Title of Invention

"AN IMPROVED DEVICE USEFUL FOR HOLDING AND EFFECTING SWINELING MOVEMENT OF A CONTRL SURFACE"

Abstract An improved device useful for holding and effecting swiveling movement of a control surface which comprises a plurality of elements (7) of an alloy having the property of shape memory such as herein defined above, characterized in that the said elements being fixed on a movable control surface (2) and a fixed surface (1) in such a manner so as to form two arrays of the elements (9 and 10) on both the sides of the control surface, the ends of the said elements (7) of the said arrays being connected to a bus bars (6) , the said bus bars (6) being connected to an electrical power source (8) so as to generate heat in the said arrays of elements (7) for effecting the desired movement of a control surface.
Full Text We Claim:
1. An improved device useful for holding and effecting swiveling movement of a
control surface which comprises a plurality of elements (7) of a shape
memory alloy, characterised in that the said elements being fixed on a
movable control surface (2) and a fixed surface (1) in such a manner so as to
form two arrays of the elements (9 and 10) on both the sides of the control
surface, the ends of the said elements (7) of the said arrays being connected
to a bus bar (6), the said bus bar (6) being connected to an electrical power
source (8) so as to generate heat in the said arrays of elements (7) for
effecting the desired movement of a control surface.
2. An improved device as claimed in claim 1 wherein the said shape memory
alloy is selected from Ni-Ti, Cu-Zn .
3. An improved device as claimed in claims 1 or 2 wherein the element used
can be in the form of foils , strips, sheets , wires , bars, strands or
combination thereof.
4. An improved device useful for holding and effecting swiveling movement of a
control surface substantially as herein described with the reference to the
drawings shown in figures 2,3,4 and 5 accompanying this specification.





The present invention relates to an improved device useful for holding and effecting swiveling movement of a control surface.
The device of the present invention is particularly useful for holding and effecting swiveling movement of one object with respect to another fixed object, as in the case of control surface.
The device of the present invention is particularly useful for effecting flight control of aerospace vehicles such as aircraft, space vehicles, remotely piloted vehicles, gliders, helicopters and also for the direction control of water-craft such as boats etc.
The devices useful for holding and effecting the swiveling movement of a control surface presently available are quite varied and include automotive applications, fire protection devices, air conditioner actuators and robotic applications.
The prior art information which is comparable, but work on principles different from our own invention is briefly described in the following paragraphs.
Aircraft control surfaces are the devices which are used to effect the desired control during flight. Rudder, flap, aileron, elevator are the typical control surfaces. Generally these control surfaces are attached to the main structure through hinges and support brackets at discrete points. They are actuated through servo hydraulic actuators as shown
in fig. 1 of the drawing accompanying this specification. In this figure the fixed surface is the fin (l), movable surface is the rudder (2) , the hinges and support brackets (3) are the load transferring members and the actuator is the hydraulic jack (4) .Whenever the pilot decides to take a turn to the left or right he will operate the hydraulic jack (4), which in turn pulls or pushes the link rod (5) , that makes the rudder (2) to rotate either towards left or right, with respect to the fin (1) which is a fixed surface. When this rudder is deflected it is subjected to aerodynamic pressure. The magnitude of the aerodynamic pressure depends upon the magnitude of deflection / rotation. This aerodynamic pressure is transferred to the fin through support brackets (3). Because these support brackets are present at discrete locations, the force concentration takes place both in rudder and fin at these locations.
The drawbacks of the conventional control surface shown in the fig.l are that the loads are transferred from control surface (1) to the adjacent structure (2) at discrete points. As a result, structural masses increase at these connecting points resulting in stress gradients, which limit the life of the structure. The control surface (1) and the adjacent structure (2) are connected by hinges (3) which are movable parts. Because of these movements there is lot of wear and tear of these parts which can adversely affect the effectiveness of the structure. The control surfaces are being actuated by hydraulic jacks which are heavy, expensive and need constant maintenance. There is a possibility of these moving parts
getting jammed. Corrosion problems are generally prevalent in and around the moving parts. The moving parts may get fused and jammed due to lightning strikes. In general the support brackets and actuators constitute about 65% of the weight and more than 70% of the cost of control surface. Because of their susceptibility to failure, it is mandatory to carry out periodic inspection and checking of these actuators, support brackets and hinges. This exercise is expensive and time consuming . Therefore, during this exercise the aircraft is not available for normal use.
In addition, in the existing system the devices for actuation and force transfer are different. For e.g. actuation is done by servo hydraulic actuators and the force transfer between the control surfaces and the main structure is through support brackets and hinges. The lack of redundancy for the actuation and force transfer is another serious limitation of the existing device.
Automatic air direction changing mechanism using Nickel-Titanium for an air conditioner is another example. This is given in the book : Engineering Aspects of Shape Memory Alloys by T.W. Duerig, K.N. Melton, D Stockel, C.M. Wayman, published by Butterworth - Hieneman, pages 324-325. In this mechanism the flap is connected at one side with a Nickel-Titanium spring and at the other side with a biasing metal spring. The other ends of both the springs are connected to two independent fixed supports. When the Nickel-Titanium spring temperature exceeds a certain value the Nickel-Titanium spring contracts to shift the
flaps of the air conditioner unit downwards so that the air is diffused downward. When diffused air temperature decreases the Nickel-Titanium alloy is expanded by the biasing spring and the flaps shift upwards to diffuse the air horizontally. In this device the shape memory alloy is used as an actuator against a biasing load which is a conventional metal spring.
The drawbacks of this device are that the Ni-Ti alloy is used as a spring, the device requires another conventional metallic bias spring not made of shape memory alloy and the device is purely an actuator, it draws energy from the flow stream and does not possess built-in redundancy.
Robotic actuator device is yet another example using Nickel-Titanium . This is given in the book : Engineering Aspects of Shape Memory Alloys by T.W. Duerig, K.N. Melton, D Stockel, C.M. Wayman, published by Butterworth - Hieneman, pages 338-340. In this device the Nickel -Titanium wire is connected to one side of a robot arm, while the other side is connected by a conventional biasing spring. The change in temperature causes the forward and backward rotational movement of the robot arm.
In this device the shape memory alloy is used as an actuator against a biasing load which is a conventional metal spring.
The drawbacks of this device are that it requires another
conventional bias spring not made of shape memory alloy, it functions purely as an actuator and does not possess built-in redundancy.
Considering the requirement of reducing the weight and cost of the structure of aircraft, space vehicles, helicopters etc and in order to make these structures more reliable, we have initiated R&D programme to develop an improved device useful for holding and effecting swiveling movement of a control surface.
The main object of the present invention is to provide an improved device useful for holding and effecting swiveling movement of a control surface which obviates the drawbacks as detailed above.
Another object of the present invention is to achieve both actuation and force transfer combined in a single unit which is distributed throughout the length, of the control surface , which will in turn eliminate the force / stress concentration. Such a device achieves the actuation due to the material property induced through a process rather than a movement generated by a mechanical device, which eliminates periodic maintenance, reduces the cost and weight of the actuating mechanisms and makes the control surfaces more reliable.
Yet another object of the present invention is to provide built-in redundancy for both actuation and force transfer by using Shape Memory Alloy - SMA in the form of an array of

elements a shown in figures 2 & 3. The term shape memory alloys is remered to a class of materials which remember their past. In these shape memory alloys pseudo-plastic strains upto about 8% is fully recoverably. These alloys, produce large recovery forces, if constrained during the phase transformation from martensite to austenite. These recovery forces are effectively used to obtain the desired shape change on the structure. In such a device the failure of one element or a few elements will not result in total failure of the system, because of the large number of elements present in the array. By this way the redundancy id ensured.
The device of this invention is illustrated in fig 2 and 3. In the drawings, fig 2 represents the schematic view of the proposed device and fig 3 represents the typical cross-section of rudder, fin along with SMA elements.
Accordingly, the present invention provides an improved device useful for holding and effecting swiveling movement of a control surface which comprises a plurality of elements (7) of a shape memory alloy characterised in that the said elements being fixed on a movable control surface (2) and a fixed surface (1) in such a manner so as to form two arrays of the elements (9 and 10) on both the sides of the control surface, the ends of the said elements (7) of the said arrays being connected to a bus bar (6), the said bus bar (6) being connected to an electrical power source (8) so as to generate heat in the said arrays of elements (7) for effecting the desired movement of a control surface.
In an embodiment of the present invention the elements having the property of shape memory is selected from Ni-Ti, Cu-Zn etc. Any other alloy having the property of shape memory can also be used for this device.The elements may be in the form of wires / strands / foils / sheets / bars / strips etc.
The improved device, useful for holding and effecting swiveling movement of a control surface, exploits a material property induced through a process to effect the desired shape control. In fig. 2 the working of the device is explained taking the example of the rudder and fin assembly of a typical aircraft. As shown in fig.2 the rudder (2) and fin (3) are connected by a number of parallel elements of the SMA (7) all along the length of the rudder, on both the sides A and B of the rudder.* The array of elements on side A is identical to the array of elements on side B. Before fixing, these elements are strained to such an extent that the strain is completely recoverable. Therefore, initially both the arrays of elements on side A (8) and side B (9) are in the deformed martensitic state i.e. at room temperature. If the array of elements on side A is energized first,using a copper bus (6) by a D.C power supply (5), then the elements reach the austenitic state and the strain is recovered i.e. they contract. The austenitic modulus for the shape memory alloy is much higher than the martensitic modulus of the array of elements on side B, which are forced to elongate the same length as the elements in the array of side A contract. Though the strains in both array of elements are the same, since

the moduli is different it results in a net force, which causes the model, that is the control surface to rotate in a given direction overcoming the external forces. De-energizing the array on side A will bring back the control surface to the neutral position. For the model to rotate in the opposite direction array on side B is energized.
In the device shown in fig. 2 as a typical example, D.C power is fed to a common bus and the voltage is varied using an adjustable power supply. Since the SMA behaviour manifests over a range of temperature, it is possible to obtain the desired angular deflection of the rudder by varying the input voltage to SMA.
The novelty of the present invention lies in achieving both actuation and force transfer combined in a single unit which is distributed throughout the length in the form of array of elements, which will in turn not only eliminate the force / stress concentration but also provide built-in rendundancy for the actuating and force transferring unit. Such a device achieves the actuation due to the material property induced through a process rather than a movement generated by a mechanical device, which eliminates periodic maintenance, reduces the cost and weight of the actuating mechanisms and makes the control surfaces more reliable.
Therefore, the device of the present invention clearly
distinguishes itself from the conventional control surface actuating mechanism using the servo hydraulic actuators, crank rods and other mechanical linkages. All the mechanical moving parts, actuators, crank rods etc. are totally dispensed with and are replaced by a material, that is, SMA which performs all the functions of the existing conventional actuating mechanism with greater reliability.
The following example is given by the way of illustration of the present invention only and therefore should not be construed to limit the scope of the present invention. This example is described with reference to fig. 4 which represents the front view of the model and fig. 5 which represents the top view of the model.
Example 1 :
In this example the movable surface ( 11 ) represents the rudder of an aircraft made of carbon composite material. This movable surface having length 285 mm, width 75 mm and height 50 mm is shown in fig.4. It ( 11 ) is connected to the fixed surface
( 18 ) representing the fin of an aircraft through two arrays of shape memory alloy elements ( 12 & 13 ) made of Ni-Ti . Each array consists of 6 elements ( wires ) of 0.5 mm diameter and length 170 mm. The array on side ( 12 ) is identical to the array on the other side ( 13 ) . The elements in both arrays
( 12 & 13 ) are in the deformed martensitic state i.e., at room temperature before the start of the experiment.
The electrical connections to the arrays are made by the
copper bus bars ( 14 ) . If the array of elements ( 12 ) are energized first, by a power supply ( 17 ), then the elements in this array reach the austenitic state and the strain is recovered. The contraction of the elements creates a rotational movement on the movable surface ( 11 ) . The elements in the array ( 13 ) elongate the same amount as the elements in the array ( 12 ) contract and in the process offer a resistance to the rotation.
However, since the modulus of the array ( 12 ) which is in the autensitic state is higher than the modulus of the array on (13) which is in martensitic state, there is a net force generated which causes the rotation. The net force generated from this model is a minimum of 10 kgs and the total included angle through which the model can swivel is a minimum of 10 degrees. The two extreme positions of the model ( 15 & 16 ) are shown in the fig. 5.
The development of an improved device useful for holding and effecting swiveling movement obviates most of the drawbacks of a control surface, such as aircraft control surfaces mentioned earlier in the prior art such as concentration of loads at connecting points, increase of the structural masses at these connecting points, friction, wear and jamming of the movable parts, high weight and high cost of the actuating mechanisms. The above drawbacks are eliminated by using elements of alloy having the property of shape memory subjected to a process in the form of arrays where -in both actuation and load transfer are combined
in a single unit.
Therefore, the device of the present invention achieves the actuation due to the material property induced through a process rather than a movement generated by a mechanical device, eliminates periodic maintenance, reduces the cost and weight of the actuating mechanisms and makes the control surfaces more reliable.
Therefore, the device of the present invention clearly distinguishes itself from the conventional control surface actuating mechanism using the servo hydraulic actuators, crank rods and other mechanical linkages. All the mechanical moving parts, actuators, crank rods etc. are totally dispensed with and are replaced by a material, that is, SMA which performs all the functions of the existing conventional actuating mechanism with greater reliability, as the use of the SMA in the form of an array provides built-in redundancy for both actuation and force transfer.
Further, subjecting the elements to a process enables it to be used for actuation, load transfer and as a biasing material The main advantages of the present invention are:
1. Eliminates the stress concentrations, resulting in
optimization of design and enhancement of fatigue life of
the structure.
2. The weight penalties due to enhanced thicknesses to
resist the local high stresses are eliminated.
3. The hinge brackets and support brackets which are expensive
and time consuming to fabricate are eliminated.
4. Hydraulic actuators which are expensive are completely
eliminated.
5. Since no moving parts are involved, it requires least
maintenance.
6. The actuation is realized owing to a property induced
through a process, which is the most reliable way of
achieving the actuation without any movement of the
mechanical parts.
7. Ideally suited with the modern trend of using software
driven computer controls.
8. Weight and cost are lower than the existing structure.
9. More reliable because of built-in redundancy in the form
of arrays of Shape Memory Alloy - SMA.

Documents:

655-del-1996-abstract.pdf

655-del-1996-claims.pdf

655-del-1996-complete specification (granted).pdf

655-del-1996-correspondence-others.pdf

655-del-1996-correspondence-po.pdf

655-del-1996-description (complete).pdf

655-del-1996-description (provisional).pdf

655-del-1996-drawings.pdf

655-del-1996-form-1.pdf

655-del-1996-form-2.pdf

655-del-1996-form-3.pdf

655-del-1996-form-4.pdf

655-del-1996-form-6.pdf


Patent Number 194305
Indian Patent Application Number 655/DEL/1996
PG Journal Number 41/2004
Publication Date 09-Oct-2004
Grant Date 03-Feb-2006
Date of Filing 27-Mar-1996
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL REAEARCH
Applicant Address RAFI MARG NEW DELHI,110001,INDIA
Inventors:
# Inventor's Name Inventor's Address
1 GIDNAHALLI NARAYANA REDDY DAYANANDA NATIONAL AEROSPACE LABORATORY BANGLORE
2 BANGALORE RAMASWAMAPPA SOMASHEKAR NATIONAL AEROSPACE LABORATORY BANGLORE
3 MADDELA SUBBA RAO NATIONAL AEROSPACE LABORATORY BANGLORE
4 RISHINARADAMANGALAM VISWANATHAN KRISHNAN A NATIONAL AEROSPACE LABORATORY BANGLORE
PCT International Classification Number B64C 27/41
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA