3-Axis Robotic Joint with Cable Transmission
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Solution Overview
Problem
Existing robotic shoulder joints face challenges in replicating human shoulder movement within a human-like form factor due to limitations in power density and form factor constraints, with both hydraulic and electric actuators presenting disadvantages such as size, noise, and safety concerns.
Innovation Solution
A 3-axis robotic joint utilizing a combination of cable transmission and differential mechanisms driven by three electric motors, positioned at the base of the shoulder within the body cavity, to achieve a wider range of motion and comply with human-like form factors, reducing inertia and increasing acceleration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydraulic actuators are used to provide high power density and force, then the joint can achieve desired strength and motion, but the system becomes messy, noisy, and requires large infrastructure that cannot fit within human-like form factors
Solution Approach 1:
The patent extracts the hydraulic power supply infrastructure (pumps, tanks, filters, accumulators) from the joint location and places it remotely, allowing the joint itself to be compact and fit within human-like form factors while still receiving hydraulic power through piping
Solution Approach 2:
The patent introduces hydraulic piping as an intermediary to transmit power from the remote power supply to the joint, enabling separation of the power generation infrastructure from the actuation location
2Force
If hydraulic actuators are used to achieve high force output, then the joint can provide desired strength, but high pressure oil can spray out and injure passersby
Solution Approach 1:
The patent removes the high-pressure hydraulic power supply components from the joint location, extracting only the necessary actuation function while eliminating the source of high-pressure spray hazards from the joint area
3Object-affected harmful factors
If electric actuators are used to provide clean and safe operation, then the joint becomes safe and maintenance-free, but the power density is insufficient to achieve desired accelerations and motion performance
Solution Approach 1:
The patent switches from electric to hydraulic actuation, using hydraulic cylinders to provide the high power density and force output needed for human-like motion performance while maintaining safety through remote power supply and controlled hydraulic systems
4Force
If hydraulic actuators are used to achieve high force output, then the joint can provide desired strength, but the achievable servo bandwidth is limited by the distance of hydraulic lines between servo valves and hydraulic cylinders
Solution Approach 1:
The patent extracts the servo valves from remote locations and places them locally at the joint, shortening the hydraulic line distance and improving servo bandwidth while maintaining the benefits of remote power supply
5Speed
If motors are placed local to the joint to drive the joint, then the joint can achieve desired motion, but the form factor constraints are violated and moving inertia increases
Solution Approach 1:
The patent extracts the motors from the joint location and places them remotely in the body cavity, eliminating the form factor conflict and reducing moving inertia while maintaining full motion control capability through cable transmission
6Speed
If motors are placed at the joint to provide direct drive, then the joint can achieve desired acceleration, but the mass of the motors increases the moving inertia and reduces load carrying capacity
Solution Approach 1:
The patent extracts the motor mass from the moving joint components and places it in the stationary body cavity, eliminating the motor mass from the moving inertia calculation while maintaining full drive capability through the cable-pulley transmission system
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 significant increase in range of motion and compliance with human-like form factors, enhancing motion performance and load-carrying capacity while ensuring safety and cleanliness, addressing the limitations of previous shoulder joint designs.
Implementation Method 1
cable transmission
Implementation Method 2
cable transmission
Implementation Method 3
differential mechanisms
Implementation Method 4
differential mechanisms
Data Source
AI summary
A robotic joint configured as a 3-axis joint configured with a shoulder or other human joint form factor. The joint includes a first link made up of a block attaching to a torso and a stationary electric actuator assembly mounted to the block. A second link is connected to the first link to rotate about a first axis and be driven by the actuator assembly. A third link is attached to the second link to rotate about a second axis orthogonal to the first axis when the third link is driven by the actuator assembly. A fourth link is connected to the third link to rotate about a third axis orthogonal to the second axis when the fourth link is driven by the actuator assembly. The actuator assembly includes three electric motors with threaded drive capstans driving pulleys in the links while being spaced apart from the rotating links.