Work machine control system and method for operating around power lines

Abstract

A control system 40 for operating a work machine 10 around an over-head power line 42 has an electric field sensor 41 and an operator input, such as a user interface 6. If the output from an electric

Description

TECHNICAL FIELD This disclosure is directed towards a control system for and method of controlling a work machine around a power line in a safe manner. BACKGROUND Excavators and other work machines often have to operate near over-head power lines or cables. There is therefore the risk of a work machine contacting a power line and causing high voltages across the work machine, endangering human operators and damaging equipment. Various safety regulations exist to reduce such risk. Known safety methods and systems can sense the power lines and generate warnings for operators and / or control movement of the work machine if the power lines are deemed to be too close. One such example is disclosed in WO02086519A1. A safety device is provided for mobile construction equipment for reducing the likelihood of contact between a plant and an overhead power line. The device includes a power line detector, which may be placed on a movable portion of the plant. In one embodiment, the device ceases or reverses movement of the plant (or a part of the plant) towards a power line. In another embodiment, the device provides a series of warnings to the operator of the plant. SUMMARY An object of the present disclosure is to provide improvements to the operation of work machines close to power lines. A further object is to provide a system in which a work machine can still safely operate close to power lines. The present disclosure therefore provides a control system and method in accordance with the claims. A problem with known safety methods and systems is that they can prevent the operation of work machines near over-head power cables when such operation is necessary. The present invention therefore achieves a suitable balance between (a) operating the work machine after detecting a power line at a further distance to reduce risk and (b) operating the work machine after detecting a power line at a closer distance to allow for work machine operation around the power line. The present disclosure therefore provides a control system for controlling a work machine around a power line, the control system being configured, by at least one control processor, to perform a series of steps as set out below. The present disclosure further provides a work machine comprising the control system, a method of performing the steps by a control processor and a non-transitory computer-readable storage medium including program code which when executed by at least one processor causes operations comprising the method. Initially, the control system determines whether a first electric field value received from the at least one electric field detection sensor has a greater magnitude than a first threshold value and thus whether the work machine has reached an outer safety boundary around the power line. If the work machine has reached the outer safety boundary, the work machine is controlled in accordance with a first control mode in which a first alert is issued, and movement of the work machine is stopped. This ensures that an operator of the work machine becomes aware of the power line as the work machine approaches it by issuing a first alert to the operator once the work machine has reached the outer safety boundary. As a result, the operator has an early warning of the presence of the power line. By stopping the movement of the work machine until receipt of a first override command, it becomes immediately apparent to the operator that an issue has arisen, which they can identify by reviewing the first alert. Therefore, it is harder for an operator to miss the first alert. As the work machine continues moving towards the power line, the control system determines that a second electric field value received from the at least one electric field detection sensor has a greater magnitude than a second threshold value, the second threshold value having a greater magnitude than the first threshold value and thus that the work machine has reached an inner safety boundary around the power line. The inner safety boundary is closer to the power line than the outer safety boundary. By having at least one additional boundary closer to the power line, different stages of control restrictions can be applied. As a result, the balance between (a) and (b) discussed above can be better met. If the work machine has reached the inner safety boundary, the control system controls the work machine in accordance with a second control mode in which a second alert is issued and movement of the work machine is stopped. Therefore, multiple stages of alert and operational capabilities can be provided before the power line is reached, each successive stage making it clearer and more urgent to the operator that the work machine is nearing a power line. In the second control mode, the control system may allow movement of the work machine towards the power line upon receipt of a second override command. As a result, an operator may be able to still operate the work machine in the second control mode, albeit at reduced performance. The work machine can then be operated more carefully to perform any task that must be carried out near the power line. The operation of the work machine may be more restricted in the second control mode than in the first control mode by the maximum velocity and / or acceleration of movement of the work machine being less in the second control mode than in the first control mode. For example, when in the second control mode, the maximum allowed