[Technical Field of the Invention]

The present invention relates to a design of a driving mechanism for a vehicle to move through uneven terrain including stairways.

[Description of the Prior Art]

For achieving the mobility on uneven terrain, the conventional mechanisms in the prior art used to add extra devices and actuators to modify the shape of a track to be suitable for the terrain shape. However, this kind of mechanism has disadvantages that the overall structure is being complicated and the energy efficiency is being lowered. Moreover, the driving speed is being decreased due to the shape change of a track, and the control on the actuators becomes to be more complicated.

[Description of the Invention]

The present invention is proposed to solve the problems mentioned above. It is therefore the object of the present invention to provide a driving mechanism for a tracked vehicle to have good adaptability to uneven terrain such as stairways without any extra devices or actuators. [Brief Description of the Drawings]

FIG. 1 is a view illustrating the overall structure of a link-type double track mechanism in accordance with the present invention. FIG. 2 is a view illustrating an example of a single-tracked vehicle climbing a stairway. FIG. 3 is a view illustrating an example of a vehicle with link-type double track mechanism climbing a stairway. FIG. 4 is a view illustrating the steps of climbing stairways with using an angle-adjusting flipper. FIG. 5 is a view for comparing the structure of an angle-adjusting flipper with that of a triangular track. FIG. 6 is a view illustrating the relative movements of two tracks. FIG. 7 is a view illustrating the structure of a rotation angle limitation mechanism. FIG. 8 is a view illustrating the high-speed driving mode mechanism. FIG. 9 is a view for explaining the driving mechanism of the angle adjusting flipper and the high-speed driving wheel. FIG. 10 is a view illustrating the application examples of the present invention.

[Detailed Description of the Embodiments]

