Travel control device, travel control method, and travel control program

Abstract

To accurately carry out autonomous traveling of a vehicle at a very low speed.SOLUTION: A travel control device (10) comprises: a motor rotation speed acquisition unit (30) for acquiring a motor rotation speed of a motor (89, 90) for driving a tire (111, 112, 121, 122) of a vehicle (100); a torque calculation unit (31) for calculating a motor torque generated in the motor; a wheel speed estimation unit (33) for estimating a wheel speed, which is the rotational speed of the tire, on the basis of the detected motor rotational speed and the calculated motor torque, and a torque control unit (34) for calculating a required torque for traveling the vehicle at a very low speed on the basis of the estimated wheel speed and controlling the motor so that the motor is driven by the calculated required torque.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a driving control device, a driving control method, and a driving control program. [Background technology]

[0002] Patent Document 1 discloses a vehicle driving assistance device that assists the vehicle's driving, and includes a step determination unit that performs a determination process to determine whether or not the step that the wheel has come into contact with is a step for stopping the vehicle, where the step is a step for stopping the vehicle, among steps that can be detected as having been contacted by the wheel, and a braking / driving force setting unit that performs stop request control to request that the vehicle be stopped by increasing the braking force of the vehicle when the determination process determines that the step is a step for stopping the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-093761 A Summary of the Invention [Problem to be solved by the invention]

[0004] There are cases where a vehicle driven by a motor needs to run autonomously at an extremely low speed of less than 1 km per hour. For example, this can occur when moving a vehicle in a narrow space, such as when automatically parking a vehicle in a parking space, or when a vehicle runs on its own at a production site for assembly. When running a vehicle autonomously, it is necessary to control the running of the vehicle based on the wheel speed.

[0005] However, when detecting the wheel speed using a pulse generation type wheel speed sensor, it is difficult to generate a vehicle speed pulse at extremely low speeds, making it difficult to detect the actual wheel speed. As a result, it may be difficult to perform accurate driving control at extremely low speeds.

[0006] The present disclosure aims to provide a driving control device, a driving control method, and a driving control program that enable a vehicle to drive autonomously at extremely low speeds with high accuracy. [Means for solving the problem]

[0007] A driving control device according to a first aspect of the present disclosure includes a motor rotational speed acquisition unit that acquires a motor rotational speed of a motor that drives tires of a vehicle, a torque calculation unit that calculates a motor torque generated in the motor, a wheel speed estimation unit that estimates a wheel speed, which is the rotational speed of the tires, based on the detected motor rotational speed and the calculated motor torque, and a torque control unit that calculates a required torque for driving the vehicle at an extremely low speed based on the estimated wheel speed, and controls the motor to be driven with the calculated required torque.

[0008] A driving control method according to a second aspect executes processing in which at least one processor acquires a motor rotational speed of a motor that drives tires of a vehicle, calculates a motor torque generated in the motor, estimates a wheel speed, which is the rotational speed of the tires, based on the detected motor rotational speed and the calculated motor torque, calculates a required torque for driving the vehicle at an extremely low speed based on the estimated wheel speed, and controls the motor to be driven with the calculated required torque.

[0009] A driving control program according to a third aspect causes at least one processor to execute processes including acquiring a motor rotational speed of a motor that drives tires of a vehicle, calculating a motor torque generated in the motor, estimating a wheel speed, which is the rotational speed of the tires, based on the detected motor rotational speed and the calculated motor torque, calculating a required torque for driving the vehicle at an extremely low speed based on the estimated wheel speed, and controlling the motor to be driven with the calculated required torque. Effect of the Invention

[0010] The present disclosure has the effect of enabling a vehicle to autonomously drive at extremely low speeds with high precision. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a vehicle configuration. [Diagram 2] FIG. 2 is a block diagram showing a hardware configuration of a driving control device. [Diagram 3] FIG. 2 is a diagram illustrating a functional configuration of a driving control device. [Figure 4] FIG. 4 is a block diagram showing a functional configuration of a wheel speed estimating unit. [Diagram 5] 4 is a flowchart of a driving control process. [Figure 6] 4 is a flowchart of an extremely low speed traveling control process. [Figure 7] 13 is a flowchart of a step estimation process. [Figure 8] FIG. 13 is a diagram showing a state in which a wheel comes into contact with a step. [Figure 9A] 1 is a graph showing a trajectory of a rotational axis of a wheel. [Figure 9B] 13 is a graph showing a trajectory angle. [Figure 10] 13 is a flowchart of a process for determining whether one or both wheels are climbing up. [Figure 11] 4 is a flowchart of a required torque calculation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0013] A schematic configuration of a vehicle 100 according to this embodiment is shown in the block diagram of Fig. 1. A vehicle cruise control device 10 according to this embodiment is mounted on the vehicle 100 and configured as a device for controlling the operation of the vehicle 100.

[0014] The vehicle 100 is equipped with a driving control device 10, four tires 111, 112, 121, 122, wheel speed sensors 81, 82, 83, 84, reduction gears 85, 86, drive shafts 87, 88, motors 89, 90 as drive sources, resolvers 91, 92, a brake oil pressure sensor 93, a longitudinal acceleration sensor 94, a lateral acceleration sensor 95, inverters 96, 97, current sensors 98, 99, a battery 110, and a brake ECU 120.

[0015] The vehicle 100 is structured to run by transmitting power from drive motors 89 and 90 to tires 111, 112, 121 and 122.

[0016] The motors 89 and 90 generate driving force with the rotation speed controlled by the inverters 96 and 97, respectively. The driving force generated by the motors 89 and 90 is then transmitted to four tires 111, 112, 121 and 122 via reduction gears 85 and 86 and drive shafts 87 and 88, respectively. The motors 89 and 90 also function as generators that regenerate braking energy generated when braking the vehicle 100 by regenerative braking, convert it into electrical energy, and charge the battery 110.

