JP2011041995A - Robot, bipedal walking robots and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot capable of solving a problem that attitude becomes unstable due to the existence of backlash. <P>SOLUTION: A bipedal walking robot 1 includes a direct-acting actuator 11 coupled with a thigh link 6 and a lower link 8 through a knee joint part 7 and swinging the lower link 8 to the thigh link 6 and an MR damper 12 for applying a damping force to the action of the lower link 8. The damping force is generated at the MR damper 12, when direction of a force acting on the lower link 8 is changed during the swing action of the lower link 8 by the direct-acting actuator 11. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a robot, in particular, a robot in which two links are connected via a joint portion, and a control method thereof.

  A robot is known that includes a first link and a second link that are connected via a joint, and an actuator that swings the second link with respect to the first link.

  For example, Patent Documents 1 to 3 include symmetrical leg portions and a trunk portion, and each leg portion is connected to the trunk portion via a hip joint portion (corresponding to a first link), The leg link (corresponding to the second link) connected to the lower end of the thigh link via the knee joint part (corresponding to the joint part), and the part where the thigh link and the leg link are separated from the knee joint part in each leg part A biped walking robot is disclosed that includes a linear motion actuator that is connected to the lower leg link and a foot that is connected to the lower end of the lower leg link via an ankle joint. These biped walking robots have improved motion performance by reducing the size of the linear actuator and reducing the moment of inertia of the thigh link and the lower leg link.

JP 2009-103204 A JP 2009-101455 A JP 2009-101456 A

  However, there is inevitably play between the robot structures including the biped robots disclosed in Patent Documents 1 to 3 in consideration of manufacturing errors and the like. Due to the presence of play, free movement within the play that does not depend on other structures is allowed, and there is a problem that the controllability deteriorates and the posture of the robot becomes unstable.

  If the backlash is made small, there is a disadvantage that the manufacturing cost increases due to the restriction of the bearing configuration, such as the fact that a sliding bearing cannot be adopted as the bearing of the joint, and it is contrary to the weight reduction. In addition, there is a drawback that the friction is increased and the energy efficiency is inferior.

  In view of the above points, an object of the present invention is to provide a robot, a biped walking robot, and a control method thereof that can eliminate the unstable posture caused by the presence of play.

  The robot of the present invention is a robot in which a first link and a second link are connected via a joint portion, and an actuator that swings and drives the second link with respect to the first link; A damper that applies a damping force to the operation of the link and a damper that generates a damping force when the direction of the force acting on the second link changes during the swinging operation of the second link by the actuator. And a control means for controlling.

  According to the robot of the present invention, when the direction of the force acting on the second link changes during the swinging motion of the second link by the actuator, the damper generates a damping force to attenuate the operation of the second link. During the swinging operation of the second link by the actuator, an appropriate backlash is achieved. In this state, if the direction of the force acting on the second link changes, the second link can move freely in the play regardless of the first link or actuator due to the action of the force, and the posture of the robot is unstable. Turn into. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the second link. As a result, free movement within the play of the second link is suppressed, and the period during which the robot is in an unstable posture can be shortened.

  In the robot according to the aspect of the invention, the control unit may cause the second link to swing in a direction opposite to the swinging direction of the second link during the swinging operation of the second link by the actuator. As described above, when the actuator applies a force to the second link, the damper is preferably controlled to generate a damping force.

  When the actuator exerts a force on the second link so that the second link swings in the direction opposite to the swinging direction of the second link during the swinging motion of the second link by the actuator, the actuator reverses. The operation will start. However, due to the presence of backlash, the second link cannot immediately follow the reversing operation of the actuator, and the second link can move freely within the backlash, so the posture of the robot becomes unstable. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the second link. As a result, free movement within the play of the second link is suppressed, and the period during which the robot is in an unstable posture can be shortened.

  In the robot according to the aspect of the invention, during the swing operation of the second link by the actuator, the control means applies an external force to the second link in the same direction as the second link swings. In some cases, the damper is preferably controlled so as to generate a damping force.

  When an external force acts on the second link in the same direction as the second link swings during the swinging motion of the second link by the actuator, the second link moves freely in the backlash due to the presence of backlash. However, the posture of the robot becomes unstable. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the second link. As a result, free movement within the play of the second link is suppressed, and the period during which the robot is in an unstable posture can be shortened.

