VECTOR STEERING FOR TRACKED VEHICLE

Abstract

A technique for steering a tracked vehicle includes controllably deforming at least a portion of a vehicle's track into a curved shape, causing the vehicle to follow a curve-shaped path as it drives. As the vehicle naturally tends to follow a curved path defined by the track's curvature, steering is accomplished with greatly reduced skidding against the ground.

Claims

1. A tracked vehicle, comprising: a vehicle body; a set of wheels coupled to the vehicle body and including a steerable wheel configured to turn left and right relative to the vehicle body; and a deformable track that surrounds the set of wheels and engages the steerable wheel, the deformable track configured to deform into a curved shape in response to the steerable wheel turning left or right.

2. The tracked vehicle of claim 1, wherein the deformable track includes a plurality of track links attached together to form a loop in which a first track link is left-right pivotably coupled to a second track link immediately adjacent to the first track link.

3. The tracked vehicle of claim 2, wherein the first track link includes a channel adapted to receive a tab that extends from the second track link, and wherein the first track link is attached to the second track link via a fastener that extends through the tab.

4. The tracked vehicle of claim 2, wherein the first track link and the second track link include respective upward projections constructed and arranged to engage with a circumferential channel of the steerable wheel as the track advances around the steerable wheel.

5. The tracked vehicle of claim 1, wherein the set of wheels includes another steerable wheel configured to turn left and right relative to the vehicle body, and wherein the deformable track further engages the other steerable wheel.

6. The tracked vehicle of claim 1, wherein the steerable wheel is coupled to the vehicle body via a thrust actuator configured to controllably retract and extend relative to the vehicle body for respectively moving the steerable wheel toward and away from the vehicle body.

7. The tracked vehicle of claim 6, wherein the trust actuator is configured to retract in response to the steerable wheel turning in one or a left or right direction and to extend in response to the steerable wheel turning in the other of the left or right direction.

8. The tracked vehicle of claim 1, wherein the set of wheels includes a non-steerable wheel coupled to the vehicle body via a thrust actuator configured to controllably retract the non-steerable wheel relative to the vehicle body as the steerable turns in one of a left or right direction and to extend the non-steerable wheel relative to the vehicle body as the steerable wheel turns in the other of the left or right direction.

9. The tracked vehicle of claim 1, further comprising a second set of wheels distinct from the set of wheels, the second set of wheels coupled to the vehicle body and including a second steerable wheel configured to turn left and right relative to the vehicle body; and a second deformable track that surrounds the second set of wheels and engages the second steerable wheel, the second deformable track configured to deform into a curved shape in response to the second steerable wheel turning left or right.

10. A tracked vehicle, comprising: a vehicle body; a first set of wheels coupled to the vehicle body and including a first steerable wheel configured to turn left and right relative to the vehicle body; a second set of wheels coupled to the vehicle body and including a second steerable wheel configured to turn left and right relative to the vehicle body; a first deformable track that surrounds the first set of wheels and engages the first steerable wheel; and a second deformable track that surrounds the second set of wheels and engages the second steerable wheel, wherein the first deformable track is configured to deform into a first curved shape in response to the first steerable wheel turning left or right, and wherein the second deformable track is configured to deform into a second curved shape in response to the second steerable wheel turning left or right, the second curved shape having a different turning radius than the first curved shape.

11. A method of steering a tracked vehicle that includes— a vehicle body, a first set of wheels coupled to the vehicle body and including a first steerable wheel configured to turn left and right relative to the vehicle body, and a second set of wheels coupled to the vehicle body and including a second steerable wheel configured to turn left and right relative to the vehicle body, the method comprising: providing a first deformable track that surrounds the first set of wheels and engages the first steerable wheel; providing a second deformable track that surrounds the second set of wheels and engages the second steerable wheel; and in response to turning the first steerable wheel and the second steerable wheel, the first deformable track and the second deformable track respectively deforming into first and second curved shapes that arc left or right.

12. The method of claim 11, further comprising turning the first steerable wheel and the second steerable wheel in response to steering input received from a driver of the tracked vehicle.

13. The method of claim 12, further comprising processing the steering input to: (i) turn the first and second steerable wheels in response to the steering input and (ii) advance the first and second deformable tracks at respective speeds in response to the steering input.

