Pneumatic Haptic Actuator Pressure Estimation for Contact Force Control
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Solution Overview
Problem
Soft inflatable actuators in haptic technologies face challenges in measuring contact force due to their deformable nature, making it difficult to integrate rigid or bulky sensors, which are typically required for accurate force measurement.
Innovation Solution
A method and system for estimating and adjusting contact force in pneumatic actuators using pressure-based interaction state estimation, incorporating pressure sensors to determine fluid mass, height, and contact force without additional external sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rigid or bulky sensors are added to measure contact force in soft actuators, then measurement precision is improved, but device complexity and ease of operation deteriorate due to integration difficulty in deformable structures
Solution Approach 1:
The patent replaces mechanical force sensors with a pneumatic system that uses internal air pressure measurements to infer contact force. The soft actuator incorporates pressure sensors that measure the air pressure inside the pneumatic chamber, and contact force is calculated based on the relationship between pressure, volume change, and actuator deformation. This substitution eliminates the need for rigid mechanical sensors and simplifies integration into soft deformable structures.
Solution Approach 2:
The patent introduces air pressure as an intermediary parameter to indirectly measure contact force. Instead of directly measuring force with sensors at the contact interface, the system measures the intermediate parameter (internal air pressure) and uses a mathematical model to derive the contact force. This intermediary approach enables accurate measurement while maintaining the softness and deformability of the actuator.
2Measurement precision
If additional external sensors are integrated at the actuator interface, then measurement precision is improved, but ease of operation and adaptability worsen due to the soft, deformable nature of pneumatic actuators
Solution Approach 1:
The patent replaces external mechanical force sensors with internal pneumatic pressure sensing. The pressure sensors are integrated within the pneumatic actuator structure itself, measuring the air pressure that naturally changes during actuation and contact. This eliminates the need for additional external sensors at the actuator interface, maintaining ease of operation while enabling accurate contact force measurement through the pressure-force relationship.
3Device complexity
If pressure sensors are used to estimate contact force, then device complexity is reduced and ease of operation is improved, but measurement precision may worsen without additional external sensing
Solution Approach 1:
The patent implements a feedback-based estimation system where internal pressure measurements are continuously monitored and used to calculate contact force in real-time. The system uses the measured pressure values, combined with known actuator parameters (cross-sectional area, volume relationships), to provide accurate contact force estimation. This feedback approach compensates for the simplicity of the sensing mechanism by using dynamic measurement and calculation to maintain precision.
Solution Approach 2:
The patent exploits the dynamic relationship between pneumatic parameters (pressure, volume) and mechanical parameters (force, displacement). By measuring pressure changes and using the known geometric and physical parameters of the actuator, the system calculates contact force through parameter transformation. This approach achieves accurate measurement using simple pressure sensors by leveraging the inherent parameter relationships in pneumatic systems.
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 estimation and control of contact force in haptic systems, ensuring proper fit and haptic feedback, reducing the need for cumbersome external sensors and enhancing user interaction in wearable devices.
Implementation Method 1
pneumatic actuators are soft, robust, lightweight, and compact
Implementation Method 2
receiving a pressure measurement of a fluid in an actuator
Implementation Method 3
receiving a pressure measurement of a fluid in an actuator; determining, based on the pressure measurement, a mass of the fluid in the actuator
Data Source
AI summary
Methods, systems, and apparatuses for combining pressure measurement with a dynamic system model to estimate the air mass within an actuator, and then estimate the applied contact force which may be based on a quasi-static deformation model. An example method includes, in response to a request to apply a contact force by an actuator at a first actuator pressure, determining a second actuator pressure for the actuator to apply the contact force. The contact force is generated using one or more components of a haptic assembly, and the second actuator pressure is determined based on one or more of properties of the components of the haptic assembly and pressure data obtained via one or more sensors. The example method further includes causing the haptic assembly to adjust the first actuator pressure to the second actuator pressure such that the actuator applies the contact force.