Variable Stiffness Control via Capacitance Estimation
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Solution Overview
Problem
Existing variable stiffness mechanisms with dielectric elastomers face challenges in accurately controlling stiffness and estimating electrostatic capacitance without mutual interference, as direct measurement of relative displacement and elastic deformation is difficult due to structural restrictions and the insulating nature of elastomers.
Innovation Solution
A control device with separate power sources for controlling stiffness and estimating electrostatic capacitance, using a first power source to apply voltage for stiffness control and a second power source to estimate capacitance without influencing the total stiffness, and an electrostatic capacitance estimating unit to acquire and process current detection values for accurate capacitance estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a displacement sensor is used to measure the relative displacement between two members, then the amount of relative displacement can be measured, but structural restrictions occur and the measurement reliability is low due to the flexible deformation of elastomers
Solution Approach 1:
The patent replaces the mechanical displacement sensor with an electrical measurement system. Instead of mechanically measuring the displacement between members, the system uses the electrostatic capacitance of the elastomer as a sensor to detect deformation, converting a mechanical measurement problem into an electrical one that can be solved remotely without structural interference.
Solution Approach 2:
The elastomer itself serves as an intermediary element that converts mechanical deformation into electrical signal changes. The electrostatic capacitance of the elastomer acts as a mediator between the mechanical displacement and the measurement system, allowing indirect but reliable measurement without direct contact sensors.
2Adaptability or versatility
If voltage is applied to control the stiffness of dielectric elastomers, then the stiffness can be varied over an extensive range, but the electrostatic capacitance changes making accurate capacitance estimation difficult
Solution Approach 1:
The patent divides the elastomers into two separate groups: one group dedicated to stiffness control and another group dedicated to capacitance measurement. This segmentation allows each group to perform its specific function independently, with the measurement group providing accurate capacitance data while the control group manages stiffness variation.
Solution Approach 2:
The system uses the measured electrostatic capacitance values as feedback to monitor the state of the elastomers. By continuously measuring capacitance and using this information to understand the relationship between voltage and deformation, the system can accurately estimate capacitance even during stiffness control operations.
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 parallel and accurate control of total stiffness and estimation of electrostatic capacitance without interference, allowing reliable estimation of relative displacement between members.
Implementation Method 1
when a voltage is applied thereto, the dielectric elastomer is compressed by Maxwell stress in the direction of an electric field produced by the applied voltage
Implementation Method 2
the elastomers are electrical insulators, so that the elastomers function as capacitive elements. Further, the electrostatic capacitance of the elastomers as the capacitive elements are highly correlated to the thicknesses of the elastomers
Data Source
AI summary
A control device of a variable stiffness mechanism controls a total stiffness by variably outputting a voltage from a DC power source 10 to an “m” number of stiffness control elastomers 1 among a plurality of dielectric elastomers 1 of a variable stiffness mechanism 100. Further, in a state in which a square-wave signal is being output from a square-wave power source 11 to an “n” number of electrostatic capacitance estimation elastomers 1, a detection value of energizing current is acquired and the acquired detection value is used to estimate an electrostatic capacitance.