Method for detecting an error condition, pneumatic actuating device and gripper

Abstract

The invention relates to a method for detecting a fault condition, in particular a leakage condition, a jammed condition and / or a spring break condition, of a pneumatic actuating device (1) for industrial automation, comprising the following steps carried out by a computer unit (5): determining a first air mass flow flowing during a first pneumatic actuation of the pneumatic actuating device (1), calculating a first air mass based on the first air mass flow, determining a second air mass flow flowing during the first pneumatic actuation or during a second pneumatic actuation of the pneumatic actuating device (1), calculating a second air mass based on the second air mass flow, and detecting the fault condition based on the first air mass and the second air mass.

Description

The invention relates to a method for detecting a fault state, in particular a leakage state, a clamping state and / or a spring break state, of a pneumatic actuating device for industrial automation. A pneumatic actuating device is to be understood as a device which is pneumatically actuatable.The pneumatic actuating device comprises, for example, a pneumatic drive unit, in particular a pneumatic drive cylinder. Preferably, the pneumatic actuating device further comprises a valve device for supplying compressed air to the pneumatic drive unit and / or for discharging compressed air from the pneumatic drive unit.The leakage state is a state in which leakage occurs. For example, in the leakage state, (unwanted) air escapes from the pneumatic actuating device, in particular from a pressure chamber of the pneumatic actuating device.The clamping state is a state in which a component, in particular a drive element, for example a piston, of the pneumatic actuating device is clamped.The spring breakage state is a state in which a spring (acting on, for example, a driving member) of the pneumatic actuator is broken.DE 103 55 250 B4 relates to a method for determining leakage in a working device having a fluidic actuator.An object of the invention is to detect the fault condition.The object is achieved by a method according to claim 1. The method comprises the following steps carried out by a computer unit: ascertaining a first air mass flow flowing during a first pneumatic actuation of the pneumatic actuating device, calculating a first air mass on the basis of the first air mass flow, ascertaining a second air mass flow flowing during the first pneumatic actuation or during a second pneumatic actuation of the pneumatic actuating device, calculating a second air mass on the basis of the second air mass flow, and detecting the fault state on the basis of the first air mass and the second air mass.For example, during the first pneumatic actuation of a first pressure chamber, compressed air is supplied to the pneumatic actuating device in order to transfer the pneumatic actuating device from a first state to a second state. For example, the first state corresponds to a first pressure in the first pressure chamber and the second state corresponds to a second pressure in the first pressure chamber. Furthermore, the first state can correspond to a first position of the drive element of the pneumatic actuating device, for example a retracted position, and the second state can correspond to a second position of the drive element, for example an extended position. For example, during the second pneumatic actuation, compressed air is discharged from the first pressure chamber in order to transfer the pneumatic actuating device from the second state back into the first state.Preferably, the first air mass flow flowing during the first pneumatic actuation is integrated to calculate the first air mass, and the second air mass flow flowing during the second actuation is integrated to calculate the second air mass.On the basis of how the two calculated air masses behave with respect to one another, the computer unit can then identify whether a fault state is present. If no fault state, in particular no leakage state, is present, the first air mass should correspond to the second air mass, in particular in such a way that a deviation between the first air mass and the second air mass lies within a predetermined tolerance range. In other words, by considering the air mass balance, it can be concluded whether the fault state, in particular the leakage state, is present.According to a further exemplary embodiment, in the case of both pneumatic actuations, compressed air can be fed into the first pressure chamber or compressed air can be discharged from the first pressure chamber. The first pneumatic actuation can take place in particular in a reference state in which no fault state, in particular no leakage state, is present. The calculated first air mass then represents a reference air mass. By comparing the second air mass with this reference air mass, the computer unit then expediently identifies the fault state, in particular the leakage state, for example in response to the second air mass being greater than the reference air mass (and this deviation expediently lying outside a predetermined tolerance range).If, for example, the clamping state or the spring break state (or else the leakage state) is present as the fault state, the second air mass changes with respect to the reference air mass, and on the basis of this change it is possible to infer the clamping state