A hybrid floor saw comprising an electric power take-off with a combined charging system, ccs, interface

Description

The present disclosure relates to floor saws designed to saw kerfs in hard surfaces such as concrete and asphalt surfaces. At least some of the floor saws described herein are powered by hybrid drivelines comprising a combination of an internal combustion engine and an electric machine.BACKGROUNDFloor saws, also known as road saws or slab saws, are specialized, powerful sawing machines designed for making kerfs, i.e., cuts, in hard surfaces such as concrete, asphalt, and other materials typically encountered in construction and road repair work.Floor saws come in various forms and sizes, each suited to a different scale of operation. Walk-behind floor saws are manually operated machines that an operator walks next to in order to control it and guide it during the sawing operation. Some larger floor saws are self-propelled, meaning that they comprise some form of drive unit which moves the saw over the surface. Many floor saws comprise steerable wheels for maneuvering the saw on the surface. So-called early-entry saws, or soff-cut saws, are floor saws that are specifically designed for cutting into semi-matured concrete surfaces.The cutting blade on a floor saw is often diamond-tipped, allowing it to cut through hard materials such as concrete, asphalt and other hard surface materials.EP3094461A1 describes a combustion engine powered floor saw equipped with an advanced steering system.It is an objective of the present disclosure to provide improved construction equipment such as floor saws, demolition robots, and power trowels. This objective is at least in part obtained by a floor saw according to claim 1 .According to an example, the floor saw comprises a chassis supported on a surface by at least two wheels, a spindle for supporting a saw blade on the chassis, a control unit, and a hybrid driveline arranged to power the spindle. The hybrid driveline comprises an internal combustion engine (ICE) and an electric machine (EM). The control unit is arranged to control a transfer of power between the ICE, the EM, and the spindle, in dependence of an operating configuration or operating condition of the floor saw. This hybrid driveline is versatile in that power can be transferred between the different components to improve functionality and performance of the floor saw, as will be elaborated on below. The efficiency of the floor saw in terms of fuel consumption and production rate can be improved by the control of power between the components of the driveline and the spindle. The EM can, for instance, be interleaved in-between the ICE and the spindle in a serial configuration. Alternatively, the ICE and the EM can be connected in parallel configuration to the spindle.The ICE in the drivelines discussed herein can be arranged to provide an output power of at least 10kW and preferably at least 25kW, while the EM may be arranged to provide an output power of at least 5kW and preferably at least 20kW. Thus, the drivelines discussed herein are powerful enough to drive a large saw blade, e.g., on the order of 1000mm in diameter.According to a preferred embodiment, the hybrid driveline comprises a first clutch arranged to disconnect the ICE from the hybrid driveline. By disconnecting the ICE from the driveline, a fully electric driveline is obtained, which is not hampered in any way by the ICE. This feature improves the versatility of the driveline and allows efficient operation in fully electric mode of operation.The hybrid driveline may also comprise a second clutch arranged to disconnect the spindle from the driveline. By disconnecting the spindle from the driveline, it is possible to use the driveline as a gen-set to produce electrical energy at a work site. This electrical energy can be stored in the ESS of the floor saw or fed out to other devices via an electrical power take-off (PTO), which is an advantage.Any of the first and second clutches may comprise a gearbox with a neutral gear arranged to disconnect at least one input axle from an output axle of the gearbox. A gearbox allows optimization of gear ratio in the driveline, which is an advantage. For instance, different saw blade sizes often require different spindle drive torques. By adjusting the gear ratios of the driveline, a more efficient operation can be obtained.Any of the first and second clutches may also comprise an electromagnetic clutch mechanism which allows the control unit to automatically disconnect and connect the different components of the driveline in an efficient and reliable manner. The electromagnetic clutch mechanism has a fast response to electric control signals and can therefore be disconnected and connected rapidly as needed.According to some aspects, the control unit is arranged to operate the first clutch to disconnect the ICE from the driveline in an electric mode of operation of the floor saw. The electric mode of operation may, e.g., be selected by an operator by manipulating a control interface of the floor saw. Some work tasks may require fully electric operation, e.g., if the floor saw is being used indoors. The operator can configure the floor saw in fully electric mode of operation in a convenient manner, which is an advantage.The control unit may also be arranged to control an axle speed of the driveline by the EM to reduce a speed difference between a speed of an output axle of the ICE and the axle speed of the driveline, prior to engaging the first clutch. This reduces the need for speed synchronization between the input and output axles of the first clutch, which is particularly important if the first clutch comprises a gearbox, since this gearbox then has a reduced need for synchronization between input and outputs, allowing the gearbox design to be simplified and less costly, which is an advantage.The control unit can also be arranged to operate the second clutch to disconnect the spindle from the driveline in a generator mode of operation of the floor saw. By operating the second clutch in this manner, e.g., by manipulation of a control interface of the floor saw, an operator obtains a genset function, which is an advantage. This means that the floor saw can be used as generator at a work site when the floor saw is not actively used for sawing.According to some aspects, the control unit is arranged to execute an ICE start routine comprising cranking the ICE by the EM with the first clutch engaged. This feature avoids the need for a separate start-motor to crank the ICE, which reduces overall system complexity and cost of the floor saw.The control unit can also be arranged to execute a low-rev start boost routine comprising controlling the EM to provide a drive torque corresponding to a difference between a desired drive torque of the spindle and a current torque output from the ICE. In other words, the EM can bear the grunt of the load on the spindle if the ICE is not yet ready to bear it. It is for instance possible that the ICE has not yet reached sufficient operating temperature, or axle speed of rotation, or has not yet reached an operating point with sufficient torque to drive the spindle. This way an operator can start the floor saw from a cold state and more or less immediately begin sawing, which is an advantage. There is no longer a need for warming up the ICE prior to work task start, which saves time.The floor saw may comprise an electrical heating system arranged to control a temperature of the ICE and the control unit can be arranged to control the temperature of the ICE to reach a desired ICE temperature in preparation for starting the ICE. This way the ICE does not have to be run at idle to warm up, which is an advantage.According to some aspects, the control unit is arranged to obtain data indicative of a desired spindle speed of rotation, and to modulate an output axle torque of the EM to reduce a difference between a current spindle speed of rotation and the desired spindle speed of rotation. This way a more consistent speed of rotation of the saw blade is obtained, which is an advantage since it improves overall performance of the floor saw and also provides a better user experience.The control unit can furthermore be arranged to reduce a drive torque applied at a drive wheel or a driven axle of the floor saw in case the desired spindle speed of rotation cannot be maintained at maximum output axle torque of the EM. In other words, the floor saw can be configured to back off in sawing speed over the surface if the driveline cannot support the load exerted on the spindle by the saw blade. This way an optimized sawing speed can be obtained in an automated manner.The floor saw may also comprise a temperature sensor arranged to obtain temperature data indicative of a temperature of the spindle, the saw blade, and / or one or more driveline components. The control unit can in this case be arranged to reduce a drive torque applied at a drive wheel of the floor saw in case the temperature data fails to satisfy an acceptance criterion, such as a threshold or a more advanced statistical test. This way the risk of overheating parts of the floor saw is reduced, which is an advantage.According to some aspects, the control unit is arranged to obtain data indicative of an efficiency of the ICE as function of ICE output axle speed and ICE output axle torque, and to modulate an output axle torque of the EM to reduce a difference between a current operating efficiency of the ICE and a desired operating efficiency of the ICE. In other words, the EM can be used to move the operating point of the ICE closer to a preferred operating point, such as an optimal operating point. By optimizing the operating point of the ICE in this manner several advantages can be obtained, such as reduced fuel consumption, lower emissions, reduced ICE wear, and so on.The control unit can also be arranged to obtain data indicative of an efficiency of the ICE as function of ICE output axle speed and ICE output axle torque, and to obtain data indicative of an efficiency of the EM as function of EM output axle speed and EM output axle torque. The control unit can then be configured to determine a joint efficiency metric indicative of a total efficiency of the driveline, and to control the ICE and the EM to reduce a difference between a current total efficiency of the driveline and a desired total efficiency of the driveline. Thus, the total efficiency of the driveline can be improved, which is an advantage. It is noted that different aspects can be factored into the total efficiency, such as fuel economy, power output, component wear, emission, and so on.The floor saw may also comprise a wheel speed sensor arranged to sense a longitudinal speed of the floor saw over the surface, i.e., how fast the floor saw travels over the surface in the forward direction. The control unit is arranged to control a drive torque applied at a drive wheel or a driven axle of the floor saw in dependence of a speed difference between the longitudinal speed of the floor saw over the surface and the rotation speed of the drive wheel. This way the propulsion force can be improved or even optimized, as will be explained in more detail below.According to a preferred embodiment, the floor saw comprises an electrical energy storage (ESS) that is arranged to power the EM. The ESS has a height measured in a direction normal to the surface that is smaller than a length and a width of the ESS measured parallel to the surface in use. This flat form factor ESS is arranged between the surface and the ICE of the floor saw. By mounting the ESS low on the chassis in this manner a more stable floor saw is obtained. The flat form factor also allows the ESS to be relatively large without hampering the overall form factor of the floor saw, which is an advantage. A voltage of the ESS is preferably below 112V, and preferably at or below 100V or even below 96V. An electrical storage capacity of the ESS is at least 5kWh, and preferably at least 20kWh.According to some aspects, the control unit is configured to obtain a current state of change (SoC) of the ESS, and a depletion rate of the ESS. The control unit can then be configured to determine a time remaining until depletion based on the current SoC and the depletion rate. This allows an operator to understand how much longer the ESS will support operations and can adjust operations by the floor saw accordingly. The control unit