Method for monitoring functional states A pressure driven actuator and Pressure-actuatable actuator

Abstract

The invention relates to a method for monitoring a functional state of a pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall, the actuator being actuated by applying pressure to the actuator compartment by means of an operating pressure supply, a work process being carried out to actuate the actuator, which process is accompanied by the actuator transitioning from a starting configuration to an end configuration. The pressure the pressure applied to the actuator compartment is measured depending on time by means of a sensor apparatus during the transition from the starting configuration to the end configuration. The invention also relates to a pressure-driven actuator.

Claims

1. Method for monitoring a functional state of a pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall, the actuator being actuated by applying pressure to the actuator compartment by means of an operating pressure supply, a work process being carried out to actuate the actuator, which process is accompanied by the actuator transitioning from a starting configuration to an end configuration, characterised in that the pressure is measured depending on time by means of a sensor apparatus for measuring the pressure applied to the actuator compartment during the transition from the starting configuration to the end configuration.

2. Method according to claim 1, characterised in that a characteristic curve (a, b, c, d) representing the progression of the pressure over time during the work process is determined and is stored in a storage apparatus.

3. Method according to claim 1, characterised in that the pressure is only measured at specified time intervals (t1; t2) from the start of the work process and is compared with reference values stored in a storage apparatus, and/or the deviation from the reference values is determined.

4. Method according to claim 2, characterised in that the pressure is continuously measured and the characteristic curve is compared with a specified and limited number of pressure reference values for distinct reference times (t1; t2), and/or the deviation from the reference values is determined.

5. Method according to claim 2, characterised in that the determined characteristic curve is compared with a reference characteristic curve stored in a storage apparatus, and/or the deviation from the reference characteristic curve is determined.

6. Method according to claim 1, characterised in that the operating pressure supply is controlled and/or the application of pressure to the actuator compartment is controlled such that the pressure applied to the actuator compartment corresponds to a target value predefined in each case at specified time intervals from the start of the work process, or in that the deviation from the target value predefined in each case is at most a predefined tolerance deviation.

7. Method according to claim 1, characterised in that the operating pressure supply provides a specified output and/or a specified volumetric flow of working fluid in order to actuate the actuator to carry out the work process.

8. Method according to claim 1, characterised in that, in addition to the work process, a calibration process is carried out in which a specified and reproducible load is applied to the actuator and the operating pressure supply provides a specified output and/or a specified volumetric flow of working fluid, the actuator transitioning from the starting configuration to the end configuration, and the time dependency of the pressure being determined in the form of a reference characteristic curve representing the progression of the pressure over time and being stored in a storage apparatus.

9. Method according to claim 1, characterised in that functional data which represent a functional state of the actuator are determined from the pressure measured depending on time.

10. Method according to claim 1, characterised in that a force acting on the actuator as a load is determined from the progression of the measured pressure over time.

11. Method according to claim 1, characterised in that a plurality of work processes are cyclically repeated and are carried out in succession.

12. Pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall such that the actuator can be actuated by applying pressure to the actuator compartment, the actuator transitioning from a starting configuration into an end configuration under deformation of the flexibly deformable wall, characterised in that a sensor apparatus is provided for the time-dependent measurement of the pressure applied to the actuator compartment.

13. Pressure-driven actuator according to claim 12, characterised in that a controller is provided which is designed to carry out a method for monitoring a functional state of the pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall, the actuator being actuated by applying pressure to the actuator compartment by means of an operating pressure supply, a work process being carried out to actuate the actuator, which process is accompanied by the actuator transitioning from a starting configuration to an end configuration, characterised in that the pressure is measured depending on time by means of a sensor apparatus for measuring the pressure applied to the actuator compartment during the transition from the starting configuration to the end configuration.

14. Pressure-driven actuator according to claim 12, wherein the actuator is a vacuum pick-up device comprising a suction compartment forming the actuator compartment, to which a vacuum can be applied in order to pick up an object.

15. Pressure-driven actuator according to claim 12, wherein the actuator is a vacuum tube lifter comprising a tube interior of a vacuum lifting tube forming the actuator compartment, wherein the vacuum lifting tube can be transferred from an extended starting configuration into a contracted end configuration by means of a vacuum being applied to the tube interior.