  In the robot according to the aspect of the invention, the control unit may cause the damper to generate a damping force when an external force is applied to the second link in the direction of the joint during the swinging operation of the second link by the actuator. It is preferable to control so as to.

  If an external force is applied to the second link in the direction of the joint during the swinging motion of the second link by the actuator, the presence of the backlash causes the second link to move freely in the backlash in the direction of the joint. Becomes unstable. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the second link. As a result, free movement within the play of the second link is suppressed, and the period during which the robot is in an unstable posture can be shortened.

  In the robot of the present invention, it is preferable that the damper is a magnetorheological fluid damper that varies the viscosity of the magnetorheological fluid by a magnetic field.

  Since the viscosity of the magnetorheological fluid damper changes according to the current value applied to the magnetism generating means such as a coil, the damping force can be easily changed and the response is excellent. Therefore, it is possible to immediately generate a damping force having a value suitable for attenuating the operation of the second link. The magnetorheological fluid damper can be reduced in size and is suitable for mounting on a robot.

  In the robot according to the aspect of the invention, it is preferable that the actuator is a linear motion actuator that connects the first link and the second link at a portion separated from the joint portion.

  Since the linear actuator can be reduced in size, it is suitable for mounting on a robot. Further, even if an external force is input via the second link due to the damping force generated by the damper, the linear motion actuator is not likely to be damaged.

  According to the robot control method of the present invention, the first link and the second link are connected via a joint portion, the actuator that swings and drives the second link with respect to the first link, and the second link A control method of a robot including a damper that applies a damping force to a swinging operation, wherein the direction of the force acting on the second link changes during the swinging operation of the second link by the actuator. The damper is controlled so as to generate a damping force.

  According to the robot control method of the present invention, when the direction of the force acting on the second link changes during the swinging motion of the second link by the actuator, the damper generates a damping force, and the second link operates. Attenuate. During the swinging operation of the second link by the actuator, an appropriate backlash is achieved. In this state, if the direction of the force acting on the second link changes, the second link can move freely in the play regardless of the first link or actuator due to the action of the force, and the posture of the robot is unstable. Turn into. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the second link. As a result, free movement within the play of the second link is suppressed, and the period during which the robot is in an unstable posture can be shortened.

  The biped walking robot of the present invention includes a symmetrical leg and a torso, each leg having a thigh link connected to the torso via a hip joint, and a knee joint at the lower end of the thigh link. A biped walking robot having a crus link connected via a leg and a foot connected to the lower end of the crus link via an ankle joint, wherein the thigh link and the A linear motion actuator that connects the crus link at a portion spaced from the knee joint, a damper that applies a damping force to the swinging motion of the crus link relative to the thigh link, and the crus by the expansion and contraction motion of the linear motion actuator And a control means for controlling the damper to generate a damping force when the direction of the force acting on the lower leg link changes during the swinging motion of the link.

  According to the biped walking robot of the present invention, when the direction of the force acting on the lower leg link changes during the swinging movement of the lower leg link by the linear actuator, the damper generates a damping force to attenuate the lower leg link movement. Let During the swinging motion of the crus link by the linear actuator, an appropriate backlash is achieved. In this state, if the direction of the force acting on the crus link changes, the crus link can move freely in the play regardless of the thigh link and the linear motion actuator due to the action of the force, and the posture of the biped walking robot is It becomes unstable. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the lower leg link. As a result, the free movement of the lower leg link is suppressed, and the period during which the biped robot is in an unstable posture can be shortened.

  A biped walking robot control method according to the present invention includes symmetrical leg portions and a torso portion, each leg portion being connected to the torso portion via a hip joint portion, and a lower end of the thigh link. A crus link connected via a knee joint part, a linear motion actuator for connecting the thigh link and the crus link in each leg part at a portion spaced from the knee joint part, and the crus link to the thigh link A biped walking robot control method comprising: a damper that applies a damping force to a swinging motion of a leg; and a foot portion that is coupled to a lower end of the lower leg link via an ankle joint portion, wherein the linear actuator When the direction of the force acting on the crus link changes during the swinging operation of the crus link by the telescopic movement, the damper is controlled so as to generate a damping force.

