METHOD FOR CONTROLLING AND IN PARTICULAR MONITORING AN ACTUATOR, IN PARTICULAR OF A WINCH, A HOIST OR A CRANE, AND SYSTEM FOR CARRYING OUT SUCH A METHOD

Abstract

A method and system for controlling an actuator, in particular an actuator of a winch, a hoist or a crane, wherein the actuator is controlled using a fail-safe control unit. In order to improve a corresponding method, according to the invention, set point values are calculated in the fail-safe control unit, on the basis of which values the actuator is controlled.

Claims

1.-10. (canceled)

11. A method for controlling an actuator of a winch, a hoist or a crane via a fail-safe control unit, wherein said method comprises: calculating desired values in the fail-safe control unit based on which the actuator is controlled; determining actual values via a sensor system comprising a single position measuring sensor or speed sensor; and monitoring the actuator via the fail-safe control unit by comparing the desired values to the actual values; wherein the actual values are fed back to the fail-safe control unit via a single hardware channel of the sensor system that connects the actuator to the fail-safe control unit.

12. The method as claimed in claim 11, wherein said calculating the desired values, determining the actual values, and comparing the desired values to the actual values are each performed cyclically.

13. The method as claimed in claim 12, wherein a tolerance range is specified relative to the desired values, and wherein a settable time interval of a timer is started and is awaited if the actual values go outside the tolerance range, and wherein the monitored actuator is shut off if the actual values are outside the tolerance range even after the time interval has elapsed.

14. The method as claimed in claim 12, wherein the controlled and monitored actuator is a driving actuator, and wherein a second actuator is controlled and monitored via the fail-safe control unit with the second actuator configured as an actuating element of a holding brake, and wherein in order to control and monitor the second actuator in dependence upon the desired values calculated for the driving actuator a settable time interval of a timer is started and is waited, and wherein the driving actuator is shut off if an actual position of the second actuator does not correspond to a desired position of the second actuator even after the time interval has elapsed.

15. The method as claimed in claim 12, wherein the controlled and monitored actuator is a driving actuator, and wherein via the fail-safe control unit an end switch is monitored in dependence upon the desired values calculated for the driving actuator, wherein the driving actuator is slowed down or shut off if an actual position of the monitored end switch does not correspond to a desired position of the end switch as a desired value of the driving actuator is achieved.

16. The method as claimed in claim 11, wherein the controlled and monitored actuator is part of an electric motor that serves as a drive motor for a winch, a hoist, or a crane, and wherein the electric motor comprises a frequency converter-controlled electric motor, a pole-changing electric motor, or a line-commutated electric motor.

17. The method as claimed in claim 11, wherein a tolerance range is specified relative to the desired values, and wherein a settable time interval of a timer is started and is awaited if the actual values go outside the tolerance range, and wherein the monitored actuator is shut off if the actual values are outside the tolerance range even after the time interval has elapsed.

18. The method as claimed in claim 11, wherein the controlled and monitored actuator is a driving actuator, and wherein a second actuator is controlled and monitored via the fail-safe control unit with the second actuator configured as an actuating element of a holding brake, and wherein in order to control and monitor the second actuator in dependence upon the desired values calculated for the driving actuator a settable time interval of a timer is started and is waited, and wherein the driving actuator is shut off if an actual position of the second actuator does not correspond to a desired position of the second actuator even after the time interval has elapsed.

19. The method as claimed in claim 11, wherein the controlled and monitored actuator is a driving actuator, and wherein via the fail-safe control unit an end switch is monitored in dependence upon the desired values calculated for the driving actuator, wherein the driving actuator is slowed down or shut off if an actual position of the monitored end switch does not correspond to a desired position of the end switch as a desired value of the driving actuator is achieved.

20. A method for controlling an actuator of a winch, a hoist or a crane via a fail-safe control unit, wherein said method comprises: calculating desired values in the fail-safe control unit based on which the actuator is controlled; determining actual values via a sensor system comprising a single position measuring sensor or speed sensor; and monitoring the actuator via the fail-safe control unit by encoder-less monitoring.

21. The method as claimed in claim 20, wherein a tolerance range is specified relative to the desired values, and wherein a settable time interval of a timer is started and is awaited if the actual values go outside the tolerance range, and wherein the monitored actuator is shut off if the actual values are outside the tolerance range even after the time interval has elapsed.

