Steering control device and steering control method

Abstract

A steering mechanism is configured to convert the rotation power of a motor to power for steering a steered wheel. A steering control device according to the present invention is configured to execute a vibration process and an elimination determination process. The vibration process is for causing vibration of the torque of the motor when an abnormality occurs in which the force required for steering increases due to freezing of the steering mechanism. The elimination determination process is for determining that the abnormality has been eliminated on the basis of the rotational displacement of the motor and the temperature around the steering mechanism.

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 attempts to eliminate a frozen state by the torque of a motor when a steering mechanism freezes. This device determines whether the freezing has been eliminated by the rotation of the motor. 【0003】 Chinese Patent Application Publication No. 116573038 【0004】 When it is determined that the freezing has been eliminated by the rotation of the motor as described above, in reality, there is a concern that the elimination of the freezing is insufficient, the displaceable steering angle range is limited, or the sticking abnormality due to freezing may occur again. 【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 the power for steering a steering wheel. The steering control device is configured to execute vibration processing and elimination determination processing. The vibration processing is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering increases due to freezing of the steering mechanism. The elimination determination processing is a process of determining that the abnormality has been eliminated based on the rotational displacement of the motor and the temperature around the steering mechanism. 【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 the power for steering a steering wheel. The steering control method includes execution of vibration processing and execution of elimination determination processing. The vibration processing is a process of vibrating the torque of the motor when an abnormality occurs in which the force required for steering increases due to freezing of the steering mechanism. The elimination determination processing is a process of determining that the abnormality has been eliminated based on the rotational displacement of the motor and the temperature around the steering mechanism. 【0007】This is a block diagram showing the configuration of a steering control device and steering device according to one embodiment. This is a block diagram showing a part of the processing performed by the steering control device of Figure 1. This is a flowchart showing the procedure for processing related to ice formation prediction performed by the steering control device of Figure 1. This is a flowchart showing the procedure for processing related to locking determination performed by the steering control device of Figure 1. This is a flowchart showing the procedure for setting the torque amplitude performed by the steering control device of Figure 1. This is a flowchart showing the procedure for processing related to de-icing determination performed by the steering control device of Figure 1. This is a diagram illustrating the substrate temperature at the time of the final determination in the processing of Figure 6. This is a diagram illustrating the counter at the time of the final determination in the processing of Figure 6. This is a time chart illustrating the operation of the same embodiment. 【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 substrate 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: 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 is the same as the sign of the steering torque Th when the steering shaft 14 is steered to the right. The PU 62 determines whether or not there is a request to update the reference point (S56). The PU 62 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 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 it to indicate that there is no request to update the reference point (S61). 【0033】 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. 【0034】 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. 【0035】 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. 【0036】 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. 【0037】 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). 【0038】 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. 【0039】 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. 【0040】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 the process of setting the amplitude of vibration 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. 【0041】 In the series of processes shown in Figure 5, PU62 first determines whether the logical OR of the condition that a warning judgment has been made and the condition that a lock judgment has been made is true (S70). If PU62 determines that the logical OR is true (S70: YES), it obtains the outside temperature To (S72). Next, PU62 determines whether a warning judgment has been made (S74). If PU62 determines that a warning judgment has been made (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 a warning is present (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. 【0042】 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. 【0043】Also, map data is paired data consisting of discrete values of input variables and values of output variables corresponding to each of the values of the input variables. Also, the map operation may be any process such that 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 such that 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 interpolation of the values of a plurality of output variables included in the map data is the operation result. Also, alternatively, the map operation may be any process such that 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. 【0044】 On the other hand, when determining that the lock determination has been made (S74: NO), if there is a sticking abnormality, the PU 62 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 the input variable and the amplitude Am is the 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 the lock determination has been made than when the prediction determination has been made. 【0045】 When the processes of S76 and S78 are completed, the PU 62 substitutes, into the amplitude Am, a value obtained by multiplying the unit sine wave "sinωt" for the vibration torque Tf. 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. 