JP2005224941A - Power sensor overload protection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism for protecting a power sensor from being broken by external force over a measurable range or overload, during a working action of an anthropomorphic robot, an assembly working robot, etc. <P>SOLUTION: When applied to the power sensor 23 installed for use between an arm 21 and an end effector 22 in a manipulator, the mechanism is comprised of active engaging members 28, 29 having driving sections 36, 37 thereof fixed to the arm 21, and a passive engaging member 24 fixed to the end effector 22. Thus by driving the active engaging members to engage with the passive engaging member, the arm 21 and the effector 22 are fixed to each other, and by releasing the engagement, the power sensor 23 is actuated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an overload prevention device for a force sensor that is used by being attached to a manipulator or hand of an industrial robot.

  For general-purpose industrial robots and industrial robots dedicated to various types of equipment, force sensors are installed in each part to detect the force handled by the robot or other unscheduled force and adjust the force. However, there are those that perform a desired work by performing a series of operations. In particular, in high-grade robots such as assembly robots and humanoid robots that perform work by force control, information on the force acting on the object by the hand or manipulator corresponding to the hand and the reaction force received from the object or others is controlled. Therefore, it is desirable to incorporate and use a 6-axis force sensor.

  Since the force sensor is installed between the base part connected to the robot body such as a shoulder and arm and the end effector, it can withstand the weight and inertial force of the end effector itself, and the action of the end effector and the object. It is necessary to have a sturdy structure that can withstand the force and withstand the impact force when it collides with an obstacle. In the first place, the force sensor measures based on a change in physical quantity due to an acting force, usually a distortion of a member. Therefore, if the rigidity of the portion acting on the sensitive member is high, highly sensitive measurement cannot be performed. Therefore, when measuring based on deformation of a sturdy member, it is difficult to expect measurement resolution and measurement accuracy, and it is difficult to provide high sensitivity that is sensitive to weak force and minute changes in force. is there.

  Therefore, in particular, when measuring accuracy is a problem, a high-sensitivity sensor is used even if it is somewhat delicate, and naturally it tends to break down and tends to suffer from maintenance repairs. The force sensor is expensive, and since it takes a long time to replace a sensor incorporated in a robot, it is desirable to prevent damage and failure as much as possible. On the other hand, in a work environment of a humanoid robot or an assembly robot, interference with surrounding objects is likely to occur, so that the force sensor incorporated in the robot is easily damaged. Despite these circumstances, no protection mechanism has been found that accurately protects the high-precision 6-axis force sensor used in robots.

  In addition, as an overload protection device, there is a so-called mechanical lock that prevents a predetermined amount of deformation from occurring by a mechanism that presses and fixes a convex tapered surface provided on one of the arm and the hand against a concave tapered surface provided on the other. . The mechanical lock can sufficiently cope with a very large load far exceeding the rating of the sensor. However, there is a limit to the manufacturing accuracy, so the sensor can be protected by locking it close to the load that the force sensor is trying to detect, especially so that it does not need to be calibrated even when the sensor is reused. The target load cannot be set. Therefore, even if the mechanism is protected by using the mechanical lock, the sensor mechanism can be prevented from being damaged, but it is usually necessary to readjust the sensor calibration matrix. In some cases, the strain gauge is damaged and an overhaul is required.

  Further, as disclosed in Patent Document 1 and Patent Document 2, the robot arm and the hand are interposed and fixed to each other so that the hand can be moved relative to the arm when necessary. There is a so-called tool floating device that absorbs misalignment. For example, a floating device for a hand described in Patent Document 1 includes an intermediate moving member having a plurality of rigid balls supported in a housing fixed to an arm, and a spherical receiving means is provided inside the intermediate moving member. The rotating member is provided, and the hand is fixed to the rotating member. The intermediate moving member is movable in the x and y directions with respect to the housing and is rotatable about the hand axis. The rotating member rotates about the center with respect to the intermediate moving member. Furthermore, the hand can be fixed at a predetermined position with respect to the arm by pressing the positioning ball against the tapered surface of the ball receiver provided in the housing by the air drive piston charged in the rotating member.

