Robot Center-of-Gravity Estimation Without Force Sensors

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Solution Overview

Problem

Legged robots equipped with force sensors face high manufacturing and operation costs due to the fragility and frequent replacement needs of these sensors, especially when subjected to heavy loads.

Innovation Solution

An information processing device estimates the center of gravity of a robot device without using a force sensor by calculating reaction forces from torque applied to each joint, allowing for stable walking and posture control even with unknown load weights or shapes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a force sensor is used to determine the center of gravity, then the accuracy of center of gravity estimation is improved, but the manufacturing cost increases and the reliability decreases due to sensor fragility

Engineering Contradiction:

Improvecenter of gravity estimation accuracyVSAvoidsensor durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical force sensor system with a computational approach using torque sensor data and center of gravity calculation algorithms. The torque sensor measures rotational force at the hip joint, and the control device calculates the center of gravity position through mathematical computation rather than direct mechanical measurement, thereby eliminating the need for fragile force sensors on the sole.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a force sensor is installed on the sole to measure ground reaction force, then the center of gravity can be determined accurately, but the operation cost increases due to frequent sensor replacement

Engineering Contradiction:

Improvecenter of gravity determination accuracyVSAvoidoperation cost

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent substitutes the force sensor measurement system with a torque-based computational system. The torque sensor on the hip joint measures rotational force, and the control device computes the center of gravity position through mathematical relationships between torque, leg length, and gravity, eliminating the need for expensive and fragile force sensors on the sole that require frequent replacement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces the torque sensor as an intermediary measurement device that indirectly provides information about the center of gravity through torque measurement, rather than directly measuring ground reaction force. This intermediary approach allows for more reliable and cost-effective operation while maintaining sufficient measurement accuracy for control purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Extent of automation

If a force sensor is used on the leg portion, then real-time center of gravity data is available for posture control, but the device complexity and manufacturing cost increase

Engineering Contradiction:

Improvereal-time posture control capabilityVSAvoidsensor system complexity

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The patent replaces the complex force sensor system with a simpler torque sensor and computational algorithm. The torque sensor measures hip joint torque, and the control device uses mathematical calculations to derive real-time center of gravity information, achieving the same automation capability with reduced device complexity and lower manufacturing costs.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical 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

This approach reduces production and operation costs by eliminating the need for expensive force sensors, improving the stability and cost-effectiveness of legged robots by estimating the center of gravity based on torque and reaction forces.

Implementation Method 1

a torque detection unit configured to detect a magnitude of torque applied to each joint of the plurality of leg portions (20)

Methodology Applied

Scientific EffectTorque: Torque

Implementation Method 2

calculating a magnitude of reaction force applied to each of the plurality of leg portions (20) from a ground contact surface on the basis of the magnitude of the torque applied to each joint of the plurality of leg portions (20) and a length of each link of the plurality of leg portions (20)

Methodology Applied

Scientific EffectMechanical Force calculation: Mechanical Force

Implementation Method 3

estimating a plan position of a center of gravity of an entire robot device (1) including the load (40) on the basis of the magnitude of the reaction force applied to each of the plurality of leg portions (20) from a ground contact surface

Methodology Applied

Scientific EffectGravitation: Gravitation

Data Source

PatentEP3785867B1Information processing device, information processing method, and program

Publication Date: 2024.12.18 SONY GROUP CORP

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AI summary

A center of gravity of a robot device is estimated without utilization of a force sensor or the like. An information processing device including: a center-of-gravity estimation unit that calculates, on the basis of torque applied to one or more joints included in each of a plurality of leg portions, reaction force applied from a ground contact surface to each of the plurality of leg portions, and that estimates a center of gravity of a robot device including the plurality of leg portions on the basis of the calculated reaction force on the plurality of leg portions.