【0046】Note that when the processing of S80 is completed and when a negative determination is made in the processing of S70, the PU62 temporarily ends the series of processes shown in FIG. 5. "Processing related to thawing determination" FIG. 6 shows the procedure of the processing related to the determination of thawing in which the locked state after the above lock determination is released. The processing shown in FIG. 6 is realized by the PU62 repeatedly executing the program stored in the storage device 64, for example, at a predetermined cycle. 【0047】 In the series of processes shown in FIG. 6, the PU62 first determines whether or not the lock determination flag F2 is "1" (S90). The lock determination flag F2 indicates a state in which a lock determination has been made when it is "1". The lock determination flag F2 indicates a state in which no lock determination has been made when it is "0". When the PU62 determines that the lock determination flag F2 is "0" (S90: NO), it determines whether or not a lock determination has been made (S92). When the PU62 determines that a lock determination has been made (S92: YES), it substitutes "1" into the lock determination flag F2 (S94). Then, the PU62 operates the user interface 80 shown in FIG. 1 to display visual information indicating a warning that operation is impossible due to a lock abnormality (S100). 【0048】 On the other hand, when the PU62 determines that the lock determination flag F2 is "1" (S90: YES), it determines whether or not the provisional determination flag F3 is "1" (S102). The provisional determination flag F3 indicates a state in which a provisional determination of thawing has been made when it is "1". The provisional determination flag F3 indicates a state in which no provisional determination of thawing has been made when it is "0". When the PU62 determines that the provisional determination flag F3 is "0" (S102: NO), it acquires the angular velocity ωm and the angular acceleration αm of the motor 32 (S104). The angular velocity ωm and the angular acceleration αm are calculated by the PU62 based on the rotation angle θm as an input variable. 【0049】 Next, the PU62 determines whether or not the logical product of the following conditions J and condition K is true (S106). Condition J is a condition that the absolute value of the angular velocity ωm is equal to or greater than the threshold value ωmth. 【0050】Condition K is the condition that the absolute value of the angular acceleration αm is greater than or equal to the threshold αmth. This process determines whether or not the movable part of the steering mechanism rotates due to vibration processing. If PU62 determines that the above logical AND is true (S106: YES), it increments counter C3 (S108). PU62 determines whether or not counter C3 is greater than or equal to the threshold C3th (S110). If PU62 determines that counter C3 is greater than or equal to the threshold C3th (S110: YES), it makes a preliminary determination of de-icing and assigns "1" to the preliminary determination flag F3 (S112). Then PU72 determines whether or not the substrate temperature sensor 70 is normal (S96). PU72 may determine that it is normal if, for example, the substrate temperature Tb is greater than or equal to its lower limit and less than or equal to its upper limit. 【0051】 If PU72 determines that the substrate temperature sensor 70 is functioning normally (S96: YES), it substitutes the substrate temperature Tb into the substrate temperature Tb0 (S98). The substrate temperature Tb0 represents the substrate temperature Tb at the time when a preliminary determination of defrosting is made. 【0052】 On the other hand, if PU62 determines that the provisional judgment flag F3 is "1" (S102: YES), it determines whether the substrate temperature sensor 70 is functioning normally (S114). If PU62 determines that the substrate temperature sensor 70 is functioning normally (S114: YES), it determines whether the following condition L is met (S116). 【0053】 Condition L is the condition that the substrate temperature Tb is greater than or equal to the substrate temperature Tb0 plus a predetermined amount ΔTb and "(-1)・K1・To". If PU62 determines that condition L is true (S116: YES), it makes a final determination that defrosting has occurred and sets "0" to both the lock determination flag F2 and the provisional determination flag F3 (S118). PU62 stops displaying the warning that operation is not possible due to a lock abnormality (S120). Then, PU62 switches the vibration processing to the processing used during the pre-determination (S122). In other words, PU62 sets the amplitude of the vibration torque Tf by the processing in S76. 【0054】On the other hand, if PU62 determines that there is an abnormality in the substrate temperature sensor 70 (S114: NO), it increments counter C4 (S124). Counter C4 measures the elapsed time since the provisional determination was made. PU62 determines whether the following condition M is met (S126). 【0055】 Condition M is the condition that the counter C4 is greater than or equal to the value obtained by adding "(-1) * K2 * To" to the predetermined value C40. If PU62 determines that condition M is true (S126: YES), it proceeds to the process in S118. 【0056】 Furthermore, when PU62 completes the processes in S98, S100, S112, and S122, or when it makes a negative determination in the processes in S92, S96, S106, S110, S116, and S126, it temporarily terminates the series of processes shown in Figure 6. 【0057】 <Operation and Effects of This Embodiment> The PU 62 determines whether there are signs of a seizing abnormality caused by freezing, and whether a seizing abnormality has occurred. When the PU 62 determines whether there are signs of a seizing abnormality or whether it has locked, 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 with angular velocity ω and amplitude Am. This vibration can contribute to breaking the ice on the movable parts of the steering mechanism. In addition, when the torque of the motor 32 is vibrated, the amount of heat generated by the motor 32 and inverter 36 is greater than when it is not vibrated. The heat generated by the motor 32 and inverter 36 can contribute to melting the ice on the movable parts of the steering mechanism or to suppressing the solidification of moisture on the movable parts. 【0058】When PU62 performs vibration processing in conjunction with a lock determination, it determines whether or not the ice has thawed and the lock state has been released. Figure 7 illustrates the determination of whether or not ice has thawed. As shown in Figure 7, when the rotation angle θm of the motor 32 vibrates due to the vibration processing, at time t1, when the logical AND of conditions J and K is true for a period defined by the threshold C3th, PU62 makes a provisional determination that ice has thawed. Subsequently, at time t2, when the substrate temperature Tb has risen by "ΔTb - K1・To" from the substrate temperature Tb0 at the time of the provisional determination, PU62 makes a final determination that ice has thawed. Then PU62 changes the vibration processing to the processing used for the pre-determination. 