Steer-by-wire device

Abstract

Provided is a steer-by-wire device capable of reducing noise and vibration generated from a rotary electric machine in which two sets of windings are provided in a reaction force motor, and which, when the terminals of one set of windings are short-circuited and the terminals of the other set of windings are supplied with power by means of an inverter, is capable of reducing an imbalance in the currents between the two sets and of reducing an imbalance in an electromagnetic excitation force between the two sets. The steer-by-wire device calculates a short-circuit side d-axis current, calculates a d-axis current command value of the drive-side winding on the basis of the short-circuit side d-axis current, calculates a voltage command value of the drive-side winding on the basis of the d-axis current command value and the q-axis current command value, and performs on / off-control of a power converting circuit for a reaction force on the basis of the voltage command value.

Description

Steer-by-wire system

[0001] The present disclosure relates to a steer-by-wire system.

[0002] Examples of conventional systems include steer-by-wire systems disclosed in Patent Documents 1 to 3. Patent Document 1 discloses a double-inverter three-phase motor in which at least one winding of the steering motor and the reaction motor is duplicated, and each of the duplicated windings is independently driven by two inverters, to achieve a steer-by-wire electric power steering system that ensures safety without using a backup clutch. Patent Document 2 discloses a system in which the inverter and motor are dual-systemized, similar to Patent Document 1, and includes a fault detection means for detecting at least one of short-circuit and open-circuit faults in each switching element. In response to a fault detected by the fault detection means, the current control means sets the switching element connected to the same potential side of each phase of the inverter on the faulty side to the same state as the fault, and continues to control the inverter on the normal side other than the faulty side. Patent Document 3 also discloses a reaction torque motor control means that, when an abnormality detection means detects an abnormal state in which reaction force generation stops, intermittently shorts the terminals of the reaction motor based on the steering wheel operating angle detected by the operating angle detection means, thereby generating a reaction torque.

[0003] International Publication No. 2017 / 115411 Patent No. 5449429 JP 2012-144111 A

[0004] Compared to conventional direct-coupled electric power steering systems, steer-by-wire systems tend to be more expensive because they require more components to ensure safety, making it a challenge to balance safety and cost.

[0005] Patent Documents 1 and 2 require two inverter systems, which increases costs. Patent Document 3 proposes a system that ensures safety by short-circuiting windings to generate braking torque on the shorted side when a fault is detected. If one system is constantly short-circuited, braking torque can be generated constantly by the current flowing when the windings are shorted, without the need for an inverter. This reduces the number of inverters by half, thereby reducing costs. However, when one system is simply short-circuited, current controlled by the inverter flows to the non-shorted side, while current caused by the short circuit between the windings flows to the shorted side. This can result in a large current imbalance between the two systems, which can cause imbalances in electromagnetic excitation forces and noise. Prior art does not consider the imbalances in current and electromagnetic excitation forces that occur when one system is short-circuited.

[0006] Therefore, an object of the present disclosure is to provide a steer-by-wire system that can reduce the noise and vibration generated from a rotating electric machine that can reduce the imbalance in current between the groups and the imbalance in electromagnetic excitation force between the groups when two groups of windings are provided in a reaction motor, the terminals of one group of windings are short-circuited, and the terminals of the other group of windings are supplied with power from an inverter.

[0007] A steer-by-wire system according to the present disclosure comprises: a steering input mechanism having a steering wheel operated by a driver; a reaction motor that applies a steering reaction force to the steering wheel; a reaction power conversion circuit that converts power to be supplied to the reaction motor; a control device that controls the reaction motor via the reaction power conversion circuit; a turning motor that outputs a turning force; and a steering mechanism that turns steered wheels using the turning force of the turning motor, wherein the reaction motor has two sets of multi-phase windings, one set of multi-phase windings being drive-side windings to which power is supplied from the reaction power conversion circuit, and the other set of multi-phase windings being short-circuit-side windings whose winding terminals are short-circuited to each other, The control device calculates a q-axis current command value, calculates a short-circuit side d-axis current that is the d-axis current of the short-circuit side winding based on a detected value of a physical quantity related to the short-circuit side winding, calculates a d-axis current command value for the drive-side winding based on the short-circuit side d-axis current, calculates a voltage command value to be applied to the drive-side winding based on the d-axis current command value and the q-axis current command value, and controls on and off a plurality of switching elements of the reaction force power conversion circuit based on the voltage command value.

[0008] According to the steer-by-wire system of the present disclosure, the d-axis current on the short-circuit side is calculated, and a current command value for the d-axis on the drive side is calculated based on the d-axis current on the short-circuit side. Therefore, the d-axis current on the drive side can be made closer to the d-axis current on the short-circuit side based on the d-axis current on the short-circuit side, and the deviation of the electromagnetic excitation forces between the sets caused by the d-axis currents of the sets can be reduced, thereby reducing noise and vibration.

[0009] 1 is a schematic configuration diagram of a steer-by-wire system according to a first embodiment. FIG. 1 is a schematic configuration diagram of a reaction force power conversion circuit and a reaction force motor according to the first embodiment. FIG. 2 is a diagram showing torque characteristics (brake torque) of a short-circuited winding with respect to rotational angular velocity according to the first embodiment. FIG. 3 is a block diagram of a control device according to the first embodiment. FIG. 4 is a hardware configuration diagram of the control device according to the first embodiment. FIG. 5 is a diagram showing characteristics of a short-circuited d-axis current and a q-axis current with respect to rotational angular velocity according to the first embodiment. FIG. 6 is a schematic configuration diagram of a reaction force power conversion circuit and a reaction force motor when a short-circuited current sensor is provided according to the first embodiment. FIG. 7 is a diagram for explaining changes in the d-axis current command value of the comparative example, the short-circuited d-axis current, and the d-axis current command value of the first embodiment with respect to changes in rotational angular velocity according to the first embodiment. FIG. 8 is a diagram for explaining changes in the d-axis current command value of the comparative example, the short-circuited d-axis current, and the d-axis current command value of the second embodiment with respect to changes in rotational angular velocity according to the second embodiment. FIG. 9 is a diagram for explaining changes in inductance with changes in rotation angle according to the third embodiment. FIG. 10 is a diagram for explaining changes in the resistance value of the short-circuited winding and changes in interlinkage magnetic flux with changes in motor temperature according to the fourth embodiment. 10 is a diagram for explaining on / off control when a switching element on the positive electrode side has a short circuit failure according to embodiment 5. FIG. 11 is a diagram for explaining on / off control when a switching element on the negative electrode side has a short circuit failure according to embodiment 5. FIG. 12 is a schematic configuration diagram of a power conversion circuit for reaction force and a reaction force motor according to embodiment 6.

