Variable Stiffness Transmission Mechanism for Human-Robot Interaction Safety
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Solution Overview
Problem
Existing mechanical transmission mechanisms face limitations in controlling stiffness during task execution, leading to potential biological damage in interactions with humans, particularly due to amplified inertia, fixed compliance, and lack of precision in positioning and acceleration phases.
Innovation Solution
A transmission mechanism with variable stiffness that allows independent control of motion and impedance through flexible transmission devices, such as timing belts and magneto-rheological fluids, enabling continuous impedance adjustment during acceleration, uniform motion, and deceleration phases, thereby reducing the risk of biological damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rigid transmission mechanisms are used, then positioning precision is improved, but the reflected inertia is amplified by the square of the gear ratio, limiting maximum admissible velocity and creating safety risks
Solution Approach 1:
The patent applies a variable stiffness transmission mechanism that dynamically adjusts the stiffness of the elastic element during operation. During acceleration phases, the stiffness is reduced to limit reflected inertia and improve safety. During uniform motion phases, the stiffness is increased to maintain positioning precision. This dynamic adjustment resolves the contradiction between precision and safety risks.
2Object-affected harmful factors
If deformable transmission mechanisms with fixed compliance are used, then safety is improved by limiting maximum opposable resistance, but positioning precision deteriorates due to slowness in acceleration phases and ease of triggering oscillations
Solution Approach 1:
The variable stiffness mechanism allows the transmission to be compliant during acceleration and deceleration phases to ensure safety, while becoming rigid during uniform motion phases to maintain positioning precision. This dynamic switching resolves the contradiction between safety and precision that plagues fixed compliance mechanisms.
3Object-affected harmful factors
If variable stiffness transmission mechanisms are used, then safety is improved by reducing reflected inertia, but device complexity increases due to the need for rapid controllability during task execution
Solution Approach 1:
The patent changes the physical parameter of the elastic element (stiffness) to resolve the contradiction. By using an elastic element whose stiffness can be varied through parameter changes (such as temperature, magnetic field, or mechanical adjustment), the system achieves rapid controllability without requiring complex active control mechanisms, thus improving safety while limiting complexity increases.
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
The mechanism ensures safe operation by reducing mechanical impedance during interactions with humans, optimizing motion characteristics, and minimizing damage by dynamically adjusting stiffness and impedance in real-time.
Implementation Method 1
The variation is regulated by modifying values of a controller variable 91, for example, tension. [0016] FIG. 6 shows schematically, in section, an alternative preferable form of the mechanism, which utilizes magneto-rheological fluids
Data Source
AI summary
A transmission mechanism between two or more shafts of devices that interact or could possibly interact with people. The transmission mechanism has a particular application to the sector of machines for muscular training and/or rehabilitation, devices for entertainment such as carousels and amusement-park rides, service machines and robots that physically interact with human beings, and industrial robots that operate in close proximity to the operator.