WO2014120110A1

WO2014120110A1 - Rolling resistance reduction from improved wheel systems

Info

Publication number: WO2014120110A1
Application number: PCT/US2013/000139
Authority: WO
Inventors: Andrew Howells
Original assignee: Andrew Howells
Priority date: 2013-01-30
Filing date: 2013-05-24
Publication date: 2014-08-07

Abstract

The present disclosure is directed to vehicle wheel systems having multiple wheels on one or more axles. The wheels on each axle exhibiting characteristics that differ from the wheels on other axles. The axles of the wheel systems are configured to adjust the amount of contact the wheels are making with the ground relative to the wheels on other axles. In some examples, the vehicle wheel system includes a lift assembly. In some further examples, the vehicle wheel system includes a control system for receiving and interpreting driving conditions, and an actuator to enable the axle adjustment.

Description

ROLLING RESISTANCE REDUCTION FROM IMPROVED WHEEL SYSTEMS

TECHNICAL FIELD

[0001] The present disclosure relates generally to vehicle wheel systems. In particular, vehicle wheel systems capable of receiving input and dynamically altering wheel system characteristics are described.

BACKGROUND ART

[0002] Known wheel systems are not entirely satisfactory for the range of applications in which they are employed. For example, existing wheel systems have fixed handling

characteristics requiring modification for adapting to various driving conditions.

[0003] The dynamic nature of a vehicle and the driving environment create changes on an ongoing basis to driving conditions. The conditions can include such things as driving surface topography, ambient temperature, velocity, cornering speed, surface incline, elevation, climate, and the disposition of other vehicles or collision hazards, among others.

[0004] Existing vehicle wheel systems are not well configured for adapting to changing conditions and the result is decreased vehicle performance. In certain conditions, a vehicle experiences loss of control, increased fuel consumption, diminished ride quality, increased braking distance, decreased acceleration, or higher rolling resistance.

[0005] In addition, conventional wheel systems are poorly configured for adjustments en route. Typical multi-axle multi-wheel systems have wheels with approximately fixed relative positions, apart from steering wheels and the slight relative motion due to suspension systems. Furthermore, the wheels and tires attached to the fixed axles exhibit approximately fixed driving characteristics. The fixed nature of existing wheel systems makes them unable to dynamically optimize performance by varying position and driving characteristics.

[0006] The problems exhibited with current wheel system designs are especially apparent when the vehicle in question has a wide wheel base, a long chassis, dual or tandem axles, a high Gross Vehicle Weight (GVW), or a tall overall profile. Each of these characteristics individually or a combination thereof can increase the effect of changes in system or environmental conditions on vehicle performance.

[0007] Finally, current wheel systems lack a satisfactory means of receiving and assessing pertinent driving condition data. Often, existing systems rely solely on a driver for interpreting and reacting to changes in environment and system conditions. Much of the time, l of 16 the driver is unaware of the existence of subtle but important conditions or is ill prepared to quickly respond to them.

[0008] Thus, there exists a need for a wheel system that improves upon and advances the design of known vehicle wheel systems. Examples of new and useful vehicle wheel systems relevant to the needs existing in the field are discussed below.

SUMMARY OF INVENTION

[0009] The present disclosure is directed to vehicle wheel systems having multiple wheels on one or more axles. The wheels on each axle exhibiting characteristics that differ from the wheels of other axles. The axles of the wheel systems are configured to adjust the amount of contact the wheels are making with the ground relative to the wheels on other axles. In some examples, the vehicle wheel system includes a lift assembly. In some further examples, the vehicle wheel system includes a control system for receiving and interpreting driving conditions, controlling an actuator to enable the axle adjustment

BRIEF DESCRIPTION OF DRAWINGS

[0010] Fig. 1 is a side view of a first example of a semi-truck and trailer incorporating an improved wheel system.

[0011] Fig. 2 is a rear view of the semi-truck and trailer incorporating an improved wheel system depicting an adjustable concentric axle.

[0012] Fig. 3 is a diagram of the improved wheel system including a range of inputs, a control system, and one or more adjustable axles.

[0013] Fig. 4 is a rear view of the semi-truck and trailer depicting an improved wheel system depicting an adjustable concentric axle with its low pressure tires engaged with the ground and high pressure tires clear of the ground mounted on another concentric axle.

