Abstract:
A method is provided for operating a transport vehicle provided with a container with due regard to a weight of a received material in the container. The method includes receiving information associated to the weight of the received material in the container from an external source, and in response to the weight information controlling operation of the vehicle.

Description:
BACKGROUND AND SUMMARY 
     The present invention relates to a method for operating a transport vehicle provided with a container with due regard to a weight of a received material in said container. The invention is further directed to such a transport vehicle. 
     The present invention further relates to a method for controlling operation of a work site comprising a work machine configured for loading material at an elevated position above the ground and a transport vehicle provided with a container, which is configured for receipt of material from the work machine. The invention is further directed to such a work site system. 
     The invention is particularly directed to a transport vehicle configured for transportation of heavy material, such as earth, stones or gravel in areas where there are no roads, for example for transports in connection with road or tunnel building, sand pits, mines and similar environments. 
     The invention will below be explained for a transport vehicle in the form of a work machine of the type of an articulated hauler. This application should however only be regarded as a preferred example of a transport vehicle and the invention can be realized for other types of transport vehicles, such as a dump truck with a rigid frame. 
     It is known with an onboard weight measurement apparatus in an articulated hauler. In one such known apparatus, the weight is measured via a strain gage rigidly attached to a bogie beam in a bogie arrangement. Information of the measured weight is presented for an operator on a screen in the cab. More specifically, the weight of the payload is monitored in order to prevent overloading of the specific type of articulated hauler. 
     However, such a weight measurement apparatus does not achieve a required accuracy and reliability in aggressive environments in the long run. More specifically, the strain gage is exposed to dust, dirt and material and would therefore be subjected to wear and possibly failure in this aggressive environment. 
     It is desirable to achieve a method for operating a transport vehicle with due regard to a load weight, which is reliable, cost-efficient and suitable for application in an aggressive environment. 
     According to an aspect of the present invention, a method comprises the step of receiving information associated to the weight of the received material in said container from an external source, and in response to the weight information controlling operation of said vehicle. 
     Thus, the transport vehicle receives the weight information from the external source. The external source is configured to measure the weight of the material loaded on the container of the transport vehicle and communicate the information to the transport vehicle. In this way, the transport vehicle does not have to be provided with an onboard weight measurement apparatus. Thus, the invention creates conditions for an improved operation in response to the weight of the loaded material on the container while maintaining a cost efficient transport vehicle. 
     Further, by automatically controlling operation of the transport vehicle in response to the received weight information, an improved operation can be achieved in that different vehicle systems can be controlled accordingly in order to improve fuel efficiency, operator comfort etc. 
     In a work site, a plurality of transport vehicles moves between different designations for loading and unloading material. Further, loading vehicles, such as wheel loaders and excavators are positioned at different loading designations for loading the transport vehicles. 
     According to a preferred embodiment, the method comprises the step of receiving information associated to the weight of the received material from a work machine loading the material on the container. Thus, according to this embodiment, the loading vehicle (for example the wheel loader) forms the external source mentioned above. A loading vehicle, such as a wheel loader, is more suitable for being equipped with an onboard weight measurement system than an articulated hauler, since a load sensor can easily be arranged in connection with the hydraulic system for operating a bucket. 
     Thus, the loading vehicle is provided with an onboard weight measurement apparatus and comprises means for sending a signal to the transport vehicle with said weight information. Especially, both purchase and control of a fleet of work machines (comprising both transport vehicles and wheel loaders) can be cost-efficient. The cost efficiency is particularly evident for work sites comprising a larger number of transport vehicles than loading vehicles. 
     A wheel loader provided with such an onboard weight measurement apparatus for preventing overloading thereof is known. Thus, the embodiment above creates conditions for achieving a value of the weight of the loaded material for controlling the operation of the transport vehicle by using a known weight measurement apparatus and only providing the transport vehicle with minor structural features, such as an antenna, and corresponding software in a controller. 
     According to a further development, the method comprises the step of receiving information associated to the weight of the received material directly from the work machine loading the material on the container. Preferably, there is a wireless communication between the loading vehicle and the transport vehicle. This wireless communication is at least one-way, from the loading vehicle to the transport vehicle. According to an alternative or complement, the weight information is sent from the loading vehicle to a central station on the work site for further distribution to the transport vehicle. 
     According to a preferred embodiment, the method comprises the step of, in response to the weight information, controlling operation of said vehicle when said vehicle transports the received material to a designation. Preferably, at least one vehicle system, such as a suspension system or a powertrain, is automatically controlled. In this way, operation of the transport vehicle can be significantly improved. 
     Preferably, the specific control of the transport vehicle is set to a standard mode (default mode) associated to an unloaded container. After loading, a mode corresponding to the weight of the load in the container is determined, and the vehicle is controlled accordingly on its way to the unloading destination. 
