HK1195289B - Towbarless airplane tug - Google Patents

Abstract

A towbarless airplane tug comprising: a chassis mounted on a plurality of tug wheels, at least some of said plurality of tug wheels being steerable tug wheels; an airplane wheel support assembly, mounted on said chassis, for supporting rotatable wheels of a nose landing gear of an airplane; at least one tug wheel driver operative to drive said plurality of tug wheels in rotation to provide displacement of said chassis; and at least one tug controller operative to control speed of said tug, said at least one tug controller employing at least one feedback loop utilizing a mapping of speed limits along a travel path traversed by said tug and said airplane at said airport as well as an indication of the instantaneous location of said tug and said airplane along a travel path.

Description

Airplane tractor without draw bar

The application is a divisional application of Chinese patent application with the application number of 200880024713.4, the application date of 2008, 4 and 2, and the invention name of 'airplane tractor without traction rod'.

Reference to related application

The following unpublished patent applications are related to the present application and the disclosures thereof are hereby incorporated by reference:

U.S. patent application No. 11/528,647 entitled "system and method for transferring aircraft", filed on 28.9.2006; united states patent application number 11/798,777 entitled "system and method for transferring aircraft", filed on 16.5.2007; PCT patent application No. IL2007/001172 entitled "system and method for transferring aircraft", filed 24.9.2007; and PCT patent application No. IL2008/000036 entitled "system and method for transferring aircraft", filed on 8/1/2008.

Thus, the following applications are claimed in accordance with 37CFR1.178(a) (4) and 5 (i): united states patent application number 11/798,777 entitled "system and method for transferring aircraft", filed on 16.5.2007; PCT patent application No. IL2007/001172 entitled "system and method for transferring aircraft", filed 24.9.2007; and PCT patent application No. IL2008/000036 entitled "system and method for transferring aircraft", filed on 8/1/2008.

Technical Field

The present invention relates generally to systems for ground movement of aircraft and, more particularly, to ground vehicles for moving aircraft at airports.

Background

The following patent publications may be considered to represent the state of the art:

6,945,354 th; 6,739,822, respectively; 6,675,920, respectively; 6,751,588, respectively; 6,600,992, respectively; 6,405,975, respectively; 6,390,762, respectively; 6,357,989, respectively; 6,352,130, respectively; 6,305,484, respectively; 6,283,696, respectively; 6,209,671, respectively; 5,860,785, respectively; 5,680,125, respectively; 5,655,733, respectively; 5,562,388, respectively; 5,549,436, respectively; 5,516,252, respectively; 5,511,926, respectively; 5,480,274, respectively; 5,381,987, respectively; 5,346,354, respectively; 5,314,287, respectively; 5,308,212, respectively; 5,302,076, respectively; 5,302,075, respectively; 5,302,074, respectively; 5,261,778, respectively; 5,259,572, respectively; 5,219,033, respectively; 5,202,075, respectively; 5,176,341, respectively; 5,151,003, respectively; 5,110,067, respectively; 5,082,082, respectively; 5,078,340, respectively; 5,054,714, respectively; 5,051,052, respectively; 5,048,625, respectively; 5,013,205, respectively; 4,997,331, respectively; 4,976,499, respectively; 4,950,121, respectively; 4,923,253, respectively; 4,917,564, respectively; 4,917,563, respectively; 4,913,253, respectively; 4,911,604, respectively; 4,911,603, respectively; 4,836,734, respectively; 4,810,157, respectively; 4,745,410, respectively; 4,730,685, respectively; 4,658,924, respectively; 4,632,625, respectively; 4,482,961, respectively; 4,375,244, respectively; 4,225,279, respectively; 4,113,041 and 4,007,890;

2003/095854 U.S. patent publication;

WO 93/13985; PCT patent publication Nos. WO89/03343 and WO 98/52822;

RU 2302980; RU 2271316; EP 1623924; EP 1190947; JP 2279497; JP 4138997; JP 57070741; JP 56002237; GB 1249465; DE 3844744; DE 4446048; DE 4446047; DE 4131649; DE4102861, DE 4009419; DE 4007610; DE 19734238; DE 3534045; DE 3521429; DE 3327629; DE 3327628; DE 4340919; patent publications FR2581965 and FR 2675919.

Disclosure of Invention

The present invention seeks to provide a novel robotic tow vehicle for taxiing aircraft.

There is thus provided in accordance with a preferred embodiment of the present invention a towbarless airplane tug including: a chassis mounted on a plurality of tractor wheels, at least some of the plurality of tractor wheels being steerable tractor wheels; a base assembly mounted on a tractor chassis; an aircraft nose wheel support turret assembly rotatably mounted on the base assembly for supporting the wheels of an aircraft nose landing gear; at least one force sensor operable to detect a force applied to the nose landing gear of the aircraft in at least one approximately horizontal direction resulting from at least one of braking, deceleration and acceleration controlled by the aircraft pilot; at least one tractor wheel driver unit for driving rotation of the plurality of tractor wheels to provide movement of the chassis; at least one tractor wheel steering mechanism for steering steerable tractor wheels during aircraft taxiing; and at least one tractor controller for operating at least partially in response to an output of the at least one force sensor indicative of aircraft pilot controlled braking of the aircraft to operate the at least one tractor wheel driver unit to reduce forces exerted on the aircraft nose landing gear by the aircraft pilot controlled braking.

Preferably, the towbarless aircraft tractor further comprises at least one rotation detector for detecting rotation of the aircraft nose wheel support turret assembly relative to the chassis due at least to pilot controlled steering of the aircraft over the ground, and the at least one tractor controller is further at least for controlling operation of the at least one tractor wheel steering mechanism, the at least one tractor controller operating at least in part in response to an output of the at least one rotation detector indicating pilot controlled steering of the aircraft to steer the at least one tractor wheel steering mechanism to steer the steerable tractor wheels to move the chassis in a direction indicated by the pilot controlled steering.

There is also provided in accordance with another preferred embodiment of the present invention a towbarless airplane tug including: a chassis mounted on a plurality of tractor wheels, at least some of the plurality of tractor wheels being steerable tractor wheels; an aircraft nose wheel support turret assembly rotatably mounted on the chassis for supporting a rotatable wheel of an aircraft nose landing gear; at least one rotation detector for detecting rotation of the aircraft nose wheel support assembly relative to the chassis due at least to pilot controlled steering of the aircraft over the ground; at least one tractor wheel drive for driving rotation of the plurality of tractor wheels to provide movement of the chassis; at least one tractor wheel steering mechanism for steering steerable tractor wheels; and at least one tractor controller at least for controlling operation of the at least one tractor wheel steering mechanism, the at least one tractor controller operating at least partially in response to an output of the at least one rotation detector indicating aircraft steering controlled by the aircraft pilot to steer the at least one tractor wheel steering mechanism to steer steerable tractor wheels to move the chassis in a direction indicated by the pilot-controlled steering.

