Handling Appliance Having an Adaptive Collision Protection System

Abstract

A handling appliance, in particular a robot, includes at least one handling device that is movable in at least one direction of movement, a collision protection device configured for limiting contact forces due to collisions of the handling device with objects, and an acquisition device. The collision protection device includes a kinematic system that mechanically enables a relative movement of the handling device relative to the carrier of the handling device and that can be inhibited by at least one actuator device. The acquisition device determines forces acting on the actuator device and/or the handling device and on components of the collision protection device decoupled by the actuator device, and the collision protection device accounts for the forces and, via the actuator device, in the absence of a collision prevents, and in the case of a collision triggers and/or enables, relative movement of the handling device relative to the carrier.

Claims

1. A handling appliance, comprising: at least one handling device that is movable in at least one direction of movement; a collision protection device configured to limit contact forces due to collisions of the handling device with objects, the collision protection device comprising a kinematic system that mechanically enables a relative movement of the handling device with respect to a carrier of the handling device, said kinematic system being configured to be inhibited by at least one actuator device and to enable the relative movement in a collision; and an acquisition device configured to determine forces acting on the at least one actuator device and/or on the handling device and on components of the collision protection device decoupled by the at least one actuator device, wherein the collision protection device is configured to account for the determined forces and, via the at least one actuator device, the collision protection device is configured to: in the absence of a collision, prevent relative movement of the handling device with respect to the carrier of the handling device, and in response to a collision, trigger and/or enable relative movement of the handling device with respect to the carrier of the handling device.

2. The handling appliance according to claim 1, further comprising a computation device configured to determine a counterforce that prevents the handling device from withdrawing despite forces that occur as a result of a movement and/or an orientation.

3. The handling appliance according to claim 1, further comprising a control device configured to control the actuator device by open-loop and/or closed loop control taking into account the determined forces determined by the acquisition device.

4. The handling appliance according to claim 1, wherein a mechanical system of the handling appliance is realized in such a way that a first actuator device of the at least one actuator device blocks a retraction in one axial direction and simultaneously blocks an opposite direction with a reduced force or with no force.

5. The handling appliance according to claim 1, wherein the at least one actuator device includes one or more actuator devices assigned to each degree of freedom of movement of the relative movement of the handling device with respect to the carrier of the handling device.

6. The handling appliance according to claim 1, wherein the acquisition device is configured to acquire kinematic parameters of the handling device.

7. The handling appliance according to claim 6, further comprising at least one sensor device configured to sense an acceleration, position and/or orientation of the handling device.

8. The handling appliance according to claim 1, wherein at least components of the collision protection device are arranged between the handling device and a carrier of the handling device.

9. The handling appliance according to claim 1, wherein the kinematic system is a serial, parallel or mixed kinematic system.

10. The handling appliance according to claim 1, wherein the collision protection device is configured to ensure a minimum lever between a rotation point of the kinematic system and a collision force application point via a housing protected from contact by sensors.

11. The handling appliance according to claim 1, wherein the handling appliance is configured such that forces resulting from movement and/or orientation of the handling device do not hinder the kinematic system of the collision protection device from enabling movement of the handling device.

12. The handling appliance according to claim 1, wherein: the at least one actuator device includes first actuators of at least one first axis and second actuators of at least one second axis, and a mechanical system of the collision protection device is at least partially serial and includes a monitoring device configured to trigger the first actuators of the at least one first axis and, upon triggering the first actuator, switch off at least the second actuators of the at least one second axis that further counteract the collision so as to enable a retraction in the at least one second axis even below the triggering threshold.

13. The handling appliance according to claim 1, wherein the handling appliance is a robot.

14. A method for operating a handling appliance having at least one handling device that is movable in at least one direction of movement and a collision protection device configured to limit contact forces due to collisions of the handling device with objects, the collision protection device including a kinematic system that enables a relative movement of the handling device with respect to a carrier of the handling device, said kinematic system configured to be inhibited by at least one actuator device and to trigger or enable the relative movement in a collision, the method comprising: determining, with an acquisition device, forces acting on the handling device and/or on components of the collision protection device decoupled by the actuator device resulting from movement and/or orientation of the handling device and of the collision protection device; and accounting for the determined forces with the collision protection device and triggering or enabling relative movement of the handling device with respect to the carrier of the handling device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Further advantages and embodiments are given by the appended drawings. There are shown therein:

[0088] FIG. 1 a schematic representation illustrating the forces that occur;

[0089] FIG. 2 a representation describing the procedure according to the disclosure;

[0090] FIG. 3 a representation of the structure according to the disclosure;

[0091] FIG. 4 a representation illustrating the problems of previous mechanical systems;

[0092] FIG. 5 a representation illustrating separate axes;

[0093] FIG. 6 a representation illustrating separate axes in a lever-operated mechanical system;

[0094] FIG. 7 a representation illustrating separate axes in the case of a position change;

[0095] FIG. 8 a representation relating to the force ratio of cumulative acceleration forces and collision forces against an actuator force;

[0096] FIGS. 9a-c a design of a serial kinematic system;

[0097] FIGS. 10a-c a design of a parallel kinematic system;

[0098] FIGS. 11a-b a representation of mixed kinematic system; and

[0099] FIG. 12 a representation of the mixed kinematic system from above.

DETAILED DESCRIPTION

[0100] Illustrated in FIG. 1 are the forces occurring during the movement of handing devices 5. On the one hand, an inertial force F.sub.T occurs, which is opposed to the acceleration of the center of gravity, or the corresponding force F.sub.a. In evaluation of the inertial force, it is also necessary in this case to take into account the height h.sub.T that denotes the length of a lever arm, which corresponds to the distance between the center of mass and the bearing point of the end effectors in the collision protection system 10. In addition, there is also the weight force F.sub.g due to the handling device and/or a workpiece held by it.

[0101] Based on these forces, a model may be calculated that, in turn, serves to output the respective kinematic data. The calculation of such a model may be performed, for example, on a control board that preferably also controls the actuator devices or the actuator device by closed-loop control.

[0102] This preferably results in a kind of black box as shown in FIG. 2. The control data used may be extended by the velocity, depending on how the actuator devices are activated. For example in this case, input data E1 to E5 may be entered. Thus, for example, the input value E1 may be an attached mass, the input value E2 may be center of gravity coordinates, the input value E3 may be a TCP (tool center point) acceleration, the input value E4 may be a TCP position, and the input value E5 may be a triggering threshold. Based on this model, it can be calculated whether an emergency stop is to be performed (output value A). Preferably, however, only default values for the activation of the actuator device are calculated, i.e. in particular retention forces or vectors.

[0103] FIG. 3 shows a very basic and schematic structure of a system according to the disclosure. The mechanical part of the system in this case is arranged between a robot flange 32 and a peripheral device 5 such as, for instance, a gripping device. This mechanical part, which for example comprises a housing 12, allows retraction in different degrees of freedom. The reference 4 denotes, in highly schematic form, an acquisition device for acquiring the input data E1-E5. In this case sensor devices (not shown) may be provided, or acquisition may also be effected from the programming of the control system.

[0104] Reference 6 indicates, also schematically, a computation device that calculates at least one triggering threshold from which an evasive or backward movement is to be initiated in the event of a collision. On the basis of this calculated triggering threshold, an actuator device (not shown in FIG. 3) can be set and, in particular, set to a specific counterforce, which is usually at least partially overcome in the event of a collision.

[0105] The rotational degrees of freedom about the x-, y- and z-axis, as well as a translational z-axis, are useful here.

[0106] With the introduction of each additional degree of freedom, the mechanics become more complex, but a reduction results in constrained guidance in the case of a retraction movement.

[0107] If it is possible to create a minimum lever in the z-direction with respect to the central rotation point of the construction by means of a housing 12, the latter preferably having a protective device (such as a sensor skin), then translational collisions (e.g. in the x- and y-direction) will also trigger the rotational axes (x and y).

[0108] Here, the lever 16 swivels with the e.g. gripping device 5 arranged thereon, and thus movements in x and y can also be triggered. The following figures each show a highly simplified 2D model of a hitherto common concept, to illustrate the disclosure. In principle, however, any selection and number of degrees of freedom are possible.

[0109] References 14a and 14b denote support elements, and reference 16, as mentioned, denotes a lever. When the lever is moved, the left and right sides of the support plate 15, for example, may be raised. Corresponding actuators are not represented in FIG. 3. These prevent the lever 16 from swiveling relative to the housing, up to a certain threshold value, i.e. the triggering threshold. At forces exceeding this (in particular in the event of a collision), such a swiveling is made possible, and thus also a withdrawal, or an emergency stop, of the handling device 5.

