JPS61102187A - Method of detecting load torque of actuator using reduction gear - Google Patents

Abstract

PURPOSE:To accurately detect a load torque by storing in advance the twisting characteristic of a machine system which has a reduction gear, and reading out data of a memory while detecting the twisting angle at real operation time. CONSTITUTION:A twisting characteristic between a motor shaft 4 and an output shaft 5 is stored in advance in a memory 18. When a motor M is operated, the load torque of an actuator always varies in accordance with the operating state. Accordingly, the relative twisting angle of the motor shaft 4 and the shaft 5 is detected by a subtractor 13. A computer MPU22 compares to collate the data of the torque with respect to the twisting angle read out from the memory 18 and the data of twisting angle input from the subtractor 13 to obtain the present load torque of the actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a load torque detection method suitable for use in an actuator incorporating a reduction gear.

[Background of the invention]

A method for detecting torsion in a mechanical system including a speed reducer is conventionally known as disclosed in Japanese Patent Application Laid-Open No. 54-31877. However, the concept of actuator load torque has not yet been recognized. On the other hand, there is also known a method of incorporating vibrations of a mechanical system including an elastic body into a control circuit, as described in Japanese Utility Model Application Publication No. 57-89394 and Japanese Patent Application Publication No. 55-9264. However, unlike a reduction gear, no consideration is given to torque detection of nonlinear elements such as backlash.

[Purpose of the invention]

An object of the present invention is to provide a load torque detection method capable of detecting the torque of the output shaft of an actuator including a reduction gear having nonlinear torsional characteristics, and obtaining information that enables highly accurate speed control and position control of the actuator. Our goal is to provide the following.

[Summary of the invention]

The present invention measures and stores the torsional characteristics of the mechanical system including the motor and reducer in advance, and detects the torsional angle of the mechanical system including the reducer using a sensor that detects the rotation angle of the motor shaft and output shaft. The load torque is then detected by comparing this torsion angle with torsion characteristics stored in advance.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an actuator incorporating a reduction gear and its torque detection section. In FIG. 1, a motor MU is composed of a rotor 1 and a stator 2, and rotational torque is obtained by energizing the stator 2. The rotor 1 of the motor M is coupled with an encoder 7 for detecting the rotation angle of the motor shaft and an input shaft 4 of a reduction gear. The reduction gear used is a monolithic drive. A wave generator 24 is coupled to the input shaft 4 of this reducer, and a circular spline 23 of the harmonic drive is coupled and fixed to the frame of the actuator. As the wave generator 24 rotates, the flexspline 3 rotates while being decelerated. The flexspline 3 is connected to an output shaft 5 of the actuator, and the output shaft of the actuator is further connected to a load 6. Furthermore, an encoder 8 for detecting the rotation angle of the actuator is coupled to the output shaft 5 of the actuator.

The output signal of the encoder 7.8 installed on the motor shaft and the output shaft of the actuator is sent to the signal processing circuit 9.1.
0 respectively. The signal processing circuits 9 and 10 respectively process the output signals of the encoders 7.8 and convert them into a pulse train in the forward direction and a pulse train in the reverse direction. The signal passed through the signal processing circuit 9.10 is input to an up/down counter 11.12 which takes out a rotation angle signal of the motor shaft and a rotation angle signal of the output shaft. These two counters 11
, 12 are input to a subtracter 13, and the difference therebetween is determined. This makes it possible to know the twist angle between the motor shaft and the output shaft.

On the other hand, the memory 18 stores in advance the torsion characteristics between the motor shaft and the output shaft. The reason why memory is used here is that, for example, as shown in Figure 2, the torsional characteristics of the mechanical system, including the reducer, are nonlinear, and the conventional way of thinking about it as a simple spring constant does not provide sufficient torque detection accuracy. is.

This torsional characteristic is, for example, as shown in FIG.
7 is fixed, external torque ffi is applied to the output shaft of the reducer 27 via the torque pickup 30, and the output signal of the encoder 29 provided on the output shaft is sent to the up/down counter via the signal processing circuit 31. By further inputting the output signal of the torque pickup 30, the output signal of the 7-up down counter 32, and the total recorder 33, it is possible to easily measure the torsion characteristics with respect to the rotation angle.

The data obtained in this way is recorded in the memory 18 in advance. It should be noted that the data in the memory 18 is written as the torque value with respect to the torsion angle, contrary to that shown in FIG. This is because a digital memory such as ROM or RAM is used as the memory. When the motor M is operated in such a state, the load torque of the actuator constantly changes according to the operating condition. Therefore, the mutual relationship between the motor shaft and the output shaft 5 can be detected by the subtractor 13 as a relative torsion angle.

The relationship between the torsion angle and torque is nonlinear and has hysteresis characteristics, although there are some differences in mechanical systems including reduction gears, as shown in FIG. 3, for example. Therefore, in order to detect torque that changes from time to time, the torsion angle including the history of hysteresis shown in FIG. 3 must be known. Therefore, in the embodiment shown in FIG. 1, basically two types of data regarding the torsional characteristics of the speed reducer are stored. That is, a curve 25 in the direction in which the torque increases and a curve 26 in the direction in which the torque decreases are recorded in the memory 18. Therefore, the torsion angle signal of the mechanical system including the reducer obtained from the subtracter 13 is taken into the computer (MPU) 22 through the parallel input/output circuit (PIA) 14. The MPU 22 constantly monitors the increase/decrease in the twist angle, that is, the increase/decrease in the output signal of the subtracter 13, and changes the address of the memory 18 to the parallel input/output circuit (PIA) according to the state change when the torque increases or decreases. ) 15, and data on one of the curves 25 and 26 in FIG. 2 is read out in response to the change in torque state. Then, the current load torque of the actuator is determined by comparing and collating the read torque data for the torsion angle with the torsion angle data taken in from the subtracter 13.