14. The method of claim 12, further comprising: providing a first steering mode in which the tracked vehicle is steered by vector steering based on turning the first steerable wheel and the second steerable wheel in response to the steering input; providing a second steering mode in which the tracked vehicle is steered by skid steering in which the first deformable track and the second deformable track are advanced at different speeds in response to the steering input while the first steerable wheel and the second steerable wheel are pointed straight ahead; and selecting between the first steering mode and the second steering mode based on the steering input.

15. The method of claim 14, further comprising: providing a third steering mode that blends vector steering with skid steering; and selecting between the first steering mode, the second steering mode, and the third steering mode based on the steering input.

16. The method of claim 15, further comprising receiving the steering input from a steering wheel or joystick, wherein selecting between the first steering mode, the second steering mode, and the third steering mode is based on the steering input received from the steering wheel or joystick.

17. The method of claim 12, further comprising: when turning the tracked vehicle in a first direction, extending the first steerable wheel but not the second steerable wheel away from the vehicle body; and when turning the tracked vehicle in a second direction opposite the first direction, extending the second steerable wheel but not the first steerable wheel away from the vehicle body.

18. The method of claim 12, wherein the first set of wheels includes a first non-steerable wheel, wherein the second set of wheels includes a second non-steerable wheel, and wherein the method further comprises: when turning the tracked vehicle in a first direction, extending the second non-steerable wheel but not the first non-steerable wheel away from the vehicle body; and when turning the tracked vehicle in a second direction opposite the first direction, extending the first non-steerable wheel but not the second non-steerable wheel away from the vehicle body.

19. The method of claim 12, further comprising, when making a turn by the tracked vehicle, advancing the first deformable track and the second deformable track at different speeds to account for different distances traveled by the first deformable track and the second deformable track while making the turn.

20. The method of claim 12, wherein the first set of wheels includes a first additional steerable wheel, wherein the second set of wheels includes a second additional steerable wheel, and wherein the method further comprises: when turning the first steerable wheel in one of a left or right direction, turning the first additional steerable wheel in the other of the left or right direction; and when turning the second steerable wheel in one of a left or right direction, turning the second additional steerable wheel in the other of the left or right direction.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] The foregoing and other features and advantages will be apparent from the following description of particular embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same or similar parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments.

[0017] FIG. 1 is a front perspective view of an example tracked vehicle.

[0018] FIG. 2 is a top plan view of an example tracked vehicle performing skid steering.

[0019] FIG. 3 is a top plan view of an example tracked vehicle performing vector steering.

[0020] FIG. 4 is a perspective view of example articulating track segments that support vector steering in the tracked vehicle of FIG. 3.

[0021] FIGS. 5A and 5B are top views of an example tracked-vehicle wheel arrangement for supporting vector steering, or both vector steering and skid steering, showing both a straight-ahead steering arrangement (FIG. 5A) and a turned steering arrangement (FIG. 5B).

[0022] FIG. 6 is a block diagram showing an example control system for controlling vector steering, or for controlling both vector steering and skid steering.

[0023] FIG. 7 is a flowchart showing an example method for controlling steering in a tracked vehicle.

DETAILED DESCRIPTION

[0024] Embodiments of the improved technique will now be described. One should appreciate that such embodiments are provided by way of example to illustrate certain features and principles but are not intended to be limiting.

[0025] An improved technique for steering a tracked vehicle includes controllably deforming at least a portion of a vehicle's track into a curved shape, causing the vehicle to follow a curve-shaped path as it drives. As the vehicle naturally tends to follow a curved path defined by the track's curvature, steering is accomplished with greatly reduced skidding against the ground, promoting a smoother ride, avoiding damage to the ground and to vehicle components, and enabling stealthier operation.

[0026] FIG. 1 shows an example tracked vehicle 110 having left and right tracks 120L and 120R, respectively. The tracked vehicle 110 is configured to drive on the tracks 120, e.g., in response to a motor or engine (not shown) applying rotation to wheels 130. The vehicle 110 may be configured for vector steering, or for both vector steering and skid steering.

[0027] FIG. 2 is a top view of the vehicle 110 of FIG. 1 (or a similar vehicle). As shown, the vehicle 110 has left and right sides 110L and 110R, respectively, as well as a front 110F and a back 110B. The vehicle 110 may accomplish skid steering by propelling the two tracks 120 at different speeds 210L and 210R. For example, the vehicle 110 may turn to the left by driving the right track 120R at a higher speed than the left track 120L. It may likewise turn to the right by driving the left track 120L at a higher speed than the right track 120R. It may drive straight ahead by driving both tracks 120 at the same speed. To turn on the spot, the vehicle 110 may drive one track forward and the other track backward. Skid steering of this kind can be highly effective for tight turns, but it also tends to cause wear to the tracks 120 and other components and may cause damage to any surface on which the vehicle 110 is driving.

