Cable Actuator Wire-Curvature Sensing for Precise Force Feedback
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Solution Overview
Problem
Existing cable actuators with effort sensors face challenges such as bulkiness, high costs, and reduced sensitivity due to the need for oversized sensors to withstand shocks and vibrations, which limits their diffusion.
Innovation Solution
The cable actuator incorporates a distance sensor arranged to create a change of curvature in the thread at a specific point, improving sensor sensitivity and reducing the maximum racing of the sensor, thereby enhancing the signal/noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force sensors are mounted directly on the actuator output, then force measurement capability is provided, but the sensors become bulky, expensive, and less sensitive due to oversizing requirements
Solution Approach 1:
The patent introduces a wire as an intermediary element that transmits mechanical displacement from the nut to the distance sensor. This mediator allows the sensor to be positioned away from the high-vibration actuator output while still measuring the relevant mechanical movement, thus avoiding the need for oversized ruggedized sensors.
Solution Approach 2:
The patent replaces direct mechanical coupling of force sensors with a wire-based displacement measurement system. Instead of measuring force directly at the output, the system measures the displacement of the wire that is mechanically coupled to the nut, substituting a fragile but precise distance sensor for a robust but bulky force sensor.
2Length of moving object
If sensors are positioned to measure full stroke displacement, then complete travel range is captured, but sensor sensitivity is reduced due to increased maximum travel distance
Solution Approach 1:
The patent changes the parameter of wire routing geometry by introducing a change of curvature at an intermediate point. This geometric modification allows the wire to achieve the necessary displacement measurement over a reduced linear distance, effectively increasing sensor sensitivity without sacrificing measurement range through the use of curved path mechanics.
Solution Approach 2:
The patent utilizes curvature in the wire path by positioning a change of curvature point at a specific distance from the extreme point. This curved routing allows the wire to amplify small nut displacements into larger sensor-measurable movements, improving sensitivity while maintaining full stroke measurement capability.
3Ease of manufacture
If distance sensor is used instead of force sensor, then manufacturing and maintenance costs are reduced, but measurement capability must be maintained
Solution Approach 1:
The patent creates a mechanical copy of the nut's displacement through the wire system. The distance sensor measures the copy (wire displacement) rather than the original (nut position directly), and through the change of curvature mechanism, this copy accurately reflects the nut's angular position and linear displacement with high precision.
Solution Approach 2:
The wire serves as an intermediary that transfers the mechanical movement information from the nut to the distance sensor. This intermediary allows the use of a low-cost distance sensor to accurately measure parameters that would traditionally require expensive force sensors, maintaining measurement precision while reducing manufacturing costs.
Data Source
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AI summary
Cable actuator (100) comprising: - a frame (10); - a screw (2) rotatably mounted on the frame (10) and extending along a first axis (Ox); - a nut (4) cooperating with the screw (2); - means for determining (30) an angular displacement of the nut (4) around the first axis (Ox) relative to the frame (10); and a distance sensor (30) with a winder (33) of wire (32) fixed to the frame (10), one end (32.1) of the wire (32) being connected to the nut (4) at a connection point (4.1), in which the distance sensor (30) is arranged so that the wire (32) undergoes a change of curvature at a first point (34) located in a first plane (P1) orthogonal to the first axis (Ox).