can for instance be configured to control a transfer of power between the ICE, the EM, and the spindle, to reduce a difference between the time remaining until depletion and a desired time remaining until depletion.Some examples of the floor saws discussed herein comprise an electrical power take-off (PTO) and an optional switch configured to selectively connect the PTO to the ESS. The control unit is then arranged to control the switch in response to a user input command. This allows an operator or user to obtain electrical energy from the floor saw, e.g., if the floor saw is operating in generator mode to produce electrical energy. Given the relatively powerful ICE and EM components of the driveline, the PTO may deliver an output power of at least 5kW and preferably at least 15kW. Thus, the PTO can comprise a combined charging system (CCS) interface to charge vehicles on the work site and other heavy-duty equipment requiring high power.The floor saw optionally comprises an inverter arranged inbetween the ESS and the PTO such that the PTO may output an alternating current (AC) from the inverter.According to some aspects, the floor saw comprises at least one support wheel arranged to engage the surface inbetween a drive wheel axle of the floor saw and an axis of rotation of the spindle. A normal load sensor is arranged in connection to the support wheel to sense a load exerted by the floor saw on the support wheel. The control unit can then be arranged to trigger an automated action in case an output signal value of the normal load sensor deviates from a desired output signal value range. The normal load sensor can, for instance, detect a climbing condition of the floor saw using the normal load sensor, i.e., when the saw blade starts to climb out of the kerf due to too high drive force on the driven wheels. The control unit can for instance be configured to detect a climbing condition of the floor saw in case the output signal value of the normal load sensor fails to satisfy an acceptance criterion, such as a threshold. The control unit can be configured to reduce a drive torque applied to the drive wheels of the floor saw in case the output signal value of the normal load sensor deviates from the desired output signal value range and / or fails to satisfy the acceptance criterion, and also adapt a torque applied to the spindle in case the output signal value of the normal load sensor deviates from the desired output signal value range.According to preferred aspects, the control unit is arranged to obtain data related to a type and / or size of a saw blade mounted to the spindle, and to automatically configure an operating parameter of the floor saw based on the type and / or size of the saw blade. This greatly simplifies use of the floor saw since the need for calibration of operating parameters prior to onset of a work task is greatly reduced. The operating parameter of the floor saw may, e.g., comprise any of a configuration of a steering function of the floor saw, a desired drive torque to be applied at drive wheels of the floor saw, and / or a drive speed of the floor saw over the surface. The operating parameter of the floor saw may also comprise a desired drive torque and / or drive speed to be applied at the spindle. The floor saw configuration parameters may also comprise any of a desired steering angle, a steered axle angle, a desired spindle rotation speed, a desired total drive torque to be applied at the spindle, a desired gear ratio of the driveline, and a desired direction of rotation of the spindle.The control unit can be arranged to retrieve floor saw configuration parameters from a storage medium of the floor saw, in dependence of a current saw blade type and / or size mounted on the spindle or about to be mounted on the spindle. The floor saw configuration parameters comprises at least a configuration of a steering function of the floor saw.The current saw blade type and / or size may be selectable or configurable via a control interface of the floor saw. However, the control unit may also be arranged to detect the current saw blade type and / or size based on an identifier on the saw blade.According to some aspects, the control unit is arranged to store a set of floor saw configuration parameters by the storage medium and retrieve the stored set of floor saw configuration parameters in response to an operator command.This allows an operator to store a floor saw setting after he or she has calibrated its operation, allowing the setting to be retrieved at a later point in time.According to some aspects, the floor saw comprises a portable remote-control device arranged to communicate with the control unit via a wireless or a wired communication link. The floor saw also comprises a supporting bracket for releasably holding the remote-control device in fixed position on the floor saw. This way an operator can choose if he or she wants to walk around the floor saw in use to control it, while viewing progress from different angles, or if he or she want to control the floor saw from a fixed position, which is an advantage. The portable remote-control device preferably comprises an internal battery pack arranged to be charged by electrical power from the floor saw when received in the supporting bracket. The supporting bracket preferably also comprises a wired communications interface configured to allow the remote control device to communicate with the control unit via wired communication link when received in the supporting bracket.According to some aspects, the floor saw comprises a kerf position sensor system that is arranged to detect a position of an existing kerf and / or a marking line in relation to the saw blade. The control unit can then be arranged to control floor saw propulsion and steering to traverse along the existing kerf, which is an advantage. The kerf position sensor may be based on a vision sensor such as a camera or an infra-red detection. The kerf position sensor may also comprise a mechanical sensor which is arranged to follow the kerf as the floor saw traverses along the path of the kerf. According to a preferred example, the control unit is configured to control propulsion and steering of the floor saw to forward and reverse along the existing kerf or marking line repeatedly, while lowering the saw blade into the surface by an amount each repetition. This way deep kerfs can be made in an automated manner, which is an advantage.According to some aspects, the control unit is arranged to lock a rotation of the spindle by the EM via the driveline, in response to a spindle locking command.This simplifies mounting and removal of a saw blade to and from the spindle since the spindle will be locked. The EM is optionally also arranged to determine a torque applied at the output axle of the EM, and to transmit data indicative of the applied torque to the control unit. In this case the control unit can be configured to trigger generation of an indication of the applied torque to a user of the floor saw, thus simplifying mounting of a new saw blade with correct torque. The risk of too low tightening torque or too high tightening torque is significantly reduced in this way, which is an advantage.According to a preferred embodiment, the control unit is configured to obtain a desired saw blade fastening element torque, e.g., as function of saw blade type or as a predetermined value, and to determine a difference between the desired saw blade fastening element torque and a currently applied fastening element torque, and to indicate the difference to a user of the floor saw. This way an operator mounting a new saw blade receives guidance in how much torque to apply when fastening the saw blade arbor nut. The control unit is optionally arranged to indicate the difference between desired saw blade fastening element torque and currently applied fastening element torque by an audio signal and / or by a visual signal, thereby simplifying mounting of a new saw blade even more.According to some aspects, the control unit is arranged to brake the spindle by the EM via the driveline, in response to inactivation of the floor saw. This reduces the time the saw blade spins after deactivation of the floor saw, which reduces the risk that a person is injured by the spinning saw blade. The control unit can for instance be arranged to generate a negative torque on an output axle of the EM to brake the spindle via the driveline. In this case the EM can be arranged to output electrical energy to the ESS as a result of generating the negative torque, thereby recuperating some of the kinetic energy stored in the rotating saw blade.Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will now be described in more detail with reference to the appended drawings, whereFigures 1A-B illustrate an example floor saw;Figure 1C shows a remote-control device for controlling a floor saw;Figure 1D-E illustrate another example floor saw;Figure 2A schematically illustrates a serial hybrid driveline for a floor saw;Figure 2B illustrates an example floor saw hybrid driveline;Figure 3 shows an example parallel hybrid driveline for a floor saw;Figure 4 is a graph showing a modulated applied torque over time;Figure 5 is a graph showing efficiency of an example combustion engine;Figure 6 is a graph showing efficiency of an example electric machine;Figure 7 is a graph showing propulsion force as function of wheel slip;Figure 8 illustrates a floor saw comprising a support wheel;Figure 9 is a graph showing state of charge vs. time;Figures 10A-D are flow charts illustrating methods;Figure 11 shows an example control unit comprising processing circuitry; Figure 12 shows an example demolition robot; andFigure 13 shows an example power trowel.DETAILED DESCRIPTIONThe invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.It is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.Figures 1A-E illustrate various aspects of example floor saws 100. Each of the example floor saws comprises a chassis 110 arranged to be supported on a surface 101 by two or more wheels 150, 160. The front wheel 160 is in this case vertically adjustable as illustrated schematically by the dotted wheel 160 in Figure 1D. The front wheel 160 in Figure 1D is shown in a lowered position where it has been used to raise the saw blade 125 up from the surface 101.The front wheels 160 in the illustrated examples rotate about a front wheel axle of rotation 161. This axle of rotation may a continuous axle or an axle comprising two aligned separate axle parts on either side of the floor saw.The chassis 110 is a rigid structure, such as a metal frame, which supports the different components of the floor saw.The floor saws in the illustrated examples comprise two rear wheels 150 and two front wheels 160, although other support wheel configurations are also possible. A single support roller can for instance replace a wheel pair. The rear wheels 150 are driven wheels which are also steered, which means that the rear wheels 150 can be rotated about an axis normal to the surface 101 to provide a steering function of the floor saw 100. An example of this type of rear wheel steering is discussed in EP3094461 A1. Some floor saws are instead steered using the front wheels 160 or steered using both front and rear wheels. The example in Figure 1B shows a pair of rear wheels attached to a rear axis 152 which is pivotable about a pivot point 153. An actuator 154 controls the pivot angle of the rear axis to give a desired steering angle. A single wider roller element can be used as support instead of the front wheel pair. An operator can also use the handles 115 to guide the floor saw on the surface.A spindle 120 for supporting a saw blade 125 is mounted onto the chassis 110. The spindle 120 comprises an interface where a saw blade 125 can be attached. Many floor saws comprise spindles which are configured to carry a saw blade on both sides of the machine 100, as illustrated in Figure 1B. This way a kerf can be made close to a wall or other obstacle, regardless of if the obstacle is on the left-hand or right-hand side of the machine in use. A blade guard 122 protects the saw blade 125.The saw blade on a floor saw may have a diameter of 500mm up to about 1200mm.An up-cut direction of rotation indicated as u-c in Figure 1A, is a rotation of the saw blade 125 in which the saw blade teeth or abrasive elements exit the kerf in an upwards direction. A down-cut direction of rotation indicated as d-c in