JPS60183515A - Method and device for measuring absolute position - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The invention relates to position measurement for numerically controlled machines. In particular, the present invention relates to the measurement of the absolute position of a movable mechanical member relative to a fixed reference position.

BACKGROUND OF THE INVENTION For the numerical control of the movements of the various parts of a machine, it is desirable to produce a unique position measuring signal for all positions of one moving part, pronation. This glaze trace, which is called absolute position measurement, is a method in which the position of the glaze is recorded and maintained during periods when the unryuuable member is not subject to numerical control, such as during maintenance and inspection of a numerical control device. It has the advantage of providing accurate information regarding the position of the movable member, whether or not it is moved.

Absolute position measurements for moving members of numerically controlled machines are constrained by dual resolution and axial distance requirements. Absolute position measuring systems are known in all mechanical fields using a plurality of measuring devices, each operating at a different resolution and each serving to make a unique measurement over a portion of the axial distance of the machine. When such a system is constructed using a measuring device W containing a rotating element, the drive section for the measuring device used is Requires a considerable gear reduction ratio. If such a system is constructed using a linear measuring device, the scale required to produce a unique tc constant signal over the full axis separation of the two machines becomes enormous.

(Problem to be solved by the invention) Other known points of the absolute position system.

It is easy to account for errors caused by the measuring device itself or the internal drive frame associated with the measurement device itself.

Errors arising from such sources adversely affect the overall machine positioning accuracy.

Therefore, it is an object of the present invention to have a mechanical part capable of HDT that can be operated over the entire range of the striking force, and that each can be applied over the entire mechanical part's striking force movement range. An object of the present invention is to provide an absolute position measuring device and method that requires no more than two measuring devices.

Another object of the invention is to use two cyclic measuring devices,
Another object of the present invention is to provide an absolute position measuring device that has a certain tolerance for errors in the relative position performed by two measuring devices.

Yet another object of the invention is to develop a movable machine using a measuring device and a measuring device, each of which produces a periodic measuring signal as the mechanical member moves over its range of motion. Acts over the entire range of motion of the member.

An object of the present invention is to provide an apparatus and method for determining an absolute position in which a periodic sub-measurement signal is not repeated more than one time in rotation than a periodic main measurement signal.

Yet another object of the invention is to act over the entire range of motion of a movable mechanical member comprising two fixed devices, each having a rotatable element and each producing a periodic measuring signal. The rotating elements are mutually driven in absolute positions such that one measuring device does not produce more than one cycle of its measurement signal more than the other measuring device over the range of motion of the axis to be determined. Providing measuring equipment.

Other objects and advantages of the invention will become apparent from the two drawings and the related description.

SUMMARY OF THE INVENTION In accordance with the foregoing, there is provided an absolute position measuring device and method that operates over the entire range of movable mechanical components. A primary measuring device and a secondary measuring device are provided, each producing a measuring signal proportional to the displacement of a movable member of the machine. The oil 11 constant signal is unique within the limited range of the machine member, and the unique value repeats periodically over the entire range of motion of the machine member. The measuring signal of the restraining device 11 does not exceed the measuring signal of the leading device by more than one cycle within one moving part of the mechanical member.

Absolute position by calculating the difference between them.

It is also calculated from the measured signal by using the result to calculate a value representing the number of cycles of the main I+constant signal. This calculated value is constant for any position within the range of motion of the nine machines and is independent of position recording and maintenance during periods when the movable members of the two machines are not subject to numerical control. Relative errors in machine side displacement measurements of less than one main measurement cycle between the two measuring devices are eliminated by the procedure used to calculate the absolute position from the main and control constant signals.

To illustrate the invention, a preferred embodiment as applied to an industrial manipulator manufactured by the assignee of the invention will be described. It is to be understood that the specific details of the construction of the invention as exemplified by the preferred embodiments are not to be construed as limiting non-invention. and all equivalent answers.

(Embodiment) In the block diagram of FIG.
6.18 is shown connected. The measuring device chosen by the applicant for use in the industrial manipulator is of a known type, such as a resolver with electromagnetically coupled rotor and stator elements.

