US2859315A - Rheostat - Google Patents

Description

Nov. 4, 1958 w. A. JOERNDT 2,359,315

RHEOSTAT Original Filed April 8, 1954 I 2 Sheets-Sheet 1 ROLL ERROR SIGNAL, APP RATU Q s I /3 INPUT ERROR SIGNAL /5 20 I /0 Y FIG. 4. 4?

mun 'ro HORILFIN SERVO RIGHT LEFT (OUTPUT) (INPUT) ur-oovm (mmm INVENTORS FIG. W/LBUR A. JOERNDT BY Q BMWBRNEYS f d States Patent RHEOSTAT Wilbur A. Joerndt, Albuquerque, N. Mex., assignor to the United States of America as represented by the Secretary of the Navy Original application April 8, 1954, Serial No. 421,991. and this application July 17, 1957, Serial No.

1 Claim. (Cl. 201-55) This invention relates in general to roll compensation systems for guided missiles, and in particular it relates to apparatus for generating roll compensated guide beam err-or signals when a guided missile is rolling.

This application is a division of copending application Serial No. 421,991, filed on April 8, 1954, for Roll Compensator for Guided Missiles, by applicant.

It is one of the objects of this invention to provide apparatus for modifying target misalignment signals of a guided missile, and for adjusting the position of the fins to correct for guide beam misalignment to roll compensate the missile.

Another object of the invention is to provide apparatus for applying guide beam error signals modified to compensate for roll of a missile to the servo-stabilizing system of a guided missile in order to roll compensate the missile.

Still another object of the inveniton is to provide apparatus for determining and applying guide beam error signals modified to roll compensate a missile, which is compact, easy to manufacture and install in the missile, and eflicient and reliable in operation.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

Fig. 1 is a schematic of a guided missile, showing apparatus for generating roll compensated guide beam error signals;

Fig. 2 is a perspective view of the apparatus for determining roll compensated guide beam error signals, embodying features of the invention;

Fig. 3 is a perspective view, partly schematic, of the apparatus shown in Fig. 2, with the casing removed, and showing in detail some of the features of the invention;

Fig. 4 is a schematic of the circuitry for the apparatus of Figs. 2 and 3;

Fig. 5 is a cross section along line S5 of Fig. 2; and

Fig 6 is a schematic illustrating the position of the missile in a guidance beam of electromagnetic energy.

I In accordance with the invention, apparatus is provided for determining and applying guide beam error signals compensated for roll movements of a guided missile to the servo-stabilizing system thereof. This apparatus comprises means for producing a resistance path variation responsive to roll movements of the missile. These means comprise a plane resistance surface which is immovable relative to the missile, with one or more pairs of contacts bearing on the resistance surface and being rotatable relative to the resistance surface as by a free gyroscope stabilizing the contacts against roll. Any shifting of the surface relative to the contacts produces a change in the path of current flow in the surface. The contacts pick up parts of. the voltage drops due to the guide beam error signals. These modified error signals are fed to amplifying means where they are amplified and are used to con trol a hydraulic servo system. The hydraulic servo sys- A 2,859,315 Patented Nov. 4, 1958 ice tern, in turn, is utilized to adjust the position of the missile fins to return the missile to the guide beam.

Referring now to Fig. 1 of the drawings, there is shown an aerial missile 10 of either the rocket or ramjet type, which has a plurality of fixed wings 12 for flying the missile and a plurality of fins 14 for steering the missile while it is in aerial flight along a trajectory.

As illustrated in Fig. 6, a standard radar transmitter 11, located at a remote point in space and having a pulse repetition rate frequency modulated in synchronism with its scan rate, is utilized to project a guidance beam 8 of electromagnetic energy to guide the missile 10.

When the missile 10 is not travelling centrally along the guide beam, input error signals are picked up by an antenna 13 mounted on one of the fins 14 of the missile 10 and are fed to suitable conventional means, such as a guide beam error measuring device 17, and thence to a guide beam error signal modifying apparatus 20. A free gyroscope 18 is mechanically connected to a shaft 28 (Fig. 2) in such a way that when rolling of the missileoccurs, this shaft will be stabilized against turning by the gyroscope 18. Apparatus 20 modifies the up-down misalignment signal, as well as the right-left misalignment signal of the missile 10 responsive to roll. These modified guide beam error signals are then fed to a suitable amplifying means 22, and are used to control a hydraulic servo system 24. The latter, in turn, controls the position of the missile fins 14 to correct the heading of the missile 10.