Figure 1A is opposite to the up-cut direction of rotation. The teachings herein are applicable to both up-cut and down-cut operation. The direction of rotation of the saw blade can in some examples be configured by an operator via a user interface of the floor saw.An upwards direction (up) of the floor saw is generally directed up from the surface 101, or up from a support plane of the wheels 150, 160. The downwards direction is opposite to the upwards direction. The front of the floor saw is the part facing the intended direction of motion. The handles are normally arranged at the back of the floor saw 100. The floor saw has a height h measured along the upwards direction normal to the surface 101 in use. A length I of the floor saw 100 is measured parallel to the surface in a direction aligned with the saw blade plane. A width w of the floor saw 100 is measured perpendicular to the height h and the length I, as illustrated in Figure 1 A.The vertical position of the front wheels 160 in the example floor saw 100 relative to the chassis 110 is adjustable so as to pivot the floor saw about the rear wheel axle. The vertical height of the saw blade axis of rotation can be adjusted by lowering or raising the front wheels 160. The depth of the kerf made by the saw blade can be adjusted by adjustment of the front wheel vertical position in this manner. Figure 1D shows an example floor saw 100 in transport position, where the spindle 120 has been raised up over the surface 101 by adjustment of the front wheel vertical position.The floor saw 100 also comprises a control unit 130 that is arranged to control various functions of the floor saw 100. The control unit 130 may be formed as a single physical unit or comprise several spatially separated processing devices, input devices for receiving operator commands, and output devices for controlling various actuators and driveline components of the floor saw 100. An example control unit 130 will be discussed in more detail below in connection to Figure 11. The control unit 130 may also comprise communications circuitry for communicating wirelessly or via wire to one or more remote units, such as the portable remote control device 190 shown in Figure 1C.Several tens of kilowatts are normally required to operate the saw blade 125, especially if a deep kerf is to be made in a hard material surface. The example floor saws 100 in Figures 1A-B and in Figures 1D-E comprises a hybrid driveline 140 arranged to power the spindle 120 and possibly also one or more other components of the floor saw 100. The hybrid driveline 140 comprises an internal combustion engine (ICE) and an electric machine (EM) which cooperate to provide the necessary power to the spindle 120 for driving the saw blade 125.The floor saw 100 also comprises an electrical energy storage (ESS) 170 arranged to power the EM 230 and possibly also other electrical components on the floor saw 100. The ESS 170 normally comprises a battery pack with battery cells, but it is also possible that the ESS comprises capacitors or some other type of electrical energy storage. A fuel cell system can also be used to generate electrical power on-board the floor saw 100. A voltage rating of the ESS 170 is preferably below 112V, and more preferably at or below 100V or even below 96V. This relatively low voltage ESS is advantageous in the sense that it is safer and not associated with as strict regulations as higher voltage systems, e.g., 400-600V systems.The ESS capacity may be on the order of at least 5kWh, and preferably at least 20kWh, i.e., quite large. Some applicable ESS examples may even be as large as 27kWh or larger. This means that the ESS 170 is relatively heavy and will occupy a significant volume on the chassis 110 of the floor saw 100. It has been realized that it is advantageous to position the ESS 170 close to the surface 101, i.e., low on the floor saw 100, since this improves stability of the floor saw in use. A flat ESS geometry is preferred, in order to fit the ESS low on the floor saw, i.e., a geometry with a height h measured in a direction normal to the surface 101 that is smaller than a length I and a width w of the ESS 170 measured parallel to the surface 101 in use. The ESS 170 is preferably arranged between the surface 101 and the ICE 210 of the floor saw 100, as indicated in, e.g., Figures 1D-E.The ESS 170 can be bolted onto the chassis 110 in order to provide a stable support for the ESS. It may be preferred to add some form of suspension or resilient bushings or the like between the ESS 170 and the chassis 110, in order to isolate the ESS from the vibrations that propagate from the saw blade 125 to the chassis 110 in use.The ICE of the driveline may comprise one or more internal combustion engine units, possibly of different type. Possible combustion engine types comprise Diesel engines, gasoline engines, and various forms of gas engines, such as propane engines. Hydrogen combustion engines may be used with advantage in a floor saw of the kind discussed here, and also ammonia combustion engines. It is an advantage to complement these combustion engines with an EM, e.g., to reduce peak power requirements, and requirements on acceleration of the combustion engine.The EM of the driveline may also comprise one or more electric machine units, which may be of the same type or of different type. Both direct current (DC) motors and alternating current (AC) motors can be used in the type of drivelines discussed herein. A combination of induction motors and permanent magnet motors may be used with advantage in a floor saw of the kind discussed herein.The drive wheels 150 on the floor saw may be driven by separate Ems 155a, 155b as illustrated in Figure 1 B, or by the driveline 140 via some form of power take-off.The control unit 130 is arranged to control a transfer of power between the ICE 210, the EM 230, and the spindle 120, in dependence of an operating configuration or operating condition of the floor saw 100. This means that the control unit 130 is able to adjust the flow of power between the ICE, the EM, and the spindle based on how the system is configured and also in dependence of the scenario in which the floor saw is used. An operator may, for instance, set a desired saw blade speed to be maintained, which is then an operating configuration of the floor saw 100 which governs how power is transferred from the power sources to the spindle. An operator may also configure a desired ESS depletion rate, as will be discussed in more detail below in connection to Figure 9, set the floor saw 100 in a fully electric mode of operation, to give a few examples. The control unit can also control the transfer of power between the ICE 210, the EM 230, and the spindle 120 in dependence of an operating condition of the floor saw 100, such as how much resistance that is encountered by the saw blade in use.During normal operation, i.e., when the floor saw is used for sawing, power is transmitted from the ICE and from the EM to the spindle to drive the saw blade. Flowever, power may also be transmitted in reverse, e.g., if the EM is used to brake the saw blade 125, in which case the EM 230 may recuperate some of the kinetic energy held by a rotating saw blade. In this case the ICE is preferably disconnected from the driveline, i.e., the EM is used to brake the saw blade while disconnected from the ICE. This is an advantage since otherwise the EM has to brake the EM also, which may reduce the retardation of the saw blade speed. The transfer of power may, generally, be from the ICE to the EM to generate electrical power by the EM, from the EM to the ICE to crank the ICE or support the ICE operation, from the EM and / or ICE to the spindle to drive the spindle, and also from the spindle to the EM to recuperate kinetic energy stored in the saw blade.The drivelines disclosed herein are associated with several advantages, as will be discussed in more detail in the following. For instance, the EM can absorb quick changes in load applied to the saw blade, e.g., as the saw blade encounters different materials. This means that the ICE will experience a more constant load with less variation, allowing use of more specialized engine design that has been optimized for a given operating point in terms of output axle speed and engine torque. The EM can also provide many of the different functions found on a stand-alone ICE, such as its start motor function, allowing for cost reductions on the ICE system.The technical features, functions, and methods of the present disclosure are primarily illustrated by means of an example floor saw 100. It is, however, appreciated that many of the features are more generally applicable, e.g., in a demolition robot 1200 and in a power trowel 1300, as exemplified in Figure 12 and in Figure 13, respectively. In particular, the technical features related to the driveline 140 and the ESS 170 are also applicable in a demolition robot and in a power trowel. The demolition robot 1200 may be arranged to carry a saw blade on the distal end 1230 of the tool carrier arm. The features related to control of the saw blade spindle 120 are not applicable to the power trowel, which lacks this type of spindle 120.The example demolition robot 1200 in Figure 12 comprises a rotatable tower 1210 to which a tool carrier arm 1220 is attached. The arm 1220 is arranged to carry a tool at its distal end 1230, such as a saw blade. The distal end of the tool carrier arm 1220 then supports a form of spindle. The demolition robot 1200 is propelled over the surface by endless tracks 1240, and may be supported by lowerable support legs 1250, 1260. A connection to electrical mains 1270 may be present. The demolition robot 1200 comprises a hydraulic system 1280 which is powered at least in part by the driveline 140, which means that the driveline 140 is used to power a hydraulic pump of the hydraulic system 1280.The example power trowel 1300 in Figure 13 does not comprise a saw blade, hence the aspects related to the saw blade spindle 120 are not always applicable to the power trowel. The power trowel, however, may comprise the ESS 170, as well as the driveline 140. The power trowel 1300 comprises a chassis 110 supported on a surface 101 by rotatable trowel tools 1310, 1320. The power trowel 1300 can be controlled from an on-board control position 1330 or by remote control 190.The floor saw 100, the demolition robot 1200, and the power trowel 1300 may be collectively referred to as construction equipment.Figures 2A-B and Figure 3 illustrate different example architectures for hybrid drivelines 200, 300 that can be used in a floor saw 100. Both driveline types comprise an ICE 210 and an EM 230 that are connected to the spindle 120 in order to jointly provide power to drive the saw blade 125. The ICE 210 may be arranged to provide an output power of at least 10kW and preferably at least 25kW or even at least 35kW, while the EM 230 is preferably arranged to provide an output power of at least 5kW and preferably at least 20kW. Thus, the total output power of the hybrid driveline 140 may according to some examples be above 45kW, such as around 60kW.The example 200 schematically illustrated in Figure 2A is a serial configuration where the EM 230 is interleaved inbetween the ICE 210 and the spindle 120. In this example the torque generated by the ICE 210 is carried via a transmission past the EM 230 before reaching the spindle 120. An example realization of a hybrid driveline in serial configuration is shown in Figure 2B, where the different components of the driveline have been indicated.The example 300 schematically illustrated in Figure 3 is a parallel configuration of a hybrid driveline 140 where the ICE 210 and the EM 230 are connected in parallel to the spindle 120 via a transmission. In this case the torque generated by the ICE 210 and the EM 230 does not pass via the other power source before reaching the spindle 120.The floor saw 100 may also comprise a temperature sensor 290 arranged to obtain temperature data indicative of a temperature of the spindle 120, the saw blade 125, and / or one or more driveline components such as the ICE 210, the first clutch 220, the EM 230, and the second clutch 240. The control unit 130 can in this case be arranged to reduce the drive torque F applied at the drive wheels 150 of the floor saw 100 in case the temperature data fails to satisfy an acceptance criterion, such as being above a pre-determined threshold or