Description

[0043] The invention is explained in greater detail in the following with reference to the drawings, in which:

[0044] FIG. 1 is a schematic view of an actuator according to the invention for carrying out a method according to the invention;

[0045] FIG. 2 is an example of characteristic curves for various operating conditions of the actuator;

[0046] FIG. 3 is an example showing the comparison with reference values at specified reference times;

[0047] FIG. 4 is an example showing further influencing factors on the characteristic curves;

[0048] FIG. 5 is another embodiment of an actuator according to the invention in its starting configuration;

[0049] FIG. 6 shows the actuator according to FIG. 5 in its end configuration.

[0050] In the following description and in the drawings, the same reference signs are used in each case for identical or corresponding features.

[0051] FIG. 1 is a schematic view of a pressure-driven actuator 10. The actuator 10 is only designed as a vacuum pick-up device by way of example. The actuator comprises an actuator compartment 12 defined by a flexibly deformable wall 14. In the example shown, the flexibly deformable wall is designed as a flexibly deformable bellows 14.

[0052] In order for pressure to be applied to the actuator compartment 12, the actuator compartment 12 is in a pressure connection and/or flow connection with an operating pressure supply 16.

[0053] The actuator 10, which is designed as a vacuum pick-up device in FIG. 1, comprises a contact surface 18 comprising a suction opening 20 that communicates with the actuator compartment 12. In order to pick up an object 22, the contact surface 18 comprising the suction opening is brought into contact with the object 22 and a vacuum is applied to the actuator compartment 12.

[0054] However, actuators comprising other types of actuator compartment 12 can also be used in principle, for example a vacuum lifting tube as an actuator, the actuator compartment 12 being surrounded by a vacuum lifting tube wall (e.g. a corresponding wall 14). In the same way, the actuator 10 can be designed as a fluidic elastomer actuator that changes its shape when pressure is applied thereto.

[0055] In order to operate the actuator 10, pressure is applied to the actuator compartment 12. If this is a vacuum-operated actuator, as in FIG. 1, a vacuum is applied to the actuator compartment 12 relative to the surroundings.

[0056] The actuator 10 comprises a sensor apparatus 24 (here, a pressure sensor), which is designed to measure the pressure applied to the actuator compartment 12. The actuator 10 may also comprise a controller 26 (see FIG. 1), which interacts with the sensor apparatus 24 such that the pressure applied to the actuator compartment 12 can be measured in a time-dependent manner. In particular, the actuator 10 may comprise a storage apparatus, for example as a component of the controller. Measured data can be stored in the storage apparatus.

[0057] The functional state of the actuator 10 can be monitored while a work process is being carried out. In order to carry out the work process, pressure (a vacuum in the example shown) is applied to the actuator compartment 12 by the operating pressure supply 16. This means that the actuator transitions from a starting configuration to an end configuration. In the example in FIG. 1, the starting configuration is an extended configuration of the flexibly deformable wall 14, as shown in FIG. 1. When evacuating the actuator compartment 12, the configuration of the actuator 10 (more precisely, the configuration of the wall 14 or the bellows 14 in FIG. 1) changes due to compression in the compression direction 28. The end configuration is reached when the bellows 14 is completely contracted according to its material properties and geometric properties. In this respect, the transition from the starting configuration to the end configuration is accompanied by deformation of the flexible wall 14.

[0058] By means of the sensor apparatus 24, the pressure applied to the actuator compartment 12 or the pressure prevailing in the actuator compartment 12 is measured depending on time from the start of the work process, i.e. from the beginning of the transition from the starting configuration to the end configuration. The progression of the pressure over time may be recorded in the form of a characteristic curve representing the dependency of the pressure on time, and for example may be stored in the controller 26 or a storage device.

[0059] FIGS. 2 to 4 show different characteristic curves and the influences of different operating states of the actuator 10 on the characteristic curves.

[0060] For example, FIG. 2 shows characteristic curves of the pressure applied to the actuator compartment 12 for different work processes. Here, each work process begins at the time to =0 and ends at the time tE.

[0061] For example, the operating pressure supply 16 can be actuated such that it provides a constant output throughout the entire work process. Here, the time tE marks the end of the work process, which is defined by reaching the end configuration of the actuator.

[0062] The various work processes to which the various characteristic curves are assigned in FIG. 2 differ by way of example on account of the mass of the object 22 picked up by the actuator 10. Different masses of the object 22 lead to different load states for the actuator 10. In the example shown in FIG. 1, different load states correspond to different weight forces, which counteract a transition of the actuator compartment 12 from the starting configuration to the end configuration on account of the object 22 picked up.

