JPH0551846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an absolute position detection method for detecting the absolute position of a movable part from a reference position. The present invention relates to an absolute position detection method capable of detecting the entire position.

Prior Art In order to control the position of a movable part to a target position, it is necessary to detect the absolute position of the movable part and perform position control based on the difference from the target position. In order to detect the absolute position of this movable part, absolute position detectors such as resolvers and absolute encoders are widely used.
Since this absolute position detector has a limited resolution, in order to perform detection with higher precision, it is necessary to configure a plurality of such detectors connected in multiple stages. FIG. 1 shows such an absolute position detector with a multi-stage configuration, in which detectors D1 and D2 have the same configuration, and gears G1 and D2 have the same configuration, respectively.
Its rotating shaft is connected by G2. If this gear ratio is G, then for one rotation of detector _D1 ,
The detector D2 rotates by G, and the detector D2 rotates by G as shown in FIG.
The detector D2 indicates a change of G cycles for a change of one cycle of 1, and the detector D1 can be used to detect the absolute position of the upper digit and the detector D2 can be used to detect the absolute position of the lower digit. In this configuration, if the resolution of one detector is α, the resolution is G·α, and position detection can be performed with higher precision. Note that one of the gears G1 and G2 is gear-coupled to the rotating shaft of the motor.

When the motor of the movable part is connected to the shaft of the gear G1, the gear speeds up and the detector D2 rotates multiple times for one rotation of the motor, so the range in which absolute position detection is possible is within one rotation of the motor. However, it is possible to increase the resolution of the detector.
Conversely, when the motor is connected to the shaft of the gear G2, the gear is reduced in speed, and the absolute position can be detected for multiple rotations of the motor.

Problems with the Prior Art However, in such a conventional method, when the lower digit detected by the lower detector D2 is carried up or down, the higher digit detected by the upper detector D1 needs to change. Extremely high detection accuracy is required. An optical type or a magnetic type is used for this upper level detector, but it is difficult to obtain one in which the relationship between the detected output value Ud and the rotational position is completely linear as shown in Figure 1B. Because of the slight fluctuation, it is virtually difficult to obtain a detector with extremely high detection accuracy, and even if it were obtained, it would be extremely expensive, creating the problem of actually hindering the improvement of the accuracy of absolute position detection. Ta.

OBJECTS OF THE INVENTION An object of the present invention is to provide an absolute position detection method that allows highly accurate absolute position detection even if the detection accuracy of the upper level detector is not so high.

Summary of the Invention In the present invention, a plurality of position detectors that detect displacement in a unit cycle length as an absolute amount are coupled to a movable part by gears, and a gear ratio is established between these detectors in a superior and subordinate relationship. In an absolute position detection method that detects the absolute position of the movable part over a plurality of cycle lengths of the lower detector by removing a detection error in the upper detector based on the detection value of each detector, The first step is to read the detection value of each detector and the detection value of each detector at an arbitrary point.
a second step of calculating the deviation of the detected value at the reference point of the lower detector and an arbitrary point; a third step of calculating the integer cycle number by rounding the cycle number of the lower detector corresponding to the distance to the point; and calculating the movable part from the integer cycle number and the deviation in the second step. The present invention is characterized in that it has a fourth step of detecting the absolute position of the reference point as the absolute position from the reference point. That is, the present invention converts the distance obtained based on the detection value of the upper detector and the detection value of the lower detector into the number of cycles of the lower detector, and calculates the converted number of cycles and the detection value of the lower detector. Since the distance is determined by the above, even if there is a detection error in the upper-level detector, highly accurate absolute position detection is possible without being affected by this error.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

Fig. 2 is an explanatory diagram of the present invention, and Fig. 2A shows the position versus upper detected value characteristics, and the length of one cycle is shown in Fig. 2A.
Let's call it Wu. FIG. 2B shows the position vs. lower detected value characteristic, where the length of one cycle is Wl. here,
When the gear ratio is G, the upper detection unit length l is as follows: l=G・Wl/Wu (1).

Here, two points (P ₀ ,
M ₀ and M ₁ are the detected values of the upper detector D1 at P ₁ ).
Then, the distance x calculated from the detection value of the upper detector D1 between P ₀ and P ₁ is x = (M ₁ - M ₀ )・l = (M ₁ - M ₀ )・G・Wl/Wu (2) becomes. As mentioned above, if the detection value of the upper detector D1 has an error range of E, then the distance x in equation (2)
is ±E・G・Wl/Wu for the true distance K・Wl
is within the error range.

Therefore, the following equation holds.

K・WL＋E・G・Wl／Wu＋(L ₁ −L ₀ )≧x≧K・Wl−E
・G・Wl/Wu+(L ₁ −L ₀ )……(3) l+E・G・Wl/Wu≧(M ₁ −M ₀ )・G・Wl/Wu≧K・Wl
−E・G・Wl／Wu……(4) When formula (4) is divided by Wl, K+E・G/Wu≧(M ₁ −M ₀ )・G/Wu ≧K−E・G/Wu…… (5) becomes.