some more advanced statistical acceptance test comprising, e.g., digital, or analog filtering or statistical analysis of the temperature data. Such methods are known in the art and will therefore not be discussed in more detail herein. By using data from the temperature sensor 290, the floor saw can optimize operation to increase production rate, i.e., to increase sawing speed, without risking overheating of the saw blade or other components of the floor saw 100. A temperature sensor can be mounted in or on the saw blade 125, as described in, e.g., Swedish national patent application No. 2051497-2. Temperature sensors can of course also be mounted in connection to the different driveline components using techniques known in the art.According to preferred aspects the hybrid driveline 140 comprises a first clutch 220 arranged to disconnect the ICE 210 from the hybrid driveline 140. This first clutch 220 provides the possibility to separate the ICE from the rest of the driveline transmission, essentially transforming the driveline 140 into a fully electric driveline without losses incurred from having the ICE 210 connected to the driveline. The control unit 130 can be arranged to operate the first clutch 220 to disconnect the ICE 210 from the driveline 140 in an electric mode of operation of the floor saw 100. In the parallel version of the driveline the first clutch comprises two inputs and one output. The first clutch may in this case be implemented as a differential, e.g., by using a planetary gear arrangement, in combination with some form of clutch mechanism that allows separation of any of the inputs from the output, such that the ICE or the EM can be disconnected from the spindle.The hybrid driveline 140 optionally also comprises a second clutch 240 arranged to disconnect the spindle 120 from the rest of the driveline 140. This second clutch 240 allows the driveline to be used, e.g., as a generator or genset to produce electrical energy without driving the saw blade 125, which is an advantage. The control unit 130 can be arranged to operate the second clutch 240 to disconnect the spindle 120 from the driveline 140 in a generator mode of operation of the floor saw 100.By implementing both the first clutch 220 and the second clutch 240 a versatile power system is obtained which can be used as a stand-alone electrical driveline and also as a genset to produce electrical energy. The control unit 130 can switch between the different modes of operation by operating the clutches 220, 240.Any of the first and second clutches 220, 240 may comprise a gearbox with a neutral gear arranged to disconnect at least one input axle from an output axle of the gearbox. The neutral gear then provides a clutch disengagement function, while the gears provide a clutch engagement function at different gear ratios and / or different directions of rotation. The first clutch 220 shown in the serial version 200 of the driveline 140 has a single input and a single output. The first clutch 220 shown in the parallel version of the driveline 300 comprises two inputs, one from the ICE 210 and one from the EM 230, and one output for transmitting torque towards the spindle 120.According to some aspects, the control unit 130 is arranged to control an axle speed of the driveline 140 by the EM 230 to reduce a speed difference between a speed of an output axle of the ICE 210 and the axle speed of the driveline 140, prior to engaging the first clutch 220. This reduces the need for speed synchronization between the input and output axles of the first clutch 220, which is particularly important if the first clutch 220 comprises a gearbox, since this gearbox then has a reduced need for synchronization between input and outputs. The ICE 210 can always be operated at a constant speed, and the control unit will use the EM 230 to control rotation speed of the other driveline components to match the constant speed of the ICE prior to engaging the first clutch. This way a smooth operation of the floor saw can be obtained, with very little jerk as the ICE 210 is connected to the driveline 140 by engagement of the first clutch 220. The first clutch may be implemented as a gearbox with a neutral gear. The mechanical design of this gearbox can be simplified since it does not need advanced synchronization mechanisms between input axle and output axle.Any of the first and second clutches 220, 240 optionally comprises an electromagnetic clutch mechanism. Electromagnetic clutches are devices that use electromagnetic force to engage and disengage the connection between a driving and a driven axle, allowing for controlled transmission of torque. An electromagnetic clutch may be controlled via control output signals from the control unit 130. A principle behind an electromagnetic clutch is the use of an electromagnet to create a magnetic field. When electrical current is applied to the electromagnet, it generates a magnetic force that pulls an armature or clutch plate towards a rotor or driving member. This contact enables the transfer of torque from the driving axle to the driven axle. When the electrical current is cut off, the magnetic field dissipates, and the armature disengages, stopping the torque transfer. Electromagnetic clutches offer several advantages, among those a rapid response to control input, as well as a smooth engagement and disengagement. Additionally, they can be operated without mechanical linkages, allowing for easy integration into automated and remotely controlled systems. An electromagnetic clutch can be combined with a gearbox in order to reverse the direction of rotation of the output axle or provide different selectable gear ratios between input and output axles of the clutches.The EM 230 can also be used to crank the ICE 210 by transmitting torque from the EM to the ICE via the first clutch 220, preferably with the second clutch disengaged. This way there is no need for a start motor to crank the ICE which reduces overall cost of the driveline 140. The control unit 130 can for instance be arranged to execute an ICE start routine comprising cranking the ICE 210 by the EM 230 with the first clutch 220 engaged.The electrical system of the hybrid driveline 140 can also be used to control the temperature of the ICE 210, primarily to increase temperature of the ICE up to a desired operating temperature in preparation for starting and using the ICE. In other words, some of the floor saws 100 discussed herein comprises an electrical heating system that is arranged to control a temperature of the ICE 210. The control unit 130 can be arranged to control the temperature of the ICE 210 to reach a desired ICE temperature, e.g., in preparation for starting the ICE 210.One of the main advantages of having an EM connected to the same transmission as the ICE is that the EM can provide extra torque to support the ICE when the ICE is not outputting peak power. The torque output from the EM can be changed rapidly, while the torque output from the ICE takes longer time to change.For instance, the control unit 130 can be arranged to execute a low-rev start boost routine that comprises controlling the EM 230 to provide a drive torque corresponding to a difference between a desired drive torque of the spindle 120 and a current torque output from the ICE 210. This way the ICE 210 can be started up from standstill and the saw blade 125 can be brought into engagement with the surface 101 before the ICE has reached its intended operating speed and target output power. The EM is then used to provide a boost torque to compensate for the lack of output power from the ICE during the transient start-up time period.The floor saw 100 may comprise a spindle speed sensor 131 arranged to obtain data indicative of a rotation speed of the spindle 120 and the saw blade 125. The spindle speed sensor 131 may comprise, e.g., a Hall effect device or the like arranged in connection to the spindle 120, in connection to the saw blade 125, or somewhere along the driveline to determine a rotation speed of the saw blade 125. Given the rotation speed at some point in the driveline, and information about a current state of any gearboxes in the driveline, the speed of rotation of the saw blade can be determined in a straight-forward manner. If the saw blade radius is also known, the speed of rotation of the saw blade can be converted into a kerf speed of the abrasive elements on the periphery of the saw blade 125 relative to the surface 101. Kerf speed vk is given byvk = Rωwhere R is the radius of the saw blade 125 and ω is the angular velocity of the spindle 120. It is often desired to maintain a constant abrasive element kerf speed vk.The control unit 130 can control the power sources of the driveline 140, i.e. , the ICE 210 and the EM 230, in order to maintain a target rotation speed of the saw blade ω. In case the current rotation speed of the saw blade 125 is below the target speed, giving a sub-optimal kerf speed vk, then the EM 230 can be used to quickly add more torque in order to increase the speed of rotation. The same can be done if, for some reason, the rotation speed ω of the saw blade 125 goes above the target rotation speed of the saw blade, in which case the EM 230 can be used to quickly brake the spindle rotation to slow down the saw blade 125. In other words, according to an example, the EM 230 of the driveline 140 is used to modulate torque of the driveline 140 to maintain a target spindle speed of rotation and thus also a target saw blade speed of rotation.Figure 10A shows a flow chart that illustrates a method related to control of spindle speed of rotation. This method will be discussed in more detail below.Figure 4 shows a graph 400 that illustrates a principle of operation of the hybrid driveline 140. The ICE 210 in this example outputs a torque 410 shown by a dash-dotted line which is almost constant over time. This torque output by the ICE may, e.g., be determined based on efficiency characteristics of the ICE to give a good fuel economy of the floor saw 100. To maintain saw blade kerf speed vk close to a desired kerf speed, the control unit 130 controls the EM 230 to modulate the total driveline torque. The torque output 420 from the EM 230 is shown by the solid line, and it is noted that this torque is both positive and negative over the time period, to illustrate that the EM can be used to both accelerate and to brake the saw blade in order to obtain a close to optimal kerf speed. The total torque output 430 of the driveline 140 is the sum of the two output torques (disregarding any gearbox ratio effects).These rapid changes in applied torque would be challenging to achieve using an ICE but are possible in an EM where torque can be changed much faster compared to in an ICE. The result is a saw blade speed of rotation speed ω which has a small variation, which is an advantage since this almost constant speed of rotation of the saw blade can be optimized for improved cutting efficiency. The fast torque modulation by the EM also means that the ICE sees an almost constant load, which allows the output torque of the EM to be kept close to a high efficiency operating point of the ICE. The control unit 130 can use the output signal f(ω) from the spindle speed sensor 131 of some other signal indicative of saw blade rotation speed to modulate the output torque of the EM 230.To summarize, the control unit 130 can according to an example be arranged to obtain data indicative of a desired spindle speed of rotation ω, and to modulate an output axle torque of the EM 230 to reduce a difference between a current spindle speed of rotation and the desired spindle speed of rotation. This way the spindle speed of rotation can be kept constant, or at least close to constant, which gives a consistent and smooth operation by the floor saw. The efficiency of the saw blade 125 is normally also improved if its abrasive elements are subject to a constant kerf speed with little variation. The kerf speed can be configured in dependence of a drive force F generated by the drive wheels. A desired drive force for a given kerf speed and saw blade type can be configured in a storage medium 1130 of the control unit 130, e.g., as a look-up table. Likewise, a desired kerf speed can be listed for a range of drive forces and saw blade types. Thus, a number of optimal configurations can be stored in the storage medium 1130, where they can be accessed by the control unit 130 and applied to the operations of the