Steering control device and steering control method

Abstract

According to the present invention, a steering mechanism is configured to convert the rotational power of a motor into power for turning turning wheels. This steering control device is configured to execute oscillation processing and modification processing. The oscillation processing is processing for causing the torque of the motor to oscillate in the event of an abnormality that increases the force required for steering. The modification processing is processing for modifying an oscillation component resulting from the oscillation processing in accordance with the situation in which the steering mechanism is placed.

Description

Steering control device and steering control method 【0001】 The present disclosure relates to a steering control device and a steering control method. 【0002】 For example, Patent Document 1 below describes a device that applies vibration to an electric power steering system by vibrating the torque of a motor when freezing of the electric power steering system is detected. 【0003】 Japanese Patent Translation Publication No. 2018-520052 【0004】 Patent Document 1 does not describe what kind of vibration should be applied during freezing. 【0005】 In one aspect of the present disclosure, a steering control device is provided. The steering mechanism is configured to convert the rotational power of a motor into power for steering a steering wheel. The steering control device is configured to execute a vibration process and a change process. The vibration process is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering increases. The change process is a process of changing the vibration component by the vibration process according to the situation where the steering mechanism is placed. 【0006】 In another aspect of the present disclosure, a steering control method is provided. The steering mechanism is configured to convert the rotational power of a motor into power for steering a steering wheel. The steering control method includes execution of a vibration process and execution of a change process. The vibration process is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering increases. The change process is a process of changing the vibration component by the vibration process according to the situation where the steering mechanism is placed. 【0007】 It is a block diagram showing the configuration of a steering control device and a steering device according to an embodiment. It is a block diagram showing a part of the process executed by the steering control device of FIG. 1. It is a flowchart showing the procedure of the process related to the freezing prediction determination executed by the steering control device of FIG. 1. It is a flowchart showing the procedure of the process related to the lock determination executed by the steering control device of FIG. 1. It is a flowchart showing the procedure of the torque amplitude setting process executed by the steering control device of FIG. 1. 【0008】 The following describes one embodiment with reference to the drawings. "Steering System" Figure 1 shows the configuration of the steering system according to this embodiment. As shown in Figure 1, the electric power steering device 10 includes a steering shaft 14 that rotates integrally with the steering wheel 12. The rotational power of the steering shaft 14 is converted into axial displacement power of the rack shaft 16. The axial displacement power of the rack shaft 16 is converted into power to steer the steering wheels 20 via the tie rods 18. 【0009】 The motor unit 30 houses the motor 32 and the control board 34 within its casing. The drive pulley 40 is connected to the rotating shaft 32a of the motor 32 so as to be able to rotate integrally with the rotating shaft 32a. The rotational power of the drive pulley 40 is transmitted to the driven pulley 44 via the belt 42. The rotational power of the driven pulley 44 is converted into axial displacement power of the rack shaft 16 via the ball screw mechanism 46. The drive pulley 40 and the motor 32 are located vertically below the rack shaft 16. 【0010】 The rack shaft 16, drive pulley 40, belt 42, driven pulley 44, and ball screw mechanism 46 are housed in the rack housing 50. The connection between the rack shaft 16 and the tie rod 18 is surrounded by a bellows-shaped boot 52 that spans both the rack housing 50 and the tie rod 18. The purpose of the boot 52 is to prevent liquids such as rainwater from entering the rack housing 50. 【0011】 A control device 60 is mounted on the control board 34. The control device 60 includes a PU 62 and a storage device 64. The PU 62 is a software processing unit such as a CPU. The storage device 64 stores a program that commands the processing to be performed by the PU 62. 【0012】 The control device 60 controls the motor 32. The control device 60 operates the inverter 36 mounted on the control board 34 in order to control the amount controlled by the control device by having the PU 62 execute the above program. 