robot arm

Abstract

The invention relates to a robot arm with several joints (12, 14, 16), at least one drive, the force and / or torque of which is transmitted by means of at least one traction cable (18a, 18b) via an intermediate joint (12, 14) to a target joint (16), wherein the intermediate joint (12, 14) has two cylinders (20a, 20b) that roll against each other and are connected to each other in such a way that the rotation of one cylinder (20a) is transferred to the other cylinder (20b), wherein the two cylinders (20a, 20b) of the intermediate joint (12, 14) are each connected to a deflection roller (22a, 22b, 24a, 24b) which is arranged in particular coaxially and axially offset to the respective cylinder (20a, 20b), wherein the pull rope (18a, 18b) is guided over the deflection pulleys (22a, 22b, 24a, 24b) through the intermediate joint (12, 14) such that it passes the intermediate joint (12, 14) in a plane which is axially offset from the plane in which the two rolling cylinders (20a, 20b) of the intermediate joint touch.

Description

[0001] The invention relates to a robot arm with multiple joints.

[0002] Current traction-driven robotic fingers utilize a wide variety of configurations to actuate their individual degrees of freedom. These degrees of freedom are coupled to each other to perform various functions, such as adjusting joint stiffness or reducing the number of drive units. However, this coupling also leads to increased difficulties and computational load in controlling these mechanisms, as the couplings must be considered for every movement.

[0003] Joint concepts exist that minimize or completely eliminate this coupling, but they do not allow both configurations or establish serial kinematics. Furthermore, concepts for coupling-free operation are only known for the one-dimensional case. For the two-dimensional case, coupling-free traction element routing is not known in the current state of the art.

[0004] A robot joint known from the prior art is described in: Anthropomorphic Low-Inertia High-Stiffness Manipulator for High-Speed ​​Safe Interaction - Yong-Jae Kim

[0005] Couplings between the joints increase the complexity of the control system and can limit various movements.

[0006] The joints of current finger solutions inevitably lead to couplings between them due to their mechanical design and must be taken into account during operation.

[0007] The traction elements are subjected to high loads and significantly reduce their service life, as they are usually located behind the gearbox, thus in the immediate load path.

[0008] There are rolling joints with two degrees of freedom, but only one traction element can be moved without coupling. Moving multiple traction elements is physically impossible, as they would have to intersect at the intersection of the two axes of movement.

[0009] The object of the invention is to provide a robot arm with multiple joints in which a pull cable for a target joint can be guided through an intermediate joint without coupling.

[0010] According to the invention, the problem is solved by a robot arm according to claim 1.

[0011] The robot arm according to the invention has several joints and at least one drive, the force and / or torque of which is transmitted to a target joint via an intermediate joint by means of at least one traction cable. Preferably, the robot arm has several intermediate joints.

[0012] The intermediate joint has two cylinders that roll against each other and are connected in such a way that the rotation of one cylinder is transmitted to the other. This can be achieved, for example, by designing the two cylinders as gears or by connecting them via two tension elements such as two ropes or two belts. The cylinders need not be physical cylinders; they can also be virtual cylinders, as will be shown in connection with a particular embodiment.

[0013] According to the invention, the two cylinders of the intermediate joint are each connected to a deflection roller, which is preferably arranged coaxially and offset in the axial direction to the respective cylinder. The deflection roller is preferably rotatable about the common axis.

[0014] The pull rope is guided over the deflection pulley through the intermediate joint in such a way that it passes the intermediate joint in a plane that is axially offset from the plane in which the two rolling cylinders of the intermediate joint touch.

[0015] The robot arm according to the invention enables the pull cable to pass through the intermediate joint in both coupled and uncoupled operation. Multiple pull cables can also be guided through the intermediate joint.

[0016] It is preferred that the ratio of the diameters of the two cylinders rolling against each other is identical to the ratio of the diameters of the two deflection pulleys. This enables coupling-free operation. The traction cable runs radially through the point where the two cylinders touch, but axially offset.

[0017] In coupled operation, however, the traction cable runs offset from the aforementioned point of contact between the two cylinders, even when viewed in the radial direction.

[0018] It is further preferred that an intermediate joint has several deflection pulleys, each over which a pull cable is guided, so that several pull cables are guided through the intermediate joint. In this way, it is possible to operate several joints located distal to the intermediate joint by means of several pull cables.

[0019] It is further preferred that all deflection pulleys are offset axially to their respective cylinders and to each other. This ensures that the pull cables are also offset axially to each other and thus do not overlap axially. In this embodiment, it is also possible for one or more pull cables to be guided through the intermediate joint in uncoupled operation, while one or more of the other pull cables are guided through the intermediate joint in coupled operation.

