Robot Arm Kinematics for Large Workspace and Constant Tool Orientation
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Solution Overview
Problem
Existing robot arm designs face challenges in achieving a lightweight, high-speed, and high-safety configuration with a large workspace, as they often require significant space and compromise on workspace size due to limitations in kinematic chain design and actuator placement.
Innovation Solution
A robot arm design featuring a first actuator rotating an inner arm-assemblage about a first axis, connected to an outer arm-linkage pivotably around a second axis, with a third actuator rotating a shaft to form a third kinematic chain, allowing for three degrees of freedom without actuators in the arm structure, using a combination of parallel links and gearing mechanisms for precise end-effector control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If actuators are mounted on the arm structure to provide multiple degrees of freedom, then the robot can achieve complex end-effector motion control, but the arm weight increases and high-speed performance deteriorates
Solution Approach 1:
The patent extracts the actuators from the moving arm structure and relocates them to a fixed base station. The arm structure retains only passive kinematic chains (links and joints) that transmit motion, eliminating the weight of motors and power transmission components from the moving parts. This enables high-speed operation while maintaining full 6-DOF control capability through the base-mounted actuators.
Solution Approach 2:
The patent introduces passive kinematic chains as intermediaries between the base-mounted actuators and the end-effector. These kinematic chains (comprising links and joints without active components) serve as motion transmission mechanisms that enable complex end-effector motion control without adding weight to the moving arm structure, resolving the contradiction between control capability and weight.
2Speed
If a parallel kinematic structure is used to reduce arm weight, then high-speed performance is improved, but the workspace becomes restricted and adaptability deteriorates
Solution Approach 1:
The patent segments the robot system into two functional parts: a fixed base station containing all actuators and a lightweight moving arm structure containing passive kinematic chains. This segmentation allows the arm to be optimized for high-speed motion while the base provides the computational and actuation capability needed for large workspace coverage, resolving the contradiction between speed and adaptability.
Solution Approach 2:
The base-mounted actuator system serves multiple functions simultaneously: it provides power for high-speed arm movement, enables complex end-effector orientation control through the passive kinematic chains, and maintains a large workspace. The passive kinematic chains in the arm structure enable both high-speed positioning and versatile end-effector attitudes, achieving multi-functionality without compromising speed or workspace.
3Productivity
If a lightweight arm structure is used for high-speed operation, then productivity is improved, but the ability to maintain constant end-effector orientation deteriorates
Solution Approach 1:
The patent extracts all active control elements (actuators) from the lightweight arm structure and places them in the fixed base station. The passive kinematic chains in the lightweight arm are designed to naturally maintain constant end-effector orientation during movement, achieving both high-speed operation and precise orientation control without the weight penalty of active components in the arm.
Solution Approach 2:
The passive kinematic chains in the lightweight arm structure are designed to self-maintain constant end-effector orientation through their geometric configuration during high-speed movement. The mechanism inherently preserves orientation precision without requiring additional active control components in the moving arm, enabling both high productivity and manufacturing precision.
Data Source
AI summary
A robot arm includes a first kinematic chain from a first actuator to an end-effector platform, providing a first degree of freedom for positioning the end-effector platform; a second kinematic chain from a second actuator to the end effector platform, providing a second degree of freedom for positioning the end effector platform; a third kinematic chain from a third actuator to the end-effector platform, providing a third degree of freedom for positioning the end-effector platform; and a fourth kinematic chain configured to transmit movement of a fourth actuator to a corresponding orientation axis of an end-effector. The fourth kinematic chain includes an orientation linkage mounted to an inner arm assemblage via at least one bearing mounted to the end-effector platform, wherein the orientation linkage includes an end-effector rotation link and joints that provide at least two degrees of freedom for each end joint of the end-effector rotation link.