【0013】The control device 60 refers to the following detected values ​​for controlling the controlled quantity. Specifically, the control device 60 refers to the substrate temperature Tb, which is the temperature of the control board 34 detected by the temperature sensor 70. The control device 60 refers to the output line currents iu, iv, and iw of the inverter 36. The control device 60 refers to the rotation angle θm of the rotation shaft 32a of the motor 32 detected by the rotation angle sensor 72. The control device 60 refers to the steering torque Th detected by the torque sensor 74. The steering torque Th is the torque input by the driver via the steering wheel 12. In this embodiment, the sign of the steering torque Th and the sign of the rotation angle θm are aligned. That is, the sign of the change in the rotation angle θm when the rotation angle θm rotates the steering shaft 14 to the right is the same as the sign of the steering torque Th when the steering shaft 14 rotates to the right due to the steering torque Th. The control device 60 refers to the vehicle speed V detected by the vehicle speed sensor 76. The control device 60 refers to the ambient temperature To detected by the ambient temperature sensor 78. It is desirable that the ambient temperature sensor 78 be placed in a location in the vehicle that is less affected by heat-generating elements. It is also desirable that the ambient temperature sensor 78 be placed in a well-ventilated area. 【0014】 "Basic Processing for Freezing Prevention" Figure 2 shows some of the processing performed by the control device 60. The processing shown in Figure 2 is achieved by the PU 62 repeatedly executing a program stored in the storage device 64, for example, at a predetermined period. 【0015】 The basic assist amount calculation process M10 calculates the basic assist amount Ta0 based on the steering torque Th and vehicle speed V as input variables. The superposition process M12 is a process that superimposes the vibration torque Tf onto the basic assist amount Ta0 and substitutes that value into the assist amount Ta. Note that the vibration torque Tf may be zero in a steady state. 【0016】The operation signal generation process M14 generates and outputs an operation signal MS for operating the inverter 36 in order to bring the torque of the motor 32 closer to the assist amount Ta. The pre-fault determination process M20 determines whether or not there are signs of a seizure abnormality caused by freezing of the steering mechanism. Here, the steering mechanism includes a steering shaft 14, a rack shaft 16, a tie rod 18, a drive pulley 40, a belt 42, a driven pulley 44, and a ball screw mechanism 46, etc. Freezing of the steering mechanism causes an abnormality in which the force required for steering increases. In other words, freezing of the steering mechanism interferes with the rotational drive of the movable parts of the steering mechanism by the motor 32. In this embodiment, the drive pulley 40 is provided in the vertically downward direction of the rack shaft 16. Therefore, if moisture enters the rack housing 50 through a scratch in the boot 52, water is likely to accumulate near the drive pulley 40. Furthermore, if the water freezes, it becomes difficult for the motor 32 to assist steering by rotating the drive pulley 40. Also, if the water freezes, it becomes difficult to steer the steering wheels 20 by rotating the steering wheel 12. 【0017】 The lock detection process M22 determines whether or not there is a seizure abnormality due to freezing of the steering mechanism. Hereafter, the determination that there is a seizure abnormality will be referred to as a lock detection. The vibration process M16 outputs a vibration torque Tf if it is determined that there is a sign of a seizure abnormality or if a lock detection is made. The vibration torque Tf is, as an example, a sinusoidal torque with amplitude Am. 【0018】 "Predictive Determination Process M20" Figure 3 shows the detailed procedure of predictive determination process M20. The process shown in Figure 3 is realized by the PU 62 repeatedly executing a program stored in the memory device 64, for example, at a predetermined period. In the following, the step number of each process is represented by a number preceded by "S". 【0019】In the series of processes shown in Figure 3, the PU 62 first obtains the steering torque Th and the assist amount Ta (S10). Next, the PU 62 substitutes the sum of the steering torque Th and the assist amount Ta into the combined torque Tt (S12). The combined torque Tt is the torque applied to steer the steering wheel 20. The PU 62 also obtains the rotation angle θm (S14). 【0020】 PU62 determines whether the stick detection history flag F1 is "1" (S16). The stick detection history flag F1 is set to "1" when it is determined that the system is in a stick state. The stick state is a state in which the steering angle θh hardly changes even when the absolute value of the steering torque Th increases. The steering angle θh is, for example, the rotation angle of the steering wheel 12 as an angular variable that correlates with the steering angle of the steering wheel 20. The stick detection history flag F1 is set to "0" when it is not determined that the system is in a stick state. 