[0014] Fig. 5 is a rear view of the semi- truck and trailer incorporating an improved wheel system depicting an adjustable concentric axle with its high pressure tires engaged with the ground and low pressure tires clear of the ground mounted on another concentric axle.

[0015] Fig. 6 is a side view of a second example of an improved wheel system including an adjustable axle featuring high pressure tires and a separate axle featuring low pressure tires.

[0016] Fig. 7 is a rear view of the second example of an improved wheel system of Fig. 6 where the axle featuring the low pressure tires is in a raised position.

[0017] Fig. 8 is a rear view of the third example of an improved wheel system where the axle features both the low pressure tires and high pressure tires, and the high pressure tires are fully inflated, such that the low pressure tires are not in contact with the ground.

[0018] Fig. 9 is a rear view of the third example of an improved wheel system where the axle features both the low pressure tires and high pressure tires, and the high pressure tires are partially inflated, such that the low pressure tires are also in contact with the ground.

DETAILED DESCRIPTION OF EMBODIMENTS

[0019] The disclosed wheel systems will become better understood through review of the following detailed description in conjunction with the figures. The detailed description and figures provide merely examples of the various inventions described herein. Those skilled in the art will understand that the disclosed examples may be varied, modified, and altered without departing from the scope of the inventions described herein. Many variations are contemplated for different applications and design considerations. However, for the sake of brevity, not all contemplated variations are individually described in the following detailed description.

[0020] Throughout the following detailed description, examples of various wheel systems are provided. Related features in the examples may be identical, similar, or dissimilar in different examples. For the sake of brevity, related features will not be redundantly explained in each example. Instead, the use of related feature names will cue the reader that the features with a related name may be similar to the related feature in an example explained previously.

Features specific to a given example will be described in that particular example. The reader should understand that a given feature need not be the same or similar to the specific portrayal of a related feature in any given figure or example.

[0021] With reference to Figs. 1 - 5, a first example of a vehicle wheel system, wheel system 10, will now be described. Wheel system 10 includes a first wheel 20, operatively connected to a first axle 30, a second wheel 40, operatively connected to a second axle 50 both wheels being disposed on a first lateral side 12 of a vehicle 14.

[0022] Wheel system 10 further includes an actuator 60 operatively connected to second axle 50, configured to selectively raise and lower second axle 50 in response to input from control system 70, which in turn receives input from various data sources such as the sensor 81.

[0023] Collectively, components of wheel system 10 combine to create a vehicle wheel system capable of selectively adapting vehicle handling characteristics in response to driving condition data.

[0024] Wheel system 10 is attached at various locations along a chassis 16 of vehicle 14.

In the example, vehicle 14 is a standard semi-truck as commonly known in the art. In another example the vehicle is a military transport vehicle. In a different example the vehicle is a motor home. In yet other examples the vehicle is any vehicle that relies on wheel systems for locomotion.

[0025] As shown in Fig. 1, chassis 16 defines the entirety of the vehicle not expressly listed as components of wheel system 10. In this example the chassis includes a cab, a motor compartment, a fuselage, a hitch, a trailer, a frame, a sub-frame, and other vehicle components not expressly set forth as parts of wheel system 10. In other examples the chassis includes more, less, or the same number and types of components listed here.

[0026] Chassis 16 is described here generally, representing an attachment surface between vehicle 14 and the components of wheel system 10 and need not limit or expand the application of wheel system 10 as described.

[0027] The following paragraphs describe a recommended implementation of the improved vehicle wheel systems, wheel system 10, with reference to the included Figs. 1 - 5. The wheel 20 is an example member of the first set of wheels. The wheel 40 is an example member of the second set of wheels. The actuator 60 is an example of the actuators described below.

[0028] In a recommended implementation of the improved vehicle wheel systems, the vehicle would include a first set of wheels which are designed for low rolling resistance. These would be different from conventional road vehicle wheels in that they would be pneumatic tires with significantly higher internal pressure or non-pneumatic tires such as semi-rigid or rigid tires, so as to reduce rolling resistance. To reduce rolling resistance, they may optionally have a different tread pattern than conventional tires of road vehicles. This tread pattern may be more simple, or the tires may have no tread at all. They may also have a slightly different material composition than conventional tires, such that the elastomer material of which they are primarily made would be either slightly harder or slighdy softer than the elastomer material which conventional pneumatic tires are primarily made of. Conventional pneumatic tires of road vehicles typically operate with a pressure difference between internal and external air near 240 to 380 kilo Pascals. Implemented are recommended to consider having the low rolling resistance tires operate at pressure as high as 480 to 900 kilo Pascals.

