Motor control device and electric power steering device

Abstract

Provided is a motor control device capable of starting the application of steering assist force in an early period when starting a vehicle. Specifically, when a command value (A2) (alternative value) from a second microcomputer (19) was being transmitted at the time of completion of an initial diagnosis of a first system (1000), a first microcomputer (18) receives the command value (A2) (alternative value) transmitted from the second microcomputer (19), corrects a command value (A1) (second command value) calculated by the first microcomputer (18) so as to gradually approach said command value (A1) (second command value) from the received command value (A2) (a specific alternative value (A2')), transmits a command value (A1') that is the corrected command value (A1) (second command value) to the second microcomputer (19), additionally limits the absolute value of the command value (A1') to a value equal to or less than an upper limit value which gradually increases from "0" to a predetermined set value, and drives a first motor drive unit (26) of the first system (1000) on the basis of the limited command value (A1') (a target current command value (Ir)).

Description

Motor control device and electric power steering device

[0001] The present invention relates to a motor control device and an electric power steering device.

[0002] Conventionally, for example, a motor control device has been proposed for an electric motor having two winding sets, which has a master control unit that controls the current of one winding set and a slave control unit that controls the current of the other winding set (see, for example, Patent Document 1). In the motor control device described in Patent Document 1, the master control unit calculates command values ​​for both control units, controls the current of one winding set based on the calculated command value, and transmits the command value to the slave control unit, which controls the current of the other winding set based on the transmitted command value.

[0003] Patent No. 7027808

[0004] Typically, when a driver operates the ignition switch at the start of a vehicle, a motor control device starts an initial diagnosis, and after the initial diagnosis is completed, the motor control device starts control of the electric motor. Therefore, when applied to a motor control device having a master control unit and a slave control unit, the initial diagnosis is started in each of the master control unit and the slave control unit, and control of the electric motor starts after both initial diagnoses are completed. In other words, control of the electric motor and application of steering assist force to the steering system begin after waiting for completion of the initial diagnosis in the master control unit or the slave control unit that completes the initial diagnosis later. An object of the present invention is to provide a motor control device and an electric power steering device that can start application of steering assist force early when the vehicle is started.

[0005] In order to achieve the above object, a motor control device according to one aspect of the present invention is a motor control device that (a) controls the driving of an electric motor having a plurality of winding sets, and includes: (b) a plurality of drive circuits that supply power to the winding sets; and (c) a plurality of control units that generate control signals to drive the drive circuits based on command values. (d) A group of components including the winding sets, drive circuits, and control units that are formed corresponding to each other is defined as a first system, and another group of components is defined as a second system. (e) A first control unit that is a control unit of the first system controls the command values ​​of the first control unit, and and a second control unit that is a control unit of the second system, and drives the drive circuit of the first system based on a first command value that is the command value of the first control unit calculated, and transmits a second command value that is the command value of the second control unit calculated to the second control unit; (f) the second control unit receives the second command value transmitted from the first control unit, and drives the drive circuit of the second system based on the received second command value; (g) the second control unit further includes a diagnosis completion detection unit that detects completion of the initial diagnosis of the first system, and (h) a substitute value calculation unit that calculates a substitute value for the second command value; When the initial diagnosis of the systems is completed, if the diagnosis completion detection unit does not detect the completion of the initial diagnosis of the first system, the drive circuit of the second system is driven based on the substitute value calculated by the substitute value calculation unit, and the substitute value is further transmitted to the first control unit. Thereafter, when the diagnosis completion detection unit detects the completion of the initial diagnosis of the first system, the drive circuit of the second system is driven based on the second command value transmitted from the first control unit. (j) When the substitute value has been transmitted from the second control unit when the initial diagnosis of the first system is completed, the first control unit receives the substitute value transmitted from the second control unit. The second command value calculated by the first control unit is corrected so that it gradually approaches the second command value calculated by the first control unit from the specific substitute value, which is the received substitute value, and the corrected second command value is sent to the second control unit.Furthermore, the first command value calculated by the first control unit is corrected so that it gradually approaches the first command value calculated by the first control unit from the specific substitute value.The absolute value of the corrected first command value is limited to an upper limit value that gradually increases from "0" to a predetermined set value, and the drive circuit of the first system is driven based on the first command value after the limit.

[0006] Another aspect of the present invention is an electric power steering device that includes (a) the motor control device described above, and (b) an electric motor controlled by the motor control device, and (c) applies a steering assist force to the steering system of the vehicle by the electric motor.

[0007] According to one aspect of the present invention, it is possible to provide a motor control device and an electric power steering device that can start applying a steering assist force early when starting a vehicle.

[0008] 1 is a diagram showing the overall configuration of an electric power steering device according to a first embodiment; FIG. 2 is a diagram showing the internal configuration of an electronic control unit; FIG. 3 is a diagram showing the operation of the electronic control unit; FIG. 4 is a diagram showing the operation of the electronic control unit; FIG. 5 is a diagram showing the operation of the electric power steering device in the first mode; FIG. 6 is a diagram showing the operation of the electric power steering device in the second mode or the fourth mode; FIG. 7 is a diagram showing the operation of the electric power steering device in the third mode; FIG. 8 is a diagram showing the operation of the electric power steering device immediately after switching to the fourth mode; FIG. 9 is a diagram showing the configuration of a cross-fade section of modified example (1); FIG. 10 is a diagram showing the operation of the electronic control unit of modified example (1); FIG. 11 is a diagram showing the operation of the electronic control unit of modified example (1); FIG. 12 is a diagram showing the operation of a second command value generating section of modified example (2); FIG. 13 is a diagram showing the operation of the electric power steering device of modified example (2); FIG. 14 is a diagram showing the operation of a first microcomputer of modified example (3);

[0009] The inventors have conducted extensive research into motor control devices that can begin providing steering assist force early when starting a vehicle, and have devised a configuration in which one of the master and slave control units, whichever control unit completes an initial diagnosis first, begins controlling the electric motor without waiting for the other control unit to complete its initial diagnosis. However, with this configuration, if the initial diagnosis of the slave control unit is completed before the initial diagnosis of the master control unit and control of the electric motor is performed solely by the slave control unit, there is a possibility that the motor output of the electric motor will suddenly change once the initial diagnosis of the master control unit is completed and control of the electric motor based on the command value calculated by the master control unit begins. This may cause a sudden change in the steering assist force provided to the steering system, which may cause a discomfort to the driver.

[0010] Below, examples of a motor control device and an electric power steering device according to embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the configuration, arrangement, etc. of the components described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims. Furthermore, although the following description describes a case in which the present invention is applied to an electric power steering device, the present invention is not limited to application to an electric power steering device and can be applied to various other applications. For example, the present invention may be applied to an electric brake device or to a drive device for an actuator that drives the joints of a robot.

