JPS6340906A - Gravity compensating device for industrial robot - Google Patents

Abstract

PURPOSE:To execute the gravity compensation with high accuracy by inputting the weight of a holding object, executing the gravity compensation by this input weight, and also, executing a correction by a moment variation. CONSTITUTION:A worker inputs directly a difference of weight of a load at the time when an object is held, and not held, and a different of the weight of the holding object, by an input means 20. In accordance with a difference of this input load weight, an output to a motor of a driving control means 10 is controlled by an output means, and also, an output to a motor M2 of the driving means 10 is controlled by a means 40 for calculating and correcting a moment variation in accordance with an operating state of a joint use arm of each joint. In this way, a compensation at the time when the object is held, and not held is executed, and also, in accordance with weight of the holding object,the gravity compensation can be executed with high accuracy against a disturbance based on its gravity.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a gravity compensation device for an industrial robot.
This invention relates to a gravity compensation device for an industrial robot having an arm that can swing through a joint that rotates around a horizontal axis.

(Prior art) Generally, an industrial robot grips a workpiece or a working machine such as a sealing gun at the wrist at the tip of the arm, and controls the gripped object to be positioned at a predetermined target position with high precision. It is configured to do so.

Conventionally, in order to meet the demands for highly accurate positioning control of the robot arm, for example, in order to reduce the influence of disturbance torque due to gravity on the arm, springs, counterweights, etc. have been used to counteract the weight of the arm. Mechanical compensation measures are in place.

In addition, when controlling the drive of the arm, the weight of the object to be grasped is
There is also known a device that performs gravity compensation by detecting the weight at a joint that supports the weight, performing calculations based on the detected weight, and estimating the influence of gravity.

(Problems to be Solved by the Invention) However, mechanical compensation means such as springs and counterweights are not always effective because the balance changes between when an object is gripped and when it is not gripped.

In addition, with the method using weight detection described above, it is possible to compensate for disturbance torque caused by the weight of the gripped object, and an improvement in the compensation effect can be expected, but it is necessary to detect the weight of the gripped object during control. Based on this detected weight, it is necessary to estimate the gravitational influence and control the motor drive to compensate for gravity, so the control time becomes longer due to weight detection and the estimation of the gravitational influence, and the estimation error increases. There were some problems, such as getting too big.

In the present invention, the gripping object attached to the arm is the same in one process in the production line, and even if the gripping object is replaced or changed due to a change in process, there are at most several types of gripping objects. This invention was invented at a young age, and its purpose is to enable a worker to input the weight of an object to be grasped, and to perform gravity compensation using this input weight, as well as to make it possible to calculate joint angles based on the input weight. By calculating and correcting the moment change, the control time will not be increased, and it will not only compensate for the gravity when the object is gripped and when it is not gripped, but also compensate for the gravity based on the input weight of the gripped object. The object of the present invention is to provide a gravity compensation device for an industrial robot that can perform gravity compensation with high precision.

(Means for solving the gap) Therefore, the present invention provides a gravity compensation device for an industrial robot having an arm that can swing through a joint that rotates around a horizontal axis, and which acts on the arm. a drive control means (10) for the motor that compensates for the gravity by driving the motor that drives the arm; an input means (20) for inputting the load weight when gripping an object and when not gripping the object; The drive control means (1) based on the gravity signal from the
output means (30) for controlling the output to the motor of 0);
Correction means (40), which has a calculation unit that calculates a moment change based on the joint angle at the joint, and corrects the output of the drive control means (10) to the motor. : It is characterized by having the following.

(Function) The input means (20) allows the worker to easily directly input the difference in the load weight between when an object is gripped and when it is not gripped, as well as the difference in the weight of the gripped object, and does not perform complicated weight detection. There is no need, and the output means (30) controls the output to the motor of the drive control means (10) according to the difference in the input load weight, and the joint angle of each joint, that is, the arm By controlling the output to the motor of the drive means (10) by the correction means (40) according to the operating state of the Therefore, highly accurate gravity compensation can be performed for disturbances caused by gravity.

