WO2021149039A1

WO2021149039A1 - Device and method for automatically controlled steering of a continuous track vehicle

Info

Publication number: WO2021149039A1
Application number: PCT/IL2020/051230
Authority: WO
Inventors: Israel Leib SCHALLHEIM; Yuval Daniel SHAPIRA; Gavriel Davidov
Original assignee: Elbit Systems Land Ltd.
Priority date: 2020-01-20
Filing date: 2020-11-29
Publication date: 2021-07-29
Also published as: IL272216B

Abstract

A method of steering a continuous track vehicle is disclosed. The method may include: receiving a steering command for the continuous track vehicle; determining a radius based on the steering command; while driving the continuous track vehicle along the route, receiving, from at least one first sensor, an angular velocity of the continuous track vehicle; receiving, from at least one second sensor, a linear velocity of the continuous track vehicle; estimating a real-time turning radius based on the received angular velocity and the received linear velocity; and if the estimated real-time turning radius differs from the determined turning radius, changing a speed difference between a first track and a second track of the continuous track vehicle to steer the vehicle according to the steering command.

Description

DEVICE AND METHOD FOR AUTOMATICALLY CONTROLLED STEERING OF

A CONTINUOUS TRACK VEHICLE

FIELD OF THE INVENTION

[001] The present invention relates generally to methods and devices for steering continuous tracks. More specifically, the present invention relates to automatic methods and devices for steering continuous tracks.

BACKGROUND OF THE INVENTION

[002] Automatic and autonomous driving of vehicles are well established technologies, in particular in wheeled vehicles. In wheeled vehicles there is a direct correlation between the movement of the steering wheel and the movement of the drive wheels. Accordingly, any steering command made by the steering wheel, for example, to steer the vehicle to the left, is directly terraformed to a left movement of the driving wheels (e.g., rear wheels in rear-wheel drive), unless the vehicle is slipping. Accordingly, there is a direct relation between the direction of the driving wheels and the vehicle’s turning radius. Therefore, automatic or autonomous control of a wheeled vehicle is relatively easy to archive with a simple control law that determines the steering wheel position, for each road curvature.

[003] However, in continuous track vehicles, no such correlation exists between the steering command and the resulting turning radius. Continuous track, also called tank tread or caterpillar track, is a system of vehicle propulsion in which a continuous band of treads is driven by two or more wheels. In order to steer a continuous track, a relative sliding is formed between the right and left continuous tracks. The relative sliding is achieved by providing different velocities to the wheels rolling the chain (or any other) tracks. The sharper the turn to be taken, the higher is the difference between the velocities. However, the resulting turning radius depends not only on the velocity difference, but also on ground properties, slops, trains and the like.

[004] Therefore, automatic or autonomous control of continuous track vehicles is complicated. Known methods uses look up table that include known correlation between steering commands and the speed difference between a first track and a second track. However, since there is no direct relation between speed difference of the tracks and turning radius, the resulting trajectory of the vehicle is difficult to predict.

[005] Accordingly, there is a need to an accurate automatic or autonomous steering control of continuous track vehicles that may allow to either provide a full autonomous driving of the continuous track vehicles or may allow to add a user interface device that mimic a “ steering wheel” that may provide to a driver driving the continuous track vehicle the same driving experience as driving a wheeled vehicle

SUMMARY OF THE INVENTION

[006] Some aspects of the invention may be directed to a method of steering a continuous track vehicle. In some embodiments, the method may include: receiving a steering command for the continuous track vehicle; determining a radius based on the steering command; while driving the continuous track vehicle along the route, receiving, from at least one first sensor, an angular velocity of the continuous track vehicle; receiving, from at least one second sensor, a linear velocity of the continuous track vehicle; estimating a real-time turning radius based on the received angular velocity and the received linear velocity; and if the estimated real-time turning radius differs from the determined turning radius, changing a speed difference between a first track and a second track of the continuous track vehicle to steer the vehicle according to the steering command.

[007] In some embodiments, the method may further include determining the speed difference based on the difference between the estimated real-time turning radius and the determined turning radius. In some embodiments, changing the speed difference between a first track and a second track may include correcting positions of a first piston and a second piston, wherein each piston is connected to a corresponding control stick and wherein a first control stick is configured to control the speed of the first track and the second stick is configured to control the speed of the second track. In some embodiments, changing the speed difference between a first track and a second track may include controlling the speed provided by two electric motors each driving a different track. In some embodiments, changing the speed difference between a first track and a second track may include controlling one of: a hydraulic driving unit, an electrical driving unit and a mechanical driving unit.

