Anomaly detection device and anomaly detection method

Abstract

To provide an abnormality detection device and an abnormality detection method that suppress false detection of motor abnormalities. [Solution] The abnormality detection device according to the embodiment is provided in an electric vehicle that drives a motor based on a target rotational speed. The abnormality detection device includes a controller. The controller detects a motor abnormality when the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality determination threshold, and when the generation of regenerative current by the motor is not detected.

Description

Technical Field

[0001] The present invention relates to an abnormality detection device and an abnormality detection method.

Background Art

[0002] In an electric vehicle driven by a motor, when an abnormality occurs in the motor, it is generally performed to detect the abnormality of the motor. For example, a technique for detecting an abnormality of the motor when a state where the difference between the actual rotation speed of the motor and the target rotation speed of the motor is large is detected is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, for example, when an electric vehicle is traveling on a downhill slope and regenerative braking force is generated by the motor, due to the influence of the weight of the electric vehicle, the deviation of the actual rotation speed of the motor from the target rotation speed of the motor may become large. Therefore, even if the motor is normal, the difference between the target rotation speed of the motor and the actual rotation speed of the motor may become large, and there is a risk that the abnormality of the motor is erroneously detected.

[0005] The present invention has been made in view of the above, and an object thereof is to suppress the erroneous detection of the abnormality of the motor.

Means for Solving the Problems

[0006] An abnormality detection device according to one embodiment is installed in an electric vehicle that drives a motor based on a target rotational speed. The abnormality detection device includes a controller. The controller detects a motor abnormality when the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality determination threshold, and when the generation of regenerative current by the motor is not detected.

[0007] Furthermore, an abnormality detection device according to another embodiment is installed in an electric vehicle that drives a motor based on a target rotational speed. The abnormality detection device includes a controller. The controller determines that there is a motor abnormality when the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality determination threshold. The controller masks the determination that there is a motor abnormality when the generation of regenerative current by the motor is detected. [Effects of the Invention]

[0008] The abnormality detection device according to the embodiment can suppress false detection of motor abnormalities by detecting whether or not an abnormality has occurred in the motor according to the detection status of the regenerative current in the motor, even when the difference between the target rotational speed of the motor and the actual rotational speed of the motor becomes large. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of a vehicle according to this embodiment. [Figure 2] Figure 2 is a block diagram illustrating the control device according to the embodiment. [Figure 3] Figure 3 is a flowchart illustrating the first anomaly detection process according to the embodiment. [Figure 4] Figure 4 shows the motor rotation speed when the accelerator lever is moved in small increments while a vehicle is traveling down a steep incline. [Figure 5] Figure 5 is a flowchart illustrating the second anomaly detection process according to the embodiment. [Figure 6] Figure 6 is a flowchart illustrating the vehicle speed limiting process according to the embodiment. [Figure 7]Figure 7 shows the motor rotation speed when the accelerator lever is moved to a large extent while a vehicle is traveling down a steep incline. [Figure 8] Figure 8 is a flowchart illustrating the first anomaly detection process related to a modified example. [Modes for carrying out the invention]

[0010] The abnormality detection device and abnormality detection method according to the embodiment will be described in detail below with reference to the attached drawings. However, this embodiment does not limit the present invention.

[0011] Vehicle 1 according to this embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram of Vehicle 1 according to this embodiment. Vehicle 1 is an electric vehicle driven by a motor 7. Vehicle 1 may be a normal vehicle intended to travel on roadways, but a vehicle with a low travel speed intended to travel on sidewalks, etc., is more preferable. Examples of vehicles with a low travel speed include mobility scooters and electric wheelchairs.

[0012] Vehicle 1 comprises a main body 2, wheels 3, a steering wheel 4, an accelerator lever 5, a brake lever 6, a motor 7, an inverter 8, a battery 9, and a control device 10 (anomaly detection device). The main body 2 is provided with a seat 2a in which the driver sits. An accelerator pedal or the like may be provided instead of the accelerator lever 5.

[0013] In the following explanation, the direction in front of the driver seated on seat 2a, facing the direction in which the steering wheel 4 is located (upper side of Figure 1), will be referred to as the front, and the opposite side as the rear. Furthermore, the right side of the driver seated on seat 2a will be referred to as the right, and the left side of the driver will be referred to as the left. Additionally, the vertical direction will be referred to as downward, and the opposite side as upward.