  The floating device described in Patent Document 1 is applied to a hand equipped with a force sensor. At the time of measurement, the coupling of the floating device is released and the arm and the hand are coupled via a force sensor. It is conceivable that the force sensor is protected by operating the device and fixing the hand to the arm. However, since this floating device is equipped with a pneumatic drive device on the hand side, the load on the hand increases and the sensitivity of the force sensor is impaired, and the load changes when the pressurized air is applied and when it is released. There are difficulties in calibration. Further, the mechanism of the floating device is complicated, which increases the cost of the device.

  The floating device described in Patent Document 2 also incorporates an air cylinder that is driven by pressurized air so that the piston is brought into close contact with the contact surface or floated from the contact surface to be free. This floating device cannot release all six axes. That is, only a limited axis can be released even if a force exceeding a certain level is applied. Therefore, it is not preferable to protect all six axes because the size of the end effector such as a hand is increased and the force control is complicated. Moreover, since a complicated pneumatic device is provided on the hand side, there is a difficulty similar to that described in Patent Document 1. These floating devices use a passive mechanism that releases the coupling when a certain level of force is applied. For protection of the force sensor, the arm is actively activated at an appropriate load level based on the output of the force sensor. It is necessary to connect the hand and protect the sensor.

In the six-axis force sensor, it is preferable that all six axes are released from the mechanism at the time of measurement and an acting force is applied to the sensor pressure sensing unit, and at this time, no other external force acts. On the other hand, when the sensor is protected, it is necessary to mechanically fix the hand and the arm so that no force acts on the sensor pressure-sensitive portion. Thus, a protection device having a technical idea of fixing a hand and an arm in order to protect a sensor has not existed before. In the present situation where the force sensor cannot be protected, it is necessary to select the measurement range of the sensor so as to withstand the maximum force that can occur during the robot operation cycle. Has been invited.
In order to accurately and efficiently maintain and manage bridges and other structures, it is necessary to periodically diagnose the state of the structure or evaluate the performance to quantitatively grasp the remaining life and strength.
Japanese Patent Laid-Open No. 07-096487 Japanese Patent Application Laid-Open No. 07-051954

  Therefore, the problem to be solved by the present invention is to provide a mechanism for preventing the force sensor from being destroyed by an external force or an overload exceeding the measurement range in a work operation of a humanoid robot or an assembly robot. It is.

  The force sensor overload protection device of the present invention is applied to a force sensor that is installed and used between an arm and an end effector in a manipulator, and includes an active engagement member having an actuator fixed to the arm and an end effector. A passive engagement member fixed to the arm, and driving the active engagement member to engage the passive engagement member to fix between the arm and the effector and release the engagement to activate the force sensor. It is what you do.

  In the force sensor overload protection device of the present invention, the active engagement member includes a core side rod having a flange and a sheath side rod having a contact surface, and the core side rod and the sheath side rod are opposite to each other. A plurality of telescopic rods, wherein the passive engagement member has a hole through which the core side rod of the telescopic rod passes, and is provided with a receiving portion that is sandwiched between the hole and the contact surface around the hole. When the rod is driven, the telescopic rod engages with the receiving portion of the passive engagement member to fix between the arm and the end effector. In the structure using the telescopic rod, a force for rotating the engagement member does not work, so a complicated structure for balancing the force is not required.

  According to the force sensor overload protection device of the present invention, at the time of measurement, the coupling between the arm and the end effector is released so that the reaction force applied to the end effector acts directly on the force sensor, thereby improving the force measurement accuracy. When the sensor is protected, the end effector is fixed to the arm, and no force is transmitted from the end effector to the force sensor, so that the sensor is completely protected even if an unexpected large force is applied from the outside. In addition, the force sensor overload protection device provided on the end effector side is passive, so unlike the mechanism using springs or air pressure, no force is generated when the engagement is released. Since the measurement is not adversely affected, the measurement accuracy of the sensor can be ensured.

