DE102011084007B4 - Robot and drive module for safely handling a heavy load - Google Patents

Abstract

A robot and a drive module for a robot joint are disclosed. According to one example of the invention, the drive module for a robot joint comprises the following components: an actuator associated with the joint, which is designed to execute a movement of the associated arm segment in accordance with a control signal generated by a robot controller, as well as a mechanically coupled to the actuator elastic coupling, which is adapted to ensure a decoupled from the respective actuator movement of the joint, wherein the coupling comprises two coupling halves and an elastic buffer arranged therebetween. An angle sensor device coupled to the clutch is designed to determine a rotation between the two coupling halves. Finally, an evaluation device is provided, which is designed to control the actuator independently of the control signal and depending on the measured rotation.

Description

Standard robots (manipulators) consist of several arm segments, each hinged together. With a corresponding number of degrees of freedom, a so-called Tool Center Point (TCP) can be positioned at the end of the last segment within the working area of the manipulator in each room point.

Especially when handling heavy loads, the robot has to fulfill special requirements with regard to safety. This is particularly true if the robot is to interact with humans during operation (eg a robot positions the load, a human attaches it to the target position).

In standard industrial robots, the problem may arise that in case of failure (eg in case of power failure, or in a malfunction of the robot) all drives must be rigidly braked, so that when a person is trapped, a self-liberation of the person is virtually impossible because the Weight forces of the load and the robot itself can act on the person. Furthermore, because of the high forces necessary for free movement in space, the risk of serious injury is high.

DE 28 52 821 B1 discloses a robot with a lifting device and a robot arm articulated on this lifting device. US 2009/0 233 720 A1 shows a coupling with an overload protection. pamphlet WO 2009/102 088 A1 describes a joint with spring elements between input and output. JP 2011-115 878 A shows a control device for a drive device, which has a force transmission element with elastic characteristics.

The object underlying the invention is to provide a robot which is constructed so that even in the manipulation of heavy loads, the risk of trapping persons low and in case of emergency self-emption of trapped persons is possible.

This object is achieved by a robot according to claim 1. Exemplary embodiments are subject of the dependent claims.

According to one aspect of the invention, vertical movement (lifting movement) and horizontal movement of the tool center point (TCP) are decoupled from each other. The weight of a (heavy) load is picked up by a lifting device, which only carries out a vertical lifting movement if it is ensured by safety measures that persons are not exposed to any danger. The lifting device has a holder with a joint on which a first arm segment is mounted. At the other end of the arm segment, a second arm segment is articulated via another joint. At the free end of the second arm segment is e.g. an end-effector with the TCP. Both joints are designed such that the two arm segments can only perform a movement in a horizontal plane. The vertical position of this plane of movement of the robot arm segments is determined by the lifting device, at the moving part of which the robot arm segments are articulated.

The above-described construction of the robot arm has the advantage that the weight of the load-bearing structure of the arms and the (heavy) load acting on the TCP is substantially absorbed by the lifting device. The positioning of the load in the horizontal plane can be done via the robot arm (in the example described above consisting of two arm segments) with very little effort. In principle, the actuators responsible for positioning in the horizontal plane only have to compensate for frictional forces in the joints and (except for quasi-static motion) inertial forces. The limit for an overload shutdown can therefore be set relatively low. If a person should be trapped by the robot arm, only small forces act on it. In any event, the weight of the load is only picked up by the lifting device (e.g., by a self-locking gear, brakes, or the like) and can not act on a trapped person.

In order to still allow a trapped person in the case of rigidly braked drives a self-emptying comprises at least one joint drive module comprising an actuator associated with the relevant joint (eg electric motor incl. Gear) and a flexible coupling (or generally an elastic mechanical coupling element), the between the joint and the actuator is arranged and is adapted to ensure a decoupled from the actuator movement of the respective arm segment. For this purpose, in the drive module between the joint and the actuator, for example, be arranged a coupling having two coupling shells and an intermediate elastic buffer (eg a rubber buffer), in a predetermined angular range (eg ± 2 ° to ± 15 °) an elastically sprung relative movement allows. Thus, even with braked (and therefore rigid) actuators, a trapped person is able to move the arm segments within a predeterminable adjustment range by muscular force and in this way release the clamping. Even with interruption of the power supply is a self-liberation this way possible. Falling of the load is in any case prevented by the lifting device (eg by its self-locking gear).

