Tractive electric drive control on an articulated power machine

Abstract

An articulated power machine includes an articulation angle actuator (270) coupled to a power source (222) and configured to rotate an articulation joint (216) that rotatably couples front and rear frame members. A steering control unit (365) is configured to control the articulation angle actuator (270) coupled to the articulation joint (216) to change an angle of articulation between the front frame member (212) and the rear frame member (214) when a turning operation is underway. A tractive drive system (326) is coupled to the power source (222) and based on the angle of articulation is configured to prevent ground disturbance by commanding control signals to each of a plurality of electric drive motors that correspond with each of the inner and outer tractive elements to independently rotate each of the inner and outer tractive elements on the front and rear frame members.

Description

TRACTIVE ELECTRIC DRIVE CONTROL ON AN ARTICULATED POWER MACHINEBACKGROUND

[0001] This disclosure is directed toward power machines. More particularly, this disclosure is directed to a differential velocity control on articulated power machines.

[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] In articulated power machines, when steering or turning, an angle of an articulation joint between front and rear portions of the machine is changed. When the angle of the articulation joint is changing, one or more wheels of the power machine can skid across the ground or other support surface causing ground disturbance. This can be undesirable, particularly when operating the power machine on turf or other surfaces that can be damaged.

[0004] 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

[0005] An articulated power machine includes a power source, a front frame member having at least inner and outer tractive elements and a rear frame member having at least inner and outer tractive elements. An articulation angle actuator is coupled to the power source and is configured to rotate an articulation joint that rotatably couples the front and rear frame members. A steering control unit is configured to control the articulation angle actuator coupled to the articulation joint to change an angle of articulation between the front frame member and the rear frame member when a turning operation is underway. A tractive drive control is coupled to the power source and based on the angle of articulation the tractive drive system is configured to prevent ground disturbance by commanding control signals to each of a plurality of electric drive motors thatcorrespond with each of the inner and outer tractive elements to independently rotate each of the inner and outer tractive elements on the front and rear frame members.

[0006] An articulated power machine includes a power source, a front frame member having at least first and second tractive elements and a rear frame member having at least first and second tractive elements. An articulation angle actuator is coupled to the power source and is configured to rotate an articulation joint that rotatably couples the front and rear frame members. A steering control unit is configured to control the articulation angle actuator coupled to the articulation joint to change an angle of articulation between the front frame member and the rear frame member when a turning operation is underway. An articulation sensor is configured to sense the articulation angle between the front and rear frame members. A tractive drive system is coupled to the power source and includes a plurality of electric drive motors each configured to drive a corresponding first or second tractive element of the front frame member or a corresponding first or second tractive element of the rear frame member. Based on the sensed angle of articulation the tractive drive system is configured to prevent ground disturbance by commanding control signals to each of the plurality of electric drive motors to independently actuate each of the first and second tractive elements on the front and rear frame members.

[0007] A method of preventing ground disturbance in an articulated power machine includes providing power to an articulation angle actuator to rotate an articulation joint that rotatably couples front and rear frame members. The articulation angle actuator coupled to the articulation joint is controlled to change an angle of articulation between the front frame member and the rear frame member when a steering operation is underway. The angle of articulation is determined. Control signals are commanded to each of a plurality of electric drive motors configured to drive a corresponding inner tractive element or outer tractive element of the front frame member or a corresponding inner tractive element or outer tractive element of the rear frame member based on the angle of articulation to independently rotate each of the inner and outer tractive elements on the front frame member and the inner and outer tractive elements on the rear frame member.

[0008] 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

[0009] 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.

[0010] FIG. 2 is a perspective view showing generally a front of a power machine in the form of an articulated loader on which embodiments disclosed in this specification may be advantageously practiced.

[0011] FIG. 3 is a perspective view showing generally a back of the articulated loader shown in FIG. 2.

[0012] FIG. 4 is a block diagram illustrating components of a power system of a power machine such as the power system in the articulated loader illustrated in FIGS. 2 and 3.

[0013] FIG. 5 is a top view of the power machine illustrated in FIGS. 2 and 3 and showing a left turn that may cause ground disturbance.

