JP5617437B2 - Industrial equipment rotary joint control device - Google Patents

Description

  The present invention relates to a technique related to an arm of an industrial robot, and more particularly to arm drive control.

  The arm of an industrial robot is typically operated by shifting drive torque generated by an electric motor with a transmission to transmit rotational power (rotational power) to the arm. Transmission of rotational power between the arm and the transmission is transmitted by a fastening structure that mechanically connects the arm and the transmission. Conventionally, the design specification of the fastening structure assumes a state (worst case) in which the maximum torque, which is the maximum torque applied to the fastening structure within the operation range assumed in advance, is applied to the drive torque of the electric motor. It was set on the assumption that a torque limit was provided. The torque limit protects the industrial robot from excessive torque and realizes a weight reduction of the structure of the industrial robot such as a fastening structure.

JP-A-6-190770

  However, the present inventor has found that the state in which the maximum torque is applied to the fastening structure (worst case) occurs during braking (deceleration) of the arm, and the fastening structure is used during driving of the arm (during acceleration). It has been found that the applied torque is significantly smaller than that during braking. According to this knowledge, the characteristics such as the structural strength and rigidity of the fastening structure are not fully utilized when the arm is driven.

  The present invention has been created to solve the above-described conventional problems, and in torque control for supplying torque to a rotational load using a transmission, detection of a torque supply state such as a driving state or a braking state is detected. It aims to make it possible. If such detection becomes possible, it is possible to limit the torque according to the supply state of the torque and to fully utilize the characteristics such as the structural strength and rigidity of the fastening structure, and to detect other problems such as failure detection of the rotary joint control device. It can also be used for purposes.

  Hereinafter, effective means for solving the above-described problems will be described while showing effects and the like as necessary.

Means 1. A rotary joint control device for industrial equipment that controls torque generated by a rotary joint device that supplies rotational power to a rotational load,
The rotary joint device includes a drive torque generating unit that generates a drive torque, an input shaft that inputs the drive torque, and an output shaft that outputs the rotational power of the rotational speed shifted at a predetermined rotation ratio with a predetermined efficiency. A transmission having a torque transmission structure for transmitting an output side torque that is a torque transmitted from the output shaft to the rotational load;
A driving state in which the transmission is supplied with rotational power from the input shaft and outputs the rotational power to the output shaft at the predetermined efficiency; and the transmission is configured to transmit rotational power from the output shaft. A transmission state determination unit that determines at least one of two transmission states: a braking state that is a transmission state that receives supply and outputs rotational power to the input shaft at the predetermined efficiency;
The transmission state determination unit, based on a comparison between the lossless torque obtained by dividing the drive torque by the rotation ratio and the output side torque, when the output side torque is smaller than the lossless torque, And when the output side torque is larger than the lossless torque, the braking state is determined,
The output-side torque is calculated using a product of a rotation acceleration of the input shaft, the rotation ratio, and an inertia moment of the rotation load.

  The means 1 compares the output-side torque and the lossless torque, so that the rotational joint device is driving the rotational load, and the braking state (brake state) in which the rotational joint device is braking the rotational load. Is determined. The output side torque is calculated using the product of the rotation acceleration and rotation ratio of the input shaft and the inertial moment of the rotation load, and the lossless torque is calculated by dividing the drive torque generated by the drive torque generator by the rotation ratio. Therefore, there is no need to provide a sensor for measuring the output side torque on the output shaft, and simple mounting can be realized. As a result, the driving state and the braking state (braking state) can be easily discriminated, so that the state of the controlled object can be accurately detected and used for detecting the failure of the rotary joint control device and improving the control performance. Note that the determination content may be either the driving state or the braking state, or both the driving state and the braking state.

  Mean 2. When it is determined that the rotary joint device is in the driving state, the driving torque is limited by a driving torque limit value that is larger than a braking torque limit value that is a torque limiting value in the braking state. The rotary joint control device according to claim 1, further comprising a torque limiting unit.

  In the means 2, since the driving torque is limited in the driving state with a torque limit value larger than that in the braking state, the torque limitation in the driving state can be relaxed. The relaxation of the torque limitation is realized by paying attention to the fact that in the driving state, the driving torque (motor torque in the embodiment) is transmitted to the torque transmission structure while being attenuated by the loss in the transmission. . The driving state is a state in which the transmission receives supply of rotational power from the input shaft, and rotational power is output to the output shaft with a predetermined efficiency. Thereby, the output range of the driving torque of the rotary joint device that supplies the rotational driving force can be expanded. The rotation ratio is the ratio of the rotational speeds of the input shaft and the output shaft, and has a broad meaning including a reduction ratio and a speed increase ratio. The torque limit value is generally set as a value that allows the transmission of torque by the torque transmission structure.

