Variable-Gain Screw Actuator for Peak Thrust Compensation
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Solution Overview
Problem
Existing actuators with variable mechanical gain face inefficiencies due to peak thrust force variations, requiring high motor torque values and resulting in larger, heavier, and more costly systems with reduced performance.
Innovation Solution
The actuator system optimizes kinematic gain by varying the slope of helical guides to systematically compensate for peak thrust forces, allowing for a constant motor torque and reducing the size and cost of the motor, while improving performance through lighter and smaller designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the motor torque is increased to handle peak thrust force variations, then the actuator can deliver maximum required forces, but the motor size and system weight increase
Solution Approach 1:
The patent applies dynamics by making the mechanical gain variable throughout the actuator's travel range. The helical guide profile is specifically designed to vary the mechanical gain dynamically, providing higher gain during phases requiring force delivery and lower gain during phases requiring speed, thereby eliminating the need for a motor sized for peak forces alone.
Solution Approach 2:
The patent changes the parameter of mechanical gain from constant to variable. By designing the helical guide with a varying profile, the mechanical gain changes continuously throughout the travel, allowing the system to optimize the trade-off between force and speed at different positions, thus reducing peak motor torque requirements.
2Force
If the motor torque is increased to handle peak thrust force variations, then the actuator can deliver maximum required forces, but the system cost increases
Solution Approach 1:
The dynamic variation of mechanical gain through the helical guide profile allows the system to deliver peak forces only when necessary, rather than maintaining constant high torque capability. This reduces the overall system cost by avoiding the need for an oversized motor and associated high-cost components.
3Force
If the motor torque is increased to handle peak thrust force variations, then the actuator can deliver maximum required forces, but the bandwidth and performance decrease
Solution Approach 1:
The variable mechanical gain optimizes the balance between force and speed throughout the travel. During phases requiring force delivery, the gain is higher; during phases requiring speed, the gain is lower. This dynamic optimization maintains high bandwidth and performance while still delivering the required peak forces.
4Device complexity
If a constant mechanical gain is used, then the actuator design is simpler, but the motor must be sized for peak forces resulting in inefficiency
Solution Approach 1:
The patent changes the mechanical gain from constant to variable, which increases design complexity but dramatically improves motor efficiency. The variable gain allows the motor to operate closer to its optimal torque-speed curve throughout the travel, reducing energy waste and improving overall system efficiency.
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 optimization results in a more efficient, lighter, and less costly actuator system with improved bandwidth and energy usage, capable of delivering forces from 0 to maximum values with reduced peak motor torque requirements.
Implementation Method 1
a screw 10 with given pitch P1 adapted to be driven in rotation about an axis in one direction or in another direction by a motor M
Implementation Method 2
Successive values of the slope all along the profile or profiles of one or more respective helical guides are such that the slope systematically compensates at least one peak of the desired thrust force
Data Source
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 or 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 ae 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.