floor saw 100 in use.The control unit 130 can also be arranged to reduce a drive torque F applied at a drive wheel 150 of the floor saw 100 in case the desired spindle speed of rotation ω cannot be maintained at maximum output axle torque of the EM 230. Thus, if the hybrid driveline 140 is not able to support operation at the desired spindle speed of rotation, then the load on the saw blade is automatically reduced by reducing the drive force F. This way the floor sawing operation can be optimized to provide consistent operation and a high rate of production in terms of sawed distance per unit of time.All engines are associated with some form of efficiency metric η which indicates how efficient the motor operation is for different operating points, e.g., in terms of output axle speed and applied axle torque. The efficiency of an ICE such as a Diesel engine or a gasoline engine is often defined as the ratio of the useful work done to the heat generated. The efficiency of an ICE is normally well below 50%. Engines using the Diesel cycle are usually more efficient than gasoline engines. Modern Diesel engines have a maximum thermal efficiency of more than 50%, but most gasoline engines operate at efficiencies between 20% to 40%. Many engines would be capable of running at higher thermal efficiency but at the cost of higher wear and emissions.Motor efficiency in an electric machine is normally defined as the ratio of the mechanical power output of the motor to the electrical power input. It quantifies how effectively the electric machine converts electrical energy into mechanical energy and vice versa. A higher efficiency indicates that a greater proportion of the electrical power is being converted into useful mechanical work, with less energy wasted as heat or other forms of energy loss. Electrical motors can have efficiencies on the order of 90% or more. Note, however, that a direct comparison between combustion efficiency numbers and efficiency of electrical drive systems cannot be made as the two are different in nature.Figure 5 shows an example efficiency map 500 for a general ICE. An efficiency map indicates how the efficiency changes as function of operating point in terms of output axle torque and output axle rotation speed. There is normally a maximum output torque 410 that can be provided as function of speed, and there is almost always an operating point 420 which is the most efficient. It is normally desired to operate an ICE as close as possible to the optimum operating point. In other words, the optimal efficiency operating point 420 is normally also the desired operating point. However, other operating points may also be selected as desired operating points, if other factors are taken into account, such as total driveline efficiency, floor saw component wear, saw blade wear, service intervals, and so on.Figure 6 shows an example efficiency map 600 for a general electric machine. There is a peak output torque 610 which can be output from the EM as function of output axle speed, and also an optimum operating point 620. As for the ICE, the optimal efficiency operating point 610 is normally the desired operating point, but the desired operating point can also be some other point, if other aspects are also factored in, such as total driveline efficiency, floor saw component wear, saw blade wear, service intervals, and so on.Efficiency maps such as the efficiency maps 500, 600 can be stored in a memory of the control unit 130 and used to control the hybrid driveline in order to improve the overall efficiency of the driveline. An efficiency map can be stored as a look-up table (LUT) or in some other format that can be accessed and read by the control unit 130. The efficiency data can be preconfigured, i.e., stored in a memory device accessible by the control unit 130.Suppose now that the ICE 210 is operating at an output axle speed close to the optimum output axle speed 430, because the control unit 130 controls the ICE to operate close to this axle speed, and that the output torque of the ICE is determined at least in part based on the torque contribution from the EM 230 to obtain a desired saw blade kerf speed vk. It is then realized that the operating point of the ICE can be moved up and down in torque by modulating to output torque of the EM 230. Thus, the EM output torque can be configured so as to move the operating point of the ICE close to the ideal operating point 420. This way the fuel consumption of the ICE can be reduced, and also its emissions, and / or wear on the combustion engine, which is an advantage. The control unit 130 can for instance be arranged to obtain data indicative of an efficiency 500 of the ICE 210 as function of ICE output axle speed and ICE output axle torque, and to modulate an output axle torque of the EM 230 to reduce a difference between a current operating efficiency of the ICE 210 and a desired operating efficiency of the ICE 210. This way the EM can be used to set the operating point of the ICE close to a desired operating point in terms of applied output axle torque and applied output axle speed. The ICE will experience close to constant operating conditions in terms of load and can therefore be kept close to its optimal operating point 420 with little variation in both axle rotation speed and torque.It is also possible to formulate a joint efficiency metric rytot by weighting the efficiency metrics of the ICE and the EM. The joint efficiency metric rytot can for instance be given aswhere ryICE is an efficiency metric of the ICE and ηΕΜ is an efficiency metric of the EM, and where W-L and w2 are weight that determine which of the two contributions are considered the most important to the overall efficiency metric. To summarize, the control unit 130 can be arranged to obtain data indicative of an efficiency 500 of the ICE 210 as function of ICE output axle speed and ICE output axle torque, and to obtain data indicative of an efficiency 600 of the EM 230 as function of EM output axle speed and EM output axle torque. The control unit 130 can then be configured to determine a joint efficiency metric indicative of a total efficiency of the driveline 140, and to control the ICE 210 and the EM 230 to reduce a difference between a current total efficiency of the driveline 140 and a desired total efficiency of the driveline 140.Figure 10B shows a flow chart that illustrates a method related to control of driveline efficiency. This method will be discussed in more detail below.Longitudinal wheel slip λχ of a wheel rolling on a surface may be defined aswhere R is an effective wheel radius in meters, ωχ is the angular velocity of the wheel, and vx is the longitudinal speed of the wheel (in the coordinate system of the wheel). Thus, λχ is bounded between -1 and 1 and quantifies how much the wheel is slipping with respect to the road surface.In order for a wheel to produce a wheel force by engaging a ground surface 101, wheel slip must occur. Figure 7 is a graph 700 which schematically illustrates an example relationship between generated wheel force that pushes the floor saw 100 over the surface 101 and the wheel slip that is present at the drive wheels of the floor saw 100. For smaller slip values the relationship between slip and generated force is approximately linear, where the proportionality constant is often denoted as the slip stiffness of the wheel. The achievable wheel force decreases with decreasing surface friction μ, as exemplified in the graph 700.It is noted that the obtained wheel force increases with wheel slip up to a point where peak force is obtained. After this point any further increase in wheel speed of rotation ωχ relative to the surface will result in a decrease in obtained wheel force. The location of the peak force in terms of wheel slip normally does not change much with friction. Hence, a target wheel slip λρ configured for some nominal surface friction value is reasonably close to optimum also for other friction conditions. The control unit 130 can be arranged to control wheel speed of the drive wheels 150 as function of speed over ground vx of the floor saw in order to set a given wheel slip, such as a wheel slip close to λν in order to obtain a propulsion force which is close to the maximum obtainable propulsion force of the floor saw 100. The control unit 130 can also be arranged to limit wheel speed to wheel speeds below some wheel slip limit Xlim in order to avoid excessive wheel slips that can result in significant loss in propulsion force.Figure 8 schematically illustrates a floor saw 100 comprising at least one drive wheel 150 and at least one support wheel 160. The support wheel is an undriven wheel and therefore does not slip as much relative to the surface 101 as the drive wheel does when it is used to push the floor saw 100 over the surface 101. The floor saws discussed herein may comprise a wheel speed sensor (WS) 810 arranged in connection to the undriven wheel, to measure the longitudinal speed vx of the floor saw 100 over the surface 101. This ground speed sensor is advantageously arranged as a wheel speed sensor which senses the speed of an undriven wheel, but there are other ways to measure speed over ground known in the art, such as ground speed radars and also vision-based systems.The wheel rotation speed ωχ of the driven wheel or wheels can be determined from the control of the drive motor used to power the driven wheel or wheels, or by using another wheel speed sensor arranged to sense the speed of rotation of the driven wheel 150. The radius of the driven wheel is often known a-priori and can be input to the control unit 130 as a configuration parameter. The radius of the driven wheel can also be measured by moving the floor saw along a known distance and counting wheel rotations. Hence the wheel slip of the drive wheel or wheels can be determined by the control unit 130 in real time, and the control unit 130 can optimize the drive control to maintain a desired wheel force. The propulsion force of the driven wheels will be more constant if the control unit controls the wheel speed of the driven wheels to maintain a given wheel slip compared to if the driven wheels are controlled based on an applied drive torque.To summarize, at least some of the floor saws 100 discussed herein may, according to an example, comprise a wheel speed sensor 810 arranged in connection to an undriven support wheel 160 of the floor saw 100 to sense a speed of the floor saw 100 over the surface 101. The control unit 130 can then be arranged to control a drive torque F applied at a drive wheel 150 of the floor saw in dependence of a speed difference between the speed of the undriven support wheel 160 and the speed of the drive wheel 150, such as to maintain a target wheel slip λ.With reference to Figures 1A-B, Figures 1D-E, and Figure 8, the floor saw 100 preferably comprises at least one support wheel 160 arranged to engage the surface 101 inbetween a drive wheel axle 151 of the floor saw 100 and an axis of rotation 121 of the spindle 120. The drive wheel axle is in this example also a rear wheel axle 151 of the floor saw. This support wheel 160 can, as mentioned above, be used to adjust the cutting depth of the saw blade 125 and also to lift the saw blade 125 above the surface 101, e.g., to transport the floor saw 100 as in Figure 1D. A normal load sensor (LS) 820 can be arranged in connection to the support wheel 160 to sense a load exerted by the floor saw 100 on the support wheel 160. This way the control unit 130 can obtain information about the alignment of the chassis 110 relative to the surface 101. If the load suddenly decreases, it is likely that the saw blade 125 has started to climb out from the kerf and up onto the surface 101, which is undesired. This type of climbing normally only occurs during down-cut operation, and not during up-cut operation, unless the floor saw 100 is operated at negative longitudinal velocity, i.e., in reverse over the surface 101. The control unit 130 can be arranged to trigger an automated action in case an output signal value of the normal load sensor 820 deviates from a desired output signal value range.The control unit 130 can for instance be configured to detect a climbing condition of the floor saw, in case the output signal value of the normal load sensor 820 fails to satisfy an acceptance criterion, such as a load threshold or acceptable load range, or some more advanced acceptance criteria comprising a statistical