  According to the control method of the biped walking robot of the present invention, when the direction of the force acting on the lower leg link is changed during the swinging movement of the lower leg link by the linear actuator, the damper generates a damping force, Damping movement. During the swinging motion of the crus link by the linear actuator, an appropriate backlash is achieved. In this state, if the direction of the force acting on the crus link changes, the crus link can move freely in the play regardless of the thigh link and the linear motion actuator due to the action of the force, and the posture of the biped walking robot is It becomes unstable. Therefore, when such a force is applied, a damping force is generated in the damper to attenuate the operation of the lower leg link. As a result, the free movement of the lower leg link is suppressed, and the period during which the biped robot is in an unstable posture can be shortened.

The block diagram which shows the bipedal walking robot which concerns on embodiment of this invention. The block diagram which shows the functional structure of a control unit. The flowchart which shows control of MR damper. The flowchart which shows other control of MR damper. The flowchart which shows other control of MR damper.

  A biped robot (robot) 1 according to an embodiment of the present invention will be described with reference to the drawings.

  Referring to FIG. 1, the biped walking robot 1 includes a body portion 2 and a pair of left and right legs 3. In the drawing, only one leg 3 is shown.

  Each leg portion 3 is connected to a lower end of the body portion 2 via a hip joint portion 5 and a lower end of the thigh link 6 via a knee joint portion (joint portion) 7. A lower leg link (second link) 8 and a foot part 10 connected to the lower end of the lower leg link 8 via an ankle joint part 9. Each leg portion 3 includes a linear motion actuator (actuator) 11 and an MR damper (damper) 12 that connect the thigh link 6 and the crus link 8 at a portion separated from the knee joint portion 7. The torso part 2 and the thigh link 6 and the crus link 8 and the foot part 10 are also connected by a linear actuator not shown.

  The knee joint portion 7 is composed of a uniaxial joint having a degree of freedom of rotation about the lateral Y axis. Specifically, the support shaft 13 provided at the upper end portion of the crus link 8 swings through a bearing in a shaft hole 14 formed at the lower end portion of the thigh link 6 and having an axis parallel to the Y axis. It is supported freely. Thereby, the lower leg link 8 is swingable in the front-rear direction with respect to the thigh link 6 about the Y axis. Hereinafter, the swinging motion of the crus link 8 means that the crus link 8 swings relative to the thigh link 6. Moreover, both the hip joint part 4 and the ankle joint part 9 are comprised by the biaxial joint.

  The knee joint portion 7 is provided with a swing angle sensor 15 including a strain sensor that detects a swing angle of the lower leg link 8 around the Y axis. Further, the ankle is connected via a six-axis force sensor (floor reaction force sensor) 16 that detects reaction forces (translational forces in the three axial directions of front and rear, left and right, and upper and lower directions, and moments about three axes) acting on the foot portion 10. The joint part 9 and the foot part 10 are connected. The crus link 8 is provided with an external force sensor 17 (see FIG. 2) that detects the value and direction of the external force that acts on the crus link 8.

  Although not shown in detail, the linear actuator 11 includes a nut member that is rotated by an electric motor 18 via a belt, and a screw shaft that is screwed to the nut member via a ball held by the nut member. It has a ball screw mechanism. The nut member is pivotally supported in the nut case via a bearing. The electric motor 18 includes an encoder 19 (see FIG. 2) that detects the actual rotation angle of the electric motor.

  A support shaft 20 integrated with the nut case is pivotally supported via a bearing in a shaft hole 21 formed in the upper portion of the thigh link 6 with an axis parallel to the Y axis. A support shaft 23 provided at the tip of the rod shaft 22 connected to the screw shaft can swing through a bearing in a shaft hole 24 formed in the crus link 8 having an axis parallel to the Y axis. It is supported by. Thereby, the axial movement of the screw shaft accompanying the rotation of the electric motor 18 causes the rod shaft 22 connected to the screw shaft to expand and contract, and the swinging motion of the crus link 8 relative to the thigh link 6 is performed.