[0014] The wheel 3 includes a front wheel 11 and a rear wheel 12. The front wheel 11 is pivotally supported by a shaft extending in the left-right direction. The rear wheel 12 is provided behind the front wheel 11. The rear wheel 12 includes a left rear wheel 12L provided on the left side and a right rear wheel 12R provided on the right side. The rear wheel 12 is pivotally supported by a shaft extending in the left-right direction.

[0015] The handle 4 is attached to the main body 2 via an attachment portion extending in the up-down direction. The handle 4 extends, for example, in the left-right direction and is gripped by the driver. By operating the handle 4, the steering angle of the front wheel 11 is changed. Instead of the handle 4, a joystick or the like may be provided.

[0016] The brake lever 6 is attached to the handle 4. By operating the brake lever 6, the target rotational speed of the motor 7 is set so that the output of the motor 7 becomes zero. When the brake lever 6 is operated during the running of the vehicle 1, the regenerative braking of the motor 7 is activated.

[0017] The motors 7 are provided on the rear wheels 12 respectively. That is, the motor 7 includes a left motor 7L provided on the left rear wheel 12L and a right motor 7R provided on the right rear wheel 12R. The motor 7 drives the rear wheel 12. The motor 7 generates a driving force and a braking force according to the operation amount of the accelerator lever 5. When there is an operation amount of the accelerator lever 5 and the operation amount is not smaller than the previous (immediately preceding) operation amount, the motor 7 is in a power running state and generates a driving force. When the accelerator lever 5 is not operated, the motor 7 does not generate a driving force and a braking force. When the operation amount of the accelerator lever 5 becomes smaller than the previous (immediately preceding) operation amount during running, the motor 7 is in a regenerative state and functions as a generator. When the motor 7 functions as a generator and a regenerative current is generated, a regenerative braking force is generated in the vehicle 1.

[0018] The inverter 8 generates an alternating current drive signal for driving the motor 7 and outputs the generated drive signal to the motor 7. The drive signal is generated based on an instruction signal transmitted from the control device 10. The instruction signal is the target rotational speed of the motor 7. That is, the inverter 8 is a motor controller that controls the motor 7 based on the target rotational speed of the motor 7 transmitted from the control device 10. The inverter 8 is connected to the control device 10 by CAN (Controller Area Network) communication. The inverter 8 transmits information such as the rotational speed of the motor 7, specifically, the rotational speed of the rotating shaft of the motor 7, to the control device 10.

[0019] The inverter 8 is provided for the left motor 7L and the right motor 7R, respectively. That is, the inverter 8 includes a left inverter 8L provided for the left motor 7L and a right inverter 8R provided for the right motor 7R.

[0020] The battery 9 supplies power to the motor 7 and other electrically operated devices provided in the vehicle 1 such as the control device 10 (not shown). Also, when the motor 7 functions as a generator, the battery 9 is charged by the regenerative current of the motor 7. Further, the battery 9 is charged by being connected to an external power source via a charging cable (not shown). The battery 9 is removable from the vehicle 1, and it may be configured to be connected to a charger provided at home or the like for charging after being removed from the vehicle 1.

[0021] As shown in FIG. 2, the control device 10 includes a controller 20 and a storage unit 21. FIG. 2 is a block diagram for explaining the control device 10 according to the embodiment.

[0022] The storage unit 21 is realized by a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a flash memory. Various data and various programs are stored in the storage unit 21.

[0023] The controller 20 corresponds to a so-called processor. The controller 20 is implemented by a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphical Processing Unit), etc. The controller 20 executes a program according to an embodiment not shown in the diagram, which is stored in the memory unit 21, using RAM as the working area. The controller 20 can also be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0024] The controller 20 is connected to a vehicle speed sensor 30, an accelerator sensor 31, a start switch 32, a reverse switch 33, a tilt sensor 34, and a brake sensor 35, among others. The controller 20 acquires signals output from the vehicle speed sensor 30, the start switch 32, and other devices.