[008] In some embodiments, determining a radius based on the steering command may include, receiving from a database a lookup table comprising correlations between turning radiuses and steering command values. In some embodiments, the at least one first sensor comprises one of: a gyroscope and two tachometers each measure angular velocity of the sprocket of a different continuous track. In some embodiments, the at least one second sensor is a global navigation satellite system (GNSS) for measuring the linear velocity. In some embodiments, the at least one second sensor comprises at least one camera and the method may further include: receiving a stream of images from the camera; and determining the linear and angular velocities using visual odometry process. [009] In some embodiments, the method may further include, receiving the steering command from a database or a user devise; and autonomously driving the continuous track vehicle according to the steering command. In some embodiments, the method may further include, receiving, from a user interface, in real time, the steering command; and driving the continuous track vehicle in response to the received steering command. In some embodiments, the user interface is one of: a joystick, a wheel-like joystick and a touchscreen.

[0010] Some other aspects of the invention may be related to a system for of steering a continuous track vehicle. The system may include: at least one first sensor configured to measure an angular velocity of the continuous track vehicle; at least one second sensor configured to measure a linear velocity of the continuous track vehicle; and a computing device configured to: receive a steering command for the continuous track vehicle; determine a radius based on the steering command; during a driving the continuous track vehicle along the route: receive, from the at least one first sensor, the angular velocity; receive, from the at least one second sensor, the linear velocity; estimate a real-time turning radius based on the received angular velocity and the received linear velocity; and if the estimated real-time turning radius differs from the determined turning radius, change a speed difference between a first track and a second track of the continuous track vehicle to steer the vehicle according to the steering command.

[0011] In some embodiments, the computing device may be further configured to: determine the speed difference based on the difference between the estimated real-time turning radius and the determined turning radius. In some embodiments, changing the speed difference between a first track and a second track comprises correcting positions of a first piston and a second piston, wherein each piston is connected to a corresponding control stick and wherein a first control stick is configured to control the speed of the first track and the second stick is configured to control the speed of the second track. In some embodiments, changing the speed difference between a first track and a second track may include controlling the speed provided by two electric motors each driving a different track. In some embodiments, changing the speed difference between a first track and a second track may include controlling one of: a hydraulic driving unit, an electrical driving unit and a mechanical driving unit.

[0012] In some embodiments, determining a radius based on the steering command may include, receiving from a database a lookup table comprising correlations between turning radiuses and steering command values. In some embodiments, the at least one first sensor comprises one of: a gyroscope and two tachometers each measure angular velocity of the sprocket of a different continuous track. In some embodiments, the at least one second sensor is a global navigation satellite system (GNSS) for measuring the linear velocity. In some embodiments, the at least one second sensor may include at least one camera and the computing device may further configured to: receive a stream of images from the camera; and determine the linear and angular velocities using visual odometry process.

[0013] In some embodiments, the computing device may further be configured to: receive the steering command from a database or a user devise; and autonomously driving the continuous track vehicle according to the steering command.

[0014] In some embodiments, the computing device may further be configured to: receive, from a user interface, in real time, the steering command; and driving the continuous track vehicle in response to the received steering command. In some embodiments, the user interface is one of: a joystick, a wheel-like joystick and a touchscreen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0016] Fig. 1 is a block diagram, depicting a computing device which may be included in a device for steering continuous tracks according to some embodiments of the invention;

[0017] Fig. 2 is a block diagram of a system for steering continuous tracks according to some embodiments of the invention;

[0018] Fig. 3 is a block diagram, depicting a control loop according to some embodiments of the invention;

[0019] Fig. 4 is a flowchart of a method of steering a continuous track vehicle according to some embodiments of the invention;

[0020] Fig. 5 is an illustration of velocities of a continuous track vehicle during steering according to some embodiments of the invention;

[0021] Figs 6A and 6B are graphs of estimated real-time turning radiuses according to some embodiments of the invention;

[0022] Figs. 7A and 7B are illustration of real-time turning performance of a continuous track vehicle in response to two steering command having two different steering radiuses according to some embodiments of the invention. [0023] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0024] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0025] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0026] Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,”

“establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer’s registers and/or memories into other data similarly represented as physical quantities within the computer’s registers and/or memories or other information non-transitory storage medium that may store instructions to perform operations and/or processes.

[0027] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms

“plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term set when used herein may include one or more items. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0028] The term set when used herein can include one or more items. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0029] Embodiments of the present invention disclose a method and a system for steering a continuous track vehicle. A method and a system according to embodiments of the invention may allow a full autonomous driving of the continuous track vehicles or may allow to add a user interface device that mimic a “ steering wheel” that may provide to a driver driving the continuous track vehicle the same driving experience as driving a wheeled vehicle. To achieve these goals an accurate control of the steering must be provided to the continuous track vehicle. This may be done by creating an artificial relation between the steering commands, and the resulting turning radius. Therefore, following receiving a steering command (e.g., from a preprogramed path or from a user via a user interface (e.g., a steering wheel-like joystick)) a continuous track vehicle may perform an accurate turn defined by the steering command.

[0030] In some embodiments, such a system may allow to provide a driver the same driving experience as driving a wheeled vehicle since for every “steering” of the steering wheel -like joystick the continuous track vehicle may turn exactly to the same direction and in same measure proportional to the steering of the wheel -like joystick.

[0031] In some embodiments, the system may receive a steering command that include a turning radius and may provide an initial instruction to a driving unit of the continuous track vehicle to change a speed difference between a first track and a second track of the continuous track vehicle, based for example on a lookup table. The system may then estimate the real time turning radius and compare the real time turning radius with the turning radius of the steering command and cause a correction of the speed difference between the first track and the second track, if the two are not substantially the same. In some embodiments, the estimation of the real time turning radius may be based on measurements of the angular velocity and the linear velocity of the continuous track vehicle, received from sensors (e.g., a gyroscope and a GNSS).

[0032] As used herein, a continuous track vehicle may be any vehicle traveling on continuous tracks. For example, a continuous track vehicle may be, armed personal carrier, tank, continuous track tractors and the like. A continuous track vehicle according to embodiments of the invention may include a track propulsion unit running on a continuous band of treads, sprockets or track plates driven by two or more wheels.

[0033] As used herein, diving unit may include any unit configured to directly control the velocity of the right and left tracks, by controlling the velocities of the driving wheels of the track propulsion unit. For example, the diving unit may include two control sticks, such that, a first control stick is configured to control the speed of the first track and the second stick is configured to control the speed of the second track. In other examples, the driving unit may include a hydraulic driving unit, an electrical driving unit (e.g., two electrical motors each controlling the speed of one track) and a mechanical driving unit.

[0034] As used herein, a steering command may include a command to steer the continuous track vehicle at a turning radius and optionally also turning rate.

[0035] As used herein, an angular velocity of the continuous track vehicle is the velocity measured around a vertical to the ground axis located on the vehicle. For example, the angular velocity may be measured by a gyroscope included in a navigation system of the continuous track vehicle or located on the continuous track vehicle.

[0036] As used herein, a linear velocity of the continuous track vehicle is the velocity of the vehicle in the driving direction. The linear velocity can be calculated using temporal data received from global navigation satellite system (GNSS) , inertial navigation system (INS) or visual aided navigation (Visual odometry).

[0037] Reference is now made to Fig. 1, which is a block diagram depicting a computing device, which may be included within an embodiment of a system for steering a continuous track vehicle, according to some embodiments.

[0038] Computing device 10 may include a controller 2 that may be, for example, a central processing unit (CPU) processor, a chip or any suitable computing or computational device, an operating system 3, a memory 4, executable code 5, a storage system 6, input devices 7 and output devices 8. Controller 2 (or one or more controllers or processors, possibly across multiple units or devices) may be configured to carry out methods described herein, and/or to execute or act as the various modules, units, etc. More than one computing device 10 may be included in, and one or more computing devices 10 may act as the components of, a system according to embodiments of the invention.

