SE2051110A1

SE2051110A1 - Floor sawing equipment with controllable supporting wheels

Info

Publication number: SE2051110A1
Application number: SE2051110A
Authority: SE
Inventors: Johan Sandwall; Tobias Gustafsson
Original assignee: Husqvarna Ab
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2022-03-25
Also published as: SE545678C2

Abstract

A floor saw (100) for early entry sawing in a maturing concrete surface segment (160), the floor saw comprising a circular cutting blade (110), at least two drive wheels (120) arranged to support the floor saw on the concrete surface segment (160), a sensor arrangement (140) configured to determine a current yaw motion of the floor saw, and a control unit (130) configured to receive a desired yaw motion setting,wherein the at least two drive wheels (120) are arranged to be driven at respective first and second wheel speeds, andwherein the control unit (130) is arranged to control a difference between the first and second wheel speeds to reduce a difference between the current yaw motion of the floor saw and the desired yaw motion setting.

Description

TITLE Floor sawing equipment with controllable supporting wheels TECHNICAL FIELD The present disclosure relates to concrete processing and in particular to earlyentry concrete sawing. There are disclosed floor saws, systems and methodswhich allow for mitigating floor saw drifting due to a cutting blade mountedoffset to a side of the floor saw.

BACKGROUND Early entry concrete sawing is a concrete processing technique where shallowcuts, often in straight lines, are made in concrete surfaces within the first oneor two hours after finishing surface preparation, i.e., after the concrete hasreached a certain level of maturity but before the concrete has set completely,a period often referred to as the 'green zone". lt is not always easy to predictwhen this period is to occur. The shallow cuts create a weakened surfaceplane, thus encouraging cracking to occur at the location of the cuts in acontrolled manner rather than the cracks appearing anywhere in the concrete,resulting in a more visually appealing surface. One example of early entryconcrete saws are the Soff-Cut range of early entry concrete saw productsmanufactured by Husqvarna AB.

Many early entry concrete saws are arranged with a saw blade that is offset toone side of a center line of the saw, i.e., offset transversally to the cuttingdirection of the floor saw. This offset allows, e.g., for making cuts close to awall or other obstacle. The offset, however, creates an imbalance in the sawwhich often results in the saw drifting towards the side where the saw blade ismounted. Some different ways of compensating for this 'natural' drifting in earlyentry concrete saws are known. For instance, different fixed gear ratios on theleft and right driven wheels can be used to bias the drive and thereby counterthe drift. The entire driven axle on the floor saw can also be steered, i.e., adjusted, to compensate for the drift. These methods of compensating for thedrift are seldom perfect. Thus, it is often seen in field that the operator of theearly entry floor saw manually compensates for residual drift by body weight,which is not ideal since it makes the concrete processing operation moredifficult and places additional strain on the operator.

There is a need for improved floor saws which enable a more efficient and convenient early entry sawing.

SUMMARY lt is an object of the present disclosure to provide improved floor saws whichalleviate at least some of the issues mentioned above. The object is at least inpart obtained by a floor saw for early entry sawing in a maturing concretesurface segment or slab. The floor saw comprises a circular cutting bladearranged transversally offset from a centrum line of the floor saw, whichcentrum line is aligned with a forward direction of the floor saw. The floor sawfurther comprises at least two supporting wheels arranged to support the floorsaw on the concrete surface, a sensor arrangement configured to determine acurrent yaw motion of the floor saw, and a control unit configured to obtain adesired yaw motion setting. At least one of the supporting wheels is arrangedon an opposite side of the centrum line compared to the circular cutting bladeand arranged to generate a respective variable wheel force. The control unit isarranged to control a difference between the wheel forces of the supportingwheels to reduce a difference between the current yaw motion of the floor sawand the desired yaw motion setting. Thus, drifting by the floor saw due to theoffset cutting blade can be compensated for by the control unit varying thewheel force at one or both wheels. The drift compensation systems presentedherein can be used with a cutting blade offset to any side of the centrum line,i.e., a cutting blade mounted on the left side or the right side of the cuttingmachine. Since the yaw motion can be continuously or at least regularlysensed, drift compensation can easily be automatically updated as the concrete surface segment matures and becomes more hard.

According to aspects, the at least two supporting wheels are driven wheels,and the control unit is arranged to control the difference between the wheelforces of the supporting wheels by controlling respective wheel torques and/orspeeds of the at least two driven wheels. This way of compensating for drift isparticularly suitable if one or both supporting wheels are driven by an electricmachine with variable output torque or speed. ln other words, the floor sawoptionally comprises a first drive wheel and a second drive wheel, where eachdrive wheel is driven by a respective first and second electric machinecontrolled by the control unit.

According to aspects, the floor saw comprises a first supporting wheelarranged on an opposite side of the centrum line compared to the circularcutting blade. This first supporting wheel comprises a wheel brake arranged tobe controlled by the control unit to generate a negative wheel torque. Thus, itis appreciated that drift compensation can be performed also by braking onewheel. This method of compensating for drift is particularly suitable if bothwheels are driven by the same motor at constant torque or speed, such as bythe motor driving the cutting blade of the floor saw.

According to aspects, the floor saw comprises a weight and an actuatorarranged to move the weight transversal to the forward direction. The controlunit is then arranged to control the actuator to reduce a difference between thecurrent yaw motion of the floor saw and the desired yaw motion setting. Byvarying the position of the weight, the normal forces acting on the supportingwheels are redistributed. The resulting change in friction for the wheels willhave an impact on the wheel forces which are possible to generate in theforward or longitudinal direction, and thus the position of the weight can beused for drift compensation in a low complex manner even if the wheels are driven by the same constant torque motor.

According to aspects, the sensor arrangement comprises an inertialmeasurement unit (IMU) configured to detect the current yaw motion by thefloor saw. The ll\/IU is able to detect acceleration, which in turn can be used to estimate the yaw motion in a cheap and reliable manner. The ll\/IU is optionally arranged distally mounted on a guiding arm extending in the forward direction.This distal mounting amplifies the acceleration by the Ieverage effect it provides and therefore simplifies measurement of acceleration.

According to aspects, the sensor arrangement comprises one or more vision-based sensors configured to detect the current yaw motion by the floor saw bychanges in a forward direction view over time. Vision-based sensors canprovide a highly accurate estimation of the yaw motion, which is an advantage.The type of vision-based sensors required for yaw motion estimation can be ofrelatively low resolution, and therefore also of low cost, which is an advantage.

According to aspects, the sensor arrangement comprises a receiverconfigured to receive a wireless signal from a beacon and to detect the currentyaw motion by the floor saw and/or a current heading of the floor saw basedon the received wireless signal. The beacon can be deployed by an operatorand the floor saw can be made to saw along a line towards the beacon. Thisis a way of providing a floor saw with a degree of autonomy, which is anadvantage since the operator may not necessarily need to constantly monitorthe progress of the floor saw. Even if an operator is required, the operator canobtain guiding support from the deployed beacon, and also an improved drift compensation, thus providing for a more convenient floor sawing operation.

According to aspects, the sensor arrangement comprises an electroniccompass configured to measure the forward direction of the floor saw inrelation to magnetic north, wherein the control unit is configured to determinethe current yaw motion of the floor saw based on measurements of the forwarddirection in relation to magnetic north over time. Electronic compasses areboth low cost and reliable sources for yaw motion estimation. Disturbances inEarths magnetic field have little effect on the drift compensation, since theresulting magnetic compass deviation does not affect the relative compass measurements used for yaw motion estimation.