【0059】 Thus, based on the continuation of the state in which the logical AND of conditions J and K is true, PU62 continues the vibration processing during the lock determination for a while even after making a provisional determination. Furthermore, PU62 continues to display a warning that the vehicle cannot be driven for a while even after making a provisional determination. This ensures that when the de-icing determination is made, a situation in which steering is impaired can be reliably avoided. 【0060】 Furthermore, according to this embodiment, the following effects and benefits can be obtained. (1) Figure 8 shows the measurement results of the relationship between the amount of rise in substrate temperature Tb from the provisional determination until the locked state is reliably resolved and the ambient temperature To. As shown in Figure 8, the amount of rise in substrate temperature Tb during the period until the locked state is reliably resolved increases as the ambient temperature To decreases. 【0061】 Therefore, when the substrate temperature sensor 70 is functioning normally, the PU 62 sets the amount of increase in substrate temperature when making the final determination that defrosting has occurred, based on the rise in substrate temperature Tb, as follows. Specifically, the PU 62 changes the amount of increase in substrate temperature Tb for the final determination when the ambient temperature To is low, provided that this amount is greater than or equal to the amount of increase in substrate temperature Tb when the ambient temperature To is high. This makes it possible to achieve a desirable balance between minimizing the time until the final determination is made and improving the accuracy of the final determination. 【0062】(2) Figure 9 shows the measurement results of the relationship between the time T required from the provisional determination until the lock state is reliably resolved and the outside temperature To. As shown in Figure 9, the time T required for resolution increases as the outside temperature To decreases. 【0063】 Therefore, if there is an abnormality in the substrate temperature sensor 70, PU 62 sets the predetermined time for making a final determination that defrosting has occurred, based on the fact that a predetermined time has elapsed after the preliminary determination, as follows. That is, PU 62 changes the predetermined time according to the ambient temperature To, provided that the predetermined time when the ambient temperature To is low is greater than or equal to the predetermined time when the ambient temperature To is high. This makes it possible to achieve a desirable balance between minimizing the time until the final determination is made and improving the accuracy of the final determination. 【0064】 <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. 【0065】 Regarding the provisional determination process: It is not mandatory for the provisional determination process to be a process that provisionally determines that the ice has been thawed based on the fact that the logical AND of condition J and condition K is true. The provisional determination process may, for example, be a process that provisionally determines that the ice has been thawed based on the fact that the logical OR of the above condition J and condition K is true. Alternatively, for example, the provisional determination process may be a process that provisionally determines that the ice has been thawed if condition K is true. 【0066】 "Regarding the first and second temperature sensors" - The first and second temperature sensors are not limited to the substrate temperature sensor 70 and the ambient temperature sensor 78. For example, the first temperature sensor may be a temperature sensor attached to the motor 32. 【0067】Regarding the resolution determination process: It is not mandatory that the resolution determination process determines that the ice has been thawed if condition L is met, or if condition M is met. The resolution determination process may, for example, determine that the ice has been thawed if the logical OR of condition L and condition M is true. Alternatively, the resolution determination process may determine that the ice has been thawed if the logical AND of condition L and condition M is true. 【0068】 - It is not mandatory for the defrosting determination process to determine that defrosting has occurred based on the amount of increase in substrate temperature Tb from the provisional determination. For example, the defrosting determination process may determine that defrosting has occurred based on the amount of increase in substrate temperature Tb from the start of vibration torque Tf application. 【0069】 "Regarding notification processing" - Notification processing to notify that a locking abnormality has occurred is not limited to processing that displays warning information that the vehicle cannot be driven due to a locking abnormality. Notification processing may also be, for example, processing that outputs an audio signal indicating that the vehicle cannot be driven due to a locking abnormality. 【0070】 "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. 【0071】 - 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. 【0072】 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. 【0073】 - The ambient temperature of the steering mechanism, used as an input variable when changing the amplitude Am, is not limited to the ambient temperature To. The ambient temperature may be, for example, the value detected by a temperature sensor attached to the rack housing, etc. 【0074】 - It is not mandatory to modify the amplitude Am based on the ambient temperature of the steering mechanism as an input variable. For example, the vibration processing may include a process to modify the amplitude Am based on the substrate temperature Tb as an input variable. 【0075】 - It is not necessary that the object modified by the process of changing the vibration component be the amplitude Am. The process of changing the vibration component may, for example, be a process of changing the frequency of a periodically fluctuating torque. Specifically, the process of changing the vibration component may be a process of changing the frequency according to the ambient temperature To, for example, 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. 【0076】 "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. 【0077】"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". 【0078】 "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. 【0079】 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. 【0080】"Other" - The process of notifying the driver is not limited to the process of notifying that the vehicle cannot be driven due to a lock malfunction. The process of notifying the driver may also include, for example, the process of notifying the driver if it is determined that there are signs of a lock malfunction during that period.