[0010] 1. Embodiment 1 A steer-by-wire system 1 according to Embodiment 1 will be described with reference to the drawings. The steer-by-wire system 1 is an electric power steering system using a steer-by-wire system. Fig. 1 shows a schematic configuration diagram of the steer-by-wire system 1.

[0011] The steer-by-wire system 1 comprises a steering input mechanism 22 , a reaction motor 7 , a power conversion circuit 13 for reaction, a control device 30 , a turning motor 12 , a power conversion circuit 14 for turning, and a turning mechanism 27 .

[0012] The steering input mechanism 22 includes a steering wheel 4 operated by the driver, a steering shaft 5 connected to the steering wheel 4, and a torque sensor 20 and a steering angle sensor 6 attached to the steering shaft 5. The torque sensor 20 detects the steering torque applied by the driver. The steering angle sensor 6 detects the steering angle of the steering wheel 4 applied by the driver.

[0013] The reaction force motor 7 applies a steering reaction force to the steering wheel 4. The reaction force motor 7 is connected to the steering wheel 4 via the steering shaft 5. A reaction force power conversion circuit 13 converts the power supplied to the reaction force motor 7. The control device 30 controls the reaction force motor 7 via the reaction force power conversion circuit 13.

[0014] Steering mechanism 27 steers the steered wheels using the steering force of steering motor 12. In this embodiment, the steered wheels are left and right wheels 8a, 8b. Tie rods 10a, 10b are connected to knuckle arms 9a, 9b of left and right wheels 8a, 8b, and tie rods 10a, 10b are connected to rack shaft 11. The movement of rack shaft 11 is transmitted to the left and right wheels 8a, 8b via tie rods 10a, 10b and knuckle arms 9a, 9b, thereby steering the left and right wheels 8a, 8b.

[0015] A steering motor 12 is connected to rack shaft 11, and rack shaft 11 is driven by the driving force of steering motor 12. In this example, two steering motors 12a, 12b are attached to the left and right of rack shaft 11. A steering power conversion circuit 14 converts the power supplied to steering motor 12. A control device 30 controls steering motor 12 via steering power conversion circuit 14. Control device 30 calculates a target steering angle of the steered wheels based on the steering angle of the steering wheel detected by steering angle sensor 6, and controls the rotation angle of steering motor 12 so that the steering angle of the steered wheels approaches the target steering angle. Various known methods can be used to control steering motor 12.

[0016] 2 shows a schematic diagram of the reaction force power conversion circuit 13 and the reaction force motor 7. The reaction force motor 7 includes a stator 15 and a rotor 16 disposed radially inside the stator 15. The stator 15 is provided with two sets of multi-phase (three-phase in this example) windings, and the rotor 16 is provided with a permanent magnet 17. Each set of three-phase windings may be star-connected or delta-connected.

[0017] One set of three-phase windings is a driving-side winding to which power is supplied from the reaction force power conversion circuit 13, and the other set of three-phase windings is a short-circuited-side winding whose winding terminals are short-circuited to each other. In this embodiment, the driving-side windings are a first set of three-phase windings Cu1, Cv1, and Cw1, and the winding terminals of each phase of the first set are connected to the reaction force power conversion circuit 13. The short-circuited-side windings are a second set of three-phase windings Cu2, Cv2, and Cw2, and the winding terminals of each phase of the second set are short-circuited to each other by wiring. The reaction force power conversion circuit 13 has an inverter 13a that supplies power to the first set of three-phase windings Cu1, Cv1, and Cw1.

[0018] The rotor 16 is provided with a rotation sensor 2 for detecting the rotation angle of the rotor. An output signal from the rotation sensor 2 is input to the control device 30. The rotation sensor 2 may be any of various sensors, such as a Hall element, a resolver, or an encoder. Alternatively, the rotation sensor 2 may not be provided, and the rotation angle (magnetic pole position) may be estimated based on current information obtained by superimposing harmonic components on a current command value (described later) (a so-called sensorless method).

[0019] 1-2. Reaction Force Power Conversion Circuit 13 The reaction force power conversion circuit 13 includes a set of inverters 13a. The inverter 13a has three sets of series circuits (legs) corresponding to each of the three phases, each set having a positive-side switching element SP connected to the positive side of a DC power supply 13b and a negative-side switching element SN connected to the negative side of the DC power supply 13b connected in series. The junction of the two switching elements in each series circuit is connected to the winding of the corresponding phase. Specifically, in the U1-phase series circuit, the positive-side switching element SPu1 of the U1 phase and the negative-side switching element SNu1 of the U1 phase are connected in series, and the junction of the two switching elements is connected to the U1-phase winding Cu1. In the V1-phase series circuit, the V1-phase positive switching element SPv1 and the V1-phase negative switching element SNv1 are connected in series, and the junction of the two switching elements is connected to the V1-phase winding Cv1. In the W1-phase series circuit, the W1-phase positive switching element SPw1 and the W1-phase negative switching element SNw1 are connected in series, and the junction of the two switching elements is connected to the W1-phase winding Cw1.

[0020] The switching elements may be IGBTs (Insulated Gate Bipolar Transistors) with diodes connected in anti-parallel, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), bipolar transistors with diodes connected in anti-parallel, etc. A gate terminal (not shown) of each switching element is connected to the control device 30 via a gate drive circuit or the like. Each switching element is turned on or off by switching signals GPu to GNw output from the control device 30.

[0021] The DC power supply 13b outputs a DC voltage Vdc to the inverter 13a. The DC power supply 13b may be any device that outputs the DC voltage Vdc, such as a battery, a DC-DC converter, a diode rectifier, or a PWM rectifier. The DC power supply 13b may be provided with a voltage sensor that detects the DC voltage Vdc, and the output signal of the voltage sensor may be input to the control device 30, or the control device 30 may perform control using the detected DC voltage Vdc.

[0022] A current sensor 13c is provided to detect the current flowing through the winding of each phase. The current sensor 13c is a current sensor such as a shunt resistor or a Hall element. The output signal of the current sensor 13c is input to the control device 30.

[0023] The current sensor 13c is provided in the series circuit of the two switching elements of each phase. Alternatively, the current sensor 13c may be provided on the electric wire connecting the series circuit of the two switching elements of each phase and the coil of each phase. Alternatively, the current sensor may be provided on the electric wire connecting the inverter 13a and the DC power supply 13b, and the current in the winding of each phase may be detected by the well-known "bus-shunt system."

[0024] 3 shows an example of the torque characteristics (brake torque) of the short-circuited winding with respect to the rotational angular velocity ωc of the reaction motor 7. By providing the short-circuited winding, even if the inverter 13a fails and the drive-side winding no longer generates a reaction torque, it is possible to generate a reaction torque due to the brake torque of the short-circuited winding. Therefore, without providing two inverters, reaction torque can be generated when one inverter fails, and the reduction in the number of inverters allows for an inexpensive system to be constructed.