[0017] In this manner, the motors 89 and 90 are configured to function as electric motors as well as generators, and are called motor generators (MG).

[0018] In this embodiment, the vehicle 100 is described as a four-wheel drive vehicle that is provided with two motors 89, 90 and drives four wheels, namely, front wheels 111, 112 and rear wheels 121, 122. However, the present invention is not limited to such a case, and the technology disclosed herein can be similarly applied to a case where only the front wheels 111, 112 are driven, or a case where only the rear wheels 121, 122 are driven.

[0019] In addition, in this embodiment, the present invention is applied to an electric vehicle whose only driving sources are motors 89, 90, but the technology disclosed herein can also be applied to a hybrid vehicle equipped with a gasoline engine and a motor.

[0020] The wheel speed sensors 81, 82, 83, and 84 detect the wheel speeds, which are the rotational speeds of the tires 111, 112, 121, and 122, respectively, and output the detected wheel speeds to the cruise control device 10 as vehicle speed pulses.

[0021] The brake oil pressure sensor 93 detects the brake oil pressure generated when braking the vehicle 100, and outputs brake torque information to the driving control device 10. The brake ECU 120 performs brake control when braking the vehicle 100.

[0022] The longitudinal acceleration sensor 94 detects the longitudinal acceleration G of the vehicle 100. X The lateral acceleration sensor 95 is a G sensor that detects the lateral acceleration G of the vehicle 100 and outputs the detected acceleration G to the cruise control device 10. Y The G sensor detects the acceleration and output the detected acceleration to the cruise control device 10.

[0023] The resolvers 91 and 92 are provided to rotate together with the motors 89 and 90, and detect the motor rotation speed ω M It functions as a rotation speed detection unit that detects the rotation speed.

[0024] Further, current sensors 98, 99 are provided on the inverters 96, 97, respectively. The current sensors 98, 99 detect the motor currents flowing through the motors 89, 90, respectively, and output the detected motor currents to the driving control device 10 as information on the motor current values.

[0025] The driving control device 10 controls the driving of the vehicle 100 based on information input from various sensors and the like as described above, and calculates the MG required torque T MG The inverters 96 and 97 output the information of the MG required torque T MGBased on this, the drive control of the motors 89 and 90 is performed using power supplied from the battery 110.

[0026] Fig. 2 is a block diagram showing the hardware configuration of the driving control device 10. As shown in Fig. 2, the driving control device 10 includes a control unit 21. The control unit 21 is configured from a device including a general computer.

[0027] 2, the control unit 21 includes a central processing unit (CPU) 21A, a read only memory (ROM) 21B, a random access memory (RAM) 21C, and an input / output interface (I / O) 21D. The CPU 21A, the ROM 21B, the RAM 21C, and the I / O 21D are connected to each other via a bus 21E. The bus 21E includes a control bus, an address bus, and a data bus.

[0028] In addition, a communication unit 22 and a storage unit 23 are connected to the I / O 21D.

[0029] The communication unit 22 is an interface for communicating with the brake ECU 120 and the various sensors described above.

[0030] The storage unit 23 is configured with a non-volatile external storage device such as a hard disk, etc. As shown in Fig. 2, the storage unit 23 stores a driving control program 23A and the like.

[0031] The CPU 21A is an example of a computer. The term "computer" used here refers to a processor in a broad sense, and includes a general-purpose processor (e.g., a CPU) or a dedicated processor (e.g., a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a programmable logic device, etc.).

[0032] The driving control program 23A may be stored in a non-volatile non-transitory recording medium, or may be distributed via a network and appropriately installed in the driving control device 10, thereby being stored in the storage unit 23. The driving control program 23A may also be appropriately updated by so-called OTA (Over The Air).

[0033] Examples of non-volatile non-transient recording media include CD-ROMs (Compact Disc Read Only Memory), magneto-optical disks, HDDs (Hard Disk Drives), DVD-ROMs (Digital Versatile Disc Read Only Memory), flash memories, memory cards, and the like.

[0034] Fig. 3 is a block diagram showing a functional configuration of the CPU 21A of the driving control device 10. As shown in Fig. 3, the CPU 21A functionally includes a motor rotation speed acquisition unit 30, a torque calculation unit 31, a vehicle speed calculation unit 32, a wheel speed estimation unit 33, a torque control unit 34, and a step estimation unit 35.

[0035] The driving control device 10 has functions other than those shown in FIG. 3, but functions other than those related to this embodiment are omitted in FIG.

[0036] The motor rotation speed acquisition unit 30 acquires the motor rotation speeds of the motors 89, 90 that drive the tires of the vehicle 100. Specifically, the motor rotation speed acquisition unit 30 acquires the motor rotation speeds from resolvers 91, 92 provided in the motors 89, 90.

[0037] The torque calculation unit 31 calculates the motor torque generated in the motors 89, 90. Specifically, the torque calculation unit 31 detects the motor torque generated in the motors 89, 90 based on the motor current values ​​detected by the current sensors 98, 99.

[0038] The vehicle speed calculation unit 32 calculates the longitudinal acceleration GX The vehicle speed of the vehicle 100 is calculated by integrating

[0039] The wheel speed estimation unit 33 estimates the motor rotation speed ω detected by the resolvers 91 and 92 when the vehicle 100 is moving at an extremely low speed. M and the motor torque T calculated by the torque calculation unit 31. M Based on the above, the wheel speed ω tire Estimate.

[0040] More specifically, the wheel speed estimation unit 33 estimates the motor rotation speed ω M and motor torque T M In addition, the wheel speed ω is calculated by using the transmission characteristics when the driving force of the motors 89 and 90 is transmitted at the connection parts connecting the motors 89 and 90 and the tires 111, 112, 121, and 122. tire Estimate.