velocity and / or acceleration towards the power line may be less than the maximum allowed velocity and / or acceleration away from the power line. The operation of the work machine may be more restricted in the second control mode than in the first control mode by the direction of movement of the work machine being more restrained in the second control mode than in the first control mode. For example: Movement of the work machine may be restrained to a safe direction of travel, away from the power line such that a reducing magnitude of electric field values are detected by the at least one electric field detection sensor. Thus, the work machine may only be able to move away from the power line, unless the aforementioned second override command is provided; and / or The control system prevents further movement of the work machine in the direction of travel of the work machine when the second control mode was initialised / when entering the inner safety boundary. Therefore, if the work machine has been travelling at a particularly high speed towards the power line, such movement may be stopped. In the second control mode, the control system may also indicate a safe direction of travel and a reducing magnitude of electric field values from the at least one electric field detection sensor away from the power line on a display for the operator to view. Therefore, the operator has clear instructions as to how to move the work machine away from the power line. The control system may additionally or alternatively, once the work machine initialises the first control mode, start recording data indicative of the movement of the work machine. This movement data may be used to determine a safe direction of travel away from the power line, such as displaying to an operator the operation of the work machine in the opposite direction of its travel along the movement data. The control system may be further configured, by the control processor, to determine that a third electric field value received from the at least one electric field detection sensor has a greater magnitude than a third threshold value, the third threshold value having a greater magnitude than the second threshold value, and thus that the work machine has reached an override safety boundary around the power line. The override safety boundary is closer to the power line than the inner safety boundary. The control system may then further initialise control of the work machine in accordance with a third control mode in which a third alert is issued and movement of the work machine is stopped until a third override command is received. The third override command is different to the second override command and may only be accessed through at least one level of security, such as a pin code or password. As a result, if the operator is inexperienced, they may not be provided with the means to pass the security. Once the movement is stopped, an experienced operator can be brought in to move the work machine safely away from the power line. In the third control mode, the movement of the work machine may be restricted in a similar manner to the second control mode. In particular, movement of the work machine may be restrained to a safe direction of travel, from the override safety boundary into the inner and / or outer safety boundary away from the power line. The maximum velocity and / or acceleration may be similarly restricted, optionally to a greater extent than in the second control mode. The present disclosure is directed towards any suitable type of work machine required to operate near power lines. In some embodiments, the work machine comprises an arm arrangement and / or tool configurable into different orientations by the control system and / or an operator and the method and control system may be directed to avoiding contact between the arm arrangement and / or tool and power lines. The work machine may further comprise, additionally or alternatively, an undercarriage to which a main body is rotatably mounted, such as via a swing system. The work machine may therefore comprise an excavator, backhoe, shovel, dragline, a drill and / or material handler or the like. The work machine may alternatively comprise a dozer, shovel, wheeled tractor scraper, motor grader or a hauling machine, such as a dump truck, off- highway truck, mining truck, on-highway truck or lorry / truck or articulated hauler or the like. The tool may be of any suitable type and may, for example, be a grapple, bucket, tiltable bucket, tilt rotator, hammer, handling arm, multi-processor, pulveriser, saw, shears, blower, grinder, tiller, trencher, winch, auger, broom, cutter, planer, delimber, felling head, mulcher, or rake. In the present disclosure, determining the location of the work machine and / or determining whether the work machine has reached a safety boundary refers to making such a determination in respect of any part of the work machine that reaches the safety boundary. The position and / or orientation of the work machine, and thus whether it has reached a safety boundary, is determined by the magnitude of the electric field values from the at least one electric field sensor. In some embodiments the control system may determine the location of the arm arrangement and / or tool and / or whether the arm arrangement and / or tool have reached the safety boundary, since these parts of the work machine will typically extend upwards towards power lines and can be the furthest part of the work machine from the operator. The determination may be that of the location of the at least one electric field sensor and / or whether the at least one electric field sensor has reached the safety boundary. BRIEF DESCRIPTION OF THE DRAWINGS By way of example only, embodiments of the present disclosure are now described with reference to, and as shown in, the accompanying drawings, in which: Figure 1 is an illustration of a work machine in proximity to an over-head power line in accordance with the present disclosure; Figure 2 is a chart illustrating threshold values from at least one electric field sensor on the work machine of the present disclosure for determining boundaries around a power line; Figure 3 is a schematic flowchart illustrating a first control mode of a method of operating a work machine in accordance with the present disclosure. Figure 4 is a schematic flowchart illustrating further control modes of a method of operating a work machine in accordance with the present disclosure. DETAILED DESCRIPTION The ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the invention. Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that embodiments may be practised without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments. Also, it is noted that the embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed but could have additional steps not included in the figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function. Moreover, as disclosed herein, the term "storage medium" may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and / or other machine readable mediums for storing information. The term "computer-readable medium" includes but is not limited to portable or fixed storage devices, optical storage devices, wireless channels, and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as storage medium. A processor(s) may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and / or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Figure 1 illustrates an embodiment of a work machine 10, in this case an excavator for excavating material from the ground, terrain and / or worksite, according to the present disclosure. The work machine 10 may comprise a main body 12 having a cab 8 for an operator and an arm arrangement 14 and / or tool 15 attached to the main body 12. The work machine 10 may comprise an undercarriage 30 to which the main body 12 is rotatably mounted, such as via a swing system 31. The work machine 10 comprises a power system, comprising for example an internal combustion engine and / or electrical power system with at least one battery providing power to at least one motor, for driving at least one wheel and / or track 13 for driving the work machine 10 along a terrain 33. The work machine 10 may comprise a tool 15 connected to the arm arrangement 14 via a coupling arrangement 11. The arm arrangement 14 may comprise a boom 16, a stick 17 and a linkage arrangement 20 pivotally attached to one another. The coupling arrangement 11 may be mounted to the stick 17 and linkage arrangement 20. The arm arrangement 14 may comprise hydraulic actuators 18, 19, 21 for controlling the orientation and movement of the boom 16, stick 17 and linkage arrangement 20 and thereby the orientation and movement of the coupling arrangement 11 and tool 15. The undercarriage 30 may comprise a chassis 32 to which the at least one wheel and / or track 13 may be mounted. The swing system 31 may be mounted to a top of the chassis 32 and the at least one wheel and / or track 13 may be mounted to opposing sides of the chassis 32. The swing system 31 may comprise at least one swing motor for rotating the main body 12 relative to the undercarriage 30. The work machine 10 may comprise a hydraulic system 5 for operating the arm arrangement 14 and / or at least one tool 15 and around which fluid may be circulated. The hydraulic system 5 may comprise the first, second and third hydraulic actuators 18, 19, 21 for controlling the pivoting of the arm arrangement 14 and the tool 15. The work machine 10 may comprise a control system 40 for controlling the hydraulic system 5 automatically or based upon inputs received from the user interface 6 and / or automatically. The user interface 6 may comprise an input device controllable by an operator in the main body 12, such as a joystick or at least one button, and may comprise at least one display for displaying information to a user, such as a screen or lighting. The control system 40 may be configured to perform the methods of the present disclosure. The control system 40 comprises a control processor 49 configured to perform operations based upon the instructions. The control system 40 may comprise a controller, which may comprise a memory, which may store instructions or algorithms in the form of data, and the control processor 49. The controller may be of any suitable known type and may comprise an engine control unit (ECU), machine electronic control module or the like. The memory may comprise any suitable computer-accessible or non-transitory storage medium for storing computer program instructions, such as RAM, SDRAM, DDR SDRAM, RDRAM, SRAM, ROM, magnetic media, optical media and the like. The control processor 49 may comprise any suitable processor capable of executing memory-stored instructions, such as a microprocessor, uniprocessor, a multiprocessor and the like. The controller may further comprise a graphics processing unit for rendering objects for viewing on the display of the user interface 6, and / or a separate display of the control system. The controller may also be in communication with an external computing system via a wired or wireless network (such as Ethernet, fibre optic, satellite communication network, broadband communication network, cellular, Bluetooth). The external computing system may comprise computing systems, processors, servers, memories, databases, control systems and the like. The control processor 49 may be communicatively connected (via a wired or wireless connection) to the