  The present invention was created based on the following findings by the inventors. If the torque limit of the driving torque generated by the driving torque generator is a constant value, the braking state, that is, the state where the rotational power is regenerated in the transmission while decelerating the rotational load becomes the design standardized state. This is because the braking torque (negative driving torque) generated in the driving torque generator is minimized when the torque transmission structure generates the maximum torque in the specification. If an allowable value (torque limit) of the drive torque is set based on the design standardized state, torque exceeding the design specification is not applied to the torque transmission structure within the operation range assumed in advance. Become.

  However, in the state where the driving state, that is, the driving torque is supplied to the transmission device and the rotational load is increased, the inventor sets the design specification for the torque transmission structure even if the driving torque exceeds the above limit value. It has been found that no torque exceeding is applied. Depending on the characteristics of the transmission, a relatively small braking torque (negative driving torque) is regenerated in the braking state relative to the torque in the torque transmission structure. This is because a relatively large driving torque is required.

  The characteristics of the transmission are characterized by a transmission function of receiving rotational power (working power) and outputting rotational power at a predetermined efficiency by changing the rotational speed. This transmission function works in both directions, but has a characteristic that a loss always occurs at the destination of the rotational power. Furthermore, in general, the predetermined efficiency means the torque transmission efficiency in the transmission, and since there is no loss (efficiency) in the rotational speed, a torque that is reduced with respect to the input torque is output. Means.

Means 3. The drive state is determined when the output side torque is smaller than a first threshold value that is smaller than the lossless torque and larger than a product of the predetermined efficiency and the lossless torque. ,
The braking state is when the output side torque is larger than a second threshold that is set in advance as a value that is larger than the lossless torque and smaller than the product of the inverse of the predetermined efficiency and the lossless torque. The rotary joint control apparatus according to means 1 or 2 to be determined.

  In the means 3, the driving state is determined when the output side torque is smaller than the first threshold value which is set in advance as a value smaller than the lossless torque and larger than the product of the predetermined efficiency and the lossless torque. . The meaning of “determine the drive state when the output side torque is smaller than the lossless torque” of the means 1 means that the first efficiency is set between the product of the predetermined efficiency and the lossless torque and the lossless torque. It has a broad meaning including a configuration in which comparison is made with a threshold value of 1 as a reference. On the other hand, for example, the closer the first threshold value is to the product of the predetermined efficiency and the lossless torque, the harder it is to determine the driving state. Therefore, the setting of the first threshold value can improve the determination reliability of the driving state. Design flexibility can be provided.

  On the other hand, the braking state is determined when the output side torque is larger than a second threshold that is set in advance as a value that is larger than the lossless torque and smaller than the product of the reciprocal of the predetermined efficiency and the lossless torque. . The meaning of “meaning that the braking state is determined when the output side torque is larger than the lossless torque” of the means 1 is set between the product of the reciprocal of the predetermined efficiency and the lossless torque and the lossless torque. Further, it has a broad meaning including a configuration in which the second threshold is used as a reference. On the other hand, for example, the closer the second threshold is to the product of the reciprocal of the predetermined efficiency and the lossless torque, the more difficult it is to determine the braking state. Therefore, the setting of the second threshold increases the determination reliability of the braking state. It is possible to provide design flexibility such as

Means 4. An inertia moment estimator that measures the rotational acceleration of the rotational load by operating the drive torque with respect to the rotational load, and estimates the inertia moment of the rotational load based on the drive torque and the measured rotational acceleration With
The rotary joint control device according to any one of means 1 to 3, wherein the transmission state determination unit determines the transmission state based on the estimated moment of inertia.

  The means 4 can estimate the moment of inertia of the rotational load based on the measured rotational acceleration and driving torque of the rotational load, and can determine the torque limit value based on the estimated value. A torque limit value can be automatically determined for the device. Thereby, the simple mounting of this invention can be enabled.

  The present invention can be realized not only in a rotary joint control device but also in the form of a torque control method, a computer program for realizing torque control, a recording medium for storing the program, and the like.

