Electric motor control device and ship propulsion system

Abstract

The present invention provides an electric motor control device (1a) for each electric motor (2a) that drives each of a plurality of propulsion devices (8a) and these electric motor control devices (1a) monitor each other, the electric motor control device (1a) being characterized by comprising: a switching circuit (11); a control signal generation unit (13) that generates a control signal for the switching circuit; a control speed calculation unit (23) that calculates a control speed from the control signal; a control speed reduction determination unit (21) that determines a reduction in the control speed when the control speed is equal to or less than a control speed threshold value; and a control speed limit request unit (34) that requests the control speed of the switching circuit of another electric motor control device to be limited when the reduction in the control speed is determined. The present invention also provides a ship propulsion system (100) provided with a plurality of electric motor control devices (1a, 1b), electric motors (2a, 2b), and propulsion devices (8a, 8b).

Description

Electric motor control device and ship propulsion system

[0001] The present application relates to an electric motor control device and a marine propulsion system.

[0002] An outboard motor is a removable propulsion device that can be attached to a boat. An outboard motor is composed of a drive unit such as an electric motor, a propeller driven by the drive unit, a rudder, and an electric motor control unit that controls the electric motor. The outboard motor is attached to the outside of the stern plate at the rearmost part of the boat's hull.

[0003] A boat may be equipped with multiple outboard motors to form a boat propulsion system, either to improve the failure tolerance of the boat's propulsion device or to increase propulsive power. The use of multiple outboard motors is called a multi-motor system. In some cases, an inboard motor, which is a propulsion device installed inside the boat's hull, serves as the main propulsion device, and an outboard motor serves as an auxiliary propulsion device.

[0004] Consider the case where a boat equipped with outboard motors is propelled solely by the inboard motor that serves as the main propulsion unit, or by only some of the outboard motors. In these cases, the unused outboard motor is tilted up and raised above the waterline. However, there are cases where the tilt-up operation of the unused outboard motor is forgotten, or the tilt-up operation is not performed intentionally.

[0005] In cases where tilt-up is not intentional, the outboard motor's propeller may be rotated by the water current to generate electricity for the electric motor and charge the battery. Another example is when the outboard motor is used as a brake to rotate the hull, performing pivot turns or spin turns.

[0006] In such a case, when the boat is sailing at high speed, the water current causes the propeller of the outboard motor, which is stopped or rotating at a low speed, to rotate at high speed, generating excessive regenerative power. In this case, excessive voltage may be applied to the electric motor, switching circuits such as the inverter that supplies power to the electric motor, and the battery that is charged with the regenerative power, potentially shortening their lifespan and degrading their performance. To address this issue, technology has been disclosed that provides a path adjustment device, such as an electromagnetic brake or electromagnetic clutch, in the power transmission path of the outboard motor to prevent over-rotation of the electric motor and inverter failure (see, for example, Patent Document 1).

[0007] Japanese Patent Application Laid-Open No. 2014-80077

[0008] According to the technology described in Patent Document 1, it is necessary to add mechanical parts such as an electromagnetic brake or electromagnetic clutch to the power transmission path of the outboard motor as a path adjustment means. This increases the weight of the outboard motor, which is undesirable for outboard motors where power-to-weight ratio is important. Furthermore, adding such mechanical parts also increases costs.

[0009] The present application has been made to solve these problems. The purpose of the disclosed technology of the present application is to provide an electric motor control device that prevents overspeed of the electric motor of an outboard motor that is not tilted up and prevents malfunctions of the electric motor, switching circuit, and battery without increasing weight or cost. It is also an object of the present application to prevent overspeed of the electric motor of an outboard motor that is not tilted up and prevent malfunctions of the electric motor, switching circuit, and battery in a marine propulsion system that includes multiple propulsors driven by electric motors controlled by the electric motor control device.