[0011] The embodiments of the present invention will be described in the following order: 1. Overall configuration of the electric power steering device 2. Operation of the electric power steering device 3. Modified examples

[0012] [1. Overall Configuration of Electric Power Steering Device] Figure 1 is a diagram showing the overall configuration of an electric power steering device 100 according to a first embodiment. As shown in Figure 1, a steering shaft 2 of a steering wheel 1 is connected to steered wheels 8L, 8R via hub units 7a, 7b via a reduction gear 3, universal joints 4a, 4b, a pinion-rack mechanism 5, and tie rods 6a, 6b, which constitute a reduction mechanism. The pinion-rack mechanism 5 has a pinion 5a to which steering force is transmitted from the universal joint 4b, and a rack 5b that meshes with the pinion 5a. The pinion-rack mechanism 5 converts the steering force transmitted to the pinion 5a into linear motion in the vehicle width direction using the rack 5b. Also attached to the steering shaft 2 are a first torque sensor 9 and a second torque sensor 10 that detect a driver's steering torque Th, and a steering angle sensor 11 that detects a steering angle θh of the steering wheel 1. Here, the steering torque Th detected by the first torque sensor 9 and the second torque sensor 10 will be slightly different values ​​due to individual differences between the sensors.

[0013] An electric motor 12, which applies a steering assist force to the steering system, is connected to the steering shaft 2 via a reduction gear 3. The electric motor 12 may be, for example, a polyphase motor having multiple winding sets. In the first embodiment, the electric motor 12 is a three-phase motor having two winding sets in which a first system coil 13 and a second system coil 14 (see FIG. 2 ) are wound within the same motor housing, rotating a common rotor with the coils of the two systems. In other words, the electric motor 12 is a dual-winding motor having two three-phase winding sets with equivalent electrical characteristics. An electronic control unit (ECU) 200, which controls the electric power steering device 100, receives power from a battery 15 and an ignition key signal from an ignition switch 16.

[0014] The electronic control unit 200 is also connected to a vehicle CAN (Controller Area Network) 17, and receives various types of vehicle information from the vehicle CAN 17. For example, information on the vehicle speed Vh of the vehicle detected by a vehicle speed sensor (not shown) is received from the vehicle CAN 17. The electronic control unit 200 performs PWM (Pulse Width Modulation) control on the electric motor 12 via an inverter (first motor drive unit 26 and second motor drive unit 37 in FIG. 2 ) based on the steering torque Th detected by the first torque sensor 9 and the second torque sensor 10, the steering angle θh detected by the steering angle sensor 11, and the vehicle speed Vh received from the vehicle CAN 17.

[0015] The electronic control unit 200 includes a computer having, for example, a first microcomputer 18 (broadly speaking, a "controller," "first control unit," or "master control unit"), a second microcomputer 19 (broadly speaking, a "controller," "second control unit," or "slave control unit"), and peripheral components such as a memory unit 20. The first microcomputer 18 and the second microcomputer 19 may be, for example, a central processing unit (CPU) or a microprocessing unit (MPU). The memory unit 20 may be, for example, a semiconductor memory unit, a magnetic memory unit, or an optical memory unit. Examples of such memories include registers, cache memories, and memories such as read-only memories (ROMs) and random access memories (RAMs) used as main memories. The functions of the electronic control unit 200 described below are realized, for example, by the first microcomputer 18 and the second microcomputer 19 of the electronic control unit 200 executing computer programs stored in the memory unit 20. The memory unit 20 stores various data necessary for executing the computer programs, such as a first gain G1 and a second gain G2, which will be described later.

[0016] FIG. 2 is a diagram showing the internal configuration of the electronic control unit 200. As shown in FIG. 2, the electronic control unit 200 includes a first initial diagnosis unit 21, a first command value generation unit 22, a cross-fade unit 23, a first output limiting unit 24, a first current control unit 25, a first motor drive unit 26 (broadly referred to as a "drive circuit"), a first voltage detection unit 27, a first current detection unit 28, a first temperature detection unit 29, a first rotation angle detection unit 30, and a first power supply unit 31. Each of the first initial diagnosis unit 21 to the first current control unit 25 is realized by the first microcomputer 18 executing a computer program stored in the storage unit 20. The first initial diagnosis unit 21 to the first power supply unit 31, together with the first torque sensor 9 and the first system coil 13, constitute a group of components (hereinafter also referred to as a "first system 1000") that control the drive of the electric motor 12. That is, the first system 1000 is a group of components including the first system coil 13, the first motor drive unit 26, and the first microcomputer 18, which are formed corresponding to each other.

[0017] Similarly, the electronic control unit 200 includes a second initial diagnosis unit 32, a second command value generation unit 33 (broadly referred to as a "substitute value calculation unit"), a diagnosis completion detection unit 34, a second output limiting unit 35, a second current control unit 36, a second motor drive unit 37 (broadly referred to as a "drive circuit"), a second voltage detection unit 38, a second current detection unit 39, a second temperature detection unit 40, a second rotation angle detection unit 41, and a second power supply unit 42. Each of the second initial diagnosis unit 32 to the second current control unit 36 ​​is realized by the second microcomputer 19 executing a computer program stored in the storage unit 20. The second initial diagnosis unit 32 to the second power supply unit 42, together with the second torque sensor 10 and the second system coil 14, constitute a group of components (hereinafter also referred to as a "second system 2000") that control the drive of the electric motor 12. That is, the second system 2000 is a group of components including the second system coil 14, the second motor drive unit 37, and the second microcomputer 19, which are formed corresponding to each other. The first microcomputer 18 and the second microcomputer 19 are capable of communicating with each other (transmitting and receiving data) via a bus line 43.

[0018] As will be described later, when the initial diagnosis of the first system 1000 is completed but the initial diagnosis of the second system 2000 is not yet complete, the electronic control unit 200 enters a first mode in which the drive of the electric motor 12 is controlled only by the first system 1000. After that, when the initial diagnosis of the second system 2000 is completed, the electronic control unit 200 switches to a second mode in which the drive of the electric motor 12 is controlled by both the first system 1000 and the second system 2000. On the other hand, when the initial diagnosis of the second system 2000 is completed but the initial diagnosis of the first system 1000 is not yet complete, the electronic control unit 200 enters a third mode in which the drive of the electric motor 12 is controlled only by the second system 2000. After that, when the initial diagnosis of the first system 1000 is completed, the electronic control unit 200 switches to a fourth mode in which the drive of the electric motor 12 is controlled by both the first system 1000 and the second system 2000.

[0019] The first initial diagnosis unit 21 performs an initial diagnosis of the first system 1000. The initial diagnosis may be, for example, a diagnosis performed when the vehicle is started to verify whether each component of the first system 1000 operates normally. For example, when the driver operates the ignition switch 16, the first initial diagnosis unit 21 determines whether the output values ​​of the first voltage detection unit 27, the first current detection unit 28, the first temperature detection unit 29, the first rotation angle detection unit 30, the first torque sensor 9, etc. are appropriate values ​​with respect to a predetermined reference, such as a command value A1 set by the first command value generation unit 22. The operation (calculation) for applying a steering assist force by the first system 1000 is stopped until the initial diagnosis of the first system 1000 is completed, and is resumed after the initial diagnosis of the first system 1000 is completed.

[0020] When the first initial diagnosis unit 21 completes the initial diagnosis of the first system 1000, the first command value generation unit 22 calculates a target steering torque based on the steering torque Th output from the first torque sensor 9, the vehicle speed Vh received from the vehicle CAN 17, the steering angle θh output from the steering angle sensor 11, and the steering angular velocity ωh calculated from the steering angle θh. The target steering torque is the total amount of steering assist force that assists the driver in steering the steering wheel 1. The first command value generation unit 22 also converts the calculated target steering torque into a current command value Ir0. As the current command value Ir0, for example, a q-axis current command value or a d-axis current command value can be used. Furthermore, the first command value generation unit 22 distributes the converted current command value Ir0 to the first system 1000 and the second system 2000, and sets a current command value to be used in the first system 1000 (hereinafter also referred to as the "first command value") and a current command value to be used in the second system 2000 (hereinafter also referred to as the "second command value"). FIG. 2 illustrates a case in which the first command value and the second command value are each set to the same command value A1, which is half the value of the current command value Ir0. The command value A1 is output to the cross-fade unit 23. That is, the first command value generation unit 22 calculates the command value A1 (first command value) of the first microcomputer 18 and the command value A1 (second command value) of the second microcomputer 19.

[0021] The cross-fade unit 23 has a first multiplier 44, a second multiplier 45, and an adder 46. A first gain G1 used in the first multiplier 44 and a second gain G2 used in the second multiplier 45 are each a numerical value set in the range of 0 to 1.

[0022] When the initial diagnosis of the first system 1000 by the first initial diagnosis unit 21 is completed, the second multiplier 45 multiplies the command value A2 transmitted from the second command value generation unit 33 or the command value A2 received at the start of calculation of the command value A1 by the first command value generation unit 22 (hereinafter also referred to as the "specific substitute value A2'") by the second gain G2 to calculate a multiplication result (hereinafter also referred to as the "second multiplication result"). Specifically, when the command value A2 (substitute value) is not transmitted from the second microcomputer 19 at the time the initial diagnosis of the first system 1000 is completed (hereinafter also referred to as the "first state"), the second multiplier 45 sets the numerical value of the second gain G2 to "0" and multiplies the command value A2 by the second gain G2 to calculate G2*A2 as the second multiplication result. The "first state" occurs when the initial diagnosis of the first system 1000 is completed before the initial diagnosis of the second system 2000.

[0023] On the other hand, if the command value A2 (substitute value) is being transmitted from the second microcomputer 19 at the completion of the initial diagnosis of the first system 1000 (hereinafter also referred to as the "second state"), the second multiplier 45 gradually changes the value of the second gain G2 from "1" to "0" over time and multiplies the specific substitute value A2' by the second gain G2 to calculate G2*A2' as the second multiplication result. The "second state" occurs in the third mode in which the initial diagnosis of the second system 2000 is completed before the initial diagnosis of the first system 1000 and the drive of the electric motor 12 is controlled solely by the second system 2000. As a result, if the drive of the electric motor 12 is controlled by the second system 2000 before the completion of the initial diagnosis of the first system 1000, the second multiplication result G2*A2' gradually changes from "A2'" to "0." The second multiplication result is output to the adder 46.

[0024] As a method for setting the specific substitute value A2', for example, after the initial diagnosis of the first system 1000 is completed, when switching from the third mode to the fourth mode in which the drive of the electric motor 12 is controlled in both the first system 1000 and the second system 2000, a command value A2 transmitted from the second microcomputer 19 is received and the received command value A2 is set as the specific substitute value A2'. Note that in the first embodiment, when the second gain G2 is gradually changed from "1" to "0", the amount of change in the second gain G2 per change is kept constant. As a result, when the diagnosis of the first system 1000 is completed, the time required for the output of the cross-fade unit 23 to change from the specific substitute value A2' to the command value A1 can be set to a constant value (e.g., 50 μs), as will be described later.

[0025] When the initial diagnosis of the first system 1000 by the first initial diagnosis unit 21 is completed, the first multiplier 44 multiplies the command value A1 (which serves as both the first command value and the second command value) set by the first command value generation unit 22 by the first gain G1 to calculate the multiplication result (hereinafter also referred to as the "first multiplication result G1*A1"). The value of the first gain G1 is set to, for example, G1=1-G2. As a result, if the state at the completion of the initial diagnosis is the first state, the first multiplication result G1*A1 becomes "A1". On the other hand, if the state is the second state, the first multiplication result G1*A1 gradually changes from "0" to "A1". The first multiplication result G1*A1 is output to the adder 46.

[0026] When the initial diagnosis of the first system 1000 by the first initial diagnosis unit 21 is completed, the adder 46 adds the first multiplication result G1*A1 and the second multiplication result G2*A2 or G2*A2' to calculate the sum (hereinafter also referred to as the "command value A1'"). As a result, if the state at the time of completion of the initial diagnosis is the first state, the command value A1' becomes "A1." On the other hand, if the state is the second state, the command value A1' gradually changes from the "specific substitute value A2'" to "A1." That is, if the state is the second state, the command value A1 is corrected from the specific substitute value A2' to the command value A1 (first command value, second command value) calculated by the first command value generation unit 22, to obtain the command value A1'. The command value A1' (corrected first command value, second command value) is output to the first output limiting unit 24 and also transmitted to the second microcomputer 19. In other words, the first microcomputer 18 is configured to sequentially send an added value (G1*A1+G2*A2') obtained by adding the command value A1 and the specific substitute value A2' sequentially calculated by the first command value generating unit 22 at a predetermined ratio G1:G2 as the command value A1' to the second microcomputer 19. The first microcomputer 18 is also configured to change the predetermined ratio G1:G2 so that the ratio of the command value A1 becomes "0" at the start of the addition (addition of G1*A1 and G2*A2') and then gradually increases from "0".

