Optical Force Sensors Using Movable Mask Windows
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Solution Overview
Problem
There is a need for new force measurement apparatus and methods that can accurately measure forces on structures in various applications, such as robotic arms and surgical instruments, to provide haptic feedback and monitor structural integrity without modifying the existing structures.
Innovation Solution
The solution involves an apparatus with optical sensors mounted on a load-carrying element, comprising a light source, photosensor, and an opaque mask with a movable window, allowing for deformation-based force measurement in multiple degrees of freedom, processed by electronic circuits and a processor to yield precise force and torque data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are mounted on a load-carrying element to measure forces, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical force sensors with an optical sensing system. Light sources emit beams that pass through a movable window in an opaque mask to photosensors. When force deforms the load-carrying element, the window position changes relative to the light path, modulating the light signal detected by photosensors. This optical substitution eliminates mechanical contact and friction while achieving high measurement precision.
Solution Approach 2:
The patent introduces an opaque mask with a movable window as an intermediary between the light source and photosensor. The window's position, which changes with deformation of the load-carrying element, modulates the light signal without direct mechanical coupling between the sensor components and the measured structure. This intermediary enables indirect measurement while maintaining isolation between the sensing system and the measured object.
2Measurement precision
If multiple optical sensors are used to measure forces in multiple degrees of freedom, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the sensing system into multiple independent optical sensor units, each capable of measuring force components in specific directions. By arranging multiple sensors with different orientations around the load-carrying element, the system can independently measure forces in multiple degrees of freedom. Each sensor segment contributes to the overall measurement capability without requiring complex integration.
Solution Approach 2:
The patent extends the measurement capability from single-axis to multi-axis by adding sensors in different spatial dimensions. Sensors are oriented at various angles around the load-carrying element, enabling measurement of forces in X, Y, and Z directions as well as torques. This dimensional expansion allows comprehensive 6-DOF force measurement while maintaining modular sensor design.
3Measurement precision
If the window is made movable relative to the photosensor to detect deformation, then measurement precision is improved, but the structure becomes more complex
Solution Approach 1:
The patent merges the movable window with the opaque mask into a single integrated component. The window is formed as part of the mask structure, eliminating the need for separate movable parts or complex mechanical linkages. When the load-carrying element deforms, the mask (with its window) moves relative to the light path, directly translating structural deformation into optical signal modulation without additional mechanical complexity.
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 approach enables robust, non-invasive force measurement across multiple degrees of freedom, providing accurate feedback and structural monitoring without altering the existing structure, with the ability to retrofit existing machines or structures and offering high sensitivity and flexibility in force measurement.
Implementation Method 1
Each of the optical sensors comprises a light source, a photosensor, and an opaque mask positioned in a light path between the light source and the photosensor
Data Source
AI summary
Apparatus for measuring forces on a load-carrying element comprises optical sensors mounted to the load-carrying element. Each optical sensor includes a light source, a photosensor and an opaque mask positioned in a light path between the light source and the photosensor. The mask has a window that is movable relative to the photosensor and is located such that light from the light source that passes through the window forms an illuminated region on the photosensor. Each of the optical sensors has a first part which includes the light source and the photosensor that is coupled to the load-carrying element at a first location and a second part that includes the mask that is attached to the load-carrying element at a second location spaced apart from the first location.