Control Device, Control Method, and Work Machine

The present disclosure relates to a control device, a control method, and a work machine.

Priority is claimed on Japanese Patent Application No. 2022-134211, filed Aug. 25, 2022, the content of which is incorporated herein by reference.

Patent Document 1 discloses a control device that detects a tilt angle of an operation lever of work equipment by two detection units, compares the detected tilt angles, determines whether or not there is an abnormality on the basis of a comparison result, and controls the work equipment on the basis of a detection result of a tilt angle that is smaller in a case where there is the abnormality. The two detection units disclosed in Patent Document 1 have characteristics in which one detection unit decreases a voltage of a detection signal as an angle increases and the other detection unit increases the voltage of the detection signal as the angle increases. The control device determines whether or not there is an abnormality by comparing a total value of the two detection signals with a normal value.

Patent Document 1: Japanese Unexamined Patent Application, First Publication

In a case where it is determined that there is an abnormality, the control device disclosed in Patent Document 1 controls the work equipment based on a detection result of the smaller angle between the detection results of the two detection units. Therefore, for example, in a case where one detection unit is normal, there is a problem that the work equipment may not be operated in a case where an abnormality occurs such that only a signal corresponding to a neutral position can be output in an abnormal detection unit.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a control device, a control method, and a work machine capable of appropriately dealing with a case where an abnormality occurs in the detection of a tilt amount of an operation lever of the work equipment.

According to an aspect of the present disclosure, there is provided a control device of a work machine including work equipment, the control device including: an acquisition unit configured to acquire a first detection signal output according to a tilt amount of an operation lever by a first tilt amount sensor configured to detect the tilt amount of the operation lever of the work equipment tilted from a neutral position in a first direction or a second direction opposite to the first direction, and a second detection signal output according to the tilt amount by a second tilt amount sensor configured to detect the tilt amount; and a control unit configured to determine whether or not the first detection signal and the second detection signal are a value corresponding to the neutral position at a time of start of the work machine, generate and output a predetermined control signal for controlling the work equipment based on the first detection signal in a case where both of the first detection signal and the second detection signal are the value corresponding to the neutral position, and in a case where any one of the first detection signal or the second detection signal is not the value corresponding to the neutral position, generate and output the control signal based on the other of the first detection signal or the second detection signal, and output predetermined information corresponding to a case where the one is not the value corresponding to the neutral position from a predetermined output unit.

According to an aspect of the present disclosure, there is provided a control method of a work machine including work equipment, the control method including: a step of acquiring a first detection signal output according to a tilt amount of an operation lever by a first tilt amount sensor configured to detect the tilt amount of the operation lever of the work equipment tilted from a neutral position in a first direction or a second direction opposite to the first direction, and a second detection signal output according to the tilt amount by a second tilt amount sensor configured to detect the tilt amount; and a step of determining whether or not the first detection signal and the second detection signal are a value corresponding to the neutral position at a time of start of the work machine, generating and outputting a predetermined control signal for controlling the work equipment based on the first detection signal in a case where both of the first detection signal and the second detection signal are the value corresponding to the neutral position, and in a case where any one of the first detection signal or the second detection signal is not the value corresponding to the neutral position, generating and outputting the control signal based on the other of the first detection signal or the second detection signal, and outputting predetermined information corresponding to a case where the one is not the value corresponding to the neutral position from a predetermined output unit.

According to an aspect of the present disclosure, there is provided a work machine including: a work equipment; an acquisition unit configured to acquire a first detection signal output according to a tilt amount of an operation lever by a first tilt amount sensor configured to detect the tilt amount of the operation lever of the work equipment tilted from a neutral position in a first direction or a second direction opposite to the first direction, and a second detection signal output according to the tilt amount by a second tilt amount sensor configured to detect the tilt amount; and a control unit configured to determine whether or not the first detection signal and the second detection signal are a value corresponding to the neutral position at a time of start of the work machine, generate and output a predetermined control signal for controlling the work equipment based on the first detection signal in a case where both of the first detection signal and the second detection signal are the value corresponding to the neutral position, and in a case where any one of the first detection signal or the second detection signal is not the value corresponding to the neutral position, generate and output the control signal based on the other of the first detection signal or the second detection signal, and output predetermined information corresponding to a case where the one is not the value corresponding to the neutral position from a predetermined output unit.

According to the control device, the control method, and the work machine of the present disclosure, it is possible to appropriately cope with a case where an abnormality occurs in detection of a tilt amount of an operation lever of work equipment.