[0027] As described above, the first embodiment illustrates a case where the "first command value" and the "second command value" are the same command value A1. Therefore, in the above description of the adder 46, the "first command value" and the "second command value" are collectively described as "command value A1 (first command value, second command value)" and "command value A1' (corrected first command value, second command value)." In contrast, if the command value A1 indicating the "first command value," the command value A1 indicating the "second command value," and the command value A1' indicating the "corrected first command value" and the command value A1' indicating the "corrected second command value" are described separately, the above description of the adder 46 can also be expressed as follows: "That is, in the second state, the command value A1 (first command value) is corrected to become a command value A1' so as to gradually approach the command value A1 (first command value) calculated by the first command value generation unit 22 from the specific substitute value A2'. The command value A1' (corrected first command value) is output to the first output limiting unit 24. Furthermore, the command value A1 (second command value) is corrected to become a command value A1' so as to gradually approach the command value A1 (second command value) calculated by the first command value generation unit 22 from the specific substitute value A2'. The command value A1' (corrected second command value) is transmitted to the second microcomputer 19."

[0028] The first output limiting unit 24 sets the target current command value Ir by limiting the absolute value of the command value A1' (corrected first command value) output from the cross-fade unit 23 to a predetermined upper limit value U1 or less. For example, the first output limiting unit 24 replaces a command value A1' exceeding "U1" with "U1" and a command value A1' below "-U1" with "-U1." Furthermore, when the first initial diagnosis unit 21 completes the initial diagnosis of the first system 1000, the first output limiting unit 24 first sets the absolute value of the upper limit value U1 to "0" and then gradually increases it from "0" to a predetermined set value. As a result, the target current command value Ir of the first system 1000 becomes "0" immediately after the initial diagnosis of the first system 1000 is completed, and then gradually changes from "0" to the command value A1'. Therefore, for example, when switching from the third mode to the fourth mode, the steering assist force by the first system 1000 can be set to "0" immediately after the switching, and the target current command value Ir gradually increases, thereby suppressing a sudden change in motor output. The amount of change in the upper limit value U1 per change is set constant so that the time required to reach the "set value" is constant (e.g., 1 s). Furthermore, the first output limiting unit 24 may set the set value to a lower value when the temperature of the electric motor 12 or the first motor drive unit 26 detected by the first temperature detection unit 29 is higher than a predetermined temperature than when the temperature is lower. The target current command value Ir is output to the first current control unit 25.

[0029] The first current control unit 25 generates a voltage control command value Vref by feedback control such as proportional-integral (PI) control based on the deviation between the fed-back current value Im of the first system coil 13 and the target current command value Ir. For example, the current value Im may be a q-axis current iq and a d-axis current id obtained by converting the phase currents of the first system coil 13 for the respective phases A, B, and C. For example, the voltage control command value Vref may be a voltage command value for each phase A, B, and C. Based on the generated voltage control command value Vref, the first current control unit 25 generates a gate signal (PWM signal) for driving a first motor drive unit 26 (e.g., an inverter). That is, the first current control unit 25 generates a PWM signal (control signal) for driving the first motor drive unit 26 based on the target current command value Ir (the command value A1 after limitation).

[0030] With this configuration, if the state at the completion of the initial diagnosis of the first system 1000 is the first state (i.e., if the initial diagnosis of the first system 1000 is completed before the initial diagnosis of the second system 2000), the first microcomputer 18 switches to the first mode, sets the command value A1 calculated by the first command value generator 22 to a command value A1' (= A1), and starts driving the first motor driver 26 of the first system 1000 based on the command value A1' (corrected first command value). The first microcomputer 18 also transmits the command value A1' (corrected second command value) to the second microcomputer 19. Thereafter, when the initial diagnosis of the second system 2000 is completed, the first microcomputer 18 switches to the second mode, and continues generating the command value A1' (= A1) and continues driving the first motor driver 26 of the first system 1000 based on the command value A1'. In the second mode, the second motor drive unit 37 is driven by the second microcomputer 19 of the second system 2000, as will be described later.

[0031] On the other hand, if the state at the completion of the initial diagnosis of the first system 1000 is the second state (i.e., if the initial diagnosis of the second system 2000 is completed before the initial diagnosis of the first system 1000), the first microcomputer 18 switches from the third mode to the fourth mode, corrects the command value A1 so that it gradually approaches the specific substitute value A2' to the command value A1 calculated by the first command value generator 22, as shown in Figure 3, outputs the corrected command value A1 (command value A1') to the first output limiter 24, and also transmits the command value A1' to the second microcomputer 19. Figure 3 is a diagram showing the operation of the electronic control unit 200, where Figure 3(a) is a diagram showing the relationship between the command value and time, Figure 3(b) is a diagram showing the relationship between the gain and time, and Figure 3(c) is a diagram showing a case where the command value A2 is immediately switched to the command value A1. In the fourth mode, as shown in FIG. 4, the first microcomputer 18 sets the target current command value Ir by limiting the command value A1' to an upper limit value U1, which gradually increases from "0" to a predetermined set value, and drives the first motor drive unit 26 of the first system 1000 based on the target current command value Ir. FIG. 4A shows the operation of the electronic control unit 200, with FIG. 4A illustrating the relationship between the target current command value Ir, the upper limit value U1, and time for the first system, and FIG. 4B illustrating the relationship between the target current command value Ir, the upper limit value U2, and time for the second system. In the fourth mode, the second microcomputer 19 of the second system 2000 drives the second motor drive unit 37, as will be described later.

[0032] The first motor drive unit 26 is a drive circuit that supplies power to the first system coil 13. The first motor drive unit 26 is driven by a PWM signal output from the first microcomputer 18, and supplies a current (power) to the first system coil 13 of the electric motor 12 such that the deviation between the current value Im of the first system coil 13 of the electric motor 12 and the target current command value Ir becomes "0." That is, the first motor drive unit 26 drives the first motor drive unit 26 based on the PWM signal (a signal based on the limited command value A1'). An inverter, for example, can be used as the first motor drive unit 26.

[0033] The first voltage detection unit 27 detects the voltage of the first motor drive unit 26. The first current detection unit 28 detects the phase current of each phase of the first system coil 13. The first temperature detection unit 29 detects the temperature of the electric motor 12 or the first motor drive unit 26. The first rotation angle detection unit 30 detects the rotation angle θm of the electric motor 12. The detected voltage, phase current, temperature, and rotation angle θm are output to the first microcomputer 18.