[0025] The vehicle speed sensor 30 detects the vehicle speed of vehicle 1. The vehicle speed sensor 30 outputs a signal indicating the detected vehicle speed to the controller 20. The accelerator sensor 31 detects the amount of operation of the accelerator lever 5. The accelerator sensor 31 outputs a signal indicating the detected amount of operation of the accelerator lever 5 to the controller 20.

[0026] The start switch 32 is a switch that switches the vehicle 1 on and off. The reverse switch 33 is a switch that switches the vehicle 1 on and off. When the reverse switch 33 is ON and the amount of movement of the accelerator lever 5 is not zero, the vehicle 1 moves in reverse. When the reverse switch 33 is OFF and the amount of movement of the accelerator lever 5 is not zero, the vehicle 1 moves forward.

[0027] The tilt sensor 34 detects the tilt of the vehicle 1. That is, the tilt sensor 34 detects the inclination angle of the road surface on which the vehicle 1 is traveling. The tilt sensor 34 outputs a signal indicating the detected inclination angle to the controller 20. The tilt sensor 34 is, for example, a G-sensor.

[0028] The brake sensor 35 detects whether or not the brake lever 6 is being operated. The brake sensor 35 turns ON when the brake lever 6 is operated. The brake sensor 35 turns OFF when the brake lever 6 is not being operated. The brake sensor 35 outputs a signal to the controller 20 regarding whether or not the brake lever 6 is being operated.

[0029] The controller 20 controls the electromagnetic brake 15 by outputting an instruction signal to the electromagnetic brake 15 to activate it. When the electromagnetic brake 15 is activated and turned ON, the wheels 3, for example, the rear wheels 12, are locked, and the vehicle 1 becomes immobile. The electromagnetic brake 15 is activated and turned ON, for example, when a fail-safe mechanism described later is executed. The electromagnetic brake 15 can also be activated and turned ON by manual operation by the driver. For example, when the brake lever 6 is fixed in a predetermined lock position, the electromagnetic brake 15 is activated and turned ON. In this case, when the brake lever 6 is released from the predetermined lock position, the electromagnetic brake 15 becomes inactive and turns OFF.

[0030] Furthermore, an inverter 8 is connected to the controller 20. The controller 20 generates an instruction signal based on the amount of movement of the accelerator lever 5 and transmits the generated instruction signal to the left inverter 8L and the right inverter 8R. The controller 20 controls the motor 7 via the inverter 8.

[0031] The controller 20 acquires signals output from the current sensor 40, rotation speed sensor 41, and temperature sensor 42, etc., via the inverter 8.

[0032] The current sensor 40 detects the current value of the motor 7. The current value of the motor 7 is positive when the motor 7 is in the powering state. Conversely, the current value of the motor 7 is negative when the motor 7 is in the regenerative state, that is, when a regenerative current is generated due to the regenerative braking of the motor 7.

[0033] The rotation speed sensor 41 detects the rotation speed of the motor 7. Specifically, the rotation speed sensor 41 detects the rotation speed of the motor 7's rotating shaft. The temperature sensor 42 detects the temperature of the motor 7.

[0034] The controller 20 acquires signals from the left inverter 8L and the right inverter 8R, respectively. In other words, the current sensor 40 and the like are provided for the left motor 7L and the right motor 7R, respectively.

[0035] Next, the first abnormality detection process performed by the controller 20 will be explained with reference to Figure 3. Figure 3 is a flowchart illustrating the first abnormality detection process according to the embodiment. For example, when the power to the vehicle 1 is turned on, the controller 20 performs the first abnormality detection process according to a preset first processing cycle. The first abnormality detection process is a process for detecting abnormalities in the motor 7. The first abnormality detection process is performed for the left motor 7L and the right motor 7R, respectively.

[0036] The controller 20 determines whether or not an abnormality has occurred in the inverter 8 (S100). For example, the controller 20 determines that an abnormality has occurred in the inverter 8 if the temperature of the motor 7 is above a predetermined temperature. The controller 20 also determines that an abnormality has occurred in the inverter 8 if a communication abnormality occurs with the inverter 8.

[0037] If the controller 20 determines that an abnormality has occurred in the inverter 8 (S100: Yes), it terminates the current process. Note that the controller 20 may also terminate the current process without performing the processes described in step S101 onwards if an abnormality occurs in any part of the vehicle 1, not just the inverter 8, such as a motor 7. In other words, if any abnormality has already occurred before detecting the abnormal rotational speed of the motor 7 as described below, the controller 20 may terminate the current process.