【0021】 If PU62 determines that the stick judgment history flag F1 is "0" (S16: NO), it determines whether the following condition A is met (S18). Condition A is that the absolute value of the combined torque Tt is greater than or equal to the threshold Tth. The threshold Tth is set to an amount that would normally cause the steering angle θh to change. If PU62 determines that condition A is met (S18: YES), it determines whether the following condition B is met (S20). 【0022】 Condition B is the condition that the change in the rotation angle θm is less than or equal to a predetermined amount Δθth. Specifically, PU62 quantifies the change in the rotation angle θm by the absolute value of the value obtained by subtracting the rotation angle θm(n-k) at the previous execution timing from the rotation angle θm(n) at the current execution timing of the series of processes shown in Figure 3. Here, k is an integer of 1 or more. In order to make the change in the rotation angle θm apparent, k may be set to around 5 to 15. 【0023】If PU62 determines that the logical AND of condition A and condition B is true (S20: YES), it increments counter C1 (S22). Counter C1 is used to measure the duration of the state in which the logical AND of condition A and condition B is true. 【0024】 PU62 determines whether counter C1 is greater than or equal to threshold C1th (S24). This process determines whether the state in which the logical AND of condition A and condition B is true has continued for a predetermined period of time. If PU62 determines that counter C1 is greater than or equal to threshold C1th (S24: YES), it assigns "1" to the stick determination history flag F1 (S26). In other words, PU62 determines that a stick phenomenon has occurred if it determines that the state in which the logical AND of condition A and condition B is true has continued for a predetermined period of time. PU62 also initializes counter C1. Furthermore, PU62 assigns the current total torque Tt(n) to the total torque Tt0 at the time of stick determination. 【0025】 On the other hand, if PU62 determines that the stick determination history flag F1 is "1" (S16: YES), it determines whether the determination condition for being in a stick state is no longer met (S27). This process determines whether the logical AND of the above conditions A and B is false. If PU72 determines that the determination condition for being in a stick state is not met (S27: YES), it increments counter C2 (S28). Counter C2 is used to measure the elapsed time after the stick determination is not met. PU62 determines whether counter C2 is less than the threshold C2th (S30). If PU62 determines that counter C2 is less than the threshold C2th (S30: YES), it determines whether the following conditions C, D and E are met (S32, S34, S36). 【0026】 Condition C is a condition that the absolute value of the combined torque Tt is decreasing. Specifically, PU62 may determine that condition C is true, for example, if the current absolute value of the combined torque Tt is smaller than the absolute value of the combined torque Tt at the point when the logical AND of conditions A and B becomes false. 【0027】 Condition D is that the sign of the total torque Tt0 at the time of stick detection and the sign of the angular acceleration αm of the motor 32 are the same. Condition E is that the absolute value of the angular acceleration αm is greater than or equal to the threshold αmth. 【0028】 PU62 determines that there is a sign of the steering mechanism freezing if it determines that the logical AND of conditions C to E is true (S32-S36: YES). In other words, PU62 determines that there is a sign of the steering mechanism freezing if the logical AND of conditions C to E becomes true within a predetermined time defined by the threshold C2th after the stick condition occurs. Then PU62 initializes the stick determination history flag F1 (S40). Also, PU62 initializes the counter C2 (S42). 【0029】 On the other hand, if PU62 determines that counter C2 is greater than or equal to the threshold C2th (S30: NO), it proceeds to the process in S40. Also, if PU62 determines that the result is negative in the process in S18 or S20, it initializes counter C1 (S44). 【0030】 Furthermore, when PU62 determines that a negative result is obtained in processes S24, S27, S32, S34, and S36, or when it completes processes S26, S42, and S44, it temporarily terminates the series of processes shown in Figure 3. 【0031】 "Lock determination process M22" Figure 4 shows the procedure for the lock determination process M22. The process shown in Figure 4 is realized by the PU 62 repeatedly executing a program stored in the storage device 64, for example, at a predetermined period. 【0032】In the series of processes shown in Figure 4, the PU 62 first obtains the steering torque Th and the assist amount Ta (S50). Then, the PU 62 substitutes the sum of the steering torque Th and the assist amount Ta into the combined torque Tt (S52). The PU 62 also obtains the steering angle θh (S54). The steering angle θh is calculated by the PU 62 using the integration process of the rotation angle θm. The sign of the steering angle θh is consistent with the sign of the steering torque Th. That is, the sign of the change in the steering angle θh when the steering shaft 14 rotates to the right coincides with the sign of the steering torque Th when the steering shaft 14 is steered to the right. 