Brake turning in an articulated loader

Abstract

A method for turning a power machine (100, 200) is disclosed. The power machine (100, 200) includes a front (212) and a rear (214) frame member that pivot about an articulation joint (216). The front frame member (212) includes left front (226A) and right front (226B) independently controllable motors operably connected to left front (242A) and right front (242B) wheels, respectively. The rear frame member (214) includes left rear (226C) and right rear (226D) independently controllable motors operably connected to left rear (242C) and right rear (242D) wheels, respectively. The method includes pivoting the front (212) and rear (214) frame members in a turn about an articulation angle (376), resulting in first and second inside wheels (242) and first and second outside wheels (242). One method includes rotating the outside wheels (242) in a first direction and rotating the inside wheels (242) in an opposite direction. Another method comprises rotating the front wheels (242A, B) in a first direction and rotating the rear wheels (242C, D) in a second direction that is opposite the first direction.

Description

BRAKE TURNING IN AN ARTICULATED LOADER BACKGROUND

[0001] This disclosure is directed toward power machines. More particularly, this disclosure is directed to tight turning structures and methods in a small articulated loader (SAL) for greatly enhanced maneuverability, particularly in narrow spaces.

[0002] Power machines, for the purposes of this disclosure, include any type of machine that generates power to accomplish a particular task or a variety of tasks. One type of power machine is a work vehicle. Work vehicles, such as loaders, are generally self-propelled vehicles that have a work device, such as a lift arm (although some work vehicles can have other work devices) that can be manipulated to perform a work function. Work vehicles include loaders, excavators, utility vehicles, tractors, and trenchers, to name a few examples.

[0003] The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.SUMMARY

[0004] In an exemplary embodiment, a method for turning a power machine is disclosed. The power machine comprises a front frame member, a rear frame member, and an articulation joint. The front frame member comprises left front and right front independently controllable motors operably connected to left front and right front wheels, respectively. The rear frame member comprises left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively. The front frame member and the rear frame member pivot with respect to each other about the articulation joint. The method for turning the power machine comprises pivoting the front frame member relative to the rear frame member in a turn about an articulation axis so that first and second inside wheels are on the inside of the turn and first and second outside wheels are on the outside of the turn. In an embodiment, the method comprises determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the inside wheel of the frame member that bears more weight, allowing the machine to scrub the other wheels to accomplish a tighter turn than in normal operation.

[0005] In one aspect, a method comprises rotating the first and second outside wheels in a first direction and rotating the first and second inside wheels in a second direction that is opposite the first direction. In another aspect, a method comprises rotating the left front and right front wheelsin a first direction and rotating the left rear and right rear wheels in a second direction that is opposite the first direction.

[0006] This disclosure, in its various combinations, may also be characterized by the following listing of items:1. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively; a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn; and reducing a rotation speed of the first inside wheel of the front frame member or the rear frame member relative to the second inside wheel.2. The method of item 1 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.3. The method of item 1 or 2, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.4. The method of any one of items 1 to 3, wherein reducing the rotation speed of the motor correlating to the first inside wheel results in braking the first inside wheel.5. The method of any one of items 1 to 4, comprising rotating each of the two outside wheels at a greater speed than rotating each of the two inside wheels.6. The method of any one of items 1 to 5, comprising rotating each of the two outside wheels in an opposite direction than rotating each of the two inside wheels.7. The method of any one of items 1 to 6, comprising reversing a rotation direction of the first inside wheel.8. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively; a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn;rotating the first and second outside wheels in a first direction; androtating the first and second inside wheels in a second direction that is opposite the first direction.9. The method of item 8 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.10. The method of item 9, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.11. The method of any one of items 8 to 10, comprising rotating each of the two outside wheels at a greater speed than rotating at least one of the two inside wheels.12. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively; a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn;rotating the left front and right front wheels in a first direction; androtating the left rear and right rear wheels in a second direction that is opposite the first direction.13. The method of item 12 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.14. The method of item 13, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.15. The method of any one of items 12 to 14, comprising rotating each of the two outside wheels at a greater speed than rotating at least one of the two inside wheels.

[0007] This Summary and the Abstract are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary and the Abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter.DRAWINGS

[0008] FIG. 1 is a block diagram illustrating functional systems of a representative power machine on which embodiments of the present disclosure may be advantageously practiced.

[0009] FIG. 2 is a front perspective view of a power machine in the form of an articulated loader on which embodiments disclosed in this specification may be advantageously practiced.

[0010] FIG. 3 is a back perspective view of the articulated loader shown in FIG. 2.

[0011] FIG. 4 is a block diagram illustrating components of a power system of a power machine such as the articulated loader illustrated in FIGS. 2 and 3.

[0012] FIG. 5 is diagrammatic illustration of related components useful in understanding operation of steering an articulated loader.

[0013] FIG. 6A is a perspective view of frame and wheel components for an articulated loader.

[0014] FIG. 6B is an exploded view of components of an exemplary electric wheel assembly.

[0015] FIG. 6C shows the assembled components in another exemplary embodiment of an electric wheel assembly.

[0016] FIG. 7 is a top view of an articulated loader in a right turn configuration.

