JPH09204216A - Acceleration/deceleration control method for articulated robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage to a decelerator and the reduction of service life even in the operating state in which the reactive force received from the operation of other axles cannot be ignored. SOLUTION: In each axle of an articulated robot, a torque margin rate ξi of the axle is calculated (13) from torque Ci caused by centrifugal force and Coliolis force, imbalance torque Pi and the torque value of the smaller of the generated torque limit Tm of a motor and the tolerable torque Tg of the decelerator, the minimum value among all of the calculated torque margin rates of the axles is extracted (14) as a minimum torque margin rate ξmin , an allowable maximum angular velocity αmaxi of each axle is calculated from the torque value of the smaller of the generated torque limit Tm of the motor for each axle and the tolerable torque Tg of the decelerator, minimum torque margin rate ξmini and inertia Ji of the axle (15), and the acceleration/deceleration is controlled so that the angular velocity αi of the axle (i) of the articulated robot under operation cannot exceed the allowable maximum angular acceleration αmaxi .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method during acceleration / deceleration of an articulated robot having a plurality of drive axes.

[0002]

2. Description of the Related Art In an articulated robot having a plurality of drive axes, the maximum allowable angular acceleration α _maxi of each axis is calculated from the characteristics of the drive axis motor, the form of the arm, etc., and the angle of each axis of the operating robot is calculated. The acceleration α _i is the maximum allowable angular acceleration α _maxi
It is controlled not to exceed. Then, the maximum permissible angular acceleration α _max of the robot in motion is the torque τ _i generated on the i-axis.
Is limited so as not to exceed the maximum permissible torque T _splyi of this shaft. Here, the maximum allowable torque T _splyi of each axis is
It is given by the torque value of the smaller one of the torque limit Tm generated by the drive shaft motor for driving each shaft and the allowable torque Tg of the speed reducer.

Generally, the generated torque τ _i on the i-axis is
The inertia of the i-axis is J _i (θ _1, θ _2, ..., θ _n ), i
The angular acceleration of the axis is α _i , the torque due to the centrifugal force and the torque due to the Coriolis force on the i axis are C _i (ω _1, ω _2, ...,
ω _n , θ _1, θ _2, ..., θ _n ), and the unbalance torque on the i-axis is P _i (θ _1, θ _2, ..., θ _n ),
It is given by equation (1).

[0004]

[Equation 1]

In equation (1), (θ _1, θ _2, ..., Θ
_n ) is the arm angle from 1 axis to n axis, and (ω _1, ω _2, ...
., Ω _n ) is the arm angular velocity from 1 axis to n axis. Substituting the maximum allowable torque T _splyi for each axis into the left side of Expression (1), the maximum allowable angular acceleration α _{maxi for} each axis is as shown in Expression (2).

[0006]

[Equation 2]

In the actual acceleration / deceleration control of the articulated robot,
The angular acceleration α _i of each axis is controlled so as not to exceed the maximum allowable angular acceleration α _maxi . Since the posture and angular velocity of each axis are taken into consideration in the equation (2), when the robot arm is operated at a relatively low speed, the maximum allowable angular acceleration α _maxi of each axis calculated by the equation (2) is calculated. By controlling each axis based on this, it becomes possible to prevent damage to the reducer and shorten the life of the reducer.

[0008]

However, since the formula (2) does not take into consideration the force received from the motion of other axes, that is, the reaction force, when a plurality of axes operate simultaneously at high speed or when abrupt acceleration / deceleration occurs. In an operation mode in which the reaction force received from another axis cannot be ignored, for example, the angular acceleration α _i of each axis is calculated based on the maximum allowable angular acceleration α _maxi of each axis calculated by equation (2). If controlled, there is a problem that the maximum allowable torque T _splyi of each axis may be exceeded. In an extreme case, even if the angular acceleration α _i of a certain axis during operation is 0, the generated torque τ _{i of} this axis may exceed the maximum allowable torque T _splyi .

The present invention has been made in order to solve the above-mentioned problems of the prior art, and the operation of other axes such as the case where a plurality of axes operate simultaneously at high speed or the case of performing rapid acceleration / deceleration. Even in an operation mode in which the reaction force received from the shaft cannot be ignored, the generated torque τ _{i of the} shaft is equal to the maximum allowable torque T
_{An object} of the present invention is to provide an acceleration / deceleration control method for an articulated robot capable of preventing damage to the reducer and shortening the life of the reducer without exceeding _splyi .

