Joint assembly with differential gear and cable pull for a robot, as well as robot arm and robot

Abstract

The invention relates to a joint arrangement (3) for a robot arm (2) of a robot (1), comprising: - a first support element (4) which is arranged about a pitch axis (6) relative to a receiving segment (5) of the robot arm (2) which receives the first support element (4); - a second support element (7) which is pivotably arranged about a yaw axis (8) relative to the first support element (4); - an end effector (9) which is pivotably arranged about a roll axis (10) relative to the second support element (7); - a differential gear (11) comprising two symmetrical bevel gears (12, 13) and a pinion gear (14) meshing with both bevel gears (12, 13), wherein each bevel gear (12, 13) has an associated deflection pulley (15, 16) for receiving a respective cable pulley (17, 18) with two cable strands (19, 20, 18). 21, 22) is arranged in a rotationally fixed manner, wherein the respective deflection pulley (15, 16) is operated by means of the associated cable pulley (17,18) is rotatable in opposite directions of rotation in order to pivot the second support element (7) about the yaw axis (8) and / or the end effector (9) about the roll axis (10), and an actuating device (23) configured to pivot the first support element (4) about the pitch axis (6) by means of a connecting rod (24). The invention further relates to a robot arm (2) and a robot (1).

Description

The invention relates to a joint arrangement for a robot arm of a robot, in particular a cable pull robot. The invention further relates to a robot arm having at least one such joint arrangement. The invention also relates to a robot having such a robot arm.From the prior art, robot joints with cable drives are known in order to carry out a pitch, yaw and roll movement on an end effector, in particular a wrist, of a robot arm. The cable drive reduces the inertia of the robot arm and makes it safe for the human-robot interaction. By implementing the cable drive on the wrist of the robot arm, people are less prone to injury if the robot arm accidentally hits the person, since the joint is light and has a low moment of inertia. The pitch and roll motion is usually implemented by a cable-driven differential gear. However, the yaw motion is driven by two twisted ropes. The friction of the two cables which are twisted into one another can lead to durability problems over the service life.For example, DE 10 2004 059 235 B3 discloses a driven joint unit for a robot, comprising two drive rollers which are driven by a motor in each case and are mounted coaxially in a frame, a differential bevel gear stage, consisting of two deflection bevel gears which form a first bevel gear pair and are mounted coaxially in the frame parallel to the axes of the coaxial drive rollers and whose axes running in the direction of a first robot axis form a first joint axis, and two coaxially arranged output bevel gears which form a second bevel gear pair and whose axes run in the direction of a second joint axis perpendicular to the first joint axis. One of the two output bevel gears is firmly connected to the output, and the other, opposite coaxial output bevel gear is mounted rotatably freely movable. Furthermore, prestressed traction means are provided, of which at least two traction means fastened to the two drive rollers are guided in each case in opposite directions around a part of the respectively adjoining deflection bevel gear and are fastened to the adjacent driven bevel gear that is freely movable in rotation or to the driven bevel gear that is firmly connected to the output.Further joint arrangements are also disclosed in DE 27 44 903 A1, JP 2001-170 883 A, JP 2022-016 327 A and WO 2025 / 136 055 A1, wherein WO 2025 / 136 055 A1 is post-published.The object of the invention is to improve the durability and precision of a cable operated joint arrangement and to reduce the mechanical load of the cables. The object is achieved by the subject matter of claim 1.A joint arrangement according to the invention for a robot arm of a robot comprises a first carrier element which is arranged such that it can be pivoted about a pitch axis relative to a receiving segment of the robot arm receiving the first carrier element, a second carrier element which is arranged such that it can be pivoted about a yaw axis relative to the first carrier element, an end effector which is arranged such that it can be pivoted about a roll axis relative to the second carrier element, a differential gear having two symmetrical ring wheels and a pinion bevel gear which is in toothed engagement with both ring wheels, wherein an associated deflection roller for receiving a respective cable pull having in each case two cable pulls is arranged such that it cannot rotate, and wherein the respective deflection roller can be rotated by means of the associated cable pull in opposite rotational directions in order to pivot the second carrier element about the yaw axis and / or the end effector about the roll axis, and an actuating device which is designed to pivot the second carrier element about the