Embodiments of the present disclosure will be described below with reference to the drawings. In addition, in each drawing, the same reference numerals are used for the same or corresponding components, and the description thereof will be omitted as appropriate.

In the present embodiment, a local coordinate system is set in a work machine, and a positional relationship of each of units will be described with reference to the local coordinate system. In the local coordinate system, a first axis extending in a right-left direction (vehicle width direction) of the work machinewill be defined as an X-axis, a second axis extending in a front-rear direction of the work machinewill be defined as a Y-axis, and a third axis extending in an up-down direction of the work machinewill be defined as a Z-axis. The X-axis and the Y-axis are orthogonal to each other. The Y-axis and the Z-axis are orthogonal to each other. The Z-axis and the X-axis are orthogonal to each other. A +X-direction is the right direction, and a −X-direction is the left direction. A +Y-direction is the front direction, and a −Y-direction is the rear direction. A +Z-direction is the up direction, and a −Z-direction is the down direction.

is a side view showing the work machineaccording to the present embodiment. For example, the work machineaccording to the present embodiment is a wheel loader. Hereinafter, the work machinewill be referred to as a wheel loaderas appropriate.

As shown in, the wheel loaderhas a vehicle body, a cab, a traveling device, and work equipment. The wheel loadertravels on a work place by using the traveling device. In the work place, the wheel loadercarries out work by using the work equipment. The wheel loadercan use the work equipmentto carry out the work, such as excavation work, loading work, transport work, and snow removal work.

The cabis supported by the vehicle body. Inside the cab, a driver's seaton which an operator sits, an operation deviceto be described later, a display and input unit, and an output unitare disposed.

The traveling devicehas rotatable wheels. The wheelssupport the vehicle body. The wheel loadercan travel on a road surface (or ground) RS by the traveling device. It should be noted thatshows only a front wheelF and a rear wheelR on a left side.

The work equipmentis supported by vehicle body. The work equipmentis configured by a bucketas an example of a work tool, and a movable support sectionthat changes a position and a posture of the bucket. In the example shown in, the movable support sectionincludes a boom, a boom cylinder, a bucket cylinder, a bell crank, and a link.

The boomis rotatably supported with respect to the vehicle body, and moves in the up-down direction according to expansion and contraction of the boom cylinder. The boom cylinderis an actuator that generates power for moving the boom, and has one end portion connected to the vehicle bodyand the other end portion connected to the boom. In a case where the operator operates the boom operation lever() included in the operation device, the boom cylindercontracts and extends. As a result, the boommoves in the up-down direction. The boom cylinderis, for example, a hydraulic cylinder.

The buckethas bucket teethT and is a work tool for performing excavation of the object to be excavated such as earth or loading thereof. The bucketis rotatably connected to the boom, and is rotatably connected to one end portion of the link. The other end portion of the linkis rotatably connected to one end portion of the bell crank. The bell crankhas a central portion connected to the boomto be rotationally movable, and the other end portion rotatably connected to one end portion of the bucket cylinder. The other end portion of the bucket cylinderis rotatably connected to the vehicle body. The bucketis operated by power generated by the bucket cylinder. The bucket cylinderis an actuator that generates power for moving the bucket. In a case where the operator operates the bucket operation lever(), the bucket cylinderis contracted and extended. As a result, the bucketswings. The bucket cylinderis, for example, a hydraulic cylinder. The bucket teethT has a shape of chevron teeth, flat teeth, or the like, and is attached to an end portion of the bucketto be replaceable.

is a block diagram showing a configuration example of the control system of the wheel loaderaccording to the present embodiment. As shown in, the wheel loaderincludes a power source, a power take off (PTO), a hydraulic pump, a control valve, an operation device, a display and input unit, an output unit, and a controller.

The power sourcegenerates a driving force for operating the work machine. An internal combustion engine and an electric motor are exemplary examples of the power source.

The PTOtransmits at least a part of the driving force of the power sourceto the hydraulic pump. The PTOdistributes the driving force of the power sourceto the traveling deviceand the hydraulic pump.

The hydraulic pumpis driven by the power source, and discharges a hydraulic oil. At least a part of the hydraulic oil discharged from the hydraulic pumpis supplied to each of the boom cylinderand the bucket cylindervia the control valve. The control valvereceives a predetermined control signal from the controllerand controls the flow rate, the pressure, and the direction of the hydraulic oil supplied to each of the boom cylinderand the bucket cylinderfrom the hydraulic pump. The work equipmentis operated by the hydraulic oil from the hydraulic pump.