[0014] FIG. 6 is diagrammatic illustration of related components useful in understanding operation of steering an articulated loader to minimize or prevent ground disturbance according to an embodiment.

[0015] FIG. 7 is a top view of the power machine illustrated in FIGS. 2 and 3 and showing a left turn that minimizes or prevents ground disturbance.

[0016] FIG. 8 are various illustrations of a top view of the power machine illustrated in FIGS. 2 and 3 and showing a process of a turn while the power machine is at zero velocity that minimizes or prevents ground disturbance.DESCRIPTION

[0017] 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 carried out 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.

[0018] Disclosed embodiments include an all-electric tractive drive system for an articulated frame power machine. The drive system includes independent electric motors which drive eachwheel via a planetary gearbox. However, in one instance, if a matched velocity control is provided to all four wheel motors during articulation of the power machine, either the inner wheels will slip and / or the outer wheels will drag causing significant ground disturbance in certain environments. In another instance, if the power machine is at rest or at zero speed and a command for articulation is received, the wheels may skid and scrub, causing ground disturbance. In yet another instance, either the front or rear wheels may experience low traction, for example, going down-hill with a load on the workgroup, and therefore articulating the power machine to steer may not actually result in the loader turning.

[0019] To prevent ground disturbance and incidences of low traction, the disclosed embodiments command different travel speeds or velocities of the inner and / or outer wheels based on a sensed articulation angle of the power machine. As a result, the loader will minimize ground disturbances during articulation and the loader will turn regardless of low traction events.

[0020] 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, including power machines of different types from the representative power machine shown in FIGS. 2-3. 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 a power 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.

[0021] 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. As mentioned above, at the most basic level, power machines for the purposes of this discussion include a frame, a power source, and a work element. The 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-propelledwork vehicle, it also has tractive elements 140, which are themselves work elements provided to move the power machine over a support surface and an operator station 150 that 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.

[0022] 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, 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.

[0023] 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 work element, 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 element with implement interfaces, each of which may, but need not, have an implement carrier for receiving implements. Some other powermachines 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.

[0024] Frame 110 includes a physical structure that can support various other components that are attached thereto or positioned thereon. The 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.

[0025] 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.

[0026] 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 120to propel the power machine 100. Tractive elements can be, for example, wheels attached to an axle, track assemblies, and the like. Tractive elements can be mounted to the frame such that movement of the tractive element is limited to rotation about an axle (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.

[0027] 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.

[0028] FIGS. 2-3 illustrates 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 arm 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 descriptionshould 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. Unless specifically noted otherwise, embodiments disclosed below can be practiced on a variety of power machines, with the loader 200 being only one of those power machines. For example, some or all of the concepts discussed below can be practiced on many other types of work vehicles such as various other loaders, excavators, trenchers, and dozers, to name but a few examples.

[0029] 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 arm 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.

[0030] 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. Actuationof 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.

[0031] 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 assists 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. Other power machines, such walk behind loaders may not have a cab nor an operator compartment, nor a seat. The operator position on such loaders is generally defined relative to a position where an operator is best suited to manipulate operator input devices.

[0032] 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 an axis 217 (FIG. 3) to accomplish a turn.

[0033] The front frame member 212 supports and is operably coupled to the lift arm 230 at joint 216. A lift arm actuator (not shown, 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 (the axles do not pivot 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.

[0034] 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. Power system 220 is discussed in more detail below. 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. When the loader 200 is pointed in a straight direction (i.e., the front frame portion 212 is aligned with the rear frame portion 214) a portion of the cab is positioned over the rear frame portion 214.

[0035] 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 power machines 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 216 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 joint 216. A telescoping member 234 may be slidably inserted into the boom 232 and telescoping cylinder (not shown) is coupled to the boom and the telescoping member and is operable to extend and retract the telescoping member underpower. The telescoping member 234 is shown in FIGS. 2 and 3 in a fully retracted position. The implement interface 270 including implement carrier 272 and power couplers 274 are operably coupled to the telescoping member 234. An implement carrier mounting structure 276 is mounted to the telescoping member. The implement carrier 272 and the power couplers 274 are mounted to the positioning structure. 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.