Preferably, the aircraft nose wheel support turntable assembly is rotatably mounted on the chassis by a bearing. Preferably, the towbarless aircraft tow vehicle further comprises at least one energy absorber assembly fitted between the aircraft nose wheel support turret assembly and the chassis to absorb energy due to inertial forces of the tow vehicle that would otherwise act on the nose landing gear of the aircraft.

Preferably, the towbarless tow vehicle further comprises at least one aircraft wheel engagement assembly for positioning an aircraft wheel on the aircraft nose wheel support turret assembly such that the horizontal centre of rotation of the aircraft nose landing gear is located at the centre of rotation of the aircraft nose wheel support turret assembly relative to the chassis. Additionally, the at least one aircraft wheel engagement assembly may be adapted to hold the wheel of the aircraft nose landing gear in a position such that the horizontal centre of rotation of the wheel of the aircraft nose landing gear is located at the centre of rotation of the aircraft nose wheel support turntable assembly relative to the chassis. Additionally or alternatively, the at least one aircraft wheel engagement assembly may be adapted to the size of the aircraft wheel so as to locate the aircraft wheel on the aircraft wheel support assembly and to hold the aircraft wheel in position so that the wheel of the aircraft nose landing gear is located on the centre of rotation of the aircraft nose wheel support turntable assembly relative to the chassis.

Preferably, the aircraft nose wheel support turntable assembly is pivotally mounted relative to the chassis to allow tilting of the wheels of the aircraft nose landing gear during movement of the aircraft. Additionally or alternatively, the towbarless aircraft tug has an operating mode for airplane pushback, controlled by the tug driver, and an operating mode for movement of the airplane during taxiing following at least one of pushback and landing, controlled by the airplane pilot.

Preferably, the towbarless aircraft tug has an autonomous mode of operation for movement of the aircraft during taxiing following at least one of pushback and landing. Further, in this autonomous mode of operation, the tractor controller may respond to commands received from the airport commands and control center. Additionally or alternatively, in this autonomous mode of operation, the tractor controller may respond to preprogrammed driving paths and speed limits, as well as to tractor position information received via tractor position functions mounted on the tractor.

Preferably, the towbarless aircraft tractor has an autonomous mode of operation for returning the tractor from the takeoff area to the pushback position.

Preferably, the towbarless aircraft tow vehicle has a tow vehicle speed control function which allows the tow vehicle to travel at different locations in the airport up to different speed limits.

Preferably, the at least one tractor controller is operable to control acceleration and deceleration of the tractor to limit the force applied to the nose landing gear of the aircraft, the at least one tractor controller using at least one force feedback loop that utilizes input from the at least one force sensor and at least one of: readings of known inclinations at various locations along the aircraft running surface traversed by the tow vehicle, wherein the locations are identified to the at least one tow vehicle controller by tow vehicle position and inclination detection functionality; a reading of wind forces acting on the aircraft; readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein the locations are identified to the at least one towing vehicle controller by a location detection function; and obstacle detection readings. In another preferred embodiment, the at least one force feedback loop utilizes input from the at least one sensor and the following inputs: readings of known inclinations at various locations along the aircraft running surface traversed by the tow vehicle, wherein the locations are identified to the at least one tow vehicle controller by tow vehicle position and inclination detection functionality; a reading of wind forces acting on the aircraft; readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein the locations are identified to the at least one towing vehicle controller by a location detection function; and obstacle detection readings.

Preferably, the at least one tractor controller is operable to control the speed of the tractor and to use at least one speed feedback loop that utilizes at least one of the following inputs: readings of known desired velocities at various locations along the aircraft running surface traversed by the tow vehicle are obtained by the at least one tow vehicle controller using tow vehicle position detection functionality and a predetermined aircraft running surface map indicative of speed limits along the roadway; and information of the required speed provided by the aircraft main controller to the at least one tractor controller.

Preferably, the at least one tractor controller is operable to control the steering of the tractor by using at least one position feedback loop which utilises at least the rotation readings of the wheels of the aircraft nose landing gear provided by the at least one rotation detector.

There is also provided in accordance with yet another preferred embodiment of the present invention a towbarless airplane tug including: a chassis mounted on a plurality of tractor wheels, at least some of the plurality of tractor wheels being steerable tractor wheels; an aircraft wheel support assembly mounted on the chassis for supporting a rotatable wheel of an aircraft nose landing gear; at least one force sensor operable to detect forces exerted on the nose landing gear of the aircraft in at least one approximately horizontal direction; at least one tractor wheel drive operable to drive rotation of the plurality of tractor wheels to provide movement of the chassis; at least one tractor controller operable to control acceleration and deceleration of the tractor to limit forces acting on the nose landing gear of the aircraft, the at least one tractor controller using at least one force feedback loop that utilizes input from the at least one force sensor and at least one of: readings of known inclinations at various locations along the aircraft running surface traversed by the tow vehicle, wherein the locations are identified to the at least one tow vehicle controller by tow vehicle position and inclination detection functionality; a reading of wind forces acting on the aircraft; readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein the locations are identified to the at least one towing vehicle controller by a location detection function; and obstacle detection readings.

Preferably, the at least one tractor controller uses at least one feedback loop that utilizes input from the at least one force sensor and at least two of: readings of known inclinations at various locations along the aircraft running surface traversed by the tow vehicle, wherein the locations are identified to the at least one tow vehicle controller by tow vehicle position and inclination detection functionality; a reading of wind forces acting on the aircraft; readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein the locations are identified to the at least one towing vehicle controller by a location detection function; and obstacle detection readings.

Preferably, the at least one tractor controller uses at least one feedback loop that utilizes input from the at least one force sensor and all of the following: readings of known inclinations at various locations along the aircraft running surface traversed by the tow vehicle, wherein the locations are identified to the at least one tow vehicle controller by tow vehicle position and inclination detection functionality; a reading of wind forces acting on the aircraft; readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein the locations are identified to the at least one towing vehicle controller by a location detection function; and obstacle detection readings.

Preferably, the towbarless aircraft tow vehicle further comprises at least one energy absorber assembly mounted on the chassis to absorb forces generated by the inertia of the tow vehicle that would otherwise act on the nose landing gear of the aircraft. Additionally or alternatively, the aircraft nose wheel support turntable assembly is rotatably mounted on the chassis by a bearing.