[0039] Operating system 3 may be or may include any code segment (e.g., one similar to executable code 5 described herein) designed and/or configured to perform tasks involving coordination, scheduling, arbitration, supervising, controlling or otherwise managing operation of Computing device 10, for example, scheduling execution of software programs or tasks or enabling software programs or other modules or units to communicate. Operating system 3 may be a commercial operating system. It will be noted that an operating system 3 may be an optional component, e.g., in some embodiments, a system may include a computing device that does not require or include an operating system 3.

[0040] Memory 4 may be or may include, for example, a Random Access Memory (RAM), a read only memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM (SD-RAM), a double data rate (DDR) memory chip, a Flash memory, a volatile memory, a non-volatile memory, a cache memory, a buffer, a short term memory unit, a long term memory unit, or other suitable memory units or storage units. Memory 4 may be or may include a plurality of, possibly different memory units. Memory 4 may be a computer or processor non-transitory readable medium, or a computer non-transitory storage medium, e.g., a RAM. In one embodiment, a non-transitory storage medium such as memory 4, a hard disk drive, another storage device, etc. may store instructions or code which when executed by a processor may cause the processor to carry out methods as described herein.

[0041] Executable code 5 may be any executable code, e.g., an application, a program, a process, task or script. Executable code 5 may be executed by controller 2 possibly under control of operating system 3. For example, executable code 5 may be an application that may control the steering of a continues track as further described herein. Although, for the sake of clarity, a single item of executable code 5 is shown in Fig. 1, a system according to some embodiments of the invention may include a plurality of executable code segments similar to executable code 5 that may be loaded into memory 4 and cause controller 2 to carry out methods described herein. [0042] Storage system 6 may be or may include, for example, a flash memory as known in the art, a memory that is internal to, or embedded in, a micro controller or chip as known in the art, a hard disk drive, a CD-Recordable (CD-R) drive, a Blu-ray disk (BD), a universal serial bus (USB) device or other suitable removable and/or fixed storage unit. Instruction as to control the steering a continuous track vehicle may be stored in storage system 6 and may be loaded from storage system 6 into memory 4 where it may be processed by controller 2. In some embodiments, some of the components shown in Fig. 1 may be omitted. For example, memory 4 may be a non-volatile memory having the storage capacity of storage system 6. Accordingly, although shown as a separate component, storage system 6 may be embedded or included in memory 4.

[0043] Input devices 7 may be or may include any suitable input devices, components or systems, e.g., a detachable keyboard or keypad, a mouse and the like. Output devices 8 may include one or more (possibly detachable) displays or monitors, speakers and/or any other suitable output devices. Any applicable input/output (I/O) devices may be connected to Computing device 10 as shown by blocks 7 and 8. For example, a wired or wireless network interface card (NIC), a universal serial bus (USB) device or external hard drive may be included in input devices 7 and/or output devices 8. It will be recognized that any suitable number of input devices 7 and output device 8 may be operatively connected to Computing device 10 as shown by blocks 7 and 8.

[0044] A system according to some embodiments of the invention may include components such as, but not limited to, a plurality of central processing units (CPU) or any other suitable multi purpose or specific processors or controllers (e.g., controllers similar to controller 2), a plurality of input units, a plurality of output units, a plurality of memory units, and a plurality of storage units. [0045] Reference is now made to Fig. 2, which is a block diagram of a system for controlling the steering of a continuous track vehicle according to some embodiments of the invention. A system 100 may include a computing device 10 in communication with at least some of: database 20, a user interface 30, a first sensor 40 and a second sensor 50. In some embodiments, computing device 10 may be in communication with continuous track vehicle 60 driving unit. Data base 20 may be any database, for example, storage system 6, configured to store data and/or instructions related to the method. For example, database 20 may store a lookup table associating steering commands (e.g., required turning radiuses) with speed differences between a first track and a second track of the continuous track vehicle (e.g., continuous track vehicle 60). Continuous track vehicle 60 driving unit may include two control sticks for controlling the speed of each track. In some embodiments, each control sticks may be connected to a piston (e.g., hydraulic or pneumatic), an electric motor, a hydraulic motor or any other device that allow controllably moving each stick following a steering command, thus cause barking (e.g., reducing the velocity) of one track or both tracks. In some embodiments, computing device 10 may control the movement of the two pistons as to change the required speed difference (e.g., reduction via braking) between the two tracks. As would have known to one skilled in the art, the driving of a continuous track vehicle, such as continuous track vehicle 60, is performed for straight movement, such that the entire differential rotates and the idlers do not rotate relative to the vehicle cage. To steer vehicle 60, one idler is forced to rotate relative to the cage by applying the appropriate steering brake. This in turn forces one half shaft to rotate slower than the other.

