MOBILE ELEVATED WORK PLATFORM VEHICLES WITH NOVEL STEERING SYSTEM AND RELATED METHODS

Abstract

A vehicle steering system for a compact mobile elevating work platform (“MEWP”) or other vehicle and a method for dynamically determining independent wheel steering angles such that a predetermined steering geometry between steerable wheels of the vehicle are described. The steering system determines coordination of the independent wheels based on angle differences of the steerable wheels. The independent master and follower wheels of the present system are not mechanically linked, and the absence of mechanical linkages between the independent steerable wheels allows for efficiency of spatial efficiency and steering geometry accuracy. The independent operation facilitates accommodation of the steering actuators into confined lateral compartments, which itself enables the machine lifting mechanism to occupy a space hitherto used for a mechanical steering connection between the wheel assemblies.

Claims

1. A mobile elevated work platform vehicle, comprising: a. a vehicle chassis b. a first independently steerable wheel; c. a first steering actuator in mechanical communication with said first independently steerable wheel; d. a second independently steerable wheel; and e. a second steering actuator in mechanical communication with said second independently steerable wheel.

2. (canceled)

3. (canceled)

4. (canceled)

5. The vehicle of claim 1, wherein the vehicle chassis includes a central compartment spans spanning from the front of the vehicle chassis to the back of the vehicle chassis.

6. The vehicle of claim 1, further comprising directionally static rear wheels independently mounted at or near a back end of the vehicle chassis, wherein there is no mechanical linkage between the rear wheels.

7. The vehicle of claim 5, wherein the first steering actuator is nested within a first lateral compartment and is not present in said central compartment.

8. The vehicle of claim 5, wherein the second steering actuator is nested within a second lateral compartment and is not present in said central compartment.

9. The vehicle of claim 1, further comprising a controller having a processor for processing data, a memory, and a data storage device for storing data.

10. (canceled)

11. The vehicle of claim 9, wherein the data storage device stores machine readable instructions to cause the system upon execution of the by the processor to perform the steps of: a. receiving a first signal representative of a first toe angle of said first independently steerable wheel, b. calculating a target toe angle for said second independently steerable wheel based on first toe angle and a predetermined steering geometry, c. receiving a second signal representative of a starting toe angle of said second independently steerable wheel, d. calculating an angular difference between said target toe angle and said second toe angle to determine an angle adjustment for said second independently steerable wheel, and e. sending a steering command from said controller to a steering actuator for said second independently steerable wheel to turn said second independently steerable wheel according to said angle adjustment.

12. A mobile elevated work platform vehicle, comprising: a. a vehicle chassis having i. a central compartment, ii. a first lateral compartment, and iii. a second lateral compartment; b. a first independently steerable wheel; c. a first steering actuator in mechanical communication with said first steering wheel, wherein said first steering actuator and said first independently steerable wheel are nested in said first lateral compartment; d. a second independently steerable wheel; and e. a second steering actuator in mechanical communication with said second steering wheel, wherein said second steering actuator and said second independently steerable wheel are nested in said first lateral compartment.

13. The vehicle of claim 12, wherein there is no mechanical connection between said first independently steerable wheel and said second independently steerable wheel.

14. (canceled)

15. (canceled)

16. (canceled)

17. (canceled)

18. (canceled)

19. The vehicle of claim 12, wherein the central compartment spans from the front of the vehicle chassis to the back of the vehicle chassis.

20. The vehicle of claim 12, further comprising directionally static rear wheels independently mounted at or near a back end of the vehicle chassis, wherein there is no mechanical linkage between the rear wheels.

21. (canceled)

22. (canceled)

23. The vehicle of claim 12, further comprising a controller having a processor for processing data, a memory, and a data storage device for storing data.

24. (canceled)

25. The vehicle of claim 24, further comprising the data storage device bearing instructions to cause the system upon execution of the instructions by the processor to perform the machine-implemented steps of: a. receiving a first signal representative of a first toe angle of a first independently steerable wheel, b. calculating a target toe angle for a second independently steerable wheel based on a predetermined steering geometry, c. receiving a second signal representative of a second toe angle of a second independently steerable wheel, d. calculating an angular difference between said target toe angle and said second toe angle to create a steering command, and e. sending said steering command from said controller to a steering actuator for said second independently steerable wheel to turn said second independently steerable wheel according to the angular difference.