  The MR damper 12 is a damping force variable damper using a magneto-rheological fluid (MRF). The MR damper 12 fills the cylinder 25 with a magnetorheological fluid, provides a coil on a piston 26 that slides within the cylinder 25, and passes through the port of the piston 26 by a magnetic field generated by energizing the coil. The damping force (resistance force) is controlled by changing the viscosity of the.

  A control box 27 is built in the body portion 2. With reference to FIG. 2, the control box 27 includes a control unit (control means) 31 that controls the operation of the joints 4, 6, and 8 of each leg 3, and the electric motor 18 of each linear actuator 11. A motor drive circuit 32 for controlling energization, a damper drive circuit 33 for controlling energization of the MR damper 12, and the like are accommodated. The control unit 31 is configured by an electronic circuit including a microcomputer or the like, and includes a gait generator 34, a motor controller 35, and a damper controller 36 as functional components.

  The gait generator 34 determines gait parameters (step length, walking cycle, etc.) that define the target gait of the leg 3 of the biped walking robot 1 in accordance with an external command or preset teaching data. To create a goal gait.

  The motor control unit 35 controls the electric motors of the linear actuators of the joints 4, 6, 8, including the electric motor 18 of the linear actuator 11 of the knee joint 7. The motor control unit 35 detects the target gait generated by the gait generation unit 34, the actual swing angle of each joint 4, 6, 8 detected by the swing angle sensor 15, and the six-axis force sensor 16. Based on the actual floor reaction force of the foot portion 10 to be performed, the actual rotation angle of the electric motor 18 and the like detected by the encoder 19 and the like, a command value for energizing current to be supplied to each electric motor is generated. Then, the motor control unit 35 outputs the generated command value to the motor drive circuit 32 and energizes each electric motor with a current corresponding to the command value via the motor drive circuit 32.

  The damper control unit 36 controls the MR damper 12. The damper control unit 36 detects the target gait generated by the gait generation unit 34, the actual swing angle of each joint 4, 6, 8 detected by the swing angle sensor 15, and the six-axis force sensor 16. The actual floor reaction force of the foot portion 10 to be detected, the actual rotation angle of the electric motor 18 detected by the encoder 19, the command value generated by the motor control unit 35, the crus link 8 detected by the external force sensor 17 A command value for a current to be supplied to the MR damper 12 is generated based on an external force that acts on the MR damper 12. Then, the damper control unit 36 outputs the generated command value to the damper drive circuit 33, and causes the MR damper 12 to pass a current corresponding to the command value via the damper drive circuit 33.

  By the way, in consideration of manufacturing errors and the like, there is inevitably play (including semantic concepts such as gap, play, backlash, play) between structures. Here, as specific play, a play between the thigh link 6 and the linear motion actuator 11 (that is, play between the shaft hole 21 and the support shaft 20), and a belt between the electric motor 18 and the nut member are used. , Looseness between the nut member in the linear actuator 11, ball, screw shaft, looseness between the crus link 8 and the linear actuator 11 (that is, looseness between the shaft hole 24 and the support shaft 23). And between the thigh link 6 and the crus link 8 (that is, play between the shaft hole 14 and the support shaft 13).

  While the relative movement of the two structures forming the backlash is performed without decelerating in a certain direction, there is no adverse effect due to the backlash, and the movement of the two structures is stable. However, when the relative movement of the two structures forming the backlash changes direction or involves deceleration, the movement of the two structures is unstable because one of the structures moves to cause backlash. become.

  Therefore, when the direction of the force acting on the crus link 8 changes during the swinging motion of the crus link 8 by the linear actuator 11, the damper controller 36 causes the MR damper 12 to appropriately attenuate the operation of the crus link 8. Generates a command value of a current to be supplied to the MR damper 12.

  While the crus link 8 is steadily and continuously swinging by the linear actuator 11, an appropriate backlash is achieved. In this state, if the direction of the force acting on the crus link 8 changes, the crus link 8 can move freely in the play regardless of the thigh link 6 or the linear motion actuator 11 due to the action of the force. The posture of the robot 1 becomes unstable. Therefore, when such a force is applied, a damping force is generated in the MR damper 12 to attenuate the operation of the lower leg link 8. As a result, free movement within the play is suppressed, and the period during which the biped robot 1 is in an unstable posture can be shortened. Furthermore, since free movement within the play is suppressed, the allowable range of play is increased, and the manufacturing cost of the biped walking robot 1 can be reduced.

