STEERING CONTROL DEVICE

Abstract

A steering control device for controlling an electric power steering device (8) having an electric rotary machine (80), the steering control device comprising: a control circuit (120, 220) arranged to control the electric rotary machine (80); and a control unit (130, 230) arranged to control a drive of the electric rotary machine (80) by generating a control signal relating to a drive of the drive circuit (120, 220) and controlling a current flowing in the electric rotary machine (80), wherein the control unit (130, 230) is designed to switch a control mode including a manual steering mode and an automatic steering mode and to perform a different current control according to the control mode, the manual steering mode is used to control the electric rotary machine (80) in accordance with a manual steering operation of a steering element (91), and the automatic steering mode is used to control the electric rotary machine (80) independently of the manual steering of the steering element (91); and the control unit (130, 230) includes a current limiting unit (135, 235) configured to set a current limit value for limiting the current flowing in the electric rotary machine (80); characterized in that the current limiting unit (135, 235) is designed to form the current limit value differently as a current controller according to the control mode; the electric rotary machine (80) has a plurality of winding sets (180, 280); the drive circuit (120, 220) and the control unit (130, 230) are arranged in correspondence to a respective winding set (180, 280) to form a system (L1, L2); the control unit (130, 230) includes an individual current limit calculation unit (131, 231) configured to calculate an individual current limit as a value relating to a current limit of one system, obtain the individual current limit of another system, and switch between a common current limit state for setting the same current limit as that of the other system and an independent current limit state for setting an independent current limit independent of that of the other system; and the control unit (130, 230) forms a common verification threshold provided to switch between the common current limit state and the independent current limit state differently for the manual steering mode and the automatic steering mode.

Description

[0001] The present invention relates to a steering control device.

[0002] An electric power steering (EPS) device is known that is capable of switching its operating mode between automatic steering control and manual steering control. For example, in JP 6 004 145 B1, an operating mode is smoothly switched by gradually changing a control torque for torque control and a command value for position / speed control.

[0003] However, it is not possible to properly perform torque control and position / speed control by simply changing the command.

[0004] EP 3 517 402 B1 discloses a steering system comprising: a reaction drive device that applies a reaction force to a steering element, a steering operation drive device that rotates steered wheels, a movement drive device that moves the steering element between an operating position and a retracted position, a mode switching circuit that switches between a manual driving mode and an automatic driving mode based on an input to a mode input device, a movement control circuit that moves the steering element to the operating position when switching to the manual driving mode and moves the steering element to the retracted position when switching to the automatic driving mode, a reaction control circuit,which controls the reaction drive device in the manual driving mode based on steering information of the steering element and steering operation information of the steering operation drive device, and an operation restriction circuit which restricts the operation of the steering element caused by the reaction drive device in the automatic driving mode.

[0005] EP 2 977 296 B1 discloses an electric power steering system comprising: a steering angle control section that calculates a motor current command value, and a switching section that receives the motor current command value for switching, wherein the steering angle control section comprises a feedback control section that generates a feedback control current command value, a compensation section that generates a compensation current command value; and an output section that generates the motor current command value from the feedback control current command value and the compensation current command value, wherein the switching section is switched depending on a switching command for an automatic steering mode or a manual steering mode, and wherein a motor is driven based on the motor current command value in the automatic steering mode.

[0006] DE 10 2016 223 929 A1 discloses a vehicle guidance system comprising a hydraulic steering cylinder for controlling a steering angle of a steerable wheel of a vehicle. A hydraulic steering valve controls a flow of hydraulic fluid to the hydraulic steering cylinder. A stepper motor moves a shaft coupled to the hydraulic steering valve according to a control signal from a vehicle guidance controller. A position sensor of the stepper motor measures the movement of the shaft. A steering angle estimator estimates the steering angle based on measurements from the position sensor. A positioning receiver provides position data and heading data. A vehicle guidance controller provides the control signal based on the estimated steering angle, the position data, and the heading data.

[0007] DE 10 2018 102 103 A1 discloses a method for operating an occupant protection device of a steer-by-wire steering system. The steer-by-wire steering system comprises a steering wheel and an adjustable steering column connected to the steering wheel, which is adjustable between a retracted position and an extended position by means of an adjustment mechanism. The steer-by-wire steering system has a feedback actuator that can be acted upon by a driver via the steering wheel with a driver's command for a steering angle and outputs a feedback signal to the steering wheel in response to the driver's command and a driving state of the motor vehicle. The method comprises: detecting an accident, detecting a hands-off situation or a hands-on situation if a hands-off situation has been detected, moving the steering column into an accident position by means of the adjustment mechanism, and deploying a steering wheel airbag during or after the adjustment process.

[0008] DE 10 2016 216 797 A1 discloses a steering reaction force control device for a vehicle, including a driving assistance device that controls an electric power steering device via a control device such that a steering angle of steered wheels reaches a target steering angle. When the driving assistance device operates, the control device calculates a target steering return torque based on a corrected steering angle corrected by a target steering angle. When the magnitude of the corrected steering angle is below a reference value, the target steering return torque is calculated such that the magnitude of the target steering return torque becomes larger when the driving assistance device operates compared to when the driving assistance device does not operate.

[0009] DE 11 2014 006 797 T5 discloses a steering control device having a manual steering mode in which a traveling direction of a vehicle is controlled according to a steering wheel state variable indicating an operation amount of a steering wheel, and a forced automatic steering mode in which the traveling direction is automatically controlled, and which controls a steering wheel state variable to be applied to the steering wheel according to the manual steering mode or the forced automatic steering mode, the steering control device comprising: steering mode selecting means for switching between the manual steering mode and the forced automatic steering mode;and a steering wheel control amount calculating means for calculating the steering wheel control amount based on information indicating a driving state when the manual steering mode is selected, and calculating the steering wheel control amount having an amount different from the steering wheel control amount calculated in the manual steering mode based on the information indicating the driving state when the forced automatic steering mode is selected;

[0010] The present invention addresses the above-mentioned problem, and its object is to provide a steering control device capable of appropriately controlling an electric rotary machine according to a control mode. This object is achieved by a steering control device having the features of claim 1. Advantageous further developments emerge from the subclaims. Fig. 1 is a schematic diagram showing a steering system including an electric power steering apparatus according to a first embodiment; Fig. 2 is a schematic diagram showing motor winding sets according to the first embodiment; Fig. 3 is a timing chart showing a power supply phase difference according to the first embodiment; Fig. 4 is a cross-sectional view showing a driving device according to the first embodiment; Fig. 5 is a cross-sectional view taken along the line VV in Fig. 4; Fig. 6 is a block diagram showing an EPS-ECU according to the first embodiment; Fig. 7 is a block diagram showing a control unit according to the first embodiment; Fig. 8 is a block diagram for explaining current feedback control performed by summing and differing according to the first embodiment; Fig. 9 is a block diagram for explaining an independent feedback control according to the first embodiment; Fig. 10 is a flowchart for explaining control mode switching control processing according to the first embodiment; Fig. 11 is a flowchart for explaining angle calculation processing according to the first embodiment; Fig. 12 is a diagram showing a current limit value according to the first embodiment; Fig. 13 is a timing chart showing a current limit value according to the first embodiment; Fig. 14 is a timing chart showing a current limit value according to the first embodiment; Fig. 15 is a timing chart showing a current limit value according to the first embodiment; Fig. 16 is a timing chart showing a current limit value according to the first embodiment; Fig. 17 is a timing chart showing a current limit value according to a second embodiment; Fig. 18 is a timing chart showing a current limit value according to the second embodiment; Fig. 19 is a timing chart showing a current limit value according to a third embodiment; Fig. 20 is a timing chart showing a current limit value according to the third embodiment; Fig. 21 is a block diagram explaining a fully independent feedback control according to a fourth embodiment; Fig. 22 is a flowchart for explaining current limit processing according to a fifth embodiment; Fig. 23 is a timing chart showing a current limit value according to the fifth embodiment; Fig. 24 is a timing chart showing a current limit value according to the fifth embodiment; Fig. 25 is a block diagram showing a control unit according to a sixth embodiment; Fig. 26 is a flowchart for explaining current limiting processing according to the sixth embodiment; and Fig. 27 is a timing chart showing a current limit value according to the sixth embodiment.

[0011] Hereinafter, a steering control device according to the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, substantially the same structural components are denoted by the same reference numerals to simplify description. (First embodiment)

[0012] A first embodiment is shown in the Fig. 1 to 16. As shown in Fig. 1, an EPS-ECU 10 (EPS: Electric Power Steering; ECU: Electronic Control Unit) is arranged as a steering control device according to the present embodiment, and is used for an electric power steering device 8 that assists a steering operation of a vehicle with a motor 80 arranged as an electric rotary machine. Hereinafter, the EPS-ECU 10 will be simply referred to as ECU 10. Fig. 1 shows an overall configuration of a steering system 90 including the electric power steering device 8. The steering system 90 includes a steering wheel 91, a steering shaft 92, a pinion gear 96, a rack shaft 97, road wheels 98, and the electric power steering device 8.

[0013] The steering wheel 91 is connected to the steering shaft 92. A torque sensor 94 is arranged on a portion of the steering shaft 92 to detect a steering torque Ts. The pinion gear 96 is arranged at the end of the steering shaft 92. The pinion gear 96 meshes with the rack shaft 97. The pair of road wheels 98 are coupled to respective two ends of the rack shaft 97 via, for example, tie rods.