[0038] If the controller 20 determines that there is no abnormality in the inverter 8 (S100: No), it determines whether the vehicle 1 is in a drivable state (Ready On state) (S101). The controller 20 determines that the vehicle 1 is in a drivable state if the start switch 32 is ON and there are no other abnormalities in the vehicle 1. The controller 20 determines that the vehicle 1 is not in a drivable state if the start switch 32 is OFF or if there are other abnormalities in the vehicle 1. Other abnormalities are pre-set abnormalities, such as an abnormality in the battery 9, or other abnormalities related to the operation of the vehicle 1.

[0039] If the controller 20 determines that vehicle 1 is not in a drivable state (S101: No), it terminates the current process.

[0040] When the controller 20 determines that the vehicle 1 is in a drivable state (S101: Yes), it determines whether the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to an abnormality detection threshold. The target rotational speed of the motor 7 is set, for example, according to the amount of operation of the accelerator lever 5. The actual rotational speed of the motor 7 is detected by the rotational speed sensor 41. The difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is an absolute value. That is, the controller 20 determines whether the deviation of the actual rotational speed of the motor 7 from the target rotational speed of the motor 7 is large. The abnormality detection threshold is a preset value. The abnormality detection threshold is the difference between the target rotational speed and the actual rotational speed that occurs when an abnormality occurs in the motor 7.

[0041] The controller 20 terminates the current process if it determines that the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 is less than the abnormality detection threshold (S102: No). The controller 20 determines that there is no abnormality in motor 7 if the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 is less than the abnormality detection threshold.

[0042] If the controller 20 determines that the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to an abnormality detection threshold (S102: Yes), it determines whether or not the generation of regenerative current by the motor 7 has been detected (S103). If the current value of the motor 7 is less than or equal to the regenerative current threshold, the controller 20 determines that the generation of regenerative current by the motor 7 has been detected. If the current value of the motor 7 is greater than the regenerative current threshold, the controller 20 determines that the generation of regenerative current by the motor 7 has not been detected.

[0043] The regenerative current threshold is a preset value. The regenerative current threshold is a negative value that allows for the determination of whether regenerative current is being generated by the motor 7. It is desirable that the regenerative current threshold be set to a value that is not too small so that the generation of regenerative current by the motor 7 can be detected quickly. The controller 20 determines that regenerative current is being generated when the current value of the motor 7 is less than or equal to the negative value of the regenerative current threshold (for example, when the negative value is greater than the regenerative current threshold). The controller 20 also determines that no regenerative current is being generated when the current value of the motor 7 is greater than the negative value of the regenerative current threshold (for example, when the value is positive, or when the value is negative from 0 to the regenerative current threshold).

[0044] If the controller 20 determines that it has detected the generation of regenerative current by the motor 7 (S103: Yes), it masks the detection of an abnormality in the motor 7 (S104). Even if the controller 20 determines in step S102, based on the rotational speed of the motor 7, that an abnormality has occurred in the motor 7, it will not determine that an abnormality has occurred in the motor 7 if regenerative current is being generated.

[0045] Furthermore, the controller 20 does not need to perform any special processing in step S104 to mask the detection of an abnormality in the motor 7. In other words, if it determines that the generation of regenerative current by the motor 7 has been detected (S103: Yes), it may terminate the process at that point.

[0046] If the controller 20 determines that no regenerative current is being generated by the motor 7 (S103: No), it determines whether the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the abnormality detection threshold, and whether the state in which no regenerative current is being generated has continued for a first duration (predetermined duration) or longer (S105). The first duration is a preset time. The first duration is the time in which it is possible to accurately determine the occurrence of an abnormality by the motor 7. The controller 20 measures the duration in which the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the abnormality detection threshold, and whether the state in which no regenerative current is being generated has continued for a first duration or longer.

[0047] If the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 is greater than or equal to the abnormality detection threshold, and the state in which no regenerative current is detected does not continue for a first duration or longer (S105: No), the controller 20 returns to step S102 and repeats the above process. The measured duration is reset, for example, when the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 falls below the abnormality detection threshold. Alternatively, the controller 20 may return to step S100 and repeat the above process.