[0041] Note that the wheel speed estimation unit 33 actually calculates an average wheel speed of the front wheels and an average wheel speed of the rear wheels, rather than calculating the wheel speed of each of the tires 111, 112, 121, and 122. Specifically, the wheel speed estimation unit 33 calculates the average of the wheel speeds of the tires 111 and 112 as the average wheel speed of the front wheels, and calculates the average of the wheel speeds of the tires 121 and 122 as the average wheel speed of the rear wheels.

[0042] Here, the connecting portion is composed of reduction gears 85, 86 for reducing the number of rotations generated in the motors 89, 90, and drive shafts 87, 88 for transmitting the rotation of the reduction gears 85, 86 to the tires 111, 112, 121, 122.

[0043] The reduction gears 85, 86 also function as differential gears (differential devices) that absorb the difference in rotation speed between the left and right tires when the vehicle 100 goes around a curve or the like.

[0044] When the vehicle 100 is traveling at a normal speed, the cruise control device 10 is able to detect the wheel speed of each of the tires 111, 112, 121, and 122 from the vehicle speed pulses from the wheel speed sensors 81-84. However, when the vehicle is traveling at an extremely low speed, such as less than 1 km per hour (1 kph), it becomes difficult for the wheel speed sensors 81-84 to generate vehicle speed pulses. Therefore, when the cruise control device 10 of this embodiment is traveling at an extremely low speed at which the wheel speed sensors 81-84 do not generate vehicle speed pulses, the wheel speed ω estimated by the wheel speed estimation unit 33 is not generated. tire The driving control of the vehicle 100 is performed using the above.

[0045] Next, a detailed configuration of the wheel speed estimating unit 33 will be described with reference to the block diagram of FIG.

[0046] The wheel speed estimation unit 33 estimates the motor rotation speed ω M Using the above, the wheel speed ω tire Estimate.

[0047] Specifically, the wheel speed estimation unit 33 estimates the motor rotation speed ω M The rotation angle θ of the motor is calculated based on M A tire rotation angle correction value θ is calculated by adding up the angle component caused by the twisting of the drive shafts 87 and 88, the angle component caused by the inertia of the motor, and the angle component caused by the backlash in the reduction gears 85 and 86. revise The tire rotation angle θ tire The calculated tire rotation angle θ tire By differentiating the wheel speed ω tire Estimate.

[0048] In order to carry out the above-mentioned processing, the wheel speed estimation unit 33 is composed of a motor rotation angle calculation unit 40, a tire rotation angle correction value calculation unit 41, a subtractor 42, and a differential operation unit 43, as shown in Fig. 4. The calculation formula used by the wheel speed estimation unit 33 to calculate the wheel speed is shown below.

[0049] JPEG2025050113000002.jpg1489 JPEG2025050113000003.jpg1589 JPEG2025050113000004.jpg2189

[0050] 1, driving force is transmitted between motors 89, 90 and tires 111, 112, 121, 122 via connections such as reduction gears 85, 86 and drive shafts 87, 88. Therefore, in order to accurately predict the wheel speed, which is the rotational speed of tires 111, 112, 121, 122, from the rotational speed of motors 89, 90, it is necessary to correct the torsion components of drive shafts 87, 88, the inertia components of motors 89, 90, and the backlash components of reduction gears 85, 86.

[0051] The motor rotation angle calculation unit 40 calculates the motor rotation speed ω M The motor rotation angle θ M Calculate.

[0052] The tire rotation angle correction value calculation unit 22 calculates the motor rotation speed ω M and the motor torque T calculated by the torque calculation unit 31. M Using the above, the tire rotation angle correction value θ revise The tire rotation angle correction value θ revise The calculation method will be described in detail later.

[0053] As shown in the above formula (2), the subtractor 42 subtracts the motor rotation angle θ M From the above, the tire rotation angle correction value θ calculated by the tire rotation angle correction value calculation unit 41 is revise By subtracting the tire rotation angle θ tire Calculate.

[0054] As shown in the above formula (3), the differential calculation unit 43 calculates the tire rotation angle θ tire By differentiating the wheel speed ω tireCalculate.

[0055] In addition, the tire rotation angle correction value calculation unit 41 calculates the motor torque T M When the polarity of the reduction gears 85, 86 is reversed, a backlash passing flag F is generated, which indicates that the driving force from the motors 89, 90 is not being transmitted to the drive shafts 87, 88 due to backlash in the reduction gears 85, 86. BL Output.

[0056] Here, backlash means a gap between gears or a dead zone between forward and reverse rotation caused by play. Since the reduction gears 85 and 86 are composed of multiple gears, backlash exists in the reduction gears 85 and 86, and the motor torque T M Even if the polarity of the drive force is reversed, the drive force is not transmitted in the opposite direction until the backlash is passed.

[0057] Next, the tire rotation angle correction value θ revise The calculation method will now be described in detail.

[0058] As described above, the tire rotation angle correction value calculation unit 41 calculates the tire rotation angle correction value θ by adding up the drive shaft torsion angle, which is an angle component generated by the torsion of the drive shafts 87 and 88, the inertia equivalent angle, which is an angle component due to the inertia of the motor, and the backlash angle, which is an angle component based on the backlash in the reduction gears 85 and 86, as shown in the following formula (4). revise Calculate.

[0059] JPEG2025050113000005.jpg9116

[0060] Here, the drive shaft torsion angle is expressed by the motor torque T M The spring constant K indicates the stiffness of the drive shafts 87 and 88. ds It is calculated by dividing by

[0061] JPEG2025050113000006.jpg1895

[0062] The inertia equivalent angle is calculated based on the following formula (6): M is the inertia of the motors 89 and 90. In other words, the inertia equivalent angle is calculated from the rotation acceleration of the motors 89 and 90.