【0033】 PU62 determines whether or not there is a request to update the reference point (S56). PU62 determines that there is a request to update the reference point even if the reference point has not yet been set. If PU62 determines that there is a request to update the reference point (S56: NO), it determines whether or not the absolute value of the combined torque Tt is greater than or equal to a predetermined value Ttth (S58). The predetermined value Ttth is set to a value that is assumed to allow the steering angle θh to be changed under normal circumstances. If PU62 determines that it is greater than or equal to the predetermined value Ttth (S58: YES), it sets the reference point using the combined torque Tt and steering angle θh obtained in the processes of S52 and S54 (S60). Specifically, PU62 substitutes the combined torque Tt and steering angle θh obtained in the processes of S52 and S54 into the combined torque Ttr and steering angle θhr, respectively. Then PU62 sets that there is no request to update the reference point (S61). 【0034】 On the other hand, if PU62 determines that there is no request to set a reference point (S56: YES), it determines whether the following condition F is met (S62). Condition F is that the absolute value of the difference between the steering angle θh and the steering angle θhr used to determine the reference point is less than or equal to a predetermined amount Δθh. 【0035】The process in S62 is to determine whether or not the steering angle θh has changed due to the combined torque Tt. If PU62 determines that the above condition F is not met (S62: NO), it sets a request to update the reference angle (S65). In other words, PU62 generates a request to update the reference point based on the determination that the steering angle θh has changed due to the combined torque Tt. 【0036】 On the other hand, if PU62 determines that the above condition F is true (S62: YES), it determines whether the logical OR of the following conditions G and H is true (S63). Condition G is the condition that the summation torque Tt that defines the reference point is positive AND the summation torque Tt is positive. 【0037】 Condition H is a condition that the summation torque Tt used to define the reference point is negative and the summation torque Tt is also negative. Conditions G and H are processes to determine whether the summation torque Tt and the summation torque Tt at the reference point have the same sign. 【0038】 If PU62 determines that the above logical OR is false (S63: NO), it proceeds to the process in S65. On the other hand, if PU62 determines that the above logical OR is true (S63: YES), it determines whether the following condition I is satisfied (S64). 【0039】 Condition I is the condition that the absolute value of the difference between the total torque Tt and the total torque Tt that defines the reference point is greater than a predetermined amount ΔTt. The process in S64 is to determine whether or not the steering angle θh does not change despite the application of a total torque Tt with a large absolute value. In other words, the process in S64 is to determine whether or not a sticking abnormality has occurred. 【0040】 If PU62 determines that the above condition I is met (S64: YES), it determines that a sticking abnormality has occurred (S66). Then, PU62 notifies the driver that the vehicle cannot be driven due to a sticking abnormality by operating the user interface 80 shown in Figure 1 (S68). Specifically, if the user interface 80 is equipped with a display device, PU62 may, as an example, display visual information on the display device. 【0041】 Furthermore, when the processes in S61, S65, and S68 are completed, or when a negative determination is made in the process of S58, the PU 62 temporarily terminates the series of processes shown in Figure 4. "Details of Vibration Processing M16" Figure 5 shows the procedure for setting the amplitude of vibrations generated by vibration processing M16. The process shown in Figure 5 is realized by the PU 62 repeatedly executing a program stored in the storage device 64, for example, at a predetermined period. 【0042】 In the series of processes shown in Figure 5, PU62 first determines whether the logical OR of the following conditions J and K is true (S70). Condition J is a condition indicating that a warning has been detected. 