EP3093400B1

EP3093400B1 - Method of controlling a wheel loader

Info

Publication number: EP3093400B1
Application number: EP16169375.9A
Authority: EP
Inventors: Kwang-Seok Park; Yeon-Haeng HEO; Woo-Seok Oh; Soo-Kyung HEO; In-Dong Kim; Sung-Il Kim
Original assignee: Doosan Infracore Co Ltd
Current assignee: HD Hyundai Infracore Co Ltd
Priority date: 2015-05-12
Filing date: 2016-05-12
Publication date: 2018-08-01
Anticipated expiration: 2036-05-12
Also published as: EP3093400A1

Description

BACKGROUND

1. Field

The invention relates to a method of controlling a wheel loader. More particularly, the invention relates to a method of determining a work state of a wheel loader to automatically control the wheel loader.

2. Description of the Related Art

In general, an industrial vehicle such as a wheel loader is widely used to excavate sand, gravel, and the like and load it into a dump truck.
When the wheel loader performs a series of work states, work load, which consumes a power output of an engine of the wheel loader, may changes according to the work states. However, it is difficult and very burdensome to manually select an optimal power mode adapted for the changing work states. These work states may be detected and then the engine or a transmission of the wheel loader may be controlled automatically based on the detected results, thereby improving fuel efficiency and preventing deterioration of operating performance. Accordingly, a new technique capable of precisely detecting a current work state and a current work load state in real time and automatically control the wheel loader may be required. EP 2 868 901 A1 relates to a wheel loader includes detectors and a controller. The detectors include at least an accelerator pedal angle detector (46) that detects an accelerator displacement.

SUMMARY

The invention sets-out to solve the above-mentioned problems of the art and provides a method of controlling a wheel loader, which reduces fuel consumption and improves operating performance.
According to embodiments of the invention, in a method of controlling a wheel loader, signals representing a state of work currently performed by the wheel loader, are received from sensors installed in the wheel loader. One or more signals are selected of the received signals, the one or more signals able to be used to determine whether or not to be within a respective one of a plurality of individual load areas, wherein the individual load areas are divided according to work load which consumes a power output of an engine during a series of work states performed by the wheel loader. Output values representing as to whether or not to be within the respective one of the plurality of individual load areas, are calculated by using the selected signal. The output values are analyzed to determine whether or not a current load state is one of a travelling work state, an excavation work state and a travelling and boom raising work. An engine power output is controlled such that an upper limit of an output torque of the engine is limited to be smaller than a maximum output torque of the engine based on the determination result.
Controlling the engine power output includes performing a first torque control mode such that the upper limit of the output torque in the first torque control mode is be limited to a first ratio of the maximum output torque of the engine when the current work state is determined as the travelling and boom raising work state, performing a second torque control mode such that the upper limit of the output torque in the second torque control mode is be limited to a second ratio smaller than the first ratio of the maximum output torque of the engine when the current work state is determined as the excavation work state, and performing a third torque control mode such that the upper limit of the output torque in the third torque control mode is be limited to a third ratio smaller than the second ratio of the maximum output torque of the engine when the current work state is determined as the excavation work state.
In example embodiments, the first ratio may range between 85% and 95%, the second ratio may range between 70% and 85%, and the third ratio may range between 40% and 70%.
In example embodiments, the method may further include performing an engine speed control in a range of a predetermined engine speed or more.
In example embodiments, at least one of a boom cylinder pressure signal, an FNR signal, a main pressure signal of a hydraulic pump, a vehicle speed signal, a boom position signal and a torque converter speed ratio signal may be used to determine whether or not to be within a light load area and a heavy load area of the wheel loader, and at least one of the main pressure signal of the hydraulic pump, the vehicle speed signal, a boom position signal and the torque converter speed ratio signal may be used to determine whether or not to be within a medium load area of the wheel loader
In example embodiments, calculating the output values may include performing prediction algorithms obtained through training on the selected signal. The prediction algorithm may include neural network algorithm.
In example embodiments, the method may further include analyzing the output values to determine whether or not the current load state is an acceleration travelling work state and controlling the engine power output such that the output torque of the engine is limited in an initial acceleration section and an engine speed is limited in a conversion section between an acceleration section and a constant speed section, when the current work state is determined as the acceleration travelling work state.
In example embodiments, wherein controlling the engine power output in the acceleration travelling work state may include limiting the output torque of the engine and the engine speed in a middle acceleration section.
In example embodiments, the method may further include analyzing the output values to determine whether or not the current load state is the excavation work state, and controlling the engine power output without causing a tire slip when the current work state is determined as the excavation work state.
In example embodiments, controlling the engine power output in the excavation work state may include controlling the engine power in the excavation work state comprising limiting the output torque of the engine and the engine speed.
According to example embodiments, whether or not a current work state of a wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state or whether or not the current work state of the wheel loader is one of an acceleration work state and the excavation work state may determined by using prediction algorithms obtained through training such as neural network algorithms, and may automatically control an engine power output based on the determination result.
Thus, the time and burden spent on calculations in order to determine a load state of work currently performed by the wheel loader may be reduced and the accuracy of the determinations may be improved. Further, the engine may be controlled based on the finally determined work load state to thereby improve operating performance and fuel efficiency.
At least some of the above and other features of the invention are set out in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. FIGS. 1 to 17 represent non-limiting, example embodiments as described herein.

FIG. 1 is a side view illustrating a wheel loader in accordance with example embodiments.
FIG. 2 is a block diagram illustrating a system for controlling the wheel loader in FIG. 1.
FIG. 3 is a block diagram illustrating a control apparatus for a wheel loader in accordance with example embodiments.
FIG. 4 is a block diagram illustrating a signal selector, an individual load area determiner and a load state determiner of the control apparatus in FIG. 3.
FIG. 5 is a view illustrating a neural network circuit in the individual load area determiner in FIG. 4.
FIG. 6 is a view illustrating a signal transfer in each layer of the neural network in FIG. 5.
FIG. 7 is graphs illustrating engine torque curves respectively preset in torque control modes stored in a storage portion of the control apparatus in FIG. 3.
FIG. 8 is a graph illustrating an engine torque curve in an acceleration travelling work state of a wheel loader.
FIG. 9 is a graph illustrating a vehicle speed in the acceleration travelling work state in FIG. 8.
FIG. 10 is a graph illustrating an engine torque curve in an excavation work state of a wheel loader.
FIG. 11 is a graph illustrating a frequency count versus engine speed in the excavation work state in FIG. 10.
FIG. 12 is a flow chart illustrating a method of controlling a wheel loader in accordance with example embodiments.
FIG. 13 is a view illustrating V-shape driving of a wheel loader in accordance with example embodiments.
FIG. 14 is graphs illustrating output values representing whether or not to be within a respective one of individual load areas in each work state in the V-shape driving of FIG. 13.
FIG. 15 is a graph illustrating a final load state obtained from the output values of FIG. 14.
FIG. 16 is a flow chart illustrating a method of controlling an engine of a wheel loader in accordance with example embodiments.
FIG. 17 is a flow chart illustrating a method of controlling an engine of a wheel loader in accordance with example embodiments.