According to aspects, the control unit is arranged to receive the desired yawmotion setting via wireless radio link from a remote control device. This means that the drift prevention system can be used also as a remote control system.

By indicating a desired yaw motion setting the floor saw can be made to followa desired path, including turning maneuvers. For instance, the remote controldevice can be configured to transmit a desired yaw motion settingcorresponding to sawing along a straight line, or corresponding to sawingalong an arcuate curve having a configurable radius, or corresponding to apath with a deviation defined by a number of degrees from a set course aftera controlled turning maneuver. Optionally, the remote control device can beconfigured to control one or more further floor saws in addition to the floor saw.This allows a single operator to control more than one saw, which reduces theneed for operators and/or allows an operator to produce more floor saw cutsin a fixed amount of time compared to if that operator only controls a single floor saw.

According to other aspects, the floor saw comprises an arrangementconfigured to determine a weight and/or volume of accumulated dust or slurryin a dust container mounted on the floor saw. The control unit is then arrangedto detect when the weight and/or volume of accumulated dust or slurry exceedsa preconfigured threshold and to transmit a signal to the remote control deviceindicating that the weight and/or volume of accumulated dust or slurry is abovethe preconfigured threshold. Thus, advantageously, the operator does nothave to monitor the dust container regularly to see if there is enough dust andslurry to merit emptying the dust container.

According to aspects, the control unit is arranged to determine a level of driftcompensation applied via the at least two supporting wheels to reduce thedifference between the current yaw motion of the floor saw and the desiredyaw motion setting. The control unit is in this case arranged to determine aconcrete hardness level in dependence of the determined level of driftcompensation, and to configure a desired speed of the floor saw in the forwarddirection in dependence of the concrete hardness level. As the concretematures it becomes harder and harder. The harder the concrete becomes themore resistance is encountered when sawing, and the worse the drift becomes. By adjusting the floor saw speed in dependence of the hardness, the load on the cutting blade can be optimized for a given criterion, such as cutting blade lifetime.

According to aspects, the control unit is arranged to determine a current speedof the floor saw in the forward direction and a desired speed of the floor sawin the forward direction, where the desired speed is determined in dependenceof an estimated maturity level or hardness of the concrete surface segmentand/or in dependence of a measured temperature of the circular cutting blade,and to control the at least two drive wheels to reduce a difference between thecurrent speed and the desired speed. This way the floor sawing operation canbe optimized. For instance, floor sawing speed can be reduced if the cuttingblade gets too hot in order to spare the cutting blade and thereby prolong itslifetime. Floor sawing speed can also be configured in dependence of theconcrete maturity level or concrete hardness, perhaps such that the speed isreduced when the concrete gets more and more hard in order to spare theblade from cutting too fast in hard concrete. The speed of the floor saw canalso be optimized to avoid glazing of the cutting segments on the cutting bladeby balancing rotational speed of the cutting blade against forward speed bythe floor saw, as will be explained in more detail below.

According to aspects, the control unit is arranged to determine whether anoperator is in position to perform manual control of floor saw steering, and totrigger a warning signal and/or halt the floor saw in response to determiningthat an operator is not performing manual control of the floor saw steering. Thisfeature is similar to a lane assist function in a car, where the floor saw mayproceed with cutting in a straight line without manual control as long as anoperator is in position to perform manual control, e.g., in case something goeswrong. To be in position to perform manual control may comprise, e.g., anoperator having his hands on a control handle or remote control, or simply thatan operator is in vicinity of the floor saw, such as in the same room or within a certain distance from the floor saw.

According to aspects, the control unit is arranged to receive concrete maturity data indicating a concrete maturity level of the concrete surface segment from a concrete maturity sensor arranged external to the floor saw, to determinean onset of a suitable time slot for early entry sawing based on the concretematurity data, and to indicate the onset of the time window to an operator.Thus, the operator receives assistance in when to start using the floor saw,i.e., when the concrete is in the green zone mentioned above, which is an advantage.

There are also disclosed herein early entry concrete saws, power trowels, andother types of concrete processing equipment, as well as methods associatedwith the advantages mentioned above.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwiseherein. All references to "a/an/the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. The steps of any method disclosed herein do not have to beperformed in the exact order disclosed, unless explicitly stated. Furtherfeatures of, and advantages with, the present invention will become apparentwhen studying the appended claims and the following description. The skilledperson realizes that different features of the present invention may becombined to create embodiments other than those described in the following,without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described in more detail with reference tothe appended drawings, where Figures 1A,B show example concrete processing equipment;Figure 2 schematically shows a drive arrangement for a floor saw;Figure 3 illustrates a remote controlled floor saw; Figure 4 shows a concrete processing system; Figure 5 is a graph illustrating wheel force vs wheel slip; Figure 6 is a graph illustrating concrete maturity as function of time;Figure 7 is a flow chart illustrating methods; Figure 8 schematically illustrates a control unit; Figure 9 schematically illustrates a computer program product; Figures 10A,B illustrate contact force F as function of rotationa| velocity V; Figure 11 schematically illustrates an up-cut based floor saw; and Figure 12 schematically shows a control unit.

DETAILED DESCRIPTION The invention will now be described more fully hereinafter with reference to theaccompanying drawings, in which certain aspects of the invention are shown.This invention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments and aspects set forth herein;rather, these embodiments are provided by way of example so that thisdisclosure will be thorough and complete, and will fully convey the scope ofthe invention to those skilled in the art. Like numbers refer to like elements throughout the description. lt is to be understood that the present invention is not limited to theembodiments described herein and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

Figures 1A and 1B illustrate early entry concrete floor saws 100a, 100b. Asmentioned above, this type of saw is used to cut shallow cuts in concretesurfaces after finishing surface preparation, but before the concrete has set completely.

A concrete surface is associated with a concrete surface segment whichcomprises the top surface of the concrete and a segment immediately below the surface. The thickness of the concrete surface segment through which sawing is done varies, but is normally below 10-15 cm.

An early entry concrete floor saw generally comprises a circular cutting blade110 aligned with a forward direction F of the floor saw. Thus, the forwarddirection is parallel to the cutting blade plane. The floor saw also comprisessupporting wheels 120 to support the floor saw against the concrete surfacesegment 160 to be cut. One or more of the supporting wheels may be drivenwheels, which means that they are connected to a propulsion device, such asan electric machine 150, arranged to provide positive torque to the wheel inorder to move the saw in the forward direction. On or more of the supportingwheels may also comprise respective wheel brakes arranged to providenegative torque to the wheel. lt is appreciated that a floor saw may compriseone or more supporting wheels with respective wheel brakes even if there areno driven wheels, e.g., if the cutting blade rotation is used as sole means for propulsion.

The floor saws discussed herein also comprise a control unit 130 configuredto control various functions on the floor saw, such as controlling two or moredriven wheels on the floor saw, and/or one or more wheel brakes. The controlunit 130 may be connected to one or more sensor devices 140 configured tosense a motion behavior of the floor saw such as a current yaw motion and/or a current speed in the forward direction.

The floor saw generates dust and slurry as a result of the cutting operation.This dust and slurry may be collected in a dust container, such as theLongopac dust bin system which is well known in the art. The dust and slurryis then transported via conduit from the cutting blade area to the dust containerby a dust extractor, i.e., a vacuum device in a known manner. This dustextractor can be a separate unit arranged, e.g., to be towed by the floor saw,or it can be integrated with the floor saw. A dust container 170 may, accordingto some aspects, be mounted on the floor saw, as schematically illustrated inFigure 1 B, or comprised in a dust extractor arranged external to the floor saw. ln case the floor saw is remote controlled, a signal can be transmitted to the remote control indicating when the dust container has reached its holding capacity, which feature will be discussed in more detail below.

