Hand grip with microprocessor for controlling a power machine

Information

  • Patent Grant
  • 6550562
  • Patent Number
    6,550,562
  • Date Filed
    Friday, December 8, 2000
    24 years ago
  • Date Issued
    Tuesday, April 22, 2003
    21 years ago
Abstract
A control system controls actuation of a hydraulic cylinder on a skid steer loader. The control system includes a movable element, such as a hand grip. The hand grip is intelligent in that each contains a microprocessor or other digital controller which monitors user actuable elements (such as switches, buttons, paddles, etc.). The controller sends a communication signal to a main control computer. The communication signal is indicative of the state of the user actuable elements and is, in one embodiment, a serial communication signal.
Description




INCORPORATION BY REFERENCE




The following U.S. Patents and Patent Applications are hereby incorporated by reference:




U.S. Pat. No. 5,425,431, issued on Jun. 20, 1995, to Brandt et al., entitled INTERLOCK CONTROL SYSTEM FOR POWER MACHINE, assigned to the same assignee as the present application; and




U.S. Pat. No. 5,187,993 issued on Feb. 23, 1993, to Nicholson et al.




U.S. Pat. No. 5,577,876, issued on Nov. 26, 1996, entitled “HYDRAULIC INTERLOCK SYSTEM” and assigned to the same assignee as the present application.




U.S. patent Ser. No. 09/495,729, filed Feb. 1, 2000, entitled IMPROVED ATTACHMENT CONTROL DEVICE.




BACKGROUND OF THE INVENTION




The present invention deals with power machines. More specifically, the present invention deals with electronic controls of hydraulic cylinders on a skid steer loader.




Power machines, such as skid steer loaders, typically have a frame which supports a cab or operator compartment and a movable lift arm which, in turn, supports a work tool such as a bucket. The movable lift arm is pivotally coupled to the frame of the skid steer loader and is powered by power actuators which are commonly hydraulic cylinders. In addition, the tool is coupled to the lift arm and is powered by one or more additional power actuators which are also commonly hydraulic cylinders. An operator manipulating a skid steer loader raises and lowers the lift arm and manipulates the tool, by actuating the hydraulic cylinders coupled to the lift arm, and the hydraulic cylinder coupled to the tool. Manipulation of the lift arm and tool is typically accomplished through manual operation of foot pedals or hand controls which are attached by mechanical linkages to valves (or valve spools) which control operation of the hydraulic cylinders.




Skid steer loaders also commonly have an engine which drives a hydraulic pump. The hydraulic pump powers hydraulic traction motors which provide powered movement of the skid steer loader. The traction motors are commonly coupled to the wheels through a drive mechanism such as a chain drive. A pair of steering levers are typically provided in the operator compartment which are movable fore and aft to control the traction motors driving the sets of wheels on either side of the skid steer loader. By manipulating the steering levers, the operator can steer the skid steer loader and control the loader in forward and backward directions of travel.




It is also common for the steering levers in the operator compartment of the skid steer loader to have hand grips which support a plurality of buttons or actuable switches. The switches are actuable by the operator and are configured to perform certain functions. However, the hand grips simply contain, for example, actuable switches which are each wired to a main electronic controller or other circuit located remotely from the hand grip. This requires a fairly extensive wire harness or wiring assembly, to be incorporated into the hand grips during manufacturing. Also, different hand grips or wiring assemblies must often be used with different machine models because machine operation or functionality is slightly different or contains different options.




SUMMARY OF THE INVENTION




A control system controls actuation of a hydraulic cylinder on a skid steer loader. The control system includes movable elements, such as hand grips. The hand grips are intelligent in that each contains a microprocessor or other digital controller which monitors user actuable elements (such as switches, buttons, paddles, etc.). The controller sends a communication signal to a main control computer. The communication signal is indicative of the state of the user actuable elements and is, in one embodiment, a serial communication signal.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a side view of a skid steer loader according to the present invention.





FIGS. 2

is a block diagram of one embodiment of a control system in accordance with the present invention.