[0017] FIG. 8 is similar to FIG. 7 but shows the articulated loader in a schematic representation of a first exemplary motion configuration.

[0018] FIG. 9 is a schematic top representation of an articulated loader in a brake turning scenario with a minimal turn radius, in a second exemplary motion configuration.

[0019] FIG. 10 is a top schematic view of an articulated loader in a third exemplary motion configuration.

[0020] FIG. 11 is a top schematic view of an articulated loader in a fourth exemplary motion configuration.DESCRIPTION

[0021] The concepts disclosed in this discussion are described and illustrated by referring to exemplary embodiments. These concepts, however, are not limited in their application to the details of construction and the arrangement of components in the illustrative embodiments and are capable of being practiced or being conducted in various other ways. The terminology in this document is used for the purpose of description and should not be regarded as limiting. Words such as “including,” “comprising,” and “having” and variations thereof as used herein are meant to encompass the items listed thereafter, equivalents thereof, as well as additional items.

[0022] Disclosed embodiments include methods of controlling wheel direction and speed, with knowledge of the articulation angle, to achieve tight turning radius capabilities in a small articulated loader (SAL) for greatly enhanced maneuverability, particularly in narrow spaces.

[0023] These concepts can be practiced on various power machines, as will be described below. A representative power machine on which the embodiments can be practiced is illustrated in diagram form in FIG. 1 and one example of such a power machine is illustrated in FIGS. 2-3 and described below before any embodiments are disclosed. For the sake of brevity, only one power machine is discussed. However, as mentioned above, the embodiments below can be practiced on any of a number of power machines. Power machines, for the purposes of this discussion, include a frame, at least one work element, and a power source that can provide power to the work element to accomplish a work task. One type of power machine is a self-propelled work vehicle. Self-propelled work vehicles are a class of power machines that include a frame, work element, and apower source that can provide power to the work element. At least one of the work elements is a motive system for moving the power machine under power.

[0024] FIG. 1 is a block diagram illustrating the basic systems of a power machine 100 upon which the embodiments discussed below can be advantageously incorporated and can be any of a number of different types of power machines. The block diagram of FIG. 1 identifies various systems on power machine 100 and the relationship between various components and systems. At the most basic level, power machine 100 has a frame 110, a power source 120, and a work element 130. Because power machine 100 shown in FIG. 1 is a self-propelled work vehicle, it also has tractive elements 140, which are themselves work elements provided to move the power machine over a support surface; an operator station 150 provides an operating position for controlling the work elements of the power machine. A control system 160 is provided to interact with the other systems to perform various work tasks at least in part in response to control signals provided by an operator.

[0025] Certain work vehicles have work elements that can perform a dedicated task. For example, some work vehicles have a lift arm to which an implement such as a bucket is attached such as by a pinning arrangement. The work element 130, i.e., the lift arm can be manipulated to position the implement to perform the task. In some instances, the implement can be positioned relative to the work element, such as by rotating a bucket relative to a lift arm, to further position the implement. Under normal operation of such a work vehicle, the bucket is intended to be attached and under use. Such work vehicles may be able to accept other implements by disassembling the implement / work element combination and reassembling another implement in place of the original bucket. Other work vehicles, however, are intended to be used with a wide variety of implements and have an implement interface such as implement interface 170 shown in FIG. 1. At its most basic, implement interface 170 is a connection mechanism between the frame 110 or a work element 130 and an implement, which can be as simple as a connection point for attaching an implement directly to the frame 110 or a work element 130 or more complex, as discussed below.

[0026] On some power machines, implement interface 170 can include an implement carrier, which is a physical structure movably attached to a work element. The implement carrier has engagement features and locking features to accept and secure any of a number of different implements to the work element. One characteristic of such an implement carrier is that once an implement is attached to it, the implement carrier is fixed to the implement (i.e. not movable with respect to the implement) and when the implement carrier is moved with respect to the workelement, the implement moves with the implement carrier. The term implement carrier as used herein is not merely a pivotal connection point, but rather a dedicated device specifically intended to accept and be secured to various different implements. The implement carrier itself is mountable to a work element 130 such as a lift arm or the frame 110. Implement interface 170 can also include one or more power sources for providing power to one or more work elements on an implement. Some power machines can have a plurality of work elements with implement interfaces, each of which may, but need not, have an implement carrier for receiving implements. Some other power machines can have a work element with a plurality of implement interfaces so that a single work element can accept a plurality of implements simultaneously. Each of these implement interfaces can, but need not, have an implement carrier.

[0027] Frame 110 includes a physical structure that can support various other components that are attached thereto or positioned thereon. Frame 110 can include any number of individual components. Some power machines have frames that are rigid. That is, no part of the frame is movable with respect to another part of the frame. Other power machines have at least one portion that can move with respect to another portion of the frame. For example, excavators can have an upper frame portion that rotates with respect to a lower frame portion. Other work vehicles have articulated frames such that one portion of the frame pivots with respect to another portion for accomplishing steering functions.