[0029] The recommended implementation of the improved vehicle wheel systems would also include a second set of wheels. These wheels would be distinct from the first set in that they would offer traction characteristics significantly closer to that of conventional tires of heavy vehicles. The defining characteristic of the set is that it would offer traction nearly as good as, or better than conventional road vehicle wheels would when operated under adverse conditions that reduce traction of tires, and that are likely to be encountered on roads, such as wet or icy roads, roads with small amounts of loose gravel or oil on them, etc. The wheels may achieve this by having pneumatic tires which are designed to operate at pressure significantly closer to conventional tires of road vehicles. The tread patterns on the tires and the material composition may be closer to that of conventional tires as well.

[0030] The first set of wheels would be robust enough, and be distributed about the vehicle in such a way that the vehicle could safely rely on the first set of wheels to support the majority of the mass of the vehicle while the vehicle is driving at typical driving speeds.

Likewise, the second set of wheels would be robust enough, and be distributed about the vehicle in such a way that the vehicle could safely rely on the second set of wheels to support the majority of the mass of the vehicle while the vehicle is driving at typical driving speeds. An actuator system would be included with the ability to quickly raise or lower many of the wheels of the vehicle, such that it could shift the majority of the weight of the vehicle from being supported by the first set of wheels, to being supported by the second set of wheels. The system would be able to perform such transitions rapidly and frequently, avoiding the need for extensive effort from human operators. It is recommended that the system could perform such transitions in a time period of less than 900 seconds. It is valuable for the system to be able to perform such transitions in less than 20 seconds and while the vehicle is driving at typical driving speeds. This would allow a control system to monitor driving conditions and automatically switch the vehicle between the different wheel sets according to rapidly changing environmental or driving conditions.

[0031] The recommended implementation of the improved vehicle wheel systems would be operating in the following way. The main intent of the design may be to improve fuel efficiency without compromising safety by compromising traction. In order to accomplish this, it is ideal to operate the wheel system in such a manner that the vehicle is usually supported primarily by the low rolling resistance set of wheels when it is driving in conditions in which it is safe to do so. The low rolling resistance wheels must be designed in such a way that it is safe to rely primarily on them a significant portion of the time. Whenever it is not safe to rely on the low rolling resistance wheels, the vehicle would need to rely on the second set of wheels which offer better traction. The control system would typically be able to detect such conditions and transition the vehicle accordingly just in time to ensure the correct set of wheels is in use.

[0032] Conditions which may be detected by sensors supplying essential information to the control system 70 may include road conditions, driving conditions, and vehicle conditions.

[0033] Examples of relevant road conditions include temperature. If the sensors report that the road or ambient air is below freezing temperature, there may be a risk that traction could be reduced due to ice on the road. The sensors may detect water on the road or rain or other moisture in the air. The control system may be designed to respond by shifting to the set of wheels which offer better traction under these conditions. The control system may receive weather information well in advance so as to assist in predicting road conditions. Road conditions also may include information about the quality of the roads, stored in the form of a map readable by the control system. Examples of quality information may include information about the sharpness of turns, steepness of incline, the quality of pavement, location of intersections, location of temporary road hazards such as rock slides, construction, or vehicle accidents. Such a map may, instead of including information about the quality of the roads, merely encode information instructing the control system as to which wheel set should be primarily relied on in various locations, although this may prevent the control system from dynamically taking road conditions, driving conditions and vehicle conditions unknown to the map maker into consideration, unless sufficient other sources of information are available . Alternatively, transmitter systems, such as a radio transmitter could supply warnings to the control system. For example, a transmitter may be installed to warn the control system of a location where a sharp turn exists, of weather conditions, or where an accident, construction, or other road hazards exist. The control system may also be able to communicate with other vehicles, for example by radio or optical signals. If the control system detects that the vehicle is at risk of needing to maneuver abruptly to avoid a collision, it may trigger the actuators to switch to the wheel set which offers better traction.