Referring now in particular to Fig. 2 there is shown the guide beam error signal modifying apparatus 20 in perspective. This apparatus can conveniently be enclosed in a casing 26 of suitable insulating material. The casing 26 supports the shaft 28 which is mechanically connected to the gyroscope 18. A suitable bearing 30 is provided at one end of the casing 26 to provide support for the shaft 28. This bearing also serves as a cover or closure for one end of the casing 26.

Shaft 28, as illustrated in Fig. 3, carries a cylinder 32, which is likewise made of a suitable insulating material, and upon which are located four (4) slip rings 34, 36, 38, and 40. Upon the slip rings rest the ends of four (4) conductors 42, 44, 46, and 48, which are made of relatively fine wire and which are arranged to bear resiliently on the slip rings 34, 36, 38, and 40, respectively.

Slip rings 34, 36, 38, and 40, in turn, are connected to contacts 50, 52, 54, and 56, by means of leads 58, 60, 62, and 64, as shown by dotted lines. Contacts 50, 52, 54, and 56 may be of any desired shape. However, they are shown here as metal spheres which are carried in corresponding apertures 65, 66, 68, and 70, in an insulating disk 72. Insulating disk 72 is secured to the cylinder 32 so as to rotate therewith when the latter rotates with shaft 28.

It is to be understood, furthermore, that while two types of contact members are shown, namely, the resilient type of contacts for the conductors 42, 44, 46, and 48, which engage the slip rings 34, 36, 38, and 40, respectively, and the metal spherical type of contacts 50, 52, 54, and 56, the springs and the spheres may all be of a single type. Regardless of the type of contacts associated with the disk 72, each such contact will bear resiliently against the adjacent surface of a stationary disk 74.

The stationary disk 74, which is mounted in the enlarged portion of the casing 26, has a coating of highresistance material on the face 75 thereof adjacent disk 72. For example, this material can comprise carbon or anequivalent thereof. However, a suitable coating would be one such that a one (l)-inch square made thereof would have a resistance of the order of 400 ohms between opposite sides. This coating, in turn, may be carried or placed on any suitable insulating material, on the disk 74.

Electrical contact is made with this coating by means of four (4) metal terminal members 78, 80, 82, and 84, such as illustrated in Fig. 4. These metal contact members are arcuate, and each is equivalent in length to 45. These contact members 78, 80, 82, and 84, are arranged symmetrically around the disk 74. Conductors 86, 88, 90, and 92 connect to the terminal contacts 78, 80, 82, and 84, respectively, with opposite ones, for example, 86 and 90, and 88 and 92, constituting paired circuit conductors for receiving the respective misalignment signals from the error signal guide beam apparatus 17, that is, the up-down and right-left misalignment signals due to errors in direction of travel of the missile 10.

An electrical field is set up in the plane of the disk 74, the value of which at any point is the vector sum of the electrical fields due to the misalignment signals applied at the pairs of terminals 78, 82, and 80, 84. Assuming, for example, the application of instantaneously equal misalignment signals at contact terminals 78, 82, and 8t), 84, the field vector in the neighborhood of the central region of the disk 74, upon which the contacts 50, 52, 54, and 56 bear, would bisect the angle between the component fields. If it is assumed that the electrical field is uniform over the central region bounded by the contacts 50, 52, 54, and 56, then the potential difference between opposite contacts 50 and 54, or 52 and 56 is given by the projection of the resultant vector upon the line joining such pairs of contacts multiplied by their distance apart.

Let F -i-F be the component fields in the disk 74 due to the separate misalignment signals, r the distance of the contacts 58, 52, 54, and 56 from the axis of rotation of the shaft 28, and 0 the angle between the line joining opposite contacts 52, 56 or 50, 54, and the y and x axes of the disk 74.