test or filtering of the data from the load sensor.The control unit 130 is optionally configured to reduce a drive torque F applied to the drive wheels 150 of the floor saw 100 in case the output signal value of the normal load sensor 820 deviates from the desired output signal value range and / or fails to satisfy the acceptance criterion. By reducing the drive torque F, or, equivalently, the drive wheel slip λ as discussed above, the tendency of the saw blade to climb out of the kerf is reduced. The control unit 130 may also be configured to adapt a drive torque applied to the spindle 120 by the driveline 140 in case the output signal value of the normal load sensor 820 deviates from the desired output signal value range. An increase in drive torque (or drive speed) often reduces the tendency of the saw blade to climb out of the kerf during operation.According to preferred aspects, the control unit 130 continuously or at least periodically adjusts the operating parameters of the floor saw to increase production rate, i.e., the rate at which the kerf is being sawed in the surface. An increase in sawing speed is obtained by increasing the wheel force generated by the drive wheels 150, possibly in combination with an increase in drive torque applied by the driveline 140 at the spindle 120. The wheel force is increased until the load sensor 820 starts to indicate that the load reduces, which is indicative of a tendency of the saw blade to start climbing out of the kerf. When this happens the control unit 130 can back off in drive wheel force a bit, or, equivalently, reduce the wheel slip to a lower wheel slip value. This way the control unit 130 can maintain a close to optimum production rate, without overshooting such that the saw blade climbs out of the kerf.The control unit 130 can also be arranged to obtain data related to a type and / or size of a saw blade 125 mounted to the spindle 120, and to automatically configure an operating parameter of the floor saw 100 based on the type and / or size of the saw blade 125, such as a desired drive torque to be applied at drive wheels 150 of the floor saw, and / or a drive speed over the surface 101 to be maintained by the floor saw 100, and also an applied steering to obtain a kerf having a desired form, such as a straight kerf or a kerf with a desired curvature. The operating parameter of the floor saw 100 may also comprise a desired drive torque and / or drive speed to be applied at the spindle 120. It may, for instance, be desired to reduce the spindle speed in case a larger diameter saw blade is mounted compared to if a smaller diameter saw blade is mounted on the spindle, to maintain the same peripheral speed of the saw blade abrasive segments. Some saw blade types are also able to withstand larger forces compared to other saw blades.The data related to saw blade type and / or size can be input manually by an operator of the floor saw 100 or be downloaded to a memory of the control unit based on an identification of a saw blade mounted to the spindle 120. The control interface of the floor saw may present a selection of saw blade options to an operator, which may simplify the configuration of saw blade type and / or size. The identification can also be made, e.g., by radio frequency identification (RFID) or by some other means of identification in a known manner. Swedish national patent application No. 2051497-2 discusses use of RFID for identification of saw blades.The identification of saw blade type can also be performed by the control unit 130 in an automated manner. Different saw blade types, particularly those having different sizes and / or weights, can be identified by an acceleration test of the spindle. The control unit 130 can start the spindle from a standstill state and measure the power required to accelerate the saw blade to some given speed of rotation using the EM 230. The speed of rotation can be obtained from the spindle speed sensor 131 discussed above and the applied torque by the EM can be obtained, e.g., by measuring the power consumed by the EM, or directly from a motor controller of the EM. The required power for accelerating the saw blade can then be mapped against at least saw blade diameter using a look-up table or the like, configured in a memory accessible by the control unit 130. Swedish national patent application SE2250443-5 describes methods for identifying a saw blade type based on a monitored acceleration by the saw blade in response to an applied torque.State of charge (SoC) is a measure of how much electrical energy that remains in an electrical energy storage system. The SoC can be given as a percentage or as an absolute value, e.g., in kWh. A low SoC indicates that there is not much energy left in the ESS, while a high SoC indicates that there is a significant amount of energy left in the ESS, in relation to the capacity of the ESS. The control unit 130 can be configured to obtain a current state of charge (SoC) of the ESS 170, and also a depletion rate of the ESS 170, i.e., data indicative of how fast the energy held in the ESS decreases. The control unit 130 can then determine a time remaining until depletion based on the current SoC and the depletion rate.Figure 9 shows a graph 900 that schematically illustrates ESS depletion in terms of SoC over time. The actual SoC 910 over a usage time period Tw is monitored by the control unit 130. This energy depletion can be extrapolated in time, using a least-squares fit, a straight-forward averaging operation, or some other extrapolation method known in the art. An example extrapolation is indicated by the dashed line 920 and it reaches total depletion (0% SoC) at time T1, which is then an estimated time of depletion given the current driveline configuration. Suppose now that the time remaining until completion of the work task is Tr, i.e., that the sawing by the floor saw 100 will be concluded at time T2, which is sooner than the estimated time of depletion T1. This may be undesired, e.g., if ICE fuel consumption is to be minimized and use of the EM maximized. The control unit 130 can then increase the power contribution by the EM, resulting in a higher depletion rate 930, such that full depletion is reached at time T2 close to when the work task is expected to be completed.In other cases, it may be desired to keep some electrical energy in the ESS 170 even after work task completion. This could, for instance, be the case if electrical energy is required for transporting the floor saw 100 after work task completion. In this case the control unit can instead decrease the power contribution by the EM 230 to reduce the depletion rate, as illustrated by the example extrapolation 940 which has a predicted time of full depletion at T3 well after completion of the work task, meaning that the ESS will have a SOC at level indicated by reference numeral 950 at work task completion, as illustrated schematically in the drawing.To summarize, the control unit 130 is according to an example configured to control a transfer of power between the ICE 210, the EM 230, and the spindle 120, to reduce a difference between the time remaining until depletion and a desired time remaining until depletion.The control unit 130 can be configured to adjust an expected time of depletion, or equivalently a depletion rate of the ESS 170, by increasing or decreasing the power outtake from the EM 230, in order to reduce a difference between the expected time of depletion and a desired time of depletion. This way the control unit can maximize use of electrical energy in order to use less ICE fuel. It is also possible for the control unit to conserve some electrical energy for other tasks, i.e., avoid full depletion of the ESS in case electrical energy is needed for other purposes, such as transporting the floor saw on the surface 101 or cranking the ICE 210.The floor saw 100 may also comprise an electrical power take-off (PTO) 180 and optionally also a switch configured to selectively connect the PTO 180 to the ESS 170, where the control unit 130 is arranged to control the switch in response to a user input command. This enables an external electrical power consumer to be attached to the ESS 170 and be at least partly powered therefrom. The external power consumer may, e.g., be a dust extractor, a water fog system, or some type of battery charger. The PTO can be activated when the floor saw 100 is stationary with the second clutch 240 disengaged.The PTO 180 may provide an output power of at least 5kW and preferably at least 15kW or even at least 20kW, i.e., enough to charge even larger devices such as electrical vehicles and the like. According to some aspects, the PTO comprises a combined charging system (CCS) interface. The Combined Charging System (CCS) is a standard for charging electric vehicles. It can use Combo 1 (CCS1) or Combo 2 (CCS2) connectors to provide power at up to 350 kW, although these levels of power cannot normally be provided by the floor saw 100. These two connectors are extensions of the IEC 62196 Type 1 and Type 2 connectors, with two additional direct current (DC) contacts to allow high-power DC fast charging.The floor saw 100 may also comprise an inverter arranged inbetween the ESS 170 and the PTO 180. In this case the PTO 180 can be arranged to output an alternating current (AC) from the inverter to power AC equipment.With reference to Figure 1C, the floor saw 100 may comprise a remote control device 190 arranged to communicate with the control unit 130 via a wireless or a wired communication link. The remote-control device 190 in Figure 1C is just an example. It is appreciated that the remote-control device may take on many different forms and have different types of input devices. The remotecontrol device 190 does not have to comprise joysticks.The remote control device preferably comprises a display device 191 for presenting information to an operator and a control interface 192 for inputting control commands and selecting various functions and control options of the floor saw 100. The operator of the floor saw 100 can also use the display device to input information to the floor saw, such as parameters of the saw blade 125 currently mounted on the spindle 120. The operator can also input data about the work task, such as an expected length of kerf to be sawed, allowing the control unit to determine an expected time of completion of the work task, taking parameters such as drive speed into account.It has been realized that the remote-control device can be re-used as fixed control interface on the floor saw 100. The floor saw 100 may comprise a supporting bracket 195 for releasably holding the remote-control device 190 in fixed position on the floor saw 100. An operator wishing to, e.g., manually guide the floor saw 100 may then simply attach the remote-control device 190 to the floor saw 100 using the bracket and use the control device as if it were a fixed control device permanently assembled on the floor saw 100. The remotecontrol device 190 preferably comprises an internal battery pack arranged to be charged by electrical power from the floor saw 100 when received in the supporting bracket 195.According to some aspects, the supporting bracket 195 on the floor saw 100 comprises a wired communications interface configured to allow the remotecontrol device 190 to communicate with the control unit 130 via wired communication link when received in the supporting bracket 195. The supporting bracket may also comprise a radio transceiver and an antenna arrangement which allows the floor saw 100 to communicate with the remotecontrol device 190 when the remote-control device is not received in the support bracket 190. This way the control unit 130 is communicatively coupled to the remote-control device regardless of if the remote-control device is received in the bracket or not.The floor saw 100 may also comprise a kerf sensor system 135 that is arranged to detect a position of an existing kerf and / or a marking line in relation to the saw blade 125. The kerf sensor system 135 is schematically illustrated in Figure 1A. Various sensor types can be used to identify where the existing kerf or marking line is in relation to the saw blade. However, a vision-based sensor such as a camera may be preferred, possibly in combination with a directed light source to illuminate the kerf in front of the saw blade and / or behind the saw blade. The control unit 130 can be configured to identify the position of