[0046] In some embodiments, each track may be driven by an electric motor and computing device 10 may directly control the velocity of each track. [0047] In some embodiments, the lookup table may further associate the turning radius with positions of vehicle 60 diving unit. For example, the look up table may associate the desired turning radius with positions of a first piston and a second piston, such that each piston may be connected to a corresponding control stick and a first control stick is configured to control the speed (e.g., by braking) of the first track and the second stick is configured to control the speed (e.g., by braking) of the second track. In yet another example, when each track is driven by one or more electric motors, the look up table may associate the velocities of the two electric motors with the turning radius.

[0048] In some embodiments, user interface 30 may include any device, unit or component that may allow a user (e.g., the driver of continuous track vehicle 60) to communicated with computing device 10. In some embodiments, the user may send steering commends to be executed by computing device 10. In some embodiments, user interface 30 may include a joystick to be operated by the user, for example, steering wheel -like joystick, that may be operated at the same way a” normal” steering wheel is operated. In some embodiments, user interface 30 may include a touchscreen, a mouse, any other type of joystick and the like.

[0049] In some embodiments, first sensor 40 may be any sensor, device or unit that is configured to measure the angular velocity of the vehicle. For example, first sensor 40 may be a gyroscope that measures the yaw rate, when the yaw is defined as the angle around the vertical to the ground axis. In another example, first sensor 40 may include two tachometers, each measures an angular velocity of the sprocket of a different continuous track.

[0050] In some embodiments, second sensor 50 may be any sensor, device or unit that is configured to measure the linear velocity of the vehicle. For example, second sensor 50 may be a GNSS providing time dependent locations of vehicle 60 that may allow calculating the linear velocity, an inertial navigation system (INS) or a visual aided navigation (Visual odometry). [0051] Reference is now made to Fig. 3 which is the control loop of system 100. An initial steering command 310 may be received from one of, user interface 30 or database 20 or any other user device (e.g., a mobile user device). Steering command 310 may be converted 320 to an initial steering radius 325, for example, based on lookup tables stored in database 20. The lookup tables may be generated using experimental data and/or calculations. Initial steering radius 325 may be associated with a steering function 330 that commands continuous track vehicle 60 driving unit to steer continuous track vehicle 60. A real time radius estimation 340 may be conducted based on received real time measurements of angular velocity from first sensor 40 and linear velocity from second sensor 50. Proportional-integral-derivative (PID) 350 may compare the estimated radius to the initial steering radius as to provide a rea time corrected steering radius 360 command to continuous track vehicle 60 driving unit. A detailed disclosure of the control method is discussed herein below with respect to Fig. 4.

[0052] Reference is now made to Fig. 4 which is a flowchart of a method of steering a continuous track vehicle according to some embodiments of the invention. The method of Fig. 4 may be executed by computing device 10 of system 100 or by any other suitable computer. In step 410, a steering command for the continuous track vehicle may be received. The steering command may include at least one of: the turning radius, turning direction and the turning speed. For example, computing device 10 may receive from user interface 30 (e.g., a steering wheel-like joystick) a steering command to turn vehicle 60 to the right at a radius of 10 meters while lowering the speed of vehicle 60 in 30%. In yet another example, computing device 10 may receive from database 20 a preprogramed path that includes one or more steering commands to be executed according to the preprogramed path and optionally sensory data received while autonomously driving vehicle 60. [0053] In step 420, a radius based on the steering command may be determined. For example, a lookup table stored in database 20 may include correlations between steering commands and radiuses.

[0054] In some embodiments, computing device 10 may convert the received steering command and/or determined radius to an initial speed difference between a first track and a second track of the continuous track vehicle. Computing device 10 may control or may command the diving unit of vehicle 60 to cause the initial speed difference, based for example, on correlations between, steering commands, turning radiuses and speed differences stored in database 20. In some embodiments, vehicle 60 may be steered using the initial speed difference.