[0025] 1-3. Control device 30 Control device 30 controls reaction force motor 7 via reaction force power conversion circuit 13. Control device 30 also controls steering motor 12 via steering power conversion circuit 14. The configuration of control device 30 that controls steering motor 12 and various well-known general motors and control devices are used for steering motor 12, so a description thereof will be omitted. Below, the configuration of control device 30 that controls reaction force motor 7 will be described.

[0026] As shown in Fig. 4, the control device 30 includes functional units such as a current detection unit 31, a rotation detection unit 32, a current command value calculation unit 33, a voltage command value calculation unit 34, and a switching control unit 35. Each function of the control device 30 is realized by a processing circuit included in the control device 30. Specifically, as shown in Fig. 5, the control device 30 includes, as processing circuits, an arithmetic processing device 90 (computer) such as a CPU (Central Processing Unit), a storage device 91 that exchanges data with the arithmetic processing device 90, an input circuit 92 that inputs external signals to the arithmetic processing device 90, and an output circuit 93 that outputs signals from the arithmetic processing device 90 to the outside.

[0027] The arithmetic processing device 90 may be an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), various logic circuits, various signal processing circuits, etc. Furthermore, the arithmetic processing device 90 may be a plurality of devices of the same type or different types, and each process may be shared and executed. The storage device 91 may be a RAM (Random Access Memory) configured to be able to read and write data from the arithmetic processing device 90, a ROM (Read Only Memory) configured to be able to read data from the arithmetic processing device 90, etc. The input circuit 92 is connected to various sensors such as the rotation sensor 2, the current sensor 13c, and the torque sensor 20, and includes an A / D converter and the like that inputs output signals from these sensors to the arithmetic processing device 90. The output circuit 93 is connected to electrical loads such as a gate drive circuit that drives switching elements on and off, and includes a drive circuit and the like that outputs control signals from the arithmetic processing device 90 to these electrical loads.

[0028] 1-3-1. Rotation Detector 32 The rotation detector 32 detects the rotation angle θc of the rotor in electrical angle (magnetic pole position θc of the rotor). In this embodiment, the rotation detector 32 detects the rotation angle θc in electrical angle (magnetic pole position θc) based on the output signal of the rotation sensor 2. The rotation angle θc is the angle (position) of the N pole (magnetic pole) in electrical angle with respect to the U1-phase winding. The rotation detector 32 differentiates the rotation angle θc to calculate the rotation angular velocity ωc. Note that the rotation detector 32 may be configured to estimate the rotation angle (magnetic pole position) without using a rotation sensor (so-called sensorless method) based on current information obtained by superimposing harmonic components on a current command value.

[0029] 1-3-2. Current Detector 31 Based on the output signal of current sensor 13c, current detector 31 detects currents Ius1, Ivs1, and Iws1 flowing through the three-phase windings on the drive side (in this example, the first set of three-phase windings). Based on the output signal of current sensor 13c, current detector 31 detects current Ius1 flowing through the U1-phase winding, current Ivs1 flowing through the V1-phase winding, and current Iws1 flowing through the W1-phase winding. Note that current sensor 13c may be configured to detect two-phase winding currents, and the winding current of the remaining phase may be calculated based on the detected values ​​of the two-phase winding currents. For example, current sensor 13c may detect winding currents Ivs1 and Iws1 of the V1-phase and W1-phase windings, and U1-phase winding current Ius1 may be calculated using the equation Ius1 = -Ivs1 - Iws1.

[0030] 1-3-3. Voltage Command Value Calculation Unit 34 The voltage command value calculation unit 34 calculates a voltage command value based on the d-axis current command value Ido1 and the q-axis current command value Iqo1. In this embodiment, the voltage command value calculation unit 34 calculates three-phase voltage command values ​​Vuo1, Vvo1, and Vwo1 to be applied to the three-phase windings on the drive side based on the d-axis current command value Ido1 and the q-axis current command value Iqo1.

[0031] In this embodiment, the voltage command value calculation unit 34 includes a current coordinate conversion unit 341 , a dq-axis voltage command value calculation unit 342 , and a voltage coordinate conversion unit 343 .

[0032] The current coordinate converter 341 converts the three-phase winding current detection values ​​Ius1, Ivs1, and Iws1 into d-axis and q-axis current detection values ​​Ids1 and Iqs1 based on the rotation angle θc. In this embodiment, the current coordinate converter 341 converts the three-phase winding current detection values ​​Ius1, Ivs1, and Iws1 into d-axis and q-axis current detection values ​​Ids1 and Iqs1 by performing three-phase to two-phase conversion and rotational coordinate conversion based on the rotation angle θc, as shown in the following equations.

[0033] The d-axis is defined in the direction of the magnetic pole (N pole) of the rotor, and the q-axis is defined in the direction 90 degrees ahead of the d-axis in electrical angle. In this example, since coordinate transformation is performed based on the rotation angle θc, the direction of the rotation angle θc becomes the d-axis.

[0034] The dq-axis voltage command value calculation unit 342 performs current feedback control to change the d-axis voltage command value Vdo1 and the q-axis voltage command value Vqo1 using PI control or the like so that the d-axis current detection value Ids1 approaches the d-axis current command value Ido1 and the q-axis current detection value Iqs1 approaches the q-axis current command value Iqo1, as shown in the following equation.

[0035] Here, Kd and Kq are proportional gains, Td and Tq are integral time constants, and s is the Laplace operator.

[0036] Feedforward control may be performed to eliminate interference between the d-axis current and the q-axis current. That is, "-ωc×Lq×Iqs1" may be added to the d-axis voltage command value Vdo1, and "ωc×(Ld×Ids1+ψ)" may be added to the q-axis voltage command value Vqo1. Lq is the q-axis inductance, Ld is the d-axis inductance, and ψ is the flux linkage caused by the magnetomotive force of the magnet linking the windings.

[0037] Alternatively, the dq-axis voltage command value calculation unit 342 may calculate the d-axis voltage command value Vdo1 and the q-axis voltage command value Vqo1 in a feedforward manner using electrical constants based on the d-axis current command value Ido1 and the q-axis current command value Iqo1. In this case, a voltage equation such as Equation (1-4) described later is used.

[0038] The voltage coordinate converter 343 converts the d-axis and q-axis voltage command values ​​Vdo1, Vqo1 into three-phase voltage command values ​​Vuo1, Vvo1, Vwo1 based on the rotation angle θc. In this embodiment, the voltage coordinate converter 343 converts the d-axis and q-axis voltage command values ​​Vdo1, Vqo1 into three-phase voltage command values ​​Vuo1, Vvo1, Vwo1 by performing fixed coordinate conversion and two-phase to three-phase conversion based on the rotation angle θc, as shown in the following equations.