Figure 2 schematically illustrates a drive arrangement for a floor saw 200. Thecircular cutting blade 110 is offset O to one side of the centrum line C, whichcentrum line is aligned with the forward direction F. i.e., the centrum line C isparallel with an axis extending in the forward direction. The centrum line is alsoparallel to the plane defined by the circular cutting blade 110. This offset fromthe centrum line (and from the mass center of the floor saw) generates a yawmotion by the floor saw during use. Thus, if no countermeasures are taken,the floor saw will drift towards the side with the saw blade, as indicated by the curved arrow D in Figure 2.

Some floor saws allow for mounting the circular cutting blade on either side ofthe machine, i.e., to the right or to the left of the centrum line C. This has beenillustrated in Figure 2 by a dashed line cutting blade on the left hand side. Thissimplifies reaching certain places close to objects and will of course affect thedirection of the drift. lt is appreciated that the teachings of the presentdisclosure are not dependent on which side the cutting blade is located. Thesensor arrangements disclosed herein are optionally capable of detecting yawmotion in any direction, and the drive arrangements are optionally configuredto compensate for drift in any direction.

The cutting blade 110 may be configured for either down-cut D or up-cut Uoperation 230. Up-cut operation is common for early-entry saws such as theSoff-cut range of floor saws, while down-cut is more common on regular floorsaws. The techniques disclosed herein are applicable for both down-cut as well as up-cut operation. ln some rare cases the floor saw may drift away from the side with the sawblade, i.e., to the left in Figure 2. The techniques disclosed herein can beadapted to compensate for such drifts in a straightforward manner by varyingwheel forces to compensate for the drift. Also, as will be understood from thebelow description, the floor saw can be steered by generating a controlled amount of desired drift to either left or right hand side. 11 According to some aspects, the floor saw comprises a drive arrangement withone or more separate electrical machines 150a, 150b arranged to controlrespective supporting wheels 120a, 120b. The electrical machines may bepowered by an electrical storage device, such as a battery or a fuel cellarrangement. The electric machines 150a, 150b are arranged to be controlledby the control unit 130 to generate a desired wheel torque Ta, Tb, and/or adesired wheel speed Va, Vb. Thus, it is appreciated that one or moresupporting wheels may be driven wheels capable of generating positive torqueand therefore a wheel force acting in the forward direction F. Generally anelectrical machine can be configured also for generating a negative torque byapplying a regenerative braking function. The electrical machines discussedherein may or may not comprise such regenerative braking functions. Anelectrical machine without regenerative braking function may also be referred to as an electrical motor.

One objective of the present disclosure is to provide floor saws withcontrollable drive wheels which can be used to dynamically compensate forthe drift D, thus providing an early entry floor saw with a reduced tendency forunwanted drifting towards the side with the cutting blade 110. Towards thisend, the floor saws comprise a control unit 130 which controls the drive wheelsto obtain a desired yaw motion by the floor saw. Notably, this desired yawmotion may be a zero yaw motion (corresponding to cutting along a straightline, or a non-zero desired yaw motion (corresponding to cutting along a pre- determined arcuate path).

Thus, with reference to at least Figures 1A, 1B and Figure 2, there is disclosedherein a floor saw 100, 100a, 100b for early entry sawing in a maturingconcrete surface segment 160. The floor saw comprises a circular cuttingblade 110 arranged transversally offset O from a centrum line C, whichcentrum line C is aligned with a forward direction F of the floor saw. The floorsaw comprises at least two supporting wheels 120, 120a, 120b arranged tosupport the floor saw on the concrete surface segment 160, a sensorarrangement 140 configured to determine a current yaw motion of the floor saw, and a control unit 130 configured to obtain a desired yaw motion setting. 12 At least one of the supporting wheels 120, 120a, 120b is arranged on anopposite side of the centrum line C compared to the circular cutting blade 110and arranged to generate a respective variable wheel force. The control unit130 is arranged to control a difference between the wheel forces of thesupporting wheels, thereby reducing a difference between the current yawmotion of the floor saw and the desired yaw motion setting to provide a drift compensation function.

A yaw motion is herein to be interpreted as a rotation about some point of thefloor saw, such as a mass center or a center of inertia. A positive yaw motionis herein defined as a clockwise rotation when seen from above, such as theview in Figure 2. Thus, a positive yaw motion in combination with a forwardmotion results in an arcuate path to the right as illustrated by the curved arrowD in Figure 2.

A wheel force is the force generated in the longitudinal direction of the floorsaw by a supporting wheel, i.e., in the forward direction F or in a reversedirection opposite to the forward direction. With reference to Figure 2, if thewheel 120a generates less force in the forward direction F than the wheel120b, then a drift D towards the side of the cutting blade 110 will be counteredand the floor saw will move with less drift. A wheel force can be generated byapplying a torque Ta, Tb, to the respective wheel axles, or generating a wheelspeed Va, Vb about the wheel axles. Application of a wheel brake also resultsin a wheel force, acting in the reverse direction. lt is appreciated that, although most of the present disclosure relates to electricmachines arranged to generate the respective variable wheel force, variablewheel forces can also be generated by a combustion engine, or a hydraulicengine. The variation in wheel force for a combustion engine drive can, forinstance, be generated by means of separate clutches or variable geartransmission. The variation in wheel force can also be achieved, e.g., by atorque vectoring system, or one or more wheel brakes arranged to selectivelybrake a wheel to reduce the wheel force generated at this wheel. A variable 13 wheel normal force can also be obtained by arranging a movable weight aswill be discussed in more detail below.

Figure 5 shows a graph 500 illustrating the general relationship betweengenerated wheel force (longitudinal force Fx in the forward direction F andlateral force Fy transversal to the forward direction) and wheel slip, i.e., thedifference between wheel rotational speed and the speed of the floor saw. lt isseen that a wheel force can be generated by setting a wheel speed higher thanthe speed of the floor saw to generate a positive wheel slip, at least when thewheel slip is within a range 510 where the relationship is approximately linear.lt is also noted that generated lateral force declines quickly with wheel slip.

However, such large values of wheel slip are not to be expected in a floor saw.

Generally, it is appreciated that the control unit 130 may be arranged to controlthe difference between the first wheel force and the second wheel force bycontrolling respective wheel torques and/or wheel speeds of at least onesupporting wheels 120, 120a, 120b. This wheel may be a driven wheel or awheel with a wheel brake. The wheel force may also be controlled by adjustinga wheel normal load, i.e. the weight distribution between the supportingwheels, as will be discussed in more detail below. The floor saw may forinstance as mentioned above comprise a first drive wheel 120a and a seconddrive wheel 120b, where each drive wheel is driven by a respective first andsecond electric machine 150a, 150b controlled by the control unit 130. Electricmachines like the electric machines 150a, 150b can be controlled byrequesting a torque or a wheel speed, both options can be used with thetechniques discussed herein for controlling a yaw motion of a floor saw.

The first and the second electric machine may optionally be powered by an on-board electrical storage device 210, such as a battery, a super-capacitor, or afuel-cell arrangement. This is an advantage since the floor saw can then betransported shorter distances by means of the driven wheels. The electricmachines may of course also be powered by cable from electric mains.