[0063] JPEG2025050113000007.jpg2191

[0064] And the backlash angle is θ backlash When expressed as above, the tire rotation angle correction value θ revise is expressed as the following equation (7).

[0065] JPEG2025050113000008.jpg18149

[0066] Then, the tire rotation angle correction value calculation unit 41 calculates a backlash angle θ backlash Calculate.

[0067] Specifically, the tire rotation angle correction value calculation unit 41 calculates the backlash angle θ by the following formula (8): backlash Calculate.

[0068] JPEG2025050113000009.jpg20103

[0069] Here, the LPF is a second-order delay transfer function that represents the resonance of the drive shafts 87 and 88, and is expressed by the following equation (9). In this equation, s is the Laplace operator, and ω ds is the resonant angular frequency of the drive shafts 87 and 88. ds is the inertia I of motors 89 and 90 M and the spring constant K of the drive shafts 87 and 88. dsIt is calculated from the following formula (10).

[0070] JPEG2025050113000010.jpg2275 JPEG2025050113000011.jpg2480

[0071] Moreover, θ in the above formula (8) is expressed by the following formula (11). Here, θ a is the maximum value of the backlash angle of the reduction gears 85 and 86, and is set based on an actual measurement value or a design value. In addition, the backlash angle θ backlash(old) is the backlash angle θ backlash is the previous value.

[0072] JPEG2025050113000012.jpg15118

[0073] Furthermore, the tire rotation angle correction value calculation unit 41 determines whether or not the backlash is passing through the backlash by using a determination formula such as the following formula (12). BL Here, the backlash passing flag F BL When the value is 1 (ON), it indicates that a backlash is passing through, and the backlash passing flag F BL When it is 0 (off), it indicates that the backlash has been passed.

[0074] JPEG2025050113000013.jpg40126

[0075] As described above, in the cruise control device 10 of this embodiment, the wheel speed estimator 33 calculates the wheel speed ω tire Therefore, the wheel speed ω at a very low speed where the wheel speed sensors 81 to 84 do not generate a vehicle speed pulse is tire In addition, it is possible to estimate the wheel speed ω from which the resonance components due to the torsional resonance of the drive shafts 87 and 88 have been removed. tire can be estimated.

[0076] When an instruction is given from a higher-level device to perform extremely low-speed running control for autonomously running the vehicle 100 at an extremely low constant speed, the torque control unit 34 calculates the wheel speed ω tire Based on this, the required torque T for running the vehicle 100 at a very low speed is calculated. MG Calculate the required torque T MG The motors 89 and 90 are controlled to be driven by the motors 89 and 90.

[0077] Specifically, the torque control unit 34 calculates the wheel speed ω estimated by the wheel speed estimation unit 33. tire By performing feedback control based on the above, the required torque T for running the vehicle 100 at an extremely low speed is obtained. MG The feedback control may be a so-called PI feedback control, a PD feedback control, or a PID feedback control.

[0078] By performing such extremely low-speed driving control, it is possible to cause the vehicle 100 to autonomously drive at an extremely low constant speed without requiring accelerator or brake operation, for example, when moving the vehicle in a narrow space, such as when automatically parking the vehicle in a parking space, or when driving the vehicle to assemble it at a production site.

[0079] On the other hand, when the upper device instructs normal driving control rather than very low speed driving control, the torque control unit 34 generates a driver requested torque to be output to the motors 89, 90 based on the accelerator opening degree of the accelerator operation by the driver, and calculates the generated driver requested torque as requested torque T MG and outputs the signal to inverters 96 and 97.

[0080] The torque control unit 34 controls the motor torque T M When the polarity of the rotational angle of the motors 89 and 90 is reversed, if the difference between the rotational angle of the tires 111, 112, 121, and 122 is less than the maximum value of the backlash angle of the reduction gears 85 and 86, the wheel speed ω tireIn this case, the torque control unit 34 may perform control to reduce the feedback gain in the feedback control for controlling the rotation of the motors 89, 90 by changing the required torque to be output to the motors 89, 90 based on the backlash passing flag F BL When the control is on, control may be performed to reduce feedback gains such as a P gain (proportional gain), an I gain (integral gain), and a D gain (differential gain) in the feedback control.

[0081] By performing the above control, the motor torque T M Even if the polarity of the feedback signal is reversed, the feedback gain is weakened while the backlash is passing, thereby making it possible to suppress the occurrence of hunting, which is a phenomenon in which the drive system vibrates.

[0082] The step estimating unit 35 estimates the height of the step with which the tires 111, 112, 121, and 122 are in contact.

[0083] In this case, the torque control unit 34 calculates the required torque T based on the first torque for driving the vehicle 100 at a very low speed and the second torque according to the step. MG The torque control unit 34 further uses a third torque according to the gradient of the road surface to calculate the required torque T MG That is, the torque control unit 34 may calculate the required torque T based on the first torque, the second torque, and the third torque. MG may be calculated.

[0084] The CPU 21A reads and executes a driving control program 23A stored in the storage unit 23, thereby functioning as each of the functional units shown in FIG.

[0085] Next, a driving control process executed by the CPU 21A of the control unit 21 will be described with reference to Fig. 5. The driving control process shown in Fig. 5 is executed when the system of the vehicle 100 is turned on, and is repeatedly executed until the system is turned off. In addition, the following describes a case where the tires 111, 112 are driven by the motor 89, that is, a case where the vehicle is front-wheel driven.