[0028] FIG. 3 shows the vehicle 110 adapted for vector steering in accordance with improvements hereof. Here, tracks 120L and 120R have been deformed such that they respectively assume curved shapes 310L and 310R. The curved shapes 310L and 310R enable the vehicle to turn with much less skidding that typically accompanies skid steering (FIG. 2), as the vehicle 110 can merely follow the curved paths established by the tracks 120. The left and right curvatures 310L and 310R may differ slightly from each other to account for differences in the respective turning radii. Likewise, the left and right tracks 120L and 120R preferably run at slightly different speeds 320L and 320R, given that the outer track must cover more ground than the inner track to complete any given turn in the same amount of time.

[0029] FIG. 4 shows an example pair of links 400 from which tracks 120 may be assembled. For example, each track 120 may include a series of links 400 (e.g., 50 links, 100 links, etc.) strung together to form a respective loop. Each link 400 includes a body 410 made of rubber or some other rigid or semi-rigid material. A tab 420 extends from the body 410 of each link 400. The tab 420 is adapted to insert into a channel 430 formed within the body 410 of an immediately adjacent link 400. The channel 430 may have an open bottom or may have a hole (not shown) in the bottom. The tab 420 has a through-hole 422. To join each link 400 to its neighbor, the tab 420 of a current link is inserted into the channel 430 of its neighbor. A screw or other fastener 424 may then be inserted upwardly through the hole in the bottom of the channel 430 and through the hole 422 in the tab 420 of the current link. Each link 400 may include an upward projection 440, also referred to herein as a “shark fin,” which receives the screw or other fastener 424 and retains it in place. With the depicted arrangement, each link 400 may rotate slightly left and right about the fastener 424. When links 440 are assembled together into a track 120, the resulting track 120 is capable of being deformed so as to establish curvatures necessary for vector steering.

[0030] One should appreciate that the depicted links 400 are merely one example of ways in which tracks 120 can be made to deform. For example, a continuous track 120 may be created from a composite material or from a single material having varying geometry in respective regions, which provides flexibility in the direction of lateral thrust.

[0031] FIGS. 5A and 5B show an example wheel arrangement suitable for accomplishing vector steering, or both vector steering and skid steering. Four wheels 130 are shown on each side of the vehicle 110, but this is merely an example for illustration, as different numbers of wheels may be provided. The wheels 130 may be moveable in ways that are not common for tracked vehicles. For example, some or all of the wheels 130 may be left-right turnable. Also, some or all of the wheels 130 may be laterally moveable, i.e., toward or away from a main body of the vehicle 110.

[0032] As shown in FIG. 5A, front and back wheels 130LF, 130LB, 130RF, and 130RB are left-right turnable, e.g., by operation of respective joints 510, such as CV (constant velocity) joints or universal joints. Middle wheels 130LM1, 130LM2, 130RM1, and 130RM2 do not require joints 510, but such joints 510 may be provided if desired. In some examples, only front wheels 130LF and 130RF are left-right turnable, or only back wheels 130LB and 130RB are left-right turnable. Various mechanisms for achieving left-right turning of vehicle wheels are known in the art and are not covered here.

[0033] Middle wheels 130LM1, 130LM2, 130RM1, and 130RM2 may include thrust actuators 520, which are configured to move respective wheels laterally. The thrust actuators 520 may include telescoping members 520a and 520b, as shown, but they may alternatively use screws or the like. In some examples, all of the wheels 130 include thrust actuators 520, or a different number of them may. In some examples, the middle wheels 130LM1, 130LM2, 130RM1, and 130RM2 are laterally fixed, and only the outer wheels 130LF, 130LB, 130RF, and 130RB are laterally moveable. Many arrangements are possible.

[0034] FIG. 5B shows the same arrangement as in FIG. 5A, but here the wheels 130 are shown during execution of a left turn. Front wheels 130LF and 130RF each turn to the left on respective joints 510, and back wheels 130LB and 130RB each turn to the right. Left-middle wheels 130LM1 and 130LM2 retract, via respective thrust actuators 520, toward the body of the vehicle 110, while right-middle wheels 130RM1 and 130RM2 extend outwardly. The illustrated arrangement allows left and right tracks 120L and 120R to assume curved shapes 310L and 310R.

