Legged Robot Foot Structure with Distributed Force Sensing
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Solution Overview
Problem
Existing legged mobile robots require large and costly force sensors to withstand the load and impact of walking, making it difficult to reduce the size, weight, and cost of the robot's feet while effectively detecting floor reaction force.
Innovation Solution
A foot structure with an instep member, a sole member, an elastic supporting member, and multiple sensor mechanisms that use force sensors with a small withstand load, where the sensor pressing member applies pressure to the force sensor based on the distance between the instep and sole members, allowing for elastic support and distributed force detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor is used to detect floor reaction force, then posture control and stable walking are improved, but the sensor requires large withstand load which increases size, weight, and cost
Solution Approach 1:
The foot is divided into multiple independent sensor mechanisms, each with its own force sensor and sensor pressing member. This segmentation allows each sensor to handle only a portion of the total load, enabling the use of smaller, lighter sensors while still achieving accurate overall force detection through combination of multiple sensor outputs.
Solution Approach 2:
A sensor pressing member acts as an intermediary between the force sensor and the load. This intermediary component transfers and distributes the floor reaction force to the force sensor in a controlled manner, allowing the sensor to measure force without directly bearing the full impact load, thus enabling use of sensors with smaller withstand load capacity.
2Reliability
If a force sensor with large withstand load is used, then the robot can withstand large loads and impacts, but the size and cost of the foot increase
Solution Approach 1:
The foot structure is segmented into multiple sensor mechanisms that share the total load. Each force sensor only needs to withstand a fraction of the total robot weight and impact forces, allowing the use of cheaper, smaller sensors while maintaining overall system reliability and load resistance capability.
Solution Approach 2:
The elastic supporting member and sensor pressing member structure provides beforehand cushioning by elastically deforming under load to protect the force sensor from direct impact. This cushioning mechanism allows the use of sensors with smaller withstand load ratings while still protecting them from damage during walking impacts.
3Measurement precision
If the sensor pressing member has high rigidity, then force transmission is improved, but the sensor becomes vulnerable to damage from impact loads
Solution Approach 1:
The rigidity parameter of the sensor pressing member is optimized to a moderate level - not too high to cause sensor damage from impacts, but not too low to compromise force transmission. This parameter optimization allows the sensor pressing member to effectively transmit floor reaction forces to the force sensor while simultaneously providing protective cushioning against impact loads.
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 configuration enables legged mobile robots to detect floor reaction force effectively without breaking under large loads or impacts, using smaller and less expensive force sensors, while maintaining stability and posture control.
Implementation Method 1
an elastic supporting member that is attached to the sole member and elastically supports the instep member against the load
Implementation Method 2
a sensor pressing member that is an elastic body having rigidity lower than that of the elastic supporting member and has a supporting point deployed on the other of the instep member and the sole member to exert pressing force to the force sensor, according to a change in distance between the instep member and the sole member
Data Source
AI summary
A configuration that exerts floor reaction force directly to a force sensor in a foot of a legged mobile robot requires a sensor having a large withstand load. A foot (10f) includes an upper frame (44) that is connected to a movable leg and receives the load of a robot, a lower frame (48) that is deployed under the upper frame (44) and contacts with a walking surface, a high rigidity spring (50) attached the lower frame (48) and elastically supporting the upper frame (44) against the load, and a plurality of sensor mechanisms that detect floor reaction force at positions different from each other on the lower frame (48). Each of the sensor mechanisms includes a force sensor (62) attached to one of the upper frame (44) and the lower frame (48) and a sensor spring (52) that is an elastic body having rigidity lower than that of the high rigidity spring (50) and has a supporting point deployed on the other one of the upper frame (44) and the lower frame (48) so as to exert pressing force to the force sensor (62) according to a change of the distance between the upper frame (44) and the lower frame (48).