The cutting blade on the floor saw may be powered by a separate combustion engine. This engine can then be used to charge the electrical energy source, 14 thus allowing for operating the driven wheels without access to electrical mains or other battery charging means.

A negative wheel torque can be generated by a wheel brake, such as a frictionbrake. Thus, if a wheel brake is applied at the left wheel 120a, then a drift tothe right in Figure 2 will be countered. lt is appreciated that the control unit 130may be arranged to generate variable wheel forces by applying wheel brakesat one or more of the wheels. ln other words, a first supporting wheel 120aarranged on an opposite side of the centrum line C compared to the circularcutting blade 110 may be configured with a wheel brake arranged to becontrolled by the control unit 130 to generate a negative wheel torque. Thisnegative wheel torque can then be used to counter a drift D towards the sideof the circular cutting blade 110.

According to some aspects, the drive arrangement 200 also comprises aweight 220 and an actuator arranged to move the weight transversal to theforward direction F. The actuator may, e.g., be connected to a spindle or thelike for moving the weight, and the control unit 130 may then move the weighttransversally to the forward direction by the actuator. The weight 220 can beused to shift normal load between the supporting wheels 120a, 120b, thusgenerating more or less traction on a given wheel and consequently also adifferent wheel force at each wheel. This increased and/or reduced tractioncan be used by the control unit to compensate for the drift D.

Figure 2 also shows a sensor arrangement 140. This sensor arrangement 140is configured to determine the current yaw motion of the floor saw and it canbe realized in a number of different ways as will be explained in the following.Of course, combinations of different sensors may also be used to provide morerobust and accurate estimates of the current yaw motion. The control unit 130is configured to receive sensor data from the sensor device 140 and toestimate a current yaw motion from the sensor data. This estimation of currentyaw motion can be implemented as a filtering operation, e.g., an averagingoperation, or as more advanced signal processing techniques, comprising aKalman filter or the like.

The sensor arrangement 140 may for instance comprise an inertialmeasurement unit (IMU) configured to detect the current yaw motion by thefloor saw via measurements of acceleration. To improve the accelerationmeasurement, the ll\/IU is optionally arranged distally mounted on a guidingarm 170 extending in the forward direction F, as shown in Figures 1A and 1B.The IMU will most likely be subject to significant vibration and perhaps alsoshock, which implies that the sensor data from an IMU may need to be heavilyfiltered to extract the current yaw motion in order to suppress effects fromvibration. The ll\/IU can optionally also be mounted on a resilient memberconfigured to suppress vibrations.

The sensor arrangement 140 may also comprise one or more vision-basedsensors configured to detect the current yaw motion by the floor saw. This canbe done, for instance, by sequentially recording scenes in the forwarddirection, and correlating two or more consecutive recorded scenes with eachother to detect offsets to the left or to the right, which offsets then indicate adrift and a yaw motion. Optionally, a scaling operation can be performed onthe recorded scenes to compensate for the forward motion by the floor saw.However, if the scenes are recorded frequently enough, such as at a rate of acouple of Hz or so, then no such scaling should be necessary. lf a given objectcontinuously shifts to the left in a captured sequence of images, the floor sawis assumed to be drifting to the right. lt is also possible to deploy some visualmarker (such as a signpost or the like) which a vision-based sensor can locatein the captured images and track over time to detect a yaw motion by the floorsaw. The control unit may also be configured to navigate towards a deployedvisual mark and thereby generate a cut along a straight line from an initial position towards the visual mark.

Various wireless signals can also be used to detect a yaw motion. For instance,the sensor arrangement 140 may comprise a receiver configured to receive awireless signal from a beacon 450, and to detect the current yaw motion bythe floor saw and/or a current heading of the floor saw based on the signal. AnRF beacon can be used together with a directive antenna to detect if the floorsaw is veering off course, which will be detected by a reduced received signal 16 power. An infrared (IR) beacon can be used together with an IR sensor todetect a relationship between a course of the floor saw and a direction of theIR beacon. A yaw motion can be detected by comparing the bearing to the IR beacon to the floor saw over time.

The sensor arrangement 140 may of course also comprise an electroniccompass configured to measure the forward direction F of the floor saw inrelation to magnetic north. The control unit 130 can then be configured todetermine the current yaw motion of the floor saw based on measurements ofthe forward direction F in relation to magnetic north over time. lf the compassdevice is accurate enough, an operator can set a course to be followed by themachine. The machine can then be placed in a semi-autonomous mode tocomplete a cut over a configured length, where the length of the cut can bedetermined based on dead reckoning, based on an indoor positioning system,or the like.

According to some aspects, the floor saw comprises a radar sensor or an ultra-sound sensor configured to detect obstacles in front of the floor saw. The floorsaw can then be controlled by the control unit 130 to cut in a certain directionuntil it reaches an obstacle such as a wall or the like, whereupon the floor sawautomatically halts in response to a signal from the radar or ultrasound sensor.Of course, a stereo vision sensor can also be used to detect distances toobstacles in the forward direction.

Figure 3 illustrates a floor sawing system 300 comprising a floor saw and aremote control device 310. The control unit 130 is here arranged to receive thedesired yaw motion setting via wireless radio link 320 from the remote controldevice 310. Thus, an operator may steer the floor saw via the remote control.The steering may just be a command to start sawing along a straight line withno drift, or to saw along some arcuate path, perhaps specified by a radiusconfigured on the remote control device 310. ln other words, the remote controldevice 310 is optionally configured to transmit a desired yaw motion settingcorresponding to sawing along a straight line or corresponding to sawing along an arcuate curve having a configurable radius. 17 The operator may also wish to generate a cut at a deviation from a defineddirection or path. The machine may then be configured to execute a controlledturning maneuver along an arcuate path with a radius that does not jeopardizethe cutting blade and to continue cutting along the new direction after thedeviation has been reached.

Figure 4 schematically illustrates a concrete processing system where one ormore floor saws 100, 100' are used to make early entry cuts 440a, 440b, 440cin a concrete surface segment 160. The one or more floor saws 100, 100' areconnected via wireless link 320 to the remote control device 310. Thus, theremote control device 310 may be configured to control one or more furtherfloor saws 100 in addition to the floor saw. The remote control device maycomprise a selector for selecting a floor saw in a fleet of floor saws, andcontrolling the selected floor saw to perform a sawing task.

The remote control device here comprises a transceiver unit 410 tocommunicate via the wireless link 320 to the one or more floor saws 100, 100',and a processing unit 420, as well as an optional database 430.

Figure 4 shows an example beacon 450 towards which one of the floor sawsis steering in an autonomous or a semi-autonomous manner. This beacon mayalso be connected via wireless link 460 to the remote control device 310. Thisway an operator may activate beacons selectively so as to not confuse sensordevices on the different floor saws operating in the area. Thus, the remotecontrol device 310 may be arranged to remotely control one or more of thebeacons discussed above, i.e., one or more RF beacons or one or more IRbeacons.

Figure 4 also shows a concrete maturity sensor 470 arranged to continuouslymeasure moisture and/or temperature in the concrete slab. This maturity datacan be used to optimize floor saw control of both cutting speed and drift compensation, as will be discussed in more detail below. lt is appreciated that concrete slabs become harder as they mature. Thus, aconcrete maturity level can be translated into a concrete hardness level and vice versa. This type of conversion can be made using a look-up table or the 18 like. lt is appreciated that the translation between maturity and hardness maybe dependent on the type of concrete, i.e., on the concrete recipe. Thus, it isappreciated that concrete maturity level and concrete hardness are often at least approximately equivalent in terms of information content.