the kerf from the output data of the kerf sensor system 135, and to control floor saw propulsion and steering to traverse along the existing kerf. The control unit 130 can be configured to control propulsion and steering of the floor saw 100 to forward and reverse along the existing kerf or marking line repeatedly, while lowering the saw blade 125 into the surface 101 by an amount each repetition. This way a deep cut can be made in the surface 101.Most floor saws require careful configuration of parameters such as applied steering, drive wheel force, spindle speed of rotation, and so on in order to operate efficiently and produce the intended kerf, which is normally a straight line kerf but can also be a kerf having a curvature. An operator often has to fine-tune various configuration parameters of the floor saw at the start of a work task, which can be time consuming. The configuration parameters for successful floor saw operation often change considerably with saw blade type and / or size, such as the type of abrasive elements of the saw blade and the size of the saw blade. Some saw blades also comprise multiple discs, as discussed in International patent application WO2011 / 093764A1.To simplify configuration of the floor saws discussed herein, the control unit 130 can be arranged to retrieve preconfigured floor saw configuration parameters from a storage medium 1130 of the floor saw, i.e., a digital memory, in dependence of a current saw blade type and / or size. The floor saw configuration parameters thus retrieved comprises at least a configuration of a steering function of the floor saw 100. Thus, given the current saw blade type and / or size to be used for a given work task, an automated or at least partly automated configuration of the floor saw can be triggered, which simplifies the work task since it reduces the need for setting up the floor saw in preparation for a given work task.The current saw blade type and / or size can, for instance, be selectable or configurable via a control interface 192 of the floor saw 100. The operator then inputs saw blade data, such as the saw blade diameter, and the floor saw 100 is then automatically configured in terms of at least steering parameters to provide, e.g., a straight kerf. The floor saw configuration parameters optionally also comprises any of a desired steering angle, a steered axle angle, a desired rotation speed of the spindle 120, a desired total drive torque to be applied at the spindle 120, a desired gear ratio of the driveline 140, and a desired direction of rotation of the spindle 120.According to some aspects, the control unit 130 is arranged to detect the current saw blade type and / or size based on an identifier on the saw blade 125. The identifier can, for instance, be a radio frequency identification tag (RFID) arranged on the saw blade, which can be read out by the control unit 130 using techniques known in the art. Swedish national patent application No.2051497-2 discusses this type of identification and provides several examples that can be applied together with a saw blade 125 for use with the floor saw 100.The control unit 130 can also be arranged to store a current set of floor saw configuration parameters by the storage medium 1130 and retrieve the stored set of floor saw configuration parameters in response to an operator command. Thus, an operator can save a given parameterization, and later retrieve it for another work task. Thus, once the operator is content with the operation of the floor saw, he or she can store the settings by the storage medium 1130, and later retrieve the settings for some other work task, most likely one comprising use of the same saw blade type and / or saw blade size.Figure 10C shows a flow chart that illustrates a method related to automated floor saw parameterization by means of saw blade type and or based on previously stored parameters. This method will be discussed in more detail below.The saw blade 125 is often held in position on the spindle 120 by a nut or other fastening arrangement. When mounting a new blade on the spindle it is normally desired to lock the spindle so that it cannot rotate. The control unit 130 can be arranged to lock rotation of the spindle 120 by the EM 230 via the driveline 140, in response to a spindle locking command. When an operator desires to remove the saw blade 125 from the spindle 120 or mount a new saw blade 125 to the spindle 120, he or she can trigger the locking mode of the driveline 140. The control unit 130 then controls the EM 230 to provide a locking torque which resists rotation of the spindle 120.The EM 230 can also be arranged to determine a torque applied at the output axle of the EM, and to transmit data indicative of the applied torque to the control unit 130. The control unit 230 can then trigger generation of an indication of the applied torque to a user of the floor saw 100, allowing the user to determine when the correct torque has been applied to the fastening arrangement holding the saw blade in position on the spindle. The indication can be a visual indication, e.g., a torque scale where a current torque is indicated in relation to the desired torque. An audio signal can also be used as indication, such as a series of beeps with decreasing time in-between beeps as the applied torque approaches the desired torque, similar to some parking assist systems found on passenger cars. In other words, the control unit 130 is optionally configured to obtain a desired saw blade fastening element torque, and to determine a difference between the desired saw blade fastening element torque and a currently applied fastening element torque, and to indicate the difference to a user of the floor saw 100. The saw blade fastening element is normally an arbor nut, although other fastening elements are also possible.The control unit 130 can also be arranged to brake the spindle 120 by the EM 230 via the driveline 140, in response to inactivation of the floor saw 100. This is a safety feature that prevents the saw blade from moving when the floor saw is inactivated. The control unit 130 can also be arranged to generate a negative torque on an output axle of the EM to brake the spindle 120 via the driveline 140 in which case the EM 230 may output electrical energy to the ESS 170 as a result of generating the negative torque. This way some of the kinetic energy of the rotating saw blade can be recuperated as electrical energy.Many if not all of the technical features and functions discussed herein can be described as computer-implemented methods, performed, e.g., by the control unit 130 or by the remote control device 190. Some of these methods are illustrated by the flow charts in Figures 10A-C.Figure 10A illustrates a first computer-implemented method for controlling a floor saw 100 as described herein. The floor saw 100 comprises a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and an electric machine, EM, 230 arranged to drive the spindle 120. The method comprises obtaining Sa1 data indicative of a desired speed of rotation ω of the spindle 120, such as by manual or automated spindle speed configuration. The desired speed of rotation ω of the spindle 120 can be retrieved from the storage medium 1130 as discussed above, or simply input by an operator using a control interface like the control interface 192 discussed above.The method also comprises obtaining Sa2 data indicative of a current speed of rotation ω of the spindle 120, e.g., from the spindle speed sensor 131 or from a current state of the driveline 140, and modulating Sa3 an output axle torque of the EM 230 to reduce a difference between the current speed of rotation ω of the spindle and the desired speed of rotation ω of the spindle.This type of torque modulation was discussed above in connection to Figure 4.The at least two wheels 150, 160 normally comprises at least one drive wheel 150. In this case the method may comprise reducing Sa4 a drive torque F applied at the drive wheel 150 of the floor saw 100 in case the desired speed of rotation ω of the spindle cannot be maintained at maximum output axle torque of the EM 230. Thus, if the spindle starts to stall, i.e., starts to slow down even though full power is transferred to it by the driveline, then the drive speed of the drive wheel or wheels is backed off to reduce the load on the saw blade.The method may also comprise increasing Sa5 a drive torque F applied at the drive wheel 150 of the floor saw 100 up to a drive torque limit or drive wheel speed limit in case the desired speed of rotation ω of the spindle can be maintained at a current output axle torque of the EM 230. This means that the driving force is increased up to a point where the spindle starts to stall, or up to a maximum drive wheel speed. This way the production rate of the floor saw can be improved, which is an advantage. The drive torque limit or drive wheel speed limit is preferably configured in dependence of a wheel slip limit of the drive wheel 150.Figure 10B illustrates a second computer-implemented method for controlling a floor saw 100 as discussed herein, e.g., a floor saw 100 which comprises a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120. The hybrid driveline 140 comprises an ICE 210 and an EM 230. The method comprises obtaining Sb1 data indicative of an efficiency 500 of the ICE 210 as function of ICE output axle speed and ICE output axle torque, as discussed above in connection to Figure 5, determining Sb2 a current operating efficiency of the ICE 210 as function of current ICE output axle speed and current ICE output axle torque, and modulating Sb3 an output axle torque of the EM 230 to reduce a difference between the current operating efficiency of the ICE 210 and a desired operating efficiency of the ICE 210.Figure 10C illustrates a third computer-implemented method for controlling a floor saw 100 as discussed herein. The method comprises obtaining Sc1 saw blade data related to a saw blade type and / or size of a saw blade 125, as discussed above, and retrieving Sc2 floor saw configuration parameters from a storage medium 1130 of the floor saw 100 in dependence of the saw blade data, where the floor saw configuration parameters comprises at least a configuration of the steering function of the floor saw 100, and configuring Sc3 the steering function according to the retrieved floor saw configuration parameters. The floor saw configuration parameters may also comprise any of a desired steering angle, a desired spindle rotation speed, a desired total drive torque to be applied at the spindle 120, a desired gear ratio of the driveline 140, and a desired direction of rotation of the spindle 120.Optionally, according to an example, the method comprises obtaining Sc11 the saw blade data from an operator via a control interface 192 of the floor saw 100.Optionally, according to an example, the method comprises detecting Sc12 the saw blade type and / or size of the saw blade 125 based on an identifier on the saw blade 125.Optionally, according to an example, the method comprises retrieving Sc21 the floor saw configuration parameters from the storage medium 1130 as a set of previously stored configuration parameters.Optionally, according to an example, the method comprises storing ScO a current set of floor saw configuration parameters by the storage medium 1130. This way an operator can configure the floor saw for a given work task, and, once he or she is content with the performance of the floor saw, the configuration can be stored, so that it can be retrieved and re-used for other work tasks.Figure 11 schematically illustrates, in terms of a number of functional units, the general components of a control unit 130, or a remote control device 1110. Processing circuitry 1110 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 1130. The processing circuitry 1110 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.Particularly, the processing circuitry 1110 is configured to cause the control unit 130, or the remote control device 1110, to perform a set of operations, or steps, such as the methods discussed herein. For example, the storage medium 1130 may store the set of operations, and the processing circuitry 1110 may be configured to retrieve the set of operations from the storage medium 1130 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 1110 is thereby arranged to execute methods as herein disclosed.The storage medium 1130 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.The device 130, 1110 may further comprise an interface 1120 for communications with at least one external device, such as a wheel speed sensor 810 or a load sensor 820. As such the interface 1120 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.The processing circuitry 1110 controls the general operation of the control unit 130, 1110, e.g., by sending data and control signals to the interface 1120 and the storage medium 1130, by receiving data and reports from the interface 1120, and by retrieving data and instructions from the storage medium 1130.According to some aspects the storage medium 1135 comprises floor saw configurations parameters for operating a floor saw 100. The floor saw configurations parameters may for instance comprise a configuration of a steering function of the floor saw 100. The floor saw configuration parameters may also comprise any of a desired steering angle, a desired spindle rotation speed, a desired total drive torque to be applied at the spindle 120, a desired gear ratio of the driveline 140, and a desired direction of rotation of the spindle.The processing circuitry can be arranged to store a set of floor saw configuration parameters, such as a current set of configuration parameters, by the storage medium 1130, and later on retrieve the stored set of floor saw configuration parameters in response to an operator command.There is also disclosed herein a computer readable medium carrying a computer program comprising program code means for performing the methods discussed herein, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product.It is appreciated that many of the technical features and functions discussed herein are applicable on their own, i.e., not inextricably linked to the other features of the floor saw discussed above. Some of these features are set out below.