FIGS. 3A-3E

illustrate a hand grip assembly and button configuration according to one embodiment of the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS





FIG. 1

is a side elevational view of one embodiment of a skid steer loader


10


according to the present invention. Skid steer loader


10


includes a frame


12


supported by wheels


14


. Frame


12


also supports a cab


16


which defines an operator compartment and which substantially encloses a seat


19


on which an operator sits to control skid steer loader


10


. A seat bar


21


is pivotally coupled to a front or rear portion of cab


16


. When the operator occupies seat


19


, the operator then pivots seat bar


21


from the raised position (shown in phantom in

FIG. 1

) to the lowered position shown in FIG.


1


.




A pair of steering levers


23


(only one of which is shown in

FIG. 1

) are mounted within cab


16


. Levers


23


are manipulated by the operator to control forward and rearward movement of skid steer loader


10


, and in order to steer skid steer loader


10


. It should be noted that levers


23


can be replaced by, for example, a joystick assembly, one embodiment of which is illustrated in greater detail with respect to

FIGS. 3A-3E

.




A lift arm


17


is coupled to frame


12


at pivot points


20


(only one of which is shown in

FIG. 1

, the other being identically disposed on the opposite side of loader


10


). A pair of hydraulic cylinders


22


(only one of which is shown in

FIG. 1

) are pivotally coupled to frame


12


at pivot points


24


and to lift arm


17


at pivot points


26


. Lift arm


17


is coupled to a working tool which, in this embodiment, is a bucket


28


. Lift arm


17


is pivotally coupled to bucket


28


at pivot points


30


. In addition, another hydraulic cylinder


32


is pivotally coupled to lift arm


17


at pivot point


34


and to bucket


28


at pivot point


36


. While only one cylinder


32


is shown, it is to be understood that any desired number of cylinders can be used to work bucket


28


or any other suitable tool.




The operator residing in cab


16


manipulates lift arm


17


and bucket


28


by selectively actuating hydraulic cylinders


22


and


32


. In prior skid steer loaders, such actuation was accomplished by manipulation of foot pedals in cab


16


or by actuation of hand grips in cab


16


, both of which were attached by mechanical linkages to valves (or valve spools) which control operation of cylinders


22


and


32


. However, in accordance with the present invention, this actuation is accomplished by moving a movable element, such as a foot pedal or a hand grip or user actuable switch or button on a hand grip on steering lever


23


or on a joystick assembly, and electronically controlling movement of cylinders


22


and


32


based on the movement of the movable element. In one embodiment, movement of the movable elements is sensed by a controller in the hand grip and is communicated to a main control computer used to control the cylinders and other hydraulic or electronic functions on a loader


10


.




By actuating hydraulic cylinders


22


and causing hydraulic cylinders


22


to increase in length, the operator moves lift arm


17


, and consequently bucket


28


, generally vertically upward in the direction indicated by arrow


38


. Conversely, when the operator actuates cylinder


22


causing it to decrease in length, bucket


28


moves generally vertically downward to the position shown in FIG.


1


.




The operator can also manipulate bucket


28


by actuating cylinder


32


. This is also illustratively done by pivoting or actuating a movable element (such as a foot pedal or a hand grip or a button or switch on a hand grip) and electronically controlling cylinder


32


based on the movement of the element. When the operator causes cylinder


32


to increase in length, bucket


28


tilts forward about pivot points


30


. Conversely, when the operator causes cylinder


32


to decrease in length, bucket


28


tilts rearward about pivot points


30


. The tilting is generally along an arcuate path indicated by arrow


40


.




While this description sets out many primary functions of loader


10


, a number of others should be mentioned as well. For instance, loader


10


may illustratively include blinkers or turn signals mounted to the outside of the frame


12


. Also loader


10


may include a horn and additional hydraulic couplers, such as front and rear auxiliaries, which may be controlled in an on/off or proportional fashion. Loader


10


may also be coupled to other tools which function in different ways than bucket


28


. Therefore, in addition to the hydraulic actuators described above, loader


10


may illustratively include many other hydraulic or electronic actuators as well.




System Block Diagram




1. Control System


42







FIG. 2

is a block diagram which better illustrates operation of a control system


42


according to one embodiment of the present invention. Control system


42


includes an operator moveable element such as hand grip assembly


44


, user actuable buttons, switches or triggers


45


on hand grip assembly


44


, a foot pedal assembly, or another suitable movable element. Control system


42


also includes position sensor


46


, controller


47


mounted to hand grip assembly


44


, controller


48


, actuator


50


, valve spool


52


and hydraulic cylinder


54


, and other actuators or controllers collectively referred to by number


56


. In the preferred embodiment, control system


42


is also coupled to an interface control system


58


which includes a plurality of sensors


60


, an operator interface


62


and an interface controller


64


.




Hand grip assembly


44


is illustratively pivotally mounted to one of steering levers


23


in loader


10


or to a joystick assembly, such as that illustrated in

FIGS. 3A-3E

. Position sensor


46


, in one illustrative embodiment, is a potentiometer, resistive strip-type position sensor, or a Hall Effect sensor. As hand grip assembly


44


is pivoted, position sensor


46


senses movement of hand grip assembly


44


and provides a position signal indicative of the position of hand grip assembly


44


. This signal is illustratively provided to controller


47


(but can alternatively be provided directly to controller


48


). Controller


47


also illustratively receives signals from hand grip buttons, switches, triggers, paddles, etc . . . (collectively referred to as buttons


45


). Controller


47


is illustratively a microprocessor, microcomputer, programmable controller or other type of digital controller, mounted to hand grip


44


, and provides a signal, illustratively over a serial or parallel communication link, to controller


48


. The signal is representative of the state of the buttons


45


and sensor


46


. In one illustrative embodiment, controller


47


periodically polls the buttons


45


and sensor


46


, but can be interrupt driven as well.




Controller


48


is illustratively a programmable digital microcontroller, microprocessor or microcomputer, and receives the communication signal from controller


47


. Controller


48


is mounted on loader


10


remotely from controller


47


, such as on or under the dash or control panel in loader


10


, or to one side of the operator's compartment. In response to the position signal, controller


48


provides a control signal to actuator


50


or other actuators or controllers


56


.




Actuator


50


is illustratively a linear actuator which is coupled to valve spool


52


by a suitable linkage. In response to the control signal provided by controller


48


, actuator


50


moves valve spool


52


in a desired direction. It should be noted that actuator


50


can also be any suitable actuator such as, for example, one which is integrally formed with the valve which it actuates or spool


52


. The precise mode by which spool


52


is moved is not critical to the primary inventive features of the invention. Valve spool


52


is coupled to hydraulic cylinder


54


and controls flow of hydraulic fluid to hydraulic cylinder


54


in response to the output from actuator


50


. In the preferred embodiment, hydraulic cylinder


54


is one of hydraulic cylinders


22


and


32


. Therefore, control system


42


manipulates lift and tilt cylinders


22


and


32


based on pivotal movement of hand grip assembly


44


.




Controller


48


also may illustratively receive a feedback signal which indicates the position of valve spool


52


. In one embodiment, controller


48


receives the feedback signal from actuator


50


indicating the position of actuator


50


. This, in turn, indicates the position of valve spool


52


. In another embodiment, controller


48


receives the feedback signal from valve spool


52


which directly indicates the position of valve spool


52


. Upon receiving the feedback signal from either actuator


50


or valve spool


52


, controller


48


compares the actual position of valve spool


52


to the target or input position from hand grip assembly


44


and makes necessary adjustments. Thus, controller


48


illustratively operates in a closed loop fashion.




As mentioned above, controller


48


can also control other actuators and controllers


56


based on the operator inputs (and thus represented by the communication signal received from controller


47


). For example, other actuators and controllers


56


can be include blinkers, a horn, valve spool actuators which control hydraulic fluid flow to front or rear auxiliary couplers, an attachment control device (ACD) used to control attachments, a proportional controller used to control hydraulic flow in a proportional or on/off fashion, or other hydraulic or electronic actuators or controllers.




2. Interface Control System


58






Interface control system


58


is described in greater detail in U.S. Pat. No. 5,425,431, issued on Jun. 20, 1995, to Brandt et al., entitled INTERLOCK CONTROL SYSTEM FOR POWER MACHINE, assigned to the same assignee as the present application, and hereby incorporated by reference. Briefly, interface control system


58


receives input signals from a plurality of sensors


60


which indicate operating parameters such as operator presence from a seat sensor, and such as seat bar position from a seat bar sensor. Interface controller


64


also receives inputs from operator interface


62


which, in one preferred embodiment, is simply an ignition switch and a display. Based on the inputs received, interface controller


64


controls certain hydraulic and electrical components in skid steer loader


10


. Interface controller


64


illustratively inhibits certain operation of loader


10


until some certain combination of inputs from sensors


60


is received. For instance, upon receiving appropriate signals, interface controller


64


may enable operation of wheels


14


, or may enable certain hydraulic functions performable by skid steer loader


10


.




Interface controller


64


is also illustratively a digital computer, microcontroller, or other suitable controller. Interface controller


64


is connected to controller


48


by a serial bus, a parallel bus, or other suitable interconnection.




3. Interaction Between Systems


42


and


58


.




Interface controller


64


is also configured to disable operations performable by controller


48


under certain circumstances. For example, upon power-up, interface controller


64


inhibits the operations performable by controller


48


until sensors


60


indicate that seat bar


21


is in the lowered position and that the operator has requested operation. At that point, interface controller


64


provides controller


48


with a signal enabling controller


48


to perform functions. If, however, sensors


60


were to indicate that the operator is not in seat


19


, or that the seat bar


21


is not in the lowered position, interface controller


64


would continue to provide controller


48


with a signal inhibiting actuation of cylinders


22


or


32


until the sensors


60


provide appropriate signals. Once sensors


60


provide signals which allow controller


64


to “unlock” controller


48


, controller


48


can also perform certain diagnostic or calibration functions.




While the above description has proceeded describing controllers


48


and


64


as separate controllers, it is to be understood that the functions performed by each can be combined into a single controller, or can be divided among a greater number of controllers. Such a combination or division of functions may be desirable depending on a given application.




4. Float




Controller


48


also illustratively controls cylinder


54


to accomplish another function. It may be desirable, at certain times, for the operator of skid steer loader


10


to cause lift arm


17


(or the tool, such as bucket


28


) to float. By floating it is meant that there is no positive hydraulic control of the particular cylinder which is floating.




For instance, the operator of skid steer loader


10


may wish to operate skid steer loader


10


so that bucket


28


, and lift arm


17


, follow the terrain over which loader


10


is traveling. In that case, the operator simply actuate one of the buttons


45


on hand grip


44


the state of this button is communicated (such as over a serial link) from controller


47


to controller


48


and this indicates to controller


48


that the operator wishes to cause the particular hydraulic cylinder under control to float. In response, controller


48


provides a control signal to actuator


50


causing actuator


50


to move valve spool


52


to a position which effectively connects both hydraulic inputs to hydraulic cylinder


54


together. In this way, the oil which actuates hydraulic cylinder


54


is not pressurized and is free to move from one end of cylinder


54


to the other in response to forces exerted on the cylinder by changes in the terrain.




Hand Grip Assembly


44







FIGS. 3A and 3B

illustrate one embodiment of a hand grip


44


coupled to a joystick assembly


100


. In

FIG. 3A

, hand grip


44


is viewed from the rear (or operator) side, illustrating buttons


45


.

FIG. 3B

is illustrated from the operator's right hand side.




Both

FIGS. 3A and 3B

illustrate phantom figures which show hand grip


44


pivoted from its neutral position. In

FIG. 3A

, hand grip


44


is pivoted to the operator's left hand side (as shown in phantom) in the direction indicated by arrow


102


. Of course, it will be noted that hand grip


44


can be pivoted to the user's right hand side as well.

FIG. 3B

shows hand grip


44


pivoted in the aft direction (toward the user as shown by arrow


104


) as also shown in phantom. Of course, hand grip


44


can also be pivoted in the forward direction.




In one illustrative embodiment, the range of motion (from the solid image to the phantom image shown in both

FIGS. 3A and 3B

) is approximately 4.25 inches, and is offset by an angle of approximately 20 degrees. It should also be noted that, in one embodiment, joystick assembly


100


is a commercially available joystick assembly produced and available from the Sauer Company.





FIGS. 3A and 3B

also schematically illustrate controller


47


which is embedded within hand grip


44


. In one illustrative embodiment, controller


47


is contained in a module with associated memory, that is embedded within the interior of hand grip


44


while a flex circuit couples buttons


45


to controller


47


. In one embodiment, the exterior of hand grip


44


is hard or soft plastic or rubber, or a hard material with a friction increasing surface (such as texture or a softer gripping material) disposed where the user's hand engages the hand grip


44


, such as under the palm region, the finger region and/or the finger tip region. The controller


47


(and possibly an associated circuit board) are illustratively, securely attached within an inner cavity of hand grip


44


through adhesive, screws, clamps or another mechanical attachment mechanism. In one illustrative embodiment, a three conductor serial communication link is provided between controller


47


and controller


48


. The three conductors include power, ground, and a serial communication conductor. In another embodiment, controller


47


includes a wireless transmitter while controller


48


includes a wireless receiver. Wireless communication is then effected between the two using radiation, such as radio signals, infrared signals or other electromagnetic radiation.