  Next, a control example of such a biped walking robot 1 will be described with reference to the drawings. When the reversal operation occurs in the crus link 8, the process of the flowchart shown in FIG. 3 is executed.

  First, during the swinging motion of the lower leg link 8 by the linear actuator 11 (STEP 1: YES), the current command value newly generated by the motor control unit 35 is the difference between the positive and negative directions with respect to the current command value so far. If there is, a deceleration action (brake) occurs in the expansion / contraction operation of the linear motion actuator 11. Specifically, for example, when the command value generated by the motor control unit 35 is a constant positive current value, a current command value having a negative difference, that is, a command value with a reduced current value is newly added. When generated, the rotation of the electric motor 18 is decelerated. Along with this, a negative acceleration occurs in the operation of extending the rod shaft 22, and the elongation of the rod shaft 22 is decelerated. At this time, the crus link 8 cannot immediately follow the deceleration of the rod shaft 22 due to its inertial motion and the presence of backlash, and thus freely moves in the backlash. Therefore, the operation of the lower leg link 8 becomes unstable until the play is completed, and the posture of the biped walking robot 1 becomes unstable.

  Therefore, when the motor control unit 35 generates a current command value having a difference between the positive and negative directions (STEP 2: YES), the MR damper 12 is energized (STEP 3). Specifically, the damper control unit 36 generates a current command value corresponding to the magnitude of the difference, and energizes the MR damper 12 with a current based on the command value via the damper drive circuit 33. Thereby, the MR damper 12 generates a damping force corresponding to the energized current value, and decelerates the operation of the lower leg link 8 (STEP 4).

  Thereafter, when the angular velocity of the knee joint portion 7 is reversed (STEP 5: YES), the energization to the MR damper 12 is stopped (STEP 6). The fact that the angular velocity of the knee joint portion 7 has been reversed means that the backlash has been completed and the crus link 8 has started a swinging motion that follows the expansion and contraction motion of the rod shaft 22 again. Then, since the damping force by the MR damper 12 becomes a resistance to the operation of the crus link 8, the energization to the MR damper 12 is stopped.

  Thus, when the linear motion actuator 11 starts a deceleration operation (STEP 2: YES) during the swinging motion of the crus link 8 (STEP 1: YES), the crus link 8 can immediately follow this deceleration operation. It will be in the state which can move freely in the backlash. However, at this time, since the operation of the lower leg link 8 is attenuated by the MP damper 12 (STEP 4), the free movement in the play of the lower leg link 8 is suppressed, and the bipedal walking robot 1 is in an unstable posture. It can be shortened.

  In STEP 2, the deceleration operation of the linear motion actuator 11 is predicted based on the fact that the motor control unit 35 generates a current command value having a difference between positive and negative directions. However, the fact that the linear motion actuator 11 has actually started a deceleration operation may be used as a determination criterion in STEP2. This can be determined, for example, by detecting the reversal of the actual angular acceleration of the electric motor 18 by the encoder 19 and detecting a decrease in the current value actually supplied to the electric motor 18. Moreover, it is good also as a discrimination | determination reference | standard in STEP2 that the free exercise | movement in the backlash was started. This can be determined, for example, by detecting a swing angle change of the knee joint portion 7 by the swing angle sensor 15 or a swing change of the lower leg link 8 by a gyro sensor (not shown) mounted on the lower leg link 8 or the like.

  Further, in STEP 5, it is determined that the rattling has been completed, with the time when the angular velocity of the knee joint portion 7 is reversed as a criterion. However, the fact that the linear motion actuator 11 has started to operate in the reverse direction may be used as a determination criterion in STEP 5. This can be determined, for example, by detecting an increase in the actual angular velocity of the electric motor 18 with the encoder 19 or detecting an increase in the current value that is actually energized in the electric motor 18. In addition, since the time until the play is completed is substantially constant, the elapse of the predetermined time may be used as a determination criterion in STEP5.

  When an external force that swings the crus link 8 is applied to the crus link 8 in the same direction as the swinging direction of the crus link 8, the process of the flowchart shown in FIG.