power system and hydraulic system 5 for providing control signals thereto and receiving sensor signals therefrom in order to control the operation of the work machine 10. The control processor 49 may communicate with the user interface 6, for receiving an input and controlling the work machine 10 and for displaying information to the operator. Although the control system 40 is described herein as being part of the work machine 10, it will be appreciated that the control system 40 may be entirely or partially located on an external server to the work machine 10 such that the control steps and method disclosed herein are partially or entirely implemented on the external server. The control system 40 is configured to determine the location of the work machine 10 relative to a power line 42. In particular, the control system 40 may determine whether the work machine 10 has reached a series of operational safety boundaries 45, 46, 47 or envelopes around a power line 42. Each safety boundary 45, 46, 47 may represent a certain distance from the power line 42. The control system 40 may define an outer safety boundary 45, which is furthest from the power line 42, and an inner safety boundary 46, which is closer to the power line 42 than the outer boundary 45. The control system 40 may further define an override safety boundary 47, which is closer to the power line 42 than the inner safety boundary 46. The control processor 49 may determine whether the safety boundaries 45,46,47 have been reached based upon the output from at least one electric field sensor 41. In particular, the control processor 49 receives electric field signals indicative of electric field values from the at least one electric field detection sensor 41. The control system 40 determines whether the work machine 10 has reached the outer, inner or override safety boundary 45, 46, 47 based upon whether the output from the at least one electric field sensor 41 indicates that a first, second or third threshold value 50, 51, 52 respectively has been reached. For example, as illustrated in Figure 2, the first, second and third threshold values 50, 51,52 illustrate predetermined electric field strengths. The third threshold value 52 has a greater magnitude than the second threshold sensor 51 measurement and the second threshold value 51 has a greater magnitude than the first threshold value 50. Hence if the third threshold value 52 is reached, it is indicative of the at least one electric field sensor 41 being closer to the power line 42 than if the first or second threshold values 50, 51 are reached. A further boundary may be defined, namely the reverse threshold boundary, Erev-threshold, at a fourth threshold value 53. The fourth threshold value 53 may be between the first and second threshold values 50, 51. The fourth threshold value 53 may represent the reverse threshold boundary between the risk area within the inner safety boundary 46 and the 3D space beyond the outer safety boundary 45 where it is safe to operate. The operation of the control system 40 and method of the present disclosure are now described with reference to Figures 3 and 4. The control system 40 operates the work machine 10 in a normal mode 95 when the work machine 40 is not near the power line 42 and thus has not reached the outer safety boundary 45 and / or the first threshold value 50 has not yet been met. In particular, the control processor 49 is configured to determine that a normal electric field value received from the at least one electric field detection sensor 41 has a lower magnitude than the first threshold value 50 and initialise control of the work machine 10 in accordance with the normal control mode. In the normal control mode, control of the work machine 10 may be unrelated to the proximity of power lines 42. Once the work machine 10 is moved, by the operator and / or control system 40, so that a first electric field value received from the at least one electric field detection sensor 41 has a greater magnitude than the first threshold value 50 and the outer safety boundary 45 is reached, the control system 40 implements a first control mode 60. In the first control mode 60, the operator is informed that the work machine 10 has moved so as to reach the outer boundary 45, and thus that a power line 42 is close, by the control processor 49 issuing a first alert 62 to the operator. The first alert 62 may be provided via the user interface 6 or display of the control system 40 and / or may comprise an audiovisual output located in the cab 8. For example, the first alert 62 may comprise an orange light or warning. The control processor 49 also stops 63 the movement of the work machine 10 upon entering the first control mode 60. Movement may only be enabled by the control system 40 upon receipt of a first override command 64 from an operator for indicating their awareness of the power line. The first override command 64 may be provided to the user interface 6. Once the first control mode 60 has been initiated, the control processor 49 may initialise recording tracking data 61 indicative of the movement of the work machine 10. The tracking data 61 may be stored on the memory of the control system 40 and / or transferred to a remote computer system for storage thereon. The tracking data 61 may be utilised by the control processor 49 to assist with movement of the work machine 10 safely away from the power line 42, as discussed further below. Once the work machine 10 is moved by the operator such that a second electric field value received from the at least one electric field detection sensor 41 has a greater magnitude than the second threshold value 51 and the inner safety boundary 46 is reached, the control system 40 may implement a second control mode 