[0010] The electric motor control device according to the present application is characterized in that the electric motor control device is provided for each electric motor that drives a plurality of propulsors, and includes: a switching circuit that supplies power to the electric motor that drives the propulsor; a control signal generation unit that generates a control signal that controls the on / off of the switching circuit; a control speed calculation unit that calculates the control speed of the switching circuit from the control signal generated by the control signal generation unit; a control speed reduction determination unit that determines a reduction in the control speed when the control speed of the switching circuit calculated by the control speed calculation unit is equal to or less than a predetermined control speed threshold; and a control speed limit request unit that requests a limit on the control speed that controls the on / off of a switching circuit of another electric motor control device provided for another electric motor that drives another propulsor, when a reduction in the control speed is determined by the control speed reduction determination unit.

[0011] The marine vessel propulsion system according to the present application includes a plurality of electric motor control devices, electric motors, and propulsors.

[0012] The motor control device according to the present application can prevent overspeed of the motor of an outboard motor that is not tilted up and prevent failures of the motor, switching circuit, and battery without increasing weight or cost. The boat propulsion system according to the present application includes a plurality of motor control devices that control the motors that drive the propulsors, and can prevent overspeed of the motor of an outboard motor that is not tilted up and prevent failures of the motor, switching circuit, and battery without increasing weight or cost.

[0013] Fig. 1 is a block diagram showing a configuration of a motor control device according to embodiment 1. Fig. 2 is a hardware configuration diagram of the motor control device according to embodiment 1. Fig. 3 is a flowchart showing a control speed limit request process of the motor control device according to embodiment 1. Fig. 4 is a block diagram showing a configuration of a motor control device according to embodiment 2. Fig. 5 is a flowchart showing a control speed limit request process of the motor control device according to embodiment 2.

[0014] Hereinafter, an electric motor control device and a marine vessel propulsion system according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are designated by the same reference numerals.

[0015] 1. Embodiment 1 <Configuration of electric motor control device> Figure 1 shows the configuration of electric motor control devices 1a and 1b connected to each other by a communication line according to embodiment 1. While Figure 1 illustrates a boat propulsion system 100 equipped with two outboard motors 3a and 3b as a whole, the boat propulsion system may also include three or more outboard motors. Furthermore, although Figure 1 illustrates the outboard motors 3a and 3b as the target, the electric motor control devices 1a and 1b according to embodiment 1 can also be applied to inboard motors driven by electric motors.

[0016] The two outboard motors 3a, 3b have similar configurations, each equipped with a propeller 8a, 8b, electric motor 2a, 2b, and electric motor control device 1a, 1b. Therefore, the outboard motor 3a will be described as a representative. The motor control device 1a and electric motor 2a are housed in the cowling of the outboard motor 3a, and the electric motor 2a drives the propeller. The external high-voltage power supply 4 is connected to the outboard motor 3a via a relay 6a. The external low-voltage power supply 5 is connected to the outboard motor 3a via a relay 7a.

[0017] The external high-voltage power supply 4 is a DC power supply that stores energy mainly for driving the electric motor 2a and often has a power supply voltage of 48 V to several hundred V. The external low-voltage power supply 5 is a DC power supply that often has a power supply voltage of 12 V. The electric motor 2a drives a propeller 8a to generate propulsion power for the vessel. The electric motor 2a is supplied with AC power by the electric motor control device 1a.

[0018] <Switching Circuit> The motor control device 1a has a switching circuit 11, a smoothing capacitor 12 (not shown), a control signal generation unit 13, an insulation unit 14, a low-voltage power supply circuit 15, a high-voltage power supply circuit 20, a control speed reduction determination unit 21, a voltage detection unit 22, a control speed calculation unit 23, a control speed limit unit 24, and a control speed limit request unit 34.

[0019] The switching circuit 11 is a power conversion device. Examples of power conversion devices include an AC / DC (Alternate Current / Direct Current) converter that converts AC power to DC power, an inverter that converts DC power to AC power, and a DC / DC (Direct Current / Direct Current) converter that changes the input and output voltage levels of DC power. These power conversion devices often include a semiconductor switching element.

