Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
MANIPULATOR AND METHOD INVOLVING A MANIPULATOR FOR MOVEMENT OF AN OBJECT, COMPRISING AT LEAST TWO DRIVING PARALLEL KINEMATIC CONNECTING CHAINS
Document Type and Number:
WIPO Patent Application WO/2003/078111
Kind Code:
A1
Abstract:
A manipulator (2) arranged for movement of an object (3) in space, comprising a stationary platform (4), a movable platform (5) on which the object (3) is arranged, and at least two driving parallel kinematic connecting chains (6, 7) arranged between the platforms (4, 5), wherein a first single-axle joint (8) with a first axis of rotation (A), included in the first parallel kinematic connecting chain (6), is arranged on the stationary platform (4), and a second single-axle joint (10) with a second axis of rotation (B), included in the second parallel kinematic connecting chain (7), is arranged on the stationary platform (4).

Inventors:
Smede, Jan (Skvallergränd 4, Västerås, S-722 15, SE)
Brogårdh, Torgny (Plåtverksgatan 140, Västerås, S-724 79, SE)
Application Number:
PCT/SE2003/000421
Publication Date:
September 25, 2003
Filing Date:
March 13, 2003
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ABB AB (Kopparbergsvägen 2, Västerås, S-721 83, SE)
Smede, Jan (Skvallergränd 4, Västerås, S-722 15, SE)
Brogårdh, Torgny (Plåtverksgatan 140, Västerås, S-724 79, SE)
International Classes:
B23K26/08; B23K26/10; B25J9/10; B25J17/02; G01B5/008; (IPC1-7): B25J9/10; B25J17/02
Attorney, Agent or Firm:
ABB GROUP SERVICES CENTER AB (Legal & Compliance/Intellectual Property, Forskargränd 8, Västerås, S-721 78, SE)
Download PDF:
Claims:
CLAIMS
1. A manipulator (2) arranged for movement of an object (3) in space, comprising a stationary platform (4), a movable platform (5) on which the object (3) is arranged, and at least two driving parallel kinematic connecting chains (6, 7) arranged between the platforms (4,5), wherein a first singleaxle joint (8) with a first axis of rotation (A), included in the first parallel kinematic connecting chain (6), is arranged on the stationary platform (4), and a second singleaxle joint (10) with a second axis of rotation (B), included in the second parallel kinematic connecting chain (7), is arranged on the stationary platform (4), characterized in that a third singleaxle joint (12) with a third axis of rota tion (C), included in the second parallel kinematic connec ting chain (7), is arranged to cross the second axis of rotation (B), the object (3) is adapted to rotate around the third axis of rotation (C) when the first parallel kinematic connec ting chain (6) is driving, the object (3) is adapted simultaneously to rotate around the second (B) and third (C) axes of rotation when the second parallel kinematic connecting chain (7) is driving.
2. A device according to claim 1, wherein the first and second axes of rotation (A, B) are arranged to intersect each other.
3. A device according to claim 1, wherein the first and second axes of rotation (A, B) are arranged to be parallel.
4. A device according to claim 3, wherein the first and second axes of rotation (A, B) are arranged to coincide in a common fourth axis of rotation (E).
5. A device according to any of claims 14, wherein a first actuator arm (6a) with a first longitudinal axis (D), in cluded in the first parallel kinematic connecting chain (6), is arranged on the movable part/actuator (8a) of the first joint (8).
6. A device according to claim 5, wherein a first linkage system (11), included in the first parallel kinematic con necting chain, is arranged to connect the first actuator arm (6a) to the movable platform (5).
7. A device according to claim 5 or 6, wherein the first actuator arm (6a) is secured to the first actuator (8a).
8. A device according to claim 5 or 6, wherein the first actuator arm (6a) is articulately connected to the first actuator (8a) in a fourth singleaxle joint (22) with a fifth axis of rotation (F).
9. A device according to claim 5, wherein the first longi tudinal axis (D) is adapted to cross the first, second and third axes of rotation (A, B, C), respectively.
10. A device according to claim 6, wherein the linkage sys tem (11) comprises a first link (13) and two threeaxle joints (14,15) arranged to be interconnected.
11. A device according to claim 4, wherein the third axis of rotation (C) is arranged perpendicular to the fourth axis of rotation (E).
12. A device according to claim 11, wherein the third axis of rotation (C) intersects the fourth axis of rotation (E).
13. A device according to claim 8, wherein the fifth axis of rotation (F) intersects the fourth axis of rotation (E) at right angles.
14. A device according to claim 8, wherein the linkage sys tem comprises a second link (23) arranged in a parallel kinematic manner in relation to the first link (13).
15. A device according to claim 4, wherein a second actua tor arm (7a), included in the second parallel kinematic connecting chain (7), is arranged on the movable part/actuator (10a) of the second joint (7).
16. A device according to claim 4, wherein a second actua tor arm (10a) is arranged on the second actuator (10).
17. A device according to any of the preceding claims 114, wherein the manipulator (2) constitutes a wrist in an in dustrial robot.
18. A method involving a manipulator (2) arranged for move ment of an object (3) in space, comprising a stationary platform (4), a movable platform (5) on which the object (3) is arranged and at least two driving parallelkinematic connecting chains (6,7) arranged between the platforms (4, 5), wherein a first singleaxle joint (8) with a first axis of rotation (A), included in the first parallelkinematic connecting chain (6), is arranged on the stationary platform (4), and a second singleaxle joint (10) with a second axis of rotation (B), included in the second parallelkinematic connecting chain (7), is arranged on the stationary platform (4), characterized in that the object (3) is brought to rotate around a third axis of rotation (C), arranged in the second connecting chain (7) and at an angle to the second axis of rotation (B), by rotation in the first joint (8), and that the object (3) is brought simultaneously to rotate around the second (B) and third (C) axes of rotation by rotation in the second joint (10).
19. A method according to claim 18, wherein the object is brought to be manipulated under endless rotation around a common axis of rotation (E).
20. A method according to claim 19, wherein the object (3) is brought to pivot in a normal plane to the axis of rota tion (E) in case of synchronous pivoting of the first (8) and second (10) joints.
21. A method according to claim 19, wherein the object (3) is brought to pivot in a normal plane to the axis of rota tion (C) in case of asynchronous pivoting between the first (8) and second (10) joints.
22. Use of a manipulator according to claims 117 and a method according to claims 1922 for CMM measurement.
23. Use of a manipulator according to claims 117 and a method according to claims 1922 in a servo positioning head for laser machining.
24. An industrial robot including a manipulator according to any of claims 117 arranged for industrial high precision applications.
Description:
Manipulator TECHNICAL FIELD The present invention relates to a parallel kinematic manipulator, a PKM, for automatic movement and orientation of an object in space. A PKM comprises at least two arms, each forming a parallel kinematic connecting chain of joints between a stationary platform and a movable plat- form. The actuators of the manipulator are usually arranged on the stationary platform and each of them drives a kine- matic connecting chain. In that way, forces are transmitted to move the arms in parallel such that the platform is set in motion. The movable platform supports the object to be manipulated and its task is to directly or indirectly support a tool or object intended for a certain applica- tion. The present invention is primarily intended for industrial applications with requirements for high preci- sion.