[0014] In a manual steering mode, the steering shaft 92, which is connected to the steering wheel 91, rotates when a driver of the vehicle turns the steering wheel 91. The rotational movement of the steering shaft 92 is converted by the pinion 96 into a linear movement of the rack shaft 97. The two road wheels 98 are steered at an angle corresponding to a displacement amount of the rack shaft 97. In an automatic steering mode, the steering amount of the road wheels 98 is controllable by a driving force of the motor 80, independently of a manual operation of the steering wheel 91 by the driver. The automatic steering mode is also referred to as the automatic driving mode.

[0015] The electric power steering device 8 includes a driver 40 including the motor 80 and the ECU 10, and a reduction gear 89 as a power transmission mechanism that reduces the rotation of the motor 80 and transmits the motor rotation to the steering shaft 92. The electric power steering device 8 is of the column-assist type. Alternatively, it may be of the rack-assist type, which transmits the rotation of the motor 80 to the rack shaft 97. The steering shaft 92 corresponds to a driven object.

[0016] The motor 80 outputs all or part of the assist torque required for steering operation. The motor 80 is powered by electrical energy supplied by two batteries 191 and 291 (see Fig. 6), which are DC power sources, to rotate the reduction gear 89 in the forward and reverse directions. The motor 80 is a brushless three-phase motor and has a rotor 860 and a stator 840 (see Fig. 4).

[0017] As it is in Fig. 2, the motor 80 includes a first motor winding set 180 and a second motor winding set 280. The first motor winding set 180 includes a U1 winding 181, a V1 winding 182, and a W1 winding 183. The second winding set 280 includes a U2 winding 281, a V2 winding 282, and a W2 winding 283. In Fig. 2 and Fig. 6, the first motor winding set 180 is indicated as the first motor winding set, and the second motor winding set 280 is indicated as the second motor winding set.

[0018] The first motor winding set 180 and the second motor winding set 280 have the same electrical properties, as is known. These motor winding sets 180 and 280 are wound around a common stator 840 in a cancellation winding form, shifted by an electrical angle of 30 degrees relative to each other. For this reason, the motor winding sets 180 and 280 are controlled such that phase currents having a phase difference φ of 30 degrees are supplied, as shown in Fig. 3 is shown. In Fig. 3, a U-phase voltage Vu1 of the first motor winding set 180 and a U-phase voltage Vu2 of the second motor winding set 280 are shown as examples. By optimizing the power supply phase difference (excitation phase difference), the output torque is improved. Furthermore, by setting the power supply phase difference to the electrical angle of 30 degrees, it is possible to reduce sixth-order torque ripple (see equation (i)). sin6(ωt)+sin6(ωt+30)=0

[0019] Because the current through the power supply is averaged with the phase difference, it is possible to maximize the cancellation of noise and vibration. Since heat generation is also averaged, it is possible to reduce the temperature-dependent error between systems, such as the detection values of the respective sensors and the torque, and to average the magnitude of the current that can be supplied. Noise and vibration are abbreviated as NV in the following description.

[0020] Hereinafter, a combination of a first inverter circuit 120 and a first control unit 30 and the like relating to the drive control for the first motor winding set 180 is referred to as a first system L1, and a combination of a second inverter circuit 220 and a second control unit 230 and the like relating to the drive control of the second motor winding set 280 is referred to as a second system L2. In the present embodiment, the inverter circuits 120 and 220 correspond to drive circuits. The configuration relating to the first system L1 is basically denoted by reference numerals having 100-s numerals, and the configuration relating to the second system L2 is basically denoted by reference numerals having 200-s numerals.In the first system L1 and the second system L2, the same or similar configurations are indicated with reference symbols that have the same reference numbers in at least the last two digits.

[0021] The configuration of the control device 40 is described with reference to the Fig. 4 and Fig. 5. In the drive device 40 of the present embodiment, the ECU 10 is integrally arranged on one side in the axial direction of the motor 80 according to an engine electronics integrated type. Alternatively, the motor 80 and the ECU 10 may be arranged separately without integration. The ECU 10 is arranged coaxially with an axis Ax of the shaft 870 opposite the output shaft of the motor 80.

[0022] Alternatively, the ECU 10 may be arranged on the output shaft side of the motor 80. By using the machine-electronics integrated type, it is possible to efficiently arrange the ECU 10 and the motor 80 in a vehicle having limited mounting space.

[0023] The motor 80 includes a stator 840, a rotor 860, and a housing 830 in which the stator 840 and the rotor 860 are housed. The stator 840 is fixed to the housing 830, and the motor winding sets 180 and 280 are wound therearound. The rotor 860 is disposed radially within the stator 840 and rotatable with respect to the stator 840.

[0024] The shaft 870 is fixedly mounted in the rotor 860 so that it rotates integrally with the rotor 860. The shaft 870 is rotatably supported by the housing 830 through bearings 835 and 836. The axial end portion of the shaft 870 on the ECU 10 side protrudes from the housing 830 toward the ECU 10 side. A magnet 875 is disposed at the axial end of the shaft 870 on the ECU 10 side.

[0025] The housing 830 includes a bottomed cylindrical container 834 having a rear end frame 837 and a front end frame 838 disposed on the open side of the container 834. The container 834 and the front end frame 838 are fastened to each other by screws or the like. Lead wire insertion holes 839 are formed in the rear end frame 837. Lead wires 185 and 285 connected to respective phases of the motor winding sets 180 and 280 are inserted through the lead wire insertion holes 839. The lead wires 185 and 285 are led out from the lead wire insertion holes 839 to the ECU 10 side and connected to a circuit board 470.

[0026] The ECU 10 includes a cover 460, a heat sink 465 fixed to the cover 460, the circuit board 470 fixed to the heat sink 465, and other electronic components mounted on the circuit board 470.

[0027] The cover 460 serves to protect the electronic components from external impacts and to prevent dust and water from entering the ECU 10. In the cover 460, a cover main body 461 and a connector member 462 are integrally formed. The connector member 462 may alternatively be separated from the cover main body 461. Terminals 463 of the connector member 462 are connected to the circuit board 470 via wires (not shown) or the like. The number of connectors and the number of terminals may vary according to the number of signals and the like. The connector member 462 is arranged at the end portion in the axial direction of the drive device 40 and is open on the side facing away from the motor 80. The connector member 462 includes each connector described later.

[0028] The circuit board 470 is, for example, a printed circuit board and is arranged facing the rear end frame 837. On the circuit board 470, the electronic components of the first and second systems are mounted independently for each system, so that the two systems are arranged in a completely redundant manner. In the present embodiment, the electronic components are mounted on a single circuit substrate 420, but the electronic components may alternatively be mounted on multiple circuit substrates.

[0029] Of the two main surfaces of the circuit board 470, one surface on the side of the motor 80 is referred to as the motor-side surface 471, and the other surface opposite to the motor 80 is referred to as the cover-side surface 472. As shown in Fig. As shown in Fig. 5, switching elements 121 constituting the inverter circuit 120, switching elements 221 constituting the inverter circuit 220, rotation angle sensors 126, 226, associated ICs 159, 259, and the like are mounted on the motor-side surface 471. The rotation angle sensors 126 and 226 are mounted at positions facing the magnet 875 to be able to detect a change in the magnetic field caused by the rotation of the magnet 875.

[0030] On the cover-side surface 472, capacitors 128, 228, coils 129, 229 and microcomputers forming control units 130, 230 are mounted. Fig. 5, reference numerals 130 and 230 are assigned to the microcomputers serving as the respective main components of the control unit 130 and 230. The capacitors 128 and 228 smooth an input power supplied from batteries 191 and 291 (see Fig. 6). The capacitors 128 and 228 support the supply of electrical power to the motor 80 by storing electrical charges. The capacitors 128, 228 and the coils 129, 229 form respective filter circuits to reduce noise transmitted from other devices that also use the batteries 191, 291, and also to reduce noise transmitted from the drive device 40 to the other devices that also use the batteries 191, 291. Although Fig. 5, power supply circuits 116, 216, motor relays, current sensors 125, 225 and the like are also mounted on the motor-side surface 471 or the cover-side surface 472.

[0031] As it is in Fig. 6, the ECU 10 includes the inverter circuits 120, 220 and the control units 130, 230. The ECU 10 has a first power connector 111, a first torque connector 113, a second power connector 211, and a second torque connector 213.

[0032] The first power supply connector 111 is connected to the first battery 191, and the second power supply connector 211 is connected to the second battery 291. A first alternator 193 is connected to the first battery 191, and a second alternator 293 is connected to the second battery 291. The first power supply connector 111 is connected to the first inverter circuit 120 via a first power supply circuit 116. The second power supply connector 211 is connected to the second inverter circuit 220 via a second power supply circuit 216. The power supply circuits 116 and 216 are, for example, power supply relays.

[0033] The torque connectors 113 and 213 are connected to the torque sensor 94. In detail, the first torque connector 113 is connected to a first sensor unit 194 of the torque sensor 94. The second torque connector 213 is connected to a second sensor unit 294 of the torque sensor 94. In Fig. 6, the first sensor unit 194 is referred to as the first torque sensor, and the second sensor unit is referred to as the second torque sensor.