[0048] The controller 20 detects an abnormality in the motor 7 (S106) if the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to an abnormality detection threshold, and the condition in which no regenerative current is detected continues for a first duration or longer (S105: Yes).

[0049] Next, we will explain the rotational speed of motor 7 when the amount of operation of the accelerator lever 5 is reduced in vehicle 1, which is traveling on a steep downhill slope and there is no abnormality in motor 7, with reference to Figure 4. Figure 4 is a diagram showing the rotational speed of motor 7 when the amount of operation of the accelerator lever 5 is reduced in vehicle 1, which is traveling on a steep downhill slope.

[0050] At time t0, if the amount of movement of the accelerator lever 5 decreases, the target rotational speed of the motor 7 decreases in proportion to the amount of movement of the accelerator lever 5, and the actual rotational speed of the motor 7 also decreases. As the amount of movement of the accelerator lever 5 decreases, the motor 7 enters a regenerative state, regenerative braking force is generated on the vehicle 1, and the vehicle 1 decelerates.

[0051] When vehicle 1 travels down a steep incline, its deceleration decreases due to its own weight, causing a delay in the decrease in the actual rotational speed of motor 7. This can result in a significant deviation of the motor's actual rotational speed from its target rotational speed. In other words, even if there is no abnormality in motor 7, its actual rotational speed may deviate significantly from its target rotational speed. This deviation of the motor's actual rotational speed from its target rotational speed is more likely to occur when the inverter 8 has poor performance.

[0052] For example, in the comparative example, where an abnormality in motor 7 is detected based on the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7, if the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 exceeds the abnormality detection threshold at time t1, an abnormality in motor 7 is detected. In other words, the comparative example falsely detects an abnormality in motor 7.

[0053] In contrast, the controller 20 according to the embodiment determines the occurrence of a motor abnormality based on the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7, as well as the presence or absence of regenerative current generated by the motor 7. The controller 20 detects a motor abnormality if the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the abnormality detection threshold, and no regenerative current is detected from the motor 7. Furthermore, the controller 20 masks the detection of a motor abnormality if the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the abnormality detection threshold, and regenerative current is detected from the motor 7.

[0054] In this way, the controller 20 can accurately detect abnormalities in the motor 7 by detecting whether or not an abnormality has occurred in the motor 7 according to the detection status of the regenerative current in the motor 7, and can suppress false detections of abnormalities in the motor 7. Even when a low-performance, inexpensive inverter 8 is used, the controller 20 can accurately detect abnormalities in the motor 7 and can suppress false detections of abnormalities in the motor 7.

[0055] The controller 20 detects a malfunction in the motor 7 if no malfunction is detected in the inverter 8, the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the malfunction detection threshold, and the condition in which no regenerative current is detected from the motor 7 continues for a first duration or longer. This allows the controller 20 to accurately detect a malfunction in the motor 7.

[0056] Next, the second abnormality detection process performed by the controller 20 will be explained with reference to Figure 5. Figure 5 is a flowchart illustrating the second abnormality detection process according to the embodiment. For example, the controller 20 performs the second abnormality detection process according to a preset second processing cycle. The second abnormality detection process is a process for detecting abnormalities in the motor 7. The second abnormality detection process is performed for the left motor 7L and the right motor 7R, respectively. The abnormality detection result of the motor 7 in the second abnormality detection process is applied preferentially to the first abnormality detection process.

[0057] The controller 20 determines whether or not stop control for motor 7 is being performed (S200). If the controller 20 detects a stop request from the driver, it determines that stop control for motor 7 is being performed. In other words, the controller 20 detects that stop control for motor 7 is being performed. If the controller 20 does not detect a stop request from the driver, it determines that stop control for motor 7 is not being performed. In stop control for motor 7, the target rotational speed of motor 7 is set to zero.

