Robot Arm Impedance Control for Fast Liquid Container Handling

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Solution Overview

Problem

Existing robot control systems fail to effectively manage the movement of robots holding containers with liquids, particularly in preventing liquid spillage during speed changes.

Innovation Solution

A robot control system that includes an impedance control unit to predict liquid displacement and adjust arm impedance based on these predictions, allowing speed changes without spilling, using a combination of hardware and software components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the robot speed is increased to improve productivity, then the movement efficiency is improved, but the liquid in the container may spill due to insufficient impedance control

Engineering Contradiction:

Improverobot movement speedVSAvoidliquid spillage prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The impedance control unit performs preliminary prediction about liquid displacement before the robot actually changes speed. By predicting the displacement that would occur when speed changes from first speed to second speed, the system prepares appropriate impedance values in advance, preventing spillage before it happens.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the impedance magnitude of the robot arm based on predicted liquid displacement. Instead of using fixed impedance values, the impedance control unit changes the impedance magnitude according to the predicted displacement, allowing the robot to move faster while maintaining liquid stability through real-time adaptation.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the robot arm impedance is increased to prevent liquid spillage, then the liquid stability is improved, but the robot movement speed must be reduced

Engineering Contradiction:

Improveliquid stabilityVSAvoidrobot movement speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The system changes the impedance parameter dynamically based on speed changes and liquid displacement predictions. By adjusting the impedance magnitude according to specific conditions (speed transitions and predicted displacement), the system optimizes both liquid stability and robot speed rather than using conservative fixed high impedance values.

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If the robot moves at high speed to improve efficiency, then the operation time is reduced, but the liquid displacement increases causing potential spillage

Engineering Contradiction:

Improveoperation timeVSAvoidliquid displacement

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The impedance control unit uses feedback from the predicted liquid displacement to adjust the impedance magnitude. The system continuously monitors the relationship between speed changes and predicted displacement, using this feedback to optimize impedance settings that allow faster movement while compensating for displacement effects.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12515329B2Robot control system, robot control method, and non-transitory storage medium

Publication Date: 2026.01.06 TOYOTA JIDOSHA KK

AI summary

A robot control system includes: an impedance control unit configured to, while a robot holding a container with an arm is moving at a first speed, make prediction about displacement of a liquid in the container that occurs when a speed of the robot is changed to a second speed higher than the first speed, and control a magnitude of a first impedance of the arm in a horizontal direction based on a result of the prediction; and a movement control unit configured to change the speed of the robot to the second speed in response to reduction in the first impedance.