or the spring break state (or else the leakage state). By means of the pneumatic actuation, an inward and / or outward movement of the drive element expediently takes place.According to a further exemplary embodiment, the pneumatic actuating device can have a double-acting pneumatic drive unit having a first pressure chamber and a second pressure chamber. During the first pneumatic actuation, compressed air is supplied to the first pressure chamber, for example, and compressed air is discharged from the second pressure chamber, in order expediently to set a piston of the pneumatic drive unit in a movement. In this example, the air mass supplied to the first pressure chamber can be calculated as the first air mass and the air mass discharged from the second pressure chamber can be calculated as the second air mass. On the basis of how the two calculated air masses behave with respect to one another, the computer unit can then identify whether a fault state is present.Further advantageous embodiments are the subject matter of the dependent claims.The invention further relates to a pneumatic actuating device for industrial automation, comprising a computer unit which is designed to carry out the method explained above.The invention further relates to a gripper comprising a first gripping element and the pneumatic actuating device, wherein the first pneumatic actuation and / or the second pneumatic actuation serves to set the gripping element in motion.Further exemplary details and exemplary embodiments are explained below with reference to the figures. This shows FIG. 1 is a schematic illustration of a system of a source of pressurized air and a pneumatic actuator connected to the source of pressurized air, FIG. 2 shows a schematic illustration of a pneumatic drive unit with a spring, FIG. 3 is a schematic illustration of a system of a compressed air source and a gripper connected to the compressed air source.FIG. 1 shows a system with a compressed air source 2 and a pneumatic actuating device 1 which is connected to the compressed air source 2. The pneumatic actuating device 1 can also be provided separately, i.e. without the compressed air source 2.The pneumatic actuating device 1 is preferably used for use in industrial automation. The pneumatic actuating device 1 preferably comprises a first pressure chamber 7, a valve device 4, a computer unit 5, a pressure sensor device 6 and / or a position sensor device 22. By way of example, the pneumatic actuating device 1 comprises a pneumatic drive unit 3 and the first pressure chamber 7 is part of the pneumatic drive unit 3. Optionally, the pneumatic actuating device 1 has an air discharge device 8, which preferably comprises at least one, by way of example two, pneumatic outputs 9 (in particular to the environment of the pneumatic actuating device 1), which are in particular designed as sound absorbers. The pneumatic actuating device 1 comprises a line arrangement 10 comprising one or more pneumatic lines for pneumatically connecting the valve device 4 and the first pressure chamber 7, in particular the pneumatic drive unit 3, to one another and / or for providing a pneumatic connection from the compressed air source 2 to the valve device 4.By way of example, the pneumatic drive unit 3 also has a second pressure chamber 12.By way of example, the pneumatic drive unit 3 is a drive cylinder. The pneumatic drive unit 3 has a drive element 13, which is exemplarily designed as a piston. By way of example, the pneumatic drive unit 3 has a drive unit body 14, relative to which the drive element 13 is movable. The drive element 13 can be set in motion by pneumatic actuation-i.e. by supplying or discharging compressed air-of the first pressure chamber 7 and / or second pressure chamber 12. For example, the driving member 13 separates the first pressure chamber 7 from the second pressure chamber 12.The valve device 4 expediently has a first valve unit 11 a, by means of which the first pressure chamber 7 can be connected pneumatically selectively to the compressed air source 2 or the air discharge device 8. The first valve unit 11 acan be designed, for example, as a 3 / 2-way valve, or alternatively can be formed by two 2 / 2-way valves. Optionally, the valve device 4 has a second valve unit 11 b,via which the second pressure chamber 12 can be connected pneumatically to the compressed air source 2 or the air discharge device 8, as desired. The second valve unit 11 bmay be designed, for example, as a 3 / 2-way valve or alternatively may be formed by two 2 / 2-way valves. The valve device 4 expediently has one or more piezo valves. For example, the 2 / 2-way valves are designed as piezoelectric valves. Optionally, all valves of the valve device 4 are designed as piezo valves (or by means of piezo valves).The first valve unit 11 aincludes a first valve port that is opened in a supply state of the first valve unit 11 a, so that compressed air from the compressed air source 2 flows into the first pressure chamber 7 through the first valve port. In a discharge state of the first valve unit 11 a, the first valve opening is closed, so that no compressed air can flow from the compressed air source 2 into the first pressure chamber 7 through the first valve opening.The first valve unit 11 aincludes a second valve port that is opened in the discharge state of the first valve unit 11 a, so that compressed air flows from the first pressure chamber 7 to the discharge device 8 through the second valve port. In the supply state of the first valve unit 11 a, the second valve opening is closed, so that compressed air cannot flow from the first pressure chamber 7 to the discharge device 8 through the second valve opening.The second valve unit 11 bhas a third valve opening which is opened in a supply state of the second valve unit 11 a, so that compressed air from the compressed air source 2 flows into the second pressure chamber 12 through the third valve opening. In a discharge state of the second valve unit 11 b, the second valve opening is closed, so that no compressed air can flow from the compressed air source 2 into the second pressure chamber 12 through the second valve opening.The second valve unit 11 bhas a fourth valve opening opened in the discharge state of the second valve unit 11 bsuch that compressed air flows from the second pressure chamber 12 through the second valve opening to the discharge device 8. In the supply state of the second valve unit 11 b, the fourth valve opening is closed, so that compressed air cannot flow from the second pressure chamber 12 to the discharge device 8 through the fourth valve opening.The pressure sensor device 6 has, by way of example, a first pressure sensor unit 15 awhich serves, in particular, to detect a compressed air pressure assigned to the first pressure chamber 7. By way of example, the first pressure sensor unit 15 ais designed to detect the pressure of compressed air flowing into the first pressure chamber 7, namely (in the direction of flow of the compressed air) behind the first valve opening, for example behind the first valve unit 11 a, and / or to detect the pressure of compressed air flowing out of the first pressure chamber 7, namely (in the direction of flow of the compressed air) before the first valve opening, for example before the first valve unit 11 a. In particular, the first pressure sensor unit 15 ais designed to detect a pressure from the side of the first valve opening assigned to the first pressure chamber (pneumatically). By way of example, the first pressure sensor unit 15 ais arranged on or in a line section of the line arrangement 10 leading from the first valve unit 11 ato the first pressure chamber 7.The pressure sensor device 6 has, by way of example, a second pressure sensor unit 15 b, which serves in particular to detect a compressed air pressure assigned to the compressed air source 2. By way of example, the second pressure sensor unit 15 bis designed to detect the pressure of compressed air flowing into the first pressure chamber 7, specifically (in the direction of flow of the compressed air) before the first valve opening, by way of example before the first valve unit 11 a. In particular, the second pressure sensor unit 15 bis designed to detect a pressure from the side of the first valve opening assigned (pneumatically) to the compressed air source 2. By way of example, the second pressure sensor unit 15 bis also designed to detect the pressure of compressed air flowing into the second pressure chamber 12, specifically (in the direction of flow of the compressed air) before the third valve opening, by way of example before the second valve unit 11 b. In particular, the second pressure sensor unit 15 bis designed to detect a pressure from the side of the third valve opening assigned (pneumatically) to the compressed air source 2. By way of example, the second pressure sensor unit 15 bis arranged on or in a line section of the line arrangement 10 leading from the compressed air source 2 to the first valve unit 11 aand / or the second valve unit 11 b.The pressure sensor device 6 has, by way of example, a third pressure sensor unit 15 cwhich is used in particular to detect a compressed air pressure assigned to the second pressure chamber 12. By way of example, the third pressure sensor unit 15 cis designed to detect the pressure of compressed air flowing into the second pressure chamber 12, namely (in the direction of flow of the compressed air) behind the third valve opening, for example behind the second valve unit 11 b, and / or to detect the pressure of compressed air flowing out of the second pressure chamber 12, namely (in the direction of flow of the compressed air) before the third valve opening, for example before the second valve unit 11 b. In particular, the third pressure sensor unit 15 cis designed to detect a pressure of the third valve opening on the side of the third valve opening assigned (pneumatically) to the second pressure chamber 12. By way of example, the third pressure sensor unit 15 cis arranged on or in a line section of the line arrangement 10 leading from the second valve unit 11 bto the second pressure chamber 12.Optionally, the pressure sensor device 6 has at least one pressure sensor unit (not shown in the figures) for detecting an air pressure assigned to a pneumatic outlet 9, for example an air pressure of the environment of the pneumatic actuating device 1.As explained below, the computer unit 5 serves in particular for detecting a fault state of the pneumatic actuating device 1. The computer unit 5 is communicatively connected to the pressure sensor device 6, for example via corresponding electrical lines, in order to receive from the pressure sensor device 6 one or more pressure signals which map one or more detected pressures. The computer unit 5 is expediently communicatively connected to the position sensor device 22 in order to receive at least one position signal which