Piezoelectric actuator
AssigneeMcDonnell Douglas Corporation
InventorRobert E. Head
Life of this patent
Estimating the term…
Abstract
A piezoelectric actuator includes a plurality of linearly axially expandable hard piezoelectric rods located between two plates and are distributed about a central twistable core fastened between the plates, with the axis of the rod skew to the axis of the core, resembling a squirrel cage. The actuator produces a twisting movement between the plates, responsive to voltage induced expansion of those piezoelectric rods. Fly by Wire aircraft control is realized with the actuator in various systems providing all electric control of aerodynamic surfaces, including an electronic helicopter swashplate by which the effective pitch of the main rotor blade is controlled.
Claims15
An electromechanical transducer, comprising:
- a cylindrical shaped core, said core being torsionally flexible and longitudinally stiff, said core further defining an axis and having first and second ends;
- first and second end support plates fixed to the respective ends of said core, each said end plate including a peripheral portion extending radially outward beyond the outer surface of said core;
- a plurality of elongate rods of piezoelectric material, said plurality being equal to the integral number N, said rods being positioned about said core in non-intersecting relationship and skew to said core axis, with all of said rods being inclined at the same angle to said first support plate as measured in a counterclockwise direction about said core axis;
- said elongate rods having first and second ends attached respectively to said first and second end plates;
- each said rod being axially expandable to increase in length, responsive to and in dependence upon application of voltage of a first polarity applied between said rod ends, whereby one of said support plates rotationally moves through a circular arc relative to the other of said support plates.
In a helicopter having a fuselage, a driven hub, a rotor, said rotor being periodically rotated by said hub through 360 degrees, said rotor comprising at least a pair of rotor blades, pilot control stick means carried in said fuselage for permitting control of the vertical lift and horizontal direction of travel the helicopter;
- and blade angle control means, responsive to said pilot control stick means, for controlling the pitch of said rotor blades as a function of azimuth during each revolution of said rotor blades;
- the improvement therein wherein said blade angle control means comprises:
- electrically operated rotary actuator means coupled to each said blade for changing the blade pitch, said rotary actuator means being coupled mechanically to said respective blade for circular rotation by said hub jointly with said blade and said rotary actuator means comprising piezoelectric motor means.
In a powered aircraft, an electronic control system for controlling an airfoil of said aircraft for determining direction of the aircraft's travel, said control system including electro-optical means for conveying control signals to an actuator located at said airfoil, said actuator comprising a piezoelectric actuator for producing a torque on said airfoil;
- and wherein said piezoelectric actuator further comprises:
- a cylindrical shaped core, said core being torsionally flexible and longitudinally stiff, said core further defining an axis and having first and second ends;
- first and second end support plates fixed to the respective ends of said core, each said end plate including a peripheral portion extending radially outward beyond the outer surface of said core;
- a plurality of elongate rods of piezoelectric material, said rods being positioned about said core in non-intersecting relationship and skew to said core axis;
- said support plates each having a plurality of N peripheral locations on said peripheral portion, said plurality being equal in number to said plurality of rods, said plurality of peripheral locations being equally angularly spaced from one another about the perimeter of a circle centered on the axis of said support plate;
- said N peripheral locations of said first support plate being axially aligned with said N peripheral locations of said second support plate;
- whereby the first location on said first plate is aligned with the first location on the said second plate, said second location on said first plate is aligned with said second location on said second plate, and so on in order, through said Nth location on said first plate being aligned with said Nth location on said second plate;
- said elongate rods having first and second ends attached respectively to said first and second end plates connected in accordance with the following relationship:
- said first end of said nth rod is connected to said nth location on said first support plate and said second end of said nth rod connected to said (n+p)th location on said second support plate, where (n+p) is less than N, and to the ((n+p)-N)th location on said second support plate, where (n+p) is greater than N;
- where n is the number of said respective rod selected from the series of integers 1, 2, 3, . . . N;
- and
- where p, representing the selected difference in positional spacing between the front and back ends of each respective rod, is an integer;
- each said rod being axially expandable to increase in length, responsive to and in dependence upon application of voltage of a first polarity applied between said rod ends, whereby one of said support plates rotationally moves through a circular arc relative to the other of said support plates.
Dependencies are inferred from the claim text.