Control device, agricultural machine, construction machine, control method, and control program

Abstract

A control device (7) controls a rotary electric machine (54a) that drives a work implement (5) with which a vehicle is equipped, the control device (7) comprising: an inverter control unit (32) that controls an inverter (10) that supplies electric power to the rotary electric machine, which is a drive source of an electric cylinder (54) including a mechanical element for driving the work implement; and a control unit (31) that, upon detecting a locked state in which the rotary electric machine does not rotate when the rotary electric machine is energized, repeatedly changes the torque generated by the rotary electric machine so that the electrical angle of the rotary electric machine changes by a predetermined value.

Description

Control device, agricultural machine, construction machine, control method, and control program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from patent application serial number 2024-146936, filed August 28, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a control device, an agricultural machine, a construction machine, a control method, and a control program.

[0003] Patent Document 1 discloses a technology for driving a work implement, such as a boom, arm, or bucket of an excavator, using an electric cylinder incorporating a ball screw type reduction gear. By replacing the drive force transmission means of the work implement from a conventional hydraulic cylinder with an electric cylinder, the work implement can be rotationally driven by a link connection similar to that of a hydraulic cylinder. Furthermore, compared to when a hydraulic cylinder is used, the system for driving the rotating electric machine is simplified, allowing the overall system to be made smaller and lighter, and the weight of the vehicle equipped with the work implement can be reduced.

[0004] Japanese Patent Application Laid-Open No. 2003-082707

[0005] However, after detailed investigations by the inventors, the inventors discovered a problem with the conventional technology of Patent Document 1: when, for example, a bucket hits a large rock while excavating soil, causing a high load condition in which the rotating electric machine is barely able to rotate, current may concentrate in a winding of a specific phase of the rotating electric machine or in a switch element of a specific phase in the inverter driving the rotating electric machine. In other words, when the rotating electric machine is in a locked state in which it is barely rotating, the energized phase does not change, and current may concentrate in a specific phase among the U, V, and W phases. If current continues to flow through a specific phase for a specific period of time, there is a risk of overheating the winding, switch element, etc. of that phase. To avoid this, conventional techniques have been proposed to limit output (torque) and reduce thrust when a current above a certain threshold flows through a winding, etc., which can cause problems in driving a driven object such as a work machine. Thus, the conventional technology leaves room for improvement in terms of preventing overheating of the winding, switch element, etc. of a specific phase while driving the driven object.

[0006] The present disclosure aims to provide a control device, agricultural machinery, construction machinery, control method, and control program that can prevent overheating of windings, switch elements, etc. of a specific phase while driving a driven object.

[0007] A control device according to a first aspect of the present disclosure is a control device that controls a rotating electric machine that drives a work machine provided on a vehicle, and includes: an inverter control unit that controls an inverter that supplies power to the rotating electric machine, which is a driving source of an electric cylinder that includes a mechanical element that drives the work machine; and a control unit that, when a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine is detected, repeatedly changes the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

[0008] A control program according to a second aspect of the present disclosure causes at least one processor to execute processing including controlling an inverter that supplies power to a rotating electric machine that is a driving source for an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle, and, when a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine is detected, repeatedly changing the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

[0009] A control method according to a third aspect of the present disclosure executes processing including: at least one processor controls an inverter that supplies power to a rotating electric machine that is a driving source of an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle; and, when a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine is detected, repeatedly changing the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

[0010] According to the present disclosure, a control device, agricultural machinery, construction machinery, control method, and control program are provided that can prevent overheating of a winding, switch element, etc. of a specific phase while driving a driven object.

[0011] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. In the drawings, FIG. 1 is a diagram illustrating a vehicle 100 equipped with a control device 7 according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of an electric cylinder 54. FIG. 3 is a diagram illustrating a hardware configuration of the control device 7 according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example configuration of a drive unit 60 including a rotating electric machine 54a and an inverter 10. FIG. 5 is a block diagram illustrating an example functional configuration of a CPU 21A of the control device 7. FIG. 6 is a timing chart illustrating the rotation speed, electrical angle, and torque of the rotating electric machine 54a. FIG. 7A is a diagram illustrating the relationship between the electrical angle and phase current before and after adjustment. FIG. 7B is a diagram illustrating the relationship between the electrical angle and phase current before and after adjustment. FIG. 8 is a flowchart illustrating a control process for the torque output from the rotating electric machine 54a. FIG. 9 is a diagram illustrating the torsion angle of a mechanical element 540.