  Furthermore, the force sensor overload protection device of the present invention can protect the force sensor by driving the active engagement member when an overload condition is detected based on the output of the force sensor. If the operation is based on the measured value of the force sensor, the force sensor is extremely safe because a protective action can be taken immediately when a suitable load is detected to prevent danger in the measurable range of the force sensor. Thus, there is no need to worry about damage to the sensor unit, and it is not necessary to perform calibration again when the protection state is released.

  In the force sensor overload protection device of the present invention, the active engagement member is a belt including an actuator that fixes one end and pushes and pulls the other end, and the passive engagement member engages with the belt. It may be. When the belt is pulled by the actuator, it can engage with the receiving portion to fix the arm and the effector. The belt is preferably arranged in a position that is divided about the axis of the end effector for the time being. The belt tightening device can be manufactured with a very simple structure.

  Furthermore, the force sensor overload protection device of the present invention is a plurality of claw-attached rotary rods in which an active engagement member is fixed to the tip with an eccentric disk having outer edges with different distances from the axis of rotation. On the other hand, the passive engagement member is a receiving member having a recess that presses and engages the outer edge portion having a large distance from the rotation axis of the disk, and is composed of the active engagement member and the passive engagement member. May be. The eccentric disc can be rotated easily even with a simple drive mechanism with low output, and the arm and end effector are securely fixed by pressing the pawl of the eccentric disc against the innermost part of the recess. Can be combined.

  In addition, the engagement dent is provided on the inner side of the receiving material toward the arm and end effector shaft, and the claw rotating rod is provided on the inner side of the engagement dent to push the eccentric disk outward. You may make it fix by hitting. In addition, the engagement recess is provided toward the outside of the receiving material, and the plurality of claw rotating rods are provided outside the engagement recess and when driven, the eccentric disk is pressed inward and fixed. You may be made to do. The claw rotating rods are provided on the inside and outside of the receiving material, and the engagement dents are provided on both the inside and outside of the receiving material so that the inner rotating rod and the outer rotating rod sandwich the receiving material. It goes without saying that it may be made to do.

  In addition, it is preferable that even number of claw rotating rods are provided and arranged so that the operating moments are canceled with respect to the passive engagement member in units of pairs rotating in opposite directions. If the rotating rods are rotated in the same direction, the end effector is driven to rotate in the same direction, so it may not function effectively as a robot hand, but if the rotating rods are rotated in pairs in opposite directions, The end effector can be stationary by canceling the rotation.

  Further, it is preferable that the rotation shaft of the claw rotating rod is arranged in a direction parallel to the arms and the end effector, and the engagement recess of the receiving member is formed on a surface parallel to the arms and the end effector. The end effector is not intended to have a neutral effect on the end effector by causing the engagement concave surface and the claw of the rotating rod to act perpendicularly and the acting force to be perpendicular to the arm end effector axis. It can be prevented from moving in the direction.

  Hereinafter, the force sensor overload protection device of the present invention will be described in detail using embodiments. The overload protection device of the present invention is a device that protects a force sensor by fixedly coupling between an arm and a hand when an excessive force is applied between the arm and the hand.

  FIG. 1 is a partial cross-sectional view illustrating a force sensor overload protection device according to a first embodiment, and FIGS. 2 to 4 are explanatory views illustrating examples of a locking mechanism.

