Robot system

Abstract

To estimate reduced state of gas pressure inside a gas spring of a robot, regardless of the posture or the driven state of the robot.SOLUTION: A robot system 1 comprises: a robot 10 including an arm 4a, an arm 4b rotatably supported by the arm 4a via a joint 6a, a drive motor 7a for driving the arm 4b, and a gas spring 20 which is fixed to the arm 4a and the arm 4b and assists output of the drive motor 7a; a measuring unit 36 measuring deformation amount of a fixed portions 8 in the arm 4a, to which the gas spring 20 is fixed; and an estimating unit 38 which estimates reduced state of gas pressure inside the gas spring 20 on the basis of the deformation amounts measured by the measuring unit 36.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a robot system including a robot having an output assistance mechanism fixed to one arm and the other arm and assisting the output of a drive motor.

Background Art

[0002] In a robot in a robot system including an arm driven by a drive motor, it is known to provide an output assistance mechanism for reducing the load applied to the drive motor due to the gravity acting on the arm. For example, in the robot disclosed in Patent Document 1 below, a gas spring is provided as an output assistance mechanism for the arm, and the load applied to the drive motor is reduced by the auxiliary torque output by the gas spring. The gas spring includes a cylinder and a piston rod that is slidable within the cylinder and compresses a high-pressure gas enclosed within the cylinder. As the piston rod is inserted into the cylinder and the length of the gas spring becomes shorter, the gas pressure enclosed within the cylinder increases. The gas spring outputs an auxiliary torque by the reaction force (expansion and contraction force) due to this gas pressure.

[0003] Here, in the gas spring, the internal gas pressure may decrease due to the gradual leakage of the internal gas due to the sliding of the piston rod or the sudden leakage of the internal gas due to a failure of the gas spring. When the gas pressure decreases, the reaction force of the gas spring decreases, and the auxiliary torque due to the reaction force decreases. As a result, the load on the drive motor increases, and there is a risk that the arm cannot be supported by the drive motor. In order to suppress such a situation, it is necessary to estimate the assistance state of the gas spring and perform maintenance (maintenance including inspection, repair, replacement, replenishment, etc.) of the gas spring based on the estimated assistance state.

[0004] Patent Document 1 below proposes a method for estimating the decrease in internal gas pressure as an auxiliary state of a gas spring. In this method, the decrease in auxiliary torque output by the gas spring, and consequently the decrease in internal gas pressure of the gas spring, is estimated by comparing the theoretical value of the torque that the drive motor should bear assuming that there is no gas leakage in the gas spring with the measured value of the torque actually borne by the drive motor. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-159402 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, when the arm is operated near a dead center where the direction of extension and contraction of the gas spring and the rotation axis of the arm are in a straight line, the auxiliary torque from the gas spring is almost eliminated. Therefore, when the robot repeatedly performs movements near this dead center, it is difficult to determine whether the decrease in auxiliary torque estimated by the method disclosed in Patent Document 1 is due to a decrease in gas pressure inside the gas spring or to other factors such as noise or measurement errors.

[0007] Furthermore, in the method disclosed in Patent Document 1, in order to estimate the state of decreased gas pressure, it is necessary to first release the electromagnetic brake provided on the drive motor to make the arm rotatable, and then support the arm with the torque from the drive motor and the auxiliary torque from the gas spring. For this reason, if the internal gas pressure has dropped extremely low due to a gas spring failure or the like, the arm cannot be supported by the torque from the drive motor alone, and there is a risk that the arm will fall as soon as the electromagnetic brake is released.

[0008] As described above, the method disclosed in Patent Document 1 has the problem that it is difficult to estimate the auxiliary state of the gas spring as an output auxiliary mechanism when the robot is in a specific posture state or when the drive motor is braked by an electromagnetic brake and the robot is stopped.