[0034] Examples of relevant driving conditions include speed and acceleration, including turning. Driving characteristics may also include the characteristics of the driver. For example, some drivers may have a tendency to accelerate or decelerate more aggressively than others. The control system may be designed to respond by shifting to the set of wheels which offer better traction under these conditions. The control system may be designed to accept manual input from a human operator to override its default behavior. Furthermore, the control system may include optical sensors or other sensors, to look at road conditions ahead, such as the disposition of other vehicles, or to sense the disposition of the hands or feet of a human operator relative to control pedals, a steering wheel, or other control interfaces, to predict when the operator is about to turn, accelerate, or decelerate aggressively, and take this into consideration when determining which mode the vehicle should be in. An example of a recommended manner in which the control system should respond to driving conditions is the following. If the vehicle exceeds a certain speed which it should never deliberately exceed, the control system is recommended to immediately switch to the set of wheels which offer better traction, since it is likely the vehicle is at risk of losing traction control under such circumstances. [0035] Examples of relevant vehicle conditions include the mass and distribution of the load, tire pressure, the type of tires which are installed, the age, wear, or temperature of the tires, the temperature or the brakes, the configuration of trailers, etc.

[0036] With such a broad variety of inputs possible, and considering that the inputs to the control system described above may change rapidly, the reader should understand that there is great value in designing the implementation in such a way that the system can respond as quickly as possible to changing conditions. There is value in being able to complete transitions in as little as less than 500, or even less than 50 milliseconds to ensure maximum traction in emergencies while also maximizing the fraction of driving time that the low rolling resistance set of wheels may be relied on. Note that the reader should not assume that the control system would always cause the vehicle to rely exclusively on one set of wheels or the other, but not both simultaneously, apart from during transitions where it is deliberately raising or lowering the wheels of one set relative to the other. It may instead be useful to have some wheels from one set in use while some from the other are also deliberately in use. This may be useful to reduce the pressure that the wheels apply to the ground, for example when driving off road on soft terrain, or to compensate for a damaged tire.

[0037] While the above paragraphs focused on the differences between the tires of the 2 sets, and the operation of the control system, the following discussion is focused on mechanical design. Consider a design such as the wheel system shown in figs. 1 - 5. In this design, we have a large diameter hollow short axle 50 with 2 wheels from the second set mounted on it, one, such as the wheel 40, at each end. A smaller diameter longer axle 30 is located inside of the axle 50, in approximately a coaxial arrangement. There are 2 wheels from the low rolling resistance first set mounted at the ends of the axle, including the low rolling resistance wheel 20. Such a coaxial axle arrangement may allow reducing the cost and mass of the chassis of a vehicle by allowing the axles that support wheels of either set to share attachment points to the chassis, as well as suspension system components, and brakes. To minimize problematic rocking of the vehicle from side to side, an implementer is recommended to place some of the wheels from the first set in a more lateral position, while on another axle, one or more of the wheels from the first set would be in a more medial position relative to the nearest wheel from the second set. If the implementer is less concerned with this side to side swaying of the vehicle, an implementer may favor placing more of the wheels from the second set which offer better traction in a more lateral position, since when turning corners, the vehicle will tend to require better traction, and it will lean in such a way that more pressure is placed on the more lateral wheels relative to the medial wheels. The ground is identified as 90 in the figures.

[0038] An alternative to the coaxial axle arrangement described above is a tandem axle arrangement. Such a design, designated 110, is shown in Figs. 6 - 7, the reference characters in the figure are identical to their counterparts in the preceding figures, except prefixed with the digit "1." As with the other figures, wheels from the second set, which more closely resemble conventional wheels, are shown with additional lines in their representative symbols to indicate the presence of more tread, so as to distinguish them from the low rolling resistance wheels of the first set which have less or no tread. As the reader can see, on each axle, all of the wheels on each axle are from the same set as the other wheels on the same axle. It is possible for a vehicle to use the coaxial arrangement for some axles, and the tandem arrangement for others.

[0039] To minimize the cost of the system, it is not necessary to have actuators capable or raising and lowering both set of wheels. Instead, it is only necessary to raise or lower the axles of just one of the sets of wheels relative to the axles of the other. To minimize the cost of the system, it is not necessary to raise an unfavored set of wheels totally off of the ground. It is recommended to raise a temporarily unfavored set only approximately the minimum amount necessary, which may mean that even in a fully raised position, its wheels may still frequently touch the ground, albeit with generally reduced pressure.

[0040] Rolling resistance contributes greatly to the inefficiency of modern road vehicles.