[0020] 1, the switching circuit 11 is an inverter that converts DC power into AC power and supplies the AC power to the electric motor 2a. The switching circuit 11 has a switching element, such as an IGBT (Insulated Gate Bipolar Transistor). The switching element may be a normal bipolar transistor, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or the like.

[0021] The smoothing capacitor 12 is disposed in the upstream stage of the switching circuit 11, and is provided between the positive electrode side and GND side of the output of the external high-voltage power supply 4. The smoothing capacitor 12 smoothes the voltage applied to the switching circuit 11.

[0022] The control signal generator 13 generates a control signal for controlling the on / off of the switching circuit 11 in accordance with a required control amount requested from the outside. The required control amount input from the outside includes a required torque, a required current, a required rotation speed, etc., and Fig. 1 shows an example in which the required rotation speed Neobj is given.

[0023] <Control Signal Generator> The control signal generator 13 operates on power supplied from the external low-voltage power supply 5 and output by the low-voltage power supply circuit 15. The region in which it operates on the low-voltage power supply circuit 15 is shown as a low-voltage region 9a. In Fig. 1, the regions other than the low-voltage region 9a are high-voltage regions.

[0024] Insulation may be required between the low voltage region 9a and the high voltage region. For this reason, the output of the control signal generating unit 13 transmits a control signal to the switching circuit 11 in the high voltage region via an insulating unit 14. The insulating unit may be a photocoupler, an open collector type transistor circuit, an FET circuit, or the like.

[0025] The control speed reduction determination unit 21, voltage detection unit 22, control speed calculation unit 23, control speed limit unit 24, and control speed limit request unit 34 are operated by the power supply of the voltage output by the high-voltage power supply circuit 20 from the power supply supplied by the external high-voltage power supply 4. In Fig. 1, these are operated by the power supply of the voltage output by the high-voltage power supply circuit 20, but they may be arranged in the low-voltage region 9a and operated by the voltage output by the low-voltage power supply circuit 15. Furthermore, the control speed reduction determination unit 21, control speed calculation unit 23, control speed limit unit 24, control speed limit request unit 34, etc. may be configured as functional blocks of the arithmetic processing unit of the motor control device 1a together with the control signal generation unit 13.

[0026] <Voltage Detection Unit> The voltage detection unit 22 detects the voltage of the smoothing capacitor 12 connected to the switching circuit 11. If the voltage detected by the voltage detection unit 22 exceeds a predetermined voltage threshold Vth, it can be determined that the electric motor 2a is being rotated by the propeller 8a to generate electricity and generate a regenerative current. In this case, it is considered possible that the regenerative current will become excessive, causing an overvoltage to be applied to the switching circuit 11.

[0027] <Control Speed ​​Calculation Unit> The control speed calculation unit 23 calculates the control speed SPDsw of the switching circuit 11 from the control signal output from the control signal generation unit 13. Here, the control speed SPDsw of the control signal may be the frequency of the on / off signal itself. Furthermore, the switching circuit 11 functions as an inverter and can rotate the electric motor 2a, which is an AC motor, by changing the duty of the on / off signal. The rotation speed NE of the electric motor 2a may be calculated from the change in the duty of the on / off signal at this time, and this may be used as the control speed SPDsw.

[0028] The control speed calculation unit 23 transmits the calculated control speed SPDsw to the control speed reduction determination unit 21. A filter may be provided within the control speed calculation unit 23 to prevent malfunction of the control speed calculation by the control speed calculation unit 23. For example, a digital filter may be used to determine the on or off state of the on / off signal. This makes it possible to deal with cases where noise is superimposed on the control signal. Furthermore, when calculating the control speed SPDsw, a first-order lag filter may be used to calculate the frequency (period) of the on / off signal.

[0029] Furthermore, for example, if the drive switching frequency of the switching circuit 11 is fixed in advance, the control speed calculation unit 23 may set a judgment time based on that drive switching frequency, and if a switching waveform cannot be confirmed within the judgment time, the control speed may be calculated as 0. In this case, it means that the switching circuit 11 is not operating. Also, if the on / off frequency of the switching circuit 11 is variable, for example, the drive switching frequency at the time of the previous calculation may be stored in a nonvolatile memory, and the judgment time may be set based on that memory.