[0034] The first control unit 130 obtains a torque signal Ts concerning a steering torque Ts from the first sensor unit 194 of the torque sensor 94 via the torque connector 113 and a torque input circuit 118. The second control unit 230 obtains a torque signal Ts concerning a steering torque Ts from the second sensor unit 294 of the torque sensor 94 via the torque connector 213 and a torque sensor input circuit 218. The control units 130 and 230 thus calculate the steering torques Ts based on the torque signals.

[0035] The first inverter circuit 120 is a three-phase inverter that includes the switching elements 121 and converts electrical power supplied to the first motor winding set 180. The switching elements 121 are turned on and off based on control signals output from the first control unit 130.

[0036] The second inverter circuit 220 is also a three-phase inverter that includes the switching elements 221 and converts electrical power supplied to the second motor winding set 280. The switching elements 221 are turned on and off based on control signals output from the second control unit 230.

[0037] A first current sensor 125 detects a first U-phase current Iu1, a first V-phase current Iv1, and a first W-phase current Iw1 supplied to the three phases of the first motor winding set 180 and supplies the detected values to the first control unit 130. A second current sensor 225 detects a second U-phase current Iu2, a second V-phase current Iv2, and a second W-phase current Iw2 supplied to the three phases of the second motor winding set 280 and supplies the detected values to the second control unit 230.

[0038] Hereinafter, the U-phase current, V-phase current, and W-phase current are collectively referred to as phase current or winding current. Furthermore, a d-axis current and q-axis current are collectively referred to as "dq-axis current." Voltages are also collectively referred to in a similar manner.

[0039] A first rotation angle sensor 126 detects a rotation angle of the motor 80 and outputs a detected value to the first control unit 130. A second rotation angle sensor 226 detects a rotation angle of the motor 80 and outputs a detected value to the second control unit 230.

[0040] A first temperature sensor 127 is arranged, for example, in a region in which the first inverter circuit 120 is arranged, and detects a base temperature H1 relating to the first system L1. A second temperature sensor 227 is arranged, for example, in a region in which the second inverter circuit 220 is arranged, and detects a temperature H2 relating to the second system L2. The base temperature H1 is, for example, a heat sink temperature of the region in which the first inverter circuit 120 is arranged. The base temperature H2 is, for example, a heat sink temperature of the region in which the second inverter circuit 220 is arranged.

[0041] A first power supply voltage sensor 117 is arranged between the first power supply circuit 116 and the first inverter circuit 120 and detects a battery voltage Vb1 supplied from the first battery 191. A second power supply voltage sensor 217 is arranged between the second power supply circuit 216 and the second inverter circuit 220 and detects a battery voltage Vb2 supplied from the second battery 291.

[0042] Power is supplied to the first control unit 130 via the first power supply connector 111 and a regulator (not shown) or the like. Power is supplied to the second control unit 230 via the second power supply connector 211 and a regulator (not shown) or the like. The first control unit 130 and the second control unit 230 have communication units 170 and 270, as shown in Fig. 7, and are configured to communicate between the control units 130 and 230. Hereinafter, communication between the control units 130 and 230 is referred to as inter-computer communication as appropriate. As a communication method between the control units 130 and 230, any method such as serial communication such as SPI or SENT, CAN communication (CAN: Control Area Network), FlexRay communication, or the like can be used.

[0043] As it is in Fig. As shown in Figure 7, the control units 130 and 230 of the EPS-ECU 10 are connected to an (ADS-ECU) 15 via a vehicle communication network 16 such as a CAN. In the figure, the automatic cruise ECU 15 is referred to as the ADS-ECU. The ADS-ECU 15 manages automatic cruise control of a vehicle. Fig. 7, the control units 130 and 230 are both connected to the ADS-ECU 15 at a position outside the EPS-ECU 10. The control units 130 and 230 may alternatively be connected inside the EPS-ECU 10. Furthermore, one of the control units 130 and 230 may be connected so as to be capable of communicating with the ADS-ECU 15, and the other may exchange information from the control unit connected to the ADS-ECU 15 through inter-computer communication or the like. Furthermore, the control units 130 and 230 are configured so as to be capable of acquiring various information regarding a behavior of the vehicle, for example, a vehicle speed VS.

[0044] Each of the control units 130 and 230 is mainly composed of a microcomputer or the like, and internally includes a CPU, a ROM, a RAM, an I / O (not shown), a bus line for connecting these components, and the like. Each process executed by the control units 130 and 230 may be software processing or hardware processing. The software processing may be implemented by the CPU executing a program. The program may be stored in advance in a storage device such as a ROM, that is, a readable non-volatile storage medium. The hardware processing may be implemented by a special dedicated electronic circuit.

[0045] The first control unit 130 includes a first individual current limit calculation unit 131, a first current limiting unit 135, a first control signal calculation unit 140, a first communication unit 170, and the like. The second control unit 230 includes a second individual current limit calculation unit 231, a second current limiting unit 235, a second control signal calculation unit 240, a second communication unit 270, and the like. The functions of these units can be performed by executing computer programs by the CPU. Since the first control unit 130 and the second control unit 230 operate in substantially the same manner, the following description will be made mainly regarding the operation of the first control unit 130, and the description of the second control unit 230 will be simplified.The operation of the second control unit 230 becomes apparent by replacing the values of the first system with the values of the second system.

[0046] The individual current limit calculation unit 131 calculates a first individual current limit Ilim_k1. The individual current limit calculation unit 131 calculates, for example, an overheat protection current limit, a power supply voltage reference current limit, a steering operation speed reference current limit, and a current difference reduction current limit, and sets a minimum value from the calculated values as the first individual current limit Ilim_k1. The overheat protection current limit is calculated based on the phase currents Iu1, Iv1, Iw2, the base temperature H1, and the like. The power supply voltage reference current limit is calculated based on the battery voltage Vb1. The steering operation speed reference current limit is calculated based on the steering angular velocity ω.The current difference reduction current limit is calculated based on a winding current I1 of the first system L1 and a winding current I2 of the second system L2. The first individual current limit Ilim_k1 is transmitted to the second control unit 230 via the communication unit 170. Furthermore, the second individual current limit Ilim_k2 calculated by the second individual current limit calculation unit 231 is transmitted to the first control unit 130 via the communication unit 270.

[0047] Each limit value can be calculated in the individual current limit calculation unit 131 in the same way regardless of the control mode, or in a different way using different characteristic maps or arithmetic equations depending on the control mode. For example, in the ADS mode described later, the current difference between the systems is reduced by calculating the limit value lower than in the EPS mode.

[0048] The current limiting unit 135 calculates the current limit value Ilim1 based on the individual current limit values Ilim_k1 and Ilim_k2, the switching state of the operation mode, and the like. The current limiting unit 235 calculates the current limit value Ilim2 based on the individual current limit values Ilim_k1 and Ilim_k2, the switching state of the operation mode, and the like.

[0049] In the present embodiment, the current limit is arbitrated or selected among the systems with unlimited minimum value selection or limited minimum value selection according to the switching state of the operation mode. In a case of unlimited minimum value selection, the smaller of the individual current limit values Ilim_k1 and Ilim_k2 is set as the current limit values Ilim1 and Ilim2, and the current limit is always shared by the systems.

[0050] In the case of limited minimum value selection, if the individual current limits Ilim_k1 and Ilim_k2 are both equal to or greater than a common verification threshold Ilim_th, the smaller of the individual current limits Ilim_k1 and Ilim_k2 is set as the current limits Ilim1 and Ilim2, and the current limit is always used jointly. On the other hand, if at least one of the individual current limits Ilim_k1 and Ilim_k2 is less than the common verification threshold Ilim_th, the first individual current limit Ilim_k1 is set as the first current limit Ilim1, and the second individual current limit Ilim_k2 is set as the second current limit Ilim1, and the current limit is not used jointly. The common verification threshold Ilim_th is set arbitrarily, for example, to 50% of the rated current.

[0051] When the joint verification threshold Ilim_th is set to 0, the same control can be performed in the same way as with the unbounded minimum value selection. That is, the joint verification thresholds Ilim_th differ depending on the unbounded minimum value selection and the limited minimum value selection. Thus, the limited minimum value selection has the joint verification threshold Ilim_th greater than that of the unbounded minimum value selection.

[0052] In the case where the base current command value Ib1* converted from the torque command value is greater than the current limit value Ilim1, the current limiting unit 135 limits the current command value I1* to the current limit value Ilim1. If the base current command value Ib1* is equal to or less than the current limit value Ilim1, the base current command value Ib1* is used as the current command value Ib1* as it is. Similarly, the second control unit 230 calculates a base current command value Ib2* from the torque command value. The current limiting unit 235 calculates a current command value I2* using one of the base current command values Ib1* and Ib2*. The current command values Ib1*, I1*, Ib2*, I2* are values concerning a sum of the currents of the respective motor winding sets 180, 280 and are, for example, in Fig. 8 a value concerning the q-axis current.

[0053] The control signal calculation unit 140 generates a control signal based on the current command value I1* through current feedback control (current control) and outputs it to the inverter circuit 120. Feedback is abbreviated here as FB. The control signal calculation unit 140 switches a control mode between sum-and-difference FB control and independent FB control. The sum-and-difference FB control is in Fig. 8, and the independent FB control is Fig. 9 shown. In Fig. 8 and Fig. 9 mainly describes the calculation regarding the q-axis. Since the calculation regarding the d-axis is similar to that regarding the q-axis, the calculation regarding the d-axis is described in a simplified manner. In Fig. 8, for simplification purposes, the communication units 170 and 270 are shown as divided into two parts. In Fig. 9, the configuration that does not perform any computing operation is not shown. Note that Fig. 8 and Fig. 9 are only examples of the sum-and-difference FB control and the independent FB control. The sum-and-difference FB control and the independent FB control can be implemented differently. This also applies to Fig. 21.