70. In the second control mode 70, movement of the work machine 10 may be more restricted and / or the performance is derated 80 than in the first control mode 60, unless an second override command is provided, as discussed further below. In the second control mode 70, the control processor 49 is configured to issue a second alert 71 to the operator and stop 72 movement of the work machine 10. The second alert 71 may be provided via the user interface 6 or display of the control system 40 and / or may comprise an audiovisual output located in the cab 8. The second alert 71 may be configured to indicate a greater danger or higher warning level than the first alert 62. For example, the second alert 71 may comprise a red light or warning. Movement may only be enabled by the control system 40 upon receipt of an second override command 73 from an operator for indicating their awareness of the power line 42. The second override command 73 may be provided to the user interface 6. In the second control mode 70, the control processor 49 may also cause external alerts 74 to generate. For example, external alerts 74 may be generated on the outside of the work machine 10, such as through flashing lights, warning others on the worksite that the work machine 10 is moving closer to the power line 42. Furthermore, the control processor 49 may initialise the sending of signals to the external computing system for generating an alert 75 thereon. As a result, a site manager working at the external computing system can be made aware that the work machine 10 is being operated closer to power lines 42. In the second control mode 70, the control system 40 may derate the performance 80 by implementing a lower maximum velocity and / or acceleration of movement of the work machine than any maximum velocity and / or acceleration of movement in the first control mode. In particular, the control system 40 may implement a maximum velocity and / or acceleration of the swing system 31 (i.e. velocity or acceleration of rotation of the main body 12 about the undercarriage 30) that is lower in the second control mode 70 than any maximum velocity and / or acceleration of the swing system 31 in the first control mode 60. The control system 40 may implement a maximum velocity and / or acceleration of the arm arrangement 14 and / or tool 15 (i.e. operation of the hydraulic system 5 is restricted accordingly) that is lower in the second control mode 70 than any maximum velocity and / or acceleration of the arm arrangement 14 and / or tool 15 in the first control mode. In the second control mode 70, the control system 40 may also apply different maximum velocities and / or accelerations depending upon the direction of movement. For example, when in the second control mode 70, the maximum allowed velocity and / or acceleration towards the power line may be less than the maximum allowed velocity and / or acceleration away from the power line. In the second control mode 70, the control system 40 may also restrain the direction of movement of the work machine 10. Such directional restraint may be for ensuring that the operator moves the work machine 10 away from the power line 42. Movement of the work machine 10 may be restrained by the control system 40 to a safe direction of travel, from the inner safety boundary 46 to the outer safety boundary 45 away from the power line 42. For example, the control system 40 may define a movement envelope within which the operator must move the work machine 10 away from the power line 42. The control system 40 may also prevent further movement of the work machine 10 in the direction of travel of the work machine 10 when entering the inner safety boundary 46. In the second control mode 70, the control system 40 may also indicate a safe direction of travel 81 away from the power line 42. The safe direction of travel may be shown on the user interface 6 and / or display. The safe direction of travel 81 may be based on the historical motion of the work machine 10. This safe direction 81 may be based on the reverse of preceding movements stored in the tracking data 61. Simultaneously, the movement envelope may be shown on the user interface 6 and / or display of the control system whilst also restraining movement to the movement envelope. This provides significant assistance to the operator in moving away from the power line 42. In the second control mode 70, the control system 40 allows movement of the work machine 10 upon receipt of a manual override command 83 without one or more of the aforementioned restrictions. For example, movement towards the power line 42 may be possible, but in accordance with the derated performance so that the operator cannot operate the work machine 10 too quickly, increasing the risk of contact with the power line 42. Once the work machine 10 is moved, by the operator and / or control system 40, such that a third electric field value received from the at least one electric field detection sensor 41 has a greater magnitude than the third threshold value 52 and the override safety boundary 47 has been reached, the control system 40 may implement a third control mode 90. The override safety boundary 47 may be indicative of the closest distance the work machine 10 can be to the power line 42. In the third control mode 90, movement of the work machine 10 is stopped. However, it cannot be restarted as easily as if a stop occurs upon entering the alert and / or second control modes 60, 70. Movement of the work machine 10 may be initiated again once the machine control system 40 receives a third override command 91. The third override command 91 is different to, and may require a higher level of security to access on the user interface 6 than, the second override command 73 and first override command 64. The third override command 91 may only be accessed through at least one level of security, such as a pin code or password. In the third control mode 90, the movement of the work machine 10 may be restricted in a similar manner to and / or to a greater extent than in the second control mode 70 once the third override command 91 has been received. In the third control mode 90, the control system 40 may derate the performance by implementing a lower maximum velocity and / or acceleration of movement of the work machine than any maximum velocity and / or acceleration of movement in the second control mode 70. The control system 40 may also apply different maximum velocities and / or accelerations depending upon the direction of movement in a similar manner to in the second control mode 70. In the third control mode 90, the control system 40 may also restrain the direction of movement of the work machine 10. Such directional restraint may be for ensuring that the operator moves the work machine 10 away from the power line 42. Movement of the work machine 10 may be restrained by the control system 40 to a safe direction of travel, from the override safety boundary 47, to the inner safety boundary 46 and outer safety boundary 45 away from the power line 42. For example, the control system 40 may define the movement envelope within which the operator must move the work machine 10 away from the power line 42. In a similar manner to the when in the second control mode 70, in the third control mode 90 the control system 40 may also indicate a safe direction of away from the power line 42. The control system may stop recording 95 the movement of the work machine once the control system determines that the work machine has reached the reverse threshold boundary, between the inner and outer boundaries 46, 45. The first, second and third threshold values 50, 51, 52 may be fixed values or may be dynamic, variable values. In particular, the magnitude of the first, second and third threshold values 50, 51,52 may be variable based upon the velocity of movement of the machine 10. If the velocity of the machine 10, particularly of the arm arrangement 14 and / or tool 15 thereof, is relatively high, the magnitude of the first, second and third threshold values 50, 51, 52 may be lowered accordingly. As a result, the first, second and third threshold values 50, 51,52 may be calibrated to account for variable stopping times of the machine 10 based upon its velocity. In particular, each of the first, second and third threshold values 50, 51, 52 may be determined based upon the equation Emax.v= constant, in which Emaxis a predetermined maximum allowable value of each of the first, second and third threshold values 50, 51, 52 and vis the velocity of the machine 10, particularly of the arm arrangement 14 and / or tool 15. Emax and the constant may be calibrated based upon the expected reaction time before beginning deceleration and the expected stopping distance. INDUSTRIAL APPLICABILITY As the work machine 10 is operated at a safe distance from an over-head power line 42, the control processor 49 operates the control system 40 in the normal mode 95. However, once the first electric field value exceeding the first threshold value 50 is received, indicating that the work machine 10 has reached the outer safety boundary 45 (such as by the arm arrangement 14 and / or tool 15 being operated closer to the over-head power line 42), the control processor 49 implements the first control mode 60. Movement of the work machine 10 is stopped at step 63, a first alert 62 is issued to the operator and recording of movement of the work machine 10 at step 61 may begin. The operator then provides a first override command 64 at the operator input 6 so that they can begin moving the work machine 10 again. Once the second electric field value exceeding the second threshold value 50 is received, indicating that the work machine 10 has reached the inner safety boundary 46 (such as by the arm arrangement 14 and / or tool 15 being operated even closer to the over-head power line 42), the control processor 49 implements the second control mode 70. Movement of the work machine 10 is stopped at step 72, a second alert 71 is issued to the operator and external alarms 74 may be issued, such as to an external administrator, at steps 74 and 75. The operator then provides a second override command 73 at the operator input 6 so that they can begin moving the work machine 10 again. However, in the second control mode 70 the performance of the work machine 10 may be derated at step 80. Such derating of performance can be overridden by a manual derate override command 83. The operator may also be shown a preferred safe direction away from the over-head power line 42 at step 81. Whilst the operator can move the machine 10 if the electric field values are below the third threshold value 52, if the third threshold value 52 is reached by the third electric field value the third control mode 90 is implemented and a “hard” stop applies. An administrator or third override command 91 may be required to restart movement and the ability to enter the third override command 91 may be restricted. For example, a security step must be overcome and / or the third override command 91 cannot be applied at the operator input 6 and may only be applied via the external computing system. As the operator continues to move the work machine 10 away from the over-head power line 42, the electric field values reduce below the third, second and first threshold values 52, 51, 50. Once the electric field values fall below the first threshold value 50, the normal operating 5 mode 95 is implemented and normal operation of the work machine 10 can resume.