The operation deviceis disposed inside the cab. The operation deviceis operated by the operator. The operator operates the operation deviceto adjust a traveling direction and a traveling speed of the wheel loader, switches between forward and rearward movement, and operates the work equipment. The operation deviceincludes, for example, a steering, a shift lever, an accelerator pedal, a brake pedal, a boom operation lever, and a bucket operation lever. The boom operation leveris an operation lever for operating the posture of the boom. The boom operation leverincludes a main angle sensorand a sub angle sensor, and outputs two detection signals indicating the tilt amount of the operation lever. The bucket operation leveris an operation lever for operating the posture of the bucket. The bucket operation leverincludes a main angle sensorand a sub angle sensor, and outputs two detection signals indicating the tilt amount of the operation lever.

In a case where the boom operation leverand the bucket operation leverare collectively referred to, the boom operation leverand the bucket operation leverare referred to as operation levers. In a case of collectively referring to the main angle sensor, the sub angle sensor, the main angle sensor, and the sub angle sensor, the main angle sensor, the sub angle sensor, the main angle sensor, and the sub angle sensorare referred to as an angle sensor. In addition, in a case where the main angle sensorand the main angle sensorare collectively referred to, the main angle sensorand the main angle sensorare referred to as a main angle sensor. In addition, in a case where the sub angle sensorand the sub angle sensorare collectively referred to, the sub angle sensorand the sub angle sensorare referred to as a sub angle sensor. The angle sensor detects a tilt amount of the operation lever and outputs a detection signal indicating a detection result by an analog voltage value. The tilt amount can be represented by a value corresponding to, for example, the tilt angle, a movement amount of a grip portion, and the like. The angle sensor can be configured by, for example, a combination of a variable resistor (potentiometer) and a signal processing circuit, a combination of a hall element and a signal processing circuit, or the like. In addition, each detection signal is set such that a total value of a voltage value of the detection signal of the main angle sensor and a voltage value of the detection signal of the sub angle sensor is a constant value. In addition, in the following, the main angle sensor may be simply referred to as a main, and the sub angle sensor may be simply referred to as a sub.

The display and input unitis configured by a combination of an input device and a display device, an input display device, such as a touch panel, and the like. The operator inputs, for example, a set value or the like in the control of the work equipment using the display and input unit. The output unitincludes a display device, an output device for a synthetic voice, an alarm sound, or a notification sound, a display lamp such as a warning lamp, or the like, and outputs predetermined information.

The main angle sensor is an example of a first tilt amount sensor according to the present disclosure. In addition, the sub angle sensor is an example of a second tilt amount sensor according to the present disclosure.

are cross-sectional views showing the boom operation leverand the bucket operation leveraccording to the present embodiment. The boom operation leverand the bucket operation levermay have the same configuration, and hereinafter, the boom operation leverwill be described as an example.shows a case where a tilt position of the boom operation leveris a neutral position, andshows a case where the tilt position of the boom operation leveris a position reaching a stroke end in a rear direction. The boom operation leveris also tilted in the front direction in the same manner. The boom operation leverhas a mechanism that automatically returns the position of the operation lever to the neutral position in a state where a certain or more operation force is not applied to the operation lever. In the present embodiment, the angle sensor is provided below the operation lever and detects the tilt amount of the operation lever. A springis provided at a tilting center of the operation lever. The springhas a function of automatically returning the position of the operation lever to the neutral position. A detent solenoidis provided below the operation lever. The detent solenoidhas a function of holding the operation lever at a position where the operation lever is most tilted even in a case where the hand is released from the operation lever when the operation lever is most tilted in a case where the current flows to the detent solenoid. The operation lever according to the present embodiment is the operation lever of the work equipmentthat is tilted from the neutral position in the first direction (for example, the front direction) or the second direction (for example, the rear direction) opposite to the first direction.

is an output characteristic diagram of the angle sensor according to the embodiment of the present disclosure. A horizontal axis is the output voltage, and a vertical axis is the operation lever stroke. In this case, the operation lever stroke is represented by a percentage in a case where the stroke end is set to “1”. In addition, the neutral position is set to “0%”, and for example, a case where the operation lever is tilted forward is represented by a negative value, and a case where the operation lever is tilted backward is represented by a positive value. Here, the positive and negative directions may be reversed. A voltage value Vis, for example, “0 V”, and a voltage value Vis, for example, “5 V”. In the present embodiment, a range of a signal voltage in the controlleris a direct current of 0 to 5 V. A voltage value Vis a determination voltage for a ground failure, and a voltage value Vis a determination voltage for a power supply failure. In a case where the voltage of the detection signal output by the angle sensor is Vor less, it can be determined that the ground failure occurs. In a case where the voltage of the detection signal output by the angle sensor is Vor more, it can be determined that the power supply failure occurs. A range of the detection signal of the angle sensor is smaller than a range of the voltage value Vto the voltage value V. In addition, the voltage value Vis a voltage corresponding to the neutral position, and is, for example, “2.5 V”. In this example, the total value of the voltage value Vm of the detection signal of the main angle sensor and the voltage value Vs of the detection signal of the sub angle sensor is constant, for example, “5 V”. In, a solid line indicates a voltage value Vm of the detection signal of the main angle sensor, and a one-dot chain line indicates a voltage value Vs of the detection signal of the sub angle sensor. Output characteristics indicated by a two-dot chain line are an example in a case where the output characteristics indicated by the solid line fall due to some kind of problem. For example, in a case where the voltage value of the detection signal of the main angle sensor is decreased to Vm′, the sum of Vm′ and Vs is less than 5 V.

