GB2115779A

GB2115779A - Industrial robot

Info

Publication number: GB2115779A
Application number: GB08303274A
Authority: GB
Inventors: Eckehart Schulze
Original assignee: Hartmann and Lammle GmbH and Co KG
Current assignee: Voith Turbo H and L Hydraulic GmbH and Co KG
Priority date: 1982-02-06
Filing date: 1983-02-07
Publication date: 1983-09-14
Also published as: GB8303274D0; IT8319440A0; FR2521056B1; FR2521056A1; GB2115779B; IT1161876B; DE3204180A1; JPS58192775A

Abstract

An industrial robot, capable for instance of picking up a workpiece from a feeding arrangement and moving it into a defined desired position in a processing machine, has two articulated arms 11, 12 the kinematics of which correspond largely to those of the human locomotor system. As shown each of the articulated arms has a three-way shoulder joint 23, 24, an elbow joint 31, 32 and a three-way wrist joint 37, 36 so that grippers or working units 13, 14 provided on the wrist joints have seven degrees of freedom of pivotal movement. There is associated to each degree of freedom of pivotal movement of the articulated arms a separate hydraulic pivot drive which drives are designed partly as rotary- vane hydraulic motors and partly as hydraulic motors with rotary housing and stationary vane. The hydraulic motors associated with the three-way shoulder and wrist joints are so arranged that; their axes of rotation intersect in one point. The hydraulic supply system and an electric control unit provided for controlling the movements of the arms are accommodated in the robot body 17 which is rotatable about a vertical axis by a pinion engaging a ring gear on base 18. <IMAGE>

Description

SPECIFICATION Industrial robot The present invention relates to an industrial robot having an arm which is pivotable about a carrier and has a twist joint supporting a working unit such as a gripper. In a preferred embodiment of the invention, the arm is largely analogous to a human arm as regarding the number and arrangement of joints, pivot drives, and degrees of freedom of motion.

One known robot having these features is the one-armed robot offered and marketed by Messrs.

ELAC Ingenieurtechnik GmbH under the model designation IR-D 1260, which has an articulated arm with a total of up to six degrees of freedom of rotation.

The drive units associated with the individual joints and/or axes of rotation take the form of pivot drives comprising a rotary-piston hydraulic cylinder with pilot valve and a swing-angle measuring system.

When equipped with one gripping device on the free end of the arm, this robot can be used as positioning device capable of bringing a workpiece into any desired position within a substantially cup-shaped spatial area defined by the maximum pivot angle of the joints.

The essential drawback of this known industrial robot is to be seen in the fact that if short setting times are to be obtained, the pivot drives associated with the individual axes must be designed for relatively heavy duty as quite considerable inertia forces may be encountered even with relatively light workpieces when they must be rotated about the axis of their greatest moment of inertia to bring them into the required position. These inertia forces must be absorbed by the joints and/or the pivot drives of the robot. Very considerable forces are to be absorbed in particular during the deceleration of positioning movements if "overshooting" of the workpiece to be positioned beyond its desired position is to be reliably prevented.The known robot requires considerable constructional expenditure if on the one hand a sufficiently high stiffness of its arm against torsion and, on the other hand, the positive and negative accelerations necessary for rapid and exact positioning are to be achieved.

The dead weight of the articulated arm of a robot of the known type designed for a given working load amounts, therefore, to a multiple of the weight of the workpiece.

Now, it is the object of the present invention to provide a robot of the type described above which, though designed for a working load comparable to that of the known robot requires considerably lower drive powers for its pivot drives and altogether much less weight.

According to the invention, this problem is solved in a simple manner by the features set forth in claim 1.

According to these features, the robot of the invention is of the two-armed type, each arm being provided-in an embodiment intended for use as positioning device-with a gripping device coupled with the forearm joint of the associated articulated arm by means of a three-way articulation whose degrees of freedom of swing and rotation correspond to those of the human wrist. Further, at least one of the two arms is coupled by way of a likewise three-way "shoulder joint" with the robot body which can rotate about a vertical axis, while the other articulated arm is pivoted on the said rotatable column to pivot at least about one horizontal axis.

A workpiece which has a high moment of inertia about axes extending vertically to its longitudinal axis, for instance because of its elongated shape, can be gripped and held by the robot of the invention at two points arranged at a relatively great distance from each other and then moved within a very extensive sector of a substantially cup-shaped spatial area along freely selectable paths of movement, for instance from a vertical initial position into a horizontal and/or desired position in a processing machine.The movements of the workpieces achievable with the aid of a robot of the invention correspond to those of the freely movable link of a four-bar linkage which is connected via universal joints with two links of variable length both pivoted on a support, the one by means of a one-way pivot joint and the other by means of a universal joint, the support being in turn rotatable about a vertical axis.