Preferably, the towbarless tow vehicle further comprises at least one aircraft wheel engagement assembly for locating an aircraft wheel on the aircraft wheel support assembly such that the aircraft nose landing gear is centered in rotation of the aircraft wheel support assembly relative to the chassis. Additionally, the at least one aircraft wheel engagement assembly may be used to hold the aircraft wheel in position so that the wheel of the aircraft nose landing gear is centered in rotation of the aircraft wheel support turret assembly relative to the chassis. Additionally or alternatively, the at least one aircraft wheel engagement assembly may be adapted to the size of the aircraft wheel so as to locate the aircraft wheel on the aircraft wheel support assembly and to hold the aircraft wheel in position so that the aircraft nose landing gear is located on the centre of rotation of the aircraft wheel support assembly relative to the chassis.

Preferably, the at least one energy absorber assembly comprises a plurality of pistons that absorb energy as the tow vehicle accelerates or decelerates relative to the aircraft.

Preferably, the at least one tractor controller is responsive to input signals from the airport command and control system.

There is also provided in accordance with another preferred embodiment of the present invention a towbarless airplane tug including: a chassis mounted on a plurality of tractor wheels, at least some of the plurality of tractor wheels being steerable tractor wheels; an aircraft wheel support assembly mounted on the chassis for supporting a rotatable wheel of an aircraft nose landing gear; at least one tractor wheel drive operable to drive rotation of the plurality of tractor wheels to provide movement of the chassis; and at least one tractor controller operable to control the speed of the tractor, the at least one tractor controller using at least one feedback loop that utilizes a plot of speed limits along a travel path traversed by the tractor and aircraft at the airport and a reading of instantaneous positions of the tractor and aircraft along the travel path.

Drawings

The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a schematic illustration of a towbarless aircraft tow vehicle constructed and operative in accordance with a preferred embodiment of the present invention;

FIG. 1B is a cross-sectional view of a towbarless aircraft towing vehicle constructed and operative in accordance with a preferred embodiment of the present invention, taken along line 1B-1B in FIG. 1A;

FIG. 1C is a top view of the towbarless airplane tug of FIGS. 1A and 1B;

2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I and 2J are schematic illustrations of various stages in a prognostic push and push operation, respectively, of the towbarless aircraft towing vehicle of FIGS. 1A-1C;

FIGS. 3A, 3B, 3C, 3D and 3E are schematic illustrations of various stages in a pilot-controlled taxiing operation of the towbarless aircraft tug of FIGS. 1A-1C, respectively, in accordance with one embodiment of the present invention;

4A, 4B, 4C, 4D and 4E are schematic illustrations of various stages in autonomous taxi operation of the towbarless aircraft tow of FIGS. 1A-1C, respectively, in accordance with an alternative embodiment of the present invention;

FIGS. 5A, 5B, 5C, 5D and 5E are schematic illustrations of various stages in an autonomous return operation of the towbarless aircraft tow vehicle of FIGS. 1A-1C, respectively; and

fig. 6A, 6B and 6C are illustrations of the steering function of the towbarless aircraft tug of fig. 1A-1C, respectively.

Detailed Description

The present invention relates to a new type of robotic tractor for taxiing an aircraft from a garage door to a takeoff runway without the use of an aircraft jet engine. According to a preferred embodiment of the invention, the robotic tractor is preferably operated in a taxi mode controlled by the aircraft pilot, in which mode the aircraft pilot steers and brakes as if the aircraft were moving using its own engine power, and the speed of the tractor is controlled by the controller. The tow vehicle preferably autonomously returns to a pre-tow position at the garage door under the control of the airport command and control system when the aircraft is finished taxiing. Preferably, the tractor driver performs a push-back operation, after which he leaves the tractor, which is controlled by the aircraft pilot during taxiing. According to an alternative embodiment of the invention, the tow vehicle may be operated in an autonomous mode of operation during taxiing of the aircraft. Throughout, the term "autonomous" is used broadly to include operations under the control of airport command, control and communication systems (preferably, aircraft pilot priority).

Referring now to fig. 1A, 1B and 1C, there is shown a towbarless aircraft tow 100 constructed and operative in accordance with a preferred embodiment of the present invention. As seen in fig. 1A, 1B and 1C, the towbarless tractor 100 preferably includes a chassis 102 supported on 6 wheels, including front steerable wheels 104 and 106, rear steerable wheels 108 and 110, and intermediate non-steerable wheels 112 and 114. It is conceivable that: alternatively, wheels 112 and 114 may be steerable. The centers of rotation of steerable wheels 104, 106, 108 and 110, indicated by reference numerals 115, 116, 117 and 118, respectively, preferably define the vertices of a rectangle having a length a defined by the spacing between the centers of rotation of the respective front and rear wheels on the same side of tractor 100 and a width B defined by the spacing between the centers of rotation 115 and 116 of respective front wheels 104 and 106 and the spacing between the centers of rotation 117 and 118 of respective rear wheels 108 and 110.

Each of the wheels 104, 106, 108, 110, 112 and 114 is preferably controllably driven by a corresponding hydraulic motor (not shown) powered by a corresponding hydraulic pump (not shown) driven by the vehicle's diesel engine (not shown) in response to speed and torque control signals from a controller 119. Each of the steerable wheels 104, 106, 108 and 110 is preferably steered by one or more steering pistons (not shown) in response to steering control signals from the controller 119.

The driver control interface assembly, which preferably includes a steering wheel 120, brakes (not shown), and optionally other control devices, is preferably interfaced with the controller 119 so that the driver can control the operation of the towbarless aircraft tow 100 before and during pushback, and/or in the event of an emergency or tow control system failure. According to a preferred embodiment of the present invention, the towbarless aircraft tug 100 operates under the control of the aircraft Pilot (PIC) via a controller 119 to taxi to or near the takeoff point. Near the takeoff point, in response to commands received from an airport command and control center or tractor position sensor 121 (such as a GPS sensor or any other suitable tractor position sensor), controller 119 automatically disengages tractor 100 from the aircraft, and tractor 100 operates under the control of controller 119 to autonomously return from the takeoff point to the desired post-propulsion position. The tractor 100 is also preferably equipped with: a wind sensor 122; one or more obstacle detection sensors 123, such as radar and/or laser sensors (e.g., a Velodyne HDL-64E laser scanner), output to controller 119; and one or more steering cameras 124 that enable remote steering of the tractor 100, such as through a remote command and control center. The drive camera 124 may be rotatable to have selectable pan/tilt heads to enable an operator to view different locations on or near the tractor 100.