DESCRIPTION OF EMBODIMENTS

Various example embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some example embodiments are shown. The present inventive concept may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this description will be thorough and complete, and will fully convey the scope of the present inventive concept to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.
It will be understood that when an element or layer is referred to as being "on," "connected to" or "coupled to" another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. Like numerals refer to like elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, third, fourth etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present inventive concept.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present inventive concept. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
FIG. 1 is a side view illustrating a wheel loader in accordance with example embodiments. FIG. 2 is a block diagram illustrating a system for controlling the wheel loader in FIG. 1.
Referring to FIGS. 1 and 2, a wheel loader 10 may include a front body 12 and a rear body 14 connected to each other. The front body 12 may include a work apparatus and a front wheel 160. The rear body 14 may include a driver cabin 40, an engine bay 50 and a rear wheel 162.
The work apparatus may include a boom 20 and a bucket 30. The boom 20 may be freely pivotally attached to the front body 12, and the bucket 30 may be freely pivotally attached to an end portion of the boom 20. The boom 20 may be coupled to the front body 12 by a pair of boom cylinders 22, and the boom 20 may be pivoted upwardly and downwardly by expansion and contraction of the boom cylinders 22. A tilt arm 34 may be freely rotatably supported on the boom 20, almost at its central portion. One end portion of the tilt arm 34 may be coupled to the front body 12 by a pair of bucket cylinders 32 and another end portion of the tilt arm 34 may be coupled to the bucket 30 by a tilt rod, so that the bucket 30 may pivot (crowd and dump) as the bucket cylinder 32 expands and contracts.
The front body 12 and the rear body 14 may be rotatably connected to each other through a center pin 16 so that the front body 12 may swing side to side with respect to the rear body 14 by expansion and contraction of a steering cylinder (not illustrated).
A travel apparatus for propelling the wheel loader 10 may be mounted at the rear body 14. An engine 100 may be provided in the engine bay 50 to supply an output power to the travel apparatus. The travel apparatus may include a torque converter 120, a transmission 130, a propeller shaft 150, axles 152, 154, etc. The output power of the engine 100 may be transmitted to the front wheel 160 and the rear wheel 162 through the torque converter 120, the transmission 130, the propeller shaft 150 and the axles 152 and 154, and thus the wheel loader 10 may travels.
In particular, the output power of the engine 100 may be transmitted to the transmission 130 through the torque converter 120. An input shaft of the torque converter 120 may be connected to an output shaft of the engine 100, and an output shaft of the torque converter 120 may be connected to the transmission 130. The torque converter 120 may be a fluid clutch device including an impeller, a turbine and a stator. The transmission 130 may include hydraulic clutches that shift speed steps between first to fourth speeds, and rotation of the output shaft of the torque converter 120 may be shifted by the transmission 130. The shifted rotation may be transmitted to the front wheel 160 and the rear wheel 162 through the propeller shaft 150 and the axles 152 and 154 and thus the wheel loader may travel.
The torque converter 120 may have a function to increase an output torque with respect to an input torque, i.e., a function to make the torque ratio 1 or greater. The torque ratio may decrease with an increase in the torque converter speed ratio e (=Nt/Ni), which is a ratio of the number of rotations Nt of the output shaft of the torque converter 120 to the number of rotations Ni of the input shaft of the torque converter 120. For example, if travel load is increased while the vehicle is in motion in a state where the engine speed is constant, the number of rotations of the output shaft of the torque converter 120, i.e., the vehicle speed may be decreased. At this time, the torque ratio may be increased and thus the vehicle may be allowed to travel with a greater travel driving force (traction force).
The transmission 130 may include a forward hydraulic clutch for forward movement, a reverse hydraulic clutch for reverse movement, and first to fourth hydraulic clutches for the first to the fourth speeds. The hydraulic clutches may be each engaged or released by pressure oil (clutch pressure) supplied via a transmission control unit (TCU) 140. The hydraulic clutches may be engaged when the clutch pressure supplied to the hydraulic clutches is increased, while the hydraulic clutches may be released when the clutch pressure is decreased.
When travel load is decreased and the torque converter speed ratio e is increased to be equal to or greater than a predetermined value eu, a speed step may be shifted by one step. On the other hand, when travel load is increased and the torque converter speed ratio e is decreased to be equal to or less than a predetermined value ed, the speed step may be shifted by one step.
The transmission 130 may be operable in a manual transmission mode or in a plurality of auto transmission modes. The transmission mode may be determined by a changed by manipulation of a mode shift lever (not illustrated). For example, the transmission 130 may include manual transmission mode, 1-4 auto transmission mode and 1-3 auto transmission mode. When the manual transmission mode is selected, a speed step may be selected by a transmission shift lever. When the 1-4 auto transmission mode or the 1-3 auto transmission mode is selected, a speed step may be automatically changed between speed steps equal to or less than a speed step selected by the transmission shift lever.
A variable capacity hydraulic pump 200 for supplying a pressurized hydraulic fluid to the boom cylinder 22 and the bucket cylinder 32 may be mounted at the rear body 14. The variable capacity hydraulic pump 200 may be driven using a portion of the power outputted from the engine 100. For example, the output power of the engine 100 may drive the hydraulic pump 200 for the work apparatus and a hydraulic pump (not illustrated) for the steering cylinder via a power take-off (PTO) such as a gear train 110.
A pump control device (EPOS, Electronic Power Optimizing System) may be connected to the variable capacity hydraulic pump 200, and a discharge fluid from the variable capacity hydraulic pump 200 may be controlled by the pump control device. A main control valve (MCV) including a boom control valve 210 and a bucket control valve 212 may be installed on a hydraulic circuit of the hydraulic pump 200. The discharge fluid from the hydraulic pump 200 may be supplied to the boom cylinder 22 and the bucket cylinder 32 through the boom control valve 210 and the bucket control valve installed in a hydraulic line 202 respectively. The main control valve (MCV) may supply the discharge fluid from the hydraulic pump 200 to the boom cylinder 22 and the bucket cylinder 32 according to a pilot pressure in proportion to an operation rate of an operating lever.
A maneuvering device may be provided within the driver cabin 40. The maneuvering device may include an accelerator pedal 142, a brake pedal 144, an FNR travel lever, the operating levers for operating the cylinders such as the boom cylinder 22 and the bucket cylinder 32, etc.
As mentioned above, the wheel loader 10 may include a traveling operating system for driving the travel apparatus via the PTO and a hydraulic operating system for driving the work apparatus such as the boom 20 and the bucket 30 using the output power of the engine 100.
Further, a control apparatus 300 for the wheel loader 10 such as a portion of a vehicle control unit (VCU) or a separate control unit may be mounted in the rear body 14. The control apparatus 300 may include an arithmetic processing unit having a CPU which executes a program, a storage device such as a memory, other peripheral circuit, and the like.
The control apparatus 300 may receive signals from various sensors (detectors) which are installed in the wheel loader 10. For example, the control apparatus 300 may be connected to an engine speed sensor 102 for detecting a rotational speed of the engine, an accelerator pedal detection sensor 143 for detecting an operation amount of the accelerator pedal 142, a brake pedal detection sensor 145 for detecting an operation amount of the brake pedal 144, an FNR travel lever position sensor 146 for detecting a manipulation position of the FNR travel lever, for example, the speed steps, forward (F), neutral (N) and reverse (R), and a parking detection sensor for detecting a selection of a parking switch.
Additionally, the control apparatus 300 may connected to a rotational speed sensor 122a for detecting the number of rotations Ni of the input shaft of the torque converter 120, a rotational speed sensor 122b for detecting the number of rotations Nt of the output shaft of the torque converter 120, and a vehicle speed sensor 132 for detecting a rotational speed of an output shaft of the transmission 130, i.e., a vehicle speed v.