22. The method as claimed in claim 20, wherein the controlled and monitored actuator is a driving actuator, and wherein a second actuator is controlled and monitored via the fail-safe control unit with the second actuator configured as an actuating element of a holding brake, and wherein in order to control and monitor the second actuator in dependence upon the desired values calculated for the driving actuator a settable time interval of a timer is started and is waited, and wherein the driving actuator is shut off if an actual position of the second actuator does not correspond to a desired position of the second actuator even after the time interval has elapsed.

23. The method as claimed in claim 20, wherein the controlled and monitored actuator is a driving actuator, and wherein via the fail-safe control unit an end switch is monitored in dependence upon the desired values calculated for the driving actuator, wherein the driving actuator is slowed down or shut off if an actual position of the monitored end switch does not correspond to a desired position of the end switch as a desired value of the driving actuator is achieved.

24. The method as claimed in claim 20, wherein the controlled and monitored actuator is part of an electric motor that serves as a drive motor for a winch, a hoist, or a crane, and wherein the electric motor comprises a frequency converter-controlled electric motor, a pole-changing electric motor, or a line-commutated electric motor.

25. A system for controlling and monitoring an actuator of a winch, a hoist or a crane, said system comprising: an actuator; and a fail-safe control unit; wherein the actuator can be controlled and monitored via the fail-safe control unit according to the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a system for controlling and monitoring a driving actuator in accordance with the prior art;

[0027] FIG. 2 shows a system, in accordance with the invention, for controlling and monitoring the driving actuator of FIG. 1;

[0028] FIG. 3 shows a schematic view of desired values, calculated by means of the fail-safe control unit, in the form of a speed ramp;

[0029] FIG. 4 shows a schematic view of the position monitoring of an actuator effected by means of the fail-safe control unit; and

[0030] FIG. 5 shows a schematic view of the braking contactor monitoring effected by means of the fail-safe control unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] FIG. 1 shows a system for controlling and monitoring a driving actuator 1 in accordance with the prior art already described in the introduction. In this case, the actuator 1 is part of an electric motor 1a which is designed by way of example as a frequency converter-controlled electric motor and can be a drive motor of a winch, a hoist or a crane. An operating part (not illustrated) which is also defined as a control point and can be for example a radio remote control or radio controller can be used to control the actuator 1, in that, by means of actuating an operating element of the operating part, control commands can be specified for the actuator 1. The control commands can be for example movement at maximum speed in the forwards direction or movement at a speed of 1 m/min in the rearwards direction. Starting from the operating part, signals corresponding to the respective control command are transmitted from a fail-safe control unit 2 via a control line 2a to a converter 4, which is designed as a frequency converter and serves to actually control the actuator 1. In the converter 4, the specified control commands are used for calculating desired values in the form of a ramp-shaped desired speed progression. This is also defined as a ramp calculation. The actuator 1 is then controlled by means of the desired values calculated in the converter 4.

[0032] The monitoring of the actuator 1, i.e. its actual implementation of the desired values, is effected, as already described above, in a static manner by the fail-safe control unit 2, in that a two-channel sensor system 3 determines actual values, which are compared in the fail-safe control unit 2 to fixedly specified thresholds. For this purpose, the sensor system 3 comprises two hardware channels 3a each having a speed sensor 3c or special-purpose sensor, allocated to the actuator 1, and a corresponding evaluation unit 3b each having a pulse counter in the form of a so-called counter card. The actual values are transmitted via the hardware channels 3a to the associated evaluation units 3b and are transmitted from the evaluation units 3b to the fail-safe control unit 2 so that the actual values can be compared there to the specified thresholds.

[0033] In contrast thereto, FIG. 2 shows a system in accordance with the invention for controlling and monitoring the driving actuator 1 of FIG. 1. The system in accordance with the invention shown in FIG. 2 differs from that shown in FIG. 1 by virtue of the fact that the sensor system 3 has only one single hardware channel 3a and one position measuring sensor 3d. The position measuring sensor 3d can be a simple incremental encoder for determining relative actual positions or can even be an absolute value measuring system for determining absolute actual positions. Instead of the position measuring sensor 3d, a speed sensor 3c can also be used. The second hardware channel 3a provided in the prior art shown in FIG. 1 and the associated components (sensor or encoder and evaluation unit) are replaced in accordance with the invention by an aforementioned software channel within the fail-safe control unit 2. In this regard, provision is made that the ramp calculation is no longer effected, as in the prior art, within the converter 4 but instead is effected within the fail-safe control unit 2 itself. This is followed by a transmission, also defined as a ramp output, of the ramp-shaped desired speed progression, which is calculated with the aid of the control commands, to the converter 4 so that the converter can hereby control the actuator 1.

