HYDRAULIC ACTUATOR, ROBOT ARM, ROBOT HAND AND OPERATING METHOD

Abstract

The hydraulic actuator comprises a hydraulic drive cylinder, a first hydraulic output cylinder which is hydraulically coupled to the drive cylinder, and a pressure valve which limits the pressure on the output limiting cylinder depending on an action time of a force on the drive cylinder and/or output piston, wherein the pressure limiting valve is arranged opposite a second output cylinder for limiting pressure and/or in a second output cylinder for relieving pressure, and wherein the second output cylinder is hydraulically coupled to the drive cylinder. The method is a method for operating such a hydraulic actuator, wherein the drive actuator is deflected with deflections having a deflection duration at a deflection frequency for the duration of an acting or a non-acting phase of the hydraulic actuator, wherein the deflection duration defines a movement stiffness of the hydraulic actuator and the deflection frequency defines the resulting deflection speed of the hydraulic actuator.

Claims

1. A hydraulic actuator comprising: a hydraulic drive cylinder comprising: a drive piston guided in the hydraulic drive cylinder; and a first hydraulic output cylinder hydraulically linked to the hydraulic drive cylinder and a pressure limiting valve that as a function of an action time of a force on the hydraulic drive cylinder, the drive piston, or the hydraulic output cylinder and drive piston in terms of pressure limits the first hydraulic output cylinder, wherein the pressure limiting valve is configured for limiting pressure in relation to a second output cylinder or for relieving pressure into the second output cylinder, and wherein the second output cylinder is hydraulically linked to the hydraulic drive cylinder.

2. The hydraulic actuator of claim 1, wherein the first output cylinder by way of a first pretensioned stop valve is linked to the hydraulic drive cylinder, and the second output cylinder by way of a second pretensioned stop valve is linked to the hydraulic drive cylinder, wherein the first pretensioned stop valve and the second pretensioned stop valve in relation to the drive cylinder include opposite blocking directions.

3. The hydraulic actuator of claim 1, wherein the first and the second output cylinder are hydraulically linked collectively by a multi-port valve.

4. The hydraulic actuator of claim 1, wherein the hydraulic actuator comprises a drive actuator that is linked to the drive cylinder or to the drive piston.

5. The hydraulic actuator of claim 1, wherein the drive actuator is a piezo actuator or an electro-dynamic or an electro-magnetic actuator.

6. The hydraulic actuator of claim 1, wherein the drive cylinder by way of a stop valve and of a first throttle is hydraulically linked to a pretension volume that is located in a pretension hydraulic cylinder comprises a pretension piston, wherein the pretension hydraulic cylinder or the pretension piston represents the pressure limiting valve.

7. The hydraulic actuator of claim 1, wherein the pretension volume by way of a second throttle is hydraulically connected to the second output cylinder.

8. A robot arm or robot hand comprising: a hydraulic actuator comprising: a hydraulic drive cylinder comprising: a drive piston guided in the hydraulic drive cylinder; and a first hydraulic output cylinder hydraulically linked to the hydraulic drive cylinder and a pressure limiting valve that as a function of an action time of a force on the hydraulic drive cylinder, the drive piston, or the hydraulic output cylinder and drive piston in terms of pressure limits the first hydraulic output cylinder, wherein the pressure limiting valve is configured for limiting pressure in relation to a second output cylinder or for relieving pressure into the second output cylinder, and wherein the second output cylinder is hydraulically linked to the hydraulic drive cylinder.

9. A method for operating a hydraulic actuator or a robot arm or a robot hand the method comprising: deflecting at least one actuator for the duration of an operative or non-operative phase of the hydraulic actuator for a deflection duration at a deflection frequency; establishing by the deflection duration a motional rigidity of the hydraulic actuator; and establishing by the deflection frequency a resulting deflection velocity of the hydraulic actuator.

10. The method of claim 9, wherein a multi-port valve is actuated preferably for operating the hydraulic actuator in mutually opposed directions.

Description

FIGURES

[0023] FIG. 1 schematically depicts a known hydraulic actuator in a hydraulic block diagram;

[0024] FIG. 2 schematically depicts three operating modes (a), (b), and (c) of the hydraulic actuator according to FIG. 1, in a diagrammatic illustration; and

[0025] FIG. 3 schematically depicts a hydraulic actuator according to an embodiment including a first and a second output cylinder.

DESCRIPTION

[0026] The hydraulic actuator 5 depicted in FIG. 1 includes a piezo actuator 10 that in terms of motion is linked to a drive piston 15 of a hydraulic drive cylinder 20.

[0027] The drive cylinder 20 includes a hydraulic drive volume 25 that is filled with hydraulic oil. The drive volume 25, by way of a stop valve 30 that opens at a sufficiently high opening pressure, is hydraulically linked to a hydraulic output cylinder 35. The stop vale 30 is correspondingly pretensioned. The output cylinder 35 at the drive side includes an output volume 40 that moves an output piston 45 that is located at the output side.

