As for now, our patent: WO2015197069, has been granted in EU, Australia, Japan and China. It is in the national phase in USA, Canada, South Korea and Israel.
Summary from the patent: The present invention relates to a chassis for vehicle, comprising: a rigid frame, a pair of side wheels in a parallel configuration, a steerable front wheel, a steerable rear wheel, at least one electric motor, wherein at least one of said front wheel or rear wheel is connected to and driven by the at least one electric motor, and wherein said front and rear wheels are mutually connected through a turning mechanism arranged to turn said front and rear wheels simultaneously and synchronously between a middle position in which the axles of the front and rear wheels are substantially parallel with the axles of side wheels, and left or right positions, in which the axles of the front and rear wheels are substantially perpendicular to the axles of the side wheels.
The illustration of the frame is from the patent and is only an example of possible terrain adaption. The possible terrain adapting and suspension systems are many and are also covered by the patent.
Illustration left: A differential wheeled robot varies the drive output of its two drive wheels in a differential manner to generate curvilinear motion. This method’s drive path is unpredictable due to its reliance on friction with the surface, wear on tires, and the distance between the driving wheels.
Illustration middle: Omni-directional wheel robots rely on a complex combination of drive wheels comprised of smaller diagonal castors and differential steering to generate curvilinear motion. This approach requires high drive torque on all wheels to overcome friction and steer into its desired path, and like differential wheeled they are complex to predict and vulnerable to slippery surfaces.
Illustration right: Our solution has steering, and drive forces separated through its innovative frame-approach. Thus, it becomes simpler to predict its drive paths, and movements become more energy efficient since all available drive torque goes into the direction of the forward motion.
By the combined toque effort of both the front and rear wheel motors, our solution can seamlessly and efficiently traverse obstacles up to 40% of wheel height. And this regardless of whether the obstacle is sharp or rounded, or if one or all wheels encounter the obstacle..
When first encountering an obstacle, our solution behaves similarly to an omni-directional wheeled robot. By pulling over the obstacle with its front wheel and pushing with its rear wheel, it can effectively power over obstacles up to 40% of wheel height.
As soon as the front wheel has traversed the obstacle, the side wheels are then able to be pulled up over the obstacle by the combined effort of front and rear wheels which inherently stabilizes the operation. This is furthermore strengthened due to the pull angle, going from the front wheel to the side wheels.
Once the side wheels have cleared the obstacle and gained stability, the rear wheel can then be pulled over the obstacle, by a combination of its own torque and the pulling force of the front wheel. As for the side wheels, this is furthermore strengthened due to the pull angle, going from the side wheels to the back wheel.
When encountering sharp obstacles differential steered robots are severely limited by their castor wheels, since the size of the castor wheels are limited by height. The smaller wheels, the lesser climb ability. The drive torque is transmitted from the middle of the robot and as such has no "pull up" effect. The robot must be able to push its castor wheels over a given obstacle, and therefore is dependent on their height. Furthermore caster wheels tend to turn 90 degrees from the driving direction when meeting a vertical obstacle, blocking the climb.
Omni-directional wheeled mobile robots, while able to pull over with their front wheel and pushing with their rear wheels, suffer from the weakness of the wheel design itself. The smaller castor wheels that make up omni-directional wheels are inherently sensitive to sharp edges and thus sudden obstacles. Furthermore, a slip from a wheel will make the robot turn to the side. The caster wheels, due to their size, do not allow for deep grip treads, but are normally slick and as such not suited to climb obstacles.