The essential advantage of this robot of the invention is to be seen in the fact that by suitably selecting the distance at which the grippers grip the workpiece, the moment of inertia effective during a rotary movement can be kept considerably smaller than in the case of the known robot. For comparison, we will assume that the workpiece has the mass m and the shape of an elongated circular cylindrical rod of the length I which is gripped and held by the known robot in the area of its centre of gravity and by the grippers of a robot according to the invention at two points at 1/4 distance from the centre of gravity.When the workpiece is manipulated by means of the known robot, the moment of inertia effective during rotation of the workpiece about an axis extending vertically to its longitudinal axis amounts to ml2. In contrast, the moment of inertia effective during manipulation of the workpiece by means of the robot of the invention, which is equal to the sum of the moments of inertia of the rod halves held by the grippers, related to parallel axes of rotation of the grippers, amounts to only my2/2.

For the great majority of applications of practical interest this means that the total drive power required for driving the articulated arms of the robot of the invention corresponds to only one half of the value required for a robot of the known type. And the constructional expenditure required to achieve satisfactory static stability of the articulated arm arrangement is also reduced in a corresponding proportion. Accordingly, the working load/dead weight ratio is much higher for the robot of the invention than for the known robot.

The embodiment of the robot of the invention defined by the features of claim 2 offers a considerably enlarged spatial area within which a workpiece or another working unit, such as a drilling or milling unit, can be manipulated at will.

The extra expenditure required for thismaximally two additional pivot drives-is small.

The design of the three-way wrist and shoulder joints of the robot arms in accordance with claim 3 provides simple and clear kinematics lending themselves for simple programming of a numerical control, for instance in spherical coordinates.

The features of claim 4 define a combined arrangement of hydraulic pivot drives with a rotary vane and/or rotary housing, in which the three-way wrist and/or shoulder joints of the robot arms are realized in a simple manner and so that the joint axes intersect in one point. It is an advantage of such joint arrangements which altogether exhibit the properties of a universal joint, that they are space-saving and yet permit large swing angles about the individual axes.

The features of claim 5 define for the abovementioned purpose simple designs of hydraulic pivot drives which can be realized with conveniently small dimensions and permit very exact setting of the pivot angles.

Further it is of advantage if-according to the features of claim 6-the elbow joints of the robot arms are also designed as hydraulic motors having a rotatable housing arranged between the parallel fork legs of the respective upper arm link.

The features of claims 7 to 9 define designs of the pivot drives which though being very simple provide a great variety of possible paths of motion along which a workpiece or working unit can be guided.

The robot of the invention particularly suited for this last-mentioned application is that defined by the features of claim 10 in which the arms are interconnected by means of a bridge carrying the working unit. Since the robot of the invention can do with a comparatively low connected power, it is possible without difficulty-as provided by the features of claims 11 and 12-to accommodate not only the electro-hydraulic supply system of the robot, in particular the hydraulic pump and the electric drive motor for the latter, but also a permanently programmed or freely programmable computer-monitored CNC control unit in the robot body itself. Thus, an extremely space-saving overall design of the robot is achieved and the variety of possible applications is considerably extended.

Further details and features of the invention are apparent from the following description of one particular embodiment of the invention and the drawings in which: Fig. 1 shows a simplified, schematic front view of an industrial robot in accordance with the invention; Fig. 2 is a side view of the robot shown in fig.

1, with the articulated arm folded off; Figs. 3 and 4 show simplified, partially broken longitudinal cross-sections through suitable hydraulic pivot drives for the robot shown in figs.

1 and 2 and Figs. 5a to Sc are simplified, schematic representations of different operating conditions of the pivot drive shown in fig. 3, illustrating the function of the hydraulic pivot drives employed in the robot of the invention.

In the particular embodiment of the two-armed industrial robot 10 shown in figs. 1 and 2, to the details of which express reference is herewith made, the articulated arms generally designated 11 and 12 are each equipped with one gripper 13 and 14, respectively, for gripping a workpiece 16, for instance an elongated shaft, by portions which are spaced at a relatively great distance.

Without limiting the generality, it is found that the embodiment of the robot 10 shown in figs. 1 and 2 is particularly suited for positioning the workpiece 1 6 in a processing unit, such as a milling or grinding machine. In this case, the workpiece 1 6 is supplied to the robot 10 in a defined position, for instance by means of suitable feeding means, and the robot has to bring the workpiece into a defined desired position relative to the processing unit. For simplicity's sake, the mentioned additional devices and units are not shown in the drawing.