(Example) The robot shown in FIG. 2 is a robot to which the gravity compensation device according to the present invention is applied, and has three first to third bending joints (Pl) (P2) (P3) rotating around a horizontal axis. ),
Through these joints, three arms (1) (2) (5)
The first arm (1) is relative to the torso (4), the second arm (2) is relative to the first arm (1), and the wrist (5) is relative to the arm that serves as the reference for its operation. Each of the second arms (2) is swingable relative to the second arm (2).

Moreover, the said trunk|drum (4) and the 1st. Second arm (1) (2
) comprises three first to third rotational joints (R1) (R2) (R3) that rotate around axes extending in the length direction, and the body (4) is attached to the base (3). On the other hand, the first arm (1) is connected to the second arm (2) with respect to the body (4).
are each rotatable with respect to the first arm (1).

Each arm (4) (1) that swings or rotates as described above.
), (2), and (5) alternately move the bending joint (Pl) and the rotational joint (R1) from the base (3), which is the fixed part of the robot, that is, R1. -P 1-R2-R
2-R3-R3, and these arms (4) (1) (2) (5) are connected to six motors (Ml) (M2) that drive each joint. )...
It is driven as follows.

■ The trunk (4) rotates around the axis extending in the length direction of the base (3) (vertical axis in the case of Fig. 2) at the first rotation amount node (R).
01 rotation via 1).

(2) The first arm (1) swings by θ2 about an axis (horizontal axis) perpendicular to the length direction of the chest (4) via the first bending joint (Pl).

(2) Similarly, the first arm (1) rotates by 033 around the axis extending in the length direction of the body (4) via the second rotation node (R2).

■ The second arm (2) has a second bending relation m (R
2), it swings by θ4.

(2) Similarly, the second arm (2) rotates by θ55 around the axis extending in the length direction of the first arm (1) via the third rotation node (R3).

(2) The wrist portion (8) swings by θB via the third bending joint (R3) around an axis (horizontal axis) perpendicular to the length direction of the second arm (2).

In other words, in the one in Figure 2, the six joints described above connect the wrist (5) at the tip of the robot.
), the wrist part (
5) at any position in three-dimensional space (X+7+Z)
and any pose (α, β.

γ), and the first and second arms (12), which are the material parts (12) of the robot.
) (2), the first rotation amount node (R1) and the second
Drive rotation with the rotation amount node (R2) and the first bending joint (
Pl) provides a degree of freedom that allows for tilting while maintaining the position and direction of the wrist portion (5). 1 and the second bending joint in the second arm (1) (2) (
Increase the elbow height without changing the joint angle of R2) H)
The structure is changed as shown by the dashed line in Figure 2 to allow it to swing freely.

Therefore, the gravity compensation device for the robot constructed as described above is constructed as shown in FIG. That is, (1) a drive control means (10) is provided which compensates for the gravity acting on each of the arms (1), (2), and (5) that performs a swinging operation by the drive torque of a motor that swings each arm.

(2) An input means (20) is provided for inputting the load weight on the wrist (5) when various objects such as workpieces and working machines are being gripped and when not being gripped.

(2) An output means (30) is provided for controlling the output of the drive control means (10) to the motor based on the gravity signal from the input means (20).

■, Joint angle (θ2) at each joint (Pl)...
), Pa, etc., and a correction means (40) for correcting the output of the drive control means (10) to the motor.

More specifically, the drive control means (10) controls each motor that drives each arm (1), (2), and (5) to act on each motor. )
This control means (10) provides a driving torque sufficient to overcome the disturbance torque based on the weight of (5), and this control means (10)
It is connected to the input picture of each motor on the output side of the amplifier (11) in the control system (100) regarding the position and orientation of each motor. Additionally, the control system (100)
This constitutes a feedback loop in which the command signal regarding the position and orientation of each arm is used as a target value, and the actually detected position and orientation information of each arm is used as a feedback loop.

For example, the drive control means (10) is connected to the first arm (1
) is applied to the motor (M2) provided corresponding to the first bending joint (Pl), the three arms (1), (2) ( 5) A driving torque sufficient to overcome the disturbance torque caused by the heavy metal is given to the motor (M2), and as a result,
The motor (M2) can be driven by a predetermined joint angle (swing angle θ2).