26. A system for determining steering geometry of toe angles independent wheels of a vehicle, comprising: a. a controller having a processor for processing data, a memory, a data storage device for storing data; b. an input device for inputting steering command data; and c. the data storage device storing instructions to cause the system upon execution of the instructions by the processor to perform the machine-implemented steps of: i. receiving a first signal representative of a first toe angle of a first independently steerable wheel, ii. calculating a target toe angle for a second independently steerable wheel based on a predetermined steering geometry, iii. receiving a second signal representative of an initial toe angle of a second independently steerable wheel, iv. calculating an angular difference between said target toe angle and said initial toe angle to create a steering command, and v. sending said steering command from said controller to a steering actuator for said second independently steerable wheel to turn said second independently steerable wheel according to said angular difference.

27. The system of claim 26, further comprising a steering mechanism operable to adjust said toe angle of said first independently steerable wheel, said steering mechanism in electronic communication with said controller.

28. (canceled)

29. (canceled)

30. The system of claim 26, wherein said predetermined steering geometry is an Ackermann geometry, and determining an Ackermann angle of said second independently steerable wheel based on the second toe angle of said first independently steerable wheel.

31. The system of claim 30, determining the steering command comprises the steps of: a. calculating an electrical signal value operable to actuate said steering actuator of said second independently steerable wheel to achieve said Ackerman angle; and b. said electrical signal value from aid controller to said electrical steering actuator of said second independently steerable wheel.

32. The system of claim 27, wherein the controller is further operable to receive a third signal representative of a third toe angle of the first independently steerable wheel when the first independently steerable wheel is being turned to a second direction by manipulation of the steering mechanism.

33. The system of claim 32, calculating a second target toe angle for said second independently steerable wheel based on said third toe angle and said predetermined steering geometry.

34. The system of claim 33, calculating a second angular difference between said second target toe angle and a toe angle of said second independently steerable wheel to create a second steering command.

35. (canceled)

36. (canceled)

37. (canceled)

38. (canceled)

39. (canceled)

40. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWING

[0021] FIG. 1 provides a perspective view of a MEWP vehicle according to an embodiment of the present invention.

[0022] FIG. 2 provides a first side view of a MEWP vehicle according to an embodiment of the present invention.

[0023] FIG. 3 provides a second side view of a MEWP vehicle according to an embodiment of the present invention.

[0024] FIG. 4 provides a perspective view of a MEWP vehicle according to an embodiment of the present invention with the platform assembly removed revealing lower structures.

[0025] FIG. 5 provides a front view of a MEWP vehicle according to an embodiment of the present invention with the front plate of the chassis removed revealing interior structures.

[0026] FIG. 6 provides a perspective view of a MEWP vehicle according to an embodiment of the present invention with the platform assembly extended and elevated.

[0027] FIG. 7 provides an overhead view of an interior of a chassis of a MEWP vehicle according to an embodiment of the present invention.

[0028] FIG. 8 provides a close-up view of an interior of a wheel compartment of a MEWP vehicle according to an embodiment of the present invention.

[0029] FIG. 9 provides an overhead view of an interior of a chassis of a MEWP vehicle during a turning operation according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in reference to these figures and certain implementations and examples of the embodiments, it will be understood that such implementations and examples are not intended to limit the invention. To the contrary, the invention is intended to cover alternatives, modifications, and equivalents that are included within the spirit and scope of the invention as defined by the claims. In the following disclosure, specific details are given to provide a thorough understanding of the invention. References to various features of the “present invention” throughout this document do not mean that all claimed embodiments or methods must include the referenced features. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details or features.

[0031] Reference will be made to the exemplary illustrations in the accompanying drawings, and like reference characters may be used to designate like or corresponding parts throughout the several views of the drawings.