[0034] The first power supply unit 31 is interposed between the battery 15 and the first microcomputer 18 and first motor drive unit 26, and connects or disconnects the battery 15 to the first microcomputer 18 and first motor drive unit 26 in response to control signals output from the first microcomputer 18, etc. This starts or stops the supply of power from the battery 15 to the first microcomputer 18 and first motor drive unit 26. A relay, for example, can be used as the first power supply unit 31.

[0035] The second initial diagnosis unit 32 performs an initial diagnosis of the second system 2000. For example, the initial diagnosis may be a diagnosis performed when the vehicle is started to verify whether each component of the second system 2000 operates normally. For example, when the driver operates the ignition switch 16, the second initial diagnosis unit 32 determines whether the output values ​​of the second voltage detection unit 38, the second current detection unit 39, the second temperature detection unit 40, the second rotation angle detection unit 41, the second torque sensor 10, etc. are appropriate values ​​with respect to a predetermined standard, such as the command value A2 set by the second command value generation unit 33. The operation (calculation) for applying a steering assist force by the second system 2000 is stopped until the initial diagnosis of the second system 2000 is completed, and is resumed after the initial diagnosis of the second system 2000 is completed.

[0036] When the second initial diagnosis unit 32 completes the initial diagnosis of the second system 2000, the second command value generation unit 33 calculates a substitute value for the command value A1 transmitted from the first command value generation unit 22 (substitute value for the second command value; hereinafter, also referred to as "command value A2"). Specifically, the second command value generation unit 33 calculates a target steering torque based on the steering torque Th output from the second torque sensor 10, the vehicle speed Vh received from the vehicle CAN 17, the steering angle θh output from the steering angle sensor 11, and the steering angular velocity ωh calculated from the steering angle θh. The second command value generation unit 33 also converts the calculated target steering torque into a current command value Ir0. The second command value generation unit 33 also distributes the converted current command value Ir0 to the first system 1000 and the second system 2000, and sets a first command value to be used in the first system 1000 and a second command value to be used in the second system 2000. 2 illustrates an example in which the first command value and the second command value are set to the same command value A2, which is half the current command value Ir0. The command value A2 is output to the second output limiting unit 35.

[0037] Here, the steering torque Th output from the first torque sensor 9 and the steering torque Th output from the second torque sensor 10 are not completely the same due to individual differences between the sensors, etc. Therefore, due to differences in the steering torque Th, the command value A1 calculated by the first command value generating unit 22 and the command value A2 calculated by the second command value generating unit 33 will be slightly different numerical values.

[0038] The diagnosis completion detection unit 34 detects the completion of the initial diagnosis of the first system 1000. As described above, if the initial diagnosis of the first system 1000 is not completed, the first microcomputer 18 does not start calculating or transmitting the command value A1′. Therefore, the diagnosis completion detection unit 34, for example, determines whether the command value A1′ is being sequentially transmitted from the first microcomputer 18. If the command value A1′ is being sequentially transmitted, the diagnosis completion detection unit 34 determines that the initial diagnosis of the first system 1000 is completed. If the command value A1′ is not being transmitted, the diagnosis completion detection unit 34 determines that the initial diagnosis of the first system 1000 is not completed. The detection result is output to the second command value generation unit 33 and the second output limiting unit 35.

[0039] The second output limiting unit 35 sets the target current command value Ir by limiting the absolute value of the command value A1' transmitted from the first microcomputer 18 or the command value A2 output from the second command value generating unit 33 to a predetermined upper limit value U2 or less. Specifically, when the diagnosis completion detecting unit 34 detects the completion of the initial diagnosis of the first system 1000, the second output limiting unit 35 sets the target current command value Ir by limiting the command value A1' to a predetermined upper limit value U2 or less. On the other hand, when the diagnosis completion detecting unit 34 does not detect the completion of the initial diagnosis of the first system 1000, the second output limiting unit 35 sets the target current command value Ir by limiting the command value A2 to a maximum upper limit value U2 or less. For example, the command value A1' or command value A2 exceeding "U2" is replaced with "U2," and the command value A1' or command value A2 below "-U2" is replaced with "-U2." In addition, when the initial diagnosis of the second system 2000 by the second initial diagnosis unit 32 is completed, the second output limiting unit 35 first sets the absolute value of the upper limit value U2 to "0", and then gradually increases it from "0" to a predetermined set value.

[0040] As a result, the target current command value Ir for the second system 2000 becomes "0" immediately after the completion of the initial diagnosis of the second system 2000, and then gradually changes from "0" to the command value A1'. Therefore, for example, when switching from the first mode to the second mode, the steering assist force of the second system 2000 can be set to "0" immediately after the switch. Furthermore, the target current command value Ir gradually increases, thereby suppressing a sudden change in motor output. The amount of change in the upper limit value U2 per change is set constant so that the time required to reach the "set value" is constant (e.g., 1 s). Furthermore, the second output limiting unit 35 may set the set value to a lower value when the temperature of the electric motor 12 or the second motor drive unit 37 detected by the second temperature detection unit 40 is higher than a predetermined temperature. The target current command value Ir is output to the second current control unit 36.

[0041] The second current control unit 36 ​​generates a voltage control command value Vref by feedback control such as proportional-integral (PI) control based on the deviation between the fed-back current value Im of the second system coil 14 and the target current command value Ir. For example, the current value Im may be a q-axis current iq and a d-axis current id obtained by converting the phase currents of the second system coil 14 for the respective phases A, B, and C. For example, the voltage control command value Vref may be a voltage command value for each phase A, B, and C. The second current control unit 36 ​​generates a gate signal (PWM signal) for driving a second motor drive unit 37 (e.g., an inverter) based on the generated voltage control command value Vref. That is, the second current control unit 36 ​​generates a PWM signal (control signal) for driving the second motor drive unit 37 based on the target current command value Ir (the command value A2 after limitation).

[0042] With this configuration, when the command value A1 has not been transmitted from the first microcomputer 18 at the time of completion of the initial diagnosis of the second system 2000 (hereinafter also referred to as the "third state"), the second microcomputer 19 enters the third mode and drives the second motor drive unit 37 based on the command value A2 (a substitute value for the second command value) calculated by the second command value generator 33. The second microcomputer 19 also transmits the calculated command value A2 (a substitute value for the second command value) to the first microcomputer 18. Thereafter, when the initial diagnosis of the first system 1000 is completed and the diagnosis completion detector 34 detects the completion of the initial diagnosis of the first system 1000, the second microcomputer 19 switches to the fourth mode, receives the command value A1' (a corrected second command value) transmitted from the first microcomputer 18, and drives the second motor drive unit 37 of the second system 2000 based on the received command value A1'. On the other hand, if the command value A1 has been transmitted from the first microcontroller 18 when the initial diagnosis of the second system 2000 is completed (hereinafter also referred to as the "fourth state"), the second microcontroller 19 switches from the first mode to the second mode, receives the command value A1' (the corrected second command value) transmitted from the first microcontroller 18, and drives the second motor drive unit 37 of the second system 2000 based on the received command value A1'.

