WO1994018460A2

WO1994018460A2 - Forcibly coupled double joint

Info

Publication number: WO1994018460A2
Application number: PCT/EP1994/000269
Authority: WO
Inventors: Wolfgang Schröter
Original assignee: Schroeter Wolfgang
Priority date: 1993-02-01
Filing date: 1994-01-31
Publication date: 1994-08-18
Also published as: DE4303152A1; WO1994018460A3

Abstract

Rotary joints allow bodies movable around one or several axes to be rotated with respect to a fixed base body. The joint also allows possible forces and moments to be transmitted. There are provided rotary joints with non-aligned axes, in which the essential forces and moments are transmitted by prestressable traction and compression elements.

Description

description

"Forced coupled double gels ke"

Rotational joints (RG) are frequently used construction elements in technology and especially in mechanical engineering. Such joints consist of a fixed base body (GK) and a body attached to it, but rotatable about one or more axes (iF referred to as a rotating body or DK), the bearing and the axis, which is firmly connected to the GK and on which the DK rotates (Müller, HW: Kompendium Maschinenelemente, Darmstadt-Eber-Stadt: 1980, p. 7/1). A basic distinction is made between rotary joints with an aligned and non-aligned axis of rotation (guideline VDI 2861, sheet 1). The possibility of turning an RG is known as the degree of freedom (FG). For the kinematic modeling of an RG, the origin of the base coordinate system of the joint is usually laid. into the stationary base body so that the axis of rotation of the RG is identical to the z-axis of this coordinate system (notation according to Denavit / Hartenberg).

In technology, several RGs are often coupled together. In such cases, one speaks of kinematic chains (Warnecke, H.-J .; Schraft, R.D. [ed.]: Industrieroboter. Handbuch für Industrie und Wissenschaft, Berlin, etc.: 1990, p. 9). An example of such a kinematic chain is the classic universal or industrial robot (Warnecke, H.-J .; Schraft, R.D .: op. Cit., P.25).

In addition to the task of enabling rotary movements, an RG must also be able to transmit loads in the form of occurring forces and moments. These arise through the earth or rotary acceleration of the RG itself and, if applicable, in connection with the acceleration of payload masses which are coupled to the DK. In principle, six forces and six moments are possible as loads, considering the three translational and three rotational degrees of freedom in space and taking into account the possible signs + and -. The size of these loads determines the necessary load-bearing capacity of an RG.

In conventional RG, these loads are essentially transmitted by means of the cardan shaft. This is to be designed for multiple loads (pull, push, push). Since the most unfavorable case is always to be taken as a basis for the dimensioning, the cardan shafts of conventional RG have to be dimensionally overdimensioned.

The multiple loading also leads to superimposed deformations in the articulated shaft, so that the cause (lateral force bending, torsion etc.) cannot be recognized immediately or no longer at all. For controlled precision mechanisms such as This would be desirable for robots.

For use in precision mechanisms, RG also require the option of preloading. For example, Rolling bearings are preloaded axially in order to reduce or even eliminate the axial and radial bearing play. However, the axial preloading of bearings leads to increased friction, since the preload forces act on the full circumference of the bearing in addition to the normal operating forces. This type of preload goes hand in hand with a corresponding reduction in the efficiency of the bearing and thus with the RG as well as with increased wear (Müller, H.W .: op. Cit., P. 9/1 - p. 9/11).

A pivot range is characteristic of an RG with a non-aligned axis of rotation. A swivel range of 360 degrees and more is only achieved here if the longitudinal axis of the DK has a lateral offset to the longitudinal axis of the GK (incl. game: Elbow joint on the MANUTEC R3 robot, see also Warnecke, H.-J .; Schraft, RD: loc. Cit., P.109).

The protection claims submitted deal with a new type of construction for rotary joints with a non-aligned axis of rotation, in which, depending on the design, some or all possible external forces and moments are transmitted by tension and compression elements in the sense of a "one-purpose application", ie that tensile forces eg through ropes, tapes or straps, compressive forces e.g. by compression rods and shear forces e.g. with cruciate ligaments, which can also be found in a similar way in the human knee joint. Due to the uniaxial loading of the elements, these elements, which are ideal constructions in terms of lightweight construction, can be designed to be mass-minimal without effort (Wiedemann, J .: Leichtbau, Vol. 1: elements, pp. 1-7, Berlin, etc.: 1986).

With the registered construction principle, the tension and compression elements are arranged along the force paths in the joint. This way, the deformations of the tension and compression elements can be used to infer the causal loads and their negative influence e.g. take into account the positioning and repeatability of a robot directly in the system control.

The design of the novel joint principle also enables a joint preload that only acts in the direction of the operating loads. This specific type of preload has only a minor influence on the efficiency and wear of the RG.

The registered joint principle also allows a swivel range of 360 degrees or more without the longitudinal axes of the GK and DK having a lateral offset. This is made possible kinematically by two rotation axes that are connected in series and are positively coupled to one another. Because of this, the designation of the invention was also called "Forced Coupled Double-Joint" (ZDG). The principle of the ZDG can be clearly illustrated using a construction that is based on two cylinders that roll on each other (Fig. 1 b), which only touch at the moment pole (Fig. 1b: 7) and a combination of tension elements (Fig. 2a: 1; Image 3: 2 and 3; Image 4a: 1 and 2; Image 4b: 1 and 2; Image 4c: 1 and 2) are guided in their relative movement. The pictures 4a, 4b and 4c represent variants which can be used independently or in combination. In this view model, the instantaneous pole lies on the normal which connects the two axes of rotation of the cylinders to one another.

The two cylinder axes represent one of the two axes of the ZDG kinematically, which is about the function

are coupled, with which the trajectory (Figure 1c: 8) of point P (Figure 1c: 9) is clearly defined. The index i quantifies the angle of rotation of the cylinder relative to the base coordinate system of the ZDG, which represents the locally fixed GK, and the index (i-1) that of the cylinder, which represents the angle of rotation of the DK relative to the base coordinate system of the ZDG. With the same diameter of the two cylinders, the coupling is consequently

q, = q _μι = q / 2 (Fig. 1d).

Which elements are responsible for the transmission of the possible external loads +/- F _X , +/- F _y , +/- F _Z , +/- M _X , +/- M _y and +/- M _Z (Fig. 3) can be illustrated at the joint position q = 0 degrees (Figure 1b):

The tensile force + F _X is absorbed by tensile elements (Fig. 2a: 1 and 2)

- For example, as a tension belt - are guided over belt wheels (Fig. 2a: 5, 6, 7, 8), one of which has a wheel on the adjacent joint body (Image 2a: 3 or 4) and the other must be rotatably mounted. For example, one wheel (Fig. 2a: 6) can be attached to the adjacent joint body (Fig. 2a: 3), while the other wheel (Fig. 2a: 5) is rotatably mounted on the joint body (Fig. 2a: 4). On the opposite side, the wheel (Figure 2a: 8) can be mounted on the joint body (Figure 2a: 4) shown here, while the associated other wheel (Figure 2a: 7) is mounted in the body (Figure 2a: 3). This construction can only be rotated if the diameter of the base body (Fig. 2a: 3, 4) is larger than that of the rotatably mounted wheels, so that they do not touch each other at the moment (Fig. 1b: 7).

The corresponding pressure force -F _x is transmitted between the cylinders via the instantaneous pole of the rolling motion (Fig. 1 b: 7). A variant is possible by means of a force transmission using a pressure rod (Fig. 2b: 1), which must then be articulated on both sides, for example on a bearing journal (Fig. 2b: 2).

The shear forces +/- F _y are transmitted through the outer cruciate ligaments (Fig. 3: 2, 3), which are to be fixed at their end points.

- The shear forces +/- F _Z are determined by the so-called inner cruciate ligaments (Figure 4a:

1, 2; Image 4b: 1, 2; 4c: 1, 2), which are to be fixed at their end points.

The moments +/- M _X are transmitted as an antimetric force pair by means of the external cruciate ligaments.

The moments +/- M _y are also offset by an antimetric force pair: the tensile force component via the elements (Fig. 2a: 1) on the respective tensile side, the associated compressive force component via the instantaneous pole on the pressure side (Fig. 1 b: 7) or over the pressure rod (Image 2b: 1).

The moments +/- M ₂ are transmitted in terms of their pressure component via the tension belts on both sides of the ZDG, while the pressure component can be supported via the momentary pole or the pressure rods (Fig. 2b: 1). When using the ZDG for driven joints, +/- M _{z could represent} the drive torque.

When the joint angle q changes, this assignment changes mathematically continuously. The only exceptions are the shear forces +/- F _Z. Their transmission is guaranteed for all q by the inner cruciate ligaments. The change in the load transmission is, due to the joint kinematics, unique for each joint angle q.

Claims

Claims "Forcibly coupled double spirits"

1. Rotary joint (RG) with a non-aligned axis of rotation for applications as a construction element, characterized by two rolling bodies that roll on each other and touch each other at the momentary pole (Fig. 1 b: 7) and can be rotated around the two positively coupled axes (Fig. 3: 6, 7) (Fig. 1b 1 and 2) with a cylindrical shape and with the radii R1 (Fig. 1b 3) and R2 (Fig. 1 b: 4) and the joint angles q, (Fig. 1 b: 5) and q _M (Fig. 1 b

6), where q = q _; + q (Figure 1 b) and where for the case R1 = R2 it holds that q = q _; = q _M = q / 2 (Fig. 1d), due to the ability to measure the possible forces +/- F _X , +/- F _y , +/- F _Z (Fig. 1a) and the possible moments +/- M _X , +/- M _y and +/- M _Z (Fig. 1a) through the combination of single-purpose power transmission elements fixed or mounted at the end points (Fig. 2a: 1; Fig. 3: 2, 3;

Image 4a: 1, 2; Image 4b: 1, 2; 4c: 1, 2) to be transferred.

2. RG according to claim 1, characterized by a pressure force transmission in the form of a pressure rod rotatably mounted at the end points (Figure 2b: 1).

3. RG according to claim 2, characterized by more than one pressure rod.

4. RG according to claim 1, characterized by arbitrarily designed joint body with the same function as in claim 1.

5. RG according to claim 1, characterized by articulated bodies that are not in contact in the moment tan pole.

6. RG according to claim 1, wherein the tension elements (Figure 2a: 1; Figure 3: 2, 3; Figure 4a: 1, 2, Figure 4b: 1, 2; Figure 4c: 1, 2) in each case with the same function in multiple execution are available.

7. RG according to claim 1, wherein only one or a part of the possible loads is transmitted by single-purpose power transmission elements.

8. RG according to claim 1, wherein the number of positively coupled axes (Figure 3: 6, 7) is not equal to two.

9. RG according to claims 1 to 8, in which the power transmission elements (Figure 2a: 1; Figure 3: 2, 3; Figure 4a: 1, 2; Figure 4b: 1, 2; Figure 4c: 1, 2) in addition to one Individual loads also have to endure tensile, pressure and thrust in any combination.