[0030] 1, the control speed calculation unit 23 is configured to calculate the control speed SPDsw of the switching circuit 11 from the control signal output from the control signal generation unit 13 after it has passed through the insulating unit 14. As described above, the control speed calculation unit 23, together with the control signal generation unit 13, may be a functional block of the arithmetic processing unit 90 of the motor control device 1a.

[0031] <Control Speed ​​Reduction Determination Unit> The control speed reduction determination unit 21 determines that the control speed has decreased when the control speed SPDsw of the switching circuit calculated by the control speed calculation unit 23 is equal to or less than a predetermined control speed threshold SPDth. A value close to 0 may be set as the control speed threshold SPDth, and the control speed reduction may be determined when the control speed SPDsw is equal to or less than this value, thereby determining that the switching circuit 11 is stopped. The timing at which the control speed reduction determination unit 21 performs the determination may be set to a timing corresponding to the cycle at which the control signal generation unit 13 generates the control signal. By performing the determination at the generation cycle of the control signal or a multiple of that cycle, it is possible to perform a quick and stable determination.

[0032] <Control Speed ​​Limit Request Unit> When the control speed reduction determination unit 21 determines that the control speed is decreasing, the control speed limit request unit 34 requests the motor control device of the other outboard motor to limit the control speed of the control signal of the other switching circuit. In the case of Figure 1, the control speed limit request unit 34 requests the motor control device 1b to limit the control speed of the switching circuit 11 that supplies power to the electric motor 2b that drives the propeller 8b of the other outboard motor 3b, thereby reducing the output of the propeller 8b of the outboard motor 3b.

[0033] For example, if the control speed reduction determination unit 21 determines from the output of the control speed calculation unit 23 that the switching circuit 11 has stopped operating, it may send a control speed limit request signal to the control speed limiter 24 of the other outboard motor 3a to stop the drive of that outboard motor 3a. In this way, it is possible to prevent the propeller 8a of the stopped outboard motor 3a from rotating due to the water flow and the electric motor 2a from generating electricity, thereby preventing an overvoltage from occurring.

[0034] The motor control device 1b is similar to the motor control device 1a shown in Fig. 1, and therefore, a description of the motor control device 1b will be omitted here.

[0035] <Hardware Configuration of Motor Control Device> Fig. 2 is a hardware configuration diagram of the motor control device 1a according to the first embodiment. The configuration of Fig. 2 can also be applied to the motor control device 1b, but here, the configuration will be described using the motor control device 1a as a representative. In this embodiment, each function of the motor control device 1a is realized by a processing circuit provided in the motor control device 1a. Specifically, as shown in Fig. 2, the motor control device 1a includes, as processing circuits, an arithmetic processing device 90 (computer) such as a CPU (Central Processing Unit), a storage device 91 that exchanges data with the arithmetic processing device 90, an input circuit 92 that inputs external signals to the arithmetic processing device 90, and an output circuit 93 that outputs signals from the arithmetic processing device 90 to the outside.

[0036] The arithmetic processing device 90 may include an application-specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), various logic circuits, various signal processing circuits, etc. Furthermore, the arithmetic processing device 90 may include a plurality of the same or different types of devices, each performing a different process. The storage device 91 may include a random access memory (RAM) configured to be able to read and write data from the arithmetic processing device 90, a read-only memory (ROM) configured to be able to read data from the arithmetic processing device 90, a flash memory, etc. The input circuit 92 is connected to various sensors and switches and includes an A / D converter and the like that inputs output signals from the sensors and switches to the arithmetic processing device 90. The output circuit 93 is connected to electrical loads such as switching elements and includes a drive circuit and the like that converts and outputs control signals from the arithmetic processing device 90 to the electrical loads. The motor control device 1a includes a switching circuit 11 in the output circuit 93 and is capable of driving the electric motor 2a.

