JPH01210643A - Controller for planet differential type reduction gear - Google Patents

Abstract

PURPOSE:To improve accuracy in feedback control with simple constitution by incorporating the output of a memory having a power transmission error property related to deceleration of a planet differential type reduction gear in the input information of a motor driving power controlling means. CONSTITUTION:A motor 2 is connected to the input side of a planet differential type reduction gear 1 to control a drive force of the motor 2 through a controller 5 and a motor drive circuit 4. To the input of side circuit 4 are supplied signals of the controller 5, memory 6 and encoder 7, and a power transmission error property related to the deceleration of the reduction gear 1 is stored in the memory 6. Thus, accuracy in feedback control can be improved by simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a planetary differential type reducer, and is provided, for example, in a joint part of an industrial robot, and is a high-speed reducer that drives an arm member of the robot. The present invention relates to a control device for a ratio reducer.

(Conventional technology) Recently, with the advancement of industrial robots in various industries,
Various speed reduction devices with high reduction ratios have been devised in order to cooperate with a motor to drive the arm members of a robot based on a predetermined program and to delicately control the movement thereof.

A typical example of such a speed reducer is a planetary differential type speed reducer, including the Cyclo trademark speed reducer,
Includes Harmonic Drive trademark reduction stages.

To control a robot using this type of reducer, a position detector (for example, an encoder) is usually provided on the input side of the reducer to detect the input rotation angle and use the controller to perform work such as machining the workpiece. Feedback control.

(Problem to be solved by the invention) However, in such a conventional control device,
The system was configured to detect the rotational position of the input side of the reducer and control operations such as workpiece machining as feedback.
There was a problem that the detection accuracy was not necessarily good. In other words, the rotational position of the input side is detected, the rotational position of the output side via the deceleration mechanism is predicted from this detection result, and this is used as input information for feedback control, so errors and delays due to deceleration intervene, and the control There are limits to accuracy improvement.

(Objective of the Invention) Therefore, the present invention adds power transmission error characteristics related to deceleration of the reducer to one of the control input information, thereby appropriately controlling the input end driving force of the reducer, and achieving a simple configuration. The purpose is to improve the accuracy of feedback control.

(Means for Solving the Problems) In order to achieve the above object, the control device for a planetary differential type reducer according to the present invention controls the driving force of the motor by a control means, reduces the speed by the planetary differential type reducer, and outputs the output. In a control device for a planetary differential type reduction gear which transmits a driving force to the output side and performs a predetermined operation using the output side driving force, a storage means is provided for storing power transmission error characteristics regarding deceleration of the planetary differential type reduction gear; The control means incorporates at least the output of the storage means into the input information for controlling the driving force of the motor, and controls the driving force of the motor to perform a predetermined work.

(Function) In the present invention, the power transmission error characteristics related to deceleration of the planetary differential type reducer are stored in the storage means, and at least the output of the storage means is incorporated into the input information for motor driving force control to drive the motor. The force is controlled and a given task is performed.

Therefore, the input side driving force of the reducer is appropriately controlled,
Control accuracy is improved with a simple configuration.

(Example) Hereinafter, the present invention will be explained based on the drawings.

1 to 3 are diagrams showing an embodiment of a control device for a planetary differential type reduction gear according to the present invention.

First, the configuration will be explained. In Fig. 1, 1 is a planetary differential type reducer in which an external gear meshing with an internal gear performs an eccentric rocking motion, similar to the cyclo reducer, and 1 also includes a harmonic drive reducer, etc. But that's fine. A motor 2 is connected to the input side of the reducer 1, and the reducer 1 rotates by receiving the driving force of the motor 2, and uses an internal planetary differential type gear reduction mechanism to reduce the input rotation speed and output it. Communicate to the side. A robot arm 3 is connected to the output side of the reducer 1, and the robot arm 3 is operated by the reduced driving force from the motor 2 to perform a predetermined work (for example, machining or gripping a member).

The motor 2 rotates in response to power supplied from a motor drive circuit 4, and signals from a controller 5, a memory 6, and an encoder 7 are input to the motor drive circuit 4. The encoder 7 detects the rotation speed of the motor 2, and the input side rotation speed of the reducer 1 is determined from this.

The encoder 7 is placed near the output shaft of the motor 2, for example, and outputs a Z-phase signal (Ip/r
ev) is output. The memory 6 has a function as a storage means, and stores power transmission error characteristics regarding deceleration of the reducer 1 as data. Specifically, various errors caused by the machining accuracy of the components of the reduction mechanism in the reducer 1, such as gear tooth profile errors and concentricity errors between gear tooth profiles and gear support bearings, are stored internally in the form of a map or the like. This can be determined in advance for each model through experiments and the like. The controller 5 controls initial settings and control conditions for moving the robot arm 3 (for example, target values for feedback control).
, and outputs signals such as position command control pulses to the motor drive circuit 4 according to control conditions.