Further, the control apparatus 300 may be connected to a pressure sensor 204 installed in the hydraulic line in front end of the main control valve (MCV) to detect a pressure of the discharge fluid from the hydraulic pump 200, and a boom cylinder pressure sensor 222 for detecting a cylinder head pressure at a head of the boom cylinder 22. Furthermore, the control apparatus 300 may be connected to a boom angle sensor 224 for detecting a rotational angle of the boom 20 and a bucket angle sensor 234 for detecting a rotational angle of the bucket 30.
The signals detected by the sensors may be inputted into the control apparatus 100, as indicated by arrows in FIG. 2. As mentioned later, the control apparatus 300 may select one or more signals of the signals received from the sensors installed in the wheel loader 10, perform prediction algorithms obtained through training such as neural network algorithms to calculate output values representing whether or not to be within individual work load areas and analyze the output values to determine a load state of a current work or a current work state of the wheel loader 10. Further, the control apparatus 300 may output a control signal to an engine control unit (ECU), the transmission control unit (TCU) 140, and the pump control device (EPOS), etc, to selectively control the engine 100, the transmission 130, the hydraulic pump 200, etc., based on the determined work load state or work state.
Hereinafter, the control apparatus for controlling the wheel loader will be explained.
FIG. 3 is a block diagram illustrating a control apparatus for a wheel loader in accordance with example embodiments. FIG. 4 is a block diagram illustrating a signal selector, an individual load area determiner and a load state determiner of the control apparatus in FIG. 3. FIG. 5 is a view illustrating a neural network circuit in the individual load area determiner in FIG. 4. FIG. 6 is a view illustrating a signal transfer in each layer of the neural network in FIG. 5. FIG. 7 is graphs illustrating engine torque curves respectively preset in torque control modes stored in a storage portion of the control apparatus in FIG. 3. FIG. 8 is a graph illustrating an engine torque curve in an acceleration travelling work state of a wheel loader. FIG. 9 is a graph illustrating a vehicle speed in the acceleration travelling work state in FIG. 8. FIG. 10 is a graph illustrating an engine torque curve in an excavation work state of a wheel loader. FIG. 11 is a graph illustrating a frequency count versus engine speed in the excavation work state in FIG. 10.
Referring to FIGS. 3 to 11, a control apparatus for a wheel loader 300 may include a work load determiner 310, a control signal generator 320 and a storage portion 330.
The work load determiner 310 may determine a load state of work currently performed by the wheel loader 10 or a state of work currently performed by the wheel loader 10. The control signal generator 320 may determine a control type, for example, an output torque control of an engine, an rpm control of an engine, a transmission control of a transmission, etc., based on the determined load state of the current work or the state of the current work. The storage portion 330 may store data required for learning in a predictive model and calculation in a neural network algorithm which are performed in the work load determiner 310, a control map required for determination of a control signal which is performed in the control signal generator 320, etc.
In example embodiments, the work load determiner 310 may include a signal receiver 312, a signal selector 314, an individual load area determiner 316 and a load state determiner 318.
The signal receiver 312 may receive the signals capable of representing a state of work from the sensors installed in the wheel loader 10. For example, the signal receiver 312 may receive a boom cylinder pressure signal from the boom cylinder pressure sensor 222, an FNR signal from the FNR travel lever position sensor 146, a main pressure signal from the pressure sensor 204 of the hydraulic pump 200, a vehicle speed signal from the vehicle speed sensor 132, a boom position signal from the boom angle sensor 224, a torque converter speed ratio (ratio of the number of rotations Ni of the input shaft and the number of rotations Nt of the output shaft) signal from the rotational speed sensors 122a and 122b, an accelerator pedal position signal from the accelerator pedal detection sensor 143, etc. However, it may be understood that the signals received in the signal receiver 312 may not be limited thereto, and various signals able to be used in determining a load state of work of the wheel loader or a work state of the wheel loader may be received in the signal receiver.
Further, the signal receiver 312 may receive a selection signal of an operator. The operator may operate an operation lever or a button to select a manual mode or an auto mode. When the auto mode is selected by the operator, the control apparatus for the wheel loader according to example embodiments may operate to determine the state of a current work of the wheel loader and automatically control the wheel loader.
The signal receiver 312 may include a data post processing portion. The data post processing portion may filter the inputted sensor signals to remove noise and normalize the signals.
The signal selector 314 may select one or more signals able to be used to determine whether or not a load state of work which is currently being performed by the wheel loader is within a respective one of a plurality of individual load areas, for example, a respective one of at least four individual load areas, and may output the selected signal(s) to corresponding individual determining circuits (NN_1, NN_2, NN_3, NN_4) of the individual load area determiner 316. The signal selector 314 may select one or more signals able to be used to determine whether or not the load state of work currently performed by the wheel loader is within a respective one of at least first to fourth individual load areas which are divided according to work load which consumes the power output of the engine during a series of work states. For example, the individual load areas (individual load states) may include a light load area, a medium load area, a heavy load area and an acceleration/inclined-ground load area according to the work load which consumes the power output during a series of work states performed by the wheel loader.
At least one signal selected from the group consisting of the received signals may be an indicator effectively representing a specific load state, i.e., at least one of the light load area, the medium load area, the heavy load area and the acceleration/inclined-ground load area.
The boom cylinder pressure signal may be an indicator directly representing a load state of work which is currently performed by the wheel loader, because the boom cylinder pressure signal is determined depending on a weight of sand, gravel and the like loaded in the bucket 30, a height of the boom 20, etc. The boom cylinder pressure signal may be used to determine a traveling work state and a multiple work state (traveling and boom raising work state) of a current work of the wheel loader.
The FNR signal may be an indicator distinguishing a shift between work states such as an initiation of a reverse traveling work state after an excavation work state or a swift between forward and reverse traveling work states during a traveling work state. The FNR signal may be used to determine a traveling work state and a multiple work state (traveling and boom raising work state) of a current work of the wheel loader.
The main pressure signal of the hydraulic pump, that is, an input end pressure of the MCV, may be an indicator representing an excavation work state or an operation of the boom 20 and the bucket 30, because the main pressure is maintained at a constant initial pressure when the operator does not operate the boom/bucket operation levers. The main pressure signal of the hydraulic pump may be used to determine a traveling work state, a multiple work state (traveling and boom raising work state) and an excavation work state of a current work of the wheel loader.
The vehicle speed signal may be an indicator representing a travel speed of the wheel loader. The vehicle speed signal may be used to determine a traveling work state, a multiple work state (traveling and boom raising work state) and an excavation work state of a current work of the wheel loader.
The boom position signal may be an indicator distinguishing a work state between a traveling work state, an excavation work state and a dumping work state depending on the boom position difference threrebetween. The boom position signal may be used to determine a traveling work state, a multiple work state (traveling and boom raising work state) and an excavation work state of a current work of the wheel loader.
The torque converter speed ratio may be an indicator representing the excavation work state and an inclined-ground travelling work state depending on a travel load of the wheel loader. The torque converter speed ratio may be used to determine a traveling work state, a multiple work state (travelling and boom raising work state), an excavation work state and an acceleration (inclined-ground) travelling work state.
The accelerator pedal position signal may be an indicator representing an acceleration intention of the operator. The accelerator pedal position signal may be used to determine an acceleration travelling work state.
