KR20120064813A - Caster wheel mechanism having dual offset structure and omnidirectional mobile robot using the same - Google Patents

Caster wheel mechanism having dual offset structure and omnidirectional mobile robot using the same Download PDF

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Publication number
KR20120064813A
KR20120064813A KR1020100126020A KR20100126020A KR20120064813A KR 20120064813 A KR20120064813 A KR 20120064813A KR 1020100126020 A KR1020100126020 A KR 1020100126020A KR 20100126020 A KR20100126020 A KR 20100126020A KR 20120064813 A KR20120064813 A KR 20120064813A
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South Korea
Prior art keywords
caster
steering
motor
driving
gear
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KR1020100126020A
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Korean (ko)
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KR101204147B1 (en
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정우진
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고려대학교 산학협력단
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J11/00—Manipulators not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J5/00—Manipulators mounted on wheels or on carriages
    • B25J5/007—Manipulators mounted on wheels or on carriages mounted on wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B19/00—Wheels not otherwise provided for or having characteristics specified in one of the subgroups of this group
    • B60B19/003—Multidirectional wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B19/00—Wheels not otherwise provided for or having characteristics specified in one of the subgroups of this group
    • B60B19/12—Roller-type wheels
    • B60B19/125—Roller-type wheels with helical projections on radial outer surface translating rotation of wheel into movement along the direction of the wheel axle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D15/00—Steering not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B2900/00—Purpose of invention
    • B60B2900/30—Increase in
    • B60B2900/351—Increase in versatility, e.g. usable for different purposes or different arrangements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S901/00—Robots
    • Y10S901/01—Mobile robot

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Arrangement And Driving Of Transmission Devices (AREA)
  • Robotics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)

Abstract

The present invention relates to an omnidirectional wheel mechanism having a dual offset structure and an omnidirectional mobile robot using the same. An omnidirectional wheel mechanism having a dual offset structure according to the present invention includes: a caster module located below the traveling body traveling by the omnidirectional wheel mechanism; A traveling motor and a steering motor installed in the traveling body; A steering shaft assembly configured to connect the driving body and the caster module so that the caster module is rotatable about a steering shaft with respect to the driving body, and rotate the caster module about the steering shaft according to the rotation of the steering motor; A caster wheel rotatably installed on the caster module, the center of rotation of the caster wheel being spaced apart from the steering shaft by a driving direction offset and a lateral offset, respectively, in a driving direction of the caster wheel and a rotation axis direction of the caster wheel; Installed in the module—and; And a travel shaft assembly configured to transmit the rotational force of the travel motor to the caster wheel so that the caster wheel rotates according to the rotation of the travel motor. Accordingly, the traveling motor and the steering motor are installed in the traveling body and the dual offset is applied, thereby realizing the holographic driving capability and the omnidirectional traveling capability.

Description

Omni-directional wheel mechanism with dual offset structure and omnidirectional mobile robot using the same {CASTER WHEEL MECHANISM HAVING DUAL OFFSET STRUCTURE AND OMNIDIRECTIONAL MOBILE ROBOT USING THE SAME}

The present invention relates to an omnidirectional wheel mechanism having a dual offset structure and an omnidirectional mobile robot using the same. More particularly, in the application of an active omnidirectional wheel mechanism, it is possible to realize holographic driving capability and omnidirectional driving capability. The present invention relates to an omnidirectional wheel mechanism having a dual offset structure and an omnidirectional mobile robot using the same.

In modern robotics, in addition to production-based industries, various attempts have been made to extend robotics to non-productive applications such as surgery, disability assistance, floor cleaning, and building patrols. And, with the rapid development of information technology, attempts to extend robotic technology to unproductive applications are accelerating.

In non-productive applications such as disability assistance, floor cleaning, building patrols, etc., robots are premised on driving and mobile robots. Research must be premised.

The most common wheel mechanism used for the implementation of a mobile robot is the differential steering nonholonomic wheel mechanism. However, the differential steering non-holonic wheel mechanism, despite its simplicity in mechanics, has the disadvantage of being difficult to control due to the non-holographic mechanical constraints.

If a holographic omnidirectional mobile platform can be implemented, it provides simplicity of control in various application fields, for example, autonomous navigation or trailer control. You can do it. In other words, the Holonomic omnidirectional mobile platform is ideal for the implementation of easy control algorithms or for the abundant movement of mobile robots.

In addition, since the mobile robot runs in various types of floor conditions such as concrete, carpet, tiles, and the like, the wheel mechanism must have reliability and durability to be applicable to various floor conditions.

Recently, various kinds of omnidirectional wheel mechanisms have been proposed. Representative omni-directional wheel mechanisms include the universal wheel mechanism, which consists of a series of rollers formed along the rolling direction. However, since the universal wheel mechanism causes many problems such as vertical vibration or inaccurate positioning caused by the discontinuity of contact, much effort has been made to solve this problem. It has been.

In addition, with respect to the omni-directional wheel mechanism, a synchronous drive robot may be implemented using a centered oriented wheel or an off-centered orientable wheel. Steering and driving motion of each wheel are linked by kinematic belts and chains, and each motion is driven synchronously. Thus, the wheel direction is always the same, and in all directions, that is, in all directions, the desired speed direction can be obtained by the steering wheel direction.

In addition, in the synchronous traveling robot, the direction of the robot chassis is not changed. At times, turrets in synchronous traveling robots are applied to change the orientation of the robot chassis.

The main advantage of the synchronous drive robot is that movement in all directions can be achieved by the use of only two actuators. Since this structure ensures synchronous steering and driving motion, relatively less control is required for the overall motion control of the synchronous drive robot. This includes the fact that the Odometry information is relatively accurate and that the forces for driving are evenly distributed by all the wheels.

On the other hand, a disadvantage of the synchronous driving robot is a complicated mechanical structure. In addition, if there is a reverse rotation or a loose chain connection, a speed difference occurs between the wheels, which reduces the accuracy of the control. And, in order to achieve omnidirectional movement, the wheel direction has to be aligned in the desired velocity direction prior to movement because of the non-Holononomic velocity constraints.

On the other hand, another example of the omni-directional wheel mechanism is the spherical wheel mechanism (Spherical wheel mechanism). In a spherical wheel, the rotation of the sphere is constrained by a roller that forms a rolling contact with the sphere. The role of the roller is divided into a driving roller (Driving roller) responsible for the actual driving, and a supporting roller (Supporting roller) to assist this.

Here, the sphere is driven by the driving of the driving roller. The cloud contact provides a nonholonomic constraint, and the resultant motion of the sphere module becomes holonomic. This means that the mobile robot can move at the desired line / angular velocity at any time. By the use of such a spherical wheel mechanism, it becomes possible to implement a holographic omnidirectional mobile robot, and the mobile robot can obtain smooth and continuous contact between the sphere and the ground.

However, in spherical wheel mechanisms, the design of the sphere supporting structure associated with the supporting roller is difficult, and there is a constraint that the load acting on the sphere due to point contact by the sphere, i.e., the overall load of the mobile robot, must be very small. . In addition, the spherical wheel mechanism has a disadvantage that the surface of the sphere is easily contaminated in the ground conditions, such as the soil floor, difficult to overcome irregular ground conditions.

Accordingly, the present invention has been made to solve the problems of the conventional wheel mechanism as described above, in the application of the active omni-directional wheel mechanism, having a dual offset structure capable of realizing the holographic driving capability and the omnidirectional driving capability An object of the present invention is to provide an omnidirectional wheel mechanism and an omnidirectional mobile robot using the same.

According to the present invention, there is provided an omnidirectional wheel mechanism having a dual offset structure, comprising: a caster module located below the traveling body traveling by the omnidirectional wheel mechanism; A traveling motor and a steering motor installed in the traveling body; A steering shaft assembly configured to connect the driving body and the caster module so that the caster module is rotatable about a steering shaft with respect to the driving body, and rotate the caster module about the steering shaft according to the rotation of the steering motor; A caster wheel rotatably installed on the caster module, the center of rotation of the caster wheel being spaced apart from the steering shaft by a driving direction offset and a lateral offset, respectively, in a driving direction of the caster wheel and a rotation axis direction of the caster wheel; Installed in the module—and; In the omni-directional wheel mechanism having a dual offset structure having a dual offset structure characterized in that it comprises a traveling shaft assembly for transmitting the rotational force of the traveling motor to the caster wheel so that the caster wheel rotates in accordance with the rotation of the traveling motor. Is achieved by

Here, the lateral offset may be set in proportion to the radius of the caster wheel and the gear reduction of the traveling shaft assembly, respectively.

Further, the lateral offset is based on equation b = k g × r, where b is the lateral offset, k g is the gear reduction, and r is the radius of the caster wheel. Can be set.

Here, the steering shaft assembly is one side is connected to the caster module, the other side is rotatably installed in the traveling body around the steering shaft, the main shaft portion formed with a gear groove along the outer diameter; A gear tooth meshing with the gear groove of the main shaft portion may be formed to rotate according to the rotation of the steering motor to include a steering transmission gear for rotating the main shaft portion.

The traveling shaft assembly may include: a first bevel gear installed inside the caster module and rotating according to the rotation of the traveling motor rotating around the steering shaft; A second bevel gear that meshes with the first bevel gear and rotates to convert a rotational force of the traveling motor about the steering shaft into a rotational force about a transmission shaft that intersects the steering shaft; It may include a transmission gear unit to rotate in accordance with the rotation of the second bevel gear to transfer the rotational force of the second bevel gear to the caster wheel.

The main shaft portion of the steering shaft assembly has a tubular shape in which a driving shaft hole communicating between the traveling body and the caster module is formed; The travel shaft assembly may further include a travel shaft connected to the travel motor and the first bevel gear through the travel shaft hole to transmit rotational force of the travel motor to the first bevel gear.

The transmission gear unit may include a first travel gear and a second travel gear that mesh with each other and rotate about parallel rotation axes; A first parallel shaft which connects the first bevel gear and the first travel gear to transfer the rotational force of the first bevel gear to the first travel gear; It may include a second parallel shaft connecting the caster wheel and the second driving gear to transfer the rotational force of the second driving gear to the caster wheel.

On the other hand, the above object can also be achieved by an omnidirectional mobile robot to which the omnidirectional wheel mechanism having the dual offset structure is applied according to another embodiment of the present invention.

Through the above configuration, according to the present invention, the traveling motor and the steering motor are installed in the traveling body and the dual offset is applied, whereby the holographic driving ability and the omnidirectional traveling ability can be realized, and the operation of various motions and The application to the trailer control field will provide an easy effect.

In addition, the control simplicity of the control is provided by separately controlling the driving and the steering through the control of the driving motor and the steering motor, thereby providing a path planner for the removal of the nonholomonic mechanical constrain. Effective design of path planners or tracking controls is possible.

In addition, the caster wheel is based on a conventional wheel structure, which enables reliable driving regardless of ground conditions, and transmits rotation of the driving motor and the steering motor through a gear connection, thereby ensuring durability. Can be. Therefore, it is easy to apply in practical application.

In addition, the kinematic structure that enables holographic driving and omnidirectional driving is realized only by the driving motor, the steering motor, and the gear connecting structure that transmits the rotational force thereof, thereby providing mechanical simplicity. The simple kinematic structure allows for accurate positioning performance.

1 is a front view of the omni-directional wheel mechanism having a dual offset structure according to the present invention,
2 is a side view of the omni-directional wheel mechanism having a dual offset structure according to the present invention;
3 to 7 are views for explaining the holographic driving capability and the omnidirectional driving capability of the omni-directional wheel mechanism according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

FIG. 1 is a front view of the omni-directional wheel mechanism 1 having a dual offset structure according to the present invention, and FIG. 2 is a side view of the omni-directional purging mechanism having a dual offset structure according to the present invention.

As shown in FIGS. 1 and 2, the omnidirectional wheel mechanism 1 having the dual offset structure according to the present invention includes the caster module 20, the traveling motor 30, the steering motor 31, and the caster wheel ( 60), steering shaft assembly 40 and traveling shaft assembly 51, 52, 53, 54.

The caster module 20 is located under the travel body 10. Here, the driving body 10 is a chassis of the mobile robot, for example, which is driven by the wheel mechanism according to the present invention. In the present invention, the omnidirectional wheel mechanism 1 is applied to the mobile robot. do. The caster wheel 60 is installed at the caster module 20 so that the caster module 20 operates as a wheel of the mobile robot.

The travel motor 30 and the steering motor 31 are provided in the travel main body 10 as shown in FIGS. 1 and 2. Here, the driving motor 30 generates a rotational force for driving the omnidirectional wheel mechanism 1 according to the present invention, the steering motor 31 is a rotational force for steering of the omnidirectional wheel mechanism 1 according to the present invention. Occurs. The driving and steering mechanism of the omnidirectional wheel mechanism 1 by the traveling motor 30 and the steering motor 31 will be described in detail later.

The caster wheel 60 is rotatably installed in the caster module 20. Here, the caster wheel 60, as shown in FIG. 2, the caster module 20 such that its rotation center is spaced apart from the steering shaft As by the driving direction offset a in the traveling direction of the caster wheel 60. Is installed on. In addition, the caster wheel 60, as shown in FIG. 1, the caster module 20 such that its center of rotation is spaced apart only from the steering shaft As in the rotational axis direction of the caster wheel 60 by the side direction offset b. Is installed on.

That is, in the present invention, the center of rotation of the caster wheel 60 is eccentric by the driving direction offset (a) and the lateral direction offset (b) in the traveling direction of the caster wheel 60 and the rotation axis direction of the caster wheel 60, respectively. By being installed in the module 20, it is possible to implement a non-holographic omnidirectional mobile robot, a detailed description thereof will be described later.

On the other hand, the steering shaft assembly 40 connects the traveling body 10 and the caster module 20 so that the caster module 20 can rotate about the steering shaft As with respect to the traveling body 10. That is, the steering shaft assembly 40 rotates the caster module 20 about the steering shaft As as the steering motor 31 rotates.

Here, the steering shaft assembly 40 according to the present invention, as shown in Figures 1 and 2, may include a main shaft portion 41 and the steering transmission gear 42.

One side of the main shaft portion 41 is connected to the caster module 20, and the other side thereof is rotatably installed on the travel body 10 about the steering shaft As. The main shaft portion 41 is formed with a gear groove along its outer diameter.

The steering transmission gear 42 has a gear tooth meshed with the gear groove of the spindle 41 to rotate in accordance with the rotation of the steering motor 31 to rotate the spindle 41. That is, the steering transmission gear 42 is connected to the steering motor 31 through the steering shaft and rotates according to the rotation of the steering motor 31. In addition, the gear tooth and the gear groove are rotated in accordance with the rotation of the steering transmission gear 42 so that the main shaft portion 41 rotates about the travel main body 10 about the steering shaft As, thereby causing the main shaft portion ( The caster module 20 connected to 41 rotates about the steering shaft As.

At this time, as described above, the center of rotation of the caster wheel 60 provided in the caster module 20, as shown in Figs. 1 and 2, the rotation axis of the caster module 20, that is, the steering shaft As Since the position is spaced apart by the driving direction offset (a) and the lateral direction offset (b) relative to, the direction of travel of the caster wheel 60 is changed in accordance with the rotation about the steering axis (As) of the caster module 20 The steering direction of the omni-directional wheel mechanism 1 according to the present invention can be adjusted.

Here, in the conventional passive caster wheel 60, only the driving direction offset (a) shown in FIG. 2 was formed, and the present invention additionally forms a lateral direction offset (b) on the caster wheel 60 to rotate for steering. The bad condition which arises by the coupling of rotation for overtraveling is solved. Detailed description thereof will be described later.

Meanwhile, the travel shaft assemblies 51, 52, 53, and 54 transmit the rotational force of the travel motor 30 to the caster wheel 60 so that the caster wheel 60 rotates according to the rotation of the travel motor 30. 1 and 2, the traveling shaft assemblies 51, 52, 53, and 54 according to the present invention may include a first bevel gear 51, a second bevel gear 52, and a transmission gear unit 54. It may include.

The first bevel gear 51 is installed in the caster module 20 and rotates according to the rotation of the traveling motor 30 rotating around the steering shaft As. In addition, the second bevel gear 52 rotates in engagement with the first bevel gear 51 to intersect the rotational force of the travel motor 30 centered on the steering shaft As and the steering shaft As. Switch to the rotational force around (). Here, if the first bevel gear 51 and the second bevel gear 52 are engaged with each other to rotate to convert the rotational force around the steering axis As to a rotational force around the transmission axis Ap, the straight bevel It may be provided in the form of a gear or a helical bevel gear.

In addition, the travel shaft assemblies 51, 52, 53, and 54 may include a travel shaft 53 that transmits the rotational force of the travel motor 30 to the first bevel gear 51. Here, the main shaft portion 41 of the steering shaft assembly 40, as shown in Figs. 1 and 2, the cylinder formed with a driving shaft hole 41a for communicating between the traveling body 10 and the caster module 20 The driving shaft 53 may be connected to the driving motor 30 and the first bevel gear 51 through the driving shaft hole 41a of the main shaft portion 41.

Accordingly, the rotational force of the steering motor 31 is transmitted to the caster module 20 using the main shaft portion 41 of the steering shaft assembly 40 as the steering shaft As, and the driving formed in the main shaft portion 41 in the same manner. The driving shaft 53 connected through the shaft hole 41a transmits the rotational force of the traveling motor 30 to the caster module 20 by the steering shaft As as the rotating shaft.

On the other hand, the transmission gear unit 54 is rotated in accordance with the rotation of the second bevel gear 52 to transmit the rotational force of the second bevel gear 52 to the caster wheel 60. The transmission gear unit 54 according to the present invention, as shown in FIGS. 1 and 2, has a first travel gear 55, a second travel gear 56, a first parallel shaft 57 and a second parallelism. It may include a shaft 58.

The first travel gear 55 and the second travel gear 56 mesh with each other and rotate about an axis of rotation parallel to each other. Here, the first travel gear 55 and the second travel gear 56 may be provided in the form of a spur gear or a helical gear.

The first parallel shaft 57 interconnects the first bevel gear 51 and the first travel gear 55 to transmit the rotational force of the first bevel gear 51 to the first travel gear 55. In addition, the second parallel shaft 58 connects the caster wheel 60 and the second travel gear 56 to transmit the rotational force of the second travel gear 56 to the caster wheel 60 to thereby cast the caster wheel 60. ) Rotate in the direction of travel.

According to the configuration as described above, the rotational force of the travel motor 30 and the steering motor 31 installed in the travel main body 10 are transmitted to the caster module 20 side with the steering shaft As as the rotation axis, Since the center of rotation of the caster wheel 60 is spaced apart from the steering shaft As by a dual offset, that is, a driving direction offset a and a side direction offset b, the omnidirectional wheel mechanism 1 according to the present invention is holographic. Driving ability and omnidirectional driving ability can be realized.

Hereinafter, the omnidirectional wheel mechanism 1 according to the present invention will implement the holographic driving capability and the omnidirectional driving capability with reference to FIGS. 3 to 7, and coupling of the traveling motor 30 and the steering motor 31 may be performed. It will be described in detail having a structure for removing a bad condition that occurs according to.

Prior to the description of the omni-directional wheel mechanism 1 according to the invention, as shown in Figs. 3 and 4, in the conventional manual caster wheel mechanism, that is, the caster wheel mechanism in which only the driving direction offset (a) is present, The example which applied two motors is demonstrated. That is, FIGS. 3 and 4 are modifications of the omnidirectional wheel mechanism 1 according to the present invention in order to explain the performance of the omnidirectional wheel mechanism 1 according to the present invention, and are applied to a conventional passive caster wheel mechanism. Hereinafter, the wheel mechanism illustrated in FIGS. 3 and 4 will be described as an active caster wheel mechanism 100.

As shown in FIG. 3 and FIG. 4, the steering motor 131 may be installed in the travel main body 110, and the driving motor 130 may be installed in the caster module 120. As described above, only the travel direction offset a exists, and the lateral direction offset b is zero. In addition, the rotational force of the traveling motor 130 is transmitted to the caster wheel 160 by a pair of spur gears 156 and 157 which rotate in engagement with each other, and the rotational force of the steering motor 131 is an omnidirectional wheel mechanism according to the present invention. Corresponding to the configuration of 1), it is configured to be transmitted to the caster module 120 by the steering shaft assembly 140 composed of the main shaft portion 141 and the steering transmission gear 142.

FIG. 5 shows the kinematic relationship between the speed input and the combined speed acting on the travel body 110 at the steering center of the caster module 120 in the active caster wheel mechanism 100 shown in FIGS. 3 and 4. . Here, FIG. 5 illustrates a top view concept viewed from the top to the bottom of FIGS. 3 and 5. FIG. 5B is a diagram illustrating a linear speed V_ Driving when the driving motor 130 operates in a state where the steering motor 131 does not operate, and FIG. 5C illustrates the driving motor 30. ) Is a diagram showing the linear velocity (V_ Steering ) when the steering motor 131 operates in a state where the steering motor 131 is not operated, and FIG. 5 (a) shows a combined speed obtained by combining FIGS. A diagram showing the vector sum of. 6 and 7 are shown correspondingly to FIG. 5.

As shown in FIG. 5, the combined speed at the steering axis As of the active caster wheel mechanism 100 can be represented by a vector sum, which is a linear speed according to two speed components, namely steering motor 31. (V_ Steering ) and the line speed (V_ Driving ) according to the driving motor 30 is perpendicular to each other.

3 and 4, based on the structure of the existing manual caster wheel mechanism, a steering motor 131 is installed on the traveling body 110 side, and the traveling motor (on the caster module 120 side). The structure for installing 130 has the following important problems even though its structure is simple.

First, the joint range of steering is limited by the length of the cable for connection with the travel motor 130 installed in the caster module 120. That is, since the traveling motor 130 is installed in the caster module 120, the steering range of the caster module 120 is restricted by a cable for supplying power to the traveling motor 130 or applying a control signal. The infinite steering range of passive caster wheel mechanisms cannot be realized.

In addition, the travel motor 130 is installed in the caster module 120 to increase the volume and weight of the caster wheel 160, and as a result, a large inertial torque is applied to the steering motor 131. Therefore, it acts as a cause of increasing the capacity of the steering motor 131.

On the other hand, in the case of the omni-directional wheel mechanism 1 according to the present invention, the traveling motor 30 is installed in the traveling body 10, thereby removing the cable installed across the traveling body 10 and the caster module 20. Therefore, the limitation of the steering range according to the length of the cable can be eliminated, and the inertial torque applied to the steering motor 31 can be reduced.

On the other hand, the running angular velocity generated by the rotation of the travel motor 30 in the omnidirectional wheel mechanism 1 according to the present invention, as shown in Figures 1 and 2, the traveling shaft installed along the steering shaft (As) Transmission to the caster wheel 60 on the caster module 20 side by 53 is as described above. Therefore, the composite angular velocity ω d of the caster wheel 60 can be expressed as shown in [Equation 1].

[Equation 1]

Figure pat00001

Here, k g is a gear reduction with respect to the travel motor 30, ω d_motor is an input angular speed of the travel motor 30, and ω s is a steering angular speed according to the rotation of the steering motor 31. Equation 1 means that the input angular velocity of the travel motor 30 is coupled with the steering angular velocity. That is, it means that the caster wheel 60 also rotates in the travel direction by the rotation of the steering motor 31.

If it is assumed that the lateral offset b is '0', the kinematic relationship can be represented as shown in FIG. As shown in FIG. 6, it can be seen that the two speed components, V_ Driving and V_ Steering , are not vertical, which means that there is a kinematic Ill-condition between the input and the output.

As shown in FIG. 6, as the instantaneous center moves away from the position of the caster wheel 60, the traveling motor 30 and the steering motor 31 achieve the unit output velocity. High speed rotations should be applied. Here, since it is not easy to increase the maximum angular velocity of the travel motor 30 and the steering motor 31, in the state where the lateral offset b is '0', the maximum speed is determined by the steering angular velocity and the travel motor 30. There is a problem that is reduced by the coupling between inputs.

Therefore, it is desirable to eliminate the failure condition according to the above coupling, and the omnidirectional wheel mechanism 1 according to the present invention solves this by adding a lateral offset b.

FIG. 7 is a view showing a kinematic relationship in a state in which dual offset, that is, driving direction offset a and side direction offset b are simultaneously applied, as in the omnidirectional wheel mechanism 1 according to the present invention. Here, the driving direction offset a is defined as a as shown in FIG. 2, and the lateral direction offset b is defined as b as shown in FIG. 1.

In the omni-directional wheel mechanism 1 according to the invention, as shown in Fig. 7, the steering motor is decoupled with two speed elements and the instantaneous center of rotation for steering, ie the travel motor 30 is stopped. The instantaneous center of rotation of the caster module 20 according to the rotation of 31 is as shown in FIG.

In this case, the angular velocity of the caster wheel 60 may be expressed as shown in [Equation 2] based on [Equation 1].

[Equation 2]

Figure pat00002

Equation 2 may be derived from Equation 3, and as a result, Equation 4 may be obtained.

&Quot; (3) "

Figure pat00003

&Quot; (4) "

Figure pat00004

In the above equations, b is the lateral offset b, as described above, and r is the radius of the caster wheel 60.

Through the above [Equation 4], the size of the lateral offset (b) in the omni-directional wheel mechanism 1 according to the present invention is the radius of the caster wheel 60 and the traveling shaft assembly (51, 52, 53, 54) It can be seen that the proportional to the gear reduction of each.

Here, when the kinematic parameter satisfies [Equation 3] and [Equation 4], it can be seen that the two speed components are perpendicular to the caster wheel 60 to which the dual offset is applied. This orthogonality means a well-conditioned kinematic model. Thus, it is possible to travel faster than the wheel mechanism to which the lateral offset b is not applied. With the limited maximum speed of the motor, the dual offset wheel mechanism can be driven faster than other mechanisms.

Although several embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various modifications may be made without departing from the principles and spirit of the invention . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (8)

In the omni-directional wheel mechanism having a dual offset structure,
A caster module located below the travel main body traveling by the omnidirectional wheel mechanism;
A traveling motor and a steering motor installed in the traveling body;
A steering shaft assembly configured to connect the driving body and the caster module so that the caster module is rotatable about a steering shaft with respect to the driving body, and rotate the caster module about the steering shaft according to the rotation of the steering motor;
A caster wheel rotatably installed on the caster module, the center of rotation of the caster wheel being spaced apart from the steering shaft by a driving direction offset and a lateral offset, respectively, in a driving direction of the caster wheel and a rotation axis direction of the caster wheel; Installed in the module—and;
And a travel shaft assembly configured to transmit a rotational force of the travel motor to the caster wheel so that the caster wheel rotates in accordance with the rotation of the travel motor. The method of claim 1,
And the lateral offset is set in proportion to the radius of the caster wheel and the gear reduction of the travel shaft assembly, respectively. The method of claim 2,
The lateral offset is set based on equation b = k g × r, where b is the lateral offset, k g is the gear reduction, and r is the radius of the caster wheel. Omni-directional wheel mechanism having a dual offset structure, characterized in that. The method of claim 2,
The steering shaft assembly,
One side is connected to the caster module, the other side is rotatably installed in the traveling body around the steering shaft, the main shaft portion formed with a gear groove along the outer diameter;
And a steering transmission gear having a gear tooth meshing with the gear groove of the main shaft portion to rotate in accordance with the rotation of the steering motor to rotate the main shaft portion. The method of claim 2,
The traveling shaft assembly,
A first bevel gear installed inside the caster module and rotating according to the rotation of the traveling motor rotating around the steering shaft;
A second bevel gear that meshes with the first bevel gear and rotates to convert a rotational force of the traveling motor about the steering shaft into a rotational force about a transmission shaft that intersects the steering shaft;
And a transmission gear unit rotating according to the rotation of the second bevel gear to transmit the rotational force of the second bevel gear to the caster wheel. The method of claim 5,
The main shaft portion of the steering shaft assembly has a cylindrical shape in which a driving shaft hole communicating between the traveling body and the caster module is formed;
The driving shaft assembly further includes a driving shaft connected to the driving motor and the first bevel gear through the driving shaft hole to transmit the rotational force of the driving motor to the first bevel gear. Omni-directional wheel mechanism having. The method of claim 5,
The transmission gear unit,
A first travel gear and a second travel gear that mesh with each other to rotate about parallel rotation axes;
A first parallel shaft which connects the first bevel gear and the first travel gear to transfer the rotational force of the first bevel gear to the first travel gear;
And a second parallel shaft which connects the caster wheel and the second driving gear to transmit the rotational force of the second driving gear to the caster wheel. An omnidirectional mobile robot having an omnidirectional wheel mechanism having a dual offset structure according to any one of claims 1 to 7.
KR20100126020A 2010-12-10 2010-12-10 Caster wheel mechanism having dual offset structure and omnidirectional mobile robot using the same KR101204147B1 (en)

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PT106574B (en) * 2012-10-10 2014-12-12 Inst Superior Técnico WHEEL DRIVE AND ORIENTATION UNIT IN OMNIDIRECTIONAL VEHICLES
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CN108819612A (en) * 2018-07-31 2018-11-16 宁波舜宇贝尔自动化有限公司 Omnidirectional driving wheel
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PT106574B (en) * 2012-10-10 2014-12-12 Inst Superior Técnico WHEEL DRIVE AND ORIENTATION UNIT IN OMNIDIRECTIONAL VEHICLES
KR20180128700A (en) * 2017-05-24 2018-12-04 한국과학기술연구원 Power Assistive Modular Robot
CN107415904A (en) * 2017-07-14 2017-12-01 深圳市招科智控科技有限公司 Harbour container is horizontal to carry unmanned vehicle exchange system and method
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CN108819612A (en) * 2018-07-31 2018-11-16 宁波舜宇贝尔自动化有限公司 Omnidirectional driving wheel
CN108819612B (en) * 2018-07-31 2024-03-05 宁波舜宇贝尔机器人有限公司 Omnidirectional driving wheel
CN110293835A (en) * 2019-07-10 2019-10-01 杭州极木科技有限公司 A kind of ultra-thin universal driving wheel

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