[0058] The controller 20 determines that a driver has requested to stop and that motor 7 is being controlled to stop when the brake sensor 35 is turned ON. The controller 20 also determines that a driver has requested to stop and that motor 7 is being controlled to stop when the start switch 32 is turned OFF. Furthermore, the controller 20 determines that a driver has requested to stop and that motor 7 is being controlled to stop when the accelerator lever 5 is not moved to zero and the brake sensor 35 is turned ON. Additionally, the controller 20 determines that a driver has requested to stop and that motor 7 is being controlled to stop when the accelerator lever 5 is moved to zero and the reverse switch 33 is turned OFF.

[0059] If the controller 20 determines that the motor 7 has not been stopped (S200: No), it terminates the current process.

[0060] If the controller 20 determines that stop control for motor 7 is being performed (S200: Yes), it determines whether vehicle 1 has stopped (S201). Specifically, the controller 20 determines whether the vehicle speed is below the stop determination threshold. The stop determination threshold is a preset value. The stop determination threshold is an extremely low vehicle speed. If the vehicle speed is below the stop determination threshold, the controller 20 determines that vehicle 1 has stopped. If the vehicle speed is equal to or greater than the stop determination threshold, the controller 20 determines that vehicle 1 has not stopped. The controller 20 may also determine whether vehicle 1 has stopped based on the actual rotational speed of motor 7.

[0061] If the controller 20 determines that vehicle 1 has stopped (S201: Yes), it terminates the current process.

[0062] If the controller 20 determines that vehicle 1 is not stopped (S201: No), it determines whether the state in which vehicle 1 is not stopped has continued for a second duration (predetermined period) or longer (S202). The second duration is a preset time. The second duration is the time from when the stop control of motor 7 is started until vehicle 1 comes to a stop, provided that no abnormality occurs in motor 7. The controller 20 measures the time since the stop control of motor 7 was started and determines whether the measured time is equal to or greater than the second duration.

[0063] If the controller 20 determines that vehicle 1 has not been in a state of not being stopped for a period of time greater than the second duration (S202: No), it returns to step S200 and repeats the above process.

[0064] The controller 20 detects a malfunction in the motor 7 (S203) if it determines that the vehicle 1 has not stopped for a period of time greater than the second duration (S202: Yes). In other words, the controller 20 detects a malfunction in the motor 7 if the motor 7 stop control is being executed and the vehicle 1 does not stop for the second duration.

[0065] As a result, even if the detection of an abnormality in the motor 7 is excessively masked by the first abnormality detection process, the controller 20 can detect an abnormality in the motor 7 if the vehicle 1 does not stop despite the motor 7 being stopped.

[0066] Next, the controller 20 performs a fail-safe (S204). Specifically, the controller 20 cuts off the power supply to the inverter 8 and activates the electromagnetic brake 15 to lock the rear wheels 12, thereby forcibly stopping the vehicle 1.

[0067] As a result, the controller 20 can enhance driver safety by forcibly stopping vehicle 1 if it fails to stop despite a stop request from the driver. Furthermore, even if the motor 7 malfunction is excessively masked by the first malfunction detection process, the controller 20 can still forcibly stop vehicle 1 if it fails to stop despite a stop request from the driver.

[0068] The controller 20 detects when it detects a stop request from the driver and executes stop control of the motor 7. Therefore, if the vehicle 1 does not stop in response to the driver's stop request, the controller 20 can detect that an abnormality has occurred in the motor 7.

[0069] Next, the vehicle speed limiting process according to the embodiment will be described with reference to Figure 6. Figure 6 is a flowchart illustrating the vehicle speed limiting process according to the embodiment. For example, the controller 20 executes the vehicle speed limiting process according to a preset third processing cycle.

[0070] The controller 20 determines whether vehicle 1 is traveling on a ramp with a downward slope of a first incline threshold or greater (S300). The first incline threshold is a preset value. For example, the first incline threshold is the value at which vehicle 1 begins to move due to its own weight on a downward slope. If the incline angle detected by the incline sensor 34 is greater than or equal to the first incline threshold, the controller 20 determines that vehicle 1 is traveling on a ramp with a downward slope of a first incline threshold or greater. If the incline angle detected by the incline sensor 34 is less than the first incline threshold, the controller 20 determines that vehicle 1 is not traveling on a ramp with a downward slope of a first incline threshold or greater. The incline angle is the pitch angle. The incline angle may also be the pitch angle and the roll angle.