  In the overload protection device of this embodiment, a 6-axis force sensor 3 is interposed between the arm 1 and the hand 2. The arm 1 and the force sensor 3 are respectively fixed to the front and back of the arm mounting base 4, and the force sensor 3 and the hand 2 are fixed to the front and back of the other hand mounting base 5. A disk-shaped ridge 6 is provided on the outer periphery of the arm mounting base 4, and a plurality of rotary motors 7 are fixed on the ridge 6 at appropriate intervals. The rotary motor 7 drives the rotary rod 8 to rotate. An eccentric disk 9 is fixed to the tip of the rotating rod 8. Further, a ring 10 having a wedge-shaped recess 11 formed inside is fixed downward on the outer peripheral portion of the hand mounting base 5. Needless to say, an air-driven rotary actuator or the like can be used instead of the electric rotary motor as the rotary motor for rotating the rotary rod 8.

  As shown in FIG. 2, the eccentric disc 9 has a different distance from the axis of the rotating rod 8 to the outer periphery depending on the rotation angle. The outer periphery 12 of the eccentric disk 9 that was initially separated from the inner surface of the ring 10 approaches the inner surface of the ring 10 as the rotating rod 8 rotates, and eventually comes into contact with the surface of the wedge-shaped recess 11. Further, when the rotating rod 8 rotates, the wedge-shaped dent 11 is pulled in the vertical direction and moves to a position where the tip of the eccentric disc 9 is placed in the innermost portion 13 of the dent. Since the plurality of rotating rods 8 are simultaneously operated to adjust the positions of the wedge-shaped dents 11 so that the tip of the eccentric disk 9 is stretched to the innermost part 13, the positions of the arm 1 and the hand 2 do not change relative to each other. Fixed to. Therefore, no stress acts on the force sensor 3 and it is completely protected from overload. 2 is the inner ridge line 14 of the ring 10. In FIG.

  Further, when the rotating rod 8 is driven in the opposite direction so that the tip of the eccentric disk 9 is separated from the ring 10 so that the hand 2 and the arm 1 are coupled via the force sensor 3, the force sensor 3 operates. 6-axis force applied to the hand 2 can be measured. In the measurement state, the extra part added to the portion connected to the hand 2 is almost only the ring 10. Since this ring 10 is relatively lightweight and has no drive mechanism attached, it is a passive element, so that it does not interfere strongly with the reaction force measurement.

  In the force sensor overload protection device of this embodiment, the force sensor 3 can be protected by driving the rotary motor 7 when an overload state is detected based on the output of the force sensor 3. If the force sensor 3 is operated based on the measured value of the force sensor 3, a protective action can be taken immediately when an appropriate load in the measurable range of the force sensor 3 is detected. Since it can be protected at a set level with a low force, it is extremely safe and there is no fear of damage to the sensor unit, and it is not necessary to perform calibration again when the protection state is released.

  When an even number of rotating rods 8 are installed and are urged to rotate in pairs in opposite directions, the hand 2 is fixed when the eccentric disk 9 is pressed against the recess 11 inside the ring 10 to fix the hand 2. No unnecessary rotation moment is generated in 2 and the force sensor 3 is not affected.

  The rotating rod 8 may be arranged inside the ring 10 as shown in FIG. 2, but may be arranged outside the ring 10 as shown in FIG. When the rotating rod 8 is disposed outside the ring 10, the wedge-shaped recess is formed outside the ring 10, and the eccentric disk 9 is pressed from the outside to the innermost portion 13 of the recess to hold the hand 2 at a fixed position. To be fixed to. Further, as shown in FIG. 4, the rotating rods 8 may be provided as a pair on the outer side and the inner side of the ring 10 and pressed so as to sandwich the ring 10 from both sides.

  According to the force sensor overload protection device of the present embodiment, during normal measurement, an accurate force can be detected without applying extra force such as spring force or piping tension force, and when the force sensor is protected. The arm and the hand can be fixed so that the acting force does not reach the force sensor. Further, since the overload level to be protected can be accurately determined using the measurement result of the force sensor, the sensor can be reliably prevented from being damaged. Furthermore, by selecting the measurement range of the force sensor to a range that matches the level that requires measurement, the sensor sensitivity can be increased and the measurement accuracy can be greatly improved.