The front view which shows the outline | summary of the robot apparatus of embodiment. Sectional drawing which shows the internal structure in the joint part of the robot apparatus of embodiment. The functional block diagram which shows the content of the drive control of a robot apparatus. The schematic diagram and table | surface which show the transmission state of the driving force in forward transmission. The schematic diagram and table | surface which show the transmission state of the driving force in reverse transmission.

  Hereinafter, an embodiment in which the present invention is embodied as a vertical articulated robot will be described with reference to the drawings. The robot of this embodiment is used in an assembly system such as a machine assembly factory as an industrial robot device, for example.

(Robot device configuration)
FIG. 1 is a front view illustrating an outline of the robot apparatus according to the embodiment. The robot apparatus 10 is a six-axis robot, and has a first axis J1, a second axis J2, a third axis J3, a fourth axis J4, a fifth axis J5, and a sixth axis J6 as rotation center axes. Yes. In the present embodiment, the robot apparatus 10 is installed at a robot installation location such as a floor so that the first axis J1 extends in the vertical direction. In the following description, the vertical direction in FIG. 1 indicates the vertical direction.

  The main components of the robot apparatus 10 are as follows. The robot apparatus 10 includes a base 11 that is fixed to the floor, a lower arm 15, an upper arm 16, a wrist portion 17, and a hand portion 18. The base 11 has a fixed portion 11A and a rotating portion 11B that are connected to each other so as to be rotatable around the first axis J1. The upper arm 16 is divided into two arm portions, ie, a first upper arm 16A on the base end side and a second upper arm 16B on the distal end side that are connected to each other so as to be rotatable about the fourth axis J4. Configured. The proximal first upper arm 16 </ b> A is connected to the lower arm 15. The second upper arm 16 </ b> B on the distal end side is connected to the wrist portion 17.

  Each component of the robot apparatus 10 is rotatably connected as follows. The robot apparatus 10 is fixed to a floor or the like by a fixing part 11 </ b> A of the base 11. A rotating part 11B is connected to the fixed part 11A so as to be rotatable in the horizontal direction (floor reference) about the first axis J1. The lower arm 15 is coupled to the rotating portion 11B so as to be rotatable in the vertical direction (floor reference) about the second axis J2. A first upper arm 16A on the base end side of the upper arm 16 is connected to the lower arm 15 so as to be rotatable in the vertical direction (floor reference) about the third axis J3. The second upper arm 16B on the distal end side is connected to the first upper arm 16A so as to be rotatable about the fourth axis J4. The wrist 17 is connected to the second upper arm 16B so as to be rotatable about the fifth axis J5. A hand portion 18 is connected to the wrist portion 17 so as to be rotatable about the sixth axis J6.

  Each axis J1-J6 of the robot apparatus 10 is connected to each servo motor (not shown) via a speed reduction mechanism. Below, the connection part (joint part) of the 2nd axis line J2 is illustrated and the detail is demonstrated.

  FIG. 2 is a cross-sectional view showing the internal structure of the connecting portion that connects the lower arm 15 and the rotating portion 11B. 2 corresponds to a cross-sectional view taken along line II-II in FIG. The lower arm 15 and the rotating portion 11B are connected by a bearing 50 so as to be rotatable relative to each other in the lower arm cover 15a. The rotating part 11B is rotatably connected to the fixing part 11A in the fixing part cover 11Ba.

  The connecting portion between the lower arm 15 and the rotating portion 11 </ b> B is configured as a connection that can be rotated by the bearing 50. That is, the lower arm 15 includes an arm frame 41 as a main structural member, and a plurality of bolts 42 that fasten the arm frame 41 to the inner ring 49 of the bearing 50. The rotating part 11 </ b> B includes a base frame 21 as its main structural member and a plurality of bolts 24 that fasten the base frame 21 to the two outer rings 29 a and 29 b of the bearing 50. Since the outer rings 29a and 29b and the inner ring 49 of the bearing 50 are rotatable relative to each other around the second axis J2, the lower arm 15 and the rotating portion 11B are also mechanically connected to each other so as to be rotatable relative to each other. become.

