Robot Hand Force Sensing Using Fingertip 3-Axis Sensors
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Solution Overview
Problem
Industrial robot hands face challenges in accurately detecting forces and moments during assembly due to the size and reliability issues of existing six-axis force sensors, which can lead to interference with workpieces and complex calibration processes.
Innovation Solution
A robot hand design that incorporates force sensors capable of detecting forces in three axis directions and calculating moments about three axes based on measured values and positional information, using a simplified structure with magnetic three-axis force sensors or strain gauges, allowing for accurate control without the need for large six-axis sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If six-axis force sensors are incorporated near the fingers of a robot hand, then force detection precision is improved, but the size of the finger portion increases and reliability deteriorates due to interference with workpieces and complex calibration
Solution Approach 1:
The patent divides the force detection function into two separate components: three-axis force sensors mounted on gripping fingers and moment calculation through coordinate transformation. This segmentation allows the physical sensors to remain small and simple while the computational aspect handles the full six-axis force and moment detection, resolving the contradiction between detection precision and reliability
Solution Approach 2:
The patent introduces a control device as an intermediary that performs coordinate transformation and moment calculation. This intermediary processes the raw three-axis force data to derive six-axis force and moment information, eliminating the need for complex six-axis sensors on the fingers while maintaining detection precision and improving reliability
2Measurement precision
If six-axis force sensors are incorporated near the fingers of a robot hand, then force detection precision is improved, but device complexity increases due to calibration requirements
Solution Approach 1:
The patent extracts the moment calculation function from the physical sensor and relocates it to the control device. By taking out the computational aspect of six-axis detection from the finger-mounted sensors, the system achieves force detection precision without the complexity of calibrating six-axis sensors on each finger
Solution Approach 2:
The patent creates a virtual six-axis force sensor through coordinate transformation in the control device. Instead of physically mounting six-axis sensors on fingers, the system copies the detection capability through mathematical transformation of three-axis sensor data, significantly reducing device complexity while maintaining precision
3Object-affected harmful factors
If the finger portion size is reduced to avoid interference with workpieces, then object-affected harmful factors are reduced, but force detection precision deteriorates without adequate sensor mounting space
Solution Approach 1:
The patent replaces the mechanical approach of mounting large six-axis sensors directly on fingers with a hybrid system combining simple three-axis force sensors and computational moment calculation. This substitution allows compact finger design without sacrificing detection precision, as the moment information is derived through coordinate transformation rather than physical sensor placement
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 solution enables accurate assembly operations by reducing the size of the finger portion, improving reliability, and simplifying the assembly process by calculating forces and moments in real-time, thus reducing the risk of interference and disconnection issues.
Implementation Method 1
using a simplified structure with magnetic three-axis force sensors or strain gauges
Data Source
AI summary
Force sensors capable of measuring only forces in xyz coordinate axis directions are installed in fingertips, respectively, and forces and moment forces acting on a robot hand are calculated based on positional information about each fingertip. This structure eliminates the need for using large force sensors to thereby enable downsizing of each fingertip, and enables detection of loads and moment forces acting on the robot hand.