maps a position of the drive element 13. Optionally, the computer unit 5 is designed as a control unit and is used in particular for controlling the valve device 4, in particular the first valve unit 11 aand / or the second valve unit 11 b. By way of example, the computer unit 5 is communicatively connected to the valve device 4, for example via corresponding electrical lines.The line arrangement 10 comprises, by way of example, a first line section which pneumatically connects the compressed air source 2 to a first port of the first valve unit 11 a. Optionally, the first line section pneumatically connects the compressed air source 2 to a first port of the second valve unit 11 b. By way of example, the first line section is designed as a Y line section. The line arrangement 10 comprises, by way of example, a second line section which pneumatically connects a second port of the first valve unit 11 ato the first pressure chamber 7. The line arrangement 10 comprises, by way of example, a third line section which pneumatically connects a second port of the second valve unit 11 bto the second pressure chamber 12.FIG. 2 shows an alternative embodiment of the drive unit 3. For example, the drive unit 3 is here designed as a single-acting drive unit, in particular as a single-acting drive cylinder. The drive unit 3 comprises - like the drive unit 3 discussed in connection with FIG. 1 - a first pressure chamber 7, by means of the pneumatic actuation of which the drive element 13 can be set in motion. The drive unit 3 further comprises a spring 16, which expediently acts on the drive element 13, specifically in particular counter to a pneumatic drive force provided by the first pressure chamber 7. By way of example, the drive unit 3 according to this alternative embodiment does not have a second pressure chamber. By way of example, the drive unit 3 has a drive unit body 14 and the drive element 13 is mounted movably relative to the drive unit body 14. Optionally, the spring 16 is located in a pressure chamber, in particular the first pressure chamber 7, and / or acts together with the compressed air.According to an optional embodiment of the pneumatic actuating device 1, a single-acting drive unit, in particular the drive unit 3 discussed in connection with FIG. 2, is used as the drive unit 3 of the pneumatic actuating device 1.FIG. 3 shows a system comprising a gripper 17 and a compressed air source 2. the gripper 17 can also be provided by itself, i.e. without the compressed air source 2. The gripper 17 comprises a pneumatic actuating device 1, which is designed in particular like the pneumatic actuating device 1 explained above and is connected by way of example to the compressed air source 2.Expediently, the gripper 17 comprises a gripper housing 18, in which the pneumatic actuating device 1 is preferably arranged. The gripper 17 comprises a first gripping element 19, which is exemplarily designed as a first gripping finger and / or is movable relative to the gripper housing 18. The gripper 17 additionally comprises, by way of example, a second gripping element 20, which is embodied by way of example as a second gripping finger. The pneumatic actuating device 1 expediently serves to set the first gripping element 19 into a movement 21, in particular a gripping movement. By way of example, during the movement 21, the first gripping element 19 is moved toward the second gripping element 20, in particular in such a way that a gripping object arranged between the two gripping elements 19, 20 can be gripped by the two gripping elements 19, 20. In particular, the first gripping element 20 is coupled to the drive element 13, in particular is fastened thereto, such that the first gripping element 19 can be displaced into the movement 21, in particular the gripping movement, by means of a pneumatically effected movement of the drive element 13. Optionally, the gripper 17 comprises one or more springs.In the following, a detection of the fault state by the computer unit 5 will be discussed in more detail.The computer unit 5 is designed to detect the fault state of the pneumatic actuating device 1. The fault state is, for example, a leakage state, a clamping state and / or a spring break state. The leakage state is a state in which leakage occurs. For example, in the leakage state, air escapes (unintentionally) from the pneumatic actuating device 1, in particular from the first pressure chamber 7 and / or the second pressure chamber 12. The spring breakage state is a state in which the spring 16 is broken.The computer unit 5 is designed to determine, in particular to calculate, a first air mass flow flowing during a first pneumatic actuation of the pneumatic actuating device, for example on the basis of a first pressure detected by the first valve unit 11 a(for example a first pressure profile) and / or a second pressure detected by the second valve unit 11 b(for example a second pressure profile). For example, during the first pneumatic actuation, compressed air is supplied to the first pressure chamber 7, in particular by means of the first valve unit 11 a. The first air mass flow in this case flows into the first pressure chamber 7.The computer unit 5 is designed to calculate a first air mass on the basis of the first air mass flow, for example by integrating the first air mass flow. The calculated first air mass expediently indicates which air mass was supplied to the first pressure chamber 7 during the first pneumatic actuation.The computer unit 5 is further configured to determine, in particular to calculate, a second air mass flow flowing during the first pneumatic actuation or during a second pneumatic actuation of the pneumatic actuating device. The second air mass flow is calculated, for example, on the basis of a third pressure (for example, a third pressure profile) detected by the first valve unit 11 aand / or an ambient pressure.Preferably, during the second pneumatic actuation, compressed air is discharged from the first pressure chamber 7, in particular by means of the first valve unit 11 a. The second air mass flow in this case flows out of the first pressure chamber 7.Alternatively, compressed air can be supplied to the first pressure chamber 7 during the second pneumatic actuation; in this case, the second air mass flow flows into the first pressure chamber 7; in this case, the second air mass flow is calculated, for example, on the basis of a pressure detected by the first valve unit 11 a(for example, a pressure profile) and / or a pressure detected by the second valve unit 11 b.Furthermore, it is possible for the second air mass flow to flow during the first pneumatic actuation; for example, the second air mass flow flows out of the second pressure chamber 12, in particular by means of the second valve unit 11 b, during the first pneumatic actuation. In this case, the second air mass flow is calculated, for example, on the basis of a pressure detected by the third valve unit 11 c(for example, a pressure profile) and / or an ambient pressure.The computer unit 5 is designed to calculate the second air mass on the basis of the second air mass flow, for example by integrating the second air mass flow. The calculated second air mass expediently indicates which air mass was discharged from the first pressure chamber 7 during the second pneumatic actuation.The computer unit 5 is designed to recognize the fault state on the basis of the first air mass and the second air mass. The computer unit 5 is preferably designed to provide fault state information on the basis of the detected fault state, said fault state information indicating the detected fault state.The determination of the first air mass flow, the calculation of the first air mass flow, the determination of the second air mass flow, the calculation of the second air mass flow and the detection of the fault state are expediently also to be referred to as fault state detection procedure. Optionally, the computer unit 5 is designed to carry out a separate fault state detection procedure for each pressure chamber 7, 12. The computer unit 5 preferably carries out the fault state detection procedure during the ongoing operation of the pneumatic actuating device 1, that is to say in particular in a state in which the pneumatic actuations are carried out for a purpose other than the mere detection of the fault state. Optionally, no moving to an end position and / or a specific position is required for the fault state detection procedure.The computer unit 5 preferably recognizes the fault state in response to a deviation between the first air mass and the second air mass lying outside a predetermined tolerance range. The predetermined tolerance range is expediently stored in the computer unit, for example by means of a threshold value. Optionally, the first pneumatic actuation and the second pneumatic actuation are selected such that in a state in which the fault state is not present, the deviation lies within the tolerance range. Optionally, the first pneumatic actuation and the second pneumatic actuation are selected such that under ideal conditions the first air mass is equal to the second air mass.In particular, the air mass balance reveals that a leakage air mass equals a supplied air mass (for example the first air mass) minus a flowed-off air mass (for example the second air mass).The computer unit 5 is preferably designed to form a quotient of the first air mass and the second air mass and to compare it with a limit value, for example 1.2, and, in response to the quotient exceeding the limit value, to recognize the fault state and, for example, to output a warning, in particular a leakage warning.In the following, different variants will be discussed as to how the first and second pneumatic actuation can take place.According to a preferred embodiment, the pneumatic actuating device 1 is moved from a first state to a second state by the first pneumatic actuation and is moved from the second state back to the first state by the second pneumatic actuation. For example, the first state corresponds to a first pressure in the first pressure chamber 7 and the second state corresponds to a second pressure in the first pressure chamber 7. furthermore, the first state can correspond to a first position of the drive element 13 of the pneumatic actuating device, for example a retracted position, and the second state can correspond to a second position of the drive element 13, for example an extended position. For example, the drive element 13 is moved in a first direction of movement, in particular from the first position into the second position, on account of the first pneumatic actuation, and the drive element 13 is moved in a second direction of movement opposite the first direction of movement, in particular from the second position into the first position, on account of the second pneumatic actuation. The movements carried out by the drive element 13 are in