US1851596A - Method of and apparatus for compensating for hysteresis - Google Patents

Description

March 29, 1932. v A. s. REYNOLDS v 5 I IETHOD OF AND APPARATUS FOR COMPENSATING FOR HYSTERESIS Filed Dec 5, 1922 2 Sheets-Sheet l INST READ,

INVENTOR Match 1932- A. ,s. REYNQLDS 1,

IETHQD OF AND APPARATUS FOR COMPENSATING FOR HYSTERESIS Filed Dec..5, 1922 2 Sheets-Sheet 2 Patented Mar. 29, 1932 UNITED- STATES PATENT OFFICE" ANITA S. REYNOLDS, OF GREENWICH, CONNECTICUT METHOD OF AND APPARATUS FOR COMPENSATING FOR HYSTERESIS I 7 Application filed December 5, 1922. Serial No. 605,128.

This invention relates to means to compensate for the hysteresis or lag in the translation or transfer of a stress into the resulting strain. More particularly it relates to means for obtaining a condition of an hysteresis by addiing, in the case of an increasing stress, an 1ncrement approximately equivalent to the resulting lag, or in the case of a decreasing stress, an approximately equivalent decre- 10 ment.

Some of the objects of the invention are to provide forcorrecting the readings of instruments and the like, wherein the hysteresis or frictional losses cause the readings to lag behind the forces being measured; or for the compensation of control mechanism whichv may be similarly affected due to frictional losses;'or to anticipate or retard the result of a motion or movement in a mechanism or device of any kind.

One feature of the invention is the means which it provides for automatically varying the magnitude of the correction factor where the amount of lag may'not be constant at different periods of a complete cycle, or at different positions of operation. For example in some forms of indicating devices it may be found that the lag at low readings is different than at higher readings or different at average readings than at extreme readin Under such conditions it is a part of this invention to automatically adjust the compensating increment or decrement, as the case may be, to the various parts of the scale or periods of operation. This same adjustment will apply also to devices having for their object automatic control functions.

Another object is to provide a dragging or retarding action which will function smoothly and efficiently.

Another object is to make the various possible forms of this invention adjustable as-to limits of correction and also as to periods of application of the variable adjustment.

Another object is to apply the method of operation to linear movements and to rotary and other movements. 4

Another object is to provide a smooth friction which can be very light for the small and delicate movements and also a heavier friction or retardation effect for use where more power is available and required.

Another object is the provision of means to make the change quickly from a condition resulting from an increasing stress to one due to a decreasing stress. In this case the frictional effect also changes but in reverse direction to the major movement and may be either linear or rotary, depending upon the character of the major movement.

Another object. is the provision of means for making the compensation effective only in one direction, e. g. in the case of increaslng stresses only or in the case of decreasing. stresses only. Under these conditions the effect of the friction surface may be smoothed out or removed at certain periods.

Another object is to provide means whereby the fluttering or oscillating action of a mechanism in coming to rest by a damping action is decreased. It is also a purpose of the invention to decrease backlash.

Another object is to provide means for anticipating a movement or event.

lVhile this invention has been illustrated as applied particularly to a device for indieating the speed of an air ship through the air, or the speed of the wind, it is not my intention to limit it to such a device, for it is believed that the principle involved will be applicable to, and useful for, avariety of purposes. The invention may be applied to weighing, measuring, indicating and recording instruments, involving forces, pressures, movements, volume, speed, or, in fact, to any instrument where a change in-condition being measured, or detected, is followed by a corresponding change in reading with a slight difference between the cause and effect due to the hysteresis loss of the mechanism.

It can also be used toadvantage in various forms of control mechanism, where a change in weight, force, pressure, movement, volume or other condition is followed by an equivalent change in some associated mechanism, and where there is a lag involved in the translation of the efiect of the weight, force. etc. to the associated mechanism.

These and further objects will more fully appear in the following specification and accompanying drawings, considered together or separately.

