JP2013035112A - Joint actuator for robot, and leg type mobile robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint actuator for a robot of novel structure capable of transmitting output of a driving source to a joint, while reducing the output speed of the driving source.SOLUTION: A first member 35 and a second member 33 are rotatably connected to each other through a connecting shaft 34. The first member 35 includes a support shaft 41 at a position separated from the connecting shaft 34. The second member 33 includes a driving shaft 37 as a second support shaft at a position separated from the connecting shaft 34. Extendable mechanisms 38, 39 and 40 change a distance between the first support shaft 41 and the second support shaft 37 so that the second member 33 rotates around the connecting shaft 34 relatively to the first member 35.

Description

  The present invention relates to a joint actuator and a legged mobile robot for a robot that drives a joint of a robot in which a first member and a second member are rotatably connected via a connecting shaft.

  In recent years, legged mobile robots such as a biped walking robot that walks while balancing with two legs like a human being have been developed. Each leg of the legged mobile robot is configured by sequentially connecting a plurality of links from the body through a plurality of joints. For example, each leg is configured by sequentially connecting links corresponding to portions including the thigh, the shin, and the sole from the body of the robot via the hip joint, knee joint, and ankle joint. In order to move the robot by providing a joint actuator such as a servomotor at each joint of each leg and applying torque to the link corresponding to the part including the thigh, shin, and sole. Get leg movements.

  As a conventional joint actuator, an example is known in which an output shaft of a servo motor is arranged at each joint, a link such as a thigh is directly attached to the output shaft of the servo motor, and the link is rotated by the servo motor. Also, as another joint actuator, the servomotor output shaft is placed at a position away from the joint, and the power of the servomotor is transmitted to the speed reducer placed in the joint via a transmission consisting of a belt and a pulley. An example of rotating a link attached to an output shaft of a machine is also known (see Patent Document 1).

JP 2006-51558 A

  However, in the former joint actuator in which the output shaft of the servo motor is arranged at the joint and the link is directly attached to the output shaft, a servo motor with a large torque that places a heavy burden on the output shaft of the servo motor is required. There is a problem that a large impact directly enters the servo motor when it falls.

  Further, in the latter joint actuator in which a speed reducer is arranged at the joint, there is a problem that the joint becomes larger due to the speed reducer, and the weight of the joint increases.

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a joint actuator and a legged mobile robot having a new structure capable of decelerating the output of a drive source and transmitting it to a joint. For the purpose.

  In order to solve the above-described problem, the present invention provides a joint actuator that drives a joint of a robot in which a first member and a second member are rotatably connected via a connecting shaft, and the first member is attached to the first member. A first support shaft provided at a position away from the connection shaft; a second support shaft provided at a position away from the connection shaft on the second member; the first support shaft and the second support; An expansion / contraction mechanism that changes a distance between the first support shaft and the first support shaft by changing the distance between the first support shaft and the second support shaft. The second member is a joint actuator of a robot in which the second member relatively rotates around the connecting shaft.

  According to the present invention, the first support shaft and the second support shaft are provided at positions away from the connecting shaft of the first member and the second member, and the first support shaft and The distance between the second support shaft is changed, and thereby the second member is rotated relative to the first member around the connecting shaft. Since the output of the drive source can be decelerated and transmitted to the joint, a large output can be taken out with a small drive source. Further, since the joint connecting shaft and the telescopic mechanism are separated, the strength of the joint actuator can be improved.

1 is a front view of a legged mobile robot incorporating a joint actuator according to an embodiment of the present invention. Side view of the legged mobile robot of FIG. Schematic diagram of the lower body of a legged mobile robot The figure which shows the hip joint of a leg type mobile robot (FIG. 4 (A) shows a front view, FIG.4 (B) shows a rear view.) FIG. 3 is a schematic skeleton diagram of the lower half of a legged mobile robot in which a left leg is in a standing state and a right leg is in a swinging state. FIG. 6 (A) shows an initial position of the left leg, FIG. 6 (B) shows a state in which the left leg is bent inward (inner position), and FIG. (C) shows the state where the left leg is swung outward (outside position)) The schematic diagram which shows the other example of the joint actuator of this invention

  FIG. 1 is an external view showing an overall configuration of a legged mobile robot according to the present embodiment. FIG. 2 is a right side view of the legged mobile robot according to the present embodiment. In the present embodiment, the left and right are the left and right viewed from the legged mobile robot side shown in the figure. Therefore, the left side is the left side as seen from the legged mobile robot. The left leg refers to the right leg toward the page.

  The legged mobile robot 10 according to the present embodiment is manufactured as a housework robot, and is installed on two left and right side surfaces of the body unit 11 and two legs 12 installed below the body unit 11. The two arm portions 13 and one head portion 14 installed above the body portion 11 are configured.

  The legged mobile robot 10 is configured to maintain an upright state as shown in FIG. 1 even when the power is turned off if there is no disturbance such as an external pressing force. In particular, since the two leg portions 12 are configured to always be in a linearly extended state when stopped, the two leg portions 12 are excellent in safety and stability. Further, when the two legs 12 are walking on two legs, the stepping action by the two legs 12 is executed.

  On the other hand, the two arm portions 13 can move freely around the body portion 11 and are configured such that the arm portion 13 hangs downward when the power is turned off. . Furthermore, since the hand part 13a is installed in the front-end | tip of the arm part 13, it is possible to grasp and pick an object using this hand part 13a.

  A CCD camera 15 is installed on each of the head 14 and the body 11. With this CCD camera 15, the situation around the legged mobile robot 10 can be collected as image data.

  The legged mobile robot 10 is a robot configured to be remotely operable, and an operator operates an operation manipulator (not shown) located at a distant position so that an operation according to the movement of the operation manipulator is performed. 10 can be executed. Therefore, the operator can grasp the surroundings of the legged mobile robot 10 while staying at a remote place via a wireless communication means such as an Internet line or the CCD camera 15 installed on the legged mobile robot 10. The legged mobile robot 10 can be operated.

  FIG. 3 shows a skeleton diagram of the lower body of the legged mobile robot. Since the skeleton diagram is basically symmetrical, only the left leg will be described for the sake of simplicity. The leg portion 12 is fixed to the pelvis of the trunk portion 11 via a direction changing joint 21. A roll joint 22 and a pitch joint 23 are disposed under the direction changing joint 21. When the direction changing joint 21 rotates, the leg 12 turns around the yaw axis. When the roll joint 22 rotates, the leg 12 swings around the roll axis. When the pitch joint 23 rotates, the leg 12 swings around the pitch axis. These three joints 21, 22, and 23 are arranged so that their output axes are orthogonal to each other, and constitute a hip joint.

  A thigh link 24 is coupled to the pitch joint 23. A knee joint 25 is coupled under the thigh link 24. A shin link 26 is coupled under the knee joint 25. Ankle joints 27 and 28 are disposed under the shin link 26. The foot joints 27 and 28 include a pitch joint 27 and a roll joint 28 orthogonal thereto. A foot portion 29 that is in contact with the walking road surface is coupled under the ankle joints 27 and 28. The position of each joint is controlled by a servo motor driven by electrical energy. In addition, the dashed-two dotted line in a figure shows the upper body part 30 couple | bonded with a pelvis. As described above, the upper body portion 30 includes the body portion 11, the arm portion 13, and the head portion 14.

  FIG. 4 shows the joint actuator 31 of this embodiment that is incorporated as a roll joint 22 in the hip joint. 4A shows a front view of the hip joint, and FIG. 4B shows a rear view of the hip joint. The pelvis 32 is provided with two left and right joint actuators 31. The left leg joint actuator 31 in FIG. 4A swings the left leg outward, and the right leg joint actuator 31 keeps the right leg upright. The two left and right joint actuators 31 are symmetrical.

  The joint actuator 31 includes a waist frame 35 as a first member, a leg support portion 33 as a second member, and a connecting shaft 34 that rotatably connects the waist frame 35 and the leg support portion 33. The connecting shaft 34 functions as a roll shaft. The joint actuator 31 swings the leg 12 around the connecting shaft 34.

