Variable-Gain Screw Actuator with Helical Torque Clipping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable mechanical gain actuator systems face challenges in optimizing cinematics, leading to high engine torque requirements and inefficient motorization.
Innovation Solution
The actuator system incorporates a helical guidance with a variable slope profile, where the slope is inversely proportional to the intended effort, ensuring constant engine torque and optimized kinematics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional variable mechanical gain actuator is used, then the actuator can provide variable kinematic ratio, but the engine torque requirements become excessively high due to unoptimized kinematics
Solution Approach 1:
The patent applies dynamics by making the mechanical gain variable through the nut's ability to switch between locked and free rotation states. The system dynamically adjusts the kinematic ratio during operation, allowing the mechanical advantage to vary with the operational phase, thereby reducing peak torque requirements while maintaining thrust force capability.
Solution Approach 2:
The patent changes the mechanical parameter of the system by varying the apparent pitch of the screw through the nut's rotational state. When the nut is locked, the full pitch is utilized; when free to rotate, the apparent pitch reduces. This parameter change optimizes the force-torque relationship across different operational phases.
2Force
If the actuator is designed to meet peak thrust force requirements, then the maximum thrust force can be achieved, but the motor and actuator components become oversized and more expensive
Solution Approach 1:
The system uses dynamic variation of mechanical gain to provide high thrust force only when needed, rather than maintaining constant high-force capability. The nut transitions between locked and free rotation states to dynamically adjust the force multiplication, allowing smaller, more cost-effective motor and actuator components.
Solution Approach 2:
The apparent pitch parameter is varied to match the operational requirements. During phases requiring high thrust, the system configuration provides maximum mechanical advantage; during other phases, the apparent pitch is reduced. This prevents oversizing of components while ensuring peak force capability when required.
3Reliability
If the nut is locked in rotation during the first phase, then the screw provides reliable kinematic connection, but the translational speed of the nut is limited by the screw pitch
Solution Approach 1:
The system dynamically switches the nut's rotational constraint between locked and free states. During the first phase, the nut is locked for reliable kinematic connection; during the second phase, the nut is freed to rotate, changing the speed-transmission mechanism from direct screw-driven translation to a combination of screw rotation and nut rotation that achieves higher speeds.
Solution Approach 2:
The system employs periodic switching between two operational modes: a first phase with locked nut rotation for reliable connection, and a second phase with free nut rotation for increased speed. This periodic action between contrasting states allows the system to achieve both reliability and speed at different times in the operational cycle.
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 reduces the maximum engine torque required, resulting in a lighter, smaller, and cheaper actuator system with improved performance and bandwidth.
Implementation Method 1
a screw 10 in one step P1 given suitable for being driven in rotation around an axis, in one direction or in an opposite direction
Implementation Method 2
The ball screw 10 must have very good reverse efficiency
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An actuator for providing a thrust force over a determined travel, comprising a nut, a screw, a sleeve configured to surround the screw in an axial direction (X-X) of the screw, a plurality of rollers, the nut being configured to cooperate with the screw, the nut being secured to the rollers, which are free to rotate, the rollers being configured to each move in particular in the one of at least one helical guide of the sleeve, the screw being configured in order, when it is turned, to operate the actuator, to rotate the nut when it bears via the rollers on a profile of the helical guide and to thus advance in the axial direction (X-X) of the screw at greater or lesser speed along a slope of the profile of the helical guide. The actuator further comprises a motor configured to turn the screw. Successive values of the slope all along the profile or profiles of respectively the one or more helical guides are adapted to ensure that the slope systematically compensates for at least one peak of the desired thrust force in order to carry out clipping of the maximum values of the thrust force such that the motor, the screw and the nut are dimensioned to a motor torque value corresponding to the value of the thrust force after clipping.