[0039] The voltage coordinate conversion unit 343 may apply known modulation such as two-phase modulation or third-order harmonic superposition to the three-phase voltage command values ​​Vuo1, Vvo1, and Vwo1.

[0040] The switching control unit 35 turns on and off a plurality of switching elements included in the inverter 13a based on voltage command values ​​(in this example, three-phase voltage command values ​​Vuo1, Vvo1, and Vwo1). The switching control unit 35 uses a known carrier comparison PWM or space vector PWM.

[0041] When carrier comparison PWM is used, the switching control unit 35 compares the carrier wave with each of the three-phase voltage command values ​​Vuo1, Vvo1, and Vwo1 and turns on and off multiple switching elements based on the comparison results. The carrier wave is a triangular wave that oscillates with an amplitude of Vdc / 2, half the value of the DC voltage, centered at 0 during the PWM period Tc. For each phase, when the carrier wave is below the voltage command value, the switching control unit 35 turns on the switching signal GP for the positive-side switching element to turn on the positive-side switching element. When the carrier wave exceeds the voltage command value, the switching control unit 35 turns off the switching signal GP for the positive-side switching element to turn off the positive-side switching element. On the other hand, for each phase, when the carrier wave falls below the voltage command value, the switching control unit 35 turns off the switching signal GN of the negative side switching element, turning off the negative side switching element, and when the carrier wave exceeds the voltage command value, it turns on the switching signal GN of the negative side switching element, turning on the negative side switching element.

[0042] In addition, for each phase, a short circuit prevention period (dead time) in which both the positive and negative switching elements are turned off may be provided between the on period of the positive switching element and the on period of the negative switching element.

[0043] When space vector PWM is used, the switching control unit 35 generates a voltage command vector from three-phase voltage command values ​​Vuo1, Vvo1, and Vwo1, determines the output time distribution of seven basic voltage vectors in a PWM cycle based on the voltage command vector, and generates switching signals for turning on and off each switching element in a PWM cycle based on the output time distribution of the seven basic voltage vectors. Note that the seven basic voltage vectors are determined by the states of the positive and negative switching elements of the U1, V1, and W1 phases. For example, a state in which the positive side of the U1 phase is ON and the positive sides of the V1 and W1 phases are OFF is defined as one basic voltage vector. Since there are two states for each of the U1, V1, and W1 phases: one in which the positive side is ON and one in which the negative side is ON, a total of eight voltage vectors can be generated. However, since the eight voltage vectors include a zero vector in which the switching elements of all three phases are in the same state, there are seven types of basic voltage vectors, which are defined as the basic voltage vectors.

[0044] 1-3-5. Current command value calculation unit 33 The current command value calculation unit 33 calculates a current command value. In this embodiment, the current command value calculation unit 33 calculates a d-axis current command value Ido1 and a q-axis current command value Iqo1.

[0045] 1-3-5-1. Calculation of d-Axis Current Command Value Ido1 The current command value calculation unit 33 calculates the short-circuit side d-axis current Id2, which is the d-axis current of the short-circuit side winding, based on the detected values ​​of physical quantities related to the short-circuit side winding (in this example, the second set of three-phase windings). In addition, the current command value calculation unit 33 calculates the short-circuit side q-axis current Iq2, which is the q-axis current of the short-circuit side winding, based on the detected values ​​of physical quantities related to the short-circuit side winding.

[0046] <Calculation of d-axis and q-axis currents on the short-circuit side based on rotational angular velocity ωc> There are several methods for calculating the d-axis and q-axis currents Id2 and Iq2 on the short-circuit side. First, a method for calculating the d-axis and q-axis currents Id2 and Iq2 on the short-circuit side based on the motor rotational angular velocity ωc will be described. The steady-state relationship between current and voltage in the d- and q-axis coordinate system can be expressed by the following equation.

[0047] Here, Vd2 is the d-axis voltage on the short-circuit side, Vq2 is the q-axis voltage on the short-circuit side, Id2 is the d-axis current on the short-circuit side, Iq2 is the q-axis current on the short-circuit side, R2 is the resistance value of the winding on the short-circuit side, Ld is the d-axis inductance, Lq is the q-axis inductance, ψ is the flux linkage that occurs when the magnetomotive force of the magnet links with the winding, and ωc is the rotational angular velocity.

[0048] Next, since the applied voltage to the windings of each phase on the short-circuit side is 0 and the d-axis voltages Vd2 and Vq2 on the short-circuit side are also 0, the d-axis current Id2 and q-axis current Iq2 on the short-circuit side can be expressed by the following equations from equation (1-4): In this embodiment, the motor is a surface permanent magnet type, and Ld = Lq = L.

[0049] The current command value calculation unit 33 calculates the short-circuit side d-axis current Id2 based on the detected rotational angular velocity ωc using the first equation of equation (1-5).The current command value calculation unit 33 calculates the short-circuit side q-axis current Iq2 based on the detected rotational angular velocity ωc using the second equation of equation (1-5).Preset values ​​are used for the electrical constants R2, Ld, Lq, and φ.

[0050] 6 shows the characteristics of the short-circuit side d-axis current Id2 and q-axis current Iq2 with respect to the rotational angular velocity ωc. These correspond to the short-circuit side d-axis current Id2 and q-axis current Iq2 calculated by equation (1-5). The current command value calculation unit 33 may refer to a d-axis current map in which the relationship between the rotational angular velocity ωc and the short-circuit side d-axis current Id2 is preset, and calculate the short-circuit side d-axis current Id2 corresponding to the current rotational angular velocity ωc. The current command value calculation unit 33 may also refer to a q-axis current map in which the relationship between the rotational angular velocity ωc and the short-circuit side q-axis current Iq2 is preset, and calculate the short-circuit side q-axis current Iq2 corresponding to the current rotational angular velocity ωc.

[0051] <Calculation of d-axis and q-axis currents on the short-circuit side based on detected current values ​​on the short-circuit side> Next, a method for calculating the d-axis current Id2 and the q-axis current Iq2 on the short-circuit side based on detected current values ​​in the windings of each phase on the short-circuit side will be described. In this method, as shown in Fig. 7, a short-circuit side current sensor 21 is provided to detect the current in the windings of each phase on the short-circuit side, and the output signal of the short-circuit side current sensor 21 is input to the control device 30. A current sensor such as a shunt resistor or a Hall element is used as the short-circuit side current sensor 21.