[0028] Frame 110 supports the power source 120, which can provide power to one or more work elements 130 including the one or more tractive elements 140, as well as, in some instances, providing power for use by an attached implement via implement interface 170. Power from the power source 120 can be provided directly to any of the work elements 130. tractive elements 140, and implement interfaces 170. Alternatively, power from the power source 120 can be provided to a control system 160, which in turn selectively provides power to the elements that are capable of using it to perform a work function. Power sources for power machines may include an engine, such as an internal combustion engine, and a power conversion system, such as a mechanical transmission or a hydraulic system that is capable of converting the output from an engine into a form of power that is usable by a work element, or other types of power sources including electrical sources provided by, for example, batteries, or a combination of power sources, known generally as hybrid power sources.

[0029] FIG. 1 shows a single work element designated as work element 130, but various power machines can have any number of work elements. Work elements are typically attached to the frame of the power machine and movable with respect to the frame when performing a work task. In addition, tractive elements 140 are a special case of work element in that their work function is generally to move the power machine 100 over a support surface. Tractive elements 140 are shown separate from the work element 130 because many power machines have additional work elements besides tractive elements, although that is not always the case. Power machines can have any number of tractive elements, some or all of which can receive power from the power source 120 to propel the power machine 100. Tractive elements can be, for example, wheels attached to an axle or frame, track assemblies, and the like. Tractive elements can be mounted to the frame such that movement of the tractive element is limited to rotation (so that steering is accomplished by a skidding action) or, alternatively, pivotally mounted to the frame to accomplish steering by pivoting the tractive element with respect to the frame.

[0030] Power machine 100 includes an operator station 150 that includes an operating position from which an operator can control operation of the power machine. In some power machines, the operator station 150 is defined by an enclosed or partially enclosed cab. Some power machines on which the disclosed embodiments may be practiced may not have a cab or an operator compartment of the type described above. For example, a walk behind loader may not have a cab or an operator compartment, but rather an operating position that serves as an operator station from which the power machine is properly operated. More broadly, power machines other than work vehicles may have operator stations that are not necessarily similar to the operating positions and operator compartments referenced above. Further, some power machines such as power machine 100 and others, whether they have operator compartments, operator positions or neither, may be capable of being operated remotely (i.e. from a remotely located operator station) instead of or in addition to an operator station adjacent or on the power machine. This can include applications where at least some of the operator-controlled functions of the power machine can be operated from an operating position associated with an implement that is coupled to the power machine. Alternatively, with some power machines, a remote-control device can be provided (i.e. remote from both the power machine and any implement to which is it coupled) that is capable of controlling at least some of the operator-controlled functions on the power machine.

[0031] FIGS. 2-3 illustrate a loader 200, which is one particular example of a power machine of the type illustrated in FIG. 1 where the embodiments discussed below can be advantageously employed. Loader 200 is an articulated loader with a front mounted lift aim assembly 230, which in this example is a telescopic lift arm. Loader 200 is one particular example of the power machine 100 illustrated broadly in FIG. 1 and discussed above. To that end, features of loader 200 described below include reference numbers that are generally similar to those used in FIG. 1. For example, loader 200 is described as having a frame 210, just as power machine 100 has a frame 110. The description herein of loader 200 with references to FIGS. 2-3 provides an illustration of the environment in which the embodiments discussed below can be employed, and this description should not be considered limiting especially as to the description of features of loader 200 that are not essential to the disclosed embodiments. Such features may or may not be included in power machines other than loader 200 upon which the embodiments disclosed below may be advantageously practiced.

[0032] Loader 200 includes frame 210 that supports a power system 220 that can generate or otherwise provide power for operating various functions on the power machine. For example, power system 220 may provide electrical power for operating various functions on the power machine. Frame 210 also supports a work element in the form of lift arm assembly 230 that is powered by the power system 220 and that can perform various work tasks. As loader 200 is a work vehicle, frame 210 also supports a traction system 240, which is also powered by power system 220 and can propel the power machine over a support surface. The lift aim assembly 230 in turn supports an implement interface 270 that includes an implement carrier 272 that can receive and secure various implements to the loader 200 for performing various work tasks and power couplers 274 (shown diagrammatically), to which an implement can be coupled for selectively providing power to an implement that might be connected to the loader. Power couplers 274 can provide sources of hydraulic or electric power or both. The loader 200 includes a cab 250 that defines an operator station 255 from which an operator can manipulate various control devices to cause the power machine to perform various work functions. Cab 250 includes a canopy 252 that provides a roof for the operator compartment and is configured to have an entry 254 (for example, the left side as illustrated in FIG. 3) on one side of the seat to allow for an operator to enter and exit the cab. Although cab 250 as shown does not include any windows or doors, a door or windows can be provided.

[0033] The operator station 255 includes an operator seat 258 and the various operation input devices 260, including control levers that an operator can manipulate to control various machine functions. Operator input devices can include a steering wheel, buttons, switches, levers, sliders, pedals and the like that can be stand-alone devices such as hand operated levers or foot pedals or incorporated into hand grips or display panels, including programmable input devices. Actuation of operator input devices can generate signals in the form of electrical signals, hydraulic signals, and / or mechanical signals. Signals generated in response to operator input devices are provided to various components on the power machine for controlling various functions on the power machine. Among the functions that are controlled via operator input devices on power machine 100 include control of the tractive system 240, the lift arm assembly 230, the implement carrier 272, and providing signals to any implement that may be operably coupled to the implement.

