JP6943906B2 - robot - Google Patents

Description

The present disclosure relates to robots.

An articulated robot having a plurality of joints and each joint having a torque sensor for detecting torque around the axis of the joint is known (see, for example, Patent Document 1). The robot of Patent Document 1 corrects the torque around the axis of one joint by using the torque detected by the torque sensor of another joint located on the tip side of the one joint.
This is because the torque around the axis of one joint fluctuates due to the influence of the load applied in a direction other than around the axis of one joint.

Japanese Unexamined Patent Publication No. 2017-80841

However, in the method of Patent Document 1, since it is premised that torque sensors are arranged in all joints, the robot becomes expensive. Further, if an external force by an operator is applied to the arm connecting the joint for which the torque is calculated and the joint on the distal end side by a lead-through instruction or the like, the torque around the axis of the joint cannot be calculated correctly. By increasing the rigidity of the body of the torque sensor, the influence of the load applied other than around the axis of the joint can be reduced, but the torque sensor itself becomes large, the robot becomes large, and the robot mass increases.

One aspect of the present disclosure, detects a plurality of joints and rotating around its own axis Ru linked by robot components, the axis around torque is one object joint of the plurality of the joints, it is detected The torque includes a torque sensor and all or a part of the plurality of joints, including a torque acting around the axis of the target joint by the inertial force of the robot component generated by the operation of the robot and the weight of the robot component. Information related to the rotation angle around the axis of the Based on the information of all or a part of the plurality of joints, the amount of fluctuation of the torque detected by the torque sensor due to a load other than the torque around the axis of the target joint is estimated, and the load is calculated. The torque fluctuation amount estimation unit, which is a load acting on the target joint due to the inertial force of the robot component and the weight of the robot component, and the torque detected by the torque sensor using the estimated fluctuation amount are obtained. Provided is a robot including a correction unit that corrects and calculates a torque around the axis of the target joint with improved accuracy.

It is a schematic plan view of the robot which concerns on one Embodiment of this disclosure. It is a schematic side view of the connection part of the base of the robot of FIG. 1 and a swivel body. It is a block diagram of the torque control of a motor by the control part of the robot of FIG. It is a graph which shows an example of the change of the detection torque with respect to the rotation angle of the swivel cylinder around the J1 axis. It is a graph which shows an example of the correction torque calculated based on the detection torque shown in FIG. It is a perspective view which shows an example of the 1st torque sensor provided in the robot of FIG.

The robot 100 according to the embodiment of the present disclosure will be described below with reference to the drawings.
The robot 100 according to the present embodiment is a vertical articulated robot having six joints that are rotationally driven around each axis.

As shown in FIG. 1, the robot 100 includes a base 1 fixed to an installation surface and a swivel body (robot configuration) rotatably supported around a J1 axis (target joint) extending in a vertical direction with respect to the base 1. (Parts) 2, the first arm (robot component) 3 rotatably supported around the horizontal J2 axis (joint) orthogonal to the J1 axis with respect to the swivel body 2, and J2 with respect to the first arm 3. Around the second arm (robot component) 4 rotatably supported around the J3 axis (joint) parallel to the axis, and around the J4 axis (joint) at a twisted position with the J3 axis with respect to the second arm 4. A rotatably supported first wrist element (robot component) 5 and a rotatably supported second wrist element (robot) around the J5 axis (joint) orthogonal to the J4 axis with respect to the first wrist element 5. It includes a component 6) and a third wrist element 7 rotatably supported around the J6 axis (joint) orthogonal to the J5 axis with respect to the second wrist element 6.

Further, the robot 100 is arranged between the base 1 and the swivel cylinder 2 and is located between the first torque sensor (torque sensor) S1 for detecting the torque around the J1 axis and between the swivel cylinder 2 and the first arm 3. A second torque sensor S2 that is arranged to detect the torque around the J2 axis and a third torque sensor S3 that is arranged between the first arm 3 and the second arm 4 to detect the torque around the J3 axis are provided. ing.

Further, the robot 100 includes motors MT1 to MT6 for driving each part around the J1 to J6 axes, and each encoder (angle-related information detection unit) EN1 provided in each motor MT to detect the rotation angle around the J1 to J6 axes. ~ EN6 and a control unit 10 that controls driving around the J1 to J6 axes of each unit by using the detected rotation angle around each axis are provided. The motor MT1 and the encoder EN1 that drive the swivel cylinder 2 around the J1 axis with respect to the base 1 are shown in FIG. 2, and are not shown in FIG.

