Multivariable Flow Measurement Device Using Lookup Tables
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Solution Overview
Problem
Existing multivariable process fluid flow devices require iterative algorithms to calculate flow rates, leading to potential delays and instability in process fluid control due to computational complexity and power constraints, necessitating faster and more efficient flow value provision.
Innovation Solution
A process fluid flow device with integrated process communication circuitry, a processor, and measurement circuitry that computes flow values using current differential pressure and previous flow-related values, employing Chebychev curve fits and integer math to provide flow outputs within approximately 50 milliseconds, while operating on limited power and alternating between low power sleep and measurement modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative algorithms (direct substitution or Newton-Raphson) are used to calculate flow rates, then measurement precision is improved, but response time deteriorates due to multiple iterations required for convergence
Solution Approach 1:
The patent pre-calculates and stores discharge coefficient values in lookup tables corresponding to different Reynolds number ranges before operation. During flow rate calculation, the system determines the appropriate discharge coefficient from these pre-computed tables based on measured parameters, eliminating the need for iterative convergence to find the discharge coefficient. This preliminary preparation of computational data resolves the contradiction by providing accurate coefficients instantly rather than through repeated iterations.
2Loss of time
If sophisticated algorithms like Newton-Raphson are used, then convergence speed is improved, but computational complexity and power consumption increase
Solution Approach 1:
The patent replaces complex iterative computational algorithms with a lookup table-based retrieval system. Instead of performing multiple cycles of Newton-Raphson iterations requiring derivative calculations and convergence checks, the system substitutes this mechanical computational process with direct table lookups based on measured Reynolds number or discharge coefficient ranges. This substitution dramatically reduces computational complexity and power consumption while maintaining calculation accuracy.
3Use of energy by moving object
If simpler computational algorithms are used to minimize power consumption, then power budget is improved, but response time and accuracy deteriorate
Solution Approach 1:
The system pre-computes and stores discharge coefficient values in lookup tables during manufacturing or initialization, organizing them by Reynolds number ranges or discharge coefficient ranges. During operation, the microprocessor simply retrieves the appropriate coefficient from the table based on current measurements, avoiding all iterative computation. This preliminary preparation enables instantaneous coefficient selection with minimal power consumption while maintaining high measurement accuracy.
Solution Approach 2:
The patent creates a simplified computational model by copying pre-calculated discharge coefficient values into lookup tables that represent the complex fluid dynamics relationships. Instead of repeatedly solving the full iterative flow equations, the system uses these copied coefficient values that capture the essential physics. This copying approach enables fast, low-power computation while preserving the accuracy of the original complex model.
Data Source
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AI summary
A process fluid flow device (12) includes process communication circuitry (20), a processor (26), and measurement circuitry (28). The process communication circuitry (20) is configured to communicate with at least one additional process device. The processor (26) is coupled to the process communication circuitry (20) and is configured to execute instructions to provide a plurality of cycles, wherein each cycle includes a number of flow- related calculations. Measurement circuitry (28) is operably coupleable to a plurality of process variable sensors to obtain an indication of differential pressure during each cycle, and to obtain static pressure, and process fluid temperature. The processor (26) is configured to compute a process fluid flow value using a current differential pressure sensor indication and at least one flow-related value calculated during a previous cycle. The process communication circuitry (20) communicates the computed process fluid flow value to the at least one additional process device.