[0012] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0013] FIG. 1 is a diagram showing a vehicle 100 equipped with a control device 7 according to an embodiment of the present disclosure. The vehicle 100 may be interpreted as an agricultural construction machine (hereinafter, agricultural construction machine). The agricultural construction machine may include agricultural machinery and construction machinery. The agricultural construction machine may include an electric tractor, an electric wheel loader, an electric bulldozer, an electric backhoe, an electric crane, and the like. FIG. 1 shows an electric backhoe as an example of agricultural machinery. The agricultural construction machine may include a vehicle 100 that moves using crawlers as well as a vehicle 100 that moves using tires. Note that the control device 7 according to the present disclosure may be provided in a vehicle 100 other than an agricultural construction machine. The control device 7 may be interpreted as a device that controls a rotating electric machine 54a that drives a work implement 5 provided on the vehicle 100.

[0014] The vehicle 100 may include a traveling device 2 and a main body 3. The traveling device 2 may be provided below the main body 3 and may support the main body 3 so that it can rotate freely in the horizontal direction. The traveling device 2 may include a pair of left and right crawlers. The main body 3 may include a cab 4 in which an operator rides, a work implement 5 provided in front of the cab 4, a battery 6, and a control device 7.

[0015] (Control Device 7) The control device 7 may be interpreted as a device that controls one or more electric cylinders 54. Specifically, the control device 7 may independently control the rotation speed, rotation direction, rotation torque (hereinafter, torque), etc. of the rotating electric machine 54a included in each of, for example, three electric cylinders 54. For example, the control device 7 may rotate the rotating electric machine 54a included in the electric cylinder 54 that drives the boom 51 in a first rotation direction, while rotating the rotating electric machine 54a included in the electric cylinder 54 that drives the arm 52 in a second rotation direction opposite to the first rotation direction. At this time, the control device 7 may stop the rotation of the rotating electric machine 54a included in the electric cylinder 54 that drives the bucket 53.

[0016] (Battery 6) The battery 6 is a storage battery for supplying power to the rotating electric machine 54a. The battery 6 is, for example, a lithium ion battery.

[0017] (Working Machine 5) The working machine 5 may have a multi-joint structure including a boom 51, an arm 52, and a bucket 53. The boom 51 may be supported so as to be swingable in the vertical direction relative to the cab 4. The arm 52 may be supported so as to be swingable at the tip of the boom 51. The bucket 53 may be supported so as to be swingable at the tip of the arm 52. Each of the boom 51, the arm 52, and the bucket 53 may be driven by an electric cylinder 54.

[0018] (Electric Cylinder 54) The electric cylinder 54 may be interpreted as a mechanism in which the rod 54b is reciprocated by being driven by the rotating electric machine 54a. As shown in Fig. 2, the electric cylinder 54 may include the rotating electric machine 54a, a speed reduction mechanism 54c, a case 54d, a nut 54e, a ball screw 54f, and the rod 54b.

[0019] The reduction mechanism 54c reduces the rotation speed of the rotating electric machine 54a and transmits the torque of the rotating electric machine 54a to the ball screw 54f in the case 54d. The reduction mechanism 54c may reduce the rotation speed by, for example, using a small-diameter first pulley 54c1 connected to the rotating shaft 54a1 of the rotating electric machine 54a, a large-diameter second pulley 54c2 connected to the ball screw 54f, and a belt 54c3 connecting the first pulley 54c1 and the second pulley 54c2. The configuration of the reduction mechanism 54c is not limited thereto, and the reduction mechanism 54c may reduce the rotation speed by, for example, using a small-diameter gear connected to the rotating shaft 54a1 of the rotating electric machine 54a and a large-diameter gear connected to the ball screw 54f.

[0020] The ball screw 54f may convert the rotational motion of the rotating electric machine 54a into the linear motion of linearly moving members such as the nut 54e and the rod 54b. The ball screw 54f may include a screw shaft 54f1 and balls 54f2. The balls 54f2 may be interpreted as rolling elements provided between the nut 54e and the screw shaft 54f1.

[0021] When the rotating electric machine 54a rotates, i.e., when the rotary shaft 54a1 rotates, the torque of the rotating electric machine 54a is transmitted to the ball screw 54f. As the ball screw 54f rotates, the rotational motion of the ball screw 54f is converted into linear motion of the nut 54e provided in the case 54d. As a result, the rod 54b connected to the nut 54e reciprocates, i.e., moves forward and backward, relative to the case 54d.

[0022] The rotating shaft 54a1, the reduction gear mechanism 54c, the ball screw 54f, the nut 54e, etc. may be considered as a mechanical element 540 that moves the rod 54b, which drives the work machine 5, forward and backward. More strictly, the rotating shaft 54a1, the first pulley 54c1, the belt 54c3, the second pulley 54c2, the ball screw 54f, and the nut 54e may be considered as the mechanical element 540 that moves the rod 54b forward and backward. Note that the electric cylinder 54 of the present disclosure may include the rotating electric machine 54a, the case 54d, the nut 54e, the ball screw 54f, and the rod 54b without including the reduction gear mechanism 54c. In this case, the rotating electric machine 54a may be directly or indirectly connected to the ball screw 54f.