[0086] In step S100, the CPU 21A judges whether the very low speed travel control flag is ON. For example, when the vehicle 100 is to be autonomously traveled at a constant very low speed without requiring accelerator or brake operation, such as when the vehicle is to be moved in a narrow space, such as when the vehicle is to be automatically parked in a parking space, or when the vehicle is to be self-propelled and assembled at a production site, the very low speed travel control flag is set to ON by a higher-level device (not shown). On the other hand, when normal travel control is to be performed by the driver's accelerator and brake operations, rather than the very low speed travel control, the very low speed travel control flag is set to OFF by a higher-level device (not shown). Note that when the vehicle is self-propelled and assembled at a production site, the very low speed travel control flag is set to ON during production, and the very low speed travel control flag is set to OFF during shipping.

[0087] If the extremely low speed running control flag is ON, the process proceeds to step S101, and if the extremely low speed running control flag is OFF, the process proceeds to step S103.

[0088] In step S101, the CPU 21A stops the diagnostic fail-safe function. The diagnostic fail-safe function is a safety function that performs abnormality diagnosis and performs control such as stopping the vehicle 100 when some abnormality occurs. When performing the extremely low-speed traveling control, the diagnostic fail-safe function is stopped to prevent erroneous detection of an abnormality.

[0089] In step S102, the CPU 21A executes the extremely low speed traveling control shown in FIG.

[0090] On the other hand, in step S103, the CPU 21A starts a diagnostic fail-safe function. That is, when the normal driving control is executed, the diagnostic fail-safe function is started, and if any abnormality occurs during the normal driving control, a safety function such as stopping the vehicle 100 is activated.

[0091] In step S104, the CPU 21A executes normal driving control, that is, controls the vehicle 100 so that the vehicle 100 drives in response to the accelerator operation and the brake operation of the driver.

[0092] Next, the extremely low speed traveling control in step S102 will be described in detail with reference to FIG.

[0093] In step S200, the CPU 21A, functioning as the wheel speed estimation unit 33, calculates the wheel speed ω tire Estimate.

[0094] In step S201, the CPU 21A, as the step estimation unit 35, executes the step estimation process shown in Fig. 7. Note that, if it is known in advance that there is no step on the road surface on which the vehicle 100 is moved at an extremely low speed, the process of step S201 may be omitted.

[0095] In step S202, the CPU 21A, functioning as the torque control unit 34, executes a required torque calculation process shown in FIG.

[0096] In step S203, the CPU 21A determines whether the extremely low speed traveling control flag has been turned OFF. If the extremely low speed traveling control flag is ON, that is, if the extremely low speed traveling control is to be continued, the process returns to step S200 and the processes of steps S200 to S202 are repeated. On the other hand, if the extremely low speed traveling control flag has been turned OFF, this routine is ended.

[0097] Next, the step estimation process in step S201 will be described in detail with reference to FIG.

[0098] In step S300, the CPU 21A calculates the maximum value h max Specifically, first, the vertical load Fz is calculated. The vertical load Fz is a force applied downward to the tires 111, 112. The vertical load Fz is calculated as the total value of the forces applied to the tires 111, 112 by the following formula.

[0099] JPEG2025050113000014.jpg19128...(13)

[0100] In the first term on the right side of the above equation (13), "m" is the weight of the vehicle 100. "g" is the gravitational acceleration. "l" is the length of the wheelbase of the vehicle 100. "lr" is the length in the front-rear direction from the center of gravity of the vehicle 100 to the central axis of rotation of the rear wheels (tires 121, 122). "G X " is the acceleration in the direction of travel of the vehicle 100, i.e., the forward / rearward direction. cg " is the height from the road surface to the center of gravity of the vehicle 100. The first term on the right side of the above equation (13) represents the downward component of the force applied to each of the tires 111, 112 as a dynamic load when the vehicle 100 is traveling.

[0101] The second term on the right side of the above equation (13) is "d S " is the damping coefficient of the damper (not shown) of the vehicle 100. spd " is the traveling speed of the vehicle 100 along the longitudinal direction. spd is, for example, the wheel speed ω estimated by the wheel speed estimation unit 33. tire It can be calculated based on the following: old " is the value of the trajectory angle θ calculated in the previous control cycle. When the process of FIG. 7 is executed for the first time, θ old For example, 0 is used as the value of . The second term on the right side of the above equation (13) represents the force applied to each of the tires 111 and 112 in association with the expansion and contraction of the damper.

[0102] Next, the trajectory angle θ is calculated. Here, the trajectory angle θ is explained. The "trajectory angle" is the angle that the trajectory of the rotational center axis of the tire 111 etc. forms with the road surface.

[0103] 8 is a schematic diagram showing a state in which the tire 111 is on a road surface RD. A step ST that serves as a wheel stopper is provided on the road surface RD, and a part of the tire 111 is in contact with the step ST. If the vehicle 100 attempts to move further to the right (i.e., toward the step ST) from the state shown in FIG. 8, the tire 111 will run up onto the step ST.

[0104] The graph shown by the solid line in Fig. 9A represents the relationship between the travel distance (horizontal axis) of the vehicle 100 and the height (vertical axis) of the rotation center axis AX of the tire 111 when the vehicle 100 travels toward the right as described above. It can be said that this graph represents the trajectory of the rotation center axis AX while the vehicle 100 is traveling. θ shown in Fig. 9A is the angle that the trajectory of the rotation center axis AX of the tire 111 etc. makes with the road surface, and represents the trajectory angle when the vehicle 100 is at the position X1. Such a trajectory angle θ can be defined corresponding to each position of the vehicle 100.

[0105] As mentioned above, the "path angle" refers to the angle that the path of the rotation axis AX of the tire 111, etc., makes with respect to the road surface, but the "path of the rotation axis AX" here refers to the path of the rotation axis AX when the vehicle 100 is viewed in its left-right direction (vehicle width direction). The path of the rotation axis AX as shown in the graph of FIG. 9A reflects to some extent the shape of the step ST indicated by the dashed line in the figure. The reason why the two shapes are different from each other is that the tire 111 is not a rigid body and is deformed when it hits the step ST.