[0009] Therefore, the present invention aims to provide a robot system that can estimate the auxiliary state of the output assist mechanism regardless of the robot's posture or driving state. [Means for solving the problem]

[0010] The robot system according to the present invention comprises a robot having one arm, another arm rotatably supported on the first arm via a joint, a drive motor for driving the other arm, and an output assist mechanism fixed to the first arm and the other arm for assisting the output of the drive motor; a measuring unit for measuring the amount of deformation of a fixed part on the first arm to which the output assist mechanism is fixed; and an estimation unit for estimating the assist state of the output assist mechanism based on the amount of deformation measured by the measuring unit.

[0011] Furthermore, the measuring unit measures the amount of deformation using a strain gauge provided on the fixed part.

[0012] Furthermore, the estimation unit estimates the auxiliary state based on the predetermined standard deformation amount and the deformation amount measured by the measurement unit.

[0013] Furthermore, the measuring unit measures the amount of deformation when the drive motor is stopped.

[0014] Furthermore, the output assist mechanism is a gas spring. [Effects of the Invention]

[0015] According to the present invention, the auxiliary state of the output assist mechanism can be estimated regardless of the robot's posture or driving state.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a schematic configuration of a robot system according to an embodiment of the present invention. [Figure 2A] It is a diagram showing a gas spring when the arm in FIG. 1 is in a posture along the direction of gravity. [Figure 2B] It is a diagram showing a gas spring when the arm in FIG . 1 is in a posture inclined in a direction intersecting the direction of gravity. [Figure 3] It is a block diagram showing an example of the functional configuration of the control device in FIG. 1. [Figure 4] In the robot system according to the embodiment of the present invention, it is a flowchart showing an example of the flow of processing performed by each functional configuration in FIG. 3.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention (hereinafter, appropriately referred to as "the present embodiment") will be described with reference to the accompanying drawings. For ease of understanding of the description, the same reference numerals are given to the same elements or elements having the same function in each drawing as much as possible, and redundant descriptions are omitted.

[0018] <Overall Configuration> FIG. 1 is a diagram showing a schematic configuration of a robot system 1 according to the present embodiment.

[0019] As shown in FIG. 1, the robot system 1 includes, for example, an articulated robot (hereinafter, simply referred to as "robot") 10 composed of a vertical multi-joint, a gas spring 20, a strain gauge 26, and a control device 30.

[0020] The robot 10 has a base 2, arms 4a, 4b, 4c, and joints 6a, 6b.

[0021] The base 2 is an installation part for installing the robot 10 on the floor or the like. The arms 4a, 4b, and 4c are provided on the base 2 and are arranged in the order of the arm 4a, the arm 4b, and the arm 4c from the base 2 side. One of the arms, the arm 4a, is erected on the base 2 and is supported so as to be rotatable about the rotation axis J1 with respect to the base 2. The arm 4a supports the other arm, the arm 4b, via the joint 6a. The arm 4b is supported so as to be rotatable about the rotation axis J2 with respect to the arm 4a via the joint 6a. The arm 4c is supported so as to be rotatable about the rotation axis J3 with respect to the arm 4b via the joint 6b. A hand 5 is attached to the tip of the arm 4c.

[0022] The joints 6a and 6b are connecting parts that connect adjacent arms 4a, 4b, and 4c. Specifically, the joint 6a connects the arm 4a and the arm 4b, and the joint 6b connects the arm 4b and the arm 4c. The joint 6a has a drive motor 7a for driving the arm 4b. The joint 6b also has a drive motor 7b for driving the arm 4c. The drive motors 7a and 7b are, for example, servo motors. Each of the drive motors 7a and 7b is rotationally controlled by the control device 30 and rotates about the rotation axes J2 and J3, respectively. By the rotation of the drive motors 7a and 7b, the respective arms 4b and 4c rotate. Although not shown in the figure, a drive motor for driving the arm 4a is also provided at the joint connecting the base 2 and the arm 4a. Since this drive motor is the same as the drive motors 7a and 7b, detailed description thereof is omitted.

[0023] The drive motors 7a and 7b are provided with a brake mechanism (not shown) such as an electromagnetic brake. The electromagnetic brake is operationally controlled by the control device 30. As is well known, when the robot 10 stops, the electromagnetic brake is in a state where no voltage is applied by the control device 30, brakes the rotation axes J2 and J3 of the drive motors 7a and 7b, and holds the stopped state of the robot 10. On the other hand, when the robot 10 is operating, the electromagnetic brake is in a state where a voltage is applied by the control device 30, and releases the braking of the rotation axes J2 and J3 of the drive motors 7a and 7b.