FIGS. 3C and 3D

better illustrate the arrangement of buttons


45


on hand grip


44


. Buttons


45


include a pair of rocker switches


106


and


108


, a pair of push button toggle switches


110


and


112


, a paddle


114


, a push button toggle switch


116


, and a trigger


118


. Both the left and right hand grips


44


are, in one illustratively embodiment, identical. Therefore, only the right hand grip


44


is illustrated in

FIGS. 3A-3E

.




In one illustrative embodiment, the buttons


45


on the left hand grip


44


control a number of functions, including the left blinker, a stability override function, a left ski up and left ski down function, the rear auxiliary control, a boom extension function, the horn and, for an all wheel drive machine, a driving mode change function. For example, in one embodiment, switch


110


is the left blinker switch. Therefore, when the operator depresses button


110


, the left blinker turns on, and when the operator again depresses button


110


, the left hand blinker turns off. Rocker switch


105


controls the raising and lowering of skis coupled to an attachment. The rocker switch


106


controls a side shift function associated with the rear auxiliaries, paddle


114


controls a boom extension function, push button


116


controls the horn, and trigger


118


controls the steering mode change.




In one illustrative embodiment, the right hand grip


44


includes a number of different functions as well. In one embodiment, push button


110


is a spare user input, while push button


112


controls the right hand blinker. Rocker switch


105


controls flow of hydraulic fluid to the front auxiliaries in the first direction and a second direction (depending on the position of the rocker switch), rocker switch


106


controls the loader to operate in a fast or slow mode in two speed operation (depending on the position of the rocker switch), button


116


controls the float operation, and trigger


118


provides a detent function to the auxiliary hydraulic output. It has been found that these functions, associated with these buttons, are particularly useful to users. However, it should be noted that other functions could be assigned to the buttons as well.





FIGS. 3D and 3E

illustrate the spacing and separation of the various buttons


45


, in accordance with one illustrative embodiment. It should be noted that paddle


114


is generally located centrally of buttons


45


and is easily assessable by the user's thumb. The remainder of the buttons are also within an ergonomic range which provides ease of access through a normal thumb swing from paddle


114


.




Paddle


114


has a center-to-center spacing from button


116


illustrated by A in FIG.


3


E. This is, in one illustrative embodiment, in a range of 0.75-1.25, and is illustratively approximately one inch. Button


116


has a center-to-center spacing from the lower pad of rocker switches


104


and


105


illustrated by B which is, illustratively, in a range of 0.5-0.9 inches and may be illustratively, approximately 0.7 inches. Similarly, button


116


has a center-to-center spacing from the upper pad of rocker switches


105


and


106


which is illustratively in a range of 0.7-1.1 inches and may be approximately 0.9 inches. The lower and upper pads of rocker switches


105


and


106


have a center-to-center spacing D which is illustratively in a range of 0.45-0.65 inches, and may be approximately 0.57 inches. The center-to-center spacing E between button


116


and the lower pad of rocker switches


105


and


106


(in the vertical direction) is in a range of approximately 0.6-0.75 inches and may be approximately 0.68 inches. Switches


116


and


110


and


112


have a center-to-center spacing in the vertical direction labeled F which is illustratively in a range of approximately 1.50-2.00 inches, and may be approximately 1.75 inches. Switches


110


and


112


have a center-to-center spacing G, in the horizontal position which is illustratively in a range of 0.60-1.00 inches, and may be 0.8 inches. Similarly, paddle


114


and switches


110


and


112


have a center-to-center spacing, in the horizontal direction, labeled H, which is illustratively in a range of 0.20-0.60 inches, and may be approximately 0.4 inches. The center of trigger


118


is also located a dimension I from the base of hand grip


44


. In one illustrative embodiment, the dimension I is in a range of 4.00-5.00 inches, and may be approximately 4.54 inches. While other suitable dimensions could be used as well, it has been found that these dimensions provide an ergonomic benefit in the form of comfort and accessibility to the user.




