JPS61163406A - Robot control device - Google Patents

Abstract

PURPOSE:To carry out control taking in most suitably a load inertia by computing a speed gain corresponding to the inertia of a actuator making a reference value of a speed gain and a value of a change width of the speed gain basis and computing an output value of a servo system based on it. CONSTITUTION:A command angle data 12 has a position feed back data 27 subtracted at a position servo loop 10 to be a deviation signal 13. The signal 13 receives a position gain Kp to be a position output 15. The output 15 has a speed feed back data 29 subtracted at a minor loop 11 of a speed to be a deviation signal 16. The signal 16 receives a servo gain KA and an amplifying output 18 is applied to a motor M. In the motor M, in accordance with a torque constant Kt, a generating torque 20 is obtained an this torque 20 is integrated in time and converted into a rotating speed 22 divided by an inertia. Such a speed 22 is integrated in time to appear as a rotating angle 24 of the motor.

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention relates to a robot control device, and in particular,
The present invention relates to a robot control device for controlling a robot having a rotational degree of freedom by incorporating the effects of variations in inertia that vary depending on the amount of operation of an actuator.

<Summary of the Invention> The robot control device of the present invention makes the operating amount of the actuator of the robot correspond to the reference value of the speed gain in the position servo system, and the value of the fluctuation width of the speed gain with respect to changes in the mass of the workpiece. Store it in a storage means,
When the detection means detects the amount of movement of the actuator, it reads out the reference value of the speed gain and the value of its fluctuation range according to the amount of movement, and calculates the speed gain according to the inertia of the actuator based on these values, Thereafter, the output value of the servo system is calculated based on this speed gain, and thereby, the output value of the servo system is calculated based on the speed gain. This makes it possible to precisely set the response of the servo system.

<Background of the Invention> In robots having rotational degrees of freedom, such as articulated robots and polar coordinate robots.

The load inertia related to the rotational degree of freedom varies depending on the amount of operation of the actuator. Such fluctuations in inertia affect the response of the servo system, so it is necessary to incorporate them into the control system in some way.

However, in a servo system composed of analog circuits,
Due to its nature, it is impossible to incorporate such fluctuations. Furthermore, in multi-joint robots, joints near the base are greatly affected by variations in load inertia, so a reduction gear with a large reduction ratio must be used to reduce such effects. Because of this, this type of deceleration already results in increased costs and decreased efficiency.

This method has many drawbacks, such as increased load fluctuations, increased backlash, and difficulty in fine-feeding.

In addition, when configuring a position servo system using software, calculate the inertia around the axis of each joint from the joint angles of multiple joints, find the velocity gain corresponding to that inertia, and based on that, output in the position servo system. It is necessary to calculate the values, which requires a large amount of calculation time. For this reason, it is difficult to calculate the speed gain mentioned above in real time while the robot is operating. Conventionally, the speed gain is calculated off-line using the target angle of movement in advance, and the calculation result is It was stored in a memory, and during operation, the stored speed gain values were sequentially read out and used in the servo system. However, with this method, the above-mentioned offline processing is not possible during teaching operations, and in sensor feedback control using an external sensor such as a camera, it is impossible to change and move the target point during operation. It has the disadvantage that it is possible.

<Object of the Invention> The present invention provides a speed gain value corresponding to the amount of operation of each actuator to the servo system in real time during the operation of the robot.

The main objective is to provide a robot control device that optimally incorporates variations in load inertia under various control conditions. Another object of the present invention is to provide a pot control device that can implement such control without reducing economic efficiency or deteriorating other performance.

<Configuration and Effects of the Invention> In order to achieve the above-mentioned object, the robot control device according to the present invention is configured to control the movement amount of the actuator of the robot, the reference value of the speed gain in the position servo system, and the speed gain with respect to changes in the mass of the workpiece. a storage means for storing the values of the fluctuation range in correspondence with each other, and a reference value of the speed gain and the value of the fluctuation range thereof are read from the storage means in accordance with the movement amount of the actuator detected by the detection means. A speed gain according to the inertia of the actuator is calculated based on the speed gain reference value and the fluctuation range value read by the readout means, and the output of the servo system is calculated based on this speed gain. It was configured to calculate values.

According to this robot control device, the servo system is controlled in response to changes in the amount of movement of the robot's actuators, and therefore inertia changes due to changes in the robot's position and posture and changes in the workpiece held by the robot. The response can be set optimally. In particular, the above effects can be achieved even when the target route or target position is changed during operation, such as in external sensor feedback. In addition, there is no deterioration in controllability such as oscillation or vibration due to inertia fluctuations, and it is possible to use a mechanism with a low reduction ratio, which reduces costs, improves efficiency, reduces load fluctuations, and reduces play. I can do it.

<Description of Embodiments> Hereinafter, embodiments of the present invention will be described by taking as an example the control device for an articulated robot shown in FIG. The articulated robot RB in Fig. 2 has six degrees of freedom, and six joints.
~6, rotational degrees of freedom of θ1・~06 (
In this specification, in addition to the original rotation, the rotation degree of freedom is also referred to as "
called the rotational degree of freedom. It has a These joints 1
~6 is a servo motor M as a drive mechanism, ~a pigeon (second
(not shown in the figure).

FIG. 3 shows a schematic configuration of the control device 7 of the articulated robot RB shown in FIG. 2. The keyboard 8 is connected to the CPU (
Central Processing Unit)
9 This is for input/output of the hexagon, and the CPUg executes command analysis, command value calculation, arithmetic operations in the position control servo system, etc. The output of CPU9 is given to servo amplifiers A and ~, and the gain of these servo amplifiers is C.
Each output value from PUg is amplified and given to each of the above-mentioned servo motors. Encoders E1 to E6 are
A photo encoder is attached to each of the servo motors M, to M6, and detects the rotation angle of each motor and provides it to the cpug.

FIG. 4 is a block diagram of a position servo system for one joint, and in this embodiment there are a total of six similar servo systems. This servo system includes a velocity minor loop 11 in a position servo loop 1o.

Command angle data 12 created based on teaching information stored in a memory (not shown) and commands issued from the keyboard 8 in FIG. The feedback data 27 is subtracted to obtain the deviation signal 13.

This deviation signal 13 receives a position gain Kp in a block 14 to become a position output 15, and this position output 15 becomes a deviation signal 16 by subtracting the speed feedback data 29 fed back through the speed minor loop 11. Become. This deviation signal 16 is subjected to a servo amplifier gain KA in a servo amplifier 17 (one of the above Al), and its amplified output 18 is given to a motor M (one of the above M).

In this motor M, the torque constant K in block 19 is
[The generated torque becomes 2o, and this generated torque 20
is time-integrated in block 21 and converted into rotational speed 22 divided by inertia. In addition, in the figure, S
is the Laplace operator, and J is the inertia around the joint axis converted to around the motor axis. The T0 rotation speed 22 is further time-integrated in block 23 and appears as the rotation angle 24 of the motor.

The rotational speed 22 of the motor is determined by the encoder E (the above E, ,
E), the encoder gain K
It is encoded while receiving E, resulting in encoded output 25. However, in FIG. 3, encoders E, ~E
6 is for detecting the rotational angle, but in FIG. 4, for convenience of illustrating the concept, it is assumed that the rotational speed 22 is detected. After the encoder output 25 is time-integrated in block 26, it becomes position feedback data 27 that returns to the previous stage of block 14, and becomes velocity feedback data 29 under the influence of velocity gain Kv in block 28. In addition, in these, for simplicity, -viscous resistance is ignored.

The transfer function C, (s) in the servo system in Fig. 4 is 1
It is expressed as the following equation (1).

However, ω. and ξ are the natural angular frequency and damping coefficient, respectively, and are given by. Further, the mechanical resonance angular frequency ωS for each joint is expressed as follows using the inertia J and the spring constant around the rotation axis. Here, the above-mentioned natural angular frequency ω. and the damping coefficient ξ is set to ω in order to prevent the operation of the robot 1-RB from becoming oscillatory. ≦DingωS...(5)ξ=
1...set to about (6).

Hereinafter, the handling of velocity gain will be explained using the joint 1 in FIG. 2 as an example. The causes of variations in the inertia J regarding the joint 1 include the joint angles of the joints 2 to 6 and the mass of a workpiece (not shown) held by the robot 1-RB. In the specific example of robot RB in Fig. 2, the minimum value J of inertia J
There is a relationship between min and the maximum value Jrmx.

Jmin = 5 Jmax・
(7) By the way, as can be seen from equations (2) and (4), the natural angular frequency ωn is the same as the resonance angular frequency ωS, that is, it is proportional to 1iJT and depends on the inertia J. Therefore, when the inertia J changes due to the above-mentioned causes, four changes occur in ωn and ωS at the same ratio. Therefore, even if the inertia J changes, (
5) Equation will always be satisfied. On the other hand, the damping coefficient ξ
When the value of inertia J changes, the value of Equation (3) changes accordingly, and Equation (6) is no longer satisfied. For example, 1...(8)J==
If the value of speed gain Kv is set so that equation (6) is satisfied under the condition of T (Jmin + Jmax), then when J = Jmin, ξ = 1.87...
(9) J==Jmax, ξ=0.76
...Since αa, J < CJmin 1 Jmax) ・
... (Company) has the following for over-damping: 1 ... (2) J > T
(Jmin + Jmax) results in insufficient attenuation. Therefore, the speed gain Kv.

If T is configured to vary according to the inertia J so that v r=constant °(13).

Therefore, even if the inertia J changes by 1, the damping coefficient ξ
remains a constant value, and stable control can be achieved.

By the way, among the causes of variation in inertia J mentioned above, the variation in the joint angles of joints 4 to 6 is relatively small compared to other causes, so in this example, the joint angles of joints 2 and 3 and the workpiece The configuration is such that the value of the velocity gain Kv is changed depending on the mass of the vehicle. Moreover, these correspondence relationships also depend on the joint angle θ2. Divide the operating range of θ3 into multiple regions (16 in the example below), and calculate the optimal speed gain Kvo when the mass of the workpiece is zero and the maximum payload MMAX corresponding to each of the regions. The optimum speed gain KVMAX at the time and the speed gain X applied to the zero mass
The difference ΔKv from VO is calculated in advance and stored in a memory such as a RAM.

This kind of correspondence regarding joints 1 to 3.

They are shown in Tables 1 to 3, respectively. Taking Table 1 as an example, the joint angle θ2 of joint 2 is the area (interval > i <, i
= 1 to 16), the joint angle θ of joint 3.

exists in each region j (j=1 to 16), the value of Kv OJ is the velocity gain Kv for joint 1
o, and ΔKv1 is the value of the fluctuation width ΔXV. In this case, assuming that the mass of the workpiece is mckg], the velocity gain Kv to be used in the servo loop is calculated using the following equation.

Table 1 Also, the velocity gain Kv for joint 2 in Table 2.

The value of is the joint angle θ of joint 3 because it ignores the dependence on the joint angle changes of joints 4 to 6.

Kvoi is written for the region i to which ΔKv belongs, and the fluctuation range ΔKv is written as ΔKvi.

In this case, if the workpiece mass is mc k g l), the speed gain Kv to be used in the servo loop is
is calculated using the above equation 151.

Furthermore, since the speed gain Kvo for joint 3 ignores the effect of rotation of joints 4 to 6, it depends only on the mass of the workpiece.
It is calculated using the above formula (151).

Table 2 Table 3 The values of velocity gain Kvo and fluctuation range ΔKv are determined by joint angle θ2. The inertia J for a given value in each region of θ, for example, the rotation angle corresponding to the median value of that region.
This is the value obtained from the value of this inertia J by calculating the above equation U. In this embodiment, joints 4 to 6 use the same method as joint 3.

FIG. 1 shows the calculation of the velocity gain Kv and the control operation of the robot using the calculated value. First, in step 31 of the figure, the mass of the workpiece is read. In this step 31, the procedure differs slightly depending on whether there is one type of work or multiple types of work. That is, in the former case, first, by detecting the opening and closing of the band of the robot RH, it is determined whether or not the first hand is holding a workpiece, and the workpiece is retrieved from the table in the memory specified in advance. Read the mass of 8 guns.

When there are multiple types of workpieces, from the operation program,
Know the type of work that robot RB is currently holding,
Find the corresponding mass from the workpiece mass table.

In the next step 32, the respective values of velocity gain Kv□ and variation width jKv for joint 3.4.5°6 are read from a table in the memory corresponding to the contents of Table 3. Then, the read speed gain Kv□ and fluctuation width ΔK
A speed gain Kv is calculated using the value of v and the mass of the workpiece, and the calculated value is written to a gain table in the memory. In the next step 33, the joint angle θ is detected and it is determined to which region it belongs. This detection is
This may be done by reading out the target angle of movement from the memory, or the actual joint angle may be detected by the encoder E3. In any case, robots 1
- The values of the joint angles during the movement of the RB are determined, and in this specification, the joint angles detected by these methods are referred to as "current values."