In the accompanying drawings which illustrate one embodiment of the invention, like parts in all of the several figures, are designated by corresponding characters of reference, and in which Fig. 1 is a plan view of an air speed measuring device, showing one form of the present invention.

Fig. 2 is a side elevation of the same.

Fig. 3 is a side elevation of the associated indicator.

Fig. 4 is a plan view of the latter.

Fig. 5 is a section on the line 22 of Fig. 2. I

Fig. 6 is a section on the line 11 of Fig. 2.

Fig. 7 shows a set of three curves showing: (A) The readings obtained with a device similar to Figures 1 and 2, on a gradually increasing wind pressure without present invention, (B) curve of decreasing wind pressure, and (C) an approximately true curve.

obtained with present invention.

Fig. 8 is a detail view of the compensator tilted in the position taken as the speed increases.

Fig. 9 is a detail View of the compensator tilted in the position taken as the speed decreases.

Fig. 10 is an alternative form of spring operating on a roughened surface.

Fig. 11 is an enlarged view of the spring arrangement shown in Figures 2 and 5.

Fig. 12 is a plan view of a form of the inventionapplied to a rotating movement such as a tachometer with the needle shown in its decreasing position.

Fig. 13 is a similarfview with the needle shown in its increasing position.

Fig. 14 is a side elevation of Fig. 12.

Fig. 15 is a plan view of a simpler form of a type adapted for very light movements.

Fig. 16 is a side elevation of Fig. 15.

Referring to the drawings, in which Figures 1, 2, 3 and 4, illustrate an air speed indicator, to which the present invention has been attached: 1 is a frame mounted in such manner with respect to the wind that the vane 2 is held normal tothe wind.

Mounted in bearings in the frame is a shaft 3 having a screw thread portion 4 with which a nut 5 co-operates. On the nut 5 is pivotally mounted a yoke or lever arm 6, having projections 7 and 8 at its lower end which slidably straddle a base plate 9, forming a .portion of the frame, thus preventing the nut 5 from turning when shaft 3 with threaded portion 4 is turned. This permits nut 5, however, to travel forward or back as the shaft 3 is rotated in one direction or the other.

Losely mounted on the shaft 3 are two spaced oppositely-disposed bevel gears 10 and 11 each of which meshes with a pinion 12 which is rotatably mounted on the frame 1.

The gear 11 is driven in the clockwise direcgear 11 carries a similar lug 20. The clutch.

yoke 16 is adapted to be moved into the path of the lug 19 or the lug 20, as the yoke may be swung on its pivot, thus causing shaft 3 to be rotated in one direction or the other, as the case ma be.

The ring 18 is mounted upon the ends of two bars 23 and 24 which are pivotally mounted to the lower ends of yokes 25 and 26.

. Yokes 25 and 26 are pivotally mounted on posts 27 and 28 which are supported on the frame plate 9. Two bars 29 and 30 are pivotally mounted on the upper ends of the yokes 25 and 26, and above the pivot thereof.

Attached to the bars 29 and 30 are two supports 31 and 32 which mount the surface or vane 2 which is exposed to wind pressure.

The bars 29 and 30 are secured together by,

the means of a cross member 33 to which is secured oneend of a compression spring 34, the opposite end of which is attached to the nut 5.

Attached to the upper end of the yoke 6 is a section of piano wire 35 which is led through a sheath 36 and adapted to be attached to a flexible endless wire 38 which passes over idle pulley 39, and a pulley 40 attached to an indicator wheel 41, being an chored to the latter. By this means the movements of the nut 5 and lever 6 may be read at a distance.