[0054] As it is in Fig. 8, the control signal calculation unit 140 includes a dq-axis current calculation unit 141, an adder 142, a subtractor 143, a switching unit 145, a current FB calculation unit 150, a system voltage command value calculation unit 157, a PWM signal generation unit 158, and the like.

[0055] The dq-axis current calculation unit 141 calculates a first d-axis current detection value Id1 and a first q-axis current detection value Iq1 by dq conversion based on the detection value of the current sensor 125 (in Fig. 8 not shown) and the electrical angle.

[0056] The first dq-axis current detection values Id1 and Iq1 are transmitted to the second control unit 230 through inter-computer communication. The second dq-axis current detection values Id2 and Iq2 are transmitted to the first control unit 130 through inter-computer communication. The switching unit 145 is controlled such that the obtained second q-axis current detection value Iq2 is input to the adder 142 or the subtractor 143.

[0057] The adder 142 adds the first q-axis current detection value Iq1 and the second q-axis current detection value Iq2. The subtractor 143 subtracts the second q-axis current detection value Iq2 from the first q-axis current detection value Iq1.

[0058] The current FB calculation unit 150 includes subtractors 151, 152, controllers 153, 154, a switching unit 155, and an adder 156. The subtractor 151 subtracts a q-axis current sum Iq1 + Iq2 from the current command value I1* to calculate a current sum deviation Δlq_a1. The subtractor 152 subtracts a q-axis current difference Iq1 - Iq2 from the q-axis current command value Iq_d1* to calculate a current difference deviation Δlq_d1. In the present embodiment, the q-axis current difference command value Iq_d1 is set to 0. However, it can be set to a value other than 0 so that it has a difference.

[0059] The controller 153 calculates a base voltage command value through a proportional and integral (PI) calculation or the like so that the current sum deviation Δlq_a1 is reduced to 0. In the sum and difference FB control, the switching unit 155 is controlled so that the differential voltage command value is input to the adder 156. The adder 156 adds the base voltage command value and the differential voltage command value to calculate the two-system voltage command value.

[0060] The system voltage command value calculation unit 157 multiplies the two-system voltage command value by 0.5 to calculate a first system voltage command value Vq1*. The PWM signal generation unit 158 calculates the three-phase voltage command values through inverse dq conversion based on the dq-axis voltage command values Vd1*, Vq1*, and the electrical angle. The PWM signal generation unit 158 generates PWM signals through PWM calculation based on the three-phase voltage command values. The switching elements 121 of the inverter circuit 120 are turned on and off based on the generated PWM signals.

[0061] The second control unit 230 includes a switching unit 236 that selects whether to use the first current command value I1* obtained from the first control unit 130 or the second current command value I2* calculated by the second control unit 230. In the sum-and-difference FB control, the second control unit 230 controls the switching unit 236 such that the first current command value I1* obtained from the first control unit 130 is input to the current limiting unit 235.

[0062] As it is in Fig. As shown in Fig. 9, in the independent FB control, the current FB control is performed for each system without controlling the sum and the difference. In the present embodiment, the switching unit 145 is controlled so that the first q-axis current detection value Iq1 is input to the adder 142 instead of the second q-axis current detection value Iq2. A value twice as large as the first q-axis current detection value Iq1 is input to a negative side of the subtractor 151. In addition, the calculation related to the control of the difference is stopped.

[0063] The EPS ECU 10 is capable of switching between three control modes: a manual steering mode, an automatic driving mode, and an override mode. The manual steering mode is for controlling the motor 80 according to a driver's manual steering operation. The automatic driving mode is an automatic steering mode for controlling the motor 80 based on a command from an automatic driving ECU 15 without a driver's manual steering operation. The override mode is a switching mode for switching from the automatic steering mode to the manual steering mode. Hereinafter, the automatic steering mode is referred to as the ADS mode, and the manual steering mode is referred to as the EPS mode, as appropriate. The override mode can also be regarded as a control mode in which elements of manual control are added to automatic control.

[0064] In the automatic steering mode, it is necessary to ensure automatic driving safety. In the manual steering mode, it is necessary to reduce vibration and noise to increase driver comfort. Thus, the required control characteristics are different for the control modes. Therefore, in the present embodiment, by switching the current control according to the control mode, optimal characteristics are achieved in each control.

[0065] Fig. 10 is a flowchart showing control mode switching processing. This processing is executed by the ADS-ECU 15 in predetermined cycles. Hereinafter, "step" in each processing is simply abbreviated as "S."

[0066] In S101, the ADS-ECU 15 checks whether a vehicle is being manually driven. If it is determined that manual driving is being performed (S101: Yes), S108 is executed. If it is determined that manual driving is not being performed (S101: No), S102 is executed.

[0067] In S102, the ADS ECU 15 checks whether an override request has been generated. If it is determined that an override request has been generated (S102: Yes), S105 is executed. If it is determined that no override request has been generated (S102: No), S103 is executed to clear an override counter. In S104, the ADS ECU 15 sets the control mode to the ADS mode.

[0068] In S105, which is executed when it is determined that the overrule request has been generated (S102: Yes), the ADS-ECU 15 increments the overrule counter. In S106, the ADS-ECU 15 checks whether a count value Cor of the overrule counter is greater than a check threshold X1. If it is determined that the count value Cor of the overrule counter is equal to or less than the threshold X1 (S106: No), the control mode is set to the overrule mode in S107. If it is determined that the count value Cor of the overrule counter is greater than the threshold X1 (S106: Yes), the control mode is set to the EPS mode in S113.

[0069] In S108, which is executed when it is determined that manual driving is being performed (S101: Yes), the ADS-ECU 15 checks whether an automatic driving request has been generated. If it is determined that no automatic driving request has been generated (S108: No), an automatic driving start counter is cleared in S109. Then, the control mode is set to the EPS mode in S113. If it is determined that an automatic driving request has been generated (S108: Yes), the automatic driving start counter is incremented in S110.

[0070] In S111, the ADS-ECU 15 checks whether a count value Csd of the automatic travel start counter is greater than a check threshold X2. If it is determined that the count value Csd of the automatic travel start counter is greater than the threshold X2 (S111: Yes), S112 is executed. If it is determined that the count value Csd of the automatic travel start counter is equal to or less than the threshold X2 (S111: No), the control mode is set to the EPS mode in S113.

[0071] In S112, the ADS-ECU 15 checks whether it is possible to switch the control mode to the automatic driving mode. Here, it is determined that it is possible to switch the control mode to the automatic driving mode if all predetermined conditions are met. The predetermined conditions may be that no steering operation is performed, no abnormality is present, no current limit is performed, and the vehicle speed VS is within a range where switching to the automatic driving mode is permitted. Such conditions may also be fewer or more. If it is determined that the required conditions for switching to the automatic driving mode are not met (S112: No), the control mode is set to the EPS mode in S113. If it is determined that the required conditions for switching to the automatic driving mode are met (S112: Yes), the control mode is set to the ADS mode in S104.

[0072] The ADS-ECU 15 reports the control mode determined in S104, S107, or S113 to the EPS-ECU 10. The EPS-ECU 10 controls the drive of the motor 80 based on the received determination result.

[0073] The following describes the current control processing according to the switching state of the control mode with reference to the flowchart of Fig. 11. Since the control units 130 and 230 perform similar processing, only the processing in the control unit 130 will be described here. Since there is no difference in a current limit arbitration process and a current FB process at the time of switching from one of the ADS mode and the override mode to the other in the present embodiment, the relevant processing is not shown in the flowchart.

[0074] In S201, the control unit 130 checks whether the current control mode is the override mode. If it is determined that the current control mode is not the override mode (S201: No), step S207 is executed. If it is determined that the current control mode is the override mode (S201: Yes), step S202 is executed.

[0075] In S202, the control unit 130 checks whether there is a transition request from the override mode to the EPS mode. If it is determined that there is no request to transition to the EPS mode (S202: No), S205 is executed. If it is determined that there is a request to transition to the EPS mode (S202: Yes), S203 is executed.

[0076] In S203, the control unit 130 checks whether there is a steering determination. If it is determined that the steering operation is being performed, the result of the determination is affirmative (Yes). If it is determined that the steering determination is not being performed (S203: No), S212 is executed. If it is determined that there is a steering determination (S203: Yes), a transition wait flag is set in S204. In the figure, a state in which the transmission wait flag is set is assumed to be "1", and the state in which it is not set is assumed to be "0".

[0077] S205 is executed when the override mode or the ADS mode continues, and the current limiting unit 135 continues limited minimum value selection as a method for arbitrating the current limit. In S206, the control signal calculation unit 140 continues independent FB control as current FB control.

[0078] In S207, the control unit 130 checks whether the current control mode is the EPS mode. If it is determined that the current control mode is not the EPS mode (S207: No), that is, if the current control mode is the ADS mode, S218 is executed. If it is determined that the current control mode is the EPS mode (S207: Yes), step S208 is executed.