Several different measures of concrete hardness are known, such as the Mohsscale. Hardness is seen as an "attribute" of objects that are difficult tophysically alter when subjected to different forms of deformation. Fully curedconcrete is a relatively hard material, as its hardness varies between 3 and 7Mohs. Although this measurement does not indicate anything relevant toconcrete, it bears a remarkable relationship to its strength. Hardness is not atrue property of materials, since it depends on certain properties of a material,such as ductility, resistance, rigidity, elasticity, viscosity, deformation, amongothers. Rather, it is a property that is attributed to any object capable ofresisting change when it is subject to abrasion or scratching. Objects such aswood, which can be easily scratched, have a lower hardness compared to steelor granite, since it is difficult to scratch them. Hardness of a concrete surfacesegment can be measured using a non-destructive test which consists ofevaluating the impact resistance of a concrete structural element. To performit, an instrument called Schmidt's hammer, also known as a sclerometer, isused. A scratch test can also be performed, which consists of scratching theconcrete surface with a series of 4 pencils, each one with a standardized pointand calibrated according to the Mohs scale. The measure of concretehardness used has no significant impact on the methods and techniquesdisclosed herein. A simple scale without unit from, say 0-100, is sufficient formost of the features discussed herein.

According to some aspects, the processing unit 420 in the control unit 130 isarranged to receive concrete maturity data indicating a concrete maturity levelof the concrete surface segment 160 from the one or more concrete maturitysensors 470 embedded in the concrete surface segment 160, and to adjust acontrol loop parameter of the control unit for driving the at least two drivewheels in dependence of the concrete maturity data. The control loopadjustment can be done continuously or at least regularly in order to optimize 19 operation to the current conditions. Given a concrete maturity level, andpotentially also a concrete recipe comprising the concrete composition and anyadditives, stored in the database 430 or received from an external source, anideal floor saw speed in the forward direction F can be determined byconsulting the database 430. The control unit 130 may then configure the drivewheels on the floor saw to move the floor in the ideal floor saw speed. Thisresults in a cutting speed which is near optimal for the circular cutting blade110, thereby minimizing cutting blade wear. lt is appreciated that this featurecan be implemented in combination with other features discussed herein orindependently from the other features discussed herein.

The sensor data reported over the first communication links 480 to the dataprocessing system 310 by the concrete sensors 470 indicates a currentmaturity state of the concrete slab. However, in some situations it may beadvantageous to be able to estimate a future maturity state of a concrete slab.

Figure 6 is a graph 600 which illustrates concrete maturity 610 over time, on atime scale of several hours. Concrete maturity can be estimated from sensordata, e.g., as a percentage relative to total maturity or to some other referencevalue. The maturing process is seldom an entirely linear process. lnstead, therate of change often varies over time. Nevertheless, its rate of change can beestimated, e.g., by low-pass filtering the sensor data or by applying moreadvanced signal processing operations such as a Kalman filter configured toestimate the evolution over time of the concrete maturity, e.g., as an averagerate of change 615. The control units 130 discussed herein may be configuredto generate extrapolated temperature and/or moisture level data from theconcrete maturity sensor data, and to predict a future onset and/or a futurecessation of the time slot for early entry sawing. Thus, a contractor can receiveinformation of an upcoming time slot for early entry sawing, thus greatly simplifying planning.

A given floor saw may be associated with a first range 620 of concrete maturitywhen processing is at its best, this range corresponds to a first time window 630 with an onset and a cessation time instant. lt is appreciated that the onset time instant and the cessation time instant are not necessarily determined ona second-basis. Rather the onset and cessation can be given in moreapproximate terms, e.g., on a half-hour basis or the like.

Another floor saw may be associated with another ideal range of concretematurity (possibly even overlapping the first range 620), this range then corresponds to a second time window.

The maturity values corresponding to the ideal time slots for early entry sawingwith a given type of floor saw can be stored in the control unit 130 and/or inthe database 430 in the control unit. Thus, an operator may configure whichfloor saw is to be used, and possibly also which circular cutting blade that iscurrently mounted on the saw, and then receive information regarding the idealtime slot for early entry sawing. According to an example, a visual indicatorcan be arranged as a display of the remote control device 310 or floor sawwhich indicates when it is time to start early entry sawing in a given area. Thisdisplay may also indicate a future point in time when the time slot is estimatedto start. The visual indicator may also be less advanced, e.g., just a green lightarranged on the floor saw, which is activated by the control unit 130 during thetime slot for ideal early entry sawing.

The harder the concrete is, the stronger the longitudinal force generated bythe circular cutting blade 110 due to the increased resistance from theconcrete. Thus, the database 430 or an equivalent database comprised in thecontrol unit 130 may comprise information which allows to translate betweena given drift or drift compensation and a concrete maturity level or measure ofconcrete hardness. The control unit 130 may thus be arranged to determine alevel of drift compensation applied via the at least two drive wheels 120, 120a,120b to reduce the difference between the current yaw motion of the floor sawand the desired yaw motion setting. The control unit 130 can then determine aconcrete hardness and/or concrete maturity level in dependence of thedetermined level of drift compensation and configure a desired speed of thefloor saw in the forward direction F in dependence of the hardness and/or concrete maturity level. Thus, minimizing tool wear or maximizing cutting 21 speed, or any trade-off there in-between, can be achieved by maintaining anideal cutting speed, i.e., machine speed in the forward direction F, independence of the concrete maturity level.

Glazing refers to an effect where the abrasive cutting segments on the cuttingblade become dull and stop cutting. Glazing occurs when the cutting segmentmatrix holding the abrasive particles overheat and cover the abrading particles,i.e., the diamonds. The risk of glazing is a function of the applied cutting bladecontact pressure, i.e., the force with which the cutting blade engages theconcrete to be cut and the rotation velocity of the cutting segments on the blade110. The contact pressure can be varied by adjusting wheel forces, and therotational velocity of the cutting blade can be controlled by, e.g., adjusting thecutting blade engine throttle. ln particular, the risk of glazing increases if thecutting blade is operated at high rotational velocity and low contact pressure.With higher contact pressure, a larger rotational velocity can normally betolerated and vice versa. This means that there is an undesired operatingregion where the risk of glazing is increased. The size and shape of thisundesired operating region depends on the type of cutting segment and on thematerial to be cut, i.e., the maturity level and recipe of the concrete. Thisundesired operating region may be configured in a memory accessible by thecontrol unit 130, and the control unit may then control the floor saw wheelforces and the rotational velocity of the cutting blade to avoid operation in theundesired operating region.

According to a first example, illustrated in Figure 10A, the undesired operatingregion 1000 is determined by two thresholds; A rotation velocity threshold ThVand a contact force threshold ThF. ln this case it is not desired to operate thefloor saw for prolonged periods of time above ThV and below ThF. ln case arotational velocity above ThV is desired, then the contact force F should beincreased to a value above ThF.

According to a second example, illustrated in Figure 10B, the undesiredoperating region 1010 starts at a first rotational velocity value ThV1 where the 22 corresponding undesired contact force F increases gradually up to a threshold value ThF at a corresponding tangential velocity value ThV2.

Each circular cutting blade 110 may be associated with a desired rotationspeed range or even an optimal rotation speed as function of cutting bladecontact pressure. Each blade is normally associated with a preferred range ofcontact pressure and corresponding blade rotation speed. The techniquesdisclosed herein allow for estimating a concrete maturity level, and from therea concrete hardness, which estimate can optionally be refined by also takingthe concrete recipe into account. Given the concrete hardness, the forwarddrive speed and/or wheel forces of the floor saw can be configured togetherwith the rotation speed of the cutting blade to obtain a desired cuttingcharacteristic outside of the undesired operating region or even at an optimalcombination of blade rotation speed and contact pressure. lt is understood that the optimality criterion can be based on either cuttingspeed, i.e., the floor saw speed in the forward direction, or cutting bladelifetime, or anywhere in-between. Thus, an operator can configure the desiredoptimality criterion, and the floor saw control unit 130 can then adjust theforward drive speed and blade rotation speed to optimize performance against the optimality criterion.

This way the tool lifetime can be extended, which is an advantage.Alternatively, the cutting speed, i.e., the floor saw speed in the forwarddirection, can be improved, which is also an advantage.

There is also disclosed herein a floor saw 100, 100a, 100b for early entrysawing in a maturing concrete surface segment 160. The floor saw comprisesa circular cutting blade 110 arranged transversally offset O from a centrum lineC, which centrum line C is aligned with a forward direction F of the floor saw.The floor saw further comprises at least two supporting wheels 120, 120a,120b arranged to support the floor saw on the concrete surface segment 160,wherein the supporting wheels 120, 120a, 120b are arranged to generate avariable floor saw speed in the forward direction. The floor saw further comprises a control unit 130 arranged to determine a measure of concrete 23 hardness of the maturing concrete surface segment, e.g. based on anestimated maturity level of the concrete, and to configure a desired speed ofthe floor saw in the forward direction F in dependence of the concretehardness. The control unit 130 is optionally arranged to determine the measureof concrete hardness at least of the maturing concrete surface segment basedon any of: a level of drift by the floor saw, a type or recipe of the concrete in the concrete surface segment and/or a concrete maturity level.

With reference to Figure 1 and Figure 2, there is also disclosed herein a floorsaw 100, 100a, 100b for early entry sawing in a maturing concrete surfacesegment 160. The floor saw comprises a circular cutting blade 110 arrangedtransversally offset O from a centrum line C, which centrum line C is alignedwith a forward direction F of the floor saw. The floor saw further comprises atleast two supporting wheels 120, 120a, 120b arranged to support the floor sawon the concrete surface segment 160, wherein the supporting wheels 120,120a, 120b are arranged to generate a variable floor saw speed in the forwarddirection. The floor saw further comprises a control unit 130 arranged todetermine a measure of concrete hardness of the maturing concrete surfacesegment, and to configure a desired speed of the floor saw in the forwarddirection F in dependence of the concrete hardness. Thus, in line with thediscussion above, this floor saw is able to optimize the cutting speed in theforward direction based on the determined concrete hardness. The desiredspeed corresponding to a given concrete hardness may be obtained, e.g., froma look up table or pre-determined function. The look-up table may bepopulated, e.g., by experimental data from one or more trials. lt is appreciatedthat this particular feature may be implemented as a stand-alone feature. Forinstance, the configuration of the desired speed is not dependent on any driftcompensation function, although the two features can be advantageouslycombined into a floor saw with automatic speed control and drift prevention.

According to aspects, the control unit 130 is arranged to determine themeasure of concrete hardness of the maturing concrete surface segmentbased on any of: a level of drift by the floor saw, a type or recipe of the concrete in the concrete surface segment and/or a concrete maturity level. 24 lt is an advantage that this variation in forward speed is continuously adjustedin dependence of the concrete hardness, thereby adjusting cutting operationto the current concrete hardness.

With reference to Figure 11, there is shown a floor saw 100 according to atleast some of the aspects discussed above. The floor saw is arranged for up-cut operation U. The cutting blade therefore acts as a resistance which thedriven supporting wheels 120 must overcome by a wheel force Fw in order togenerate a speed Vf in the forward direction F. The speed in the forwarddirection of course corresponds to a speed of the cutting blade through theconcrete surface segment. The relationship between wheel force Fw andspeed in the forward direction Vf can be used to determine an approximateconcrete hardness level. The harder the concrete becomes, the moreresistance is encountered by the circular cutting blade, and the more wheelforce is required to maintain a desired cutting speed. For instance, dataregarding estimated concrete hardness level can be gathered in a matrixindexed by wheel force Fw and speed in the forward direction Vf. Thus, givena wheel force value and a speed, a corresponding concrete hardness level canbe obtained. Different such matrixes can be generated for different types of concrete to further improve the estimate of concrete hardness.

Thus, the control unit 130 in Figure 11 may, according to some aspects, bearranged to determine the current speed of the floor saw 100 in the forwarddirection Vf indicating a speed of the circular cutting blade 110 through theconcrete surface segment 160. This speed can, e.g., be determined by a freerolling supporting wheel 120' via its rotational velocity Vw and its radius, by aradar sensor arranged on the floor saw, or by some form of positioning system,such as a global positioning system (GPS) receiver or an indoor positioning system based on deployed beacons.

The control unit 130 is also arranged to determine the wheel force Fwgenerated by the supporting wheels 120 in the forward direction. This can bedone, e.g., by measuring wheel slip as discussed in connection to Figure 5, i.e., the normalized difference in speed between the wheel rotation and the floor saw relative to the concrete surface, or more simply by measuringgenerated torque T by the motor driving the supporting driven wheels 120, or even more simply by measuring current or power drawn by an electric motor.

With reference also to Figure 12, the control unit 130 is, according to someaspects, configured to determine the concrete hardness level H based on thewheel force Fw and on the current speed in the forward direction Vf. This canbe done via a predefined function f1(), which may be in the form of an empiricallook-up table as discussed above. The function f1() can also be an analyticalor semi-analytical function determined based on, e.g., computer simulation. Bydetermining or estimating the wheel force Fw, and the speed of the cuttingblade Vf through the concrete, a measure of concrete hardness level can beobtained. This hardness level can then be used to optimize operations asdiscussed above.

The hardness level H can be taken as input to a second function f2() which isconfigured to determine a desired velocity Vf based on the hardness. Thus afeedback loop is closed which controls the cutting speed of the floor saw independence of the concrete hardness level. This means that, as the concretematures, the forward speed is adjusted to account for the variation in concretehardness level.

The control unit 130 is optionally further arranged to configure a rotationalvelocity of the circular cutting blade 110 in dependence of the concretehardness level and of the current speed in the forward direction Vf. This waycutting performance can be optimized to, e.g., avoid glazing as discussed inconnection to Figures 10A and 10B, or to maximize the lifetime of the cuttingblade, or to maximize the cutting speed, i.e., the speed Vf.

The control unit 130 may also arranged to obtain data indicating a specificationof the circular cutting blade 110, and to configure the desired speed of the floorsaw in the forward direction F in dependence of the specification. The datamay, e.g., be manually input by an operator, or read from a wirelessidentification tag on the circular cutting blade. This data can, for instance, indicate a type of cutting segments mounted on the circular cutting blade 110, 26 which can be used to determine a preferred contact pressure (which isproportional to the wheel force Fw), and a rotational velocity of the cuttingblade 110. lt is appreciated that these features can be implemented in combination withother features discussed herein or independently from the other featuresdiscussed herein.

According to some aspects, the control unit 130 is arranged to determine acurrent speed of the floor saw in the forward direction F and a desired speedof the floor saw in the forward direction F. The desired speed is determined independence of an estimated maturity level and/or hardness level of theconcrete surface segment 160 and/or in dependence of a measuredtemperature of the circular cutting blade 110. The control unit is also configuredto control the at least two drive wheels 120, 120a, 120b to reduce a differencebetween the current speed and the desired speed. lt is appreciated that thisfeature is independent of the other features discussed above, i.e., this featurecan be implemented as a stand-alone feature without requiring anymodification to the other features of the floor saw.