BACKGROUND ART In industrial high-precision measurement, a coordinate measurement machine, CMM, is usually used to carry out the measurement work. Equipment comprising a CMM manages high- precision measurement but has the disadvantage of operating slowly. It is previously known to carry out industrial high-precision measurement with a CMM provided with a wrist that orients a measuring probe in space. The wrist used in known CMM equipment orients the measuring probe around two axes. The wrist is servo-controlled and provided with both drive means and gear units in the actual wrist. The wrist is suited for existing CMM equipment since both operate at a low speed. In industry there is a need of increasing the rate of production without lowering the precision.

One possible development in this context is to utilize a faster industrial robot for the same functions as a CMM.

Speed of action is achieved by high acceleration, accele- ration derivative and maximum speed. If high-precision measurement were to take place with a faster industrial robot, considerable demands would be placed on the ability of the robot to orient a measuring probe, that is, a measu- ring tool in space sufficiently rapidly and with suffi- ciently high precision. In such cases, the measuring probe is arranged on a wrist mounted on the robot and the orien- tation of the measuring probe takes place with the aid of the wrist. The same demands on speed of action must be placed on both the wrist and on the industrial robot. This development path is considered interesting, and consequent- ly there is a need to be able to equip a faster industrial robot with. a faster wrist.

Industrial measurement requires that the reach of the equipment should comprise all desired measuring points and should also manage to reach into narrow spaces. This places heavy demands on the design of a wrist.

The need of speed in, for example, high-precision measure- ment is based on the general need of lowering the produc- tion costs. For economic reasons, there is therefore a need of measuring equipment that rapidly moves a measuring probe between measuring points and, in addition, rapidly orients the measuring probe to the desired measuring position. An example of applications of fast precision measurement is measurement of dimensions of car-body parts and components in motors and gearboxes in the car industry.