It can thus be seen that the present invention provides a smart handle assembly in that a microprocessor is embedded in the hand grip. The microprocessor receives or senses inputs from various buttons, switches, position sensors, etc. The state of the buttons, switches, and sensors is provided to a remotely located main control computer along a communication link which may illustratively be a serial communication link. Therefore, the communication can be provided over a highly simplified wiring harness, and can be provided as, for example, serial communication, regardless of the model of the machine or the specific type of hand grip used.




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 and detail without departing from the spirit and scope of the invention.



Claims
  • 1. A control system for a power machine having actuators, the control system comprising:a main electronic controller providing outputs to control the actuators; a first user input device, remote from the main electronic controller, receiving user inputs; and a first input electronic controller, mounted on the first user input device and coupled for communication with the main electronic controller, receiving a signal indicative of user inputs and providing a communication signal to the main electronic controller, the communication signal being based on the user inputs.
  • 2. The control system of claim 1 wherein the main electronic controller is configured to control the actuators based, at least in part, on the communication signal received from the first input electronic controller.
  • 3. The control system of claim 1 wherein the first input electronic controller is coupled to the main electronic controller by a serial communication link.
  • 4. The control system of claim 3 wherein the serial communication link comprises a wireless link.
  • 5. The control system of claim 1 wherein the first user input device comprises:a first plurality of finger-actuable input devices.
  • 6. The control system of claim 5 wherein the first user input device comprises:a first hand grip and wherein the finger-actuable input devices are mounted on the first hand grip and positioned for finger-actuation.
  • 7. The control system of claim 6 wherein the first hand grip is mounted to a joystick assembly such that pivotal movement of the first hand grip causes movement of the joystick assembly.
  • 8. The control system of claim 1 and further comprising:a second user input device, remote from the main electronic controller, receiving user inputs; and a second input electronic controller, mounted on the second user input device and coupled for communication with the main electronic controller, receiving a signal indicative of user inputs and providing a communication signal to the main electronic controller, the communication signal being based on the user inputs.
  • 9. The control system of claim 8 wherein the main electronic controller is configured to control the actuators based, at least in part, on the communication signal received from the second input electronic controller.
  • 10. The control system of claim 8 wherein the second input electronic controller is coupled to the main electronic controller by a serial communication link.
  • 11. The control system of claim 10 wherein the serial communication link comprises a wireless link.
  • 12. The control system of claim 8 wherein the second user input device comprises:a second plurality of finger-actuable input devices.
  • 13. The control system of claim 12 wherein the second user input device comprises:a second hand grip and wherein the finger-actuable input devices are mounted on the second hand grip and positioned for finger-actuation.
  • 14. The control system of claim 13 wherein the second hand grip is mounted to a joystick assembly such that pivotal movement of the second hand grip causes movement of the joystick assembly.
  • 15. A user input system mountable to a power machine to provide user inputs for controlling the power machine, the user input device comprising:a first handle receiving user inputs; and a first input electronic controller, mounted to the first handle and coupled for communication with a remotely located electronic controller, the first input electronic controller receiving a signal indicative of user inputs and providing a communication signal based on the user inputs.
  • 16. The user input system of claim 15 wherein the first handle comprises:a first plurality of finger-actuable input devices.
  • 17. The user input system of claim 16 wherein the first handle comprises:a first hand grip and wherein the finger-actuable input devices are mounted on the first hand grip and positioned for finger-actuation.
  • 18. The user input system of claim 17 wherein the first hand grip is mounted to a joystick assembly such that pivotal movement of the first hand grip causes movement of the joystick assembly.
  • 19. The user input system of claim 15 and further comprising:a second handle receiving user inputs; and a second input electronic controller, mounted on the second handle and coupled for communication with the remotely located electronic controller, the second input electronic controller receiving a signal indicative of user inputs and providing a communication signal to the main electronic controller, the communication signal being based on the user inputs.
  • 20. The user input system of claim 19 wherein the second handle comprises:a second plurality of finger-actuable input devices.
  • 21. The user input system of claim 20 wherein the second handle comprises:a second hand grip and wherein the finger-actuable input devices are mounted on the second hand grip and positioned for finger-actuation.
  • 22. The control system of claim 21 wherein the second hand grip is mounted to a joystick assembly such that pivotal movement of the second hand grip causes movement of the joystick assembly.
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