As the nut 5 travels back and forth on the worm 4, springs 42 will be moved over the roughened surface of the frame plate 9. The springs 42 are mounted on the lower section of lever 6 below its pivotal mounting 44, therefore they exert a retarding action on the low-er end of the lever 6, causing the upper end, and with it the wire 35, to take an advanced position in the direction the nut is moving. The amplitude ofpossible'movement for the lever 6 is limited by a lever 45 which, is pivotally mounted on the lower end of the nut. One end of the lever 45 is forked and straddles the lever 6. The other end of the lever 45 passes under a cam 47 being held against it by a spring 48.

The retarding spring or springs 42 are shown on an enlarged scale in Figure 11. These springs rest on a roughened surface of the base plate 9 in such manner that when the nut 5 is moved, they may pass over the plate with a caterpillar effect giving a smooth and even retardation in either direction;

vIn the embodiment of the invention illustrated, the lower end of the lever 6 carries three wi-re springs 42 of approximately spadeshape. The wires are perferably staggered whereby the points of all of them will not at lever 45 is against the high part of the cam 47, thus forcing the forked end of the lever 45 downwards and permitting only a small movement of the lever 6. In this view also the nut 5 is assumed to be advancing to higher readings, so the upper end of the lever 6' is shown advanced in the same direction i. e. towards the vane 2.

In Figure 9 the reverse conditions are assumed, i. e. the nut 5 is in a position nearer the vane 2, but is shown as moving towards the gears 10 and 11 with the .upper end of lever 6 advanced in the direction in which the nut 5 is moving, or has last. moved and the lever 45 is against the low part of the cam 47, thus raising the forked end of the lever 45 so that the lever 6 has a greater amplitude of movement.

It will, therefore, be seen that by properly shaping and positioning the cam 47 the forked ends of lever 45 can control the amount of increment and decrement added to the lever 6 at any part of its travel to suit the amount of lag that may be encountered.

As shown in Fig. 10 the springs 42 have been replaced by a flat spring or springs 49, as an alternative form of retardation for the lower end of 6. v

The operation of the apparatus as above describedis as follows: 4

Holding or mounting the device with the free face of the vane 2 normal, or broadside, to the wind, and starting the motor 14 the gears 10 and 11 will revolve in opposite directions, but being loose on shaft 4 they will run idle. The pressure of the wind on the Vane 2 will force the latter back, moving upper frame bars 29 and 30 towards the gears. This action is transmitted through the yokes 25 and 26, to the bars 23 and 24, moving them in the opposite direction, together with the clutch ring 18 which, in turn, tilts the clutch yoke 16 into engagement with the lug 19,011

the gear 10. This causes the shaft Sto rotate in a direction to advance the nut 5 and compress the spring 34 which, when sufficiently compressed, balances the pressure of the wind on the vane. lVhen a balance is reached the frame supports 31 and 32 carrying the vane As the nut 5 moves forward the springs 42 dragging on the roughened surface of the plate 9 will hold back the lower end of the lever 6, so that its upper end is advanced slightly until stopped by the fork 45. This extra movement of the lever 6 represents the increment necessary to be added to the movement of the nut 5 to compensate for the hysteresis of the mechanism.

A decreasing wind operates in the reverse way, allowing the spring 34 to force the vane forward and moving lower bars 23 and 24 backward, causing the ring 18 to move the clutch yoke 16 into engagement with the lug thereverse direction and moving the nut 5 back towards the gears, thus decreasing th pressure of the spring 34. When a balance is again reached the clutch yoke 18 is thrown out of engagement thus stopping the rotation of the shaft 3.

When the nut 5 moves back towards the gears, the springs42 drag in the opposite Way, forcing the upper end of the lever 6 to assume an advanced position in the direction that the nut 5 is moving, thus compensating for the decrement.