[0034] The basis of the system illustrated schematically in FIG. 2 is a so-called secure ramp generator which is part of the fail-safe control unit 2 and produces in accordance with settable parameters the ramp-shaped desired speed progression, also defined as a speed ramp.

[0035] FIG. 3 shows a schematic view of desired values, calculated by means of the fail-safe control unit 2, in the form of the speed ramp. The speed ramp is to be set with the parameters P1 start acceleration rounding, P2 end acceleration rounding, P3 start deceleration rounding, P4 end deceleration rounding, P5 acceleration and P7 deceleration. The desired value for the ramp, i.e. for its range P6 persistence, is generated by the control point as part of the control command and is limited by the ramp generator with reliable values. The reliable values can be specified by a pre-end switch and so, as this is being reached, for example a limitation to 25% of the maximum possible speed vmax is effected, even if the control command is 50% of vmax. Even in the event of an overload recognised by means of a load sensor, the lifting speed can be limited as a reliable value to zero. Starting from the desired value for the ramp, the reliable ramp generator generates for example desired speeds between 1000 and +1000 per mill, wherein speeds with a minus sign are directed oppositely to those with a plus sign. A speed which has a value of 1000 per mill corresponds in this case to the maximum possible speed vmax and a speed which has a value of 1 per mill corresponds to the minimum possible speed vmin. In other words, the ramp generator can thus generate speed ramps with a scaling of 1000 and corresponding resolution.

[0036] The initial value of the reliable ramp generator is transmitted to a so-called reliable position ramp function generator which, just like the ramp generator, is part of the fail-safe control unit 2 and serves to calculate a relative and/or absolute position, such as of an axle of the crane running gear unit or trolley running gear unit driven by the actuator 1. For this purpose, a distance per program cycle of the safety program stored in the fail-safe control unit 2 is calculated and added up by the position ramp function generator.

[0037] Example: Actuator of the crane running gear unit

[0038] Speed vmax: 63 m/min

[0039] Scanning rate of safety program tFZ, (FZ=fail-safe cycle): 50 ms

[0040] Constant travel vmax results in the following distance sFZ vmax per scanning rate in the safety program:

[00001]$s_{\mathrm{FZV}.Math.\max }=\frac{V^{*}.Math.1.Math.0.Math.0.Math.0}{6.Math.0}.Math.\text{:}.Math.\frac{1.Math.0.Math.0.Math.0}{t_{F.Math.Z}}=\frac{63.Math..Math.m.Math.\text{/}.Math.\min *1000}{6.Math.0}.Math.\text{:}.Math.\frac{1.Math.0.Math.0.Math.0}{50.Math..Math.\mathrm{ms}}=52.Math..Math.\mathrm{mm}$

[0041] Since the speed ramp is resolved to a scaling of 1000, at 1 per mill speed vmin the following minimum distance sFZ vmin is achieved per scanning rate in the safety program:

[00002]$s_{\mathrm{FZVmin}}=\frac{s_{\mathrm{FZVmax}}}{1.Math.0.Math.0.Math.0}=\frac{52.Math..Math.\mathrm{mm}}{1.Math.0.Math.0.Math.0}=0.Math.\text{,}.Math.052.Math..Math.\mathrm{mm}$

[0042] The reliable position ramp function generator calculates the distance travelled depending upon the desired value of the reliable ramp generator multiplied by the minimum distance per scanning rate sFZ vmin and the ramp scaling.

[0043] FIG. 4 shows a schematic view of the position monitoring of the actuator 1 effected by means of the fail-safe control unit 2. The position monitoring can thus be used for recognising faults in relation to the driving actuator 1. The position monitoring is performed with a comparison module of the fail-safe control unit 2. The comparison module is connected to both channels of the sensor system 3, i.e. connected to the software channel and the single hardware channel 3a. The desired value, i.e. a corresponding relative or absolute desired position, which is calculated by the reliable position ramp function generator provided in the safety part of the fail-safe control unit 2 is specified as a reference variable to the comparison module via the software channel The actual value, i.e. a corresponding relative or absolute actual position or a signal corresponding to the actual value, which is determined by the position measuring sensor 3d is communicated as a feedback variable via the hardware channel 3a. This can be an incremental value that is made available to the fail-safe control unit 2. In the fail-safe control unit 2, the incremental value is then converted into an actual position in particular on the basis of the resolution, the transmission factor and the wheel/drum diameter with a possible reeving arrangement.