[0043] The second motor drive unit 37 is a drive circuit that supplies power to the second system coil 14. The second motor drive unit 37 is driven by a PWM signal output from the second microcomputer 19, and supplies a current (power) to the second system coil 14 of the electric motor 12 such that the deviation between the current value Im of the second system coil 14 of the electric motor 12 and the target current command value Ir becomes "0." That is, the second motor drive unit 37 drives the second motor drive unit 37 based on the PWM signal (a signal based on the limited command value A2). An inverter, for example, can be used as the second motor drive unit 37.

[0044] The second voltage detection unit 38 detects the voltage of the second motor drive unit 37. The second current detection unit 39 detects the phase current of each phase of the second system coil 14. The second temperature detection unit 40 detects the temperature of the electric motor 12 or the second motor drive unit 37. The second rotation angle detection unit 41 detects the rotation angle θm of the electric motor 12. The detected voltage, phase current, temperature, and rotation angle θm are output to the second microcomputer 19.

[0045] The second power supply unit 42 is interposed between the battery 15 and the second microcomputer 19 and second motor drive unit 37, and connects or disconnects the battery 15 to the second microcomputer 19 and second motor drive unit 37 in response to control signals output from the second microcomputer 19, etc. This starts or stops the supply of power from the battery 15 to the second microcomputer 19 and second motor drive unit 37. A relay, for example, can be used as the second power supply unit 42.

[0046] [2. Operation of the Electric Power Steering Device] Next, the operation of the electric power steering device 100 will be described. First, when the driver operates the ignition switch 16 at the start of the vehicle, an initial diagnosis is initiated for each of the first system 1000 and the second system 2000. Here, as shown in FIG. 5 , assume that the initial diagnosis of the first system 1000 is completed first, and the first mode is initiated, in which the initial diagnosis of the second system 2000 is not completed. FIG. 5 is a diagram illustrating the operation of the electric power steering device 100 in the first mode. In this case, since the first mode is active, the cross-fade unit 23 sets the first gain G1 to "1" and the second gain G2 to "0" and outputs the command value A1 as the command value A1' (A1' = A1). As a result, in the first system 1000, control of the current of the first system coil 13 is initiated based on the command value A1 (first command value) sequentially calculated by the first command value generation unit 22. On the other hand, in the second system 2000, because the initial diagnosis of the second system 2000 has not been completed, the second microcomputer 19 cannot perform any operation other than the initial diagnosis, and does not start controlling the current of the second system coil 14. That is, in the first mode, the electric motor 12 is not driven by the second system 2000, and the command value A1 calculated in the first system 1000 is used to control the drive of the electric motor 12 only by the first system 1000 (single-system control). Therefore, compared to a method in which the application of steering assist force is started by both the first system 1000 and the second system 2000 after the initial diagnosis of the second system 2000 has also been completed, the steering assist force is smaller, but the application of the steering assist force can be started earlier.

[0047] As shown in FIG. 6 , after the initial diagnosis of the first system 1000 is completed, the initial diagnosis of the second system 2000 is completed, entering the fourth state and switching from the first mode to the second mode. FIG. 6 illustrates the operation of the electric power steering device 100 in the second mode or the fourth mode. In this case, the first system 1000 continues to control the current of the first system coil 13 based on the command value A1, as performed in the first mode. The second system 2000 starts to control the current of the second system coil 14 based on the command value A1′ (=A1, second command value) sequentially transmitted from the first microcomputer 18. That is, in the second mode, the command value A1 calculated in the first system 1000 is used to control the drive of the electric motor 12 in each of the first system 1000 and the second system 2000 (cooperative control). Therefore, the steering assist force can be increased compared to the first mode. In addition, the generation of abnormal noise and vibration due to interference between the steering assist force applied by the first system 1000 and the steering assist force applied by the second system 2000 can be suppressed.

[0048] On the other hand, after the initial diagnosis is started for each of the first system 1000 and the second system 2000, the third state is assumed to be entered, in which the initial diagnosis for the second system 2000 is completed first and the initial diagnosis for the first system 1000 is not yet completed, as shown in FIG. 7 , and the third mode is initiated. FIG. 7 is a diagram showing the operation of the electric power steering device 100 in the third mode. In this case, since the initial diagnosis for the first system 1000 is not yet completed, the first microcomputer 18 cannot perform any operation other than the initial diagnosis, and control of the current for the first system coil 13 is not initiated. On the other hand, in the second system 2000, control of the current for the second system coil 14 is initiated based on the command value A2 (alternative value) sequentially calculated by the second command value generator 33. That is, in the third mode, the electric motor 12 is not driven by the first system 1000, and the command value A2 calculated by the second system 2000 is used to control the drive of the electric motor 12 only by the second system 2000 (single-system control). Therefore, compared to a method in which the application of steering assist force is started by both the first system 1000 and the second system 2000 after the initial diagnosis of the first system 1000 is also completed, for example, the steering assist force is smaller, but the application of the steering assist force can be started earlier.

[0049] 8, after the initial diagnosis of the second system 2000 is completed, the initial diagnosis of the first system 1000 is completed, the state becomes the second state, and the mode is switched from the third mode to the fourth mode. FIG. 8 is a diagram showing the operation of the electric power steering device 100 in the fourth mode. In this case, since the fourth mode is selected, the cross-fade unit 23 gradually changes the first gain G1 from "0" to "1" and gradually changes the second gain G2 from "1" to "0." As a result, the cross-fade unit 23 receives the command value A2 (specific substitute value A2') transmitted from the first microcomputer 18, corrects the command value A1 from the received specific substitute value A2' so that the command value A1 gradually approaches the command value A1 (first command value, second command value) sequentially calculated by the first command value generation unit 22, and outputs the corrected command value A1 as the command value A1'. Furthermore, the first output limiting unit 24 gradually changes the target current command value Ir from "0" to the command value A1' based on the output command value A1'. As a result, in the first system 1000, control of the current of the first system coil 13 is performed based on the target current command value Ir of the first output limiting unit 24, i.e., the value gradually changing from "0" to the command value A1'. In addition, in the second system 2000, control of the current of the second system coil 14 is started based on the command value A1' transmitted from the first microcomputer 18, i.e., the value gradually changing from the specific substitute value A2' to the command value A1 (second command value).