[0024] Furthermore, the drive motors 7a and 7b are equipped with encoders (angle sensors) or the like for detecting the rotation angle of the drive motors 7a and 7b. In this embodiment, information indicating the posture of the arms 4b and 4c is acquired based on the rotation angle of the drive motors 7a and 7b detected by the encoders. The information indicating the posture of the arms 4b and 4c is arm angle information, which indicates the angle of the arms 4b and 4c in the direction of rotation. Note that the drive motors 7a and 7b may also be equipped with other components such as reduction gears, transmission mechanisms, or various sensors.

[0025] The gas spring 20 is fixed to arms 4a and 4b. Specifically, the base end 20a of the gas spring 20 is fixed to arm 4a, and the tip end 20b of the gas spring 20 is fixed to arm 4b. The gas spring 20 is an auxiliary mechanism that assists the torque output by the drive motor 7a for driving arm 4b. The gas spring 20 has a cylinder 22 filled with inert, high-pressure gas, and a piston rod 24 that is slidable within the cylinder 22 and compresses the gas inside the cylinder 22.

[0026] The gas spring 20 is extendable and retractable by the sliding of the piston rod 24 inside the cylinder 22. The gas spring 20 extends and retracts in response to changes in the posture of the arm 4b. The extension and retraction of the gas spring 20 due to changes in the posture of the arm 4b will be specifically explained with reference to Figures 2A and 2B. Figure 2A shows the gas spring 20 when the arm 4b is in a posture along the direction of gravity Z. Figure 2B shows the gas spring 20 when the arm 4b is tilted in a direction intersecting the direction of gravity Z. Note that in Figures 2A and 2B, the structures on the tip side of the arm 4b (joint 6b, arm 4c, hand 5, etc.) are not shown.

[0027] For example, as shown in Figure 2A, when the arm 4b is in a position aligned with the direction of gravity Z, the load on the drive motor 7a due to gravity acting on the arm 4b is minimized. The gas spring 20 generates a reaction force F due to the internal gas pressure sealed within the cylinder 22. Here, as shown in Figure 2A, when the extension and contraction direction of the gas spring 20 and the rotation axis J2 (center of rotation) of the arm 4b are in a straight line, the gas spring 20 is at its maximum length. When operating the arm 4b near such a dead center, almost no auxiliary torque is generated by the gas spring 20.

[0028] When the arm 4b rotates from the state shown in Figure 2A to the state shown in Figure 2B, the load on the drive motor 7a increases due to gravity P acting on the arm 4b. The drive motor 7a outputs a torque Tm to counteract this load. Also, as the length of the gas spring 20 shortens due to the rotation of the arm 4b, the internal gas pressure sealed in the cylinder 22 increases, and the reaction force F of the gas spring 20 increases. Here, if the extension and contraction direction of the gas spring 20 and the rotation axis J2 of the arm 4b are not in a straight line, as shown in Figure 2B, the gas spring 20 outputs an auxiliary torque Ts due to the reaction force F. The auxiliary torque Ts, like the torque Tm, acts in the opposite direction to the load applied to the drive motor 7a, assisting the torque Tm. As a result, the gas spring 20 reduces the load applied to the drive motor 7a due to gravity P.

[0029] Furthermore, as described above, the reaction force F of the gas spring 20 fluctuates depending on the posture of the arm 4b and the gas pressure inside the gas spring 20. This reaction force F causes a very small deformation (strain) in the fixing part 8 to which the base end 20a of the gas spring 20 is fixed in the arm 4a that supports the arm 4b. The amount of deformation of this fixing part 8 depends on the reaction force F of the gas spring 20, and consequently, on the posture of the arm 4b and the gas pressure inside the gas spring 20. Therefore, in this embodiment, the amount of deformation of the fixing part 8 at a predetermined posture of the arm 4b is measured using a strain gauge 26, and the decrease in the gas pressure inside the gas spring 20 is estimated based on the measured amount of deformation.