  First, during an oscillating operation of the crus link 8 by the linear actuator 11 (STEP 11: YES), when an external force that oscillates the crus link 8 acts on the crus link 8 in the same direction as the oscillating direction of the crus link 8. The swinging motion of the lower leg link 8 is accelerated. Specifically, for example, when the crus link 8 swings around the clockwise direction at a constant speed, an external force is generated in the crus link 8 due to the foot 10 landing, and the action of the external force When the direction is the direction in which the lower leg link 8 is swung clockwise, the swinging motion of the lower leg link 8 is accelerated. At this time, the crus link 8 freely moves in the backlash by its own acceleration operation. Therefore, the operation of the lower leg link 8 becomes unstable until the play is completed, and the posture of the biped walking robot 1 becomes unstable.

  Therefore, when the external force sensor 17 detects that an external force that swings the lower leg link 8 is applied to the lower leg link 8 in the same direction as the swing direction of the lower leg link 8 (STEP 12: YES), the MR damper 12 is energized. (STEP 13). Specifically, the damper control unit 36 generates a current command value corresponding to the swing direction moment component of the external force, and causes the MR damper 12 to pass a current based on the command value via the damper drive circuit 33. . Thereby, the MR damper 12 generates a damping force corresponding to the energized current value, and suppresses the rapid acceleration operation of the lower leg link 8 (STEP 14).

  Thereafter, when the current value of the electric motor 18 increases (STEP 15: YES), the energization to the MR damper 12 is stopped (STEP 16). When the swinging motion of the lower leg link 8 is accelerated by an external force, the difference between the actual rotational angle of the electric motor 18 and the rotational angle based on the current command value generated by the motor control unit 35 is increased with the acceleration of the expansion / contraction operation of the rod shaft 22. growing. In order to eliminate this difference, the motor control unit 35 changes the command value, so that the current value of the current motor 18 increases. At this time, the motor control unit 35 has started the control corresponding to the acceleration operation of the crus link 8 by the external force, and the backlashing is also completed. Then, since the damping force by the MR damper 12 becomes a resistance to the operation of the crus link 8, the energization to the MR damper 12 is stopped.

  Thus, during the swinging motion of the lower leg link 8 (STEP 11: YES), if an external force acts on the lower leg link 8 in the same direction as the swinging motion of the lower leg link 8 (STEP 12: YES), the lower leg link 8 Can move freely in the backlash, and its swinging motion can be accelerated. Therefore, when such a force is applied, a damping force is generated in the MR damper 12 (STEP 13), and the acceleration operation of the lower leg link 8 is suppressed (STEP 14). As a result, the free movement of the lower leg link 8 within the play is suppressed, and the period during which the biped walking robot 1 is in an unstable posture can be shortened.

  In STEP 12, the acceleration operation of the lower leg link 8 was determined based on the determination criterion when the external force sensor 17 detected that an external force that swings the lower leg link 8 was applied to the lower leg link 8. However, for example, the determination may be made based on a decrease in the actual angular velocity of the electric motor 18 detected by the encoder 19 or a decrease in a current value that is actually energized in the electric motor 18. Moreover, it is good also as a discrimination | determination reference | standard in STEP12 that the free exercise | movement in the backlash was started. This can be determined from, for example, a swing angle change of the knee joint portion 7 by the swing angle sensor 15 or a swing change of the lower leg link 8 by a gyro sensor (not shown) mounted on the lower leg link 8 or the like. Moreover, it is good also considering that it is estimated that the external force which rocks the crus link 8 acts on the crus link 8 in STEP2. This can be determined, for example, by predicting when the foot 10 has landed from the gait parameters generated by the gait generator 34.

  Further, in STEP 15, it is determined that the rattling has been completed based on the determination criterion that the angular velocity of the knee joint portion 7 is reversed. However, since the time until the play is completed is substantially constant, the elapse of the predetermined time may be used as the determination criterion in STEP15.

  When an external force directed toward the knee joint 7 acts on the crus link 8, the process of the flowchart shown in FIG. 5 is executed.