  The connecting portion between the lower arm 15 and the rotating portion 11B is supplied with a driving force for rotationally driving from the servo motor 51 via a speed reducer 30 called a harmonic drive (registered trademark). . The speed reducer 30 includes a wave generator 31 in which a ball bearing is assembled on the outer periphery of an elliptical cam, a thin cup-shaped flexspline (elastic gear) 32 disposed on the outside thereof, and a rigid body disposed on the outside thereof. An annular circular spline (internal gear) 33 is provided. The speed reducer 30 can drive the wave generator 31 to rotate by a servo motor 51 and transmit rotational power between the circular spline 33 and the flex spline 32 at a high reduction ratio. The circular spline 33 is fixed to the rotating part 11B side together with the servo motor 51.

  The torque transmission structure is configured as follows, for example, when the torque is transmitted to the lower arm 15 with the rotating portion 11B as a fixed reference. Since the flexspline 32 is connected to the arm frame 41 of the lower arm 15, the reduction gear 30 can transmit rotational power to the lower arm 15. The connection between the flexspline 32 and the arm frame 41 is to fasten the inner ring 49 of the bearing 50, the mounting member 45 that fastens the inner ring 49 and the flexspline 32, a plurality of bolts 44, and the inner ring 49 and the arm frame 41. It comprises a plurality of bolts 42.

  On the other hand, the rotation part 11B as a fixed reference functions as a torque transmission structure that receives torque received by the circular spline 33 as a reaction of torque transmitted from the flexspline 32 to the lower arm 15. Since the circular spline 33 is connected to the base frame 21 of the rotating part 11B, the speed reducer 30 can transmit rotational power to the rotating part 11B. The connection between the circular spline 33 and the base frame 21 includes a metal motor plate 23 having an annular shape, a plurality of bolts 22 fastening the motor plate 23 to the base frame 21, and a motor plate. And a plurality of sets of stud bolts 25 and nuts 26 that fasten a circular spline 33 to 23.

  On the other hand, the servo motor 51 is fixed to the motor support base 52, the stepped shape of the motor plate 23 is fitted into the hole of the motor plate 23, the circular spline 33 of the speed reducer 30 and the servo motor 51 This is realized by fastening with a fastening structure 28 so as to sandwich the plate 23. The circular spline 33 is fastened to the motor plate 23 by stud bolts 25 and nuts 26.

  As described above, the lower arm 15 and the rotating portion 11B are connected so as to be rotatable, and can transmit the rotational power in which the driving force of the servo motor 51 is reduced by the speed reducer 30 to become high torque. It is said that. The reduction ratio is a rotation ratio of the rotational driving force of the servo motor 51 and the rotational power generated between the circular spline 33 and the flex spline 32.

(Control of robotic devices)
FIG. 3 is a functional block diagram showing the content of drive control around the second axis J2 of the robot apparatus 10. The purpose of the control is within a range in which the driving torque generated between the lower arm 15 and the rotating part 11B does not exceed the allowable torque (torque limit) allowed for the connecting part of the lower arm 15 and the rotating part 11B. This is to bring the relative angle close to the target value θ given from the outside. The relative angle is an angle between the lower arm 15 and the rotating portion 11B. The allowable torque is a torque set as a mechanical specification of the connecting portion between the lower arm 15 and the rotating portion 11B. In other words, the connecting portion between the lower arm 15 and the rotating portion 11B is set with mechanical strength and rigidity assuming an allowable torque.

  The control target has an inertial mass, an output stage 83 that generates torque due to gravity, and a fastening member B that transmits a high driving torque (low rotational speed) from the speed reducer 30 to the output stage 83; A fastening member A that transmits a low driving torque (high rotational speed) to the speed reducer 30 and a motor 51 that supplies the fastening member A with a low driving torque are included. The high driving torque of the fastening member B is supplied from the speed reducer 30 as a torque that acts on a connecting portion between the rotating portion 11B fixed to the floor and the lower arm 15 as a free end.

  The output stage 83 includes a lower arm 15, an upper arm 16, a wrist portion 17, and a hand portion 18. When the hand unit 18 holds an object (not shown), the output stage 83 includes the object. The output stage 83 has a physical property that the moment of inertia does not change by the rotational driving around the second axis J2, and the torque caused by gravity changes. However, the moment of inertia of the output stage 83 varies depending on the rotation angle of the other axes J1, J3, J4, J5, and J6. This is because the moment arm around the second axis J2 of the output stage 83 varies.