As regards nature, arrangement and number of the degrees of freedom of movement of the two articulated arms 11 and 12 and/or the grippers 1 3 and 14, the robot 10 is largely analogous in function to the human locomotor system so that, for greater clarity and simplicity, the usual anatomical designations will be used analogously in the following description of the robot 10.

The body of the robot 10 is constituted by a vertically extending elongated cabinet 1 7 taking the form of a sturdy frame construction mounted on a foot 1 9 seated in rotatable and driving engagement on a base 18 so that the body can be rotated about its vertical center axis 20. A hydraulic or electric rotary drive provided for this purpose is generally designated by reference number 21. This rotary drive 21 comprises for example the drive motor mounted on the lower portion of the robot body 17 whose power takeoff shaft carries a pinion which engages a ring gear provided on the base 18.

The upper portion of the robot body 17 is again formed by a box-shaped shoulder joint carrier 22 on which the two articulated arms 11 and 12 are pivoted by means of three-way shoulder joints generally designated 23 and 24, for rotation about a common axis 26 intersecting the vertical axis 20 of the robot.

Viewed in the rest position of the robot 10 shown in fig. 1, in which its two articulated arms 11 and 12 hang straight down, the robot is designed symmetrically relative to its longitudinal centre plane which comprises the central vertical axis 20 and extends at a right angle to the horizontal pivot axis 26.

Each of the two articulated arms 11 and 12 comprises an upper arm element 27, 28 and a forearm element 29, 30, which are interconnected by a one-way elbow joint 31, 32 whose pivot axes 33, 34 are in alignment with each other in the rest position of the robot 10 shown in the drawing.

The grippers 14 and 13 are connected with the forearm elements 30 and 29 of the two articulated arms 12 and 11 by means of threeway joints generally designated 36 and 37, the design of which corresponds substantially to that of the shoulder joints 24 and 23.

We are now going to describe the fundamental arrangement of the shoulder, elbow and wrist joints 23 and 26, 32 and 33, and 36 and 37, using the articulated arm 12 shown in fig. 1 as an example: The shoulder joint 26 comprises a first, a second and a third hydraulic pivot drive 38, 39 and 41 by means of which the upper arm element 28 and, thus the total articulated arm 12, can be pivoted about the horizontal pivot axis 26 of the first hydraulic motor 38, the pivot axis 42 (fig. 2) of the hydraulic motor 39 extending perpendicularly thereto, and the pivot axis 43 of the third motor 41 extending again perpendicularly to the latter and coinciding with the cental longitudinal axis of the upper arm element 28.

The arrangement and design of the said pivot drives 38, 39 and 41 are such that their respective pivot axes 26, 42 and 43 intersect in one single point 44. This gives the shoulder joint 26, at least in a limited solid angle area, the properties of a universal joint, whereby favourably simple kinematics are achieved for the articulated arm 12.

The first pivot drive 38 is designed as rotary vane hydraulic motor which in the particular embodiment used here has the special constructional features apparent from fig. 3, to the details of which express reference is herewith made. The housing 46 of the said first rotary-vane hydraulic motor 38 is fixed to the shoulder joint carrier 22, the axis of its power take-off shaft 48 connected with the rotary vane 47 defining the horizontal pivot axis 26. The power take-off shaft 48 of the said first pivot drive 38 which projects laterally from the shoulder joint carrier 22 carries the crossbar 49 of a U-shaped bearing yoke 51.

The crossbar 49 is fixed to the said shaft to rotate with it, and its parallel jaws 52 and 53 hold the hydraulic motor constituting the second pivot drive whose fundamental design is apparent from fig. 4 to which express reference is herewith made. Contrary to the hydraulic motor 38 shown in fig. 3, the hydraulic motor 38 comprises a vane 54 which is stationary relative to the jaws 52 and 53 and a rotatable housing 56 whose axis of rotation defines the axis 42 extending perpendicularly to the horizontal pivot axis 26.

The third pivot drive 41 in the shoulder joint 26 takes again the form of a rotary-vane hydraulic motor of the type shown in fig. 3 whose housing is connected to rotate with the housing 56 of the second hydraulic motor 39 so that the axis of rotation 43 of its rotary vane 47 intersects the axis of rotation 42 of the housing 56 of the second hydraulic motor 39 at a right angle and passes also through the point of intersection 44 of the said axis of rotation 42 and the horizontal pivot axis 26.

To achieve a certain relief for the bearings 57 and 58 of the rotary vane 47 of the said first rotary-vane hydraulic motor 38, the bearing yoke 51 connected for rotation with the power takeoff shaft 48 is as an additional measure rotatably seated, via a cylindrical tubular piece 59 enclosing the housing 46 of the hydraulic motor 38 over part of its length, on two fixed bearings 61 and 62 provided on the shoulder joint carrier 22 and designed as radial anti-friction bearings.

