the first joint assembly J1 seen in the embodiment of figure 2. As an alternative to the universal joint 18 and the degree of additional freedom between angular joint 14 and connect the first and second end member 13 and 15, as shown with greater detail in figure 12.

he

second element from end fifteen Y  he body from

joint

twenty, a  joint 19 with three degrees from

freedom,

such how a ball joint, could replace the

Referring to Figure 14, another mechanism 600 for positioning and orienting a work tool in space with five degrees of freedom is illustrated. The mechanism 600 is similar to the embodiment of Figure 9, except that the mechanism 600 uses alternative means of influence or, more specifically, an alternative joint L3 that performs the same function as the previously described L1 and L2 junctions. The joint L3 comprises two influence arms 104 and a first and second guide arm 108 and 106. The two influence arms 104 have first and second ends, the first ends being connected to the actuator arm 3 of a respective second and third actuator end A2 and A3 by an angular joint 103 whose axis of rotation is parallel to the central axis 1a. The second ends of the influence arms 104 are mounted to the second guide arm 106 by universal joints 105. As will be recognized by those skilled in the art, universal joints 105 could be combined with a double hook joint, as described. together with figure 10. Also, they could be replaced by ball joints, as described in conjunction with figures 9 and 13, or any other articulation configuration that allows the influence arms 104 to pivot relative to the second guide arm 106 with the minus two degrees of freedom. When the angular distance between the actuator arms 3 of the second and third actuator limbs A2 and A3 changes, the universal joints 105 approach or move away from the central axis 1a.

The second guide arm 106 is further connected to the first guide arm 108 by an angular joint 107, while the first guide arm 108 is connected to a mounting arm 110 by an angular joint 109. The mounting arm 110 is rigidly coupled to platform 11. Ideally, the axes of the angular joints 107 and 109 are parallel to the main axis 12a and the secondary axis 14a of the actuator end A1. Together, the first and second guide arm 108 and 106 form a hinge that compensates for the variation of the radial distance of the universal joints 105 from the central axis 1a. As described for unions L1 and L2, it is preferred that the joint L3 has a symmetrical design such that the center between the two universal joints 105, the first common point of the first joint assembly J1, and the central axis 1a are coplanar and define a plane that is perpendicular to the main axis 12a, the secondary axis 14a, the first articulation axis of the first articulation assembly J1, and the axes of rotation of the joints 107 and 109.

Referring now to Figure 15, another mechanism 700, constructed in accordance with the indications of the present invention, to position and orient a work tool in space with five degrees of freedom. The mechanism 700 is similar to the embodiment of Figure 1, except that in the mechanism 700 the actuated angular joints 2 of the actuator ends A4 and A5 rotate around respective actuator axes that are parallel but not coincident with the central axis 1a. As shown in the embodiment, a fixed base 1c comprises the central axis 1a and two offset axes 2a and 2b. The fourth and fifth actuator limbs A4, A5 are mounted on the base 1c such that their angular actuated joints 2 allow the rotation around actuator axes that coincide respectively with the displaced axes 2a and 2b. The embodiment illustrated in Figure 15 facilitates a simpler design of the drive, or

the

transmission from drive, toward the four

joints

angular 2 powered from the extremities

actuator A2, A3, A4 and A5.

Figure 16 illustrates a mechanism 800, constructed in accordance with the indications of the present invention, for positioning a work tool in space with three degrees of freedom and a fixed orientation. The mechanism 800 is similar to the embodiment of Figure 1, except that in mechanism 800 only three actuator limbs A11, A12 and A13 are used which will move the final component 40c. Actuator limb A11 has the same structure as actuator limb A1 as described in conjunction with Fig. 1. In addition, actuator limbs A12 and A13 are similar to actuator limbs A2 and A3 described in the embodiment of Fig. 1. , except that an upper and lower forearm 5 with respective axes of the upper and lower forearm 5a are now connected to the same actuator arm 3 via two ball joints 4 which are mounted on the actuator arm 3 by an elongate element 4a. The connection or pivot points of the ball joints 4 connecting the upper forearms 5 of the actuator extremities A2 and A3 preferably move in the foreground while the connection or pivot points of the ball joints 4 connecting to the lower forearms 5 of the actuator extremities A2 and A3 preferably move in a second plane that is parallel to the first plane and perpendicular to the central axis 1a. Alternative articulation configurations, such as the triple-axis articulation assembly shown in the embodiment of Figure 4, can be used to replace the ball joints 4. In that case, the two triple-axis articulation assemblies mounted on the same actuator arm 3 can share at least one angular joint

or axis of rotation, as shown in Figure 19 in greater detail.

