Active Material Variable Impedance Joints for Robot Safety
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Solution Overview
Problem
Existing mechanical joints and links in robots and similar devices face challenges in achieving variable impedance and stiffness, leading to safety concerns during human-robot interaction and increased complexity and cost due to reliance on active compliance or passive compliance methods, which also compromise precision and control.
Innovation Solution
A mechanical implement utilizing active material-based joints or links that can change stiffness in response to activation signals, allowing for high precision and variable impedance, enabling safe human interaction and versatile task performance by selectively altering stiffness through the use of shape memory polymers and other active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active compliance feedback control is used to achieve variable impedance, then interaction safety with humans is improved, but device complexity and production cost increase significantly
Solution Approach 1:
The patent replaces complex electronic feedback control systems with a passive mechanical compliance mechanism. The variable impedance is achieved through the intrinsic mechanical properties of the compliant mechanism itself, eliminating the need for sensors, controllers, and active feedback loops while maintaining safety during human-robot interaction.
Solution Approach 2:
The patent achieves variable impedance by changing the mechanical parameters of the compliant mechanism, such as the stiffness of elastic elements or the geometry of compliant links. This allows the system to adapt its impedance characteristics through passive mechanical design rather than active control, reducing complexity while maintaining reliability.
2Reliability
If passive compliance with flexible links is used to improve safety, then interaction safety is improved, but precision and structural capacity deteriorate
Solution Approach 1:
The patent segments the robotic system into rigid segments for precision tasks and compliant segments for safe interaction. The compliant mechanism is strategically placed only where safety is required, while other parts of the system maintain rigid structures for precision, thus achieving both safety and precision without compromise.
Solution Approach 2:
The patent applies compliance locally only in specific regions of the robot where human interaction occurs, rather than making the entire system compliant. This localized approach preserves precision and structural capacity in non-compliant regions while providing safety where needed.
3Reliability
If Series Elastic Actuator is used to combine active and passive compliance, then interaction safety is improved, but a tradeoff between range of operability and hazard reduction is forced
Solution Approach 1:
The patent implements a dynamically reconfigurable compliant mechanism that can adjust its compliance characteristics based on the task requirements. The system can switch between different compliance states or configurations, allowing it to provide high safety during interaction while maintaining full range of motion and operability for various tasks, eliminating the tradeoff present in fixed-impedance SEA designs.
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 solution provides a reconfigurable apparatus that can interchange joint and link functionality, reducing damage from collisions and improving performance by offering low-impedance dynamics for human interaction and high-stiffness capabilities for precise tasks, while maintaining low operational energy consumption and avoiding the need for complex feedback systems.
Implementation Method 1
at least one variable impedance member formed of at least one active material element operable to undergo a reversible change when exposed to an activation signal
Data Source
AI summary
A mechanical implement adapted for use in an autonomously functioning device, such as a robot arm, and including an active material, such as shape memory polymer, element that when activated and/or deactivated is operable to modify the mechanical impedance of a joint or link in the device.