Variable Filter Settling Time in Force-Measuring Devices
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Solution Overview
Problem
Existing force-measuring devices, such as balances, face challenges in achieving optimal filtering of signal disturbances while maintaining a short settling time for transient oscillations, as previous solutions compromise between damping and response time, resulting in inadequate performance under stringent requirements.
Innovation Solution
The method involves optimizing filter parameters in variable analog or digital filters by resetting and varying them according to a prescribed exponential profile after detecting a load change, allowing the filter to open and close to achieve a predefined characteristic, ensuring rapid response and optimal disturbance suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the time constant of the low-pass filter is increased to achieve stronger filtering effect, then the filtering of signal disturbances is improved, but the response time and settling time of the measuring device increases
Solution Approach 1:
The patent applies dynamics by making the filter characteristic variable rather than fixed. The filter automatically adapts its time constant based on the detected state: using a first time constant during transient oscillations for rapid response, and a second, longer time constant during steady state for optimal disturbance filtering. This dynamic adaptation resolves the contradiction between fast response and strong filtering.
Solution Approach 2:
The patent changes the parameter (time constant) of the low-pass filter based on the operational state of the measuring device. By detecting whether the device is in transient or steady state and switching between different time constant values, the system achieves both rapid settling during transitions and optimal disturbance rejection during stable operation, eliminating the need to compromise between these opposing requirements.
2Loss of time
If the time constant of the low-pass filter is decreased to achieve shorter settling time, then the response time is improved, but the filtering effect on signal disturbances is reduced
Solution Approach 1:
The system dynamically switches between two time constant values based on the operational state. During transient oscillations, a shorter first time constant provides rapid response and short settling time. During steady state, a longer second time constant provides optimal filtering. This dynamic parameter adjustment resolves the contradiction between fast response and effective filtering.
Solution Approach 2:
The patent implements parameter changes by switching the filter's time constant based on detected state conditions. The system uses a first time constant value during transient phases for rapid settling, then transitions to a second, longer time constant value during steady state for optimal disturbance filtering, thereby achieving both fast response and strong filtering without compromise.
3Measurement precision
If a fixed filter characteristic is used to dampen oscillatory disturbances, then the filtering of disturbances is improved, but the response time to load changes increases
Solution Approach 1:
The patent makes the filter characteristic dynamic by switching between two fixed characteristics based on the operational state. During transient load changes, a first filter characteristic with shorter time constant enables rapid response. During steady state, a second filter characteristic with longer time constant provides strong damping of oscillatory disturbances. This dynamic switching resolves the contradiction between fast response and effective damping.
Solution Approach 2:
The system changes the filter parameter (time constant) based on the detected state of the measuring device. By using a first time constant during transient phases for rapid response to load changes, and switching to a second, longer time constant during steady state for optimal damping of oscillatory disturbances, the patent achieves both fast response and effective disturbance suppression without compromise.
Data Source
AI summary
A method serves to process output signal of a measuring transducer in a force-measuring device, in particular in a balance, wherein the measuring transducer produces a measuring signal representative of a load acting on the device and the measuring signal is filtered in a variable analog filter and/or, after processing in an analog/digital converter, the measuring signal is filtered in a variable digital filter, in order to remove unwanted signal components that are caused by disturbances affecting the force-measuring device, in particular by changes in the weighing load. The measuring signal is monitored in regard to the occurrence of a change in the weighing load and after a load change has been detected, at least one filter parameter of the filter is reset and then varied as a function of time in accordance with a prescribed time profile fc(t), so that the filter is opened after a load change has been detected and then closed again to the point where a predefined filter characteristic has been attained which is determined by the end value of the at least one filter parameter. By using this method, it is possible with simple measures to realize noticeably shortened transient settling times of the force-measuring device after a load change has occurred.