[0110] A retraction of the mechanical system is prevented, up to a certain triggering threshold, by the actuator devices (not shown). This triggering threshold is constantly controlled by closed-loop control in such a way that a retraction due only to the inertial or gravitational force (as calculated in the model) does not take place. To compensate for control deviations and latencies, a certain offset is advantageous, as mentioned above. The mechanical system is actually designed in such a way that for a force, irrespective of its direction, a certain triggering threshold is applied to trigger the collision protection. This also applies when the offset is taken into account. Preferably, the offset substantially or exclusively affects the collision force.

[0111] Existing mechanical system concepts usually block all degrees of freedom simultaneously with a single actuator. This has the advantage that it is necessary to use only one actuator device that absorbs the maximally occurring sum of inertial and weight force. In the case of adaptive operation, however, this results in the situation that in the event of a collision against the acceleration, in order to achieve triggering it is necessary to work against the actuator that is active due to the inertial and weight force.

[0112] A case in which this occurs would be a braking movement towards the collision object or the worker. Conversely, this means that with such a mechanical system only accelerations that do not activate the actuator too strongly are possible, such that in the event of a collision the triggering threshold is exceeded.

[0113] Illustrated in FIG. 4 are forces such as occur due to the inertial force F.sub.T produced contrary to the acceleration a and, in order to prevent the mechanical system from being triggered by traversal, an actuator force F.sub.A that is set accordingly. If a collision then occurs contrary to the velocity v, a force F.sub.K results, which is composed of 2 components. On the one hand, the opposing inertial force F.sub.T, but also additionally the total actuator force F.sub.A in the form of an equilibrium of moments about the resulting common rotation point D. In realistic application scenarios, this value is significantly greater than the biomechanical limit value. For simplification, this and also the following models include only the inertial force, which in the correct realization, however, corresponds to the superimposition of inertial and weight force.

[0114] FIG. 5 shows an example of a possibility for dividing the actuator devices in a manner in which each of the actuator devices 22, 24 exclusively blocks the negative or positive direction of the axis in the x-direction. In this case, the actuator devices 22, 24 may preferably be conceived of as a kind of pressure piece, which withdraw when a corresponding force is applied.

[0115] In concepts of this kind, an actuator device for one direction of the axis does not interfere with the movement in the opposite direction. FIG. 5 can also be used to illustrate the change in the direction of action of the actuator device if one imagines only one of the actuator devices, which can act on either the right or left side due to a position shift or a lever.

[0116] FIGS. 6 and 7 that follow show a design in which each of the actuator devices 22 and 24 acts with a different lever against a triggering of the mechanical system in the negative and positive x-direction, respectively. In the case of the designs shown in FIGS. 6 and 7, the actuator devices may be, for example, magnetic holding devices, such as electromagnets.

[0117] Depending on the exact placement, an actuator device that blocks one direction of a degree of freedom has no lever, or only a small lever, with respect to the opposite direction. p This means that a movement contrary to the blocking direction of the actuator device is not inhibited, or is only slightly inhibited.

[0118] The possibility of changing the position, also mentioned above, can be described by FIG. 7. Here, the magnet shifts in a three-dimensional direction under the support, with an indicated force case from left to right (for example due to a rotation), the lever changing considerably with respect to the rotation point.

[0119] The references Ha1 and Ha2, and Ha+and Ha−, in FIG. 7 denote the lever arm in position 1 and the lever arm at position 2. The reference 14 again denotes a bearing, or support, and the reference 16 the lever, or movable part. The rotation points are each denoted by the references D.

[0120] The concept presented thus far, of separating each axis into positive and negative directions with respect to the actuator devices, involved consideration in models with only two degrees of freedom.

[0121] Even if the implementation of such a collision protection system is conceivable, the implementation with a plurality of degrees of freedom for retraction is much more likely due to the application, for example, on industrial robots with movements in all 6 degrees of freedom. There then arises another problem of the kinematic systems commonly used hitherto. There, the actuator not only blocks the retraction simultaneously in the positive and negative direction of one axis, but also of a plurality of axes. This also can result in the collision having to work against an active actuator in order to achieve a triggering.

[0122] The disclosure again proposes two approaches to this problem:

[0123] On the one hand, each axis may have its own actuator device to block retraction.

[0124] On the other hand, the mechanical system may be configured so that two or more forces, each acting on a respective axis, work in the same way against a common actuator device, or to common actuator devices, irrespective of their direction.

