JPS60118478A - Controller for position of joint type robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a position control device for an articulated robot, and more particularly to a device capable of controlling the position of a robot hand with high precision.

[Background of the invention]

In recent years, in order to perform precise assembly work in articulated robots, it is required that the positioning accuracy of the hand position be on the order of .mu.m.

Control of the hand position of the robot l- is performed using geometrical conditions determined by the dimensions of the robot arm. However, in reality, since the robot arm is elastically deformed, accurate positioning is difficult. One way to avoid this elastic deformation of the robot arm is to make the entire robot extremely rigid and keep the amount of deformation within an allowable range, but this method increases costs and reduces the overall This also causes a decrease in the natural frequency, which is disadvantageous in terms of control.

For this reason, as shown in Japanese Patent Application Laid-Open No. 57-69315, a method has been proposed in which the elastic deformation of the arm is corrected by the weight of the workpiece acting on the robot arm.

However, in articulated robots, in addition to the elastic deformation of the two arms, the rigidity of the reducer of the drive system provided at the joint is a problem. That is, since the rigidity of the reducer in this drive system is very low compared to the rigidity of the arm, the low rigidity of this reducer has an adverse effect on the hand washing positioning accuracy of the robot (2).

[Purpose of the invention]

The present invention has been made based on the above-mentioned matters, and provides a position control device for an articulated robot that can correct torsional deformation caused by low rigidity on the output side of the drive system in the joint portion of the articulated robot. The purpose is to

[Summary of the invention]

In order to achieve the above object, the present invention provides an articulated robot that operates in accordance with teaching data, and includes means for determining the operating joint angles of the joints of the robot based on the teaching data, and a means for determining the operating joint angles of the joints of the robot in accordance with the teaching data. means for calculating the amount of twist of a moving joint angle caused by a gravitational torque load, and means for calculating an actual moving joint angle based on the moving joint angle and amount of twist of the robot, and outputting this to the drive system of the robot. It is something.

[Embodiments of the invention]

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

Figure 1 shows an articulated mouth (3) pot equipped with an example of the device of the present invention. In this figure, 1 is an operation panel, and this panel has switches and displays for operating the robot. Equipment is provided.

Inside the operation panel 1, there are provided a computing device for controlling the operation of the robot, a storage device, and servo actuators for operating each axis of the robot according to instructions from the computing device. 2 is an articulated robot electrically connected to the operation panel 1. This articulated robot 2 has a base 3. Swivel base 4° 1st arm 2. Second arm 6, wrist shaft 7
, 8. A gripper 9 for handling a workpiece is provided at the tip of the wrist shafts 7, 8.

The movement of this robot is based on the axis S1 of the rotating table 4 relative to the base 3.
Rotation around the axis S2 of the first arm 5 relative to the swivel base 4
rotation of the second arm 6 about the axis S3 relative to the first arm 5; rotation of the wrist shaft 7 about the axis S4 relative to the second arm 6; and rotation of the wrist shaft 8 about the axis S5 relative to the wrist shaft 7.
(4) can be obtained by appropriately combining the rotation around the gripper 9 and the opening and closing of the gripper 9.

FIG. 2 shows a drive system for rotating each member of such a robot around each rotation axis 81 to S5. In this figure, 13 is a drive motor such as a DC servo motor, 14 is a speed reducer, 15 is a component of the robot, and 12 is a rotational position detector for the drive motor 13, such as an incremental rotary encoder. Reference numeral 11 denotes a rotational speed detector of a drive motor 13 such as a tacho generator. In this drive system scenario, for example, when the component 15 of the robot is the first arm 5 and the 17th arm 5 is rotated by 02 degrees around the rotation axis S2 with respect to the swivel base 4, the reduction gear If the reduction ratio of 14 is R, then the drive motor 1
The rotation angle required for 3 is RO2. In response to this request, the arithmetic unit built into the operation panel 1 takes into consideration the required operating speed and acceleration, and performs AC
A rotation angle increment command is given to the servo system that controls the drive of the first arm 5. The servo system gives a rotation command to the drive motor 13, integrates the output pulse signal of the rotation position detector 12 generated by the rotation of the motor (5), and controls the drive motor until it matches the rotation angle increment command Aθi. 1
Rotate 3. That is, the motor 13 rotates by the required rotation angle Rθ2-flB'h by the rotation angle increment command n times. Here, the output signal of the rotational speed detector 1 on base 11 is also fed back to the servo system and used for stabilizing and smoothing the motor control operation. The rotation angle of the component 15 of this robot is uniquely related to the rotation angle of the drive motor 13.
Since only the rotation angle of 3 is controlled, due to the low rigidity of the reducer 14 in the drive system, twisting occurs due to the gravitational moment acting on the component 15 in this part.

This twist is also a function of the acting gravitational moment. Therefore, the relationship between the gravitational moment and the torsion of the rotation angle of the joint will be explained with reference to FIG.

In FIG. 3, parts with the same symbols as in FIG. 1 are the same. Assume that the weight Wo of the wrist, gripper, etc. located ahead of the tip of the second arm 6 is concentrated at the tip of the second arm 6, and the first arms 27-86 each have a length of 5° (6). S full + I22 to weight W +
= W2, and each arm weight Wl tW2
Assume that the force is acting on the center portions of the arms 5 and 6. The drive system weight W12 of the second arm 6 is the rotation axis S of the joint.
Assume that it is acting on 3. Further, the first arm 5 and the 27th to 8th 6 are each 02.0 mm from the horizontal plane as shown in the figure.
Assume that it is located at an angle of θ3. Furthermore, the direction of the coordinate system of the robot is set in the direction shown in the figure, and the origin of the coordinate system is set at the center of the rotation axis S2 of the joint. Assuming that there is no deflection in the joint, the position of the tip of the second arm 6 (Xo
yZo) is as follows.

Also, the rotation axis S2 of the joint part. Gravitational torque T2 acting on S3. T3 is as follows.

This gravitational torque T2. Due to T2, the reducer 14 undergoes (7) elastic deformation and twists Aθ2. Since Aθ3 occurs, the actual joint rotation axis S2. The rotation angles 02' and 03' of S3 are approximately as follows. However, LM is the lost motion of the reducer, K is the Hane constant, and TLM is the input torque when the lost motion of LM/2 occurs.

Next, the configuration of an example of the apparatus of the present invention will be explained with reference to FIG. In this figure, 31 is a manual input device for inputting data, operation signals, etc. for initial setting and operation of the articulated robot. 32 is a main control device that controls the motion of the articulated robot. This main control device 32 includes a robot initialization control section 33. Teaching control section 34. A storage unit 35 that stores the operating position, posture, operating conditions, etc. of the robot. Robot (8) Arm length. Storage unit 36 that stores the weight of each part, center of gravity position, etc. An interpolation calculation section 37 calculates the next motion position and posture of the robot according to the data in the storage section 35, and a motion joint angle calculation section 38 calculates the motion joint angles of the robot from the motion position and posture of the robot. Torsion angle calculation unit 39 that calculates the amount of twist of the motion joint angle of the robot. The robot is equipped with a joint angle correction calculation unit 40 that calculates the actual operating angle of each joint of the robot based on the operating joint angle and torsion angle of the robot. 41 is an adder, 42 is an up/down counter that detects the rotation angle signal of the drive system, 43 is a servo amplifier 44, which is a drive system consisting of a servo motor, a speed reducer, a rotary encoder, etc. shown in FIG. 2, and 45 is a drive system. It is one of the mechanical members of the robot driven by the robot. These elements 41 to 45 are the servo system 4
6. Although only one servo system 46 is shown in FIG. 4, in reality, the number of servo systems 46 is equal to the number of joints of the articulated robot.

Next, the operation of an example of the apparatus of the present invention described above will be explained.

(9) Using the manual input device 31, input the arm length, weight of each part, center of gravity position, etc. of the robot into the storage section 36 in advance. If the storage unit 31 is a ROM, the above data is written by a ROM writer. The robot operates by turning on the power to the robot's servo system 46 using the manual input device 31, and then using the initialization control unit 33 to move the robot to a predetermined operating origin for the robot 1.
Various calculation conditions within the control device 32 are initialized, and the position and orientation data at the origin of the robot's motion are stored in the storage unit 35. Note that when the robot is moved to the operation origin by the initialization control section 33, the servo system 4
An operation signal is output to 6, and the robot operates so that the position where the origin is detected by the origin detection sensor provided on each component of the robot is set as the origin.

When teaching a motion to the robot, the teaching control section is operated by a signal from the manual input device 31, and the current position and orientation stored in the storage section 35 are slightly corrected in the direction input from the manual input device 31. , Re(10) While storing the correction values, operation signals for each axis of the robot are output to the servo system 46 so as to move the robot to the position and orientation of the corrected values. When the robot moves minutely in this way and reaches the target position or posture, the manual input device 31
By inputting the teaching operation, the current position/orientation, the method of reaching the current position, etc. are stored in the storage unit 35. Through this series of operations, the positions, postures, working methods, etc. to be passed through during automatic operation of the robot are stored in the storage unit 35, and the teaching operation is completed. Although the method of moving the robot, the signals given to the servo system 46, and the signal transmission path are not shown here, this is the same as the method during automatic operation described below.