Considering a concrete example of a case, in point, the air speed indicator illustrated in Figures 1, 2, 3 and 4 without the addition of the present invention, starting with zero air speed and increasing by steps to a maximum, will be found to be slightly less at-each step than the true air speed, making curve A in Figure 7. If now, the speed is gradually decreased in steps to zero again, it will be found that each reading will be slightly more than the true air speed, making a curve similar to B in Figure 7. With the addition of this invention, however, an increase in speed will read slightly in advance of a similar point on curve A and correspondingly a decrease in speed will read slightly less than v a similar point on curve B, thus approximatingcurve C, which will more nearly approach the true reading desired. By proper adjustment of'the compensating parts to the particular instrument or device involved, it is possible by this means to approximate a set of readings so nearly true that they may be so considered for all practical purposes.

Figures 12, 13, and 14 show a form of the invention as applied to an instrument having a rotating spindle carrying a pointer such as' a revolution counter or a tachometer. In this design a fixed internal gear 50 is provided. A spindle 51 rotating in the center of the gear is provided with a plate 52 which carries a pinion 53, meshing, or engaging with the internal gear 50. The gearing illustrated is friction gearing but any other form may be employed. The shaft 54 carrying the spur gear also mounts a friction wheel 55 which 51, 54;, in changing from the position shown in Fig. 12 to that shown in Fig. 13, because it yields by bending when the direction of its motion is reversed. The pointer 57 is plvoted loosely on the spindle 51, and as the plate 52 is fixed to the spindle 51, the pointer 57 rotates slightly ahead of the plate 52, because the friction wheel 55 rotates in the opposite direction, causing a quick change in direction of the pointer movement when the spindle changes direction.

Figures 15 and 16 show a simpler form of this construction for light movements. In this design a fixed friction cam 58 of a shape to properly correct at any position, is mounted above a spindle 59. The latter carries a plate 60 which mounts a pointer 62 off center from the spindle at 61. The pointer 62 is slidably mounted on the plate 60 and is held in contact with the cam 58 by a small spring 63. The spindle end of the pointer 62 is split to straddle the cam, and adjustable stops 64 and 65 are provided to limit the movements of the pointer. The automatic adjustment feature for variable corrections is obtained by the cam shortening or lengthening the lever arm of the pointer, thus varying the movement obtained at the scale end. This same in and out movement can be applied to the device shown in Figure 12, or movable stops operated by a cam as shown in Figs. 1 and 2 may be employed.

In accordance with the provisions of the patent statutes the principle of the invention has been described together with the apparatus which is now considered to represent the 'best embodiment theredf, but it is desired to have it understood that the apparatus shown is merely illustrative, and that the invention may be carried out in other ways.

The invention having been described, what is claimed as new and desired to be secured by Letters Patent, is: i

1. Thecombination with a movable member, of means for transferring the movement of said member, to a second member, means for compensating for hysteresis in the movement of said first member by the addition of an increment in the transfer to said second member and means controlled in the movement of; said member for controlling said.

means. 1 2. Ina measuring apparatus, a movable member subject to a varying force, an indicator for measuring said force at any instant, means fortransferring the movement of said member to said indicator, means for automatically compensating in said transfer for the hysteresis in the movement of said men1-' ber whereby said indicator produces a substantially accurate measurement of said force and means controlled in the movement of said first means for controlling said last means.

3. In an apparatus for indicating the magnitude of a stress, means for receiving the stress, means for indicating the magnitude of the stress, means for including with the indication a component representing the lag of said apparatus, and means for, automatically varying the value of said component when said lag is not uniform.

4." In a device of the character described, a movably mounted member adapted to be subjected to changes of stress, and an element, I one end of said member slidably engaging with said element thereby retarding the movement of that end thereof and accelerating the opposite end thereof.

, 5. In a device of the character described, a movably mounted member adapted to be subjectedto changes of stress, an element, one end of said member frictionally engaging with said element thereby retarding the movement of that end thereof and accelerating the opposite end thereof, and means for varying the amount that said movementof said member is retarded.

6. In a device of the character described, a movably mounted member adapted to be sub- -jected to changes of stress, a serrated element,

one end of said member frictionally engaging with said element thereby retarding the movement of that end thereof and accelerating the opposite end thereof.