According to a preferred embodiment of the invention, a support turret 125 for the wheels of a rotatable aircraft nose landing gear is pivotally and rotatably mounted on a horizontal base assembly 126. The steady-state center of rotation of the turntable 125, which is designated by reference numeral 127, is preferably located at the geometric center of the rectangle defined by the centers of rotation 115, 116, 117 and 118 of the respective steerable wheels 104, 106, 108 and 110.

The horizontal base assembly 126 is connected to the chassis 102 in a manner that allows the horizontal base assembly 126 a limited amount of freedom of movement relative to the chassis 102 and engages the energy absorber assembly, which preferably includes a plurality of energy absorbing pistons 128, and each pivotably couples the chassis 102 and the horizontal base assembly 126. A force sensor, preferably a load sensor 129, is preferably associated with each of the energy absorbing pistons 128, which is output to the controller 119 and used by the controller 119 to control acceleration and deceleration of the vehicle.

The horizontal base assembly 126 preferably includes a circumferential base element 130 pivotally mounted to the chassis 102 by a pair of front suspended supports 132 suspended to laterally extending support bars 131 and a pair of rear suspended supports 132, wherein the rear suspended supports 132 are pivotally mounted to the chassis 102. The suspended supports 132 engage the pivotably mounted energy absorbing piston 128. The circumferential base element 130 is preferably mounted to the suspended support 132 by means of a pivotable shaft 133, wherein the shaft 133 may or may not be integrally formed with the circumferential base element 130.

Turntable 125 is preferably pivotally and rotatably mounted to base 126 by a pair of pivot bars 134, with pivot bars 134 projecting outwardly to engage bearings 135 having high load capacity, which bearings 135 in turn engage a 360 ° circumferential bearing race 136 formed in base 126. This configuration enables the turntable 125 to rotate and tilt with relatively low friction relative to the base member 130, the horizontal base assembly 126, and the chassis 102.

An upright frame 140 is fixedly mounted to the turntable 125 for adjusting the wheels of the nose landing gear of the aircraft on the turntable 125. The bars 142 of the wheels of the aircraft nose landing gear are preferably positioned in a selective manner with respect to the upright frame 140 by means of bar positioning pistons 144 anchored on the turret 125, so as to adapt the turret 125 to the different sizes of the wheels of the aircraft nose landing gear. The rotational orientation of the turntable 125 is preferably detected by a rotation sensor 145, such as a potentiometer, which sensor 145 provides a rotational orientation input of the turntable to the controller 119. The rotational orientation of the turntable 125 may be controlled by a turntable rotation motor 146.

A selectively positionable clamp assembly 147 is preferably mounted on turntable 125 and connected to upright frame 140 and is operable to selectively clamp the wheels of the aircraft nose landing gear to turntable 125 such that the center of rotation of the wheels of the aircraft nose landing gear falls as closely as possible to the center of rotation 127 of turntable 125, and as mentioned above, the center of rotation 127 is located on the geometric center of the rectangle defined by the centers of rotation of steerable wheels 104, 106, 108 and 110.

Preferably, force sensors (such as load sensor 148) are mounted on the forward facing surface of the selectively positionable clamp assembly 147 and the rearward facing surface of the bars 142 to engage the wheels of the aircraft nose landing gear to detect forces in the horizontal plane, such as forces exerted on the wheels of the aircraft nose landing gear and therefore on the aircraft nose landing gear caused by differences in acceleration and/or deceleration of the tractor 100 relative to the acceleration and/or deceleration of the aircraft thus being towed.

The ramp 150 of the wheels of the tilting aircraft nose landing gear is preferably fitted on the base element 130. A pair of engaging piston assemblies 152 for the wheels of the aircraft nose landing gear are preferably provided to push and lift the aircraft nose landing gear and to place the wheels of the aircraft nose landing gear on the turntable 125.

One of the characteristic features of the invention is: a force sensor, such as load sensor 148, may be used to detect forces applied to the nose landing gear in at least one approximately horizontal direction from at least aircraft pilot controlled aircraft braking, causing the tow vehicle to slow down, and from the tow vehicle to accelerate. The controller 119 is configured to provide speed and torque control signals to the hydraulic motors driving the wheels of the tractor 100 at least partially in response to the output of the force sensors, which output is indicative of, among other things, aircraft pilot-controlled braking that causes deceleration of the aircraft. Such control is intended to reduce and limit the forces exerted on the nose landing gear of the aircraft to a maximum allowable force that will not cause damage to the nose landing gear of the aircraft due to the aircraft pilot controlled braking causing the tractor to slow down and/or the tractor to accelerate.

In addition, one characteristic feature of the present invention is: the rotation sensor 145 may be used to detect rotation of the turntable 125 relative to the base assembly 126 (where such rotation is caused by steering of the aircraft pilot via the aircraft nose landing gear), and the controller 119 may be used to control the steering of the steerable wheels 104, 106, 108, and 110 in response to a steering command by the aircraft pilot based on the output of the rotation sensor 145.

Another characteristic feature of the invention is: force sensors, such as load sensors 129 and 148, may be used to detect forces exerted on the nose landing gear in at least one approximately horizontal direction, and thus controller 119 may be used to control acceleration and deceleration of the tractor by using at least one force feedback loop that utilizes the output of the at least one force sensor detecting the aircraft operator controlled braking, as well as at least one of the following inputs:

readings of forces resulting from known inclinations at various locations along the aircraft running surface traversed by the tow vehicle 100, where these locations are identified to the controller by a position detection function;

a reading of wind forces acting on the aircraft, wherein wind force information is provided to the controller from wind sensors at the airport and/or onboard the towing vehicle; and

readings of known towing vehicle and aircraft rolling friction at various locations along the aircraft travel surface traversed by the towing vehicle, wherein these locations are identified to the controller by a location detection function.

Another characteristic feature of the invention is: the controller 119 may be used to control the speed of the tractor 100 by using at least one speed feedback loop based on known speed limits along the path of travel traveled by the tractor and aircraft (preferably using a suitable airport map embedded in the controller 119) and the output of tractor position sensors indicating the position of the tractor 100 along the path of travel of the tractor 100 and aircraft.

According to an embodiment of the present invention, a pair of laser rangefinders 154 are mounted on the chassis 102 of the tractor 100 to determine the angular relationship between the longitudinal axis of the aircraft and the longitudinal axis of the tractor 100. In particular, this angular relationship between the longitudinal axis of the aircraft and the longitudinal axis of the tow vehicle 100 is used in an autonomous taxi mode of operation (such as described below in fig. 4A-4E).