[0050] Specifically, after the ignition switch 16 is operated, if the initial diagnosis of the first system 1000 is not completed but only the initial diagnosis of the second system 2000 is completed and the third mode is started, as shown in FIG. 7 , the first system 1000 does not start driving the electric motor 12, and the second system 2000 controls the driving of the electric motor 12 using the command value A2 calculated by the second system 2000. After that, when the initial diagnosis of the first system 1000 is completed and the third mode is switched to the fourth mode, as shown in FIG. 8 , immediately after the switch, the first microcomputer 18 outputs and transmits the specific substitute value A2′ (i.e., the command value A2 immediately before the switch) as the command value A1′. Therefore, in the second system 2000, the driving of the electric motor 12 is controlled based on the specific substitute value A2′, and the same control as immediately before the switch is performed. In the first system 1000, the target current command value Ir becomes "0" in the first output limiting unit 24, and therefore, no control is performed on the driving of the electric motor 12. Therefore, the total amount of steering assist force applied by the first system 1000 and the second system 2000 becomes the same as that immediately before the switching.

[0051] Next, the first microcomputer 18 outputs, as the command value A1', a value obtained by slightly approximating the specific substitute value A2' (fixed value) to the command value A1. Therefore, as shown in FIG. 6 , in the second system 2000, the drive of the electric motor 12 is controlled based on the new command value A1' (= A2' + Δ), and the drive of the electric motor 12 is controlled in a manner that is slightly different from that immediately before the switching. In the first system 1000, the absolute value of the target current command value Ir in the first output limiting unit 24 becomes slightly greater than "0," so the drive of the electric motor 12 is controlled slightly. Therefore, the total amount of steering assist force provided by the first system 1000 and the second system 2000 changes slightly from the total amount immediately before the switching. Therefore, when switching to the fourth mode, the total amount of steering assist force gradually changes from the total amount immediately before the switching, and a sudden change is suppressed.

[0052] Furthermore, by repeating the above calculation and control, the command value A1' gradually approaches the command value A1 (latest value) from the specific substitute value A2' (fixed value) and becomes the same numerical value as the command value A1. Furthermore, the first output limiting unit 24 outputs the command value A1' (= A1) as the target current command value Ir. Therefore, the first system 1000 and the second system 2000 each control the drive of the electric motor 12 according to the same target current command value Ir (i.e., the target current command value Ir based on the command value A1). That is, the first system 1000 and the second system 2000 each control the drive of the electric motor 12 using the command value A1 (command value A1') set in the first system 1000 (cooperative control). Therefore, the steering assist force can be increased compared to the third mode. Furthermore, the generation of abnormal noise and vibration due to interference between the steering assist force provided by the first system 1000 and the steering assist force provided by the second system 2000 can be suppressed.

[0053] [3. Modifications] (1) In the first embodiment, the cross-fade unit 23 of the first microcomputer 18 adds the command value A1 and the specific alternative value A2′ at a predetermined ratio G1:G2 to set the command value A1′, but other configurations may also be employed. For example, when switching from the third mode to the fourth mode, as shown in FIG. 9 , the cross-fade unit 23 may calculate a difference value (A1″-A2′) by subtracting the specific alternative value A2′ from the command value A1 (second command value; hereinafter, also referred to as the “acquisition-time command value A1″”) calculated when the specific alternative value A2′ is received, and then gradually reduce the calculated difference value (A1″-A2′) to obtain a reduced value (G3*(A1″-A2′)), which is then subtracted from the command value A1 (second command value) sequentially calculated by the first command value generation unit 22, to obtain a subtracted value, which may be set as the command value A1′ (or, in a broader sense, the “corrected second command value”). The third gain G3 is a numerical value set in the range of 0 to 1. Furthermore, as a method for setting the acquisition command value A1", for example, a method can be adopted in which the command value A2 is received and the command value A1 is calculated before switching to the fourth mode, and the command value A2 and command value A1 at the time of switching are set as the specific substitute value A2' and acquisition command value A1". Here, the numerical value of the third gain G3 is gradually changed from "1" to "0" over time after switching to the fourth mode.

[0054] FIG. 9 is a diagram showing an example of the configuration of the cross-fade unit 23 that performs the above-described operation. For example, when switching from the third mode to the fourth mode, the cross-fade unit 23 shown in FIG. 9 sets the third gain G3 to "1" and gradually changes the third gain G3 from "1" to "0." The output of the third gain G3 (the output of the cross-fade unit 23) gradually changes from "-(A1"-A2')" to "0," gradually bringing the command value A1' closer to the command value A1. This makes it possible to equalize the rate of change of the command value A1' and suppress sudden changes in the command value A1', as shown in FIGS. 10 and 11 . FIG. 10 is a diagram showing the operation of the electronic control unit 200. FIG. 10(a) shows the relationship between the command value and time, and FIG. 10(b) shows a case where the command value A2 is immediately switched to the command value A1. 11A and 11B are diagrams showing the operation of the electronic control unit 200, in which Fig. 11A is a diagram showing the relationship between the target current command value Ir, the upper limit value U1, and time for the first system 1000, and Fig. 11B is a diagram showing the relationship between the target current command value Ir, the upper limit value U2, and time for the second system 2000. In the third mode, as shown in Fig. 7, the first microcomputer 18 is undergoing initial diagnosis, so the operations of the first command value generating unit 22 to the first current control unit 25 are stopped, and the cross-fade unit 23 does not calculate the command value A1'.

[0055] Furthermore, for example, in the first mode and when switching from the first mode to the second mode, the following processing is performed. In the first mode, the second microcomputer 19 has not yet completed the initial diagnosis, so the cross-fade unit 23 cannot receive the command value A2. Therefore, the cross-fade unit 23 determines whether it is possible to receive the command value A2 from the second microcomputer 19. If it determines that it is not possible to receive the command value A2, it determines that the first mode is being used and sets and maintains the third gain G3 at "0." As a result, the third gain G3 (cross-fade unit 23) outputs the command value A1 as the command value A1'. Furthermore, because the third gain G3 is maintained at "0" in the first mode, even when switching from the first mode to the second mode thereafter, the third gain G3 (cross-fade unit 23) outputs the command value A1 as the command value A1'.

[0056] (2) In the first embodiment, the second command value generator 33 calculates the command value A2 when the initial diagnosis of the second system 2000 is completed before the initial diagnosis of the first system 1000. However, other configurations may be employed. For example, as shown in FIG. 12 , the second command value generator 33 may continue to calculate the command value A2 (substitute value) (step S202, see FIG. 7 ) until the diagnosis completion detector 34 detects the completion of the initial diagnosis of the first system 1000 (step S201, “No”), and then stop calculating the command value A2 (step S203, see FIG. 13 ) when the completion of the diagnosis of the first system 1000 is detected (step S201, “Yes”). This configuration may avoid unnecessary calculations and reduce power consumption.

