Robotic Foot Slip Detection Through Inter-Foot Distance Monitoring

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Solution Overview

Problem

Legged robots face challenges in maintaining balance and preventing slips on uneven or rough terrain due to the inability to effectively control ground reaction forces and detect disturbances in their gait.

Innovation Solution

The implementation of a system that uses sensors to determine the distance between a robot's feet and compare it to a threshold, adjusting the ground reaction force to prevent slips by controlling the orientation of the force within a friction cone, and reacting to detected slips or disturbances by adjusting the gait.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the robot operates on uneven or rough terrain, then the robot's mobility and adaptability are improved, but the risk of slips and loss of balance increases

Engineering Contradiction:

Improveterrain adaptabilityVSAvoidslip prevention

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control system proactively adjusts ground reaction forces before slips occur by continuously monitoring foot position and comparing estimated distances. The system calculates required force adjustments in advance and applies them preventively, rather than reacting only after a slip is detected.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses sensor data to continuously monitor foot positions and calculate distances between feet. This feedback loop allows the control system to detect disturbances and adjust ground reaction forces in real-time, maintaining balance and preventing slips on varying terrain.

Inventive Principle:

Principle #23Feedback

2Stability of the object's composition

If the robot increases ground reaction force to maintain balance, then stability is improved, but the likelihood of slipping increases due to exceeding friction limits

Engineering Contradiction:

Improvebalance stabilityVSAvoidslip occurrence

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The control system dynamically adjusts the magnitude and orientation of ground reaction forces based on real-time sensor data and calculated foot positions. By changing force parameters within the friction cone rather than simply increasing overall force, the system maintains balance without exceeding friction limits.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system continuously adapts ground reaction forces based on changing terrain conditions and robot state. Rather than applying fixed forces, the control system dynamically modifies force vectors to maintain optimal balance while staying within friction constraints, responding to disturbances as they occur.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If the robot uses complex sensor systems to detect slips, then detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improveslip detection accuracyVSAvoidsensor system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses an intermediary calculation approach, estimating foot positions and distances based on sensor data rather than directly measuring slip. By computing the distance between feet and comparing it to expected values, the system detects slips through mathematical relationships rather than requiring complex direct measurement sensors.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex mechanical slip detection sensors with a computational approach using standard sensor data. Instead of mechanical sensors that directly detect slip, the system uses processors to calculate distances and detect disturbances through mathematical analysis of existing sensor measurements.

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 solution enables legged robots to maintain balance and prevent slips on uneven terrain by dynamically controlling ground reaction forces, ensuring stable operation and adapting to changes in the environment.

Implementation Method 1

determining, by a robot having a set of sensors, based on first data received from the set of sensors, a first distance between a pair of feet of the robot

Methodology Applied

Scientific EffectSensor detection:

Implementation Method 2

controlling the orientation of the force within a friction cone

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11203385B1Slip detection for robotic locomotion

Publication Date: 2021.12.21 BOSTON DYNAMICS INC

AI summary

An example method may include i) determining a first distance between a pair of feet of a robot at a first time, where the pair of feet is in contact with a ground surface; ii) determining a second distance between the pair of feet of the robot at a second time, where the pair of feet remains in contact with the ground surface from the first time to the second time; iii) comparing a difference between the determined first and second distances to a threshold difference; iv) determining that the difference between determined first and second distances exceeds the threshold difference; and v) based on the determination that the difference between the determined first and second distances exceeds the threshold difference, causing the robot to react.