Grounded SEA Actuator With Spring-Encoder Force Sensing
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Solution Overview
Problem
Robotic systems face challenges in measuring forces acting on their components during interactions with the environment, which can lead to unintended movements and potential damage, necessitating a mechanism to determine these forces for compliance and safety.
Innovation Solution
A robotic appendage incorporating a worm drive, actuator, and springs, along with a linear position encoder, to measure forces and control movements, ensuring safety and minimizing damage by determining the position of the actuator along a shaft axis and controlling it based on detected forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robotic systems interact with the environment without force measurement, then operational simplicity is maintained, but safety and compliance are compromised due to unintended movements and potential damage
Solution Approach 1:
The patent introduces a force measurement mechanism as an intermediary between the robotic actuator and the environment. This mechanism includes a movable element that can move in response to forces applied by the actuator, and a sensor that detects the position of this movable element to determine the magnitude and direction of applied forces. This intermediary structure enables safe environmental interaction by providing force feedback without requiring complex control systems.
Solution Approach 2:
The patent replaces complex mechanical force sensing mechanisms with a simpler position detection system. Instead of using traditional force sensors or strain gauges that require complex signal processing, the invention uses a movable element whose position can be directly measured by a linear position encoder or similar sensor. This substitution simplifies the overall system while maintaining reliable force measurement capabilities for safety.
2Reliability
If force measurement mechanisms are added to robotic systems, then safety and compliance are improved, but device complexity increases
Solution Approach 1:
The force measurement mechanism uses a movable element as an intermediary that translates complex force vectors into simple linear position changes. This movable element is coupled to the actuator and moves in response to forces applied during environmental interaction. The linear position encoder then measures this displacement to determine force magnitude and direction, providing compliance capability without complex measurement electronics.
Solution Approach 2:
The movable element serves multiple functions: it acts as a force sensor, a position reference, and a mechanical coupling element between the actuator and the environment. This multi-functionality reduces the need for separate components and simplifies the overall measurement system while maintaining comprehensive force measurement capabilities for safety and compliance.
3Reliability
If bidirectional force measurement is implemented, then comprehensive safety control is achieved, but system complexity and cost increase
Solution Approach 1:
The patent uses a movable element as a mechanical intermediary that naturally provides bidirectional force measurement capability. When forces are applied in either direction during environmental interaction, the movable element shifts position accordingly, and the linear position encoder detects this displacement to determine both magnitude and direction of the applied force. This approach achieves comprehensive safety control without requiring separate sensors for each direction.
Solution Approach 2:
The movable element and position encoder system is self-sufficient for bidirectional force measurement. The mechanical design allows the movable element to respond to forces in any direction, and the position encoder automatically provides signed position readings that indicate both magnitude and direction. This self-service capability eliminates the need for additional bidirectional sensors or complex signal processing circuits.
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 effectively measures and manages forces acting on robotic components, enhancing compliance and safety by allowing precise control of movements, thereby preventing damage to both the robotic system and its environment.
Implementation Method 1
a first spring having a first end and a second end, wherein the second end is fixed, and wherein the first spring is configured to resist movement of the actuator along the shaft axis in a first direction
Implementation Method 2
a second spring having a first end and a second end, wherein the second end is fixed, and wherein the second spring is configured to resist movement of the actuator along the shaft axis in a second direction
Implementation Method 3
a linear position encoder configured to determine a position of the actuator along the shaft axis
Data Source
AI summary
A device is provided. The device includes a worm drive comprising a worm and a worm gear. The device also includes an actuator comprising a motor, a shaft, and the worm, wherein the shaft is configured to rotate about a shaft axis, and the actuator is configured to (i) drive the worm drive, and (ii) move linearly along the shaft axis. The device also includes a first spring and a second spring, wherein the second ends are fixed, and wherein the first and second springs are configured to resist movement of the actuator along the shaft axis in opposite directions as a result of forces transmitted through the worm drive. The device further includes a linear position encoder configured to determine a position of the actuator along the shaft axis.