As can be seen in Figure 19, the actuator arm 3 is connected to a common joint 76 by a first angular joint 77 with an articulation shaft 77a. Preferably, the axis 77a is parallel to the central axis 1a of the mechanism 800. The common joint 76 is also connected to both upper and lower forearms 5 via respective second angular joints 73 with pivot axes 73a, respective forks 74 and respective third angular joints 75 with rotation axes 75a. Preferably, axes 77a, 73a and 75a cross a common connection point shown in Figure 19. In addition, the axes of the upper and lower forearm 5a ideally coincide with the respective axes 75a. The articulation configuration described allows both upper and lower forearms 5a three degrees of freedom rotating with respect to the actuator arm 3.

Referring again to Figure 16, the two articulation assemblies J11 and J12 that join the actuator ends A11, A12 and A13 are similar to the articulation assemblies J1 and J2 described in Figure 2, except that the final component 40c is directly attached to the respective articulation bodies by means of angular joints 28a and 29a allowing the rotation around a first and second angular axis 28b and 29b.

Preferably, the mechanism 800 is designed such that the elongate elements 4a of both actuator ends A12 and A13, the central axis 1a, and the line connecting the common points of the articulation assemblies J11 and J12 are parallel to all positions of the mechanism 800. Thus, the final component 40c and the attached terminal element 41 move parallel to the fixed base 1 without changing its orientation or inclination. Included in the concept of this invention is that mechanism 800 can be equipped with additional actuators to allow the work tool an additional degree of freedom. Such an actuator can be added to the mechanism 800 in ways similar to those described in relation to Figures 6,7 and 8. In addition, the influence means or joints illustrated in the embodiments of Figures 9, 10, 13 and 14 can be used. to rotate platform 11 of mechanism 800.

Figure 18 shows alternative joint assemblies J13 and J14 that can be used in conjunction with the mechanism 800 shown in Figure 16. The first joint assembly J13 is similar to the first joint assembly J4 shown in Figure 17, except that the final component 40c is directly connected to the articulation body 25 by means of an angular joint 28a allowing the rotation around a first angular axis that can coincide with the first articulation axis 25a. The second joint assembly J14 is similar to the second joint assembly J5 shown in Figure 17 except that the final component 40c is directly fixed to the joint body 26 by an angular joint 29a allowing rotation around a second angular axis 26a. Preferably, the second and third articulation axis 7a and 7b are perpendicular to the first articulation axis 25a and symmetrically displaced with respect to the plane of symmetry which is ideally perpendicular to the first articulation axis 25a and crosses the central axis 1a of the mechanism 800. Similarly, it is preferred that the fourth and fifth axis of articulation 7c and 7d be symmetrically offset with respect to said plane.

Although the invention has been described herein in relation to several preferred embodiments, there is no intention of limiting the invention to those embodiments. It will be understood that various changes and modifications in the preferred embodiments will be apparent to those skilled in the art. Such changes and modifications

55 can be carried out without departing from the spirit and scope of the present invention without diminishing the advantages employed. Therefore, the included claims are intended to cover such changes and modifications.

Claims (35)

1. A mechanism to position and orient a final component in space with at least five degrees of freedom, the mechanism comprising: a base (1); a first actuating limb (A1) comprising at least one platform (11) connected to said base (1) by an angular joint (10) allowing a degree of rotational freedom around a central axis (1a), a first limb element (13) mobilely connected to said platform with a single degree of freedom actuated in relation to said platform, an actuator (101) for actuating said first end element in relation to said platform, and a second end element (15) mobile connected to said first limb element, said second limb element having at least three degrees of freedom relative to said base, in which at least one of said degrees of freedom of said second limb element is operable in relation to to that base; at least one second, third, fourth and fifth actuator limb (A2, A3, A4, A5), each of the actuator limbs comprising at least one actuator arm (3) rotatably connected to said base by means of an actuated angular joint ( 2) which allows the rotation around a respective actuator shaft (1a, 2a, 2b), an actuator to drive said actuator arm relative to said base, each of the second, third, fourth and fifth actuator limbs also comprising a forearm (5) movably connected to said actuator arm of the respective actuator limb, wherein said forearm has at least three degrees of freedom relative to said actuator arm including a degree of free rotating freedom around a respective forearm axis ( 5a); a first articulation body (20, 24, 25), wherein said second limb element is rotatably connected to said first articulation body and allows rotation relative to said first articulation body about a first axis of articulation (20a, 24a, 25a), and in which each of the forearms of said second and third actuator limb is rotatably connected to said first articulation body and allows the rotation relative to said first articulation body around a respective second and third axis of articulation (20b, 24b, 24c, 7a, 7b) that is not parallel to said forearm axis of the respective actuator limb; a second articulation body (30, 26), in which each of the forearms of said fourth and fifth actuator limb is rotatably connected to said second articulation body and allows rotation relative to said second articulation body around of a respective fourth and fifth articulation axis (30b, 7d, 7c) that is not parallel to said forearm axis of the respective actuator limb; Y the mechanism also comprising said final component (40, 40a, 40b) mobilely connected to each of said first and second articulation body, the final component having at least two degrees of freedom rotating relative to said first and second body of articulation such that said final component can move with at least five degrees of freedom relative to said base.