According to one example of the invention, the drive module for a robot joint comprises the following components: an actuator associated with the joint, which is designed to execute a movement of an associated arm segment in accordance with a control signal generated by a robot controller, and an actuator mechanically coupled to the actuator elastic coupling, which is adapted to ensure a decoupled from the respective actuator movement of the joint, wherein the coupling comprises two coupling halves and an elastic buffer arranged therebetween. An angle sensor device coupled to the clutch is designed to provide a

Determine torsion between the two coupling halves. Finally, an evaluation device is provided, which is designed to control the actuator independently of the control signal and depending on the measured rotation.

In this way, the robot controller that generates the control signal for the actuator is "bypassed" (by-passed) to initiate risk mitigation and / or emergency measures independently of the control software.

For a better understanding of the present invention will be explained with reference to embodiments shown in the figures. In the figures, like reference characters designate like or equivalent components. It shows:

1 a schematic spatial representation of the essential components of the manipulator;

2 an embodiment of a joint with an elastic coupling and an actuator;

3 a schematic representation of an output connected to a clutch;

4 a schematic representation of a flexible coupling with a sensor for measuring the displacement; and

5 in a circuit diagram, the essential components for a DC braking of an asynchronous machine.

According to the invention, almost the entire weight of the (heavy) load of a lifting device 10 (please refer 1 ).

In 1 For example, one possible embodiment of the present invention is shown schematically. The arrangement shown is based on Cartesian coordinates (x, y, z). The holder 11 a lifting device 10 is mounted on a carriage (not shown) so as to be suitably vertical in the (x, z) plane 1 along a guide unit aligned in the z-axis 13 can slide. It is possible that the vertical movement of the lifting device 10 via a pneumatic drive, an electric drive, by means of a wedge or toothed belt or an electric direct drive, for example by means of a linear motor assembly is realized. Regardless of the drive type used for vertical movement, it must be ensured that in the event of a malfunction of the vertical drive, the bracket 11 , which must absorb the weight of the load to be positioned, is braked or blocked. If, for example, no direct drive, for example a linear motor arrangement, is used, blockage of the position can be achieved, for example, by way of a suitable self-locking gearbox (eg spindle gearbox). However, any other suitable device is conceivable here as well.

The 1 further shows an exemplary embodiment of a robot arm 20 according to the invention, at least via a first joint 31 exclusively in a horizontal (x, y) plane 2 is mobile. The first joint 31 can be attached to the bracket 11 attached or in a suitable manner in the holder 11 be integrated. The first joint 31 can (but need not necessarily) be designed so that a 360 ° rotation about the z-axis is possible. At the first joint 31 is a first arm segment 21 of the robot arm 20 attached.

A robotic arm 20 with only one arm segment 21 at a first joint 31 allows the positioning of a load attached to a Tool Center Point (TCP) only along a circular path. In 1 whereas an arrangement is shown which has two degrees of freedom in the horizontal (x, y) plane 2 having. The first degree of freedom in the horizontal is through the first joint 31 allows, the second degree of freedom by a on the first arm segment 21 attached second joint 32 at which another (second) arm segment 22 is pivotally mounted. In the exemplary embodiment shown, the TCP is attached to the (useful) load on the second joint 32 opposite side of the second arm segment 22 arranged. Although in the picture the 1 only two degrees of freedom in the horizontal 2 over a first and a second joint 31 . 32 are realized, according to any number of degrees of freedom in the horizontal plane 2 be possible by the arrangement of corresponding additional joints in the robot arm 20 can be realized. All Degrees of freedom, which is a movement of the robot arm 20 outside the plane 2 but would allow through the joints 31 and 32 blocked.

The joint 31 allows movement of the first arm segment 21 by the angle α, wherein the angle is spanned by the x-axis and the axis of symmetry of the first arm segment. The joint 32 allows movement of the second arm segment 22 relative to the first arm segment by the angle β, wherein the angle β from the symmetry axis of the first arm segment 21 and the symmetry axis of the second arm segment 22 is spanned.

The joints in the robot arm 20 , For example, the illustrated first or second joint 31 . 32 , do not leave movement components of the TCP and / or the entire robot arm 20 in the vertical axis z too. In this way, the weight of the heavy weight attached to the TCP and the weight of the robot arm 20 in the holder 11 , from the bracket 11 in the leadership unit 13 and from the leadership unit 13 in the foundation 12 the lifting device 10 initiated. Movements in the horizontal plane (eg by the robot arm 20 ), and in the vertical (z-axis) by the lifting device 11 ) are thus decoupled from each other. This also applies to the forces attacking the TCP. Forces on the TCP in the vertical direction are completely from the joints 31 . 32 and the lifting device 11 while forces on the TCP in the horizontal plane 2 can cause a corresponding movement.