In step 34, the velocity gain Kv□ and the fluctuation range ΔK regarding the joint 2 are determined from a table in the memory corresponding to Table 2, depending on the region to which the determined joint angle θ belongs.
The value of v is read, the velocity gain Kv is calculated, and the calculated value is written into the gain table. Similarly, in step 35, the joint angle θ2 is detected and it is determined which region it belongs to, and in the next step 36, the joint angle θ2. The values of velocity gain Kv □ and variation width ΔKv for joint 1 corresponding to the region to which θ belongs are read from the table in the memory corresponding to the first man, velocity gain Kv is calculated, and the calculated value is the gain. written to the table.

In this way, the speed gain Kv at a specific time
Once the value of is specified for each trunk, the value of this speed gain Kv is taken into cptrg along with the robot motion command value input by the input means, other constant data, feedback data, etc. Based on this, the output value in the servo system is calculated and given to the drive mechanism (step 37). In step 38,
It is determined whether the operation command value is the final one, and the above steps are repeated until the final operation command value is obtained.

The above is the joint angle θ2 of joint 2.3. θ, and the velocity gain Kv of the servo system of joints 1 to 3 according to the mass of the workpiece.
However, if the influence of the joint angles 04 to θ of joints 4 to 6 cannot be ignored mechanically, it is possible to change the structure by incorporating the influence of the joint angles 04 to 06. good. Conversely, in cases where the influence of the mass of the workpiece can be ignored, the mass of the workpiece can be removed from the parameters.

In the above embodiment, an articulated robot is considered, and the motions are also expressed by joint angles. However, the present invention is applicable not only to articulated robots, but also to polar coordinate type robots shown in FIG. 5, and can be used for all robots having rotational degrees of freedom. In addition, in the robot shown in FIG. 5, since the amount of extension of the linear actuator 40 or the inertia around the rotating shaft 41 is affected, not only the joint angle but also the amount of movement of the various actuators is affected in general. That is, it is possible to use joint angles, extension amounts, and other quantities that affect inertia J as parameters.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an overview of the control performed in the embodiment of this invention, FIG. 2 is an explanatory diagram showing the mechanism of a robot controlled by the embodiment of this invention, and FIG. Block diagram showing the overall configuration, No. 4
The figure is a block diagram of a servo system included in the embodiment of the present invention, and FIG. 5 is a mechanical explanatory diagram showing another example of a robot controlled by the embodiment of the present invention.

Claims (3)

[Claims] (1) A robot control device for controlling a robot having a position servo system including a minor speed loop and having a rotational degree of freedom based on input information, the robot control device having a position servo system including a minor speed loop, and controlling a robot having a rotational degree of freedom based on input information, the amount of operation of an actuator of the robot and , a storage means for storing a reference value of a speed gain in the position servo system and a value of a variation width of the speed gain with respect to a change in workpiece mass in correspondence with each other; a detection means for detecting, a reading means for reading from the storage means a reference value of the speed gain corresponding to the current value of the operation amount of the actuator and a value of its fluctuation range; and a mass of the workpiece and a speed gain required for reading. a calculation means for calculating a value of a speed gain according to the inertia of the actuator based on a reference value and a value of its fluctuation width; A robot control comprising calculation means for calculating an output value in the servo system based on input information including the calculated speed gain value and feedback information obtained from the robot, and outputting the output value to the drive mechanism of the robot. Device. (2) The storage means stores information about the inertia of the actuator at a predetermined amount of motion within the motion region, corresponding to each motion region formed by dividing the motion range of the actuator into a plurality of regions. A reference value of the speed gain and a value of its fluctuation width are stored, and the reading means determines in which of the regions the current value of the operation amount is included, and reads the speed gain corresponding to the region. 2. The robot control device according to claim 1, further comprising means for reading out the reference value and its range of variation. (3) The reference value of the speed gain stored in the storage means is the optimum speed gain value when the mass of the workpiece is zero, and the range of variation of the speed gain is the optimum value at the maximum payload. claim 1 or 2, which is the difference between the value of the velocity gain applied to the zero mass and the value of the velocity gain applied to the zero mass.
The robot control device described in Section 1.