An implementer should expect an affordable implementation to offer a reduction in vehicle energy consumption approaching 15% for vehicles resembling conventional heavy commercial road vehicles in typical applications. Furthermore, systems which can conveniently shift weight between wheel sets while driving may allow tires to last longer, reducing the littering of treads along roads, reducing wear on roads by reducing the amount of time that vehicles spend driving on studs mounted into tires, reduce road noise, and reduce pollution.

[0041] Although it is not an essential characteristic necessary to gain the benefits of the system described above, it may be helpful if the actuators also support a mode wherein most of the wheels of both sets are used approximately equally to support the weight of a vehicle. This would be helpful in situations where a vehicle is heavily loaded, or where the ground is particularly sensitive to damage.

[0042] It is also possible to accomplish the above goal of changing the characteristics of a wheel system to minimize rolling resistance by relying on wheels with minimal tread and compressibility and quickly switching to tires which offer better rolling resistance under the control of a control system which relies on various inputs such as driving conditions and road conditions as described above, while relying on different mechanical designs which are similarly effective. One possibility is to use high pressure tires with minimal tread, combined with actuators which are capable of quickly changing the pressure of the tires, preferably while the vehicle is driving. The tires may feature minimal or no tread in areas that are the most in contact with the ground when the tire is inflated to high pressure, such as the medial portion of the tire. The tire may change shape somewhat when deflated such that the more lateral portions of the tire become more in contact with the ground. These portions may feature more tread so as to improve traction when the tire is partially deflated. Such a design may be operated in a manner similar to the above described mechanical designs, except that instead of switching which tires are more in contact with the ground, the system may instead operate by varying the pressure of the tires. In lower rolling resistance modes, the tires are recommended to have internal pressure substantially higher than that of conventional tires, similar to what is recommended for the previous designs. In the modes offering better traction, the tires are recommended to have internal pressure substantially closer to that of conventional tires.

[0043] There is a practical option for achieving the benefit of a tread pattern well suited to road conditions that are adverse to good traction which may be used as an alternative or in combination with the above described approach. That is to use an additional tire, with slightly smaller diameter than the high pressure tire. This additional tire is recommended to have diameter such that it is less in contact with the ground than the high pressure tire while the high pressure tire is at full pressure. The additional tire is recommended to have internal pressure similar to conventional tires, and substantially more tread than the high pressure tire. The high pressure tire is recommended to have internal pressure, when operating in its low rolling resistance mode, and minimal or no tread similar to what is recommended for the low rolling resistance tires of the previous designs. When switching to the mode of operation which offers better traction in adverse conditions, the control system would trigger actuators to reduce drastically the internal pressure of the high pressure tires such that their pressure is close to or less than that of conventional tires. This may reduce the diameter of the high pressure tire such that the adjacent additional tire would then be much more in contact with the ground relatively. If this does not reduce the diameter adequately, it may be possible to increase the pressure of the additional tire as well. Alternatively, the system could be designed such that only pressure of the low pressure tires is adjusted. To reduce the cost and complexity it is preferable to design the system in such a way that only 1 of the 2 types of tires in each set of adjacent tires of opposite types would have internal pressure adjusted by the actuators. [0044] An example of the design 210 which varies driving characteristics of vehicle 214 by varying tire pressure is shown in figs 8 - 9. The lateral wheels such as 220 feature high pressure tires which in fig. 8 are fully inflated such that the medial wheels such as 240 which feature low pressure tires are elevated clear of the ground 290. Both types of wheels may be mounted on the same axle 230. The medial portion 225 of the outer surface of the high pressure of wheel 220 is more in contact with the ground than the tread 226 of the lateral portions of the tire in fig. 8. In fig. 9, the high pressure tires are partially deflated, such that the vehicle is lowered to the point where it is supported significandy by the low pressure tires. Furthermore, the tread such as 226 from the sides of the high pressure tires has been lowered onto the ground as well. Note that in this example, the high pressure tires are lateral of the low pressure tires, but this could be reversed.

