Electroactive Polymer Actuator Sensor Device with Oscillating Current Sink
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Solution Overview
Problem
Existing electroactive material (EAM) based actuator/sensor devices require complex drive circuitry and bulky DC-biasing solutions for simultaneous sensing and actuation, which can disturb actuation and complicate charge sensing, especially when using high-frequency sensing signals.
Innovation Solution
A device with an electroactive material actuator and sensor component using an equivalent electrical circuit of a first resistor in parallel with a series combination of a capacitor and a second resistor, employing a current sensor and source for simplified sensing with an oscillating current sink, allowing simultaneous actuation and sensing without additional voltage sources or bulky components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If complex drive circuitry and bulky DC-biasing solutions are used for simultaneous sensing and actuation, then sensing and actuation functions can be achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines the sensing and actuation functions into a single integrated device structure, where the same electroactive polymer component serves both purposes. The controller merges the actuation signal generation and sensing signal processing into one control unit, eliminating the need for separate bulky DC-biasing blocks and AC-coupling components, thus reducing overall device complexity while maintaining simultaneous sensing and actuation capability
Solution Approach 2:
The electroactive polymer component performs multiple functions simultaneously - it acts as both the actuator that responds to actuation signals and the sensor that responds to sensing signals. The single component structure enables dual functionality without requiring additional specialized components, thereby simplifying the drive circuitry while achieving versatile simultaneous sensing and actuation
2Measurement precision
If high-frequency sensing signals are used for sensing, then sensing accuracy improves, but actuation is disturbed and charge sensing becomes complicated
Solution Approach 1:
The controller alternates between actuation mode and sensing mode in periodic cycles. During actuation periods, high-voltage actuation signals are applied to drive the electroactive polymer. During sensing periods, high-frequency sensing signals are applied to measure impedance changes. This periodic switching allows high-frequency sensing signals to be used for accurate measurement without continuously disturbing the actuation process
Solution Approach 2:
The controller prepares and applies sensing signals at specific predetermined times during the operational cycle, before or between actuation events. This timing strategy ensures that high-frequency sensing signals are applied when they will not interfere with the actuation process, maintaining both sensing accuracy and actuation stability
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 simultaneous sensing and actuation with reduced impact on actuation levels and eliminates the need for costly DC-biasing blocks and AC-coupling components, providing accurate resistance and capacitance measurements for effective impedance determination.
Implementation Method 1
A voltage is used to cause the electroactive polymer layer to expand in all directions as shown. FIG. 2 shows a device which is designed so that the expansion arises only in one direction. A voltage is used to cause the electroactive polymer layer to curve or bow.
Implementation Method 2
For certain classes of EAM, application of a small force (mechanical load) to the device generates an electrical signal in response. This allows a single EAM structure to be used both for actuation and for sensing.
Implementation Method 3
a current sensor for sensing a current flowing to the component; determine a resistance of the first resistor by sensing a steady state current during the activation period
Implementation Method 4
determine a capacitance of the capacitor by determining a charge flow during charging of the component at the beginning of the activation period, and taking into account the resistance of the first resistor; determine a resistance of the second resistor by controlling a current through the component using the current source during charging or discharging to have an oscillating profile
Data Source
AI summary
An electroactive material actuator and sensor is actuated with an actuation signal having an activation period for charging the actuator and a de-activation period for discharging the actuator. A parallel resistance of the actuator is determined by sensing a steady state current during the activation period and a series capacitance of the actuator is determined based on a charge flow during charging of the actuator at the beginning of the activation period. A series resistance is obtained by controlling a current through the actuator with an oscillating profile so that a phase relationship of the actuator between current and voltage can be measured. An oscillating current sink is used to enable circuit component measurements, which implement sensing functionality.