[0071] If the controller 20 determines that vehicle 1 is not traveling on a ramp with a downhill gradient greater than or equal to the first gradient threshold (S300: No), it terminates the current process. In this case, the upper limit of the vehicle speed is set to the pre-set initial upper limit of the vehicle speed. The initial upper limit of the vehicle speed is, for example, 6 km / h.

[0072] If the controller 20 determines that vehicle 1 is traveling on a ramp with a downhill gradient of a first gradient threshold or greater (S300: Yes), it reduces the upper limit of the vehicle speed (S301). The controller 20 sets the upper limit of the vehicle speed to a predetermined upper limit of vehicle speed that is smaller than the initial upper limit of vehicle speed. The predetermined upper limit of vehicle speed is a pre-set vehicle speed. The predetermined upper limit of vehicle speed may be set based on the incline angle. In this case, the predetermined upper limit of vehicle speed decreases as the incline angle increases, that is, as the downhill gradient increases.

[0073] Next, we will explain the rotational speed of motor 7 when the accelerator lever 5 is operated to a large extent in vehicle 1, which is traveling on a steep downhill slope and there is no abnormality in motor 7, with reference to Figure 7. Figure 7 shows the rotational speed of motor 7 when the accelerator lever 5 is operated to a large extent in vehicle 1, which is traveling on a steep downhill slope.

[0074] At time t10, if the amount of movement of the accelerator lever 5 increases, the target rotational speed of the motor 7 increases in proportion to the amount of movement of the accelerator lever 5, and the actual rotational speed of the motor 7 also increases.

[0075] When vehicle 1 travels down a steep incline, its acceleration increases due to its own weight, causing the actual rotational speed of motor 7 to exceed the target rotational speed, resulting in a significant deviation from the target rotational speed. In other words, even if there is no abnormality in motor 7, the actual rotational speed of motor 7 may deviate significantly from its target rotational speed.

[0076] For example, in the comparative example, where an abnormality in motor 7 is detected based on the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7, if the difference between the target rotational speed of motor 7 and the actual rotational speed of motor 7 exceeds the abnormality detection threshold at time t11, an abnormality in motor 7 is detected. In other words, the comparative example falsely detects an abnormality in motor 7.

[0077] In contrast, the controller 20 according to this embodiment can suppress an increase in the actual rotational speed of the motor 7 by reducing the upper limit speed of the vehicle 1 when the vehicle 1 is traveling on an incline with a downward gradient of 1 or more than the first incline threshold. Therefore, the controller 20 can suppress the discrepancy between the actual rotational speed of the motor 7 and the target rotational speed of the motor 7, and can suppress false detection of abnormalities in the motor 7.

[0078] The controller 20 can suppress false detection of a motor 7 malfunction by masking the malfunction detection of the motor 7 through the first malfunction detection process when the vehicle 1 decelerates on a steep downhill slope. Furthermore, the controller 20 can suppress false detection of a motor 7 malfunction by lowering the upper speed limit through the vehicle speed limiting process when the vehicle 1 accelerates on a steep downhill slope. Therefore, false detection of a motor 7 malfunction can be suppressed even when the vehicle 1 decelerates or accelerates while traveling on a steep downhill slope.

[0079] Vehicles such as mobility scooters and electric wheelchairs often carry elderly people or injured or ill individuals, so safety is required to prevent accidents. Therefore, the controller 20 can secondarily enhance safety by reducing the upper speed limit as described above.

[0080] Vehicle 1 may have the following modifications.

[0081] The controller 20 masks the detection of an abnormality in the motor 7 if the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 is greater than or equal to the abnormality detection threshold, the generation of regenerative current by the motor 7 is detected, and the vehicle 1 is traveling on a ramp with a downward slope of greater than or equal to the second incline threshold.

[0082] As shown in Figure 8, if the controller 20 determines in step S103 that regenerative current has been generated by the motor 7, it determines in step S400 whether the vehicle 1 is traveling on a ramp with a downhill gradient of 2 or greater than the second incline threshold. Figure 8 is a flowchart illustrating the first abnormality detection process according to a modified example. The second incline threshold is a preset value. The second incline threshold may be the same value as the first incline threshold. The second incline threshold may be a different value from the first incline threshold. If the incline angle detected by the incline sensor 34 is 2 or greater than the second incline threshold, the controller 20 determines that the vehicle 1 is traveling on a ramp with a downhill gradient of 2 or greater than the second incline threshold. If the incline angle detected by the incline sensor 34 is less than the second incline threshold, the controller 20 determines that the vehicle 1 is not traveling on a ramp with a downhill gradient of 2 or greater than the second incline threshold.