The individual load area determiner 316 may include a plurality of the individual determining circuits. For example, the individual load area determiner 316 may include first to fourth individual determining circuits. The first to fourth individual determining circuits may calculate output values which represent whether or not to be within the first to fourth individual load areas respectively, using the selected signals. The first to fourth individual determining circuits may calculate the output signals respectively using machine learning.
Machine learning may be related to the ability to make data-driven predictions or decisions after training. For example, machine leaning may include neural networks approach, statistical approach, structural approach, fuzzy logic approach, decision tree approach, template matching approach, etc. The neural networks approach may be a method that learns mapping between inputs and outputs and processes data based on connection weights between inputs and outputs. The decision tree approach may be a method that generates a decision tree through learning and processes data based on the decision tree. Support vector machine may be used in supervised learning methods, and may be a method that, in many hyperplanes that might classify some given data, chooses the hyperplane that has the largest distance to the nearest training-data point of any class and processes data. The statistical approach may be classified into Supervised learning and Unsupervised learning. The neural networks approach may be classified into supervised learning, unsupervised learning, and reinforcement learning.
In example embodiments, the first to fourth individual determining circuits may perform prediction algorithms obtained through training to output scale values which represent the first to fourth individual load areas respectively.
The first individual determining circuit may include a light load neural network determiner NN_1 which performs neural network algorithms to calculate an output value representing as to whether or not the current work load belongs within a light load area. The light load neural network determiner NN_1 may receive the boom cylinder pressure signal, the FNR signal, the main pressure signal of the hydraulic pump, the vehicle speed signal, the boom position signal and the torque converter speed ratio signal from the signal selector 314. The light load neural network determiner NN_1 may perform neural network algorithms to calculate a first output value representing whether or not a load area of work currently performed by the wheel loader is within the light load area. For example, the first output value may be a probability value representing whether or not the current work load corresponds to the light load state. The first output value may be quantified as a number between 0 and 1.
The second individual determining circuit may include a medium load neural network determiner NN_2 which performs neural network algorithms to calculate an output value representing as to whether or not the current work load belongs within a medium load area. The medium load neural network determiner NN_2 may receive the main pressure signal of the hydraulic pump, the vehicle speed signal, the boom position signal and the torque converter speed ratio signal from the signal selector 314. The medium load neural network determiner NN_2 may perform neural network algorithms to calculate a second output value representing whether or not a load area of work currently performed by the wheel loader is within the medium load area. For example, the second output value may be a probability value representing whether or not the current work load corresponds to the medium load state.
The third individual determining circuit may include a heavy load neural network determiner NN_3 which performs neural network algorithms to calculate an output value representing as to whether or not the current work load belongs within a heavy load area. The heavy load neural network determiner NN_3 may receive the boom cylinder pressure signal, the FNR signal, the main pressure signal of the hydraulic pump, the vehicle speed signal, the boom position signal and the torque converter speed ratio signal from the signal selector 314. The heavy load neural network determiner NN_3 may perform neural network algorithms to calculate a third output value representing whether or not a load area of work currently performed by the wheel loader is within the heavy load area. For example, the third output value may be a probability value representing whether or not the current work load corresponds to the heavy load state.
The fourth individual determining circuit may include an acceleration/inclined-ground load neural network determiner NN_4 which performs neural network algorithms to calculate an output value representing as to whether or not the current work load belongs within an acceleration/inclined-ground load area. The acceleration/inclined-ground load neural network determiner NN_4 may receive the torque converter speed ratio and the accelerator pedal position signal from the signal selector 314. The acceleration/inclined-ground load neural network determiner NN_4 may perform neural network algorithms to calculate a fourth output value representing whether or not a load area of work currently performed by the wheel loader is within the acceleration/inclined-ground load area. For example, the fourth output value may be a probability value representing whether or not the current work load corresponds to the acceleration/inclined-ground load state.
In example embodiments, the light load neural network determiner NN_1, the medium load neural network determiner NN_2, the heavy load neural network determiner NN_3 and the acceleration/inclined-ground neural network determiner NN_4 may include neural network circuits that performs neural network algorithms and calculates an output value representing an individual load state, respectively.
As illustrated in FIGS. 5 and 6, the neural network circuit may include multilayer perceptrons having a multi-input layer, a hidden layer and an output layer. Neurons may be arranged in each layer, and the neurons in each layer may be connected by connection weights. Input data may be inputted to the neurons in the input layer and transferred to the output layer though the hidden layer.
Training the neural network algorithm may be a process of tuning the interconnection weights between each nodes in order to minimize an error between an expectation value and an output value of the neural network algorithms for a specific input (actual detected data). For example, backpropagation algorithm may be used for training the neural networks. Accordingly, the neural network circuits of the individual neural network determiners (NN_1, NN_2, NN_3, NN_4) may vary the connection weights between the input layer, the hidden layer and the output layer using the collected data to provide neural network algorithms as prediction models.
Thus, the neural network circuit may perform the neural network algorithms obtained through training and calculate an output value which represents the individual load state.
The load state determiner 318 may analyze the output values from the first to fourth individual determining circuits to determine a load state of work currently performed by the wheel loader 10 or a state of work currently performed by the wheel loader 10. The load state determiner 318 may perform post-processing such as weighted applications on the output values from the individual neural network determiners (NN_1, NN_2, NN_3, NN_4) and output a final result value.
For example, the load state determiner 318 may analyze the output values to determine a current load state of work currently performed by the wheel loader 10. Accordingly, the load state determiner 318 may determine which one of the light load state, the medium load state, the heavy load state and the acceleration/inclined-ground load state is the load state of work currently performed by the wheel loader 10.
The load state determiner 318 may consider additional signals received from other sensors to determine a current state of work currently performed by the wheel loader 10. Accordingly, the load state determiner 318 may determine a current load state or a current work state of the wheel loader 10.
The control signal generator 320 may output a control signal based on the determined current load state or the determined current work state of the wheel loader 10. The control signal may be used to selectively control the engine 100, the transmission 130, the hydraulic pump 200, etc. For example, the control signal generator 320 may output a control signal for controlling engine output torque, engine rpm, transmission speed step, transmission timing, etc.
Accordingly, the control signal generator 320 may control the engine 100 and the transmission 130 based on the finally determined work load state or work state to thereby improve operating performance and fuel efficiency.
The storage portion 330 may include a first storage portion 332 connected to the work load determiner 310 and storing data required to determine a work load state, and a second storage portion 334 connected to the control signal generator 320 and storing data required to generate the control signal. The first storage portion 332 may store data required for training and performing the neural network algorithms. The second storage portion 334 may store engine torque map, engine rpm map, transmission swift control map, etc., required for determining the control signal. As illustrated in FIG. 7, the second storage portion 334 may store engine torque curves T1, T2, T3 in accordance with torque control modes.