Claims

1. A control system for operating a work machine around an over-head power line, the control system comprising:at least one electric field detection sensor;an operator input; anda control processor in communication with the at least one electric field detection sensor and operator input, the control processor being configured to:receive electric field signals indicative of electric field values from the at least one electric field detection sensor;determine that a first electric field value received from the at least one electric field detection sensor has a greater magnitude than a first threshold value and initialise control of the work machine in accordance with a first control mode in which a first alert is issued and movement of the work machine is stopped;receive, whilst in the first control mode, a first override command from the operator input and, in response, allow movement of the work machine;determine that a second electric field value received from the at least one electric field detection sensor has a greater magnitude than a second threshold value, the second threshold value having a greater magnitude than the first threshold value, and initialise control of the work machine in accordance with a second control mode in which a second alert is issued and movement of the work machine is stopped.

2. The control system of claim 1 wherein the control processor is configured to determine that a normal electric field value received from the at least one electric field detection sensor has a lower magnitude than the first threshold value and initialise control of the work machine in accordance with a normal control mode.

3. The control system of claim 2 wherein:a maximum velocity and / or acceleration of movement of the work machine is less in the first control mode than in the normal control mode; and / ora direction of movement of the work machine is more restrained in the first control mode than in the second control mode.

4. The control system of any preceding claim wherein in the second control mode the movement of the work machine is only restarted upon receipt of a second override command from an operator for indicating their awareness of the power line.

5. The control system of claim 4 wherein:a maximum velocity and / or acceleration of movement of the work machine is less in the second control mode than in the first control mode; and / ora direction of movement of the work machine is more restrained in the second control mode than in the first control mode.

6. The control system of claim 5 wherein, in the second control mode, the control system restricts movement of the work machine by:preventing further movement of the work machine in the direction of travel of the work machine when the second control mode was initialised;indicating a safe direction of travel away from the power line, on a display for the operator to view; and / orrestraining movement of the work machine to a safe direction of travel away from the power line.

7. The control system of any preceding claim wherein, in the second control mode, the control system allows movement of the work machine towards the power line upon receipt of a second override command.

8. The control system of any preceding claim wherein the control system is further configured to, by the control processor:determine that a third electric field value received from the at least one electric field detection sensor has a greater magnitude than a third threshold value, the third threshold value having a greater magnitude than the second threshold value, and initialise control of the work machine in accordance with a third control mode in which a third alert is issued and movement of the work machine is stopped until a third override command is received.

9. The control system of any preceding claim wherein once the control processor has determined that the first electric field value received has a greater magnitude than the first threshold value, the control processor initiates recording the movement of the work machine.

10. The control system of any preceding claim wherein the magnitude of the first, second and third threshold values is variable based upon the velocity of movement of the work machine.

11. The control system of any preceding claim comprising a machine electronic control module for controlling the work machine, the machine electronic control module comprising the control processor.

12. A work machine comprising the control system of any preceding claim.

13. A method of controlling a work machine around a power line, the method comprising, by a control processor:receiving electric field signals indicative of electric field values from at least one electric field detection sensor;determining that a first electric field value received from the at least one electric field detection sensor has a greater magnitude than a first threshold value and initialising control of the work machine in accordance with a first control mode in which a first alert is issued and movement of the work machine is stopped;receiving, whilst in the first control mode, a first override command from the operator input and, in response, allowing movement of the work machine;determining that a second electric field value received from the at least one electric field detection sensor has a greater magnitude than a second threshold value, the second threshold value having a greater magnitude than the first threshold value, and initialise control of the work machine in accordance with a second control mode in which a second alert is issued and movement of the work machine is stopped.

14. A non-transitory computer-readable storage medium including program code which when executed by at least one processor causes operations comprising the method of claim 13.

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