According to other aspects, the control unit 130 is arranged to receive concretematurity data indicating a concrete maturity level of the concrete surfacesegment 160 from an external concrete maturity sensor 470, to determine anonset of a suitable time slot for early entry sawing, i.e., the green zonediscussed above, based on the concrete maturity data, and to indicate theonset of the time window to an operator. The indication may, e.g., beconveniently transmitted to the remote control device 310 via the wireless link320. The indication may also comprise activating a visual indicator on the floorsaw, such as a green light. A red light on the floor saw can be activated outsideof the suitable time slot. lt is appreciated that this feature can be implementedin combination with other features discussed herein or independently from theother features discussed herein.

The floor saws discussed herein may furthermore comprise an arrangement configured to determine a weight and/or volume of accumulated dust or slurry 27 in a dust container 170 mounted on the floor saw as discussed above inconnection to Figure 1B. The control unit 130 may be arranged to detect whenthe weight and/or volume of accumulated dust or s|urry exceeds apreconfigured threshold and to transmit a signal to the remote control device310 indicating that the weight and/or volume of accumulated dust or s|urry isabove the preconfigured threshold. This way, an operator having the remotecontrol device 310 receives an indication when one of the floor saws hasaccumulated enough dust so as to warrant emptying the dust container. Theoperator can then stop the floor saw and empty the dust container. Theoperator then does not have to continuously monitor the dust containers to seeif they are full, since he receives the indication remotely. lt is appreciated thatthis feature can be implemented independently of the other features discussedherein. Thus, the signal indicating that the weight and/or volume ofaccumulated dust or s|urry in a dust container is above a preconfiguredthreshold can be sent to a remote control even if the floor saw does not implement, e.g., drift compensation.

Some vehicles such as certain cars are equipped with 'pilot assist' or 'lanekeeping' systems which assist a driver by maintaining the vehicle in the currentlane. However, for safety reasons, the driver always has to maintain manualcontrol the vehicle, e.g., by regularly moving the steering wheel, or keeping atleast one hand on the steering wheel. The floor saws discussed herein maybe arranged to perform a similar function. Thus, an operator may be requiredto perform manual control of, e.g., the steering of the floor saw, at leastintermittently. ln-between the floor saw may operate in a near autonomousmode, e.g., by going in a straight path towards a beacon as discussed above.Consequently, according to some aspects, the control unit 130 is arranged todetermine whether an operator is performing manual control of floor sawsteering and/or is in a position to perform manual control with short notice, andto trigger a warning signal and/or halt the floor saw in response to determiningthat an operator is not performing manual control of the floor saw steering. Thisalso encompasses detecting if an operator is at all present close to the floor saw, e.g., based on camera sensors or radar sensors. 28 lt is appreciated that these features are independent of the other featuresdiscussed above, i.e., this feature can be implemented as a stand-alonefeature without requiring any modification to the other features of the floor saw.

Figure 7 is a flow chart illustrating methods. There is illustrated a method forcontrolling operation of a floor saw 100, 100a, 100b for early entry sawing in amaturing concrete surface segment 160. The methods comprises providing S1a floor saw comprising a circular cutting blade 110 arranged transversallyoffset O from a centrum line C, which centrum line C is aligned with a forwarddirection F of the floor saw, wherein the floor saw further comprises at leasttwo supporting wheels 120, 120a, 120b arranged to support the floor saw onthe concrete surface segment 160 wherein at least one of the supportingwheels 120, 120a, 120b is arranged on an opposite side of the centrum line Ccompared to the circular cutting blade 110 and arranged to generate arespective variable wheel force. The method also comprises determining S2 acurrent yaw motion of the floor saw, and obtaining S3 a desired yaw motionsetting, and controlling S4 a difference between the wheel forces of thesupporting wheels to reduce a difference between the current yaw motion ofthe floor saw and the desired yaw motion setting.

Figure 8 schematically illustrates, in terms of a number of functional units, thegeneral components of a control unit 130, 420. Processing circuitry 810 isprovided using any combination of one or more of a suitable central processingunit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc.,capable of executing software instructions stored in a computer programproduct, e.g. in the form of a storage medium 830. The processing circuitry810 may further be provided as at least one application specific integratedcircuit ASIC, or field programmable gate array FPGA.

Particularly, the processing circuitry 810 is configured to cause the device 180to perform a set of operations, or steps, such as the methods discussed inconnection to Figure 6 and the discussions above. For example, the storagemedium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 29 830 to cause the device to perform the set of operations. The set of operationsmay be provided as a set of executabie instructions. Thus, the processingcircuitry 810 is thereby arranged to execute methods as herein disclosed.

The storage medium 830 may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

The device 130, 420 may further comprise an interface 820 forcommunications with at least one external device. As such the interface 820may comprise one or more transmitters and receivers, comprising analogueand digital components and a suitable number of ports for wireline or wireless communication.

The processing circuitry 810 controls the general operation of the control unit130, 420, e.g., by sending data and control signals to the interface 820 and thestorage medium 830, by receiving data and reports from the interface 820, and by retrieving data and instructions from the storage medium 830.

Figure 9 illustrates a computer readable medium 910 carrying a computerprogram comprising program code means 920 for performing the methodsillustrated in Figure 7, when said program product is run on a computer. Thecomputer readable medium and the code means may together form acomputer program product 900.

Claims

1. A floor saw (100, 100a, 100b) for early entry sawing in a maturingconcrete surface segment (160), the floor saw comprising a circular cuttingblade (110) arranged transversally offset (O) from a centrum line (C), whichcentrum line (C) is aligned with a forward direction (F) of the floor saw, the floorsaw further comprising at least two supporting wheels (120, 120a, 120b)arranged to support the floor saw on the concrete surface segment (160), asensor arrangement (140) configured to determine a current yaw motion of thefloor saw, and a control unit (130) configured to obtain a desired yaw motion setting, wherein at least one of the supporting wheels (120, 120a, 120b) is arrangedon an opposite side of the centrum line (C) compared to the circular cuttingblade (110) and arranged to generate a respective variable wheel force, and wherein the control unit (130) is arranged to control a difference between thewheel forces of the supporting wheels to reduce a difference between thecurrent yaw motion of the floor saw and the desired yaw motion setting.

2. The floor saw (100, 100a, 100b) according to claim 1, wherein the at leasttwo supporting wheels (120, 120a, 120b) are driven wheels, and wherein thecontrol unit (130) is arranged to control the difference between the wheelforces of the supporting wheels by controlling respective wheel torques and/orspeeds of the at least two driven wheels (120, 120a, 120b).

3. The floor saw (100, 100a, 100b) according to any previous claim,comprising a first drive wheel (120a) and a second drive wheel (120b), whereeach drive wheel is driven by a respective first and second electric machine(150a, 150b) controlled by the control unit (130).

4. The floor saw (100, 100a, 100b) according to claim 3, wherein the firstand second electric machine is arranged to be powered by an on-boardelectrical storage device (210).

5. The floor saw (100, 100a, 100b) according to any previous claim,comprising a first supporting wheel (120a) arranged on an opposite side of the 31 centrum line (C) compared to the circular cutting blade (110), where the firstsupporting wheel (120a) comprises a wheel brake arranged to be controlled by the control unit (130) to generate a negative wheel torque.