[0030] The strain gauge 26 is a sensor that detects changes in electrical resistance associated with the deformation (strain) of the portion to which the strain gauge 26 is attached. By using the strain gauge 26, the amount of deformation (strain) of the portion to which the strain gauge 26 is attached can be measured based on the change in electrical resistance. The strain gauge 26 is provided on the fixing portion 8 of the arm 4a. In this embodiment, the fixing portion 8 refers to the peripheral portion of the portion to which the base end portion 20a of the arm 4a is fixed, but it is not limited to the peripheral portion of that portion, and may be the portion itself, or a region that includes both that portion and its peripheral portion. A well-known strain gauge 26 can be used, and for example, it is composed of a resin base bonded to the fixing portion 8, which is the object to be measured, via an adhesive, a metal foil (resistor) formed on the resin base, and a gauge lead (leader wire) connected to the metal foil. The gauge lead of the strain gauge 26 is physically connected to the control device 30 via a metal cable (not shown).

[0031] In this embodiment, three strain gauges 26 are attached to the base end 20a on the side surface of the arm 4a between the base end 20a and the base 2, along the base end 20a. The number, position, and direction of the strain gauges 26 to be attached are not limited to this example, and the number, position, and direction of the strain gauges 26 can be attached in any number, position, and direction depending on the size, position, and direction of the area in which the amount of deformation to be measured is to be measured. In addition, multiple strain gauges may be attached with intervals between them as shown in the figure, or they may be stacked so that they overlap each other.

[0032] Returning to Figure 1, the control device 30 is connected to the robot 10 via a communication cable or the like, enabling communication and controlling the robot 10's operation. Note that communication between the robot 10 and the control device 30 is not limited to a wired connection via a communication cable or the like; it may also be a wireless connection or the like. Furthermore, the control device 30 measures the deformation of the fixed part 8 based on the change in resistance detected by the strain gauge 26. Alternatively, a small strain measuring device, physically connected to the gauge leads of the strain gauge 26 and also connected to the control device 30 for communication, may be interposed between the control device 30 and the strain gauge 26, and the deformation of the fixed part 8 may be measured using this strain measuring device. In this case, the control device 30 may measure the deformation of the fixed part 8 by receiving the deformation amount of the fixed part 8 transmitted from the strain measuring device.

[0033] The control device 30 is an information processing device equipped with a CPU (Central Processing Unit), memory, and communication devices. Based on control programs stored in memory, etc., the control device 30 drives the drive motors 7a, 7b, etc., and controls the movement of the robot 10. Furthermore, the CPU of the control device 30 executes a predetermined program stored in memory, etc., and operates the connected hardware configuration under the control of the CPU, thereby realizing the various functional configurations of the control device 30 shown in Figure 3.

[0034] <Functional Configuration> Figure 3 is a block diagram showing an example of the functional configuration of the control device 30.

[0035] As shown in Figure 3, the control device 30 functionally comprises a control unit 32, a storage unit 34, a measurement unit 36, an estimation unit 38, and a notification unit 40.

[0036] The control unit 32 controls the rotation and stopping of the drive motors 7a and 7b. Furthermore, when the drive motors 7a and 7b are stopped, the control unit 32 controls the electromagnetic brakes to brake the rotation shafts J2 and J3. Conversely, when the drive motors 7a and 7b are made to rotate, the control unit 32 controls the electromagnetic brakes to release the braking force on the rotation shafts J2 and J3. When the drive motors 7a and 7b are stopped, the control unit 32 outputs information indicating this to the measurement unit 36. The control unit 32 also acquires arm angle information of the arm 4b based on the rotation angle of the drive motor 7a detected, for example by an encoder provided on the drive motor 7a, and outputs this information to the estimation unit 38. The control unit 32 acquires arm angle information of the arm 4b at predetermined timings, such as each time the drive motor 7a is stopped or each time it is measured by the measurement unit 36, and outputs this information to the estimation unit 38.