When operating the robot l~ automatically, the manual input device 31
Operation units 37 to 40 operate according to the operation. That is, the interpolation calculation section 37 determines the position to be occupied by the robot 1 and the next position from the motion control data such as the current position, posture, and taught position, posture, motion speed, and acceleration of the robot stored in the storage section 35. The power orientation is calculated by interpolation calculation (11). Next, the motion joint angle calculating section 38 uses this data and the robot specification data stored in the storage section 36 to calculate the motion joint angles of the robot based on a relational expression such as equation (1). Melt.

Next, the torsion angle calculation unit 37 uses the operating joint angles of the robot and the specification data of the robot stored in the storage unit 36 to calculate the gravitational torque acting on each joint of the robot, for example (
2), and from this, the torsion angle of each joint is calculated, for example, by equation (4). Next, the joint angle correction calculation unit 40 corrects the torsion angle based on the requested robot movement angle and torsion angle, and performs an actual robot motion in which the position and orientation of the robot match the position and orientation given by the interpolation calculation unit 37. Calculate the angle. For example, in the case of the idea of deriving equation (3), if the ideal operating angle is 02+03° and the actual operating angles are 02' and 03', the following relationship is obtained.

Furthermore, the joint angle correction calculation unit 40 performs (12
) Obtained actual operating angle of robot 1-, for example 02'0
3' is output to the servo system 46. The servo system 46 uses an up/down counter to count the pulse signals generated by the rotation angle sensor of the drive system attached to the drive system 44, and compares the pulse signals with the motion angle signals output from the joint angle correction calculation unit 40 to control the robot. A deviation signal for operation is generated by an adder 41 and supplied to a known servo amplifier 43. The servo amplifier 43 generates a signal for operating the drive system 44 from the deviation signal, and operates the drive system 44. That is, the mechanical member 45 of the robot is operated. The servo system 46 constantly generates the deviation signal described above and operates until the deviation signal disappears. That is, the robot is operated by the servo system so as to assume the operating position and orientation instructed by the joint angle correction calculation section 40.

The operations described above, especially the operations of the components 37 to 40, are executed so that the robot moves minute by minute at time intervals of, for example, several 1.0 m5ec. It operates according to the teaching data stored in the section 35.

(13) In particular, according to the present invention, differences between the actual robot motion path, position, and posture and the teaching data caused by twisting of the robot's joint angles are eliminated, and the robot can accurately follow the teaching data. You can get the excellent effect of working.

In addition, in the above-mentioned embodiment, it was explained that all teachings of the robot are performed by manual teaching, but numerical data may be directly set in the storage unit 36 from the manual operating device 31, as shown by the broken line arrow in FIG. , or both may be used together. In addition, instead of relying solely on the manual operating device 31 for inputting various data, the computer is connected to another computer via a communication line or the like, and the data obtained through calculation processing is directly input into the storage section 35, 36, etc. It's okay.

Furthermore, in the above embodiment, since the work handled by the robot that requires high-precision positioning is small and lightweight, the gravitational torque caused by the weight of the robot body is considered to be the largest cause of errors, and the influence of the work weight Although not mentioned above, if the influence of the workpiece weight cannot be ignored, the workpiece weight is also stored in the memory (14) section 35, and the calculation processing of the torsion angle calculation section 39 is made to perform calculations for the workpiece weight. You can do it like this.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to operate the robot by correcting the low rigidity existing in the drive system of the robot and the twist in the operating joint angle caused by the gravitational moment acting on each rotary joint of the robot. As a result, the robot can operate with high precision according to the taught position and posture.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the configuration of an articulated robot to which an example of the device of the present invention is applied, Figure 2 is a block diagram of the drive system of the robot shown in Figure 1, and Figure 3 is the robot shown in Figure 1. FIG. 4 is a block diagram showing the configuration of an example of the device of the present invention. 38... Motion joint angle calculation section, 39... Torsion angle calculation section, 40... Joint angle correction calculation section. (15) ヰ 1 ward 2 巳

Claims (1)

[Claims] 1. In an articulated robot that operates according to teaching data, a means for determining the operating joint angles of the joints of the robot based on the teaching data, and a means for determining the operating joint angles caused by the gravitational torque load acting on the joints corresponding to the operating joint angles. An articulated robot characterized by comprising means for calculating the amount of twist, and means for calculating the actual joint angle based on the joint angle of the robot and the amount of twist, and outputting the calculated result to the drive system of the robot. Position control device.