  Further, in the overload protection device of the present embodiment, even if the eccentric disk or the wedge-shaped dent is worn, a completely fixed state can be ensured by adjusting the rotation angle. Note that the overload protection device of this embodiment can be used by attaching an end effector such as an arc welding torch on the tip side and fixing it to the arm. In such a method of use, the robot arm and the end effector can be prevented from being seriously damaged by cutting the connection with the arm when an unexpected external force is generated in the end effector.

  FIG. 5 is a partial cross-sectional view illustrating a force sensor overload protection device according to a second embodiment. In this embodiment, a telescopic rod is used in place of the rotating rod as the locking part. In the overload protection device of this embodiment, a six-axis force sensor 23 is interposed between the arm 21 and the hand 22 as in the first embodiment. The arm 21 and the force sensor 23 are respectively fixed to the front and back of the arm mounting base 25, and the force sensor 23 and the hand 22 are fixed to the front and back of the other hand mounting base 24. A skirt 26 having a cylindrical shape with a heel at the lower end is provided on the outer periphery of the arm mounting base 25, and a plurality of telescopic rods 27 are fixed on the skirt 26 at appropriate intervals. . The telescopic rod 27 includes a core side rod 28 and a sheath side rod 29.

  The core side rod 28 has a flange attached to its tip, and a tapered surface 30 having a diameter that decreases in the axial direction is formed below the flange. Further, the sheath side rod 29 is formed with a tapered surface 31 extending outward at the upper end. The attachment base 24 for the hand and the attachment base 25 for the arm are provided with a hole 32 through which the core side rod 28 penetrates and a hole 33 through which the sheath side rod 29 penetrates for each position of each telescopic rod 27. A taper surface 34 is formed on the upper edge of the through hole 32 of the hand mounting base 24 to which the downward taper surface 30 of the core side rod 28 is joined, and the upward taper surface of the sheath side rod 29 is formed on the lower edge. A tapered surface 35 to which 31 is joined is formed.

  The core side rod 28 and the sheath side rod 29 are each provided with a core side actuator 36 and a sheath side actuator 37 that are driven in the vertical direction, and these actuators 36 and 37 are fixed on a collar 38 provided at the lower end of the skirt 26. Is done. As the actuator, any linear drive device such as a rotary drive device using a fluid-driven cylinder or a screw can be used. The core side rod 28 and the sheath side rod 29 are driven in opposite directions. The force sensor 23 measures the force such that the tapered surfaces 30 and 31 of the rods 28 and 29 are separated from the tapered surfaces 34 and 35 of the hand mounting base 24. Further, by driving the rods 28 and 29 in opposite directions to reduce the distance between the tapered surfaces 30 and 31 and sandwiching the hand mounting base 24, the hand 22 is fixed to the arm 21 and a large force is applied to the force sensor 23. Protect it from acting.

  In the force sensor overload protection device of the present embodiment, the core side rod 28 and the sheath side rod 29 are expanded and contracted in opposite directions, so that no extra operating force is applied to the hand 22 and it is driven in a direction parallel to the axis. Do not give an extra operating moment. Further, since only the passive elements are included on the hand side and all active elements such as actuators are arranged on the arm side, the force measurement by the force sensor 3 is accurately performed. The tapered surfaces 30, 31, 34, and 35 only need to be matched with each other, and therefore any shape such as a conical shape, a pyramid shape, or a spherical shape can be selected. Even if the tapered surface is worn, the original function can be secured by adjusting the expansion / contraction stroke.