Reference is now made to fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I and 2J, which are plots of the various stages in the prognostic push and push-back operation, respectively, of the towbar-less aircraft tow vehicle of fig. 1A-1C, preferably under the control of the tow vehicle driver.

As seen in fig. 2A, a towbarless aircraft tow 100 constructed and operative in accordance with a preferred embodiment of the present invention moves under the control of a tow vehicle operator in the direction of arrow 200 toward an aircraft 202 awaiting pushback. Fig. 2B shows the wheels 204 of the nose landing gear positioned on the ramp 150. Fig. 2C shows the nose gear wheel engagement piston assembly 152 engaged with the nose gear wheel 204 to push and lift the aircraft nose gear and place the aircraft nose gear wheel on the turntable 125. Fig. 2D illustrates the positioning of the bars 142 of the wheels of the aircraft nose landing gear relative to the upright frame 140, as implemented by the bar positioning pistons 144, suitable for receiving the wheels 204 of the particular aircraft nose landing gear of the particular aircraft 202. Figure 2E shows the wheels 204 of the nose landing gear being pushed onto the turntable 125.

Fig. 2F shows the wheel 204 of the aircraft nose landing gear urged by the piston assembly 152 against the suitably arranged bar 142 such that the axis of rotation of the wheel 204 of the aircraft nose landing gear is preferably located as precisely as possible at the centre of rotation 127 of the turntable 125, wherein as mentioned above, the centre 127 is located at or near the geometric centre of the rectangle defined by the centres of rotation of the steerable wheels 104, 106, 108 and 110.

Figures 2G and 2H show the sequence of retraction of the single piston assembly 152 out of engagement with the wheel 204 of the aircraft nose landing gear and engagement of the single clamp of the selectively positionable clamp assembly 147 with the wheel 204 of the aircraft nose landing gear to clamp the wheel of the aircraft nose landing gear to the turntable 125 such that the centre of rotation of the wheel of the aircraft nose landing gear is as exactly as possible on the centre of rotation 127 of the turntable 125. Fig. 2I illustrates the pushback of the tractor 100 against the aircraft 202 under the control of the tractor driver. Fig. 2J shows the tractor driver leaving the tractor 100 after the pushback is complete. According to an alternative embodiment of the invention, the pilot remains on the tow vehicle 100 during all or part of the taxiing process and may participate in disengaging the tow vehicle from the aircraft after the engine is started.

Reference is now made to fig. 3A, 3B, 3C, 3D and 3E, which are plots of various stages in the taxiing operation of the towbarless aircraft tug 100 of fig. 1A-1C, respectively, under the control of an aircraft pilot with the assistance of a controller 119.

Fig. 3A shows rotation of the wheels 204 of the nose landing gear of the aircraft by the aircraft pilot using a conventional aircraft steering tiller 206 or pedals (not shown), which causes corresponding rotation of the turntable 125 relative to the base member 130. The rotation of turntable 125 is immediately detected by rotation sensor 145, and sensor 145 provides an output to controller 119, resulting in an immediate rotation of steerable wheels 104, 106, 108, and 110 of tractor 100, as will be described in greater detail below with reference to fig. 6A-6B.

Controller 119 preferably effects steering of towing vehicle 100 according to a feedback control loop that receives inputs from rotation sensor 145 indicative of an angle α between the direction of nose gear wheels 204, and thus turntable 125, and the longitudinal axis of towing vehicle 100 (herein designated by reference numeral 210) as the aircraft pilot steers, controller 119 rotates the steerable wheels 104, 106, 108 and 110 of towing vehicle through an angle β, respectively₁、β₂、β₃And β₄(as will be described below with reference to fig. 6A-6C), the tractor 100 is driven such that the angle α becomes zero.

Fig. 3B illustrates an intermediate stage in the movement of the towing vehicle 100 for orienting the towing vehicle 100 so that the towing vehicle 100 pulls the aircraft 202 in the direction indicated by the aircraft pilot. At this stage, the angle α between the turntable 125 and the longitudinal axis 210 of the tractor 100 is shown as 1/2 of the angle shown in fig. 3A. The angle γ is indicated between the longitudinal axis 210 of the tow vehicle 100 and the longitudinal axis (identified herein by reference numeral 220) of the aircraft 202 being towed by the tow vehicle 100, which results from the rotation of the tow vehicle 100 relative to the aircraft 202.

FIG. 3C shows towing vehicle 100 oriented with α at zero relative to wheels 204 of the nose landing gear of aircraft 202 Note the angle β of steerable wheels 104, 106, 108, and 110 of the towing vehicle₁、β₂、β₃And β₄Usually not 0. At this stage, the angle γ between the longitudinal axis 210 of the tow vehicle 100 and the longitudinal axis 220 of the aircraft 202 being towed by the tow vehicle 100 is less than γ in fig. 3B because the aircraft 202 has already begun to turn.

Fig. 3D shows the braking of the aircraft 202 by the aircraft pilot pressing down on the pedal 222. Braking of the aircraft 202 is effected by brakes on the main landing gear (not shown) of the aircraft 202 and immediately causes application of a force detected by the load sensor 148 on the clamp 147, the controller 119 receives the output of the sensor 148 and immediately decelerates the towing vehicle 100. Since there is a time delay between the braking of the aircraft 202 and the corresponding deceleration of the towing vehicle 100, a force is applied to the rear energy absorbing piston 128, which is immediately detected by the load sensor 129. The rear energy absorbing piston 128 absorbs energy generated by braking of the aircraft 202 relative to the towing vehicle 100. At this stage, load cell 129 acts as a backup to load cell 148.

Figure 3E illustrates controlled acceleration of the towing vehicle 100 by the controller 119, particularly in response to inputs received from force sensors (such as load sensors 148 and 129) for causing the aircraft's taxi rate at predetermined locations along the aircraft's path of travel to fall within predetermined speed limits and for ensuring that the forces acting on the nose landing gear do not exceed predetermined limits, taking into account one or more, preferably all, of the following factors:

forces resulting from known inclinations at various locations along the aircraft travel surface traversed by the tow vehicle 100, where these locations are identified to the controller 119 by a location detection function, such as a GPS function, where the above-described functions are provided by tow vehicle position sensors 121 (fig. 1A-1C) mounted on the tow vehicle;

wind forces acting on the aircraft 202, wherein wind force information is provided to the controller 119 from wind sensors at the airport or onboard the tractor (such as wind sensor 122 onboard the tractor), and preferably also through airport command and control functions; and

the rolling friction of the tow vehicle 100 and the aircraft 202 at various locations along the aircraft travel surface traversed by the tow vehicle 100, where these locations are identified to the controller 119 by the position detection function provided by the tow vehicle position sensor 121, and preferably also by the airport command and control functions.