  The fastening member B has a structure for connecting the flexspline 32 and the arm frame 41, an inner ring 49 of the bearing 50, a mounting member 45 for fastening the inner ring 49 and the flexspline 32, a plurality of bolts 44, and an inner ring 49. A plurality of bolts 42 for fastening the arm frame 41 are provided.

  The fastening member A includes a fastening structure 28 having bolts fastening the wave generator 31 of the speed reducer 30 and the rotation shaft (not shown) of the servo motor 51, and a motor plate that fastens the servo motor 51 to the base frame 21. 23. The motor plate 23 is configured as a structural member that functions as both the fastening member A and the fastening member B.

  However, since the rotation of the servo motor 51 is generally decelerated at a large reduction ratio (for example, 1/100) in the robot apparatus 10, the torque applied to the fastening member B is significantly larger than that of the fastening member A. become. Therefore, in general, the structural strength and rigidity of the fastening member B become the standard for the structural design of the connecting portion, and therefore, only the fastening member B needs to be considered from the viewpoint of driving torque.

  The motor 51 is a DC servo motor and generates drive torque in response to power supply from the power supply device 72. The current command value Ti is given from the control unit 71. The control unit 71 determines the current command value Ti based on a control law set in advance based on the current value supplied from the power supply device 72 to the motor 51 and the rotational speed of the motor 51. On the other hand, the motor 51 generates regenerative power when the output stage 83 is braked (during braking). The regenerative power is processed by a regenerative resistor (not shown) of the power supply device 72, for example. The current value supplied to the motor 51 can be used as an armature current that is proportional to the drive torque of the motor 51. The armature current has a current sensor (not shown) included in the power supply device 72.

  The control unit 71 has current / torque value conversion table data (not shown) representing the correspondence between the current value supplied to the motor 51 and the driving torque of the motor 51. The transmission state determination unit 71a can estimate the drive torque based on the current / torque value conversion table data and the current value measured by the current sensor.

  FIG. 4 is an explanatory diagram showing a state of transmission of rotational power when the output stage 83 is rotationally driven by the driving torque generated by the motor 51. FIG. 4A is a conceptual diagram showing a state of transmission of rotational power focusing on the reduction gear 30. FIG. 4B is a table T <b> 1 showing a driving torque applied to the fastening member A, an output side torque applied to the fastening member B, and a torque transmission state by the speed reducer 30. In this transmission state, the motor 51 supplies about 1000 W of rotational power (power) to the reduction gear 30. A state where rotational power is transmitted from the motor 51 to the output stage 83 via the speed reducer 30 is called a forward transmission state. The forward transmission state is also called a driving state. In order to make the explanation easy to understand, in FIG. 4 and FIG.

  In this transmission state, for example, as shown in Table T1, the reduction gear 30 is supplied with rotational power (about 1000 W) with a torque of 10 Nm at a rotational speed of 1000 rpm from the motor 51 via the fastening member A. On the other hand, the speed reducer 30 supplies a rotational power (about 700 W) with a torque of 700 Nm to the output stage 83 via the fastening member B at a rotational speed of 10 rpm. In other words, the reduction gear 30 is supplied with rotational power of 700 Nm of torque at a rotational speed of 10 rpm.

  The efficiency of the speed reducer 30 coincides with the torque loss because a loss of the rotational speed does not occur in a mechanism that does not involve a slip such as a harmonic drive (registered trademark) using a gear. Therefore, in the reduction gear 30 with an efficiency of 70%, the ratio to the torque increased based on the reduction ratio is obtained. That is, when the theoretical torque is increased 100 times with a reduction ratio of 1/100 to a torque of 1000 Nm, 70% of 700 Nm is output.

  In other words, the characteristics of the speed reducer 30 are characterized by a transmission function of receiving rotational power (power) and outputting rotational power at a predetermined efficiency by changing the rotational speed. This transmission function works in both directions, but has a characteristic that loss always occurs on the output side (the side on which the transmission supplies rotational power). Furthermore, the predetermined efficiency means the torque transmission efficiency in the transmission, and since there is no loss (efficiency) in the rotational speed, it means that a torque that is reduced with respect to the input torque is output. It is.

  The controller 71 operates the drive torque of the motor 51 so that the output side torque of the fastening member B does not exceed the allowable torque (torque limit) during forward transmission. Since the driving torque of the motor 51 can be measured based on the armature current of the motor 51, for example, in this example, assuming that the allowable torque of the fastening member B is 700 Nm, the driving torque of the motor 51 is 10 Nm. It is sufficient to control so as not to exceed. That is, the current command value Ti may be set with the upper limit of the current value Tin that causes the motor 51 to generate a torque of 10 Nm. Thus, in the forward transmission state (driving state), if the current value Tin is set as the upper limit, the transmission torque of the fastening member B can be controlled so as not to exceed 700 Nm.

