JP7282648B2 - robot controller - Google Patents

Description

The present invention relates to a robot controller.

Conventionally, a control method for a robot system having a plurality of joints, in which a start position and a target position including an inertia matrix, a viscosity matrix, and a gravity matrix are based on a start position, a target position, a velocity prediction value, and a robot dynamics base parameter. After calculating the robot dynamics model in and based on the calculated robot dynamics model, calculating the optimum acceleration and deceleration that satisfy the conditions of the proportional relationship of the acceleration prediction value between each joint and the allowable peak torque of each joint , synchronous processing for matching the motion times of all joints (see Patent Document 1). With this control method, it is possible to obtain the optimum acceleration/deceleration of each joint that does not exceed the allowable peak torque (allowable value) of each joint of the robot system and that allows the operation to be completed in the shortest time, thereby shortening the operation time.

JP-A-2002-91572

In a robot having a plurality of axes to be controlled in Patent Document 1, a moment may be applied to a mechanical element such as a bearing of an operating axis due to the influence of the motion of other axes.

In this case, the method of Patent Document 1 controls the torque of each axis so that it does not exceed the allowable value, but does not take into account the moment generated in the bearings due to the operation of the other axes. Therefore, for example, when multiple axes are operated at high speed simultaneously, the moment applied to the bearing exceeds the allowable value (hereinafter referred to as "permissible moment"), which may cause problems such as failure of the bearing and shortening of its service life.

On the other hand, if the adherence to the allowable moment of the bearing is emphasized, it is possible to prevent bearing failure and shortened service life, but the operating time and work time (takt time) of the robot will increase significantly.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a robot control apparatus capable of preventing failure and shortening of the life of mechanical elements of each axis and suppressing an increase in operating time of the robot. intended to

A robot control device according to one aspect of the present invention is a robot control device that controls a robot having a plurality of axes, and includes an allowable moment in a machine element that supports the axes and a velocity moment generated in the machine element due to velocity. , a gravitational moment generated in the mechanical element due to gravity; and an acceleration calculator for calculating the acceleration in the second movement section of the axis based on the allowable torque in the drive source of the axis and the allowable moment in the mechanical element of the axis. and

According to this aspect, the speed of the shaft in the first motion segment is calculated based on the minimum speed reduction coefficient in the first motion segment of the shaft. As a result, the velocity moment generated by the velocity can be reduced, and the moment applied to the mechanical element can be made equal to or less than the allowable moment of the mechanical element. Also, the acceleration in the second motion section of the shaft is calculated based on the allowable torque in the drive source of the shaft and the allowable moment in the mechanical element of the shaft. As a result, the axis is accelerated or decelerated in the second motion zone, the speed of the axis is reduced only in the first motion zone where the moment applied to the mechanical element exceeds the allowable moment, and the axis is accelerated or decelerated in the second motion zone. It is possible to change the speed. Therefore, it is possible to prevent failure and shortening of the life of the mechanical elements of each axis in the robot, and to suppress an increase in the operation time of the robot.

In the aspect described above, the acceleration calculation unit calculates a first acceleration based on the allowable torque in the drive source of the shaft and a second acceleration based on the allowable moment in the mechanical element of the shaft. is adopted as the acceleration in the second motion section of the axis.

According to this aspect, the smaller one of the first acceleration and the second acceleration is adopted as the acceleration in the second motion section of the axis. As a result, the axis can be accelerated or decelerated at an acceleration that satisfies both the allowable torque of the drive source and the allowable moment of the mechanical element.

In the above-described aspect, the acceleration calculation unit is based on the moment obtained by subtracting the velocity moment generated in the mechanical element due to the speed and the gravitational moment generated in the mechanical element due to gravity from the allowable moment in the mechanical element of the shaft. to calculate the second acceleration.

According to this aspect, based on the moment obtained by subtracting the velocity moment generated in the machine element due to speed and the gravitational moment generated in the machine element due to gravity from the allowable moment in the machine element of the shaft, the second Acceleration is calculated. As a result, the acceleration that satisfies the permissible moment of the mechanical element can be easily obtained after or before a minute time from the start point of the acceleration calculation.

The above aspect further includes a speed command generator that generates a speed command for the second motion section of the shaft based on a plurality of accelerations calculated for each predetermined time period in the second motion section.

According to this aspect, the speed command for the second motion section of the shaft is generated based on a plurality of accelerations calculated every predetermined time in the second motion section. Thereby, the speed of the shaft can be changed by accelerating or decelerating the shaft with acceleration based on the allowable torque of the drive source and the allowable moment of the mechanical element over the second operation interval.

According to the present invention, it is possible to prevent failure and shortening of the life of the mechanical elements of each axis, and to suppress an increase in the operation time of the robot.

FIG. 1 is a configuration diagram schematically showing the configuration of a robot control system according to one embodiment. FIG. 2 is a configuration diagram schematically showing the configuration of the robot control device in one embodiment. FIG. 3 is a graph showing an example of velocities and moments of axes of a robot controlled by a virtual robot controller according to the conventional method. FIG. 4 is a graph showing an example of velocities of axes of a robot controlled by a robot controller in one embodiment. FIG. 5 is a graph showing an example of moments applied to the bearings of the axes of the robot controlled by the robot controller in one embodiment. FIG. 6 is a graph showing an example of motion sections of axes of the robot controlled by the robot control device in one embodiment. FIG. 7 is a graph showing another example of velocities of robot axes controlled by the robot controller in one embodiment. FIG. 8 is a graph showing another example of the moment applied to the bearing of the axis of the robot controlled by the robot controller in one embodiment. FIG. 9 is a flowchart showing a schematic operation of the robot control device according to one embodiment to generate a speed command for a constant speed section. FIG. 10 is a flow chart showing a schematic operation of the robot control device according to one embodiment to generate a speed command for an acceleration/deceleration interval.