Fig. 3E also contemplates controlled deceleration of the towing vehicle 100 in response not only to braking of the aircraft 202 by the aircraft pilot, but also to detection of an obstacle by the obstacle sensors 123 (fig. 1A-1C). The deceleration of the towing vehicle is controlled by controller 119, particularly in response to inputs received from force sensors, such as load sensors 148 and 129, to ensure a coordinated reduction ratio between the aircraft and the towing vehicle to limit the forces acting on the nose landing gear of the aircraft 202 to within predetermined force limits.

To distinguish between normal tractive effort on the nose gear and the effort applied by the pilot applying the brakes, the controller 119 considers one or more, preferably all, of the above factors as indicated by data from various sensors (such as sensors 120, 121, 122, and 123) and the camera 124.

The controller 119 may be used to control the acceleration and deceleration of the tractor 100 to maintain a desired tractor speed, preferably by using a speed control feedback loop. The controller 119 has embedded therein an airport map indicating the relative tractor speed limits over various areas of the tractor's path of travel. This speed limit information is matched with information indicative of the instantaneous position of the tractor 100, which is preferably provided by the tractor position sensor 121. The controller 119 preferably includes an inertial navigation system that indicates the instantaneous speed of the tractor 100. The feedback loop is used to bring the actual speed as close as possible to, but not beyond, the speed limit at the instantaneous position of the tractor 100.

The controller 119 may also be used to control the acceleration and deceleration of the towing vehicle 100, preferably using a force control feedback loop, to limit the horizontal force acting on the forward landing gear of the aircraft 202 to within acceptable limits (which are currently 6% of the total weight of the aircraft). Controller 119 receives inputs from load sensors 148 and 129 indicative of a sum of forces acting on the nose landing gear of aircraft 202, caused by, among other things, wind, pitch, rolling friction, and acceleration or deceleration of aircraft 202 and/or towing vehicle 100. The force feedback loop may be used to accelerate or decelerate the towing vehicle 100 to maintain the force detected by the load sensors 148 and 129 well below acceptable limits, thereby allowing for an unintended acceleration or deceleration of the aircraft 202 or towing vehicle 100.

Reference is now made to fig. 4A, 4B, 4C, 4D and 4E, which are pictorial illustrations of various stages in autonomous taxi operation of the towbarless aircraft tug 100 of fig. 1A-1C, in accordance with an alternative embodiment of the present invention. Such autonomous taxi operations may be initiated by the driver of the tractor 100 after the pushback is complete or automatically in response to airport commands and commands from the control center.

In autonomous taxiing operation, the function of the turntable 125 is to reduce the forces (particularly the torque) acting on the nose gear in the horizontal plane to zero by maintaining the position of the nose gear's wheels 204 at the most recently selected position (which is generally parallel to the aircraft longitudinal axis 220) by the aircraft pilot. Thus, the nose gear remains in this position as the tractor 100 changes orientation along its path of travel. This means that during most steering operations of the tractor 100, the turntable will turn in the opposite direction to the tractor 100.

The aircraft pilot can immediately override the autonomous tractor control by operating the aircraft brakes on the main landing gear, which operation is immediately detected by the load sensors 148 and 129.

Autonomous taxi preferably uses the enhanced C4 function of the airport command and control center, which coordinates and optimizes taxi paths and speeds for all taxiing aircraft on the airport with the following inputs:

the location of all aircraft taxiing on the airport;

calculation of all aircraft taxi clearances and taxi paths; and

airport weather conditions and taxiway ground travel conditions.

This enhanced C4 function preferably provides the following functions:

runway encroachment is avoided;

calculating an optimal taxi speed for all aircraft to ensure minimum start and stop times during taxiing;

minimizing traffic congestion on taxiways; and

allowing immediate control by the pilot in the event of a malfunction or emergency.

Fig. 4A shows the initial orientation of the tow vehicle 100 and aircraft 202 at the beginning of the autonomous taxi operation. The wheels 204 of the nose gear of the aircraft are parallel to the longitudinal axis 210 of the towing vehicle 100 and the longitudinal axis 220 of the aircraft. Steerable wheels 104, 106, 108, and 110 of tractor 100 are also parallel to axes 210 and 220.

Figure 4B illustrates the initial turning of the tractor 100 under the control of the controller 119, which preferably occurs in response to traffic control instructions received from an airport command and control system 250, which system 250 may be based on a C4 (command, control & communications center) system. As seen in fig. 4B, in this embodiment, the aircraft pilot does not use a conventional aircraft steering tiller 206 or pedals (not shown) other than for emergency braking. Tractor 100 achieves the desired steering through rotation of steerable wheels 104, 106, 108, and 110 of tractor 100 in response to suitable instructions from controller 119. To avoid applying torque to the nose landing gear of the aircraft 202, the turret 125 is rotated by a turret rotation motor 146 through an angle- α equal in magnitude and opposite in direction to the angle α between the tractor longitudinal axis 210 and the aircraft longitudinal axis 220. Rotation of the turntable 125 is detected by a rotation sensor 145, and the sensor 145 provides a feedback output to the controller 119.

The controller 119 preferably effects steering of the tractor 100 by steering the steerable wheels 104, 106, 108, and 110 according to two feedback control loops, and rotation of the turntable 125 by the turntable rotation motor 146. A feedback loop ensures that the orientation of the tractor 100 follows the predetermined travel path established by the airport command and control system 250. The second feedback loop uses the laser rangefinder 154 to ensure that the wheels 204 of the nose landing gear are aligned parallel to the longitudinal axis 220 of the aircraft. The laser rangefinder 154 determines the angle α between the longitudinal axis 210 of the tractor 100 and the longitudinal axis 220 of the aircraft 202. The controller 119 ensures that the turntable 125 is rotated through an angle-alpha relative to the longitudinal axis 210 to ensure that the wheels 204 of the nose landing gear remain aligned with the longitudinal axis 220 of the aircraft at all times.

Fig. 4C shows a further rotation phase of the tractor 100. At this stage, the angle α between the longitudinal axis 210 of the tow vehicle 100 and the longitudinal axis 220 of the aircraft 202 and the angle α between the turntable 125 and the longitudinal axis 210 of the tow vehicle 100 are shown to be twice the angle shown in fig. 4B.