The control unit 10 shown in FIG. 1 includes a CPU (not shown), a ROM, and a RAM. When the CPU expands the program stored in the ROM into the RAM, the control unit 10 executes each program function.

As shown in FIG. 3, the control unit 10 calculates the correction torque (fluctuation amount) Tf by estimating the fluctuation amount of the torque detected by the first torque sensor S1 according to the posture change of the robot 100. The amount estimation unit (torque fluctuation amount estimation unit) 13, the correction unit 11 that corrects the detection torque T using the correction torque Tf calculated by the fluctuation amount estimation unit 13, and the torque input to drive the motor MT1. It includes a drive unit 12 that drives the motor MT1 based on the command value Ti, the detection torque T, and the correction torque Tf.

The fluctuation amount estimation unit 13 preliminarily (ships) a rotation angle characteristic consisting of a table or an approximate formula to which the detection torque T detected by the torque sensor is applied to the rotation angle when each joint is rotated around each axis. I ask for it (at times, etc.) and remember it.
For example, FIG. 4 shows the torque T0 detected by the first torque sensor S1 when only the rotation angle around the J1 axis is changed and each of the other joints is fixed at a rotation angle at which no load is applied to the J1 axis.

The posture of the robot 100 in which the load is not applied to the J1 axis is, for example, the posture of the robot 100 in which the J4 axis and the J6 axis substantially match the extension line of the J1 axis, and the state in which the mechanism on the tip side of the swivel cylinder 2 or more is removed. The posture of the robot 100 and the like can be mentioned.

If the swivel cylinder 2 rotates around the J1 axis while maintaining the posture of the robot 100 in which no load is applied around the J1 axis, ideally, the torque around the J1 axis detected by the first torque sensor S1 is zero. .. However, in reality, as shown in FIG. 6, two strain gauges G1 and G2 are attached to the surface of the body BD of the first torque sensor S1 and are detected by the amount of strain detected by G1 and G2. The torque T is determined. An error may occur in the detection torque T due to a deviation in the attachment position of the strain gauges G1 and G2.

According to FIG. 4, the torque T0 changes according to the rotation angle around the J1 axis detected by the first encoder EN1.
Therefore, as shown in FIG. 5, the fluctuation amount estimation unit 13 stores the rotation angle characteristic of the torque T0 detected by the first torque sensor S1 by a table or an approximate expression. Then, the fluctuation amount estimation unit 13 stores the rotation angle characteristics of the torque with respect to the rotation angles of all the joints by a table or an approximate expression. This table or approximate expression is experimentally obtained by plotting the correlation between the rotation angle and torque data. Calculate the coefficients of the table or approximate expression from this plot data.

The torque rotation angle characteristic may be measured by simulation as well as when the robot is actually operated for measurement.
As a result, during the actual operation of the robot, the fluctuation amount estimation unit calculates the correction torque Tf by applying or interpolating the rotation angle of each axis detected by the encoder to the stored rotation angle characteristic. be able to.

Then, as shown in the following equation (1), the correction unit 11 subtracts the correction torque Tf estimated by the fluctuation amount estimation unit 13 from the detection torque T of the first torque sensor S1 in the robot 100 during use. To calculate the estimated actual torque Tr.
Estimated actual torque Tr = Detected torque T-Corrected torque Tf ... (1)

The estimated actual torque Tr represents the actual torque around the J1 axis that is applied to the J1 axis by excluding the torque other than the torque around the J1 axis. In order to calculate the estimated actual torque Tr, the correction unit 11 may use any of addition, multiplication, and division calculation methods instead of subtracting the correction torque Tf from the detection torque T.

The drive unit 12 drives the motor MT1 with a drive torque obtained by subtracting the estimated actual torque Tr from the input torque Ti based on the input command for controlling the robot 100. As shown in FIG. 3, the detection torque T detected by the first torque sensor S1 while the motor MT1 is being driven is used for feedback control of the drive unit 12 as an estimated actual torque Tr by subtracting the correction torque Tf.

The operation of the robot 100 according to the present embodiment configured in this way will be described below.
The detected torque T detected by the first torque sensor S1 may include torque generated by a load other than the torque around the J1 axis. In the present embodiment, as shown in FIG. 6, the fluctuation amount estimation unit 13 calculates the correction torque Tf as the fluctuation amount from the stored rotation angle characteristics based on the rotation angle of each joint of the robot 100. presume. Then, the correction unit 11 corrects the detection torque T of the first torque sensor S1 by using the correction torque Tf, so that the load other than the torque around the J1 axis is excluded from the detection torque T of the first torque sensor S1. The actual torque Tr can be obtained. That is, the estimated actual torque Tr can accurately acquire the torque around the J1 axis, and the robot 100 can be controlled accurately.