Embodiments of the present invention are described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions should be determined by referring to the following description. In addition, it goes without saying that there are portions with different dimensional relationships and ratios between the drawings. Furthermore, the technical scope of the present invention should not be construed as being limited to this embodiment.

First, the configuration of a robot control system according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a configuration diagram schematically showing the configuration of a robot control system 100 according to one embodiment. FIG. 2 is a configuration diagram schematically showing the configuration of the robot control device 50 according to the first embodiment.

As shown in FIG. 1 , the robot control system 100 includes an articulated robot (hereinafter simply referred to as “robot”) R having multiple axes, and a robot control device 50 .

The robot R is, for example, an industrial robot called a 7-axis vertical articulated manipulator. The robot R has an arm shape whose axes are rotatably driven like joints. Specifically, a swivel base C2 is provided above the base C1 of the robot R so as to be swivelable about the first rotation axis J1. A first arm C3 is provided above the swivel base C2 so as to be swivelable about a second rotation axis J2. A second arm C4 is provided at the tip of the first arm C3 so as to be rotatable about a third rotation axis J3 orthogonal to the second rotation axis J2. A third arm C5 is provided at the tip of the second arm C4 so as to be rotatable around a fourth rotation axis J4 orthogonal to the third rotation axis J3. A fourth arm C6 is provided at the tip of the third arm C5 so as to be rotatable around the fifth rotation axis J5. A fifth arm C7 is provided at the tip of the fourth arm C6 so as to be rotatable about a sixth rotation axis J6 orthogonal to the fifth rotation axis J5. A tool fixing member C8 is provided at the tip of the fifth arm C7 so as to be rotatable about a seventh rotation axis J7 orthogonal to the sixth rotation axis J6. A welding torch C9 as a working tool is fixed to the tool fixing member C8, and the welding torch C9 rotates integrally with the tool fixing member C8. In the following description, the first rotating shaft J1 to the seventh rotating shaft J7 may be simply referred to as "shafts".

As shown in FIG. 2, the robot R incorporates a servomotor 10 as a drive source for rotating the swivel base C2. An output shaft 10 a of the servomotor 10 is connected to a reduction gear 11 . The first rotating shaft J1 is configured to interlock with the output shaft 11a of the speed reducer 11 by means of a belt 11b, and is fixed to the first arm C3. Also, the first rotating shaft J1 is supported by a mechanical element such as a bearing 15 . Therefore, when the output shaft 10a of the servomotor 10 rotates, the output shaft 11a of the speed reducer 11 is reduced by a predetermined reduction ratio in the speed reducer 11, and the output shaft 11a of the speed reducer 11 also rotates. Then, the swivel base C2 swivels according to the rotation of the first rotating shaft J1.

Further, the robot R incorporates a motor encoder 12 for detecting the rotation angle of the output shaft 10a of the servomotor 10. As shown in FIG. The motor encoder 12 is, for example, an incremental encoder, and outputs a pulse signal having a number of pulses corresponding to the rotation angle of the output shaft 10a of the servomotor 10. FIG. Similarly, the robot R incorporates a reduction gear encoder 13 for detecting the rotation angle of the output shaft 11 a of the reduction gear 11 . The speed reducer encoder 13 is, for example, an incremental encoder, and outputs a pulse signal having a number of pulses corresponding to the rotation angle of the output shaft 11 a of the speed reducer 11 .

Further, the robot R is provided with servo motors, reduction gears, bearings, rotating shafts, motor encoders, and reduction gear encoders corresponding to the first arm C3 to the fifth arm C7 and the tool fixing member C8, respectively. ing. Since these configurations are the same as the above-described servo motor 10, speed reducer 11, bearing 15, first rotary shaft J1, motor encoder 12, and speed reducer encoder 13 for the swivel base C2, the drawings and description thereof are omitted. omitted.

In this embodiment, the swivel base C2, the first arm C3 to the fifth arm C7, and the tool fixing member C8 all correspond to movable members that are driven according to the rotation of the shaft. Further, in the following description, these swivel base C2, first arm C3 to fifth arm C7, and tool fixing member C8 may be referred to as "movable members".

A robot controller 50 is connected to the base C1 of the robot R via a communication cable indicated by a dashed line in FIG.

The robot control device 50 is for controlling the motion of the robot R. As shown in FIG. As shown in FIG. 2 , the robot control device 50 includes an input interface 51 , a storage section 60 , a servo control section 70 and a main control section 80 . The robot controller 50 also includes a bus 52 configured to transmit signals and data between parts of the robot controller 50 .

The input interface 51 is an input interface from equipment external to the robot control device 50 . The input interface 51 is configured to receive data and signals from external equipment. The input interface 51 is connected to the motor encoder 12 and the reducer encoder 13 of the robot R.

The storage unit 60 is configured to store programs, data, and the like. The storage unit 60 includes, for example, a hard disk drive, a solid state drive, and the like. The storage unit 60 stores in advance various programs executed by the main control unit 80 and data necessary for executing the programs.

The storage unit 60 also stores an arm control sequence for controlling the turning motion of each of the movable members C2 to C8. For example, when rotating the first arm C3, the main control unit 80 performs various calculations according to this arm control sequence, and outputs a speed command Sn for rotating the output shaft 10a of the servomotor 10 to the target rotation angle. to generate This arm control sequence is generated by a speed command generator 85, which will be described later.

The servo control unit 70 is configured to supply electric power to each servo motor built in the robot R. As shown in FIG. For example, when controlling the servomotor 10, the servo control unit 70 applies a motor control voltage Vx with adjusted pulse frequency and pulse width to the servomotor 10 according to the speed command S1 input from the main control unit 80. Output. Similarly, the servo control unit 70 outputs the motor control voltage Vx adjusted according to the speed command Sn for the other servomotors.

The main control section 80 is configured to control the turning motion of each of the movable members C2-C8. Further, the main control section 80 is configured to implement each function described later by executing a program stored in the storage section 60 or the like. The main control unit 80 includes, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a processor such as an FPGA (Field Programmable Gate Array), a ROM (Read Only Memory), a RAM (Random A memory such as Access Memory) , and a buffer storage device such as a buffer.

Further, the main control unit 80 includes, as its functional configuration, a speed reduction coefficient calculation unit 81, a speed calculation unit 82, an acceleration calculation unit 83, and a speed command generation unit 85, for example.

The speed reduction coefficient calculation unit 81 calculates, based on the allowable moment in a mechanical element such as a bearing that supports the axes J1 to J7, the speed moment generated in the bearing due to speed, and the gravitational moment generated in the bearing due to gravity, It is configured to calculate a speed reduction coefficient αv.

The speed reduction coefficient αv is calculated, for example, by the following method. The moments applied to the mechanical elements supporting the axes J1-J7 of the respective movable members C2-C8 are classified into the following three types.
Acceleration moment Ma: Moment generated by acceleration Velocity moment Mv: Moment generated by velocity Gravitational moment Mg: Moment generated by gravity

The inventors of the present invention conceived of reducing the velocity moment Mv among these moments to keep the moment applied to the mechanical element below the allowable moment. Further, the inventors of the present invention found that the speed that satisfies the allowable moment of the mechanical element supporting the shaft can be calculated based on the speed reduction coefficient αv for reducing the speed moment Mv.

In the following description, the bearing 15 shown in FIG. 1 is used as an example of a mechanical element that supports the axes J1 to J7 of the movable members C2 to C8. As an example of the drive source in , the servomotor 10 and the speed reducer 11 shown in FIG. 1 are used.

Each of the acceleration moment Ma, velocity moment Mv, and gravitational moment Mg is generally a vector in a different direction. is represented by the following formula (1).
Mall=Ma+Mv+Mg (1)

In order for the moment applied to the bearing 15 to satisfy the allowable moment Ms of the bearing 15, the total moment Mall must be less than or equal to the allowable moment Ms. Therefore, the following formula (2) is established.
Mall≦Ms (2)

Equation (2) can be transformed into Equation (3) below using Equation (1) above.
Ma+Mv≤Ms-Mg (3)

Here, using the acceleration decrease coefficient αa and the speed decrease coefficient αv, the equation (3) is expressed by the following equation (4).
αa・Ma+αv・Mv≦Ms−Mg (4)

Further, when the motion in the section for which the velocity reduction coefficient αv is to be obtained is constant velocity, that is, the acceleration is zero, the acceleration moment Ma is zero. As a result, in the section of constant-speed operation, the above equation (1) is expressed by the following simplified equation (5).
Mall=Mv+Mg (5)

Therefore, from the equations (4) and (5), the speed decrease coefficient αv in the constant-speed operation section can be obtained by the following equation (6).
αv=(Ms−Mg)/Mv (6)

In Equation (6), the gravitational moment Mg is a function of the position of each axis J1-J7, specifically, the rotation angle θ of each axis J1-J7. The velocity moment Mv is a value proportional to the square of the velocity of each axis J1-J7. Moreover, since the specifications required for the bearing 15 differ for each axis, the allowable moment Ms generally has a different value for each bearing 15 .

The speed reduction coefficient calculation unit 81 calculates the allowable moment Ms in the bearing 15 of a certain axis, the speed moment Mv generated in the bearing 15 of the axis due to the speed of all seven axes, the positions of all seven axes, That is, it is preferable to calculate the velocity reduction coefficient αv using the gravitational moment Mg generated by the rotation angles θ1 to θ7. This makes it possible to obtain the minimum speed reduction coefficient αv more easily than when calculating the speed reduction coefficient αv for each of the axes J1 to J7.

The speed calculator 82 is configured to calculate the speed in the first motion section of the axes J1 to J7 based on the minimum speed reduction coefficient αv in the first motion section of the axes J1 to J7.

More specifically, the speed calculation unit 82 multiplies the speed based on the allowable torque in the driving sources of the axes J1 to J7, for example, the servomotor 10 and the speed reducer 11, by the square root of the minimum speed decrease coefficient αv to obtain the axis J1 It is configured to calculate the speed in the first operation section from J7 to J7.

The first operation section of the axes J1 to J7 is, for example, a section in which the axes J1 to J7 operate at a constant or substantially constant speed.

Here, it is known that the velocity moment Mv is proportional to the square of the velocity. In other words, the square root of the velocity moment Mv is proportional to velocity. On the other hand, as described above, the speed moment Mv is proportional to the speed reduction coefficient αv. Therefore, the speed Vnew that satisfies the allowable moment of the bearing is expressed by the following equation (7) using the speed decrease coefficient αv and the (maximum) speed Vold that satisfies the allowable torque of the servomotor 10 and the speed reducer 11. .
Vnew=αv ^1/2 Vold (7)

In the present embodiment, the speed calculator 82 uses the smallest speed reduction coefficient among the plurality of speed reduction coefficients calculated at each of the plurality of positions in the first motion section as the speed reduction coefficient αv in Equation (7).

Thus, by calculating the speed in the first motion section of the axes J1 to J7 based on the minimum speed reduction coefficient αv in the first motion section of the axes J1 to J7, the speed moment Mv generated by the speed can be calculated as follows: It is possible to reduce the moment applied to the bearing 15 to the allowable moment Ms of the bearing 15 or less. Therefore, failure and shortening of the life of the bearings 15 of the axes J1 to J7 in the robot R can be prevented.

Further, the speed based on the allowable torque in the servomotor 10 and the speed reducer 11 of the axes J1 to J7 is multiplied by the square root of the minimum speed reduction coefficient αv to calculate the speed Vnew in the first operation section of the axes J1 to J7. Therefore, the speed Vnew that satisfies the allowable moment of the bearing 15 can be easily obtained from the above equation (7).

Incidentally, each of the axes J1 to J7 preferably operates at the calculated speed Vnew over the first operation section. As a result, as explained in the above formulas (5) and (6), it becomes unnecessary to consider the acceleration moment Ma, and the speed decrease coefficient αv can be easily calculated.

The acceleration calculation unit 83 calculates the second operation section of the axes J1 to J7 based on the allowable torque in the servomotors 10 and the reduction gears 11 of the axes J1 to J7 and the allowable moment Ms in the bearings 15 of the axes J1 to J7. is configured to calculate the acceleration in

More specifically, the acceleration calculator 83 calculates a first acceleration based on the allowable torque in the servomotors 10 and the speed reducers 11 of the axes J1 to J7 and a second acceleration based on the allowable moment Ms in the bearings 15 of the axes J1 to J7. is calculated, and the smaller one of the first acceleration and the second acceleration is adopted as the acceleration in the second motion section of the axes J1 to J7.

The second operation section of the axes J1 to J7 is, for example, a section in which the axes J1 to J7 are not at a constant or substantially constant speed, that is, a section in which the axes J1 to J7 are accelerated or decelerated to operate at a changed speed. is.

Further details of the acceleration calculator 83 will be described later.

The speed command generation unit 85 generates a speed command Sn (n is an integer from 1 to 7) based on the speed Vnew of the axes J1 to J7 calculated by the speed calculation unit 82 in the first operation section of the axes J1 to J7. is configured to generate A speed command Sn is generated for each of the axes J1 to J7, that is, for each of the movable members C2 to C8, and output to each servomotor. Further, the speed command generator 85 is configured to generate a speed command Sn based on the acceleration of the axes J1 to J7 calculated by the acceleration calculator 83 in the second motion section of the axes J1 to J7. there is

More specifically, the speed command generation unit 85 generates the speed command Sn for the second motion section of the axes J1 to J7 based on a plurality of accelerations calculated every predetermined time in the second motion section. It is configured.

Each function of the main control unit 80 can be realized by a program executed by a computer (microprocessor). Therefore, each function provided in the main control unit 80 can be realized by hardware, software, or a combination of hardware and software, and is not limited to either case.

In addition, when each function of the main control unit 80 is realized by software or a combination of hardware and software, the processing can be executed in multitasking, multithreading, or both multitasking and multithreading, It is not limited to either case.

Next, with reference to FIG. 3, the velocity command generated by the virtual robot controller 50' according to the conventional method will be described. Since the configuration of the robot control device 50' is substantially the same as that of the robot control device 50 described above, illustration and description thereof will be omitted. FIG. 3 is a graph showing an example of velocities and moments of axes J1-J7 of robot R controlled by a virtual robot controller 50' according to the conventional method. In FIG. 3, the horizontal axis is time, the left vertical axis is velocity, and the right vertical axis is moment. In FIG. 3, the solid line indicates the speed of the first rotating shaft J1, the dotted line indicates the moment applied to the bearing 15 of the fourth rotating shaft J4, and the dashed line indicates the allowable moment Ms of the bearing 15 of the fourth rotating shaft J4, for example, 2000 [ Nm], respectively.

As shown in FIG. 3, the robot control device 50' controls the motion of the robot R so that the speed of the first rotation axis J1 is constant, that is, constant speed in the motion interval T1'. The robot control device 50' calculates the maximum speed Vold that satisfies the allowable torque of the servomotor 10 and the speed reducer 11, and generates a speed command S1' as the speed of the first rotation axis J1 in the motion section T1'.

However, when a plurality of axes J1 to J7 of the robot R are simultaneously operated at high speed, a moment exceeding the allowable moment of the bearing 15 of the relevant axis may be applied due to the operation of the other axes. For example, as shown in FIG. 3, the moment applied to the bearing 15 of the fourth rotating shaft J4 in the motion section T1' of the first rotating shaft J1 is two points of the section Tb' and the section Td' of the bearing 15. It exceeds the allowable moment Ms.

Next, an example of robot control by the robot control device 50 according to one embodiment will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a graph showing an example of velocities of the axes J1 to J7 of the robot R controlled by the robot controller 50 in one embodiment. FIG. 5 is a graph showing an example of moments applied to the bearings 15 of the axes J1 to J7 of the robot R controlled by the robot controller 50 in one embodiment. In FIG. 4, the horizontal axis is time and the vertical axis is speed. In FIG. 5, the horizontal axis is time and the vertical axis is moment. In FIG. 4, the solid line represents the speed of the first rotation axis J1, and for reference, the dotted line represents the speed of the first rotation axis J1 controlled by the virtual robot controller 50'. In FIG. 5, the solid line represents the moment applied to the bearing of the fourth rotation axis J4, and the dashed line represents the allowable moment of the bearing 15 of the fourth rotation axis J4. The moment applied to the bearing 15 of the fourth rotating shaft J4 to be controlled is represented by a dotted line.