[0106] The trajectory angle θ can be calculated by the following formula.

[0107] JPEG2025050113000015.jpg29125...(14)

[0108] On the right side of the above equation (14), "T M " is the motor torque of the motor 89, and "R" is the dynamic radius of the tire 111. M / R" indicates the driving force applied to the road surface by the driving wheels of the vehicle 100. M is calculated by the torque calculation unit 31.

[0109] Next, a locus angle θ′ when the tire 111 is an ideal disk is calculated from the locus angle θ by the following formula.

[0110] JPEG2025050113000016.jpg26117...(15)

[0111] Here, L is the contact length of the tire 111. The contact length L is the climb-over distance (x2-x1) in Figures 9A and 9B. The graph in Figure 9B shows an example of the change in the trajectory angle θ when the vehicle 100 climbs over a step ST as in Figure 9A.

[0112] "X1" shown in Figures 9A and 9B is the position of the vehicle 100 when the tire 111 etc. contacts the step ST. Also, "X2" shown in Figures 9A and 9B is the position of the vehicle 100 when the tire 111 etc. leaves the road surface. This position corresponds to the inflection point in the graph of Figure 9A and the peak value in the graph of Figure 9B.

[0113] The "climbing distance" is the distance from X1 to X2, that is, the distance traveled by the vehicle 100 from when the tire 111 etc. contacts the step ST until the tire 111 etc. leaves the road surface. In other words, the "climbing distance" can be said to be the distance traveled by the vehicle 100 during the period from when the trajectory angle θ starts to increase until when it starts to decrease.

[0114] The climb-up distance defined in this manner correlates with the length (L1 in FIG. 8) of the portion of the tire 111, etc., that is in contact with the road surface RD in the front-rear direction when the vehicle 100 is parked on the flat road surface RD. Therefore, the lower the air pressure of the tire 111, etc., the longer L1 shown in FIG. 8 becomes, and the climb-up distance shown in FIGS. 9A and 9B also tends to become longer.

[0115] If the tire 111 is an ideal disk, the height h of the step ST can be calculated by the following formula.

[0116] JPEG2025050113000017.jpg35118...(16)

[0117] Here, θ in the above equation (16) is set to θ, which is the maximum value of the trajectory angle θ. max Then, the maximum height of the step ST is h max can be calculated.

[0118] Trajectory angle θ max can be calculated by the following formula:

[0119] θ max = κ × L (17)

[0120] Here, κ is the rate of change of the trajectory angle θ, and can be calculated by the following formula.

[0121] JPEG2025050113000018.jpg26131...(18)

[0122] Here, filter() is a function that performs a filter process to attenuate high-frequency components, and has a function of smoothing, i.e., easing, the amount of change in the trajectory angle θ. x is the vehicle speed.

[0123] From the above, the maximum height of the step ST is h max can be calculated by the following formula:

[0124] JPEG2025050113000019.jpg18134...(19)

[0125] In the following, the maximum height of the step ST is h max is simply referred to as the height h of the step ST.

[0126] In step S301, the CPU 21A executes a one-wheel or two-wheel climbing determination process shown in FIG.

[0127] As shown in Fig. 10, in step S400, the CPU 21A judges whether the step height h calculated in step S300 in Fig. 7 is equal to or less than a predetermined height. In this embodiment, the predetermined height is set to 2 cm as an example, but is not limited to this. If the step height h is equal to or less than the predetermined height, the process proceeds to step S401, and if the step height h is higher than the predetermined height, the process proceeds to step S402.

[0128] In step S401, a flag XKATARIN, which indicates whether one wheel or both wheels are attempting to go over a step ST, is set to 0. When the flag XKATARIN is 0, it indicates that both wheels are attempting to go over a step ST, and when the flag XKATARIN is 1, it indicates that one wheel is attempting to go over a step ST.

[0129] In step S402, the CPU 21A calculates a lateral G proportional value δ according to the following equation.

[0130] JPEG2025050113000020.jpg2779...(20)

[0131] Here, G y is the lateral G, that is, the acceleration in the left-right direction of the vehicle 100, and can be obtained from the lateral acceleration sensor 95. K is a predetermined coefficient. Also, V xis the vehicle speed, r is the yaw rate, which can be obtained from a yaw rate sensor (not shown), and const is a predetermined coefficient for preventing the denominator from becoming zero.

[0132] When one wheel climbs over the step ST, the vehicle 100 tilts more than when both wheels climb over it, and this is detected as lateral G. Also, in order to cancel the lateral G generated when the vehicle 100 turns, it is determined whether one wheel or both wheels are attempting to climb over the step ST based on a lateral G proportional value δ obtained by comparing the lateral G with the lateral G calculated from the yaw rate r.

[0133] In step S403, CPU 21A determines whether the absolute value of lateral G proportional value δ calculated in step S1002 is greater than a predetermined value, and proceeds to step S404 if the absolute value of lateral G proportional value δ is greater than the predetermined value, and proceeds to step S401 if the absolute value of lateral G proportional value δ is equal to or less than the predetermined value.

[0134] In step S404, the CPU 21A sets the flag XKATARIN to 1.

[0135] Returning to Fig. 7, in step S302, the CPU 21A determines whether or not the flag XKATARIN is 0. That is, it determines whether or not both wheels are about to climb over a step ST. If the flag XKATARIN is 0, this routine is terminated, and if the flag XKATARIN is 1, the process proceeds to step S904.

[0136] In step S303, the CPU 21A doubles the height h of the step ST according to the following formula: That is, when one wheel is going over the step ST, the height h of the step ST is set to double.