[0023] When the rotating electric machine 54a rotates, the torque of the rotating electric machine 54a can cause a twist in these mechanical elements 540 as shown in equation (1). θ is the twist angle of the mechanical elements 540, T is the motor torque, l is the length of the mechanical elements 540, and GI ｐ is the torsional rigidity of the mechanical element 540 (see FIG. 9). ｐ ...(1)

[0024] For example, when the rotating electric machine 54a rotates in a first direction to raise the boom 51, the torque generated by the rotating electric machine 54a may cause a greater torsion in the mechanical element 540 than the torsion applied when the boom 51 is stationary. Furthermore, if a part of the boom 51 during raising or lowering contacts an obstacle around the work machine 5, such as a rock formation in the soil being excavated by the work machine 5 or a demolition target around the work machine 5, the movement of the work machine 5 stops. This may cause a greater torsion in the mechanical element 540 due to the torque generated by the rotating electric machine 54a than the torsion applied when the boom 51 is in operation. When the control device 7 of the present disclosure detects a locked state in which the rotating electric machine 54a does not rotate due to the work machine 5 contacting an obstacle or the like and stopping its movement, the control device 7 is configured to utilize the torsion of the mechanical element 540 to alternately increase and decrease the torque generated by the rotating electric machine 54a. The configuration of the control device 7 will be described in detail below.

[0025] The hardware configuration of the control device 7 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the hardware configuration of the control device 7 according to an embodiment of the present disclosure. The control device 7 includes a control unit 21, a communication unit 22, and a storage unit 23.

[0026] The control unit 21 is configured as a device including a general computer. The control unit 21 includes a CPU (Central Processing Unit) 21A, a ROM (Read Only Memory) 21B, a RAM (Random Access Memory) 21C, and an input / output interface (I / O) 21D. The CPU 21A, ROM 21B, RAM 21C, and I / O 21D are connected to each other via a bus 21E. The bus 21E includes a control bus, an address bus, a data bus, etc.

[0027] The I / O 21D is connected to a communication unit 22, a storage unit 23, and a sensor group 200. The communication unit 22 is an interface for communicating with external devices such as the inverter 10.

[0028] The storage unit 23 is configured as a non-volatile external storage device such as a hard disk, etc. The storage unit 23 stores a control program 23A.

[0029] The CPU 21A is an example of a computer. The term "computer" as used herein refers to a processor in a broad sense, and includes a general-purpose processor (e.g., the CPU 21A) or a dedicated processor (e.g., a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a programmable logic device, etc.).

[0030] The control program 23A may be stored in a non-volatile, non-transitory recording medium or distributed via a network and appropriately installed in the control device 7, thereby being stored in the storage unit 23. The control program 23A may also be appropriately updated via so-called OTA (Over The Air).

[0031] Examples of non-volatile non-transient recording media include CD-ROMs (Compact Disc Read Only Memory), magneto-optical disks, HDDs (Hard Disk Drives), DVD-ROMs (Digital Versatile Disc Read Only Memory), flash memories, memory cards, etc.

[0032] The sensor group 200 may include a wheel speed sensor, an acceleration sensor, a current sensor, an accelerator sensor, a temperature sensor, a gradient sensor, a brake sensor, a yaw rate sensor, a rotation speed sensor, and the like.

[0033] The rotation speed sensor may be understood as a sensor for detecting the rotation angle and rotation speed of the rotating electric machine 54 a. The rotation speed sensor is, for example, a resolver or a rotary encoder, and detects the rotation angle and rotation speed of the rotor of the rotating electric machine 54 a. A signal indicating the rotation speed detected by the rotation speed sensor is input to the control device 7.

[0034] The current sensor may be understood as a sensor for detecting the value of the current flowing through the rotating electric machine 54a. As an example, the current sensor detects the current flowing through any two windings (e.g., the V phase and the W phase) among the windings of the U phase, V phase, and W phase. A signal indicating the value of the drive current detected by the current sensor is input to the control device 7.

[0035] The temperature sensor may be interpreted as a sensor for detecting the temperatures of a plurality of switch elements included in the inverter 10. A signal indicating the temperature detected by the temperature sensor is input to the control device 7.

[0036] The inverter 10 may convert the DC power supplied from the battery 6 into AC power in accordance with instructions from the control device 7, and supply the AC power to the rotating electric motors 54a in the electric cylinders 54 provided in each of the boom 51, arm 52, and bucket 53, thereby controlling the rotation of the rotating electric motors 54a.