[0032] Referring to FIGS. 1-9, a MEWP vehicle 100 is shown. The MEWP vehicle 100 can be a scissor lift vehicle, boom lift vehicle, or similar vehicle, and is shown as a scissor lift in FIG. 1. The MEWP vehicle 100 includes a vehicle chassis 101 having a central compartment 101a, a first lateral compartment 101b, and a second lateral compartment 101c, which may each serve to house various components of the MEWP vehicle 100. The vehicle 100 includes a retractable lifting mechanism 105 that is nested and stored in central compartment 101a when in the retracted position. The retractable lifting mechanism 105 may be coupled to the chassis 101 and may support a platform assembly 102. The platform assembly 102 may be connected to the superior portion of the retractable lifting mechanism 105, such that the platform assembly 102 is raised as the retractable lifting mechanism 105 is extended from the central compartment 101A.

[0033] As depicted in FIG. 1, the retractable lifting mechanism 105 is a scissor lift structure formed of a series of linked, foldable support members 105A connected to one another using central pivot pins 105B and outer pivot pins 105C. The central pivot pins 105B and outer pivot pins 105C extend through adjacent support members 105A to pivotally couple the support members 105A in an assembly that is vertically extendable and retractable. The lowermost foldable support members 105A may be pivotally coupled to the central compartment 101A and the uppermost foldable support members 105A may be pivotally coupled to an underside of the platform assembly 102. FIG. 5 provides a front view of the MEWP 100 with the front exterior panel of the chassis 100 removed. The retractable lifting mechanism 105 is shown in the retracted position. It can be seen that the retractable lifting mechanism 105 is contained in the central compartment 101A of the chassis 101.

[0034] Adjusting the angular relationships between adjacent support members 105A vertically away from the chassis 101 and away from one another extend the retractable lifting mechanism 105, and alters the position (the height) of the platform assembly 102 relative to the chassis 101. The foldable support members 105A of the retractable lifting mechanism 105 are folded or unfolded using a lift actuator (not shown), such as a hydraulic cylinder, pneumatic cylinder, electric linear actuator, or other appropriate actuator. The lift actuator may be in electronic communication with controller 140 and may be controlled by an operator through the operator interface 102 or ground controls 131. The lift actuator controls the position of the retractable lifting mechanism 105 by selectively applying force to the retractable lifting mechanism 105. For example, extending the actuator will raise the foldable support members and reversing the lift actuator will lower the foldable support members 105A. FIG. 6 shows the retractable lifting system 105 fully extended from the chassis 101.

[0035] FIGS. 7-8 provide interior views of the chassis 101 and the structures therein. In some embodiments, the propulsion of the vehicle may be driven by electric motors 107A and 107B, which are in mechanical connection with the rear wheels 104A and 104B. Electrical motors 107A and 107B may be operable to propel rotation of wheels 104A and 104B, respectively. The electric motors 107A and 107B may be in electrical communication with the controller 140, and their operation may be controlled by the operator through an open loop command operation inputted through the operator interface 102A. In such embodiments, the steering commands may be routed directly from the steering input 102B to the electric motors 107A and 107B or may be routed through the controller 140 and relayed the electric motors 107A and 107B. The operator interface 102A may include the steering input 102B, which may be a rocker switch joystick, or other mechanism that allows the operator to select a direction based on, e.g., the steering switch commands and modulate speed based on speed controls provided at the operator interface 102A. The steering input 102B may electromechanical and may be in electronic communication with a controller 140.

[0036] In some embodiments, the steering signals may be sent from the steering input 102B to the controller 140 and then relayed by the controller 140 to the electric actuators 108A and 108B. The speed may be controlled by a speed control mechanism (e.g., a dial, a throttle switch, a depressible pad or switch, etc.) provided at the operator interface 102A. The controller 140 may track the direction and speed of the MEWP as directed by an operator through the steering input 102B. The rear wheels 104A and 104B may be directionally static, such that they are not utilized for steering the vehicle. Additionally, they may be independently mounted on the chassis 101, such that they are aligned, but not mechanically connected. The absence of a rear axle between the rear wheels 104A and 104B provides additional unobstructed space in the central compartment 101A for storage of the retractable lifting system 105. This aids in reducing the size and compactness of the chassis 101.

[0037] Front wheel assemblies 106A and 106B and rear wheel assemblies 104 may be mounted on lateral portions of the chassis 101. The front wheel assemblies 106A and 106B each having a yoke (109A and 109B, respectively) for connecting to an actuator for controlling steering of the wheel assembly. The steering system includes two separate steering actuators 108A and 108B that are independent and connected independently to wheel assemblies 106A and 106B, respectively. The steering actuator 108A is in mechanical connection with the wheel assembly 106A, and the steering actuator 108B is in mechanical connection with the wheel assembly 106B. There is no mechanical connection between the first wheel assembly 106A and the second wheel assembly 106B, or between steering actuators 108A and 108B. This allows for a compact design, since there is no mechanical linkage between the first and second wheel assemblies 106A and 106B crossing the central compartment 101A. The first wheel assembly 106A is nested and entirely housed in the first lateral compartment 101B and the second wheel assembly 106B is nested and entirely housed in the second lateral compartment 101C.

[0038] In some embodiments, the electric actuators 108A and 108B for the steerable wheels 103A and 103B may be linear actuators positioned at or near an exterior wall of the chassis. The electric actuators may be linear actuators with a stroke length in a range of about 10 mm to about 500 mm (e.g., in a range of about 50 mm to about 250 mm, in a range of about 75 mm to about 125 mm, about 100 mm, or any value or range of values therein). The actuators 108A and 108B are in electronic communication with the electronic controller 140 that provides the control signals to the actuators 108A and 108B.

[0039] The electronic controller 140 may be one or more general purpose computer(s) having at least one processor (Central Processing Unit [CPU]) operable to execute machine executable instructions and provide control signals to the actuators 108A and 108B, the boom actuator, motors 107A and 107B, and other electrical and electronic components of the vehicle 100. The system may further include other components that are well known to one of ordinary skill in the art needed for the function of the general-purpose computer (e.g., a power supply, hard drive, random access memory (RAM), internet connection devices and software, etc.). The system may include a logic unit (e.g., a package of executable instructions saved on the hard drive and executable by the processor) for receiving and processing electronic data. A machine control programming may be saved on a memory of the controller 140 and accessed and executed by the one or more processors of the controller 140. The controller 140 executing the machine control programming receives electronic data from the encoder of the master wheel electric actuator 108A to get an accurate determination of the steering angle of the master wheel. The follower wheel (e.g., wheel assembly 106B) steering angle may be determined in part from encoder data from the follower wheel electric actuator 108B. This data may be employed by the controller 140 executing the machine control programming to calculate a steering angle command for the follower wheel (e.g., wheel 103B).

[0040] The controller 140 may be operable to treat either front wheel assemblies as the master and may be operable to switch the designation of the master wheel between the left and right wheel assemblies. For example, the operator interface may have a selection mechanism for choosing the left or right wheel assembly as the master wheel assembly. The wheel assemblies selected as the master wheel may be under the direct control of the operator interface 102A. For example, the wheel assemblies 103A may be treated as the master wheel. The MEWP may utilize open-loop control with respect to the steering of the master wheel (e.g., wheel assembly 103A) and closed-loop control with regard to the follower wheel (e.g., wheel assembly 103B). Depression of a rocker switch on the operator interface 102 (or lateral movement of a joystick to the left in some embodiments) may be calibrated to rotate the master wheel to a predetermined toe angle to the left, and movement to the right may be calibrated to rotate the master wheel to a predetermined toe angle to the right. The rotational position of the master wheel may be monitored by the position detection device in the master wheel (e.g., an encoder in the electric actuator 108A) and electronically transmitted to the electronic controller 140 to provide the controller 140 with position data for the master wheel (e.g., wheel 103A). The electronic controller 140 executing the machine control programming may then calculate a steer command to the follower wheel (e.g., wheel 103B) based on the change in steering direction of the master wheel, the position of the follower wheel, and the predetermined steer geometry selected for and programmed into the machine control programming.

[0041] Upon the initiation of a turn of the master wheel (e.g., wheel 103A) by steering input on the steering input 102B, a target angle of the follower wheel (e.g., wheel 103B) may be determined by utilizing encoder data from the master wheel electric actuator 108A and from the follower wheel electric actuator 108B. The encoders for the master and follower wheel assemblies are operable to provide accurate position data to the controller 140 and allow the controller 140 to calculate the target steering angle of the follower wheel (e.g., wheel 103B). The electronic controller 140 executing the machine control programming is operable to receive feedback position data from the encoder of the master wheel (e.g., wheel 103A) and identify its position with reference to a predetermined reference point in the range of toe angles for the master wheel (e.g., wheel 103A). The position of the master wheel (e.g., wheel 103A) is determined by the distance of extension or retraction from the reference point, which may be halfway extension point of the linear actuator 108A. The position of the follower wheel (e.g., wheel 103B) is also determined by the distance of extension or retraction from the reference point, which may be halfway extension point of the linear actuator 108B. The controller 140 executing the machine control programming may calculate the target angle of the follower wheel based on the steering angles of the master wheel and the follower wheel after each instance that the steering angle of the master wheel changes. The calculation performed by the controller 140 utilizes the encoder position data from each linear actuator 108A and 108B and the predetermined steering geometry of the system. The encoders for the wheel steering actuators are not independently shown as they may be incorporated into linear actuator devices 108A and 108B In some embodiments, the predetermined steering geometry is Ackermann steering geometry.

[0042] FIG. 9 shows an exemplary turning operation according the present invention in which the predetermined steering geometry is Ackermann geometry. The fixed rear wheels 104A and 104B are aligned, but independently mounted for rotation without a connecting axle. The steerable master wheel assembly 103A and follower assembly 103B are rotatably mounted at or near the front of the chassis 101 in a laterally aligned arrangement, but are independently mounted without a connecting axle between them. The absence of axles between the front wheels and rear wheels allows them to be completely housed within the lateral compartments 101B and 101C of the chassis 101. This design conserves space in the central compartment 101A of the chassis 101 for housing the retractable lifting mechanism 105.

[0043] In Ackermann steering geometry, the outer wheel must turn at a lesser angle than the inner wheel to prevent scuffing of the wheels as the vehicle makes a turn. The center lines of the axes of the rear and front wheels are represented by the wheel axis lines A, B, and C. The lines A and B represent the axes of the master wheel assembly 103A and follower assembly 103B, respectively, and C represents the aligned axes of the rear wheels. A steering system having perfect Ackermann geometry will have an optimum rolling action relative to point D, where the axes A, B, and C intersect. As the master wheel is turned to a change in direction resulting from actuation of the master wheel actuator 108A directed by the steering input 102B, (1) the encoder of the master wheel assembly 103A measures and provides accurate data to the controller 140 of the change in the toe angle of the master wheel (e.g., angle A), (2) the encoder of the follower wheel assembly 103B measures and provides accurate data to the controller 140 of the toe angle of the follower wheel, (3) the controller calculates a target toe angle (e.g., angle B), and (4) the controller 140 sends a control signal to the follower wheel actuator 108B to turn the follower wheel from its current toe angle to the target toe angle (e.g., angle B) such that the axes of the master wheel and follower wheels intersect at the axis of the rear wheels (e.g., at point D) to achieve Ackermann steering geometry. This process is repeatedly on a continuous basis as the operator inputs various steering inputs to the steering mechanism as the operator drives the MEWP vehicle 100.

[0044] The steering system of the present invention is operable to coordinate the toe angles of the master and follower wheels through dynamic process of driving and steering the MEWP vehicle 100 more accurately according to a predetermined geometry (e.g., Ackerman geometry) than a conventional system that utilizes a mechanical linkage between steerable wheels. Mechanical linkages somewhat impair the ability of such systems to match an ideal Ackermann steering geometry. The independent actuation of the master and follower wheels of the present invention under the guidance of an electronic controller 140 provides finer and more dynamic coordination of the independent wheel assemblies, allowing a significantly closer approximation of an ideal steering geometry through an entire range of toe angles of the steerable wheels. This closer approximation of the ideal steering geometry reduces skidding and scuffing of the vehicle's wheels on the ground when advancing through turns relative to mechanically linked systems.

[0045] It is to be understood that variations, modifications, and permutations of embodiments of the present invention, and uses thereof, may be made without departing from the scope of the invention. It is also to be understood that the present invention is not limited by the specific embodiments, descriptions, or illustrations or combinations of either components or steps disclosed herein. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. Although reference has been made to the accompanying figures, it is to be appreciated that these figures are exemplary and are not meant to limit the scope of the invention. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.