[0036] Other lift arm 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.

[0037] 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 sources 222. The power conversion system 224 can also, or alternatively, include electrical power conversion or regulating circuitry. Power conversion system 224 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) 270 and may be coupled to work actuator circuit 238. Tractive drive system 326, articulation angle actuator(s) 270 and work actuator circuit 238 may alternatively be coupled directly to power source 222 depending on thetype 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 270 is a linear actuator, then articulation angle actuator 270 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 270 or work actuator 239 include other types of actuators, such as hydraulic actuators, tractive drive system 326, articulation angle actuator 270 and work actuator 239 can receive power from power conversion system 224.

[0038] 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 228A, 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 gears, such as a gearbox. Although not shown, the four drive motors 226A-D may be coupled to the tractive elements or wheels 242A-D, respectively. Under this embodiment, each drive motor 226 A, 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. In addition, the work actuator circuit 238 may be configured to provide pressurized hydraulic fluid to work actuators on an attached implement.

[0039] The description of power machine 100 and loader 200 above is provided for illustrative purposes and to provide illustrative environments on which the embodiments discussed below can be practiced. While the embodiments discussed can be practiced on a power machine such as isgenerally described by the power machine 100 shown in the block diagram of FIG. 1 and more particularly on a loader such as articulated loader 200, unless otherwise noted or recited, the concepts discussed below are not intended to be limited in their application to the environments specifically described above.

[0040] Referring now to FIG. 5, shown is a top view of articulated loader 200 being steered or turned during forward motion so that inner tractive elements or wheels 242A and 242C are turning along a first radius 262 and outer tractive elements or wheels 242B and 242D are turning along a second radius 264. When articulated loader 200 is being steered or turned with matched velocity control (illustrated by the same sized vector arrows) 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 242A and 242C), can slip and / or the two outer tractive elements or wheels, with respect to the turn (e.g., wheels 242B and 242D), can drag, causing damage to ground surfaces such as turf.

[0041] FIG. 6 is a schematic diagram of related components useful in understanding operation of steering articulated loader 200 to minimize or prevent ground disturbance. 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) 270 coupled to articulation joint 216, and 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.

[0042] 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.

[0043] Tractive drive system 326 includes a tractive drive control 327 and is coupled to power source 222 and / or power conversion system 224. Based on the angle of articulation, tractive drive control 327 is configured to prevent ground disturbance by applying 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) 270 and to reduce skidding, slipping and dragging during such a turning or articulating operation, tractive drive control 327 is configured to provide unique control signals to each of first drive motor 226A, 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.

[0044] FIG. 7 is a top view of articulated loader 200 being steered or turned while moving forward so that inner tractive elements or wheels 242A and 242C are turning along a first radius of curvature 262 and outer tractive elements or wheels 242B and 242D are turning along a second radius of curvature 264, but with ground disturbance minimized or prevented according to an embodiment. In FIG. 7, when articulated loader 200 is steered or turned, velocity control is varied between inner tractive elements 242A and 242C and outer tractive elements 242B and 242D (illustrated by larger sized vector arrows and smaller sized vector arrows), or more accurately, when the angle of articulation is changed during a steering event while traveling, each of the drive motors 226A-226D are independently controlled so that a paired velocity control is provided to inner tractive elements 242A and 242C and paired velocity control is provided to outer tractive elements 242B and 242D. In FIG. 7, with the steering of tractive elements to the left, the two inner tractive elements (e.g., tractive elements 242A and 242C), with respect to the angle of articulation, are turned at a slower velocity than the two outer tractive elements (e.g., 242B and 242D) to minimize or prevent ground disturbance. Although not illustrated, if the tractive elements were steered to the right, the two inner tractive elements (e.g., 242B and 242D), with respect to angle of articulation, would be turned at a slower velocity than the two outer tractive elements (e.g. 242A and 242C) to minimize or prevent ground disturbance.