【0043】 Condition K is a condition indicating that a lock has been determined. If PU62 determines that the above logical OR is true (S70: YES), it obtains the outside temperature To (S72). Next, PU62 determines whether or not a warning check has been performed (S74). If PU62 determines that a warning check has been performed (S74: YES), it performs a map calculation on the amplitude Am of the vibration component of the torque of the motor 32 using map data specifically for cases where there is a warning (S76). The map data is data in which the outside temperature To is the input variable and the amplitude Am is the output variable. In the process of S76, PU62 changes the amplitude Am according to the outside temperature To, provided that the amplitude Am when the outside temperature To is low is greater than or equal to the amplitude Am when the outside temperature To is high. 【0044】 Furthermore, in statements such as "change B according to A while satisfying the condition that B when A is large is greater than or equal to B when A is small," "when A is large" and "when A is small" refer to the relative magnitude relationship when comparing the two. For example, "when A is large" corresponds to "when A is the first value," and "when A is small" corresponds to "when A is the second value which is smaller than the first value." Also, the above statement means that, depending on the settings of the first and second values, B when A is the first value may be larger than B when A is the second value. Also, the above statement means that change B according to A so that A when B is large is larger than A when B is small. 【0045】 Further, the map data is paired data of discrete values of input variables and values of output variables corresponding to the respective values of the input variables. Also, the map operation may be any process as long as when the value of the input variable matches any of the values of the input variables of the map data, the value of the output variable of the corresponding map data is the operation result. Also, the map operation may be any process as long as when the value of the input variable does not match any of the values of the input variables of the map data, the value obtained by interpolating the values of a plurality of output variables included in the map data is the operation result. Alternatively, the map operation may be any process as long as when the value of the input variable does not match any of the values of the input variables of the map data, the value of the output variable of the map data corresponding to the closest value among the values of a plurality of input variables included in the map data is the operation result. 【0046】 On the other hand, when the PU 62 determines that a lock determination has been made (S74: NO), if there is a sticking abnormality, it performs a map operation on the amplitude Am of the torque vibration of the motor 32 using dedicated map data (S78). The map data is data in which the outside air temperature To is an input variable and the amplitude Am is an output variable. In the process of S78, the PU 62 changes the amplitude Am according to the outside air temperature To on the condition that the amplitude Am when the outside air temperature To is low is greater than or equal to the amplitude Am when the outside air temperature To is high. In particular, when the outside air temperature To is the same, the PU 62 sets the amplitude Am to a larger value when a lock determination has been made than when a prediction determination has been made. 【0047】 When the processes of S76 and S78 are completed, the PU 62 substitutes, into the vibration torque Tf, a value obtained by multiplying the amplitude Am by the unit sine wave "sinωt". Here, the angular velocity ω is set so as to satisfy a predetermined condition such as not overlapping with the resonance frequency of the vehicle. Also, "t" is a variable indicating time. 【0048】Incidentally, when the processing of S80 is completed, the PU62 temporarily ends the series of processes shown in FIG. 5. <Operations and Effects of the Present Embodiment> The PU62 determines the presence or absence of a sign of fixation abnormality caused by freezing and whether or not a fixation abnormality has occurred. When the PU62 makes a prediction determination or a lock determination of a fixation abnormality, it sets the assist amount Ta to a value obtained by superimposing the vibration torque Tf on the basic assist amount Ta0. As a result, the torque generated by the motor 32 vibrates at the angular velocity ω and the amplitude Am. This vibration can contribute to breaking the ice on the movable part of the steering mechanism. Also, when the torque of the motor 32 is vibrated, the heat generation amount of the motor 32 and the inverter 36 becomes larger than when it is not vibrated. And the heat generated by the motor 32 and the inverter 36 can contribute to melting the ice on the movable part of the steering mechanism or suppressing the moisture on the movable part from freezing. 【0049】 By the way, when the outside air temperature To is low, the degree of freezing and the ease of freezing of the steering mechanism become more prominent than when the outside air temperature To is high. Therefore, the PU62 changes the amplitude Am according to the outside air temperature To on the condition that the amplitude Am when the outside air temperature To is low is greater than or equal to the amplitude Am when the outside air temperature To is high. As a result, when the outside air temperature To is low, a larger torque can be applied to the steering mechanism. Also, when the outside air temperature To is low, the heat generation amount of the motor 32 and the inverter 36 can be increased. Therefore, the torque of the motor 32 can be vibrated with the minimum necessary amplitude Am. Therefore, it is possible to suppress the driver from perceiving the vibration. Also, the power consumption can be suppressed. 