Step detection device

Abstract

The purpose of the present invention is to obtain a step detection device capable of accurately detecting steps without being affected by weather, environmental conditions, and the like. A step detection device (2) according to the present invention, which detects a step (20) when a tire (10) of a vehicle (100) rides up on the step, comprises: a plurality of strain detection elements (1) that are arranged on the inner circumferential surface of the tire at prescribed intervals in the circumferential direction of the tire; and a signal processing device (4) that processes the detection signals of the plurality of strain detection elements. The signal processing device detects the step on the basis of the detection signals of two or more strain detection elements adjacent to each other among the plurality of strain detection elements.

Description

Technical Field

[0001] The present invention relates to a step detection device.

Background Art

[0002] During normal driving, a vehicle may need to cross a step or may accidentally drive onto a step. In such cases, since the vehicle immediately receives resistance from the step, when a person is driving, the driver will step on the accelerator pedal more or less than during normal driving. When the step is small, the driver can cross the step without discomfort. However, when the step is large, by stepping on the accelerator pedal more, the torque is increased to drive onto the step. At this time, since the resistance due to the step immediately decreases, the behavior of the vehicle suddenly changes, and the passengers may feel uneasy. Therefore, there is room for consideration of the control performance of the accelerator, brake system, etc. to safely cross and drive onto the step with a smooth operation without discomfort.

[0003] In addition, when a step such as a vehicle stop is blocked by the vehicle body, the driver may perform a series of operations without recognizing the step, and there is also a risk of approaching surrounding objects suddenly due to unintentional sudden acceleration, which cannot be said to be safe and secure driving.

[0004] In recent years, in order to provide a safer driving state for the realization of autonomous driving, as a step detection method, there is Patent Document 1. Patent Document 1 states that "when the sizes and rigidities of the tires mounted on the axles are different, the relationship between the load acting on the tires and the tire air pressure is different. Therefore, when using the tire air pressure, there is a possibility that the control for the tires to cross the step cannot be appropriately performed." To more appropriately execute the control for the tires to cross the step, a system is configured that includes a state detection device and a camera attached to a side mirror arranged behind the vehicle from the center of the drive tire so that the drive tire can be photographed. It is shown that the control for the tires to cross the step can be more appropriately executed. That is, the information obtained from the camera, etc. is analyzed to perform the control for crossing the step.

[0005] Meanwhile, technology for detecting strain in vehicle tires is known. For example, tire strain sensors can detect tire deformation and thereby detect the load acting on the tire. Furthermore, because the strain sensors are mounted on the inside of the tire, they are highly robust against weather and environmental changes. This is expected to prevent vehicle trouble and improve driving safety by detecting driving and road surface conditions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-142697 Summary of the Invention [Problem to be solved by the invention]

[0007] In the case of Patent Document 1, detection using a camera or the like is subject to the effects of weather and environmental changes, particularly water and mud while driving, which can degrade detection performance. Also, conventional detection methods using a single strain sensor have a limited road surface detection section, so when used to detect bumps and the like, there is an issue that measurements cannot be taken unless the bump and the sensor are aligned. An object of the present invention is to provide a step detection device that can accurately detect steps regardless of weather, environmental conditions, and the like. [Means for solving the problem]

[0008] The present invention has been made in view of the above-mentioned problems, and employs, for example, the configurations described in the claims.

[0009] The step detection device of the present invention is, for example, a step detection device that detects a step when a tire of a vehicle rides over the step, and includes a plurality of strain detection elements arranged at predetermined intervals in the circumferential direction of the tire on the inner circumferential surface of the tire, and a signal processing device that processes detection signals of the plurality of strain detection elements. The signal processing device is characterized in that it detects the step based on detection signals of two or more adjacent strain detection elements among the plurality of strain detection elements.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a step detection device that can detect a step without being affected by weather, environmental changes, etc. Problems, configurations, operations, and effects of the present invention other than those described above will be clarified by the following description of the embodiments.

