Multi-Motor Linear Actuator With Epicyclic Torque Multiplication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing linear actuators lack enhanced torque transmission and efficient motor engagement mechanisms, particularly in applications requiring multiple motors and precise control, such as aircraft flight surface control systems.
Innovation Solution
A linear actuator design featuring a plurality of motors connected to single or double stage epicyclic gearboxes, with sun and planet wheels drivingly connected by gearwheels, and equipped with rolling element bearings and buffers for enhanced torque multiplication and travel limitation, allowing for increased diameter housing and improved screw extension/retraction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If multiple motors and epicyclic gearboxes are used to increase torque multiplication, then the torque transmission capability is improved, but the device complexity and housing diameter increase
Solution Approach 1:
Multiple epicyclic gearboxes are merged into a single integrated unit where multiple planet wheels share a common sun wheel and are driven by multiple motors. This consolidation achieves torque multiplication from multiple motors while avoiding the need for separate gearbox housings, thereby reducing overall device complexity and housing diameter compared to using individual gearboxes for each motor.
2Force
If multiple motors and epicyclic gearboxes are used to increase torque multiplication, then the torque transmission capability is improved, but the housing diameter increases
Solution Approach 1:
The design nests multiple planet wheels and their associated motors within a single epicyclic gearbox structure. The planet wheels are arranged concentrically around a common sun wheel, and multiple motors are positioned to drive these planet wheels. This nested arrangement allows torque multiplication from multiple motors while containing all components within a compact housing, thereby achieving high torque transmission capability without proportionally increasing housing diameter.
3Reliability
If rolling element bearings are used to journal the screw and sun wheel, then the reliability and efficiency are improved, but the manufacturing precision requirements increase
Solution Approach 1:
Rolling element bearings are introduced as intermediary components between the screw/sun wheel assembly and the gearbox housing. These bearings provide precise radial and axial support, enabling reliable operation and efficient torque transmission. While the bearings themselves require precise manufacturing, they compensate for minor variations in the positioning of the screw and sun wheel, thereby maintaining reliability without requiring extremely high manufacturing precision across all components.
4Reliability
If buffers are provided to limit motor over-run and nut travel, then the reliability is improved, but the device complexity increases
Solution Approach 1:
Buffers are pre-installed within the epicyclic gearbox structure to limit the travel of the nut and prevent motor over-run. These buffers are positioned to engage automatically when the nut reaches its maximum travel position or when the motor attempts to over-run. By incorporating these protective elements into the existing gearbox design, the system achieves improved reliability through automatic protection mechanisms without adding significant external components or increasing overall device complexity.
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
The solution achieves significant torque multiplication and precise control by multiplying the output torque from multiple motors, ensuring reliable operation and reduced motor overload, while maintaining a compact and waterproof design suitable for demanding applications like aircraft systems.
Implementation Method 1
a rolling element bearing is provided for journalling the screw and with it the sun wheel
Implementation Method 2
a reduction gearbox housed in the housing, the motor being connected to a input of the gearbox
Implementation Method 3
sun and planet wheels drivingly connected by gearwheels
Implementation Method 4
an extension screw contained within the telescopic arm and having a driven end journalled at the motor housing end of the outer tube, in driving engagement with the motor and engaging a nut fast at the proximal end of the inner tube, rotation of the screw causing the inner tube to extend or retract with respect to the outer tube
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Referring to the drawings, an electrically driven linear actuator 1 has a motor housing 2 having an end fitting 3 with a thrust eye 4. The housing comprises an end plate 5 carrying the end fitting, a tubular body 6, a mounting plate 7 and a closure member 8. The mounting plate has six recesses 12 for receiving the output ends 15 of six gearboxes 16. Each gearbox has a respective axially-attached electric motor 17, fixed in place via its gearbox. Output shafts 18 from the gearboxes extend through the mounting plate into a recess 19 in the closure member 8. The closure member 8 carries an outer tube 22, within which extends an an inner tube 25 having an end plug 26 with an eye 27. The inner end 28 of the inner tube 25 has an internally threaded collar 29. A threaded shaft 30 extends centrally of the tubes throughout the extent of the outer tube 22. The threaded collar 29 is engaged with the threaded shaft. The innermost end 31 of the shaft receives a splined sun gearwheel 33. These are journalled to the motor housing and the outer tube by a ball bearing 39. The output shafts 18 of the gearboxes each carry planet gearwheels 41, which are thereby arranged around the central axis C. The planet wheels have bosses 42 engaged in a stabiliser ring 43 and they drivingly engage with the sun wheel. Driving of the motors in respective directions drives the threaded shaft 30 and extends or retracts the inner tube by movement of the threaded collar 29 along the thread of the screw 30.