Tangentially Mounted Canards for Bang-Bang Projectile Control
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Solution Overview
Problem
Small form factor guided projectiles face challenges in implementing advanced control and actuation systems due to bulkiness and high costs, particularly with 3-axis proportional control systems that require multiple motors, gear trains, and micro-machined parts.
Innovation Solution
The use of tangentially mounted control surfaces forming an equilateral triangle around a cylindrical projectile body, with solenoids and return springs for deflection, eliminates the need for opposing fins and minimizes length, allowing for a solenoid and return spring mechanism to control deflection, thereby reducing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 3-axis proportional control actuation system is used, then guidance control capability is improved, but device complexity and size increase due to requiring 3 motors, gear trains, and canard storage
Solution Approach 1:
The control system is segmented into three independent control surfaces arranged tangentially around the projectile body. Each control surface is independently actuated by a simple solenoid mechanism, dividing the complex 3-axis control function into three simple binary control actions. This segmentation maintains guidance capability while dramatically reducing overall system complexity.
Solution Approach 2:
Instead of using conventional proportional control with continuous adjustment mechanisms, the patent inverts the approach by using bang-bang control with discrete on/off states. The control surfaces are actuated by solenoids that provide binary deflection states, eliminating the need for complex proportional control mechanisms while maintaining effective guidance through rapid alternating control actions.
2Reliability
If a 3-axis proportional control actuation system is used, then guidance control capability is improved, but cost increases due to requiring micro machined parts, close tolerances, and high part count
Solution Approach 1:
The patent replaces expensive, precision-machined proportional control mechanisms with inexpensive solenoid actuators and simple control surfaces. The solenoids are compact, low-cost electromagnetic devices that provide sufficient control authority without requiring micro-machined parts or close tolerances. This substitution dramatically reduces manufacturing cost while maintaining guidance functionality.
Solution Approach 2:
The patent extracts and eliminates the complex proportional control mechanisms, gear trains, and precision transmission components from the actuation system. By removing these expensive elements and retaining only the essential control function through simple solenoid-actuated surfaces, the system achieves guidance capability at a fraction of the original cost.
3Device complexity
If control surfaces are tangentially mounted to generate lift force through centerline axis, then opposing fin is eliminated, but control surface configuration complexity increases
Solution Approach 1:
The control surfaces are arranged in an asymmetric tangential configuration around the projectile body, with each surface positioned at a different angular location. This asymmetric arrangement allows the lift forces to be vectored through the centerline axis without requiring symmetric opposing fins, eliminating the need for counter-rolling surfaces while maintaining aerodynamic balance.
Solution Approach 2:
The control surfaces are mounted tangentially to the projectile body rather than conventionally on flat planes. This dimensional change in mounting orientation allows the control surfaces to generate aerodynamic forces that naturally vector through the centerline axis, eliminating the need for opposing fins to counteract rolling moments.
4Stability of the object's composition
If control surfaces are sized to form an equilateral triangle, then force balance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The control surfaces are sized and positioned to form an equilateral triangle configuration, changing the geometric parameters of the control system. This specific geometric arrangement ensures that the forces generated by the three surfaces are balanced and evenly distributed, providing stable control. While this requires precise manufacturing, the tolerance requirements are reduced compared to conventional systems due to the simplicity of the solenoid actuation mechanism.
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 enables efficient bang-bang control with fewer actuators, creating equally spaced resultant force vectors, reducing the projectile's length and internal volume while maintaining effective guidance, thus addressing the challenges of small form factor and cost in guided projectiles.
Implementation Method 1
Thus, a solenoid and a return spring (or other return mechanism) may be used to control deflection of the control surfaces
Implementation Method 2
such that the lift force generated by the canards is generated through a centerline axis of the projectile
Implementation Method 3
a solenoid and a return spring (or other return mechanism) may be used to control deflection of the control surfaces
Data Source
AI summary
Control surfaces secured tangentially to a round projectile, such that the lift force generated by the control surfaces is generated through the projectiles centerline. This eliminates the need for an opposing fin to counter roll moment. Sizing the control surfaces to form an equilateral triangle gives each panel equal span, and enables the force generated by two panels to be equal and opposite to that of the opposing panel. The end effect is that each panel only has two active states (neutral and positive deflection). Thus, a solenoid and a return spring may be used to control the canards. Additionally, the control panels may fold along the surface of the projectile, which frees up internal volume and minimizes the length of the control section.