In the area of the elbow joint 31, the upper arm element 28 of the articulated arm 12 takes the form of an enlarged U section connected by means of an end plate 63 to the power take-off shaft of the third pivot drive 41, for rotation therewith. The elbow joint 32 is again designed as hydraulic pivot motor with rotary housing. Its fundamental construction corresponds to that of the second pivot drive 39 of the shoulder joint 26, and its housing 64 is seated in the manner apparent from fig. 4 on the parallel legs 65 and 70 of the enlarged U section of the upper arm element 28, for rotation about the axis 34.

The forearm element 30 of the articulated arm 12 takes the form of a sturdy tube projecting radially from the housing 64 of the hydraulic motor 32 of the elbow joint. Its outer diameter is a little smaller than the clear distance between the parallel legs of the U section of the upper arm so that when the forearm is raised, the portion of the tube 30 adjacent the joint can project a certain distance into the U section of the upper arm element 28.

The arrangement of the wrist joint 36 which comprises three hydraulic pivot drives 66, 67 and 68 is largely analogous to that of the shoulder joint 26. Its first pivot drive 66 arranged directly adjacent the forearm element 30 is again a rotary-vane hydraulic motor of the type illustrated in fig. 3, the axis of rotation of its rotary vane 47 being in alignment with the longitudinal center axis 96 of the forearm element 30. The second pivot drive 67 is again of the type shown in fig. 4, having a stationary vane 54 and a pivotal or rotatable housing 46 which is in this case seated between the parallel jaws 71 and 72 of a generally U-shaped bearing yoke 73 whose crossbar 74 is connected for rotation with the power take-off shaft 48 of the said first rotaryvane hydraulic motor 66.The axis of rotation 76 of the said second hydraulic motor 67 extends perpendicularly to the pivot axis 69 of the said first hydraulic motor 66 and intersects it in point 77.

The third pivot drive 68 of the wrist joint 36 is again a rotary-vane hydraulic motor of the type shown in fig. 3. Its housing 76 is fastened to the rotatable housing 56 of the said second pivot drive 67, and its axis of rotation 78 extends perpendicularly to the axis of rotation 76 of the said second pivot drive and also through the point of intersection 77 of the latter and the pivot axis 69 of the said first pivot drive 66 of the wrist joint 36.

The gripper 14 is coupled to rotate with the power take-off shaft 48 of the third pivot drive 48 of the wrist joint.

The design of the rotary-vane hydraulic motors 38/41 and 66/68 used in the shoulder joints 23/26 and 36/37, respectively, is shown in more detail in fig. 3 and will be explained hereafter, using the motor 38 as an example. The housing 46 of the motor 38 comprises two pressure chambers defined against each other by the rotary vane 47 which exhibits a sector-shaped crosssection, and a radial partition wall 81 of likewise sector-shaped cross-section. By connecting the two pressure chambers alternatively to the pressure (P) output or the tank (T) of the hydraulic supply system which is not shown in detail, the rotary vane can be driven in its two alternative senses of rotation.The shaft of the rotary vane 47 which projects unilaterally from the housing 46 of the hydraulic motor 38 as power takeoff shaft is seated in solid end plates 82 and 83 of the cylinder housing 86 for pivotal movement about the latter's longitudinal centre axis which defines the pivot axes 26 and 43 of the shoulder joints 23 or 24, respectively, or the pivot axes 69 and 78 of the wrist joints 36 or 37, respectively.In order to permit moving the rotary vane into, and holding it in, a pre-determined angular position, under the effect of a load acting upon its power take-off shaft 48, control means generally designated 84 are provided which serve on the one hand for presetting the nominal value of the desired angular position of the rotary vane 47 and/or the arm element or gripper 13 or 14 coupled with the latter, and on the other hand for stabilizing this angular position by controlling the pressures in the pressure chambers of the hydraulic motor 38 in a convenient manner.

This control system comprises as a component essential for its function a follow-up control valve designed as directional control valve 4/3 and generally designated 86 which is shown in figs.

5a to Sc in its different possible operating positions.

In a first position I of the said valve 86, the one pressure chamber 88 of the rotary-piston hydraulic motor 38 is connected to the highpressure end of the pump via the flow path of the follow-up control valve 86 represented by the arrow 87, while the flow path of the follow-up control valve 86 represented by the arrow 89 connects the other pressure chamber 91 of the hydraulic motor to the tank of the hydraulic pressure-supply system. The rotary vane 47 of the hydraulic motor 38 is in this case loaded in the sense of rotation indicated by the arrow 92.

