Determination device, and determination system

Abstract

To provide a determination device capable of easily determining a stopping distance, and a determination device system.SOLUTION: The determination device is a device for determining the performance of the brake device of an electric vehicle that includes wheels, a brake device, and an electric motor for driving the wheels. The determination device includes: a rotation angle acquisition unit that acquires the rotation angle of the electric motor from a point when a control signal is sent to the brake device of the electric vehicle traveling at a predetermined speed until the wheel stops rotating; and a comparison unit that compares the rotation angle with a predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a determination device and a determination system for determining braking performance of an electric vehicle. [Background technology]

[0002] Autonomous unmanned electric vehicles are used in a variety of fields. Electric vehicles are required to be able to drive autonomously without coming into contact with obstacles such as people or objects. In particular, when a collision with an obstacle is predicted, the vehicle is required to activate its brakes and stop reliably before the collision occurs.

[0003] The stopping distance is an indicator of brake system performance. The stopping distance is the sum of the free running distance and the braking distance. The free running distance is the distance the vehicle travels from when the control device issues an activation signal to the brake system until the brake system begins to work, and the braking distance is the distance the vehicle travels from when the brake system begins to work until the vehicle stops.

[0004] The time from when the control device issues an activation signal to the brake system until the brake system begins to work is roughly constant for each vehicle, and the free running distance is roughly proportional to the driving speed just before the brakes are applied. On the other hand, the braking distance varies depending on various conditions such as the total weight of the vehicle itself plus the weight of luggage, the slope and friction coefficient of the road surface, and the wear of the brake pads, and the braking distance is roughly proportional to the square of the driving speed just before the brakes are applied.

[0005] Patent Document 1 describes a technique for detecting wear of brake pads of an electric vehicle.

[0006] Patent Document 2 describes a technique for evaluating the performance of a braking device by determining the braking distance of an electric vehicle. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-182534 [Patent Document 2] Japanese Patent Application Publication No. 2023-107421 Summary of the Invention [Problem to be solved by the invention]

[0008] In order for an electric vehicle to stop reliably before colliding with an obstacle, it is necessary to issue an activation signal to the brake device before the distance from the obstacle to the electric vehicle falls below the stopping distance of the electric vehicle, i.e., when the distance to the obstacle is greater than the stopping distance. Therefore, it is important to accurately grasp the stopping distance for safe autonomous driving. Because the stopping distance varies depending on various conditions such as road conditions and total vehicle weight, it is desirable to grasp the stopping distance frequently.

[0009] In addition, if the stopping distance becomes longer due to wear of the brake pads, the settings of the electric vehicle can be changed to apply the brakes earlier, or the electric vehicle can be pre-programmed to apply the brakes earlier, assuming that the stopping distance will be longer from the start. However, with such settings, the brakes may be applied more frequently when traveling in places where the distance to obstacles tends to be close, such as in crowded areas, which can make it difficult to travel smoothly. Therefore, if the stopping distance is long, measures such as replacing the brake pads may be necessary.

[0010] Although the technology of Patent Document 1 can evaluate the amount of wear on the brake pads, it does not obtain the stopping distance of the electric vehicle, and therefore cannot evaluate whether the electric vehicle can travel safely without colliding with an obstacle.

[0011] The technology in Patent Document 2 calculates the braking distance but not the stopping distance, and therefore cannot evaluate whether the electric vehicle can travel safely without colliding with an obstacle. Furthermore, since the vehicle in Patent Document 2 is assumed to be a vehicle that can carry people, when calculating the braking distance, the vehicle is run at a speed of about several tens of kilometers per hour, and it takes several tens of meters to stop, so a large test site is required and the test is large-scale.

