Current-controlled adjustment of the holding current of a holding brake of an electric drive

Abstract

A holding brake (5) is assigned to an electric drive (1), in particular a servomotor. The holding brake (5) is actuated by means of an electromagnetic actuator (6). The actuator (6) transfers the holding brake (5) from a blocking state, in which the holding brake (5) blocks the electric drive (1), into a release state, in which the holding brake (5) does not block the electric drive (1) as soon as an operating current (I) above a minimum pull-in current (I1) is applied to the actuator (6). The actuator (6) holds the holding brake (5) in the release state as long as an operating current (I) above a minimum holding current (I2) is applied to the actuator (6) after the holding brake (5) has been transferred into the release state, wherein the minimum holding current (I2) is less than the minimum pull-in current (I1). The actuator (6) transfers the holding brake (5) from the release state into the blocking state as soon as an operating current (I) is no longer applied to the actuator (6) or only an operating current (I) below the minimum holding current (I2) is applied to the actuator. In normal operation, an actuator control device (11) for the actuator (6) repeatedly receives a detected measured value for the operating current (I) after the holding brake (5) has been transferred into the release state, and actuates (C) an electronic current controller (7), via which the actuator (6) is supplied with the operating current (I), repeatedly as required in such a way that the operating current (I) is lowered to a predetermined holding current (I3) above the minimum holding current (I2) and is held there.

Description

[0001] Description

[0002] Current-controlled adjustment of the holding current of a holding brake of an electric drive

[0003] The present invention is based on an operating method for a holding brake of an electric drive, in particular a servo motor, wherein the holding brake is actuated by means of an electromagnetic actuator, wherein the actuator transfers the holding brake from a locked state, in which the holding brake blocks the electric drive, to a released state, in which the holding brake does not block the electric drive, as soon as the actuator is subjected to an operating current above a minimum pull-in current, holds the holding brake in the released state as long as the actuator is subjected to an operating current above a minimum holding current after transferring the holding brake to the released state, wherein the minimum holding current is less than the minimum pull-in current, and transfers the holding brake from the released state to the locked state,as soon as the actuator is no longer supplied with an operating current or is only supplied with an operating current below the minimum holding current.

[0004] The present invention is further based on a drive arrangement, wherein the drive arrangement comprises an electric drive, in particular a servo motor, wherein the drive arrangement comprises a holding brake which interacts with the electric drive in such a way that it blocks the drive in a blocking state of the holding brake and does not block it in a release state, wherein the holding brake has an electromagnetic actuator by means of which the holding brake can be transferred from the blocking state to the release state by applying an operating current above a minimum pull-in current to the actuator, after transferring to the release state by applying an operating current above a minimum holding current which is smaller than the minimum pull-in current,is maintained in the release state and can be transferred from the release state to the lock state by applying an operating current below the minimum holding current to the actuator or by not applying an operating current. Such operating methods and the associated drive arrangements are generally known.

[0005] Electric drives, especially servo motors, are often equipped with a holding brake. Such a holding brake blocks the drive's movement in a locked state. In an enabled state, it does not block the drive's movement. In the enabled state, the drive's movement is therefore enabled.

[0006] The holding brake is actuated by an electromagnetic actuator. For safety reasons, the holding brake is locked when de-energized.

[0007] In the prior art, the actuator is controlled voltage-based. To transfer the holding brake from the locked state to the released state, a sufficiently high voltage is applied to the actuator, resulting in a sufficiently large current, which causes the actuator to transfer the holding brake to the released state. Likewise, to hold the holding brake in the released state, a sufficiently high voltage is applied to the actuator, resulting in a sufficiently large current, which causes the actuator to hold the holding brake in the released state. The voltage for holding the holding brake in the released state can be the same voltage as the voltage for transferring the holding brake to the released state, or a lower, but still sufficiently high, voltage. To transfer the holding brake to the locked state, the actuator's power supply is switched off.

[0008] The state-of-the-art approach is associated with several disadvantages.

[0009] For example, transferring the holding brake from the locked state to the released state requires a certain amount of time. In the current state, this situation is taken into account by parameterizing a waiting time on the drive controller for the electric drive. This waiting time must elapse from the moment the actuator is activated to transfer the holding brake to the released state before the electric drive begins to move. This waiting time is commonly referred to in the current state as the brake release time.

[0010] Similarly, transferring the holding brake from the released state to the locked state also requires a certain amount of time. In the prior art, this situation is taken into account by parameterizing an additional wait time on the drive control side, which expires after the actuator control has ended before transferring the holding brake to the locked state. During this wait time, the drive is still actively controlled by the drive control such that it is held in its current position, i.e., it is not moved. Only after this wait time has elapsed is the control of the electric drive ended. In the prior art, this wait time is usually referred to as the brake application time. Before the holding brake is transferred to the locked state, the drive is therefore first actively brought to a standstill. The command to transfer the holding brake to the locked state is then sent to an actuator control device for the actuator.During the brake application time, the drive remains stationary with the corresponding active control. Only after the brake application time has elapsed is the drive control terminated.

[0011] Furthermore, the actuator must be continuously supplied with a sufficiently large operating current during the period in which the holding brake is in the release state, otherwise the holding brake would revert to the locked state. This causes the actuator to consume electrical energy.