[0045] As shown in the example illustrated in FIG. 7, when articulated loader 200 is steered or turned and articulation joint 216 changes, an angle of articulation 376 is determined. In response, tractive drive control 327 commands drive motors 226A and 226C to turn inner tractive elements (e.g., 242A and 242C) via gear systems 228A and 228C, with respect to the articulation angle 376, at a certain forward speed and commands drive motors 226B and 226D to turn outer tractive elements (e.g., 242B and 242D) via gear systems 228B and 228D, with respect to the articulation angle 376, at a certain forward speed that is greater than the forward speed of inner tractive elements (e.g., 242A and 242C) to minimize or prevent ground disturbance. For example, in FIG. 7, drive motor 226A is commanded to turn tractive element 242A in a forward direction at a first speed, drive motor 226C is commanded to turn tractive element 242C in a forward direction at the first speed, drive motor 226B is commanded to turn tractive element 242B in a forward direction at a second speed and drive motor 226D is commanded to turn tractive element 242D 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.

[0046] As illustrated in FIG. 7, articulated loader 200 is being steered in a direction towards the left. When steering left, a larger turn radius or larger articulation angle requires a smaller difference between velocity commands received by respective drive motors for paired inner tractive elements 242A and 242C and velocity commands received by respective drive motors for paired outer tractive elements 242B and 242D. A tighter turn radius or smaller articulation angle requires a greater difference between velocity commands received by the respective drive motors for the paired inner tractive elements 242A and 242C and velocity commands received by respective drive motors for the paired outer tractive elements 242B and 242D. When steering right (not shown), the commanded velocity of paired tractive elements 242B and 242D will be less than the commanded velocity of paired tractive elements 242A and 242C. The larger the turn radius or larger articulation angle requires a smaller difference between the 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 tractive elements 242A and 242C . A tighter turn radius or smaller articulation angle requires a greater 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 tractive elements 242A and 242C. While inner tractive elements are paired and outer tractive elements are paired in FIG. 7, in otherembodiments it is possible to vary the speed between paired front and back inner tractive elements and between paired front and back outer tractive elements to avoid wheel slippage and improve traction in certain situations because each of the tractive elements 226A-226D are independently controlled.

[0047] In addition to mitigating or eliminating ground disturbance, the above-described tractive drive system 326 may also be beneficial where there is a low traction condition on the front tractive elements 242A and 242B or the rear tractive elements 242C and 242D. For example, if an articulated loader is going downhill with a load on the workgroup, the rear tractive elements may have limited traction and therefore articulating the loader to steer may not actually result in the loader turning. However, tractive drive system 326 would sense the articulation angle using articulation sensor 375 and in response to the sensed articulation angle tractive drive control 327 will command different velocities to the respective drive motors for inner tractive elements (e.g., 242A and 242C) and outer tractive elements (e.g., 242B and 242D). As a result, loader 200 will still turn regardless of the low traction event.

[0048] When the power machine or articulated loader 200 is not moving (forwards or backwards), tractive system 326 is configured to provide a steering operation that also minimizes or prevents ground disturbance. FIG. 8 illustrates one embodiment of articulating or turning articulated loader 200 without causing ground disturbance while articulated loader 200 is at zero ground speed. In particular, the wheel motor breaks are released and tractive drive control 327 is configured to separately control the velocity of each tractive element 242A, 242B, 244A and 244B by commanding different forward and backward velocities to corresponding motors 226A-226D that drive each tractive element 242A, 242B, 244A and 244B using gear systems 228A-228D. As shown in the example illustrated in FIG. 8, loader 200 may be articulated about articulation joint 216 to an articulation angle 376 between front frame member 212 and back frame member 214 while loader 200 is at zero ground speed. In response, tractive drive control 327 commands drive motors 226A and 226C using gear systems 228A and 228C to turn inner tractive elements (e.g., wheels 242A and 242C), with respect to the articulation angle, at certain velocities, and in opposing directions towards each other and commands drive motors 226B and 226D using gear systems 228B and 228D to turn outer tractive elements (e.g., 242B and 242D), with respect to articulation angle, at certain velocities that are less than the velocities at which inner tractive elements (e.g., 242A and 242C) are turned, and in opposing directions away from each other. In this way, tractivedrive system 326 reduces ground disturbance (both skid and scrub) and may reduce the force required to be exerted by articulating angle actuator 270.