[0037] The memory unit 34 stores reference data 34A for the amount of deformation of the fixed part 8 on the arm 4a. Reference data 34A is data that shows, for example, the amount of deformation of the fixed part 8 when the gas inside the gas spring 20 is sufficiently filled with gas, for each arm angle information of the arm 4b. Reference data 34A is acquired and stored in advance by the designer or operator. Hereinafter, the amount of deformation shown by the reference data 34A will be referred to as the "reference deformation amount".

[0038] The measuring unit 36 ​​measures the amount of deformation of the fixed part 8 on the arm 4a using a strain gauge 26. Specifically, the measuring unit 36 ​​measures the amount of deformation of the fixed part 8 based on the change in electrical resistance detected by the strain gauge 26. The measuring unit 36 ​​measures the amount of deformation of the fixed part 8 when, for example, the drive motor 7a is in a stopped state. The stopped state of the drive motor 7a means that the drive motor 7a is stopped by the control of the control unit 32. This stopped state may include the state in which the stopped position of the drive motor 7a is maintained by the braking of the electromagnetic brake. For example, if the drive motor 7a is controlled to repeatedly switch between a stopped state and a rotating state, the measuring unit 36 ​​repeatedly measures the amount of deformation of the fixed part 8 each time the drive motor 7a is in a stopped state. Note that the measuring unit 36 ​​may measure the amount of deformation not only when the drive motor 7a is in a stopped state, but also at predetermined timings when the drive motor 7a is in a rotating state. The measurement unit 36 ​​outputs the amount of deformation of the fixed part 8, measured using the strain gauge 26, to the estimation unit 38.

[0039] The estimation unit 38 estimates the state of the decrease in gas pressure inside the gas spring 20 based on the amount of deformation measured by the measurement unit 36. For example, first, the estimation unit 38 obtains the arm angle information of the arm 4b at the time the amount of deformation was measured by the measurement unit 36 ​​from the output of the control unit 32. Next, the estimation unit 38 refers to the reference data 34A and obtains a reference deformation amount corresponding to the acquired arm angle information. Then, the estimation unit 38 estimates the state of the decrease in gas pressure inside the gas spring 20 by comparing the acquired reference deformation amount with the amount of deformation measured by the measurement unit 36.

[0040] For example, the estimation unit 38 calculates the ratio of the measured deformation to the standard deformation, or the difference obtained by subtracting the measured deformation from the standard deformation. The smaller this ratio is, or the larger this difference is, the less the deformation that should be measured by the reaction force F of the gas spring 20 in a normal state is measured, indicating that the gas pressure inside the gas spring 20 has decreased compared to the normal state. Based on this ratio or difference, the estimation unit 38 estimates the rate of decrease (what percentage) of the gas pressure inside the gas spring 20 compared to the normal state. The estimation unit 38 then outputs the estimation result to the notification unit 40.

[0041] The notification unit 40 notifies predetermined information based on the estimation results from the estimation unit 38. For example, if the rate of decrease in the gas pressure inside the gas spring 20 relative to the normal state exceeds a preset threshold, the notification unit 40 notifies information indicating that fact or information indicating that maintenance of the gas spring 20 is required. The notification unit 40 transmits this information to a predetermined external device, such as a personal computer or teaching pendant connected to the control device 30, and the external device outputs the information by displaying it or by sound.

[0042] <Processing flow> Figure 4 is a flowchart showing an example of the processing flow performed by each functional configuration in Figure 3 in the robot system 1 according to this embodiment. Note that the content and order of the processing shown in Figure 4 can be changed as appropriate.

[0043] (Step SP10) The measuring unit 36 ​​measures the amount of deformation of the fixing part 8 on the arm 4a based on the change in electrical resistance detected by the strain gauge 26 at a predetermined timing. The control unit 32 also acquires the arm angle information of the arm 4b at the timing of this measurement. Subsequently, the process moves on to step SP12.

[0044] (Step SP12) The estimation unit 38 compares the reference deformation amount in the arm angle information of arm 4b obtained in step SP10 with the measured deformation amount and estimates the rate of decrease of the gas pressure inside the gas spring 20 relative to the normal state. Then, the process proceeds to step SP14.