[0012] The object of the present invention is to provide possibilities by means of which the disadvantages of the prior art can be eliminated as far as possible.

[0013] The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject of dependent claims 2 to 6.

[0014] According to the invention, an operating method of the type mentioned at the outset is designed in that, in normal operation, an actuator control device for the actuator repeatedly receives a detected measured value for the operating current after the holding brake has been transferred to the release state and repeatedly adjusts the control of an electronic current controller, via which the actuator is supplied with the operating current, as needed, in such a way that the operating current is reduced to a predetermined holding current above the minimum holding current and is held there.

[0015] The current controller is therefore not controlled by the actuator control device in such a way that a predetermined voltage is set on the output side of the current controller, resulting in an operating current that is still above the minimum holding current, the exact value of which is unknown. In this case, the resulting operating current would not be regulated to the predetermined holding current. However, this is precisely the kind of regulation achieved by the present invention. Thus, a defined holding current can be set that is only slightly (a certain minimum reserve should be maintained) above the minimum holding current.

[0016] The present invention is therefore based on the realization that holding the holding brake in the release state depends not on the applied voltage, but on the current. This is because the current creates the magnetic field that activates the actuator.

[0017] The inventive approach allows for the electrical losses when holding the holding brake in the release state to be reduced as much as possible. Furthermore, thermal effects that influence the actuator's resistance are automatically compensated for.

[0018] The precise design of the electronic current controller is of secondary importance. For example, the current controller can be designed as a half-bridge with two semiconductor switches or as a buck converter with a single semiconductor switch. In the latter case, a freewheeling diode is also present. Other designs are also conceivable. The semiconductor switch(es) can be designed, for example, as IGBTs or as field-effect transistors. The field-effect transistors can, in particular, be designed as MOSFETs. The semiconductor switches can, for example, be based on GaN.

[0019] It is preferably provided that in normal operation, the actuator control device for transferring the holding brake to the release state controls the electronic current controller in such a way that the operating current supplied to the actuator increases to a value above the minimum pull-in current, repeatedly receives a detected measured value for the operating current and monitors the detected measured value for a brief dip, interprets the detection of a brief dip in the operating current as transferring the holding brake to the release state and immediately subsequently reduces the operating current to the holding current and / or transmits a release message to a drive control for the electric drive.

[0020] This ensures that the actuator's operating current can be reduced to the holding current as soon as possible—namely, immediately after the holding brake is transferred to the release state—or that control of the drive can begin as early as possible. This eliminates the need to wait for a pre-configured fixed waiting time (which in practice is always specified with a safety margin).

[0021] The exact value to which the operating current is set to transfer the holding brake to the release state is of secondary importance. It can be a predetermined value slightly or significantly above the minimum pickup current. Strictly speaking, however, it is not even necessary to regulate the operating current to a specific value to transfer the holding brake to the release state. The only crucial factor is that the measured value for the operating current is recorded and that the operating current is monitored for a brief dip. This dip occurs when the actuator is applied and thus when the holding brake is actually transferred to the release state. After the dip - which occurs during the transfer of the holding brake from the locked state to the held state - the reduction to the holding current can thus be initiated.

[0022] The voltage applied to the actuator for transferring the holding brake to the release state can be even higher than in the prior art. This can reduce the time required to transfer the holding brake to the release state. The relatively high voltage is harmless because, within the scope of the present invention, the operating current is regulated to the holding current immediately after the holding brake is actually transferred to the release state. An uncontrolled increase in the operating current, as could and would occur in the prior art with a relatively high voltage in conjunction with the pre-parameterized fixed brake release time, is thus immediately counteracted as soon as the holding brake is transferred to the release state.

[0023] In cases where the operating current is to be regulated to a specific value above the minimum pull-in current when transferring the holding brake from the locked state to the released state, it is preferably provided that the actuator control device controls the current controller in a special mode in such a way that an operating voltage applied to the actuator is gradually increased, repeatedly receives a recorded measured value for the operating current during the gradual increase in the operating voltage and monitors the recorded measured value for a brief dip, interprets the detection of a brief dip in the operating current as transferring the holding brake to the released state and determines the minimum pull-in current based on the measured value for the operating current shortly before and / or shortly after the dip.

[0024] The operating current immediately before or immediately after the dip corresponds to the minimum pull-in current. The pull-in current can be easily determined based on the minimum pull-in current, for example, by adding an offset or scaling with a factor greater than 1. It is sufficient if the offset is small or the factor is only slightly larger than 1. However, the offset can also be larger, or the factor can be significantly larger than 1. The operating voltage can be increased continuously or in (small) steps.

[0025] In some cases, the minimum holding current is known in advance. For example, it may be specified in a data sheet. If the minimum holding current is known in advance, it can be specified directly as a parameter to the drive controller. However, the minimum holding current is usually unknown.Regardless of whether the minimum holding current is known in advance or not, it is preferably provided that the actuator control device, in a special operation, controls the current controller after transferring the holding brake to the release state in such a way that an operating voltage applied to the actuator is gradually reduced, repeatedly receives a detected measured value for the operating current during the gradual reduction of the operating voltage and monitors the detected measured value for a brief increase, interprets the detection of a brief increase in the operating current as transferring the holding brake to the blocking state and determines the holding current for normal operation based on the measured value for the operating current shortly before the increase.