[0052] The current command value calculation unit 33 detects currents Ius2, Ivs2, and Iws2 flowing through the three-phase windings on the short-circuit side (in this example, the second set of three-phase windings) based on the short-circuit side current sensor 21. As with the drive side, the short-circuit side current sensor 21 may be configured to detect the winding currents of two phases, and the winding current of the remaining one phase may be calculated based on the detected values ​​of the winding currents of the two phases.

[0053] The current command value calculation unit 33 converts the detected current values ​​Ius2, Ivs2, and Iws2 of the three-phase windings on the short-circuit side into d-axis and q-axis currents Id2 and Iq2 on the short-circuit side by performing a three-to-two phase transformation and a rotational coordinate transformation based on the short-circuit side rotation angle θc2, as shown in the following equation: Here, the short-circuit side rotation angle θc2 is the angle (position) of the N pole (magnetic pole) in electrical angle with respect to the U2-phase winding on the short-circuit side, and is calculated by adding a predetermined phase difference between the pairs to the drive-side rotation angle θc.

[0054] 8 shows the drive-side d-axis current command value Ido1 and the short-circuit-side d-axis current Id2 according to a comparative example, which are set by the Id=0 control and the flux-weakening control with respect to changes in the rotational angular velocity ωc. In the comparative example, when the rotational angular velocity ωc is less than the base angular velocity ωbs, the Id=0 control is performed, and the d-axis current command value Ido1 is set to 0. When the rotational angular velocity ωc is equal to or greater than the base angular velocity ωbs, the flux-weakening control is performed, and the d-axis current command value Ido1 is increased in the negative direction. The base angular velocity ωbs is the upper limit rotational angular velocity at which a corresponding current can be supplied under a predetermined load condition. When the predetermined load condition is no load, the base angular velocity ωbs is equal to the rotational angular velocity at which the induced voltage generated in the drive-side winding reaches the DC voltage Vdc. In flux-weakening control, the d-axis current is increased in the negative direction to weaken the magnetic flux in the d-axis direction, reducing the induced voltage and enabling torque output. Note that in the case of an interior permanent magnet motor, maximum torque current control may be performed instead of Id=0 control, but the d-axis current does not become significantly larger. In maximum torque current control, current command values ​​for the d and q axes are calculated to maximize the generated torque for the same current.

[0055] In the comparative example of FIG. 8 , the absolute value of the short-circuited d-axis current Id2 increases from low rotational speeds, while the absolute value of the drive-side d-axis current command value Ido1 is small at low rotational speeds and increases from high rotational speeds. Therefore, a discrepancy occurs between the d-axis current Id2 of the short-circuited winding and the d-axis current Id1 of the drive-side winding. This discrepancy in the d-axis currents between the groups results in a discrepancy in the radial electromagnetic excitation forces generated by the d-axis currents of each group, resulting in increased noise and vibration. In particular, if the windings of each group are arranged in separate sections that divide the stator 15 into two circumferential sections, the electromagnetic excitation forces vary circumferentially, resulting in a significant increase in noise and vibration. In this case, the circumferential section of the stator 15 is divided into a first circumferential section and a second circumferential section, with the first set of three-phase windings arranged in the first circumferential section and the second set of three-phase windings arranged in the second circumferential section.

[0056] The current command value calculation unit 33 calculates the d-axis current command value Ido1 on the drive side based on the d-axis current Id2 on the short-circuit side. With this configuration, the d-axis current Id1 on the drive side can be made closer to the d-axis current Id2 on the short-circuit side based on the d-axis current Id2 on the short-circuit side, thereby reducing the difference in the electromagnetic excitation forces between the sets caused by the d-axis currents of the sets, and reducing noise and vibration.

[0057] The current command value calculation unit 33 sets the d-axis current command value Ido1 based on the short-circuit side d-axis current Id2 so that the difference between the short-circuit side d-axis current Id2 and the drive-side d-axis current command value Ido1 falls within a predetermined range. The predetermined range is set taking into consideration allowable noise and vibration. The predetermined range may be changed depending on the rotational angular velocity ωc. For example, the current command value calculation unit 33 sets the d-axis current command value Ido1 to a value obtained by multiplying the short-circuit side d-axis current Id2 by a setting coefficient. The setting coefficient is set taking into consideration allowable noise and vibration and may be changed depending on the rotational angular velocity ωc. For example, the setting coefficient may be set within a range of 0.9 to 1.1.

[0058] 8, the current command value calculation unit 33 sets the d-axis current command value Ido1 based on the short-circuit side d-axis current Id2 so that the d-axis current command value Ido1 coincides with the short-circuit side d-axis current Id2 (Ido1=Id2). This reduces to zero the deviation in the electromagnetic excitation forces between the sets caused by the d-axis currents of the sets, thereby further reducing noise and vibration.

[0059] 1-3-5-2. Calculation of q-axis current command value Iqo1 The current command value calculation unit 33 calculates the q-axis current command value Iqo1 based on the output command value.

[0060] In this embodiment, the reaction motor is a surface permanent magnet motor, and the torque of the reaction motor is proportional to the q-axis current. The current command value calculation unit 33 calculates the q-axis current command value Iqo1 based on the output command value and the short-circuit side q-axis current Iq2 so that the total torque of the short-circuit side torque generated by the short-circuit side winding and the drive side torque generated by the drive side winding matches the torque corresponding to the output command value.

[0061] In this embodiment, the output command value is the steering torque Ts. The output command value may be a torque command value. The current command value calculation unit 33 detects the driver's steering torque Ts based on the output signal of the torque sensor 20. The current command value calculation unit 33 sets a total q-axis current command value Iqoall corresponding to the total torque based on the steering torque Ts, as shown in the following equation.

[0062] Here, Ka is a conversion coefficient that may be changed depending on the steering torque Ts, the vehicle running speed, etc. Furthermore, the total q-axis current command value Iqoall may be set based on known compensation control according to the steering situation.

[0063] As shown in the following equation, the current command value calculation unit 33 sets the value obtained by subtracting the short-circuit side q-axis current Iq2 from the total q-axis current command value Iqoall as the q-axis current command value Iqo1.

[0064] Alternatively, if the reaction motor is an interior permanent magnet motor in which Ld and Lq do not match, a change in the d-axis current will change the reluctance torque, even with the same q-axis current, and therefore the torque of the motor. Therefore, the current command value calculation unit 33 may calculate the q-axis current command value Iqo1 based on the output command value, the short-circuit side q-axis current Iq2, and one or both of the d-axis current command value Ido1 and the d-axis current Id2 of the short-circuit side winding so that the total torque of the short-circuit side torque generated by the short-circuit side winding and the drive-side torque generated by the drive-side winding matches the torque corresponding to the output command value.

[0065] According to this configuration, even if the d-axis current command value Ido1 is changed according to the d-axis current Id2, the q-axis current command value Iqo1 is set taking into account the change in drive-side torque due to the change in the d-axis current command value Ido1, thereby suppressing changes in the total torque.