Here, if the gear ratio G is selected so that E・G/Wu<0.5, that is, G<0.5・Wu/E+(L ₁ −L ₀ )...(6), equation (5) becomes K+0 .5＞( _M1 − _M0 )・G/Wu＞K−0.5……(7).

Equation (7) is the two points obtained from the upper detection values M ₁ and M ₀ .
If we divide the distance x between P ₀ P ₁ by the 1-cycle length Wl of the lower detector D2 and round off the quotient below the decimal point, we get
This means that the number of cycles K of the lower detector is found.

In other words, the distance x calculated from the upper detection value is converted to the number of cycles of the lower detector, and this does not include the error E of the upper detector, and does not affect the error of the upper detector. I don't accept it.

Next, a method for finding the distance between two arbitrary points P ₀ P ₁ will be described. It is assumed that the gear ratio G satisfies the condition of equation (6), and the upper and lower detected values for the position P ₀ P ₁ are respectively M ₀ , L ₀ , M ₁ , and L ₁ , and the values in the vicinity of R ₀ and R ₁ are Let the positions where the lower detected values match each other (in FIG. 2, the positions where the lower detected values are zero) be R ₀ and R ₁ , respectively. Here, if the detection error of the lower-order detector is ignored, the following relationship holds true.

_{0 0} = L ₀ …(8) _{1 1} = L ₁ …(9) _{0 1} = x = (M ₁ − M ₀ )・G・Wl/Wu …(10) Therefore, _{0 1} = _{0 1} + _{0 0 1 1} = (M ₁ −M ₀ )・G・Wl/Wu+L ₀ −L ₁ ……(11). If the distance between R ₀ R ₁ is divided by the one-cycle length Wl of the lower detector, and the rounded value of the quotient is K, then K represents the number of cycles of the lower detector between R ₀ and R ₁ , and K= [{(M ₁ −M ₀ )・G・Wl/Wu+L ₀ −L ₁ } /Wl] ...(12) However, [ ] indicates rounding to the nearest whole number.

becomes.

Next, the distance D of P ₀ P ₁ is D=R ₀ R ₁ +L ₁ −L ₀ =K·Wl+L ₁ −L ₀ (13).

The distance thus determined does not include the error of the upper detector. Furthermore, if a coordinate system is set with P ₀ as the reference point, the coordinate value of any position P ₁ can be easily determined from the distance between P ₀ P ₁ . Also, L ₀ ,
_L1 is the detection value itself of the lower-order detector D2.

Next, a specific example will be explained.

Let Wl = Wu = 1000, G = 50, E = 7, and the detected values are M ₀ = 254, M ₁ = 585, L ₀ = 223, L ₁ =
478.

At this time, the condition for the gear ratio G is 0.5・Wu/E=0.5×1000/7=71.43 from equation (6), and the gear ratio G=50 is determined by the condition G<
The relationship of 0.5・Wu/E is satisfied.

Next, calculate the number of cycles K from equation (12), K = {(585-254)・50・1000/1000+223
−478}/1000=16.295 ∴K=16, and finding D from equation (13) yields D=16・1000+478−223=16255. On the other hand, if we calculate D using the conventional method, D=(M ₁ −M ₀ )・G+(L ₁ −L ₀ )……(14) =(585−254)・50+(478−223)= 16805, which shows the high accuracy of the method of the present invention.

Next, a configuration for realizing the present invention will be described.

FIG. 3 is a block diagram of an embodiment for realizing the present invention. In the figure, the same parts as in FIG. 1 are indicated by the same symbols, and the MPU is a microprocessor that performs calculation operations. MEM is a memory that stores data.

Next, the operation of the configuration shown in FIG. 3 will be explained using the process flow diagrams shown in FIGS. 4 and 5.

First, at the reference point P ₀ , the processor MPU reads the upper detection value M ₀ of the upper detector D1 and the lower detection value L ₀ of the lower detector D2 from both detectors D1 and D2, and stores them in the memory MEM (fourth (see figure). The memory MEM stores the known 1 cycle length Wu of the upper detector D1, the 1 cycle length Wl of the lower detector D2,
The gear ratio G is various.

When the movable part moves and a detection command is input to the processor MPU, the processor
The MPU reads the current detected values M ₁ and L ₁ of both detectors D1 and D2. And the processor MPU is memory
Data stored in MEM Wl, Wu, G, M ₀ , L ₀
and the read M ₁ and L ₁ to calculate equation (12),
The number of cycles K is determined by rounding off the calculation result to the nearest whole number. Furthermore, the processor MPU calculates the distance D by calculating equation (13).

In the above example, a two-stage configuration was explained, but the present invention can also be applied to a three-stage configuration.

