Universal Joint Arm Device with Orthogonal Slipring Joints
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Solution Overview
Problem
Existing master controllers for robots, particularly in surgical applications, face challenges with gimbal lock, which limits the operator's freedom of movement and can lead to suboptimal surgical procedures due to the need for active joints to prevent gimbal lock, resulting in bulkier and more expensive systems.
Innovation Solution
The arm device incorporates a universal joint configuration with a first wrist joint, a second wrist joint, and a first elbow joint, each comprising a slipring with a rotor and stator for infinite rotation, and an elbow joint with a hinge configuration, designed to minimize the risk of gimbal lock by ensuring that the third axis is normal to both the first and second axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active joints are used to bias against gimbal lock, then the risk of gimbal lock is reduced, but the device becomes bulky and more expensive
Solution Approach 1:
The joint is divided into two independent rotational mechanisms: a first rotation mechanism about a first axis and a second rotation mechanism about a second axis that is normal to the first axis. This segmentation allows each mechanism to operate independently, eliminating the need for active biasing while maintaining freedom from gimbal lock.
Solution Approach 2:
Instead of using active joints to prevent gimbal lock, the invention inverts the approach by using passive joints with orthogonal axes of rotation. The second axis is positioned normal to the first axis, which passively prevents the alignment that causes gimbal lock without requiring motors or active control.
2Adaptability or versatility
If three rotational axes are used to measure pitch, yaw and roll, then complete hand gesture control is achieved, but gimbal lock occurs when axes align
Solution Approach 1:
The second rotation mechanism is oriented with its axis normal to the first axis, creating an asymmetric orthogonal configuration. This asymmetric arrangement ensures that the axes cannot align or become parallel, thereby preventing gimbal lock while maintaining three degrees of freedom for complete hand gesture control.
3Device complexity
If passive joints are used, then the device is simpler and less expensive, but gimbal lock cannot be actively biased against
Solution Approach 1:
The orthogonal configuration of the two rotation mechanisms is designed in advance to prevent gimbal lock before it can occur. By positioning the second axis normal to the first axis from the outset, the design proactively eliminates the condition that leads to gimbal lock, making active biasing unnecessary.
Data Source
AI summary
An arm device comprising a universal joint, which universal joint comprises a first wrist joint, a second wrist joint and a first elbow joint wherein: each wrist joint comprises a first part, a second part and a slipring, which slipring comprises a rotor coupled to the first part and a stator coupled to the second part, which rotor is coaxially engageable with the stator and infinitely rotatable relative to the stator such that: the first part of the first wrist joint is infinitely rotatable relative to the second part of the first wrist joint about a first axis, and the first part of the second wrist joint is infinitely rotatable relative to the second part of the second wrist joint about a second axis; the first elbow joint comprises a first portion and a second portion, which first portion is rotatably engageable with the second portion about a third axis; the first wrist joint is coupled to the first elbow joint; and first elbow joint is coupled to the second wrist joint.