Cranes occupy a crucial role within industry. They are used throughout the world in thousands of shipping yards, construction sites, steel mills, warehouses, nuclear power and waste storage facilities, and other industrial complexes. The significant role that these systems maintain in the world can hardly be overestimated.
Cranes are highly flexible in nature, generally responding in an oscillatory manner to external disturbances and motion of the overhead support unit (e.g., the bridge or trolley). In many applications this oscillation has adverse consequences. Swinging of the payload or hook makes precision positioning time consuming and inefficient for an operator. This condition is exacerbated in double-pendulum cranes where the payload motion is a combination of oscillations at two different frequencies. The oscillations of the payload and/or hook can present control problems for operators and safety hazards to both personnel and equipment.
Embodiments of the present disclosure are related to methods and systems for double-pendulum crane control.
Briefly described, one embodiment, among others, comprises a method for determining a specified insensitivity (SI) input shaper for controlling a double-pendulum crane. The method comprises determining a plurality of insensitivity ranges based upon operational parameters associated with the double-pendulum crane; and determining SI input shaper parameters based upon tolerances corresponding to the plurality of insensitivity ranges, the SI input shaper parameters including an amplitude and a time corresponding to each impulse of the SI input shaper.
Another embodiment, among others, comprises a double-pendulum crane system. The system comprises an input control configured to transmit an input command in response to an operator input; and a specified insensitivity (SI) input shaper module including a SI input shaper. The SI input shaper module is configured to: receive the input command; convolve the input command with the SI input shaper to produce the shaped velocity command; and transmit the shaped velocity command to a crane drive system configured to control movement of the double-pendulum crane in response to the velocity impulse command.
Another embodiment, among others, comprises a double-pendulum crane system. The system comprises means for providing an input command in response to an operator input; means for providing a shaped velocity command in response to the input command based upon a specified insensitivity (SI) input shaper; and means for controlling movement of the double-pendulum crane in response to the velocity impulse command.
Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Disclosed herein are various embodiments of methods and systems related to double-pendulum crane control. Reference will now be made in detail to the description of the embodiments as illustrated in the drawings, wherein like reference numbers indicate like parts throughout the several views.
Cranes are often driven by pressing on-off buttons that issue constant-velocity commands to the crane. On-off inputs tend to induce substantial payload oscillations. Therefore, a practical real-time oscillation controller filters out unwanted excitations from the human-generated command signal. This can be accomplished by convolving the human-generated command with a sequence of impulses.
Many cranes operate with a single-pendulum oscillation mode. However, under certain conditions double-pendulum dynamics can arise. For example, these effects occur when a lumped payload is suspended a significant length below the crane hook, as shown in
In the example of
where θ1 and θ2 describe the swing angles of the two pendulums, R is the ratio of the payload mass to the hook mass, and g is the acceleration due to gravity. Double-pendulum crane dynamics can also arise when the payload 310 is a long distributed mass connected to a massless hook as illustrated in
The linearized frequencies of the double-pendulum dynamics modeled above in equation (1) are:
The two pendulum oscillation frequencies (ω1,2) depend on the two cable lengths (L1, L2) and the mass ratio (R). It is of interest to investigate how the frequencies change as a function of the system parameters. Such information can be used to design an effective input-shaping controller.
Consider a subset of crane manipulation tasks where the sum of the two cable lengths stays constant.
The low frequency (first mode 410) is maximized when the two cable lengths are equal, L1=L2 (e.g., 3 m in the embodiment of
The variations of the first and second modes (410 and 420) of
The responses of the two swing angles, θ1 and θ2, to an impulse of magnitude A, introduced at time t0, are:
Assuming small swing angles, then the impulse response of the payload 210 in the horizontal direction can be approximated as:
The two coefficients, C1 and C2, indicate the contributions of each mode to the overall payload response. In the case of payloads 310 (
To design an input shaper 120 (
Vamp=|C1|+|C2| (10)
Based on this relationship, the contribution of the second mode becomes apparent and indicates when two-mode input shaping may be needed. For example, in the embodiment of
The maximum residual vibration amplitude given above in equation (10) can be used as a constraint equation by constraining the vibration amplitude, Vamp, to less than some tolerable threshold value, Vtol. Robustness of the crane 200/300 control over a range of operational conditions may be improved if the vibration is limited to a small value, rather than forced to be exactly zero. In the limiting case, when Vtol is set equal to zero, the constraints reduce to two-mode Zero Vibration (ZV) constraints. An expression for percentage of residual oscillation amplitude can be formed by dividing the amplitude when input shaping is used by the amplitude without input shaping:
Ai and ti are the amplitudes and time locations of the impulses 140 in the input shaper 120 (
Vtol≧V(ωn,ζ) (14)
While limiting percentage vibration is theoretically convenient, equation (10) allows the residual oscillation (or vibration) amplitude to be limited to specific dimensions values. In this case, Vtol can expressed as the sum of the maximum dimensional amplitudes from each mode, C1 and C2.