[0034] Loaders can include human-machine interfaces including display devices that are provided in the cab 250 to give indications of information relatable to the operation of the power machines in a form that can be sensed by an operator, such as. for example audible and / or visual indications. Audible indications can be made in the form of buzzers, bells, and the like or via verbal communication. Visual indications can be made in the form of graphs, lights, icons, gauges, alphanumeric characters, and the like. Displays can be dedicated to provide dedicated indications, such as warning lights or gauges, or dynamic to provide programmable information, including programmable display devices such as monitors of various sizes and capabilities. Display devices can provide diagnostic information, troubleshooting information, instructional information, and various other types of information that assist an operator with operation of the power machine or an implement coupled to the power machine. Other information that may be useful for an operator can also be provided.

[0035] Various power machines that can include and / or interact with the embodiments discussed below can have various different frame components that support various work elements. The elements of frame 210 discussed herein are provided for illustrative purposes and should not be considered to be the only type of frame that a power machine on which the embodiments can be practiced can employ. As mentioned above, loader 200 is an articulated loader and as such has two frame members that are pivotally coupled together at an articulation joint. For the purposes of this document, frame 210 refers to the entire frame of the loader. Frame 210 of loader 200 includes a front frame member 212 and a rear frame member 214. The front and rear frame members 212,214 are coupled together at an articulation joint 216 (FIG. 3). Actuators (not shown) are provided to rotate the front and rear frame members 212, 214 relative to each other about a vertical axis 217 (FIG. 3) to accomplish a turn. As illustrated in FIG. 2, loader 200 has six degrees of movement. These include vertical up and down translation along vertical axis 217, back and forth translation along a longitudinal axis 215, side-to-side translation along a lateral axis 219, rotational roll 221 about longitudinal axis 215, rotational yaw 223 about vertical axis 217 and rotational pitch 225 about lateral axis 219.

[0036] The front frame member 212 supports and is operably coupled to the lift arm 230. A lift arm actuator (not visible - positioned beneath the lift arm 230) is coupled to the front frame member 212 and the lift arm 230 and is operable to raise and lower the lift arm under power. The front frame member 212 also supports at least two front tractive elements or wheels 242A and 242B. Front tractive elements or wheels 242A and 242B are mounted to rigid axles or are mounted to the frame without an interconnecting axle (the wheels do not turn left or right with respect to the front frame member 212). The cab 250 is also supported by the front frame member 212 so that when the front frame member 212 articulates with respect to the rear frame member 214, the cab 250 moves with the front frame member 212 so that it will swing out to either side relative to the rear frame member 214, depending on which way the loader 200 is being steered.

[0037] The rear frame member 214 supports various components of the power system 220. In exemplary embodiments, the power system is an electric or hybrid electric power system. In addition, one or more hydraulic pumps may be coupled to an engine or an electric motor and supported by the rear frame member 214. In such embodiments, the hydraulic pumps are part of a power conversion system to convert power from the power system 220 into a form that can be used by actuators (such as cylinders) on the loader 200. However, some disclosed embodiments utilize only electric actuators and motors, and therefore do not require a hydraulic system. In addition, at least two rear tractive elements or wheels 242C and 242D are mounted to rigid axles that are in turn mounted to the rear frame member 214 (or the rear wheels 242C and 242D are mounted to the rear frame member 214 without an interconnecting axle). When the loader 200 is pointed in a straight direction (i.e., the front frame portion 212 is longitudinally aligned with the rear frame portion 214) a portion of the cab is positioned over the rear frame portion 214.

[0038] The lift arm assembly 230 shown in FIGS. 2-3 is one example of many different types of lift arm assemblies that can be attached to a power machine such as loader 200 or other powermachines on which embodiments of the present discussion can be practiced. The lift arm assembly 230 is a radial lift arm assembly, in that the lift arm is mounted to the frame 210 at one end of the lift arm assembly and pivots about the mounting joint as it is raised and lowered. The lift arm assembly 230 may be a telescoping lift arm. The lift arm assembly includes a boom 232 that is pivotally mounted to the front frame member 212 at a joint. A telescoping member may be slidably inserted into boom 232; in this case, a telescoping cylinder (not shown) is coupled to the boom and the telescoping member and is operable to extend and retract the telescoping member under power.

[0039] In an exemplary embodiment, a tilt actuator 278 is pivotally mounted to both the implement carrier mounting structure 276 and the implement carrier 272 and is operable to rotate the implement carrier with respect to the implement carrier mounting structure under power. Among the operator controls 260 in the operator compartment 255 are operator controls to allow an operator to control the lift, telescoping, and tilt functions of the lift arm assembly 230.

[0040] Other lift ami assemblies can have different geometries and can be coupled to the frame of a loader in various ways to provide lift paths that differ from the radial path of lift arm assembly 230. For example, some lift paths on other loaders provide a radial lift path. Others have multiple lift arms coupled together to operate as a lift arm assembly. Still other lift arm assemblies do not have a telescoping member. Others have multiple segments. Unless specifically stated otherwise, none of the inventive concepts set forth in this discussion are limited by the type or number of lift arm assemblies that are coupled to a particular power machine.