[0037] 4 is a diagram showing an example configuration of a drive unit 60 including a rotating electric machine 54a and an inverter 10. The rotating electric machine 54a includes a stator 153, a rotor 154, a current sensor 203, and a rotation speed sensor 211. The rotating electric machine 54a is a three-phase motor generator, and the stator 153 has windings 155U, 155V, and 155W of multiple phases. The winding 155U is a U-phase winding, the winding 155V is a V-phase winding, and the winding 155W is a W-phase winding. The current sensor 203, for example, detects the current flowing through the winding 155V and the current flowing through the winding 155W. The rotation speed sensor 211 is, for example, a resolver, and detects the rotation angle and rotation speed of the rotor 154.

[0038] The inverter 10 has six power elements 156Uu, 156Ud, 156Vu, 156Vd, 156Wu, and 156Wd. Hereinafter, when there is no need to distinguish between the six power elements 156Uu, 156Ud, 156Vu, 156Vd, 156Wu, and 156Wd, the six power elements 156Uu, 156Ud, 156Vu, 156Vd, 156Wu, and 156Wd will be referred to as "power elements 156." These power elements 156 may be interpreted as inverter elements or switch elements. Each power element 156 is, for example, a power transistor. The power elements 156Uu and 156Ud are U-phase power elements, the power elements 156Vu and 156Vd are V-phase power elements, and the power elements 156Wu and 156Wd are W-phase power elements. The power elements 156Uu and 156Ud are bridge-connected to the winding 155U, the power elements 156Vu and 156Vd are bridge-connected to the winding 155V, and the power elements 156Wu and 156Wd are bridge-connected to the winding 155W.

[0039] The inverter 10 has a plurality of temperature sensors 157. The temperature sensor 157 may be provided for each of the plurality of power elements 156.

[0040] Next, an example of the functional configuration of the CPU 21A of the control device 7 will be described with reference to FIGS. 5, 6, 7A, and 7B. FIG. 5 is a block diagram illustrating an example of the functional configuration of the CPU 21A of the control device 7. FIG. 6 is a timing chart showing the rotation speed, electrical angle, and torque of the rotating electric machine 54a. FIG. 6 shows changes in the rotation speed, electrical angle, and torque of the rotating electric machine 54a over time. As shown in FIG. 6, the rotation angle of the rotor 154 during lockup avoidance control (described later) is approximately zero, and the cylinder speed indicated by the solid line is also approximately zero. The electrical angle may be interpreted as an angle where one cycle of switching of the switch element is 360 degrees. For example, in a two-pole, three-slot rotating electric machine 54a, the mechanical angle and the electrical angle are the same, while in a four-pole, six-slot rotating electric machine 54a, the mechanical angle is 360 degrees and the electrical angle is two cycles. The torque may be interpreted as the thrust generated by the rotating electric machine 54a. FIGS. 7A and 7B are diagrams showing the relationship between the electrical angle and phase current before and after adjustment.

[0041] 5, the CPU 21A reads and executes a control program 23A stored in the storage unit 23 (see FIG. 3) to function as each functional unit shown in FIG. 5. The CPU 21A may include a control unit 31 and an inverter control unit 32.

[0042] The control unit 31 may include a rotation speed calculation unit 31a, a lock determination unit 31b, a lock avoidance control unit 31c, a torque limiting unit 31d, and a torque calculation unit 31e. The inverter control unit 32 may include a vector control unit 32a.

[0043] (Rotational Speed ​​Calculation Unit 31a) The rotational speed calculation unit 31a calculates the rotational speed of the rotating electric machine 54a based on the rotational angle detected by the rotational speed sensor 211, i.e., a signal indicating the electrical angle, and inputs the calculated rotational speed to the lock determination unit 31b.

[0044] The torque calculation unit 31e may calculate a command torque that serves as a target for causing the rotation speed of the rotating electric machine 54a to follow a required target speed. The target speed is calculated based on, for example, the amount of operation of a lever provided on the vehicle 100 by the driver.

[0045] (Lock-up Determination Unit 31b) The lock-up determination unit 31b may perform a lock-up determination, i.e., may detect a locked state in which the rotating electric machine 54a is barely rotating, based on a signal from at least one of the rotating electric machine 54a and the inverter 10. The signal may include a signal indicating a change in the rotation speed of the rotating electric machine 54a generated in response to a command torque of the rotating electric machine 54a. The signal may also include a signal indicating a temperature difference between a plurality of switch elements included in the inverter 10. Specifically, the signal may include the rotation speed calculated by the lock-up determination unit 31b and the rotation speed calculation unit 31a, the command torque calculated by the torque calculation unit 31e, the temperatures of the switch elements included in the inverter 10, and the like. By using these signals, it is possible to perform a lock-up determination in real time while the rotating electric machine 54a and the inverter 10 are operating.