2.

A mechanism according to claim 1, wherein the respective actuator axis of each of said second and third actuator limb is substantially coincident with said central axis (1a).

3.

A mechanism according to claim 1, wherein the respective actuator axis of each of said fourth and fifth actuator limbs is substantially parallel with said central axis (1a).

Four.

A mechanism according to claim 1, wherein the respective actuator axis of each of said fourth and fifth actuator limbs is substantially coincident with said central axis (1a).

5.

A mechanism according to claim 1, wherein said second and third axis of articulation (20b, 7a, 7b) are substantially parallel to each other and perpendicular to said first axis of articulation (20a, 25a).

6.

A mechanism according to claim 1, wherein said second and third articulation axes (20b) are substantially coincident and perpendicular to said first articulation axis (20a) and wherein said first, second and third articulation axes and axes of the forearms

(5a) of said second and third actuator limbs cross a first common point (P1).

7.

A mechanism according to claim 1, wherein said fourth and fifth axis of articulation (30b, 7d, 7c) are substantially parallel to each other.

8.

A mechanism according to claim 1, wherein said fourth and fifth axis of articulation (30b) are substantially coincident and wherein said fourth and fifth axis of articulation and axes of the forearm (5a) of said fourth and fifth actuator limbs pass through a second common point (P2).

9.

A mechanism according to claim 1, wherein said first limb element (13) is connected to said platform (11) by means of an actuated angular joint (12) allowing rotation around a main axis (12a), and said second element of limb (15) is connected to said first limb element by means of an angular joint allowing rotation around a secondary axis (14a), and wherein said main axis, said secondary axis, and said first articulation axis (20a, 24a, 25a) are substantially parallel to each other and perpendicular to said central axis (1a).

10.

A mechanism according to claim 1, wherein said final component (40, 40a, 40b) is connected to said first articulation body by a first (22) and second

(23) angular joint in series allowing rotation around the respective first and second angular axis (23a), and wherein said final component is connected to said second articulation body by a third (32) and a fourth (33) angular joint in series allowing the rotation around the respective third and fourth angular axis (33a).

eleven.

A mechanism according to claim 10, wherein said first angular axis is substantially coincident with said first articulation axis (20a, 24a, 25a), and wherein said second angular axis (23a) is perpendicular to said first angular axis e intersects with said first angular axis and said central axis (1a), and wherein said fourth angular axis (33a) is perpendicular to said third angular axis and intersects with said third angular axis.

12.

A mechanism according to claim 1, wherein said forearm (5) and said actuator arm (3) of at least one of said second, third, fourth and fifth limbs

actuator

(A2, A3, A4, TO 5) is it so connected by three

joints

angular in Serie (72, 73, 75), having

sayings

joints angular axes from turn that

intersect and mutually non-parallel (72a, 73a, 75a).

13.

A mechanism according to claim 1, wherein said forearm (5) and said actuator arm (3) of at least one of said second, third, fourth and fifth actuator extremities (A2, A3, A4, A5) are connected by a kneecap (4).

14.

A mechanism according to claim 1, further comprising a work tool (44, 49, 50) movably mounted on said final component (40, 40a, 40b) for the actionable movement relative thereto.

fifteen.

A mechanism according to claim 14, further comprising an actuator (45) mounted on said base (1, 1b) and operatively attached to said work tool (49, 50), said actuator driving said work tool to move with relation to said final component (40a, 40b).

16.

A mechanism according to claim 14, further comprising an actuator (42) mounted on said final component (40) and operatively attached to said work tool (44), said actuator driving said work tool to move relative to said final component

17.