particular linear movements.The computer unit 5 expediently recognizes by means of the position sensor device 22 and / or the pressure sensor device 6 that the respective state-i.e. the first state or the second state-is present and, in response to this recognition, terminates the respective pneumatic actuation-i.e. the first pneumatic actuation or the second pneumatic actuation.As already mentioned above, the first air mass flow can flow into the first pressure chamber 7 during the first pneumatic actuation-in particular in order to transfer the pneumatic actuating device 1 from the first state into the second state-and the second air mass flow can flow out of the first pressure chamber during the second pneumatic actuation-in particular in order to transfer the pneumatic actuating device 1 from the first state into the second state.In a state in which the fault state does not exist, the first air mass which is supplied to the first pressure chamber 7 in order to transfer the pneumatic actuating device 1 from the first state to the second state would have to correspond to the second air mass which is discharged from the first pressure chamber 7 in order to transfer the pneumatic actuating device 1 from the second state back to the first state.In this embodiment, it is thus taken into account, for example, which air mass is supplied to a pressure chamber, in particular to the first pressure chamber 7, during a process and which air mass is subsequently discharged again from this pressure chamber. In particular, in this embodiment, air mass flows in the case of movements of the drive element 13 that take place in two different directions are taken into account.According to a further embodiment, the first air mass flow flows into the first pressure chamber 7 during the first pneumatic actuation and the second air mass flow flows into the first pressure chamber 7 during the second pneumatic actuation.According to this embodiment, in the case of both pneumatic actuations, compressed air can be fed into the first pressure chamber or compressed air can be discharged from the first pressure chamber. In particular, in this embodiment, each of the pneumatic actuators serves to move the driving member 13 in the same direction.The first pneumatic actuation can take place in particular in a reference state in which no fault state, in particular no leakage state, is present. The first pneumatic actuation can also be referred to as a reference actuation. The calculated first air mass represents a reference air mass. By comparing the second air mass with this reference air mass, the computer unit then expediently identifies the fault state, in particular the leakage state, for example in response to the second air mass being greater than the reference air mass (and this deviation expediently lying outside a predetermined tolerance range).The reference actuation expediently comprises a reference travel of the drive element 13. Optionally, a recalibration of the system, in particular of the reference air mass and / or of a limit value, can take place at a later point in time, and thereafter the detection of the fault state can take place using the newly determined reference air mass and / or of the newly determined limit value.Expediently, in this embodiment, the drive element 13 is moved in the same direction in each case during both pneumatic actuations. Optionally, further pneumatic actuations take place in which the computer unit 5 determines the air mass flow and calculates the air mass, and the computer unit 5 compares these further calculated air masses with one another and / or with the reference air mass in order to detect the fault state.According to a further embodiment, the first air mass flow flows into the first pressure chamber 7 during the first pneumatic actuation and the second air mass flow flows out of the second pressure chamber 12 during the first pneumatic actuation.According to this further embodiment, the pneumatic actuating device 1 can have the double-acting pneumatic drive unit 3 with the first pressure chamber 7 and the second pressure chamber 12. During the first pneumatic actuation, compressed air is supplied to the first pressure chamber 7, for example, and compressed air is discharged from the second pressure chamber 12 in order to expediently set the drive element 13 of the pneumatic drive unit 3 in a movement. In this example, the air mass supplied to the first pressure chamber 7 can be calculated as the first air mass and the air mass discharged from the second pressure chamber 12 as the second air mass. On the basis of how the two calculated air masses behave with respect to one another, the computer unit 5 can then identify whether a fault state is present.In the following, it will be discussed in more detail how the air mass flow can be determined. If an air mass flow is mentioned below, this means in particular the first air mass flow and / or the second air mass flow. The term "ascertained air mass flow" means in particular a value which maps the air mass flow.Preferably, the determination of the first air mass flow and / or the determination of the second air mass flow takes place without the use of a flow sensor. The pneumatic actuating device 1, in particular the gripper 17, preferably does not comprise a flow sensor.For example, the air mass flow is calculated on the basis of one or more pressures detected by means of the pressure sensor device 6.For example, the first air mass flow