Digital Resonance Circuit With PI Amplitude Control for Flowmeters
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Solution Overview
Problem
In high precision Coriolis mass flowmeters, the use of digital resonance circuits leads to phase shifts due to delays in digital signal processing, resulting in deteriorated vibration control and measurement precision, and existing amplification factor control methods can cause steady-state deviations and instability in the control system.
Innovation Solution
The implementation of an amplification factor controller that combines proportional control with integral control, using an integrator to reduce steady-state deviations between actual and target amplitudes, and incorporating an integration reset function to prevent excessive integration and maintain system stability, along with a configuration that switches between steady-state and startup-state paths to optimize amplitude control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a digital resonance circuit is used, then the circuit board area is reduced and costs are lowered, but phase shifts occur due to processing delays, deteriorating vibration control and measurement precision
Solution Approach 1:
The patent applies preliminary action by measuring the actual processing delay of the digital signal processing circuit in advance, and then pre-compensating for this delay in the excitation signal generation. The delay amount is measured during circuit assembly and stored, then used to adjust the phase of the excitation signal to counteract the anticipated phase shift, thereby maintaining measurement precision while using a compact digital circuit.
2Ease of operation
If an amplification factor controller with proportional control is used, then vibration control is achieved, but steady-state deviations occur and system stability is compromised
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual vibration amplitude and comparing it with the target amplitude to generate an error signal. This error signal is then fed back to the amplification factor controller, which adjusts the excitation signal amplitude accordingly. The controller incorporates both proportional control for rapid response and integral control for eliminating steady-state deviations, ensuring both ease of operation and system stability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the amplification factor based on the error between target and actual amplitudes. The amplification factor is modified in real-time according to the control algorithm, changing system parameters adaptively to maintain stable operation while achieving precise vibration control. The integral component accumulates past errors to gradually adjust the amplification factor, eliminating steady-state deviations without causing instability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces steady-state deviations without destabilizing the control system, ensuring precise amplitude control and improved measurement accuracy by integrating proportional and integral control methods, and addressing issues related to air bubble entrainment and amplitude stabilization.
Implementation Method 1
a resonance circuit 132 for generating an excitation signal based on output signals of the sensors
Implementation Method 2
a Coriolis mass flowmeter is a measuring instrument using a Coriolis force acting when vertically vibrating a measurement tube
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A resonance circuit is configured to receive a pulse density signal obtained by ΔΣ-modulating an analog displacement signal by a ΔΣ modulator and a multi-bit signal obtained from the pulse density signal and to generate an excitation signal based on the pulse density signal and the multi-bit signal. The resonance circuit includes an amplification factor controller configured to set an amplification factor depending on a vibration signal obtained from the multi-bit signal, a multiplier configured to amplify a level of the pulse density signal by the amplification factor, and a circuit group configured to generate the excitation signal based on a pulse density signal obtained by further ΔΣ-modulating an output of the multiplier. The amplification factor controller is configured to set the amplification factor using a proportional control and an integral control based a difference between an amplitude signal obtained from the vibration signal and a target amplitude value.