[0026] This makes it easy to determine the predetermined holding current. In particular, the measured value for the operating current shortly before the increase corresponds to the minimum holding current. The holding current can be easily determined based on the minimum holding current, for example by adding a (small) offset or scaling with a factor that is (slightly) greater than 1. The operating voltage can be reduced continuously or in (small) steps. This procedure is based on the fact that, due to the inductance of the actuator, a brief increase occurs when the electromagnetic actuator drops out and thus when the holding brake is transferred to the blocking state. The operating current immediately before the drop corresponds to the minimum holding current.

[0027] It is preferably provided that the actuator control device, in normal operation, blocks the current controller to transfer the holding brake to the blocking state, so that the operating current gradually decreases, repeatedly receives a detected measured value for the operating current and monitors the detected measured value for a brief increase, interprets the detection of a brief increase in the operating current as transferring the holding brake to the blocking state and, based on the detection of the brief increase in the operating current, transmits a blocking message to a drive control for the electric drive.

[0028] This approach is based on the fact that the inductance of the actuator causes the operating current to drop gradually (in principle exponentially) to zero rather than abruptly. However, when the actuator drops off and thus when the holding brake is actually transferred to the locked state, there is a brief increase in the operating current, contrary to the essentially exponential drop. However, only when the holding brake is in the locked state can the drive control (by means of which the drive must be actively held in its position until this point in time) be terminated. Due to the lock message, the drive controller can terminate the active control of the drive as early as possible, namely immediately after the holding brake is transferred to the locked state. The drive controller therefore does not have to wait for a pre-parameterized fixed waiting time (and in practice always determined with a safety margin).

[0029] It is preferably provided that the actuator control device regulates the operating current in normal operation by means of a current regulator which determines a proportional correction component and an integral correction component based on the deviation of the operating current from a target operating current, both of which are included in the determination of the control of the current controller, that the proportional correction component results from the product of a constant gain factor and the deviation of the operating current from the target operating current, that the actuator control device varies an operating voltage to which the actuator is subjected in a special operation and records the respectively resulting operating current, that the actuator control device determines a resistance of the actuator based on the operating voltages and the respectively associated operating currents and that the actuator control device determines the gain factor based on the determined resistance.

[0030] The current controller, which determines the control of the current regulator, thus comprises at least a proportional component and an integral component. The current controller is therefore designed as a PI controller or better. The procedure for determining the gain factor ensures that, during normal operation, the proportional correction component alone provides fast and excellent control to the respective target operating current, thus leaving only a small lag error. This lag error is compensated for by the integral correction component. The design of the integral component of the current controller is therefore uncritical and can be easily determined by a specialist.

[0031] Varying the operating voltage and detecting the resulting operating current can be performed in a separate operating mode. However, preferably, varying the operating voltage and detecting the resulting operating current are performed in conjunction with the gradual increase in the operating voltage as part of determining the minimum pull-in current and / or in conjunction with the gradual decrease in the operating voltage as part of determining the holding current.

[0032] The object is further achieved by a drive arrangement having the features of claim 7. According to the invention, a drive arrangement of the type mentioned at the outset is designed in that the drive arrangement has an electronic current controller, by means of which the actuator can be supplied with the operating current, that the drive arrangement has a detection device assigned to the current controller or the actuator for detecting the operating current, that the drive arrangement has an actuator control device for the actuator, which is connected to the current controller for controlling the current controller and is connected to the detection device for receiving the respectively detected operating current, and that the actuator control device is designed, in particular programmed, in such a way thatthat in normal operation, after the holding brake has been transferred to the release state, it repeatedly receives a measured value for the operating current from the detection device and, if necessary, repeatedly adjusts the control of the current controller in such a way that the operating current is reduced to a predetermined holding current above the minimum holding current and is maintained there.

[0033] The resulting advantages correspond to those of the operating procedure.

[0034] Preferably, the actuator control device is further configured, in particular programmed, to implement the method steps of the preferred embodiments of the operating method. Here, too, the resulting advantages correspond to those of the corresponding embodiment of the operating method.

[0035] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. In this case, in a schematic representation:

[0036] FIG 1 a drive arrangement,

[0037] FIG 2 shows another drive arrangement,

[0038] FIG 3 a voltage-time diagram,

[0039] FIG 4 a current-time diagram,

[0040] FIG 5 a state-time diagram,

[0041] FIG 6 a flow chart,

[0042] FIG 7 a flow chart,

[0043] FIG 8 a flow chart,

[0044] FIG 9 a controller structure and

[0045] FIG 10 a flow chart.

[0046] 1 and 2, a drive arrangement comprises an electric drive 1. The drive 1 can in particular be designed as a servomotor. The drive 1 is generally supplied with power from a DC voltage circuit 3 via a converter unit 2. The converter unit 2 is controlled by a drive controller 4. Both the design and the mode of operation of the drive controller 4 are conventional and are therefore not explained in more detail below. The drive arrangement further comprises a holding brake 5. The holding brake 5 interacts with the electric drive 1, as indicated by a dashed line in FIGS. 1 and 2. In particular, the holding brake 5 can alternatively be in a locked state or in an enabled state. In the locked state, the holding brake 5 blocks movement of the drive 1; in the enabled state, it does not block movement of the drive 1.In the enable state, drive 1 is thus enabled and can be moved by appropriate control of converter unit 2 by drive controller 4. The holding brake 5 is actuated, as shown in FIGS. 1 and 2, by an electromagnetic actuator 6, which is supplied with an operating current I via an electronic current controller 7. The state in which the operating current I has the value 0 corresponds to a non-application of the operating current I.