     According to a development of the last-mentioned embodiment, the method comprises the step of interrupting the control of the transport vehicle operation in response to the weight information when the vehicle has reached the designation. In this way, the transport vehicle is again controlled in accordance with an empty container (i.e. according to the default mode). 
     It is desirable to achieve transport vehicle provided with a container, which is configured for receipt of material, configured for controlling its operation with due regard to a load weight, which is reliable, cost-efficient and suitable for application in an aggressive environment. 
     According to an aspect of the present invention, a transport vehicle comprises a means for wirelessly receiving information associated to a weight of a material received in the container and a controller operatively connected to said receipt means, wherein the controller is adapted for controlling for at least one system in the vehicle in response to the weight information. 
     It is desirable to achieve a method for controlling operation of a work site comprising a work machine configured for loading material at an elevated position above the ground and a transport vehicle provided with a container, which is configured for receipt of material from the work machine, which is reliable, cost-efficient and suitable for application in an aggressive environment. 
     According to an aspect of the present invention, a method comprises the steps of weighing a material and loading the material on the container, wirelessly transmitting information associated to the weight of the material to said transport vehicle, and in response to the transmitted weight information controlling operation of said transport vehicle. 
     It is desirable to achieve work site system comprising a work machine configured for loading material at an elevated position above the ground and a transport vehicle provided with a container for receiving material from the work machine, which is reliable, cost-efficient and suitable for application in an aggressive environment. 
     According to an aspect of the present invention, a work machine comprises a means for weighing the material which is loaded on the container and a means for sending a signal with information associated to the weight of the material, said transport vehicle comprises a means for receiving a signal with information associated to the weight of the material received in the container, and a controller operatively connected to said receipt means, wherein the controller is adapted for controlling at least one system in the vehicle in response to the weight information. 
     Other advantageous features and functions of various embodiments of the invention are set forth in the following description and in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained below, with reference to the embodiments shown on the appended drawings, wherein 
         FIG. 1  shows a wheel loader in a side view, 
         FIG. 2  shows an articulated hauler in a side view, 
         FIG. 3  shows an operation of the wheel loader and the articulated hauler on a work site, 
         FIG. 4  schematically shows a system for controlling operation of the articulated hauler, and 
         FIG. 5  shows a flow chart of an embodiment example of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a frame-steered work machine constituting a wheel loader  101  in a side view. The body of the wheel loader  101  comprises a front body section  102  and a rear body section  103 , which sections each has an axle  112 , 113  for driving a pair of wheels. The rear body section  103  comprises a cab  114 . The body sections  102 , 103  are connected to each other in such a way that they can pivot in relation to each other around a vertical axis by means of two first actuators in the form of hydraulic cylinders  104 , 105  arranged between the two sections. The hydraulic cylinders  104 , 105  are thus arranged one on each side of a horizontal centerline of the vehicle in a vehicle traveling direction in order to turn the wheel loader  101 . 
     The wheel loader  101  comprises an equipment  111  for handling objects or material. The equipment  111  comprises a load-arm unit  106  and an implement  107  in the form of a bucket fitted on the load-arm unit. A first end of the load-arm unit  106  is pivotally connected to the front vehicle section  102 . The implement  107  is pivotally connected to a second end of the load-arm unit  106 . 
     The load-arm unit  106  can be raised and lowered relative to the front section  102  of the vehicle by means of two second actuators in the form of two hydraulic cylinders  108 , 109 , each of which is connected at one end to the front vehicle section  102  and at the other end to the load-arm unit  106 . The bucket  107  can be tilted relative to the load-arm unit  106  by means of a third actuator in the form of a hydraulic cylinder  110 , which is connected at one end to the front vehicle section  102  and at the other end to the bucket  107  via a link-arm system  115 . 
       FIG. 2  shows an articulated hauler (also called frame-steered dumper)  201  in a side view. The articulated hauler comprises a front vehicle section  202  comprising a front frame  203 , a front wheel axle  204  and a cab  206  for a driver. The articulated hauler  201  also comprises a rear vehicle section  207  comprising a rear frame  208 , a front wheel axle  209 , a rear wheel axle  210  and a tiltable container  211 . 
     A first pivot joint  225  is adapted in order to allow the front frame  203  and the rear frame  208  to be pivoted relative to one another about an imaginary-longitudinal axis, that is to say an axis which extends in the longitudinal direction of the vehicle  201 . 
     The front frame  203  is connected to the rear frame  208  via a second joint  221  which allows the front frame  203  and the rear frame  208  to be pivoted relative to one another about a vertical axis  234  for steering (turning) the vehicle. Actuators in the form of a pair of hydraulic cylinders  224  are arranged on respective sides of the rotary joint  221  for steering the vehicle. The hydraulic cylinders are controlled by the driver of the vehicle via a wheel and/or a joystick (not shown). 