The vibration caused by an input shaper 120 (
Ai>0. i=1, . . . n (15)
where n is the number of impulses 140 in the input shaper 120. A second amplitude constraint is enforced so that the shaped command 130 (
The constraint in (14) can be used twice to limit the vibration at a set of pendulum oscillation frequencies (ω1 and ω2). If the actual crane 200/300 frequencies coincide with those used to design the input shaper 120, then the oscillation will be eliminated. However, to ensure robustness to modeling errors and parameter variations, the oscillation can be suppressed at several points near the modeling frequencies, as illustrated in
A final design constraint is to minimize the duration of the input shaper 120 (i.e., minimize the time (Δ of
The low and high insensitivity ranges (e.g., 510 and 520 of
In some embodiments, the range limits may be the set by the highest and lowest frequencies determined based on the operational parameters. In other embodiments, a margin for error may be added to the highest and lowest frequencies to set the range limits. Alternatively, a nominal frequency may be determined and a range about the nominal frequency (e.g., ±20%) may be used to define the insensitivity ranges.
The vibration (or oscillation) amplitude tolerance is received in block 630. The allowable total tolerance, Vtol, will depend on the application and the user's requirements. For example, at nuclear power plants it is common for crane payloads 210/310 to be positioned within a two inch tolerance. Cranes 200/300 utilized in ports for positioning containers on trucks for transport may need an accuracy of about three inches. Alternatively, some applications may need a crane positioning accuracy of one centimeter or less. A dimensional tolerance can be converted to a percentage tolerance based upon a vibration response to baseline movement of the payload 210/310. In some cases, this baseline move could be a move that causes the most endpoint vibration or oscillation.
In some embodiments, tolerances for the low and high ranges, Vtol1 550 and Vtol2 560 (
V(ω1,ζ)=2V(ω2,ζ) (17)
Given that the vibration from both modes will combine to given the total vibration, we have:
V(ω1,ζ)+V(ω2,ζ)=Vtol (18)
Therefore, if the first mode is limited to Vtol1=ε, then the limit on the second mode can be set twice as large, Vtol2=2ε. To find the value of ε, we satisfy:
Vtol1+Vtol2=Vtol (19)
The result in this case is ε=(⅓)Vtol.
In other embodiments, the total vibration tolerance, Vtol, is received and used to determine the tolerances for the low and high ranges, Vtol1 550 and Vtol2 560. Alternatively, embodiments may utilize other variations such as, but not limited to:
1. Use the same Vtol for both the low and high frequency ranges.
2. Receive a constant Vtol1 for the low frequency range and vary Vtol2 until the combined vibration from mode 1 and mode 2 reach the tolerable overall level, Vtol. By loosening the constraints of Vtol2, the input shaper 120 (
3. Vary both Vtol1 and Vtol2 while satisfying the limit on vibration tolerance, and minimize the input shaper 120 duration.