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,where the hybrid driveline 140 comprises a second clutch 240 arranged to disconnect the spindle 120 from the driveline 140,where the control unit 130 is arranged to operate the second clutch 240 to disconnect the spindle 120 from the driveline 140 in a generator mode of operation of the floor saw 100.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,where the hybrid driveline (140) comprises a first clutch (220) arranged to disconnect the ICE (210) from the hybrid driveline (140),where the control unit 130 is arranged to execute an ICE start routine comprising cranking the ICE 210 by the EM 230 with the first clutch 220 engaged.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,where the control unit 130 is arranged to execute a low-rev start boost routine comprising controlling the EM 230 to provide a drive torque corresponding to a difference between a desired drive torque of the spindle 120 and a current torque output from the ICE 210.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,the driveline 140 comprising an electric machine, EM, 230,where the control unit 130 is arranged to obtain data indicative of a desired spindle speed of rotation ω, and to modulate an output axle torque of the EM 230 to reduce a difference between a current spindle speed of rotation and the desired spindle speed of rotation.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,the driveline 140 comprising an electric machine, EM, 230,where at least one of the wheels 150, 160 is a drive wheel 150,where the control unit 130 is arranged to reduce a drive torque F applied at the drive wheel 150 of the floor saw 100 in case a desired spindle speed of rotation ω cannot be maintained at maximum output axle torque of the EM 230.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,where the control unit 130 is arranged to obtain data indicative of an efficiency 500 of the ICE 210 as function of ICE output axle speed and ICE output axle torque, and to modulate an output axle torque of the EM 230 to reduce a difference between a current operating efficiency of the ICE 210 and a desired operating efficiency of the ICE 210.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,where at least one of the wheels 150, 160 is a drive wheel 150,where the control unit 130 is arranged to control a drive torque F applied at the drive wheel 150 of the floor saw in dependence of a speed difference between a longitudinal speed of the floor saw 100 over the surface 101 and a rotation speed of the drive wheel 150.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,the floor saw 100 further comprising an electrical energy storage, ESS, 170 arranged to power the EM 230, where the ESS 170 has a height h measured in a direction normal to the surface 101 that is smaller than a length I and a width w of the ESS 170 measured parallel to the surface 101 in use, where the ESS 170 is arranged between the surface 101 and the ICE 210 of the floor saw 100.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,the floor saw 100 further comprising an electrical energy storage (ESS) 170 arranged to power the EM 230,where the control unit 130 is configured to control a transfer of power between the ICE 210, the EM 230, and the spindle 120, to reduce a difference between a time remaining until depletion of the ESS 170 and a desired time remaining until depletion of the ESS 170.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a hybrid driveline 140 arranged to power the spindle 120,the hybrid driveline 140 comprising an internal combustion engine, ICE, 210 and an electric machine, EM, 230,the floor saw 100 further comprising an electrical energy storage, ESS, 170 arranged to power the EM 230, an electrical power take-off (PTO) 180 and an optional switch configured to selectively connect the PTO 180 to the ESS 170, where the control unit 130 is arranged to control the switch in response to a user input command.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,the floor saw 100 further comprising at least one support wheel 160 arranged to engage the surface 101 inbetween a drive wheel axle 151 of the floor saw 100 and an axis of rotation 121 of the spindle 120,where a normal load sensor 820 is arranged in connection to the support wheel 160 to sense a load exerted by the floor saw 100 on the support wheel 160,where the control unit 130 is arranged to trigger an automated action in case an output signal value of the normal load sensor 820 deviates from a desired output signal value range.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,where the control unit 130 is arranged to obtain data related to a type and / or size of a saw blade 125 mounted to the spindle 120, and to automatically configure an operating parameter of the floor saw 100 based on the type and / or size of the saw blade 125.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,where the control unit 130 is arranged to retrieve floor saw configuration parameters from a storage medium 1130 of the floor saw 100, in dependence of a current saw blade type and / or size, where the floor saw configuration parameters comprises at least a configuration of a steering function of the floor saw 100.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,the floor saw 100 further comprising a remote-control device 190 arranged to communicate with the control unit 130 via a wireless or a wired communication link, and a supporting bracket 195 for releasably holding the remote-control device 190 in fixed position on the floor saw 100.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 arranged to power the spindle 120,the floor saw 100 further comprising a kerf position sensor system 135 arranged to detect a position of an existing kerf and / or a marking line in relation to the saw blade 125, where the control unit 130 is arranged to control floor saw propulsion and steering to traverse along the existing kerf.According to an example, there is disclosed a floor saw 100 comprising a chassis 110 supported on a surface 101 by at least two wheels 150, 160, a spindle 120 for supporting a saw blade 125 on the chassis 110, a control unit 130, and a driveline 140 comprising an EM 230 arranged to power the spindle 120,where the control unit 130 is arranged to lock a rotation of the spindle 120 by the EM 230 via the driveline 140, in response to a spindle locking command.As mentioned above, the driveline 140 and the ESS 170 can also be used in a remote controlled demolition robot 1200 as exemplified in Figure 12 and also in a power trowel 1300 as exemplified in Figure 13.Consequently, there is disclosed herein a demolition robot 1200 comprising a chassis 110 supported on a surface 101 by endless tracks 1240, a control unit 130, and a hybrid driveline 140 arranged to power a hydraulic system 1280 of the demolition robot. The hybrid driveline 140 comprises an ICE 210 and an EM 230 as discussed above. The control unit 130 is arranged to control a transfer of power between the ICE 210, the EM 230, and the hydraulic system 1280, in dependence of an operating configuration or operating condition of the demolition robot 1200.There is also disclosed herein a demolition robot 1200 comprising the ESS 170 described herein. The ESS 170 on the demolition robot can be used to power a hybrid electric driveline of the demolition robot, i.e. , the demolition robot can be power partly from electrical mains 1270 and partly from the ESS 170, with or without an ICE 210.There is furthermore disclosed herein a power trowel 1300 comprising a chassis 110 supported on a surface 101 by rotatable trowel tools 1310, 1320, a control unit 130, and a hybrid driveline 140 arranged to power at least the rotatable trowel tools 1310, 1320. The hybrid driveline 140 comprises an ICE 210 and an EM 230 as discussed above. The control unit 130 is arranged to control a transfer of power between the ICE 210, the EM 230, and the rotatable trowel tools 1310, 1320, in dependence of an operating configuration or operating condition of the power trowel 1300.There is also disclosed herein a power trowel 1300 comprising the ESS 170 described herein. The ESS 170 on the power trowel 1300 can be used to power a driveline of the power trowel 1300.

Claims

1. A floor saw (100) comprising a chassis (110) supported on a surface (101) by at least two wheels (150, 160), a spindle (120) for supporting a saw blade (125) on the chassis (110), a control unit (130), and a hybrid driveline (140) arranged to power the spindle (120),the hybrid driveline (140) comprising an internal combustion engine, ICE, (210) and an electric machine, EM, (230),the floor saw (100) further comprising an electrical energy storage, ESS, (170) arranged to power the EM (230), and an electrical power take-off, PTO, (180) comprising a switch configured to selectively connect the PTO (180) to the ESS (170), where the control unit (130) is arranged to control the switch in response to a user input command.

2. The floor saw (100) according to claim 1, where the PTO comprises a combined charging system, CCS, interface.

3. The floor saw (100) according to claim 1 or 2, comprising an inverter arranged in-between the ESS (170) and the PTO (180), where the PTO (180) is arranged to output an alternating current, AC, from the inverter.

4. The floor saw (100) according to any previous claim, where the PTO (180) is arranged to provide an output power of at least 5kW and preferably at least 15kW.

5. The floor saw (100) according to any previous claim, where the hybrid driveline (140) comprises a first clutch (220) arranged to disconnect the ICE (210) from the hybrid driveline (140).

6. The floor saw (100) according to any previous claim, where the hybrid driveline (140) comprises a second clutch (240) arranged to disconnect the spindle (120) from the driveline (140).

7. The floor saw (100) according to claim 5 or 6, where any of the first and second clutches (220, 240) comprises a gearbox with a neutral gear arranged to disconnect at least one input axle from an output axle of the gearbox.

8. The floor saw (100) according to any of claims 5-7, where any of the first and second clutches (220, 240) comprises an electromagnetic clutch mechanism.

9. The floor saw (100) according to any of claims 5-8, where the control unit (130) is arranged to operate the second clutch (240) to disconnect the spindle (120) from the driveline (140) in a generator mode of operation of the floor saw(100).

10. The floor saw (100) according to any previous claim, where a voltage of the ESS (170) is below 112V, and preferably at or below 100V or even below 96V.