  First, when the external force acting on the knee joint portion 7 is applied to the lower leg link 8 during the swinging motion of the lower leg link 8 by the linear motion actuator 11 (STEP 21), the lower leg link 8 faces the knee joint portion 7 direction. Moving. During the swinging motion of the crus link 8, the support shaft 13 of the crus link 8 is in contact with the shaft hole 14 of the thigh link 6 at the foot 10 side as shown in FIG. 1. At this time, when an external force acting in the direction of the knee joint portion 7 acts on the crus link 8, the support shaft 13 of the crus link 8 tends to move to the hip joint portion 5 side in the backlash with the shaft hole. Therefore, the operation of the crus link 8 becomes unstable and the posture of the biped walking robot 1 becomes unstable until the support shaft 13 comes into contact with the hip joint 5 side of the shaft hole 14 and the rattling is completed.

  Therefore, when the 6-axis force sensor 16 detects that the external force acting on the knee joint portion 7 is applied to the crus link 8 (STEP 22: YES), the MR damper 12 is energized (STEP 23). Specifically, the damper control unit 36 generates a current command value corresponding to the value of the external force, and energizes the MR damper 12 with a current based on the command value via the damper drive circuit 33. Thereby, the MR damper 12 generates a damping force corresponding to the energized current value, and suppresses the movement of the crus link 8 in the direction of the knee joint portion 7 (STEP 24).

  Thereafter, when the swinging motion of the lower leg link 8 returns to normal (STEP 25: YES), the energization to the MR damper 12 is stopped (STEP 26). When the lower leg link 8 moves in the direction of the knee joint 7, the normal correspondence between the current command value to the electric motor 18 and the swing angle of the knee joint 7 detected by the swing angle sensor 15 is lost, and The swing operation becomes abnormal. However, after that, the crus link 8 is loosened, and the swinging motion of the crus link 8 returns to the normal state. Then, since the damping force by the MR damper 12 becomes a resistance to the operation of the crus link 8, the energization to the MR damper 12 is stopped.

  As described above, when an external force acts on the lower leg link 8 in the direction of the knee joint portion 7 (STEP 22: YES) during the swinging motion of the lower leg link 8 (STEP 21: YES), the lower leg link 8 moves in the back of the knee joint portion. Move freely in 7 directions. Therefore, when such an external force is applied, a damping force is generated in the MR damper 12 (STEP 23), and the movement operation of the crus link 8 is suppressed (STEP 24). As a result, the free movement of the lower leg link 8 within the play is suppressed, and the period during which the biped walking robot 1 is in an unstable posture can be shortened.

  In STEP 22, the moving operation of the linear actuator 11 is predicted based on the fact that an external force directed in the direction of the knee joint 7 detects that an external force is applied to the crus link 8. However, for example, the determination may be made based on a decrease in the actual angular velocity of the electric motor 18 detected by the encoder 19 or a decrease in the current value supplied to the electric motor 18. Moreover, it is good also as a discrimination | determination reference | standard in STEP22 that the free exercise | movement in the backlash was started. This can be determined from, for example, a swing angle change of the knee joint portion 7 by the swing angle sensor 15 or a swing change of the lower leg link 8 by a gyro sensor (not shown) mounted on the lower leg link 8 or the like. Further, it may be determined that the external force in the direction of the knee joint portion 7 is predicted to be applied to the crus link 8 in STEP 22. This can be determined, for example, by predicting when the foot 10 has landed from the gait parameters generated by the gait generator 34.

  Further, in STEP 25, when the swinging motion of the crus link 8 has returned to normal, it is determined that the rattling has been completed with the criterion of discrimination. However, it can be determined, for example, by detecting an increase in the actual angular velocity of the electric motor 18 by the encoder 19 and detecting an increase in the current value supplied to the electric motor 18. Further, since the time until the loosening is completed is substantially constant, the elapse of a predetermined time may be used as a determination criterion in STEP25.

  In addition, this invention is not limited to what was mentioned above. For example, in the embodiment, the case where the MR damper 12 that connects the thigh link 6 and the crus link 8 of the biped walking robot 1 is provided has been described. However, an MR damper may be provided that connects between the torso part 2 and the thigh link 6 and between the crus link 8 and the foot part 10.