4. Vary Vtol1 and/or Vtol2 as a function of the frequency over each frequency suppression range.
In block 640, the parameters (e.g., impulse number, amplitudes, and times) are determined for the SI input shaper 120. The impulse 140 (
Constraints based on vibration tolerances, Vtol1 and Vtol2, are determined for the suppression points in each range in block 720. Constraint equations (11)-(14) may be used to limit the vibration below a vibration tolerance level, Vtol1, over the low frequency range and the vibration tolerance level, Vtol2, over the high frequency range. The impulse 140 amplitudes and time locations are determined so as to minimize the duration of the input shaper 120 in block 730. In some embodiments, computer programs such as, but not limited to, MATLAB® and other numerical analysis programs or software, may be used to find the impulse amplitudes and times that satisfy the vibration constraints by minimizing (e.g., using a minimization command with a minimization tolerance) the duration of the SI input shaper 120 (i.e., the smallest time location of the last impulse 140). In other embodiments, the constraints may be iteratively solved until the change or the rate of change in the last impulse time is within a predefined tolerance. The response time of the crane controller is maximized by minimizing the duration of the SI input shaper 120.
If there is a solution to determining the impulse amplitudes and times based on the constraints (block 740), then the SI input shaper parameters (e.g., impulse number, amplitudes, and times) are saved and the method returns to block 710. The number of input shaper impulses is reduced by one (block 710) and impulse amplitudes and times are determined (block 730) based on revised constraints (block 720). This sequence continues until there is no solution available for the current number of impulses.
If there is have been no solutions to the determination of impulse 140 amplitudes and times (block 750), then the number or suppression points is increased and the method returns to block 720. In one embodiment, one or more additional suppression points are added to both the low and high ranges. In other embodiments, one or more points are added to only a single range.
If there has been a solution to the determination of impulse 140 amplitudes and times (block 750), then SI input shaper 120 parameters from the solution with the shortest duration are provided in block 760. In alternative embodiments, the vibration tolerances for the low and high frequency ranges may also be iteratively adjusted to minimize the duration of the input shaper 120.
Referring next to
Coupled to the processor system 800 are various peripheral devices such as, for example, a display device 813, a keyboard 819, and a mouse 823. In addition, other crane sensors 826 (peripheral devices that allow for the capture of various operational parameters for a crane system 200/300) may be coupled to the processor system 800 such as, for example, vision or image capture devices (e.g., cameras or other imaging devices and/or scanning equipment), load cells, strain gages, and encoders. The image capture device may comprise, for example, a digital camera or other such device that generates images that comprise patterns to be analyzed to determine system parameters such as, but not limited to, suspension and rigging cable lengths, payload 210/310 dimensions, and connector and/or payload 210/310 oscillations. Encoders may be used to determine changes in cable lengths and crane 200/300 position. Load sensors may be used to determine connector and/or payload 210/310 mass.
Stored in the memory 806 and executed by the processor 803 are various components that provide various functionality according to the various embodiments of the present disclosure. In the example shown, stored in the memory 806 is an operating system 853 and an input shaper determination system 856. In addition, stored in the memory 806 are various operational parameters 859, input shaper parameters 863, and vibration (or oscillation) tolerances 867. The operational parameters 859 may be associated with a corresponding crane and payload combination. Other information that may be stored in memory 806 includes, but is not limited to, crane manufacturer database(s), payload dimensions and weights, double-pendulum dynamics and constraint equations, and numerical analysis programs and software (e.g., MATLAB®). The operational parameters 859, input shaper parameters 863, and vibration (or oscillation) tolerances 867 may be stored in a database to be accessed by the other systems as needed. The operational parameters 859 may comprise ranges of suspension lengths, payload ranges, and connection information. In the case of distributed payloads 310 (
The input shaper determination system 856 is executed by the processor 803 in order to determine SI input shaper 120 (
The memory 806 is defined herein as both volatile and nonvolatile memory and data storage components. Volatile components are those that do not retain data values upon loss of power. Nonvolatile components are those that retain data upon a loss of power. Thus, the memory 806 may comprise, for example, random access memory (RAM), read-only memory (ROM), hard disk drives, floppy disks accessed via an associated floppy disk drive, compact discs accessed via a compact disc drive, magnetic tapes accessed via an appropriate tape drive, and/or other memory components, or a combination of any two or more of these memory components. In addition, the RAM may comprise, for example, static random access memory (SRAM), dynamic random access memory (DRAM), or magnetic random access memory (MRAM) and other such devices. The ROM may comprise, for example, a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other like memory device.