FIG. 6 is a configuration diagram in which the detector is configured in three stages: upper, middle, and lower, where detector D1 is the upper stage and detector D2 is the upper stage.
constitutes the middle position, detector D3 constitutes the lower position, and each gear G
1, G2', and G3 are connected by gears. and,
The upper, middle, and lower detectors and each one cycle length are Wu,
Let Wm and Wl be the lower to middle gear ratios and the middle to upper gear ratios to be G1 and G2. To explain the detection method of this configuration using the explanatory diagram in Fig. 7, first, the reference point
The upper, middle, and lower detected values of P ₀ are N ₀ , M ₀ , and L ₀ , and the upper, middle, and lower detected values of arbitrary point P ₁ are N ₁ ,
Let M ₁ and L ₁ .

First, finding the number of cycles J of the intermediate detector D2 between R ₀ ′ and R ₁ ′, by modifying equation (12), J=[{N ₁ −N ₀ )・G ₁・Wm /Wu+M ₀ −M ₁ } /Wm〕 …(14)′ In the intermediate detection unit, the distance D′ between P ₀ and P ₁ is
By transforming equation (13), it becomes D′=J・Wm+M ₁ −M ₀ ……(15).

Next, the number of cycles K of the lower-order detector D3 between R ₀ and R ₁ is obtained by modifying equation (12) as follows: K=[{D′・G ₂・Wl/Wm+L ₀ −L ₁ }/Wl ) ...(16) becomes.

In the lower detection unit, the distance D between P ₀ P ₁ is
By transforming equation (13), it can be found from the following equation.

D=K・Wl+L ₁ −L ₀ ...(17) Therefore, in the case of a three-stage configuration, the (14)'th
The distance D can be obtained by calculating equations (17), and a configuration similar to that shown in FIG. 3 can be used to realize this.

In the above example, we explained a three-stage configuration, but
The present invention can be similarly applied to n-stage configurations such as 4-stage and 5-stage configurations.

Effects of the Invention As can be understood from the above explanation, the method of the present invention includes a plurality of position detectors that detect displacement in a unit cycle length as an absolute amount, which are connected to a movable part by a gear, and which detect A gear ratio is set between the upper and lower detectors, and the absolute position of the movable part is detected over multiple cycle lengths of the lower detector by removing detection errors in the upper detection path based on the detection values of each detector. In the absolute position detection method, the first step is to read the detection value of each detector at the reference point and the detection value of each detector at an arbitrary point, and the deviation of the detection value of the lower detector at the reference point and the arbitrary point is calculated. A second step of calculating and rounding off the number of cycles of the lower detector corresponding to the distance from the reference point to the arbitrary point based on each detection value of the upper detector and the unit cycle length of the lower detector to an integer. The third step is to calculate the number of cycles converted into an integer, and the fourth step is to detect the absolute position of the movable part from the reference point as an absolute position from the number of cycles converted into an integer and the deviation in the second step. , convert the distance obtained based on the detection value of the upper detector and the detection value of the lower detector to the number of cycles of the lower detector, and calculate the distance from the converted number of cycles and the detection value of the lower detector. Therefore, even if there is a detection error in the upper-level detector, highly accurate absolute position detection is possible without being affected by this error. Furthermore, since a detector having a detection error can be used as a higher-order detector, an inexpensive configuration is possible, which is an excellent practical effect.

Although the present invention has been explained using one example, the present invention is not limited to the above-mentioned example, and various modifications can be made in accordance with the gist of the present invention, and these are excluded from the scope of the present invention. isn't it.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a multi-stage detector to which the present invention is applied, Fig. 2 is an explanatory diagram of an embodiment of the present invention, Fig. 3 is a block diagram of an embodiment for realizing the present invention, and Fig. 4 is an explanatory diagram of an embodiment of the present invention. 5 and 5 are processing flow diagrams in FIG. 3, FIG. 6 is a configuration diagram according to another embodiment of the present invention, and FIG. 7 is an explanatory diagram of the operation in FIG. 6. In the figure, D1, D2, D3...absolute position detectors,
MPU...processor, MEM...memory.

Claims (1)

[Claims] 1. A plurality of position detectors that detect displacement in a unit cycle length as an absolute quantity are connected to the movable part by gears, and gear ratios are set between these detectors in a superior and subordinate relationship, and the lower detector In the absolute position detection method of detecting the absolute position of the movable part over a plurality of cycle lengths based on the detection value of each detector by removing a detection error in a higher-order detector, the detection value of each detector at the reference point is and a first step of reading the detection value of each detector at an arbitrary point, a second step of calculating the deviation L ₀ and L ₁ of the detection value of the lower detector's reference point and an arbitrary point, and a third step of calculating an integer cycle number by rounding the number of cycles of the lower detector corresponding to the distance from the reference point to the arbitrary point based on each detected value and the unit cycle length of the lower detector; , a fourth step of detecting the absolute position of the movable part as an absolute position from a reference point from the integer cycle number and the deviations L ₀ and L ₁ in the second step. Detection method.