yaw axis and / or the end effector about the roll axis, pivoting the first carrier element about the pitch axis by means of a connecting rod.While the yaw and roll movement takes place by actuation of the differential gear by means of the cable pulls, the pitch movement is realized by a mechanical actuation of the first carrier element with a connecting rod. The advantages of such a joint arrangement lie in the precise control of the movements and the improved durability by decoupling the pitch movement from the cable-based drives for yaw and roll movements. Rubbing of twisted ropes as known from the prior art is thus prevented.By means of the differential gear, a yaw angle between the two carrier elements and a roll angle between the second carrier element and the end effector can be adjusted. The corresponding movements can be carried out simultaneously, if necessary. By means of the actuating device, a pitch angle of the first carrier element relative to the receiving segment of the robot arm can be adjusted. The receiving segment can be part of an arm segment of the robot arm or form the arm segment, in particular the forearm segment, of the robot. The joint arrangement realizes a 3-DOF arrangement on the receiving segment of the robot arm.By actuating the cable pulls, a rolling movement of the end effector relative to the second carrier element and / or a yaw movement of the second carrier element relative to the first carrier element is carried out via the differential gear. If a first cable strand of the respective cable pull is pulled, cable length must likewise be released on the remaining second cable strand of the same cable pull, so that the associated deflection pulley is set in rotation. The deflecting rollers can be driven via the associated cable pulls selectively in the same or in opposite directions and at different speeds. In this sense, the cable strands of the respective cable pull are operatively connected to an associated actuator in order to be able to rotate the deflection rollers or the ring wheels independently of one another or separately.Thus, the deflecting rollers can be actuated separately with the ring gears. "Separately actuatable" means in this context that the cable pulls can be actuated individually and independently of one another in order to set the roll and / or yaw angle of the joint arrangement. Each deflecting roller can be formed integrally with the associated ring gear.The actuator of the respective cable pull can have a rotationally drivable cable pulley, to which the cable strands of the respective cable pull can be fastened, in particular wound. The two cable strands of the respective cable pull can be separate cables. Alternatively, the cable strands can be a coherent, i.e. one-piece cable, which is correspondingly wound on the mentioned cable pulley of the actuator and on the associated deflection pulley. The deflecting roller can have means for fastening the cable strands. The actuator of the respective cable pull can be designed as an electric machine, comprising a stator fixed to the housing and a rotor arranged rotatably thereto, in order to wind one cable strand of the respective cable pull up and to wind the corresponding other cable strand of the same cable pull equally, depending on the direction of rotation of the rotor.If the deflecting rollers rotate in the same direction, for example at the same rotational speed, the yaw movement of the end effector relative to the second carrier element is carried out. With the same rotational speed of the deflection rollers in the same direction, the pinion bevel gear is stationary and only the second carrier element is pivoted about the yaw axis relative to the first carrier element, in that the longitudinal axis or the roll axis of the pinion bevel gear rotates about the yaw axis.However, if the deflection rollers rotate at different speeds, a corresponding rotation of the pinion bevel gear about the rolling axis takes place in order to execute the rolling movement of the end effector.Depending on the direction of rotation and the speed of rotation of the deflection rollers, a combination of rolling and yawing movements can also be carried out simultaneously.Roll-pitch-yaw angles (referred to as "roll-pitch-yaw angle") are specific position angles which are used to describe the orientation of an object in three-dimensional space. The rolling, pitching and yawing can be combined as "roll-pitch-yaw motions" (in English "roll-pitch-yaw motions" or "RPY" for short). Preferably, the roll axis crosses both the yaw axis and the pitch axis, and the yaw axis and the pitch axis do not cross.The differential gear is preferably arranged in an interior space bounded by the first and second carrier elements. The joint arrangement can thereby be configured compactly.The cable of the respective cable pull is preferably formed from fiber composite material. The cable is a high-performance cable, preferably made of Dyneema® fibers.Preferably, the two carrier elements are arranged freely pivotable about the yaw axis. The connection between the two carrier elements is effected only via the differential gear.The