  Further, the case where the MR damper 12 is provided has been described. However, in place of the MR damper 12, a magnetic fluid or a variable damping force damper having a variable orifice diameter may be provided. A damper having a constant damping force may be provided. However, since the MR damper 12 changes its viscosity according to the current value applied to the magnetism generating means such as a coil, the damping force can be easily changed, and there is an advantage that the response is excellent.

  Furthermore, in the embodiment, the case where the robot is the biped walking robot 1 has been described. However, the configuration and form of the robot are not limited as long as the robot includes two links connected via a joint portion and includes an actuator that swings and drives the other link with respect to one link. For example, the present invention may be applied to the arm portion of a humanoid robot.

  DESCRIPTION OF SYMBOLS 1 ... Biped walking robot (robot), 3 ... Leg part, 6 ... Thigh link (1st link), 7 ... Knee joint part (joint part), 8 ... Lower leg link (2nd link), 9 ... Ankle joint part , 10 ... Foot part, 11 ... Linear motion actuator (actuator), 12 ... MR damper (damper), 13, 20, 23 ... Support shaft, 14, 21, 24 ... Shaft hole, 15 ... Swing angle sensor, 16 ... 6-axis force sensor, 17 ... External force sensor, 18 ... Electric motor, 19 ... Encoder, 22 ... Rod shaft, 27 ... Control box, 31 ... Control unit (control means), 32 ... Motor drive circuit, 33 ... Damper drive circuit 35 ... Motor control unit, 36 ... Damper control unit.

Claims (9)

A robot in which a first link and a second link are connected via a joint,
An actuator that swings and drives the second link with respect to the first link;
A damper for applying a damping force to the swinging motion of the second link;
Control means for controlling the damper to generate a damping force when the direction of the force acting on the second link changes during the swinging motion of the second link by the actuator. robot.   The control means is configured so that the second link swings in a direction opposite to the swinging direction of the second link during the swinging operation of the second link by the actuator. The robot according to claim 1, wherein when the force is applied to the link, the damper is controlled so as to generate a damping force.   When the external force is applied to the second link in the same direction as the direction in which the second link swings during the swing operation of the second link by the actuator, the control unit applies a damping force to the damper. The robot according to claim 1, wherein the robot is controlled so as to be generated.   The control means controls the damper to generate a damping force when an external force acts on the second link in the direction of the joint during the swinging operation of the second link by the actuator. The robot according to claim 1.   The robot according to any one of claims 1 to 4, wherein the damper is a magnetorheological fluid damper that varies the viscosity of the magnetorheological fluid by a magnetic field.   6. The robot according to claim 1, wherein the actuator is a linear motion actuator that connects the first link and the second link at a portion spaced from the joint portion. 6. The first link and the second link are connected via a joint portion, and an actuator that swings the second link with respect to the first link, and a damping force is applied to the swing operation of the second link. A control method for a robot equipped with a damper,
A control method for a robot, wherein the damper is controlled to generate a damping force when the direction of a force acting on the second link changes during the swinging motion of the second link by the actuator. Each leg includes a thigh link connected to the torso via a hip joint, and a lower leg link connected to the lower end of the thigh link via a knee joint. A biped robot having a foot connected to the lower end of the lower leg link via an ankle joint,
A linear motion actuator that connects the thigh link and the crus link at each leg portion at a portion spaced from the knee joint portion;
A damper for applying a damping force to the swinging motion of the lower leg link with respect to the thigh link;
Control means for controlling the damper to generate a damping force when the direction of the force acting on the crus link changes during the swinging operation of the crus link by the expansion / contraction operation of the linear actuator. A featured biped robot. Each leg includes a thigh link connected to the torso via a hip joint, and a lower leg link connected to the lower end of the thigh link via a knee joint. A linear motion actuator that connects the thigh link and the crus link in each leg at a portion spaced from the knee joint, and a damper that applies a damping force to the swinging motion of the crus link with respect to the thigh link; , A control method for a biped walking robot comprising a foot part connected to the lower end of the lower leg link via an ankle joint part,
Two legs that control the damper to generate a damping force when the direction of the force acting on the crus link changes during the swinging movement of the crus link by the expansion / contraction operation of the linear actuator Control method for walking robot.

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