Articulated Robot Linear Drive Coupling for Process-Force Stiffness
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Solution Overview
Problem
Existing articulated robots face challenges in maintaining high stiffness and accuracy in positioning an end effector under process forces due to tolerance-related play and insufficient kinematic stiffness, which can lead to undesirable deviations.
Innovation Solution
The articulated robot is equipped with a design featuring a linear drive and coupling with two coupling joints, where the linear drive is arranged on a first robot element, and the coupling is articulated to both the drive element and a second robot element, forming a rod triangle configuration that minimizes the transmission of process forces to the linear drive, ensuring high stiffness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional drive train is used to control kinematic adjustments, then the robot can perform positioning tasks, but the kinematic stiffness is insufficient leading to undesirable deviations in end effector positioning under process forces
Solution Approach 1:
The robot arm is divided into multiple robot sections (first robot section, second robot section, etc.) connected by robot joints. Each section can be independently controlled by linear drives, allowing segmented control of kinematic adjustments and improving overall stiffness by distributing the load across multiple independent segments rather than a single conventional drive train.
Solution Approach 2:
The patent introduces a linear drive mechanism that operates in a dimension perpendicular to the traditional rotational joint axes. The linear drive with coupling joints creates a new degree of freedom in the kinematic chain, adding dimensional control capability that enhances stiffness without compromising positioning accuracy.
2Manufacturing precision
If tight tolerance ranges are specified to reduce play in the robot's kinematics, then positioning accuracy improves, but the complexity of the drive train increases
Solution Approach 1:
The coupling mechanism acts as an intermediary element between the linear drive and the robot sections. It translates linear motion into the appropriate rotational movement at the robot joint while absorbing tolerance variations. The coupling joints serve as mediators that decouple the drive train from direct tolerance-sensitive connections, reducing the need for extremely tight tolerances throughout the entire system.
Solution Approach 2:
The patent changes the operational parameters of the drive train by using linear drives with large stroke lengths that can accommodate tolerance variations. The linear drive operates with adjusted parameters (position, velocity, acceleration profiles) that compensate for kinematic play, allowing standard tolerances to achieve the same positioning accuracy as would require much tighter tolerances in a conventional system.
Data Source
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Figure 3a~3b
AI summary
The invention relates to an articulated robot with serial kinematics (2) for positioning an end effector (3), wherein the kinematics (2) comprises at least one partial kinematics (6, 7) with a robot joint (6.1), with a robot element (6.2) upstream of the robot joint (6.1) and a robot element (6.3) downstream of the robot joint (6.1). It is proposed that the at least one partial kinematics (6, 7) for adjusting the robot elements (6.2, 6.3) relative to each other comprises a linear drive (6.4) with a drive element (6.6) adjustable along a linear axis (6.5) and a coupling (6.7) with two coupling joints (6.8, 6.9) spaced apart from each other along the coupling extension, that the linear drive (6.4) is arranged on a first robot element (6.10) of the partial kinematics (6), and that the coupling (6.7) is connected on one side to the drive element (6.6) of the linear drive (6.4) and on the other side to the second robot element (6.11) of the partial kinematics (6), spaced apart from the geometric axis (6.1a) of the robot joint (6.1) of the partial kinematics (6).