[0035] As shown, each of the depicted wheels 130 has a respective channel 530 adapted to receive shark fins 440 of links 400 and thus to assist in keeping the tracks 120 on the wheels 130. In some examples, some or all of the channels 530 may be oversized in width to allow a degree of play in the lateral position of the tracks 120 relative to the wheels 130. For example, the channels 530 of the middle wheels 130LM1, 130LM2, 130RM1, and 130RM2 may be oversized, whereas the channels 520 of the outer wheels 130LF, 130LB, 130RF, and 130RB may not be oversized.

[0036] FIG. 6 shows an example steering control system SCS 610 that may be used in connection with the vehicle 110. Here, the SCS 610 is configured to respond to steering input 620 from a steering wheel 602, joystick 604, or the like, which may be controlled by a human driver. The SCS 610 is seen to include a set of processors 630, such as one or more microprocessors or other control hardware, and memory 640. The memory 640 includes both volatile memory, e.g., RAM (Random Access Memory), and non-volatile memory, such as one or more ROMs (Read-Only Memories), disk drives, solid state drives, and the like. The set of processors 630 and the memory 640 together form control circuitry, which is constructed and arranged to carry out various methods and functions as described herein. Also, the memory 640 includes a variety of software constructs realized in the form of executable instructions. When the executable instructions are run by the set of processors 630, the set of processors 630 carry out the operations of the software constructs. Although certain software constructs are specifically shown and described, it is understood that the memory 640 typically includes many other software components, which are not shown, such as an operating system, various applications, processes, and daemons.

[0037] As further shown in FIG. 6, the memory 640 “includes,” i.e., realizes by execution of software instructions, an angle detector 642, a speed detector 644, and a balancer 646. The angle detector 642 is configured to convert electronic input from the steering wheel 602 or joystick 604 into a corresponding representation of desired turning angle. The speed detector 644 is configured to provide a representation of vehicle speed. Balancer 646 is configured to receive input from the angle detector 642 and speed detector 644 and to generate, based on those inputs, wheel angle 650, wheel extension 660, and wheel speed 670. The wheel angle 650 provides left-right angles of each of the wheels 130 whose left-right angles can be controlled, e.g., each of the wheels 130 equipped with joints 510. The wheel extension 660 provides lateral extension for each of the wheels 130 whose lateral extension can be controlled, e.g., each of the wheels 130 equipped with thrust actuators 520. The wheel speed 670 provides a desired speed for each wheel 130 whose speed is controllable. For example, each track 120 has a single drive wheel for propelling the respective track 120 and wheel speed 670 provides a respective speed for each of them.

[0038] In example operation, a human driver operates the steering wheel 602 or joystick 604, as well as a throttle and brake (not shown). As applied steering or vehicle speed changes, the SCS 610 computes and outputs new values of wheel angle 650, wheel extension 660, and wheel speed 670. The vehicle 110 responds to the new values by establishing left-right turning angles and lateral thrust of affected wheels 130, and by setting wheel speed of drive wheels appropriately. Such operation may proceed continuously, as long as the vehicle is being driven.

[0039] In various examples, the functions of the SCS 610 are performed in whole or in part by mechanical components. For example, wheel angle 650 may be established by a mechanical steering system, such as Ackerman steering, short rack-and-pinion steering, or the like. Such systems may account for differences in steering angle between left and right wheels. Wheel extension 660 may be established passively, e.g., by allowing certain wheels 130 to move laterally in compliance with applied forces, such as forces applied by the tracks 120 against the wheels 130. Differences in wheel speed 670 may be supported using a differential gear system rather than by providing separate drive power to the drive wheel on each track. Thus, the particular use of an SCS 610 as described above should be regarded merely as one of many possible examples.

[0040] FIG. 7 shows an example method 700 that may be carried out in connection with the vehicle 110. The method 700 is typically performed, for example, by the software constructs described in connection with FIG. 6, which reside in the memory 640 of the SCS 610 and are run by the set of processors 630. The various acts of method 700 may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in orders different from that illustrated, which may include performing some acts simultaneously. Although the illustrated example shows the SCS 610 as performing the described acts, one should appreciate that similar acts may be performed in whole or in part by mechanical systems.

[0041] At 710, the SCS 610 receives steering input 620 from the steering wheel 602 or joystick 604 in response to driver input. The SCS may convert the steering input 620 to a steering angle. The SCS may also receive speed control, e.g., from a throttle. It may further receive vehicle speed, e.g., from a speedometer.