[0079] In S208, the control unit 130 checks whether there is a request to transition from the EPS mode to the ADS mode. If it is determined that there is a request to transition (S208: Yes), S216 is executed. If it is determined that there is no request to transition (S208: No), S209 is executed.

[0080] In S209, the control unit 130 checks whether the transition wait flag is set. If it is determined that the transition wait flag is not set (S209: No), S214 is executed. If it is determined that the transition wait flag is set (S209: Yes), S210 is executed.

[0081] In S210, the control unit 130 checks whether the steering determination exists, similar to S203. If it is determined that the steering determination exists (S210: Yes), the current limit arbitration method is set to the limited minimum value selection in S205, and the current FB control is set to the independent FB control in S206. If it is determined that there is no steering determination (S210: No), the transition wait flag is reset to "0" in S211.

[0082] In S212, the current limiting unit 135 changes the current limit arbitration method from limited minimum value selection to unlimited minimum value selection. In S213, the control signal calculation unit 140 changes the current FB control from independent FB control to sum-and-difference control.

[0083] If the EPS mode continues (S209: No), S214 is executed. In S214, the current limiting unit 135 continues the infinite minimum value selection as the current limit arbitration method. In S215, the control signal calculation unit 140 continues the sum-and-difference control as the current FB control.

[0084] If it is determined that there is an ADS transition request (S208: Yes), the current limiting unit 135 changes the current limit arbitration method from unlimited minimum value selection to limited minimum value selection in S216. In S217, the control signal calculation unit 140 changes the current FB control from independent FB control to sum-and-difference control.

[0085] In S218, which is executed in a case where the control mode is the ADS mode (S207: No), the control unit 130 checks whether there is a request to transition from the ADS mode to the EPS mode. If it is determined that there is a request to transition (S218: Yes), in S212, the current limit arbitration method is set to unlimited minimum value selection, and the current FB control is set to sum-and-difference control. If it is determined that there is no request to transition to the EPS mode (S218: No), in S205, the current limit arbitration method is set to limited minimum value selection, and the current FB control is set to independent FB control.

[0086] Since in the ADS mode, the steering feel does not need to be considered and the steering assist force is required, the current limit arbitration method is set to the limited minimum value selection, and the current FB control is set to the independent FB control. Since in the EPS mode, the steering feel is important, the current limit arbitration method is set to the unlimited minimum value selection, and the current FB control is set to the sum-and-difference control. In the EPS mode, the limited minimum value selection can be determined with respect to a common verification threshold Ilim_th, which is smaller than that of the ADS mode, to ensure a minimum assist force.During an override, similar to the ADS mode, the current limit arbitration method is set to the limited minimum value selection, and the current FB control is set to the independent FB control.

[0087] The Fig. Figures 12 to 16 are timing diagrams showing current limit values according to the control modes. In these figures, the first individual current limit value Ilim_k1, the second individual current limit value Ilim_k2, and the arbitrated first current limit value Ilim1 are indicated by a dashed line, a dot-dash line, and a solid line, respectively. Note that the second current limit value Ilim2 is not indicated. For simplicity, these lines are slightly shifted from each other so that the line type can be recognized.

[0088] Fig. Figure 12 shows the ADS mode up to time x12. It is assumed that when a steering torque is manually input by the driver at time x12, the mode switches from the ADS mode to the override mode. It is further assumed that the control mode switches from the override mode to the EPS mode at time x13.

[0089] When the second individual current limit Ilim_k2 decreases from time x10, the common current limit of the systems is shared by setting the first current limit Ilim1 to the second individual current limit Ilim_k2 through the minimum value selection. From time x11, the second individual current limit Ilim_k2 decreases to be smaller than the common verification threshold Ilim_th. Since at this time the control mode is ADS mode and the current limit arbitration method is the limited minimum value selection, the first current limit Ilim1 is set to the first individual current limit Ilim_k1, so the current limit is not shared. Between time x12 and time x13, the control mode is the override mode, and the current limit arbitration method is the limited minimum value selection.Since between time x12 and time x13 the second individual current limit Ilim_k2 is smaller than the common verification threshold Ilim_th, the first current limit Ilim1 there continues to be the first individual current limit Ilim_k1.

[0090] When the control mode switches from the override mode to the EPS mode at time x13, the current limit arbitration method is changed from the limited minimum value selection to the unlimited minimum value selection. At time x13, the second individual current limit Ilim_k2 is smaller than the common verification threshold Ilim_th. For this reason, during the override mode, the first current limit Ilim1 is set to the first individual current limit Ilim_k1 through the limited minimum value selection, so that the current limit is not shared. Since the unlimited minimum value selection is performed after switching to the EPS mode, the first current limit Ilim1 is changed from the first individual current limit Ilim_k1 to the second individual current limit Ilim_k2, so that the common current limit is shared.

[0091] In Fig. 13, it is assumed that although the ADS mode continues until time x22 and the control mode is changed from the ADS mode to the override mode at time x22, the control mode switching to the EPS mode is not fixed and the control mode returns to the ADS mode at time x23.

[0092] The transition of the first current limit value Ilim1 up to the time x23 is the same as the transition up to the time x13 in Fig. 12. Since in the example the Fig. 13 When the control mode is switched from the override mode to the ADS mode at time x23, the limited minimum value selection continues as the current limit arbitration process. Therefore, even after time x23, the first current limit Ilim1 is set to the first individual current limit Ilim_k1. On the other hand, when the second individual current limit Ilim_k2 increases to greater than the common verification threshold Ilim_th, the first individual current limit Ilim1 is changed from the first individual current limit Ilim_k1 to the second individual current limit Ilim_k2, so that the common current limit is shared.

[0093] In Fig. 14, it is assumed that the ADS mode continues until time x33, and the control mode changes from the ADS mode to the override mode at time x33, and the control mode also changes from the override mode to the EPS mode at time x34. Furthermore, it is assumed that the steering is operated from time x32 to time x36.

[0094] The course of the first current limit value Ilim1 up to the time x34, at which the control mode is switched from the override mode to the EPS mode, is the same as the course up to the time x13 in Fig. 13. Although the control mode switches to EPS mode at time x34, steering continues. Therefore, the current limit arbitration method is not changed, and the limited minimum value selection continues. Since the second individual current limit Ilim_k2 becomes greater than the common verification threshold Ilim_th at time x35, the first current limit Ilim1 is set to the second individual current limit Ilim_k2.

[0095] As it is in Fig. As shown in FIG. 15, in a case where the current limit value is not shared during the override at the time of switching the control mode from the override mode to the EPS mode, the non-sharing state may be continued during the steering operation. When the steering operation is terminated at time x36, the first current limit value Ilim1 may be changed from the first individual current limit value Ilim_k1 to the second individual current limit value Ilim_k2, so that the common current limit value is shared.

[0096] As it is in Fig. 16, in a case where the second individual current limit value Ilim_k2 becomes smaller than the common verification threshold value Ilim_th at time x31 and the first current limit value Ilim1 is changed from the second individual current limit value Ilim_k2 to the first individual current limit value Ilim_k1, the first current limit value Ilim1 can be gradually increased. In a case where the second individual current limit value Ilim_k2 becomes larger than the common verification threshold value Ilim_th at time x35 and the current limit value Ilim1 is changed from the first individual current limit value Ilim_k1 to the second individual current limit value Ilim_k2, the first current limit value Ilim1 can be gradually decreased in a similar manner. Fig. 16 When the first current limit value Ilim1 is changed from one of the first individual current limit value Ilim_k1 and the second individual current limit value Ilim_k2 to the other, the limit value is changed linearly and gradually. However, this may be changed nonlinearly gradually, for example, according to a quadratic function or an exponential function. Similarly, the current limit value may be changed gradually at the other switching time of the current limit value. The rate at which the current limit value is gradually changed may be varied according to at least one of the steering torque Ts, the vehicle speed VS, the steering angular velocity ω, the steering angle, and other parameters.

[0097] As described above, the EPS-ECU 10, which controls the electric power steering apparatus 8 including the motor 80 having a plurality of motor winding sets 180, 280, includes a plurality of inverter circuits 120, 220, and a plurality of control sections 130, 230. The inverter circuits 120 and 220 are arranged for the respective motor winding sets 180 and 280. The control units 130 and 230 are arranged for the motor winding sets 180 and 280, generate control signals related to the driving of the inverter circuits 120 and 220, and control currents flowing through the respective motor winding sets 180 and 280, thereby controlling the driving of the motor 80.

[0098] The control mode includes the manual steering mode for controlling the motor 80 according to the driver's manual steering operation of the steering wheel 91, and the automatic steering mode for controlling the motor 80 independently of the driver's steering operation of the steering wheel 91. The control units 130 and 230 are capable of switching the control modes and changing the current control according to the control mode. The current control includes, for example, the arbitration control of the current limit value between the systems and the current FB control. That is, the current control refers to the control performed after calculating the current command value uniquely converted from the torque command value. In the present embodiment, the current control is performed by calculations in the current limiting units 135, 235 and the control signal calculating units 140, 240.By changing the current control according to the control mode, it is possible to achieve optimal characteristics corresponding to a respective control mode.

[0099] The control units 130 and 230 include current limiting units 135 and 235 for setting the current limit values Ilim1 and Ilim2 for limiting the currents flowing through the respective motor winding sets 180 and 280. The current limiting units 135 and 235 set the current limit values Ilim1 and Ilim2 differently as current limits according to the control mode. By controlling the current differently according to the control mode, it is possible to achieve optimal characteristics corresponding to each control mode.