Then the resultant field vector F :\/F z+ 1 making an angle as with the y axis such that If the applied voltage varies, the angle varies according to the foregoing relationship. The voltage developed between a pair of contacts, such as 50 and 54, will then be given by the expression and the voltage developed between contacts will be given by the expression It will be seen that if 0 is also the angle of roll of the missile 10, and the voltages or potentials V or V are now applied to the appropriate fin servo mechanism, such as the hydraulic servo mechanism 24, modification of the original error signals to take care of roll of the missile can be achieved.

In accordance with the principles of vector combination, the two signals, which are at right angles to one another for the system indicated in Fig. 4, pass through the apparatus without mutual interference. These two signals may then be conveyed simultaneously to the amplifier arrangement 22, where they are amplified, and to the hydraulic servo stabilizing system 24.

The operation of the invention will now be explained. After the aerial missile 18 has been launched by suitable launching means (not shown) and is in flight along its trajectory, it is assumed that the missile is subjected to rolling movements. The casing 26, of the guide beam error signal modifying apparatus, is stationary with respect to the missile 10. However, means such as the free 52 and 56 gyroscope 18, is connected to the shaft 28 in such a manner that, when rolling of the missile occurs, this shaft 28 will be stabilized against roll by the gyroscope 18.

If now the up-down misalignment signal is applied to the terminals 86 and 90, and the right-left misalignment signal to the terminals 88 and 92, then currents will flow in the resistance surface of the disk 74 between the respective terminals 78 and 82, or 80 and 84, and of proper values to represent the guide signal errors existing at the moment. 'The contacts 50, 52, 54, and 56, which bear on the resistance surface of disk 74, will thus pick up proportional parts of the respective voltage drops produced by the guide signal error currents. For example, if constant D. C. voltages are maintained across terminals 86 and 90, upon rotation the contacts 42 and 46 will derive a simple harmonic voltage, that is, a sine wave voltage, therefrom. Likewise, if constant direct current voltages are maintained across terminals 88 and 92, upon rotationof shaft 28 the contacts 44 and 48 will derive a simple harmonic voltage, that is, a sine wave voltage, therefrom. These voltages are then fed simultaneously to the amplifier 22 and to the hydraulic servo system 24 and the latter is used to control the fins 14 of the missile 10 through suitable mechanical linkages, such as 15 and 16.

As previouslystated, either spheres or springs may serve as the actual contact elements. However, it has been found that it requires more torque to operate the roll error signal apparatus 29 with ball contacts than when thin wires are used. Therefore, it is preferred to use the thin Wires, since this imposes less load on the gyroscope 18, and, consequently, does not cause serious precessional movements of the gyroscope.

It is also to be pointed out that instead of having the contact rings 34, 36, 38, and 48 rotate, and the springs of contacts 42, 44, 46, and 48 remain stationary, these elements may be interchanged, so that the cylinder 32 will carry wire springs and the slip rings 34, 36, 38, and 48 will then be mounted in the stationary casing 26. This form may require more torque to operate it, inasmuch as the contacts will then be more remote from the axis of the shaft 28.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

In combination, a shaft, a set of four mutually insulated slip rings mounted subsequently along said shaft and moveable therewith, at least one contact bearing on each slip ring, a like number of contacts symmetrically spaced on and carried by said shaft and diametrically opposite contacts being connected to alternate slip rings, a stationary disc having a substantially fiat face at right angles to said shaft, said fiat face having a high resistance carbon material coated thereon, said last mentioned contacts bearing against the resistance face of said disc, and arcuate terminals equal in number to said slip rings, said terminals being symmetrically spaced around said stationary disc and electrically connected in diametrically opposite pairs to said resistance material, so that one terminal, one shaft contact, one slip ring and one slip ring contact comprise an independent circuit and any movement of said shaft will introduce an error into each of said circuits.

References (Jited in the file of this patent UNITED STATES PATENTS 2,457,178 Richardson et al Dec. 28, 1948 2,531,150 Murdick Nov. 21, 1950 2,549,389 Rosenberg Apr. 17, 1951 2,681,967 Harrison et al June 22, 1954

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