[0055] In step 430, an angular velocity of the continuous track vehicle may be received from at least one first sensor. In some embodiments computing device 10, may receive from first sensor 40 an angular velocity of vehicle 60, measured around a vertical to the ground axis located on the vehicle. The angular velocity may be received from a gyroscope placed in vehicle 60. In some embodiments, the angular velocity may be calculated from the angular velocities of the sprocket of the two continuous tracks measured by two tachometers.

[0056] In step 440, a linear velocity of the continuous track vehicle may be received from at least one second sensor. For example, second sensor 50 may be GNSS. In yet another example, second sensor 50 may include at least one camera and the method may further include and computing device 10 may be configured to: receive a stream of images from the camera and determine the linear and/or angular velocities using visual odometry process. [0057] In step 450, a real-time turning radius may be estimated based on the received angular velocity and the received linear velocity. For example, computing device 10 may use equation (1) for estimating the real-time turning radius R.

(1) R = — ' w_z

[0058] Wherein, V_x is the linear velocity and W- is the angular velocity, as illustrated for example, in Fig. 5.

[0059] Referring back to Fig. 4, in step 460, the estimated real-time turning radius may be compared to the determined radius. If the estimated real time radius is different from the determined radius, step 460- YES, a speed difference between a first track and a second track of the continuous track vehicle may be changed, in step 470, as to steer the vehicle according to the steering command. In some embodiments, determining the speed difference may be based on the difference between the estimated real-time turning radius and the determined turning radius. The new speed difference may be a correction to the determined speed deference set in step 420. [0060] In some embodiments, changing the speed difference between a first track and a second track may include correcting positions of a first piston and a second piston, such that each piston may be connected to a corresponding control stick and a first control stick may be configured to control the speed of the first track and the second stick may be configured to control the speed of the second track. Alternatively, changing the speed difference between the first track and the second track may include controlling one of: a hydraulic driving unit, an electrical driving unit and a mechanical driving unit.

[0061] If the estimated real time radius is equal to the determined radius, step 460- NO, no change in the speed difference may be caused, in step 480.

[0062] In some embodiments, following the receiving of the steering command from a database, in step 410, computing device 10 may autonomously drive continuous track vehicle 60 according to the steering command by applying the speed difference between the first track and the second track in step 470.

[0063] In some embodiments, following receiving, from a user interface, in real time, the steering command, in step 410, computing device 10 may drive continuous track vehicle 60 in response to the received steering command by applying the speed difference between the first track and the second track in step 470.

[0064] Reference is now made to Figs. 6A and Figs. 6B which are graphs showing estimated curvature which is 1/R (R=estimated steering radius calculated using equation 1), marked with thin grey line, the estimated curvature after smoothening, marked with thick grey line) in comparison to an radius received from GNSS coordinates marked in thin black line. The graph of Fig. 6A was taken for a curve of R=5.29 meters (Corresponding to a curvature of 0.18885 1/meter) and of Fig. 6B was taken for a curve of R=28.7 meters (Corresponding to a curvature of 0.03479 1/meter), As can clearly show the average estimated curvature is very accurate with an error of 0.87% in Fig. 6A and 2.4 % in Fig. 6B compared to the GNSS measurement.

[0065] Reference is now made to Figs. 7A and 7B which shows experiments of driving continuous track vehicle 60 according to two steering commands, 7.5 m radius (Fig. 7A) and 10 m radius (Fig. 7B) by applying the speed difference between the first track and the second track, according to some embodiments of the invention. As can be seen in Figs. 7A and 7B continuous track vehicle 60 (marked as a rectangle) follows (see the grey arrows) very closely on the path defined by each steering command.

[0066] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0067] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. [0068] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

1. A method of steering a continuous track vehicle, comprising: receiving a steering command for the continuous track vehicle; determining a radius based on the steering command; while driving the continuous track vehicle along the route: receiving, from at least one first sensor, an angular velocity of the continuous track vehicle, wherein the first sensor is located on the continuous track vehicle; receiving, from at least one second sensor, a linear velocity of the continuous track vehicle; estimating a real-time turning radius based on the received angular velocity and the received linear velocity; and if the estimated real-time turning radius differs from the determined turning radius, changing a speed difference between a first track and a second track of the continuous track vehicle to steer the vehicle according to the steering command.

2. The method of claim 1, further comprising, determining the speed difference based on the difference between the estimated real-time turning radius and the determined turning radius.

3. The method of claim 1 or claim 2, wherein changing the speed difference between a first track and a second track comprises correcting positions of a first piston and a second piston, wherein each piston is connected to a corresponding control stick and wherein a first control stick is configured to control the speed of the first track and the second stick is configured to control the speed of the second track.

4. The method of claim 1 or claim 2, wherein changing the speed difference between a first track and a second track comprises controlling the speed provided by two electric motors each driving a different track.

5. The method of claim 1 or claim 2, wherein changing the speed difference between a first track and a second track comprises controlling one of: a hydraulic driving unit, an electrical driving unit and a mechanical driving unit.

6. The method according to any one of the preceding claims, wherein determining a radius based on the steering command comprises: receiving from a database a lookup table comprising correlations between turning radiuses and steering command values.

7. The method according to any one of the preceding claims, wherein the at least one first sensor comprises one of: a gyroscope and two tachometers each measure angular velocity of the sprocket of a different continuous track.

8. The method according to any one of the preceding claims, wherein the at least one second sensor is a global navigation satellite system (GNSS) for measuring the linear velocity.

9. The method according to any one of the preceding claims, wherein the at least one second sensor comprises at least one camera and the method further includes: receiving a stream of images from the camera; and determining the linear and angular velocities using visual odometry process.

10. The method according to any one of claims 1-9, further comprising: receiving the steering command from a database or a user devise; and autonomously driving the continuous track vehicle according to the steering command.

11. The method according to any one of claims 1-9, further comprising: receiving, from a user interface, in real time, the steering command; and driving the continuous track vehicle in response to the received steering command.

12. The method of claim 11, wherein the user interface is one of: a joystick, a wheel like joystick and a touchscreen.

13. A system for of steering a continuous track vehicle, comprising: at least one first sensor, located on the continuous track vehicle, and configured to measure an angular velocity of the continuous track vehicle; at least one second sensor configured to measure a linear velocity of the continuous track vehicle; and a computing device configured to: receive a steering command for the continuous track vehicle; determine a radius based on the steering command; during a driving the continuous track vehicle along the route: receive, from the at least one first sensor, the angular velocity; receive, from the at least one second sensor, the linear velocity; estimate a real-time turning radius based on the received angular velocity and the received linear velocity; and if the estimated real-time turning radius differs from the determined turning radius, change a speed difference between a first track and a second track of the continuous track vehicle to steer the vehicle according to the steering command.

14. The system of claim 13, wherein the computing device is further configured to: determine the speed difference based on the difference between the estimated real time turning radius and the determined turning radius.

15. The system of claim 13 or claim 14, wherein changing the speed difference between a first track and a second track comprises correcting positions of a first piston and a second piston, wherein each piston is connected to a corresponding control stick and wherein a first control stick is configured to control the speed of the first track and the second stick is configured to control the speed of the second track.

16. The system of claim 13 or claim 14, wherein changing the speed difference between a first track and a second track comprises controlling the speed provided by two electric motors each driving a different track.

17. The system of claim 13 or claim 14, wherein changing the speed difference between a first track and a second track comprises controlling one of: a hydraulic driving unit, an electrical driving unit and a mechanical driving unit.

18. The system according to any one of claims 13-17, wherein determining a radius based on the steering command comprises: receiving from a database a lookup table comprising correlations between turning radiuses and steering command values.

19. The system according to any one of claims 13-18, wherein the at least one first sensor comprises one of: a gyroscope and two tachometers each measure angular velocity of the sprocket of a different continuous track.

20. The method according to any one of claims 13-19, wherein the at least one second sensor is a global navigation satellite system (GNSS) for measuring the linear velocity.

21. The method according to any one of claims 13-20, wherein the at least one second sensor comprises at least one camera and the computing device further configured to: receive a stream of images from the camera; and determine the linear and angular velocities using visual odometry process.

22. The system according to any one of claims 13-21, wherein the computing device is further configured to: receive the steering command from a database or a user devise; and autonomously driving the continuous track vehicle according to the steering command.

23. The system according to any one of claims 13-21, wherein the computing device is further configured to: receive, from a user interface, in real time, the steering command; and driving the continuous track vehicle in response to the received steering command.

24. The system of claim 23, wherein the user interface is one of: a joystick, a wheel like joystick and a touchscreen.