The processor 803 may represent multiple processors and the memory 806 may represent multiple memories that operate in parallel. In such a case, the local interface 809 may be an appropriate network that facilitates communication between any two of the multiple processors, between any processor and any one of the memories, or between any two of the memories etc. The processor 803 may be of electrical, optical, or molecular construction, or of some other construction as can be appreciated by those with ordinary skill in the art.
The operating system 853 is executed to control the allocation and usage of hardware resources such as the memory, processing time and peripheral devices in the processor system 800. In this manner, the operating system 853 serves as the foundation on which applications depend as is generally known by those with ordinary skill in the art.
The flow charts of
Although flow charts of
Also, where the input shaper determination system 856 may comprise software or code, it can be embodied in any computer-readable medium for use by or in connection with an instruction execution system such as, for example, a processor in a computer system or other system. In this sense, the logic may comprise, for example, statements including instructions and declarations that can be fetched from the computer-readable medium and executed by the instruction execution system. In the context of the present disclosure, a “computer-readable medium” can be any medium that can contain, store, or maintain the input shaper determination system 856 for use by or in connection with the instruction execution system. The computer readable medium can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, magnetic tapes, magnetic floppy diskettes, magnetic hard drives, or compact discs. Also, the computer-readable medium may be a random access memory (RAM) including, for example, static random access memory (SRAM) and dynamic random access memory (DRAM), or magnetic random access memory (MRAM). In addition, the computer-readable medium may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other type of memory device.
The SI input shaper module 920 receives the input command, shapes a shaped velocity command 130 (
The SI input shaper module 920 of certain embodiments of the present disclosure can be implemented in hardware, software, firmware, or a combination thereof. In the preferred embodiment(s), the SI input shaper module 920 is implemented in firmware or software that is stored in a memory and that is executed by a suitable instruction execution system. If implemented in hardware, as in an alternative embodiment, the SI input shaper module 920 can be implemented with any or a combination of the following technologies, which are all well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc.
One embodiment of an SI input shaper 120 (
The SI input shaper 120 was designed to suppress 0.25 Hz and 0.35 Hz modes, which correspond to the crane 200 frequencies when it moves a 9 kg payload 210 having a mass (i.e., the average mass of the two test payloads). Given the uncertainty in the crane 200 parameters and the changes in suspension length L1 that occur during hoisting, the SI input shaper 120 needs a moderate amount of robustness.
Note that the insensitivity constraints for the two modes are close together, so the combined effect limits all frequencies from 0.24 Hz to 0.40 Hz.
The impact of the SI input shaper 120 (
Operators used an operator pendent connected to the crane 200 by a cable as the input control 910 (
It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.
This application claims priority to copending U.S. provisional application entitled “INPUT SHAPING CONTROLLER FOR DOUBLE-PENDULUM CRANE” having Ser. No. 61/025,110, filed Jan. 31, 2008, which is hereby incorporated by reference in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
4756432 | Kawashima et al. | Jul 1988 | A |
4916635 | Singer et al. | Apr 1990 | A |
4997095 | Jones et al. | Mar 1991 | A |
5127533 | Virkkunen | Jul 1992 | A |
5526946 | Overton | Jun 1996 | A |
5529193 | Hytonen | Jun 1996 | A |
5638267 | Singhose et al. | Jun 1997 | A |
5785191 | Fedderma et al. | Jul 1998 | A |
5908122 | Robinett et al. | Jun 1999 | A |
5909817 | Wallace, Jr. et al. | Jun 1999 | A |
5938052 | Miyano et al. | Aug 1999 | A |
5960969 | Habisohn | Oct 1999 | A |
5961563 | Overton | Oct 1999 | A |
6050429 | Habisohn | Apr 2000 | A |
6102221 | Habisohn | Aug 2000 | A |
6505085 | Tuttle et al. | Jan 2003 | B1 |
6694196 | Tuttle et al. | Feb 2004 | B2 |
6920378 | Eloundou et al. | Jul 2005 | B2 |
20030018400 | Tuttle et al. | Jan 2003 | A1 |
20080281464 | Sorensen et al. | Nov 2008 | A1 |
Number | Date | Country | |
---|---|---|---|
20090194498 A1 | Aug 2009 | US |
Number | Date | Country | |
---|---|---|---|
61025110 | Jan 2008 | US |