[0047] According to FIG. 1, the current controller 7 can be designed as a half-bridge with two semiconductor switches 8 connected in series. Freewheeling diodes connected in parallel with the semiconductor switches 8 can be intrinsic components of the semiconductor switches 8 and are therefore not shown in FIG. 1. According to FIG. 2, the current controller 7 can alternatively be designed as a buck converter having a single semiconductor switch 8. In this case, a separate freewheeling diode 9 is required, as shown in FIG. 2. The structure and operation of such and other current controllers 7 are generally known to those skilled in the art and therefore need not be explained in more detail.

[0048] According to FIGS. 1 and 2, the current controller 7 is supplied with electrical energy via the same DC voltage circuit 3 that also supplies the converter unit 2 with electrical energy. While this configuration is not mandatory, it does have the advantage that if the power supply to the converter unit 2 fails, the power supply to the actuator 6 also fails automatically, thus automatically transferring the holding brake 5 to the locked state.

[0049] The functioning of the current controller 7 and the actuator 6 (and thus also of the holding brake 5) is explained below in conjunction with FIGS. 3 to 5.

[0050] FIG. 3 shows, as a function of time t, an operating voltage U applied by the current regulator 7 to the actuator 6. According to FIG. 3, the operating voltage U gradually increases from 0 to a maximum value over time t due to a corresponding control C of the current regulator 7 and then gradually decreases back to zero over time t due to a corresponding control C of the current regulator 7. The increase and decrease occur relatively slowly in the illustration according to FIG. 3 (usually in the single-digit second range).

[0051] FIG. 4 shows the corresponding operating current I as a function of time t. According to FIG. 4, the operating current I initially follows the operating voltage II. This is due to the slow increase in the operating voltage U. This is because the inductance of the electromagnetic actuator 6 is not affected, so that the operating current I can follow the operating voltage U. The quotient of the respective operating voltage U and the respective operating current I corresponds to the resistance of the actuator 6.

[0052] FIG 5 shows the corresponding state of the holding brake 5 as a function of time t. According to FIG 5, the holding brake 5 initially remains in the blocked state (state Z = 0) until the operating current I reaches a certain value 11, hereinafter referred to as the minimum pull-in current. As soon as the operating current I reaches the minimum pull-in current 11, the actuator 6 pulls in, so that it transfers the holding brake 5 to the released state (state Z = 1). As a result of the pull-in, the inductance of the actuator 6 changes. This change causes a brief characteristic dip in the operating current I, as shown in FIG 4. This dip represents a brief special state during which the operating current I cannot follow the operating voltage U.

[0053] As the operating voltage U and thus the operating current I continue to rise, actuator 5 remains in the engaged state, and holding brake 5 remains in the released state. The inductance of actuator 6 no longer changes. This allows the operating current I to again follow the operating voltage U. The quotient of the respective operating voltage U and the respective operating current I again corresponds to the resistance of actuator 6.

[0054] When the operating voltage U is reduced, the holding brake 5 initially remains in the released state. Thus, the operating current I initially follows the operating voltage U as shown in FIG 4. This is due to the slow drop in the operating voltage U. This is because the inductance of the electromagnetic actuator 6 is not affected, so that the operating current I can follow the operating voltage U. As shown in FIG 5, the holding brake 5 initially remains in the released state until the operating current I reaches a certain value I2, hereinafter referred to as the minimum holding current. However, as soon as the operating current I reaches the minimum holding current I2, the actuator 6 drops out, thus transferring the holding brake 5 to the blocked state. As a result of this drop, the inductance of the actuator 6 changes again. This change causes a brief characteristic increase in the operating current I as shown in FIG 4.This increase represents a short-term special condition during which the operating current I cannot follow the operating voltage U. The minimum holding current I2 is smaller than the minimum pickup current I1.

[0055] As the operating voltage U and thus the operating current I continue to drop, the actuator 5 remains in the de-energized state, and the holding brake 5 remains in the locked state. The inductance of the actuator 6 no longer changes. This allows the operating current I to follow the operating voltage U again.

[0056] According to FIGS. 1 and 2, the drive arrangement further comprises a detection device 10. The operating current I can be measured by means of the detection device 10. The detection device 10 can be assigned to the current controller 7 or the actuator 6, as required.

[0057] Finally, the drive arrangement has an actuator control device 11. The actuator control device 11 serves to control the current controller 7 and is connected to the current controller 7 for this purpose. Furthermore, the actuator control device 11 is connected to the detection device 10 for receiving the respectively detected operating current I (more precisely: the corresponding measured value). The actuator control device 11 is designed such that, during normal operation, it implements an operating method, as explained in more detail below in connection with FIG. 6. The actuator control device 11 can be designed as a software-programmable device. In this case, the actuator control device 11 is programmed with a corresponding control program comprising machine code that effects the corresponding configuration of the actuator control device 11.Alternatively, the actuator control device 11 can be programmed in hardware, for example in an ASIC design.