As shown.

The movable element of the resolver, or rotor, has an alternating current signal applied to its windings, from which an output signal is induced in the stator windings. The rotor and stake elements are arranged such that the periodic amplitude change in the output due to the angle of displacement of the rotor is uniform or unique everywhere within one revolution of the rotor, or for one revolution of the rotor. More than 2 times
It is possible to provide a set of windings so that it can be repeated twice. Each rotor of the resolver has one alternating current signal added to it, and the stator produces two 9# signals as output within the angular phase. That is, the input signal Esin(
wt) is the stator output signal Esin(wt)sin
(θ) and E sin (wt) cos (θ)
′? As it occurs, it is decomposed into two components. however.

E - Strength of the signal wt = Instantaneous angle of the input signal θ = Displacement angle of the rotor The displacement angle θ is calculated from the inverse trigonometric function of the ratio of the output signal. That is, θ is E sin (wt) 5in(θ)
/ E sin (wt) is equal to the arctangent of cos (θ).

It will be appreciated that another connection of the resolver (not shown) can be substituted if the input signal is applied to the stake winding and the output signal is produced by the rotor winding. In this configuration, the stator's rectangular windings can also provide input signals with a phase difference of 90°, namely E sin (wt) and E sin
(wt + 90'). The displacement angle of the rotor produces a corresponding phase shift in the output signal Esin(wt+θ), which is sensed by phase discrimination and produces a constant signal representing a fraction θ of the total cycle of the rotor displacement angle.

Inductosyn available from Farrand
It will be appreciated that an output signal of the same shape can be obtained using an electromagnetically coupled linear measurement device such as the TM.TM.

The interface circuit 16.18 provides an input signal to the resolver and receives an output signal which is sampled and converted to an appropriate '4c level for subsequent analog/digital converters 20,22. 22 each produce an output signal representing the instantaneous value of the output signal of a movable element of the measuring device. The output of the analog-to-digital converter is input to angle calculation circuits 30, 32 to calculate the displacement angle from the resolver output and to calibrate the displacement according to the selected resolution for the measured position. be done. It will be appreciated that the output signal of this angle calculation circuit 30.32 represents the displacement angle of the rotor relative to the stator and is unique only for a valid rotation cycle. That is,
If one rotation of the resolver rotor results in more than one repeated cycle of displacement angle in the force output signal, the output signal of the angle calculation circuit 30.32 will be a fraction of one rotation of the resolver rotor associated with one cycle. This results in a unique signal being generated only for those signals. Eleven A/D converters and angle calculation circuits are used for both five resolver outputs as configured in the preferred embodiment, but the conversion and calculation functions are by multiplex operations in time.

Any device capable of producing a unique measuring signal that repeats periodically over the moving parts of the moving parts of the machine can be used as the measuring device 12.14. , interface circuit 16.18. It will be obvious to those skilled in the art that this would be a suitable alternative to the combination of analog/digital converter nodule 22 and angle calculation circuit 30.32.

For this purpose, the measuring device may be a potentiometer, a rheostat, a variable transformer, or any linear measuring device that produces a unique measuring signal that is periodically reversed over the range of motion of the moving part of the machine.

The measuring device], 2.14 is configured such that the sub-tracing device 14 causes one or more cycles of its measuring signal over the movement of the movable parts of the machine than by the main tracing device 12. When a movable member of a machine advances from its reference position to the limit of its movement (Nll), the difference in the measurement signals increases. For this reason, the difference in the measurement signals always increases with respect to the fixed reference. This results in an unambiguous representation of the absolute position in terms of value.Since the measurement signal does not represent more than one complete cycle, the formation of an unambiguous representation of the absolute position requires that the difference between the constant multipliers be the moving part.

Requires no more than one complete cycle spanning the entire range. However, the difference in the fixed angle is proportional to the number of rotations applied to the rotor of the measuring device.

Merely subtracting the angle measured by the primary 11 constant from the secondary 11 constant signal does not guarantee that the required difference will be obtained. Instead, it is necessary to allow a secondary measurement to produce a negative difference that is compared to the cycle of the measurement signal of the main measurement and indicates that it will be part of the next cycle of that measurement signal. Become.