The input means (20) inputs the weight of the object gripped at the wrist (5) as a numerical value from, for example, a keyboard (7), and stores it in the memory (8).

When the weight of the gripped object is input from the input means (20), the output means (30) generates an estimated value of the disturbance torque calculated by the correction means (40), which will be described in detail below, based on this input weight. By changing the coefficient (the value of the moment of the armrest or the coefficient for changing the value of this armrest) for determining the (moment M), the correction value calculator of the correction means (40) (9) A correction value (C) of the motor input in the drive control means (1o) introduced through
, and controls the output of the drive control means (10) to the motor.

For example, in the first bending joint (Pl), the correction means (40) uses its calculation unit to calculate the three arms (1) (
2) The five joint angles (θ2.θ3.θ4.
θ5. θ6), calculate the moment (M) of the arm (L) that is applied to the joint (Pl), that is, the motor (M2), which changes depending on these five joint angles, and
The moment (M = Then, the moment calculated by this calculating section is used as the estimated value of the disturbance torque, and based on this estimated value of the disturbance torque, the estimated value of the disturbance torque is calculated via the correction value calculator (9). , the correction value (C) is set, and the output of the drive control means (10) to the motor (Mg2 in this case) is controlled.

The joint angles (θ2) used in calculating the moment of the arm (L) in the calculation unit may be calculated values, or may be calculated using potentiometers installed in each joint. Actual values detected by a meter or the like may be used.

Thus, the input means (20) allows the wrist portion (
In 5), the difference in the load weight between when the object is gripped and when it is not gripped, as well as the difference in m2 of the gripped object, can be easily and directly input by the worker, and there is no need to perform complicated weight detection. According to the input load weight difference, the output means (30) changes the estimated value of the disturbance torque in the correction means (40), and the drive control means (10)
The correction means (40) controls the output to the motor of the drive means (10) according to the joint angle of each joint, that is, the operating state of the arm, thereby controlling the output to the motor of the drive means (10). Not only can compensation be performed when the object is being gripped and when it is not being gripped, but also highly accurate gravity compensation can be performed in accordance with the weight of the gripped object and for disturbances caused by its gravity.

In the above embodiment, a robot with 6 axes of joints in which bending joints and rotational joints are arranged alternately was described, but the present invention is not limited to this 6 axes of joints; Needless to say, the present invention can be applied to any robot as long as it has a bending joint, that is, a joint that rotates around one or more horizontal axes.

(Effects of the Invention) As described above, the present invention provides a gravity compensation device for an industrial robot having an arm that is swingable via a joint that rotates around a horizontal axis. A drive control means (10) for the motor that compensates by driving the motor that drives the arm, an input means (20) for inputting the load weight when grasping an object and when not grasping the object, and a gravity input means (20) from the input means (20). output means (30) for controlling the output of the drive control means (10) to the motor based on the signal;
and a computation unit that computes a moment change based on the joint angle at the joint, and a correction unit (40) that corrects the output of the drive control unit (10) to the motor. Therefore, it is possible to compensate not only when an object is gripped and when it is not gripped, but also to compensate for disturbances caused by gravity according to the weight of the gripped object in a short time, and to perform highly accurate gravity compensation. be.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a main part of an embodiment of a robot according to the present invention, and FIG. 2 is an external view showing the overall structure of the robot. (10)...Drive control means (20)...Input means (30) Φ...Output means (40)...O--Correction means

Claims (1)

[Claims] A gravity compensation device for an industrial robot having an arm that is swingable via a joint that rotates around a horizontal axis, the motor compensating for gravity acting on the arm by driving a motor that drives the arm. drive control means (10
), an input means (20) for inputting the load weight when gripping an object and when not gripping the object, and an output to the motor of the drive control means (10) based on the gravity signal from the input means (20). an output means (30) for controlling the joint; and a correction means (40) for correcting the output of the drive control means (10) to the motor, having a calculation section for calculating a moment change based on the joint angle at the joint. A gravity compensation device for an industrial robot, characterized by comprising: