Mobile robot

A mobile robot having wheels which maintain contact forces against a surface even when the mobile robot meets an obstacle on the surface and a body of the mobile robot is forced up against the obstacle. The mobile robot easily surmounts the obstacle on the surface, without requiring any sensors, any specific controller, any specific traveling unit to surmount over the obstacle, or any specific drive unit to drive the specific traveling unit. The mobile robot includes the body, the wheels connected with the body which move arcuately relative to the body, and a wheel guide unit coupled at a first end to the body and at a second end to a hub of each of the wheels. The wheel guide unit is contracted when the body is spaced apart from the surface on which the robot moves. However, the wheel guide unit expands to allow the wheel to be in contact with the surface when the body comes into contact with the surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2003-53474, filed Aug. 1, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mobile robots, and more specifically, to mobile robots which easily surmount obstacles on surfaces.

2. Description of the Related Art

Conventional mobile robots include wheeled robots and crawler robots. The wheeled robots have the advantages of high-speed mobility and high operational efficiency while moving on flat surfaces. However, most conventional wheeled robots are problematic in that the wheeled robots may fail to operate on surfaces having obstacles, such as thresholds and/or stairs.

An example of conventional crawler robots may be found in Japanese Patent Laid-open Publication No. Sho. 60-176871. As described in the Japanese patent, some mobile robots are equipped with specific traveling units, such as crawlers, in place of conventional wheels to surmount obstacles such as thresholds and/or stairs, while moving on surfaces by use of the traveling units. However, the mobile robots equipped with the specific traveling units, such as the crawlers, require a variety of sensors, specific controllers and specific drive units in the bodies of the robots, as well as the traveling units capable of surmounting obstacles on the surfaces. Therefore, the mobile robots having the specific traveling units, such as the crawlers, have reduced amounts of effective spaces in their bodies, so that it may be difficult to install some important elements required to perform desired functions in the robots' bodies. Additional problems of the mobile robots having specific traveling units, such as the crawlers, include excessive production costs and operational noise of the robots.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide a wheeled mobile robot, of which wheels maintain contact forces against a surface even when the mobile robot must overcome an obstacle on the surface and a body of the mobile robot is forced up against the obstacle, and which thus easily surmounts the obstacle on the surface.

It is another aspect of the present invention to provide a wheeled mobile robot which does not require any sensors, any specific controller, any specific traveling unit to surmount an obstacle, or any specific drive unit to drive the specific traveling unit, in or on a body of the mobile robot, but which has a simple and small control unit to control the wheels, thus improving productivity and reducing production costs of manufacturing the mobile robot, and providing large effective spaces in the bodies of the mobile robots.

The above and/or other aspects are achieved by providing a mobile robot including a body; a wheel assembled with the body to move upward and downward relative to the body; and a wheel guide unit coupled at a first end to the body and at a second end to a hub of the wheel. The wheel guide unit is maintained in a contracted state when the body is spaced apart from a surface on which the robot moves, and the wheel guide unit expands to allow the wheel to be in contact with the surface when the body comes into contact with the surface.

The mobile robot may further include a drive motor provided on the body and a power transmission unit to transmit power from the drive motor to the wheel.

The mobile robot may further include a sub-guide unit coupled to the wheel so as to rotate around a shaft of a drive motor.

In the mobile robot, the body may include a guide slot which guides a movement of the wheel guide unit, and the wheel guide unit may include an insert part which is inserted in the guide slot of the body.

The above and/or other aspects are achieved by providing a mobile robot including a body; a wheel assembled with the body to move upward and downward relative to the body; a power spring provided in the body; and a wheel guide unit coupled at a first end to the power spring and at a second end to a hub of the wheel. The wheel guide unit is maintained in a contracted state when the body is spaced apart from a surface on which the robot moves, and the wheel guide unit is rotated when the body comes into contact with the surface, thus allowing the wheel to be in contact with the surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is an exploded perspective view of a wheel control unit of a mobile robot according to an embodiment of the present invention. The mobile robot has at least one wheel50, and the wheel control unit cooperates with the wheel50to drive and control the wheel50independently. As shown inFIG. 1, the wheel control unit of the mobile robot according to an embodiment of the present invention has a support bracket20, a drive motor10and a wheel guide unit which includes a main guide unit30and a sub-guide unit35to guide a vertical movement of the wheel50. The wheel control unit further has a power transmission unit40.

