JPH04340608A - Method and device for controlling revolving shaft - Google Patents

Abstract

PURPOSE:To secure the matching ability of the coordinate system of a device without complicating the structure by checking a non-integer rotation part to calculate the rotational frequency of a revolving shaft. CONSTITUTION:A gear A12 attached to the revolving shaft and gear B16 attached to a motor shaft are so constituted that number M of tooth of the former is not a multiple of a number N of tooth of the latter. The angle of rotation (motor displacement angle theta) from turning-on of a proximity sensor due to a dog to appearance of the motor origin is made different in each one rotation of the revolving shaft, and a controller recognizes this difference to reverse the revolving shaft by a required rotational frequency or correct the present position. Consequently, the revolving shaft can be returned to the original position including plural rotations by return to the origin though the revolving shafts are rotated plural times. If this device is applied to the revolving shaft of the front end of an industrial robot, pipings and wirings are not torn off though being provided in the front end of the revolving shaft.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and device for a machine having a rotating shaft, such as a robot, and more particularly to a method and device for returning a rotating shaft to its origin.

0002

2. Description of the Related Art A mechanical device having an axis has its own mechanical coordinate system generated by the movement of the axis, and the consistency of this coordinate system must be ensured. However, what maintains the position of the axis is an encoder installed on each axis or the rotating shaft of the drive motor, and in the case of an incremental type, if the power supply to the encoder is cut off, the position information is lost. Therefore, when the power is turned on, it is necessary to position each axis using a special procedure. This is called returning to origin. Various techniques have been developed to simplify or omit this return-to-origin procedure.

FIG. 7 shows a control device for a rotating shaft. A gear A (12) with M teeth is attached to the rotating shaft 10, and a gear B (16) with N teeth is attached to the shaft of the motor 14, where M is a multiple of N. . Furthermore, these two gears are connected by a belt 18. motor 14
An encoder 24 is attached to the motor 14, and the motor 14 is driven by a control device 26 to rotate the rotating shaft 12.

In order to detect the origin of the rotating shaft 10, a dog 20 is attached to the gear A (12), and an externally provided proximity sensor 22 detects the approach of the dog. The signal is sent to the control device 26. An encoder 24 is attached to the shaft end of the motor 14. There are two types of encoders: incremental type and absolute type, but here we will use the incremental type.

The procedure for returning to the origin in such an apparatus will be explained with reference to FIG. Step 1: Gear B (16) attached to the motor shaft rotates gear A (12) via belt 18, and the dog 20
approaches the proximity sensor 22 and turns it on. This signal causes the control device to stop the motor. Step 2: Gear B (16) is rotated at low speed in the + direction by the motor, and the motor origin 48 of the encoder is aligned with the detector 50.
is detected and the origin pulse is generated. (In Figure 3,
For simplicity, the encoder motor origin 48 is set to gear B (16
) is depicted above. ) Step 3: Stop the motor. At this time, gear A (1
Although the dog 20 and sensor 22 in 2) are at slightly shifted positions, the control device uses this state as the origin.

[0006] By following such a procedure, the rotating shaft can always be returned to a constant phase, except that the integral number of revolutions of the rotating shaft is uncertain. This essentially relies on the fact that the number M of teeth on gear A (12) is a multiple of the number N of teeth on gear B (16).

[0007]

[Problem to be Solved by the Invention] However, when such a rotating shaft is used for a robot hand, pneumatic piping and electrical wiring are often provided at the tip of the rotating shaft. If the rotating shaft rotates more than a certain number of revolutions due to return to origin, these wirings and piping will be destroyed. Such inconveniences cannot be avoided even if the encoder is changed to an absolute type.

In order to solve such inconveniences, an object of the present invention is to provide a rotating shaft that can return to its original position by returning to its origin even if the rotating shaft rotates multiple times. An object of the present invention is to provide a control method and device.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides the number M of teeth of a gear A (12) attached to a rotating shaft and the number M of teeth of a gear B (16) attached to a motor shaft. By setting N such that M is not a multiple of N,
The rotation angle from when the dog turns on the proximity sensor until the motor origin appears (this will be referred to as the motor displacement angle θ) is made to differ for each revolution of the rotation axis, and the control device recognizes this. By doing so, it is possible to reversely rotate by the required number of rotations or to correct the current position.

In FIG. 1, if the number M of teeth of gear A (12) and the number N of teeth of gear B (16) have a common divisor other than 1, they are divided in advance so that M and N are equal to each other. Make it plain. According to a well-known theorem, for any integer n, there always exist integers p and q such that pM-qN=n. In other words, when gear A (12) rotates p times, gear B (1
6) rotates q+n/N. Since n is arbitrary, the rotation angle of gear B (16) is 0/N, excluding the integer part.
1/N,. ．． ．． , (N-1)/N. Here, Δ=2π/N is defined. Furthermore, it is clear that all of these N patterns appear without duplication while the gear A (12) on the rotating shaft rotates N times.

To further explain using FIG. 2, the dog attached to the aforementioned gear A (12) turns on the proximity sensor, the motor stops, and the motor encoder 24 detects that the motor home position is at 82. The angle β (0≦
β<Δ). In this case, the motor displacement angle θ is θ=β. If the rotating shaft rotates from this state several times, that is, the gear A (12) attached to the rotating shaft rotates several times, and the motor origin reaches position 84, θ=Δ+β. Generally speaking, if the motor shaft rotates q+n/N in response to p rotations of the rotating shaft, the motor displacement angle θ will be θ=nΔ+β, and the origin position of the encoder 24 will be 82, . ．． ,88,. ．． ．． It is distributed in N ways as follows. Therefore, the rotation speed p of the rotating shaft and the motor displacement angle N
By organizing the relationship in advance and checking the motor displacement angle by the control device, it is possible to know the rotation speed p of the rotating shaft within the range of N times.