[0041] FIG. 4 illustrates power system 220 in more detail. Broadly speaking, power system 220 includes one or more power sources 222 that can generate and / or store power for operating various machine functions. On loader 200, the power system 220 may include an internal combustion engine, electric generators, rechargeable batteries, various other power sources or any combination of power sources that can provide power for given power machine components. The power system 220 may also include a power conversion system 224, which is operably coupled to the power source 222. Power conversion system 224 in various power machines can include various components, including mechanical and / or electric transmissions, hydraulic systems, and the like. For example, power conversion system 224 may include a hydrostatic drive pump and an implement pump driven by power source(s) 222. The power conversion system 224 can also, or alternatively, include electrical power conversion or regulating circuitry. Power conversion system224 may, in turn, be coupled to a tractive drive system 326, which can perform a tractive function on the power machine, may be coupled to articulation angle actuator(s) 236 and may be coupled to work actuator circuit 238.

[0042] Tractive drive system 326, articulation angle actuator(s) 236 and work actuator circuit 238 may alternatively be coupled directly to power source 222 depending on the type of power source. For example, if the power source 222 is electric and includes electric generators or rechargeable batteries and tractive drive system 326 is an all-electric drive system, then tractive drive system 326 may be directly coupled to power source 222. If, for example, power source 222 is electric and includes electric generators or rechargeable batteries and articulation angle actuator 236 is a linear actuator, then articulation angle actuator 236 may be directly coupled to power source 222. If, for example, power source 222 is electric and includes electric generators or rechargeable batteries and work actuator circuit 238 is coupled to a work actuator 239 that is a linear actuator, then work actuator circuit 238 may be directly coupled to power source 222. However, if tractive drive system 326, articulation angle actuator 236 or work actuator 239 include other types of actuators, such as hydraulic actuators, tractive drive system 326, articulation angle actuator 236 and work actuator 239 can receive power from power conversion system 224.

[0043] Some elements are described in multiples. For example, four wheel motors are depicted, and in some cases they will be differentiated by referring to the front left with reference number 226 A, the front right with reference number 226B, the rear left with reference number 226C, and the rear right with reference number 226D. However, in many aspects, the drive motors are similar; descriptions of 226, 226A, 226B, 226C and 226D apply to all embodiments unless otherwise specified. This convention also applies to other similarly numbered elements, such as gear systems 228 and wheels 242, for example.

[0044] The power source 222 or the power conversion system 224 of power machine 200 provides power to tractive drive system 326. Tractive drive system 326 includes a tractive drive control 327 coupled to drive motors 226A, 226B, 226C and 226D. Under one embodiment, the four drive motors 226A, 226B, 226C and 226D in turn are each operably coupled to four gear systems 228 A, 228B, 228C and 228D, respectively, where tractive drive control 327 may include electronic controls providing electric control signals to operate drive motors 226A-D for speed and direction and optionally to control gear systems 228A-D. For example, gear systems 228A-D may include a single gear or more than one gear, such as a planetary gearbox. Although not shown, the fourdrive motors 226A-D may be coupled to the tractive elements or wheels 242A-D, respectively. Under this embodiment, each drive motor 226A, 226B, 226C and 226D may be an electric motor that receives a power signal from power source 222 and drives each corresponding tractive element or wheel 242A, 242B, 242C and 242D. Work actuator 239 may be representative of a plurality of actuators, including the lift actuator, tilt actuator, telescoping actuator, and the like. The work actuator circuit 238 may include valves and other devices to selectively provide pressurized hydraulic fluid to the various work actuators represented by block 239 in FIG. 4 when power conversion system 224 includes hydraulic pumps, hi addition, the work actuator circuit 238 may be configured to provide pressurized hydraulic fluid to work actuators on an attached implement.

[0045] FIG. 5 is a schematic diagram of related components useful in understanding operation of steering articulated loader 200. Steering inputs 360 of the power machine 200, which can be a subset of operator input devices 260 discussed with reference to FIGS. 2-3, provide steering input signals to a steering control unit 365. For example, steering inputs 360 may include a steering wheel, joystick controls, control levers or other steering control devices. Steering control unit 365 can be a suitably configured electronic control unit, a mechanical control device or other device configured to control articulation angle actuator(s) 236 coupled to articulation joint 216. Steering control unit 365 is responsive to steering input signals from steering inputs 360, to control an angle of articulation of articulation joint 216 between front frame member 212 and rear frame member 214 when a steering or turn operation of the power machine 200 is underway.

[0046] Power machine 200 may determine the angle of articulation in different ways. In one embodiment, the angle of articulation may be determined by the steering input signals and control signals of steering control unit 365. In another embodiment, power machine 200 includes an articulation sensor 375, which senses and measures the articulation angle between front frame member 212 and back frame member 214 while a steering or turning operation is underway.

