Multi-Height ToF Sensing for Robot Obstacle and Cliff Detection
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Solution Overview
Problem
Current sensors in autonomous robots, such as amplitude-based infrared and ultrasonic sensors, are inconsistent in diverse environments and inadequate for detecting unique navigation situations like overhanging objects, obstacles, and drop-offs, due to limitations in color and reflectivity recognition and data rate.
Innovation Solution
A time of flight (ToF) system with multiple photoemitters and a controller that determines depth maps based on phase differences, allowing for consistent navigation in various environments by identifying overhanging objects, obstacles, and drop-offs, and adjusting the robot's route accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amplitude based infrared sensors are used, then the robot can detect objects in the environment, but the sensor performance becomes inconsistent in direct sunlight and varies with object color and reflectivity
Solution Approach 1:
The patent replaces amplitude-based infrared sensing with time-of-flight (ToF) based optical sensing. ToF sensors measure the time for light to travel to and from objects, providing depth information that is independent of object color, reflectivity, and ambient lighting conditions, thereby resolving the reliability issues with amplitude-based sensors
Solution Approach 2:
The patent changes the measurement parameter from amplitude (signal strength) to time of flight (phase difference). This parameter change makes the sensing system immune to variations in object color, reflectivity, and ambient light intensity, as these factors do not affect the speed of light or the phase measurement
2Reliability
If ultrasonic sensors are used, then the robot can detect objects consistently regardless of color, but the data rate is limited due to the slow speed of sound and forced delay
Solution Approach 1:
The patent replaces ultrasonic acoustic sensing with optical ToF sensing. Light travels significantly faster than sound, enabling much higher data rates and faster update frequencies while maintaining consistent detection performance. The optical system provides real-time depth mapping without the forced delays inherent in ultrasonic round-trip measurements
3Device complexity
If a single height sensor is used, then the device complexity is low, but the robot cannot detect unique navigation situations such as overhanging objects, obstacles, and drop-offs
Solution Approach 1:
The patent segments the sensing function by deploying multiple photoemitters at different heights (first, second, and third heights) with different orientations. Each photoemitter detects specific navigation situations: upper photoemitters detect overhanging objects, middle photoemitters detect obstacles, and lower photoemitters detect drop-offs. This segmentation provides comprehensive navigation awareness while maintaining reasonable system complexity
Solution Approach 2:
The patent adds the vertical dimension to sensing by positioning photoemitters at multiple heights rather than a single plane. This multi-height configuration enables detection of three-dimensional navigation hazards including overhanging objects above the robot, obstacles at robot level, and drop-offs below the robot, significantly enhancing adaptability
4Adaptability or versatility
If multiple photoemitters at different heights are used, then the robot can detect overhanging objects, obstacles, and drop-offs, but the device complexity increases
Solution Approach 1:
The patent merges multiple sensing functions into a unified ToF system with multiple photoemitters sharing common control and processing architecture. The controller coordinates all photoemitters and integrates their depth map data, providing comprehensive navigation detection while avoiding the complexity of multiple independent sensor systems. The merged approach efficiently utilizes shared resources for control, signal processing, and data fusion
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
The ToF system provides finer resolution distance information and is less affected by environmental conditions like color and lighting, enabling more precise and adaptive navigation, reducing the risk of collisions and falls.
Implementation Method 1
determine a depth map for the scene at a height corresponding to the particular photoemitter based on a phase difference between the modulated light signal and the reflected light signal
Implementation Method 2
determine a depth map for the scene at a height corresponding to the particular photoemitter based on a phase difference between the modulated light signal and the reflected light signal
Implementation Method 3
light transmitted by the first photoemitter is reflected off objects at a first height
Data Source
AI summary
A time of flight (ToF) system comprises three photoemitters, a photosensor, and a controller. The first photoemitter transmits light onto objects at first height, the second photoemitter onto objects at second, lower height, and the third photoemitter onto objects at third, lowest height. The controller causes one of the photoemitters to transmit modulated light and the photosensor to receive reflections from the scene. The controller determines a depth map for the corresponding height based on phase differences between the transmitted and reflected light. In some examples, the ToF system is included in an autonomous robot's navigation system. The navigation system identifies overhanging objects at the robot's top from the depth map at the first height, obstacles in the navigation route from the depth map at the second height, and cliffs and drop-offs in the ground surface in front of the robot from the depth map at the third height.