[0028] The drive volume by way of a stop valve 50 in a feeding-capable manner is linked to a reservoir 55.

[0029] The drive volume 25 by way of a stop valve 60 and a throttle 65 that in the flow direction is disposed behind the stop valve 60 may feed a pretension volume 70 of a hydraulic pretension cylinder 90, said throttle 65 by a pretension piston 75 controlling a pressure limiting valve 80. The pretension volume 70 by a second throttle 85 is linked to the reservoir 55. The pressure limiting valve 80 limits the pressure of the drive volume into the reservoir 55 or relieves the pressure of the drive volume in relation to the reservoir 55.

[0030] The hydraulic actuator 5 illustrated in FIG. 1 is operated as described hereunder: The individual operating modes are characterized by the actuation of the piezo actuator 10, as may be derived from the actuating travel/time diagrams (a), (b), and (c) according to FIG. 2, said diagrams being described in more detail hereunder.

[0031] In a first operating mode, the hydraulic actuator is operated by a low system rigidity and is actuated by an actuation velocity v1 that is not equal to zero.

[0032] The piezo actuator 10 is actuated as is diagrammatically shown by the curve C1 according to FIG. 2 (a): The piezo actuator 10 is rapidly deflected (e.g. the actuation path s.sub.an ascends at a steep gradient hS along with the time t). The pressure in the drive volume 25 of the drive cylinder 20 thus increases such that the stop valve 30 that links the drive volume 25 to the output volume 40, and the stop valve 60 that links the drive volume 40 to the pretension volume 70 are opened. Since the deflection of the piezo actuator 10 and thus the pressure increase in the drive volume 25 in this first operating mode are only very short, on account of the stop valve 60 that links the drive volume 25 to the pretension volume 70 almost no hydraulic oil may flow in the direction of the pretension volume 70 by virtue of the throttle 65 that is installed in series. The minimal flow of hydraulic oil runs off again into the reservoir 55 by way of the throttle 85 that links the pretension volume 70 to the reservoir Almost no pressure is thus built up in the pretension volume 70. The hydraulic oil consequently flows almost exclusively into the output volume 40 such that the output piston 45 is deployed by way of a resultant actuation path s.sub.ab of the hydraulic actuator 5.

[0033] The deflection of the piezo actuator 10 subsequently is again abruptly reduced (steep negative gradient hA of the curve C1 in FIG. 2 (a)), on account of which the stop valve 30 that links the drive volume 25 to the output volume 40, and the stop valve 60 that links the drive volume 40 to the pretension volume 70 are closed. A negative pressure is created by virtue of the reduced hydraulic oil in the drive volume 25, on account of which the stop valve 50 that links the drive volume 25 to the reservoir 55 is opened and the missing hydraulic oil may flow from the reservoir 55 into the drive volume 25.

[0034] If the cycle, that is to say the rapid deflection and resetting of the piezo actuator 10, in the first operating mode is repeated, a continuous deflection of the output piston 45 is performed. If a counter force acts on the output piston 45, the pressure in the output volume 40 is increased according to the counter force and the hydraulic cross section of the output cylinder 35. Since the threshold in the pressure limiting valve 80 by virtue of the missing pressure in the pretension volume 25 is very low, hydraulic oil flows back from the output volume 40 by the pressure limiting valve 80 into the reservoir 55 already in the event of a minor counter force on the output piston 45.

[0035] In a second operating mode the hydraulic actuator 5 is operated by way of a high system rigidity and actuated at an actuation velocity V1 that is not equal to zero.

[0036] The piezo actuator 10 is actuated as is diagrammatically depicted by the curve C2 according to FIG. 2 (b). The piezo actuator 10 is rapidly deflected, as described above (e.g. the actuation path s.sub.an again ascends at a steep gradient hS along with the time t).

[0037] Accordingly, the pressure in the drive volume 25 is increased, and the stop valve 30 that links the drive volume 25 to the output volume 40, and the stop valve 60 that links the drive volume 40 to the pretension volume 70 are opened. The pressure in the drive volume 25 drops on account of the hydraulic oil flowing off into the drive volume 40, as in the previously described operating mode.

[0038] As opposed to the previous operating mode, the deflection of the piezo actuator 10 is kept constant for a specific time (cf. part p of the curve C2 according to FIG. 2 (b)). Since the stop valve 30 that links the drive volume 25 to the output volume 40 includes a defined opening pressure, the stop valve 30 is closed when the pressure differential between the drive volume 25 and the output volume 40 is smaller than the opening pressure of the stop valve 30. Since the piezo actuator 10 is still deflected, the remaining pressure bears on the stop valve 60 that links the drive volume 25 to the pretension volume. Since the stop valve 60 that links the drive volume 25 to the pretension volume 70 is not pretensioned, hydraulic oil may flow by way of the stop valve 60 and the throttle 65 that is disposed downstream of the stop valve 60 until the pressure differential between the pretension volume 70 and the drive volume 25 is greater. While a small part of the hydraulic oil does indeed flow back into the reservoir 55 again by way of the throttle 85 that links the pretension volume 70 to the reservoir 55, the pressure in the pretension volume 70 increases. On account thereof, the opening threshold in the pressure limiting valve 80 is increased.