[0045] (Step SP14) The notification unit 40 determines whether the rate of decrease in gas pressure estimated in step SP12 is greater than or equal to a threshold. If the rate of decrease in gas pressure estimated in step SP12 is less than the threshold, the determination is rejected, and the process returns to step SP10. If the rate of decrease in gas pressure estimated in step SP12 is greater than or equal to the threshold, the determination is affirmed, and the process proceeds to step SP16.

[0046] (Step SP16) The notification unit 40 outputs information to an external device, such as a display or sound, indicating that the gas pressure inside the gas spring 20 has decreased or that maintenance is required for the gas spring 20. With this, the series of processes shown in Figure 4 is completed.

[0047] <Effects and Effects> As described above, according to the robot system 1 of this embodiment, the amount of deformation of the fixed part 8 on the arm 4a that supports the arm 4b is measured, and based on the measured amount of deformation, the state of decreased internal gas pressure, which is the auxiliary state of the gas spring 20 as an output auxiliary mechanism for the drive motor 7a, is estimated. Therefore, regardless of the posture of the arm 4b driven by the drive motor 7a (for example, even when the arm 4b is operated near the dead center as shown in Figure 2A), the state of decreased internal gas pressure of the gas spring 20 can be estimated. Furthermore, regardless of whether the arm 4b is stopped or rotating, the state of decreased internal gas pressure of the gas spring 20 can be estimated. In this way, regardless of the posture or driving state of the robot 10, the state of decreased internal gas pressure of the gas spring 20 can be estimated.

[0048] Furthermore, according to this embodiment, since the amount of deformation is measured using the strain gauge 26 provided on the fixed part 8, the amount of deformation in the fixed part 8 can be measured effectively.

[0049] Furthermore, according to this embodiment, the decrease in gas pressure inside the gas spring 20 can be appropriately estimated based on a pre-stored reference deformation amount and the deformation amount measured by the measuring unit 36.

[0050] Furthermore, according to this embodiment, when the deformation amount at the fixed part 8 is measured when the drive motor 7a is stopped, measurement errors can be suppressed compared to when the drive motor 7a is rotating, and the decrease in gas pressure inside the gas spring 20 can be estimated more appropriately. Moreover, when the stop position of the drive motor 7a is maintained by the braking of the electromagnetic brake, it is not necessary to support the arm 4b with the torque Tm from the drive motor 7a and the auxiliary torque Ts from the gas spring 20. In this state, the decrease in gas pressure inside the gas spring 20 can be estimated, so even if the gas pressure has dropped extremely low, the system can notify the system of the extremely low gas pressure before releasing the electromagnetic brake and perform maintenance on the gas spring 20. Therefore, the risk of the arm 4b falling because it cannot be supported by the torque Tm from the drive motor 7a alone at the same time as releasing the electromagnetic brake can be avoided.

[0051] <Variation> The present invention is not limited to the embodiments described above. That is, any design modifications made to the above embodiments by those skilled in the art are also included within the scope of the present invention, as long as they retain the features of the present invention. Furthermore, the elements of the above embodiments and the modifications described later can be combined to the extent that it is technically possible, and any combination thereof is also included within the scope of the present invention, as long as it retains the features of the present invention.

[0052] For example, in the above embodiment, a robot 10 having a plurality of arms 4a, 4b, 4c and a plurality of drive motors 7a, 7b that drive them was described, but the number of arms and drive motors is not limited to this, and it is sufficient to have at least one arm and at least one drive motor that drives the arm. Furthermore, the robot according to the present invention is not limited to a vertical articulated robot, but may be a horizontal articulated robot, etc. Also, in the above embodiment, arm 4a was described as an arm support part and arm 4b was described as an arm that is rotatably supported by the arm support part, but it is not limited to this. For example, a gas spring may be fixed to arm 4c and arm 4b, with arm 4b being an arm support part and arm 4c being an arm that is rotatably supported by the arm support part, and the amount of deformation of the fixed part to which the gas spring is fixed on arm 4b may be measured using a strain gauge.