[0047] Tractive drive system 326 includes a tractive drive control 327 and is coupled to power source 222 and / or power conversion system 224. Tractive drive control 327 is configured to apply independent speed and direction control or velocity control to each tractive element to independently rotate each of the inner and outer tractive elements on front frame member 212 and back frame member 214. In order to control the relationship between the four drive motors 226A-226D during a steering or turning operation in which the angle of articulation is changed by articulation angle actuator(s) 236 and to reduce skidding, slipping and dragging during such aturning or articulating operation, tractive drive control 327 is configured to provide unique control signals to each of first drive motor 226 A, second drive motor 226B, third drive motor 226C and fourth drive motor 226D. These unique control signals separately and independently control the velocity of each wheel 242A, 242B, 244A and 244B by commanding different forward or backward directions and speeds to corresponding motors 226A-226D that drive each wheel 242A, 242B. 244A and 244B.

[0048] FIG. 6 A is a front left perspective view of a frame and wheel components of an exemplary articulated loader 200. In an exemplary embodiment, a fully integrated electric wheel assembly 328 is provided for mounting respective wheels 242. However, it is to be understood that the disclosed concepts can be practiced on any articulated power machine with four independently controlled and driven wheels, which can receive motive power from any power source. FIG. 6B is an exploded view of the components of an exemplary electric wheel assembly 328. FIG. 6C shows those components assembled together in an exemplary embodiment. In the illustrated embodiments, an exemplary electric wheel assembly includes inverter 388, electric drive motor 226, brake 330, gear system 228, which can be a two stage planetary gear with mechanical freewheeling capabilities for example, bearing 332 and wheel support flange 334.

[0049] FIG. 7 is a top view of articulated loader 200 being steered or turned to the right during forward motion (as indicated by the arrows) so that inner tractive elements or wheels 242B and 242D are turning along theoretical circle having a first radius 262; outer tractive elements or wheels 242A and 242C are turning along a theoretical circle having a second radius 264. When articulated loader 200 is being steered or turned with matched velocity provided to all four wheels 242A, 242B, 242C and 242D, or more accurately, when the angle of articulation of articulation joint 216 or between front frame member 212 and rear frame member 214 is changed with matched velocity control provided to all four tractive elements or wheels 242A, 242B, 242C and 242D, the two inner tractive elements or wheels, with respect to the turn (e.g.. wheels 242B and 242D), can slip and / or the two outer tractive elements or wheels, with respect to the turn (e.g., wheels 242 A and 242C), can drag, causing damage to ground surfaces such as turf.

[0050] As disclosed, independent control of each of the speed and direction of each of the wheels 242 allows for prevention of skidding and dragging. Additionally, such control prevents wasted motive energy. In an exemplary embodiment, velocity control is varied between inner tractiveelements 242B and 242D and outer tractive elements 242A and 242C (illustrated by smaller sized vector arrows and larger sized vector arrows).

[0051] As shown in FIG. 8, a simplified schematic view of the first exemplary motion configuration of FIG. 7, when the angle of articulation is changed during a first exemplary steering event while traveling, each of the drive motors 226A-226D is independently controlled. In an exemplary embodiment, a paired velocity control is provided to inner tractive elements 242B and 242D and paired velocity control is provided to outer tractive elements 242A and 242C. With the steering of loader 200 to the right, the two inner tractive elements (e.g., tractive elements 242B and 242D), with respect to the angle of articulation, are turned at a slower velocity than the two outer tractive elements (e.g., 242A and 242C). Although not illustrated, if the tractive elements were steered to the left, the two inner tractive elements (e.g., 242A and 242C), with respect to angle of articulation, would be turned at a slower velocity than the two outer tractive elements (e.g.242B and 242D).

[0052] As shown in FIG. 7. when articulated loader 200 is steered or turned and articulation joint 216 changes, an articulation angle 376 is determined. In response, tractive drive control 327 commands drive motors 226B and 226D to turn inner tractive elements (e.g., 242B and 242D) via gear systems 228B and 228D, with respect to the articulation angle 376, at a certain forward velocity or speed and commands drive motors 226A and 226C to turn outer tractive elements (e.g., 242A and 242C) via gear systems 228A and 228C, with respect to the articulation angle 376, at a certain forward velocity or speed that is greater than the forward speed of inner tractive elements (e.g., 242B and 242D). For example, drive motor 226B is commanded to turn tractive element 242B in a forward direction at a first speed, drive motor 226D is commanded to turn tractive element 242D in a forward direction at the first speed, drive motor 226A is commanded to turn tractive element 242A in a forward direction at a second speed and drive motor 226C is commanded to turn tractive element 242C in a forward direction at the second speed. The second velocity is greater than the first velocity, and the differences in velocities are shown by the different sized vector arrows.

[0053] As illustrated in FIGS.7 and 8, articulated loader 200 is being steered in a forward direction towards the right. When steering right, a larger turn radius requires a smaller difference between velocity commands received by respective drive motors for paired inner tractive elements 242B and 242D and velocity commands received by respective drive motors for paired outer tractiveelements 242 A and 242C. A tighter turn radius requires a greater difference between velocity commands received by the respective drive motors for the paired inner tractive elements 242B and 242D and velocity commands received by respective drive motors for the paired outer tractive elements 242A and 242C. The opposite relationships will govern steering to the left (not shown).

[0054] As shown in FIG. 7, both radii 262, 264 are measured from the center 266 of the turning circles defining the trajectory of the wheels 242. Center 266 is also theoretically at the intersection of lines passing through the axles (theoretical or actual) of each of the forward set of wheels of front frame member 212 and rearward set of wheels of rear frame member 214.

