Patent Application
20220371362
The subject matter herein relates to novel drive designs for mobility applications. More specifically, it relates to a passive-articulated wheel system for driving over various terrain surfaces, including stairs.
Existing drive mechanisms utilize various heavy and complex assemblies to traverse rough terrain and climb stairs. Round wheels that are used to traverse rough terrain are large in diameter such that the height of terrain does not exceed the radius of the wheel, wherein rough terrain is defined as containing obstacles with vertical elements larger than two thirds radius of the wheel. Smooth surfaces are defined as not having obstacles greater than one twentieth the radius of the wheel. Conventional mechanisms that use tracks are typically inefficient due to the use of large, heavy, and long rotating treads to gain traction on rough surfaces. These inefficiencies in tracked driving result in slow platform speed or large power use to achieve higher speeds. Other solutions have attempted various add-ons and/or mechanisms to improve wheel performance over rough terrain but have failed to meet the mobility requirements of parts durability, reduced vibration driving over smooth surfaces, and/or shock absorption from impacts.
For mobility platforms, the ability to climb stairs, traverse rough terrain, drive at low and high speeds without excessive vibration, and survive impacts in rough terrain as well as drops in excess of several feet may be useful. Some mobility applications including robotics are hampered by weight in many ways, so light weight solutions may be useful for increased battery life, better power efficiency, drop survivability, shipping costs and portability. The use of complex pivoting mechanisms to climb stairs can be heavy and leave parts at risk of breaking during drops. Heavy and long tracked mechanisms reduce the portability and increase weight, as well as offering minimal area for shock load distribution in impact scenarios. Stairs offer a difficult challenge for mobility applications including small robotic devices. The steep and high walls are difficult to grab onto and climb without complex actively articulated joints. The platform may be lifted vertically while also providing its own forward motion, Overall, there is no current wheel design for mobility platforms and the like that is lightweight, portable, and impact resistant that is able to climb stairs.
The present disclosure includes embodiments of wheel apparatus that provides a solution of one or more, or all, the above stated problems, for example by providing a Selective Flex Zone (SFZ) wheel which meets the complex design requirements with minimal parts implementation and robust construction using a durable single construction elastomer.
An embodiment of the present disclosure is a wheel apparatus. The wheel apparatus may include one or more rigid climbing members that extend to an outer perimeter of the wheel apparatus. The one or more rigid climbing members are configured to maintain shape and relative position over all surfaces the wheel apparatus encounters. The wheel apparatus includes one or more selective flex zones located adjacent to rigid climbing members, constructed to be passively compressed when the wheel apparatus encounters an obstacle in the path of the wheel apparatus; and one or more support zones located adjacent to the one or more selective flex zones that provide support for smooth rotary motion when not traversing obstacles.
In one or more embodiments, the one or more selective flex zones support the weight of a mobility platform on flat surfaces enabling low vibration driving over surfaces without obstacles, and wherein the one or more selective flex zones deform when subjected to climbing load or an obstacle to expose at least one of the one or more rigid climbing members of the wheel apparatus that provides traction when traversing the climbing load or the obstacle. At least a portion of the selective flex zone, which is subjected to the climbing load or the obstacle, is configured to be deflected inwards from the outer periphery of the wheel apparatus.
In one or more embodiments, one or more, or each, climbing member is adjacent to two selective flex zones allowing the climbing member to be exposed when an obstacle is encountered in either direction of rotation.
In one or more embodiments, the climbing member is mechanically isolated to each of the two adjacent selective flex zones at the outer periphery of the wheel apparatus.
In one or more embodiments, a center of the wheel apparatus may comprise a compression zone configured to absorb and dissipate forces incurred from dropping or throwing a mobility platform to which the wheel apparatus is attached.
In one or more embodiments, the side of the wheel apparatus further comprises one or more side impact reduction zone constructed of one or more convex surfaces that facilitate self righting of a mobility platform to which the wheel apparatus is attached.
