Compliant Joint Cam Mechanism for Robot Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing compliant joints for robots are either complex in structure or weak when subjected to perpendicular loads, and they lack a mechanism to inherently ensure safety through passive compliance, which is crucial for preventing human injury during collisions.
Innovation Solution
A compliant joint design featuring a cam mechanism that connects and disconnects between a rotating member and a housing based on external force levels, using transmission shafts, mounting holes, rollers, cam guide units, and elastic members to maintain rigidity below a designated force and provide flexibility above it, with adjustable parameters to regulate the release force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive compliance mechanism is implemented using multiple links, then robot safety is improved, but the structure becomes complicated and weak when perpendicular load is applied
Solution Approach 1:
The compliant joint is divided into distinct functional components: a housing, a rotating member, and a cam mechanism. This segmentation allows each component to perform its specific function while maintaining overall structural simplicity and strength against perpendicular loads.
Solution Approach 2:
The cam acts as an intermediary element between the housing and rotating member, providing the compliance function through its geometric profile. This intermediary mechanism achieves passive compliance without requiring complex multi-link structures, thereby simplifying the overall design while maintaining safety.
2Reliability
If an active compliance method using sensors and controllers is used, then robot compliance is achieved, but the reaction velocity is limited and errors may occur
Solution Approach 1:
The cam mechanism is designed to automatically respond to external forces greater than a designated value through its geometric profile, without requiring external sensors or controllers. This self-service mechanism achieves both compliance control and high reaction velocity by directly translating force into motion through the cam's shape.
Solution Approach 2:
The patent replaces the electronic control system (sensors and controllers) with a purely mechanical cam-based compliance mechanism. This substitution eliminates signal processing delays and potential errors, providing instantaneous response to external forces while maintaining reliable compliance control.
3Device complexity
If the cam is always connected to the rotating member, then the structure is simple, but the robot cannot provide flexibility when external force greater than designated value is applied
Solution Approach 1:
The connection between the cam and rotating member is made dynamic rather than static. The cam is selectively connected or disconnected from the rotating member based on the magnitude of external force, allowing the system to adapt between rigid and flexible states. This dynamic connection is achieved through the cam's geometric profile that engages or disengages from the rotating member depending on the applied load.
4Manufacturing precision
If the compliant joint maintains rigidity under normal force, then operational accuracy is improved, but safety is compromised when collision occurs
Solution Approach 1:
The system changes its mechanical parameters (rigidity vs. flexibility) based on the magnitude of external force. Under normal operating conditions, the cam remains connected to the rotating member, maintaining rigidity and operational accuracy. When external force exceeds the designated threshold, the cam mechanism automatically changes state to provide flexibility, thereby protecting against impact forces while preserving precision during normal operation.
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 compliant joint achieves a simple and strong structure that ensures passive compliance, providing high reaction velocity and safety by maintaining rigidity under normal conditions and flexibility during high-force collisions, thus enhancing robot safety and operational accuracy.
Implementation Method 1
the cam is connected to the housing such that the cam can maintain the connection with the housing if an external force below a designated value is applied to the rotating member, and release the connection with the housing if the external force more than the designated value is applied to the rotating member
Implementation Method 2
a cam (30) installed between the housing (10) and the rotating member (20), and connected to the housing (10) and the rotating member (20) respectively
Data Source
AI summary
Disclosed is a compliant joint achieving passive compliance. The compliant joint includes a housing and a rotating member mutually rotatably provided; and a cam provided between the housing and the rotating member, and connected to the housing and the rotating member respectively. The cam is connected to the rotating member to rotate together with the rotation of the rotating member, or be independent of the rotating member so as to move in the axial direction of the rotating member separately from the rotating member. The cam is connected to the housing such that the cam can maintain the connection with the housing when external force below a designated value is applied to the rotating member, and release the connection with the housing in the case that external force more than the designated value is applied to the rotating member.