[0055] FIG. 8 is a simplified schematic view of the same turning configuration as shown in FIG.7 in a first motion configuration. It is provided so that different turning configurations can be easily visually compared. As shown in FIG. 8, the trajectory arc 336 defining the direction of motion of loader 200 has a center 266. Referring to FIG. 9, in a second motion configuration, turning more tightly makes the trajectory arc 336 smaller and moves its center 266 closer to loader 200. In an exemplary embodiment, in the last 5 degrees of turning (as determined by articulation sensor 375, for example) before the loader 200 reaches full articulation (maximum relative rotation between front frame member 212 and rear frame member 214 about articulation joint 216), the speed at the rear right motor 226D in such an illustrated right turn is linearly decreased to zero by tractive drive control 327, effectively applying a brake to the right rear wheel 242D. This results in a trajectory arc 336 of the fully articulated loader 200 in FIG. 9 that can be less than about half the width of the trajectory arc 336 of a typically turned loader 200 (at the same articulation angle).

[0056] In FIG. 8, each of the wheels 242 is rotated in the same forward direction. In FIG. 9, each of the three moving wheels is rotated in the same forward direction. However, many different modes of motor motion are possible, in which the independently controllable wheels 242 can be turned in different directions and at different speeds with respect to any of the other wheels 242 of the power machine. For example. FIG. 10 shows a third exemplary motion configuration in which the trajectory arc 336 of the loader 200 is generally in a forward right direction. However, in this case, the two inner wheels 242B, 242D are rotated in a reverse direction. This moves the center 266 (not shown in FIG. 10) of the trajectory arc 336 essentially onto the frame 210 of the loader 200, so that it spins about itself with a very tight turn radius. Other motion modes include, for example, all-wheel steer and crab steer, for example.

[0057] FIG. 11 shows a fourth exemplary motion configuration, in which the forward wheels 242A, 242B are rotated in a forward direction while the rearward wheels 242C, 242D are rotated in a reverse direction. With the front frame member 212 articulated about joint 216 in a right direction with respect to rear frame member 214, the trajectory arc 336 points toward the left, as the loader 200 moves sideways to the left as illustrated. It is contemplated that many other motion configurations can be achieved by independently controlling the speed and direction of each of the wheels 242 while also changing the relative positions of front frame member 212 and rear frame member 214 about the articulation joint 216.

[0058] In an exemplary embodiment, the articulation sensor 375 signals to the tractive drive control 327 that the turn is in about the last 5 degrees of vehicle articulation, and the tractive drive control 327 automatically ramps down the speed of the inner wheel of interest. The software used by the tractive drive control 327 can also determine, based on a work element weight or pressure sensor, which of the inner wheels (front or rear) should have a brake applied. This determination is based on the weight balance between the front frame member 212 and the rear frame member 214. In an exemplary embodiment, a pressure sensor 378 is positioned on the lift arm cylinder. A threshold pressure is programmed at which below the threshold pressure, the loader 200 is rear heavy (relatively greater weight on rear frame member 214) and above the threshold pressure, the loader 200 is front heavy (relatively greater weight on front frame member 212). Whichever of the front or rear frame members has the most weight, correlating to the most friction upon the ground supporting surface, the inner wheel, depending upon the turn direction, that is on the heavier front or rear frame member is the one to which the motor velocity is reduced to and held at zero. In such a case, the inner wheel with less weight will exhibit lower frictional characteristics and therefore laterally slip in response to the braking of the inner wheel sustaining more vehicle weight in combination with the increased velocity command of the outer wheels to decrease the turning arc.

[0059] Generally, it is desirable to apply a brake to the inner wheel that has the higher ground pressure as determined by sensor 378 (more weight on it, as increased friction between the wheel and the ground surface facilitates greater holding torque at that wheel, while the other wheels with less ground pressure may scrub or skid about the center 266 of the trajectory arc 336 with relative ease). Referring to FIG. 9, while a brake is illustrated as being applied to the rear right wheel 242D being held at zero velocity, in another implementation, the zero velocity could alternatively be commanded to the front inner wheel 242B if the front frame member 212 carries more weight thanthe rear frame member 214 (for example, if a front implement such as a bucket is heavily loaded). In this case, the moving inner wheel would be the lightly laden rear right wheel 242D. This choice of braking the wheel on the heavier of the front or rear frame members results in easier pivoting about the highly frictionally engaged wheel while less turf damage is caused by the lighter wheels.

[0060] Software for the tractive drive control 327 can also offer advanced drive features. To increase traction, the respective traction motors 226 can be slowed down or sped up to control wheel slippage. Moreover, intermittent loss of traction on the braked wheel can cause the brake turning feature to be ineffective on rough terrain. Applying suspension structures would greatly reduce this issue. Generally, reducing the turn radius using the brake turning feature is most successful and reliable on even ground surfaces such as concrete because of even tire engagement with the ground surface. This may be counterintuitive because a concrete ground surface also offers relatively high friction compared to more organic surfaces.

[0061] Because scrubbing and torque holding require a high energy level, reducing this wasted energy allows for an increase in run time of the power machine 100, 200 for a given power supply. This can be particularly advantageous in a fully electric power machine 100, 200 that has a reduced power supply in the form of stored electrical energy in a battery when compared to an internal combustion engine fuel supply, for example.