[0053] Furthermore, in the above embodiment, an example was described in which a strain gauge 26 is provided on the lower fixing part of the gas spring 20, i.e., the fixing part 8 on the arm 4a, and the decrease in gas pressure inside the gas spring 20 is estimated based on the amount of deformation at the fixing part 8, but the invention is not limited to this. For example, in addition to or instead of the fixing part 8, a strain gauge may be provided on the upper fixing part of the gas spring 20, i.e., the fixing part on the arm 4b to which the tip 20b of the gas spring 20 is fixed, and the decrease in gas pressure inside the gas spring 20 may be estimated based on the amount of deformation at the fixing part measured using the strain gauge.

[0054] Furthermore, in the above embodiment, an example was described in which the piston rod 24 side is the base end 20a (the side fixed to the arm 4a) of the gas spring 20 and the cylinder 22 side is the tip end 20b (the side fixed to the arm 4b) of the gas spring 20. However, the orientation of the gas spring 20 may be reversed. That is, the piston rod 24 side may be the tip end 20b (the side fixed to the arm 4b) of the gas spring 20 and the cylinder 22 side may be the base end 20a (the side fixed to the arm 4a) of the gas spring 20.

[0055] Furthermore, in the above embodiment, an example was described in which the decrease in gas pressure inside the gas spring 20 is estimated as the auxiliary state of the output assist mechanism. However, it is not limited to the decrease in gas pressure, but the current gas pressure state itself may also be estimated. For example, the storage unit 34 may store data for each arm angle information that associates the gas pressure inside the gas spring 20 with the deformation amount of the fixing part 8 as reference data for the normal state of the gas spring 20, and the estimation unit 38 may estimate the current gas pressure state based on the reference data and the measured deformation amount. For example, the estimation unit 38 may refer to the reference data, extract the deformation amount that is closest to the measured deformation amount from the stored deformation amounts, and estimate the gas pressure corresponding to the extracted deformation amount as the current gas pressure.

[0056] Furthermore, although the above embodiment describes an example in which the reference deformation amount of the fixed part 8 is acquired and stored in advance for each arm angle information, the invention is not limited to this. For example, the control device 30 may store three-dimensional model information of the arm 4a in advance, calculate the reference deformation amount of the fixed part 8 according to the arm angle based on the three-dimensional model information, and estimate the gas pressure decrease state based on the reference deformation amount obtained by calculation.

[0057] In the above embodiment, a gas spring 20 was described as an output assist mechanism, but it is not limited to a gas spring 20; any mechanism capable of outputting an assist torque to assist the torque of the drive motor 7a for driving the arm 4b may be used.

[0058] Furthermore, in the above embodiment, it was shown that the robot system 1 consists of a robot 10 and a control device 30. Also, although it was shown that the control device 30 is provided separately from the robot 10, it is of course not limited to this, and the robot 10 and the control device 30 may be integrally formed. [Explanation of symbols]

[0059] 1: Robot system, 4a: Arm (one arm), 4b: Arm (the other arm), 7a: Drive motor, 8: Fixing part, 10: Robot, 20: Gas spring (output assist mechanism), 26: Strain gauge, 36: Measurement part, 28: Estimation part

Claims

1. One arm and, The other arm is rotatably supported by the first arm via a joint, A drive motor for driving the other arm, An output assist mechanism is fixed to one arm and the other arm and assists the output of the drive motor, A robot having, A measuring unit that measures the amount of deformation of the fixed part using a strain gauge provided on the fixed part to which the output assist mechanism of one of the arms is fixed, An estimation unit estimates the auxiliary state of the output assist mechanism based on the amount of deformation measured by the measurement unit, A robot system characterized by having the following features.

2. The robot system according to claim 1, characterized in that the estimation unit estimates the auxiliary state based on a pre-stored reference deformation amount and the deformation amount measured by the measurement unit.

3. The robot system according to claim 1, characterized in that the measuring unit measures the amount of deformation when the drive motor is stopped.

4. The robot system according to any one of claims 1 to 3, characterized in that the output assist mechanism is a gas spring.

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