As shown in FIG. 4, the speed Vnew of the first rotating shaft J1 calculated based on the minimum speed change coefficient αv in the first operation section decreases to approximately 1.5 [rad/s]. As a result, the operating section T1 is longer than the operating section T1' shown in FIG.

On the other hand, as shown in FIG. 5, by reducing the speed Vnew of the first rotating shaft J1, the moment applied to the bearing 15 becomes 2000 [Nm] or less, which is the allowable moment Ms.

The minimum speed change coefficient αv when calculating the speed Vnew is, for example, preferably the smallest of the plurality of speed reduction coefficients αv calculated at each of the plurality of positions (time points) in the motion section T1. . As a result, for example, even if the moment applied to the bearing 15 in the motion section T1 changes rapidly as indicated by the dashed line in FIG. be able to.

Although FIGS. 4 and 5 show an example of calculating the speed Vnew of the first rotating shaft J1 based on the minimum speed change coefficient αv, the present invention is not limited to this. The first rotation axis J1 is a representative example, and the speed Vnew of each of the other axes J2 to J7 may be calculated based on the minimum speed change coefficient αv.

3 to 5 show an example in which the moment applied to the bearing 15 of the fourth rotation axis J4 exceeds the allowable moment Ms as a result of simultaneously operating a plurality of axes of the robot R at high speed, but the present invention is not limited to this. not something. In the axes J1, J2, J3, J5, J6, and J7 other than the fourth rotation axis J4, the moment applied to the bearing 15 may exceed the allowable moment Ms. At the axis, the moment applied to the bearing 15 may exceed the allowable moment Ms.

Here, as shown in FIG. 3, in the robot R controlled by the virtual robot control device 50' according to the conventional method, in the two sections Tb' and Td', the rotation of the fourth rotation axis J4 is The moment applied to the bearing 15 exceeds the allowable moment.

On the other hand, the robot controller 50 controls the operation including the interval Tb' and the interval Td' based on the minimum speed reduction coefficient αv so that the moment applied to the bearing 15 of the fourth rotating shaft J4 is equal to or less than the allowable moment. The speed is reduced over the entire section T1'.

Therefore, as shown in FIG. 4, the operation section T1 in which the speed is reduced is longer than the operation section T1' shown in FIG. As a result, the operation time and working time (takt time) of the robot R may increase significantly.

To solve this problem, the inventors of the present invention proposed that the operating section T1' shown in FIG. In the section Tb' and section Td' where the allowable moment in the mechanical element of the shaft exceeds the allowable moment, the speed moment Mv is reduced to make the moment applied to the mechanical element less than the allowable moment. .

Then, the inventors of the present invention, in order to reduce the speed according to the speed moment of the section Tb' and the section Td', of the operation section T1' shown in FIG. The idea was to accelerate or decelerate the axis in the interval. The inventors of the present invention also found that the acceleration when accelerating or decelerating the shaft can be calculated based on the allowable moment in the mechanical elements of the shaft and the allowable torque in the drive source of the shaft.

Next, another example of control of the robot by the robot control device according to one embodiment will be described with reference to FIGS. 6 to 8. FIG. FIG. 6 is a graph showing an example of motion sections of the axes J1 to J7 of the robot R controlled by the robot control device 50 in one embodiment. FIG. 7 is a graph showing another example of the velocities of the axes J1 to J7 of the robot R controlled by the robot controller 50 in one embodiment. FIG. 8 is a graph showing an example of moments applied to the bearings 15 of the axes J1 to J7 of the robot R controlled by the robot controller 50 in one embodiment. 6 and 7, the horizontal axis is time and the vertical axis is speed. In FIG. 8, the horizontal axis is time and the vertical axis is moment. In FIG. 6, the thick line represents the speed of the first rotation axis J1, and for reference, the dotted line represents the speed of the first rotation axis J1 of the robot R controlled by the virtual robot controller 50'. there is In FIG. 7, the thick line represents the speed of the first rotation axis J1 of the robot R controlled by another example of the speed command generated by the robot controller 50. In FIG. For reference, the dotted line indicates the speed of the first rotation axis J1 of the robot R controlled by the virtual robot controller 50′. The solid line represents the speed of the first rotation axis J1. In FIG. 8, the thick line indicates the moment applied to the bearing 15 of the fourth rotation axis J4 of the robot R controlled by another example of the speed command generated by the robot controller 50, and the dashed line indicates the moment applied to the bearing 15 of the fourth rotation axis J4. Each represents the allowable moment. For reference, the moment applied to the bearing 15 of the fourth rotation axis J4 of the robot R controlled by the virtual robot controller 50' is indicated by a dotted line, and is controlled by an example of the speed command generated by the robot controller 50. The solid line represents the moment applied to the bearing 15 of the fourth rotating shaft J4 of the robot R to be rotated.

As shown in FIG. 6, the robot controller 50 divides the motion section T1' shown in FIG. 3 into sections Ta to Te. Section Tb is a section corresponding to section Tb' shown in FIG. 3, and the speed of the first rotating shaft J1 is reduced. The speed Vnewb of the first rotating shaft J1 in the section Tb is calculated by the speed calculator 82 . Since the speed Vnewb in the section Tb is lower than the speed in the operation section T1', the section Tb is longer than the section Tb' shown in FIG. 3 (section Tb>section Tb'). Similarly, the section Td is a section corresponding to the section Td' shown in FIG. 3, and reduces the speed of the first rotating shaft J1. The speed Vnewd of the first rotating shaft J1 in the section Td is calculated by the speed calculator 82 . Since the speed Vnewd in the section Td is lower than the speed in the operation section T1', the section Td is longer than the section Td' shown in FIG. 3 (section Td>section Td'). Note that the section Tb and the section Td correspond to an example of the "first operation section" of the present invention.