The support bracket20constitutes a part of a body of the mobile robot, and has a locking hole21, an arc-shaped guide slot22and an annular boss26. The annular boss26defines a motor shaft hole25therein to receive a motor shaft11of the drive motor10.

The drive motor10generates rotational power to rotate the wheel50. In the present embodiment, a conventional electric motor, such as an AC motor or a step motor, may be used as the drive motor10. The drive motor10has the motor shaft11which passes through the motor shaft hole25of the annular boss26of the support bracket20when the drive motor10is assembled with the support bracket20.

The main guide unit30which guides the vertical movement of the wheel50has a spring guide31and a spring34which is a coil spring fitted over the spring guide31to be held thereby. The spring guide31has a cylinder32which forms an upper portion of the spring guide31, and a piston33which forms a lower portion of the spring guide31. A cylindrical coupling boss32ais provided at an upper end of the cylinder32to couple the cylinder32to the locking hole21of the support bracket10while allowing the cylinder32to rotate around the locking hole21of the support bracket20. An insert part33ais provided at a lower end of the piston33. The insert part33aextends toward the support bracket20. A locking boss33cis provided at the lower end of the piston33while extending in a direction opposite to the insert part33a. The locking boss33cof the piston33engages with a second end of the sub-guide unit35. First and second spring stop surfaces32band33bto support both ends of the spring34of the main guide unit30are provided on the upper end and the lower end of the piston33, respectively.

The sub-guide unit35which guides the vertical movement of the wheel50, has the following structure. A first end of the sub-guide unit35has a coupling ring35awhich is fitted over the annular boss26of the support bracket20to be in contact with an outer surface of the annular boss26. The first end of the sub-guide unit35thus rotates around the annular boss26. The second end of the sub-guide unit35has a locking hole35cand a gear support boss35b. The locking hole35cof the sub-guide unit35opens toward the main guide unit30, while the gear support boss35bextends in a direction opposite to the main guide unit30. In this embodiment, the wheel control unit may effectively control the vertical movement of the wheel50by only the main guide unit30, without the sub-guide unit35. However, in the embodiment ofFIG. 1, the sub-guide unit30which is securely assembled with the support bracket20desirably distributes a force imposed on both the power transmission unit40and the main guide unit30, and enhances durability of the wheel control unit to lengthen the life span of the wheel control unit, regardless of repeated use of the mobile robot. Furthermore, when a power spring is coupled to the sub-guide unit35, the sub-guide unit35may guide the vertical movement of the wheel50without the main guide unit30.

The power transmission unit40includes a drive gear41and a driven gear42. The drive gear41of the power transmission unit40has a shaft hole41a at its center to receive the motor shaft11. The driven gear42which engages with the drive gear41has an axle boss42aat its center. A locking hole42bis formed along the central axis of the axle boss42aof the driven gear42so as to receive the gear support boss35bof the sub-guide unit35.

The wheel50has an open hub50aat its center to receive the axle boss42aof the driven gear42.

The above-mentioned elements of the wheel control unit of the mobile robot are assembled as follows.

The drive motor10ofFIG. 1is mounted to the support bracket20. In such a case, the motor shaft11is inserted in the motor shaft hole25of the annular boss26of the support bracket20. The main guide unit30is fabricated by fitting the spring34over the cylinder32of the spring guide31. The piston33is inserted into the cylinder32. After fabricating the main guide unit30, the cylindrical coupling boss32aof the cylinder32is inserted into the locking hole21of the support bracket10so as to allow the cylinder32to rotate around the locking hole21of the support bracket20. The insert part33aof the piston33is inserted into the arc-shaped guide slot22of the support bracket20. Thereafter, the coupling ring35aof the sub-guide unit35is fitted over the annular boss26of the support bracket20, while the locking hole35cof the sub-guide unit35is fitted over the locking boss33cof the piston33. The drive gear41of the power transmission unit40is assembled with the motor shaft11by inserting the motor shaft11into the shaft hole41aof the drive gear41. The gear support boss35bof the sub-guide unit35is inserted into the locking hole42bof the axle boss42aof the driven gear42. Thereafter, the wheel50is assembled with the driven gear42by fitting the axle boss42aof the driven gear42into the open hub50aof the wheel50.

The wheel control unit is operated as follows when the mobile robot surmounts an obstacle while moving on a surface, as shown in FIGS.2and3A-3E.

While the mobile robot normally moves on a flat surface, as shown in the left-side ofFIG. 2, the spring34of the main guide unit30is compressed due to the weight of the mobile robot. However, when a lower surface of the body of the mobile robot comes into contact with an obstacle on the surface to raise the wheel50over the surface, the wheel50is released from a load which has been applied to the wheel50due to the weight of the mobile robot. The spring34expands as shown in the right-side figure ofFIG. 2. In accordance with the expansion of the spring34, the insert part33aof the piston33moves downward along the arc-shaped guide slot22of the support bracket29. In such a case, the insert part33aof the piston33angularly moves around the motor shaft11. Due to the downward movement of the insert part33aof the piston33along the arc-shaped guide slot22, the gear support boss35bof the sub-guide unit35, the center of the driven gear42and the hub of the wheel50which are coaxially coupled to the insert part33aof the piston33move in the same direction as the insert part33a. Therefore, the wheel50moves downward to come into contact with the surface, thus maintaining a contact force against the surface.

Accordingly, while the mobile robot normally moves on a flat surface as shown inFIG. 3A, the wheel50is maintained at a predetermined position relative to the body of the mobile robot, due to the weight of the mobile robot. However, when the mobile robot must overcome an obstacle on the surface, an inclined front portion of the body of the mobile robot is raised over the surface by the obstacle, as shown inFIG. 3B, so that the wheel50is released from a load which has been applied to the wheel50due to the weight of the mobile robot. When the load is removed from the wheel50, the wheel50moves downward to maintain a contact force against the surface. Therefore, the mobile robot continuously moves forward on the surface while surmounting the obstacle, as shown inFIGS. 3C,3D and3E. While the mobile robot surmounts the obstacle as shown inFIGS. 3C,3D and3E, the spring34of the main guide unit30is compressed again due to the weight of the mobile robot, so that the wheel50moves upward to restore an original position relative to the body of the mobile robot. Every time the mobile robot meets obstacles while moving on the surface, the wheel50moves downward as described above, so that the mobile robot continuously moves forward on the surface while surmounting the obstacles without stopping.

As described above, a power spring may be used in place of the general-type coil spring34, so as to move the wheel50downward to allow the mobile robot to surmount an obstacle.

When using a power spring in place of the general-type coil spring34, the power spring is mounted at a first end to the support bracket20, and at a second end to the cylindrical coupling boss32aof the cylinder32of the main guide unit30or to a portion of the sub-guide unit35. While the mobile robot normally moves on a flat surface, the power spring is maintained in a tightened state due to the weight of the mobile robot. Therefore, the wheel50is maintained at a particular position relative to the body of the mobile robot. However, when the mobile robot meets an obstacle and the wheel50is released from a load which has been applied to the wheel50due to the weight of the mobile robot, the power spring is loosened to allow the wheel guide unit and the wheel50to move downward, thus bringing the wheel50into contact with the surface. The mobile robot thus continuously moves forward on the surface while surmounting the obstacle.

Accordingly, a wheeled mobile robot, of which wheels maintain contact forces against a surface even when the mobile robot meets an obstacle on the surface and the body of the mobile robot is forced up against the obstacle, thus easily surmounts the obstacle on the surface.

The wheeled mobile robot does not require any sensors, any specific controller, any specific traveling unit to surmount an obstacle, or any specific drive unit to drive the specific traveling unit, in or on its body, but has a simple and small control unit to control the wheels, thus improving productivity and reducing production costs of manufacturing the mobile robot. The mobile robot further includes a large effective space in its body to contain important elements required to perform desired functions of the robot.