The motor drive circuit 4 has a memory 6 that is read in synchronization with the output of the controller 5 and the signal from the encoder 7.
A control value for feedback controlling the robot arm 3 to the target value is calculated based on the data and the signal from the encoder 7, and a drive signal for driving the motor 2 is generated and output to the motor 2. The motor drive circuit 4 and controller 5 constitute a control means 8.

Next, the operation will be explained, but first the basic principle of the present invention will be explained.

Generally, the angular transmission error (difference between the rotation angle of the theoretically rotated output shaft and the rotation angle of the actually rotated output shaft) in a planetary differential type reducer occurs in synchronization with the eccentric movement of the gear reduction mechanism. , this situation is shown in FIG. now,
For example, when the characteristics of the angular transmission error (θer) of the speed reducer 1 are analyzed in terms of frequency, it is expressed by the following equation (2).

θer= a sin θ+bsin 2θ+csin
3θ0dsin4θ0... ■ However, θ: Revolutionary rotation angle of external gear (planetary gear) a, bSc: Constant determined by the machining quality level of N-speed machine Here, it is expressed by the formula 0, and θer is Although the number of harmonics of the 5th order and above is included, as shown in Figure 3, which shows the level of each harmonic at θer, in actual equipment, harmonics of the 4th order and above can be ignored. Conceivable. Therefore, if the harmonic components up to the third order are added to one of the feedback control information in some form and corrected appropriately, when using a sensor that detects the input side data of the reducer in the same way as a conventional sensor. Even so, the angular transmission error can be brought close to rr O++ on the output side of the reducer.

Based on the above basic principle, in this embodiment, first, a control target value for the robot arm 3 is set by the controller 5, and then a feedback control process is performed so that the actual control value matches this target value.

The value is calculated, a drive signal is generated by the motor drive circuit 4, the motor 2 rotates, and the reducer 1 is driven. The detection data of the reducer l for feedback control is performed by detecting the input rotation angle of the motor 2, and this is taken into the motor drive circuit 4 as a pulse signal for each unit angle, for example. Conventionally, reduction gear 1 was
However, even if the model is the same, the control accuracy cannot be improved by uniform estimation due to differences in processing accuracy, etc.

On the other hand, in this embodiment, the data is synchronized with the increment pulse (ip/rev) from the encoder 7, that is, using this pulse edge as a trigger, the information from the memory 6 is sent to the speed reducer 1.
Data regarding the error θer is added to the motor drive circuit 4. In this case, the data in the memory 6 is created by measuring the characteristics of the reducer 1 for each model in advance, even if the model is the same, and is different from the estimated information described above, so the accuracy of the feedback control is It can be improved significantly.

In addition, the above embodiment does not require any special parts and can be made of ordinary parts, so there is an advantage that a simple structure is required.

Note that the above memory data is, for example, corrected to "0°."

Decelerate in the state [Measure the angular transmission error of 1, a, b of equation 0
, c and the point at which the angular transmission error begins to occur are detected. By doing so, data of a, b, c or one rotation of eccentric movement (or one rotation of the output shaft), that is, eccentric movement x reduction ratio, will be created in the memory, and these data will be used when actually operating. Therefore, a highly accurate correction operation is performed.

Although the above embodiment is an example in which the present invention is applied to a robot arm, the present invention is not limited to this, but can be widely applied to various machine tools, industrial machines, etc. Applicable to various types.

Furthermore, the data in the memory may be initially written only once, but in addition to this, the data may be updated by re-measuring as it changes over time, or data learning may be controlled to further improve accuracy. You may try to do so.

(Effects) According to the present invention, since the power transmission error characteristic of the speed reducer is added to one of the control accuracy, it is possible to improve the accuracy of feedback control with a simple configuration.

[Brief explanation of the drawing]

1 to 3 are diagrams showing an embodiment of a control device for a planetary differential type reducer according to the present invention, and FIG. 1 is an overall configuration diagram thereof;
FIG. 2 is a graph showing the state of the error θer, and FIG. 3 is a graph showing frequency analysis of the error θer. DESCRIPTION OF SYMBOLS 1...Reducer, 2...Motor, 3...Robot arm, 4...Motor drive circuit, 5...Controller, 6 ... Memory (storage means), 7 ... Encoder, 8 ... Control means.

Claims (1)

[Claims] In the control device for the planetary differential type reducer, the driving force of the motor is controlled by a control means, the speed is reduced by the planetary differential type reducer, and transmitted to the output side, and a predetermined work is performed using the output side driving force. A storage means for storing power transmission error characteristics regarding deceleration of the planetary differential type reducer is provided, and the control means incorporates at least the output of the storage means into the input information for controlling the driving force of the motor to control the driving force of the motor. 1. A control device for a planetary differential type speed reducer, characterized in that the control device controls the speed reducer to perform a predetermined work.