     The container  211  is connected to the rear frame  208  via an articulation (not shown) at a rear portion of the rear frame. A pair of tilting cylinders  232  are connected to the rear frame  208  with a first end and connected to the platform body  211  with a second end. The tilting cylinders  232  are positioned one on each side of the central axis of the vehicle in its longitudinal direction. The platform body  211  is therefore tilted in relation to the rear frame  208  on activation of the tilting cylinders  232 . 
     The container typically is in the form of a box with a closed bottom, side walls, a front wall and an open top. During dumping the contents slide out of the box onto the ground or into a waiting receptacle. 
     With reference to  FIG. 3 , an operation of the wheel loader  101  and the articulated hauler  201  is shown in a work site. The wheel loader  101  is used to scoop up material from a loading position (excavating a natural ground  301 ) with the bucket  107  and unload it onto the container  211  of the articulated hauler  201 . 
       FIG. 3  shows a driving pattern comprising a series of steps from excavation to loading onto the articulated hauler  201 . Specifically, the wheel loader  101  travels forward, see arrow  302 , to the natural ground  301  in a straight position, wherein the front and rear vehicle parts are in line. When it approaches the natural ground  301 , it thrusts into the natural ground, see arrow  303 . The lifting arm unit is raised, wherein the bucket  107  is filled with material from the natural ground. 
     When the excavation is finished, the wheel loader  101  is retreated from the excavating operation position at a high speed, see arrow  303  and the wheel loader is turned to the right (or to the left), see arrow  305 . The wheel loader  101  then moves forward, see arrow  306 , while turning hard to the left (or right), then straightens out the vehicle to travel to approach the articulated hauler  201 , see arrow  307 . The lifting arm unit  106  is raised, the bucket  107  tilted and the material is deposited on the container of the articulated hauler. When a loading operation of the dump truck  320  is finished, the wheel loader  101  moves away in reverse from the articulated hauler  201 , see arrow  308 , turns  309  to a stop position and is driven forwards again  310  towards the natural ground  301 . The operation of the wheel loader  101  is repeated until the container  211  is filled. 
     When the container  211  is filled up with material, the articulated hauler  201  is moved from its loading position  311  to a designation  313 , in the form of an unloading position, via a path  312 . The contents in the container  211  are unloaded at a position  314  by tilting the container  211 . 
       FIG. 4  shows a system  401  for controlling operation of the articulated hauler. The system  401  comprises the wheel loader  101  and the articulated hauler  201 . 
     The wheel loader  101  comprises means  403 ,  405 ,  407  for determining a weight of the material in the bucket  107 . Said weight determination means comprises at least one sensor  403  adapted for sensing a position of the bucket  107 . More specifically, a first position sensor is adapted to sense a vertical position of the bucket  107 , and more precisely the angular position of the lift arm  106  relative to the frame  102 . A second sensor is adapted to sense an angular position of the bucket  107  relative to the lift arm  106 . The first and second sensors may for example be formed by angular sensors arranged in the respective pivot joint, or by linear sensors arranged to detect a linear displacement of the respective cylinder. 
     Said weight determination means further comprises a sensor  405  adapted for sensing a pressure in the hydraulic system, which is indicative of the load exerted on the system. The sensor  405  is preferably adapted to sense a pressure in the lift cylinder  108 , 109 . 
     Said weight determination means further comprises a controller  407 , which is adapted to receive signals with position and pressure information from the sensors  403 ,  405 . The controller  407  comprises software for determining a weight of the material based on the information in the sensor signals and producing a corresponding weight signal. 
     The wheel loader  101  further comprises a means  409  for sending a weight signal produced by the controller  407 . The sending means  409  preferably comprises an antenna, which is operatively connected to the controller  407  and configured for transmitting electromagnetic waves, such as radio waves. 
     The articulated hauler  201  comprises a means  411  for receiving the weight signal from the wheel loader  101 . The receiving means  411  preferably comprises an antenna configured for receiving the electromagnetic waves. 
     The articulated hauler  201  further comprises a controller  413 , which is operatively connected to the antenna  411  for receiving the weight signal. The controller  411  comprises software for determining and producing an output signal to at least one vehicle system  415 ,  417  or vehicle component for controlling the same. 
     A first vehicle system is exemplified by a powertrain  415 . A power source in the form of an internal combustion engine (a diesel engine)  419  is adapted for propulsion of the hauler  201 . The powertrain further comprises a main gearbox  421  in the form of an automatic gearbox, which is operationally connected to an output shaft from the engine  419 . The powertrain further comprises an intermediate gearbox  423  (transfer gear box) for distributing driving power between the front axle  204  and the rear axles  209 , 210  (see  FIG. 2 ). 