[0042] At 720, the SCS 610 compares the steering angle with a first threshold. If the steering angle is less than the first threshold, operation proceeds to 740, whereupon the SCS 610 applies pure vector steering, i.e., by deforming the tracks 120 into curved shapes, such as shapes 310L and 310R. The SCS 610 may compute wheel angle 650, wheel extension 660, and wheel speed 670 as described above to so as to accomplish vector steering with minimal skidding.

[0043] Returning to 720, if the steering angle is greater than the first threshold, then at 730 the SCS 610 determines whether the steering angle exceeds a second threshold, which is greater than the first threshold. If so, operation proceeds to 760, whereupon the SCS 610 applies pure skid steering, i.e., effecting steering of the vehicle 110 by driving the two tracks 120L and 120R at different speeds but without deforming the tracks 120 into curved shapes.

[0044] If at 730 the steering angle is greater than the first threshold but less than the second threshold, operation proceeds to 750, whereupon the SCS 610 applies a hybrid steering mode, which blends vector steering with skid steering. For example, as the steering angle varies between the first threshold and the second threshold, the SCS 610 changes the balance of vector steering and skid steering to use more vector steering for angles close to the first threshold and to use more skid steering for angles close to the second threshold. In some examples, the proportion of vector steering to skid steering is varied linearly between the two thresholds.

[0045] Regardless of which steering mode is selected, the SCS 610 drives the associated actuators (e.g., steering, thrust, and power) in accordance with the selected mode. Operation then returns to act 710, whereupon steering input 620 is again received and the process repeats. Operation may proceed in this fashion indefinitely.

[0046] An improved technique has been described for steering a tracked vehicle 110. The technique includes controllably deforming at least a portion of a vehicle's track 120 into a curved shape, causing the vehicle 110 to follow a curve-shaped path as it drives. As the vehicle 110 naturally tends to follow a curved path defined by the track's curvature, steering is accomplished with greatly reduced skidding against the ground. Drivers thus have greater control over steering and enjoy smoother rides, while ground surfaces and vehicle components are spared much of the damage that normally results from skid steering. Detection is easier to avoid, as well, as vector steering causes less detectable disturbance to ground surfaces.

[0047] Having described certain embodiments, numerous alternative embodiments or variations can be made. Further, although features have been shown and described with reference to particular embodiments hereof, such features may be included and hereby are included in any of the disclosed embodiments and their variants. Thus, it is understood that features disclosed in connection with any embodiment are included in any other embodiment.

[0048] Further still, the improvement or portions thereof may be embodied as a computer program product including one or more non-transient, computer-readable storage media, such as a magnetic disk, magnetic tape, compact disk, DVD, optical disk, flash drive, solid state drive, SD (Secure Digital) chip or device, Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), and/or the like (shown by way of example as medium 780 in FIG. 7). Any number of computer-readable media may be used. The media may be encoded with instructions which, when executed on one or more computers or other processors, perform the process or processes described herein. Such media may be considered articles of manufacture or machines, and may be transportable from one machine to another.

[0049] As used throughout this document, the words “comprising,” “including,” “containing,” and “having” are intended to set forth certain items, steps, elements, or aspects of something in an open-ended fashion. Also, as used herein and unless a specific statement is made to the contrary, the word “set” means one or more of something. This is the case regardless of whether the phrase “set of” is followed by a singular or plural object and regardless of whether it is conjugated with a singular or plural verb. Also, a “set of” elements can describe fewer than all elements present. Thus, there may be additional elements of the same kind that are not part of the set. Further, ordinal expressions, such as “first,” “second,” “third,” and so on, may be used as adjectives herein for identification purposes. Unless specifically indicated, these ordinal expressions are not intended to imply any ordering or sequence. Thus, for example, a “second” event may take place before or after a “first event,” or even if no first event ever occurs. In addition, an identification herein of a particular element, feature, or act as being a “first” such element, feature, or act should not be construed as requiring that there must also be a “second” or other such element, feature or act. Rather, the “first” item may be the only one. Also, and unless specifically stated to the contrary, “based on” is intended to be nonexclusive. Thus, “based on” should not be interpreted as meaning “based exclusively on” but rather “based at least in part on” unless specifically indicated otherwise. Although certain embodiments are disclosed herein, it is understood that these are provided by way of example only and should not be construed as limiting.

[0050] Those skilled in the art will therefore understand that various changes in form and detail may be made to the embodiments disclosed herein without departing from the scope of the following claims.