In one or more embodiments, the wheel apparatus is formed from a single elastomer material, the outer perimeter of the wheel apparatus further comprises locations for at least one of replaceable tread inserts and replaceable traction pads on the climbing face of the one or more rigid climbing members.
In one or more embodiments, one or more wheel apparatuses described herein may be provided, wherein one or more, or each, of the one or more wheel apparatuses may be attached to a mobility platform.
Embodiments of the present disclosure include a selective flex zone (SFZ) wheel apparatus. The wheel apparatus includes a rigid climbing member, a support zone, a selective flexibility zone, and an impact compression zone. SFZ wheels as described herein are configured to maintain their circular shape and operate in a rolling motion over smooth surfaces and to change their shape to operate in a climbing motion over rough surfaces. The SFZ wheel may also maintain its circular shape for optimum rolling motion when it encounters a rough surface. The rough surface induced climbing loads cause internal movement of components within the wheel to change from its smooth surface circular shape to the climbing shape. The actuated change from smooth surface shape to climbing shape due to the induced rough terrain climbing loads defines the passive articulation of the SFZ wheel.
The SFZ wheel uses a core wheel design with a novel arrangement of one or more rigid climbing members in combination with flexibility zones and support zones in order for the wheel to grip stairs for climbing and for traversing rough terrain. When traveling over a smooth surface, the SFZs also allows the wheel to roll in a rotation that minimizes drive vibration as the SFZ maintains its shape. Additionally, all components of the wheel may be manufactured as a single component from flexible elastomer to allow the wheel to compliantly respond to impacts that are often encountered when deploying mobility platforms, such as tossing or dropping them from moving vehicles. The SFZ wheels, when mounted on a mobility platform, can climb standardized stairs using simple rotary drive motion. The SFZ wheels, when embodied on a three or more wheeled mobility platform that has the front and rear spaced appropriately for the vertical face and top surface of the stair allow efficient stair climbing. The SFZs are designed to be passively activated by the presence of a targeted load revealing the rigid climbing member zone, thereby allowing for additional grip and function.
The climbing member zones include a climbing member arm in one or more positions symmetrically located around the wheel axis of rotation. The climbing member zone section of the wheel has a symmetrical hammer-shaped climbing member head where there is a high traction pad on the climbing member face 403. When climbing stairs, the climbing member face of the climbing member is configured to approximately match the contact angle of the stair top surface for increased traction. The support zone is placed between the rigid climbing members. The support zone, however, does not support the area directly in front of the climbing member zones, thus allowing for each individual selective flex zone to compress inwardly in that space.
The outer edge of the support zone lies along the outer perimeter of the wheel. The selective flex zone may include cantilever member reaching from and attached to the support zone. An outermost end of the cantilever member aligns with the outer perimeter of the wheel. The outermost end of the cantilever member is truncated just before the climbing member. The cantilever member is supported using columns configured to remain supportive under driving forces encountered on smooth surfaces and buckle or flex when subjected to the additional forces induced when climbing stairs or other steep and rough surfaces. An advantageous feature of a single body construction is that it allows for significantly reduced parts and optimal lightweight construction.
The SFZ wheel is constructed using an elastomer. In one example, an entirety of the wheel is formed with an elastomer. While an elastomer is used to form the material, materials with similar properties may be used as well. An elastomer material is defined as having a high failure strain along with a low Young's modulus compared to other materials, such as plastics and polymers which are more brittle. High failure strain is defined as having a percent elongation greater than one hundred percent at yield and low Young's modulus is defined as less than one Giga pascal. In one or more embodiments, the SFZ wheel could be designed by someone skilled in the art to deflect only within the elastic zone of a materials properties as defined in the stress strain curve. The SFZ wheel constructed from elastomer material may be stretched and/or flexed greater than 100 percent elongation and return to its initial form due to the elastic characteristic of the material, high strain failure and low Young's modulus. Properties of elastomers increase durability by repeatedly returning to the original shape without being deformed permanently. In one or more embodiments, perhaps for example using an elastomer based SFZ wheel, the deflection of the members in the zones are defined as minimal when the elongation is less than five percent of full elastic strain and considered large when at five percent or greater of full elastic strain.