[0020] Furthermore, it is preferred that the pull rope in the target joint is connected to an end point via a pulley system arranged eccentrically to the axis of rotation of the target joint. This creates a reduction gear, so that the pull rope has to transmit less force. This also allows the required drive to be smaller.

[0021] Preferably, the target joint also has a second pulley system arranged antagonistically to the first pulley system. This second system is also arranged eccentrically to the axis of rotation of the target joint. A second pull rope is connected to a second endpoint via this second pulley system.

[0022] It is further preferred that the two cylinders are elliptical in shape. This applies at least to the sides or edges of the cylinders that face the other cylinder. The remainder of a cylinder pointing in a different direction may have a shape other than an ellipse. In this embodiment, the deflection rollers are not arranged coaxially with the cylinders, but are offset from them in the axial direction.

[0023] In this embodiment, it is preferred that each cylinder has two deflection pulleys, each arranged at one of the two foci of the ellipse. More specifically, the deflection pulleys are positioned such that, in the deflected state of the joint, the tangential lifting points of the deflection pulleys lie at the foci of the respective ellipse. The tangential lifting points are those points at which the pull cord, which is guided around the deflection pulley, leaves its circumference, i.e., no longer touches the deflection pulley.

[0024] This has the initial advantage that two pulleys can be used side by side per ellipse. In contrast, with a circular cylinder, two pulleys must be arranged coaxially (i.e., one above the other), which results in twice the overall height. Even in this design, several pulleys can be arranged axially one above the other, for example, to allow more cables to pass through a single joint.

[0025] If the deflection pulleys are arranged at the focal points of the elliptical cylinder, the pull ropes always run through the projection of the point of contact of the two elliptical cylinders, thus enabling coupling-free operation.

[0026] Preferred embodiments of the invention are explained below with reference to figures.

[0027] They show: Fig. 1a - 1c different embodiments of the cylinders according to the invention with deflection rollers; Fig. 2a and Fig. 2b an embodiment for actuation by pulleys in the target joint; Fig. 3 an embodiment of a robot arm according to the invention; Fig. 4a - 4c further embodiments of a robot arm according to the invention; Fig. 5a and Fig. 5b further embodiments of a robot arm according to the invention. Figures 6a and 6b show an elliptical design of the cylinders. Fig. 7 another embodiment with virtual elliptical cylinders. Fig. 8 a sectional view of the embodiment according to Fig. 7.

[0028] Fig. Figure 1a shows an intermediate joint 12 through which a pull rope 18a is passed. This is connected to a target joint (not shown) in order to trigger an actuation of the target joint.

[0029] The intermediate joint 12 has two cylinders 20a, 20b that roll against each other and are connected in such a way that the rotation of one cylinder 20a is transferred to the other cylinder 20b. This can be, as shown in Fig. As shown in Figure 1b, the rotation is transmitted via two traction elements 30a, 30b, for example, traction cables, which act antagonistically to each other and which are connected at their respective ends to a cylinder, for example, on its outer circumference. Alternatively, the rotation can also be transmitted via a toothed connection using gears 26, 28, as shown in Figure 1b. Fig. Figure 1c is shown. In this embodiment, cylinders 18a and 18b have a gear-shaped base.

[0030] As in Fig. As shown in Figure 1a, the two cylinders 20a, 20b of the intermediate joint 12 are each connected to a deflection pulley 22a, 22b, which is arranged coaxially and axially offset from the respective cylinder 20a, 20b. The pull rope 18a is guided through the intermediate joint 12 via the deflection pulleys 22a, 22b, such that it passes through the intermediate joint 12 in a plane that is axially offset from the plane in which the two rolling cylinders 20a, 20b of the intermediate joint 12 touch.

[0031] In the illustrated embodiment, the ratio of the diameters of the two converging cylinders 20a, 20b is identical to the ratio of the diameters of the two guide rollers 22a, 22b. This enables coupling-free operation, since the traction cable 18a, viewed radially, runs precisely through the point of contact between the two cylinders 20a, 20b. This would not be the case if the ratio of the diameters of the two cylinders 20a, 20b were not identical to the ratio of the diameters of the two guide rollers 22a, 22b. In other words, the traction element thus runs through the projection of the point of contact between the two converging cylinders 20a, 20b.

[0032] One possibility for actuating a target joint 16 is in Fig. Figure 2a shows the actuation. Actuation is achieved via two antagonistically arranged pulleys 32a, 32b, which are positioned eccentrically to the axis of rotation of the target joint 16. The two pull ropes 18a, 18b are each connected to an endpoint 34 at the target joint via a pulley 32a, 32b. This is shown in Fig. 2b visible. The pulleys thus form a reduction gear, which allows the use of smaller drives. Furthermore, the forces acting on the pull rope and the joints can be significantly reduced. A key advantage over the prior art is that the pull ropes are located in front of the gearbox and therefore not in the load path.

