Touchpad Finger Force Estimation with Palm Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing force sensing touchpads with capacitive transducers face limitations in dynamic range due to limited travel distance between sensing pads and base plates, leading to saturation issues when a palm applies a large force, preventing accurate measurement of finger force.
Innovation Solution
The implementation of a force sensing touchpad with a base plate and resiliently spaced capacitive force sensors, where the forces produced by a palm are calculated and used to determine the finger force by excluding saturated sensors and periodically updating palm force maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If capacitive force sensors are used with limited travel distance between sensing pads and base plates, then the device structure is compact, but the dynamic range of force sensing is limited causing sensor saturation when palm applies large force
Solution Approach 1:
The system segments the force measurement task by separating palm force measurement from finger force measurement. When a sensor is saturated by palm force, the system identifies this saturation and excludes that sensor from finger force calculations, using only non-saturated sensors to maintain measurement accuracy.
Solution Approach 2:
The system dynamically changes the set of active sensors based on saturation detection. By monitoring capacitance values and identifying saturated sensors, the system adapts which sensors contribute to finger force measurement, effectively expanding the usable dynamic range without changing the physical sensor structure.
2Area of stationary object
If multiple capacitive force sensors are used to increase measurement coverage, then the force sensing coverage is improved, but the device complexity increases
Solution Approach 1:
The same array of capacitive force sensors serves multiple functions: detecting both palm contact and finger contact, measuring both palm force and finger force, and providing redundancy when saturation occurs. This multi-functionality increases coverage without proportionally increasing complexity.
Solution Approach 2:
The system continuously monitors capacitance values from all sensors and uses this feedback to identify saturated sensors. This feedback mechanism allows the system to adaptively select which sensors to use for finger force measurement, managing complexity through intelligent control rather than hardware changes.
3Ease of manufacture
If the touchpad structure is kept simple with minimal components, then the manufacturing cost is reduced, but the ability to distinguish between palm and finger contact is compromised
Solution Approach 1:
The capacitance measurements serve as an intermediary that indirectly reveals both the location and magnitude of applied forces. By analyzing patterns in capacitance changes across multiple sensors, the system can infer whether contact is from a palm or finger without requiring specialized sensor types or complex hardware modifications.
Solution Approach 2:
The system performs preliminary identification of palm contact by detecting which sensors show saturation patterns characteristic of palm pressure. This preliminary action allows the system to prepare by excluding saturated sensors before calculating finger force, ensuring accurate discrimination between palm and finger contact.
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
This configuration allows for accurate estimation of finger force even when the palm is also contacting the touchpad, effectively extending the dynamic range of force sensing and enabling simultaneous palm and finger input recognition.
Implementation Method 1
the touchpad utilizes capacitance measurements to estimate a force applied to the touchpad
Data Source
AI summary
Methods and computing devices for estimating a finger force exerted on a touchpad are disclosed. In one example, a method comprises calculating a plurality of forces produced by a palm at a plurality of capacitive force sensors of the touchpad, where at least one of the sensors is saturated. After calculating the forces produced by the palm, the method determines that the touchpad is being contacted by the palm and a finger. The method uses the forces produced by the palm to determine the finger force exerted on the touchpad by the finger.