Electric parking system
The electric parking device uses front and rear acceleration sensors to set a reference acceleration for generating parking braking force, addressing the issue of sensor data unavailability and ensuring effective vehicle positioning on varying gradients.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ADVICS CO LTD
- Filing Date
- 2024-11-29
- Publication Date
- 2026-06-10
AI Technical Summary
Existing electric parking devices may fail to generate an appropriate parking braking force when they cannot acquire detection values from on-board acceleration sensors, leading to potential issues with maintaining vehicle position on varying road gradients.
The electric parking device utilizes front and rear acceleration sensors to acquire effective acceleration values, sets a reference acceleration based on maximum and minimum values, and generates parking braking force accordingly, even when sensor data is unavailable.
Ensures generation of an appropriate parking braking force regardless of sensor data availability, maintaining vehicle position effectively on different road gradients.
Smart Images
Figure 2026094924000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an electric parking device provided in a vehicle.
Background Art
[0002] Patent Document 1 discloses an electric parking device that generates a parking braking force for a vehicle based on the gradient of the road surface where the vehicle has stopped. The control unit of the electric parking device calculates an estimated value of the road surface gradient based on the running state of the vehicle during the running of the vehicle as a dynamic estimated road surface gradient. When the vehicle has stopped, the control unit calculates an estimated value of the road surface gradient based on the acceleration acting on the vehicle as a static estimated road surface gradient. When the static estimated road surface gradient is greater than the dynamic estimated road surface gradient, the control unit generates a parking braking force for the vehicle that is greater than the braking force corresponding to the dynamic estimated road surface gradient.
Prior Art Documents
Patent Documents
[0003] [[ID=2,1]] [[ID=2,2]]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the above electric parking device, when the control unit can acquire the detection value of the in-vehicle acceleration sensor, the control unit can generate the parking braking force as described above. However, if the control unit cannot acquire the detection value before generating the parking braking force, the control unit cannot calculate the static estimated road surface gradient. As a result, there is a possibility that the control unit cannot generate a parking braking force of an appropriate magnitude according to the road surface gradient where the vehicle is located.
Means for Solving the Problems
[0005] An electric parking device for solving the above problems is a device that drives an electric motor to generate parking braking force in a vehicle. The electric parking device includes an acquisition unit that, when it can receive detection values from front and rear acceleration sensors provided in the vehicle, acquires the detected values as effective acceleration; a setting unit that acquires the minimum and maximum values of the effective acceleration and sets a reference acceleration based on the maximum value of the minimum and the minimum value of the maximum; and a parking control unit that executes a parking process to drive the electric motor to generate parking braking force in the vehicle according to the reference acceleration. [Effects of the Invention]
[0006] The above-described electric parking system has the effect of generating an appropriate amount of parking braking force in the vehicle even if it becomes impossible to obtain detection values from the on-board longitudinal acceleration sensors after the vehicle has stopped. [Brief explanation of the drawing]
[0007] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with an electric parking device according to the first embodiment. [Figure 2] Figure 2 is a flowchart showing a series of processes performed in the control device of the electric parking system shown in Figure 1 to set the reference acceleration. [Figure 3] Figure 3 is a flowchart showing a series of processes performed in the control device of the electric parking system shown in Figure 1 to generate parking braking force. [Figure 4] In Figure 4, (a) is a timing chart showing the change in effective acceleration, and (b) is a timing chart showing the change in reference acceleration. [Figure 5] Figure 5 is a flowchart showing a portion of the series of processes performed to set the reference acceleration in the control device of the electric parking system of the second embodiment. [Figure 6] Figure 6 is a timing chart showing the changes in effective acceleration and reference acceleration in the electric parking system of the second embodiment. [Figure 7]Figure 7 is a flowchart showing a portion of the series of processes performed to set the reference acceleration in the control device of the third embodiment of the electric parking system. [Figure 8] Figure 8 is a flowchart showing a series of processes performed to set the reference acceleration in the control device of the electric parking system of the fourth embodiment. [Figure 9] Figure 9 is a timing chart showing the changes in effective acceleration and reference acceleration in the electric parking system of the fourth embodiment. [Modes for carrying out the invention]
[0008] (First Embodiment) The first embodiment of the electric parking device will be described below with reference to Figures 1 to 4. Figure 1 illustrates a vehicle 10 equipped with an electric parking system 30. In addition to the electric parking system 30, the vehicle 10 is equipped with a plurality of control devices 11. An example of the plurality of control devices 11 is an electronic control device. The parking control device 40 of the electric parking system 30, which will be described later, and the plurality of control devices 11 can communicate with each other via an in-vehicle network 12. An example of the in-vehicle network 12 is a CAN bus. CAN is an abbreviation for "Controller Area Network".
[0009] One of the multiple control devices 11 receives the detection signal from the longitudinal acceleration sensor 21. The longitudinal acceleration sensor 21 detects the longitudinal acceleration of the vehicle 10. The control device 11 acquires a longitudinal acceleration detection value Gx, which is the longitudinal acceleration based on the detection signal from the longitudinal acceleration sensor 21. The longitudinal acceleration detection value Gx corresponds to the "detection value from the longitudinal acceleration sensor 21". The control device 11 transmits the longitudinal acceleration detection value Gx to the in-vehicle network 12 at predetermined intervals.
[0010] When the vehicle 10's power system is operating, communication takes place between the multiple control devices via the in-vehicle network 12. However, if the power system is shut down, such as when the vehicle 10's ignition switch is turned off, communication between the multiple control devices via the in-vehicle network 12 stops.
[0011] <Electric parking system> The electric parking system 30 comprises a plurality of parking actuators 31A, 31B and a parking control device 40 that controls the plurality of parking actuators 31A, 31B.