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 resolution determination 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 increases due to freezing of the steering mechanism, and the resolution determination processing is a process of determining that the abnormality has been resolved based on the rotational displacement of the motor and the temperature around the steering mechanism.

2. The steering control device according to claim 1, wherein the resolution determination process includes a provisional determination process, the provisional determination process is a process that provisionally determines that the abnormality has been resolved on the condition that the motor has undergone rotational displacement, the resolution determination process is a process that determines that the abnormality has been resolved when a predetermined period of time has elapsed after the provisional determination has been made, and is configured to execute a modification process, the modification process is a process that changes the length of the predetermined period according to the ambient temperature on the condition that the length of the predetermined period when the ambient temperature around the steering mechanism is low is equal to or greater than the length of the predetermined period when the ambient temperature is high.

3. The motor and the steering control device are housed in a single housing and are configured to perform a first temperature acquisition process and a second temperature acquisition process, wherein the first temperature acquisition process is a process to acquire a first temperature, which is the temperature inside the housing, detected by a first temperature sensor, and the second temperature acquisition process is a process to acquire a second temperature, which is the temperature outside the housing and around the steering mechanism, detected by a second temperature sensor, the predetermined period is the period from when the provisional determination is made until the first temperature rises to or above a predetermined temperature, and the change process includes a process to change the predetermined temperature according to the second temperature, provided that the predetermined temperature when the second temperature is low is equal to or higher than the predetermined temperature when the second temperature is high.

4. The steering control device according to claim 3, wherein the resolution determination process includes determining that the abnormality has been resolved when an abnormality occurs in the first temperature sensor, and the predetermined period is defined as the period from the provisional determination until a predetermined time has elapsed, and the modification process includes changing the predetermined time according to the second temperature when an abnormality occurs in the first temperature sensor, provided that the predetermined time when the second temperature is low is greater than or equal to the predetermined time when the second temperature is high.

5. The steering control device according to claim 1, wherein the resolution determination process is a process that determines that the abnormality of the steering mechanism being stuck due to freezing has been resolved, the vibration process is a first vibration process and is configured to execute a second vibration process, and the second vibration process is a process that vibrates the torque of the motor with a smaller amplitude than the first vibration process after the resolution determination process has determined that the abnormality of the steering mechanism being stuck due to freezing has been resolved.

6. The steering control device according to claim 1, wherein the resolution determination process is a process that determines that the sticking abnormality due to freezing of the steering mechanism has been resolved, and is configured to execute a notification process, the notification process is a process that notifies that a sticking abnormality has occurred until the resolution determination process determines that the sticking abnormality due to freezing has been resolved.

7. 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 the method includes the execution of vibration processing and the execution of resolution determination 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 due to freezing of the steering mechanism, and the resolution determination processing is a process of determining that the abnormality has been resolved based on the rotational displacement of the motor and the temperature around the steering mechanism.

Images