Claims

1. A wheel system for a vehicle including a chassis, comprising:

a first wheel on a first lateral side of the vehicle;

a second wheel on the first lateral side of the vehicle and providing a different driving characteristic than the first wheel;

a first axle operatively connected to the chassis and coupled to the first wheel, the first axle defining a first axis about which the first wheel may rotate;

a second axle operatively connected to the chassis and coupled to the second wheel, the second axle:

defining a second axis about which the second wheel may rotate, the second axis extending substantially in line with the first axis, and

being vertically movable between a raised position where first wheel is in contact with the ground to a greater degree than the second wheel and a lowered position where the second wheel is in contact with the ground to a greater degree than the first wheel; and

an actuator operatively connected to the chassis and to the second axle, the actuator being configured to selectively move the second axle between the raised position and the lowered position while the vehicle is in transit.

2. The wheel system of claim 1, further comprising a control system configured to dynamically receive driving condition data corresponding to certain driving conditions and to dynamically activate the actuator to selectively move the second axle between the raised position and the lowered position based on the driving condition data.

3. The wheel system of claim 1, wherein the first axle has one or more wheels providing similar driving characteristics and the second axle has one or more wheels providing driving characteristics different than those of the first axle.

4. The wheel system of claim 3, wherein the first axle is disposed within the second axle.

5. The wheel system of claim 3, wherein the second axle is disposed within the first axle.

6. The wheel system of claim 1, wherein the first and second axles are arranged in tandem.

7. The wheel system of claim 1, wherein the driving characteristics of the first wheel include reduced rolling resistance.

8. The wheel system of claim 1, wherein the driving characteristics of the second wheel include reduced rolling resistance.

9. The wheel system of claim 1, wherein the vehicle defines a semi-truck.

10. The wheel system of claim 1, wherein the first wheel is equipped with a high- pressure tire.

11. The wheel system of claim 1, wherein the second wheel is equipped with a high- pressure tire.

12. The wheel system of claim 10, wherein the tire has no tread.

13. The wheel system of claim 11, wherein the tire has no tread.

14. The wheel system of claim 1, wherein the second wheel is raised to a position where the second wheel is not in contact with the ground when the second axle is in the raised position.

15. A wheel system for a vehicle including a chassis, comprising:

a first wheel operatively connected to the chassis on a first lateral side of the vehicle: a lift assembly coupled to the chassis on the first lateral side of the vehicle in a position laterally adjacent to the first wheel, the lift assembly being configured to extend and retract while the vehicle is in transit between a raised position proximate the chassis and a lowered position distal the chassis; and

a second wheel mounted an a rotational bearing which is in turn mounted to the lift assembly and providing different driving characteristics than the first wheel, the second wheel being in contact with the ground to a greater degree than the first wheel when the lift assembly is in the lowered position and the first wheel being in contact with the ground to a greater degree than the second wheel when the lift assembly is in the raised position.

16. The wheel system of claim 15, further comprising a control system configured to dynamically receive driving condition data corresponding to current driving conditions and to dynamically activate the lift assembly to selectively extend and retract based on the driving condition data.

17. The wheel system of claim 15, wherein one or more of the wheels, whose vertical position relative to the other wheels of the wheel system is controlled by the lift assembly while the vehicle is in transit, features a tire which is significantly more rigid than a typical pneumatic tire and which features an elastomer covered surface.

18. A wheel system for a vehicle including a chassis, comprising:

a first wheel operatively connected to the chassis on a first lateral side of the vehicle; a second wheel operatively connected to the chassis on the first lateral side of the vehicle in a position laterally adjacent to the first wheel, the second wheel providing a different driving characteristic than the first wheel;

an actuator operatively coupled to the chassis, the actuator being configured to raise and lower the second wheel relative to the first wheel while the vehicle is in transit between a lowered position where the second wheel is in contact with the ground to a greater degree than the first wheel and a raised position where the first wheel is in contact with the ground to a greater degree than the second wheel; and

a control system configured to dynamically receive driving condition data corresponding to current driving conditions and to dynamically activate the actuator to selectively move the second wheel between the lowered position and the raised position based on the driving condition data.

19. The wheel system of claim 18, when driving condition data includes

environmental conditions and system conditions.

20. The wheel system of claim 18, wherein environmental conditions include ambient temperature, humidity, road temperature, elevation, terrain slope, and terrain surface.

21. The wheel system of claim 18, wherein environmental conditions include, braking system temperature, braking system pressure, speed, gross vehicle weight, load distribution, direction, velocity, tire pressure, driver input, and driver driving characteristics.

22. The wheel system of claim 18, wherein the actuator raises and lowers the second wheel relative to the bottom surface of the first wheel by varying the pressure of the first wheel.