actuating device is an actuator for carrying out the pitching movement of the joint arrangement, in particular of the wrist of the robot arm, about the pitching axis. The actuating device realizes a precise, direct, i.e. non-translated, actuation of the first carrier element. The connecting rod of the actuating device holds the joint arrangement together with the receiving segment of the robot arm in its position and controls the pitching movement of the entire joint arrangement by corresponding actuation of the actuating device. The connecting rod is connected in an articulated manner to the first carrier element. By extending or telescoping or by retracting or pushing together the connecting rod by a corresponding actuator of the actuating device, the first carrier element can be pivoted about the pitch axis. It is conceivable that several connecting rods are provided in order to provide the construction with more stability.Preferably, the cable strands of the cable pulls are deflected on the first carrier element. This leads to an improved cable routing and reduces mechanical loads. The cable strands can be deflected by rods, bolts, deflection rollers or the like. The cable strands slide off at the deflection points.According to one exemplary embodiment, each cable strand is deflected on a first deflection rod arranged on the first carrier element. Preferably, all cable strands are deflected on a common second deflection rod which is arranged lying on the pitch axis. In the longitudinal extension of the cable strands, the first deflection rods are thus each arranged between the second deflection rod and the associated deflection roller. Each cable strand is deflected via a respective first deflection rod, wherein all cable strands are deflected jointly via the common second deflection rod. The cable strands are therefore deflected twice thereafter. A rotational or multiple deflection is also conceivable in principle.Preferably, the second deflection rod is arranged spatially between the first deflection rods of the first cable pull and the first deflection rods of the second cable pull. Accordingly, the cable strands are guided from the respective first deflection rod toward a central axis of the joint arrangement or toward the center of the receiving segment on which the joint arrangement is arranged. This arrangement optimizes load distribution and cable routing.The invention includes the technical teaching that the cable strands of the respective cable pull are each wound multiple times around the associated deflection pulley. Accordingly, the deflection roller is in each case designed as a drum disk. The multiple winding of the deflection pulley improves the durability of the cable pull and the stability and reliability of the system. Alternatively, the respective deflecting roller can also be designed as a simple pulley for the simple deflection of the cable pull.Preferably, the ring gears and the deflection rollers are arranged coaxially and axially spaced apart from one another and freely rotatable on the second carrier element. The ring gears and the deflection rollers can be rotatably mounted on a support element of the second support element. The longitudinal axis of the pinion-bevel gear is pivotable about the longitudinal or rotational axes of the ring gears for carrying out the yaw movement.According to a second aspect of the invention, a robot arm for a robot comprises a joint arrangement according to the first aspect of the invention. The robot arm is also to be understood as a manipulator arm. The robot may comprise one or more such robot arms which are separately controllable from each other.According to a third aspect of the invention, a robot comprises a robot arm according to the second aspect of the invention and / or a joint arrangement according to the first aspect of the invention. In particular, the joint arrangement according to the invention is arranged in a robot arm or robot arm segment, for example in a robot wrist joint. The robot can be a so-called articulated robot, the robot arm of which has a base and a plurality of robot arm segments arranged one behind the other and connected to one another via joints. The joint arrangement is arranged at the end of the robot arm opposite the base, wherein a further device, such as a gripping device, a manipulation device or the like, can be arranged on the joint arrangement, in particular on the end effector. The robot is preferably a cable robot.Each robot arm segment is designed to absorb forces and moments which are introduced into the robot arm in particular by a tool arranged on the joint arrangement, and to transmit them from one joint to a subsequent joint to the base. In addition, forces and moments which originate from the self-weight force of the robot arm are also transferred into the base of the robot arm. Each robot arm segment of the robot arm has for this purpose at least one structural part which is designed to be able to absorb and transmit these forces and moments.The above definitions and statements regarding technical effects, advantages and advantageous embodiments regarding the joint arrangement