Electromechanical Actuator Force Sensing With Offset Sleeve Mounting
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Solution Overview
Problem
Existing electromechanical actuators face challenges in accurately measuring forces in both axial directions due to varying sensitivity caused by axial preload and cable damage during assembly and operation, leading to reduced reliability and precision.
Innovation Solution
The electromechanical cylinder features a force sensor mounted on an intermediate sleeve radially between the casing and bearings, axially offset from the bearing, which allows for consistent sensitivity in both directions and reduces friction-related measurement errors, with the sensor and cable routed through grooves on the sheath for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the force sensor is mounted on the bearing to measure axial deformation, then the sensor can detect force in both axial directions, but the sensitivity varies depending on axial preload and assembly deformations
Solution Approach 1:
The patent introduces an intermediate mounting structure (the sheath or housing) as a mediator between the bearing and the force sensor. This intermediary element provides a stable reference frame that is not affected by bearing preload or assembly deformations, allowing the sensor to measure axial forces consistently in both directions without the sensitivity variations that would occur if mounted directly on the bearing.
Solution Approach 2:
The patent segments the mounting system into distinct functional components: the bearing assembly (for mechanical support), the sheath (for structural stability), and the force sensor (for measurement). By separating the sensor mounting from the bearing assembly and attaching it to the sheath instead, the system eliminates the coupling between bearing preload and sensor sensitivity, resolving the measurement consistency issue.
2Ease of manufacture
If the electrical connection cable is routed during assembly operations, then the cable connects the force sensor to the processing card, but the cable may be damaged during rotation and operation
Solution Approach 1:
The patent implements a protective routing structure where the electrical connection cable is nested within a protective channel or groove in the sheath. This nested configuration protects the cable from mechanical damage during assembly operations and normal operation, while still allowing the cable to be routed and connected during assembly.
Solution Approach 2:
The sheath acts as an intermediary protective structure that provides a dedicated pathway for the electrical cable. This intermediary element shields the cable from external mechanical stresses and rotations during assembly and operation, maintaining cable integrity while enabling electrical connection.
3Measurement precision
If the force sensor is mounted on the actuating rod, then the sensor measures axial force, but the sensor is subjected to friction and wear during rod movement
Solution Approach 1:
The patent uses the sheath as an intermediary mounting structure that transfers the force measurement function away from the moving actuating rod. The sensor mounted on the stationary sheath measures the axial force through the sheath's deformation, eliminating direct contact and friction between the sensor and the moving rod, thereby improving reliability and longevity.
Solution Approach 2:
The patent extracts the force sensor from the moving actuating rod and relocates it to the stationary sheath. This extraction removes the sensor from the high-friction, high-wear environment of the moving rod while preserving the sensor's ability to measure axial force through the sheath's elastic deformation.
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 enhances measurement precision and reliability by maintaining consistent sensitivity in both axial directions and protecting the electrical connection, reducing the risk of cable damage during assembly and operation.
Implementation Method 1
measure the deformation in the axial direction of this ring during movements of the actuating rod
Data Source
Figure 1
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AI summary
The electromechanical actuator comprises a housing 12, an actuating rod 14 mounted longitudinally relative to the housing, an electric motor 16 with a rotating rotor shaft 26, a mechanism 18 for converting the rotational motion of the electric motor's rotor shaft into a linear translational motion of the actuating rod, and at least one bearing 30 for guiding the rotation of the electric motor's rotor shaft 26 relative to the housing 12 and for supporting the rotor shaft. The actuator further comprises a sleeve 36 fixed to the housing 12 and within which the bearing 30 is mounted, and at least one force sensor 38 mounted on the sleeve, axially offset from the bearing.