[0046] When the lockup determination unit 31b determines that a lockup state has occurred, it inputs a signal indicating that a lockup state has occurred to the lockup avoidance control unit 31c. A more specific example of lockup determination will be described below.

[0047] (First Example of Lockout Determination) The lockout determination unit 31b may determine that a lockout state has occurred when the rotational speed of the rotating electric machine 54a is equal to or lower than a specific threshold and the command torque is equal to or higher than a specific threshold, i.e., when the conditions of rotational speed≦threshold and command torque≧threshold are met. When this condition is met, for example, the work machine 5 comes into contact with an obstacle present in its surroundings, causing the rotational speed of the rotating electric machine 54a to be low relative to the command torque corresponding to the user's operation, which is likely to result in concentrated current flow in a specific phase. Even when such a state occurs, the lockout avoidance control described below can be executed to prevent current from flowing exclusively in the switch element or winding of a specific phase.

[0048] (Second Example of Lockout Determination) The lockout determination unit 31b may calculate the angular acceleration of the rotating electric machine 54a based on the calculated rotation speed, and determine that a lockout state has occurred if the angular acceleration is equal to or less than a threshold value based on the command torque, i.e., if the condition "angular acceleration≦command torque" is met. The angular acceleration can be calculated from the change per unit time in the rotation angle detected by the rotation speed sensor 211. A case in which this condition is met would be, for example, if the work machine 5 comes into contact with an obstacle in its surroundings, causing the angular acceleration of the rotating electric machine 54a to be low relative to the command torque corresponding to the user's operation, which likely results in current flowing in a concentrated manner in a specific phase. Even if such a state occurs, the lockout avoidance control described below can be executed to prevent current from flowing in a concentrated manner in only the switch element or winding of a specific phase.

[0049] (Third Example of Lockout Determination) The lockout determination unit 31b may compare the temperatures of multiple switch elements detected by the inverter 10 and determine that a lockout state has occurred if the temperature difference between the switch elements is equal to or greater than a specific threshold, that is, if the condition "temperature difference between each element is equal to or greater than the threshold" is met. An example of a case in which this condition is met is when the temperature difference between the upper-arm U-phase switch element and the average temperature of the other five switch elements is equal to or greater than a specific threshold. In this case, there is a high possibility that current is flowing in a concentrated manner in the upper-arm U-phase switch element. Even if such a state occurs, the lockout prevention control described below can be executed to prevent current from flowing in a concentrated manner in only the upper-arm U-phase switch element or the winding connected to that phase.

[0050] (Fourth Example of Lockup Determination) The lockup determination unit 31b may determine whether a lockup state has occurred by referring to a specific map. For example, the specific map may associate a plurality of command torques having different values ​​with rotation speeds at which a lockup state has occurred. When the command torque calculated by the torque calculation unit 31e is input, the lockup determination unit 31b may refer to the map to read out the rotation speed corresponding to the command torque, and compare the read-out rotation speed with the actually detected rotation speed. If the detected rotation speed is lower, the lockup determination unit 31b may determine that a lockup state has occurred.

[0051] (Lockup Avoidance Control Unit 31c) When the lockup determination unit 31b detects a locked up state, the lockup avoidance control unit 31c executes control to avoid the locked up state. Specifically, when a locked up state in which the rotating electric machine 54a does not rotate when current is applied to the rotating electric machine 54a is detected, the lockup avoidance control unit 31c may repeatedly change the torque generated by the rotating electric machine 54a so that the electrical angle of the rotating electric machine 54a changes by a predetermined value. A more specific example of lockup avoidance control will be described below.

[0052] When the lock avoidance control unit 31c detects a locked state, it may repeatedly change the torque by alternately reducing the torque so as to release the torsion applied to the mechanical element 540 and increasing the torque so as to apply torsion to the mechanical element 540.

[0053] For example, even if the bucket 53 comes into contact with a rock bed contained in the soil being excavated at time t1 shown in Fig. 6 and the movement of the work implement 5 stops, the rotating electric machine 54a in the electric cylinder 54 that drives the boom 51 and part of the mechanical element 540 continue to rotate in the first rotation direction R1 with a constant torque. Therefore, the torsion of the mechanical element 540 increases from time t1 to time t2 shown in Fig. 6.