[0063] As can be seen in FIG. 2, the work process has portions X and Y (and thus there are different regions of the progression of the characteristic curves) in which the characteristic curves deviate from one another for different load states (here, masses of the object 22) in a characteristic manner. By way of example, characteristic curves a, b, c, d are plotted for the different masses.

[0064] This makes it possible to determine to which load state the actuator 10 is subjected by analysing the progression of a plotted characteristic curve. A functional state, e.g. the mass of the object picked up, can be determined in this case by measuring the characteristic curve.

[0065] Since the characteristic curves deviate from one another in the characteristic portions X and Y for different load states, it may be sufficient not to evaluate the different characteristic curves over the entire work process, but only at set, distinct reference times t1 and t2. This is shown in FIG. 3. The functional state of interest (here, the mass of the object 22) can also be determined on the basis of the characteristic progression in portions X and Y from the values of the characteristic curves at the times t1 and t2. In the example in FIGS. 2 and 3, this means that the characteristic curves a, b, c, d (see FIG. 2) may already differ at the reference times t1 and t2 by the characteristic values.

[0066] By measuring the pressure applied to the actuator compartment 12 depending on time, various types of information regarding the functional state of the actuator 10 can be determined. For this purpose, the fact that various influencing factors often influence various characteristic regions of the characteristic curves can be utilised. This is shown in FIG. 4. This figure shows a range of different characteristic curves for different load states of the actuator due to different weight forces. As explained on the basis of the example in FIG. 2, the characteristic curves deviate from one another in a characteristic manner in a portion X of the work processes depending on the load due to weights.

[0067] In FIG. 4, the two characteristic curves denoted by e1 and e2 correspond to a load state having an identical weight or mass. In this respect, the characteristic curves e1 and e2 substantially correspond in said region X.

[0068] In the case of FIG. 4, however, the characteristic curves e1 and e2 are incorporated in two functional states of the actuator 10, which differ in terms of the degree of deformability of the actuator compartment 12. The degree of deformability is influenced by the configuration of the flexibly deformable wall 14, for example. If this is a bellows 14, for example, compression may take place together with deformation until a compressed state of the material is reached in which the individual folds are in contact with one another. In the same way, material fatigue or material wear may lead to a change in the mechanical properties and thus to altered deformation behaviour. As can be seen in FIG. 4, the characteristic curves e1 and e2 differ in a characteristic portion Z of the work process which deviates from the portion X.

[0069] Overall, information regarding the load state of the actuator and at the same time also information regarding the degree of deformability or regarding potential material fatigue can be determined by analysing the characteristic curves both in portion X and portion Z.

[0070] The characteristic curves may for example be stored and evaluated in the controller 26 as a data set. As explained at the outset, the evaluation may for example include a comparison with a reference characteristic curve. Functional data that characterise the functional state of the actuator can then be determined from the characteristic curves or values of the characteristic curve at specified reference times. For this purpose, the controller 26 may comprise a correspondingly configured evaluation unit comprising a processor.

[0071] FIGS. 5 and 6 show another advantageous field of application. Here, the actuator 10 is designed as a fluidic elastomer actuator. Said actuator comprises an actuator compartment 12 surrounded by a wall 14 made of an elastomer. Working fluid can be supplied to the actuator compartment 12 through an inlet 30. In the example shown, the actuator comprises two finger-like portions that are preferably each completely enclosed by the wall 14 relative to the surroundings (except for the inlet 30). A specified and/or defined region 32 of the wall 14 may be formed so as to be folded (cf. FIG. 5).

[0072] FIG. 5 shows the actuator 10 in its starting configuration. When pressure is applied to the actuator compartment 12, the flexibly deformable wall 14 of the actuator 10 expands. This results in the shape of the actuator 10 changing. If e.g. a specified region 32 of the wall 14 is formed so as to be folded, when pressure is applied thereto, the folded region 32 expands to a greater extent than the rest of the regions of the flexibly deformable wall 14. As a result, the fluidic elastomer actuator 10 assumes an end configuration as shown in FIG. 6. The end configuration differs from the starting configuration in terms of its overall geometry. This can be utilised to pick up an object 22. In the example shown, the finger-like portions of the actuator 10 enclose the object 22 in the end configuration (cf. FIG. 6).