[0100] A combination of the motor winding set 180, the inverter circuit 120, and the control unit 130 is defined as one system. Another combination of the motor winding set 280, the inverter circuit 220, and the control unit 230 is defined as another system. The control units 130 and 230 include the individual current limit calculation units 131 and 231 for calculating individual current limit values Ilim_k1 and Ilim_k2, which are values for a respective system related to current limitation. Furthermore, the control units 130 and 230 are capable of obtaining the individual current limit values Ilim_k2 and Ilim_k1 of the other system, respectively.

[0101] Each of the control units is capable of switching the control mode between the common current limit state in which the same value as that of the other system is set as the current limit values Ilim1 and Ilim2, and the independent current limit state in which the individual current limit of its own system is set to the current limit of the same system. In the present embodiment, in the independent current limit state, the first individual current limit Ilim_k1 is set as the first current limit Ilim1, and the second individual current limit Ilim_k2 is set as the second current limit Ilim2. The common verification threshold Ilim_th concerning the switching determination between the common current limit state and the independent current limit state is different for the manual steering mode and the automatic steering mode.

[0102] In the manual steering mode, the current limiting units 135 and 235 limit the common verification threshold Ilim_th to 0 and set the minimum value from the individual current limit values Ilim_k1 and Ilim_k2 as the current limit values Ilim1 and Ilim2, respectively, through the unlimited minimum value selection, thereby setting the common current limit state. In the automatic steering mode, the current limiting units 135 and 235 set the common verification threshold Ilim_th to a value greater than 0 and switch the control mode between the common current limit state and the individual current limit state in the following manner. When the individual current limit values Ilim_k1 and Ilim_k2 of all systems are equal to or greater than the common verification threshold Ilim_th, the minimum value of the individual current limit values Ilim_k1 and Ilim_k2 is set as the current limit values Ilim1 and Ilim2.If at least some of the individual current limits Ilim_k1 and Ilim_k2 of the systems are smaller than the common verification threshold Ilim_th, the current limit is set by the limited minimum value selection, which sets the current limits Ilim1 and Ilim2 depending on the system. That is, in manual steering mode, the common verification threshold Ilim_th is set to a smaller value than in automatic steering mode.

[0103] In the automatic steering mode, the steering feel is not important, but the steering assist force is important. On the other hand, in the manual steering mode, the steering feel is important. In the case where the steering assist force is insufficient, the driver's steering assist force must be supplemented. Therefore, in the automatic steering mode of the present embodiment, by setting the current limit values Ilim1 and Ilim2 through the limited minimum value selection, priority is given to ensuring the motor output (motor power) rather than jointly using the common current limit. In the manual steering mode, by setting the current limit values Ilim1 and Ilim2 through the unlimited minimum value selection, priority is given to jointly using the current limit to ensure the steering operation feel. Thus, optimal characteristics can be achieved in each control mode.

[0104] When the common verification threshold Ilim_th is set to 0, the current limits Ilim1 and Ilim2 can be used together regardless of the individual current limits Ilim_k1 and Ilim_k2. When the common verification threshold Ilim_th is set to any value greater than 0, the current limits Ilim1 and Ilim2 can be switched between being used together and not being used together. When the common verification threshold Ilim_th is set to a value as large as possible, such as an upper current limit, the current limits Ilim1 and Ilim2 cannot be used together regardless of the individual current limits Ilim_k1 and Ilim_k2. By changing the common verification threshold Ilim_th in this way, it is possible to appropriately switch the state of using the current limits Ilim1 and Ilim2 together.

[0105] In addition to the automatic steering mode and the manual steering mode, the control mode includes the override mode, which is the transition mode from the automatic steering mode to the manual steering mode. In the override mode, the current limiting units 135 and 235 set the common verification threshold Ilim_th to the same value as in the automatic steering mode and set the current limit values Ilim1 and Ilim2 through the limited minimum value selection. As a result, the current limit values Ilim1 and Ilim2 can be set during the override mode similarly to the automatic steering mode.

[0106] When the current limit values Ilim1 and Ilim2 are changed according to the switching from one of the common current limit state and the independent current limit state to the other of the states, the current limit units 135 and 235 can gradually change the current limit values Ilim1 and Ilim2, respectively. Therefore, it is possible to prevent a sudden change in the current limit values Ilim1 and Ilim2.

[0107] The control units 130 and 230 include the control signal calculation units 140 and 240, which generate the respective control signals related to the current feedback control drive of the inverter circuits 120 and 220. The control signal calculation units 140 and 240 achieve different current feedback control as the current control corresponding to the control mode. Specifically, the current detection value used for the current feedback control is different. By different current control based on the control mode, it is possible to achieve optimal characteristics corresponding to each control mode.

[0108] When the control mode is the automatic steering mode, the control signal calculation units 140 and 240 generate the control signals through independent feedback control using the current detection value of the own system. When the control mode is the manual steering mode, the control signal calculation units 140 and 240 use the current detection values of the own system and the other system and generate the control signals through sum-and-difference control, which controls the sum and difference of the currents flowing in the motor winding sets 180 and 280. In the present embodiment, the sum-and-difference control is performed as coordinated feedback control.

[0109] In the automatic steering mode, by using independent feedback control as the current FB controller, it is possible to prevent all outputs from becoming faulty together in the event of an abnormality, detection error, or the like occurring in some of the systems. Furthermore, in the manual steering mode, using coordinated feedback control can reduce vibration and noise, and ensure steering feel.

[0110] When the control mode is the override mode, the control signal calculation units 140 and 240 use independent feedback control as the current feedback control. As a result, the same current FB control as in the automatic steering mode can be performed during override.

[0111] The control units 130 and 230 switch the current control at the time when the driver is not steering. Specifically, with respect to the current FB control, switching from the sum-and-difference control to the independent FB control and vice versa is prohibited during the steering operation period and performed during the non-steering period. Furthermore, with respect to the arbitration of the current limits, switching from one to the other of the unlimited minimum value selection and the limited minimum value selection is prohibited during the steering operation period and performed during the non-steering period.Here, if it is assumed that the common verification threshold Ilim_th is not used during the driving period and is used during the non-driving period, the change from one to the other of the common current limit state and the independent current limit state is prohibited during the driving period and performed during the non-driving period, as described with reference to FIG. Fig. 15. Consequently, it is possible to prevent a reduction in comfort due to a change in current control during steering operation. (Second embodiment)

[0112] A second embodiment is shown in the Fig. 17 and Fig. 18. In the first embodiment, the current control in the override mode is the same as in the ADS mode. That is, the arbitration method of the current limit is set to the limited minimum value selection, and the current FB control is set to the independent FB control. In the present embodiment, the current control in the override mode is the same as in the EPS mode. That is, in the present embodiment, in the override mode, the arbitration method of the current limit is set to the unlimited minimum value selection, and the current FB control is set to the sum-and-difference control.

[0113] Fig. 17 and Fig. 18 are timing diagrams showing current limit values according to the control modes. Similar to Fig. 12 shows Fig. 17 the ADS mode until time x12, the override mode from time x12 to time x13 and the EPS mode after time x13. The first current limit value Ilim1 until time x12 is the same as in Fig. 12.

[0114] In this embodiment, when the control mode is switched from the ADS mode to the override mode at time x12, the current limit is switched from the limited minimum value selection to the unlimited minimum value selection. The first current limit Ilim1 is accordingly changed from the first individual current limit Ilim_k1 to the second individual current limit Ilim_k2. Although the control mode is switched from the override mode to the EPS mode at time x13, the limited minimum value selection continues as the current limit arbitration method.

[0115] In Fig. 18 is similar to Fig. 13, the control mode until time x22 is the ADS mode, and from time x22 to time x23, the override mode. It is assumed that the control mode change to the EPS mode is not fixed, and the control mode returns to the ADS mode. The operation from time x20 to time x23 is the same as that from time x10 to time x13 in Fig. 17. When the control mode switches from the override mode to the ADS mode at time x23, the current limit arbitration method is changed from unlimited minimum value selection to limited minimum value selection. At this time, since the second individual current limit Ilim_k2 is less than the common verification threshold Ilim_th, the first current limit Ilim1 is set to the first individual current limit Ilim_k1, so that the current limit is not shared as a common value. When the second individual current limit Ilim_k2 increases to be greater than the common verification threshold Ilim_th at time x24, the first current limit Ilim1 is changed from the first individual current limit Ilim_k1 to the second individual current limit Ilim_k2, so that the common current limit is shared by the minimum value selection.This configuration also achieves the same effect as in the embodiment described above. (Third embodiment)

[0116] A third embodiment is in Fig. 19. In the present embodiment, a change from the EPS mode to the ADS mode is described. In Fig. 19, the EPS mode continues until time x41. It is assumed that the control mode is switched from the EPS mode to the ADS mode at time x41, for example, by the driver's operation of the control mode switching switch. In the present embodiment, when the individual current limit value of one system is less than the common check threshold Ilim_th in the limited minimum value selection in the ADS mode, the current limit value of the other system is set as the common check threshold Ilim_th. Furthermore, in the above embodiment, the current limit value may be independent and not shared by setting the current limit value of the system having the individual current limit value greater than the common check threshold Ilim_th through the limited minimum value selection as the common check threshold Ilim_th.