One or more SFZ wheels 100 are configured to be coupled to a mobility platform (not shown), thereby enabling the mobility platform to move on smooth surfaces and rough terrain as well as to climb stairs or obstacles. The mobility platform, for example, may include, but is not limited to, a robot, a car, an all-terrain vehicle, or a wheelchair. The mobility platform may comprise a mechanical and/or electrical mechanism for moving the SFZ wheel 100, when the SFZ wheel 100 is coupled to the mobility platform. The SFZ wheel 100 allows for the mobility platform to drive over smooth surfaces with an axle height displacement less than ten percent of the diameter of the wheel, as referenced to the surface being traveled over. The flexible elastomer and design absorbs omnidirectional impacts to the mobility platform.
As depicted in
In the example depicted in
The SFZ 202 is the zone in the perimeter of the SFZ wheel 200, where the outer contact edges 204 connecting to the central compression zones 205 and the support zones 203 of the SFZ wheel 200 creates a support that may compress (as depicted in
The climbing member zone 201 including the climbing member 207 is a rigidly designed section, based on the elastomer material properties. The climbing member 207 reaches the outer perimeter of the SFZ wheel 200 and has a hammer-shaped head 402, as depicted in
A support zone 203 of the SFZ wheel 200 is located in between two selective flex zones 202 along the perimeter of the SFZ wheel 200, as depicted in
The central compression zone 205 may absorb large impacts and/or may act as a shock absorber for the connected apparatus. The central compression zone 205 comprises a plurality of radial members. The shape and size of the radial members in the central compression zone 205 are designed to compress toward the center of the SFZ wheel 200 when an impact force greater than climbing and driving loads acts inwards toward the center of the wheel. The thickness and shape of the elastomer are designed to have minimal deflection under driving loads and large deflection under loads greater than climbing loads. The center of the central compression zone is attached to the driving axle of the mobility platform. The radial members are rigid enough that forces acting at the outer perimeter of the SFZ wheel 200 parallel to the driving axis at the center of the SFZ wheel 200 do not cause the wheel to fold over due to the flexibility of the elastomer. The central compression zone 205 has radially extending members that maintain torsional rigidity due to thickness and shape when torque from the central hub is acting on the climbing member 207 at the outer perimeter/periphery of the SFZ wheel 200.
The side impact reduction zone SIRZ 301 dissipates shock loads enacted along the driving axis of the SFZ wheel 200. The elastomer shapes of the SIRZ 301 are designed to compress under impact loads, the distance of the compression lessens the peak impact forces on the main body connected to the SFZ wheel 200. The SIRZ is constructed of one or more convex surfaces that reach from the maximal height at the center of the wheel to the perimeter of the wheel. In one or more embodiments, the SIRZ 301 may include the rounded profile it creates perpendicular to the main diameter of the wheel. The rounded profile and the maximal height of the profile arc 302. creates an unstable system so that the connected mobility application (603, 605) rolls back to the main driving surface of the wheel. Wherein the maximal height to the perimeter of the wheel creates a surface that when rested on the center of mass of the mobility platform falls outside of the created surface base.
An implementation of typical use is robotic applications. Often in a hazardous area for the user to enter, the application may be reliable at self-righting 301 and/or getting over obstacles including steps without further assistance. There may be a risk of the robot falling, perhaps for example due to the hazards of the area and/or to get to a certain hazardous area. These devices are often deployed through a drop or throw and the ability to self right while in motion may be useful.
Replaceable tread inserts are located around the perimeter of the wheel. The treads may be a wear item that may be replaced over time and have material properties that have a greater coefficient of friction on surfaces than the elastomer. On the face of the climbing member 403, the surface may be coated and/or may have a replaceable insert that creates a higher coefficient of friction with surfaces than the elastomer.