[0039] After a specific time, the piezo actuator 10 is again abruptly reset to the original actuation path s.sub.an thereof (steep negative gradient hA of the curve C2 in FIG. 2 (b)). On account thereof, hydraulic oil is suctioned from the reservoir 55 into the drive volume 25, as in the case of the previously described first operating mode. Were the throttle 85 that links the pretension volume 60 to the reservoir 55 not installed, hydraulic oil would not only be suctioned from the reservoir 55 but also from the pretension volume 70.

[0040] The cycle described, that is the deflection and the resetting of the piezo actuator 10, is subsequently repeated. If a counter force acts on the output piston 45, the pressure in the output volume 40 is thus again increased. However, the threshold in the pressure limiting valve 80 by virtue of the increased pressure in the pretension volume 70 is higher than in the previously described operating mode, on account of which a higher force on the output piston 15 may be built up and an outflow of hydraulic oil from the output volume 40 is reduced. On account thereof, the system rigidity of the hydraulic actuator 5 is enhanced. The level of the rigidity is thus set by way of the actuation profile of the piezo actuator 10.

[0041] In a third operating mode, the hydraulic actuator 5 is operated at a high system rigidity and is not actuated (that is to say actuated at an actuation velocity v0=0).

[0042] To this end, the piezo actuator 10 is actuated as is diagrammatically depicted by the curve C3 according to FIG. 2 (c).

[0043] On account of the slow deflection (comparatively minor gradient nS) of the piezo actuator 10, the pressure in the drive volume 25 barely increases, on account of which only the stop valve 60 that links the drive volume 25 to the pretension volume 70 is opened, but not the stop valve 30 that links the drive volume 25 to the output volume. On account thereof, no hydraulic oil is pumped into the output volume 40 but only into the pretension volume 70, on account of which the threshold of the pressure limiting valve 80 and thus the system rigidity of the hydraulic actuator 5 increases without the output piston 45 being deflected.

[0044] After a specific time, the piezo actuator 10 is again abruptly reset to the original actuation path s.sub.an thereof (steep negative gradient hA of the curve C3 in FIG. 2 (c)).

[0045] In further embodiments (not illustrated in a dedicated manner) that otherwise correspond to the embodiment illustrated in FIGS. 1 and 2, an electro-dynamic actuator or an electro-magnetic actuator is present instead of a piezo actuator 10.

[0046] In further embodiments (not illustrated in a dedicated manner) hydraulic cylinders in the manner of bellows without pistons guided therein instead of hydraulic cylinders including pistons guided therein may also be provided for drive cylinders and/or output cylinders and/or pretension cylinders.

[0047] By contrast, the actuator illustrated in FIG. 3 includes a second output cylinder 200 instead of the reservoir 55. In a manner similar to the first output cylinder 35 described above, a second output volume 205 that drives the second output piston 210 is present in the second output cylinder 200.

[0048] The second output cylinder 200 consequently assumes the function of the reservoir of the examples described above. However, the second output piston 210 in the second output cylinder 200 additionally assumes the function of a further actuator component that in the embodiment depicted in FIG. 3 provides an output by way of an actuator path s.sub.ab2 in an output direction that is opposite to the output direction of the first output piston 45 of the first output cylinder 35 as described above. Consequently, the hydraulic actuator depicted in FIG. 3 is configured so as to actuate in mutually opposed directions.

[0049] In the case of the hydraulic actuator according to FIG. 3 the first output cylinder 35 and the second output cylinder 200 by a multi-port valve 100 are hydraulically linked collectively to the remaining part of the hydraulic actuator. The roles of the first output cylinder 35 and of the second output cylinder 200 that in a first position assumes the function of the reservoir 55 of the examples mentioned at the outset may be swapped by switching the multi-port valve 100; that is to say that the second output cylinder 200 in a first position of the multi-port valve assumes the role of the reservoir 55, while the first output cylinder 35 in a second position of the multi-port valve however assumes the role of a reservoir 55.

[0050] The hydraulic actuator depicted in FIG. 3 otherwise corresponds to the example hydraulic actuator depicted in FIG. 1.

[0051] The robot arm and the robot hand (not illustrated in a dedicated manner) include in each case one or a plurality of hydraulic actuators as described above, and include in each case one control device that actuates the piezo actuator 10 of each actuator depending on the required deflection velocity and the desired system rigidity.

[0052] It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present disclosure. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

[0053] While the present disclosure has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.