and / or the second air mass flow is a setpoint mass flow determined as part of a regulation. For example, the computer unit 5 carries out a regulation of the pressure of the first pressure chamber 7 and / or the position of the drive element 13 and calculates a desired mass flow, for example as a control variable, within the scope of this regulation. This setpoint mass flow calculated as part of a regulation can be expediently used by the computer unit 5 as the first air mass flow and / or the second air mass flow.The first air mass flow and / or the second air mass flow is preferably an actual mass flow calculated on the basis of a pressure detected by the pressure sensor device 6.For example, the computer unit 5 calculates the air mass flow on the basis of a primary pressure and a secondary pressure, the primary pressure being upstream of the valve opening through which the air mass flow flows, and the secondary pressure being downstream of the valve opening through which the air mass flow flows, in the direction of flow of the air mass flow. The primary pressure and / or the secondary pressure are expediently detected by means of the pressure sensor device 6.In particular, the air mass flow can be calculated with the aid of the C-b-value method, specifically in particular according to the following equation: ≅ is the calculated air mass flow; δ is the standard density of the air (standard-specific constant); C max is the conductance of the valve of the valve device 4 that conducts the air mass flow (valve-specific constant; u is the normalized valve opening as a value between 0 and 1; p pri is the primary pressure-in particular the pressure of the compressed air upstream of the valve opening (in the flow direction of the air mass flow); P sec is the secondary pressure-in particular the pressure of the compressed air downstream of the valve opening (in the flow direction of the air mass flow); b is the critical pressure ratio of the valve (valve specific constant).The computer unit 5 expediently calculates the air mass flow taking into account a flow area of the valve opening through which the air mass flow flows. For example, the valve device 4 has a stroke sensor system with which a stroke of a valve member determining the valve opening is detected, and the throughflow area is calculated on the basis of the detected stroke. Furthermore, in particular in the case in which no stroke sensor system is present, for example in the case of a corresponding piezo valve, the stroke can be calculated on the basis of a voltage with which the valve device 4 is actuated, and the throughflow area can be calculated on the basis of the stroke.Optionally, the conductance is calculated as a function of a detected bender stroke and / or a piezo voltage of the valve of the valve device 4 providing the valve opening.In the following, it will be discussed in more detail how the air mass can be calculated. If an air mass is mentioned below, this means in particular the first air mass and / or the second air mass.The air mass is preferably calculated by integration of the underlying air mass flow over time, in particular over the period of the associated pneumatic actuation. In particular, the air mass can be calculated according to the following equation: m is the calculated air mass; t start is expediently the start time of the respective air mass flow, i.e. in particular the start of the respective pneumatic actuation; t end is expediently the end time of the respective air mass flow, i.e. in particular the end of the respective pneumatic actuation; m is the respective air mass flow; m 0 is an air mass already present in the pneumatic actuating device 1, for example in the respective pressure chamber.The computer unit 5 expediently has software, in particular a calculation rule and / or an algorithm, for carrying out the integration of the air mass flows. For example, the computer unit 5 comprises a microcontroller on which this software is executed. The microcontroller is preferably arranged on a printed circuit board.The first pneumatic actuation and / or the second pneumatic actuation is preferably carried out by means of the valve device 4 and the first air mass on the basis of the first air mass flow is calculated exclusively for a first period of time during which the first valve opening of the valve device 4, through which the first air mass flow flows, is opened. Preferably, the second air mass is calculated on the basis of the second air mass flow exclusively for a second period of time during which the first valve opening or the second valve opening of the valve device 4 through which the second air mass flow flows is open.In particular, the computer unit 5 determines t start and t end for the integral to be calculated (for the calculation of the respective air mass) such that only integration is carried out over a period in which the respective valve opening is open.The computer unit 5 expediently establishes on the basis of a control signal for the valve device 4 that the first time period and / or the second time period is present and calculates the first air mass and / or the second air mass on the basis of this ascertainment. In particular, the computer unit 5 thus determines on the basis of the control signal that the respective valve opening is open and accordingly calculates the integral (for the calculation of the respective air mass) exclusively for a period in which the respective valve opening is open.