[0137] h = h × 2 (21)

[0138] Next, details of the required torque calculation process in step S202 in FIG. 6 will be described with reference to FIG.

[0139] 11, in step S500, the CPU 21A sets a target vehicle speed. In this embodiment, the target vehicle speed is set to be faster than 0 kph and less than 1 kph as an example of an extremely low speed.

[0140] In step S501, the CPU 21A calculates a feedback driving torque Tfb (first torque) for performing PI feedback control so that the vehicle speed becomes the target vehicle speed set in step S1200, by the following equation.

[0141] JPEG2025050113000021.jpg1357...(22)

[0142] Here, e is the difference between the target vehicle speed and the actual vehicle speed. The actual vehicle speed is calculated from the wheel speed estimated by the wheel speed estimation unit 33. Kp is a proportional gain. Ki is an integral gain. Furthermore, Tfb is limited between a predetermined upper limit value and a predetermined lower limit value. Note that, instead of the above equation (22), an equation for PD feedback control or an equation for PID feedback control may be used. Furthermore, when performing feedback control, control may be performed to reduce the above-mentioned feedback gain.

[0143] In step S502, the CPU 21A calculates a step correction torque TL (second torque) that cancels out the load torque according to the height h of the step ST, using the following equation.

[0144] TL = R × Fz × tan(θ) (23)

[0145] In step S503, the CPU 21A calculates the required torque T MG is calculated by the following formula and output to the inverter 96.

[0146] T MG =Tfb+TL+T slope ···(twenty four)

[0147] Here, T slopeis a gradient torque (third torque) that is set according to the gradient of the road surface, and is calculated by the following equation (25).

[0148] T slope = m × g × LPF(G x -G vspd ,0.5Hz)×R ···(25)

[0149] Here, m is the weight of the vehicle 100. g is the gravitational acceleration. G x is the acceleration of the vehicle 100 in the longitudinal direction. vspd is the wheel acceleration calculated from the wheel speed estimated by the wheel speed estimation unit 33. R is the dynamic radius of the tire. LPF() is a low pass filter, and 0.5 Hz is the cutoff frequency.

[0150] In addition, when it is known in advance that the road surface on which the vehicle 100 is traveling has no gradient, the gradient torque T slope The calculation of may be omitted.

[0151] As described above, in this embodiment, the motor rotation speed of the motor that drives the tires of the vehicle 100 and the motor torque T M Based on this, the wheel speed ω tire and estimate the estimated wheel speed ω tire Based on this, the required torque T for running the vehicle 100 at a very low speed is calculated. MG Calculate the required torque T MG This enables the vehicle 100 to autonomously travel at extremely low speeds with high precision.

[0152] The present disclosure is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the gist of the present disclosure.

[0153] The configuration of the driving control device 10 described in the above embodiment (see Figures 2 to 4) is just one example, and it goes without saying that unnecessary parts may be deleted and new parts may be added without departing from the spirit of the present disclosure.

[0154] Furthermore, the processing flow of the driving control program 23A described in the above embodiment (see Figures 5 to 7, 10, and 11) is also one example, and it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be rearranged within the scope of the present disclosure.

[0155] The control unit and the method described herein may be implemented by a special-purpose computer having a processor programmed to execute one or more functions embodied in a computer program. Alternatively, the device and the method described herein may be implemented by a special-purpose computer having a processor configured by dedicated hardware logic circuits. Alternatively, the device and the method described herein may be implemented by one or more special-purpose computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by the computer.

[0156] The following notes are disclosed regarding the technology of the present disclosure.

[0157] <Additional Notes> (Appendix 1) a motor rotation speed acquisition unit (30) that acquires a motor rotation speed of a motor (89, 90) that drives tires (111, 112, 121, 122) of a vehicle (100); a torque calculation unit (31) for calculating a motor torque generated in the motor; a wheel speed estimation unit (33) that estimates a wheel speed, which is the rotational speed of the tire, based on the detected motor rotational speed and the calculated motor torque; a torque control unit (34) that calculates a required torque for running the vehicle at a very low speed based on the estimated wheel speed, and controls the motor to be driven with the calculated required torque; A driving control device (10) equipped with the same. (Appendix 2) a step estimation unit (35) that estimates the height of a step with which the tire is in contact, The torque control unit calculates the required torque based on a first torque for causing the vehicle to travel at the extremely low speed and a second torque corresponding to the step. 2. The driving control device according to claim 1. (Appendix 3) The torque control unit calculates the required torque by further using a third torque according to a gradient of a road surface. 3. A driving control device as described in appended claim 2. (Appendix 4) The very low speed is a speed of less than 1 kph. 4. The driving control device according to claim 1 , (Appendix 5) The motor rotation speed acquisition unit acquires the motor rotation speed from a resolver (91, 92) provided in the motor. 5. The driving control device according to claim 1 . (Appendix 6) The driving control device according to any one of claims 1 to 5, wherein the wheel speed estimation unit estimates the wheel speed by using a transmission characteristic when the driving force of the motor is transmitted at a connection portion that connects the motor and the tire. (Appendix 7) 7. The driving control device according to claim 6, wherein the connecting portion is composed of reduction gears (85, 86) for reducing the number of rotations generated by the motor, and drive shafts (87, 88) for transmitting the rotation of the reduction gears to the tires. (Appendix 8) 8. The driving control device according to claim 7, wherein the wheel speed estimating unit calculates a rotational angle of the tire by subtracting, as correction values, an angle component generated by torsion of the drive shaft, an angle component due to an inertial body of the motor, and an angle component due to backlash in the reduction gear from the rotational angle of the motor calculated based on the motor rotation speed, and estimates the wheel speed by differentiating the calculated rotational angle of the tire. (Appendix 9) 9. The vehicle driving control device according to claim 8, wherein the wheel speed estimator calculates an angle component based on backlash in the reduction gear using a quadratic transfer function that represents torsional resonance of the drive shaft. (Appendix 10) When the polarity of the motor torque is reversed, if a difference between a rotation angle of the motor and a rotation angle of the tire is less than a maximum value of a backlash angle of the reduction gear, the torque control unit performs control to reduce a feedback gain in feedback control that controls the rotation of the motor by changing a required torque to be output to the motor based on the wheel speed. 10. The driving control device according to any one of claims 7 to 9. (Appendix 11) At least one processor (21A) Acquire a motor rotation speed of a motor that drives tires of a vehicle; Calculating a motor torque generated in the motor; A wheel speed, which is a rotational speed of the tire, is estimated based on the detected motor rotational speed and the calculated motor torque; calculating a required torque for driving the vehicle at a very low speed based on the estimated wheel speed, and controlling the motor so as to be driven with the calculated required torque; A driving control program (23A) for executing a process including the above. (Appendix 12) At least one processor has Acquire a motor rotation speed of a motor that drives tires of a vehicle; Calculating a motor torque generated in the motor; A wheel speed, which is a rotational speed of the tire, is estimated based on the detected motor rotational speed and the calculated motor torque; calculating a required torque for driving the vehicle at a very low speed based on the estimated wheel speed, and controlling the motor so as to be driven with the calculated required torque; A driving control program that causes a process including the above to be executed. [Explanation of symbols]