By this decoupling, an advantage of the present invention is achieved. The at the joints 31 . 32 of the robot arm 20 Acting actuators (drives) must, when moving in the horizontal (x, y) plane 2 Beyond inertia, only overcome friction in the joints, bearings, and driveline, but not support the weight of the load and robotic arm. These are from the lifting device 10 added.

In accordance with another aspect of the present invention, at least one of the hinges is in the robotic arm 20 For example, the joint 32 , an elastic coupling 33 on (see 2 ). This elastic coupling 33 allows the position of the robot arm 20 or the TCP by external mechanical action slightly in the horizontal 2 to change (eg, by a person's muscular strength), since the weight of the load and the robot arm at any time by the lifting device 10 is recorded. Under an elastic coupling 33 is understood in general any elastic coupling element, which is arranged in the drive train.

When industrial use of a manipulator arrangement according to the invention as exemplified in 1 is shown, it can happen that by an accident or a mistake a person through the robot arm 20 is trapped. A joint, for example the joint 32 , is in the 2 shown in more detail. One in the joint 32 arranged elastic coupling 33 allows this person to use the robotic arm 20 in the horizontal plane 2 to move slightly and thus to liberate because he, to perform this slight movement, only the friction and the elastic restoring forces of the clutch 33 must overcome.

An important component of an elastic coupling 33 is an elastic buffer 34 which can be arranged between two interlocking coupling shells. Does not mechanically touch the robot arm during normal operation 20 acted (ie no external forces except the load), so is the elastic buffer 34 in a defined rest position. This buffer 34 is so in the clutch 33 arranged that the buffer 34 in the case of an external mechanical action experiences an elastic deformation, whereby the coupling also in a static (eg braked) robot arm 20 a movement of the joint 32 allows. In general, elastic couplings used according to the invention in the case of an external mechanical action allow a deflection of about 2 ° from its rest position (the rest position being that position in which the elastic buffer 34 not deformed). Depending on the construction can be due to the elastic coupling 33 Also, a much larger deflection (eg by 5 °, 10 ° or even 15 ° and more) are possible. In robotics, the terms "elastic flange" or "elastic buffer" are used equally. As mentioned above, the elastic buffer may be, for example, a rubber buffer. Alternatively, the elastic buffer can also be realized by means of springs or spring / damper elements.

In the 2 are other components of one in a joint 32 integrate drive module shown. So are exemplary actuators 41 , in particular electrical and / or pneumatic actuators, shown, the arm segments 21 . 22 via wedge and / or toothed belt transmission 42 move relative to each other. The 2 shows vividly how two arm segments 21 . 22 a robot arm 20 via a flexible coupling 33 in a (eg horizontal) plane can be arranged rotatable to each other. Such or similar joint arrangement can for any number of joints in the robot arm 20 be used.

An overload of the manipulator arrangement according to the invention can not be excluded in industrial operation, for example. It may happen that an obstacle can not complete a desired movement in a vertical and / or horizontal direction. In such an overload case, the actuators are to be switched off and / or rigidly connected. For example, when an electric motor is an impact torque by collision of the robot arm 20 with an obstacle, the armature current of the motor increases to the same extent. Even with a simple control of the motor threshold values can be set for the armature current, when exceeded, the regulation regulates the power back or rigidly holds the drive by a brake in position. When using pneumatic actuators in the actuators, a pressure sensor can be realized for this purpose, are set in accordance with thresholds for the applied pressure. In addition, in the case of electrical and pneumatic drives, a large number of possibilities for handling the overload operation are conceivable. The present invention is not exhausted in the explicitly mentioned options.

The coupling 33 includes, as in 4 represented, a shell 331 and a lower part 332 , When moving a robot arm, these two parts move against each other. 3 shows a schematic representation of a coupling 33 with an attached output 5 , By a rotation of the clutch 33 the downforce is also moving 5 (eg in a position 5 ' ).

Is the twist of the clutch 33 (Angle φ) known, it can be calculated from the acting moment. The moment M _P is generally the cross product M _P = r × F _A (1) a vectorial quantity F _A with respect to a point P. Here, r is the position vector of P to the point of application A of the force F _A. Specifically, here M _{P is formed} from the scalar multiplication of the angle of rotation φ and the spring stiffness of the elastic buffer c M _P = φ · c (2).