[0058] According to FIG 6, in a step S1, the actuator control device 11 sets the state Z of the holding brake 5 to the value 0. As already mentioned, the value 0 corresponds to the locked state. In a step S2, the actuator control device 11 checks whether the release state has been transmitted to it by the drive controller 4 as the target state Z* of the holding brake 5. It therefore checks whether the target state Z* has the value 1. If this is the case, the actuator control device 11 checks in a step S3 whether the state Z of the holding brake 5 already corresponds to the release state, i.e., whether the state Z also has the value 1, and thus the holding brake 5 has already been transferred to the release state. If this is the case, the actuator control device 11 proceeds to further steps S4 to S10. Steps S4 to S10 represent the core subject matter of the present invention.

[0059] In step S4, the actuator control device 11 receives a detected measured value for the operating current I.

[0060] In step S5, the actuator control device 11 checks whether the operating current I exceeds a predetermined holding current I3 (possibly by more than a predetermined limit). The holding current I3 is—see FIG. 4—above the minimum holding current I2. It can, for example, be between 1.1 and 1.3 times the minimum holding current I2.

[0061] If the operating current I exceeds the holding current I3, the actuator control device 11 takes measures in step S6 that cause the operating current I to decrease. For example, in step S6, the actuator control device 11 can reduce a target operating voltage II* that the current controller 7 should apply to the actuator 6. The actuator control device 11 then proceeds to step S7. In step S7, the actuator control device 11 determines a control C for the current controller 7. The determination is made, if necessary, taking into account the measures taken in step S6. Finally, in step S8, the actuator control device 11 controls the current controller 7 according to the determined control C.

[0062] If the operating current I does not exceed the holding current I3, the actuator control device 11 checks in step S9 whether the operating current I falls below the holding current I3 (possibly by more than a predetermined limit). If the operating current I falls below the holding current I3, the actuator control device 11 takes measures in step S10 that cause the operating current I to increase. For example, the actuator control device 11 can increase the target operating voltage II* in step S10. The actuator control device 11 then proceeds again to step S7. If the operating current I neither exceeds nor falls below the holding current I3, the actuator control device 11 proceeds directly to step S7. In this case, the control C of the current controller 7 remains unchanged.

[0063] The actuator control device 11 then returns to step S2, so that the actuator control device 11 repeatedly runs through steps S2 to S10 iteratively.

[0064] Since transferring the holding brake 5 to the release state presupposes that the minimum pull-in current I1 has been exceeded, the repeated execution of steps S2 to S10 initially causes the actuator control device 11 to reduce the operating current I to the holding current I3. Subsequently, the repeated execution of steps S2 to S10 further causes the actuator control device 11 to maintain the operating current I at the holding current I3. In both sections of this procedure, the actuator control device 11 repeatedly adjusts the control C of the current controller 7 as needed. Furthermore, the actuator control device 11 repeatedly receives the respective measured value for the operating current I, both in the early stages (during the reduction to the holding current I3) and thereafter (during holding at the holding current I3), in order to be able to determine the corresponding deviations of the operating current I from the holding current I3.

[0065] If the release state is transmitted to the actuator control device 11 by the drive controller 4 as the target state Z* of the holding brake 5, but the state Z of the holding brake 5 still corresponds to the locked state, the holding brake 5 must be transferred to the release state. The transfer of the holding brake 5 to the release state must occur if the actuator control device 11 determines in step S3 that the state Z of the holding brake 5 does not yet correspond to the release state.

[0066] Various procedures are possible for transferring the holding brake 5 to the release state. Currently, a procedure as explained below in connection with FIG. 6 and steps S11 to S15 therein is preferred.

[0067] In step S11, the actuator control device 11 controls the current controller 7 such that the operating current I supplied to the actuator 6 increases to a value above the minimum pull-in current I1. For example, the actuator control device 11 can determine the control C of the current controller 7 such that the operating current I is regulated to a pull-in current I4 (see FIG. 4) that is above the minimum pull-in current I1. It is also possible to determine the control C of the current controller 7 such that a predetermined, sufficiently high operating voltage U is applied to the actuator 6.

[0068] In step S12, the actuator control device 11 receives a recorded measured value for the operating current I. In step S13, the actuator control device 11 checks the recorded measured value for a brief dip. As long as this check is negative, i.e., no dip is detected, the actuator control device 11 returns to step S2. If, however, the actuator control device 11 detects a brief dip, the actuator control device 11 interprets this dip as a transfer of the holding brake 5 to the release state. Therefore, in step S14, it sets the state Z of the holding brake 5 to the value 1.

[0069] The actuator control device 11 now returns to step S2. However, the next time step S3 is executed, the check there is positive, so the actuator control device 11 does not proceed to step S11 again, but rather to step S4. Thus, steps S4 to S10 are now executed, in which the actuator control device 11 reduces the operating current I to the holding current I3 and maintains it there.

[0070] Step S15 is no longer mandatory. However, it is preferably included. In step S15, the actuator control device 11 transmits a release message M1 to the drive control 4.