[0049] For example, in FIG. 8, where loader 200 at zero ground speed is shown in three configurations. Loader 200, in the bottom illustration, is in an unsteered configuration. In the unsteered configuration, a front center point 380 between tractive element 242A and 242B is in alignment with articulation joint 216 and vehicle center and in alignment with a back center point 382 between tractive element 242C and 242D.

[0050] Loader 200, in the middle illustration, is in a first steered configuration or being steered to the left while at zero ground speed. To attain the first steered configuration from the unsteered configuration in the bottom illustration, drive motor 226A is commanded by tractive drive control 327 to turn tractive element 242A in a backward direction at a first speed, drive motor 226C is commanded by tractive drive control 327 to turn tractive element 242C in a forward direction at a second speed, drive motor 226B is commanded by tractive drive control 327 to turn tractive element 242B in a forward direction at a third speed and drive motor 226D is commanded by tractive drive control 327 to turn tractive element 242D in a backward direction at a fourth speed. The first speed of tractive element 242A is greater than the third speed of tractive element 242B and the second speed of tractive element 242C is greater than the fourth speed of tractive element 242D, and the differences in magnitude is shown by the different sizes and direction of the vector arrows.

[0051] Loader 200, in the top illustration, is in a second steered configuration while at zero ground speed. To attain the second steered configuration from the unsteered configuration in the bottom illustration, drive motor 226A is commanded by tractive drive control 327 to turn tractive element 242A in a backward direction at a first speed, drive motor 226C is commanded by tractive drive control 327 to turn tractive element 242C in a forward direction at a second speed, drive motor 226B is commanded by tractive drive control 327 to turn tractive element 242B in a forward direction at a third speed and drive motor 226D is commanded by tractive drive control 327 to turn tractive element 242D in a backward direction at a fourth speed. The first speed of tractive element 242A is greater than the third speed of tractive element 242B and the second speed of tractive element 242C is greater than the fourth speed of tractive element 242D, and the differences in magnitude is shown by the different sizes and direction of the vector arrows.

[0052] The wider or greater the articulation angle (as shown in the middle illustration) when steering at zero ground speed, the smaller the speeds that tractive element 242A-242D rotate. . The tighter or smaller the articulation angle (as shown in the top illustration) when steering at zero ground speed, the greater the speeds that tractive elements 242A-242D rotate. .

[0053] In another example (not shown), where loader 200 is to be steered to the right while at zero ground speed, drive motor 226B is commanded by tractive drive control 327 to turn tractive element 242B in a backward direction at a first speed, drive motor 226D is commanded by tractive drive control 327 to turn tractive element 242D in a forward direction at a second speed, drive motor 226A is commanded by tractive drive control 327 to turn tractive element 242A in a forward direction at a third speed and drive motor 226C is commanded to turn tractive element 242C in a backward direction at a fourth speed. The first speed of tractive element 242B is greater than the third speed of tractive element 242A. The second speed of tractive element 242D is greater than the fourth speed of tractive element 242C. The wider or greater the articulation angle when steering at zero ground speed, the smaller the speeds that tractive elements 242A-242Drotate. The tighter or smaller the articulation angle when steering at zero ground speed, the greater the speeds that tractive elements 242A-242D rotate.

[0054] With reference back to FIG. 6, it should be understood that the schematic diagram of power machine 200 may also be instructive in understanding operation of a power machine that is not an articulated vehicle. For example, a power machine 200 may include a power source, a single frame member (rather than front and rear frame members) that supports and has at least front inner and outer tractive elements and rear inner and outer tractive elements 242A-D, steering input(s) 360 configured to be manipulated by an operator to produce steering control signals, a steering control unit 365 coupled to steering input(s) 360 and configured to receive the steering control signals and responsively steer the inner and outer tractive elements 242A-D, and a tractive drive system 326 that includes tractive drive control 327, drive motors 226A-D and gear systems 228A-D. In this embodiment, tractive drive control 327 is coupled to the power source and is configured to apply differential velocity control to independently rotate each of the front and rear inner and outer tractive elements 242A-D on the frame member when a turning operation is underway.