[0066] For example, the current command value calculation unit 33 corrects the q-axis current command value Iqo1 calculated by equation (1-8) based on the d-axis current command value Ido1 or the short-circuit side d-axis current Id2 so as to cancel out the torque change due to the d-axis current.

[0067] Alternatively, the current command value calculation unit 33 calculates the total torque command value Toall based on the steering torque Ts as shown in the following equation: where Kb is a conversion coefficient, which may be changed depending on the steering torque Ts, the vehicle running speed, etc.

[0068] The current command value calculation unit 33 then calculates the short-circuit torque T2 based on the short-circuit q-axis current Iq2 and the short-circuit d-axis current Id2, where P is the number of pole pairs of the reaction motor. The d-axis current command value Ido1 may be used instead of the short-circuit d-axis current Id2.

[0069] Then, the current command value calculation unit 33 calculates the q-axis current command value Iqo1 based on the total torque command value Toall, the short-circuit torque T2, and the d-axis current command value Ido1 using the second equation of equation (1-11) so that the drive-side winding generates torque T1, which is the total torque command value Toall minus the short-circuit torque T2. The short-circuit d-axis current Id2 may be used instead of the d-axis current command value Ido1.

[0070] 2. Second Embodiment A steer-by-wire system 1 according to a second embodiment will be described. Description of the same components as those in the first embodiment will be omitted. The basic configuration of the steer-by-wire system 1 according to this embodiment is the same as that of the first embodiment, but the method of calculating the d-axis current command value Ido1 differs from that of the first embodiment.

[0071] FIG. 9 shows the drive-side d-axis current command value Ido1 and the short-circuit-side d-axis current Id2 in the comparative example, which are set by Id=0 control and flux-weakening control, with respect to changes in rotational angular velocity ωc. In the reaction motor 7 according to the present embodiment, the absolute value of the short-circuit-side d-axis current Id2 is smaller than the d-axis current command value Ido1 in the comparative example shown in FIG. 8 of the first embodiment. As a result, at high rotational speeds, the d-axis current command value Ido1 in the comparative example, which is set by flux-weakening control, is smaller than the short-circuit-side d-axis current Id2 (Ido1<Id2). In this case, if Ido1=Id2 is set as in the first embodiment, the d-axis current is insufficient compared to the d-axis current required for flux-weakening control. This prevents sufficient flux-weakening, resulting in voltage saturation and making it impossible to maintain the drive-side torque. When maximum torque current control is performed in an interior permanent magnet motor, if the d-axis current command value Ido1 set by the maximum torque current control is smaller than the d-axis current Id2 on the short-circuit side, setting Ido1=Id2 will prevent the motor's performance from being fully utilized.

[0072] Therefore, in this embodiment, the current command value calculation unit 33 calculates the d-axis basic current command value Idbso1. In the case of a surface permanent magnet motor, the current command value calculation unit 33 calculates the d-axis basic current command value Idbso1 based on the rotational angular velocity ωc using Id=0 control and flux-weakening control. In the case of an interior permanent magnet motor, the current command value calculation unit 33 calculates the d-axis basic current command value Idbso1 and the q-axis basic current command value Iqbso1 based on the rotational angular velocity ωc and the output command value of the drive-side winding using maximum torque current control and flux-weakening control. For example, the output command value of the drive-side winding uses the drive-side torque T1 calculated by the first equation of equation (1-11) in the first embodiment.

[0073] When the d-axis basic current command value Idbso1 is smaller than the short-circuit side d-axis current Id2, the current command value calculation unit 33 sets the d-axis basic current command value Idbso1 as the d-axis current command value Ido1. On the other hand, when the d-axis basic current command value Idbso1 is equal to or greater than the short-circuit side d-axis current Id2, the current command value calculation unit 33 calculates the d-axis current command value Ido1 based on the short-circuit side d-axis current Id2, as in the first embodiment. For example, the short-circuit side d-axis current Id2 is set as the d-axis current command value Ido1.

[0074] In the case of a surface permanent magnet motor, regardless of whether the d-axis basic current command value Idbso1 is smaller than the short-circuit side d-axis current Id2, the current command value calculation unit 33 calculates the q-axis current command value Iqo1 using the same method as in embodiment 1.

[0075] On the other hand, in the case of an interior permanent magnet motor, if the d-axis basic current command value Idbso1 is smaller than the short-circuited d-axis current Id2, the current command value calculation unit 33 calculates the q-axis basic current command value Iqbso1 as the q-axis current command value Iqo1. If the d-axis basic current command value Idbso1 is equal to or greater than the short-circuited d-axis current Id2, the current command value calculation unit 33 calculates the q-axis current command value Iqo1 in the same manner as in the first embodiment.

[0076] 3. Embodiment 3 A steer-by-wire system 1 according to embodiment 3 will be described. Description of the same components as those in embodiment 1 or 2 will be omitted. The basic configuration of the steer-by-wire system 1 according to this embodiment is the same as that of embodiment 1 or 2, but the method of calculating the d-axis current Id2 and q-axis current Iq2 on the short-circuit side differs from that of embodiment 1 or 2.

[0077] FIG. 10 shows an example of the rotation angle θc of the reaction motor and the variation of inductance L relative to the rotation angle θc. In this example, inductance L changes with a period six times the rotation period. Equation (1-5) in the first embodiment was based on the assumption that inductance L does not change with rotation angle θc. Therefore, for a motor in which inductance L varies as described above, calculation errors occur in the d-axis current Id2 and q-axis current Iq2 on the short-circuit side. Therefore, for a surface permanent magnet motor, the current command value calculation unit 33 calculates inductance L (L = Ld = Lq) based on the rotation angle θc, and then uses the calculated inductance L in equation (1-5) to calculate the d-axis current Id2 and q-axis current Iq2 on the short-circuit side. On the other hand, in the case of a surface permanent magnet motor, the current command value calculation unit 33 calculates the d-axis inductance Ld and the q-axis inductance Lq based on the rotation angle θc, and then calculates the short-circuit side d-axis current Id2 and q-axis current Iq2 using the calculated d-axis and q-axis inductances Ld and Lq in equation (1-5). It is preferable to use an inductance map in which the relationship between the rotation angle θc and the inductance is preset. In this way, the current command value calculation unit 33 calculates the short-circuit side d-axis current Id2 and q-axis current Iq2 based on the detected rotation angular velocity ωc and rotation angle θc.

[0078] 4. Embodiment 4 A steer-by-wire system 1 according to embodiment 4 will be described. Description of the same components as those in embodiment 1, 2 or 3 will be omitted. The basic configuration of the steer-by-wire system 1 according to this embodiment is the same as that of embodiment 1, 2 or 3, but differs from embodiment 1, 2 or 3 in the method of calculating the d-axis current Id2 and q-axis current Iq2 on the short-circuit side.