[0071] If the locking state (Z* = 0) is transmitted to the actuator control device 11 by the drive controller 4 as the target state Z* of the holding brake 5, the actuator control device 11 proceeds from step S2 to step S16, by transferring the holding brake 5 to the locking state or holding it in the locking state. Various procedures are possible for transferring the holding brake 5 to the locking state and maintaining the holding brake 5 in the locking state. Currently, a procedure as explained below in connection with FIG. 6 and steps S16 to S21 therein is preferred.

[0072] In step S16, the actuator control device 11 blocks the current controller 7. As a result, the operating current I gradually decreases.

[0073] In step S17, the actuator control device 11 checks whether the state Z of the holding brake 5 corresponds to the locked state (Z = 0). If this is the case, no further action is required. The actuator control device 11 can return directly to step S2. If the state Z of the holding brake 5 does not yet correspond to the locked state, the actuator control device 11 proceeds to step S18. In step S18, the actuator control device 11 receives a detected measured value for the operating current I. In step S19, the actuator control device 11 checks the detected measured value for a brief increase. As long as this check is negative, i.e., no increase is detected, the actuator control device 11 returns to step S2. If, however, the actuator control device 11 detects a brief increase, the actuator control device 11 interprets this increase as transferring the holding brake 5 to the locked state.Therefore, in step S20, it sets the state Z of the holding brake 5 to the value 0. Furthermore, in step S21, the actuator control device 11 transmits a blocking message M2 to the drive control 4.

[0074] A possible procedure that can be executed by the actuator control device 11 in a special mode is explained below in conjunction with FIG. Within the scope of the procedure shown in FIG. 7, the holding current I3 is determined. The procedure shown in FIG. 7 assumes that the holding brake 5 has previously been transferred to the release state.

[0075] According to FIG. 7, in a step S31, the actuator control device 11 sets the target operating voltage U* to a maximum value Umax*. In a step S32, the actuator control device 11 waits for a (short) waiting time öt. In a step S33, the actuator control device 11 determines the associated control C of the current controller 7 based on the target operating voltage U*. In a step S34, the actuator control device 11 controls the current controller 7 accordingly.

[0076] In a step S35, the actuator control device 11 receives the respective measured value for the operating current I. The actuator control device 11 can either evaluate the measured value immediately or, as shown in FIG 7, store it in a step S36.

[0077] In a step S37, the actuator control device 11 checks whether the target operating voltage U* has reached a minimum value Umin*, for example, has dropped to zero. As long as this is not the case, the actuator control device 11 reduces the target operating voltage U* in a step S38. It then returns to step S32.

[0078] When the target operating voltage U* has reached the minimum value Umin*, the actuator control device 11 proceeds to step S39. In step S39, the operating current I is evaluated, specifically, the time when a brief increase occurred is checked. Based on the measured value for the operating current I shortly before the increase, the actuator control device 11 determines the holding current I3. For example, the actuator control device 11 can first determine the minimum holding current I2 and then, based on this, determine the holding current I3.

[0079] Step S32, i.e. waiting for the short waiting time öt, causes the actuator control device 11 to reduce the operating voltage U of the current controller 7 gradually, rather than abruptly.

[0080] The immediate or subsequent evaluation of the measured value for the operating current I corresponds to monitoring the measured value for a brief increase. This increase can, as explained in conjunction with FIGS. 3 to 5, be interpreted by the actuator control device as transferring the holding brake 5 to the blocking state and thus as a fall below the minimum holding current I2. Thus, the actuator control device 11 can determine the holding current I3 based on the operating current I shortly before the increase.

[0081] A possible procedure is explained below in conjunction with FIG. 8, which can also be executed by the actuator control device 11 in a special mode. The procedure shown in FIG. 8 determines the starting current I4. The procedure shown in FIG. 8 assumes that the holding brake 5 is initially in the locked state.

[0082] The procedure of FIG 8 can be combined with the procedure of FIG 7. In this case, the procedure of FIG 8 is usually executed first.

[0083] According to FIG. 7, in a step S41, the actuator control device 11 sets the target operating voltage U* to the minimum value Umin*. In a step S42, the actuator control device 11 waits for the (short) waiting time öt. In a step S43, the actuator control device 11 determines the corresponding control C of the current controller 7 based on the target operating voltage U*. In a step S44, the actuator control device 11 controls the current controller 7 accordingly.

[0084] In a step S45, the actuator control device 11 receives the respective measured value for the operating current I. The actuator control device 11 can either evaluate the measured value immediately or, as shown in FIG 8, store it in a step S46.

[0085] In a step S47, the actuator control device 11 checks whether the target operating voltage U* has reached the maximum value Umax*. As long as this is not the case, the actuator control device 11 increases the target operating voltage II* in a step S48. It then returns to step S42.

[0086] When the target operating voltage II* has reached the maximum value Umax*, the actuator control device 11 proceeds to step S49. In step S49, the operating current I is evaluated, specifically, the check is made to determine when a brief dip occurred. Based on the measured value for the operating current I shortly before and / or shortly after the dip, the actuator control device 11 determines the starting current I4. For example, the actuator control device 11 can first determine the minimum starting current I1 and, based on this, determine the starting current I4.