A mechanism according to claim 1, wherein the forearm (5) of each of said second and third actuator limbs (A2, A3) is connected to the respective actuator arm (3) with three degrees of freedom rotating around a point of connection, and in which the connection points of said second and third actuator limbs move substantially in the same plane.

18.

A mechanism according to claim 1, wherein said second end element (15) is connected to said first articulation body (20, 24, 25) by means of an angular joint (17) allowing rotation around said first articulation axis (20a, 24a, 25a), and in which the forearms (5) of said second and third actuator limbs (A2, A3) are connected to said first articulation body (20, 24, 25) by respective angular joints (7 , 9) allowing the rotation of said second and third axis of articulation (20b, 24b, 24c, 7a, 7b),

and wherein the forearms (5) of said fourth and fifth actuator limbs (A4, A5) are connected to said second articulation body (30, 26) by respective angular joints (7) allowing rotation around said fourth and fifth articulation shaft (30b, 7d, 7c).

19.

A mechanism according to claim 1, further comprising influencing means (L1, L2, L3), said influence means squeezing said platform (11) to rotate it around said central axis (1a) by at least one of the actuator arms ( 3) of said second and third actuator tip (A2, A3).

twenty.

A mechanism according to claim 1, further comprising influence means (L1, L2, L3), said influence means tightening said platform (11) to rotate it around said central axis (1a) such that the actuator arms (3) of said second and third actuator limb (A2, A3) remain at a substantially equal angular distance from said first limb element (13).

twenty-one.

A mechanism according to claim 20, wherein said influence means (L1, L2) comprise:

a guide arm (94, 99) rotatably connected to said platform (11) by an angular joint (95) allowing a degree of rotational freedom; Y a first and second influence arm (92, 98) pivotally connected to the actuator arm (3) of a respective of said second and third actuator limb (A2, A3) by first influence joints (91) allowing at least two degrees of freedom rotating, each of said first and second influence arm also being pivotally connected to said guide arm by second influence joints (93, 97) allowing at least two degrees of freedom rotating.

22

A mechanism according to claim 21, wherein at least one of said first and second influence articulation (91, 93, 97) is a kneecap.

2. 3.

A mechanism according to claim 21, wherein at least one of said first and second influence articulation (91, 93, 97) is a universal articulation.

24.

A mechanism according to claim 20, wherein said influence means (L3) comprise:

a first guide arm (108) which is rotatably connected to said platform (11) by an angular joint (109) allowing a degree of rotational freedom; a second guide arm (106) rotatably connected to said first guide arm by an angular joint (107) allowing a degree of rotational freedom; and a first and second influence arm (104) connected to the actuator arm (3) of a respective of said second and third actuator limb (A2, A3) by respective angular joints (103) allowing a degree of rotational freedom, each of said first and second influence arm being further pivotally connected to said second guide arm by universal joints (105) allowing two degrees of freedom. 25. A mechanism (800) for positioning and orienting a final component (40c) in space with at least three degrees of freedom, including the mechanism: A base (1); a first actuating limb (A11) comprising at least one platform (11) connected to said base by an angular joint (10) allowing a degree of rotational freedom around a central axis (1a), a first limb element (13) mobilely connected to said platform with a single degree of freedom actuated in relation to said platform, an actuator (101) for actuating said first end element in relation to said platform, and a second end element (15) connected so mobile to said first limb element, said second limb element having at least three degrees of freedom relative to said base, in which at least one of said degrees of freedom of said second limb element is operable in relation to said base ; at least a second and third actuator limb (A12, A13), each of the actuator limbs comprising at least one actuator arm (3) rotatably connected to said base by means of an actuated angular joint (2) that allows the rotation around a respective actuator shaft, an actuator for actuating said actuator arm relative to said base, each of said second and third actuator limb further comprises an upper and lower forearm (5) mobilely connected to said actuator arm of the respective actuator limb, in which each of said upper and lower forearms has at least three degrees of freedom relative to said actuator arm including a degree of free rotating freedom around a respective upper and lower forearm axis (5a); a first articulation body (20, 25), wherein said limb element is connected to said first articulation body by an angular joint (17) allowing rotation around a first articulation axis (20a, 25a), and wherein each upper forearm of said second and third actuator limb is connected to said first articulation body by an angular articulation (7) allowing the rotation around a respective second and third articulation axis (20b, 7a, 7b) that does not it is parallel to said axis of the upper forearm of the respective actuator limb; a second articulation body (30, 26), in which each of the lower forearms of said second and third actuator limb is connected to said second articulation body by an angular joint (7) allowing the rotation around a respective fourth and fifth articulation axis (30b, 7d, 7c) that is not parallel to said axis of the lower forearm of the respective actuator limb; Y said mechanism also comprises said final component (40c) mobilely connected connected to said first and second articulation body, the final component having at least a degree of rotational freedom relative to said first and second articulation body such that said final component can move with at least three degrees of freedom in relation to that base.

26.

A mechanism according to claim 25, wherein the respective actuator axis of each of said second and third actuator limb (A12, A13) is substantially coincident with said central axis (1a), and in which each of the upper forearms (5) of said second and third actuator limb is connected to the respective actuator arm (3) with three degrees of freedom rotating around a respective first connection point, and in which each of the lower forearms (5) of said second and third actuator limb is connected to the respective actuator arm (3) with three degrees of freedom rotating around a respective second connection point, and wherein said first connection points move in the foreground and said second connection points are they move in the background substantially parallel to said foreground.

27.

A mechanism according to claim 25, wherein said second and third axis of articulation (20b, 7a, 7b) are substantially parallel to each other and perpendicular to said first axis of articulation (20a, 25a), and wherein said fourth and Fifth axis of articulation (30b, 7d, 7c) are substantially parallel to each other.

28.

A mechanism according to claim 25, wherein said first, second and third axis of articulation (20a, 20b) and the axes of the upper forearm (5a) of said second and third actuator limb (A12, A13) cross a first common point (P1), and wherein said fourth and fifth articulation axes (30b) and the axes of the lower forearm (5a) of

said second and third actuator limb pass through a second common point (P2).

29.

A mechanism according to claim 25, wherein said first end member (13) is connected to said platform (11) by an angular joint (12) allowing rotation around a main shaft (12a), and said second element of limb (15) is connected to said first limb element by an angular joint (14) allowing the rotation around a secondary axis (14a), and wherein said main axis, said secondary axis and said first articulation axis (20a , 25a) are substantially parallel to each other and perpendicular to said central axis (1a).

30

A mechanism according to claim 25, wherein said final component (40c) is connected to said first articulation body (20, 25) by an angular joint (28a) allowing rotation around a first angular axis (28b), and wherein said final component is connected to said second articulation body (30, 26) by an angular joint (29a) allowing the rotation around a second angular axis (29b), wherein said first and second angular axis and said First axis of articulation (20a, 25a) are parallel to each other.

31.

A mechanism according to claim 25, wherein said final component (40c) is connected to said first articulation body (20, 25) by an angular joint (28a) allowing rotation around a first angular axis (28b), and wherein said final component is connected to

said second articulation body (30, 26) by an angular joint (29a) allowing the rotation around a second angular axis (29b), wherein said first and second angular axis are parallel to each other and in which said first axis angular coincides with said first axis of articulation (20a, 25a).

32

A mechanism according to claim 25, wherein each of said upper and lower forearm (5) of at least one of said second and third actuator limb (A12, A13) is connected to said actuator arm (3) by three angular joints (72, 73, 75) in series, said angular joints having intersecting and mutually non-parallel axes of rotation (72a, 73a, 75a).

33.

A mechanism according to claim 25, wherein at least one of said second and third actuator end (A12, A13) further comprises a common joint (76) connected to said actuator arm (3) by a first angular joint (77), and wherein said common joint is connected to each of said upper and lower forearms (5) by a second and third angular joint (73, 75) in series, said first angular joint having the respective second and third angular joint axes of rotation (73a, 75a, 77a) that intersect and mutually non-parallel.

3. 4.

A mechanism according to claim 25, wherein each of said upper and lower forearm (5) of at least one of said second and third actuator limb (A12, A13) is connected to said actuator arm (3) by a kneecap ( 4).

35

A mechanism according to claim 25, further comprising a work tool (44, 49, 50) movably mounted on said final component (40c) for the actionable movement relative thereto.

A mechanism according to claim 25, further comprising an actuator (45) mounted on said base (1) and operatively attached to said work tool (49, 50), said actuator driving said work tool to move in relation to said final component (40c). A mechanism according to claim 35, further comprising an actuator (42) mounted on said final component (40c) and operatively attached to said work tool (44), said actuator driving said work tool to move with relation to said final component. A mechanism according to claim 25, further comprising influence means (L1, L2, L3), said influence means pushing said platform (11) to rotate around said central axis (1a) such that the actuator arms ( 3) of the second and third actuator limb 20 (A12, A13) remain at a substantially equal angular distance from said first limb element (13).