In example embodiments, the control signal generator 320 may determine whether or not the determined current work state of the wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state, and output an engine power control signal for controlling the engine depending on the determined result.
The control signal generator 320 may output a first engine power control signal for performing a first torque control mode (high torque control mode) when the current work state is the travelling and boom raising work state. The engine control unit (ECU) may receive the first engine power control signal and adjust an amount of fuel injection to control the engine power output that an upper limit of an output torque of the engine is limited to be smaller than a maximum output torque of the engine.
The control signal generator 320 may output a second engine power control signal for performing a second torque control mode (middle torque control mode) when the current work state is the excavation work state. The engine control unit (ECU) may receive the second engine power control signal and adjust the fuel injection amount to control the engine power output that the upper limit of the output torque of the engine is limited to be smaller than the maximum output torque of the engine.
The control signal generator 320 may output a third engine power control signal for performing a third torque control mode (low torque control mode) when the current work state is the travelling work state. The engine control unit (ECU) may receive the third engine power control signal and adjust the fuel injection amount to control the engine power output that the upper limit of the output torque of the engine is limited to be smaller than the maximum output torque of the engine.
As illustrated in FIG. 7, a first torque curve T1 may represent a power output capacity of the engine in the first torque control mode. An upper limit of the output torque in the first torque control mode may be limited to a first ratio with respect to a maximum output torque Tm of the engine. The first ratio may range between 85% and 95%. For example, the upper limit of the output torque in the first torque control mode may be limited to 90 percent of the maximum output torque of the engine.
A second torque curve T2 may represent a power output capacity of the engine in the second torque control mode. An upper limit of the output torque in the second torque control mode may be limited to a second ratio less than the first ratio with respect to the maximum output torque Tm of the engine. The second ratio may range between 70% and 85%. For example, the upper limit of the output torque in the second torque control mode may be limited to 80 percent of the maximum output torque of the engine.
A third torque curve T3 may represent a power output capacity of the engine in the third torque control mode. An upper limit of the output torque in the third torque control mode may be limited to a third ratio less than the second ratio with respect to the maximum output torque Tm of the engine. The third ratio may range between 40% and 70%. For example, the upper limit of the output torque in the third torque control mode may be limited to 50 percent of the maximum output torque of the engine.
In the first to third torque control modes, an engine speed control may be performed in a range of a predetermined engine speed or more. For example, an engine speed may be controlled such that the engine speed may be limited at a range over a rated speed Nr at which the engine reaches its maximum engine power output (rated power output). Additionally, the engine speed in each of the torque control modes may be limited to be a predetermined engine speed smaller than a maximum speed of the engine. For example, a maximum speed in each of the first to third torque control modes may be limited to be smaller than the maximum speed of the engine. Further, the maximum speed in the second torque control mode may be limited to be smaller than the maximum speeds in the first and third torque control modes.
According to operation characteristics of the wheel loader, the wheel loader may require a large torque during the multiple work state such as the travelling and boom raising work state, and the performance of the wheel loader in the travelling work state may be more dependent on the engine speed (rpm) than the large torque. For example, in V-shape driving of the wheel loader, a higher accelerating ability may cause unnecessary fuel consumption. Accordingly, the output torque of the engine may be controlled to be limited depending on the work state of the wheel loader, thereby improving fuel efficiency.
In example embodiments, the control signal generator 320 may determine whether or not the determined current work state of the wheel loader is one of an acceleration travelling work state and an excavation work state and output an engine control signal for controlling an engine power output depending on the determined result.
The control signal generator 320 may output a fourth engine power control signal for performing an engine power control mode when the current work state is the acceleration travelling work state. The engine control unit (ECU) may receive the fourth engine power control signal and limit an output torque of the engine or an engine speed to control the engine power output.
As illustrated in FIGS. 8 and 9, a maximum torque curve Tmax may represent an obtainable maximum output torque of the engine, and a control torque curve for an acceleration travelling work state may be compared with a torque curve in a conventional power mode. The output torque of the engine may be limited in an initial acceleration section I of the acceleration travelling work state, the output torque of the engine and the engine speed may be limited in a middle acceleration section II, the engine speed may be limited in a conversion section III, and the engine speed may be limited in a constant speed section IV. The limited output torque of the engine in the initial acceleration section I and the middle acceleration section II may be smaller than a limited output torque of the engine in the conventional power mode. The limited engine speed in the middle acceleration section II and the conversion section III may be smaller than a limited engine speed in the conventional power mode. For example, an optimal range of the limited output torque of the engine and the limited engine speed may be determined through an empirical or simulation method.
The control signal generator 320 may output a fifth engine power control signal for performing an engine power control mode when the current work state is the excavation work state. The engine control unit (ECU) may receive the fifth engine power control signal and limit the output torque of the engine or the engine speed to control the engine power output.
As illustrated in FIGS. 10 and 11, a maximum torque curve Tmax may represent an obtainable maximum output torque of the engine, and a control torque curve for an excavation work state may be compared with a torque curve in a conventional power mode. The output torque of the engine and the engine speed may be limited in a middle excavation section II' in a certain period of time (for example, 0.5 seconds) after an initial excavation section I' and a final excavation section III' of the excavation work state. The limited output torque of the engine and the engine speed in the middle excavation section II' and the final excavation section III' may be smaller than a limited output torque of the engine and a limited engine speed in the conventional power mode (section II and section III). For example, an optimal range of the limited output torque of the engine and the limited engine speed may be determined through an empirical or simulation method.
The control signal generator 320 may output a sixth engine power control signal for performing an engine power control mode when the current work state is the travelling and boom raising work state, the inclined-ground travelling work state or an even-ground travelling work state. The engine control unit (ECU) may receive the sixth engine power control signal and limit the output torque of the engine or the engine speed to control the engine power output.
According to operation characteristics of the wheel loader, a conventional engine power output of the wheel loader may be unnecessarily excessive in a certain period of time (for example, 1.5 seconds) after the initial acceleration section from a stop state, and thus, the engine power output in these sections may be forcibly limited to maximize fuel efficiency without deteriorating acceleration performances. Additionally, an output balance between the traveling operating system and the hydraulic operating system may be an importance matter in the excavation work state, and thus, the engine power output may be controlled with 1 step quick down control without a tire slip, thereby improving operating performance and fuel efficiency. Further, the travelling and boom raising work state or the inclined-ground travelling work state may require maximum power output conditions, and thus, an optimized power output curve may be applied in these work states, and the engine power output may be limited to be lower in the even-ground travelling work state, thereby improving fuel efficiency.