[0062] In a variation of the motion configuration of FIG. 9, referred to as “rear frame skid steer with articulation,” the wheel controlled by motor 226D (wheel 242D) can be rotated in a rearward direction while the other three wheels receive forward rotation commands. If the forward speed of rear outer wheel 242C is greater than the forward speed of the two forward wheels 242 A, 242B, the center 266 of the trajectory arc 336 can be moved rearward to thereby further reduce the turning radius.

[0063] In a non-limiting, exemplary embodiment, a method for turning a power machine 100, 200 is disclosed. The power machine 200 comprises a front frame member 212, a rear frame member 214, and an articulation joint 216. The front frame member 212 comprises left front 226A and right front 226B independently controllable motors operably connected to left front 242A and right front 242B wheels, respectively. The rear frame member 214 comprises left rear 226C and right rear 262D independently controllable motors operably connected to left rear 242C and right rear 242D wheels, respectively. The front frame member 212 and the rear frame member 214 pivot with respect to each other about the articulation joint 216. The method for turning the powermachine 200 comprises pivoting the front frame member 212 relative to the rear frame member 214 in a turn about an articulation angle 376 so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn; determining which of the front frame member 212 or the rear frame member 214 bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member 212 or the rear frame member 214 that bears more weight, in response to the determination of the weight balance between the front and rear frame members.

[0064] In exemplary embodiment, maximum pivoting between the front frame member 212 and the rear frame member 214 is referred to as full articulation. In exemplary embodiment, reducing the rotation speed of the motor correlating to the first inside wheel begins at about 5 degrees from full articulation, as determined by an articulation sensor 375. In exemplary embodiment, reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction. In exemplary embodiment, reducing the rotation speed of the motor correlating to the first inside wheel results in braking the first inside wheel, as depicted in FIG. 9, for example.

[0065] An exemplary method comprises rotating each of the two outside wheels at a greater speed than rotating each of the two inside wheels, as depicted in FIGS. 8 and 9, for example. An exemplary method comprises rotating each of the two outside wheels in the same direction, which is an opposite direction than that of the rotating two inside wheels, as depicted in FIG. 10, for example. An exemplary method comprises reversing a rotation direction of the first inside wheel, as depicted in FIGS. 10 and 11, for example. An exemplary method comprises reversing a rotation direction of a second inside wheel, as depicted in FIG. 10, for example. An exemplary method comprises reversing a rotation direction of an outside wheel, as depicted in FIG. 11. for example. An exemplary method comprises rotating the left front wheel in an opposite direction than rotating the left rear wheel, as depicted in FIG. 11, for example. An exemplary method comprises rotating the right front wheel in an opposite direction than rotating the right rear wheel, as depicted in FIG.11, for example.

[0066] Although the present disclosure presents preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail to the disclosed embodiments without departing from the scope of the concepts discussed herein.

Claims

WHAT IS CLAIMED IS:

1. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively; a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn; and reducing a rotation speed of the first inside wheel of the front frame member or the rear frame member relative to the second inside wheel.

2. The method of claim 1 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.

3. The method of claim 1 or 2, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.

4. The method of any one of claims 1 to 3, wherein reducing the rotation speed of the motor correlating to the first inside wheel results in braking the first inside wheel.

5. The method of any one of claims 1 to 4, comprising rotating each of the two outside wheels at a greater speed than rotating each of the two inside wheels.

6. The method of any one of claims 1 to 5, comprising rotating each of the two outside wheels in an opposite direction than rotating each of the two inside wheels.

7. The method of any one of claims 1 to 6, comprising reversing a rotation direction of the first inside wheel.

8. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively;a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn;rotating the first and second outside wheels in a first direction; androtating the first and second inside wheels in a second direction that is opposite the first direction.

9. The method of claim 8 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.

10. The method of claim 9, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.

11. The method of any one of claims 8 to 10, comprising rotating each of the two outside wheels at a greater speed than rotating at least one of the two inside wheels.

12. A method for turning a power machine that comprises:a front frame member comprising left front and right front independently controllable motors operably connected to left front and right front wheels, respectively; a rear frame member comprising left rear and right rear independently controllable motors operably connected to left rear and right rear wheels, respectively; and an articulation joint about which the front frame member and the rear frame member pivot with respect to each other;the method comprising:pivoting the front frame member relative to the rear frame member in a turn about an articulation angle so that first and second inside wheels are on an inside of the turn and first and second outside wheels are on an outside of the turn;rotating the left front and right front wheels in a first direction; androtating the left rear and right rear wheels in a second direction that is opposite the first direction.

13. The method of claim 12 comprising:determining which of the front frame member or the rear frame member bears more weight; and reducing a rotation speed of the motor correlating to the first inside wheel of the front frame member or the rear frame member that bears more weight.

14. The method of claim 13, wherein reducing the rotation speed of the motor correlating to the first inside wheel follows a linear speed reduction.

15. The method of any one of claims 12 to 14, comprising rotating each of the two outside wheels at a greater speed than rotating at least one of the two inside wheels.

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