Continuing the description with reference to FIG. 1, the calculation of the difference or the compensation for the required result is carried out by a difference circuit which produces a positive output in all cases.

If this subtraction operation results in a negative difference, then a value equal to a complete cycle is added to this difference.

The difference signal represents a portion of a complete cycle and is directly proportional to the number of cycles of the main measurement signal, which corresponds to the amount of displacement of the movable member of the machine from a fixed reference position to its current position.

Since the displacement angle is in the ratio of 1+11 to the number of cycles of the main measurement signal, the absolute position is easily calculated knowing the difference in the measurement signals. The absolute position is calculated by the absolute position calculation circuit 26 of FIG. 1 using the calculated number of cycles of the main measurement signal. The absolute position is expressed as a value representing the same solution as the main measuring device.

Although the absolute position value can be calculated simply by factoring the number of cycles of the main and constant signals, the applicant has proposed a preferred embodiment in order to eliminate errors in the measurement signals of the sub-measuring device relative to the main measuring device. The second flowchart, which uses a random algorithm and a more sophisticated algorithm, illustrates the procedure that may be used in the preferred embodiment for absolute position measurements. This procedure calculates the closest number of complete cycles of the main measurement signal corresponding to the distance from the reference position to the current position to synthesize the value of P versus position.

In the flowchart in Figure 2, step 2 is step 4.
Starting at 0, where each part of a complete cycle? The values of the main measuring signal X and the sub-measuring signal Y are read. In step 42, the measurement signals X and Y are scaled to represent a value of 2 for the desired resolution, for example several tenths of an inch of rotation angle.

Either in decision step 44, where a difference value is calculated by subtracting the primary measurement value from the secondary measurement value, the results of processing step 42 are examined to determine whether a negative value of °C has occurred. If not, execution of the procedure continues at process step 48. But if negative values are detected.

Execution of the procedure continues to process step 46, where a value equal to one complete cycle of the main measurement signal is added. Either the result of process step 4.6-1: or step 42 in the positive case is then used by process step 48 to calculate the integer number of cycles of the main resolver's measurement signal.

The number of cycles of the main measurement signal can be expressed as a phase of two complete cycles, one and a partial cycle. Only partial cycles are represented by the main measurement signal X. The rotor of the secondary measuring device is related to the rotor of the main measuring device by a relative ratio (M+, 1)/M, where 2M is equal to the number of cycles of the main measuring signal that are missed during the rotation of the moving parts of the machine. shall be granted.

If we also assume that each revolution of the rotors of both devices produces one cycle of each tune, the cycle of the 1il11 measuring device is equal to (I+X+I/M+X/M).

Once again, only part of the complete cycle is clothed by the 1st and 11th Josengo Y. Restraint 11 constant device pond; constant multiplier +5Y or greater than or equal to main device's constant signal Equal to the magnitude of the measured signal. If Hatake 1j measurement multiple Y is smaller than the main measurement signal X, the phase of the last three terms is larger than the magnitude of the sub measurement signal Y by one. Therefore, the cycle (2) of the integer value of the main constant signal can be calculated using the known quantity from the equation below. Ialchi.

I = M(DIFF)-X where DIFF is the difference value (Y-X) that has not been adjusted to produce a positive result as stated earlier.

In processing step 48, the difference signal is used to generate an integer cycle signal 1 representing an integer number of cycles of the primary resolver.
Arise. The difference value DIFF is the measurement value.

multiplied by the number of cycles M of the secondary resolver over the

The part of the cycle represented by the target i constant value of the main constant signal X is subtracted from the result of the product. The difference in the results corresponds to the number of solutions in the cycle of the main resolver's measurement signal - 1 - the scale factor? Divided by S. Relative errors in the measurement signal will cause this result to appear as a residual R outside of the total number. In the filling step 49, the size of the residual R is measured. If the residual R is greater than or equal to half the cycle of the main measurement signal, the integer value I is
Increment by 1 at 0. If the residual R is made smaller than half of one cycle of the antemortem/constant signal, no change occurs to the integer value T. In processing step 52, the integer value obtained as a result from processing steps 48 to 50 is
, the product of the number of revolutions included in one cycle of the main measurement coefficient and the corresponding scale factor S is read out in a process step 40 and added to the value of the main measurement signal X.