[0117] When the second individual current limit Ilim_k2 decreases from time x40, the current limit is shared by the systems by setting the first current limit Ilim1 to the second individual current limit Ilim_k2 through the minimum value selection. When the control mode is switched from EPS mode to ADS mode at time x41, the current limit arbitration method is changed from unlimited minimum value selection to limited minimum value selection, and the first current limit Ilim1 is changed from the second individual current limit Ilim_k2 to the common verification threshold Ilim_th. As shown in Fig. 20, the current limit value at the time of transition from the EPS mode to the ADS mode can be gradually changed so that the driver does not feel uncomfortable.

[0118] When the second individual current limit value Ilim_k2 becomes greater than the common verification threshold value Ilim_th at time x42, the first current limit value Ilim1 is set to the second individual current limit value Ilim_k2, and the current limit value is shared by the minimum value selection. This configuration also achieves a similar effect to the embodiments described above. (Fourth Embodiment)

[0119] A fourth embodiment is shown in Fig. 21. In the above-described embodiments, as the current control in the ADS mode, the current limit arbitration method is set to the limited minimum value selection, and the current FB control is set to the independent FB control. That is, in the above embodiments, the current command value is shared with a limit.

[0120] In the present embodiment, the current control in the ADS mode is a completely independent FB control that does not share a command value. As shown in Fig. 21, in the fully independent FB control, a switching unit 236 is controlled such that a current command value I2* calculated by the control unit 230 is input to the current limiting unit 235. In the fully independent FB control, the current limiting unit 235 does not arbitrate the current limit value, but sets the individual current limit value Ilim_k1 of the own system as the current limit value Ilim1. Similarly, the current limiting unit 235 does not arbitrate the current limit value, but sets the individual current limit value Ilim_k2 of the own system as the current limit value Ilim2.

[0121] As a result, independence between the systems is further ensured, and thus, it is possible to prevent erroneous outputs in both systems. The present embodiment achieves the same advantages as the above embodiments. (Fifth embodiment)

[0122] A fifth embodiment is shown in the Fig. 22 to 24. In the present embodiment, the switching between sharing and non-sharing of the common current limit in the ADS mode is different from the above embodiments, and thus this difference will be mainly described.

[0123] The current limiting processing of the present embodiment will be explained with reference to the flowchart of Fig. 22. In S301, the control units 130 and 230 check whether automatic travel is being performed. If it is determined that automatic travel is not being performed (S301: No), the current limitation is performed according to the control mode without performing the following steps (see Fig. 11). If it is determined that automatic travel is being performed (S301: Yes), S302 is executed. In the case where the result of the determination in S218 of the Fig. 11 is negative, S302 can be executed instead of this step. This also applies to S401 in Fig. 26.

[0124] In S302, the control units 130 and 230 check whether the vehicle speed VS is equal to or greater than a vehicle speed verification threshold VSth. The vehicle speed verification threshold VSth is set to a value (for example, 5 km / h) at which the vehicle can be safely stopped even when the steering assistance is insufficient. If it is determined that the vehicle speed VS is lower than the vehicle speed verification threshold VSth (S302: No), S305 is executed. If it is determined that the vehicle speed VS is equal to or greater than the vehicle speed verification threshold VSth (S302: Yes), S303 is executed.

[0125] In S303, the control units 130 and 230 check whether at least one of the first individual current limit value Ilim_k1 and the second individual current limit value Ilim_k2 is equal to or less than the common verification threshold Ilim_th. If it is determined that the first individual current limit value Ilim_k1 and the second individual current limit value Ilim_k2 are greater than the common verification threshold Ilim_th (S303: No), S305 is executed. If it is determined that at least one of the first individual current limit value Ilim_k1 and the second individual current limit value Ilim_k2 is greater than the common verification threshold Ilim_th (S303: Yes), S304 is executed.

[0126] In S304, the current limit is not shared. The first control unit 130 sets the first current limit Ilim1 to the first individual current limit Ilim_k1, and the second control unit 230 sets the second current limit Ilim2 to the second individual current limit Ilim_k2.

[0127] In S305, the current limit is shared as a common current limit. Control units 130 and 230 set the current limit values Ilim1 and Ilim2 to the smaller of the individual current limit values Ilim_k1 and Ilim_k2.

[0128] Fig. 23 and Fig. 24 are time charts showing current limit values corresponding to a driving state of the vehicle during the ADS mode. In the figure, it is assumed that a driving state in which the vehicle speed VS is equal to or greater than the vehicle speed verification threshold VS_th is "normal driving," and a driving state in which the vehicle speed VS is less than the vehicle speed verification threshold VS_th is "low-speed driving." Low-speed driving may even include a vehicle stop. It is assumed that normal driving continues until time x51, low-speed driving continues from time x51 to time x53, and normal driving resumes again from time x53. In addition, in the entire time period shown in Fig. 23 and Fig. 24, the second individual current limit Ilim_k2 is smaller than the first individual current limit Ilim_k1. This means that Ilim_k2 < Ilim_k1. This also applies to Fig. 27.

[0129] Since before time x50 the driving state is normal driving and the individual current limit values Ilim_k1 and Ilim_k2 are both equal to or greater than the common verification threshold Ilim_th, the current limit values Ilim1 and Ilim2 are set to the second individual current limit value Ilim_k2.

[0130] At time x50, the second individual current limit value Ilim_k2 decreases to become smaller than the common verification threshold value Ilim_th. Since the vehicle is driving normally in ADS mode at this time, the first current limit value Ilim1 is set to the first individual current limit value Ilim_k1. By setting the current limit value to be independent and not shared, priority is given to ensuring output (performance) during driving in automatic steering mode.

[0131] When the driving state changes from normal driving to low-speed driving at time x51, the first current limit Ilim1 is set to the second individual current limit Ilim_k2 to share the current limit. During low-speed driving, priority is given to overheat protection and NV reduction, because the vehicle can be safely stopped even when the steering assistance is insufficient, and the current limit is shared.

[0132] At time x52, the second individual current limit value Ilim_k2 becomes equal to or greater than the common verification threshold value Ilim_th. When the traveling state changes from low-speed traveling to normal traveling at time x53, the first current limit value Ilim1 is set to the second individual current limit value Ilim_k2, and a state in which the current limit value is shared is maintained.

[0133] As it is in Fig. As shown in Figure 24, by setting the common verification threshold Ilim_th to a value as small as possible, the current limit can be used independently during normal driving and jointly during low-speed driving. S303 in Fig. 22 can be omitted in the case where the current limit values Ilim1 and Ilim2 are not used together during normal driving, regardless of the individual current limit values Ilim_k1 and Ilim_k2. At times x50 and x51 in Fig. 23 as well as at times x51 and x53 in Fig. 24, the current limit can be gradually changed at a time of changing the current limit. The same applies to the times x61 and x62 in Fig. 27.

[0134] In the present embodiment, when the vehicle speed VS, which is the traveling speed of the vehicle, is equal to or greater than the vehicle speed check threshold VSth in the automatic steering mode, the current limiting units 135 and 235 do not use the current limit in common, or switch the state between the common current limit state and the independent current limit state according to the independent current limits Ilim_k1 and Ilim_k2. When the vehicle speed VS is lower than the vehicle speed check threshold VSth, the common current limit state is set. As a result, insufficient torque can be prevented during traveling by giving priority to the output (power). (Sixth Embodiment)

[0135] A sixth embodiment is shown in the Fig. 25 to 27. As shown in Fig. As shown in FIG. 25, the control units 130 and 230 of the present embodiment include demand torque calculation units 134 and 234. The demand torque calculation units 134 and 234 calculate estimated required steering torques Tr required for the steering operation, respectively, based on a road surface condition and the traveling state. The estimated required steering torque Tr is calculated based on parameters such as a current position of the vehicle (i.e., curved or straight), a friction coefficient of a road surface, and the vehicle speed. The parameters and calculation methods used in this calculation are not limited.

[0136] Current limit processing of the present embodiment will be explained with reference to the flowchart of Fig. 26. In S401, the control units 130 and 230 check similarly to S301 of the Fig. 22, whether automatic travel is performed. If it is determined that automatic travel is not performed (S401: No), the current limitation is performed according to the control mode without performing the following steps (see Fig. 11). If it is determined that automatic travel is performed (S301: Yes), S402 is executed.

[0137] In S402, the control units 130 and 230 check whether the estimated required steering torque Tr is equal to or greater than a torque verification threshold Tr_th. The torque verification threshold Tr_th is set to an arbitrary value indicating a need to prioritize ensuring output (power) over heat protection and NV reduction. If it is determined that the estimated required steering torque Tr is equal to or greater than the torque verification threshold Tr_th (S402: Yes), S403 is executed, and the current limit is used independently. If it is determined that the estimated required steering torque Tr is less than the torque verification threshold Tr_th (S402: No), S404 is executed, and the current limit is used jointly. The details of S403 and S404 are similar to those of S304 and S305 in Fig. 22.

[0138] Fig.Figure 27 is a timing chart showing the current limit corresponding to the estimated required steering torque Tr in the ADS mode. Before time x61, the first current limit Ilim1 is set to the first individual current limit Ilim_k1 because the estimated required steering torque Tr is equal to or greater than the torque verification threshold Tr_th. By setting the current limit independent and not shared, priority is given to ensuring output (performance) in a state where a relatively large steering torque is required.