【0050】As described above, the following effects can be obtained with respect to this embodiment: (1) When a sticking abnormality has already occurred, resolving the situation tends to require more energy than when there are signs of a sticking abnormality and measures are taken to prevent it from occurring. Therefore, when the ambient temperature To is the same, the PU 62 sets the amplitude Am to a larger value when a lock has been determined than when a warning sign has been determined. This makes it possible to vibrate the torque of the motor 32 with the minimum necessary amplitude Am depending on whether it is a warning sign of a sticking abnormality or a sticking abnormality. As a result, it is possible to suppress the driver from sensing vibrations. In addition, power consumption can be reduced. 【0051】 <Other Embodiments> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically. 【0052】 "Regarding vibration processing" - It is not necessary for the process of changing the amplitude Am to be a process that performs a mapping operation on the amplitude Am. The process of changing the amplitude Am may be, for example, a process in which the PU62 calculates the amplitude Am using a polynomial function such as a linear function in which the outside temperature To is an independent variable and the amplitude Am is an output variable. 【0053】 - It is not mandatory for the vibration processing to include a process that changes the magnitude of the amplitude Am depending on whether it is a pre-impact detection or a lock detection. - It is not mandatory for the vibration processing to be a process that superimposes a sinusoidal periodic torque on the basic assist amount Ta0. For example, the vibration processing may be a process that superimposes a sawtooth-shaped periodic torque on the basic assist amount Ta0. 【0054】 It is not mandatory that the vibration processing involves superimposing a vibration component onto the basic assist amount Ta0. For example, if a lock is detected when the vehicle is started, the motor torque may be periodically varied while the vehicle is prohibited from driving and the basic assist amount Ta0 is set to zero. 【0055】"Regarding the modification process" - The ambient temperature around the steering mechanism, which is used as an input variable when the modification process changes the amplitude Am, is not limited to the ambient temperature To. The ambient temperature around the steering mechanism may be, for example, the value detected by a temperature sensor attached to the rack housing, etc. 【0056】 It is not mandatory that the modification process changes the amplitude Am based on the ambient temperature of the steering mechanism as an input variable. For example, the modification process may change the amplitude Am based on the substrate temperature Tb as an input variable. 【0057】 - The change process does not necessarily have to modify the amplitude Am. The change process could, for example, modify the frequency of a periodically fluctuating torque. Specifically, the change process could, for example, modify the frequency according to the ambient temperature To, under the condition that the frequency when the ambient temperature To is low is greater than or equal to the frequency when the ambient temperature To is high. 【0058】 "Regarding abnormalities that increase the force required for steering" - Abnormalities that increase the force required for steering are not limited to abnormalities related to freezing of the steering mechanism. For example, it may also be an abnormality caused by rust in the steering mechanism. Even in that case, it is effective to change the vibration depending on whether it is a seizing abnormality caused by rust or a precursor to it. 【0059】 "Regarding Assist Processing" - It is not mandatory for assist processing to include a basic assist amount calculation process M10 that calculates a basic assist amount Ta0 based on the steering torque Th and vehicle speed V as input variables. Assist processing may, for example, include a process of substituting an input variable for feedback control of the steering torque Th to a target steering torque into the basic assist amount Ta0. 