  FIG. 5 is an explanatory diagram showing a transmission state of the braking power when the motor 51 is rotated by the braking torque generated by the braking (braking) of the output stage 83. In this transmission state, as shown in Table T2, for example, the output stage 83 supplies 1500 W of rotational power (power) to the speed reducer 30, and 1000 W of power is regenerated from the speed reducer 30 to the motor 51. Yes. As described above, the state in which the braking torque is transmitted from the output stage 83 to the motor 51 via the speed reducer 30 is called a reverse transmission state. The reverse transmission state is also called a braking state.

  The controller 71 operates the driving torque (braking torque) of the motor 51 so that the output side torque of the fastening member B does not exceed the allowable torque during reverse transmission. In this example, as shown in Table T3, for example, assuming that the allowable torque of the fastening member B is 700 Nm, the driving torque (braking torque) of the motor 51 must be controlled so as not to exceed 4.9 Nm. It will not be. In other words, the current command value Ti must be set with the current value Tir that causes the motor 51 to generate a driving torque (braking torque) of 4.9 Nm as an upper limit, assuming a reverse transmission state. Thus, in the reverse transmission state (braking state), unless the excessively low current value Tir is set as the upper limit, the transmission torque of the fastening member B will exceed 700 Nm.

  As described above, if the upper limit of the current command value Ti is set assuming both the forward transmission state and the reverse transmission state, the driving torque (braking torque) of the motor 51 must be controlled so as not to exceed 4.9 Nm. It will not be. In the forward transmission state, a loss is generated in the output side torque of the fastening member B, which is the standard for torque limitation, whereas in the reverse transmission state, the drive torque (braking torque) received by the motor 51 is lost. It is because it has occurred. Thus, in the forward transmission state, even if the torque of the motor 51 reaches 10 Nm, the fastening member B has sufficient strength and rigidity (equivalent to 700 Nm for the fastening member B), but 4.9 Nm. It has been found by the present inventor that the upper limit (corresponding to about 350 Nm for the fastening member B) is the upper limit.

  In order to solve such a problem, it is usual to equip the fastening member B with a torque sensor. However, the provision of the torque sensor complicates the configuration of the robot apparatus 10 and causes an increase in size and cost. Has the problem of becoming. However, the present inventor has succeeded in creating a new method for solving the above-described problem only by changing the control law of the control unit 71, that is, only by rewriting software, without providing a new torque sensor. .

順伝達判定式Ｆ１は、順伝達状態であることを判定するために使用される判定式である。順伝達判定式Ｆ１の左項は、減速機３０が無損失（効率１００％）で作動すると仮定したときの無損失トルクの大きさ（絶対値）を算出する式である。無損失トルクは、たとえば１／１００の減速比では、モータトルクの１００倍のトルクとなる。順伝達判定式Ｆ１の右項は、出力段トルクの大きさの推定値である。出力段トルクの大きさは、出力段８３の慣性質量Ｉとモータ５１の回転加速度αと減速比の逆数とを使用して、その積として算出される。出力段８３の慣性質量Ｉは、予め取得しておいた値である。 (Method of judging the transmission status)
Determination formulas F1 and F2 shown below are used in a transmission state determination method.

The forward transmission determination formula F1 is a determination formula used to determine that the forward transmission state is set. The left term of the forward transmission determination formula F1 is an equation for calculating the magnitude (absolute value) of the lossless torque when it is assumed that the speed reducer 30 operates without loss (efficiency 100%). The lossless torque is, for example, 100 times the motor torque at a reduction ratio of 1/100. The right term of the forward transmission determination formula F1 is an estimated value of the magnitude of the output stage torque. The magnitude of the output stage torque is calculated as a product of the inertia mass I of the output stage 83, the rotational acceleration α of the motor 51, and the reciprocal of the reduction ratio. The inertia mass I of the output stage 83 is a value acquired in advance.

