Compliant Robot Arm Control for Wafer Transport Vibration Reduction
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Solution Overview
Problem
Existing robotic systems for transporting goods, particularly sensitive items like wafers, face challenges in minimizing dynamic loads and vibrations during transport, which can damage the goods.
Innovation Solution
A robot with a compliantly controlled multi-axis arm that simulates a spring-damper arrangement through impedance control, reducing accelerations and vibrations by detecting loads and counteracting them, and switching between transport modes to optimize handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the robot arm is rigidly controlled or blocked by brakes during transport, then the platform can be moved stably, but accelerations and vibrations increase significantly
Solution Approach 1:
The robot arm transitions from a static rigidly controlled state to a dynamic compliantly controlled state during transport. The control mode is switched to allow the arm to move flexibly with the platform, absorbing vibrations and accelerations dynamically rather than resisting them rigidly, thereby reducing harmful forces on transported goods.
Solution Approach 2:
The control parameters of the robot arm are changed during transport mode. The stiffness and damping parameters are adjusted through compliant control to match the dynamic characteristics of the moving platform, transforming the arm into a vibration-damping element that reduces accelerations and vibrations while maintaining stability.
2Object-affected harmful factors
If the robot arm is compliantly controlled during transport, then accelerations and vibrations are reduced, but the handling precision and positioning accuracy decrease
Solution Approach 1:
The system dynamically switches control modes based on the operational phase. During transport, compliant control is active to reduce vibrations. During positioning and handling operations, the system transitions to rigid position control, ensuring high precision when needed while maintaining vibration reduction during transport.
Solution Approach 2:
The control mode alternates periodically between compliant and rigid states depending on the operational requirements. The system enters compliant mode during transport phases and switches to rigid mode during positioning phases, creating a periodic alternation that optimizes both vibration reduction and positioning accuracy at different times.
3Object-affected harmful factors
If vibration dampers are added as hardware components, then accelerations and vibrations are reduced, but the device complexity increases
Solution Approach 1:
The patent replaces physical vibration damper hardware with a software-based compliant control system. The control algorithm simulates the effect of vibration dampers by dynamically adjusting the robot arm's stiffness and damping characteristics through control signals, achieving vibration reduction without adding mechanical components.
Solution Approach 2:
The control system acts as an intermediary between the robot arm and the transported goods. Instead of adding physical dampers between components, the control algorithm mediates the forces and movements, dynamically adjusting the arm's response to platform movements to reduce vibrations transmitted to the goods.
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
This approach significantly reduces dynamic loads and vibrations during transport, effectively protecting sensitive goods like wafers by using the robot arm as a vibration damper and allowing for precise handling and positioning.
Implementation Method 1
a load, in particular an inertial load, in one embodiment a torque, is detected in one or more joints of the robot arm (respectively)
Implementation Method 2
To reduce accelerations, in particular vibrations, so-called vibration dampers, in particular (vibration) absorbers, are known, which in one design have spring-damper arrangements designed as hardware
Implementation Method 3
which in one design have spring-damper arrangements designed as hardware
Implementation Method 4
the robot arm is impedance-controlled in the gentle transport mode. In the present case, this is understood, in particular in the technical sense, to mean that one or more joints of the robot arm and/or a reference fixed to the robot arm, in particular the TCP, is/are bound to a predetermined target position or pose by one or more virtual springs and/or, in one embodiment, speed-dependent, in particular speed-proportional, dampers
Data Source
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Figure 2~3
AI summary
In a method according to the invention for the handling, in particular transport, of goods, in particular wafers, by a robot, which has a mobile platform (10), a multiaxial robot arm (20) and a controller (30) for commanding drives of the robot arm, the robot arm is compliantly controlled in a safe transport mode (S20) during a transport movement of the platform, in particular with a free end effector (21), in order to reduce accelerations, in particular vibrations, of the robot, in particular of the platform.