Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
2001-01-16
2002-06-18
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C180S006200, C180S006500, C180S252000
Reexamination Certificate
active
06408230
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an omnidirectional vehicle that exhibits the so-called holonomic moving characteristics. More specifically, the present invention relates to an omnidirectional vehicle that is able to immediately move or start to turn from an arbitrary vehicle position to a desired direction without a waiting time for setup for preparing, for example, the change of orientation of the wheels thereof, in changing the turning speed or moving direction, or in changing from the stop condition to movement or in starting to turn the direction. The vehicle also may change the moving direction or turning direction even during the middle of moving operation. The present invention relates also to a method of controlling the omnidirectional vehicle that exhibits the holonomic moving characteristics.
The omnidirectional vehicle is a vehicle that is capable of controlling three situations freely, i.e. moving or travelling velocity in a moving direction, traveling or travelling velocity perpendicular to the traveling direction, and angular velocity around a vertical axis of the vehicle. Many inventions have been disclosed on the omnidirectional vehicle. The omnidirectional vehicles may be classified into a non-holonomic vehicle and a holonomic vehicle.
It is necessary for the non-holonomic vehicle to conduct a setup operation and a setup time for changing the setup of a part of the mechanisms in the vehicle, such as changing the orientation of each wheel in changing the traveling direction of the vehicle or in shifting to a turning motion. This vehicle has a mechanism that has two free situations. The non-holonomic vehicle is unable to simultaneously control the three free situations of the vehicle independently. The non-holonomic vehicle sets two of the three free situations one by one, and finally, controls the three free situations of the vehicle.
Therefore, the non-holonomic vehicle is unable to trace a trajectory having a right angle corner without spending a setup time. In tracing a right angle corner, the non-holonomic vehicle will trace a circular trajectory if the vehicle does not wait for the setup time. Or, it is necessary for the non-holonomic vehicle to stop at the right angle corner and to resume traveling after the setup time has elapsed. An example of the non-holonomic vehicle is the omnidirectional vehicle that steers all the wheels thereof.
On the other hand, the holonomic vehicle is able to start moving and turning in all the directions instantaneously to an arbitrary orientation from an arbitrary position without changing the setup of the internal mechanisms thereof. The specific feature of the holonomic vehicle is that the holonomic vehicle is capable of simultaneously controlling the three free situations independently. Examples of the holonomic vehicle include an omnidirectional vehicle that employs a spherical wheel, and an omnidirectional vehicle that employs a special wheel mechanism including a large wheel and many rollers arranged around the large wheel and capable of freely rolling laterally.
The holonomic omnidirectional vehicle disclosed by the present inventor in Japanese Patent Unexamined Publication No. 9-164968 includes two or more driving wheel mechanisms, each including an actuator for driving a caster-type wheel and an actuator for driving the steering shaft of the caster-type wheel, to obtain an omnidirectional movement with the three free situations. The wheel mechanism disclosed in the above identified patent publication can use ordinary tires, such as gum tires and pneumatic tires, and obtain a smooth and swift omnidirectional movements.
Since the wheel mechanism disclosed in Japanese Patent Unexamined Publication No. 9-164968 includes the steering shaft that continuously rotates endlessly, the actuator for driving the wheel shaft and the actuator for driving the steering shaft are mounted on a body of the vehicle due to the ease of wiring. Since the rotational movements of the actuators are transmitted via rotating mechanisms such as gears, velocity interference occurs between the actuators.
More in detail, even when the actuator for driving the steering shaft is operated to change the orientation of the wheel while the actuator for driving the wheel is stopped, both the steering shaft and the wheel rotate. In contrast, when the actuator for driving the wheel is operated while the actuator for driving the steering shaft is stopped, only the wheel rotates. Thus, unidirectional velocity interference occurs from the actuator for driving the steering shaft to the actuator for driving the wheel.
To remove the velocity interference described above, it is necessary to conduct a motion control by adding in advance a predetermined rate of the rotating velocity of the steering shaft to the actuator for driving the wheel. In other words, it is necessary to employ an actuator that rotates faster than the maximum rotation frequency necessary only for driving the wheel.
Moreover, it is necessary for the actuator of the steering shaft to generate torque high enough to sustain the torque transmitted to the wheel irrespective of whether the steering shaft is rotating or not, since the torque for driving the wheel acts on the wheel via a fulcrum, that is a certain part, e.g. a gear, of the transmission mechanism of the steering shaft. This means that the torque is exerted suddenly to the steering shaft while the vehicle is accelerating or decelerating or while the vehicle is climbing up or down a step. The torque is nothing but an external turbulence to the actuator for driving the steering shaft.
When an error occurs in the rotating velocity of the steering shaft by the torque from the actuator for driving the wheel, the vehicle deviates from the intended course, further causing a running error of the vehicle. This running error causes a serious problem on the omnidirectional vehicle.
Japanese Patent Unexamined Publication No. 9-164968 also discloses an omnidirectional vehicle including a driving unit having a caster formed of two wheels and an actuator for turning the body of the vehicle. This omnidirectional vehicle controls the translational movement and the rotational movement thereof by controlling three actuators for driving two wheels and for driving the steering shaft of the driving unit. The omnidirectional vehicle avoids the over-restricted state (vehicle is controlled by the actuators more than the number of the actuators for the freedom situations) of the vehicle that employs a plurality of singlewheel-type casters.
Since the actuator for driving the steering shaft is mounted on the driving unit including a caster formed of two wheels, it is necessary to drive the body of the vehicle in the direction opposite to the rotating direction of the driving unit to compensate the orientation change of the driving unit even when the vehicle is not turning, i.e. even when the vehicle is executing a simple translational movement. Therefore, it is necessary for the control calculation in the actuator for controlling the turning of the vehicle to take into account the movements of the vehicle in the direction of the translational movement. This requirement complicates the control system and it becomes necessary to mount an actuator with an extremely high capacity for turning the body of the vehicle.
In short, the interference between a plurality of actuators for driving the vehicle impairs the traveling or moving precision of the vehicle, complicates the control system and increases the capacities of the actuators.
The foregoing problems will be described more in detail below with reference to
FIGS. 19 and 20
.
FIG. 19
is a side view of a conventional caster-type driving wheel mechanism.
FIG. 20
is a plan view of the conventional caster-type driving wheel mechanism. The caster-type driving wheel mechanism shown in
FIGS. 19 and 20
is a modification of the driving wheel mechanism according to an embodiment disclosed in Japanese Patent Unexamined Publication No. 9-164968.
Referring now to thes
Cuchlinski Jr. William A.
Fuji Electric & Co., Ltd.
Hernandez Olga
Kanesaka & Takeuchi
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