[0037] Each function of the motor control device 1a is realized by an arithmetic processing device 90 executing software (programs) stored in a storage device 91 such as a ROM, and cooperating with other hardware of the motor control device 1a, such as the storage device 91, an input circuit 92, and an output circuit 93. Setting data such as thresholds and judgment values ​​used by the motor control device 1a are stored in the storage device 91 such as a ROM as part of the software (programs). The functions of the components of the motor control device 1a will be described below. Each function of the motor control device 1a may be configured as a software module, or may be configured as a combination of software and hardware.

[0038] <Control Speed ​​Limit Request Processing> Fig. 3 is a flowchart showing the control speed limit request processing of the motor control device 1a according to embodiment 1. The processing of the flowchart in Fig. 3 can also be applied to the motor control device 1b, but here the motor control device 1a will be described.

[0039] The process shown in Fig. 3 is executed by the arithmetic processing unit of the motor control device 1a. The process of Fig. 3 may be executed at predetermined time intervals (for example, every 5 ms). Alternatively, the process may be executed for each event, such as every predetermined cruising distance or every communication, instead of at predetermined time intervals. In the motor control device 1a of the outboard motor 3a, the control signal generating unit 13 generates a control signal for rotating the motor in accordance with the required rotation speed Neobj. The process for this purpose is executed separately from the process of Fig. 3.

[0040] When the process starts, in step S101, it is checked whether a control speed limit request has been received from the motor control device 1b of the other outboard motor 3b. If a control speed limit request has not been received in step S102 (determination is NO), the process proceeds to step S104.

[0041] In step S102, if a control speed limit request is received (determination is YES), the process proceeds to step S103, where control speed limit processing is executed. Specifically, the operation of the switching circuit 11 may be stopped. Alternatively, the frequency of the control signal to the switching circuit 11 may be limited. Furthermore, the rotation speed NE of the electric motor 2a may be limited. After step S103, the process proceeds to step S104.

[0042] In step S104, the control speed calculation unit 23 calculates the control speed SPDsw from the control signal of the control signal generation unit 13. Next, in step S107, the voltage detection unit 22 detects the switching circuit voltage Vsw.

[0043] In step S108, it is determined whether the switching circuit voltage Vsw is higher than the voltage threshold Vth. If the switching circuit voltage Vsw is not higher than the voltage threshold Vth (determination is NO), the process ends. If the switching circuit voltage Vsw is not higher than the voltage threshold Vth, this means that the propeller 8a of the outboard motor 3a is not constrained to rotate due to the water current, the electric motor 2a is not rotating to generate electricity, and no regenerative power is being generated, meaning that there is no need to reduce the output of the other outboard motor 3b. However, the process of step S108 may be omitted, and the need to reduce the output of the other outboard motor 3b may be determined based solely on the control speed of the switching circuit 11, regardless of the value of the switching circuit voltage Vsw.

[0044] If, in step S108, the switching circuit voltage Vsw is higher than the voltage threshold Vth (the determination is YES), the process proceeds to step S109. In step S109, it is determined whether the control speed SPDsw is equal to or less than the control speed threshold SPDth. If the control speed SPDsw is not equal to or less than the control speed threshold SPDth (the determination is NO), the control ends. In this case, the switching circuit 11 is operating, and the outboard motor propeller is not being rotated unintentionally by the water current due to a failure to tilt up the boat, for example.

[0045] If the control speed SPDsw is equal to or less than the control speed threshold SPDth (determination is YES) in step S109, the process proceeds to step S110. In step S110, a control speed limit request is sent to the other motor control device 1b. This reduces the output of the other outboard motor 3b, preventing the propeller 8a of the outboard motor 3a from being rotated by the water current and causing an overvoltage due to the power generation current of the motor 2a. Then, the process ends.