[0079] FIG. 11 shows an example of the change in resistance R2 and flux linkage φ of the short-circuited winding with respect to changes in motor temperature Tmp. As shown in FIG. 11, the resistance R2 and flux linkage φ change with changes in motor temperature Tmp. Equation (1-5) in the first embodiment was based on the assumption that the resistance R2 and flux linkage φ do not change with motor temperature Tmp. Therefore, when the resistance R2 and flux linkage φ fluctuate as described above, calculation errors occur in the d-axis current Id2 and q-axis current Iq2 on the short-circuited side.

[0080] The current command value calculation unit 33 calculates the resistance value R2 of the winding on the short-circuited side and the interlinkage magnetic flux φ based on the temperature Tmp of the reaction force motor 7. For example, the following equations are used.

[0081] Here, RT0 is the resistance value when the temperature is T0° C., αT0 is the resistance temperature coefficient when the temperature is T0° C., φT0 is the flux linkage when the temperature is T0° C., βT0 is the flux temperature coefficient when the temperature is T0° C., and Tmp is the temperature of the reaction motor. Note that instead of equation (4-1), a resistance value map in which the relationship between the reaction motor temperature Tmp and the resistance value R2 of the short-circuited winding is preset, and a flux map in which the relationship between the reaction motor temperature Tmp and the flux linkage φ is preset may be used.

[0082] The current command value calculation unit 33 may detect the temperature Tmp of the reaction motor based on the output signal of a temperature sensor provided in the reaction motor 7, or may estimate the temperature Tmp of the reaction motor based on the operating state of the reaction motor (e.g., current, voltage, rotational angular velocity, torque), etc.

[0083] Then, the current command value calculation unit 33 calculates the short-circuit side d-axis current Id2 and q-axis current Iq2 using the calculated resistance value R2 and flux linkage φ of the short-circuit side winding in equation (1-5). That is, the current command value calculation unit 33 calculates the short-circuit side d-axis current Id2 and q-axis current Iq2 based on the detected rotational angular velocity ωc and the detected or calculated value of the reaction motor temperature Tmp. Note that the inductance calculated based on the rotation angle θc described in embodiment 3 may also be used.

[0084] 5. Fifth Embodiment A steer-by-wire system 1 according to a fifth embodiment will be described. Description of components similar to those of the first, second, third, or fourth embodiment will be omitted. The basic configuration of the steer-by-wire system 1 according to this embodiment is similar to that of the first, second, third, or fourth embodiment, but control in the event of a short-circuit failure of a switching element is further added.

[0085] In this embodiment, as shown in FIG. 12 , when the switching control unit 35 detects a short-circuit fault in the switch element SP on the positive electrode side of any phase of the inverter 13 a, it turns on the switch elements SP on the positive electrode side of all other phases and turns off the switch elements SN on the negative electrode side of all other phases.

[0086] Furthermore, as shown in FIG. 13, when the switching control unit 35 detects a short-circuit fault in the switch element SN on the negative electrode side of any phase of the inverter 13a, it turns on the switch elements SN on the negative electrode sides of all other phases and turns off the switch elements SP on the positive electrode sides of all other phases.

[0087] For example, a short circuit fault in each switching element may be detected by a known determination method based on the on / off control pattern of each switching element and the detected current value of each phase. Alternatively, the drive circuit of each switching element may have a function to detect a short circuit fault.

[0088] With this configuration, even if a short-circuit failure of a switching element prevents the drive-side winding from generating torque normally, the terminals of the drive-side three-phase winding are short-circuited to each other via the switch element SP on the positive or negative side of the three phases that is turned on, allowing the drive-side three-phase winding to generate braking torque.

[0089] 6. Sixth Embodiment A steer-by-wire system 1 according to a sixth embodiment will now be described. Descriptions of components similar to those of the first, second, third, fourth, or fifth embodiment will be omitted. The basic configuration of the steer-by-wire system 1 according to this embodiment is similar to that of the first, second, third, fourth, or fifth embodiment, except that each set of multi-phase windings is connected to each set of reaction force power conversion circuit. Figure 14 shows a configuration diagram of the reaction force power conversion circuit 13 and reaction force motor 7 according to this embodiment.

[0090] The windings of the multiple phases of each group are connected to the corresponding reaction force power conversion circuit 13. That is, the three-phase windings Cu1, Cv1, and Cw1 of the first group are connected to the first inverter 13a1, and the three-phase windings Cu2, Cv2, and Cw2 of the second group are connected to the second inverter 13a2. The first DC power supply 13b1 is connected to the first inverter 13a1, and the second DC power supply 13b2 is connected to the second inverter 13a2. The first DC power supply 13b1 and the second DC power supply 13b2 may be combined into a single DC power supply. The configuration of each inverter is similar to that of the inverter 13a of the first embodiment, and therefore description thereof will be omitted.

[0091] Control device 30 controls the energization state of each group of windings via each group of inverters. Control device 30 includes a current command value calculation unit 33 for each group, a voltage command value calculation unit 34 for each group, and a switching control unit 35 for each group. Voltage command value calculation unit 34 and switching control unit 35 for each group are similar to voltage command value calculation unit 34 and switching control unit 35 in the first embodiment, and therefore description thereof will be omitted.

[0092] If a short circuit fault in the switching element of each inverter group is not detected, the current command value calculation unit 33 for each group calculates the d-axis current command value Ido and the q-axis current command value Iqo for each group based on the output command value and rotational angular velocity ωc of each group. In the case of a surface permanent magnet motor, Id=0 control and flux-weakening control are executed, and in the case of an interior permanent magnet motor, maximum torque current control and flux-weakening control are executed. The total output command value is distributed to calculate the output command value for each group.

[0093] On the other hand, if a short-circuit fault is detected in a switching element of an inverter in each group, the following control is performed: In a fault-detected group in which a short-circuit fault in a switching element is detected, all-phase short-circuit control similar to that in embodiment 5 is performed and set to the winding on the short-circuited side. On the other hand, in a fault-undetected group in which a short-circuit fault in a switching element is not detected, calculation processing of d-axis current command values ​​and q-axis current command values ​​for the drive-side winding is performed similar to that in embodiments 1 to 4.

[0094] That is, the control device 30 (the switching control unit 35 of the fault detection group) turns on all switching elements on the positive or negative side of the inverter in the fault detection group in which a short-circuit fault has been detected, and turns off all switching elements on the positive or negative side in which a short-circuit fault has not been detected, and sets the three-phase winding of the fault detection group to the winding on the short-circuit side.