according to the first aspect of the invention also apply analogously to the robot arm according to the second aspect of the invention and to the robot according to the third aspect of the invention, and vice versa.Further measures which improve the invention are illustrated in more detail below together with the description of a preferred exemplary embodiment of the invention on the basis of the figures, identical or similar components being provided with the same reference sign. This shows FIG. 1 shows a schematic perspective illustration of a robot according to the invention, which is only partially illustrated, in the form of a cable-pull robot, and FIG. 2 shows a schematic view of a joint arrangement according to the invention of the robot according to FIG. 1.According to FIG. 1 in conjunction with FIG. 2, a robot arm 2, shown here only partially, of a robot 1 is shown. The robot 1 is designed as a cable robot, wherein the robot arm 2 correspondingly forms a cable robot arm. FIG. 1 shows a part of the forearm of the robot arm 2 in the form of a receiving segment 5. At the free end of the receiving segment 5, a joint arrangement 3 according to the invention is arranged, which forms the wrist of the robot arm 2. The structure and function of the joint arrangement 3 will be described in more detail below.The joint arrangement 3 comprises a fork-shaped first carrier element 4 which is arranged such that it can be pivoted about a pitch axis 6 relative to the receiving segment 5 of the robot arm 2. The receiving segment 5 has a plurality of arm rails 30 with a bolt 31 which lies on the pitch axis 6. Furthermore, an actuating device 23 with a connecting rod 24 is provided, wherein the connecting rod 24 is arranged directly articulated on the first carrier element 4. An actuator 32 of the actuating device 23 indicated in FIG. 2 is designed to actuate the connecting rod 24 in such a way that the first carrier element 4 can be pivoted precisely about the pitch axis 6. The operating device 23 adjusts the inclination of the wrist. The connecting rod 24 can be designed or arranged to be axially displaceable or retractable or extendable in the direction of a double arrow 33 shown in FIG. 2. The actuation of the first carrier element 4 with the connecting rod 24 improves the accuracy of the robot arm 2 compared to pure cable drives.The joint arrangement 3 also comprises a likewise fork-shaped second carrier element 7, which is arranged such that it can be pivoted about a yaw axis 8 relative to the first carrier element 4, and an end effector 9, which is arranged such that it can be pivoted about a roll axis 10 relative to the second carrier element 7. The end effector 9 is mounted rotatably, for example slidingly, relative to the second carrier element 7.Spatially arranged between the first and second carrier elements 4, 7 is a differential gear 11 which has a first ring gear 12 which is connected in a rotationally fixed manner to a first deflection roller 15 and a second ring gear 13 which is connected in a rotationally fixed manner to a second deflection roller 16. Ring gear-deflection roller combinations are configured symmetrically to one another. The ring gears 12, 13 mesh with a pinion bevel gear 14, which in turn is connected to the end effector 9 in a rotationally fixed manner. The ring gears 12, 13 and the deflection rollers 15, 16 are arranged coaxially to one another and freely rotatably on the second carrier element 7. In addition, a support element 34 is provided on the second support element 7, which holds the ring gears 12, 13 and the deflection rollers 15, 16 in position and rotatably supports them.The first deflection pulley 15 is provided for receiving a first cable pull 17, the first cable pull 17 has two cable strands 19, 20. The cable strands 19, 20 of the first cable pull 17 are each deflected in the direction of the pitch axis 6 by an associated first deflection rod 25, wherein the mentioned bolt 31 forms a second deflection rod 27 in order to deflect the cable strands 19, 20 of the first cable pull 17 a second time, such that the cable strands 19, 20 of the first cable pull 17 can be guided in the central region of the receiving segment 5 to an associated actuator 28 indicated in FIG. 2.The second deflection pulley 16 is provided for receiving a second cable pull 18, the second cable pull 18 having two cable strands 21, 22, the second deflection pulley 16 being rotatable in opposite rotational directions by means of the second cable pull 18. The cable strands 21, 22 of the second cable pull 18 are each deflected by an associated first deflection rod 26 in the direction of the pitch axis 6 and by the second deflection rod 27 a second time, so that the cable strands 21, 22 of the second cable pull 18 can be guided in the central region of the receiving segment 5 to an associated actuator 29 indicated in FIG. 2. The second deflection rod 27 is situated spatially between the first deflection rods 25 of the first cable pull 17 and the first deflection rods 26 of the second cable pull 18.The cable strands 19, 20, 21, 22 of the cable pulls 17, 18 are wound multiple times around the associated deflecting roller 15, 16, wherein the deflecting rollers 15, 16 can be rotated separately from one another and at different rotational directions and rotational speeds. Rotation of the pulleys 15, 16 at the same speed and direction of rotation causes the pinion bevel gear 14 and the end effector 9 to pivot about the yaw axis 8 to adjust the yaw angle of the wrist. The yaw movement is carried out at the same rotational speed of the deflection rollers 15, 16, without the end effector 9 being rotated. If the deflection rollers 15, 16 rotate at different speeds in terms of amount, the pinion bevel gear 14 or the end effector 9 is set into a rolling movement about the rolling axis 10 alternatively or additionally to the yaw movement.By controlled control of the cable pulls 17, 18, the second carrier element 7 can thus be pivoted about the yaw axis 8 and / or the end effector 9 can be pivoted about the roll axis 10, wherein, decoupled therefrom, the directly controllable pitch movement of the first carrier element 4 can be controlled by means of the actuating device 23. The joint arrangement 3 is thus a 3-degree-of-freedom joint arrangement (3-DOF).List of reference characters1 Robot 2 Robot arm 3 Joint arrangement 4 First carrier element 5 Receiving segment 6 Pitch axis 7 Second carrier element 8 Yaw axis 9 End effector 10 Rolling axis 11 Differential gear 12 First ring gear 13 Second ring gear 14 Pinion bevel gear 15 First deflection roller 16 Second deflection roller 17 First cable 18 Second cable 19 First cable strand of the first cable 20 Second cable strand of the first cable 21 First cable strand of the second cable 22 Second cable strand of the second cable 23 Actuating device 24 Connecting rod 25 First deflection rod of the first cable 26 First deflection rod of the second cable 27 Second deflection rod 28 Actuator of the first cable 29 Actuator of the second cable 30 Arm rail 31 Bolt 32 Actuator of the actuating device 33 Double arrow 34 Support element

Claims

Joint arrangement (3) for a robot arm (2) of a robot (1), comprising - a first carrier element (4) which is arranged such that it can be pivoted about a pitch axis (6) relative to a receiving segment (5) of the robot arm (2) receiving the first carrier element (4), - a second carrier element (7) which is arranged such that it can be pivoted about a yaw axis (8) relative to the first carrier element (4), - an end effector (9) which is arranged such that it can be pivoted about a roll axis (10) relative to the second carrier element (7), - a differential gear (11) having two symmetrical ring gears (12, 13) and a pinion bevel gear (14) which is in toothed engagement with the two ring gears (12, 13), wherein an associated deflection roller (15, 16) for receiving a respective cable pull (17, 18) having in each case two cable strands (19, 20, 21, 22) is arranged such that it cannot rotate on each ring gear (12, 13), wherein the respective deflection pulley (15, 16) can be rotated in opposite rotational directions by means of the associated cable pull (17, 18) in order to pivot the second carrier element (7) about the yaw axis (8) and / or the end effector (9) about the roll axis (10), and - an actuating device (23) which is designed to pivot the first carrier element (4) about the pitch axis (6) by means of a connecting rod (24).Joint arrangement (3) according to Claim 1, characterized in that the cable strands (19, 20, 21, 22) of the cable pulls (17, 18) are deflected on the first carrier element (4).Joint arrangement (3) according to Claim 2, characterized in that each cable strand (19, 20, 21, 22) is deflected on a first deflecting rod (25, 26) arranged on the first carrier element (4).Joint arrangement (3) according to Claim 3, characterized in that all cable strands (19, 20, 21, 22) are deflected on a common second deflecting rod (27) which is arranged on the pitch axis (6).Joint arrangement (3) according to Claim 3 in conjunction with Claim 4, characterized in that the second deflection rod (27) is arranged spatially between the first deflection rods (25) of the first cable pull (17) and the first deflection rods (26) of the second cable pull (18).Joint arrangement (3) according to one of the preceding claims, characterized in that the cable strands (19, 20, 21, 22) of the respective cable pull (17, 18) are operatively connected to an associated actuator (28, 29).Joint arrangement (3) according to one of the preceding claims, characterized in that the cable strands (19, 20, 21, 22) of the respective cable pull (17, 18) are each wound several times around the associated deflecting roller (15, 16).Joint arrangement (3) according to one of the preceding claims, characterized in that the ring gears (12, 13) and the deflecting rollers (15, 16) are arranged coaxially with respect to one another and freely rotatably on the second carrier element (7).Robot arm (2) for a robot (1) comprising a joint arrangement (3) according to any of the preceding claims.Robot (1) comprising a robot arm (2) according to claim 9 and / or a joint arrangement (3) according to any one of claims 1 to 8.

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