[0012] The present disclosure aims to provide a device that can easily determine the braking performance of an electric vehicle in a small space. [Means for solving the problem]

[0013] The determination device according to the present disclosure is a determination device that determines the performance of a brake device of an electric vehicle that includes wheels, an electric motor that drives the wheels, and a brake device, and the determination device includes a rotation angle acquisition unit that acquires the rotation angle of the electric motor from the time a control signal is issued to the brake device of the electric vehicle traveling at a predetermined speed until the rotation of the wheels stops, and a comparison unit that compares the rotation angle with a predetermined threshold value to determine the performance of the brake device. [Effects of the Invention]

[0014] According to the present disclosure, the braking performance of an electric vehicle can be easily determined in a small space. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing an electric vehicle. [Figure 2] FIG. 2 is a diagram illustrating a functional configuration of an electric vehicle. [Figure 3] 10 is a flowchart showing a diagnosis of stopping distance. [Figure 4] FIG. 1 is a diagram showing a state in which an electric vehicle is placed on a slope of a charging station. [Figure 5] FIG. 10 is a diagram showing a modified example in which an electric vehicle is arranged at a charging station. [Figure 6] FIG. 10 is a diagram illustrating a state in which an electric vehicle receives an external force at a charging station. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the components, the arrangement and connection of each component, and each step and the order of each step shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0017] Furthermore, each drawing is a schematic diagram and is not necessarily an exact illustration. In each drawing, substantially the same components are denoted by the same reference numerals, and redundant explanations will be omitted or simplified.

[0018] Fig. 1 is a schematic diagram showing an electric vehicle 1. Fig. 2 is a diagram showing the functional configuration of the electric vehicle 1. A pair of drive wheels 3 as rear wheels and a pair of driven wheels 4 as front wheels are provided on a vehicle body 2 of the electric vehicle 1. An electric motor 5 supplied with power from a battery 13 is connected to the drive wheels 3 via a reduction gear (not shown), and each wheel is driven independently.

[0019] Braking devices 6 are provided on the driving wheels 3 and the driven wheels 4. The braking devices 6 may be of any type, such as a type that acts directly on the wheels, a type that acts on brake discs provided on the axles, or a type that acts on the electric motor 5.

[0020] Furthermore, a non-excitation actuated brake can be used for the brake device 6. A non-excitation actuated brake is configured so that it operates by spring force when no current is applied to the brake actuator, and the brake is released against the spring force when current is applied to the actuator.

[0021] The electric motor 5 is provided with a rotation angle detector 7 that detects the rotation angle of the electric motor 5. The rotation angle detector 7 may be of a mechanical type such as an encoder or potentiometer, an optical type, a magnetic type, an electromagnetic induction type, or the like. The rotation angle detector 7 may also be provided to detect the rotation angle of the wheels.

[0022] The speed detector 10 is a sensor that detects the speed of the electric vehicle 1, and detects the speed based on the rotational angular velocity of the wheels, the rotational angular velocity of the motor, and the like.

[0023] An alarm device 12 that notifies the driver of the state or abnormality of the electric vehicle 1 is provided on the side of the vehicle body 2. The alarm device 12 has a small display, an LED lamp, a speaker, and the like.

[0024] The obstacle detector 11 is a sensor such as an ultrasonic sensor or a LiDAR (Light Detection and Ranging) sensor, and detects the distance and direction to an obstacle around the electric vehicle 1.

[0025] Each device is supplied with power from a battery 13 provided in the vehicle body 2. The battery 13 is a rechargeable battery, and may be configured to be rechargeable at a predetermined charging station.

[0026] The electric vehicle 1 has a control device 8 such as a CPU or a processor. The control device 8 is provided in the vehicle body 2 together with a storage device 9, and is connected to various sensors such as the electric motor 5, the brake device 6, the rotation angle detector 7, the speed detector 10, and the obstacle detector 11, the alarm device 12, the battery 13, and the storage device 9.

[0027] The brake control unit 15 controls the brake device 6 to decelerate or stop the electric vehicle 1.

[0028] The drive control unit 16 controls the drive of the electric motor 5 to make the electric vehicle 1 travel at a predetermined speed.

[0029] The speed acquisition unit 17 acquires a signal of the speed of the electric vehicle 1 detected by the speed detector 10 .

[0030] The rotation angle acquisition unit 18 acquires a signal of the angle by which the electric motor 5 has rotated from the time when the brake control unit 15 issues a signal to the brake device 6 until the time when the speed acquisition unit 17 acquires that the speed of the electric vehicle 1 has become 0.

[0031] The stopping distance calculation unit 19 calculates the stopping distance of the electric vehicle 1 based on the rotation angle of the electric motor 5 acquired by the rotation angle acquisition unit 18. Specifically, the stopping distance calculation unit 19 calculates the stopping distance based on the distance traveled by the electric vehicle 1 per unit rotation angle of the electric motor 5, which is determined in advance, and the rotation angle of the electric motor 5 acquired by the rotation angle acquisition unit 18.

[0032] The comparison unit 20 compares the stopping distance calculated by the stopping distance calculation unit 19 with a predetermined threshold value stored in the storage device 9, and determines whether the stopping distance exceeds the threshold value.

[0033] The notification control unit 21 transmits the result of the comparison by the comparison unit 20 to the notification device 12. Specifically, if the stopping distance exceeds a predetermined threshold, the notification is displayed externally by turning on a red lamp or displaying a message to that effect on a display.

[0034] The obstacle acquisition unit 22 acquires signals of the distance and direction to the obstacle detected by the obstacle detector 11, and based on the acquired results, the electric vehicle 1 travels autonomously while accelerating, decelerating, and stopping by controlling the electric motor 5 by the drive control unit 16 and the brake device 6 by the brake control unit 15.

[0035] In addition, the vehicle body 2 is provided with various accessories such as a loading platform and various working devices depending on the intended use of the electric vehicle 1. The vehicle body 2 may also have a communication device for connecting to a communication network.

[0036] Next, the stopping distance measurement process performed by the control device 8 will be described. The stopping distance is measured by running the electric vehicle 1 at a predetermined speed and detecting the rotation angle of the electric motor 5 from when the brake control unit 15 issues an activation signal to the brake device 6 until the electric vehicle 1 stops. In the case of an unmanned autonomous vehicle, the brake device 6 is activated while the vehicle is running at a normal running speed of about 1 to 4 km / h. The measurement may be performed by the user operating a predetermined switch to instruct the electric vehicle 1, or the control device 8 may perform the measurement automatically.

[0037] Note that the above-mentioned value of 1 to 4 km / h is one example. In the electric vehicle 1 of the present disclosure, the rotation angle of the electric motor 5 is detected, and the rotation angle can be clearly detected even if the stopping distance is short. Therefore, the performance of the brake device 6 can be easily determined even when the electric vehicle 1 is run at a lower speed in a narrow space. Furthermore, by performing such a test in an environment where the road surface and external force conditions are known in advance, such as the example of a charging station described below, the accuracy of determining the performance of the brake device 6 can be further improved even at a lower speed.

[0038] 3 is a flowchart of the stopping distance measurement process performed by the control device 8. The measurement process starts from a state in which the braking device 6 has been activated and the vehicle has stopped. When the measurement process starts, the brake control unit 15 releases the braking device 6 (step S1).

[0039] When the brake device 6 is released, the electric vehicle 1 accelerates (1) by driving the electric motor 5, (2) by descending an inclined surface, or (3) by being pressed by a pressing member. The method of acceleration may be set in advance by an operator or may be set each time a measurement is performed.

[0040] In the method (1), the electric vehicle 1 is braked to a stop, and then the brake is released, and the electric motor 5 is driven to accelerate the vehicle to a predetermined speed, as in the case of normal driving of the electric vehicle 1.

[0041] In the method (2), the electric vehicle 1 applies the brakes on a predetermined inclined surface, stops, and then releases the brakes, and accelerates down the inclined surface by gravity, accelerating to a predetermined speed.

[0042] In the method (3), the electric vehicle is braked and stopped, and then the brake is released, and the electric vehicle 1 is accelerated to a predetermined speed by applying an external force with a pressing member.

[0043] 4 is a diagram showing an example of a device for carrying out method (2). Reference numeral 30 denotes a charging station for charging an electric vehicle 1. Charging station 30 has an inclined surface portion 31, a support pole 32 erected on inclined surface portion 31, and a charging connector 33 attached to support pole 32. Electric vehicle 1 autonomously travels up to the inclined surface portion 31, and when it reaches a position where it can be charged, it activates brake device 6 to stop it. In this state, it is charged via charging connector 33.