[0044] The reference variable (desired position) is then compared to the feedback variable (actual position) in each program cycle of the safety program. The respective positions are illustrated in FIG. 4, wherein by way of example a position value range of 0 to 10000 is shown on the Y-axis. If the deviation in the desired and actual positions is within a settable hysteresis, the position is graded as OK. Therefore, there is no fault in relation to the monitored actuator 1, which in FIG. 4 corresponds to the fault value 0. If the feedback variable leaves the hysteresis, a timing element is started. After a settable time has elapsed, the position would be considered to be not OK and therefore would be considered as a fault in the monitored actuator 1 and the monitored actuator is shut off or at least stopped. This corresponds in FIG. 4 to the fault value 1. Should the feedback variable then be within the hysteresis during the set time, the fault value then changes to 0 without the actuator 1 being shut off. Upon leaving the hysteresis once again, the timing element or the set time then starts anew. The hysteresis is configured in a fail-safe data module within the fail-safe control unit 2. Position regulation in the standard program of the fail-safe control unit 2 ensures that the desired position of the actuator 1 or of the axle drive by the actuator 1 is maintained.

[0045] In this case, the actuator 1 does not have to be part of a frequency converter-controlled electric motor 1a but instead can also be part of a pole-changing and in particular line-commutated electric motor 1a.

[0046] The described position monitoring of the driving actuator 1 can also be used for monitoring and thus for recognising faults in relation to a second actuator, wherein the second actuator can be designed as an actuating element of a holding brake or as an end switch, in particular a pre-end switch. In the case of the monitoring of an end switch/pre-end switch, the driving actuator 1 as part of the corresponding electric motor 1a is slowed down or shut off if an actual position of the monitored end switch/pre-end switch does not correspond to a desired position of the end switch as a specified desired value of the driving actuator 1 is achieved. In this case, it is also possible to monitor two end switches in the manner described above by specifying a corresponding distance as a desired value.

[0047] In the case of the monitoring of a holding brake, the driving actuator 1 is shut off if an actual position of the second actuator does not correspond to a desired position of the second actuator even after a settable time interval of the timing element has elapsed. If the second actuator which is designed as an actuating element of a holding brake is a braking contactor, braking contactor monitoring is thus effected in this manner

[0048] FIG. 5 shows a schematic view of the braking contactor monitoring effected by means of the fail-safe control unit 2. Possible actual or desired positions of the braking contactor are not dropped out or 0 for an open brake or dropped out or 1 for a closed brake.

[0049] If the actuator 1 is to perform a movement starting from a standstill, the associated ramp desired value is limited by the ramp generator to a parameterisable value in order to give the converter 4 time to open the brake via the braking contactor. At the same time, a timing element is started which monitors that the braking contactor changes its position to not dropped out within a parameterisable time interval t1. The time interval t1 corresponds at least to the reaction time tR1 of the braking contactor, wherein both t1 and tR1 relate to the corresponding change in the ramp desired value. If the position is changed to not dropped out at the end of the reaction time tR1 and thus within t1, this corresponds in FIG. 5 to the fault value 0. For reasons of improved clarity, only tR1, and not t1, is illustrated for the fault value 0. If the time interval t1 which is also defined as the monitoring time is exceeded without the position changing to not dropped out, this is recognised as a defective braking contactor or as a defect in the rotational speed adjuster. This corresponds in FIG. 5 to the fault value 1.

[0050] The same applies if, upon completion of the movement of the driving actuator 1, the ramp desired value then reaches 0. At the same time, a timing element is then started which monitors that the braking contactor changes its position to dropped out within a parameterisable time interval t2. If the position is changed to dropped out at the end of the reaction time tR2 and thus within t2, this corresponds in FIG. 5 to the fault value 0. For reasons of improved clarity, only tR2, and not t2, is illustrated for the fault value 0. If the corresponding time interval t2 is exceeded, without the position changing to dropped out, this is also recognised in this case as a defective braking contactor or as a defect in the rotational speed adjuster. This corresponds in FIG. 5 to the fault value 1. The time interval t2 also corresponds at least to the reaction time tR2 of the braking contactor, wherein both t2 and tR2 relate to the corresponding change in the ramp desired value. The length of the time intervals t1 and t2 can be the same or different.