[0087] The step S42, i.e. the waiting of the short waiting time öt, has the effect, as before in FIG 7, that the actuator control device 11 does not reduce the operating voltage U of the current controller 7 abruptly, but gradually.

[0088] The immediate or subsequent evaluation of the measured value for the operating current I corresponds to monitoring the measured value for a brief dip. This dip can, as explained in conjunction with FIGS. 3 to 5, be interpreted by the actuator control device as transferring the holding brake 5 to the release state and thus as exceeding the minimum pull-in current I1. Thus, the actuator control device 11 can determine the pull-in current I4 based on the operating current I shortly before and / or shortly after the dip.

[0089] According to FIG 9, the actuator control device 11 implements a current controller 12 for controlling the operating current I. The current controller 12 operates at least in normal operation, often also in special operation.

[0090] The current controller 12 includes a node 13, where the deviation of the operating current I from a setpoint operating current I* (control deviation) is determined. Depending on the operating situation, the setpoint operating current I* can, for example, correspond to the holding current I3, the pull-in current I4, or the value 0 (for transferring the holding brake 5 to the blocking state).

[0091] The current controller 12 is (at least) designed as a PI controller. Therefore, it determines a proportional correction component and an integral correction component based on the control deviation. The proportional correction component is the direct product of a constant gain factor k1 and the control deviation. An integration time constant k2 is used to determine the integral correction component. The output signal of the current controller 12 is the sum of the various correction components. This procedure is generally known and familiar to experts. The output signal of the current controller can, for example, be the target operating voltage II*, which is fed to a determination element 14, which in turn determines the control C for the current controller 7.

[0092] The integration time constant k2 can be determined in a conventional manner. The amplification factor k1 is preferably determined by the actuator control device 11 in a corresponding special mode. This special mode is explained below in conjunction with FIG. 10.

[0093] According to FIG. 10, the actuator control device 11 sets the operating voltage U (or the associated setpoint II*) in a step S51. In a step S52, the actuator control device 11 controls the current controller 7 so that it applies the operating voltage U to the actuator 6. In a step S53, the actuator control device 11 records the resulting operating current I (or the corresponding measured value).

[0094] In a step 54, the actuator control device 11 checks whether the determination of the operating voltages U and the detection of the associated operating currents I have been completed. If this is not the case, the actuator control device 11 varies the operating voltage U in a step S55 and then returns to step S52.

[0095] Once the determination of the operating voltages U and the detection of the associated operating currents I are complete, the actuator control device 11 proceeds to step S56. In step S56, the actuator control device 11 determines a resistance R of the actuator 6 (more precisely: the value of the resistance) based on the operating voltages U and the respective associated operating currents I. Based on this, the actuator control device 11 determines the gain factor k1 in step S57.

[0096] The procedure of FIG 10 can be integrated into the procedure of FIG 7 and / or the procedure of FIG 8.

[0097] In summary, the present invention relates to the following:

[0098] A holding brake 5 is assigned to an electric drive 1, in particular a servomotor. The holding brake 5 is actuated by means of an electromagnetic actuator 6. The actuator 6 transfers the holding brake 5 from a locked state, in which the holding brake 5 blocks the electric drive 1, to a released state, in which the holding brake 5 does not block the electric drive 1, as soon as the actuator 6 is supplied with an operating current I above a minimum pull-in current 11. The actuator 6 holds the holding brake 5 in the released state as long as the actuator 6 is supplied with an operating current I above a minimum holding current I2 after the holding brake 5 has been transferred to the released state, wherein the minimum holding current I2 is less than the minimum pull-in current 11.The actuator 6 transfers the holding brake 5 from the release state to the blocking state as soon as the actuator 6 is no longer supplied with an operating current I or is only supplied with an operating current I below the minimum holding current I2. In normal operation, an actuator control device 11 for the actuator 6 repeatedly receives a recorded measured value for the operating current I after the holding brake 5 has been transferred to the release state and, if necessary, repeatedly adjusts the control C of an electronic current controller 7, via which the actuator 6 is supplied with the operating current I, in such a way that the operating current I is reduced to a predetermined holding current I3 above the minimum holding current I2 and is held there.

[0099] The present invention offers many advantages. The design is simple, cost-effective, and reliable. Electrical losses can be reduced. Furthermore, the waiting times required for the reliable transfer of the holding brake 5 from the locked state to the released state, or vice versa, can be minimized.

[0100] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1. An operating method for a holding brake (5) of an electric drive (1), in particular a servo motor, wherein the holding brake (5) is actuated by means of an electromagnetic actuator (6), wherein the actuator (6) transfers the holding brake (5) from a locked state, in which the holding brake (5) blocks the electric drive (1), to a released state, in which the holding brake (5) does not block the electric drive (1), as soon as the actuator (6) is subjected to an operating current (I) above a minimum pull-in current (I1), holds the holding brake (5) in the released state as long as the actuator (6) is subjected to an operating current (I) above a minimum holding current (I2) after the holding brake (5) has been transferred to the released state, wherein the minimum holding current (I2) is less than the minimum pull-in current (I1), and transfers the holding brake (5) from the released state to the locked state,as soon as the actuator (6) is no longer supplied with an operating current (I) or is only supplied with an operating current (I) below the minimum holding current (I2), wherein in normal operation an actuator control device (11) for the actuator (6) repeatedly receives a detected measured value for the operating current (I) after the holding brake (5) has been transferred to the release state and repeatedly adjusts the control (C) of an electronic current controller (7), via which the actuator (6) is supplied with the operating current (I), as needed, in such a way that the operating current (I) is reduced to a predetermined holding current (I3) above the minimum holding current (I2) and is held there.