[0044] When charging is completed, the brake device 6 is released, and the electric vehicle 1 accelerates down the inclined surface portion 31 due to gravity, and the stopping distance is measured.

[0045] 5 shows a modified example of a charging station for carrying out method (2). Charging station 40 has upper surface 41, a support pole 42 erected upward, and a charging connector 43 attached to support pole 42. Upper surface 41 can be transformed into a flat surface state when charging electric vehicle 1, and into an inclined surface state when measuring the stopping distance.

[0046] When measuring the stopping distance, if the brake device 6 is released with the upper surface portion 41 tilted, the electric vehicle 1 will accelerate downward on the upper surface portion 41 due to gravity.

[0047] Fig. 6 is a diagram showing an example of an apparatus for carrying out method (3). Charging station 50 has upper surface 51, support pole 52 erected upward from upper surface 51, and pressing member 53 for pressing electric vehicle 1. Note that the charging device provided on support pole 52 is not shown. Electric vehicle 1 autonomously travels to upper surface 51, and when it reaches a position where it can be charged, it activates brake device 6 to stop it. In this state, it is charged via a charging connector (not shown).

[0048] When measuring the stopping distance, if the brake device 6 is released with the pressing member 53 pressing against the electric vehicle, the electric vehicle 1 is pressed by the pressing member 53 and accelerates.

[0049] 3, the control device 8 determines whether the electric vehicle 1 has reached a predetermined speed (step S2) based on the speed acquired by the speed acquisition unit 17. If the determination is No, step S2 is repeated until the electric vehicle 1 reaches the predetermined speed.

[0050] When the electric vehicle 1 reaches a predetermined speed (Yes in step S2), the brake control unit 15 issues an activation signal to the brake device 6 (step S3), and at the same time, the rotation angle acquisition unit 18 starts measuring the rotation angle of the electric motor 5 (step S4). The control device 8 determines whether the electric vehicle has stopped (step S5), and if No, repeats step S5 until the electric vehicle 1 stops.

[0051] When the electric vehicle 1 comes to a stop (step S5: Yes), the rotation angle acquisition unit 18 ends measurement of the rotation angle of the electric motor 5 (step S6) and acquires the angle by which the electric motor 5 has rotated from the start to the end of measurement. The comparison unit 20 compares the stopping distance calculated by the stopping distance calculation unit 19 with a predetermined threshold (step S7), and if the stopping distance is equal to or less than the predetermined threshold (step S7: Yes), the notification control unit 21 issues a normal signal to the notification device 12 (step S8), and the notification device 12 issues a notification to that effect. On the other hand, if the stopping distance exceeds the predetermined threshold (step S7: No), the notification control unit 21 issues an abnormality signal to the notification device 12 (step S9), and the notification device 12 issues a notification to that effect.

[0052] Next, we will explain how to determine the predetermined threshold value to be compared with the rotation angle of the electric motor 5. The threshold value differs depending on whether the electric vehicle 1 is (1) self-propelled by the drive of the electric motor 5, (2) descending an inclined surface, or (3) being pressed by a pressing member.

[0053] In the case of (1), when the electric vehicle 1 reaches a predetermined speed, the stopping distance can be measured while continuing to drive the drive wheels 3 by the electric motor 5, or the measurement can be made after stopping the drive. In the case of (2), while measuring the stopping distance, an external force of mg sin θ (m: mass of the electric vehicle, g: gravitational acceleration, θ: inclination angle of the inclined surface portion) continues to be applied to the electric vehicle 1 due to gravity. In the case of (3), the stopping distance can be measured while continuing to press the pressing member 53, or the pressing can be stopped before measuring. Therefore, the stopping distance at a predetermined speed differs depending on the state in which the measurement is made. Accordingly, the predetermined threshold value must be individually determined.

[0054] The threshold value is set taking into consideration a predetermined error. During actual driving, the stopping distance may differ from that at the time of the stopping distance measurement process depending on conditions such as the friction coefficient of the road surface, the inclination of the road surface, the weight of the electric vehicle 1, and the deterioration of the brake device. Therefore, it is desirable to set the threshold value to a short value taking into consideration that the stopping distance may increase during actual driving.

[0055] When the electric vehicle 1 moves autonomously, the control device 8 controls the brake device 6 based on the stopping distance L1 calculated by the stopping distance measurement process. Specifically, the control device 8 activates the brake device 6 when the distance L between the electric vehicle 1 and an obstacle ahead of the electric vehicle 1 becomes equal to the stopping distance L1 plus a predetermined error ΔL.

[0056] The control device 8 measures the stopping distance L1 periodically, for example, every day, and updates the distance L daily based on the measured stopping distance L1, thereby enabling the brake device to always operate at an appropriate distance L, and allowing the electric vehicle 1 to travel safely.

[0057] As described above, according to the present disclosure, since the stopping distance is calculated based on the rotation angle of the electric motor, the stopping distance can be calculated accurately even when the traveling speed is slow, and the stopping distance can be easily calculated in a narrow space. As a result, the braking performance can be easily determined in a narrow space. Furthermore, since the test can be performed in a narrow space, it is easy to calculate the stopping distance periodically (for example, once a day), and if the stopping distance is set to be calculated automatically and periodically, fluctuations in the stopping distance can be appropriately dealt with. Furthermore, since the test can be performed with actual luggage or the like on the electric vehicle 1, the stopping distance can be calculated in a state close to reality.

[0058] Furthermore, according to the present disclosure, the stopping distance of the electric vehicle 1 is calculated using the rotation angle of the electric motor 5, so the speed of the electric vehicle 1 can be low. Although the stopping distance becomes shorter as the speed becomes lower, this is not a problem because the rotation angle of the wheels changes sufficiently. Furthermore, because the stopping distance becomes shorter the lower the speed, testing can be easily performed in a smaller space.

[0059] Furthermore, according to the present disclosure, by conducting testing using charging stations 30, 40, and 50, the testing can be carried out in an environment where the road surface and external force conditions are known in advance, so that the stopping distance can be calculated more accurately, and the accuracy of determining the performance of the brake device 6 can be improved even when the hourly speed of the electric vehicle 1 is low.

[0060] In addition, this disclosure also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art would think of, or forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the intent of this disclosure. [Industrial Applicability]

[0061] The present disclosure can be used for a determination device and a determination device system that can determine a stopping distance. [Explanation of symbols]

[0062] 1 Electric vehicles 2. Body 3 drive wheels 4 driven wheels 5 Electric motor 6 Brake system 7 Rotation angle detector 8 Control Device 9 Storage device 10 Speed ​​detector 11 Obstacle Detector 12 Alarm device 13 Battery 15 Brake control unit 16 Drive control unit 17 Speed ​​acquisition section 18 Rotation angle acquisition unit 19 Stopping distance calculation section 20 Comparison section 21 Notification control unit 22 Obstacle Acquisition Unit 30, 40, 50 Charging Station

Claims

1. Wheels and an electric motor that drives the wheels; A braking device, A determination device for determining the performance of the brake device of an electric vehicle, comprising: the determination device includes a rotation angle acquisition unit that acquires a rotation angle of the electric motor from when a control signal is issued to the brake device of the electric vehicle traveling at a predetermined speed until when rotation of the wheels stops; a comparison unit that compares the rotation angle with a predetermined threshold value to determine performance of the brake device; A determination device comprising:

2. the determination device further includes a stopping distance calculation unit that calculates a stopping distance of the electric vehicle based on the rotation angle, The comparison unit compares the stopping distance with a predetermined threshold value. The determination device according to claim 1 .

3. The determination device further includes a notification device that notifies the comparison result of the comparison unit. The determination device according to claim 1 .

4. An electric vehicle comprising the determination device according to claim 1.

5. The determination device according to claim 1 ; a slope portion on which the electric vehicle can travel; A determination system comprising:

6. the sloped surface is provided at a charging station that charges the electric vehicle. The determination system according to claim 5 .

7. The angle of the inclined surface portion is variable. The determination system according to claim 5 or 6.

8. The determination device according to claim 1 ; a pressing device that presses the electric vehicle; A determination system comprising:

9. the pressing device is provided in a charging station that charges the electric vehicle; The determination system according to claim 8 .

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