[0046] As described above, the motor control devices 1a, 1b according to the first embodiment can prevent overspeed of the motors of outboard motors that are not tilted up, and prevent failures of the motors, switching circuits, and batteries, without increasing weight or cost. Furthermore, in a boat propulsion system 100 including propulsors 8a, 8b driven by electric motors 2a, 2b controlled by the motor control devices 1a, 1b, it is possible to prevent overspeed of the motors of outboard motors that are not tilted up, and prevent failures of the motors, switching circuits, and batteries. Regarding drive control by the electric motors of multiple propulsors provided on a boat, the motor control device according to the first embodiment can also be applied to inboard motors.

[0047] 2. Second Embodiment Fig. 4 is a block diagram showing the configuration of motor control devices 1a and 1b according to a second embodiment. The diagram shows a boat propulsion system 100 equipped with two outboard motors 3a and 3b as a whole. Fig. 4 differs from Fig. 1 according to the first embodiment in that a control speed transmission unit 32 and an other switching circuit control speed acquisition unit 33, which are not shown in Fig. 1, have been added. Only the differences will be described below. The motor control device 1a according to the second embodiment will be described below. The same applies to the motor control device 1b, so its description will be omitted.

[0048] The motor control device 1a according to the second embodiment exchanges control speed information of the switching circuit 11 with the other motor control device 1b. This makes it possible to compare the control speed SPDot of the switching circuit 11 of the other outboard motor 3b with the control speed SPDsw of its own switching circuit 11, and determine whether or not a control speed limit request is required for the other motor control device 1b based on the difference in control speed (SPDot is not shown).

[0049] <Control Speed ​​Transmitter and Other Switching Circuit Control Speed ​​Acquirer> After the control speed is calculated by the control speed calculator 23, the control speed transmitter 32 transmits control speed SPDsw information to the other motor control device 1b. The timing of transmitting the control speed SPDsw information by the control speed transmitter 32 may be set to a timing corresponding to the cycle in which the control signal of the switching circuit 11 is generated. This is because by transmitting the latest control speed every time it is calculated, the latest information can be reflected in the other motor control device 1b.

[0050] Then, the other switching circuit control speed acquisition unit 33 acquires the control speed SPDot information of the switching circuit 11 of the other motor control device 1b transmitted from the other motor control device 1b. It is desirable that the other motor control device 1b calculates and transmits the control speed of the switching circuit 11 at a timing corresponding to the cycle in which the control signal of the switching circuit 11 is generated. This is because the latest information of the other motor control device 1b can be reflected.

[0051] 4, it is assumed that the motor control device 1a calculates the control speed SPDsw of the control signal of the switching circuit 11 as the rotation speed NE of the motor 2a. Then, another motor control device 1b calculates and transmits the control speed SPDot of the control signal of the switching circuit 11 as the rotation speed of the motor 2a, and the motor control device 1a receives it as NEot.

[0052] At this time, the control speed reduction determination unit 21 determines that the control speed has been reduced when the rotation speed NE of the electric motor 2a is equal to or less than the value obtained by subtracting a predetermined rotation speed difference threshold dNEth from the rotation speed NEot of the other electric motor 2b. In other words, when the difference between the rotation speed NE of the electric motor 2a and the rotation speed NEot of the electric motor 2b is equal to or greater than the rotation speed difference threshold dNEth, the control speed reduction determination unit 21 determines that the control speed has been reduced.

[0053] Here, the control speed reduction determination unit 21 may make its determination depending on the timing at which the other switching circuit control speed acquisition unit 33 acquires the control speed SPDot information of the switching circuit 11 of the other motor control device 1b. It is possible to imagine a case where the timing corresponds to the cycle at which the control signal for controlling the switching circuit 11 of the other motor control device 1b is generated, which is more desirable. This is because it allows the most recent information from the other motor control device 1b to be reflected. Then, when a control speed reduction is determined, the control speed limit request unit 34 requests the motor control device 1b of the other outboard motor 3b to limit the control speed of the control signal for the other switching circuit 11.