Hereinafter, referring to appended drawings, the structures and the operation principles of the embodiments of the present invention are described in detail. The present invention relates to a driving mechanism applicable to a vehicle able to move through uneven terrain including stairways. As described in FIG. 1 , the link-type double track mechanism in accordance with the present invention comprises: front and rear track driving sections(1 , 2); a built-in type control box(3); a set of angle- adjusting flippers(4, 5), installed at front and rear ends of the control box, for adjusting the track angle; and high-speed driving wheels(6, 7) installed at the angle-adjusting flippers and imbedded inside. Track driving sections(1 , 2) are attached to a shaft connected to a driving pulley, which actuates both track sections(1 , 2) simultaneously, by a rotational joint, and thus they can be rotated freely. With using the free rotation ability, the track device of the present invention can be passively adapted to the terrain surface by gravity without any extra actuator. Consequently, the mobility on uneven terrain such as stairways has been remarkably improved. FIG. 2 shows the example of instability occurring when a vehicle having a single-track mechanism, like a tank, is being driven over a stair. In the figure, D represents the rotation direction of the track and (B) represents a body fixed coordinate frame. And, rm represents a position vector of the center of gravity in (B) or the zero-moment- point(ZMP) in dynamic viewpoint. L represents the supporting area of the track section. Here in FIG. 2, since the overall structure is being described in two-dimensional plane, L is described as a straight line. A represents the projection of the center of gravity of the vehicle or the zero-moment-point(ZMP) in dynamic viewpoint to the supporting area. For stable movement of a vehicle, A should be remained within L. FIG. 2(A) shows the initial state of climbing a stair. In the figure, A is remained in L so that the vehicle can move stably. On the other hand, in Fig. 2(B), A goes beyond the range of L, and thus the vehicle is being turned-over. Even with a single-track mechanism, if the hump is not so high and/or the center of gravity is very low, turning-over situation can be prevented. However, there is a mechanical design-limit in lowering the center of gravity of a vehicle, and the heights of the humps in the working-field are usually uneven. Consequently, a vehicle having a single-track mechanism cannot avoid having a restriction in its mobility. FIG. 3 shows an example of a vehicle with link-type double track mechanism in accordance with the present invention climbing a hump. The figure shows a vehicle climbing over a hump in the sequence of (A) ~ (D), and the reference signs represent the same as those in FIG. 2. FIG. 3(B) shows that the track section(1 ) moves over the hump along the wall with being rotated to the shaft of driving pulley(7). FIG. 3(C) describes the state that, when the relative movement of the track sections(1 , 2) is being stopped by the rotational angle limitation mechanism, both track sections(1 , 2) are being rotated to the ground simultaneously just like a single-tracked vehicle. FIG. 3(D) shows the effect of enlarging the length of L when the track section(1 ) completely climbs over the hump. With this feature, a vehicle with link-type double track mechanism in accordance with the present invention can overcome the unstable situation described in FIG. 2. This kind of terrain adaptability is the advantage of multi-joint driving section, however, if the number of joints is increased, the structure becomes to be more complicated. Besides, if a user wants to give terrain adaptability like in FIG. 3(D) to a conventional 2,3-tracked vehicle using extra actuators, it requires large amount of circumstantial information and the control of the vehicle becomes very difficult. Thus, the vehicle cannot move with high-speed. The present invention constitutes the track sections(1 , 2) with passive- type joints to be passively adapted to the ground for simplifying the structure and the control. With this structure of passive adaptability, the vehicle can move with high-speed without a control for terrain- adaptation by a user. FIG. 4 shows the steps of climbing stairways of a track mechanism using an angle-adjusting flipper. As shown in FIG. 4(A), when a track mechanism meets a stair, the height of the mechanism is lower than that of the stair, and thus it cannot climb over the stair in an ordinary way. To overcome this kind of height difference, the mechanism first adjusts the angle of the angle-adjusting track of the flipper, installed at the front side of the track, in order for the height of the front-end of the track to be higher than that of the stair as shown in FIG. 4(B), and then approaches to the stair. Once the driving track(1 ) climbs over the stair by using these sequences, the mechanism takes the angle-adjusting flipper back to its original position as shown in FIG. 4(C), and then continues climbing the stairs. In general stairway-climbing cases, the driving tracks(1 , 2) are climbing over the stairways with being adapted to the stairway shape with maintaining the angle-adjusting flipper to be in the fixed position. In case that the driving track(1) and the angle-adjusting flipper(4) are fixed with a certain angle as shown in FIG. 5, the track mechanism is working in the same manner as that of a fixed triangular track. In general, it is most effective to use a driving track(1) and an angle- adjusting flipper(4) in combination for being adapted to various terrain types, however, if the vehicle can move around with the angle-adjusting flipper being fixed with a certain angle in a specific terrain, the driving track(1 ) and the angle-adjusting flipper(4) can be replaced by a triangular track, as shown in FIG. 5, for simplifying the track mechanism. FIG. 6 shows the movement of idle pulley(8) caused by the relative movement of the track sections(1 , 2) in case of applying a fixed triangular track described in FIG. 5. As shown in the figure, regardless of the driving pulley(7) being fixed or being moved, the relative rotation between two track frames can be occurred. In case that the driving pulley(7) is being fixed, if the track section is being rotated, the idle pulley(8) is being rotated. Thus, the relative movement is resistance- free even if the driving pulley(7) is being fixed. Here, the rotation amount of idle pulley(8) is calculated by multiplying the rotation variance of track section to the diameter ratio of the driving pulley(7) and the idle pulley(7), as depicted in Equation 1. [Equation 1] φθ = φ + δφ = φ + kθ , where φ is the rotation angle of idle pulley(8) changed by driving pulley(7), and δφ, which is represented by kθ, is a value linearly dependent upon the relative rotation variance(<9) of the track sections(1 , 2). FIG. 7 shows the structure of rotation angle limitation mechanism installed in-between free rotational shafts connecting the bodies of driving tracks(1 , 2). In FIG. 7, a supporter(1 1 ) is connected to the driving track(1 ) and a stopper(10) is installed at the driving track(2), however, the installing location is not limited as such. In general driving operation, the supporter(1 1 ) does not contact with the stopper(10) within its moving range so that free rotation can be carried out. But, when a torque generated by a motor(13) installed at the body of driving track(2) rotates the angle of the stopper(10) by a gear(12), the rotation range of the supporter(11) is being limited. In addition, if a user rotates the stopper(10) more than a preset angle, it rotates even after contacting with the supporter(11 ), and thus the user can modify the angles between the driving tracks(1 , 2) to be a desired angle. FIG. 8 shows a modified mechanism for high-speed driving mode for overcoming the large frictional force caused by high-speed movement of track-type mechanism. When the angle-adjusting flippers(4, 5) are remained within a usual angular range for being adapted to uneven terrain, the built-in type high-speed driving wheels are not being operated. However, as shown in FIG. 8, if the angle-adjusting flippers(4, 5) are folded beyond a specific angle, the built-in type high-speed driving wheels come out from the body. At this time, if a user actuates a break installed at the self-rotation shaft between the driving tracks(1 , 2) and rotates the angle-adjusting flippers(4, 5) continuously, the driving tracks(1 , 2) are to be off the ground and the high-speed driving wheels are being contacted to the ground alone. Thus, the vehicle can move faster in this mode compared with the ordinary track mode. FIG. 9 is a view for detailed explanation on the driving mechanism of the angle-adjusting flippers and the high-speed driving wheels described in FIG. 8. If the angle-adjusting flippers are moving within a usual angular range(3), the built-in type high-speed driving wheels are not being operated. The usual angular range(3) includes sufficient angles for the vehicle to climb on various stairways in general. If the angle-adjusting flippers are rotating into the angular range(1 ), the built- in type high-speed driving wheels start to come out from the body. At this time, the angular movement of the angle-adjusting flippers in the angular range(1 ) is the same as that of the high-speed driving wheels in the angular range(2). FIG. 10 shows various application examples of the present invention wherein a pan-tilt-camera(i) or a robot arm(2) is installed thereon for being used for a remote-controlled robot. FIG. 10(C) shows an application example for a military and/or a leisure utility vehicle wherein a driver(3) is on board to drive the vehicle using a control lever(4). Since those having ordinary knowledge and skill in the art of the present invention will recognize additional modifications and applications within the scope thereof, the present invention is not limited to the embodiments and drawings described above. [Industrial Applicability]

As mentioned thereinbefore, a link-type double track mechanism in accordance with the present invention does not require a complex terrain-adaptation mechanism, and thus it has advantages that the overall structure is simple and the control is very easy. A robot, the above-mentioned link-type double track being applied thereto, can be applicable for the civil use such as a lifesaver on a fire, a remote inside- monitor for a building, a substitute machine for police-work, a detector for a nuclear reactor, and/or an assistant for a disabled person as well as the military use such as a mine detector and/or a mine eliminator, a detector for enemy's territory, and so on. In addition, the present invention can be actively applied to developing a service robot available for inside and/or outside of a building. Besides, in case of being designed as a vehicle, it can be applicable for a military scouting vehicle as well as a civil utility vehicle to create an import-replacing effect and/or an export increasing effect.