High mobility vehicle

Details High mobility vehicle High mobility vehicle

2000-08-24

2001-07-31

Culbreth, Eric (Department: 3611)

Motor vehicles

Transmission mechanism

Mechanical movement transmission

C180S008200, C180S008300, C180S209000, C280S005514, C280S005520, C280S006150

Reexamination Certificate

active

06267196

ABSTRACT:

BACKGROUND OF THE INVENTION
A variety of high mobility/all-terrain vehicles have been made or proposed. These include a wide variety of tracked and wheeled vehicles.
A number of vehicles have been proposed for extraterrestrial use. Two which have been put into actual use are the four-wheeled lunar rover of the Apollo program and the six-wheeled robotic vehicle, Sojourner, of the Mars Pathfinder program. The suspensions of such vehicles are unidirectional; that is to say they function only when the vehicle is in a generally vertical orientation.
A variety of suspension systems may be used to maintain engagement of the vehicle's wheels with the ground surface. To ensure wheel engagement with particularly uneven surfaces, it is desirable that the suspension be mechanically actuated, either passively or actively, such as by hydraulics, pneumatics, motors or other actuators. In the case of a vehicle with more than three wheels, any three wheels will typically form a tripod upon which the vehicle may rest. To ensure engagement of the remaining wheels, it is necessary that the suspension have at least N-3 actuated degrees of freedom, where N is the number of wheels of the vehicle. If control over the ride height, and/or orientation are required then a system with N actuated degrees of freedom is necessary. The particular character of the actuated degrees of freedom will depend upon the chosen suspension design.
For example, the simplest of all designs would have one actuator vertically reciprocating each wheel. In the case of the Sojourner robot, each rear wheel is mounted on an arm which is pivotally actuated about a transverse axis of the robot. Each pair of front and middle wheels is carried by an arm extending between the axes of the wheels (a “rocker bogie”). The rocker bogie is pivotally moved on another arm which is pivotally actuated about the transverse axis of the robot. This provides the necessary three pivotal degrees of freedom on each side of the vehicle.
For maximizing traction, it is desirable that all wheels be driven. If individual motors are associated with each of the N wheels and individual actuators are associated with each of the N suspension degrees of freedom, then a total of 2N devices (actuators and motors) are required.
SUMMARY OF THE INVENTION
The present invention describes a vehicle where the drive motors may also be used to articulate the vehicle's suspension.
One preferred application for such a vehicle is as a rover used to explore extraterrestrial bodies, especially bodies such as asteroids where gravitational fields are much lower than on earth. In such low gravity environments, the static and dynamic forces due to gravity and vehicular momentum will be smaller than on earth and will thus interfere less with articulation of the suspension. The abilities of the vehicle to traverse rough terrain and orient and position the vehicle body for purposes of sample collecting, instrument positioning, etc. are especially advantageous in such raw environments.
In the case of many higher speed terrestrial vehicles, it is a goal to minimize the unsprung weight; e.g. that which is not carried by the suspension. This tends to increase the sprung weight; e.g. that which is carried by the suspension. The same does not necessarily apply to a vehicle for operation in low gravity environments. The cost of transporting the vehicle to the target environment places enormous penalties on total weight. Thus, by shifting weight from sprung weight to unsprung weight, the size and strength of suspension components may be reduced along with their associated weight. Furthermore, while operating at relatively low speeds, the extra weight of unsprung components may not have a significant effect on vehicle performance. By no means finally, the reduction of the sprung mass will generally have a tendency to lower the vehicle's center of gravity, and thereby increase its stability. It is therefore advantageous that the relatively heavy drive motors be included in the unsprung mass of the vehicle. This may be achieved by providing gear motors located partially or entirely within each wheel for driving the wheel. By utilizing the same motors to actuate the degrees of freedom of the suspension, significant weight savings may be achieved by avoiding separate actuators for the suspension.
Thus, in one aspect, the invention is directed to a vehicle having a body with a left side, a right side, a front, and a back and having left and right drive mechanisms. Each drive mechanism includes first and second traction elements for engaging the ground surface and transmitting a driving force between the vehicle and the ground surface. Each drive mechanism further includes first and second arms, respectively coupled to the first and second traction elements for relative rotation about first and second axes. Each mechanism further includes a rotor having a third axis. Each mechanism further includes first and second drive motors for driving the first and second traction elements, respectively. Each mechanism further includes first and second transmissions which are driven by the first and second motors, respectively, and engaged to the rotor so that respective driving of the first and second traction elements simultaneously rotates the rotor relative to the first and second arms.
The third axis of the left drive mechanism and the third axis of the right drive mechanism may be coincident and fixed relative to the body. Each drive mechanism may include a plurality of friction disks, normally irrotatably coupled to each other and carried along the third axis. The friction disks may hinder rotation of the rotor, first arm and second arm. Each drive mechanism may include a splined shaft extending along the third axis and carrying the friction disks, the rotor and the first and second arms. Each drive mechanism may further include a spring maintaining compressive engagement between the disk, rotor and first and second arms.
Each rotor may alternatively comprise an externally-toothed gear. Each transmission may comprise a gear train coupling the associated motor to the externally-toothed gear.


REFERENCES:
patent: 981329 (1911-01-01), Thornburg
patent: 2751027 (1956-06-01), McLaughlin
patent: 6112843 (2000-09-01), Wilcox et al.
patent: 206930 (1986-12-01), None
patent: 194171 (1986-12-01), None

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