[0054] This control can be used when charging a battery by rotating the propeller of an outboard motor with a water current and using the electric motor to generate electricity, or when performing a pivot turn or spin turn in which the outboard motor is used as a brake to rotate the hull. In these cases, it is possible to prevent unnecessary requests to limit the control speed of the control signal of the other outboard motor control device 1b. Furthermore, even when charging a battery with regenerative power or performing a pivot turn or spin turn, if the speed difference with the electric motor of the other outboard motor is too large, it is possible to request a limit on the control speed of the control signal of the other outboard motor. This avoids the occurrence of overvoltage and prevents damage to the electric motor, switching circuit, and battery.

[0055] <Control Speed ​​Limit Request Processing> Fig. 5 is a flowchart showing the control speed limit request processing of the motor control devices 1a and 1b according to embodiment 2. The processing of the flowchart in Fig. 5 can also be applied to the motor control device 1b, but here the motor control device 1a will be described.

[0056] The process shown in Fig. 5 is executed by the arithmetic processing unit of the motor control device 1a. The process of Fig. 5 may be executed at predetermined time intervals (for example, every 5 ms). Alternatively, it may be executed for each event, such as every predetermined cruising distance or every time communication is performed, rather than at predetermined time intervals. In the motor control device 1a of the outboard motor 3a, the control signal generating unit 13 generates a control signal for rotating the motor in accordance with the required rotation speed Neobj. The process for this purpose is executed separately from the process of Fig. 5.

[0057] The process in Fig. 5 differs from the process in Fig. 3 according to the first embodiment in that step S104 in Fig. 3 is changed to step S114, step S115, and step S116 in Fig. 5, and step S109 in Fig. 3 is changed to step S119 in Fig. 5. The changed parts will be described below.

[0058] In step S114, the control speed calculation unit 23 calculates the control speed as the rotation speed NE of the electric motor 2a from the control signal of the control signal generation unit 13. In step S115, the calculated rotation speed NE information is transmitted to the other electric motor control device 1b.

[0059] In step S116, the other switching circuit control speed acquisition unit 33 receives control speed information of the other switching circuit from the other motor control device 1b. Here, the other motor control device 1b receives rotation speed information of the electric motor 2b to which power is supplied, and acquires this as the other switching circuit control speed NEot. Then, the process proceeds to step S107.

[0060] In step S119, the control speed is compared as the rotational speed of the electric motor. It is determined whether the rotational speed NE of the electric motor 2a is equal to or less than the value obtained by subtracting the rotational speed difference threshold dNEth from the rotational speed NEot of the electric motor 2b of the other outboard motor 3b. That is, if the difference between the rotational speed NE of the electric motor 2a and the rotational speed NEot of the electric motor 2b is equal to or greater than the rotational speed difference threshold dNEth, it is determined that the control speed has decreased.

[0061] If the rotation speed NE is not equal to or less than the value obtained by subtracting the rotation speed difference threshold dNEth from the rotation speed NEot (the determination is NO), the control ends. In this case, since the rotation speed difference is smaller than the rotation speed difference threshold dNEth, it is considered that the influence of regenerative power is small even if the outboard motor propeller is rotated by the water current.

[0062] If, in step S119, the rotation speed NE is equal to or less than the value obtained by subtracting the rotation speed difference threshold dNEth from the rotation speed NEot (the determination is YES), the process proceeds to step S110. In step S110, a control speed limit request is sent to the other motor control device 1b. This reduces the output of the other outboard motor 3b, preventing the propeller 8a of the outboard motor 3a from being rotated by the water current and causing an overvoltage due to the power generation current of the motor 2a. Then, the process ends.

[0063] As described above, the motor control devices 1a and 1b according to the second embodiment can compare the control speeds of the control signals of the switching circuits 11 of the respective motor control devices 1a and 1b. This allows the difference in the operating conditions of the outboard motors 3a and 3b to be appropriately understood. This prevents unnecessary requests to limit the control speed of the control signal from the other motor control device 1b. If the difference in the control speeds of the outboard motors 3a and 3b is too large, a request to limit the control speed of the control signal from the outboard motor with the higher control speed can be made. This avoids the occurrence of overvoltage and prevents failures of the motors, switching circuits, and batteries. Note that the motor control device according to the second embodiment can also be applied to inboard motors for drive control by electric motors for multiple propulsion units on a marine vessel.