     A first drive shaft (propeller shaft) extends in the longitudinal direction of the vehicle and is operationally connected between the transfer gearbox  423  and a central gear  425  (differential gear) in the wheel axle  204 . A pair of transverse drive shafts (stick axles) extends in opposite directions from the central gear  425 . Each of the transverse drive shafts drives a wheel. 
     A second vehicle system is exemplified by a suspension system  417 . The exemplified suspension system  417  is adapted to suspend the frame  203 , 208  on the axles  204 , 209 , 210 . Specifically, the suspension system  417  is configured for a continuous control in response to turns, slopes etc. 
     The controller  411  is further adapted to produce an output signal to an operator display means  427  in order to indicate the loaded weight for the driver. The controller  411  is further adapted to produce an output signal to an electronic storage in the form of a memory  429  for storing weight information regarding an individual operator, a work shift etc. 
     Embodiment examples of a method for controlling the articulated hauler will be described below. 
     According to a first example, see  FIG. 5 , the method starts in box  501 . The method comprises the step of receiving information associated to the weight of the received material in said container from an external source  503 , and in response to the weight information controlling operation of said vehicle  505 . Specifically, the method comprises the step of receiving information associated to the weight of the received material from the work machine  101  loading the material on the container. Preferably, the method comprises the step of wirelessly receiving information associated to the weight of the received material. 
     The method further comprises the step of, in response to the weight information, controlling operation of said vehicle when said vehicle transports the received material to a designation  313 , see the travel path  312  in  FIG. 3 . More specifically, the method further comprises the step of controlling the suspension system  417  of the transport vehicle in response to the weight information. The method preferably comprises the step of automatically controlling operation of said transport vehicle in response to the weight information. 
     The method further comprises the step of interrupting the control of the transport vehicle operation in response to the weight information  507  when the vehicle has reached the designation  313 . Especially, the method comprises the step of interrupting the control of the transport vehicle operation in response to the weight information when the material has been unloaded at the designation. The method then goes back to the block  501  for starting the procedure again in a subsequent loading phase. 
     In addition to the automatic control of a vehicle system, the method preferably comprises the step of presenting information associated to the weight for a driver of said transport vehicle for manually controlling operation of said vehicle in response thereto. Preferably, information is shown on a display in the cab. For example, the driver may get notice of when the container is completely filled, or filled to a desired weight limit, wherein he can immediately start forwarding the transport vehicle to the desired destination. 
     According to a second embodiment example of the method, which may be regarded as an alternative, or complement to the first embodiment example, the method comprises the step of controlling the powertrain  415  of the transport vehicle in response to the weight information. More specifically, the method comprises the step of controlling the power source  419  of the transport vehicle in response to the weight information. More specifically, the method comprises the step of selecting an engine curve from a plurality of available curves and controlling an internal combustion engine in accordance with the selected engine curve. 
     According to an alternative or complement to any of the embodiment examples described above, the method comprises the step of selecting a gear change mode from a plurality of available gear change modes and controlling the gearbox  421  in accordance with the selected gear change mode. 
     According to a further alternative or complement to any of the embodiment examples described above, the method comprises the step of controlling a differential gear of the transport vehicle in response to the weight information. 
     According to a further alternative or complement to any of the embodiment examples described above, the method comprises the step of controlling a cruise control function in the transport vehicle in response to the weight information. 
     According to a further alternative or complement to any of the embodiment examples described above, the method comprises the step of storing the weight information in the electronic storage  429  associated to the individual driver of said transport vehicle. 
     Further, according to an alternative, the method comprises the step of receiving the material in a plurality of loading steps and in association with each loading step receiving information associated to a weight of the received material in each step. According to a second alternative, the method comprises the step of receiving the material in a plurality of loading steps and in association with a last loading step receiving information associated to a weight of the totally received material from all the steps. A loading step represents a fill of the bucket of the work machine. Accordingly, the method comprises the step of wirelessly receiving at least one signal with information associated to a weight of the received material. 
     The invention is not in any way limited to the above described embodiments, instead a number of alternatives and modifications are possible without departing from the scope of the following claims. 
     According to a further alternative or complement to any of the embodiment examples described above, a signal is sent to the driver for alerting him when the container is filled to a desired limit. The driver can then immediately start the transport of the material to the destination. Thus, the loading cycle time can be reduced. 
     According to a further alternative or complement to any of the embodiment examples described above, the gearbox is automatically put in a forward gear when the container is filled to a desired limit. In this way, the loading cycle time can be reduced. 
     According to a further alternative or complement to any of the embodiment examples described above, a brake that is actuated during the loading phase is automatically released when the container is filled to a desired limit. In this way, the loading cycle time can be reduced.