Robot Joint Constraint Structure for Accurate Force Sensing
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Solution Overview
Problem
Conventional multijoint robot systems face difficulties in accurately detecting forces in directions other than the driving axis due to interference from forces in other axial directions, leading to measurement errors and incorrect force control, especially when handling fragile or lightweight objects.
Innovation Solution
A driving mechanism with a constraining part that allows movement in one direction and constrains in another, incorporating a force sensor that directly measures forces on the link, simplifying the transfer pathway and enabling high-precision detection of forces in other axial directions, thereby correcting measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a force sensor is mounted on a joint to detect torque around a driving axis, then force control capability is improved, but measurement precision deteriorates due to interference from forces in other axial directions
Solution Approach 1:
The force sensor is divided into multiple detection elements arranged in specific orientations. Each element detects forces in specific directions, allowing the system to segment and separately measure forces in different axial directions, thereby isolating the torque around the driving axis from interfering forces in other directions.
Solution Approach 2:
Different portions of the force sensor are designed with different detection characteristics optimized for specific force directions. The sensor structure incorporates elements with varying sensitivity to forces along the driving axis versus forces in other axial directions, enabling selective measurement that prioritizes accuracy for the driving axis torque while accounting for or rejecting interfering forces.
2Ease of operation
If a torque sensor is mounted on a joint to detect force around driving axis, then force feedback control is improved, but device complexity increases due to additional constraining structures
Solution Approach 1:
The force sensor structure serves multiple functions simultaneously: it acts as both a detection element for torque around the driving axis and as part of the joint's structural framework. The sensor is integrated into the joint assembly such that it performs both measurement and structural support functions, eliminating the need for separate dedicated mounting structures and reducing overall device complexity.
Solution Approach 2:
The force sensor is merged with the joint structure itself rather than being mounted as a separate component. The sensor elements are incorporated into the joint's mechanical assembly, combining the detection function with the existing structural elements, thereby avoiding additional complexity from separate mounting mechanisms and constraining structures.
Data Source
AI summary
A sensor detection error at a joint of a robot arm is correctly detected. A joint structure that joins links and of a robot arm includes a sensor for determining force acting between the links. A driving apparatus that generates a driving force of a joint includes first and second driving parts. A constraining part that constrains the joint movable in a driving direction of the joint and be unmovable in another direction includes first and second supporting parts that are movable relative to each other in the driving direction of the joint. The driving part of the driving apparatus is fixed to the link, and the supporting part of the constraining part is fixed to the link. Also, the supporting part of the constraining part is fixed to the driving part of the driving apparatus. The sensor is fixed so as to link the supporting part and the link.