Fig. 4D illustrates an override of the autonomous mode of operation by the aircraft pilot, preferably by the aircraft pilot depressing brake pedal 222. Such overrides may be used for emergency braking and/or for the aircraft pilot to control the steering of the tractor 100, as described above with reference to fig. 3A-3E. Braking of the aircraft 202 is effected by brakes on the main landing gear (not shown) of the aircraft 202 and immediately causes application of a force detected by the load sensor 148 on the clamp 147, the controller 119 receives the output of the sensor 148 and immediately decelerates the towing vehicle 100.

The controller 119 automatically suspends autonomous mode operation of the tractor 100 and restores the tractor to operation controlled by the aircraft pilot, as described above with reference to fig. 3A-3E.

Since there is a time delay between the braking of the aircraft 202 and the corresponding deceleration of the towing vehicle 100, a force is applied to the rear energy absorbing piston 128, which is immediately detected by the load sensor 129. The rear energy absorbing piston 128 absorbs energy generated by braking of the aircraft 202 relative to the towing vehicle 100. At this stage, load cell 129 acts as a backup to load cell 148.

Recovery of autonomous mode operation typically requires input from the airport command and control system 250 or pilot commands transmitted via an Electronic Flight Bag (EFB) available from Astronautics ltd, israel.

Fig. 4E illustrates controlled acceleration of the tractor 100 in an autonomous mode of operation, controlled by the controller 119, particularly in response to inputs received from the airport command and control center 250 and force sensors (such as load sensors 148 and 129) for bringing the aircraft taxi rate at predetermined locations along the aircraft travel path within predetermined speed limits and ensuring that the forces acting on the nose landing gear do not exceed predetermined limits, taking into account one or more, preferably all, of the following factors:

forces resulting from known inclinations at various locations along the aircraft travel surface traversed by the tow vehicle 100, where these locations are identified to the controller 119 by a location detection function, such as a GPS function, where the above-described functions are provided by tow vehicle position sensors 121 (fig. 1A-1C) mounted on the tow vehicle;

wind forces acting on the aircraft 202, wherein wind force information is provided to the controller from an airport or tractor-mounted wind sensor (such as the tractor-mounted wind sensor 122), and preferably also through airport command and control functions; and

the rolling friction of the tow vehicle and aircraft at various locations along the aircraft travel surface traversed by the tow vehicle 100, where these locations are identified to the controller 119 by the position detection function provided by the tow vehicle position sensor 121, and preferably also by the airport command and control functions.

Fig. 4E also contemplates controlled deceleration of the tractor 100 not only in response to braking of the aircraft 202 by the aircraft pilot, but also in response to detection of an obstacle by either the obstacle sensor 123 or one of the pilot cameras 124 (fig. 1A-1C) or control commands received from the airport command and control center 250. The tractor's deceleration is controlled by controller 119, particularly in response to inputs received from force sensors (such as load sensors 148 and 129) to ensure a coordinated reduction ratio between the aircraft and the tractor to limit the forces acting on the nose landing gear of aircraft 202 to within predetermined force limits.

To distinguish between normal tractive effort on the nose gear and the effort applied by the pilot to apply the brakes, controller 119 considers one or more, preferably all, of the above factors as indicated by data from various sensors, such as sensors 120, 121, 122 and 123.

The controller 119 may be used to control the acceleration and deceleration of the tractor 100 to maintain a desired tractor speed, preferably by using a speed control feedback loop. The controller 119 has embedded therein an airport map indicating the relative tractor speed limits over various areas of the tractor's path of travel. This speed limit information is matched with information indicative of the instantaneous position of the tractor 100, which is preferably provided by the tractor position sensor 121. The controller 119 preferably includes an inertial navigation system that indicates the instantaneous speed of the tractor 100. The feedback loop is used to bring the actual speed as close as possible to, but not beyond, the speed limit at the instantaneous position of the tractor 100.

The controller 119 may also be used to control the acceleration and deceleration of the tractor 100 to limit the horizontal forces acting on the forward landing gear of the aircraft 202 to within acceptable limits (which are currently 6% of the total weight of the aircraft), preferably by using a force control feedback loop. Controller 119 receives inputs from load sensors 148 and 129 indicative of a sum of forces acting on the nose landing gear of the aircraft, caused by, among other things, wind, pitch, rolling friction, and acceleration or deceleration of aircraft 202 and/or towing vehicle 100. The force feedback loop may be used to accelerate or decelerate the towing vehicle 100 to maintain the forces detected by the load sensors 148 and 129 well below acceptable nose gear force limits, thereby allowing for an unintended acceleration or deceleration of the aircraft 202 or the towing vehicle 100.

When operating in the autonomous taxi mode of operation shown in fig. 4A-4E (wherein the taxi speeds of the tow vehicle 100 and the aircraft 202 being towed are typically speeds in the taxi mode of operation controlled by the pilot of the aircraft), a particular feature of the invention is: the aircraft pilot can override the autonomous system to switch to the mode of operation of the aircraft pilot's control by applying the aircraft brakes and continuing to steer the tractor with the aircraft tiller 206. The aircraft pilot may also apply the aircraft brakes in emergency situations.

Because the ground movement of all aircraft at an airport is managed in an integrated manner by command and control system 250, efficient taxi operation is provided in the autonomous taxi mode of operation, thereby avoiding the route of aircraft waiting to take off. As can be seen in fig. 4E, the command and control system 250 integrates the movement of all aircraft to maintain the desired spacing between aircraft during taxiing and to avoid start and stop movements as much as possible.

Reference is now made to fig. 5A, 5B, 5C, 5D and 5E, which are plots of the various phases in the autonomous mode of operation of the towbarless aircraft tractor 100 of fig. 1A-1C under the control of the command and control system in the airport command tower by the controller 119 for the tractor taxiing motion and the return of the tractor 100 from the takeoff area to the prognostic push position, respectively.

Figures 5A, 5B and 5C illustrate disengagement of the towing vehicle 100 from the wheels 204 of the nose landing gear of the aircraft. It can be appreciated that: disengagement of the tractor 100 from the aircraft is typically performed after the aircraft pilot has started the aircraft engines. In one embodiment of the present invention, the command and control system 250 commands the tractor 100 to effect disengagement. Alternatively, the disengagement of the tractor is automatically triggered by the detected position of the tractor at a predetermined disengagement position near the takeoff point. The disengagement command is preferably transmitted wirelessly to the controller 119. In response to a command to disengage the towing vehicle, the selectively positionable clamp assembly 147 releases the clamping engagement with the wheels 204 of the aircraft nose gear and the towing vehicle 100 moves forward while the aircraft pilot applies brakes to the aircraft 202 and controls the aircraft tiller 206 to allow the wheels of the aircraft nose gear to roll down the ramp 150 and maintain the nose gear parallel to the longitudinal axis of the aircraft 220 as the ramp 150 moves forward relative to one another.