On the other hand, in the section Ta located before the section Tb, it is necessary to decelerate the first rotation axis J1 in order to set the speed Vnewb of the first rotation axis J1 over the section Tb. Further, in the section Tc arranged between the section Tb and the section Td, the first rotation axis J1 needs to be accelerated in order to bring the first rotation axis J1 to the speed Vnew d over the section Td. Furthermore, in the section Te arranged after the section Td, it is desirable to accelerate the first rotating shaft J1 in order to operate at a speed as fast as possible without exceeding the allowable moment of the bearing 15 . Note that the section Ta, the section Tc, and the section Te correspond to an example of the "second operation section" of the present invention.

As shown in FIG. 7, in control by another example of the robot control device 50, the speed in the operation interval T1' shown in FIG. The speed in section T1' is reduced to speed Vnew d. Therefore, the control by another example of the robot control device 50 requires a longer operation time of the axis J1 than the control by the conventional virtual robot control device 50'. On the other hand, the control by another example of the robot control device 50 can suppress an increase in the operation time of the axis J1 compared to the control by the example of the robot control device 50 indicated by the solid line. takt time) can be shortened.

By calculating the acceleration of the axis J1 in the second operation section based on the allowable torque of the servomotor 10 and the speed reducer 11 of the axis J1 and the allowable moment Ms of the bearing 15 of the axis J1, As shown in FIG. 7, the speed of the shaft J1 is reduced to the velocities Vnew b and Vnew d only in the sections Tb and Td where the moment applied to the bearing 15 exceeds the allowable moment Ms. It is possible to change the speed of axis J1 by accelerating or decelerating. Therefore, an increase in the operating time of the robot R can be suppressed.

Further, by decreasing the speed of the shaft J1 to Vnew b in the section Tb and to Vnew d in the section Td, as shown in FIG. become.

Next, the operation of the robot control device according to one embodiment will be described with reference to FIGS. 9 and 10. FIG. FIG. 9 is a flowchart showing a schematic operation of the robot control device 50 according to one embodiment to generate a speed command for a constant speed section. FIG. 10 is a flow chart showing a schematic operation of the robot control device according to one embodiment to generate a speed command for an acceleration/deceleration interval.

(Constant speed section speed command processing S200)
For example, when generating the speed commands for the sections Tb and Td shown in FIG. 6, the main control unit 80 executes the constant speed section speed command processing S200 shown in FIG.

Note that, in the following description, an example of generating a speed command for the section Tb of the section Tb and the section Td shown in FIG. 6 will be used.

First, the speed reduction coefficient calculator 81 calculates speed reduction coefficients αv1, αv2, . ).

Next, the speed command generator 85 sets the subscript n of the speed command S to an initial value, for example, "1" (S202).

Next, the speed calculator 82 calculates the speed Vnew in the section Tb of the axes J1 to J7 based on the smallest one of the plurality of speed reduction coefficients αvm calculated in step S201 (S203). The axis for which the speed Vnew is calculated corresponds to the subscript n of the speed command S.

Next, the speed command generator 85 generates a speed command Sn based on the speed Vnew calculated in step S203 (S204).

Next, the speed command generator 85 updates the subscript n by adding, for example, "1" (S205).

Next, the speed command generator 85 determines whether or not the subscript n is equal to or less than the maximum value, ie, "7" or less in this embodiment (S206).

If the subscript n is less than or equal to "7" as a result of the determination in step S206, the speed calculator 82 and the speed command generator 85 repeat steps S203 to S206 until the subscript n becomes greater than "7".

As a result of the determination in step S206, if the subscript n is not "7" or less, that is, if the subscript n is greater than "7", the main control unit 80 terminates the constant speed section speed command processing S200.

In this way, for each of the axes J1 to J7, the speed Vnew in the section Tb of the axis is calculated based on the minimum speed reduction coefficient αvm, and the speed command Sn is generated.

(Acceleration/deceleration interval speed command processing S300)
For example, when generating the speed commands for the section Ta, section Tc, and section Te shown in FIG. 6, the main control unit 80 executes the acceleration/deceleration section speed command processing S300 shown in FIG.

In the following description, an example of generating a speed command for the section Tc of the axis J1 among the sections Ta, Tc, and Te of the axis J1 shown in FIG. 6 will be used.

First, the acceleration calculator 83 calculates the acceleration αtorq that satisfies the allowable torque in the servomotor 10 and the speed reducer 11 of the axis J1 (S301). Note that the acceleration αtorq corresponds to an example of the "first acceleration" of the present invention.

Next, the acceleration calculator 83 sets the acceleration subscript j to an initial value, for example, "1" (S302).

Next, the acceleration calculator 83 calculates the acceleration αmj that satisfies the permissible moment Ms in the bearing 15 of the axis J1 after a minute time Δt×subscript j from the start of the acceleration calculation (S303). Note that the start point of acceleration calculation in step S303, that is, the origin of the time axis is the start position of section Tc in the example of the present embodiment, and the velocity at that time is the velocity Vnew b of section Tb. Also, the acceleration αmj corresponds to an example of the "second acceleration" of the present invention.