  FIG. 6 is a partial cross-sectional view for explaining a force sensor overload protection device according to a third embodiment, and FIG. 7 is a perspective view thereof. In this embodiment, a band is used as a locking part. In the overload protection device of this embodiment, a six-axis force sensor 43 is interposed between the arm 41 and the hand 42. The arm 41 and the force sensor 43 are respectively fixed to the front and back of the arm mounting base 44, and the force sensor 43 and the hand 42 are fixed to the front and back of the hand mounting base 45. The hand mounting base 45 is provided with a tape winding cylinder 46 surrounding the hand 42, and a tape supporting cylinder 47 is provided on the outer periphery of the arm mounting base 44 up to the height of the tape winding cylinder 46.

  A tape end support 48 and an actuator 49 are provided inside the tape support cylinder 47, and the tape 50 is passed between them. One end of the tape 50 is fixed to the tape end support 48, the tape winding cylinder 46 is wound, the other end is engaged with the actuator 49, and the actuator 49 can be wound up or loosened. The tape 50 is wound around a multi-tape winding cylinder 46 so that the arm 41 and the hand 42 are fixed to protect the force sensor 43 so that no force imbalance occurs. It is more preferable that the tapes 50 are arranged at symmetrical positions one by one if a plurality of tapes 50 can be equally spaced. The actuator 49 can be configured using an electric motor, an air cylinder, or the like. Further, the rigidity at the time of fixing can be adjusted by the generated force of the actuator 49. The tape 50 may be a steel tape or a rubber tape, or may be a string.

  As described above, the force sensor overload protection device according to the present invention cuts off the acting force from the outside during the force sensor protection without applying extra force such as spring force, air pressure, or pipe rigidity during normal force measurement. Therefore, safety can be ensured, so that the force sensor used for the humanoid robot and the assembly robot can be prevented from being damaged by overload or abnormal external force. In particular, if the external force is actively interrupted using the measurement results of the force sensor, the measurement range of the force sensor can be limited to the required range, and the sensitivity of the sensor can be increased and highly accurate measurement can be performed. It becomes possible.

It is a partial sectional view explaining the force sensor overload protection device concerning the 1st example of the present invention. It is explanatory drawing which shows the example of the latching mechanism used for 1st Example. It is explanatory drawing which shows another example of the latching mechanism used for 1st Example. It is explanatory drawing which shows another example of the latching mechanism used for 1st Example. It is a partial sectional view explaining the force sensor overload protection device concerning the 2nd example of the present invention. It is a partial sectional view explaining the force sensor overload protection device concerning the 3rd example of the present invention. It is a perspective view explaining the force sensor overload protection device of the 3rd example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Robot arm 2 Robot hand 3 Force sensor 4 Arm mounting base 5 Hand mounting base 6 Disc-shaped rod 7 Rotating motor 8 Rotating rod 9 Eccentric disk 10 Ring 11 Wedge-shaped dent 12 Outer circumference of eccentric disk 13 innermost ridge line 14 arm 22 hand 23 force sensor 24 hand mounting base 25 arm mounting base 26 skirt 27 telescopic rod 28 core side rod 29 sheath side rod 30, 31, 34, 35 taper surface 32 core Side rod through hole 33 Sheath side rod through hole 36 Core side actuator 37 Sheath side actuator 38 鍔

Claims (2)

A manipulator for installing and using a force sensor between an arm and an end effector, comprising: an active engagement member having a drive unit fixed to the arm; and a passive engagement member fixed to the end effector. In the force sensor overload protection device, the arm and the effector are fixed by driving and being engaged with the passive engagement member, and the force sensor is activated by releasing the engagement. The active engagement member includes a core side rod having a flange and a sheath side rod having a contact surface, and is a plurality of telescopic rods driven in opposite directions to each other. A receiving portion that has a hole through which the core side rod passes and is sandwiched between the flange and a contact surface around the hole, and when the telescopic rod is driven, the telescopic rod engages with the receiving portion to engage the arm and the air. The force sensor overload protection apparatus characterized by fixing between the de-effector. 2. The force sensor overload protection device according to claim 1, wherein when the overload state is detected based on the output of the force sensor, the active engagement member is driven to engage with the passive engagement member. .

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