What is stated above shows that there is a need of an in- dustrial robot that maintains a high precision and that is faster when moving and orienting an object. The object is, for example, a measuring probe or a laser gun. The need comprises the fact that the object shall be able to reach into all the desired measuring points, also inside narrow spaces.

Applications with known CMM systems do not fulfil these needs.

SUMMARY OF THE INVENTION The object of the invention is to provide a PKM, defined as above, which facilitates the work with industrial applica- tions requiring high precision and a high rate of produc- tion. A second object of the invention is to provide a PKM that is less expensive to manufacture and simpler to in- stall for high-precision applications in an industrial robot application, for example measurement or laser cutt- ing. A third object of the invention is to provide a PKM that has a smaller and narrower physical extent while at the same time exhibiting a larger operating volume.

According to a first aspect, the invention solves the above-mentioned task by arranging a manipulator with characteristic features in accordance with the independent device claim 1, according to a second aspect by a method carried out in accordance with the independent claim 18, according to a third and a fourth aspect by the use in accordance with the independent claims 22 and 23, respec- tively, and according to a fifth aspect by an industrial robot in accordance with the independent claim 24.

Advantageous embodiments are described in the dependent claims.

In accordance with the invention, an industrial robot com- prising a manipulator is adapted for movement of an object in space. The manipulator includes a stationary platform and a movable platform, and the object is arranged on the latter. Further, at least two driving kinematic connecting chains are arranged in parallel between the platforms. A first single-axle joint with a first axis of rotation, in- cluded in the first parallel-kinematic connecting chain, is arranged on the stationary platform. Further, a second sin-

gle-axle joint with a second axis of rotation, included in the second parallel kinematic connecting chain, is arranged on the stationary platform. The invention is characterized by a third single-axle joint with a third axis of rotation, included in the second parallel kinematic connecting chain, which is adapted to cross (defined as below) the second axis of rotation. The third axis of rotation hence consti- tutes the axis of rotation of the movable platform. The object is adapted to rotate around the third axis of rota- tion when the first parallel kinematic connecting chain is driving and the object is adapted, at the same time, to rotate around the second and third axes of rotation when the second parallel kinematic connecting chain is driving.

The inventive concept comprises arranging the first and second joints on the stationary platform such that first and second axes of rotation cross each other. The determi- nation that"the axes of rotation cross each other"refers to the fact that the axes form an angle with each other and that the axes lie in different planes. The determination that"the axes of rotation intersect each other"refers to the fact that they form an angle with each other and that they lie in the same plane.

When the first and second kinematic connecting chains are simultaneously driving, the manipulator according to the invention thus allows simultaneous rotation and pivoting of an object.

The determination kinematic connecting chain, as used here, means a chain of interconnected joints and links. The de- termination driving kinematic connecting chain, as used here, means a kinematic connecting chain cooperating and actuated by at least one drive means. It is part of the inventive concept that the drive means for a parallel ki- nematic connecting chain is arranged on the stationary platform or as an external source of power. It is also part of the present invention that the drive means is built into

the parallel kinematic connecting chain, for example in a single-axle joint.

The determination"single-axle joint, with an axis of ro- tation arranged on a platform", as used here, means a single-axle joint with an axis of rotation. Further, this determination means that the joint consists of two parts, one part being secured onto the platform and the other part being movable and rotating around the axis of rotation. The present invention comprises at least one single-axle joint, arranged on the stationary platform according to the above, in the respective parallel kinematic connecting chain.

The PKM according to the present invention also comprises driving motors, including gearboxes and angle sensors, which are arranged on the stationary platform. By arranging the driving motors with their gearboxes and angle sensors on the stationary platform and, in addition, designing the parallel kinematic connecting chains from joints and links only, the moving mass is reduced most significantly. Less moving mass primarily results in the advantage of an in- creased acceleration and hence a faster robot. When a PKM according to the invention is mounted on a robot, a reduced moving mass entails reduced major torques from robot axes included in the robot, which in turn entails a faster and dynamically more accurate robot. In a manipulator according to the invention, with parallel kinematic connecting chains consisting of joints and links, the number of power trans- missions included therein is lower. Since all power trans- missions have a built-in play, which has a negative influ- ence on the accuracy, a reduction of the number of built-in power transmissions compared with the prior art results in fewer plays. Fewer plays, in turn, results in increased accuracy.

