Generalized modal space drive control system for a vibrating tube process parameter sensor
First Claim
1. A drive system for vibrating a conduit, said drive system comprising:
- a drive means positioned adjacent said conduit and responsive to a drive signal for vibrating said conduit;
L motion sensors for producing L motion signals indicative of the movement of said conduit at the respective points of attachment of said L motion sensors to said conduit, wherein L is equal to or greater than 2;
a modal response signal means that receives said L motion signals and produces N modal response signals wherein each of said N modal response signals corresponds to one of a plurality of vibration modes, wherein N is equal to or greater than 2;
N modal filter channels in said modal response signal means wherein each of said N modal filter channels receives at least two of said L motion signals as input and produces one of said N modal response signals as an output;
a drive controller means responsive to a production of said N modal response signals for producing N modal excitation signals, wherein each of said N modal excitation signals representing the modal excitation is used to achieve a desired modal response level for a respective vibration mode; and
a modal-to-physical force projector means responsive to said N modal excitation signals for producing M drive signals wherein said M drive signals cause said drive means to vibrate said conduit in desired modes, wherein M is more than 1.
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Abstract
A drive system is taught for controlling the modal content of any number of drive signals used to excite any number of drives on a vibrating conduit such as is found in a Coriolis mass flowmeter or a vibrating tube densimeter. One or more motion signals are obtained from one or more spatially distinct feedback sensors. The motion signals are preferably filtered using a multi-channel modal filter to decompose the motion signals, each of which contain modal content at a plurality of vibration modes, into n single degree of freedom modal response signals. Each modal response signal corresponds to one of the vibration modes at which the vibrating conduit is excited. The n modal response signals are input to a drive channel having a separate processing channel for each of the n modal response signals.
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Citations
20 Claims
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1. A drive system for vibrating a conduit, said drive system comprising:
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a drive means positioned adjacent said conduit and responsive to a drive signal for vibrating said conduit;
L motion sensors for producing L motion signals indicative of the movement of said conduit at the respective points of attachment of said L motion sensors to said conduit, wherein L is equal to or greater than 2;
a modal response signal means that receives said L motion signals and produces N modal response signals wherein each of said N modal response signals corresponds to one of a plurality of vibration modes, wherein N is equal to or greater than 2;
N modal filter channels in said modal response signal means wherein each of said N modal filter channels receives at least two of said L motion signals as input and produces one of said N modal response signals as an output;
a drive controller means responsive to a production of said N modal response signals for producing N modal excitation signals, wherein each of said N modal excitation signals representing the modal excitation is used to achieve a desired modal response level for a respective vibration mode; and
a modal-to-physical force projector means responsive to said N modal excitation signals for producing M drive signals wherein said M drive signals cause said drive means to vibrate said conduit in desired modes, wherein M is more than 1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
M drive means positioned adjacent said conduit and each of said M drive means responsive to one of said M drive signals.
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3. The drive system of claim 1 wherein said modal response signal means comprises:
N frequency bandpass filters each of which receives one of said L motion signals as an input and each of which outputs one of said N modal response signals.
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4. The drive system of claim 3 wherein said modal response signal means further comprises:
N integration means for integrating each of said N modal response signals.
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5. The drive system of claim 1 wherein each of said N modal filter channels comprises:
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first weighting means for applying a first weighting factor to a first one of at least two of said L motion signals to develop a first weighted signal;
second weighting means for applying a second weighting factor to a second one of said at least two of said L motion signals to develop a second weighted signal; and
modal filter summing means for combining said first weighted signal and said second weighted signal to produce one of said N modal response signals.
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6. The drive system of claim 5 wherein said first and second weighting factors are determined through trial and error.
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7. The drive system of claim 5 wherein said first and second weighting means are determined through experimental analysis.
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8. The drive system of claim 5 wherein said first and second weighting means are determined through numerical analysis.
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9. The drive system of claim 1 wherein each of said N modal response signals is substantially a single degree of freedom modal response signal corresponding to said one of said plurality of vibration modes.
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10. The drive system of claim 1 wherein said drive controller means comprises:
N drive controller channels each having as input one of said N modal response signals and each producing one of said N modal excitation signals as an output.
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11. The drive system of claim 10 wherein each of said N drive controller channels comprises:
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modal response setpoint means for setting a modal setpoint value to define a desired said modal response level for a given one of said plurality of vibration modes;
compare means for comparing said desired modal response level to the corresponding one of said N modal response signals to produce a mode error signal; and
gain means responsive to said mode error signal for producing a one of said N modal excitation signals.
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12. The drive system of claim 11 wherein said modal response setpoint means is configured to set said modal setpoint value to zero to produce said one of said N modal excitation signals having a zero level.
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13. The drive system of claim 11 wherein said modal response setpoint means is configured to set said modal setpoint value to a non-zero value to produce said one of said N modal excitation signals having a non-zero level.
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14. The drive system of claim 1 further comprising:
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selection means for selecting between multiple operating configurations of said drive system; and
adjustment means responsive to said selection means for adjusting modal response setpoints.
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15. The drive system of claim 14 wherein said selection means comprises:
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a memory containing a set of said modal response setpoints for each of said multiple operating configurations; and
an operating configuration selector for choosing one of said sets of modal response setpoints from said memory.
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16. The drive system of claim 15 wherein said adjustment means comprises:
means responsive to said operating configuration selector for replacing a first set of modal response setpoints in N drive controller channels with a second set of modal response setpoints.
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17. The drive system of claim 1 wherein said modal-to-physical force projector means comprises:
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N modal-to-physical signal transformation means each having as an input one of said N modal excitation signals and each responsive to a respective one of said N modal excitation signals for producing a drive component signal;
said drive component signal representing a force at said drive means to influence said one of said plurality of vibration modes to a desired modal response level; and
summing means for summing N drive component signals output from said N modal-to-physical signal transformation means to produce one of said M drive signals.
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18. A method of operating a drive system for vibrating a conduit, comprising the steps of:
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receiving a drive signal for vibrating said conduit;
receiving L motion signals from L motion sensors, each of said L motion signals being indicative of the movement of said conduit at the respective point of attachment of said L motion sensors to said conduit, wherein L is equal to or greater than 2;
decomposing said L motion signals to produce N modal response signals wherein each of said N modal response signals corresponds to one of a plurality of vibration modes and each of said N modal response signals is generated from at least two of said L motion signals, wherein N is equal to or greater than 2;
generating N modal excitation signals responsive to said N modal response signals wherein each of said N modal excitation signals represents the modal excitation used to achieve a desired modal response level for a respective vibration mode;
transforming said N modal excitation signals from the modal domain to the physical domain to form M drive signals, wherein M is at least 1; and
applying said M drive signals to M drivers causing said conduit to vibrate. - View Dependent Claims (19, 20)
filtering said L motion signals through N modal filter channels wherein each of said N modal filter channels receives all of said L motion signals as input and outputs one of said N modal response signals.
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20. The method of claim 18 wherein said generating step includes:
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receiving said N modal response signals in N respective drive controller channels;
subtracting a respective one of said N modal response signals from a respective modal response setpoint to generate a respective mode error signal; and
amplifying said respective mode error signal by a mode gain to generate a respective modal excitation signal within each of said N respective drive controller channels.
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Specification