Specifically, the acceleration calculator 83 calculates the acceleration αmj based on the acceleration moment Maj represented by the following equation (8).
Ma j = Ms - Mv new b - Mg j (8)

In equation (8), the velocity moment Mvnew b is the moment generated in the bearing 15 of the axis J1 due to the velocity Vnew b, and the gravitational moment Mg j is the moment the axis J1 is the moment generated in the bearing 15 of .

Thus, the acceleration moment Ma obtained by subtracting the velocity moment Mvnew b generated in the bearing 15 by velocity and the gravitational moment Mgj generated in the bearing 15 by gravity from the allowable moment Ms in the bearing 15 of the axis J1 By calculating the acceleration αm j based on j, the acceleration αm j that satisfies the allowable moment Ms of the bearing 15 can be easily obtained after a minute time Δt×subscript j from the start of the acceleration calculation.

Next, the acceleration calculator 83 compares the acceleration αtorq calculated in step S301 and the acceleration αmj calculated in step S303, and adopts the smaller one as the acceleration αj (S304). As a result, the axis J1 can be accelerated or decelerated at an acceleration αj that satisfies both the allowable torque of the servomotor 10 and the speed reducer 11 and the allowable moment Ms of the bearing 15 .

Next, the speed calculation unit 82 calculates the speed vj+1 after the lapse of minute time Δt×subscript j using the acceleration αj adopted in step S304 (S305). Note that the speed calculation unit 82 stores and saves the speed vj+1 calculated in step S305 in a memory or the like.

Velocity vj+1 is expressed by the following equation (9) using current velocity vj, acceleration αj adopted in step S304, and minute time Δt.
vj+1=vj+αj·Δt (9)

Note that the initial value (subscript j=1) at the current velocity vj is the velocity at the start position of section Tc in the example of the present embodiment, and is the velocity Vnewb of section Tb.

Next, the acceleration calculator 83 updates the subscript j by adding, for example, "1" (S306).

Next, the acceleration calculator 83 determines whether or not the value obtained by multiplying the minute time Δt by the subscript j (minute time Δt×subscript j) is equal to or less than the length of the section Tc (S307).

As a result of the determination in step S307, if the multiplied value is equal to or less than the length of section Tc, the acceleration calculator 83 and the speed calculator 82 repeat steps S303 to S307 until it becomes longer than the length of section Tc.

As a result of the determination in step S307, if the multiplied value is not equal to or less than the length of the section Tc, that is, if the multiplied value is greater than the length of the section Tc, the acceleration calculator 83 sets the acceleration subscript k to an initial value, such as "-1". is set (S308).

Next, the acceleration calculation unit 83 calculates the acceleration αmk that satisfies the allowable moment Ms in the servomotor 10 and the speed reducer 11 of the axis J1 a minute time Δt×subscript k before the acceleration calculation start time (S309 ). Note that the starting point of acceleration calculation in step S309, that is, the origin of the time axis is the end position of section Tc in the example of the present embodiment, and the velocity at that time is the velocity Vnew d of section Td. Also, the acceleration αmk corresponds to another example of the "second acceleration" of the present invention.

Specifically, the acceleration calculator 83 calculates the acceleration αmk based on the acceleration moment Mak represented by the following equation (10).
Mak=Ms-Mvnewd-Mgk (10)

In formula (10), the velocity moment Mvnew d is the moment generated in the bearings 15 of the axes J1 to J7 by the velocity Vnew d, and the gravitational moment Mgk is the moment of gravity at the position before the minute time Δt×subscript k. This is the moment generated in the bearings 15 of the axes J1 to J7.

Thus, the acceleration moment Ma obtained by subtracting the velocity moment Mvnew d generated in the bearing 15 by velocity and the gravitational moment Mgk generated in the bearing 15 by gravity from the allowable moment Ms in the bearing 15 of the axis J1 By calculating the acceleration αmk based on k, it is possible to easily obtain the acceleration αmk that satisfies the allowable moment Ms of the bearing 15 before the minute time Δt×subscript k from the start of the acceleration calculation. .

Next, the acceleration calculator 83 compares the acceleration αtorq calculated in step S301 with the acceleration αmk calculated in step S309, and adopts the smaller one as the acceleration αk (S310). As a result, the axis J1 can be accelerated or decelerated at an acceleration αk that satisfies both the allowable torque of the servomotor 10 and the speed reducer 11 and the allowable moment Ms of the bearing 15 .

Next, the speed calculator 82 calculates the speed vk−1 before the minute time Δt×subscript k using the acceleration αk adopted in step S310 (S311). Note that the speed calculator 82 stores the speed vk-1 calculated in step S311 in a memory or the like.

Velocity vk−1 is expressed by the following equation (11) using current velocity vk, acceleration αk adopted in step S310, and minute time Δt.
vk−1=vk−αk·Δt (11)

Note that the initial value (subscript k=-1) at the current velocity vk is the velocity at the end position of section Tc in the example of the present embodiment, and the velocity at that time is the velocity Vnew d of section Td.

Next, the acceleration calculator 83 subtracts, for example, "1" (adds "-1") from the subscript k to update it (S312).

Next, the acceleration calculator 83 determines whether or not the value obtained by multiplying the minute time Δt by the subscript k (the minute time Δt×the subscript k) is equal to or less than the length of the interval Tc (S313).

As a result of the determination in step S313, if the magnitude of the multiplied value is equal to or less than the length of the section Tc, the acceleration calculator 83 and the speed calculator 82 repeat steps S309 to S313 until it becomes greater than the length of the section Tc. .