As mentioned above, the control apparatus for a wheel loader 300 may select signals capable of effectively representing the individual load state (light load area, medium load area, heavy load area, acceleration/inclined-ground load area) of signals received from sensors installed in the wheel loader 10 and determine a load state of a current work or a current work state by using prediction algorithms obtained through training such as neural network algorithms. Additionally, the control apparatus 300 may determine whether or not the determined current work state of the wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state, and output an engine power control signal for controlling the engine power output depending on the determined result. Further, the control apparatus 300 may determine whether or not the determined current work state of the wheel loader is one of an acceleration travelling work state and an excavation work state and output an engine control signal for controlling an engine power output or the engine speed depending on the determined result.
Thus, the time and burden spent on calculations in order to determine a load state of work currently performed by the wheel loader may be reduced and the accuracy of the determinations may be improved. Further, the engine and the transmission may be controlled based on the finally determined work load state to thereby improve operating performance and fuel efficiency.
Hereinafter, a method of controlling a wheel loader using the control apparatus in FIG. 3 will be explained.
FIG. 12 is a flow chart illustrating a method of controlling a wheel loader in accordance with example embodiments.
Referring to FIGS. 3, 4 and 12, first, signals representing a state of work currently performed by a wheel loader (S100).
The control apparatus for a wheel loader 300 may receive signals capable of representing a work state from sensors installed in the wheel loader. For example, the signal receiver 312 of the work load determiner 310 may receive a boom cylinder pressure signal, an FNR signal, a main pressure signal of a hydraulic pump, a vehicle speed signal, a boom position signal, a torque converter speed ratio signal, an accelerator pedal position signal, etc.
Then, one or more signals able to be used to determine whether or not to be within a respective one of a plurality of individual load areas, of the received signals may be selected (S110).
The signal selector 314 may select one or more signals able to be used to determine whether or not the current work state is within a respective one of at least first to fourth individual load areas and output the selected signal to corresponding individual determining circuits (NN_1, NN_2, NN_3, NN_4) of the individual load area determiner 316.
The first to fourth individual load areas (individual load states) may correspond to a light load area, a medium load area, a heavy load area and an acceleration/inclined-ground load area according to work load which consumes the power output during a series of work states performed by the wheel loader. The received signals may be classified according to whether the signal effectively represents a specific load state, i.e., at least one of the light load area, the medium load area, the heavy load area and the acceleration/inclined-ground load area.
For example, the boom cylinder pressure signal, the FNR signal, the main pressure signal of the hydraulic pump, the vehicle speed signal, the boom position signal and the torque converter speed ratio signal of the received signals may be used to determine whether or not to be within the light load area and the heavy load area of the wheel loader, and thus may be inputted into the light load neural network NN_1 and the heavy load neural network NN_3 of the individual load area determiner 316.
The main pressure signal of the hydraulic pump, the vehicle speed signal, the boom position signal and the torque converter speed ratio signal may be used to determine whether or not to be within the medium load area, and thus may be inputted into the medium load neural network determiner NN_2 of the individual load area determiner 316.
The torque converter speed ratio signal and the accelerator pedal position signal may be used to determine whether or not to be within the acceleration/inclined-ground load area, and thus may be inputted into the acceleration/inclined-ground neural network determiner NN_4 of the individual load area determiner 316.
Then, neural network algorithms obtained through training may be performed on the selected signals to determine whether or not to be within the respective one of the plurality of the individual load areas (S120).
The light load neural network determiner NN_1, the medium load neural network determines NN_2, the heavy load neural network determiner NN_3 and the acceleration/inclined-ground neural network determiner NN_4 of the individual load area determiner 316 may perform neural network algorithms on the selective signals to calculate output values representing as to whether or not the current work load belongs within the light load area, the medium load area, the heavy load area and the acceleration/inclined-ground load area respectively.
Then, the output values may be analyzed to determine a load state of work currently performed by the wheel loader (S130).
The load state determiner 318 may analyze the output values to determine which one of the light load state, the medium load state, the heavy load state and the acceleration/inclined-ground load state is the load state of work currently performed by the wheel loader 10.
The load state determiner 318 may consider additional signals received from other sensors to determine a current state of work currently performed by the wheel loader 10.
Then, a power output of the engine of the wheel loader may be controlled depending on whether or not the determined current work state of the wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state or depending on whether or not the determined current work state of the wheel loader is one of an acceleration travelling work state and an excavation work state (S140). A method of controlling the engine power output of the wheel loader according to example embodiments will be explained later with reference to FIGS. 16 and 17.
Hereinafter, a method of determining a load state of a series of work states in V-shape driving of a wheel loader using the control method in FIG. 12 will be explained.
FIG. 13 is a view illustrating V-shape driving of a wheel loader in accordance with example embodiments. FIG. 14 is graphs illustrating output values representing whether or not to be within a respective one of individual load areas in each work state in the V-shape driving of FIG. 13. FIG. 15 is a graph illustrating a final load state obtained from the output values of FIG. 14. For your reference, FIGS. 14 and 15 include a graph of a boom cylinder pressure versus time in the V-shape driving.
Referring to FIGS. 13 to 15, a wheel loader 10 may perform V-shape driving which is one of driving methods to load a subject material such as sand (S) into a dump truck (T). In the V-shape driving, the wheel loader 10 may perform sequentially a series of work states, i.e., a forward travelling work state (a), an excavation work state (b), a reverse travelling work state (c), a forward travelling and boom raising work state (d), a dumping work state (e), and a reverse travelling and boom down work state (f).
As illustrated in FIG. 14, whether or not to be within individual load areas may be determined for each work state in the V-shape driving. A light load neural network determiner NN_1 may calculate an output value representing as to whether or not to be within a light load area with respect to a series of the work states (a∼f). A medium load neural network determiner NN_2 may calculate an output value representing as to whether or not to be within a medium load area with respect to a series of the work states (a∼f). A heavy load neural network determiner NN_3 may calculate an output value representing as to whether or not to be within a heavy load area with respect to a series of the work states (a∼f). An acceleration/inclined-ground load neural network determiner NN_4 may calculate an output value representing as to whether or not to be within a heavy load area with respect to a series of the work states (a∼f).
As illustrated in FIG. 15, the output values may be synthetically analyzed to determine a load state of work currently being performed by the wheel loader 10. A load state determiner 318 may determine which one of the light load state, the medium load state, the heavy load state and the acceleration/inclined-ground load state is the load state of a series of the work states (a∼f) currently performed by the wheel loader 10.
In the V-shape driving of the wheel loader, the forward travelling work state (a), the reverse travelling work state (c) and the reverse travelling and boom down work state (f) may be determined as the light load state, the excavation work state (b) may be determined as the medium load state, and the forward travelling and boom raising work state (d) may be determined as the heavy load state. Further, an inclined-ground travelling work state and an acceleration travelling work state of the work states performed by the wheel loader may be determined as the acceleration/inclined-ground load state.
While example embodiments have been particularly shown and described with the V-shape driving, it will be understood that the present inventive concept may be applied to various other driving, e.g., load and carry driving, I-cross driving, etc.
FIG. 16 is a flow chart illustrating a method of controlling an engine of a wheel loader in accordance with example embodiments.
Referring to FIGS. 3, 4, 7 and 16, first, it may be determined whether or not a current work state of a wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state (S141, S143, S145).