0012

[Embodiment] An embodiment of the present invention will be described below. Here, it is assumed that rotations up to 10 rotations are determined. Therefore, the number of teeth of gear B (16) is set to N=10, and the number of teeth of gear A (12) is set to M=33 so that it is prime with this number. Furthermore, both may be multiplied by an integer (for example, N=20, M=66, or N=30, M=99, etc.). Now, since there are 10 types of motor displacement angles, one rotation is divided into 10 regions as shown in Table 1. As described above, since there is the relationship θ=nΔ+β, the motor displacement angle appears within region X when n=X. In Table 1, n is set from 0 to 9, but it may be divided into positive and negative numbers, such as from -4 to 5. Also, θ
Since the detection accuracy of is usually not very high, it is important to adjust the dog to make β sufficiently larger than this detection accuracy.

Next, if p=0 based on the case where the motor displacement angle is found within region 0, the relationship between each region number n and the rotating shaft rotation speed p is expressed as pM≡n mod N (this example The case is determined by 33p≡n mod 10). If p is allocated in the range from -4 to 5, then n
The relationship between and p is shown in Table 1.

Next, the procedure for returning to the origin will be explained with reference to FIG. 3 and subsequent figures. It is assumed that the encoder is of incremental type. Step 1: The motor, that is, gear B (16) rotates clockwise, and the dog 20 of gear A (12) turns on the proximity sensor 22. This signal causes the motor to stop (Figure 3). Step 2: The motor rotates to the left at low speed, the motor origin 48 of the encoder is detected by the detector 50, and the motor is stopped (FIG. 4). The amount of motor rotation at this time is equal to the motor displacement angle θ shown in FIG. 3, and this angle θ is stored. Step 3: From the motor displacement angle θ, refer to Table 1 to determine the area number n and rotational speed p of the rotating shaft. Step 4: Rotate the motor clockwise by nΔ. This brings the motor origin 48 to the position shown in FIG. Step 5: Rotate the motor counterclockwise to rotate the gear A (12), that is, the rotating shaft, to the left by p. Set this point as the origin (
Figure 6).

In the above embodiments, the encoder is of the incremental type, but if it is of the absolute type, the procedure can be further simplified as follows. Step 1: Same as step 1 above. Step 2: Read the position at which the motor stopped in step 1 from the absolute encoder, and set this as the motor displacement angle θ. Step 3: From the motor displacement angle θ, determine the region number n and rotational shaft rotation speed p according to Table 1. Step 4: Let p×(M/N)×2π+θ be the rotation angle of the motor.

[0016]

According to the present invention, even if the rotary shaft rotates a plurality of times, it can return to its original position, so that the consistency of the machine coordinate system is always guaranteed. If applied to the rotating shaft at the tip of an industrial robot, there is no risk that piping or wiring may be torn off at the tip of the rotating shaft. Further, the present invention is configured by gear ratio selection and software in the control device, and does not require any special hardware, so there is no increase in cost at all.

[Brief explanation of drawings]

FIG. 1 is a drawing explaining the principle of the present invention.

FIG. 2 is a drawing explaining the principle of the present invention.

FIG. 3 is a diagram illustrating a procedure for returning to the origin according to the present invention.

FIG. 4 is a diagram illustrating a procedure for returning to the origin according to the present invention.

FIG. 5 is a diagram illustrating a procedure for returning to the origin according to the present invention.

FIG. 6 is a diagram illustrating a procedure for returning to the origin according to the present invention.

FIG. 7 is a conceptual diagram of a motor, a rotating shaft, a detection means, and a control device.

FIG. 8 is a diagram illustrating a procedure for returning to the origin using a conventional method.

[Explanation of symbols]

12 Gear A 14 Motor 16 Gear B 24 Encoder 26 Control device

Claims (2)

[Claims] 1. A gear attached to a motor shaft, a gear attached to a rotating shaft, a belt connecting these gears, an encoder for detecting a rotational angle coupled to the motor shaft, and an origin of the rotating shaft. Equipped with sensor means for detecting
A rotary shaft control method in which a signal from the encoder and a signal from the sensor means are input to a control device, and the control device uses these signals to control rotation of the motor,
The number of teeth of both gears is determined so that the number of teeth of the gear attached to the rotating shaft is not a multiple of the number of teeth of the gear attached to the motor shaft, and the control device controls the motor as the rotating shaft rotates an integral number of times. By recognizing a non-integer part of a non-integer rotation of the shaft, the control device identifies the rotation speed of the rotation shaft and controls the rotation angle of the rotation shaft and the motor shaft. Rotary axis control method. 2. A gear attached to a motor shaft, a gear attached to a rotating shaft, a belt connecting these gears, an encoder for detecting a rotational angle coupled to the motor shaft, and an origin of the rotating shaft. Equipped with sensor means for detecting
A rotary shaft control device in which a signal from the encoder and a signal from the sensor means are input to a control device, and the control device uses these signals to control rotation of the motor,
The number of teeth of both gears is determined so that the number of teeth of the gear attached to the rotating shaft is not a multiple of the number of teeth of the gear attached to the motor shaft, and the control device controls the motor as the rotating shaft rotates an integral number of times. By recognizing a non-integer part of a non-integer rotation of the shaft, the control device identifies the rotation speed of the rotation shaft and controls the rotation angle of the rotation shaft and the motor shaft. Rotary axis control device.