7. In a device of the character described,,a movably mounted member adapted to be subjected to changes of stress, an element, spring means carried by one end of said member and slidably engaging with said element thereby retarding the movement of thatend of said member and accelerating the opposite end of said member.

'28. In a device of the character described, no a body adapted to be moved linearly'in response to a stress applied thereto, a member pivotally mounted on said body, and an element, one end of said member engaging with said element whereby in the linear movement of said body and member that end of said member is retarded with a consequent acceleration of the other end of said member.

9. In a device of the character described, a body adapted to be moved linearly in response to a stress applied thereto, a member pivotally mounted on said body, an element, and a plurality of spring members arranged in staggered relation attached to one end of said member and engaging with said element whereby in the linear movement of said body and member that end of said member is retarded with a consequent acceleration of the" other end of said member.

10. In a measuring device, a body adapted 130 to be moved in response to a stress applied thereto, a member pivotally mounted on said body, an element, one end of said member engaging with said element whereby in the movement of said body and member that end of said member is retarded with a consequent acceleration of the other end of said member, and indicating means controlled by said member.

11. In an air speed meter, a movable vane subject to varying air pressure, an indicator, a linearly movable body, means for moving said body under control of said vane, a member pivotally supported on said body for moving said indicator, and retarding means co-operating with said member whereby an increment is added to the movement of said indicator when said vane is subjected to an increasing pressure and a decrement is added when said vane is subjected to a decreasing pressure. p

12. In an airspeed meter, a movable vane subject to varying air pressure, a spring for opposing movement of said vane, an indicator, a linearly movable body, means for moving said body under control of said vane, a member pivotally supported of said body for moving said indicator, retarding means co-operating with said member whereby an increment is added to the movement of said indicator when said vane is subjected to an increasing pressure and a decrement is added when said vane is subjected to a decreasing pressure, and means for automatically varying said retarding effect in proportion to the compression of said spring, whereby said indicator substantially registers the true pressure on said vane.

13. The combination with a movable member of a second movable member, and coupling means subject to hysteresis lag connecting said members for moving said second member under the control of said first member, said coupling means comprising an element responsive to movement of said movable member for applying an additional movement to said second member to compensate for the variable hysteresis lag in the operation of said coupling means.

14. The combination with a movable member of a second movable member, and a linkage connecting said members for moving said second member in accordance'with a variable force applied to said first member, said linkage comprising an element for adding to the movement of said second member an increment substantially equivalent to the hystere sis lag in said movement.

15. In combination, a first movable member, a second member, a linkage whereby said second member is driven by said first member and an element interposed in said linkage for imparting to said second member in addition to its simple driven effect, an increment of motion such as to render the resultant motion of said second member a substantially faithful index of the movement of said first member.

16. A movable body, a second movable body, both bodies having hysteresis loss, a linkage connecting the two said bodies and means embodied 1n said linkage whereby a movement of the first of said bodies may be transferred to the second of said bodies with an additional movement representing a corand subtracting a decrement when said lead occurs in eifect that said secondary movements will be a substantially true index of said primary movements.

I 18. In an apparatus for indicating the magnitude of a stress, means for receiving the stress, means for indicating the magnitude of the stress, a linkage connecting said means for moving saidsecond means under the control of said first means, said linkage comprising an element for compensating for the variable hysteresis lag in the movement of said second means and means for automatically varying the value of said compensation when said lag is not-uniform.

19. In an apparatus for indicating the magnitude of a stress, means for receiving the stress, means for indicating-the magnitude of the stress, a linkage connecting said means for moving said second means under the control of said first means, said linkage comprising an element for adding an incrementto the movement of said linkage representing the lag of said apparatus when this stress is increased, and means for automatically varying the value of said increment when the lag is not uniform.