Further, according to the robot 100 according to the above embodiment, when the operator directly touches the arm and applies an external force to the robot 100, the estimated actual torque Tr is used to rotate the J1 axis by the external force. The torque generated in the robot can be estimated accurately. As a result, it is possible to prevent the robot 100 from malfunctioning in the feedback control of the drive unit 12 using the detection torque T of the first torque sensor S1.

Further, according to the present embodiment, the correction unit 11 does not need the detection value of the torque sensor other than the first torque sensor S1 to calculate the correction torque Tf for correcting the detection torque T around the J1 axis. Therefore, it is not necessary to dispose torque sensors at all the joints of the robot 100, and the cost of the robot 100 can be reduced.

Further, in the present embodiment, the encoder is exemplified as the angle-related information detection unit, and the rotation angle around the J1 to J6 axes is exemplified as the angle-related information, but the present invention is not limited to this, and the angular velocity or the angle is not limited thereto. Acceleration may be detected. Further, the correction torque Tf may be calculated by using the angular velocity and / or the angular acceleration around the J1 to J6 axes in addition to the rotation angles around the J1 to J6 axes. Further, the correction torque Tf may be calculated by using the information related to the angles of some joints instead of all the joints.

Further, the fluctuation amount estimation unit 13 stores physical parameters (for example, dimensions and weight) of robot components (for example, first arm 3 and the like) that connect the J1 to J6 axes, and stores the physical parameters and rotation. The correction torque Tf may be estimated based on the angle. In this case, the fluctuation amount estimation unit 13 more accurately calculates the correction torque Tf by using the moment of inertia applied other than around the J1 axis generated by the arm weight or the like, and the tensile force or compressive force applied in the direction along the J1 axis. can.

Further, in the above embodiment, the correction unit 11 corrects the detection torque T of the first torque sensor S1, but the torque detected by the second torque sensor S2 and the torque detected by the third torque sensor S3 are measured. Similar to the detection torque T of the first torque sensor S1, the correction torque of each shaft may be used for correction. Further, the robot 100 may include a torque sensor that detects torque around the axis of a joint (for example, the J4 axis) different from the above embodiment.

Further, in the present embodiment, the correction unit 11 or the fluctuation amount estimation unit 13 may be provided on arbitrary parts on the arms 3 and 4 of the robot 100, respectively, or a robot control device for controlling the robot 100. It may be provided inside the. Further, the robot 100 may be provided inside the peripheral devices excluding the arms 3 and 4 and the robot control device, or the correction unit 11 or the fluctuation amount estimation unit 13 may be installed as a separate control unit to control the robot. It may be connected to the device. The correction unit 11 or the fluctuation amount estimation unit 13 may be provided at different locations.

The embodiment is derived from each of the following aspects of the present disclosure.
One aspect of the present disclosure is a plurality of joints that are rotationally driven around an axis, a torque sensor that detects torque around the axis of a target joint that is one of the plurality of joints, and a torque sensor around the axis of each of the joints. Based on the angle-related information detection unit that detects information related to the rotation angle and the detected information, the amount of fluctuation of the torque detected by the torque sensor due to a load other than the torque around the axis of the target joint is estimated. Provided is a robot including a torque fluctuation amount estimation unit and a correction unit for correcting torque detected by the torque sensor using the estimated fluctuation amount.

When the target joint is rotationally driven around the axis or an external force is applied around the axis of the target joint, the torque sensor detects the torque around the axis, but each joint rotates around the axis and the posture of the robot changes. Then, the torque sensor may detect a torque on which a load other than the torque around the axis of the target joint is superimposed.

According to this aspect, when each joint rotates around the axis, the angle-related information detection unit detects information related to the rotation angle around the axis of each joint, and the torque fluctuation amount estimation unit is based on the detected information. Therefore, the amount of torque fluctuation due to a load other than the torque around the axis of the target joint is estimated. Then, the torque detected by the torque sensor is corrected using the estimated fluctuation amount, so that a load other than the torque around the axis of the target joint is eliminated. As a result, the robot can be controlled accurately by accurately acquiring the torque around the axis of the target joint without arranging the torque sensor in a joint other than the target joint.

In the above aspect, the information may be a rotation angle around the axis of each of the joints.
With this configuration, the rotation angle of each joint is detected by the angle-related information detection unit, and the torque can be corrected using the amount of load fluctuation estimated according to the change in the posture of the robot.