The effect of the processing steps 48, 50, 52 is to eliminate relative errors in the values read out in the two-effect step 40. Step 4.9.50 & Detour yields an integer by effectively adding or subtracting 1"gS of the main measurement signal cycles less than or equal to half a cycle. This integer value is Corrected if necessary, the partial cycles removed in this way should be replaced by the actually traced values of the main measuring device. These nine steps correspond to one cycle of the measuring signal of the main resolver. It is effective for errors in the measurement of main and control/stationary devices that are larger than some of the solutions.

When used as a control unit for the industrial phase manipulator, the step 111g in the flowchart in FIG. 2 is converted into a program for a microprocessor capable of executing integer operations. Difference calculation circuit 24 and absolute position calculation circuit 26 in the block diagram of
is constructed using a microprocessor and a program therefor to accomplish the steps in the flowchart of FIG. Furthermore.

Temporary storage of the values used in this procedure is provided by memory locations in random access memory.

In FIG. 3, the mechanical arrangement of the main and control devices as well as the drives are shown. The main resolver 60 and the sub-resolver 62 have their respective reduction gears 64.
66 to a common drive shaft. The drive gear 68 is directly driven by the motor that drives the movable parts of the machine and can be driven by the rotary shaft;
Alternatively, the movement of the movable members of the machine may be carried out by means of a rack and pinion or other suitable device. In any case, if the main resolver 60 and the sub-resolver 62 are the same, the gear ratio of the main resolver gear 66 to the drive shaft 68 and W = the gear ratio of the sub-resolver tooth type 64 to the wheel 68. A relatively small difference in the ratio results in a required difference in the number of cycles of the start 11 constant signal compared to the main 11 constant signal over the range of motion of the movable members of the machine. For more information.

If M is the number of cycles of the primary measurement signal completed over the range of motion of the moving parts of the machine, then the required relative gear reduction ratio of the secondary resolver rotor to the primary resolver rotor is (M+1)/M. As mentioned above, this simplified gear train is also necessary in known systems in order to obtain the required solution via one measuring device and to cover all the axes of the machine by means of a second or other measuring device. This provides significant advantages over large gear reductions. From the above description, it can be seen that a single tracking device can be
It will be readily understood that one obtains a unique multiplier from the differential displacement defined by the primary and secondary measuring devices, rather than by specializing for a line range.

When used for the manipulator mentioned in the text.

Absolute position measuring device is used to measure the position of the manipulator's rotational axis.

The motion of the movable member is driven by the vehicle deceleration directly from the motor.Nevertheless, it may be necessary to drive a rotating element such as a resolver or a measuring device, such as the unstated resolver. Alternatively, by using a fixed orientation device with two scales and two read heads, the same position and method described above is also suitable for application to machines with linear interlocking axes.

Although the present invention has been illustrated by preferred embodiments and the preferred embodiments have been described in considerable detail, it is not intended that the scope of the present invention be limited to such details. On the contrary, it is intended to cover all changes, modifications, and equivalent contents that fall within the scope of the claims in the first five claims.
−j

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating an apparatus for an absolute and relative position deputy according to the invention; FIG. 2 is a flowchart illustrating the method used to determine absolute position from two periodic measurement signals; and FIG. The figure is a schematic diagram showing two measuring devices with rotating elements and associated drive drives. 12...Main measuring device, 14...Sub-tracing device, 16
. . . interface circuit, 18 . . . interface circuit, 20. 22...Analog/digital φ converter, 24...Difference calculation circuit, 26...Absolute position calculation circuit, 30.32...Angle calculation circuit,
60... Main resolver, 62... Secondary resolver, 64.
66... Reduction gear, 68... Drive gear.