[0054] When the lock determination unit 31b detects a lock at time t2 in this state where the torsion of the mechanical element 540 has increased, the lock avoidance control unit 31c reduces the torque generated by the rotating electric machine 54a. Specifically, the lock avoidance control unit 31c reduces the torque so as to release the torsion applied to the mechanical element 540 by the elastic restoring force of the mechanical element 540. By reducing the torque, the elastic restoring force of the mechanical element 540 generates a force that rotates the rotating electric machine 54a and the mechanical element 540 in the reverse direction.

[0055] As a result, the rotating electric machine 54a and a portion of the mechanical element 540 begin to rotate in a second rotation direction R2 opposite to the first rotation direction R1. For example, if the electrical angle at the time of lock detection is 90 degrees, the electrical angle at time t3 may become 180 degrees, which is the electrical angle of 90 degrees at the time of lock detection plus a predetermined value (e.g., 90 degrees). As a result, as shown in FIG. 7A , the current conduction phase changes, for example, from the U phase to the V phase.

[0056] Thereafter, the lockup avoidance control unit 31c increases the torque generated by the rotating electric machine 54a against the elastic restoring force of the mechanical element 540. Specifically, the torque is increased so as to apply a torsion to the mechanical element 540 against the elastic restoring force of the mechanical element 540. At this time, the electrical angle may return to 90 degrees, which is a predetermined value (90 degrees) less than the electrical angle of 180 degrees when the torque changed from decreasing to increasing. As a result, the current conduction phase changes, for example, from the V phase to the U phase, as shown in FIG. 7B .

[0057] As the torque increases, the torsion of the mechanical element 540 increases again, so the lockup avoidance control unit 31c reduces the torque generated by the rotating electric machine 54a at time t4, for example, thereby reversing the rotation direction of the rotating electric machine 54a. Therefore, the current conduction phase changes again.

[0058] In this way, when lockup is detected, the lockup avoidance control unit 31c alternately increases and decreases the torque, thereby preventing current from continuously flowing through only a specific phase. Also, lockup can be avoided while maintaining the thrust that allows the work implement 5 to continue working.

[0059] The lockup avoidance control unit 31c may repeatedly change the torque so that the average value of the current flowing through the switch elements included in the inverter 10 is equal to or less than the allowable current in a locked state. The allowable current may be interpreted as the rated current of the switch elements. By keeping the average current equal to or less than the allowable current, it is possible to prevent current from concentrating in only a switch element of a specific phase or a winding of a specific phase, prevent damage to the switch elements, and maintain stable switching operation. Furthermore, the torque may be increased or decreased in stages, or may be increased or decreased at a constant rate of change.

[0060] (Torque limiting unit 31d) The torque limiting unit 31d may limit the torque based on a signal from at least one of the rotating electric machine 54a and the inverter 10. Specifically, the torque limiting unit 31d may limit the torque based on at least one of the temperature of the rotating electric machine 54a and the temperature of the inverter 10. More specifically, the torque limiting unit 31d may calculate upper and lower limit torques based on at least one of the temperature of the coils in the rotating electric machine 54a and the temperature of the switch elements in the inverter 10. The upper and lower limit torques may include an upper limit torque and a lower limit torque of the rotating electric machine 54a. Applying torque exceeding the upper limit torque increases the current flowing through the switch elements, which may burn out the coils in the rotating electric machine 54a, the switch elements in the inverter 10, and the like. The upper limit torque prevents the rotational torque from exceeding the upper limit torque and generating an excessive load (i.e., a specific load) that makes it impossible to maintain rotation of the rotating electric machine 54a. The lower limit torque prevents the rotational torque from falling below the lower limit torque, thereby preventing the work machine 5 from continuing to work, i.e., preventing the thrust from decreasing too much. When the torque limiting unit 31d is in an unlocked state, i.e., when no lock has been detected, the torque limiting unit 31d selects the torque calculated by the torque calculation unit 31e as the final command torque. On the other hand, when the torque limiting unit 31d detects a locked state, the torque limiting unit 31d selects the torque calculated by the lock avoidance control unit 31c, limited by the upper and lower limit torques, as the final command torque.

[0061] (Vector Control Unit 32a) The vector control unit 32a executes torque control that corresponds to the final command torque.

[0062] FIG. 8 is a flowchart for explaining the control process of the torque output from the rotary electric machine 54a.

[0063] In step S1, the CPU 21A inputs a work command for the work implement 5, and in step S2, the CPU 21A calculates a target command torque. In step S3, the CPU 21A determines whether or not the work implement 5 is in a locked state.

[0064] If the state is unlocked (step S3, NO), the CPU 21A executes the process of step S5, and if the state is locked (step S3, YES), the CPU 21A executes the process of step S4.

[0065] In step S4, the CPU 21A calculates the torque to be increased or decreased for lockup avoidance control, and after calculating the torque to be increased or decreased, executes the process of step S5. In step S5, the CPU 21A calculates the protective torque, that is, the upper and lower limit torques.