In the above aspect, the information may be an angular velocity or an angular acceleration around the axis of each of the joints.
With this configuration, the angular velocity or angular acceleration of each joint is detected by the angle-related information detection unit, and the amount of load fluctuation is estimated according to the detected angular velocity or angular acceleration.

In the above aspect, the robot component connecting each of the joints is provided, and the information is calculated from the rotation angle, the angular velocity or the angular acceleration around the axis of each of the joints, and the physical parameters of the robot component. It may be load information applied to the joint.
With this configuration, the angle-related information detector can provide information about the rotation angle, such as the detected rotation angle, angular velocity or angular acceleration, and load information such as moment of inertia, tensile force or compressive force based on the physical parameters of the robot component. It is calculated. By calculating the load other than the torque around the axis applied to the target joint based on the calculated load information, the torque around the axis of the target joint can be acquired accurately.

In the above aspect, the load other than the torque around the axis of the target joint may be the torque around the orthogonal axis arranged in a plane orthogonal to the axis of the target joint.
In the above aspect, the load other than the torque around the axis of the target joint may be the load in the tensile and compressive directions acting in the axial direction of the target joint.

In the above aspect, the correction unit is detected by the torque sensor when the target joint is rotated around the axis of the target joint in a state where no load other than the torque around the axis of the target joint is applied. The torque detected by the torque sensor may be corrected based on the torque characteristic indicating the relationship between the torque and the information of the target joint detected by the angle-related information detection unit.

The torque characteristic represents the amount of torque fluctuation with respect to a change in the detection value of the angle-related information detection unit in a state where the torque around the axis of the target joint is not applied to the target joint. That is, since the torque characteristic represents the characteristic caused by the detection error of the torque sensor itself, the torque around the axis of the target joint is acquired more accurately by correcting the detected torque using the torque characteristic. can.

1 base (robot component)
2 Swivel cylinder (robot component)
3 First arm (robot component)
4 Second arm (robot component)
5 First wrist element (robot component)
6 Second wrist element (robot component)
7 Third wrist element (robot component)
11 Correction unit 13 Fluctuation amount estimation unit (torque fluctuation amount estimation unit)
100 Robot EN1 to EN6 encoder (angle related information detector)
J1 to J6 Joint J1 Target joint S1 1st torque sensor (torque sensor)
Tf correction torque (fluctuation amount)

Claims (7)

A plurality of joints that will be connected by the robot components to rotate driving around an axis,
The torque around the axis of the target joint, which is one of the plurality of joints, is detected, and the detected torque is determined by the inertial force of the robot component generated by the operation of the robot and the weight of the robot component. A torque sensor that includes the torque acting around the axis of the target joint,
Information related to the rotation angle of all or a part of the plurality of joints around the axis is detected, and the part of the plurality of joints includes the target joint and at least one joint other than the target joint. , Angle related information detector,
Based on the information of all or a part of the plurality of detected joints, the amount of fluctuation of the torque detected by the torque sensor due to a load other than the torque around the axis of the target joint is estimated, and the load is calculated. , A torque fluctuation amount estimation unit , which is a load acting on the target joint due to the inertial force of the robot component and the weight of the robot component.
A robot including a correction unit that corrects the torque detected by the torque sensor using the estimated fluctuation amount and calculates the torque around the axis of the target joint with improved accuracy. The robot according to claim 1, wherein the information is a rotation angle around the axis of each of the joints. The robot according to claim 1, wherein the information is an angular velocity or an angular acceleration around the axis of each of the joints. It is equipped with robot components that connect each of the joints.
The robot according to claim 1, wherein the information is load information applied to each joint calculated from a rotation angle, an angular velocity or an angular acceleration around the axis of each joint and physical parameters of the robot component. The robot according to any one of claims 1 to 4, wherein the load other than the torque around the axis of the target joint is the torque around the orthogonal axis arranged in a plane orthogonal to the axis of the target joint. The robot according to any one of claims 1 to 4, wherein a load other than the torque around the axis of the target joint is a load in the tensile and compressive directions acting in the axial direction of the target joint. The torque fluctuation amount estimation unit calculates the torque corresponding to the information of the target joint detected by the angle-related information detection unit from the torque characteristic of the target joint, and the torque characteristic is the axis of the target joint. The torque detected by the torque sensor and the target joint detected by the angle-related information detection unit when the target joint is rotated around the axis of the target joint in a state where a load other than the surrounding torque is not applied. Any one of claims 1 to 6, wherein the correction unit corrects the torque detected by the torque sensor by using the torque calculated by the torque fluctuation amount estimation unit. The robot described in.

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