It is also part of the inventive concept that the first and second axes of rotation are adapted to coincide, that is, the first and second axes of rotation consist of a common

fourth common axis of rotation. A PKM according to the in- vention provided with a common fourth axis of rotation gives a PKM with a greater orientation capacity and hence increased operating volume. In an advantageous embodiment of the invention, the third axis of rotation is arranged perpendicular to the fourth axis of rotation. In a further advantageous embodiment of the invention, the third axis of rotation intersects the fourth axis of rotation.

Further, it is part of the inventive concept that the mov- able parts of the first and second joints, respectively, are designated first and second actuators, respectively.

Irrespective of whether the drive means is integrated into the joint or is arranged on the stationary platform at a distance from the joint, the drive is on the movable part, that is, the actuator, of the respective joint in the following. According to an advantageous embodiment of the invention, the first and second actuators are coaxially arranged with and have an extent along the common fourth axis of rotation.

Advantageous embodiments of the invention are based on the fact that, out of two actuators included in the manipula- tor, at least one actuator is designed as a tube, which is concentrically and rotatably arranged for rotation around the remaining rotating actuator. Hence, the manipulator according to the invention exhibits two actuators, coaxi- ally arranged with a common axis of rotation. The two actu- ators are arranged on the stationary platform and have different extent along the common axis of rotation, that is, they have different lengths.

It is also part of the inventive concept that the actuators are arranged spaced from each other with parallel axes of rotation.

In an advantageous embodiment of the invention, the first parallel kinematic connecting chain includes a first actua-

tor arm with a first longitudinal axis. The first actuator arm is arranged on the movable part of the first joint and forms an angle with the first, second and third axes of rotation. It is part of the inventive concept that the first actuator arm is secured to the movable part of the first joint. It is also part of the inventive concept that the first actuator arm is articulately connected to the movable part of the first joint in a fourth single-axle joint with a fifth axis of rotation.

It is part of the inventive concept that the first parallel kinematic connecting chain comprises a rotating first actu- ator arranged with a first actuator arm connected to a first linkage system. In one advantageous embodiment, the first actuator arm is secured to the first actuator. The first actuator arm is adapted to form an angle, in its longitudinal direction, with the first, second, third and fourth axes of rotation included therein. In another advan- tageous embodiment, the first actuator arm is articulately connected to the first actuator in a fourth single-axle joint for rotation about a fifth axis of rotation, which intersects the fourth axis of rotation at right angles.

This advantageous embodiment increases the operating volume of the manipulator.

It is part of the inventive concept that the manipulator according to the invention consists of a wrist in an indus- trial robot. According to a preferred embodiment, the in- dustrial robot is intended for industrial high-precision applications. The movable platform consists, for example, of a measuring probe holder and the object that is manipu- lated consists of a measuring probe for CMM measurement. In another application, the manipulator constitutes a servo positioning head for laser machining.

It is further part of the inventive concept to arrange, in a PKM according to the invention, comprising a common axis of rotation for the two actuators, a second actuator arm on

the movable part of the second single-axle joint, that is, the second actuator. Thus, the manipulator comprises a first and a second parallel kinematic connecting chain, each one comprising an actuator provided with an actuator arm. The two actuator arms are arranged to form an angle, partly with each other, partly with the other symmetry axes included and mentioned above. The second connecting chain comprises two single-axle joints arranged at an angle. The second connecting chain is supplemented, in an advantageous embodiment, with a passive arm element, which has a passive function of sustaining the movable platform, whereby the manipulator functions in accordance with the invention. An advantageous embodiment of the invention functions as follows. An object is brought to rotate around a common fourth axis of rotation by rotating the two actuators syn- chronously. The object is brought to pivot around a third axis of rotation, that is, the axis of rotation of the mov- able platform, by rotating the two actuator axles asynchro- nously.

Further, the inventive concept comprises a method involving a manipulator adapted for movement of an object in space.

The manipulator comprises a stationary platform, a movable platform on which the object is arranged and at least two driving parallel kinematic connecting chains arranged be- tween the platforms, whereby a first single-axle joint with a first axis of rotation, included in the first parallel kinematic connecting chain, is arranged on the stationary platform, and a second single-axle joint with a second axis of rotation, included in the second parallel kinematic connecting chain, is arranged on the stationary platform.

The method is characterized in that the object is brought to rotate around a third axis of rotation, arranged in the second connecting chain and at an angle to the second axis of rotation, upon rotation in the first joint, and in that the object is brought to simultaneously rotate around the second and third axes of rotation upon rotation in the se- cond joint. In this way, a PKM according to the invention

is driven to pivot and rotate the object around two angled axes at the same time. In a preferred embodiment of the invention, the manipulator is adapted to manipulate the object under endless rotation around a fourth common axis of rotation for the connecting chains.

According to the inventive concept, the object is brought to pivot in a normal plane to the fourth axis of rotation in case of synchronous pivoting of the first and second actuators. Further, the inventive concept comprises bring- ing the object to pivot in a normal plane to the third axis of rotation in case of asynchronous pivoting between the first and second actuators.

The inventive concept comprises the possibility of changing the length of one of or both of the actuators.

The manipulator according to the invention permits a measu- ring probe to adopt all the positions and orientations that are required in connection with measurement. By making the movable wrist very light and since drive and measuring sys- tems are not included in the moving mass, high acceleration levels are achieved. The stationary platform according to the invention constitutes an integral part of an optional robot. Hence, the inventive concept permits designing the drive of a wrist with motors that have lower weights. This means that the moving mass of the front part of the robot arm is reduced. In that way, the motors of the robot may be made lighter and the result is a faster robot suited for high-precision applications.

Other possible applications of the manipulator according to the invention are laser welding, laser cutting, spray pain- ting, gluing, plasma cutting, and water cutting.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in greater detail by des- cription of embodiments with reference to the accompanying drawing, wherein Figure 1 a general parallel kinematic manipulator, PKM, according to the present invention, Figure 2 is a kinematic model of the manipulator in Figure 1, Figure 3 is an advantageous embodiment of a PKM according to the invention, Figure 4 is an advantageous embodiment of a PKM according to the invention, shown in two positions, Figure 5 is an advantageous embodiment of a PKM according to the invention, illustrated with its operating range, Figure 6 is a model for the operating range according to Figure 4, Figure 7 is a PKM according to Figure 5, illustrated with the movement patterns of two joints included therein, Figure 8 is a modified PKM according to Figure 7 with a larger operating volume, Figure 9 is a PKM intended for a laser cutting application, Figure 10 is a PKM comprising an actuator arm on each actu- ator axle, Figure 11 is a light-weight joint for the manipulator of Figure 10, Figure 12 is a PKM according to the invention with a measu- ring probe arranged in a first position, Figure 13 is a PKM according to Figure 12 with the measu- ring probe rotated through 90°, Figure 14 is a PKM according to Figure 10 with two actuator arms connected to a movable platform in a common joint, Figure 15 is a PKM according to Figure 10 with two actuator arms arranged on the movable part/actuator of the first joint, Figure 16 is a PKM according to Figure 15 with an alterna- tive embodiment of a movable platform,

Figure 17 is a PKM according to Figure 10 with two actuator arms arranged on the movable part/actuator of the second joint, Figure 18 is a PKM according to Figure 17 with one actuator arm arranged to be rotatable around its longitudinal axis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 is a general design of the industrial robot accor- ding to the present invention. The industrial robot 1 com- prises a parallel kinematic manipulator 2 adapted for move- ment of an object 3 in space. The manipulator includes a stationary platform 4, a movable platform 5 and two paral- lel kinematic connecting chains in the form of arms 6,7, interconnecting the platforms. The first arm 6 is connected to the stationary platform 4 in a first single-axle joint 8 with the axis of rotation A. The first joint 8 comprises a first rotatable actuator 8a and a part 8b that is secured to the platform 4. The first actuator 8a is provided with an actuator arm 6a, secured thereto, with the longitudinal axis D. The actuator 6a is articulately connected to the movable platform 5 via a linkage system 11.

The second arm 7 is connected to the stationary platform 4 in a second single-axle joint 10 with the axis of rotation B. The second joint 10 comprises a second rotatable actua- tor 10a and a part 10b secured to the platform 4. The second actuator 10a is provided with a second actuator arm 7a secured thereto, which is articulately connected to the movable platform 5 via a third single-axle joint 12 with a third axis of rotation C.

The first and second actuators 8a and 10a, respectively, are arranged with an offset and make an angle between their respective axes of rotation A and B. The axis of rotation C of the joint 12 is arranged with an offset and an angle re- lative to the axis of rotation B. During rotation of the first actuator 8a, the movable platform 5 is rotated around

the third axis of rotation C. During rotation of the second actuator 10a, the movable platform 5 is simultaneously ro- tated around the second B and third C axes of rotation.

Figure 2 is a kinematic model of the manipulator of Figure 1. The kinematics of the manipulator is illustrated by the variables L1-L10, marked in sequence, and the angles v56 and v59. An advantageous embodiment according to the inven- tion is to set the angle v56=0 degrees, the axis offset L5=0, the angle v49=90 degrees, and the axis offset L7=0.

This results in a PKM that exhibits a symmetrical and thereby optimal operating range. In addition, by setting L9=0, the mass inertia caused by the object will be minimal since the object then has a minimum mean distance to the axes of rotation of the actuators. When this first choice of parameters has been made, it remains to choose the parameters L1, L2, L3, (L4+L6), L8 and L10. The ratio of L10 to L2 should be minimized to minimize the effect of geometrical errors of the joint between L2 and L3 on the position of the tip 3a of the object. A suitable value for the measurement application is L10/L2=2 in order for the measuring object not to come too close to the link L3. Also the ratio of L2 to L1 should be minimized to maintain the propagation of errors at as low a level as possible. Here, a weighing up has to be made between operating range and accuracy and a suitable value is L2/L1=1. 3. L8 is chosen somewhat shorter than L1 for the link L3 to have an optimum mean inclination relative to the circular plane generated by the rotation of L2. Finally, the ratio of L3 to (L4+L6) should be chosen such that as large an operating range as possible is obtained. A target value is L3/ (L4+L6) =2.

Figure 3 shows a PKM according to the invention with the following parameters: the angle v56=0 degrees, the axis offset L5=0 and the axis offset L700 in the kinematic mo- del. This embodiment has an inherent stress on a part 10b of the actuator 10a, the joint 12 and the part 5b of the movable platform. By angularly adjusting the joint 12, this

stress is reduced. An angular adjustment of the joint 12 should be accompanied by an angular adjustment of the probe 3, directed in the opposite direction, relative to the part 5a of the measuring probe holder. A first actuator 8a is designed as a tube and rotatably arranged on the stationary platform 4. A first motor 9 is adapted to rotate the actua- tor 8a via a gear transmission 16. A second actuator 10a is rotatably arranged on the stationary platform 4. The first 8a and second 10a actuators are coaxially arranged for ro- tation around a common fourth axis of rotation E. The se- cond actuator 10a is articulately connected to the movable platform 5 via a single-axle joint 12 with a third axis of rotation C. A second motor 17 and a gear 18 are arranged on the stationary platform 4 for rotation of the actuator 10a.

The first actuator 8a has an extent in the longitudinal direction a, which is smaller than the longitudinal propa- gation b of the second actuator 10a. The joint 12 is arran- ged with the axis of rotation C perpendicular to and inter- secting the common axis of rotation E. A first 19 and a second angle sensor comprising a coder 20 are arranged on the respective actuators 8a and 10a for sensing the angle of the angle/rotation of the respective actuator.

Figure 4 shows a further advantageous embodiment of a PKM 2 according to the invention, which is intended for the measurement application and is arranged in accordance with the advantageous parameters chosen above. In Figure 4, for the sake of clarity, the manipulator is provided with reference numerals corresponding to those of the general manipulator in Figure 1 and the manipulator in Figure 3.

Thus, the manipulator is arranged for movement of a measu- ring probe 3 in space. The manipulator comprises a statio- nary platform 4 and a movable platform 5, which consists of the probe holder 5 on which the measuring probe 3 with the tip 3a of the measuring probe is arranged. Further, the manipulator comprises two parallel kinematic connecting chains 6,7, each of which interconnecting the two plat- forms 4,5. The first parallel kinematic connecting chain 6

comprises a first joint 8 arranged with a rotatable part, actuator, 8a. The actuator 8a is provided with a secured first actuator arm 6a. The first parallel kinematic connec- ting chain 6 comprises a linkage system 11 that connects the actuator arm 6a to the movable platform 5. The linkage 11 comprises a first link 13 provided with a three-axle joint 14,15 at each end. A first motor 9 is adapted to rotate the actuator 8a via a gear transmission 16. The second parallel kinematic connecting chain 7 comprises a second actuator 10a, which is articulately connected to the movable platform 5 via a third single-axle joint 12 with an axis of rotation C. The first 8a and second 10a actuators are rotatably arranged on the stationary platform 4 for ro- tation around a common fourth axis of rotation E. A second motor 17 with a gear 18 is arranged on the stationary plat- form 4 for rotation of the actuator 10a. The first 8a and second 10a actuators are coaxially arranged where the first actuator 8a is designed as a tube arranged to coaxially circumscribe the second actuator 10a. The first actuator 8a has an extent in the longitudinal direction a, which is smaller than the longitudinal propagation b of the second actuator 10a along the axis of rotation E. The joint 12 is arranged with the axis of rotation C perpendicular to and intersecting the common axis of rotation E of the two actu- ators. During rotation of the first actuator 8a around the axis of rotation E, the movable platform 5 is rotated around the axis of rotation C. During rotation of the se- cond actuator 10a around the axis of rotation E, a rotation 5 of the platform around both axes of rotation C and E is obtained. The drive means 9 and 17 are assumed to include gearboxes for obtaining an optimum gear ratio between the rotor of a motor included therein and the actuators 8a and 10a. Angle sensors in the form of coders 19,20 are adapted to measure the axis angles of the actuators 8a and 10a. The stationary parts of the respective angle sensors are mount- ed on a beam 21.

Figure 4 shows two extreme positions for the manipulator according to the invention, namely, position I with a measuring probe 3 in an upper position, and position II with the probe 3 pointing downwards in the picture and towards the viewer as viewed from the plane of the paper.

Figure 5 shows the PKM according to the invention with a probe 3 arranged in the very centre of the device at a point where the axes of rotation C and E intersect each other. By rotating the first 8a and second 10a actuators synchronously, circles for the tip 3a of the probe are obtained at the level given by the relative angle of rota- tion between the actuators 8a and 10a. Figure 6 illustrates an operating range that corresponds to all directions with a probe centre on the spherical hemisphere. The operating range is expressed in spherical coordinates according to the following when the radius r is kept constant: - n x 2 x Pi < V1 <-n x 2 x Pi 0 <= V2<3 x Pi/4 When the manipulator according to Figure 5 is activated, by relative movement between the two actuators 8a and 10a, the joints 14 and 15 each describe a circle shown in Figure 7.

The arrows introduced in the figure show the position 13a of the link 13 mounted between the joints 14 and 15 at dif- ferent relative actuator angles.

Figure 8 shows a modified form of the manipulator in Figure 7. The actuator arm 6a is here articulately connected to the actuator 8a in a fourth single-axle joint 22 with an axis of rotation F, which intersects the axis of rotation E at right angles. The actuator arm 6a may hence be angled upwardly and downwardly, thus obtaining a larger operating range. The upward/downward movements are given by an extra link 23. The thicker line in Figure 8 shows how the joint 14 on the actuator arm 6a moves and the arrow P shows that the operating range is now larger relative to that of Figure 7a. This modified form is equipped with a motor, a

gear and an encoder, belonging to each actuator, in accor- dance with the above.

Figure 9 is a PKM according to the invention, intended for, for example, laser applications. In simplified terms, the embodiment may be described as a PKM where the first and second actuators 8a and 10a according to Figures 1-8 have changed places. Figure 9 shows an example with a laser gun, to which a process medium is passed in a simple manner through the centre 26 of the first actuator 8a. Two mirrors 24,25 are used for deflecting the laser light. One of the mirrors 24 is secured to the gun and the other mirror 25 is secured to the second actuator 10a. The mirror 24 is centred to the gun axis G and the axis of rotation C of the platform and makes a 45'angle relative to these axes.

Besides being centred to the axis C, the second mirror 20 is also centred to the common axis of rotation E of the actuators and makes a 45° angle relative to both of these axes.

Figure 10 is a parallel kinematic manipulator 2 in accor- dance with the present invention, comprising two parallel kinematic connecting chains 6 and 7. The manipulator com- prises a first actuator 8a, which is driven to rotate by a first motor 9 via a belt transmission 27. The actuator 8a is designed as a tube coaxially arranged and rotatably journalled for rotation around a second actuator 10a. The second actuator 10a is driven to rotate by a second motor 11. The two motors 9 and 11 are secured to a stationary platform 4. A first actuator arm 6a is secured to the first actuator axle 8, and hence the motor 9 controls the pivot- ing of the parallel kinematic connecting chain 6. A second actuator arm 7a is secured to the second actuator 10a, and hence the second motor 11 controls the pivoting of the se- cond parallel kinematic connecting chain 7. The two actua- tor axles 8a and 10a are adapted to rotate around a common axis E. A third arm 28 is arranged, via a single-axle joint 12, on the second actuator axle 10a, the axis of rotation

of the joint being adapted to coincide with the axis of rotation E. The arm 28 comprises the links 28a, 28b, 28c and 28d. The third arm 28 supports a single-axle joint 12 with the axis of rotation C, on which a movable probe hol- der 25 is mounted. The measuring probe holder 29 comprises the rods 29a, 29b, 29c, 29d and 29e. The rod 29a supports the measuring probe 3. The rods 29a, 29b and 29d are, at their respective ends, arranged on one part 12a of the third joint 12. The rod 29e is connected, at one end, to the actuator arm 6a via a joint 30, a link 31 and a joint 32. The rod 29e is connected, at its other end, to the actuator arm 7a via a joint 33, a link 34 and a joint 35.