Brief Description of the Drawings

[0011] [Figure 1] A block diagram showing a schematic configuration of a vehicle equipped with the step detection device of the present embodiment. [Figure 2] It is a schematic diagram showing a state in which a tire having a plurality of strain sensors 1-1 rolls on the road surface as the vehicle progresses. FIG. 2(1) shows a state where there is no step in the tire traveling direction, and FIG. 2(2) shows a state where there is a step in the tire traveling direction and the tire is in contact with the step. [Figure 3] An explanatory diagram showing the sensor signal waveform of the strain sensor 1-1 according to the rotation state of the tire. [Figure 4A] A schematic diagram showing a state in which the tire is in contact with a step at a position between the portion where the strain sensor 1-1 of the tire is arranged and the portion where the strain sensor 1-4 is arranged, and an example showing the output signal and the differential value of the output signal of the strain sensor in that state. [Figure 4B] A schematic diagram showing a state in which the portion where the strain sensor 1-1 is arranged is in contact with a step, and an example showing the output signal and the differential value of the output signal of the strain sensor 1-1 in that state. [Figure 4C]Schematic diagram showing the state where the tire is in contact with a step at a position between the portion where the strain sensor 1-1 of the tire is disposed and the portion where the strain sensor 1-2 is disposed, and a schematic diagram showing an example of the output signal and the differential value of the output signal of the strain sensor 1-1 in that state. [Figure 5] Diagram for explaining the configuration of the signal processing device. [Figure 6] Graph showing the differential value of the output signal of each strain sensor with respect to the angular position of the tire. [Figure 7] Block diagram for explaining the configuration of the threshold determination unit. [Figure 8] Block diagram of threshold determination showing an example of the operation of the step error detection prevention method. [Figure 9] It is a determination graph showing an example of the operation by the step detection device according to the present embodiment. FIG. 9(1) is a graph showing the change in the differential value before the smoothing process, and FIG. 9(2) is a graph showing the change in the differential value after the smoothing process. [Figure 10A] Schematic diagram showing the state where the tire is in contact with a step at a position above the step by the strain sensor 1-1, and a schematic diagram showing an example of the output signal and the determination result of the strain sensor 1-1 in that state. [Figure 10B] Schematic diagram showing the state where the portion where the strain sensor 1-1 of the tire is disposed is in contact with a step, and a schematic diagram showing an example of the output signal and the determination result of the strain sensor 1-1 in that state. [Figure 10C] Schematic diagram showing the state where the tire is in contact with the road surface at a position below the step by the strain sensor 1-1, and a schematic diagram showing an example of the output signal and the determination result of the strain sensor 1-1 in that state. [Figure 11] Diagram showing the state where the tire is in contact with a step, the operation content of the determination circuit in that state, and the determination graph of the differential value of each strain sensor. [Figure 12] Diagram showing the state where the tire has stepped on gravel or the like, the operation content of the determination circuit in that state, and the determination graph of the differential value of each strain sensor. [Figure 13] Block diagram showing an example of a method for setting a threshold value used for step determination. [Figure 14]4A(1) is a time chart showing an example of changes in the output signal and the differential value when the tire comes into contact with a bump in the state shown in FIG. 4A(1). [Figure 15] 4B(2) is a time chart showing an example of changes in the output signal and the differential value when the tire comes into contact with a step in the state shown in FIG. 4B(2). [Figure 16] FIG. [Figure 17] Cross section AA of Figure 16. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, with reference to FIGS.

[0013] The step detection device 2 of this embodiment is intended to improve the control performance of the accelerator, brake system, etc., for safe and secure vehicle operation, particularly in terms of improving the accuracy of autonomous driving, and is applied to autonomous vehicles with autonomous driving functions.

[0014] In all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations will be omitted. In addition, the cross-sectional views, front views, and side views are each specified by mutually orthogonal XYZ axes, with +X being "right," -X being "left," +Y being "up," -Y being "down," +Z being "front," and -Z being "rear."

[0015] The present invention should not be construed as being limited to the description of the embodiments shown below. Those skilled in the art will readily understand that the specific configurations can be modified without departing from the spirit or intent of the present invention.

[0016] FIG. 1 is a block diagram showing a schematic configuration of a vehicle equipped with a step detection device according to this embodiment. As shown in Fig. 1, a vehicle 100 includes four tires 10, a control unit 101, and a receiver 102, and the tires 10 are equipped with a plurality of strain sensors 1 (1-1, 1-2, ... 1-n). Note that the vehicle 100 is not limited to a four-wheeled vehicle as shown in Fig. 1 that runs on a road surface 30, but may also be applied to two-wheeled vehicles and vehicles equipped with a plurality of tires, such as trucks and buses. Also, in this embodiment, a configuration is shown in which a plurality of strain sensors 1 are provided on each of all tires 10, but it is sufficient that the number of tires 10 equipped with a plurality of strain sensors 1 is one or more.

[0017] The control unit 101 is configured with an ECU (Electronic Control Unit) and has hardware including a CPU (Central Processing Unit), memories such as ROM and RAM, and an input / output interface. The memory stores executable software programs for performing various arithmetic processing. The control unit 101 executes the software programs in hardware to realize functions such as a signal processing device 4 (described later). The receiver 102 receives signals detected by the multiple strain sensors 1 via wireless communication and supplies them to the control unit 101 as output signals of each strain sensor 1. The step detection device 2 of this embodiment is configured with each strain sensor 1 and some functions of the control unit 101. The control unit 101 may be configured to perform vehicle control based on step detection in addition to step detection processing.

[0018] Fig. 2 is a schematic diagram showing a state in which a tire equipped with multiple strain sensors rolls on a road surface as a vehicle moves forward, Fig. 2(1) shows a state in which there is no step in the direction of tire travel, and Fig. 2(2) shows a state in which there is a step in the direction of tire travel and the tire is in contact with the step. The step 20 has a height sufficient for the tire 10 to ride over.

[0019] Each strain sensor 1 of this embodiment includes a strain detection element 3a (see FIGS. 16 and 17) and is mounted, for example, inside a vehicle tire 10 to detect strain in the tire 10. Each strain sensor 1 is fixed to the inner surface of the tread portion of the tire 10 (hereinafter referred to as the tire inner circumferential surface) and detects deformation in the compressive and tensile directions that occurs on the tire inner circumferential surface as strain. In this embodiment, the tire 10 is a tubeless tire that is mounted on a wheel (not shown) and has a sealed space formed between the wheel and the tire filled with high-pressure gas.

[0020] A plurality of strain sensors 1 are arranged at predetermined intervals in the circumferential direction of the tire 10. In this embodiment, as shown in Fig. 2, a total of four strain sensors 1 (1-1, 1-2, 1-3, 1-4) are arranged at 90-degree intervals from each other. The number of strain sensors 1 and the intervals between adjacent strain sensors 1 can be set according to the detection performance of the strain sensors 1.

[0021] 2(1), there is no step on the road surface 30, and the portion of the tire 10 where the strain sensor 1-4 is located is in contact with the road surface 30. In this situation, the strain sensor 1-4 detects the amount of strain corresponding to the deformation of the tire 10.

[0022] 2(2), there is a step 20 on the road surface 30, and the tire 10 is in contact with the road surface 30 and the step 20. The portion of the tire 10 where the strain sensor 1-4 is located is in contact with the road surface 30, and the portion located midway between the strain sensors 1-1 and 1-4 is in contact with the step 20. In this case, the two strain sensors 1-1 and 1-4 adjacent to the road surface 30 and the step 20 detect the amount of strain corresponding to the deformation of the tire 10. In other words, the step 20 is detected based on the detection signals of the adjacent strain sensors 1-1 and 1-4.

[0023] Here, a schematic diagram showing four strain sensors 1 mounted is used, but a configuration in which multiple strain sensors are mounted to detect a step 20 may also be used. Furthermore, the sensor numbers do not have to be arranged in the order 1-1 to 1-4, and other number combinations may also be used.

[0024] Next, with reference to FIG. 3, a sensor signal waveform 40 when one strain sensor 1-1 is used will be described.

[0025] 3 is an explanatory diagram showing a sensor signal waveform 40 of the strain sensor 1-1 according to the rotational state of the tire 10. As shown in Fig. 3, the strain sensor 1 disposed inside the tire 10 outputs a sensor signal waveform 40 that changes depending on the state of the rotating tire 10 relative to the road surface. The strain sensor 1-1 outputs a sensor signal waveform 40 that has a reference level 41, a positive level that changes more positively than the reference level 41, and a negative level that changes more negatively than the reference level 41.

[0026] The strain sensor 1-1 maintains a reference level (steady-state value) 41 of the sensor signal waveform 40 when the portion of the tire 10 where the strain sensor 1-1 is located is not in contact with or touching the road surface 30 or the bump 20. The strain sensor 1-1 outputs a positive-level peak value (maximum value) 42 of the sensor signal waveform 40 when the portion of the tire 10 where the strain sensor 1-1 is located is in contact with the road surface 30. The strain sensor 1-1 also outputs a negative-level peak value 43 of the sensor signal waveform 40 at the moment when the portion of the tire 10 where the strain sensor 1-1 is located touches or separates from the road surface 30.

[0027] Here, the moment when the portion of the tire 10 where the strain sensor 1-1 is located comes into contact with or separates from the road surface 30 is the sensor displacement point (peak value 43). The period between two sensor displacement points (peak values 43) is a contact period during which the portion of the tire 10 where the strain sensor 1-1 is located comes into contact with the road surface 30. The sensor signal waveform 40 detected in this manner changes depending on various physical quantities (load, air pressure, speed, temperature, etc.).

[0028] Here, the moment when the part of the tire 10 where the strain sensor 1-1 is located comes into contact with or separates from the road surface 30 is considered negative (compression), and the state in which the part of the tire 10 where the strain sensor 1-1 is located is in contact with the road surface 30 is considered positive (tension), but the same can be considered when the positive and negative are reversed depending on the mounting orientation of the strain sensor 1-1 with respect to the inner circumferential surface of the tire. In this way, the strain sensor 1 is mounted on the inner circumferential surface of the tire 10 and measures the amount of strain corresponding to the deformation of the tire 10.

[0029] For example, in conventional bump detection using suspension control, a method using information detected by a laser sensor showing road surface conditions has been considered, but there are concerns that laser sensors may fail to detect road surfaces depending on weather, sunlight conditions, etc. In particular, it is estimated that necessary measures will be required to deal with detection failures caused by the lens being soiled by water or mud splashes.

[0030] On the other hand, since the strain sensor 1 is attached to the inner circumferential surface of the tire, it can detect bumps regardless of the weather. Also, since the bump is determined from the deformation caused by direct contact between the bump 20 and the tire 10, it can detect bumps regardless of the vehicle's attitude, even when parked on an inclined surface such as a slope, which is not a good performance for laser sensors. Therefore, in this embodiment, by using the strain sensor 1, bump detection with high environmental robustness can be performed, compared to laser sensors used for bump detection in conventional suspension control.

[0031] Next, the output signals and differential waveforms when strain sensors 1-1 to 1-4 come into contact with a step will be described with reference to FIGS. 4A, 4B, 4C, and 5. FIG.

[0032] In Fig. 4A(1), the portion where the strain sensor 1-1 of the tire 10 is disposed is located above the step 20, the portion where the strain sensor 1-4 is disposed is in contact with the road surface 30, and the tire 10 is in contact with the step 20 at a position between the portion where the strain sensor 1-1 of the tire 10 is disposed and the portion where the strain sensor 1-4 is disposed. In this case, when the force acting from the step 20 deforms the tire 10, the strain sensor 1-1 receives a force in the compression direction and changes to a value less than the reference level 41. Therefore, as shown in Figs. 4A(2) and (3), the sensor signal waveform 40 of the sensor output signal at the step contact position where the tire 10 contacts the step 20 decreases, and its differential value becomes a negative value.

[0033] In Fig. 4B(1), the portion where the strain sensor 1-1 of the tire 10 is disposed is shown in a state of being in contact with the step 20. In this case, when the force acting from the step 20 deforms the tire 10, the strain sensor 1-1 receives a force in the tensile direction and changes to a value greater than the reference level 41. Therefore, as shown in Figs. 4B(2) and (3), the sensor signal waveform 40 of the sensor output signal at the step contact position increases, and its differential value becomes a positive value.

[0034] In Fig. 4C(1), the portion where the strain sensor 1-1 of the tire 10 is disposed is located below the step 20 and in contact with the road surface 30, the portion where the strain sensor 1-2 of the tire 10 is disposed is located above the step 20, and the tire 10 is in contact with the step 20 at a position between the portion where the strain sensor 1-1 of the tire 10 is disposed and the portion where the strain sensor 1-2 is disposed. In this case, when the tire 10 attempts to climb over the step 20, the positive force in the tensile direction acting on the tire 10 from the road surface 30 is released and transitions to the reference level 41. Therefore, if the strain sensor 1-1 is in contact with the road surface 30, as shown in Figs. 4C(2) and (3), the sensor signal waveform 40 of the sensor output signal at the step contact position decreases, and its differential value becomes a negative value.

[0035] Although not shown in the figures, if the portion of the tire 10 where the strain sensor 1-1 is located comes into contact with a bump 20 from a state in which the portion is separated from the road surface 30, the negative compressive force acting from the road surface 30 is released and the level shifts to the reference level 41, so that the sensor signal waveform 40 of the sensor output signal increases and its derivative value ' becomes a positive value. Bump detection is performed using the positive / negative value of this derivative value and the upper threshold value 64a and lower threshold value 65a set by the threshold setting unit 52.

[0036] Next, a step detection method using the step detection device 2 of this embodiment will be described with reference to FIGS. 5, 6, 7, 8, 9, 10A, 10B, and 10C.

[0037] Fig. 5 is a diagram explaining the configuration of the signal processing device, Fig. 6 is a graph showing the differential values of the output signals of each strain sensor with respect to the angular position of the tire, and Fig. 7 is a block diagram explaining the configuration of the threshold determination unit. Fig. 5 shows an example of threshold determination using the differential values of the output signals at the position where the tire 10 contacts a bump 20.

[0038] The signal processing device 4 is configured to be embodied by the internal functions of the control unit 101, and processes the detection signals of the multiple strain sensors 1-1 to 1-4. The signal processing device 4 detects a step based on the detection signals of two or more adjacent strain sensors 1 out of the multiple strain sensors 1-1 to 1-4. As shown in FIG. 5, the signal processing device 4 has a threshold determination unit 5 and a step determination unit 6.

[0039] 7, the threshold determination unit 5 uses the measurement value calculated by the measurement value calculation unit 50 to determine its derivative value using the derivative value calculation unit 51. The measurement value calculation unit 50 calculates the measurement value by performing a smoothing process on the detection signal (raw measurement value) detected by the strain sensor 1. The derivative value calculation unit 51 calculates the derivative value by differentiating the measurement value with respect to time.

[0040] The threshold value comparison unit 53 compares the threshold value previously set by the threshold value setting unit 52 with the differential value calculated by the differential value calculation unit 51, and determines whether the differential value exceeds the threshold value. The threshold value setting unit 52 sets an upper threshold value on the positive side and a lower threshold value on the negative side, and the threshold value comparison unit 53 determines that the differential value exceeds the threshold value when it is outside the threshold range between the positive and negative threshold values, and displays a logical value of '1'; otherwise, it determines that the differential value does not exceed the threshold value, and displays a logical value of '0'.

[0041] Next, the step determination unit 6 shown in FIG. 5 determines whether a step has been detected. The step determination unit 6 determines that a step has been detected when, among the differential values of the measurement values of the multiple strain sensors 1, the differential values of the measurement values of two or more adjacent strain sensors 1 exceed a threshold value. The step determination unit 6 calculates the logical product (AND) of two or more adjacent strain sensors 1 (e.g., strain sensors 1-1 and 1-4) for all strain sensors mounted on the tire 10. In this embodiment, since there are four strain sensors 1, the logical products (AND) of strain sensors 1-1 and 1-2, 1-2 and 1-3, 1-3 and 1-4, and 1-4 and 1-1 are calculated. Then, the logical sum (OR) of each calculated logical value is taken to perform a logical determination.

[0042] The step determination unit 6 determines that a step has been detected when the logical value is '1' as a result of the logical determination. The differential value of strain sensor 1-1 shown in FIG. 6(1) and the differential value of strain sensor 1-4 shown in FIG. 6(4) are greater than or equal to the threshold value at the tire rotation angle that is the step contact position, and the logical values of strain sensor 1-4 and strain sensor 1-1 at this position are both '1'. Therefore, the logical value of the logical product (AND) of these is also '1', and the logical sum (OR) of each logical value is also '1', which indicates a step. In other words, it is determined that a step has been detected.

[0043] FIG. 8 is a block diagram of threshold value determination showing an example of the operation of the step error detection prevention method, FIG. 9 is a determination graph showing an example of the operation by the step detection device 2, FIG. 9(1) is a graph showing the change in the differential value before the smoothing process, and FIG. 9(2) is a graph showing the change in the differential value after the smoothing process. In the measured value calculation unit 50, the measured raw value 54 measured by the strain sensor 1 is supplied to the differential value calculation unit 51 after being subjected to a predetermined smoothing process by the smoothing process unit 55. The smoothing process unit 55 includes a low-pass filter 56 that removes noise from the measured raw value 54 and an averaging process unit 57 that averages n raw value buffers.

[0044] As shown in FIG. 9(1), without the smoothing process in the measured value calculation unit 50, for example, when calculating the differential value from a protruding value, there is a concern that the threshold value may be exceeded and the logical value '1' may be obtained, causing an unintended false determination. In the present embodiment, by performing the smoothing process in the measured value calculation unit 50, it is possible to remove protruding values and values that deviate from others. As shown in FIG. 9(2), it is possible to determine the step from the differential value at t0 before waiting for the time ts until the change in the detection signal of the strain sensor 1 saturates. Therefore, it is possible to detect the step in real time immediately after the tire 10 contacts the step 20 and before climbing over the step 20.

[0045] 10A, 10B, and 10C, model simulations were performed to confirm that steps can be correctly detected within the sensor's road surface detection range (three representative examples). Fig. 10A is a schematic diagram showing a state in which the strain sensor 1-1 is positioned above the step 20 and the tire 10 is in contact with the step 20, and is a schematic diagram showing an example of the output signal of the strain sensor 1-1 and the determination result in that state. Fig. 10B is a schematic diagram showing a state in which the portion of the tire 10 where the strain sensor 1-1 is positioned is in contact with the step and is a schematic diagram showing an example of the output signal of the strain sensor 1-1 and the determination result in that state. Fig. 10C is a schematic diagram showing a state in which the strain sensor 1-1 is positioned below the step 20 and the tire 10 is in contact with the road surface, and is a schematic diagram showing an example of the output signal of the strain sensor 1-1 and the determination result in that state. In either case, it can be seen that the logical value changes from '0' to '1' at the step contact position, and the step can be correctly detected.

[0046] Next, an example of the operation of the method for preventing false step detection will be described with reference to FIGS. Fig. 11 shows the state in which the tire contacts a bump, the operation of the determination circuit in this state, and a determination graph of the differential values of each strain sensor. Fig. 12 shows the state in which the tire hits a small object such as gravel, the operation of the determination circuit in this state, and a determination graph of the differential values of each strain sensor. In this embodiment, the bump 20 is assumed to be a wheel stopper or similar object approximately 100 mm high from the road surface 30, as shown in Fig. 11(1). As shown in Fig. 11(3), the differential values of adjacent strain sensors 1-1 and 1-4 are greater than the upper threshold 64a, and as shown in Fig. 11(2), the logical AND result is a logical value of '1'.

[0047] For example, as shown in Fig. 12(1), when the vehicle is in motion and comes into contact with an object such as gravel 21 with a height of about 5 to 40 mm, the contact height between the tire 10 and the gravel 21 is low, and the detection range is also narrower compared to the grounding with the road surface 30 or the step 20. Therefore, the logical product (AND) result of two or more adjacent strain sensors 1 (for example, strain sensors 1-1 and 1-4) is a logical value '0'.

[0048] Also, for the logical product (AND) result of two adjacent ones among all the mounted strain sensors 1, the logical value is also '0'. Finally, for the logical sum (OR) of the finally obtained logical value, the result of the logical determination is a logical value '0'. Therefore, it is not misdetected as a step, and prevention of step misdetection can be achieved. In this way, by using the logical product (AND) of two adjacent sensors, it becomes possible to distinguish and determine between the gravel 21 and the step 20.

[0049] Fig. 13 is a block diagram showing an example of a method for setting a threshold value used for step determination.

[0050] For example, as shown in Fig. 3, when the absolute values of the differences from the reference level 41 at the peak value 42 of the positive level and the peak value 43 of the negative level are different, if the threshold value is fixed to the same value for both positive and negative, there may be a case where a change is not detected at the peak value 43 of the negative level with a small change per unit time. Therefore, in this embodiment, with the configuration of the following threshold value setting unit 52, changes are detected corresponding to both the positive threshold value and the negative threshold value.

[0051] The threshold value setting unit 52 includes a measured value holding unit 60, an upper limit threshold value setting unit 64, and a lower limit threshold value setting unit 65. For example, the measured value holding unit 60 holds the maximum value 61, the reference value 62, and the minimum value 63 for a certain period as the measured values of the strain sensor 1. The maximum value 61, the reference value 62, and the minimum value 63 are the maximum peak value of the positive level, the value of the reference level 41, and the minimum peak value of the negative level within a certain period. The upper limit threshold value setting unit 64 and the lower limit threshold value setting unit 65 set the upper limit threshold value 64a and the lower limit threshold value 65a based on the maximum value 61, the reference value 62, and the minimum value 63 held by the measured value holding unit 60.

[0052] The upper limit threshold setting unit 64 sets the upper limit threshold 64a based on the maximum value 61 and the reference value 62 held in the measurement value holding unit 60. For example, the upper limit threshold 64a is set by multiplying a certain gain by the time differential value between the maximum value 61 and the reference value 62. The upper limit threshold setting unit 64 determines that the upper limit threshold 64a is equal to or greater than a value smaller than the differential (positive slope) between the reference value 62 and the maximum value 61. The lower limit threshold setting unit 65 sets the lower limit threshold 65a based on the reference value 62 and the minimum value 63 held in the measurement value holding unit 60. For example, the lower limit threshold 65a is set by multiplying a certain gain by the time differential value between the reference value 62 and the minimum value 63. The lower limit threshold setting unit 65 determines that the lower limit threshold 65a is less than a value greater than the differential (negative slope) between the reference value 62 and the minimum value 63.

[0053] Then, the threshold comparison unit 53 logically determines that the differential value obtained by the differential value calculation unit 51 is equal to or greater than the upper limit threshold 64a or less than the lower limit threshold 65a, making it possible to detect changes in both the peak value 42 at the positive level and the peak value 43 at the negative level.

[0054] The upper limit threshold 64a and the lower limit threshold 65a are preferably set at an initial stage, but may also be configured to learn the driving state and update them in a timely manner. In this case, for example, it is also possible to distinguish between steps to be overcome and steps not to be overcome from the setting of the thresholds and detect steps.

[0055] Next, an example of the operation of the step detection device 2 at the positions of the respective strain sensors will be described with reference to FIGS. 14 and 15. FIG. 14 is a time chart showing an example of changes in the output signal and the differential value when the tire contacts a step in the state shown in FIG. 4A(1), and FIG. 15 is a time chart showing an example of changes in the output signal and the differential value when the tire contacts a step in the state shown in FIG. 4B(1). Here, an example in which four strain sensors 1 are mounted on the tire 10 is shown, but the number is not limited to this, and a plurality of sensors may be mounted to detect the step 20.

[0056] In the example shown in FIG. 14, the sensor signal waveforms 40 and the time-differentiated waveforms of each strain sensor 1 are shown until the state shown in FIG. 4A(1), that is, the tire 10 rolls and moves on the road surface 30, and the portion where the strain sensor 1-1 is disposed is located above the step 20 and the tire 10 contacts the step 20.

[0057] When the tire 10 contacts the step 20 and the force acting from the step 20 deforms the tire 10, the strain sensor 1-1 receives a force in the compression direction and changes to be negative with respect to the reference level 41 (see FIG. 3). For this reason, the differential value of the sensor signal waveform 40 at the step contact position becomes a negative value and is less than the lower limit threshold value 65a. The strain sensors 1-2 and 1-3 remain at the reference level 41 without receiving an external acting force, and no change is seen in the differential value at the step contact position.

[0058] When the tire 10 attempts to climb onto the step 20, the strain sensor 1-4 is released from the tensile-direction plus force acting from the road surface 30 and transitions to the reference level 41. Therefore, the differential value of the sensor signal waveform 40 at the step contact position becomes a negative value and is less than the lower limit threshold value 65a. Accordingly, in the positional relationship of the strain sensors 1-1 to 1-4, when the tire 10 contacts the step 20, '1' is respectively indicated for the strain sensors 1-1 and 1-4 by the threshold determination unit 5, the result of the logical determination in the step determination unit 6 becomes '1', and step detection can be performed to determine in real time that it is the step 20 at the step grounding position.

[0059] Next, in the example shown in FIG. 15, the sensor signal waveforms 40 and the time-differentiated waveforms of each strain sensor 1 are shown until the state shown in FIG. 4B(1), that is, the tire 10 rolls and moves on the road surface 30, and the portion where the strain sensor 1-1 is disposed contacts the step 20.

[0060] When the tire 10 contacts the step 20 and the force acting from the step 20 deforms the tire 10, the strain sensor 1-1 receives the force in the tensile direction and changes to a value greater than the reference level 41 (see FIG. 3). Therefore, the differential value of the sensor signal waveform 40 at the step contact position becomes a positive value and is equal to or greater than the upper threshold value 64a. The strain sensors 1-2 and 1-3 remain at the reference level 41 without receiving the external acting force, and no change is observed in the differential value at the step contact position.

[0061] When the strain sensor 1-4 contacts the step 20 from the state where the portion of the strain sensor 1-1 of the tire 10 is separated from the road surface 30, the compressive direction negative force acting from the road surface 30 is released and transitions to the reference level 41. Therefore, the differential value of the sensor signal waveform 40 becomes a positive value. Thus, also in this case, when the tire 10 contacts the step 20, '1' is respectively indicated for the strain sensors 1-1 and 1-4 by the threshold determination unit 5, the result of the logical determination in the step determination unit 6 becomes '1', and step detection can be performed to determine in real time that it is the step 20 at the step contact position.

[0062] Note that since the positional relationship in FIG. 4C(1) is the same as the case where FIG. 4A(1) is rotated by 90°, the illustration and the description of the step detection are omitted.

[0063] From the above, regardless of the positional relationship of the strain sensor 1 when the tire 10 contacts the step 20, it is possible to perform step detection in real time.

[0064] Next, an example of the strain sensor 1 in the present embodiment will be described with reference to FIGS. 16 and 17. The strain sensor 1 of the present embodiment is composed of a strain detection module 3. FIG. 16 is a plan view of the strain detection module 3, and FIG. 17 is a cross-sectional view of the AA of FIG. 16. As shown in FIG. 16, the strain detection module 3 includes a strain detection element 3a, a base member 3b, a sealing portion 3c, and an electric wire portion 3d. The strain detection element 3a is a semiconductor that outputs a distortion amount in response to a change in electrical resistance, and is, for example, a strain sensor chip that is combined with a control circuit that performs distortion detection processing and is converted to a single chip.

[0065] The strain sensor chip is an IC chip manufactured by a semiconductor process, for example, a rectangular MOSFET-type sensor chip measuring approximately 5 mm x 5 mm. The strain sensor chip is composed of, for example, a semiconductor formed by a CMOS process and a microelectromechanical system (MEMS). Note that a large strain sensor chip may be damaged when the tire 10 runs over a foreign object, so it is preferable that the strain sensor chip be smaller than 5 mm x 5 mm. Note that the strain detection element 3a is not limited to a strain sensor chip, and for example, a strain gauge may also be used.

[0066] The base member 3b is a member that fixes the strain detection element 3a to the inner circumferential surface of the tire, and is, for example, a thin metal plate with a linear expansion coefficient close to that of the semiconductor material (such as Si) that forms the strain detection element 3a. An example of a metal with a linear expansion coefficient close to that of the semiconductor material (such as Si) is 42 Alloy (42 Alloy: an alloy of iron and nickel), which has a linear expansion coefficient of about 5 ppm / °C, which is about 1 ppm / °C different from that of silicon (Si), which is about 4 ppm / °C.

[0067] In this way, by using a metal having a linear expansion coefficient close to that of the semiconductor material as the material of the base member 3b, it is possible to improve the accuracy of strain detection by the strain detection element 3a.

[0068] The base member 3b is not limited to the above metals. For example, a metal that is corrosion-resistant to sulfur gas generated from tires (stainless steel, aluminum, copper, iron-based alloys, or base metals plated with gold, nickel, tin, or the like) may be used.

[0069] The base member 3b is a thin rectangular plate so that it can easily hold the holding member 7 and accurately transmit tire strain to the strain detection element 3a. The end of the base member 3b in the +Z direction (front side) is arc-shaped, as shown in FIG. 11. The shape of the base member 3b is not limited to the above, and it may be circular, elliptical, or another polygonal shape. The strain detection element 3a is fixed to the surface (+Z side) of the base member 3b with an adhesive, such as a high-hardness epoxy adhesive.

[0070] The sealing portion 3c is a resin, such as epoxy resin, applied to the surface of the base member 3b from above the strain detection element 3a and a bonding wire (not shown) that electrically connects the strain detection element 3a and the electric wire portion 3d. The sealing portion 3c seals the strain detection element 3a and the bonding wire and protects them from the external environment. Note that the sealing portion 3c is not limited to epoxy resin, and other resins, such as urethane resin or silicone resin, may also be used.

[0071] The electric wire portion 3d is an electric wire that electrically connects the strain detection element 3a to a circuit, such as a flexible printed circuit (FPC). The strain detection element 3a is a semiconductor, such as a semiconductor strain sensor, that outputs the amount of strain according to changes in resistance. This allows for measurements with lower power consumption (e.g., about 1 / 1,000) and higher sensitivity (e.g., about 25,000 times) than strain gauges.

[0072] The control unit 101 of this embodiment includes a vehicle control device that acquires the results of the step detection by the step detection device 2 and controls the accelerator and brake of the vehicle. For example, when a tire comes into contact with a stop block in a parking space, the step detection device 2 detects the stop block as a step, and the vehicle control device can perform vehicle control such as closing the engine throttle valve to reduce driving force and operating the brakes to stop the vehicle using braking force to prevent the vehicle from going over the stop block. This suppresses sudden changes in the vehicle's behavior and prevents the occupants from feeling uneasy.

[0073] Also, when the vehicle enters a higher place by crossing a step, when the step is detected, the throttle valve of the engine is opened to increase the driving force, the tire 10 is lifted onto the step 20, and braking force is applied when the tire 10 is on the step 20 to control the vehicle so that the vehicle does not move too far forward. Therefore, it is possible to safely cross and climb over the step with a smooth operation without a sense of discomfort.

[0074] According to the step detection device 2 of the present embodiment described above, when the tire climbs onto the step, the step can be accurately detected. Therefore, based on an accurate step determination, the control of the drive system such as the accelerator and the brake can be performed, and the vehicle can be made to smoothly climb onto and cross over the step safely with a smooth operation without a sense of discomfort. Further, since the step detection is performed based on the output signal of the strain sensor 1 mounted on the inner peripheral surface of the tire, the step can be detected without being affected by the weather, environmental conditions, etc.

[0075] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention described in the claims. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

Description of Reference Numerals

[0076] 1···Strain sensor, 2···Bump detection device, 3···Strain detection module, 3a···Strain detection element, 3b···Base member, 3c···Sealing portion, 3d···Electric wire portion, 5···Threshold value judgment portion, 6···Bump judgment portion, 10···Tire, 20···Bump, 21···Gravel, 30···Road surface, 40···Sensor signal waveform, 41···Reference level, 42···Peak value of positive level, 43···Peak value of negative level 50 Measurement value calculation unit , 51... Differential value calculation unit, 52... Threshold value setting unit, 53... Threshold value comparison unit, 60... Measurement value storage unit, 61... Maximum value, 62... Reference value, 63... Minimum value, 64a... Upper limit threshold, 65a... Lower limit threshold, 100... Vehicle, 101... Control unit, 102... Receiver

Claims

1. A step detection device that detects a step when a vehicle tire rides over the step, comprising: a plurality of strain detection elements arranged at predetermined intervals in the circumferential direction of the tire on the inner peripheral surface of the tire; a signal processing device that processes detection signals of the plurality of strain detection elements, wherein the signal processing device calculates the differential values of the measured values of the plurality of strain detection elements respectively, compares the differential values of the measured values of the plurality of strain detection elements with a preset threshold value, and determines whether the differential values of the measured values of the plurality of strain detection elements exceed the threshold value; a threshold determination unit; a step determination unit that determines that the step has been detected when the differential values of the measured values of two or more adjacent strain detection elements among the differential values of the measured values of the plurality of strain detection elements exceed the threshold value; A step detection device, characterized by comprising the above.

2. The threshold determination unit includes a differential value calculation unit that obtains the measured value by smoothing the detection signals of the plurality of strain detection elements and calculates the differential value by differentiating the measured value with respect to time; a threshold setting unit that sets an upper limit threshold value and a lower limit threshold value; and a threshold comparison unit that determines that the threshold value is exceeded when the differential value falls outside the threshold range between the upper limit threshold value and the lower limit threshold value. The step detection device according to claim 1, characterized by comprising the above.

3. The threshold setting unit includes a measured value holding unit that holds the reference value, the maximum value, and the minimum value of the measured value in a certain period; an upper limit threshold value setting unit that sets the upper limit threshold value based on the reference value and the maximum value of the measured value; and a lower limit threshold value setting unit that sets the lower limit threshold value based on the reference value and the minimum value of the measured value. The step detection device according to claim 2, characterized by comprising the above.

4. The upper limit threshold value setting unit determines that the upper limit threshold value is not less than a value smaller than the differential between the reference value and the maximum value of the measured value; The lower limit threshold value setting unit determines that the lower limit threshold value is less than a value larger than the differential between the reference value and the minimum value of the measured value. The step detection device according to claim 3, characterized by comprising the above.

5. The strain detection element is a semiconductor that outputs a strain amount corresponding to a change in electrical resistance. The step detection device according to claim 1, characterized by comprising the above.

6. Obtaining a determination result of step detection from the step detection device according to claim 1, A vehicle control device, characterized by controlling the accelerator or brake of the vehicle based on the determination result.

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