[0095] On the other hand, the control device 30 (current command value calculation unit 33 for the fault undetected group) sets the three-phase windings of the fault undetected group as drive-side windings, calculates a q-axis current command value Iqo1, calculates a d-axis current Id2 for the short-circuited side based on detected values ​​of physical quantities related to the short-circuited side winding, calculates a d-axis current command value Ido1 for the drive-side winding based on the short-circuited side d-axis current Id2, calculates a voltage command value based on the d-axis current command value Ido1 and the q-axis current command value Iqo1, and controls on / off the multiple switching elements of the reaction force power conversion circuit of the fault undetected group based on the voltage command value. The method of calculating the d-axis current command value Ido1 and the q-axis current command value Iqo1 for the drive-side windings set in the windings of the fault undetected group is the same as in embodiments 1 to 4, so a description thereof will be omitted.

[0096] If a short circuit fault is detected in the switching elements of both inverters, all-phase short circuit control similar to that of embodiment 5 is performed on both inverters, generating a brake torque in the windings of both inverters.

[0097] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this disclosure specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0098] 1: steer-by-wire system, 7: reaction motor, 12: turning motor, 13: power conversion circuit for reaction force, 22: steering input mechanism, 27: turning mechanism, 30: control device, Id2: d-axis current on short circuit side, Iq2: q-axis current on short circuit side, Idbso1: basic current command value of d-axis, Ido1: current command value of d-axis, Iqo1: current command value of q-axis, Iqbso1: basic current command value, θc: rotation angle, ωc: rotation angular velocity

Claims

1. A steering input mechanism having a steering wheel operated by a driver, a reaction motor that applies a steering reaction force to the steering wheel, a reaction power conversion circuit that converts the power supplied to the reaction motor, a control device that controls the reaction motor via the reaction power conversion circuit, a turning motor that outputs a turning force, and a steering mechanism that turns steered wheels using the turning force of the turning motor, wherein the reaction motor has two sets of multi-phase windings, one set of multi-phase windings being drive-side windings to which power is supplied from the reaction power conversion circuit, and the other set of multi-phase windings being short-circuit-side windings whose winding terminals are short-circuited to each other, the control device calculates a q-axis current command value, calculates a short-circuit side d-axis current that is the d-axis current of the short-circuit side winding based on a detected value of a physical quantity related to the short-circuit side winding, calculates a d-axis current command value for the drive-side winding based on the short-circuit side d-axis current, calculates a voltage command value to be applied to the drive-side winding based on the d-axis current command value and the q-axis current command value, and controls on and off a plurality of switching elements included in the reaction force power conversion circuit based on the voltage command value.

2. A steer-by-wire system as described in claim 1, wherein the control device sets the d-axis current command value based on the d-axis current on the short-circuit side so that the difference between the d-axis current on the short-circuit side and the d-axis current command value is within a predetermined range.

3. A steer-by-wire system as described in claim 1, wherein the control device sets the d-axis current command value based on the d-axis current on the short-circuit side so that the d-axis current command value coincides with the d-axis current on the short-circuit side.

4. A steer-by-wire system according to any one of claims 1 to 3, wherein the control device calculates the d-axis current on the short-circuit side based on the detected value of the rotational speed of the reaction motor or the detected value of the current in the winding on the short-circuit side as the detected value of the physical quantity.

5. A steer-by-wire system according to any one of claims 1 to 4, wherein the control device calculates the d-axis current command value based on the detected values ​​of the rotational speed and rotational angle of the reaction motor as the detected values ​​of the physical quantities.

6. A steer-by-wire system according to any one of claims 1 to 5, wherein the control device calculates the d-axis current command value based on the detected value of the rotational speed of the reaction motor and the detected or calculated value of the temperature of the reaction motor as the detected values ​​of the physical quantities.

7. A steer-by-wire system according to any one of claims 1 to 6, wherein the control device calculates a basic current command value for the d axis, and if the basic current command value for the d axis is smaller than the d axis current on the short-circuit side, sets the basic current command value for the d axis as the current command value for the d axis.

8. A steer-by-wire system as claimed in any one of claims 1 to 7, wherein the control device calculates a short-circuit side q-axis current, which is the q-axis current of the short-circuit side winding, based on a detected value of a physical quantity related to the short-circuit side winding, and calculates the q-axis current command value based on the output command value of the reaction motor and the short-circuit side q-axis current so that the total torque of the short-circuit side torque generated by the short-circuit side winding and the drive side torque generated by the drive side winding matches the torque corresponding to the output command value of the reaction motor.

9. A steer-by-wire system as claimed in any one of claims 1 to 7, wherein the control device calculates a short-circuit side q-axis current, which is the q-axis current of the short-circuit side winding, based on a detected value of a physical quantity related to the short-circuit side winding, and calculates the q-axis current command value based on the output command value of the reaction motor, the short-circuit side q-axis current, and one or both of the d-axis current command value and the d-axis current of the short-circuit side winding, so that the total torque of the short-circuit side torque generated by the short-circuit side winding and the drive-side torque generated by the drive-side winding matches the torque corresponding to the output command value of the reaction motor.

10. A steer-by-wire system according to any one of claims 1 to 9, wherein each set of multi-phase windings is arranged in each of two divided sections that divide the stator of the reaction motor in the circumferential direction.

11. A steer-by-wire system according to any one of claims 1 to 10, wherein, when the control device detects a short-circuit fault in the positive electrode side switch element of any phase of the reaction force power conversion circuit, it turns on the positive electrode side switch elements of all other phases and turns off the negative electrode side switch elements of all phases, and when the control device detects a short-circuit fault in the negative electrode side switch element of any phase of the reaction force power conversion circuit, it turns on the negative electrode side switch elements of all other phases and turns off the positive electrode side switch elements of all phases.

12. The windings of the multiple phases of each group are connected to the power conversion circuit for the reaction force of each group, and the control device turns on all switching elements on the positive side or negative side in which a short circuit fault has been detected, and turns off all switching elements on the positive side or negative side in which a short circuit fault has not been detected, for the power conversion circuit for the reaction force of the fault detection group in which a short circuit fault has been detected in a switching element, and sets the windings of the multiple phases of the fault detection group to the winding on the short circuit side, 11. The steer-by-wire system according to claim 1, wherein a plurality of phase windings of a fault undetected group in which a short-circuit fault has not been detected are set as the drive-side windings, the q-axis current command value is calculated, a d-axis current of the short-circuited side is calculated based on a detected value of a physical quantity related to the short-circuited side winding, the d-axis current command value of the drive-side winding is calculated based on the d-axis current of the short-circuited side, the voltage command value is calculated based on the d-axis current command value and the q-axis current command value, and a plurality of switching elements of the reaction force power conversion circuit of the fault undetected group are on / off controlled based on the voltage command value.

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