[0055] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form anddetail to the disclosed embodiments without departing from the spirit and scope of the concepts discussed herein.

Claims

WHAT IS CLAIMED IS:

1. An articulated power machine comprising: a power source; a front frame member having at least an inner tractive element and an outer tractive element; a rear frame member having at least an inner tractive element and an outer tractive element; an articulation angle actuator coupled to the power source and configured to rotate an articulation joint that rotatably couples the front and rear frame members; a steering control unit configured to control the articulation angle actuator coupled to the articulation joint to change an angle of articulation between the front frame member and the rear frame member when a turning operation is underway; and a tractive drive system coupled to the power source and based on the angle of articulation the tractive drive system is configured to prevent ground disturbance by commanding control signals to each of a plurality of electric drive motors that correspond with each of the inner and outer tractive elements to independently rotate each of the inner and outer tractive elements on the front and rear frame members.

2. The articulated power machine of claim 1, wherein the plurality of electric drive motors of the tractive drive system comprise a first electric drive motor operably coupled to the inner tractive element on the front frame member, a second electric drive motor operably coupled to the outer tractive element on the front frame member, a third electric drive motor operably coupled to the inner tractive element on the rear frame member and a fourth electric drive motor operably coupled to the outer tractive element on the rear frame member.

3. The articulated power machine of claim 2, wherein when the articulated power machine is traveling over ground and the steering control unit is controlling the articulation joint in a turning operation, the tractive drive system is further configured to command control signals to drive the first electric drive motor to rotate the inner tractive element of the front frame member and to drive the third electric drive motor to rotate the inner tractive element of the rear frame member at a first speed and configured to command control signals to drive the second electric drive motor to rotatethe outer tractive element of the front frame member and to drive the fourth electric drive motor to rotate the outer tractive element of the rear frame member at a second speed, wherein the second speed is greater than the first speed.

4. The articulated power machine of claim 2, wherein when the articulated power machine is stationary or at zero ground speed and the steering control unit is controlling the articulation joint in a turning operation, the tractive drive system is further configured to command control signals to drive the first electric drive motor to rotate the inner tractive element of the front frame member at a first speed and in a first direction, command control signals to drive the third electric drive motor to rotate the inner tractive element of the rear frame member at a second speed and a second direction, command control signals to drive the second electric drive motor to rotate the outer tractive element of the front frame member at a third speed and the second direction and command control signals to drive the fourth electric drive motor to rotate the outer tractive element of the rear frame member at a fourth speed and the first direction, wherein the first and second speeds are greater than the third and fourth speeds and the second direction opposes the first direction so that the inner tractive elements are actuated towards each other and the outer tractive elements are actuated away from each other.

5. The articulated power machine of claim 1, and further comprising a steering input device configured to be manipulated by an operator to control turning operations by responsively generating steering input signals, wherein the steering control unit is configured to control the articulation angle actuator and to generate the control signal responsive to the steering input signals.

6. The articulated power machine of claim 5, wherein the steering input device comprises a joystick.

7. The articulated power machine of claim 5, wherein the angle of articulation is determined by the steering input signals and control signals of the steering control unit.

8. The articulated power machine of claim 1, further comprising an articulation sensor configured to determine the angle of articulation.

9. The articulated power machine of claim 1, wherein the power source provides electricity to the tractive drive system and the tractive drive system comprises an all-electric tractive drive system including the plurality of electric drive motors.

10. An articulated power machine comprising: a power source; a front frame member having at least a first tractive element and a second tractive element; a rear frame member having at least a first tractive element and a second tractive element; an articulation angle actuator coupled to the power source and configured to rotate an articulation joint that rotatably couples the front and rear frame members; a steering control unit configured to control the articulation angle actuator coupled to the articulation joint to change an articulation angle between the front frame member and the rear frame member when a turning operation is underway; an articulation sensor configured to sense the articulation angle between the front and rear frame members; and a tractive drive system coupled to the power source and including a plurality of electric drive motors each configured to drive a corresponding first or second tractive element of the front frame member or a corresponding first or second tractive element of the rear frame member, wherein based on the sensed articulation angle the tractive drive system is configured to prevent ground disturbance by commanding control signals to each of the plurality of electric drive motors to independently actuate each of the first and second tractive elements on the front and rear frame members.