[0010]

In order to solve the above-mentioned problems, the present invention provides an articulated robot in which the angles θ _i , angular velocities ω _i , and angular acceleration α _i of other axes are different from those of other axes. In an acceleration / deceleration control method for an articulated robot that is influenced by a force received from an operation, that is, a reaction force, a torque C _i due to a centrifugal force and a Coriolis force, an unbalance torque P _i , and a motor generation for each axis. Either the torque limit Tm or the allowable torque Tg of the reducer, whichever has the smaller value, that is, the maximum allowable torque T _splyi, is used to calculate the torque allowance ratio ξ _i of each axis, and the calculated torque allowance of all the axes. extracting those with the smallest value of the ratio as the minimum torque margin rate xi] _min, the maximum permissible torque T _Splyi, the minimum torque margin rate xi] _min, and by the inertia J _i axis, the allowable maximum angle of each axis The acceleration α _maxi is calculated, and for all axes of the articulated robot in motion,
The angular acceleration α _{i of} each axis is the maximum allowable angular acceleration α _{maxi of} this axis.
The acceleration / deceleration control method for the articulated robot is characterized in that the reduction gear is prevented from being damaged and the life of the reduction gear is prevented from being shortened.

According to the above acceleration / deceleration control method, the present invention
The maximum allowable angular acceleration α _maxi of each axis is determined based on the minimum torque margin rate ξ _min having the smallest value among the calculated torque margin rates ξ _i of each axis.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing an example of a system for carrying out the control method of the present invention. In the figure, 1 is a robot body, 2 is a servo amplifier, 4 is a command position generator, 5 is a target position generator, and 6
Is a calculation device for the maximum allowable angular acceleration α _maxi . The target position generator 5 outputs the position recorded in the memory or the position obtained by calculation to the command position generator 4 as the target position to be reached by the robot. The command position generator 4 calculates the command position θ _i of each axis for the robot to operate properly from the values of the target position, the specified speed, the current position, the acceleration limit, etc., and sends it to the servo amplifier 2. Output. Regarding the method for operating each axis satisfying the acceleration limit, which is performed in the command position generating device 4, for example, Japanese Patent Application Laid-Open No. 6-131 previously filed by the applicant of the present application.
No. 018 etc., and a smooth acceleration / deceleration method is also described in JP-A-5-297916.

The calculation device 6 for the maximum allowable angular acceleration α _maxi is
It is a device for calculating the maximum allowable angular acceleration α _maxi calculated by the control method of the present invention, the command position θ _i which is the output of the command position generator 4 is input, and the angular velocity ω _{i of} each axis and the permissible torque of the reducer are input. Tg and drive shaft motor generated torque limit T
A maximum allowable angular acceleration α _maxi is calculated from m, and a loop for outputting to the command position generator 4 is formed. Servo amplifier 2
Receives an instruction position θ _i from the instruction position generator 4 and outputs an operation instruction for operating the robot body 1. A drive shaft motor, an encoder, a speed reducer, etc., which are not shown, are attached to the robot body 1, and these constitute a servo loop.

[0014] Figure 2 is carried out in the indicated allowable maximum angular acceleration alpha _maxi computing device 6 in FIG. 1 is a flowchart illustrating a flow of a calculation process of the allowable maximum angular acceleration alpha _maxi. First, the command position θ _i of each axis for the robot to properly operate is obtained from the command position generator 4 (step 1
1), this command position θ _i and θ stored in the memory
from the command position theta _i 'before a certain time than _i, and calculates an angular velocity omega _i of each axis (step 12). From the command position θ _i and the angular velocity ω _i of each axis, the torque margin ratio ξ _i of each axis is calculated by the equation (3) (step 13).

[0015]

(Equation 3)

In equation (3), C _i (ω _1, ω _2, ...
,, ω _n , θ _1, θ _2, ..., θ _n ) are the torque due to the centrifugal force and the torque due to the Coriolis force on the i-axis, and P
_i (θ _1, θ _2, ..., θ _n ) is an unbalanced torque on the i-axis. Further, T _splyi is the maximum allowable torque, and this value is given by either the torque limit Tm of the motor or the allowable torque Tg of the speed reducer, whichever is smaller.

Next, as shown in equation (4), the torque margin rate ξ _i of each axis calculated from equation (3) having the smallest value is extracted as the minimum torque margin rate ξ _min ( Step 14).

[0018]

(Equation 4)

Next, the minimum torque margin rate ξ _min , the maximum allowable torque T _{sp lyi,} and the inertia of each axis calculated from the equation (4) are calculated from J _i (θ _1, θ _2, ..., θ _n ). , The maximum allowable angular acceleration α _maxi of each axis is calculated by equation (5) (step 15).

[0020]

(Equation 5)

Finally, the maximum allowable angular acceleration α _maxi of each axis calculated by the equation (5) is output to the command position generator 4 (step 16).