  The forward transmission determination formula F1 is determined using the fact that a loss occurs on the output stage torque side (fastening member B side) in the forward transmission state. Specifically, for example, in the robot apparatus 10 using the speed reducer 30 with a reduction ratio of 1/100, if the motor torque is 10 Nm, the magnitude of the lossless torque is calculated as 1000 Nm. On the other hand, the magnitude of the output stage torque becomes a value close to 700 Nm due to the loss of the speed reducer 30. The value of the output stage torque is calculated by the transmission state determination unit 71a of the control unit 71 using the differential value of the rotation speed of the motor 51 (see FIG. 4B).

  Thus, in the forward transmission state, the forward transmission determination formula F1 indicates that in the forward transmission state, the left term side is the output stage torque as lossless torque without loss, while the right term side is the actual output stage torque including loss. It is used as a judgment principle. According to this determination principle, in the example of Table T1, if the left term (1000 Nm)> the right term (700 Nm), the forward transmission state can be determined.

  On the other hand, the reverse transmission determination formula F2 is determined using the fact that a loss has occurred on the motor torque side (fastening member A side) in the reverse transmission state. Specifically, for example, in the robot apparatus 10 that uses the speed reducer 30 with a reduction ratio of 1/100, when the measured motor torque is 4.9 Nm, the lossless torque is large in the output stage. The height is 490 Nm. However, in the reverse transmission state, the measured motor torque is transmitted with an efficiency of 70% from the output stage, so the actual output stage torque is 700 Nm.

  Thus, the reverse transmission determination formula F2 determines that in the reverse transmission state, the left term side is the actual motor torque including loss, while the right term side is the output stage torque as lossless torque without loss. It is used as a principle. According to this determination principle, in the example of Table T3, if the left term (490 Nm) <the right term (700 Nm), the reverse transmission state can be determined.

  In order to make the determination formula F1 more reliable, the left term has a predetermined coefficient of 1 or less (for example, when the efficiency is 0.7, a value that is equal to or higher than the efficiency (for example, 0.8) is 1.0. You may make it determine using the threshold value (this threshold value is also called 1st threshold value) set by multiplying by a smaller value. In this specification, “lossless torque” means torque on the output stage side calculated from the motor torque on the assumption that the reduction gear 30 has transmitted the rotational power without loss. The closer the first threshold value is to the product of the predetermined efficiency and the lossless torque, the more difficult it is to determine the driving state. Therefore, the setting of the first threshold value allows design freedom such that the determination reliability of the driving state can be improved. Can provide the degree.

  On the other hand, in order to make the determination formula F2 more reliable, the left term has a predetermined coefficient of 1 or more (for example, when the efficiency is 0.7, a value less than the reciprocal of the efficiency (for example, 1.3) The threshold value (this threshold value is also referred to as a second threshold value) set by multiplying by a value smaller than 1.0) may be used. The closer the second threshold value is to the product of the reciprocal of the predetermined efficiency and the lossless torque, the more difficult it is to determine the braking state. Therefore, the setting of the second threshold value can increase the determination reliability of the braking state. Design freedom can be provided.

  Thereby, in this embodiment, in the driving state, the driving torque is limited by a torque limit value larger than that in the braking state, so that the torque limitation in the driving state can be relaxed. As a result, the output range of the drive torque of the motor 51 that supplies rotational power is expanded.

  The inertial mass I of the output stage 83 is considered to be available as a known value in a newly developed robot. For example, an automatic measurement function is provided for a robot after manufacture (including during operation). Is available.

  Specifically, for example, in a presumed driving range (range of angles of the axes J1 to J6), a short pulse (stepped or ramped) driving torque is applied to measure the rotational acceleration of the output stage 83. For example, the inertial mass I of the output stage 83 can be estimated from the measured rotational acceleration and the magnitude of the driving torque. Further, when the inertial mass I of the output stage 83 varies greatly in the operating state (angles of the respective axes J1 to J6), the inertial mass I of the output stage 83 can be used as a function of the operating state.

  Further, the verification of the transmission state determination can be easily realized, for example, by performing the following function confirmation test. In this function confirmation test, the output stage 83 is equipped with a plurality of accelerometers whose distances from the axis J2 are different from each other, or a gyroscope is mounted in the vicinity of the axis J2 so that the rotational state of the output stage 83 can be measured. It can also be done as a state.