20. In an apparatus for indicating the magnitude of a stress, means for receiving the stress, means for indicating the magni-' tude of the stress, a linkage connecting said means for moving said secondmeans under the control of said first means; said linkage comprising an element for adding a decrement to the movement of said linkage representing the lag of said apparatus when the stress is decreased, and means for automatically varying the value of said decrement when the lag is not uniform.

21. The method of translating, movement from a first to a second of a plurality of elements interconnected by coupling means having lost motion therein, which comprises moving the first element in two steps, the first step to take upthe lost motion and the second step to move the second element to cause an indication, and during the initial portion of the second step causing said first element to move said second element an added amount to compensate for the absence of movement of said second element during said first step.

22. The method of translating movement between a first element and a second element interconnected by coupling means having lost motion therein, which comprises producing a movement of said first element, first to take up said lost motion, then move said second element, and subsequent to the completion of the first portion ofsaid movement causing said first element to givean added movement to said second element to compensate for the lack of movement thereof during said first portion of said movement,

23. The method of indicating the movement of an element that is coupled to an indicator by driving means of a given normaloperating ratio and having lost motion therein, which comprises producing a movement of said element having a first portion sufiicient to take up said lost motion and a sec- 0nd portion'to operate said indicator, and

upon completion of said first portion of said movement causing said driving means to operate at an increased ratio so as to supply a correction to said indicator to compensate for lack of indication thereby during the first part of said movement.

24. The method of translating movement between a first element and a second element interconnected by coupling means of a given normal operating ratio and having lostmotion therein, which comprises producing a movement of said first element, first to take up said lost motion, then move said second element and subsequent to the completion of the first portion of said movement causing said coupling means to operate at a difierent ratio to vary the movement of said second element to compensate for the lack of movement thereof during said first portion of said movement.

25. The method of translating movement between a first element and a second element interconnected by coupling means of a given normal operating ratio and having lost motion therein, which comprises producing a movement of said first element, first to take up said lost motion, then move said second element, and subsequent to the completion of the first portion of said movement causing said coupling means to operate at an increased ratio and to give an added movement to said second element to compensate for the I lack of movement thereo during said first arm fixed to said spindle, a pinion rotatably mounted on one end of said arm, an internal gearmounted concentrically with said spindle and meshing with said pinion, a pointer with the working surface of said cam so that upon rotation of said arm said pointer is moved endwise.

28. In combination, an arm mounted for rocking motion around a pivot, a plate for frictionally engaging one end of said arm, means for producing relative motion between said plate and the end of said arm to cause-a rotational movement of said arm, astop for limiting the rotation of said arm, and acam for varying the position of said stop.

29. In combination, a first and a second movable element, means for coupling said elements together so that movement of said first element results in movement of said second element at a certain speed ratio,'and means responsive to the initial portion of a -movement of said first element for altering second elements so that movement of the first results in movement of the second, and control means comprising a cam and a rider therefor responsive to the movement of said first element to successive positions for operating said adjustable means and varying the relationship between said first and second ele ments, said cam and rider being adapted for relative movement proportional to that of dition to be measured, means for applying additional stress to said member to anticipate a necessary operation of said member, and

means responsive to certain ofsaid movements for rendering active said means first mentioned.

32. A measuring system comprising a mo-vable member, means responsive to changes in a condition to be measured, for causing movement of said member, and means responsive to a predetermined change in said condition for causing a faster movement of said member than would normally result from following changes in said condition, whereby anticipated errors in future relationship between the condition and the member will be obviated. p 33. A measuring device comprising an element, power means for moving said element, and control means responsive to a predetermined action of said power means for anticipating thearrival of said element at a certain point and imparting motion to said ele ment additional to the motion imparted by said power means.

' 34. A measuring instrumentcomprising an element adapted for reciprocatory movement, means for causing such movement of said member, and means responsive to amotion of said element in one direction forincreasing the speed of movement thereof upon its return motion.

This specification signed and witnessed this 4th day of Dec., 1922'.

ANITA S. REYNOLDS.

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