[0033] The endpoints of the pulleys can, for example, be connected to the two cylinders 20a, 20b along their circumference.

[0034] In Fig. Figure 3 shows an embodiment of a coupling-free joint 12 with two degrees of freedom. This is an intermediate joint.

[0035] Fig. Figures 4a-4c show an anthropomorphic finger as a coupling-free serial kinematic. As in Fig. As shown in Figure 4a, the first intermediate joint 12 has two gears that form the two cylinders 20a and 20b and roll against each other. The gear 20a is connected to two pulleys 22a and 24a, over which the two traction cables 18a and 18b are guided. At least two traction cables 18a and 18b are required because distal to the intermediate joint 12 there is another intermediate joint 14 and a target joint 16, which are operated via the two traction cables 18a and 18b.

[0036] The second cylinder 20b is arranged coaxially with the two deflection pulleys 22b, 24b, which also guide the traction cables 18a, 18b. Both traction cables run through the projection of the point of contact between the two cylinders 20a, 20b, thus enabling coupling-free operation. In this embodiment, the gears of the intermediate joint 14 are each connected only to a single deflection pulley, through which only one traction cable is guided, which in turn leads to the target joint 16.

[0037] Fig. 4b and Fig. Figure 4c shows the same robot arm from different perspectives.

[0038] In the Fig. 5a and Fig. Figure 5b shows an anthropomorphic finger in various forms. Again, two intermediate joints 12 and 14, as well as a target joint 16, are provided. The joints again exhibit characteristics similar to the embodiment shown in Figure 5b. Fig. Four gears that roll against each other.

[0039] Two antagonistically arranged pulleys 32a and 32b are located in the intermediate joint 14, mounted eccentrically to the axis of rotation of the intermediate joint 14. These actuate the intermediate joint 14. As already described, these pulleys form a reduction gear, thus reducing the required force.

[0040] The target joint 16 contains only a pulley 32a, while a spring 34 serves as the antagonist. This spring generates a force opposing the pulley 32a, so that when the pulley 32a exerts no force, the joint 16 springs back to its initial position. The robot arm according to Fig. 5a is uncoupled.

[0041] Robot arm according to Fig. 5b, on the other hand, is operated in coupled mode. This is evident from the fact that the pull rope 18a does not pass through the projection of the point of contact between the two cylinders 20a and 20b. Pulley systems are again provided for actuation. To avoid repetition, we refer to the explanations in Fig. 5a.

[0042] As in Fig. Figure 6a shows the two cylinders 20a, 20b in an elliptical shape. Similar to previous embodiments, the two cylinders 20a, 20b roll against each other. Each cylinder 20a, 20b has two deflection pulleys 22a, 22b, 24a, 24b. These are arranged such that the pull ropes 18a, 18b, which are guided on the deflection pulleys, each pass through the foci of each ellipse. This enables coupling-free operation. As shown in the deflected arrangement, which is depicted in the Fig. As can be seen in 6b, the pull ropes always run through the projection of the point of contact of the two elliptical cylinders.

[0043] Preferably, the tangential lift-off point, that is, the point at which a pull rope no longer touches the deflection pulley, is located at a focus of the respective ellipse.

[0044] In Fig. Figure 7 shows an embodiment which also has two intermediate hinges 12, 14. The first intermediate hinge 12 has two virtual ellipses as cylinders. The cylinders are therefore not formed physically, but are formed by these virtual ellipses, which are in Fig. 7 are not shown. Their function corresponds to the function of the ellipses from Fig. 6a and Fig. 6b.

[0045] The virtual ellipses 20a, 20b are in the embodiment according to Fig. 7 formed by the fact that the distances between the tangential lifting points of the deflection pulleys 22a, 24b, which are connected to each other by the pull rope 18a, and the tangential lifting points of the deflection pulleys 22b, 24a, which are connected by the pull rope 18b, always remain constant (see also Fig. 8) This is achieved by connecting the deflection pulleys 22a and 24b to each other via a first connecting lever 36a and a second connecting lever 36b to each other. The axes of rotation of the connecting levers lie on the tangential lifting point of the deflection pulleys. The constraint induced by the connecting levers forces the two virtual ellipses to roll relative to each other in such a way that the aforementioned distances are kept constant.

[0046] In a preferred embodiment, several deflection rollers can also be arranged one above the other in the axial direction. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Anthropomorphic Low-Inertia High-Stiffness Manipulator for High-Speed ​​Safe Interaction - Yong-Jae Kim

[0004]

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