Next, if the maximum allowable angular acceleration α _maxi of each axis calculated by the equation (5) is used in the acceleration / deceleration control, the commanded position θ _{i of} each axis output by the commanded position generator 4 is output.
Indicates that the torque generation limit Tm of the motor and the allowable torque Tg of the speed reducer are not exceeded. Specifically, the equation (4), assuming that the torque margin rate xi] _k of k-axis becomes No. 1 low, the torque margin rate xi] _k is the allowable maximum angular acceleration alpha _maxK No. 1 low k axis Let's calculate the generated torque τ _k when it is operated. From equation (5), the maximum allowable angular acceleration α _{maxk on} the k-axis is as shown in equation (6).

[0023]

(Equation 6)

By substituting equation (3) into equation (6), equation (6) is transformed into equation (7).

[0025]

(Equation 7)

In equation (7), P _k (θ _1, θ _2, ...
., Θ _n ) is the unbalanced torque on the k-axis.
Further, by substituting the equation (7) into the equation (1), the equation (8) is obtained.

[0027]

(Equation 8)

From equation (8), the torque margin ratio is the lowest k
Even when the shaft is operated at the maximum allowable angular acceleration α _maxk of this shaft, the torque generated at this time is the maximum allowable torque T of the k-axis.
_{It turns out to be splyk} , which means that the allowable limits of the drive shaft motor and reduction gear are not exceeded.

[0029]

FIG. 3 shows the time course of the torque evaluation index when the effect of the acceleration / deceleration control method according to the present invention on the prior art is verified in the operation of an actual articulated robot. In FIG. 3, the horizontal axis represents time [seconds] and the vertical axis represents the torque evaluation index. Here, the torque evaluation index is the formula (1) that indicates the command position θ _i , the angular velocity ω _i , and the angular acceleration α _i that are actually determined as command values for each axis.
By substituting for the generated torque τ _i of the drive shaft motor for each axis, it is expressed as the ratio (τ _i / T _splyi ) of the generated torque τ _i and the maximum allowable torque T _splyi of this shaft. is there. If the torque evaluation index is always 1 or less in all the axes, the robot is always operating at the maximum allowable torque of the drive shaft motor and the speed reducer.

In the embodiment shown in FIG. 3, in the conventional control (marked with □), the maximum value of the torque evaluation index is about 1.2, and about 20% of torque over has occurred.
In the control (marked with X) according to the present invention, the torque evaluation index is always 1.0 or less, and torque over has not occurred. Further, it can be seen that the torque evaluation index in the control of the present invention has a smaller time variation as compared with that in the conventional control, and therefore the trajectory accuracy of the robot is improved.

[0031]

As described above, according to the acceleration / deceleration control method for the articulated robot of the present invention, the maximum allowable angular acceleration α _maxi of each axis is the smallest among the calculated torque margin ratios ξ _i of each axis. Since it is determined based on the minimum torque margin ratio ξ _min that has a value, it is not possible to ignore the reaction force received from the motion of other axes, such as when multiple axes operate simultaneously at high speed or when performing rapid acceleration / deceleration. Even in such an operation mode, the generated torque of the shaft does not exceed the maximum allowable torque, which makes it possible to prevent breakage of the reduction gear and reduction in life of the reduction gear. Further, according to the present invention, since the acceleration / deceleration control is ensured within the torque that the drive shaft motor can output, it is possible to improve the trajectory accuracy of the robot.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a system for implementing a control method of the present invention.

[Figure 2] is performed in the allowable maximum angular acceleration alpha _maxi computing device 6 shown in FIG. 1 is a flowchart illustrating a flow of a calculation process of the allowable maximum angular acceleration alpha _maxi.

FIG. 3 is a graph showing a time course of a torque evaluation index when the effect of the acceleration / deceleration control method according to the present invention with respect to the related art is verified in the operation of an actual articulated robot.

Claims (1)

[Claims] 1. A multi-joint robot in motion, wherein the angles θ _i , angular velocities ω _i , and angular acceleration α _i of each axis are influenced by a force received from the motion of another axis, that is, a reaction force. In the acceleration / deceleration control method for the joint robot, whichever of the torque C _i due to the centrifugal force and the Coriolis force, the unbalance torque P _i , the torque limit Tm generated by the motor, and the allowable torque Tg of the reducer, whichever has the smaller value, is used for each axis. The torque allowance ratio ξ _i of each axis is calculated from the torque value of, that is, the maximum allowable torque T _splyi, and the minimum torque allowance ratio ξ _min is the one having the smallest torque allowance ratio of all the calculated axes. extracted, the maximum permissible torque T _Splyi, all axes of said minimum torque margin rate xi] _min, and by the inertia J _i axis, calculates the allowable maximum angular acceleration alpha _maxi of the respective axes, articulated robot in operation For,
The angular acceleration α _{i of} each axis is the maximum allowable angular acceleration α _{maxi of} this axis.
An acceleration / deceleration control method for an articulated robot, characterized in that the reduction gear is prevented from being damaged and the life of the reduction gear is prevented from being shortened.