  In this equipped state, for example, when a short pulse (stepped or ramped) driving torque is applied to the robot apparatus 10 to change from a stationary state to a rotating state (accelerated state), the braking state of the output stage 83 is not established. Since it is clear that the state quantity assumed on the assumption of the driving state is detected by the output stage 83, it can be confirmed that the operation is properly performed. On the other hand, for example, when the robot apparatus 10 is changed from the rotating state to the stationary state (decelerated state), it is clear that the output stage 83 is in the braking state. Is detected at the output stage 83, it can be confirmed that it is operating properly.

  Thus, this function confirmation test can be used as a test for confirming that one embodiment of the present invention is applied so as to exhibit its original effect. In addition, you may make it include the state which the hand part 18 grabbed the mass body (illustration omitted) assumed beforehand, and the separated state.

  As described above, the torque control method of the present embodiment can be easily mounted not only at the time of development of a new product but also at the product after delivery.

  The embodiment described above has the following advantages.

  In the present embodiment, it is possible to realize an operation that sufficiently utilizes the structural strength and rigidity (for example, the strength of the fastening member B) provided in the robot apparatus 10. This method can be implemented by changing the software without changing any hardware of the robot apparatus 10. Further, it can be easily mounted on a manufactured product.

(Other embodiments)
The embodiment is not limited to the above contents, and may be implemented as follows, for example.

  In the above embodiment, it is determined whether the state is the driving state or the braking state, and the maximum value of the current command value is changed based on the determination result. It may be used for failure detection and control performance improvement. In this determination, it is possible to discriminate between a driving state in which the rotary joint device is driving the rotational load and a braking state (brake state) in which the rotary joint device is braking the rotational load. This is because the state quantity can be accurately measured.

DESCRIPTION OF SYMBOLS 10 ... Robot apparatus, 11 ... Base, 11A ... Fixed part, 11B ... Turning part, 15 ... Lower arm, 16 ... Upper arm, 16A ... First upper arm, 16B ... Second upper arm, 17 ... Wrist part DESCRIPTION OF SYMBOLS 18 ... Hand part, 21 ... Base frame, 23 ... Motor plate, 30 ... Reduction gear, 41 ... Arm frame, 45 ... Mounting member, 50 ... Bearing, 51 ... Servo motor, 71 ... Control part, 71a ... Transmission state determination Part 72 ... power supply device 83 ... output stage.

Claims (4)

A rotary joint control device for industrial equipment that controls torque generated by a rotary joint device that supplies rotational power to a rotational load,
The rotary joint device includes a drive torque generating unit that generates a drive torque, an input shaft that inputs the drive torque, and an output shaft that outputs the rotational power of the rotational speed shifted at a predetermined rotation ratio with a predetermined efficiency. A transmission having a torque transmission structure for transmitting an output side torque that is a torque transmitted from the output shaft to the rotational load;
A driving state in which the transmission is supplied with rotational power from the input shaft and outputs the rotational power to the output shaft at the predetermined efficiency; and the transmission is configured to transmit rotational power from the output shaft. A transmission state determination unit that determines at least one of two transmission states: a braking state that is a transmission state that receives supply and outputs rotational power to the input shaft at the predetermined efficiency;
The transmission state determination unit, based on a comparison between the lossless torque obtained by dividing the drive torque by the rotation ratio and the output side torque, when the output side torque is smaller than the lossless torque, And when the output side torque is larger than the lossless torque, the braking state is determined,
The output-side torque is calculated using a product of a rotation acceleration of the input shaft, the rotation ratio, and an inertia moment of the rotation load.   When it is determined that the rotary joint device is in the driving state, the driving torque is limited by a driving torque limit value that is a torque limiting value that is larger than a braking torque limit value that is a torque limiting value in the braking state. The rotary joint control device according to claim 1, further comprising a torque limiting unit. The drive state is determined when the output side torque is smaller than a first threshold value that is smaller than the lossless torque and larger than a product of the predetermined efficiency and the lossless torque. ,
The braking state is when the output side torque is larger than a second threshold that is set in advance as a value that is larger than the lossless torque and smaller than the product of the inverse of the predetermined efficiency and the lossless torque. The rotary joint control device according to claim 1, wherein the rotary joint control device is determined. An inertia moment estimator that measures the rotational acceleration of the rotational load by operating the drive torque with respect to the rotational load, and estimates the inertia moment of the rotational load based on the drive torque and the measured rotational acceleration With
The rotary joint control device according to claim 1, wherein the transmission state determination unit determines the transmission state based on the estimated moment of inertia.

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