The rod 29e is arranged between the joints 30 and 33 and in parallel with the axis of rotation C. The symmetry of the manipulator is stated in Figure 10 based on the coordinate system introduced therein. The actuator arm 6a propagates in a direction perpendicular to the actuator 8a and the actuator arm 7a propagates in a direction perpendicular to the actuator 10a. The axis of rotation C forms an angle relative to the axis of rotation E. The symmetry causes the probe to pivot in a vertical plane when the two arms 6a and 7a are pivoted relative to each other. Further, the symme- try causes the probe to pivot in a horizontal plane when the two arms 6a and 7a are pivoted synchronously. Hence, it is possible to manipulate z to an unlimited extent and (px/ (py about 70°. This implies a possibility of imparting to a measuring probe all the orientations that are required in connection with measurement. By manufacturing the movable arm system from carbon-fibre material and since drive and measuring system are not included in the moving mass, high acceleration levels are achieved with very light motors and gearboxes.

Figure 11 is a light-weight design of the joints 30,32, 33 and 35, of which only one pair is shown in the figure. The link 31 is divided into two links 31a and 31b, which are retained by resilient elements 36 and 37. The joints 30 and 32 themselves consist of ball joints with pairs of sockets

30a, 32a and balls 30b, 32b, respectively. To make it pos- sible to change the orientation of the probe holder 29, a bearing 38 has been introduced.

Figure 12 is a manipulator according to Figure 10 with the measuring probe 3 arranged in a first direction. Figure 13 shows a corresponding manipulator in a second position, about 90 degrees relative to the direction in Figure 12. In addition, the figures show the possibility of extending the actuators 8a and 10a in a simple manner.

Figure 14 shows the manipulator in Figures 12 and 13 modi- fied by arranging both actuator arms 6a and 7a connected to the movable platform 5 in a common joint 39.

Figure 15 is a PKM with a first 6a and a second actuator arm 7a arranged on the movable part/actuator 8a of the first joint for rotation around an axis of rotation E. A movable platform 42 is articulately connected to the actuator arm 7a via the links 43 and 44. The movable plat- form 42 is articulately connected to the actuator arm 6a via the links 45 and 46. The links 43 and 44 are arranged in a triangular configuration with a common joint 47 on the outer end of the second actuator arm 7a. In the same way, the links 45 and 46 are arranged in a triangular configura- tion with a common joint 48 on the outer end of the first actuator arm 6a. All the joints arranged on the movable platform are arranged along a common axis.

Figure 16 is a PKM according to Figure 15 with a third link 49 arranged with one of its ends connected in the joint 47 and with its other end articulately connected to a lever arm 50, which is part of a movable platform 51. The third link 49 is part of a third triangular configuration, which locks the rotation of the movable platform around its longitudinal axis.

Figure 17 is an alternative embodiment of a PKM with a first 6a and a second actuator arm 7a arranged on the movable part/actuator 10a of a second joint for rotation around a common axis of rotation E. A movable platform 54 is connected to the actuator arm 7a via the links 55,56 and 57, which at one end are articulately connected to the actuator arm 7a in the common joint 52 and at their other end are connected to the movable platform, without any joints, in a triangular configuration. In this embodiment, the actuator arms 6a and 7a are arranged on the upper actuator 10a. This makes possible an extended range for the manipulator and hence the probe.

Figure 18 is a PKM according to Figure 17 with one actuator arm 58 arranged to be rotatable around its longitudinal axis H. The actuator arm 58 is connected to the movable platform 64 via two links 62 and 63. The links 62 and 63, respectively, are at one end articulately connected to the platform 64. The other ends of both links 62 and 63 are fixedly connected to a rotatably arranged bearing ring in a bearing 61 arranged on the actuator arm 58. The axis of rotation K of the bearing 61 is arranged perpendicular to the axis of rotation H of the actuator arm. A motor 59 is arranged on the actuator arm 58 to rotate the movable plat- form 64, via a transmission 60, around an axis of rotation I. The inventive concept comprises arranging a PKM accor- ding to Figure 18 in the same way as in Figure 17, that is, on an upper actuator, to improve the range (not shown).

General to all the shown embodiments of the industrial ro- bot, according to the invention, with the parallel kinema- tic manipulator is that each respective actuator is driven with its own motor arranged in the kinematic connecting chain, or, alternatively, by an external source of power arranged on or outside the stationary platform.




 
Previous Patent: WO/2003/078110

Next Patent: AUTOMATIC PROCESS CONTROL