[0064] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0065] 1a, 1b Electric motor control device, 2a, 2b Electric motor, 3a, 3b Outboard motor, 8a, 8b Propulsion unit, 11 Switching circuit, 13 Control signal generation unit, 21 Control speed reduction determination unit, 22 Voltage detection unit, 23 Control speed calculation unit, 33 Other switching circuit control speed acquisition unit, 34 Control speed limit request unit, 100 Marine propulsion system

Claims

1. In a motor control device provided for each of the electric motors that drive the plurality of propulsion units, A switching circuit for supplying power to the electric motor that drives the propulsion unit; a control signal generating unit that generates a control signal for controlling the on / off of the switching circuit; a control speed calculation unit that calculates a control speed of the switching circuit from the control signal generated by the control signal generation unit; a control speed reduction determination unit that determines a reduction in the control speed when the control speed of the switching circuit calculated by the control speed calculation unit is equal to or lower than a predetermined control speed threshold value; and a control speed limit request unit that requests, when a decrease in the control speed is determined by the control speed decrease determination unit, to limit a control speed for controlling on / off of a switching circuit of another motor control device provided for another motor that drives another propulsion unit.

2. the control speed reduction determination unit uses the control speed threshold value for determination as a value indicating a stop of on / off control of the switching circuit, 2. The motor control device according to claim 1, wherein the control speed limit request unit requests the stopping of on / off control of the switching circuit of the other motor control device as the request to limit the control speed of the switching circuit of the other motor control device.

3. The electric motor control device according to claim 1 , wherein the control speed reduction determination unit determines the reduction in the control speed at a timing corresponding to a cycle in which the control signal generation unit generates the control signal.

4. The motor control device according to claim 1 , wherein the control speed calculation unit calculates the control speed of the switching circuit based on the control signal generated by the control signal generation unit through a filter.

5. a different switching circuit control speed acquisition unit that acquires a control speed of a different switching circuit that supplies power to the different electric motor from the different electric motor control device; 2. The motor control device according to claim 1, wherein the control speed reduction determination unit determines the control speed threshold value used for the determination to be a value obtained by subtracting a predetermined control speed difference threshold value from the control speed of the switching circuit of the other motor control device acquired by the other switching circuit control speed acquisition unit.

6. The motor control device according to claim 5 , wherein the control speed reduction determination unit determines the reduction in the control speed at a timing corresponding to a cycle in which a control signal for controlling a switching circuit of the other motor control device is generated.

7. the control speed calculation unit calculates a rotation speed of the electric motor as a control speed of the switching circuit, the other switching circuit control speed acquisition unit acquires a rotation speed of the other electric motor as a control speed of a switching circuit of the other electric motor control device; The motor control device according to claim 5 , wherein the control speed reduction determination unit determines that the control speed is reduced when the rotation speed of the motor is equal to or less than a value obtained by subtracting a predetermined rotation speed difference threshold from the rotation speed of the other motor.

8. a voltage detection unit that detects a voltage applied to the switching circuit, 2. The motor control device according to claim 1, wherein the control speed limit request unit requests the other motor control device to limit the control speed of the switching circuit of the other motor control device when the voltage applied to the switching circuit detected by the voltage detection unit is greater than a predetermined voltage threshold and the control speed reduction determination unit determines that the control speed is reducing.

9. The motor control device according to claim 1 , wherein the propeller and the other propeller are mounted on a same ship.

10. 10. The motor control device according to claim 9, wherein the propulsion device is an outboard motor.

11. A marine vessel propulsion system comprising a plurality of electric motor control devices, electric motors, and propulsors according to any one of claims 1 to 10.