Claims

Method for detecting a fault state of a pneumatic actuating device (1) for industrial automation, comprising the following steps carried out by a computer unit (5): - determining a first air mass flow flowing during a first pneumatic actuation of the pneumatic actuating device (1), - calculating a first air mass on the basis of the first air mass flow, - determining a second air mass flow flowing during the first pneumatic actuation or during a second pneumatic actuation of the pneumatic actuating device (1), - calculating a second air mass on the basis of the second air mass flow, and - detecting the fault state on the basis of the first air mass and the second air mass.The method of claim 1, wherein the fault condition comprises a leak condition, a pinch condition, and / or a spring break condition.The method of claim 1 or 2, wherein the fault condition is detected in response to a deviation between the first air mass and the second air mass being outside a predetermined tolerance range.Method according to one of the preceding claims, wherein the first air mass flow and / or the second air mass flow is a setpoint mass flow determined as part of a regulation or an actual mass flow calculated on the basis of a pressure detected by a pressure sensor device (6)Method according to one of the preceding claims, wherein the determination of the first air mass flow and / or the determination of the second air mass flow takes place without the use of a flow sensor.Method according to any preceding claim, wherein the pneumatic actuator (1) is shifted from a first state to a second state by the first pneumatic actuation and is shifted from the second state back to the first state by the second pneumatic actuation.Method according to any preceding claim, wherein the pneumatic actuating device (1) has a first pressure chamber (7), the first air mass flow flows into the first pressure chamber (7) during the first pneumatic actuation and the second air mass flow flows out of the first pressure chamber (7) during the second pneumatic actuation.Method according to one of Claims 1 to 5, wherein the pneumatic actuating device (1) has a first pressure chamber (7), and wherein the first air mass flow flows into the first pressure chamber (7) during the first pneumatic actuation and the second air mass flow flows into the first pressure chamber (7) during the second pneumatic actuation, or the first air mass flow flows out of the first pressure chamber (7) during the first pneumatic actuation and the second air mass flow flows out of the first pressure chamber (7) during the second pneumatic actuation.Method according to one of Claims 1 to 5, wherein the pneumatic actuating device (1) has a first pressure chamber (7) and a second pressure chamber (12), the first air mass flow flows into the first pressure chamber during the first pneumatic actuation and the second air mass flow flows out of the second pressure chamber during the first pneumatic actuation.Method according to any preceding claim, wherein the first pneumatic actuation and / or the second pneumatic actuation is effected by means of a valve device (4) and the first air mass is calculated on the basis of the first air mass flow exclusively for a first period of time during which a first valve opening of the valve device (4) through which the first air mass flow flows is opened, and / or the second air mass is calculated on the basis of the second air mass flow exclusively for a second period of time during which the first valve opening or a second valve opening of the valve device (4) through which the second air mass flow flows is opened.Method according to Claim 10, wherein the computer unit (5) establishes on the basis of a control signal for the valve device (4) that the first time period and / or the second time period is present and calculates the first air mass and / or the second air mass on the basis of this ascertainment.Pneumatic actuating device (1) for industrial automation, comprising a computer unit (5) which is designed to carry out a method according to one of the preceding claims.Gripper (17) comprising a first gripping element (19) and a pneumatic actuating device (1) according to claim 10, wherein the first pneumatic actuation and / or the second pneumatic actuation serves to set the gripping element (19) in motion.

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