[0066] In step S6, the CPU 21A determines and outputs the final command torque. Specifically, in the unlocked state, the CPU 21A selects the initially calculated target command torque, and in the locked state, the CPU 21A selects the increased or decreased torque calculated by the lockup avoidance control, and outputs a value obtained by limiting the selected torque by the upper and lower limit torques calculated in step S5 as the final command torque.

[0067] In step S7, a plurality of switch elements in the inverter are turned on and off in accordance with the final command torque, and in step S8, the value of the torque output from the rotary electric machine 54a is controlled.

[0068] As described above, the control device 7 according to an embodiment of the present disclosure may include an inverter control unit 32 and a control unit 31 that, when a locked state in which the rotating electric machine 54a does not rotate when current is applied to the rotating electric machine 54a is detected, repeatedly changes the torque generated by the rotating electric machine 54a so that the electrical angle of the rotating electric machine 54a changes by a predetermined value.

[0069] With this configuration, when the bucket 53 of a power shovel or the like hits hard ground, it is detected and the torque is controlled, thereby preventing the lock state from continuing.

[0070] Furthermore, by repeatedly changing the torque, it is possible to maintain a high thrust even when the rotating electric machine 54a is operating at a low rotation speed. In other words, if the output torque is simply limited when a locked state is detected, the thrust for driving the work implement 5 will decrease and work cannot be continued, but by repeatedly changing the torque, it is possible to maintain a high thrust, allowing work to continue.

[0071] In addition, when a motor lock occurs due to a balance between the torque that stops the vehicle against gravity and the external load due to gravity, such as when the vehicle is stationary on a slope, suppressing the torque, i.e., releasing the torque, causes the vehicle to move downhill. This increases the rotation speed of the rotating electric machine 54a, making it possible to avoid the lock. However, as described above, in a situation where the agricultural construction machinery work implement 5 is in contact with hard ground, the external load due to gravity is not applied, and simply releasing the torque does not increase the rotation speed as intended, making it impossible to avoid the lock. When a lock state is detected, the control device 7 according to an embodiment of the present disclosure repeatedly changes the torque rather than simply releasing it. This prevents current from concentrating in only a specific phase of the switch element or the winding of a specific phase, allowing the vehicle to continue working while maintaining a high thrust.

[0072] When the control device 7 of the present disclosure is mounted on a front loader, the lock avoidance control of the present disclosure can be applied even when the bucket 53 of the front loader excavates hard ground, hard embankments, etc.

[0073] Although the present embodiment has been described above, the present disclosure is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the gist of the present disclosure.

[0074] Furthermore, the configuration of the control device 7 described in the above embodiment is one example, and it goes without saying that unnecessary parts may be deleted or new parts may be added within the scope of the present disclosure.

[0075] Furthermore, the processing flow of the control program 23A described in the above embodiment is also an example, and it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be rearranged within the scope of the present disclosure.

[0076] The present invention is also applicable to program products.

[0077] The controller and method described herein may be implemented by a special-purpose computer having a processor programmed to perform one or more functions embodied in a computer program. Alternatively, the apparatus and method described herein may be implemented by a special-purpose computer having a processor configured with dedicated hardware logic circuits. Alternatively, the apparatus and method described herein may be implemented by one or more special-purpose computers configured by a combination of a processor executing a computer program and one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0078] The following notes are provided regarding the technology of the present disclosure.

[0079] (Supplementary Note 1) A control device (7) for controlling a rotating electric machine (54a) that drives a work machine (5) provided on a vehicle, the control device comprising: an inverter control unit (32) that controls an inverter (10) that supplies power to the rotating electric machine, which is a drive source of an electric cylinder (54) that includes a mechanical element that drives the work machine; and a control unit (31) that, when detecting a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine, repeatedly changes the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

[0080] (Supplementary Note 2) The control device according to Supplementary Note 1, wherein, when the control unit detects the locked state, the control unit repeatedly changes the torque by alternately reducing the torque so as to release a torsion applied to the mechanical element and increasing the torque so as to apply a torsion to the mechanical element.

[0081] (Supplementary Note 3) The control device according to Supplementary Note 2, wherein, when the control unit detects the locked state, the control unit repeatedly changes the torque by alternately reducing the torque so as to release the torsion applied to the mechanical element by an elastic restoring force of the mechanical element, and increasing the torque so as to apply a torsion to the mechanical element against the elastic restoring force.

[0082] (Supplementary Note 4) The control device according to any one of Supplementary Notes 1 to 3, wherein the control unit repeatedly changes the torque so that an average value of a current flowing through a switch element included in the inverter is equal to or less than an allowable current in the locked state.