The spring stiffness is usually constant but may be variable (e.g., temperature or angle dependent, i.e., non-linear). The moment thus obtained is then subtracted from the moment thus obtained for an acceleration. Remains after the subtraction still a remainder, this is interpreted by the regulation of the output as a disturbance torque.

In this way, a force control can be performed very soft. In addition, less computing power is necessary because the clutch "swallows" any peaks occurring. In a collision, the resulting force peak is greatly reduced by high frequencies are strongly attenuated. By damping high frequencies, the control can be slower, so less processing power is needed.

In the event of a collision, the inertia of the individual robot arms in the effective direction of the coupling is additionally decoupled. Thus, only the inertia of the last robot arm is full, the effect of the inertia of the preceding arms is damped by the coupling, i. weakened.

At the clutch, as in 3 shown, so-called "red" areas R (eg the intervals φ ε [-5 °, -1 °] ∪ [1 °, 5 °]) and "green" areas G (eg the interval φ ε [-1 °, 1 °]), each having a range of a certain angular misalignment φ between the two coupling halves 331 . 332 define. These ranges indicate how large the relative movement is due to an external counteracting moment (eg due to contact with another object or person) and the range limits (± 1 ° in the example mentioned) can thus be used as safety thresholds. The threshold values can be adjustable here. The areas can also be further subdivided, for example, the "red area" (eg, | φ |> 1 °) in an (inner, eg | φ | <3 °) "alarm area" (second area) and in a (outer, | φ |> 3 °) "emergency area" are divided.

If the moment is very high and the resulting angular rotation φ is in the outer red area R (emergency area, ie the angular offset is greater than eg 3 °), an emergency measure can be initiated. Emergency measures can be, for example, an interruption of the power supply ("emergency stop"), a targeted, complete stopping of the drive or the active initiation of a countermovement. After a safely recognized standstill, the brakes can be released again, for example, to allow a large-scale passive counter-movement. An example of the initiation of a braking torque in an asynchronous motor 41 is in 5 given. Here, in the emergency area, the power supply of the engine 41 interrupted (switch S2) and at the same time the engine (see 41 in 2 ) by DC (rectifier GR) braked (the DC is fed with switch S1). For safety reasons, the DC sources are duplicated.

If the moment is small (i.e., the resulting angular displacement φ is less than, for example, 1 °), the resulting rotation φ will be in the green region G (first region) and no action is required.

At a slightly higher moment, the angular offset φ may be in the inner red area ("alarm area", e.g., between 1 ° and 3 °). In this case, risk-reducing measures can be provided which are intended to ensure that the moment (and therefore the angular offset φ) does not increase further in the direction of the threshold value for the emergency area. For example, depending on the measured angular offset φ, a braking torque can be generated which acts against the robot movement. Alternatively, depending on the measured angular offset φ, the drive torque of the motor in the respective joint can be limited (for example by a current limitation in the motor). Depending on the type of risk limitation, a warning signal (usually visual or audible) can also be given.

The intervention by risk-reducing measures and emergency measures takes precedence over the programmed robot control. For example, user-programmed movements of the robot are "overruled" if a threshold is exceeded and the moment is in the red region R.

This function can generally be summarized as follows: An evaluation device receiving the sensor signals is designed to initiate risk-minimizing measures (as described above) as soon as the measured rotation φ between the two coupling halves 331 . 332 outside a predefined first range (ie outside the "green" range). These are, for example, the displacement-dependent limiting of the drive torque or the issuing of an optical or acoustic warning signal, but not the complete stopping of the movement (or blocking of the motors), ie no emergency stop. The evaluation device can also be designed to initiate the above-mentioned emergency measures as soon as the measured rotation φ between the two coupling halves 331 . 332 is outside a predefined second area (lower "red" alarm area) adjacent to the first "green" area. The emergency measures are, for example, the interruption of the power supply and / or a targeted initiation of a braking torque and / or the blocking of the drive of the relevant module or all drives of the robot.

To measure the rotation of the coupling, can be on the lower part 332 the clutch is a sensor 62 (eg magnetic angle sensor), as in 4 shown. At the top 331 can be a magnet 61 be attached. The further the sensor 61 from the axis of rotation of the clutch is moved radially outward, the larger the measuring path. With a large measuring path, generally no high resolution is required. The shift of the clutch is usually a few degrees. The measuring range is therefore relatively large, which means that the sensor used need not be highly accurate.

However, it is also possible to measure the surface pressure of the clutch instead of the displacement of the clutch. The surface pressure is the force per contact surface between two solids. If the surface pressure is known, then it is possible to directly deduce the acting force and the acting moment (and the corresponding angle). Since the relationship between the angle of rotation and the moment is known, angular ranges ("red" and "green" ranges) can be converted into torque ranges. If a moment lies in a certain torque range, the angle of rotation lies in a corresponding angular range.

An integrated in a robot joint drive module, which is constructed as described above, allows at standstill despite the brake self-emptying a trapped person. After a standstill (after an emergency stop), the brakes can be released again. After an emergency stop - when the controller is restarted - the two coupling parts (when the motor is released) return to a "relaxed" position. This is how the robot starts free from interferences.

Claims (10)

A robot for safely handling a heavy load, comprising: a lifting device ( 10 ) with a holder ( 11 ), wherein the lifting device ( 10 ) is adapted to the holder ( 11 ) exclusively in a vertical direction; one with the bracket ( 11 ) associated robotic arm of the lifting device ( 20 ) comprising at least two via a first joint ( 32 ) connected arm segments ( 21 . 22 ), wherein one of the two arm segments ( 21 ) via a second joint ( 21 ) on the bracket ( 11 ), wherein the first and the second joint ( 21 . 22 ) are formed such that a movement of the robot arm ( 20 ) is possible relative to the lifting device only in a horizontal plane, so that all vertically acting forces from the joints ( 31 . 32 ) and the lifting device ( 10 ) are recorded; each associated with a joint actuators ( 41 . 42 ) which are designed to move a respective arm segment in accordance with a control signal ( 21 . 22 ) execute; and one in at least one of the two joints ( 32 ) arranged elastic coupling ( 33 ), which is arranged between the joint and the actuator and is adapted to a decoupled from the respective actuator movement of the respective arm segment ( 22 ), whereby the coupling ( 33 ) two Parts ( 331 . 332 ) with an elastic buffer ( 34 ) having; one with the clutch ( 33 ) coupled angle sensor device which is adapted to a rotation (φ) between the two parts ( 331 . 332 ) of the coupling ( 33 ), whereby risk-minimizing measures are taken when the rotation (φ) is outside a predeterminable first range (G). Robot according to claim 1, wherein emergency measures, in particular the interruption of the power supply and / or a targeted initiation of a braking torque and / or blocking the drive to be initiated as soon as the measured rotation (φ) between the two coupling halves ( 331 . 332 ) is outside a predefined second area (R) adjacent to the first area (G). Robot according to claim 1 or 2, wherein the rotation (φ) between a first and a second part ( 331 . 332 ) of the coupling ( 33 ) is measured by means of a sensor attached to one of the two parts. Robot according to claim 1 or 2, wherein the rotation (φ) indirectly via the surface pressure of the coupling ( 33 ) to eat. Robot according to one of claims 1 to 4, wherein the lifting device is driven by a self-locking gear or in which the lifting device has a braking device which actively brakes in case of power failure. Robot according to one of claims 1 to 5, further comprising means adapted to disable the actuators in case of overload and / or to brake and / or rigid. Robot according to one of claims 1 to 6, wherein the joints are formed such that the robot arm moving actuators need not compensate for weight forces of the robot or the load, but are absorbed by the joints. Drive module for a robot joint, comprising: a joint ( 32 ) associated actuator ( 41 ) which is adapted to move a corresponding arm segment in accordance with a control signal generated by a robot controller ( 22 ), one with the actuator ( 41 ) mechanically coupled elastic coupling ( 33 ), which is designed to be one of the respective actuator ( 41 ) decoupled movement of the joint ( 32 ), whereby the coupling ( 33 ) two coupling halves ( 331 . 332 ) and an elastic buffer ( 34 ), one with the coupling ( 33 ) coupled angle sensor means adapted to detect a twist (φ) between the two coupling halves; and an evaluation device, which is designed to control the actuator independently of the control signal and depending on the measured rotation (φ). Drive module according to claim 8, wherein the evaluation device is adapted to initiate risk-minimizing measures, in particular the dependent of the measured rotation limiting the drive torque or the delivery of an optical or audible warning signal as soon as the measured rotation between the two coupling halves outside a predefined first Area lies. Drive module according to claim 8 or 9, wherein the evaluation device is adapted to initiate emergency measures, in particular the interruption of the power supply and / or a targeted initiation of a braking torque and / or blocking the drive as soon as the measured rotation between the two coupling halves outside of one predefined second area adjacent to the first area.

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