[0139] When the estimated required steering torque Tr becomes less than the torque verification threshold Tr_th at time x61, the first current limit Ilim1 is set to the second individual current limit Ilim_k2, so that overheat protection and NV reduction are prioritized and the current limit is used jointly. When the estimated required steering torque Tr becomes equal to or greater than the torque verification threshold Tr_th at time x62, the first current limit Ilim1 is set to the first individual current limit Ilim_k1, so that priority is given to ensuring output (performance).

[0140] The control units 130 and 230 include demand torque estimation units 134 and 234 for calculating the estimated required steering torques Tr required for steering. In the automatic steering mode, the independent current limit value state is set when the estimated required steering torque Tr is equal to or greater than the torque verification threshold Tr_th. When the estimated required steering torque Tr is less than the torque verification threshold Tr_th, the common current limit value state is set. Thus, depending on the estimated required steering torque Tr, it is possible to appropriately select whether to use the current limit values Ilim1 and Ilim2 jointly or not jointly based on the estimated required steering torque Tr. (Other embodiments)

[0141] In the above embodiments, the individual current limit calculation unit is configured to calculate the overheat protection current limit, the power supply voltage reference current limit, the steering operation speed reference current limit, and the inter-system differential current limit, and selects the minimum value as the individual current limit through the minimum value selection. According to another embodiment, the overheat protection current limit as the temperature reference, the power supply reference current limit, or the steering operation speed reference current limit may be omitted. In the above embodiments, the temperature, battery voltage, and steering angular velocity are used as parameters related to each system, and the individual current limit is calculated based on these parameters.According to another embodiment, the battery voltage or the steering angular velocity may be omitted as a parameter concerning a respective system, or the individual current limit may be calculated based on still other parameters.

[0142] Furthermore, the current limiting unit may be configured to divide the overheat protection current limit, the power supply voltage reference current limit, the steering operating speed reference current limit, and the inter-system differential current limit into groups, with one group sharing the common value and another group not sharing the common value. For example, the steering operating speed reference current limit, which is likely to be limited during high-speed steering and has a great influence on NV improvement, is shared, but the overheat protection current limit, for example, is not shared. Regarding the steering operating speed reference current limit in the override mode, the current limit may be used independently and not shared, or the largest current limit may be used as the shared value through maximum value selection.

[0143] In the above embodiments, the current limiting unit shares the current limit value through the minimum value selection. According to another embodiment, the current limit value may be shared by a method other than the minimum value selection, for example, a maximum value selection for selecting the largest value, a geometric mean, an arithmetic mean, or the like. Furthermore, according to another embodiment, in the EPS mode, for example, a logic of current limiting by limiting based on the detection current of the other system may be appropriately added to the control mode.

[0144] In the above embodiments, the current threshold is shared through the unlimited minimum value selection in the EPS mode. According to another embodiment, the current threshold may be shared in the EPS mode through the limited minimum value selection. In this case, the shared verification threshold can be set arbitrarily, but it is desirable that it be smaller than the shared verification threshold used in the ADS mode.

[0145] The common verification threshold may be fixed at a constant value or may be varied according to, for example, the steering operating speed, battery voltage, temperature, and the like. For example, in a case of high rotational speed or low voltage, it is possible to prioritize output (power) protection over NV reduction by increasing the common verification threshold. According to another embodiment, the respective embodiments may be appropriately combined, for example.For example, the current limit may be made independent when the vehicle speed is equal to or greater than the vehicle speed verification threshold and the estimated required steering torque is equal to or greater than the torque verification threshold; the current limit may be switched between joint use or independent use based on the individual current limit; or the current limit may be used jointly when the vehicle speed is lower than the vehicle speed verification threshold or when the estimated required steering torque is equal to or greater than the torque verification threshold.In addition, the calculation of the estimated required steering torque by the required torque calculation unit can be performed by obtaining the required steering torque by the required torque calculation unit from a required steering torque calculation unit arranged externally.

[0146] In the above embodiment, two control units are arranged. According to another embodiment, the number of control units may be three or more. The number of winding sets and the number of drive circuits may also be three or more. That is, the number of systems may be three or more. Multiple drive circuits and winding sets may be arranged for one control unit.

[0147] In the above embodiments, the rotating electric machine is a three-phase brushless motor. According to another embodiment, the rotating electric machine is not limited to the brushless motor, but may be any other motor. In the above embodiments, the drive device is of the machine-electronics-integrated type in which the ECU and the motor are integrally arranged. According to another embodiment, the ECU may be arranged separately from the motor.

Claims

[1] A steering control device for controlling an electric power steering device (8) having an electric rotary machine (80), the steering control device comprising: a control circuit (120, 220) arranged to control the electric rotary machine (80); and a control unit (130, 230) arranged to control a control of the electric rotary machine (80) by generating a control signal relating to a control of the control circuit (120, 220) and controlling a current flowing in the electric rotary machine (80), wherein the control unit (130, 230) is designed to switch a control mode including a manual steering mode and an automatic steering mode and to perform a different current control according to the control mode, the manual steering mode serves to control the electric rotary machine (80) in accordance with a manual steering operation of a steering element (91), and the automatic steering mode serves to control the electric rotary machine (80) independently of the manual steering of the steering element (91); and the control unit (130, 230) includes a current limiting unit (135, 235) configured to set a current limit value for limiting the current flowing in the electric rotary machine (80); characterized by , that the current limiting unit (135, 235) is designed to form the current limit value differently as a current controller according to the control mode; the electric rotary machine (80) has a plurality of winding sets (180, 280); the drive circuit (120, 220) and the control unit (130, 230) are arranged in correspondence to a respective winding set (180, 280) to form a system (L1, L2); the control unit (130, 230) includes an individual current limit calculation unit (131, 231) configured to calculate an individual current limit as a value relating to a current limit of one system, to obtain the individual current limit of another system, and to switch between a common current limit state for setting the same current limit as that of the other system and an independent current limit state for setting an independent current limit independent of that of the other system; and the control unit (130, 230) forms a common verification threshold provided to switch between the common current limit state and the independent current limit state differently for the manual steering mode and the automatic steering mode. [2] Steering control device according to claim 1, characterized by , that the current limiting unit (135, 235) is designed to set the common current limit state in the manual steering mode by setting a common verification threshold to 0 and setting the current limit by an unlimited minimum value selection that selects a smallest value from individual current limits as the current limit; and the current limiting unit (135, 235) is further configured to switch between the common current limit state and the independent current limit state in the automatic steering mode by setting the common verification threshold to be greater than 0, setting the current limit to the smallest value among the individual current limits when the individual current limits of all systems are equal to or greater than the common verification threshold, and individually setting the current limit by the limited minimum selection when at least one of the independent current limits of the systems is less than the common verification threshold. [3] Steering control device according to claim 1 or 2, characterized by , that the current limiting unit (135, 235) sets the common verification threshold to the same value as that of the automatic steering mode when the control mode is an override mode which is a transition mode from the automatic steering mode to the manual steering mode. [4] Steering control device according to one of claims 1 to 3, characterized by , that the current limiting unit (135, 235) sets the independent current limit state or switches between the common current limit state and the independent current limit state when a vehicle speed in the automatic steering mode is equal to or greater than a vehicle speed verification threshold; and the current limiting unit (135, 235) sets the common current limit state when the vehicle speed in the automatic steering mode is lower than the vehicle speed check threshold. [5] Steering control device according to one of claims 1 to 4, characterized by , that the control unit (130, 230) further includes a demand torque calculation unit (134, 234) configured to calculate an estimated required steering torque required for steering; the current limiting unit (135, 235) sets the independent current limit state when the estimated required steering torque in the automatic steering mode is equal to or greater than a torque verification threshold; and the current limiting unit (135, 235) sets the common current limit state when the estimated required steering torque in the automatic steering mode is less than the torque verification threshold. [6] Steering control device according to one of claims 1 to 5, characterized by , that the current limiting unit (135, 235) gradually changes the current limit when the current limit is changed at a time of switching the control mode between the common current limit state and the independent current limit state. [7] Steering control device according to one of claims 1 to 6, characterized by , that the control unit (130, 230) includes a control signal calculation unit (140, 240) configured to generate the control signal by current feedback control; and the control signal calculation unit (140, 240) makes the current feedback control different from the current control according to the control mode. [8] Steering control device according to claim 7, characterized by , that the winding set (180, 280) as well as the drive circuit (120, 220) and the control unit (130, 230), which are arranged in correspondence to the winding set (180, 280), form a system; the control signal calculation unit (140, 240) is designed to generate the control signal by independent feedback control using a current detection value of a dedicated system when the control mode is the automatic steering mode; and the control signal calculation unit (140, 240) is designed to generate the control signal by coordinated feedback control using the current detection values of the own system and the other system, which controls a sum and a difference of currents flowing in the winding sets (180, 280) when the control mode is the manual steering mode. [9] Steering control device according to claim 8, characterized by , that the control signal calculation unit (140, 240) sets the current feedback control to the independent feedback control when the control mode is an override mode, which is a transition mode from the automatic steering mode to the manual steering mode. [10] Steering control device according to one of claims 1 to 9, characterized by , that the control unit (130, 230) carries out the change of the current control when no steering operation is carried out. [11] Steering control device according to claim 1, characterized by , that the control unit (130, 230) is configured to calculate the individual value of at least one of an overheat protection current limit, a power supply voltage reference current limit, a steering operation speed reference current limit, and a current difference reduction current limit.

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