According to an alternative embodiment of the invention (not shown) in which a safety driver is present on the tractor 100, disengagement may be effected in a conventional manner by the safety driver, and is typically accompanied by disconnection of the voice communication line by the safety driver.

Fig. 5D shows controlled acceleration and steering of the tractor controlled by the controller 119 to bring the travel speed of the tractor within predetermined speed limits at predetermined locations along the predetermined tractor autonomous travel path from the takeoff zone to the prognostic pushout location, taking into account one or more, preferably all, of the following factors:

the instantaneous position of the tractor 100 indicated by the tractor position sensor 121;

obstacle detection information received from the sensor 123 or the camera 124;

real-time information provided by the airport command and control system 250 regarding the location of other vehicles along the path of travel of the tractor; and

information indicative of one or more predetermined travel routes of the tractor 100 from the takeoff position to the prognostic pushback position. This information may be stored in the controller 119 or provided in real time by the airport command and control system 250.

Figure 5E shows the controlled deceleration and parking of the tractor controlled by the controller 119 in the post-pushup position.

Reference is now made to fig. 6A, 6B and 6C, which are illustrations of the steering function of the towbarless aircraft tug 100 of fig. 1A-1C, respectively, for effecting trapezoidal steering of the aircraft 202.

Referring to fig. 6A, which illustrates an aircraft 202 in which the wheels 204 of the nose gear of the aircraft 202 are traveling straight ahead along the longitudinal axis 220 of the aircraft 202, note that the following parameters dictate:

l = the distance along the longitudinal axis 220 of the aircraft 202 between the centre of rotation 302 of the wheels 204 of the nose landing gear and a line 304 connecting the main landing gear (here identified with reference numerals 306 and 308);

a = the longitudinal distance between a line 310 connecting the centers of the rear steerable wheels 108 and 110 of the tractor 100 and a line 312 connecting the centers of the front steerable wheels 104 and 106;

b = lateral distance between the centers of wheels 108 and 110 of tractor 100 and lateral distance between the centers of wheels 104 and 106; and

c = the distance along line 304 between main gear 306 and 308.

Fig. 6B shows an aircraft 202 in which the wheels 204 of the nose gear of the aircraft 202 are turned through an angle a in response to the steering performed by the aircraft pilot using the tiller 206, thereby causing a corresponding rotation of the turntable 125 relative to the chassis 102 of the tractor 100. Controller 119 causes rotation of steerable wheels 104, 106, 108, and 110 of the tractor to reorient tractor 100 such that a becomes zero, as described above with reference to fig. 3A-3E. The controller 119 also controls the movement of the tractor 100 to form a trapezoidal turn of the aircraft 202 as shown in fig. 6B according to the following parameters:

r + C/2= instantaneous radius of rotation of aircraft 202;

α = angle of rotation of the wheels 204 of the nose landing gear relative to the longitudinal axis 220 of the aircraft 202; and

β_i= steering angle of the wheels of tractor 100 (i =104, 106, 108 and 110).

Preferably β as a function of α_iIs calculated as follows:

L/[R+C/2]=tanα>>>>R=L/tanα-C/2

tanβ₁₀₈=[L-A/2cosα-B/2sinα]/[L/tanα+A/2-B/2sinα]

tanβ₁₁₀=[L-A/2cosα+(A/2tanα+B/2)sinα]/[L/tanα+(A/2tanα+B/2)cosα]

tanβ₁₀₄=[L+A/2cosα+B/2sinα]/[L/tanα-A/2+B/2sinα]

tanβ₁₀₆=[L+A/2cosα-(A/2tanα+B/2)sinα]/[L/tanα-(A/2tanα+B/2)cosα]

fig. 6C illustrates the operation of the tow vehicle 100, whereby the tow vehicle 100 is reoriented relative to the aircraft 202 such that a is 0, according to a preferred tow vehicle steering algorithm. As mentioned above with reference to fig. 3A-3E, controller 119 reorients tractor 100 by rotating the tractor's steerable wheels 104, 106, 108, and 110 as described above such that the angle α detected by rotation sensor 145 is reduced to 0. The controller 119 is preferably operable to orient the tow vehicle 100 such that the instantaneous radius of rotation R + C/2 of the aircraft 202 towed by the tow vehicle coincides with the instantaneous radius of rotation R + C/2 of the aircraft 202 itself, such that in the embodiment of fig. 3A-3E, the pilot of the aircraft steers the aircraft in the same manner regardless of whether the aircraft is being pulled by the tow vehicle 100 or is being advanced using its own power.

Those skilled in the art will recognize that: the invention is not to be limited by what has been particularly shown and described hereinabove. Rather, the invention includes both combinations and subcombinations of the various features described hereinabove as well as modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.

Claims (5)

1. A towbarless airplane tug comprising:

a chassis mounted on tractor wheels, at least some of the tractor wheels being steerable;

an aircraft wheel support assembly mounted on the chassis for supporting a rotatable aircraft wheel of an aircraft nose landing gear;

at least one tractor wheel drive for driving rotation of the tractor wheels to provide movement of the chassis;

at least one tractor controller for controlling the speed of the tractor, the at least one tractor controller using at least one feedback loop that utilizes a plot of speed limits along a travel path traversed by the tractor and the aircraft at an airport and a reading of instantaneous positions of the tractor and the aircraft along the travel path.

2. A towbarless airplane tug according to claim 1 wherein said tug controller is configured to use at least one feedback loop by utilizing inputs of known desired speeds at various locations along a travel path traversed by said tug, said inputs being obtained by the tug controller utilizing readings of instantaneous positions of said tug and a plot of speed limits along the travel path.

3. A towbarless aircraft tow truck according to claim 1, wherein the tow truck controller is configured to use at least one feedback loop by taking input of a reading of a known required velocity obtained by the tow truck controller from an aircraft master controller.

4. A towbarless airplane tug according to claim 1 and wherein a plot of speed limits along a travel path traversed by said tug is determined as a function of road and environmental conditions.

5. The towbarless airplane tug of claim 1 wherein said tug controller is further configured to utilize a suitable airport map embedded in said tug controller and the output of a tug position sensor that provides a reading indicative of the instantaneous position along the path of travel of said tug.