[0083] (Supplementary Note 5) The control device according to any one of Supplementary Notes 1 to 5, wherein the control unit changes the torque from decreasing to increasing when the electrical angle has changed by a predetermined value from the electrical angle at which the locked state was detected.

[0084] (Supplementary Note 6) The control device according to Supplementary Note 5, wherein the control unit changes the torque from increasing to decreasing when the electrical angle has changed by a predetermined value from the electrical angle at which the torque changed from decreasing to increasing.

[0085] (Supplementary Note 7) The control device according to any one of Supplementary notes 1 to 6, wherein the control unit detects the locked state based on a signal from at least one of the rotating electric machine and the inverter.

[0086] (Supplementary Note 8) The control device according to Supplementary Note 7, wherein the signal includes a signal indicating a change in the rotation speed of the rotating electric machine generated in response to a command torque of the rotating electric machine.

[0087] (Supplementary Note 9) The control device according to Supplementary Note 7, wherein the signal includes a signal indicating a temperature difference between a plurality of switch elements included in the inverter.

[0088] (Supplementary Note 10) The control device according to any one of Supplementary notes 1 to 9, wherein the control unit limits the torque based on a signal from at least one of the rotating electric machine and the inverter.

[0089] (Supplementary Note 11) An agricultural machine including the control device according to any one of Supplementary Notes 1 to 10.

[0090] (Supplementary Note 12) A construction machine equipped with the control device according to any one of Supplementary Notes 1 to 10.

[0091] (Supplementary Note 13) A control program (23A) that causes at least one processor (21A) to execute processing including: controlling an inverter that supplies power to a rotating electric machine that is a drive source of an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle; and, when detecting a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine, repeatedly changing the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

[0092] (Appendix 14) A control method that executes processing including: at least one processor controls an inverter that supplies power to a rotating electric machine that is a drive source of an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle; and, when detecting a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine, repeatedly changes the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

Claims

1. A control device (7) for controlling a rotating electric machine (54a) that drives a working machine (5) provided on a vehicle, comprising: an inverter control unit (32) that controls an inverter (10) that supplies power to the rotating electric machine, which is the driving source of an electric cylinder (54) that includes a mechanical element that drives the working machine; and a control unit (31) that, when detecting a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine, repeatedly changes the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

2. The control device according to claim 1, wherein, when the control unit detects the locked state, the control unit repeatedly changes the torque by alternately reducing the torque so as to release the torsion applied to the mechanical element and increasing the torque so as to apply torsion to the mechanical element.

3. The control device according to claim 2, wherein, when the control unit detects the locked state, the control unit repeatedly changes the torque by alternately reducing the torque so as to release the torsion applied to the mechanical element by the elastic restoring force of the mechanical element, and increasing the torque so as to apply a torsion to the mechanical element against the elastic restoring force.

4. The control device according to claim 1, wherein the control unit repeatedly changes the torque so that the average value of the current flowing through a switch element included in the inverter is equal to or less than the allowable current in the locked state.

5. The control device according to claim 1, wherein the control unit changes the torque from decreasing to increasing when the electrical angle has changed by a predetermined value from the electrical angle when the locked state was detected.

6. The control device according to claim 5, wherein the control unit changes the torque from increasing to decreasing when the electrical angle changes by a predetermined value from the electrical angle at which the torque changed from decreasing to increasing.

7. The control device according to claim 1, wherein the control unit detects the locked state based on a signal from at least one of the rotating electrical machine and the inverter.

8. The control device according to claim 7, wherein the signal includes a signal indicating a change in the rotation speed of the rotating electric machine generated in response to a command torque of the rotating electric machine.

9. The control device according to claim 7, wherein the signal includes a signal indicating a temperature difference between a plurality of switch elements included in the inverter.

10. The control device according to claim 1, wherein the control unit limits the torque based on at least one of the temperature of the rotating electrical machine and the temperature of the inverter.

11. An agricultural machine equipped with a control device according to any one of claims 1 to 10.

12. A construction machine equipped with a control device according to any one of claims 1 to 10.

13. A control program (23A) that causes at least one processor (21A) to execute processing including: controlling an inverter that supplies power to a rotating electric machine that is a drive source for an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle; and, when a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine is detected, repeatedly changing the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

14. A control method in which at least one processor controls an inverter that supplies power to a rotating electric machine that is a drive source for an electric cylinder that includes a mechanical element that drives a work machine provided on a vehicle, and when a locked state in which the rotating electric machine does not rotate when current is applied to the rotating electric machine is detected, repeatedly changes the torque generated by the rotating electric machine so that the electrical angle of the rotating electric machine changes by a predetermined value.

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