As a result of the determination in step S313, if the magnitude of the multiplied value is not equal to or less than the length of the section Tc, that is, if the magnitude of the multiplied value is greater than the length of the section Tc, the speed command generation unit 85 generates the value stored in the memory or the like. A speed command S1 is generated based on the plurality of speeds vj+1 and the plurality of speeds vk-1 (S314). The speed command S1 generated by the speed command generator 85 is a speed pattern that changes speed over time so that the speed vj+1 and the speed vk-1 match or cross each other at a certain point in the section Tc.

In this way, the speed command S1 for the section Tc of the axis J1 is calculated based on the plurality of velocities vj+1 and vk-1 obtained from the plurality of accelerations αj and the plurality of accelerations αk calculated every minute time Δt. Axis J1 is accelerated or decelerated over section Tc with acceleration αj and acceleration αk based on the allowable torque of servomotor 10 and reducer 11 and allowable moment Ms of bearing 15 to change the speed of axis J1. be able to.

After step S314, the main control unit 80 terminates the acceleration/deceleration zone speed command process S300.

In the example of the present embodiment, the acceleration/deceleration section speed command processing S300 has been described using the axis J1. Acceleration/deceleration interval speed command processing S300 is similarly executed for the other axes J2 to J7 as well.

Exemplary embodiments of the invention have been described above. According to the robot control device 50 according to one embodiment, the speed of the axes J1 to J7 in the first motion zone is calculated based on the minimum speed reduction coefficient αv in the first motion zone of the axes J1 to J7. As a result, the velocity moment Mv generated by velocity can be reduced, and the moment applied to the bearing 15 can be made equal to or less than the allowable moment Ms of the bearing 15 . Also, the acceleration of the axis J1 in the second motion section is calculated based on the allowable torque in the servomotor 10 and speed reducer 11 of the axis J1 and the allowable moment Ms in the bearing 15 of the axis J1. As a result, as shown in FIG. 7, the speed of the shaft J1 is reduced to the speeds Vnew b and Vnew d only in the sections Tb and Td in which the moment applied to the bearing 15 exceeds the allowable moment Ms. It becomes possible to change the speed of the axis J1 by accelerating or decelerating in the section Te. Therefore, it is possible to prevent failure and shortening of the life of the bearings 15 of the axes J1 to J7 in the robot R, and to suppress an increase in the operation time of the robot R.

In addition, the embodiment described above is intended to facilitate understanding of the present invention, and is not intended to limit and interpret the present invention. The present invention may be modified/improved without departing from its spirit, and the present invention also includes equivalents thereof. In other words, any embodiment appropriately modified in design by a person skilled in the art is also included in the scope of the present invention as long as it has the features of the present invention. For example, each element provided in the embodiment and its arrangement, material, condition, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. In addition, the embodiments are examples, and it goes without saying that partial substitutions or combinations of configurations shown in different embodiments are possible, and these are also included in the scope of the present invention as long as they include the features of the present invention.

DESCRIPTION OF SYMBOLS 10... Servo motor 10a... Output shaft 11... Reduction gear 11a... Output shaft 11b... Belt 12... Motor encoder 13... Reduction gear encoder 15... Bearing 50, 50', 50A... Robot controller, 51... Input interface 52... Bus 60... Storage unit 70... Servo control unit 80, 80A... Main control unit 81... Speed reduction coefficient calculation unit 82... Speed calculation unit 83... Acceleration calculation unit 85... Speed command generator 100 Robot control system C1 Base C2 Swivel base C3 First arm C4 Second arm C5 Third arm C6 Fourth arm C7 Fifth arm , C8... Tool fixing member, C9... Welding torch, J1... First rotating shaft, J2... Second rotating shaft, J3... Third rotating shaft, J4... Fourth rotating shaft, J5... Fifth rotating shaft, J6... Third 6 rotary axes, J7... seventh rotary axis, R... robot, Sn... speed command, S200... constant speed section speed command processing, S300... acceleration/deceleration section speed command processing.

Claims (4)

A robot control device for controlling a robot having a plurality of axes,
A permissible moment in a machine element supporting the shaft, a velocity moment generated in the machine element due to all the velocities of the plurality of axes , and a gravity generated in the machine element due to gravity due to all rotation angles of the plurality of shafts. a speed reduction coefficient calculation unit that calculates a speed reduction coefficient based on the moment;
a speed calculation unit configured to calculate the speed of the shaft in the first motion segment based on the minimum speed reduction coefficient in the first motion segment of the shaft , which is a segment in which the shaft moves at a predetermined speed;
Based on the allowable torque in the drive source of the axis and the allowable moment in the mechanical element of the axis, calculate the acceleration in the second operation section of the axis, which is the section in which the axis operates at an accelerated or decelerated speed. and an acceleration calculation unit for
robot controller. The acceleration calculator calculates a first acceleration based on the allowable torque in the drive source of the shaft and a second acceleration based on the allowable moment in the mechanical element of the shaft, and calculates the first acceleration and the second acceleration. adopting the smaller of them as the acceleration in the second motion segment of the axis;
The robot controller according to claim 1. The acceleration calculation unit subtracts, from the permissible moment of the mechanical element of the axis, a velocity moment generated in the mechanical element due to velocity and a gravitational moment generated in the mechanical element due to gravity, and based on the moment obtained, calculating the second acceleration;
The robot controller according to claim 2. further comprising a speed command generation unit that generates a speed command in the second motion interval of the axis based on the plurality of accelerations calculated at predetermined time intervals in the second motion interval;
The robot control device according to any one of claims 1 to 3.

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