Film-Type Force Sensor Baseline Update for Accurate Load Detection
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Solution Overview
Problem
The baseline value in film-type force sensors with a capacitance system is difficult to accurately update due to resilience effects, leading to inaccurate load detection when loads are applied and released, as the capacitance values do not return to the initial state.
Innovation Solution
A control circuit with a measurement data acquisition unit, moving average data calculation unit, load data correction unit, standard deviation calculation unit, determination unit, and baseline update unit are used to detect capacitance changes, calculate moving averages, correct load data, determine load application based on standard deviation thresholds, and update the baseline value at appropriate times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the baseline value is updated based on load data where the load calculation value is rapidly reduced, then the baseline value can be updated more frequently, but it becomes difficult to accurately determine whether a load is applied or the sensor is affected by resilience
Solution Approach 1:
The patent uses feedback by continuously monitoring the standard deviation of load calculation values and comparing them against threshold values to determine the appropriate timing for baseline updates. The system feedbacks the sensor state (loaded vs. unloaded) based on statistical analysis of recent measurements, ensuring baseline updates occur only when confidently in an unloaded state, thus maintaining measurement precision while enabling frequent updates.
Solution Approach 2:
The patent replaces direct mechanical judgment of load presence with a statistical calculation system. Instead of relying on simple threshold comparisons of individual measurements, the system uses standard deviation calculations over multiple measurements to statistically determine sensor state, substituting mechanical decision-making with computational analysis to resolve the ambiguity between load and resilience effects.
2Adaptability or versatility
If the film-type force sensor is used to detect load, then force measurements in three-axis directions can be achieved, but the sensor is affected by resilience causing capacitance values to shift in no-load state
Solution Approach 1:
The patent applies preliminary action by proactively updating the baseline value during confirmed unloaded states before load detection begins or between measurement cycles. This preliminary baseline update ensures that subsequent load measurements start from an accurate reference point, compensating for resilience effects that may have occurred during previous operations and maintaining capacitance value stability.
Solution Approach 2:
The patent changes the parameter used for baseline determination from a fixed initial value to a dynamically updated value based on recent measurement statistics. By calculating the baseline from the most recent unloaded state measurements and updating this parameter over time, the system adapts to resilience effects while maintaining reliable load detection across all three axes.
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
Enables accurate load detection by updating the baseline value at suitable timings, thereby improving the precision of load measurements in film-type force sensors.
Implementation Method 1
a sensor with a capacitance system in which upper electrodes and lower electrodes are disposed to face each other with an air layer or an elastic layer in between, and values of an applied load are calculated by using change of capacitance values generated by variation in distance between the electrodes when force (hereinafter, simplified to load) is applied
Data Source
AI summary
An input device according to the present invention includes a film-type force sensor that can acquire an updated baseline value at a suitable timing, thereby performing accurate load detection, and a control device. The control device includes a measurement data acquisition unit, a motion average data calculation unit, a load data calculation unit, a load data correction unit, a standard deviation calculation unit, a determination unit, a baseline update unit, and a storage unit. In a case where a standard deviation is less than or equal to a threshold, the determination unit determines that no load is applied to the film-type force sensor. The baseline update unit updates a baseline value by replacing the baseline value with a value at a time when it is determined that no load is applied in load data.