In example embodiments, a series of work states performed by the wheel loader may be divided and determined using prediction algorithms obtained through training such as neural network algorithms. Signals capable of representing a state of work from sensors installed in the wheel loader may be used to determine a current work state performed by the wheel loader in real time. Output values calculated by a light load neural network determiner NN_1, a medium load neural network determiner NN_2 and a heavy light load neural network determiner NN_3 may be analyzed to determine whether or not a current work state of a wheel loader is one of a travelling work state, an excavation work state and a travelling and boom raising work state.
Then, when the current work state is determined as the travelling work state, a low torque control mode may be performed (S142).
The control signal generator 320 may output an output control signal for performing the low torque control mode when the current work state is determined as the travelling work state. An engine control unit (ECU) may receive the engine power control signal and adjust the fuel injection amount to control an engine power output that an upper limit of the output torque of the engine is limited to be smaller than a maximum output torque of the engine.
A power output capacity of the engine in the low torque control mode may be controlled to follow the torque curve T3 in FIG. 7. An upper limit of the output torque in the low torque control mode may be limited to smaller than the maximum output torque Tm of the engine. For example, the upper limit of the output torque in the low torque control mode may be limited to 50 percent of the maximum output torque of the engine.
Then, when the current work state is determined as the excavation work state, a middle torque control mode may be performed (S144).
The control signal generator 320 may output an output control signal for performing the middle torque control mode when the current work state is determined as the excavation work state. The engine control unit (ECU) may receive the engine power control signal and adjust the fuel injection amount to control an engine power output that an upper limit of the output torque of the engine is limited to be smaller than a maximum output torque of the engine.
A power output capacity of the engine in the middle torque control mode may be controlled to follow the torque curve T2 in FIG. 7. An upper limit of the output torque in the middle torque control mode may be limited to smaller than the maximum output torque Tm of the engine. For example, the upper limit of the output torque in the middle torque control mode may be limited to 80 percent of the maximum output torque of the engine.
Then, when the current work state is determined as the travelling and boom raising work state, a high torque control mode may be performed (S146).
The control signal generator 320 may output an output control signal for performing the high torque control mode when the current work state is determined as the travelling and boom raising work state. The engine control unit (ECU) may receive the engine power control signal and adjust the fuel injection amount to control an engine power output that an upper limit of the output torque of the engine is limited to be smaller than a maximum output torque of the engine.
A power output capacity of the engine in the high torque control mode may be controlled to follow the torque curve T1 in FIG. 7. An upper limit of the output torque in the high torque control mode may be limited to smaller than the maximum output torque Tm of the engine. For example, the upper limit of the output torque in the high torque control mode may be limited to 90 percent of the maximum output torque of the engine.
In example embodiments, in the low, middle and high torque control modes, an engine speed control may be performed in a range of a predetermined engine speed or more. For example, an engine speed may be controlled such that the engine speed may be limited at a range over a rated speed Nr at which the engine reaches its maximum engine power output (rated power output). Additionally, the engine speed in each of the torque control modes may be limited to a predetermined ratio with respect to a maximum speed of the engine.
FIG. 17 is a flow chart illustrating a method of controlling an engine of a wheel loader in accordance with example embodiments.
Referring to FIGS. 3, 4, 8 to 12 and 17, first, it may be determined whether or not a current work state of a wheel loader is one of an excavation work state and an acceleration travelling work state (S151, S153).
In example embodiments, a series of work states performed by the wheel loader may be divided and determined using prediction algorithms obtained through training such as neural network algorithms. Signals capable of representing a state of work from sensors installed in the wheel loader may be used to determine a current work state performed by the wheel loader in real time. Output values calculated by a light load neural network determiner NN_1, a medium load neural network determiner NN_2, a heavy light load neural network determiner NN_3 and an acceleration/inclined-ground neural network determiner NN_4 may be analyzed to determine whether or not a current work state of a wheel loader is one of an excavation work state and an acceleration travelling work state.
Then, when the current work state is determined as the acceleration travelling work state, an engine power control mode may be performed (S152).
The control signal generator 320 may output an engine power control signal for performing the engine power control mode when the current work state is the acceleration travelling work state. The engine control unit (ECU) may receive the engine power control signal and limit an output torque of the engine or an engine speed to control the engine power output.
As illustrated in FIGS. 8 and 9, the output torque of the engine may be limited in an initial acceleration section I of the acceleration travelling work state, the output torque of the engine and the engine speed may be limited in a middle acceleration section II, the engine speed may be limited in a conversion section III, and the engine speed may be limited in a constant speed section IV. The limited output torque of the engine in the initial acceleration section I and the middle acceleration section II may be smaller than a limited output torque of the engine in the conventional power mode. The limited engine speed in the middle acceleration section II and the conversion section III may be smaller than a limited engine speed in the conventional power mode. For example, an optimal range of the limited output torque of the engine and the limited engine speed may be determined through an empirical or simulation method.
Then, when the current work state is determined as the excavation work state, an engine power control mode may be performed (S154).
The control signal generator 320 may output an engine power control signal for performing the engine power control mode when the current work state is the excavation work state. The engine control unit (ECU) may receive the engine power control signal and limit the output torque of the engine or the engine speed to control the engine power output.
As illustrated in FIGS. 10 and 11, the output torque of the engine and the engine speed may be limited in a middle excavation section II' in a certain period of time (for example, 0.5 seconds) after an initial excavation section I' and a final excavation section III' of the excavation work state. The limited output torque of the engine and the engine speed in the middle excavation section II' and the final excavation section III' may be smaller than a limited output torque of the engine and a limited engine speed in the conventional power mode (section II and section III). For example, an optimal range of the limited output torque of the engine and the limited engine speed may be determined through an empirical or simulation method.
In example embodiments, when the current work state is determined as the travelling and boom raising work state, the inclined-ground travelling work state or an even-ground travelling work state, an engine power control mode may be performed.
The travelling and boom raising work state or the inclined-ground travelling work state may require maximum power output conditions, and thus, an optimized power output curve may be applied in these work states, and the engine power output may be limited to be lower in the even-ground travelling work state, thereby improving fuel efficiency.
As mentioned above, the control apparatus for a wheel loader may determine a load state of a current work or a current work state using prediction algorithms obtained through training such as neural network algorithms, and may automatically control the engine power output based on the determination result.
Thus, the time and burden spent on calculations in order to determine a load state of work currently performed by the wheel loader may be reduced and the accuracy of the determinations may be improved. Further, the engine may be controlled based on the finally determined work load state to thereby improve operating performance and fuel efficiency.
The foregoing is illustrative of example embodiments of the invention and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the present inventive concept. Accordingly, all such modifications are intended to be included within the scope of the present inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be construed as limited to the specific example embodiments disclosed, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the appended claims.