[0057] (3) In the first embodiment, the time required for the command value A1′ to reach the command value A1 from the specific alternative value A2′ after switching to the fourth mode (hereinafter also referred to as the “required arrival time”) is constant. However, other configurations may be employed. For example, as shown in FIG. 14 , the required arrival time may be varied. FIG. 14 illustrates an example in which, when the steering torque Th detected by the first torque sensor 9 is equal to or greater than a predetermined value (step S301 “Yes”), the first microcomputer 18 (cross-fade unit 23) corrects the command value A1 (second command value) so that the required arrival time is shorter than when the steering torque Th is less than the predetermined value, and sets the corrected command value A1′ (broadly speaking, the “corrected second command value”) (step S302). One method for shortening the required time to reach the target value is, for example, to gradually change the first gain G1 from "0" to "1" by increasing the amount of change in the first gain G1 per change, thereby shortening the time it takes for the first gain G1 to change from "0" to "1," and shortening the time it takes for the second gain G2 to change from "1" to "0." As a result, for example, when the driver's steering torque Th is large, the proportion of the specific substitute value A2' can be reduced and the proportion of the command value A1 that reflects the large steering torque Th can be increased, thereby providing an appropriate steering assist force. Similarly, the required time to reach the target value may be shortened by performing a process of increasing the amount of change in the third gain G3 per change (see FIG. 9 ).

[0058] (4) In the first embodiment, the distribution ratio of the current command value Ir0 to the first command value and the second command value generated by the first command value generating unit 22 and the second command value generating unit 33 is set to 50:50. However, this is not limited to this, and other ratios such as 60:40 may also be used.

[0059] 1...Steering wheel, 2...Steering shaft, 3...Reduction gear, 4a, 4b...Universal joint, 5...Pinion rack mechanism, 5a...Pinion, 5b...Rack, 6a, 6b...Tie rod, 7a, 7b...Hub unit, 8L, 8R...Steering wheels, 9...First torque sensor, 10...Second torque sensor, 11...Steering angle sensor, 12...Electric motor, 13...First system coil, 14...Second system coil, 15...Battery, 16...Ignition switch, 18...First microcomputer, 19...Second microcomputer, 20...Memory unit, 21...First initial diagnosis unit, 22...First command value generation unit, 23...Cross-fade unit, 24...First output limiting unit, 25...First current control unit , 26...first motor drive unit, 27...first voltage detection unit, 28...first current detection unit, 29...first temperature detection unit, 30...first rotation angle detection unit, 31...first power supply unit, 32...second initial diagnosis unit, 33...second command value generation unit, 34...diagnosis completion detection unit, 35...second output limiting unit, 36...second current control unit, 37...second motor drive unit, 38...second voltage detection unit, 39...second current detection unit, 40...second temperature detection unit, 41...second rotation angle detection unit, 42...second power supply unit, 43...bus line, 44...first multiplier, 45...second multiplier, 46...adder, 100...electric power steering device, 200...electronic control unit, 1000...first system, 2000...second system

Claims

1. A motor control device that controls the drive of an electric motor having multiple winding sets, comprising: multiple drive circuits that supply power to the winding sets; and multiple control units that generate control signals to drive the drive circuits based on command values; where a group of components including the corresponding winding sets, the drive circuits, and the control units is defined as a first system, and the other group of components is defined as a second system; the first control unit, which is the control unit for the first system, calculates the command value for the first control unit and the command value for the second control unit, which is the control unit for the second system, and drives the drive circuits of the first system based on the calculated first command value, and transmits to the second control unit a second command value, which is the calculated command value for the second control unit; the second control unit receives the second command value transmitted from the first control unit, and drives the drive circuits of the second system based on the received second command value; and the second control unit further comprises: a diagnosis completion detection unit that detects the completion of an initial diagnosis of the first system; and a substitute value calculation unit that calculates a substitute value for the second command value, and when the completion of the initial diagnosis of the second system is not detected by the diagnosis completion detection unit, the drive circuit of the second system is driven based on the substitute value calculated by the substitute value calculation unit, and further, the substitute value is transmitted to the first control unit, and thereafter, when the completion of the initial diagnosis of the first system is detected by the diagnosis completion detection unit, the drive circuit of the second system is driven based on the second command value transmitted from the first control unit, and the first control unita motor control device that, if the substitute value has been transmitted from the second control unit when an initial diagnosis of the first system is completed, receives the substitute value transmitted from the second control unit, corrects the second command value calculated by the first control unit so that the second command value calculated by the first control unit gradually approaches the second command value calculated by the first control unit from a specific substitute value that is the received substitute value, transmits the corrected second command value to the second control unit, corrects the first command value calculated by the first control unit so that the first command value gradually approaches the first command value calculated by the first control unit from the specific substitute value, limits the absolute value of the corrected first command value to be equal to or less than an upper limit value that gradually increases from "0" to a predetermined set value, and drives the drive circuit of the first system based on the first command value after the limit.

2. A motor control device as described in claim 1, wherein the first control unit sequentially transmits to the second control unit an added value obtained by adding the second command value and the specific substitute value, which are sequentially calculated by the first control unit, at a predetermined ratio as the corrected second command value, and changes the predetermined ratio so that the ratio of the second command value becomes "0" at the start of the addition and then gradually increases from "0".

3. A motor control device as described in claim 1, wherein the first control unit calculates a difference value obtained by subtracting the specific alternative value from the second command value calculated when the specific alternative value is received, and then subtracts a gradually reduced value obtained by gradually reducing the calculated difference value from the second command value calculated sequentially by the first control unit, and sequentially transmits the resulting subtracted values ​​to the second control unit as the corrected second command value.

4. The motor control device according to claim 1, wherein the substitute value calculation unit stops calculating the substitute value when the diagnosis completion detection unit detects that the initial diagnosis of the first system has been completed.

5. A motor control device as described in claim 1, comprising a torque sensor that detects the steering torque of a driver, wherein the first control unit corrects the second command value when the steering torque detected by the torque sensor is equal to or greater than a predetermined value so that the time required to reach the second command value from the specific substitute value is shorter than when the steering torque is less than the predetermined value, and sequentially transmits the corrected second command value to the second control unit as the corrected second command value.

6. The motor control device according to claim 1, wherein the first command value and the second command value are the same command value.

7. An electric power steering device comprising: a motor control device according to any one of claims 1 to 6; and an electric motor controlled by said motor control device, said electric motor providing a steering assist force to the steering system of a vehicle.

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