[0158] 10 Driving control device, 21 Control unit, 22 Tire rotation angle correction value calculation unit, 23 Memory unit, 23A Driving control program, 30 Motor rotation speed acquisition unit, 31 Torque calculation unit, 32 Vehicle speed calculation unit, 33 Wheel speed estimation unit, 34 Torque control unit, 35 Step estimation unit, 40 Motor rotation angle calculation unit, 41 Tire rotation angle correction value calculation unit, 42 Subtractor, 43 Differential calculation unit, 85 Reduction gear, 87 Drive shaft, 89, 90 Motor, 91, 92 Resolver, 96, 97 Inverter, 100 Vehicle, 110 Battery, 111, 112, 121, 122 Tire

Claims

1. a motor rotation speed acquisition unit (30) for acquiring a motor rotation speed of a motor (89, 90) that drives tires (111, 112, 121, 122) of a vehicle (100); A torque calculation unit (31) for calculating a motor torque generated in the motor; a wheel speed estimation unit (33) for estimating a wheel speed, which is the rotational speed of the tire, based on the detected motor rotational speed and the calculated motor torque; a torque control unit (34) that calculates a required torque for running the vehicle at a very low speed based on the estimated wheel speed, and controls the motor to be driven with the calculated required torque; A driving control device (10) equipped with the device.

2. A step estimation unit (35) is provided for estimating the height of a step with which the tire is in contact, The torque control unit calculates the required torque based on a first torque for causing the vehicle to travel at the extremely low speed and a second torque corresponding to the step. The cruise control device according to claim 1.

3. The torque control unit calculates the required torque by further using a third torque according to a gradient of a road surface. The cruise control device according to claim 2.

4. The very low speed is a speed below 1 kph. The cruise control device according to claim 1.

5. The motor rotation speed acquisition unit acquires the motor rotation speed from a resolver (91, 92) provided in the motor. The cruise control device according to claim 1.

6. 2 . The cruise control device according to claim 1 , wherein the wheel speed estimator estimates the wheel speed by using a transmission characteristic when the driving force of the motor is transmitted through a connecting portion that connects the motor and the tire.

7. 7. A travel control device according to claim 6, wherein the connecting portion is composed of a reduction gear (85, 86) for reducing the number of rotations generated by the motor, and a drive shaft (87, 88) for transmitting the rotation of the reduction gear to the tire.

8. 8. The driving control device according to claim 7, wherein the wheel speed estimating unit calculates the rotational angle of the tire by subtracting, as correction values, an angle component generated by torsion of the drive shaft, an angle component due to the inertia body of the motor, and an angle component due to backlash in the reduction gear from the rotational angle of the motor calculated based on the motor rotation speed, and estimates the wheel speed by differentiating the calculated rotational angle of the tire.

9. The vehicle driving control device according to claim 8 , wherein the wheel speed estimator calculates an angle component based on backlash in the reduction gear by using a quadratic transfer function that represents torsional resonance of the drive shaft.

10. When the polarity of the motor torque is reversed, if a difference between a rotation angle of the motor and a rotation angle of the tire is less than a maximum value of a backlash angle of the reduction gear, the torque control unit performs control to reduce a feedback gain in feedback control that controls the rotation of the motor by changing a required torque to be output to the motor based on the wheel speed. The driving control device according to any one of claims 7 to 9.

11. At least one processor (21A) Acquire a motor rotation speed of a motor that drives tires of a vehicle; Calculating a motor torque generated in the motor; A wheel speed, which is a rotational speed of the tire, is estimated based on the detected motor rotational speed and the calculated motor torque; calculating a required torque for driving the vehicle at a very low speed based on the estimated wheel speed, and controlling the motor so as to be driven with the calculated required torque; A driving control program (23A) that executes a process including the above.

12. At least one processor, Acquire a motor rotation speed of a motor that drives tires of a vehicle; Calculating a motor torque generated in the motor; A wheel speed, which is a rotational speed of the tire, is estimated based on the detected motor rotational speed and the calculated motor torque; calculating a required torque for driving the vehicle at a very low speed based on the estimated wheel speed, and controlling the motor so as to be driven with the calculated required torque; A driving control program that causes a process including the above to be executed.

Images