Claims

A method of controlling a wheel loader (10), comprising:
receiving signals representing a state of work currently performed by the wheel loader (10), from sensors (102, 143, 145, 146) installed in the wheel loader (10);

selecting one or more signals of the received signals, the one or more signals able to be used to determine whether or not to be within a respective one of a plurality of individual load areas, wherein the individual load areas are divided according to work load which consumes a power output of an engine during a series of work states performed by the wheel loader (10);

calculating output values representing as to whether or not to be within the respective one of the plurality of individual load areas, by using the selected signal;

analyzing the output values to determine whether or not a current load state is one of a travelling work state, an excavation work state and a travelling and boom raising work state; and

controlling an engine power output such that an upper limit of an output torque of the engine is limited to be smaller than a maximum output torque of the engine based on the determination result,

characterized in that controlling the engine power output comprises

performing a first torque control mode such that the upper limit of the output torque in the first torque control mode is be limited to a first ratio of the maximum output torque of the engine, when the current work state is determined as the travelling and boom raising work state (S146);

performing a second torque control mode such that the upper limit of the output torque in the second torque control mode is be limited to a second ratio smaller than the first ratio of the maximum output torque of the engine, when the current work state is determined as the excavation work state (S144); and

performing a third torque control mode such that the upper limit of the output torque in the third torque control mode is be limited to a third ratio smaller than the second ratio of the maximum output torque of the engine, when the current work state is determined as the travelling work state (S142).
The method of claim 1, wherein the first ratio ranges between 85% and 95%, the second ratio ranges between 70% and 85%, and the third ratio ranges between 40% and 70%.
The method of claim 1, further comprising performing an engine speed control in a range of a predetermined engine speed or more.
The method of claim 1, wherein at least one of a boom cylinder pressure signal, an FNR signal, a main pressure signal of a hydraulic pump, a vehicle speed signal, a boom position signal and a torque converter speed ratio signal is used to determine whether or not to be within a light load area and a heavy load area of the wheel loader (10), and at least one of the main pressure signal of the hydraulic pump, the vehicle speed signal, a boom position signal and the torque converter speed ratio signal is used to determine whether or not to be within a medium load area of the wheel loader (10)
The method of claim 1, wherein calculating the output values comprises performing prediction algorithms obtained through training on the selected signal.
The method of claim 5, wherein the prediction algorithm comprises neural network algorithm.
The method of claim 1, further comprising:
analyzing the output values to determine whether or not the current load state is an acceleration travelling work state; and

controlling the engine power output such that the output torque of the engine is limited in an initial acceleration section and an engine speed is limited in a conversion section between an acceleration section and a constant speed section, when the current work state is determined as the acceleration travelling work state.
The method of claim 7, wherein controlling the engine power output in the acceleration travelling work state comprises limiting the output torque of the engine and the engine speed in a middle acceleration section.
The method of claim 7, further comprising:
analyzing the output values to determine whether or not the current load state is the excavation work state; and

controlling the engine power output without causing a tire slip, when the current work state is determined as the excavation work state.
The method of claim 9, wherein controlling the engine power output in the excavation work state comprises controlling the engine power in the excavation work state comprising limiting the output torque of the engine and the engine speed.