A method for controlling the propulsion of a work machine and its user interface inputs using parallel processing.

Abstract

This invention provides a control method for left and right towing units that operate independently in the forward and backward directions on a work machine. [Solution] The first and second user interface units generate first and second signals to issue commands to the left and right tracks, respectively, in response to user engagement. The third device generates a third signal to issue commands to both tracks in response to engagement. A computer implementation method for operating the machine provides a function to correct the course while moving in a "single pedal" movement mode, and includes the steps of: combining the first and third signals to generate a first movement command value; combining the second and third signals to generate a second movement command value; generating a control signal to an actuator to control the left track based on the first movement command value; and controlling the right track based on the second movement command value.

Description

Technical Field

[0001]

[0001] This disclosure generally relates to a work machine having a traction unit that contacts the ground and a user interface unit such as a foot pedal, and more specifically to a system and method for propulsion control of the traction unit based on parallel processing of inputs from such a user interface unit.

Background Art

[0002]

[0002] This type of work machine can include, for example, an excavation machine having a traction unit such as a skid steer loader. Conventional control of the propulsion and steering of an excavation machine is typically performed via foot pedals that independently control the left and right traction units of the machine's undercarriage. These foot pedals usually have a lever mechanically attached so that the tracking function can be manually controlled. These controls require the operator to maintain continuous engagement of both pedals, especially when controlling the movement of the work machine over a significant distance, which can make the operation uncomfortable.

Summary of the Invention

Problems to be Solved by the Invention

[0003]

[0003] Conventional solutions for facilitating operation during heavy moving operations are various, but one method is to implement a "single pedal" movement system, which allows both tracks to operate simultaneously and enables the construction of an auxiliary pedal placed beside the normal movement pedal to drive the machine in a straight line. This type of system is often implemented by sending pilot pressure to an auxiliary control valve and using a valve for controlling movement, which substantially invalidates the main pedal. As a result, it may be difficult to correct the path. To correct the moving direction of the machine (i.e., "path correction"), the operator needs to stop going straight and use the main pedal to adjust the direction of the machine. [Means for solving the problem]

[0004]

[0004] The disclosure provides an enhancement to conventional systems by introducing novel work machines, control systems, and methods for utilizing a single-pedal movement system to improve operator comfort during the “linear movement” process, and also enables course correction without the operator having to stop movement, in parallel with the single-pedal movement mode.

[0005]

[0005] In a particular exemplary embodiment, a method for controlling a plurality of independent towing units on a work machine includes the step of receiving an electronic signal comprising: a first signal representing user engagement of a first user interface unit for issuing commands to a towing unit on a first side of the work machine; a second signal representing user engagement of a second user interface unit for issuing commands to a towing unit on a second side of the work machine; and a third signal representing user engagement of a third user interface unit for issuing commands to each of the towing units on the first and second sides of the work machine. The first and third signals are combined to generate a first move command value, and the second and third signals are combined to generate a second move command value. Control signals are generated for one or more actuators for controlling the towing unit on the first side of the work machine based on the first move command value, and for controlling the towing unit on the second side of the work machine based on the second move command value.

[0006]

[0006] In one exemplary and arbitrary embodiment of the embodiments of the method described above, the values ​​corresponding to each of the first, second, and third signals can be normalized into a common unit structure. The common unit structure may, for example, comprise percentage (%) values, where the user engagement of the user interface unit for issuing forward commands to one or more of the towing units generates positive values ​​from 0% to 100%, and the user engagement of the user interface unit for issuing backward commands to one or more of the towing units generates negative values ​​from -100% to 0%.

[0007]

[0007] In another exemplary and arbitrary embodiment of the above-described embodiment of the method, for first and second movement command values ​​less than 100%, control signals for controlling the respective towing units may be generated based thereon. For first and second movement command values ​​greater than 100%, the respective movement command values ​​may be normalized to a range of + / -100%, and control signals for controlling the respective towing units may be generated based thereon.

[0008]

[0008] In another exemplary and arbitrary embodiment of the above-described method, the first and second move command values ​​can be normalized to a range of + / -100% by dividing each command value by the maximum value of the first and second command move command values, respectively.

[0009]

[0009] In another embodiment disclosed herein, the work machine may include a plurality of towing units configured to operate independently in a forward or backward direction to propel the work machine on the ground, and a plurality of user interface units. A first user interface unit is configured to generate a first signal for issuing commands to the towing units on a first side of the work machine in response to user engagement. A second user interface unit is configured to generate a second signal for issuing commands to the towing units on a second side of the work machine in response to user engagement. A third user interface unit is configured to generate a third signal for issuing commands to each of the towing units on the first and second sides of the work machine in response to user engagement. A data processing and control system is further configured to direct the execution of steps according to one or more of the embodiments of the method described above and optionally exemplary thereof.

[0010]

[0010] Many of the objects, features, and advantages of the embodiments described herein will be readily apparent to those skilled in the art when they read the following disclosure in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0011] [Figure 1]

[0011] This is a side view showing an excavator as an exemplary self-propelled work machine according to one embodiment of the present invention. [Figure 2]

[0012] This is a perspective view showing a control pedal array as an exemplary work interface tool according to an embodiment of the present disclosure. [Figure 3]

[0013] This is an overhead view showing the forward / backward movement of the excavator's track according to an embodiment of the disclosure. [Figure 4]

[0014] This is a block diagram representing an exemplary control system according to an embodiment of the present disclosure. [Figure 5]

[0015] This is a flowchart illustrating an exemplary embodiment of the method disclosed herein. [Modes for carrying out the invention]

[0012]

[0016] Next, with reference to Figures 1 to 5, various embodiments of systems and methods for operating self-propelled work machines, which in this specification may be referred to as “single-pedal” movement mode, will be described. These systems and methods specifically improve upon otherwise similar conventional techniques by providing the ability to make course corrections while moving substantially in a linear direction. For example, if an electro-hydraulic control system is used, all pedals are electronic, and their signals can be processed in parallel to improve controllability during the desired movement mode.

[0013]

[0017] Figure 1 shows a typical self-propelled work machine 120, for example, in the form of a truck-mounted excavator. While this specification primarily describes excavators as examples of work machines 120, other types of work machines within the scope of this disclosure may, in various embodiments, include, for example, loaders, bulldozers, motor graders, or other construction vehicles, agricultural vehicles, or utility vehicles.

[0014]

[0018] The work machine 120 includes a substructure 122, which includes first and second towing units 124. The towing units described herein take the form of tracks, but alternative embodiments within the scope of this disclosure may include, for example, wheels. Figure 1 shows only one of the towing units. The other towing unit is positioned parallel to the illustrated towing unit. Each of the towing units 124 may typically include a front idler, a drive sprocket, and a track chain extending around the front idler and drive sprocket. A motor for each towing device drives the respective drive sprocket. The towing units can be driven at the same speed to move the substructure forward (e.g., in the forward direction indicated by arrow 126) or backward (e.g., in the opposite direction to arrow 126) relative to the sub-terrain 128 (e.g., the ground or other material supporting the substructure). The towing units can also be driven at different speeds to allow the substructure to pivot relative to the ground at an angle to the forward direction indicated by arrow 126.

[0015]

[0019] The main frame 130 is supported from the substructure 122 by a swing bearing 132, and the main frame is pivotable about a main frame pivot axis 134 relative to the substructure. The pivot axis is substantially vertical when the lower ground terrain 128 engaged by the towing unit 124 is substantially horizontal. (In this description, “horizontal” and “vertical” refer to the plane defined by the towing unit.) A swing motor (not shown) is configured to pivot the main frame on the swing bearing about the pivot axis relative to the substructure.

[0016]

[0020] In the illustrated embodiment, the working machine 120 is an excavator, and the working tool 140 extends from the main frame 130. In Figure 1, the working tool is configured as a boom assembly. The working tool includes conventional components in the form of a boom 142, an arm 144, and a working tool 146. The working tool includes a point of interest (POI) 148 that engages with a portion of the terrain (or other material) to be moved or removed.

[0017]

[0021] The boom 142 is swivelably connected to the main frame by a boom-to-frame connecting joint 150, thereby providing a horizontal pivot axis for the boom. The arm is swivelably connected to the boom at an arm-to-boom connecting joint 152. In the illustrated embodiment, the working tool 146 is the excavator's shovel and is swivelably connected to the arm 144 at a working tool-to-arm connecting joint 154 located near the free end of the arm. In the illustrated embodiment, the first end of the dogbone connector 160 is swivelably connected to the arm at a dogbone-to-arm connecting joint 162 offset from the free end of the arm. The second end of the dogbone connector is swivelably connected to a tool link 164. In the context of the illustrated (excavator) working machine 120, the tool link is a bucket link.

[0018]

[0022] The boom 142 is movably pivoted with respect to the main frame 130 by a boom actuator 170. The boom actuator can be a hydraulic motor. In the illustrated embodiment, the boom actuator is a hydraulic piston cylinder unit to which pressurized hydraulic fluid is selectively supplied to move a piston within a cylinder to extend or retract the piston. The pressurized hydraulic fluid is supplied by a hydraulic system (not shown) and is controlled by manual control, automatic control, or a combination of manual control and automatic control. Similarly, the arm 144 is pivoted with respect to the boom by an arm actuator 172. The work tool (bucket) 146 is pivoted with respect to the arm by a work tool actuator 174 that acts on the work tool via a dog bone connector 160, a connection joint 162 between the dog bone and the arm, and a tool link 164.

[0019]

[0023] The work implement 140 extends from the main frame 130 along the working direction of the work implement (shown by arrow 176). In FIG. 1, the working direction is referenced to the main frame. In the drawing, it is depicted parallel to the forward direction (arrow 126) of the lower structure 122, but the working direction may be angled with respect to the forward direction depending on the rotational position of the main frame with respect to the lower structure. The working direction can also be said to be the working direction of the boom 142.

[0020]

[0024] As described herein, the control of the work implement 140 involves controlling the position of one or more of the associated components (e.g., boom 142, arm 144, and work tool 146) in order to control the movement of the point of interest 148 of the work tool with respect to the material being operated on (e.g., the material being moved or removed).

[0021]

[0025] The actuators 170, 172, 174 of the working implement 140 can be selectively actuated to move the boom 142 pivotally relative to each boom-to-frame connection joint 150, to move the arm 144 pivotally relative to the arm-to-boom connection joint 152, and / or to move the working tool 146 pivotally relative to the working-tool-to-arm connection joint 154. By adjusting the movements of the boom, arm, and working tool of the working implement, the point of interest of the working tool engages and acts on the material being manipulated at a target speed along a selected trajectory. The selected trajectory can be curved as shown (e.g., by pivoting the working tool about the working-tool-to-arm connection joint or by pivoting the arm about the arm-to-boom connection joint). The selected trajectory can also be made straight by adjusting the pivoting of the boom, arm, and working tool using inverse kinematics techniques or other suitable techniques (e.g., open-loop modeling) to determine the pivoting speed of each of the three components of the working implement 140.

[0022]

[0026] In the illustrated embodiment, the operator's seat 192 is disposed on the main frame 130. In the illustrated embodiment, both the operator's seat and the working implement 140 are attached to the main frame such that the operator's seat faces the working direction (arrow 176) of the working implement. In the illustrated embodiment, the control station 194 is disposed within the operator's seat.

[0023]

[0027] The main frame 130 also supports an engine 196 for powering the work machine 120. The engine can be a diesel internal combustion engine or another power source. In the illustrated embodiment, the engine drives at least one hydraulic pump (not shown) to supply hydraulic power to various operating systems of the work machine.

[0024]

[0028] As schematically shown in Figures 2 and 3, the user interface unit located in the driver's seat may include a left foot pedal 202, a right foot pedal 204, and an auxiliary foot pedal 206, each pedal having an associated element that generates signals representing user engagement and operation of the respective pedal. Although not shown, at least the left foot pedal 202 and the right foot pedal 204 may have associated mechanically mounted levers that allow their respective functions to be controlled at least partially manually. The operator may use at least the left foot pedal 202 and the right foot pedal 204 to control the travel speed of the towing units 124A and 124B by moving them by a desired distance.

[0025]

[0029] In a given operation, the operator may specify a desired speed for the engine and a desired speed for the traction unit motor via one or more speed inputs, and then the operator may fine-tune or adjust the speed of movement of the work machine 120 using at least the left foot pedal 202 and the right foot pedal 204. The operator may also use the foot pedals to control the direction of movement of the traction unit by moving the foot pedal in a desired direction, such as forward or backward. The operator may command the work machine to move forward by pushing a desired foot pedal forward (for example, by applying pressure with the ball of the operator's foot), and command the work machine to move backward by pushing a desired foot pedal backward (for example, by applying pressure with the heel of the operator's foot).

[0026]

[0030] Typically, the left foot pedal 202 generates a signal representing the desired forward or backward propulsion control of the left towing unit 124A, and the right foot pedal 204 generates a signal representing the desired forward or backward propulsion control of the right towing unit 124B. The auxiliary foot pedal 206 can often be configured to control various functions of the work machine 120, one example being the "single-pedal movement" function. This function utilizes the signals generated by the auxiliary pedal 206 to equally drive both the left towing unit 124A and the right towing unit 124B of the work machine 120, thereby providing, at least theoretically, a linear movement trajectory in either the forward or backward direction.

[0027]

[0031] As schematically shown in Figure 4, the self-propelled work machine 120 includes or is associated with a control system 200, which includes a controller 210. The controller may be part of the machine control system of the work machine 120 or it may be a separate control module. The controller is optionally mounted in a control station 194 in the driver's seat 192. The machine controller may include a control panel with a display unit 216 and may be configured to receive input signals from various user interface units (e.g., the pedals 202, 204, and 206 described above).

[0028]

[0032] Although not shown, the controller 210 may receive input signals from other user interface units (e.g., keyboards, joysticks, etc.) associated with other mechanical functions, such as the control of work tools. Also, although not explicitly shown in Figure 4, the controller 210 may receive signals from the machine control system, signals from machine positioning sensors such as a Global Navigation Satellite System (GNSS) receiver, ground speed sensors, steering sensors, and / or signals from work tool position sensors such as a rotary pin encoder mounted on a swivel pin to detect the relative rotational position of each component, or a linear encoder mounted on a hydraulic cylinder to detect the extension of each component.

[0029]

[0033] Additional sensors are provided, configured to generate signals representing the position, state, or speed of each actuator, including, for example, hydraulic piston cylinder units associated with each working machine component.

[0030]

[0034] The controller 210 can be configured to generate an output to the display unit 216 for displaying information to a human operator. Furthermore, or alternatively, the machine controller can be configured to generate control signals for controlling the operation of each actuator, or for indirect control via intermediate devices associated with the left traction unit control system 220, the right traction unit control system 222, etc. The machine controller 210 can generate control signals for controlling the operation of various actuators, such as hydraulic motors or hydraulic piston cylinder units. Control signals from the controller can be received by electro-hydraulic control valves associated with the actuators, so that the electro-hydraulic control valves control the flow of hydraulic fluid to and from each hydraulic actuator in response to the control signals from the controller, thereby controlling the operation of each hydraulic actuator.

[0031]

[0035] The controller 210 may include, or be associated with, a processor 250, a computer-readable medium 252, a communication unit 254, data storage 256 such as a database network, and the aforementioned display 216.

[0032]

[0036] The controllers described herein may be a single controller having all of the described functions, or they may include multiple controllers in which the described functions are distributed among multiple controllers. Data storage may generally include hardware such as volatile or non-volatile storage devices, drives, memory, or other storage media, as well as one or more databases residing therein.

[0033]

[0037] Although not specifically shown in Figure 4, in some embodiments, the controller 210 of the work machine 120 may further receive input from a remote device associated with the user and generate output to that remote device via a user interface, such as a display unit with a touchscreen interface. For example, data transmission between the machine control system and the remote user interface may take the form of wireless communication systems and related components conventionally known in the art. In certain embodiments, the remote user interface and vehicle control system for each work machine may be further coordinated with or otherwise interact with a remote server or other computing device to perform specific operations within the system disclosed herein.

[0034]

[0038] Various “computer implementation” operations, steps, or algorithms described in relation to the controller 210 or an alternative equivalent computing device or system can be implemented directly in hardware, in computer program products such as software modules executed by the processor 250, or a combination of both. The computer program products can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, or any other form of computer-readable medium 252 known in the art. An exemplary computer-readable medium 252 can be coupled to the processor 250 so that the processor 250 can read information from and write information to the memory / storage medium 252. Alternatively, the computer-readable medium 252 can be integrated with the processor 250. The processor 250 and the computer-readable medium 252 can reside within an application-specific integrated circuit (ASIC). The ASIC can reside within a user terminal. Alternatively, the processor 250 and the medium 252 can reside as separate components within a user terminal.

[0035]

[0039] As used herein, the term “processor” may refer to at least general-purpose or dedicated processing devices and / or logic as understood by those skilled in the art, including but not limited to microprocessors, microcontrollers, and state machines. A processor can also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor (DSP) and a microprocessor), multiple microprocessors, one or more microprocessors combined with a DSP core, or any other similar configuration.

[0036]

[0040] The communication unit 254 can support or provide communication between the machine controller 210 and an external system or device, and / or support or provide a communication interface for internal components of the self-propelled work machine 120. The communication unit 254 may include wireless communication system components (e.g., via a cellular modem, Wi-Fi® system, Bluetooth® system, etc.) and / or one or more wired communication terminals such as a universal serial bus port.

[0037]

[0041] Referring now to Figure 5, an exemplary embodiment of the method of operation 300 will be described, still using an excavator as an example of the work machine 120 for illustrative purposes. Unless otherwise expressly stated, the various steps of the method may be performed at the level of the local work machine controller 210, at the level of a computing device associated with the operator of the work machine or other users, and / or at the level of one or more remote servers communicatively linked thereto. The illustrated embodiments may include a particular arrangement of steps, inputs, outputs, etc., but unless otherwise specifically stated herein, it should be understood that in other embodiments within the scope of this disclosure, certain steps may be combined, performed in a different order, or omitted entirely.

[0038]

[0042] The illustrated method 300 may, for example, begin with the general operation of the work machine 120 in step 302, or, in some embodiments, begin with the user selection of a specific operating mode. Method 300 includes, in step 304, receiving signals from each of the user interface units 202, 204, and 206, each of which may be processed in parallel for propulsion control by at least one operating mode of the work machine. In some embodiments, in addition to at least one operating mode in which auxiliary inputs are processed in parallel with the input signals from the left user interface unit 202 and the right user interface unit 204, at least one of devices, such as an auxiliary user interface unit 206, may be used in some operating modes to control auxiliary (i.e., non-propulsion-related) machine functions.

[0039]

[0043] As mentioned above, the auxiliary user interface unit 206 can often be configured to control various functions of the work machine 120, one example being the "single-pedal movement" function. This function drives both the left towing unit 124A and the right towing unit 124B of the work machine equally, thereby providing, at least theoretically, a linear movement trajectory in either the forward or reverse direction. However, conventional operation of the work machine has known problems, such as the possibility that when moved in the "straight" direction using a single pedal, the work machine may deviate from its course and begin tracking. Various reasons why the machine may deviate from its course and begin tracking include, but are not limited to, slight deviations in the machine tracking system, causing one towing unit to operate at a slightly different speed than the other; changes in terrain, thereby causing the track or road to no longer be straight; slight tracking errors due to different towing conditions for the left and right towing units; and the machine's direction not being properly established at the start of tracking.

[0040]

[0044] Returning to the embodiment shown in Figure 5, Method 300 includes step 306 of normalizing the respective signals from the various user interface units 202, 204, and 206 to a common unit, such as a percentage (%) value, thereby generating positive signals between 0% and 100% for “forward” movement and negative signals between 0% and -100% for “backward” movement.

[0041]

[0045] Therefore, the first (i.e., left) user interface unit position value 308, the second (i.e., right) user interface unit position value 310, and the third (i.e., auxiliary) user interface unit position value 312 are established within a common unit framework.

[0042]

[0046] Since the positions of all user interface units (e.g., pedals) are established in a common unit, the method 300 according to the embodiment shown in Figure 5 proceeds to step 314 by adding the first user interface unit position value 308 and the third user interface unit position value 312 to determine the left movement command value, and further proceeds to step 316 by adding the second user interface unit position value 310 and the third user interface unit position value 312 to determine the right movement command value. This generates left and right movement command values ​​that encompass values ​​from -200% to +200%, respectively.

[0043]

[0047] If the sum of the left move command value and the right move command value remains less than 100% (i.e., the response to the query in step 318 is "no"), those commands can be applied directly to the left move function and the right move function of the work machine, respectively, in step 322. In this case, using both pedal sets simply provides an additional effect on the overall tracking function of the machine.

[0044]

[0048] If the sum of the left move command value and the right move command value is greater than 100% (i.e., the response to the query in step 318 is "yes"), method 300 may proceed to step 320 by normalizing the value to a range of + / -100%. In one embodiment, this can be achieved by dividing both signals by the maximum value of the two signals, as shown below, for example.

[0045]

number

[0046]

[0049] This technique of scaling back the signal within a range of + / -100% has the effect of potentially reducing the command to one traction unit when the operator attempts to inject a signal to the opposite traction unit. Those skilled in the art will understand that this actually has the effect of ultimately correcting the machine's course in the direction desired by the operator by decelerating the other traction unit rather than accelerating the other.

[0047]

[0050] As used herein, the phrase “one or more of ~” when used in a list of items means that one or more different combinations of items may be used, and that only one of each item in the list may be required. For example, “one or more of ~

[0048]

[0051] Accordingly, it will be found that the apparatus and methods of this disclosure readily achieve the purposes and benefits mentioned, as well as those inherent thereto. While certain preferred embodiments of this disclosure are illustrated and described for the purposes of the present invention, numerous modifications to the arrangement and configuration of components and steps may be made by those skilled in the art, and such modifications are included within the scope and spirit of this disclosure as defined by the appended claims. Each disclosed feature or embodiment may be combined with any of the other disclosed features or embodiments.

Claims

1. A method for controlling a plurality of traction units configured to operate independently in a forward or backward direction in order to propel a work machine on the ground, During the operation of the aforementioned work machine, an electronic signal occurs, A first signal representing user engagement of a first user interface unit for issuing commands to the traction unit on the first side of the work machine, A second signal representing user engagement of a second user interface unit for issuing commands to the second traction unit on the second side of the aforementioned work machine, A third signal representing user engagement of a third user interface unit for issuing commands to each of the first and second traction units on the aforementioned work machine, and The steps include receiving an electronic signal comprising, The steps include combining the first signal and the third signal to generate a first movement command value, and combining the second signal and the third signal to generate a second movement command value, The steps include: generating control signals for one or more actuators to control the traction unit on the first side of the work machine based on the first movement command value, and to control the traction unit on the second side of the work machine based on the second movement command value; A method for providing this.

2. A method according to claim 1, wherein the values ​​corresponding to each of the first, second, and third signals are normalized to a common unit structure.

3. A method according to claim 2, wherein the common unit structure comprises a percentage (%) value, the user engagement of a user interface unit for issuing forward commands to one or more of the towing units generates a positive value between 0% and 100%, and the user engagement of a user interface unit for issuing backward commands to one or more of the towing units generates a negative value between -100% and 0%.

4. The method according to claim 3, For first and second movement command values ​​less than 100%, the control signals for controlling the respective traction units are generated based on them. A method in which, for first and second movement command values ​​exceeding 100%, each of the movement command values ​​is normalized to a range of + / - 100%, and a control signal for controlling each of the towing units is generated based on this normalization.

5. A method according to claim 4, wherein the first and second movement command values ​​are normalized to a range of + / - 100% by dividing each command value by the maximum value of the first and second command movement command values, respectively.

6. It is a work machine, To propel the aforementioned work machine on the ground, a plurality of towing units configured to operate independently in the forward or backward direction, A first user interface unit configured to generate a first signal for issuing a command to the first side traction unit of the work machine in response to user engagement, A second user interface unit configured to generate a second signal for issuing a command to the second side traction unit of the work machine in response to user engagement, A third user interface unit configured to generate a third signal for issuing commands to each of the first and second traction units of the work machine in response to user engagement, A data processing and control system, The first signal and the third signal are combined to generate a first movement command value, and the second signal and the third signal are combined to generate a second movement command value. The system generates control signals for one or more actuators to control the traction unit on the first side of the work machine based on the first movement command value, and to control the traction unit on the second side of the work machine based on the second movement command value. A data processing and control system configured to perform the following: A work machine equipped with the following features.

7. A work machine according to claim 6, wherein the values ​​corresponding to each of the first, second, and third signals are normalized to a common unit structure.

8. A work machine according to claim 7, wherein the common unit structure includes a percentage (%) value, the user engagement of a user interface unit for issuing commands in the forward direction to one or more of the towing units generates a positive value between 0% and 100%, and the user engagement of a user interface unit for issuing commands in the backward direction to one or more of the towing units generates a negative value between -100% and 0%.

9. A work machine according to claim 8, wherein, for first and second movement command values ​​less than 100%, the control signals for controlling each of the traction units are generated based thereon, A work machine in which, for first and second movement command values ​​exceeding 100%, each of the movement command values ​​is normalized to a range of + / - 100%, and the control signals for controlling each of the towing units are generated based on this normalization.

10. A work machine according to claim 9, wherein the first and second movement command values ​​are normalized to a range of + / - 100% by dividing each command value by the maximum value of the first and second command movement command values, respectively.

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