Note that the MPU 22 controls the operation of each of the circuit sections described above according to the program stored in the memory 7. In addition, the parallel input/output circuits (PIA) 14 to 16 are connected to the MPU2
When the address data outputted from the address bus No. 2 matches the device address previously assigned to the circuits 14 to 16, the circuits are enabled by the output signals of the corresponding address data 19 to 21, respectively. Furthermore, the torsion characteristic data stored in the memory 18 can be converted into an analog signal by the DA converter 34 and output as required.

In this way, in this embodiment, the torque for the torsion angle of the actuator that has been measured and stored in advance is compared with the actually detected torsion angle, thereby detecting the load torque of the actuator. Therefore, even if nonlinear elements are included, the load torque can be detected with high accuracy.

Now, in a reducer with a large reduction ratio, for example, a model with a reduction ratio of 1/100, such as a no-monik drive,
It is necessary to improve the resolution of the encoder 8 as a rotation angle sensor of the output shaft of the actuator compared to the resolution of the encoder 7 as an angle sensor of the motor shaft. For this reason, specifically, the resolution of the output shaft is set higher. For example, set the number of rotation pulses of the encoder 7 of the motor shaft to 5.
In an actuator with a 001 reduction ratio of 1/1oo, the rotation pulse of the output shaft is 5ooooo pulses, which are input to the subtracter at a ratio of 1:1.

Practically, the number of 16H pulses of 5oooo pulses is set, for example, 25,000 pulses or 12,500 pulses. At this time, the output pulse of the encoder 7 on the motor shaft is set to 1/! This will be set to 0 and input to the subtracter 13.

By the way, an encoder is used to detect the angle of the motor shaft and the output shaft. By using an encoder, it can be used in common with a torque detection sensor when controlling the position and speed of the actuator, and has the advantage that it can be obtained relatively inexpensively compared to other sensors.

In addition, digital memory such as ROM5 or RAM is used as the memory, which has the advantage of being able to accommodate reducers with various characteristics without changing the nodes used to detect torque. .

Additionally, nonlinear curves are switched.

This switching can be done by any means, but
In the embodiment described above, the MPU switches according to an increase or decrease in the twist angle. Switching from the MPU has the advantage that various operations such as initializing the twist angle can be performed freely.

On the other hand, in the memory 18, memory addresses and twist angles are associated with each other, and data values are stored as torque.

This is because it has the advantage of being able to be handled with simple software that changes the address for each twist angle. Further, the amount of data is written in the memory 18 with a resolution corresponding to the number of pulses of the encoder/coder 8 attached to the output shaft 5. This has the advantage that the memory capacity is the smallest and the detection speed is the fastest.

As described above, in the present invention, the torsional characteristics of the mechanical system including the reducer are memorized in advance, and the simple operation of reading out the data stored in the memory while detecting the torsional angle during actual operation is performed. The load torque of the actuator can be detected, and the load torque can be detected more accurately than before. This means that it is now possible to detect minute changes that were impossible to detect when considering the material as a simple linear elastic body as in the past.

Note that various modifications can be made to the embodiments described above. For example, it is possible to change the reduction gear from a harmonic drive to a planetary gear, change the motor type to a DC motor, or change from a machine/coder to a resolver for detecting torsion angles. Furthermore, the angle sensor can be installed in a machine driven by all actuators, and various hardware configurations can be used to read the stored data.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is an effect that the load torque of the actuator can be detected with high accuracy even if the mechanical system including the reduction gear has nonlinear torsional characteristics. Moreover, even if the mechanism configuration is the same, it has the advantage of being compatible with reduction gears having various characteristics, and has the excellent effect of realizing a system with high industrial utility value.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of a device to which the torque detection method of the present invention is applied, Fig. 2 is a torsional characteristic diagram of a mechanical system including a reducer, and Fig. 3 is a measurement method for measuring torsional characteristics. It is an explanatory diagram. DESCRIPTION OF SYMBOLS 1...Rotor, 2...Stator, 4...Output shaft of motor, 5...Output shaft of actuator, 6...Load, 7.8...Yuncoder, 13...Subtractor , 18
...Memory, 22...Computer.

Claims (1)

[Claims] 1. In a motor that generates torque and an actuator that connects the output of this motor to a load via a reduction gear,
A sensor for detecting the rotation angle of the output shaft of the motor, a sensor for detecting the rotation angle of the output shaft of the actuator, and a memory storing torsional characteristics of the mechanical system including the reduction gear are provided, and the two sensors An actuator characterized in that the load torque of the actuator is calculated by detecting the actual torsion angle including the mechanical system of the actuator based on the detection signal and comparing it with the torsion characteristics recorded in the memory. Load torque detection method. 2. Claims characterized in that an encoder coupled to the motor shaft is used as a sensor for detecting the rotation angle of the motor, and an encoder coupled to the load shaft is used as a sensor for detecting the rotation angle of the load shaft. The load torque detection method according to item 1. 3. The sensor according to claims 1 and 2, characterized in that the resolution of the sensor that detects the rotation angle of the actuator output shaft is higher than the resolution of the sensor that detects the rotation angle of the motor output shaft. Either load torque detection method. 4. The memory stores the torsion characteristics in a state where the load torque increases and the torsion characteristics in a state where the load torque decreases, and the torsion characteristics to be read out according to the state in which the load torque decreases or increases. A load torque detection method according to any one of claims 1 to 3, characterized in that the load torque detection method is changed.