[0125] FIG. 8 illustrates this using an example. In the situation represented in FIG. 8 a circumferentially arranged actuator device is provided, and in the situation shown in FIG. 9 a centrally acting actuator device is provided. The actuator devices, with their respective forces F.sub.A, can counteract both the forces F.sub.K and F.sub.T.

[0126] The variants proposed by the disclosure may be categorized as serial, parallel or mixed kinematic systems. This is always represented by the type of axis division according to the two possibilities of the preceding descriptions.

[0127] The following are examples of implementations of the different types:

[0128] FIGS. 9a-c show a serial kinematic system. The system in this case covers the axes about x, y, z and in z.

[0129] A rotary joint 40, which is succeeded in series by the other joints, serves as a torsion take-up about z. The references 28, 29 denote the actuator devices of the two axial directions of this torsion take-up.

[0130] A cardanic suspension 30 enables retraction about the x and y axes. Despite the serial characteristics, this bearing is very compact and, due to its design, offers good possibilities for accommodating actuator devices. The actuator devices 22a/b and 24a/b act for the two directions of rotation about the Y-axis, and the actuator devices 25a and 26a act for the two directions of rotation about the X-axis, two further actuator devices having a direction of action about the X-axis not being represented, due to the sectional view shown in FIG. 10a.

[0131] Two separate rotary joints, which are less space-efficient, may also be mentioned as other exemplary solution possibilities for the implementation of the x- and y-axes. Finally, the construction has a linear bearing 52 for the translatory z-axis, also having actuator devices 27a for spring deflection. One or more other symmetrically mounted actuator devices are not represented, due to the sectional view.

[0132] With this construction, all axes are mechanically independent of each other. If each axis is now blocked separately in the positive and the negative direction with an actuator device, a purely serial kinematic system is obtained, which thus makes it possible to adjust the system to a force vector in amount and direction without preventing the triggering in the event of a collision beyond the triggering threshold.

[0133] In the case of serial kinematic systems, it can happen that triggering occurs only in one degree of freedom of the mechanical system, although the collision force vector also has components in other directions, but these are below the triggering threshold. This results, in the case of the retraction movement, in a constrained guidance in the triggered direction.

[0134] To circumvent this the disclosure proposes, in the case of a serial or mixed kinematic system, to monitor the triggering of the mechanical system in all degrees of freedom in such a way that all actuator devices are switched off upon triggering. In the case of electromagnets, for example, an inductive sensor could operate as a normally closed contact and de-energize all electromagnets.

[0135] FIGS. 10a-c show an example of a parallel kinematic system, with FIG. 10c showing a sectional view.

[0136] The system in this case covers the axes about x and y, as well as in z direction. All axes are covered by a construction in which a disk 15 is located in a cylinder 11 with a circumferential support 14. In this case the geometry of the edge of the disk is shaped in such a way that the disk 15 can tilt circumferentially on the support. A shaft 16 projects through a recess in the support 14 and connects the disk 15 to the tool flange.

[0137] If this construction is then mounted between a robot flange and the end effectors, it enables the movements about x and y, as well as in the positive z-direction.

[0138] Holding actuator devices 22, 24 (such as electromagnets) mounted circumferentially in the support surface serve to block the kinematic system. With this construction, a purely parallel structure is then obtained, both mechanically and in respect of the actuator devices.

[0139] Purely parallel kinematic systems have the advantage that exceeding the force threshold also releases the other degrees of freedom possible through the mechanical system. This means that there is only a constrained guidance due to the mechanical design, but not the activation.

[0140] FIGS. 11a,b and 12 show an example of a mixed kinematic system, in a side view and a top view.

[0141] The basic kinematic system follows the parallel kinematic system described in the previous point. This means that a parallel kinematic system works about x and y, as well as in z. Now a torsion axis about z is serially added to the concept. This is done by attaching cams on the disc 15, which are blocked laterally by actuator devices 28a/b and 29a/b.

[0142] The actuators in this case are shaped in such a way that they prevent a rotation about z. However, a rotation about x or y is still only inhibited by the circumferential actuators. As described in connection with the serial kinematic system, it is the case that circumvention of the constrained guidance by an actuator device can be intercepted by corresponding sensors/switches.

[0143] Again, it should be noted that the preceding constructions are intended to describe the disclosure only by way of example. All types of joins may be combined serially, in parallel or mixed in the manner described. This also applies to the arrangement and type of actuator device.