The controlleris configured by using, for example, a field programmable gate array (FPGA) or a microcomputer having a processor, a main storage device, an auxiliary storage device, an input/output device, and the like. The controllerincludes an acquisition unitand a control unitas a functional configuration composed of a combination of hardware, software such as a program, and the like. The controlleraccording to the present embodiment drives and controls the boom cylinderand the bucket cylinderby controlling the control valveaccording to an operation of the operation deviceand the like. The controlleris an example of a control device according to the present disclosure.

The acquisition unitrepeatedly acquires each detection signal (first detection signal) output by the main angle sensor according to the tilt amount of the operation lever and each detection signal (second detection signal) output by the sub angle sensor according to the tilt amount of the operation lever, for example, at a predetermined cycle (for example, a cycle of several milliseconds to several hundreds of milliseconds).

For example, the control unitdetermines whether or not each detection signal is normal or abnormal based on the detection signal of the main angle sensor and the detection signal of the sub angle sensor, and selects which detection signal of the angle sensor is to be used to control the control valvewhen the detection signal is abnormal. There are the following two types of determination of whether or not there is an abnormality performed by the control unit. One is determination of whether or not each detection signal is a value indicating that the operation lever is in the neutral position, on the premise that the operation lever is not operated at the time of turning on the key (at the time of starting the wheel loader) of the wheel loader. This determination is referred to as a neutral determination. The time when the key is turned on is a time shorter than a time normally required from turning on the key to starting the operation of the operation lever, and is, for example, a time of several seconds to several tens of seconds from turning on the key. Another determination is whether or not the total value of the voltage values of the main and sub detection signals is a predetermined constant value. This determination is referred to as a sum determination or an error determination. The sum determination is not limited to the start, and can be performed even during the operation of the operation lever.

For example, at the time of turning on the key of (at the time of starting) the wheel loader, the control unitdetermines whether or not the detection signal (first detection signal) of the main angle sensor and the detection signal (second detection signal) of the sub angle sensor are a value corresponding to the neutral position, and in a case where both of the first detection signal and the second detection signal are values corresponding to the neutral position, the control unitgenerates and outputs a predetermined control signal for controlling the work equipmentbased on the first detection signal. In addition, for example, in a case where any one of the first detection signal or the second detection signal does not have the value corresponding to the neutral position, the control unitgenerates and outputs the control signal based on the other of the first detection signal or the second detection signal, and outputs predetermined information corresponding to a case where one of the first detection signal or the second detection signal from the output unitdoes not have the value corresponding to the neutral position. In the example shown in, the value corresponding to the neutral position is a voltage value within V3±α. Here, a is a voltage value in an allowable range of the determination. In addition, the output of the predetermined information is, for example, display of an error code representing a case where the value does not correspond to the neutral position, notification that the abnormality is detected by a synthetic voice or an electronic sound, lighting or blinking of a predetermined display lamp, and the like. The output of the predetermined information is also referred to as error report.

In addition, for example, in a case where any one of the first detection signal or the second detection signal does not have a value corresponding to the neutral position, the control unitgenerates and outputs the control signal on the basis of the other of the first detection signal or the second detection signal after limiting the function of the work equipment. The restriction of the function of the work equipmentis a restriction of an action or an operation of the work equipment, and is, for example, a restriction of an operation speed of the work equipmentto a value lower than a normal value (for example, a normal value of several to several tens of %).

In addition, for example, in a case where the control unitdetermines that both of the first detection signal and the second detection signal are the value corresponding to the neutral position, the control unitdetermines whether or not the total value of the first detection signal and the second detection signal is a certain value, and in a case where the total value is not the certain value, the control unitgenerates and outputs a control signal to stop the operation of the predetermined actuator of the work equipment. Here, the certain value is a voltage value within a range of 2 times the voltage value V3±β described with reference to. In addition, β is a voltage value in an allowable range of the determination.