6. The floor saw (100, 100a, 100b) according to any previous claim,comprising a weight (220) and an actuator arranged to move the weighttransversal to the forward direction (F), wherein the control unit (130) isarranged to control the actuator to reduce a difference between the currentyaw motion of the floor saw and the desired yaw motion setting.

7. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe sensor arrangement (140) comprises an inertial measurement unit, ll\/IU, configured to detect the current yaw motion by the floor saw.

8. The floor saw (100, 100a, 100b) according to claim 7, wherein the ll\/IU isarranged distally mounted on a guiding arm (170) extending in the forward direction (F).

9. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe sensor arrangement (140) comprises one or more vision-based sensorsconfigured to detect the current yaw motion by the floor saw by changes in a forward direction view over time.

10. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe sensor arrangement (140) comprises a receiver configured to receive awireless signal from a beacon (450), and to detect the current yaw motion bythe floor saw and/or a current heading of the floor saw based on the received wireless signal.

11. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe sensor arrangement (140) comprises an electronic compass configured tomeasure the forward direction (F) of the floor saw in relation to magnetic north,wherein the control unit (130) is configured to determine the current yawmotion of the floor saw based on measurements of the forward direction (F) in relation to magnetic north over time. 32

12. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to receive concrete maturity data indicatinga concrete maturity level of the concrete surface segment (160) from aconcrete maturity sensor (470), and to adjust a control loop parameter of thecontrol unit for controlling at least one of the supporting wheels (120, 120a, 120b) in dependence of the received concrete maturity data.

13. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to receive the desired yaw motion setting viawireless radio link (320) from a remote control device (310).

14. The floor saw (100, 100a, 100b) according to claim 13, wherein theremote control device (310) is configured to transmit a desired yaw motionsetting corresponding to sawing along a straight line, or corresponding tosawing along an arcuate curve having a configurable radius, or correspondingto a path with a deviation defined by a number of degrees from a set course after a controlled turning maneuver.

15. The floor saw (100, 100a, 100b) according to claim 13 or 14, wherein theremote control device (310) is configured to control one or more further floorsaws (100) in addition to the floor saw.

16. The floor saw (100, 100a, 100b) according to any of claims 13-15,comprising an arrangement configured to determine a weight and/or volumeof accumulated dust or slurry in a dust container (170) mounted on the floorsaw, wherein the control unit (130) is arranged to detect when the weightand/or volume of accumulated dust or slurry exceeds a preconfiguredthreshold and to transmit a signal to the remote control device (310) indicatingthat the weight and/or volume of accumulated dust or slurry is above the preconfigured threshold.

17. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to determine a level of drift compensationapplied via the at least two supporting wheels (120, 120a, 120b) to reduce thedifference between the current yaw motion of the floor saw and the desired yaw motion setting, wherein the control unit (130) is arranged to determine a 33 concrete hardness level in dependence of the determined level of driftcompensation, and to configure a desired speed of the floor saw in the forwarddirection (F) in dependence of the concrete hardness level.

18. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to determine a current speed of the floor sawin the forward direction (F) and a desired speed of the floor saw in the forwarddirection (F), where the desired speed is determined in dependence of anestimated maturity level or hardness level of the concrete surface segment(160) and/or in dependence of a measured temperature of the circular cuttingblade (110), and to control the at least two drive wheels (120, 120a, 120b) to reduce a difference between the current speed and the desired speed.

19. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to determine whether an operator is inposition to perform manual control of floor saw steering, and to trigger awarning signal and/or halt the floor saw in response to determining that anoperator is not performing manual control of the floor saw steering.

20. The floor saw (100, 100a, 100b) according to any previous claim, whereinthe control unit (130) is arranged to receive concrete maturity data indicatinga concrete maturity level of the concrete surface segment (160) from aconcrete maturity sensor (470) arranged external to the floor saw, to determinean onset of a suitable time slot for early entry sawing based on the concretematurity data, and to indicate the onset of the time window to an operator.

21. A floor saw (100, 100a, 100b) comprising a control unit (130) arranged todetermine a level of drift compensation applied via one or more supportingwheels (120, 120a, 120b) to reduce the difference between a current yawmotion of the floor saw and a desired yaw motion setting, wherein the controlunit (130) is arranged to determine a concrete hardness level in dependenceof the determined level of drift compensation, and to configure a desired speedof the floor saw in a forward direction (F) in dependence of the concretehardness level. 34

22. A floor saw (100, 100a, 100b) comprising a control unit (130) arranged todetermine whether an operator is in position to perform manual control of floorsaw steering, and to trigger a warning signal and/or halt the floor saw inresponse to determining that an operator is not in position to perform manual control of the floor saw steering.

23. A floor saw (100, 100a, 100b) comprising a control unit (130) arranged toreceive concrete maturity data indicating a concrete maturity level at least of aconcrete surface segment (160) from an external concrete maturity sensor(470), to determine an onset of a suitable time slot for early entry sawing basedon the concrete maturity data, and to indicate the onset of the time window to an OpefatOf.

24. A floor saw (100, 100a, 100b) comprising an arrangement configured todetermine a weight and/or volume of accumulated dust or slurry in a dustcontainer (170) mounted on the floor saw, wherein the control unit (130) isarranged to detect when the weight and/or volume of accumulated dust orslurry exceeds a preconfigured threshold and to transmit a signal to a remotecontrol device (310) indicating that the weight and/or volume of accumulateddust or slurry is above the preconfigured threshold.

25. A floor saw (100, 100a, 100b) for early entry sawing in a maturingconcrete surface segment (160), the floor saw comprising a circular cuttingblade (110) arranged transversally offset (O) from a centrum line (C), whichcentrum line (C) is aligned with a forward direction (F) of the floor saw, the floorsaw further comprising at least two supporting wheels (120, 120a, 120b)arranged to support the floor saw on the concrete surface segment (160),wherein the supporting wheels (120, 120a, 120b) are arranged to generate avariable floor saw speed in the forward direction, the floor saw furthercomprising a control unit (130) arranged to determine a concrete hardnesslevel of the maturing concrete surface segment, and to configure a desiredspeed of the floor saw in the forward direction (F) in dependence of the concrete hardness level.

26. The floor saw (100, 100a, 100b) according to claim 25, wherein thecontrol unit (130) is arranged to determine the concrete hardness level of thematuring concrete surface segment (160) based on any of: a level of drift bythe floor saw, a type or recipe of the concrete in the concrete surface segment and/or a concrete maturity level.

27. The floor saw (100, 100a, 100b) according to claim 26, arranged for up-cut operation (U), wherein the control unit (130) is arranged to determine acurrent speed of the floor saw (100) in the forward direction (Vf) indicating aspeed of the circular cutting blade (110) through the concrete surface segment(160), and a wheel force (Fw) generated by the supporting wheels (120) in theforward direction (F), wherein the control unit (130) is configured to determinethe concrete hardness level (H) based on the wheel force (Fw) and on thecurrent speed in the forward direction (Vf).

28. The floor saw (100, 100a, 100b) according to claim 27, wherein thecontrol unit (130) is further arranged to configure a rotational velocity of thecircular cutting blade (110) in dependence of the concrete hardness level andof the current speed in the forward direction (Vf)..

29. The floor saw (100, 100a, 100b) according to any of claims 25-28,wherein the control unit (130) is arranged to obtain data indicating aspecification of the circular cutting blade (110), and to configure the desiredspeed of the floor saw in the forward direction (F) and/or the rotational velocityof the circular cutting blade in dependence of the specification.