11. The articulated power machine of claim 10, wherein the tractive drive system comprises a plurality of electric drive motors and a plurality of corresponding gear systems, each of the plurality of electric drive motors being configured to actuate one of the first and second tractive elements of the front frame member or one of the first and second tractive elements of the rearframe member and each of the plurality of gear systems being operably coupled to one of the plurality of electric drive motors.

12. The articulated power machine of claim 11, wherein the tractive drive system is further configured to apply a first speed and direction to the first tractive element of the front frame member and to the first tractive element of the rear frame member and apply a second speed and direction to the second tractive element of the front frame member and to the second tractive element of the rear frame member, wherein the second speed is greater than the first speed.

13. The articulated power machine of claim 11, wherein the tractive drive system is further configured to apply a first speed and a first direction to the first tractive element of the front frame member, apply a second speed and a second direction to the first tractive element of the rear frame member, apply a third speed and the second direction to the second tractive element of the front frame member and apply a fourth speed and the first direction to the second tractive element of the rear frame member, wherein the first and third speeds are greater than the second and fourth speeds and the second direction opposes the first direction so that the first tractive elements are driven towards each other and the second tractive elements are driven away from each other.

14. The articulated power machine of claim 10, wherein the power source provides electricity to the tractive drive system and the tractive drive system comprises an all-electric tractive drive system including the plurality of electric drive motors each configured to rotate one of the first or second tractive elements of the front frame member or one of the first or second tractive elements of the rear frame member.

15. A method of preventing ground disturbance in an articulated power machine comprising: providing power to an articulation angle actuator to rotate an articulation joint that rotatably couples front and rear frame members; controlling the articulation angle actuator coupled to the articulation joint to change an angle of articulation between the front frame member and the rear frame member when a steering operation is underway; determining the angle of articulation; andcommanding control signals to each of a plurality of electric drive motors configured to drive a corresponding inner tractive element or outer tractive element of the front frame member or a corresponding inner tractive element or outer tractive element of the rear frame member based on the angle of articulation to independently rotate each of the inner and outer tractive elements on the front frame member and inner and outer tractive elements on the rear frame member.

16. The method of claim 15, wherein when traveling over ground and controlling the articulation joint in the steering operation, the applying of control signals to independently rotate each of the inner and outer tractive elements on the front frame member and the inner and outer tractive elements on the rear frame member comprises applying a first speed and first direction to the inner tractive element of the front frame member and to the inner tractive element of the rear frame member and applying a second speed and direction to the outer tractive element of the front frame member and to the outer tractive element of the rear frame member, wherein the second speed is greater than the first speed.

17. The method of claim 15, wherein when stationary or at zero ground speed and controlling the articulation joint in the steering operation, the commanding of control signals to independently rotate each of the inner and outer tractive elements on the front frame member and the inner and outer tractive elements on the rear frame member comprises applying a first speed and a first direction to the inner tractive element of the front frame member, applying a second speed and a second direction to the inner tractive element of the rear frame member, applying a third speed and the second direction to the outer tractive element of the front frame member and applying a fourth speed and the first direction to the outer tractive element of the rear frame member, wherein the first and second speeds are greater than the third and fourth speeds and the second direction opposes the first direction so that the inner tractive elements are driven towards each other and the outer tractive elements are driven away from each other.

18. The method of claim 15, further comprising generating steering input signals in response to a steering input device configured to be manipulated by an operator to control the articulation angle actuator and to generate the control signal responsive to the steering input signals.

19. The method of claim 18, wherein determining the angle of articulation comprises using the steering input signals and control signals of the steering control unit.

20. The method of claim 15, wherein determining the angle of articulation comprises sensing the angle of articulation between the front frame member and the rear frame member using an articulation sensor.

Images