  The waist frame 35 is attached to the pelvis 32 so as to be able to turn around the pitch axis 36. The waist frame 35 is formed by bending the plate so that the cross section has a U-shape. The waist frame 35 includes an upper wall 35-1 coupled to the pitch shaft 36 and a pair of side walls 35-2 bent so as to be orthogonal to the upper wall 35-1. The side wall 35-2 of the waist frame 35 is elongated in the left-right direction. The end of the side wall 35-2 (the outer end when viewed from the robot) protrudes downward, and the connecting shaft 34 is rotatably attached to the protruding portion 35-2a.

  The leg support portion 33 is elongated in the left-right direction in FIG. The leg support portion 33 is sandwiched between the pair of side walls 35-2 of the waist frame 35, and can rotate around the connecting shaft 34. The thigh link 24 of the leg 12 is coupled to the leg support 33. An end of the leg support 33 (the outer end as viewed from the robot) is rotatably connected to the connecting shaft 34. The leg support portion 33 is provided with a drive shaft 37 as a second support shaft at a position away from the connecting shaft 34 inward. The drive shaft 37 is an output shaft of a servo motor (not shown), and is driven to rotate clockwise and counterclockwise by the servo motor.

  A horn 38 as a first link is non-rotatably connected to the drive shaft 37. In other words, the horn 38 is coupled to the drive shaft 37 and rotates together with the drive shaft 37. The horn 38 is formed in a triangular shape whose overall shape gradually decreases toward the tip. However, the base 38a (FIG. 4B) of the horn 38 is formed in a circular shape. As shown in FIG. 4B, an arc-shaped cut 35b corresponding to the base portion 38a of the horn 38 is formed in the waist frame 35 so that the swing angle to the inside of the leg portion 12 can be increased. The base 38a of the horn 38 and the side wall 35-2 on the back side of the waist frame 35 are arranged on the same plane.

  One end of the second link 40 is rotatably connected to the tip of the horn 38 via a link shaft 39. The other end of the second link 40 is rotatably connected to the waist frame 35 via a first support shaft 41. The second link 40 is formed by bending the cross section of the plate so that the cross section becomes a U-shape. The second link 40 includes a pair of link main bodies 40-1 disposed so as to sandwich the horn 38 and a connecting portion 40-2 connecting the link main bodies 40-1. The pair of link main bodies 40-1 are arranged so as to sandwich the side wall 35-2 on the back side of the waist frame 35. An arc-shaped cut 40a corresponding to the base portion 38a of the horn 38 is also formed in the link main body 40-1 of the second link 40 so that the swing angle to the inside of the leg portion 12 can be increased. The link body 40-1 and the base 38a of the horn 38 are arranged on the same plane.

  When the servo motor rotates the drive shaft 37, the horn 38 coupled to the drive shaft 37 rotates around the drive shaft 37. Since the second link 40 is rotatably connected to the tip of the horn 38, when the horn 38 rotates around the drive shaft 37, the horn 38 and the second link 40 are folded and contracted. It extends in a straight line or changes its shape. For this reason, the distance from the drive shaft 37 to the first support shaft 41 changes, and the leg support portion 33 rotates around the connecting shaft 34 with respect to the waist frame 35. The horn 38, the second link 40, and the link shaft 39 constitute an expansion / contraction mechanism.

  According to the joint actuator 31 of the present embodiment, the drive shaft 37 is provided at a position away from the connecting shaft 34, and the horn 38 and the second link 40 that act like a lever are used to connect the waist frame 35 and the leg support portion 33 to each other. Since the distance between them is changed, the output of the drive shaft 37 can be decelerated and transmitted to the leg support 33. For this reason, a large output can be taken out by a small servo motor.

  When the legged mobile robot walks on two legs, each leg 12 alternately repeats the walking road surface, the standing leg state installed and the free leg state away from the walking road surface. FIG. 5 is a front view of the legged mobile robot as seen from the front when running on a flat walking road surface. In FIG. 5, the left leg is in a standing state and the right leg is in a free leg state. If the center of gravity position of the legged mobile robot in this posture is Q and the mass is M, a force of Mg (g is gravitational acceleration) acts on the point Q vertically downward. If the point at which this force vector intersects the ground is P, the same force as Mg acts on P as a road reaction force vertically upward. By swinging the leg 12 in the standing state inward, P can be positioned on the foot 29, and the posture of the legged mobile robot is stabilized. Further, by swinging the leg 12 in the free leg state outward, the leg 12 in the free leg state does not interfere with the walking road surface.

  FIG. 6 shows an operation diagram of the joint actuator 31 for the right leg as viewed from the back side. 6A shows an initial position where the right leg is upright, FIG. 6B shows a state where the right leg is bent inward (inner position), and FIG. 6C swings the right leg outward. The moved state (outside position) is shown. In order to realize the walking of the legged mobile robot, the leg portion 12 is swung inward as shown in FIG. Then, in the free leg state, the leg portion 12 is swung outward as shown in FIG. By rotating the drive shaft 37 clockwise or counterclockwise, the leg portion 12 can be swung inward or swung outward. Note that FIG. 6C shows an example in which the swing angle is increased in order to make it easier to understand the swing of the leg 12 to the outside, but to the outside of the leg 12 in the actual free leg state. Is smaller than that shown in FIG.

  As shown in FIGS. 6A and 6B, when the leg 12 is in the initial position and the inner position, the link shaft 39 that connects the horn 38 and the second link 40 is the drive shaft 37. It is located on the leg 12 side (in other words, on the side opposite to the waist frame 35) from the line L1 connecting the connecting shafts 34. On the other hand, as shown in FIG. 6C, when the leg portion 12 is at the outer position, the link shaft 39 that connects the horn 38 and the second link 40 connects the drive shaft 37 and the connecting shaft 34. It is located closer to the waist frame 35 than the ellipse L1. Thereby, the rocking | swiveling angle to the outer side of the leg part 12 can be enlarged.

  As shown in FIGS. 6A and 6B, when the leg 12 is in the initial position and the inner position, the load of the upper body 30 of the legged mobile robot is transmitted to the leg 12. By disposing the link shaft 39 closer to the leg portion 12 than the line L1, the load vector F (see FIG. 6B) of the upper body portion 30 can be made difficult to act on the drive shaft 37 as a torque. In detail, as shown in the right side of FIG. 6B, the load vector F of the upper body 30 acts on the link shaft 39 in the direction of the arrow. The vector F can be divided into a vector F1 in a direction connecting the drive shaft 37 and the link shaft 39, and a vector F2 orthogonal to the vector F1. It is the vector F2 that acts on the drive shaft 37 as a torque. By arranging the link shaft 39 closer to the leg 12 than the line L1, the vector F2 can be reduced. The size of the vector F2 is also derived from an angle θ formed by a line connecting the drive shaft 37 and the link shaft 39 and a line connecting the link shaft 39 and the first support shaft 41. Since the vector F2 can be made smaller as the angle θ is smaller, it is desirable to set θ to less than 45 degrees.

  By the way, an excessive moment according to the mass of the legged mobile robot acts on the joint actuator 31 in the standing state (see FIG. 5). In order to receive this moment only with the torque of the servomotor of the joint actuator 31, it is necessary to increase the torque of the servomotor. In order to reduce or eliminate the electric energy consumed by the servo motor, a stopper that mechanically restricts the inward swing of the leg 12 in the standing state may be provided on the waist frame 35. The stopper may abut on any of the leg support 33, the horn 38, and the second link 40. Moreover, you may make it comprise a stopper by contact | abutting any one of the leg support part 33, the horn 38, and the 2nd link 40 with the remaining one.

  The reduction ratio of the joint actuator 31 when the leg 12 was changed from −10 ° to + 40 ° around the roll axis was calculated. The minus angle of the leg angle means that the leg portion 12 is swung inward, and the plus angle means that it is swung outward. The reduction ratio is calculated from the ratio between the rotation angle of the servo motor and the rotation angle of the leg 12 around the roll axis. A larger reduction ratio means that the torque of the servo motor is amplified and transmitted to the legs 12.

  Table 1 shows the calculation results.

表１の最上段の脚角度−１０°の場合、サーボモータのトルクが４．７６倍になって脚部１２に伝達することがわかる。すなわち、サーボモータのトルクが１０Ｎｍであっても、トルクが４７．６Ｎｍまで増幅して脚部１２に伝わる。サーボモータがトルクを必要とするのは脚部１２が内側に揺動する−１０°〜０°のときである。本実施形態によれば、このときに４倍以上サーボモータのトルクを増幅できる。このように脚部１２が内側に揺動したときの減速比を脚部１２が外側に揺動したときの減速比よりも大きくすることが望ましい。脚部１２が外側に揺動するときは脚部１２が持ち上がっているので、サーボモータにはそれほど大きなトルクが必要とされないが、３倍以上トルクを増大できた。

It can be seen that when the uppermost leg angle in Table 1 is −10 °, the torque of the servo motor is 4.76 times and transmitted to the leg 12. That is, even if the torque of the servo motor is 10 Nm, the torque is amplified to 47.6 Nm and transmitted to the leg 12. The servo motor requires torque when the leg 12 swings inward from −10 ° to 0 °. According to the present embodiment, the torque of the servo motor can be amplified four times or more at this time. Thus, it is desirable that the reduction ratio when the leg portion 12 swings inward is larger than the reduction ratio when the leg portion 12 swings outward. Since the leg 12 is lifted when the leg 12 swings outward, the servomotor does not require a very large torque, but the torque can be increased by a factor of 3 or more.

  The present invention is not limited to the embodiment described above, and can be embodied in various embodiments without departing from the scope of the present invention. For example, as shown in FIG. 7, an expansion / contraction mechanism 51 that expands and contracts by a ball screw or the like is provided between the first support shaft 41 of the waist frame 35 and the second support shaft 37 of the leg support portion 33. By changing the distance between the first support shaft 41 and the second support shaft 37, the leg support portion 33 may be rotated around the connecting shaft 34.

  A servo motor as a drive source for the joint actuator may be provided on the waist frame instead of being provided on the leg support. Furthermore, the joint actuator according to the present invention is not limited to the hip joint of a legged mobile robot, but can be applied to a joint such as a shoulder joint or a hip joint that tilts the upper body forward or backward. .

  Furthermore, the joint actuator of the present invention is not limited to the legged mobile robot as long as it has a joint, and can be applied to industrial robots such as vertical articulated robots and horizontal articulated robots. it can.

DESCRIPTION OF SYMBOLS 10 ... Leg type mobile robot, 11 ... Body part, 12 ... Leg part, 22 ... Roll joint, 31 ... Joint actuator, 32 ... Pelvis, 33 ... Leg support part (2nd member), 34 ... Connecting shaft, 35 ... Waist Frame (first member) 37 ... drive shaft (second support shaft) 38 ... horn (first link) 39 ... link shaft 40 ... second link 41 ... first support shaft

Claims (5)

A joint actuator that drives a joint of a robot in which a first member and a second member are rotatably connected via a connecting shaft,
A first support shaft provided on the first member at a position away from the connection shaft;
A second support shaft provided on the second member at a position away from the connection shaft;
A telescopic mechanism for changing a distance between the first support shaft and the second support shaft,
When the telescopic mechanism changes the distance between the first support shaft and the second support shaft, the second member rotates relative to the first member relative to the connection shaft. Robot joint actuator. The second support shaft is a drive shaft that is rotationally driven by a drive source;
The telescopic mechanism includes a first link that is non-rotatably coupled to the drive shaft, and is rotatably coupled to the first link via a link shaft, and the first support shaft is coupled to the first member. The joint actuator of the robot according to claim 1, further comprising: a second link that is rotatably connected via the joint. The drive shaft provided on the second member is rotatable clockwise and counterclockwise;
When the drive shaft rotates in either one of the clockwise direction and the counterclockwise direction, the link shaft that connects the first link and the second link connects the drive shaft and the connecting shaft. Than the first member side,
When the drive shaft rotates in the other direction clockwise and counterclockwise, the link shaft is located on the opposite side of the first member from the line connecting the drive shaft and the connecting shaft. The joint actuator of the robot according to claim 2. A legged mobile robot having a body part and two leg parts rotatably connected to the body part via two connecting shafts,
A legged mobile robot using the joint actuator of the robot according to any one of claims 1 to 3 as a joint actuator for a hip joint that rotates each leg portion around a roll axis with respect to a body portion. Each leg of the legged mobile robot alternately repeats the walking road surface and the standing leg state and the free leg state away from the walking road surface,
Limiting rotation of at least one of the first member, the second member, the first link, and the second link so as to limit the inward swing of the leg portion around the roll axis in the standing state. The legged mobile robot according to claim 4, further comprising a stopper.

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