Claims (1)

[Claims] 1. iJ using the measurements of no more than two measuring devices,
In a method for producing an absolute position signal having a unique value for every position within the range of motion of a movable machine member. (a) producing a main measurement signal representative of the displacement applied to the movable element of the first measuring device, the main measurement signal repeating periodically over the movement of the member of the machine; . (1) producing a sub-measurement signal representative of the displacement applied to the movable element of the second measuring device;
j! ll constant signal over the range of motion of said machine member °C
cyclically repeating, such that the number of cycles of the secondary measurement signal is not more than one greater than the number of cycles of the main measurement signal over the range of motion of the member of the machine. (cl) in response to said main measurement signal and said sub-measurement signal; producing a difference signal representative of the difference in displacement represented by the measurement signals; (d) in response to said difference signal, a member of said machine movable; 2. A method according to claim 1, characterized in that the step of generating a difference signal further comprises ( al Subtract the main measurement signal from the sub-measurement signal. (b) Check the subtraction result to detect whether it is a negative difference value. (c) In response to the detection of the negative result, subtract the main measurement signal. 3. A method according to claim 1, characterized in that the method comprises the step of adding to said result one value equal to one complete cycle of the signal!. 3. The method of claim 1. and further: (a) producing an integer number of cycle signals representing an integer number of cycles of the main measurement signal corresponding to the current position of the movable machine member; (b) producing the integer number of cycle signals for the main measurement signal; (c) scaling the addition result to produce the absolute position signal. 4. Measuring the absolute position of the movable mechanical member relative to a fixed reference position. (a) A main measuring device is provided for producing a main measurement signal representative of the displacement exerted on a movable element of the main device by the movement of the member of the machine, the main measurement signal being C repeating periodically over the range of motion. The sub-measurement signal repeats periodically over the range of motion of the mechanical member, such that the number of cycles of the sub-measurement signal is no more than one cycle greater than the number of cycles of the main measurement signal over the range of motion of the mechanical member. (c'l in response to the main measurement signal and the sub-measurement signal; °C; a device for generating a difference signal representing a difference in the amount of displacement represented by the measurement signal; (di in response to the difference signal; , a device for generating an absolute position signal representing a unique value defining the absolute position of the mechanical member. 5. Range of Percentage Precision In the device according to item 4. (a) Rotatable. fb) a drive device coupled to said movable mechanical member for imparting a rotational movement to said rotatable element. 6.@Claim 5 f) Apparatus. (a) An angle measuring device having a rotatable element. (b) The apparatus further comprises a section device coupled to the movable mechanical member to impart rotational motion to the rotatable element. 7.tp! j In the apparatus according to claim 4. Ia) a device for subtracting the main measurement signal from the sub-measurement signal; (b) A device for detecting a negative difference value. (C) means for adding the equivalent value of one cycle of the main measurement signal to the difference value in response to the detection of a negative difference value. 8. In the device according to claim 4. The device of claim 1, further comprising a device for scaling the measured displacements of the movable elements of the primary and secondary measuring devices. 9. The apparatus according to claim 8. Apparatus according to claim 1, wherein said apparatus for generating said absolute position signal further includes apparatus for scaling said difference signal. 10. In a device for measuring the absolute position of a movable mechanical member relative to a fixed reference position. (a'1 A main angle measuring device which generates a main measuring signal proportional to the displacement angle given to its rotating element; (bl) a shaft angle measuring device for generating a secondary measuring signal; and a device for driving the rotary elements of the main and secondary measuring device according to the movement of the movable mechanical member (cl above); (d) in response to the main measurement signal and the sub-measurement signal; ,
and a device for producing a difference signal representative of the difference in displacement angles of the rotating elements of both measuring devices. (e) means for generating an absolute position signal responsive to the difference signal representing a unique value defining the absolute position of the movable mechanical member. 11. In the apparatus according to claim 10. (al) a device for producing an integer number of cycle signals representing an integer number of cycles of the main measurement signal corresponding to the current position; (b) a device for adding the integer number of cycle signals and the main measurement signal to produce the absolute position signal; A device characterized by comprising: