JP2014031851A - Variable impedance servo motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weight and compact variable impedance servo motor excellent in vibration convergence and shock absorption.SOLUTION: A carrier 27 holds rotation and revolution of a planetary gear 28 and is fixedly connected to a shaft 25a of a motor 25, the planetary gear 28 is engaged with a sun gear 29 and a ring gear 30 to constitute the planetary gear, the ring gear 30 is fixedly connected to a holder 31 together with a super gear 24a, the holder is rotatably held by the sun gear 29 through a bearing 31a, an output shaft 24c is fixedly connected to the sun gear 29, and a base 32 is connected to the motor 25 and becomes a dynamic reference. A buffer 24b includes a blacket 33 for holding a damper 34 and a non-linear spring 35, a rack 36 for connecting a spring seat 36a is movably connected to the bracket 33 through a linear motion bearing 36b, the rack 36 is converted into linear motion while being contact with the super gear 24a, and the bracket 33 is fixed on a seat 32a of the base 32.

Description

The present invention relates to a variable impedance servo motor that makes a mechanical impedance of a shaft variable by using a power distribution mechanism and a passive shock absorber.

In the fields of medical care, nursing care, and general households, development of robots that work with people is progressing. In such an application, unlike a conventional industrial robot, it is necessary to have not only precise positioning but also a function of adjusting mechanical impedance so that the robot does not collide with a person and cause harm.

As a means for adjusting the mechanical impedance, a passive method using passive mechanical elements (References 1 and 2), and an active method that actively controls a motor to realize pseudo flexibility (for example, Reference 3). A double actuation system (Non-Patent Document 1) or the like in which a motor for adjusting mechanical impedance is individually provided is known.

However, it is difficult to control vibration and convergence of the passive method, and the active method has a problem in response to high frequency input, particularly impact force. The double actuation method is also difficult to use for a multi-degree-of-freedom robot due to its increased weight, capacity, cost, and the like.

US Pat. No. 5,650,704 PCT / JP2012 / 068736 JP 2004-358575 A

Byeong-Sang Kim, et al., “Double Actuator Unit with Planetary GearTrain for a Safe Manipulator”, ICRA2007.

Accordingly, an object of the present invention is to provide a variable impedance servomotor that is excellent in vibration convergence and shock absorption, and is lightweight and compact.

In order to solve the problem, a power distribution device according to any one of (1) to (3) below is provided, the power distribution device including a first rotating body, a planetary mechanism, a carrier, and a second rotating body, The one rotator, the carrier, and the second rotator rotate on the same axis, the carrier maintains the revolution of the planetary mechanism, the planetary mechanism rotates the first rotator and the second rotator at a constant rotation speed ratio, The functions of the first rotating body, the carrier, and the second rotating body are exclusively an I axis for inputting power, an O axis for outputting power, or a G axis that is dynamically grounded. A variable impedance mechanism is used, which is characterized in that the variable impedance mechanism is coupled to the substrate via a shock absorber.
(1) A sun gear, a planetary gear, a carrier, and a ring gear are provided. The sun gear, the carrier, and the ring gear rotate on the same axis, the carrier holds the revolution of the planetary gear, and the planetary gear connects the sun gear and the ring gear at a constant rotation ratio. A planetary gear characterized by being rotated.
(2) A first side gear, a pinion gear, a carrier, and a second side gear are provided. The first side gear, the carrier, and the second side gear rotate on the same axis, the carrier holds the revolution of the pinion gear, and the pinion gear A differential gear characterized by rotating a two-side gear at a constant rotation speed ratio.
(3) A first spur gear, a two-stage gear, a carrier, and a second spur gear are provided. The first spur gear, the carrier, and the second spur gear rotate on the same axis, and the carrier maintains the revolution of the two-stage gear, and the two-stage gear. Is a planetary gear characterized by rotating the first spur gear and the second spur gear at a constant rotation speed ratio.

This variable impedance mechanism makes it possible to adjust the mechanical impedance of the O-axis with respect to the I-axis by the buffer device. However, it should be noted that acceleration / deceleration may accompany between the I axis and the O axis.

The buffer device may have any form as long as the purpose is to provide a desired mechanical impedance between the I axis and the O axis. For example, the variable is characterized in that the G-axis and the base body are coaxially provided with holding bodies protruding in the longitudinal direction, and the rotation of the holding body is limited by a repulsive force exerted by the shock absorber. The impedance mechanism and the shock absorber include a direct acting buffer that exerts a repulsive force of direct acting, and a rack mechanism that converts the rotation of the G axis into direct acting, and the direct acting motion of the rack is The variable impedance mechanism may be configured to be limited by a direct acting buffer.

When accurate positioning accuracy is required, the variable impedance mechanism, the motor, and the rotary encoder are provided, the motor drives the I axis, and the rotary encoder includes the base and the O axis. A variable impedance servo motor characterized by detecting a rotation angle between the two and driving the motor based on the rotation angle may be used.

Since a direct acting mechanism can also be configured based on the above principle, a drive rack, a reference rack, a pinion gear, an input bar, and a shock absorber are provided, and the drive rack and the reference rack are each rack-and-pin with respect to the same pinion gear. -A pinion mechanism is configured, and the pinion gear is rotatably held and translated by the input rod, and the reference rack is a direct-acting variable impedance mechanism characterized by being mechanically grounded via a shock absorber. It can also be used.

By using the above variable impedance mechanism, unlike a general shaft coupling, it is not necessary to rotate the shock absorber together with the rotation of the shaft. Therefore, in terms of the effect of reducing the moment of inertia, the size of the shock absorber and the interchangeability The effect can be expected.

Regarding the method of using a rack for a shock absorber, in general, a direct acting shock absorber is easier to design and manufacture than a rotary shock absorber, and has a wealth of experience in suspensions of automobiles and the like. Therefore, there is an advantage that the existing technology can be easily applied. Further, since it is easy to select the sliding amount (reduction ratio) and sliding direction of the rack, an effect of facilitating the layout of the shock absorber can be expected.

Since the variable impedance servo motor realizes a desired mechanical impedance by a buffer device, there is an advantage that the control algorithm is remarkably simplified, unlike the active method of the conventional servo motor. Further, since worm gears, hypoid gears, high reduction ratio reduction gears and the like having poor back drivability can be used, the holding torque and the capacity of the motor can be reduced, and the power consumption can be reduced.

It is the figure which showed the type of the power distribution mechanism. It is the figure which expressed the power distribution mechanism generally. FIG. 2 is a diagram generally representing a variable impedance mechanism. It is the figure which showed the Example of the shock absorber. It is the figure which showed the Example of the shock absorber using a rack. It is the figure which showed the Example of the buffer device using a nonlinear spring. It is an Example of a variable impedance servomotor. It is an exploded view of a variable impedance servomotor. It is an example of a direct acting variable impedance mechanism. The

As shown in FIG. 1 (i), a sun gear (1), a planetary gear (2), a carrier (3) and a ring gear (4) are provided, and the sun gear (1), the carrier (3) and the ring gear (4) are coaxial. The carrier (3) holds the revolution of the planetary gear (2), and the planetary gear (2) rotates the sun gear (1) and the ring gear (4) at a constant rotation speed ratio. The planetary gear can be used as a power distribution device.

For example, in a supercharger of an internal combustion engine, the rotation of the ring gear (4) is limited by a mechanically grounded wet clutch, and the power input to the sun gear (1) is transferred to the carrier (3) and the ring gear (4). A technique for distributing is known (Japanese Patent Laid-Open No. 7-269365).

In this case, the functions of the sun gear (1), the carrier (3), and the ring gear (4) are exclusively one of an I axis for inputting power, an O axis for outputting power, and a G axis that is mechanically grounded. If the reduction ratio is neglected and only the power distribution function is focused, that function is interchangeable.

In this regard, as shown in FIG. 1 (ii), the first side gear (5), the pinion gear (6), the carrier (7), and the second side gear (8) are provided, and the first side gear (5) and the carrier (7 ) And the second side gear (8) rotate on the same axis, the carrier (7) holds the revolution of the pinion gear (6), and the pinion gear (6) keeps the first side gear (5) and the second side gear (8) constant. In the differential gear characterized in that the first side gear (5), the carrier (7), and the second side gear (8) are regarded as the I axis, the O axis, and the G axis. it can.

Similarly, as shown in FIG. 1 (iii), a first spur gear (9), a two-stage gear (10), a carrier (11), and a second spur gear (12) are provided, and the first spur gear (9) and the carrier are provided. (11) and the second spur gear (12) rotate on the same axis, the carrier (11) holds the revolution of the two-stage gear (10), and the two-stage gear (10) is connected to the first spur gear (9) and the second spur gear (2). A planetary gear characterized by rotating a spur gear (12) at a constant rotation speed ratio includes a first spur gear (9), a carrier (11), and a second spur gear (12) connected to the I axis, O axis, G It can be regarded as an axis.

Therefore, as shown in FIG. 2, these mechanisms include a first rotating body (16), a planetary mechanism (14), a carrier (15), and a second rotating body (17), and the first rotating body (16 ), The carrier (15) and the second rotating body (17) rotate on the same axis (13), the carrier (15) holds the revolution of the planetary mechanism (14), and the planetary mechanism (14) is the first rotating body. (16) and the second rotating body (17) are rotated at a constant rotation ratio, and the functions of the first rotating body (16), the carrier (15), and the second rotating body (17) are exclusively It can be generalized as a power distribution device (18) characterized by any one of an I axis for inputting power, an O axis for outputting power, and a G axis that is dynamically grounded.

Now, as means for solving the problems of the present invention, as shown in FIG. 3, the G-axis of the power distribution device (18) is coupled to the base body via a shock absorber (19). Depending on the method of constructing the impedance mechanism.

According to this configuration, the impact applied to the O-axis is distributed to the I-axis and the G-axis. Usually, since a reducer having a large moment of inertia is connected to the I-axis, most of the impact force is applied to the G-axis. Is transmitted and absorbed by the shock absorber (19).

The buffer device (19) may have any form as long as it aims to provide a desired mechanical impedance between the input and output shafts. For example, as shown in FIG. 4 (representation of components with little relation is omitted), the G-axis (20) and the base (21) are coaxially provided with holding members protruding in the longitudinal direction (20a, 21a). ), The rotation of the holding body (20a, 21a) may be limited by the repulsive force exerted by the shock absorber (19).

In this case, unlike a general shaft coupling provided with a shock absorber such as rubber, the shock absorber (19) itself does not rotate (the rotation is a part where the display is omitted), so the moment of inertia is reduced. The effect to reduce and the effect which improves the designability and maintainability regarding a buffer body can be expected.

Alternatively, as shown in FIG. 5 (i, ii) (representation of components with little relation is omitted), the shock absorber (19) includes a direct acting buffer (19) that exhibits a repulsive force of direct acting, and A rack mechanism (22) for converting the rotation of the G axis (20) into a linear motion, and the linear motion of the rack (22) is limited by the linear motion buffer (19). It's okay.

The direct acting shock absorber is relatively easy to design and manufacture, and has many achievements in the suspension of automobiles and the like, so that various existing technologies can be used. Moreover, since it is easy to select the sliding amount (reduction ratio) and sliding direction of the rack (22), it is possible to expect the effect that the shock absorber can be reduced in size and layout.

However, when a clutch or dog is used as the shock absorber, it is not intended to provide impedance between the input and output shafts, but is intended to interrupt and lock the torque. Further, the shock absorber is composed only of passive elements, and must not directly give energy by an electric motor or the like. However, methods such as dampers that use magnetorheological fluids to control dissipated energy and actuators used for spring preload to change the spring constant do not directly give energy to the shock absorber. This is not the case.

As described above, since the shock absorber needs to be a passive element, it is suitable to use a spring having non-linearity in which the spring constant gradually increases with an increase in displacement. For example, as shown in FIG. 6, the non-linear spring (23) is arranged symmetrically with respect to the protrusion (20a) of the G axis (20) and is held between the protrusion (21a) of the base body (21). According to the configuration, the nonlinear spring (23) is appropriately compressed depending on the direction and magnitude of the torque applied to the G axis (20), and stops at a point where the repulsive force and the torque are balanced.

At this time, a soft spring characteristic is exhibited for a small torque, and conversely, a hard spring characteristic is exhibited for a large torque. Since these characteristics are similar to those of biological muscles, they are suitable for applications that replace human labor such as nursing robots and home service robots.

The non-linear spring (23) may be selected appropriately from bamboo shoot springs, conical springs, taper springs, air springs, and the like, and most preferably has a repulsive force gradually increasing in the second order with respect to displacement. The relationship between the torque and the spring constant is fixedly determined by the characteristic of the nonlinear spring (23). For example, when it is desired to realize a hard spring characteristic with respect to a small torque, a pseudo control is performed by a method of dynamically controlling the I axis. Characteristics can be changed.

When accurate positioning accuracy is required, as shown in FIG. 7, the variable impedance mechanism (24), the motor (25), and the rotary encoder (26) are provided, and the motor (25) is connected to the I-axis. And a rotary encoder (26) detects a rotation angle between the base and the O-axis (24c) and drives a motor (25) based on the rotation angle. A servo motor can be configured.

FIG. 8 is an exploded view of the variable impedance servomotor. The carrier (27) holds the rotation and revolution of the planetary gear (28) and is fixedly coupled to the shaft (25a) of the motor (25). The planetary gear (28) meshes with the sun gear (29) and the ring gear (30) to form a planetary gear. The ring gear (30) is fixedly coupled to the holder (31) together with the spur gear (24a), and the holder (31 ) Is rotatably supported by the sun gear (29) via the bearing (31a), the output shaft (24c) is fixedly coupled to the sun gear (29), and the base (32) is coupled to the motor (25). The rotary encoder (26) has an inner diameter fixed to the output shaft (24c), and the main body is fixed to the base (32) via the bracket (26a). The shock absorber (24b) includes a bracket (33) that holds a damper (34) and a nonlinear spring (35), and a rack (36) that couples the spring seat (36a) is provided via a linear bearing (36b). The rack (36) is in direct contact with the spar gear (24a) and is linearly converted, and the bracket (33) is fixed to the base (32a) of the base body (32). Yes.

In such a configuration, the output shaft (24c) that receives the impact force rotates the sun gear (29), and the shaft (25a) of the motor (25) and the planetary gear (28) via the carrier (27). ) To distribute the impact force to the ring gear (30). Usually, since the reduction ratio of the motor (25) is large and the apparent moment of inertia is large, a lot of impact force is distributed to the ring gear (30). The ring gear (30) rotates the spur gear (24a) fixedly coupled thereto, and the force is absorbed by the shock absorber (24b). Since the rotation angle of the output shaft (24c) due to the impact force is detected by the rotary encoder (26), the output shaft (24c) is returned to the original position by rotating the motor (25) based on an appropriate control algorithm. ) Can be kept.

There are various methods for adjusting the mechanical impedance, not only the method of replacing the damper (34) and the nonlinear spring (35), but also the method of using a damper (34) whose damping coefficient is variable with a magnetorheological fluid, etc. 35) a method of pre-loading them facing each other and converting the spring constant, a method of using the torque value of the force sensor provided between the spring seat (36a) and the nonlinear spring (35) as a feedback signal, as described above Any method may be used in which the active control of the motor (25) is used in combination to achieve characteristics exceeding the mechanical limit of the shock absorber (24b).

By the way, in general, if the diameter of the sun gear and the ring gear is made infinite while maintaining the size of the planetary gear of the planetary gear, it becomes a linear motion mechanism in which two racks are in contact with the planetary gear. An impedance mechanism can be constructed. FIG. 9 shows a direct acting variable impedance mechanism. A drive rack (37), a reference rack (38), a pinion gear (39), an input bar (40), and a shock absorber (41) are provided, and the drive rack (37) and the reference rack (38) are respectively the same pinion gear. A rack and pinion mechanism is configured with respect to (39), the pinion gear (39) is rotatably held and translated by the input rod (40), and the reference rack (38) is a shock absorber (41). It is configured to be mechanically grounded via

When an impact is applied to the drive rack (37), the force is distributed to the input rod (40) and the reference rack (38). When the apparent inertial mass of the input rod (40) is large, most of the impact force is It is absorbed by the shock absorber (41) through the reference rack (38). In this configuration, since it is not necessary to drive the shock absorber (41) simultaneously with the input rod (40), the inertial mass of the movable part can be reduced, and the effect of improving collision safety and high speed can be expected.

Claims (5)

The power distribution device according to any one of (1) to (3) below is provided, and the power distribution device includes a first rotating body, a planetary mechanism, a carrier, and a second rotating body, and the first rotating body, the carrier, and the first rotating body. The two rotator rotates on the same axis, the carrier holds the revolution of the planetary mechanism, the planetary mechanism rotates the first rotator and the second rotator at a constant rotation speed ratio, the first rotator, the carrier, The function of the second rotating body is exclusively one of an I-axis for inputting power, an O-axis for outputting power, and a G-axis that is mechanically grounded. A variable impedance mechanism characterized by being coupled to
(4) A sun gear, a planetary gear, a carrier, and a ring gear are provided. The sun gear, the carrier, and the ring gear rotate on the same axis, the carrier holds the revolution of the planetary gear, and the planetary gear connects the sun gear and the ring gear at a constant rotation ratio. A planetary gear characterized by being rotated.
(5) A first side gear, a pinion gear, a carrier, and a second side gear are provided. The first side gear, the carrier, and the second side gear rotate on the same axis, the carrier holds the revolution of the pinion gear, and the pinion gear A differential gear characterized by rotating a two-side gear at a constant rotation speed ratio.
(6) A first spur gear, a two-stage gear, a carrier, and a second spur gear are provided. The first spur gear, the carrier, and the second spur gear rotate on the same axis, and the carrier maintains the revolution of the two-stage gear, and the two-stage gear. Is a planetary gear characterized by rotating the first spur gear and the second spur gear at a constant rotation speed ratio. The G-axis and the base body are coaxially provided with a holding body protruding in a longitudinal direction, and the rotation of the holding body is limited by a repulsive force exerted by the shock absorber. The variable impedance mechanism described. The shock absorber includes a direct acting buffer body that exerts a repulsive force of direct acting, and a rack mechanism that converts rotation of the G-axis into direct acting, and the direct acting motion of the rack is converted into the direct acting buffer. The variable impedance mechanism according to claim 1, wherein the variable impedance mechanism is limited by a body. The variable impedance mechanism according to claim 1, a motor, and a rotary encoder are provided, the motor drives the I axis, and the rotary encoder rotates between the base and the O axis. A variable impedance servomotor characterized by detecting an angle and driving a motor based on the rotation angle. A drive rack, a reference rack, a pinion gear, an input bar, and a shock absorber are provided. The drive rack and the reference rack constitute a rack-and-pinion mechanism for the same pinion gear, and the pinion gear is freely rotatable on the input bar. A linear motion variable impedance mechanism characterized in that the reference rack is mechanically grounded via a shock absorber while being held and translated.