In the position of the follow-up control valve shown in fig. 5b and designated 0, both pressure chambers 88 and 91 of the hydraulic motor 38 are blocked against the pump and/or the tank of the hydraulic pressure-supply system, and the rotary vane 47 remains fixed in the angular position occupied at the moment, at least as far as leakage losses are excluded or can be neglected.

In the second operative position of the followup control valve 86 shown in Fig. sic and designated 11, the pressure chamber 91 of the hydraulic motor 38 is connected to the pressure outlet of the pump via the flow path of the valve 86 represented by the arrow 92, while the flow path of the follow-up control valve 86 represented by the arrow 93 connects the other pressure chamber 88 of the hydraulic motor 38 to the tank of the hydraulic pressure-supply system.

The rotary vane 47 is in this case loaded in the sense of rotation indicated by the arrow 94.

The functions of the follow-up control valve 86 described above are implemented by four seat valves 96 and 97, 98 and 99 accommodated in the arrangement shown in fig. 3 in a common housing 101.

Each of the said valves 96 to 99 has a valve body 102 substantially in the form of a truncated cone, and an annular valve seat 103 fixed to the housing. Pre-stressed spiral pressure spring 104 urge the said valve bodies 102 into the blocking position of the said valves 96 to 99. The valves 96 to 99 are symmetrical relative to the transverse centre plane 106 of the housing 101 of the follow-up control valve 86 extending at a right angle to the central axis 26 and/or 43 or 69 and/or 78 of the respective hydraulic motor 38.

The valve bodies 102 of the valves 96, 99 and 97, 98 respectively, which are arranged opposite each other relative to the said transverse centre plane 106, are guided for displacement along axes 107 and 108, respectively, extending in parallel to the longitudinal axis of the pivot drive 38.

In the blocked position of the follow-up control valve 86 which corresponds to the 0 position shown in fig. 5b, all four seat valves 96 to 99 are closed and each of the valve bodies 102 is supported via a pin 109 on an actuating member 111 in the form of a radial flange which is guided for reciprocating displacement in the housing 101 in the direction of the latter's longitudinal axis.

The actuating member 111 is fixed on a tubular sleeve 112 guided for reciprocating displacement in a central bore 113 of the housing block 101 of the follow-up control valve 86, in the direction of the central axis. The said sleeve 112 comprises an elongated tube-shaped rotatable spindle nut 114 whose thread grooves are in engagement, via revolving balls 117, with the thread 118 of a spindle 119 which in the embodiment shown forms the axial extension of, and is fixed to, the shaft 48 of the rotary vane 47 of the hydraulic motor 38. The sleeve 112 carrying the actuating member 111 extends between the inner races 121 and 122 of thrust ball bearings 123 and 124 whose outer races 1 26 and 1 27 are fixed against displacement and rotation on the spindle nut 114, in the arrangement shown in fig. 3.So, the sleeve 112 and, thus, the actuating member 111 can follow any axial displacements of the spindle nut 114 resulting from a rotary movement of the latter or of the spindle 119, but does not follow itself the rotary movements performed by the spindle nut 56. The spindle nut is coupled, either directly or as shown via a suitable gearing, in positive locking relationship, to the power take-off shaft 128 of a stepping motor 1 29 which is electrically controlled in a convenient manner to rotate the spindle nut 114 by defined, predeterminable angular steps.

Now, when the spindle nut 114 is rotated by a defined angle (PR ic clockwise direction in the sense indicated by the arrow 131, this initially causes the actuating member 111 to be axially displaced in the direction indicated by arrow 132.

As a result thereof, the two seat valves 96 and 97 arranged in fig. 3 in the left-hand portion of the valve housing 101 open, while the seat valves 98 and 99 arranged in the right-hand portion of the valve housing 101 remain closed. The follow-up control valve 86 is now in its first operative position I shown in fig. 5a in which the one pressure chamber 88 of the rotary-piston hydraulic motor 38 is connected via the flow path 87 with the high-pressure outlet of the pump, while the other pressure chamber 91 of the rotary-piston hydraulic motor 38 is connected to the tank of the hydraulic pressure-supply system.

The rotary vane 47 of the hydraulic motor 38 now rotates in clockwise direction in the sense indicated by arrow 92 (fig. 5a) so that due to the mechanical feedback or countercoupling provided by the spindle drive 116, 119, the actuating member 111 will resume its neutral position illustrated in fig. 3 exactly at the moment when the pivot angle of the rotary vane 47 corresponds to the angle (PR through which the spindle nut 114 was rotated by the stepping motor 129.

From the above it results that by pre-setting a given rotary angle for the spindle nut 114 by means of the stepping motor one pre-sets the nominal value of the pivot angle of the pivot drive 38. Now, when the rotary vane 47 continues, for instance under the effect of a load acting upon the power take-off shaft 48, to rotate in clockwise direction after the rotary vane 47 has reached its neutral position (fig. 5b) corresponding to the desired rotary position of the follow-up control valve 86, the actuating member 111 will, due to the mechanical coupling provided by the spindle drive 114, 11 9, move together with the rotary vane 47 in the direction indicated by arrow 113, whereby the seat valves 98 and 99 open and the follow-up control valve 86 assumes the functional position shown in fig. sic in which the rotary vane 47 is loaded in the opposite sense of rotation represented by arrow 94. The return motion of the rotary vane 47 caused thereby ends as soon as the actuating member 111 of the follow-up control valve 86 assumes again its neutral position shown in fig. 3 and/or fig. 5b.

Insofar, the follow-up control valve 86 acts as mechanohydraulic analog control which provides effective disturbance control regardless of the type of the disturbance variables provoking a deviation of the rotary position of the rotary vane 47 from its desired position. Due to the direct feedback of the position of the vane to the position of the actuating member 111 realized by the spindle drive 114, 11 9, the control frequency fr of this analog control is favourably high, typically in the range of 500 s-1 and under particularly favourable conditions even much higher.

This applies analogously also to the hydraulic pivot motor with rotatable housing 56 generally shown in fig. 4, which is used once in the shoulder joint 26, once in the wrist joint 36 and also as elbow joint 32 of the articulated arm 12.

In the hydraulic pivot drive shown in fig. 4, presetting of the desired value of the pivot angle and levelling out of the disturbance variables influencing the respective rotary position of the housing are effected in exactly the same manner as described with respect to the pivot drive 38 with reference to fig. 3, namely by means of control means 84 identical in design and function to the control means shown in fig. 3, so that to avoid repetitions it will suffice to refer to the above explanations.

The corresponding structural and functional elements of the control means 84 and their follow-up control valves 86 have been identified in figs. 3 and 4 by the same reference numbers.

To permit a convenient utilisation of the followup control valve 86, the pivot drive 39 in fig. 4 has its rotatable housing 56 connected to rotate with the spindle 11 9 of the follow-up control valve 86.

The said housing is arranged in the manner apparent from fig. 4 and seated, for rotation about the axis 42, in a sturdy bearing yoke 51, which in the longitudinal section shown exhibits the shape of a U. The one jaw 53 of the said bearing yoke 51, shown on the left-hand side in fig. 4, is fixed to the housing 101 of the follow-up control valve 86. The vane 54 of the pivot drive 39 is carried on a sturdy shaft 134 which has one side fixed to the outer jaw 52 of the bearing yoke 51 which is to be seen on the right-hand side of fig. 4. The rotatable housing 56 is seated on the one hand on the inner end portion 136 of the said shaft 134 via its end wall 1 37 and a cup-shaped bearing sleeve 138 connecting the latter with the spindle 114, and on the other hand on the outer portion 1 39 of the said shaft, adjacent the jaw 52, via its outer end wall 141 which is additionally supported on the inner face of the jaw 52 via an axial ball bearing 142. A second axial ball bearing 143 serves to support the housing 56 also in the axial direction on the housing 101 of the followup control valve, via the cup-shaped bearing sleeve 138.The pressure lines 144 and 146 provided for alternatively connnecting the pressure chambers of the hydraulic motor 139 to the pump or the tank of the hydraulic supply system are guided as shown in fig. 4 through the crossbar 49 and the outer bearing jaw 52 of the bearing yoke 51, and the shaft 134 fixed thereto, and end in opposite radial faces of the vane 54 of the hydraulic motor 39.

It goes without saying that the joints of the robot arms 11 and 12 may be realized also with the aid of hydraulic motors having two diametrically opposite rotatable or fixed vanes, instead of the before-described hydraulic motors 38 and 39 having each only one rotatable or fixed vane 47 or 54. The reduction of the maximum pivot angle to a value of approx. 1200 to maximally 1400 which may by connected therewith, can be accepted at least for the hydraulic motors 39 mounted on the joint carriers of the shoulder joints 23 and 24, and for the hydraulic motors 39 coupled therewith, which must develop the greatest forces. The same applies analogously to the pivot drives 31 and 32 used as elbow joints.In contrast, the hydraulic motors 66, 67 and 68 used for the wrist joints 36 and 37 should conveniently be designed for the greatest possible pivot angles and, therefore, take the form of single-vane hydraulic motors. The high degree of flexibility of motion of the wrist joints 36 and 37 resulting therefrom is an advantage, for example, when the workpiece to be moved by the robot 10 has a shape which does not lend itself for symmetrical gripping by the grippers 13 and 14 of the articulated arms 11 and 12.

Because of the two-armed design of the industrial robot 10 according to the invention and the fact that its grippers 13 and 14 can grip and hold a workpiece 1 6 at points spaced at a relatively great distance, the leverage conditions achieved for initiating and decelerating rotating movements of the'workpiece 1 6 about the axis of its greatest moment of inertia, are much more favourable than those achieved in the case of a one-armed robot in which such movements must be initiated and decelerted by one single pivot joint. This makes it possible to design especially the pivot drives 66, 67 and 68 of the wrist joints 36 and 37 provided on the ends of the robot arms 11 and 12, for relatively small loads, and, thus, to save weight.The two-armed robot 10 requires a lower connected load than a comparable onearmed robot for a given lifting capacity, and can be realized altogether with less weight. The value of the connected power which depends essentially on the electric power absorption of the electric motor provided for the operation of the high-pressure pump of the hydraulic supply system, or rather the upper limit thereof, may be estimated as follows: Let us assume that the two articulated arms 11 and 12 are raised in the stretched condition by 900 by means of the shoulder joint drives 59.Let us further assume that the maximum weight of the workpiece 1 6 carried by the articulated arms 11 and 12 is 2000 N and the weight of the articulated arms 11 and 12 amounts to 1000 N each, with equal mass distribution over the length of the arms measured between the pivot axis 26 and the longitudinal axis of the workpiece, which is assumed to be 2 m. Let us further assume that the two pivot drives 59 take the form of two-vane hydraulic motors having a vane surface of 50 cm2 each, that the distance of the geometrical centres of gravity of the vane surfaces from the pivot axis 26 is 4 cm. Then the absorption volume of the two pivot drives 59, related to a rotation by 900, amounts to a total of 1,256 cm3.If it is further assumed that the pivotal movement is effected at a circumferential speed of 2m s-l, the oil consumption Q, related to one minute, amounts to 48 litres/min. Given a supply pressure of 100 bars, the following formula is obtained QP P- 612 to wherein TI defines the hydraulic overall efficiency, which has been assumed to be 0.8, of the connected power P of 9.8 kW.

Under the above-described conditions, each of the pivot drives 59 develops a driving torque of 4000 Nm, and the moment of inertial related to the horizontal pivot axis 26 resulting from the mass distribution of the articulated arms 11 and 12 and their respective shares in the load amounts to 600 Nms2 each. The angular accleration resulting therefrom, assuming a supply pressure p of 100 bar, is 6.67 s-2, which corresponds to a circumferential acceleration of 13.3 ms~2 for an arm length of 2 m.

Considering the favourably low value of the required connected load, the electric and hydraulic units required for this purpose can be accommodated without difficulty in the upper portion of the robot body 1 7 neighbouring the shoulder joint carrier 22, and the lower portion will still provide sufficient room for the accommodation of electronic control means for controlling the movements of the articulated arms 11 and 12. The robot 10 described above with particular reference to its use as positioning device can easily be converted for use a working machine. To this end, the power take-off shaft of the pivot drives 68 of the wrist joints 13 and 14 provided on the ends of the articulated arms are rigidly interconnected by means of a bridge carrying one or more working units, such as a spot welder or a drilling and/or a threading unit, for carrying out different operations on the workpiece, either one after the other or simultaneously.

Claims

1. An industrial robot comprising two arms pivotally connected to a shoulder joint carrier by respective three-way shoulder joints having a common axis of rotation and each having two other axes of rotation, the carrier being rotatable about a substantially vertical axis, and each arm having a respective wrist joint coupling the arm to a respective working unit.

2. A robot according to claim 1, wherein each wrist joint has three degrees of rotational freedom.

3. A robot according to claim 1 or claim 2, including hydraulic pivot drives associated with each of the shoulder and wrist joints.

4. An industrial robot comprising at least one articulated arm of a design corresponding largely to the human arm as regards the number and arrangement of the pivot and/or rotary joints and the arm elements and/or gripper arrangements movably connected thereby, wherein a first link forming an upper arm element is coupled on the one hand with a shoulder joint and an upright which can rotate about a vertical axis, and on the other hand via an elbow joint with a forearm element the free end of which carries, via a joint arrangement simulating the function of a wrist joint, a functional unit-a gripper or working unit-movable about three orthogonal axes which can be moved into freely selectable positions within a limited spatial area by coordinated control of the hydraulic pivot drives which constitute the rotary and/or pivot joints, respectively, and which are responsible for the pivotal movement of the coupled arm elements and/or wrist joint elements, characterized in that the robot (10) comprises two articulated arms (11 and 12) arranged for rotation about a common horizontal axis (26) on a shoulder joint carrier (22) of a robot body (17) which can rotate about a vertical axis (20), that the shoulder joint (24) of the one articulated arm (12) is of the three-way type with every pair of two axes extending perpendicularly to each other, that the other articulated arm (11) likewise comprises two upper arm and forearm elements (27 and 29) coupled by an elbow joint (31), and further joint arrangements (37) corresponding in function to the wrist joint arrangement (36) of the said first articulated arm (12) and providing the articulated connection between the said forearm element (29) and a second gripper (13) and/or a second working unit, the said second articulated arm (11) being likewise provided with hydraulic pivot drives associated with the individual joints and/or degrees of freedom of movement which drives can be controlled to obtain the desired nominal angular position.

5. A robot in accordance with claim 4, characterized in that the shoulder joint of the second articulated arm (11) is also of the multiple, preferable of the three-way type.

6. A robot in accordance with claim 4, or claim 5, characterized in that the axes of movement of each of the three-way shoulder and/or wrist joints (23 and 24, 36 and 37) of the two articulated arms (11 and 12) pass through one common point of intersection.

7. A robot in accordance with claim 6, wherein the joint drives take the form of hydraulic pivot motors, characterized in that each of the threeway shoulder and/or wrist joints (23 and 24, 36 and 37) is equipped with one hydraulic motor (39 or 67) with fixed vane (54) and rotatable housing (56) carrying a hydraulic motor (41 or 68) with rotatable vane (47), and that the vane frame of the fixed-vane (54) hydraulic motor (39 or 67) is connected to rotate with the drive shaft (48) of a rotatable-vane (47) hydraulic motor (38 or 66) whose housing (46) is connected with the rotatable shoulder joint carrier (22) of the robot body (21, 22) or the forearm element (29 or 30) of the respective articulated arm (11 or 12), and that the axes (26 and 43, 69 and 78) of the drive shafts (48) of the rotary-vane hydraulic motors (38 and 41,66 and 68) extend in a common plane and intersect the axis of rotation (42 or 76) of the fixed-vane (54) hydraulic motor (39 or 67).

8. A robot in accordance with any of claims 4 to 7, characterized in that the hydraulic motors provided as joint drives are provided with a follow-up control valve (86) comprising a feedback measuring spindle and means for presetting the nominal value controlled by a stepping motor, wherein the flow paths of the follow-up control valves (86) can be opened and blocked by means of seat valves (96 to 99) which are closed in a rest position and can be moved alternatively in pairs into their open position by means of an actuating element (111) carried on the spindle nut (114), in a manner such that the one open valve (96 or 97, 98 or 99) connects one pressure chamber of each hydraulic motor with the high-pressure side of the pump and the other pressure chamber with the tank of the hydraulic pressure supply system, and that the hydraulic motors (39 and 67) with rotary housing (54) are mounted on bearing yokes (51) comprising parallel jaws (52 and 53) between which the housing (56) of the respective motor is rotatably seated, and that the pressure oil lines (144 and 146) opening in the vanes (57) of the said hydraulic motors into their pressure chambers are guided to the vanes (57) of the hydraulic motor via the bearing yoke (51) and its jaws (52) arranged opposite the controller (86).

9. A robot in accordance with any of claims 4 to 7, characterized in that the elbow joints (32 and 33) take the form of hydraulic motors with rotatable housing (56).

10. A robot in accordance with any of claims 4 to 7, characterized in thàt the pivot angle of the elbow joints (31 and 22) of the articulated arms (11 and 12) is at least equal to 1200.

11. A robot in accordance with any of claims 4 to 7, characterized in that the pivot angle of the upper arm elements (27 and 28) of the articulated arms (11 and 12) about their common horizontal pivot axis (26) is at least equal to 900.

1 2. A robot in accordance with any of claims 4 to 7, characterized in that the pivot angle of the hydraulic motors forming the wrist arrangements (36 and 37) of the articulated arms (11 and 12) are at least equal to 1800.

1 3. A robot in accordance with any of claims 4 to 7, characterized in that the drive shafts (58) of the pivot drives (68) of the wrist joint arrangements (36 and 37) provided on the ends of the two articulated arms (11 and 12) can be rigidly interconnected by means of a bridge, and that different tool and/or working devices, such as a drilling unit, a threading unit and/or a milling unit, intended for different working operations can be provided in spaced arrangement on the said bridge.

14. A robot in accordance with any of claims 4 to 7, characterized in that the electro-hydraulic supply system of the robot-the hydraulic pump and its electric drive motor-are accommodated in the robot body (17), preferably in its upper portion neighbouring the shoulder joint carrier (22).

1 5. A robot in accordance with claim 14, characterized in that an electric control unit provided for controlling the movements of the articulated arms (11 and 12) of the robot (10) is accommodated in the lower portion of the robot body (17).

1 6. An industrial robot constructed and arranged substantially as herein described and shown in the drawings.