[0012] Of the multiple parking actuators 31A and 31B, parking actuator 31A generates a parking braking force on one of the two rear wheels of the vehicle 10. Parking actuator 31B generates a parking braking force on the other of the two rear wheels. The multiple parking actuators 31A and 31B are equipped with an electric motor 32. The multiple parking actuators 31A and 31B are configured to generate a parking braking force on the corresponding rear wheel by driving the electric motor 32. A greater amount of drive from the electric motor 32 generates a greater parking braking force.
[0013] The parking control device 40 includes a processing circuit 41 that controls multiple electric motors 32. An example of the processing circuit 41 is an electronic control device. In this case, the processing circuit 41 has a CPU 42, a first memory 43, and a second memory 44. The first memory 43 stores various control programs executed by the CPU 42. The second memory 44 stores the calculation results of the CPU 42, etc.
[0014] <Functional configuration of the parking control device 40> The processing circuit 41 of the parking control device 40 functions as a plurality of functional units for operating the parking actuators 31A and 31B by having the CPU 42 execute the control program in the first memory 43. The plurality of functional units include an acquisition unit 101, a convergence determination unit 102, a setting unit 103, and a parking control unit 104.
[0015] <Acquisition part> When the parking control device 40 can receive the longitudinal acceleration detection value Gx via the in-vehicle network 12, the acquisition unit 101 acquires the longitudinal acceleration detection value Gx as the effective acceleration Ge. Specifically, the acquisition unit 101 acquires the latest value of the longitudinal acceleration detection value Gx received by the parking control device 40 via the in-vehicle network 12 as the effective acceleration Ge. Therefore, when the parking control device 40 fails to detect the longitudinal acceleration detection value Gx, the effective acceleration Ge is held at the longitudinal acceleration detection value Gx that the parking control device 40 last received.
[0016] <Convergence determination unit> Immediately after the vehicle 10 stops, as shown in Fig. 4(a), the effective acceleration Ge, that is, the longitudinal acceleration detection value Gx, may fluctuate. The amplitude of the fluctuating effective acceleration Ge gradually decreases. Therefore, the maximum value Gpmax and the minimum value Gpmin of the waveform indicating the transition of the effective acceleration Ge gradually approach the acceleration convergence value Gc. The acceleration convergence value Gc is the longitudinal acceleration corresponding to the gradient of the road surface where the vehicle 10 is located. And the effective acceleration Ge will eventually converge to the acceleration convergence value Gc.
[0017] When the vehicle 10 stops, the convergence determination unit 102 determines whether the effective acceleration Ge has converged to the acceleration convergence value Gc. The convergence determination unit 102 determines whether the effective acceleration Ge has converged to the acceleration convergence value Gc based on the waveform indicating the transition of the effective acceleration Ge. For example, when the duration of the state where the absolute value of the increase amount ΔGe of the effective acceleration Ge per unit time is less than or equal to a predetermined value exceeds a predetermined time, the convergence determination unit 102 determines that the effective acceleration Ge has converged to the acceleration convergence value Gc. In this case, when the duration has not reached the above-mentioned predetermined time, the convergence determination unit 102 determines that the effective acceleration Ge has not converged to the acceleration convergence value Gc.
[0018] <Setting unit> The setting unit 103 sets the reference acceleration Gs, which is the reference value for longitudinal acceleration, based on the effective acceleration Ge. When the electric parking device 30 generates a parking braking force for the vehicle 10, it generates a parking braking force for the vehicle 10 that corresponds to the reference acceleration Gs. Therefore, if the reference acceleration Gs is smaller than the absolute value of the longitudinal acceleration corresponding to the road surface gradient, the vehicle 10 may not be able to maintain its stop even if a parking braking force is generated for the vehicle 10.
[0019] If the effective acceleration Ge acquired by the acquisition unit 101 is continuously being updated, the setting unit 103 observes the trend of the effective acceleration Ge and acquires the minimum value Gpmin and maximum value Gpmax of the effective acceleration Ge. Then, the setting unit 103 performs a pre-convergence setting process to set the reference acceleration Gs based on the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax acquired after the vehicle 10 has stopped. In the pre-convergence setting process, for example, the setting unit 103 sets the reference acceleration Gs to the larger of the absolute value Glw of the maximum value Gpmin and the absolute value Gup of the minimum value Gpmax.
[0020] The setting unit 103 sets the reference acceleration Gs by executing the above-mentioned pre-convergence setting process when the convergence determination unit 102 determines that the effective acceleration Ge has not converged to the acceleration convergence value Gc.
[0021] On the other hand, if the convergence determination unit 102 determines that the effective acceleration Ge has converged to the acceleration convergence value Gc, the setting unit 103 sets the reference acceleration Gs using a process different from the pre-convergence setting process described above. For example, the setting unit 103 sets the latest value of the effective acceleration Ge to the reference acceleration Gs. In this case, the setting unit 103 may also set the sum of the latest value of the effective acceleration Ge and the offset value to the reference acceleration Gs.
[0022] <Parking Control Panel> When a parking request is received, the parking control unit 104 executes a parking process by driving the electric motors 32 of the two parking actuators 31A and 31B to generate a parking braking force in the vehicle 10 corresponding to the reference acceleration Gs. In this way, the parking control unit 104 can generate a larger parking braking force in the vehicle 10 as the reference acceleration Gs increases. On the other hand, when a request to release the parking brake is received, the parking control unit 104 executes a release process by driving the electric motors 32 of the two parking actuators 31A and 31B to reduce the parking braking force to 0 (zero).
[0023] <Setting the reference acceleration> Referring to Figure 2, the series of processes performed by the processing circuit 41 when setting the reference acceleration Gs will be explained. The processing circuit 41 repeatedly performs this series of processes at predetermined control cycles when no parking braking force is generated.
[0024] In step S11, the processing circuit 41 determines whether the vehicle 10 is stopped or not. For example, if the vehicle 10's speed is 0 (zero), the vehicle 10 is considered to be stopped. On the other hand, if the vehicle 10's speed is greater than 0 (zero), the vehicle 10 is considered not to be stopped. If the processing circuit 41 determines that the vehicle 10 is stopped (S11: YES), the processing circuit 41 proceeds to step S15. On the other hand, if the processing circuit 41 determines that the vehicle 10 is not stopped (S11: NO), the processing circuit 41 proceeds to step S13.
[0025] In step S13, the processing circuit 41 functions as a setting unit 103 to set a fixed value Gs0 to the reference acceleration Gs. For example, the fixed value Gs0 is set to the maximum longitudinal acceleration that can occur in the vehicle 10 within the assumed range, or a longitudinal acceleration greater than that maximum value. After that, the processing circuit 41 temporarily terminates the series of processes shown in Figure 2.
[0026] In step S15, the processing circuit 41 determines whether or not it has received the longitudinal acceleration detection value Gx via the in-vehicle network 12. As mentioned above, if the power supply system of the vehicle 10 is stopped, the processing circuit 41 cannot receive the longitudinal acceleration detection value Gx. Also, if the longitudinal acceleration sensor 21 is malfunctioning, or if there is a malfunction in the control device 11 to which the detection signal from the longitudinal acceleration sensor 21 is input, the processing circuit 41 cannot receive the longitudinal acceleration detection value Gx.
[0027] In step S15, if the processing circuit 41 has received the longitudinal acceleration detection value Gx (S15: YES), the processing circuit 41 proceeds to step S17. On the other hand, if the processing circuit 41 has not received the longitudinal acceleration detection value Gx (S15: NO), the processing circuit 41 terminates the series of processes shown in Figure 2. In this case, the processing circuit 41 retains the reference acceleration Gs as the previous value. The "previous value" here refers to the reference acceleration Gs at the time of the previous execution of the series of processes.
[0028] In step S17, the processing circuit 41 functions as an acquisition unit 101 and acquires the latest value of the longitudinal acceleration detection value Gx received via the in-vehicle network 12 as the effective acceleration Ge.
[0029] In the following step S19, the processing circuit 41 functions as a convergence determination unit 102 to determine whether the effective acceleration Ge has converged to the acceleration convergence value Gc. If the processing circuit 41 determines that the effective acceleration Ge has converged to the acceleration convergence value Gc (S19: YES), the processing circuit 41 proceeds to step S21. On the other hand, if the processing circuit 41 determines that the effective acceleration Ge has not converged to the acceleration convergence value Gc (S19: NO), the processing circuit 41 proceeds to step S23.
[0030] In step S21, the processing circuit 41 functions as a setting unit 103 to set the longitudinal acceleration corresponding to the effective acceleration Ge as the reference acceleration Gs. For example, the processing circuit 41 sets the effective acceleration Ge as the reference acceleration Gs. After that, the processing circuit 41 temporarily terminates the series of processes shown in Figure 2.
[0031] In step S23, the processing circuit 41 functions as a setting unit 103 and performs the process of acquiring the minimum value Gpmin and the maximum value Gpmax of the fluctuating effective acceleration Ge. In this acquisition process, the processing circuit 41 can acquire, for example, the effective acceleration Ge at the point when it switches from a state in which the effective acceleration Ge is decreasing to a state in which the effective acceleration Ge is increasing as the minimum value Gpmin. The processing circuit 41 can acquire, for example, the effective acceleration Ge at the point when it switches from a state in which the effective acceleration Ge is increasing to a state in which the effective acceleration Ge is decreasing as the maximum value Gpmax.
[0032] In the following step S25, the processing circuit 41 determines whether it has been able to obtain the minimum value Gpmin and the maximum value Gpmax while the vehicle 10 is stopped. If the processing circuit 41 has already obtained at least one of the minimum value Gpmin and the maximum value Gpmax (S25: YES), the processing circuit 41 proceeds to step S29. On the other hand, if the processing circuit 41 has not yet obtained either the minimum value Gpmin or the maximum value Gpmax (S25: NO), the processing circuit 41 proceeds to step S27.
[0033] In step S27, the processing circuit 41 functions as a setting unit 103 and sets the maximum absolute value |Gemax| of the effective acceleration Ge acquired while the vehicle 10 was stopped as the reference acceleration Gs. Then, the processing circuit 41 terminates the series of processes shown in Figure 2.
[0034] In step S29, the processing circuit 41 functions as a setting unit 103 to obtain the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax. Specifically, the processing circuit 41 obtains the largest value among the minimum values Gpmin obtained while the vehicle 10 was stopped as the maximum value Glw of the minimum value Gpmin. The processing circuit 41 obtains the smallest value among the maximum values Gpmax obtained while the vehicle 10 was stopped as the minimum value Gup of the maximum value Gpmax.
[0035] In the next step S31, the processing circuit 41 functions as a setting unit 103 and sets the reference acceleration Gs to the larger of the absolute values of the maximum value Glw and the absolute value of the minimum value Gup. After that, the processing circuit 41 temporarily terminates the series of processes shown in Figure 2.
[0036] The processing circuit 41 sets the reference acceleration Gs by executing the series of processes shown in Figure 2, and then stores the reference acceleration Gs in the second memory 44. In other words, the processing circuit 41 can update the reference acceleration Gs stored in the second memory 44.
[0037] <Generation of parking brake force> Referring to Figure 3, we will now explain the series of processes that the processing circuit 41 executes after it has set the reference acceleration Gs in the series of processes shown in Figure 2.
[0038] In step S41, the processing circuit 41 determines whether or not there is a parking request. If there is a parking request (S41: YES), the processing circuit 41 proceeds to step S43. On the other hand, if there is no parking request (S41: NO), the processing circuit 41 terminates the series of processes shown in Figure 3.
[0039] In step S43, the processing circuit 41 reads the latest value of the reference acceleration Gs from the second memory 44. Then, in step S45, the processing circuit 41, acting as a parking control unit 104, performs a parking process that drives the electric motors 32 of the multiple parking actuators 31A and 31B based on the reference acceleration Gs read in step S43. After the parking process is completed, the processing circuit 41 terminates the series of processes shown in Figure 3.
[0040] <Operation of this embodiment> The operation of this embodiment will be explained with reference to Figure 4. The example shown in Figure 4 illustrates an example where the vehicle 10 stops on a downhill slope.
[0041] As shown in Figure 4(a), the vehicle 10 comes to a stop at timing t10 when the service braking force is applied to the vehicle 10. When the vehicle 10 stops, the longitudinal acceleration detection value Gx fluctuates as shown by the dashed line in Figure 4(a) due to the rebound of the vehicle body, etc. As time passes, the amplitude of this longitudinal acceleration detection value Gx gradually decreases. Then, the longitudinal acceleration detection value Gx converges to the acceleration convergence value Gc, which is the longitudinal acceleration corresponding to the gradient of the road surface on which the vehicle 10 stopped.
[0042] Before timing t10, the vehicle 10 is not yet stopped, so the effective acceleration Ge is not set. Also, a fixed value Gs0 is set as the reference acceleration Gs. Vehicle 10 stops at timing t10. Therefore, after timing t10, if the processing circuit 41 can receive the longitudinal acceleration detection value Gx, the effective acceleration Ge also fluctuates as shown by the solid line in Figure 4(a).
[0043] In the example shown in Figure 4, at timing t11, the trend of the effective acceleration Ge changes from a decreasing trend to an increasing trend. In other words, the effective acceleration Ge at timing t11 becomes the first local minimum Gpmin from the point when the vehicle 10 stopped. No local maximum Gpmax is obtained in the interval from timing t11 to timing t12. Therefore, as shown in Figure 4(b), in this interval, the absolute value of the first local minimum Gpmin, which is the effective acceleration Ge at timing t11, is set as the reference acceleration Gs.
[0044] The fluctuation trend of the effective acceleration Ge from timing t11 is increasing. At the subsequent timing t12, the fluctuation trend of the effective acceleration Ge switches from increasing to decreasing. In other words, the effective acceleration Ge at timing t12 becomes the first maximum value Gpmax from the point when the vehicle 10 stopped. From timing t12 onward, both the minimum value Gpmin and the maximum value Gpmax are obtained. Therefore, the larger of the absolute value of the minimum value Gpmin and the absolute value of the maximum value Gpmax is set as the reference acceleration Gs.
[0045] From timing t12 onward, the local minimum Gpmin and local maximum Gpmax are acquired alternately. As shown in Figure 4(a), the local minimum Gpmin increases in steps, while the local maximum Gpmax decreases in steps. In other words, both the local minimum Gpmin and local maximum Gpmax approach the acceleration convergence value Gc.
[0046] Therefore, from timing t12 onward, each time a local minimum Gpmin is obtained, the maximum value Glw of the local minimum Gpmin is updated. Similarly, each time a local maximum Gpmax is obtained, the minimum value Gup of the local maximum Gpmax is updated. Then, as shown in Figure 4(b), the larger of the absolute value of the maximum value Glw and the absolute value of the minimum value Gup is set as the reference acceleration Gs.
[0047] Subsequently, once it is determined that the reference acceleration Gs has converged, the latest value of the effective acceleration Ge is set to the reference acceleration Gs. When vehicle 10 stops on an uphill road, the acceleration convergence value Gc becomes a negative value. Therefore, before the effective acceleration Ge converges, the maximum value Glw of the minimum value Gpmin of the effective acceleration Ge becomes larger than the minimum value Gup of the maximum value Gpmax. For this reason, the maximum value Glw of the minimum value Gpmin is set as the reference acceleration Gs.
[0048] Furthermore, if a parking request occurs after the vehicle 10 has come to a stop, the electric motors 32 of multiple parking actuators 31A, 31A are driven. Specifically, the electric motors 32 are driven based on the reference acceleration Gs at the time the parking request occurs. As a result, a parking braking force corresponding to the reference acceleration Gs is generated in the vehicle 10.
[0049] <Effects of this embodiment> (1-1) At some point between the time the vehicle 10 stops and the time a parking request is made, the parking control device 40 may be unable to receive the longitudinal acceleration detection value Gx.
[0050] Here, consider a comparative example where, if the parking control device loses the ability to receive the longitudinal acceleration detection value Gx, the last received longitudinal acceleration detection value Gx is set as the reference acceleration Gs. In this comparative example, if the parking control device loses the ability to receive the longitudinal acceleration detection value Gx after the longitudinal acceleration detection value Gx has converged to the acceleration convergence value Gc, the reference acceleration Gs is set to the acceleration convergence value Gc or a value close to the acceleration convergence value Gc. Therefore, when a parking request is made and the parking process is executed, a parking braking force corresponding to the acceleration convergence value Gc is generated. However, if the parking control device loses the ability to receive the longitudinal acceleration detection value Gx while the longitudinal acceleration detection value Gx is fluctuating relatively large, there is a possibility that an acceleration smaller than the acceleration convergence value Gc will be set as the reference acceleration Gs. If the parking process is executed with the reference acceleration Gs sufficiently smaller than the acceleration convergence value Gc, the parking braking force corresponding to the reference acceleration Gs will be insufficient with respect to the road surface gradient.
[0051] Therefore, in the electric parking device 30, the processing circuit 41 acquires the maximum value Gpmax and minimum value Gpmin of the fluctuating effective acceleration Ge. Based on the maximum value Gpmax and minimum value Gpmin, the processing circuit 41 sets the reference acceleration Gs. Then, when a parking request occurs, the processing circuit 41 drives the electric motors 32 of the multiple parking actuators 31A and 31B based on the reference acceleration Gs at that time. As a result, the processing circuit 41 can generate a parking braking force for the vehicle 10 that corresponds to the reference acceleration Gs at that time.
[0052] Since the reference acceleration Gs is set based on the maximum value Gpmax and the minimum value Gpmin in this way, it is suppressed that the reference acceleration Gs becomes significantly smaller than the acceleration convergence value Gc. As a result, when the parking control device 40 is unable to receive the longitudinal acceleration detection value Gx and the parking process is executed, it is suppressed that the parking braking force corresponding to the reference acceleration Gs becomes too small for the road surface gradient.
[0053] Furthermore, even if the parking control device 40 is unable to receive the longitudinal acceleration detection value Gx via the in-vehicle network 12 while the longitudinal acceleration detection value Gx is fluctuating, the processing circuit 41 can set the reference acceleration Gs to an acceleration greater than the acceleration convergence value Gc. Therefore, even if the parking control device 40 is unable to receive the longitudinal acceleration detection value Gx after the vehicle 10 has stopped, the electric parking device 30 can generate an appropriate amount of parking braking force for the vehicle 10.
[0054] (1-2) When the effective acceleration Ge fluctuates, the effective acceleration Ge fluctuates around the acceleration convergence value Gc. The minimum value Gpmin and the maximum value Gpmax then approach the acceleration convergence value Gc in steps. In the case of the electric parking device 30, the processing circuit 41 sets the reference acceleration Gs to the larger of the absolute value of the maximum value Glw of the minimum value Gpmin and the absolute value of the minimum value Gup of the maximum value Gpmax.
[0055] As a result, the processing circuit 41 can set the reference acceleration Gs to a value close to the acceleration convergence value Gc, and to ensure that the reference acceleration Gs does not fall below the acceleration convergence value Gc. By using this reference acceleration Gs, the processing circuit 41 can perform the parking process, and even if the parking control device 40 is unable to receive the longitudinal acceleration detection value Gx, the processing circuit 41 can generate a parking braking force for the vehicle 10 that is neither too strong nor too weak for the road surface gradient.
[0056] (1-3) When the processing circuit 41 determines that the effective acceleration Ge has converged to the acceleration convergence value Gc, it sets a value corresponding to the absolute value of the effective acceleration Ge to the reference acceleration Gs. By having the processing circuit 41 perform the parking process using this reference acceleration Gs, the processing circuit 41 can generate a parking braking force on the vehicle 10 that is of an appropriate magnitude for the road surface gradient, even if the parking control device 40 is unable to receive the longitudinal acceleration detection value Gx.
[0057] (Second Embodiment) The second embodiment will be described with reference to Figures 5 and 6. The second embodiment differs from the first embodiment in the method for setting the reference acceleration immediately after the vehicle stops. In the following description, the parts that differ from the first embodiment will be mainly described, and the same reference numerals will be used for components that are the same as or equivalent to those in the first embodiment, and redundant explanations will be omitted.
[0058] <Setting the reference acceleration> Figure 5 illustrates a portion of the series of processes performed by the processing circuit 41 when setting the reference acceleration Gs.
[0059] In step S23 shown in Figure 2, when the processing circuit 41 performs the process of acquiring the minimum value Gpmin and the maximum value Gpmax of the effective acceleration Ge, the processing circuit 41 moves to step S25. In step S25, if the processing circuit 41 has already acquired at least one of the minimum value Gpmin and the maximum value Gpmax (S25: YES), the processing circuit 41 moves to step S29. In step S29, the processing circuit 41 functions as a setting unit 103 to acquire the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax.
[0060] In the next step S30, the processing circuit 41 functions as a setting unit 103 to determine whether the elapsed time Ts from the moment the vehicle 10 stopped has reached a predetermined determination time Tsth. As described above, immediately after the vehicle 10 stops, the amplitude of the effective acceleration Ge is relatively large, but as time passes, the amplitude of the effective acceleration Ge gradually decreases. Therefore, the length of time that serves as the criterion for determining whether the amplitude of the effective acceleration Ge has become relatively small is set as the determination time Tsth. If the elapsed time Ts has reached the determination time Tsth (S30: YES), the processing circuit 41 proceeds to step S31. On the other hand, if the elapsed time Ts has not reached the determination time Tsth (S30: NO), the processing circuit 41 proceeds to step S27.
[0061] The subsequent processing flow is the same as in the first embodiment described above, so a detailed explanation will be omitted. <Operation and Effects of This Embodiment> Referring to Figure 6, the differences in the operation of this embodiment compared to the first embodiment described above will be explained.
[0062] When vehicle 10 stops at timing t20, the reference acceleration Gs is changed based on the effective acceleration Ge. Timing t21 is when the determination time Tsth has elapsed from timing t20. Therefore, in the interval from timing t20 to timing t21, the maximum absolute value |Gemax| of the effective acceleration Ge obtained while vehicle 10 was stopped is set as the reference acceleration Gs.
[0063] From timing t21 onward, it can be determined that the amplitude of the effective acceleration Ge has become relatively small. Therefore, in the interval from timing t21 onward until it can be determined that the effective acceleration Ge has converged, the larger of the absolute value of the maximum value Glw and the absolute value of the minimum value Gup is set as the reference acceleration Gs.
[0064] In this embodiment, in addition to the effects (1-1) to (1-3) of the first embodiment described above, the following further effects can be obtained. (2-1) Immediately after the vehicle 10 comes to a stop, the amplitude of the effective acceleration Ge may be relatively large. Even in this case, if the larger of the absolute value of the maximum value Glw and the absolute value of the minimum value Gup is set as the reference acceleration Gs, the reference acceleration Gs is likely to fluctuate significantly.
[0065] In this embodiment, if the elapsed time Ts from the time the vehicle 10 stops has not reached the determination time Tsth, the processing circuit 41 sets the maximum absolute value of the effective acceleration Ge acquired since the time of stopping as the reference acceleration Gs. This allows the processing circuit 41 to suppress large fluctuations in the reference acceleration Gs due to fluctuations in the longitudinal acceleration detection value Gx.
[0066] (Third embodiment) The third embodiment will be described with reference to Figure 7. The third embodiment differs from the above-mentioned embodiments in the method for setting the reference acceleration immediately after the vehicle has stopped. In the following description, the parts that differ from the above-mentioned embodiments will be mainly described, and the same reference numerals will be used for components that are the same as or equivalent to those in the above-mentioned embodiments, and redundant explanations will be omitted.
[0067] <Setting the reference acceleration> Figure 7 illustrates a portion of the series of processes performed by the processing circuit 41 when setting the reference acceleration Gs.
[0068] When the processing circuit 41 obtains the maximum value Glw of the local minimum Gpmin and the minimum value Gup of the local maximum Gpmax in step S29, the processing circuit 41 proceeds to step S301.
[0069] In step S301, the processing circuit 41, functioning as a setting unit 103, determines whether the amplitude of the effective acceleration Ge is large or small. For example, if the difference between the latest value of the minimum value Gpmin and the latest value of the maximum value Gpmax is relatively large, the amplitude of the effective acceleration Ge is considered large. On the other hand, if the difference is relatively small, the amplitude of the effective acceleration Ge is considered small. In this case, the processing circuit 41 may determine that the amplitude is large if the difference is above a threshold, and that the amplitude is small if the difference is below the threshold. If the processing circuit 41 determines that the amplitude of the effective acceleration Ge is large (S301: YES), the processing circuit 41 proceeds to step S27. On the other hand, if the processing circuit 41 determines that the amplitude of the effective acceleration Ge is small (S301: NO), the processing circuit 41 proceeds to step S31.
[0070] The subsequent processing flow is the same as in the first embodiment described above, so a detailed explanation will be omitted. <Effects of this embodiment> In this embodiment, in addition to the effects (1-1) to (1-3) of the first embodiment described above, the following further effects can be obtained.
[0071] (3-1) In this embodiment, the processing circuit 41 determines whether the amplitude of the effective acceleration Ge is large after the vehicle 10 stops. If the processing circuit 41 determines that the amplitude of the effective acceleration Ge is large, the processing circuit 41 sets the maximum value of the absolute value of the effective acceleration Ge acquired after the stopping point as the reference acceleration Gs. This allows the processing circuit 41 to suppress large fluctuations in the reference acceleration Gs in accordance with fluctuations in the longitudinal acceleration detection value Gx.
[0072] (Fourth Embodiment) The fourth embodiment will be described with reference to Figures 8 and 9. In the following description, the differences from the above embodiments will be mainly described, and the same reference numerals will be used for components that are the same as or equivalent to those in the above embodiments, and redundant explanations will be omitted.
[0073] <Setting the reference acceleration> Referring to Figure 8, the series of processes performed by the processing circuit 41 when setting the reference acceleration Gs will be explained. The processing circuit 41 repeatedly performs this series of processes at predetermined control cycles when no parking braking force is generated.
[0074] In step S51, the processing circuit 41 determines whether or not it has received the longitudinal acceleration detection value Gx via the in-vehicle network 12. If the processing circuit 41 has received the longitudinal acceleration detection value Gx (S51: YES), the processing circuit 41 proceeds to step S61. On the other hand, if the processing circuit 41 has not received the longitudinal acceleration detection value Gx (S51: NO), the processing circuit 41 proceeds to step S53.
[0075] In step S53, the processing circuit 41 determines whether a reference acceleration Gs has been set. If the reference acceleration Gs has already been set (S53: YES), the processing circuit 41 terminates the series of processes shown in Figure 8. In this case, the processing circuit 41 retains the reference acceleration Gs at its previous value. On the other hand, if the reference acceleration Gs has not yet been set (S53: NO), the processing circuit 41 proceeds to step S55.
[0076] In step S55, the processing circuit 41 sets the first specified acceleration GupA to the minimum value Gup of the maximum value Gpmax of the effective acceleration Ge. The processing circuit 41 sets the second specified acceleration GlwA to the maximum value Glw of the minimum value Gpmin of the effective acceleration Ge. For example, the absolute value of the maximum longitudinal acceleration that can be set as the effective acceleration Ge is set as the first specified acceleration GupA. Alternatively, for example, the product of the first specified acceleration GupA and "-1" is set as the second specified acceleration GlwA.
[0077] In the next step S57, the processing circuit 41 functions as a setting unit 103 and sets the reference acceleration Gs to the larger of the absolute values of the maximum value Glw and the absolute value of the minimum value Gup. After that, the processing circuit 41 temporarily terminates the series of processes shown in Figure 8.
[0078] In step S61, the processing circuit 41 functions as an acquisition unit 101 and acquires the latest value of the longitudinal acceleration detection value Gx received via the in-vehicle network 12 as the effective acceleration Ge.
[0079] In the subsequent step S63, the processing circuit 41 functions as a setting unit 103 and performs the process of acquiring the minimum value Gpmin and the maximum value Gpmax of the fluctuating effective acceleration Ge. The acquisition process performed here is the same as the acquisition process in step S23 described above.
[0080] In the next step, S65, the processing circuit 41 determines whether the vehicle 10 is stopped or not, similar to step S11 in Figure 2. If the processing circuit 41 determines that the vehicle 10 is stopped (S65: YES), the processing circuit 41 proceeds to step S67. On the other hand, if the processing circuit 41 determines that the vehicle 10 is not stopped (S65: NO), the processing circuit 41 proceeds to step S55.
[0081] In step S67, the processing circuit 41 determines whether the elapsed time Tm from the time the vehicle 10 stopped has reached a predetermined convergence determination time Tmth. The convergence determination time Tmth is set to the time at which it can be determined whether the amplitude of the effective acceleration Ge has become sufficiently small. For example, the convergence determination time Tmth may be equal to the determination time Tsth mentioned above, or it may be longer than the determination time Tsth. If the elapsed time Tm has not reached the convergence determination time Tmth (S67: NO), the processing circuit 41 proceeds to step S55. On the other hand, if the elapsed time Tm has reached the convergence determination time Tmth (S67: YES), the processing circuit 41 proceeds to step S69.
[0082] In step S69, the processing circuit 41 determines whether or not it was able to obtain the minimum value Gpmin of the effective acceleration Ge after the start of braking of the vehicle 10. If the processing circuit 41 was able to obtain the minimum value Gpmin (S69: YES), the processing circuit 41 proceeds to step S71. On the other hand, if the processing circuit 41 was not able to obtain the minimum value Gpmin (S69: NO), the processing circuit 41 proceeds to step S73.
[0083] In step S71, the processing circuit 41, functioning as a setting unit 103, obtains the largest value among the minimum values Gpmin of the effective acceleration Ge after the start of braking of the vehicle 10, as the maximum value Glw of the minimum value Gpmin. Then, the processing circuit 41 proceeds to step S75.
[0084] In step S73, the processing circuit 41, functioning as a setting unit 103, acquires the second specified acceleration GlwA as the maximum value Glw. Then, the processing circuit 41 proceeds to step S75.
[0085] In step S75, the processing circuit 41 determines whether or not it was able to obtain the maximum value Gpmax of the effective acceleration Ge after the start of braking of the vehicle 10. If the processing circuit 41 was able to obtain the maximum value Gpmax (S75: YES), the processing circuit 41 proceeds to step S77. On the other hand, if the processing circuit 41 was not able to obtain the maximum value Gpmax (S75: NO), the processing circuit 41 proceeds to step S79.
[0086] In step S77, the processing circuit 41, functioning as a setting unit 103, obtains the smallest value among the maximum values Gpmax of the effective acceleration Ge after the start of braking of the vehicle 10, as the minimum value Gup of the maximum value Gpmax. Then, the processing circuit 41 proceeds to step S57.
[0087] In step S79, the processing circuit 41, by functioning as a setting unit 103, obtains the first specified acceleration GupA as the minimum value Gup. Then, the processing circuit 41 proceeds to step S57.
[0088] <Operation of this embodiment> The operation of this embodiment will be explained with reference to Figure 9. The example shown in Figure 9 illustrates an example where the vehicle 10 stops on a downhill slope.
[0089] Vehicle 10, which is being subjected to normal braking force, comes to a stop at timing t30. Prior to timing t30, the first specified acceleration GupA is set to the minimum value Gup of the maximum value Gpmax, and the second specified acceleration GlwA is set to the maximum value Glw of the minimum value Gpmin. The absolute value of the first specified acceleration GupA is equal to the absolute value of the second specified acceleration GlwA. Therefore, the absolute value of the first specified acceleration GupA is set to the reference acceleration Gs.
[0090] In the example shown in Figure 9, timing t32 is the point in time when the convergence determination time Tmth has elapsed from timing t30. Therefore, even after the vehicle 10 has stopped, before timing t32, the absolute value of the first specified acceleration GupA is set to the reference acceleration Gs.
[0091] In the electric parking device 30 of this embodiment, the process of acquiring the maximum value Gpmax and the minimum value Gpmin is executed even before the vehicle 10 comes to a stop. In the example shown in Figure 9, the oscillation amplitude of the longitudinal acceleration detection value Gx, i.e., the effective acceleration Ge, when the vehicle 10 is stopped is small. Therefore, it is difficult to acquire the maximum value Gpmax and the minimum value Gpmin after timing t31.
[0092] From timing t32 onward, the elapsed time Tm from timing t30, which is the point when the vehicle 10 stops, has exceeded the convergence determination time Tmth. Therefore, the reference acceleration Gs is set based on the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax. In other words, the larger of the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax is set as the reference acceleration Gs.
[0093] <Effects of this embodiment> In this embodiment, in addition to the effects equivalent to those in the above-described embodiments (1-1) and (1-2), the following further effects can be obtained.
[0094] (3-1) When the vehicle 10 stops with a small normal braking force applied to it, the amplitude of the oscillation of the effective acceleration Ge associated with the stopping of the vehicle 10 is relatively small. Therefore, after the elapsed time Tm from the time the vehicle 10 stops has exceeded the convergence determination time Tmth, the processing circuit 41 may not be able to obtain the maximum value Gpmax and minimum value Gpmin of the effective acceleration Ge.
[0095] Therefore, in the electric parking device 30 of this embodiment, the processing circuit 41 performs the acquisition of the minimum value Gpmin and the maximum value Gpmax from before the vehicle 10 comes to a complete stop. As a result, the occurrence of a situation where neither the minimum value Gpmin nor the maximum value Gpmax has been acquired when the elapsed time Tm has passed the convergence determination time Tmth is suppressed. Consequently, after the elapsed time Tm reaches the convergence determination time Tmth, the processing circuit 41 can set the reference acceleration Gs based on the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax.
[0096] (Example of change) The above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.
[0097] The processing circuit 41 (i.e., the setting unit 103) may set the reference acceleration Gs using a method different from the method described in the above embodiments, as long as it can set the reference acceleration Gs based on the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax. For example, the processing circuit 41 may set the reference acceleration Gs as the average value of the absolute value of the maximum value Glw and the absolute value of the minimum value Gup. Alternatively, the processing circuit 41 may set the reference acceleration Gs as the sum of the average value and a predetermined offset value.
[0098] In the first, second, and third embodiments described above, the processing circuit 41 (i.e., the setting unit 103) may set the sum of the effective acceleration Ge and a predetermined offset value as the reference acceleration Gs when it determines that the effective acceleration Ge has converged to the acceleration convergence value Gc. Alternatively, the processing circuit 41 may set the average value of the absolute value of the maximum value Glw and the absolute value of the minimum value Gup as the reference acceleration Gs when it determines that the effective acceleration Ge has converged to the acceleration convergence value Gc, or it may set the sum of the average value and a predetermined offset value as the reference acceleration Gs.
[0099] In the first, second, and third embodiments described above, the processing circuit 41 does not necessarily have to function as a convergence determination unit 102. In this case, even after the effective acceleration Ge has actually converged to the acceleration convergence value Gc, the processing circuit 41 may set the reference acceleration Gs based on the maximum value Glw of the minimum value Gpmin and the minimum value Gup of the maximum value Gpmax.
[0100] The processing circuit 41 of the parking control device 40 may include multiple processing circuits. For example, among the multiple processing circuits, the first processing circuit may have some of the multiple functional units 101 to 104, and the second processing circuit may have the remaining functional units.
[0101] The processing circuit 41 is not limited to one that includes a CPU and ROM and executes software processing. In other words, the processing circuit 41 may have any of the following configurations: (a), (b), and (c).
[0102] (a) The processing circuit 41 comprises one or more processors that perform various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.
[0103] (b) The processing circuit 41 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit". FPGA is an abbreviation for "Field Programmable Gate Array".
[0104] (c) The processing circuit 41 comprises one or more processors that execute a portion of the various processes according to a computer program, and one or more dedicated hardware circuits that execute the remaining processes of the various processes.
[0105] (Other technological ideas) This section describes the technical concepts that can be understood from the above-mentioned multiple embodiments and modifications. [Note 1] When it is determined that the effective acceleration has converged to the acceleration convergence value, the setting unit preferably sets the reference acceleration based on the acceleration convergence value.
[0106] [Note 2] In the parking process, it is preferable that the control unit drives the electric motor such that the amount of drive of the electric motor increases as the reference acceleration increases. [Explanation of symbols]
[0107] 10... Vehicles 21…Front and rear accelerometer 30…Electric parking system 31A, 31B… Parking Actuator 32… Electric motor 40... Parking control system 41…Processing circuit 101…Acquisition Department 102...Convergence determination unit 103...Settings section 104...Parking Control Unit
Claims
1. An electric parking system that drives an electric motor to generate parking braking force for a vehicle, An acquisition unit that, when it can receive the detected value from the front and rear acceleration sensors installed on the vehicle, acquires the detected value as the effective acceleration, A setting unit that acquires the minimum and maximum values of the effective acceleration and sets a reference acceleration based on the maximum value of the minimum and the minimum value of the maximum, The system includes a parking control unit that performs a parking process, which drives the electric motor to generate a parking braking force in the vehicle corresponding to the aforementioned reference acceleration. Electric parking system.
2. The setting unit sets the reference acceleration to the larger of the absolute value of the maximum value of the local minimum and the absolute value of the minimum value of the local maximum. The electric parking device according to claim 1.
3. The system includes a convergence determination unit that determines whether the effective acceleration has converged to an acceleration convergence value which is the longitudinal acceleration corresponding to the gradient of the road surface on which the vehicle is located. The setting unit determines that the effective acceleration has not converged to the acceleration convergence value, and sets the reference acceleration based on the maximum value of the local minimum and the minimum value of the local maximum. The electric parking device according to claim 1.
4. The setting unit is, In a situation where it is determined that the effective acceleration has not converged to the acceleration convergence value, If the elapsed time from the vehicle's stopping point has not reached a predetermined determination time, the maximum absolute value of the effective acceleration acquired after the stopping point is set as the reference acceleration. After the elapsed time reaches the determination time, the reference acceleration is set based on the maximum value of the minimum value and the minimum value of the maximum value. The electric parking device according to claim 3.
5. The setting unit is, In a situation where it is determined that the effective acceleration has not converged to the acceleration convergence value, If it is determined that the amplitude of the effective acceleration is large, the maximum absolute value of the effective acceleration obtained after the vehicle stops is set as the reference acceleration. If it is determined that the amplitude of the effective acceleration is not large, the reference acceleration is set based on the maximum value of the minimum value and the minimum value of the maximum value. The electric parking device according to claim 3.
6. The setting unit is, If the elapsed time from the vehicle's stopping point has not reached a predetermined convergence determination time, the maximum value of the longitudinal acceleration that can be set as the effective acceleration is set to the reference acceleration. After the elapsed time reaches the convergence determination time, the reference acceleration is set based on the maximum value of the local minimum and the minimum value of the local maximum. The electric parking device according to claim 1.