In addition, for example, at the time of turning on the key of (at the time of starting) the wheel loader, the control unitrepeatedly determines whether or not the detection signal (first detection signal) of the main angle sensor and the detection signal (second detection signal) of the sub angle sensor correspond to the neutral position from a time of the key-on for a predetermined time. The predetermined time can be, for example, about several seconds to several tens of seconds. In a case where both of the first detection signal and the second detection signal are not values corresponding to the neutral position, the control unitoutputs an alarm of that fact from the output unit. In addition, when both of the first detection signal and the second detection signal have the value corresponding to the neutral position before the predetermined time elapses, the control unitstops the output of the alarm, and generates and outputs a control signal for controlling the work equipmentbased on the first detection signal. In addition, the output of the alarm is, for example, display of an error code indicating that the operation lever is not in the neutral position, notification that the operation lever is not in the neutral position by synthetic voice or electronic sound, lighting or blinking of a predetermined display lamp indicating that the operation lever is not in the neutral position, or the like.

is a state transition diagram showing an operation example of the controller according to the embodiment of the present disclosure.are schematic diagrams for describing operation examples of the controller according to the embodiment of the present disclosure.shows a transition of a determination state (states Sto S) of whether or not there is an abnormality based on the detection signal of the main angle sensor and the detection signal of the sub angle sensor by the control unit. The state transition shown inis started in a case where the key is turned on. The initial state is the state S.

In the state S, the initial check is executed by the control unitin order to determine which of the states Sto Sthe transition is made to next. The state transitions to any one of the states Sto Sfrom the state Son the basis of the result of the initial check. The main angle sensor and the sub angle sensor are selected in the state S.shows the contents of the initial check. The control unitperforms the neutral determination in the state S. The control unitperforms the neutral determination of the main and sub at a Ttime (for example, 0.3 seconds) from the start and at a Ttime (for example, 0.5 seconds) after the elapse of the Ttime. The control unitdetermines that the state is neutral as long as the state is always within the neutral range for the Ttime. In addition, the control unitdetermines that the state is non-neutral in a case where the state is out of the neutral range even once for the Ttime.

When the condition 1 is established in the state S, the state transitions to the state S. When the condition 2 is established in the state S, the state transitions to the state S. When the condition 3 is established in the state S, the state transitions to the state S. When the condition 4 is established in the state S, the state transitions to the state S.shows a list of the conditions 1 to 7.

The condition 1 is established when the condition 2 is not established, the condition 3 is not established, and the condition 4 is not established.

The condition 2 is established when the main is neutral, the sub is non-neutral, and both of the main and the sub are out of an error detection range of disconnection, ground fault, or power supply fault. The disconnection can be determined by whether or not an output signal line of each sensor is in a high impedance state.

The condition 3 is established when the main is non-neutral, the sub is neutral, and both of the main and the sub are out of the error detection range of the disconnection, ground fault, or power supply fault.

The condition 4 is established when the main is non-neutral, the sub is non-neutral, and both of the main and the sub are out of the error detection range of the disconnection, the ground fault, or power supply fault.

The state Sis a state in which both of the main and the sub are normal (usually). The selection of the main and the sub is the main. The output of the error is in a state in which there is no error (a state in which there is no error report or alarm). When the condition 7 is established for the Ttime (for example, 0.05 seconds) in the state S, the state transitions from the state Sto a state S.

The state Sis a state in which the sub is abnormal. The selection of the main and the sub is the main. The output of the error is error report. The function of the work equipmentis limited. The state Sis maintained until the key is turned off.

The state Sis a state in which the main is abnormal. The selection of the main and the sub is the sub. The output of the error is error report. The function of the work equipmentis limited. The state Sis maintained until the key is turned off.

The state Sis a state in which both of the main and the sub are abnormal. The output of the error is an alarm. In the state S, when the condition 5 is established, the state transitions to the state S, and when the condition 6 is established, the state transitions to the state S.

The condition 5 is established when both of the main and the sub are neutral for the Ttime (for example, 0.5 seconds) or more. In a case of performing the transition, the control unitchanges the initial check result to neutral for both of the main and sub.

The condition 6 is established when the Ttime (for example, 10 seconds) elapses after the state transitions to the state S.

The condition 7 is that the total value of the main and sub voltage values is out of the range of 2×V3±B and both of the main and sub are out of the error detection range of the disconnection, the ground fault, or power supply fault.