[0083] If the controller 20 determines that vehicle 1 is not traveling on a ramp with a downhill gradient of 2 or greater than the second gradient threshold (S400: No), it executes the process in step S105. If the controller 20 determines that vehicle 1 is traveling on a ramp with a downhill gradient of 2 or greater than the second gradient threshold (S400: Yes), it executes the process in step S104 and masks the abnormality detection of motor 7.

[0084] As a result, the controller 20 can mask the detection of abnormalities in the motor 7, provided that the vehicle 1 is traveling on a ramp with a downward gradient of 2 or greater than the second gradient threshold. Therefore, the controller 20 can suppress excessive masking of abnormalities in the motor 7 and accurately detect abnormalities in the motor 7.

[0085] The controller 20 may mask the detection of abnormalities in the motor 7 when the motor 7 is in a free state, neither in a powered state nor a regenerative state. For example, the controller 20 may mask the detection of abnormalities in the motor 7 when the vehicle 1 is set to a push mode where it can be moved by hand. When the vehicle 1 in the free state moves, only the actual rotational speed of the motor 7 increases, so the difference between the target rotational speed of the motor 7 and the actual rotational speed of the motor 7 becomes large. By masking the detection of abnormalities in the motor 7 when it is in the free state, the controller 20 can prevent false detection of abnormalities in the motor 7.

[0086] Vehicle 1 may be a three-wheeled vehicle. Vehicle 1 may also be a vehicle having one motor 7 and one inverter 8.

[0087] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0088] 1. Vehicle (electric vehicle) 3 wheels 4 handles 7 Motor 8 Inverters 10 Control device (anomaly detection device) 15 Electromagnetic brake 20 controllers 30. Vehicle speed sensor 31 Accelerator sensor 32 Start switch 33 Reverse switch 34 Tilt Sensor 35 Brake Sensor 40 Current Sensor 41. Rotation speed sensor 42 Temperature Sensor

Claims

1. An abnormality detection device installed in an electric vehicle that drives a motor based on a target rotational speed, The controller detects a motor abnormality when the difference between the target rotational speed and the actual rotational speed is greater than or equal to the abnormality detection threshold, and when no regenerative current is detected from the motor. An anomaly detection device equipped with the following features.

2. The abnormality detection device according to claim 1, wherein the controller detects an abnormality in the motor when stop control of the motor is being performed and the electric vehicle does not stop for a predetermined period of time.

3. The abnormality detection device according to claim 2, wherein the controller detects the execution of the stop control of the motor when it detects a stop request from the driver.

4. The abnormality detection device according to claim 1, wherein the controller reduces the upper limit speed of the electric vehicle when the electric vehicle is traveling on an incline with a downward gradient of a gradient threshold or higher.

5. The abnormality detection device according to claim 1, wherein the controller detects an abnormality in the motor if no abnormality has been detected in the motor controller that controls the motor, the difference between the target rotational speed of the motor and the actual rotational speed of the motor is greater than or equal to the abnormality determination threshold, and the state in which the generation of the regenerative current by the motor is not detected continues for a predetermined duration or longer.

6. An abnormality detection device installed in an electric vehicle that drives a motor based on a target rotational speed, The system includes a controller that determines that the motor is abnormal if the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality detection threshold. The controller is an abnormality detection device that masks the determination that the motor is abnormal when the generation of regenerative current by the motor is detected.

7. An abnormality detection method in an electric vehicle that drives a motor based on a target rotational speed, An abnormality detection method for detecting an abnormality in a motor when the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality determination threshold, and when the generation of regenerative current by the motor is not detected.

8. An abnormality detection method in an electric vehicle that drives a motor based on a target rotational speed, An abnormality detection method that, when the difference between the target rotational speed and the actual rotational speed is greater than or equal to an abnormality detection threshold, and when the generation of regenerative current by the motor is detected, masks the detection of an abnormality in the motor.

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