【0060】"Regarding Motor Torque Control" - For example, as described in the "Regarding Steering Device" section below, if the steering device is a steer-by-wire system, the motor torque control may be performed as follows instead of the above assist process. That is, the motor torque control may be a process that sets the motor torque to the amount used to control the actual steering angle to a target steering angle determined according to the steering angle θh. In that case, the vibration process may be a process that superimposes the vibration component of the torque onto the amount used to control the steering angle to the target steering angle. Also, in that case, the steering mechanism subject to freezing determination may be a mechanism that transmits the motor's power to the steering wheels. In the case of a steer-by-wire system, the angle variable correlated with the steering angle is a variable that indicates the angle of the member mechanically connected to the steering wheel 20. That is, the above-mentioned "state in which the steering angle θh hardly changes" should be read as, for example, "state in which the steering angle hardly changes". 【0061】 "Regarding the steering control device" The steering control device is not limited to one that performs various processes using a PU. For example, it may include a dedicated hardware circuit such as an ASIC that performs at least a part of the processes performed in the above embodiment. That is, the control device may include any of the following processing circuits (a) to (c): (a) A processing circuit comprising a processing unit that performs all of the above processes according to a program and a program storage device such as a memory device that stores the program. (b) A processing circuit comprising a processing unit and a program storage device that perform a part of the above processes according to a program and a dedicated hardware circuit that performs the remaining processes. (c) A processing circuit comprising a dedicated hardware circuit that performs all of the above processes. Here, there may be multiple software execution devices comprising a processing unit and a program storage device, or multiple dedicated hardware circuits. 【0062】 Regarding the entity that executes the processes: It is not required that the entity that executes each of the above processes be a single control device, nor is it required that all of the executing entities be installed in the vehicle.

Claims

1. A steering control device in which a steering mechanism is the target of control, wherein the steering mechanism is configured to convert the rotational power of a motor into power to steer the steering wheels, and is configured to perform vibration processing and modification processing, wherein the vibration processing is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering becomes large, and the modification processing is a process of changing the vibration component generated by the vibration processing according to the conditions in which the steering mechanism is placed.

2. The steering control device according to claim 1, wherein the abnormality is an abnormality in which the force required for steering increases due to the solidification of water adhering to the steering mechanism, and the modification process includes a process to change the vibration component according to the temperature around the steering mechanism.

3. The steering control device according to claim 2, wherein the modification process includes a process to change the amplitude according to the ambient temperature, under the condition that the amplitude of the vibration component when the ambient temperature is low is greater than or equal to the amplitude when the ambient temperature is high.

4. Steering control device according to claim 1, configured to perform a lock determination process and a pre-indication determination process, wherein the lock determination process is a process to determine whether or not the steering mechanism is stuck due to the solidification of water adhering to the steering mechanism, the pre-indication determination process is a process to determine whether or not there is a pre-indication of the sticking, and the modification process includes a process to modify the vibration component depending on whether or not it is determined that the steering mechanism is stuck and whether or not there is a pre-indication.

5. The steering control device according to claim 1, wherein the steering mechanism is configured to transmit power from an operating unit to the steering wheels, the operating unit is a member in which the driver inputs the intention to steer, and is configured to perform an assist process, the assist process is a process of applying torque from the motor to the steering wheels to assist the driver's steering, and the vibration process is a process of superimposing the vibration component onto the torque of the motor generated by the assist process.

6. A steering control method in which a steering mechanism is the object of control, wherein the steering mechanism is configured to convert the rotational power of a motor into power to steer the steering wheels, and comprises the execution of vibration processing and modification processing, wherein the vibration processing is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering becomes large, and the modification processing is a process of changing the vibration component due to the vibration processing according to the conditions in which the steering mechanism is placed.

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