2. Operating method according to claim 1, characterized in that in normal operation, the actuator control device (11) for transferring the holding brake (5) into the release state controls the electronic current controller (7) in such a way that the operating current (I) supplied to the actuator (6) increases to a value above the minimum pickup current (11), repeatedly receives a detected measured value for the operating current (I) and monitors the detected measured value for a brief dip, the detection of a brief drop in the operating current (I) is interpreted as transferring the holding brake (5) to the release state and immediately subsequently reducing the operating current (I) to the holding current (I3) and / or transmitting a release message (M1) to a drive control (4) for the electric drive (1).

3. Operating method according to claim 2, characterized in that the actuator control device (11) controls the current controller (7) in a special operation such that an operating voltage (II) to which the actuator (6) is applied is gradually increased, during the gradual increase of the operating voltage (II) repeatedly receives a detected measured value for the operating current (I) and monitors the detected measured value for a brief dip, interprets the detection of a brief dip in the operating current (I) as transferring the holding brake (5) to the release state and determines the minimum pickup current (I2) based on the measured value for the operating current (I) shortly before and / or shortly after the dip.

4. Operating method according to claim 1, 2 or 3, characterized in that the actuator control device (11) in a special operation controls the current controller (7) after transferring the holding brake (5) into the release state in such a way that an operating voltage (II) to which the actuator (6) is applied is gradually reduced, during the gradual reduction of the operating voltage (II) repeatedly receives a detected measured value for the operating current (I) and monitors the detected measured value for a brief increase, interprets the detection of a brief increase in the operating current (I) as transferring the holding brake (5) into the blocking state and determines the holding current (I3) for normal operation on the basis of the measured value for the operating current (I) shortly before the increase.

5. Operating method according to one of the above claims, characterized in that that the actuator control device (11) blocks the current controller (7) in normal operation to transfer the holding brake (5) to the blocking state, so that the operating current (I) gradually decreases, repeatedly receives a detected measured value for the operating current (I) and monitors the detected measured value for a brief increase, interprets the detection of a brief increase in the operating current (I) as transferring the holding brake (5) to the blocking state and, based on the detection of the brief increase in the operating current (I), transmits a blocking message (M2) to a drive control (4) for the electric drive (1).

6. Operating method according to one of the above claims, characterized in that the actuator control device (11) regulates the operating current (I) in normal operation by means of a current regulator (12) which, based on the deviation of the operating current (I) from a target operating current (I*), determines a proportional correction component and an integral correction component, both of which are included in the determination of the control of the current controller (7), that the proportional correction component results from the product of a constant gain factor (k1) and the deviation of the operating current (I) from the target operating current (I*), that the actuator control device (11) in a special operation varies an operating voltage (U) to which the actuator (6) is applied and records the respectively resulting operating current (I),that the actuator control device (11) determines a resistance (R) of the actuator (6) on the basis of the operating voltages (II) and the respective associated operating currents (I), and that the actuator control device (11) determines the amplification factor (k1) on the basis of the determined resistance (R).

7. Drive arrangement, wherein the drive arrangement comprises an electric drive (1), in particular a servo motor, wherein the drive arrangement comprises a holding brake (5) which interacts with the electric drive (1) in such a way that it blocks the drive (1) in a locked state of the holding brake (5) and does not block it in a released state, wherein the holding brake (5) has an electromagnetic actuator (6), by means of which the holding brake (5) can be transferred from the locked state to the released state by applying an operating current (I) above a minimum pull-in current (I1) to the actuator (6), can be held in the released state after transferring to the released state by applying an operating current (I) above a minimum holding current (I2) to the actuator (6) which is less than the minimum pull-in current (I1), and can be transferred from the released state to the locked state by applying an operating current (I) below the minimum holding current (I2) to the actuator (6) or by not applying an operating current (I), wherein the drive arrangement has an electronic current regulator (7), by means of which the operating current (I) can be applied to the actuator (6),wherein the drive arrangement has a detection device (10) assigned to the current controller (7) or the actuator (6) for detecting the operating current (I), wherein the drive arrangement has an actuator control device (11) for the actuator (6), which is connected to the current controller (7) for controlling the current controller (7) and is connected to the detection device (10) for receiving the respectively detected operating current (I), and wherein the actuator control device (11) is designed, in particular programmed, such that, in normal operation, after the holding brake (5) has been transferred to the release state, it repeatedly receives a detected measured value for the operating current (I) from the detection device (10) and, if necessary, repeatedly adjusts the control of the current controller (7) such that the operating current (I) is reduced to a predetermined holding current (I3) above the minimum holding current (I2) and is maintained there.

8. Drive arrangement according to claim 7, characterized in that the actuator control device (11) is designed, in particular programmed, in such a way that it implements the method steps of at least one of claims 2 to 6.

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