Electric motor drive control device

Abstract

To provide a drive control device of an electric motor capable of suppressing increase in a circuit or a system scale caused by providing a backup system, and achieving miniaturization and cost reduction.SOLUTION: A drive control device for an electric motor includes a plurality of main drive systems 11, 12, a backup circuit unit 15, and switching circuits 14-1 to 14-6. Each of the plurality of main drive systems includes a drive circuit unit that supplies a drive current to a current-carrying phase winding and a control circuit unit that controls the drive circuit unit. The backup circuit unit backs up at least a part of the drive circuit unit, and the switching circuit switches at least a part of the drive circuit unit to the backup circuit unit. When at least a part of the drive circuit unit is replaced with the backup circuit unit, the backup circuit unit is controlled by the control circuit unit corresponding to the drive circuit unit in which the part is replaced.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The present invention relates to a drive control device for an electric motor, which drives the electric motor having a plurality of sets of multi-phase energized phase windings via a plurality of main drive systems.

BACKGROUND ART

[0002] Patent Document 1 describes a motor control device including motor drive circuits for a main system and a backup system. Each motor drive circuit is composed of a gate drive circuit and an inverter circuit. When an abnormality occurs in the main system, the motor drive circuit of the backup system energizes the motor windings with an energization pattern (UVW phases) similar to that of the main system, so as to continue driving the electric motor.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Meanwhile, in EPS (Electric Power Steering) systems that assist the steering operation of a vehicle with an electric motor, along with the expanding adoption of automated driving functions, drive control devices with dual motor drive systems have been developed and are becoming widespread in order to avoid "sudden loss of assist". In view of compatibility with Level 5 fully automated driving and SBWS (Steer-by-Wire System), the need to shift from dual to triple redundancy of control systems is increasing.

[0005] However, simple multiplexing as in Patent Document 1 has a problem in that the number of mounted components increases due to the expanded scale of circuits and systems, leading to an increase in the size of the circuit board of an ECU (Electronic Control Unit) and a rise in cost.

[0006] This invention has been made in view of the above circumstances, and its objective is to provide a drive control device for an electric motor that suppresses the increase in circuit and system size caused by the provision of a backup system, thereby enabling miniaturization and cost reduction. [Means for solving the problem]

[0007] According to one aspect of the present invention, a drive control device drives an electric motor having multiple sets of multiphase energized windings with multiple main drive systems, each having a drive circuit section that supplies drive current to the energized windings and a control circuit section that controls the drive circuit section, wherein the control device includes a backup circuit section that backs up at least a part of the drive circuit section and a switching circuit that switches at least a part of the drive circuit section to the backup circuit section, and when at least a part of the drive circuit section is replaced by the backup circuit section, the backup circuit section is controlled by the control circuit section corresponding to the drive circuit section that has been partially replaced. Each of the drive circuits of the multiple main drive systems is equipped with a multiphase bridge circuit, and the backup circuit is equipped with a half-bridge circuit, which is connected to the input wiring of the drive signals of the multiphase bridge circuit and the energized phase windings via the switching circuit. A drive control device for an electric motor is provided, characterized by the above. [Effects of the Invention]

[0008] In this invention, the control circuit section for controlling the backup system is a control circuit section corresponding to a drive circuit section in which at least a part of the main drive system has been replaced. This makes it possible to omit the control circuit section of the backup system and achieve a minimal configuration, thereby suppressing an increase in the size of the circuit and system. Therefore, it is possible to provide an electric motor drive control device that suppresses the increase in circuit and system size caused by the provision of a backup system, thereby achieving miniaturization and cost reduction. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing an example configuration of a drive control device for an electric motor according to an embodiment of the present invention. [Figure 2]This block diagram illustrates the backup operation in the electric motor drive control device shown in Figure 1, in the event of an abnormality or failure in the V-phase of the three-phase bridge circuit of the second main drive system. [Figure 3] Figure 1 shows a flowchart of the backup operation when the electric motor drive control device is applied to a vehicle's EPS system. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a schematic configuration of a drive control device for an electric motor according to an embodiment of the present invention. The drive control device 10 includes first and second main drive systems 11 and 12 for driving the electric motor M, and a backup circuit section 15 for continuing to drive the electric motor M when an abnormality occurs in one of the main drive systems. The electric motor M is a two-winding motor, and the winding arrangements of the two systems are different. The backup circuit section 15 consists of a half-bridge circuit 13 and switching circuits 14-1 and 14-2. These main drive systems 11 and 12 and the half-bridge circuit 13 are operated by a power supply voltage VB applied from a DC power supply 16.

[0011] The main drive system 11 consists of a power supply IC (power supply circuit) 21, a microcomputer (MCU) 22, a pre-driver 23, a three-phase bridge circuit (inverter circuit) 24, and switching circuits 14-3, 14-4, etc. The power supply IC 21 steps down the power supply voltage VB applied from the DC power supply 16 to generate the operating power supply voltage for the microcomputer 22 and the pre-driver 23. The microcomputer 22 generates a control signal to drive the three-phase bridge circuit 24 via the pre-driver 23 in order to drive the first winding set of the electric motor M. This control signal controls the first winding set of the electric motor M, for example, using PWM (Pulse Width Modulation) control.

[0012] In the main drive system 11, the three-phase bridge circuit 24 is a drive circuit that supplies drive current to the energized phase windings, and the microcomputer 22 and pre-driver 23 are control circuit sections that control the drive circuit.

[0013] The switching circuits 14-3 and 14-4 are each composed of relays and switching elements connected to the wiring of each phase (UVW). Here, MOSFETs, which are semiconductor switching elements, are used and are controlled on / off by the microcomputer 22. During normal operation (when there are no malfunctions or abnormalities), all MOSFETs constituting these switching circuits 14-3 and 14-4 are turned on.

[0014] The main drive system 12, like the main drive system 11, is composed of a power supply IC (power supply circuit) 31, a microcomputer 32, a pre-driver 33, a three-phase bridge circuit (inverter circuit) 34, and switching circuits 14-5, 14-6, etc. The power supply IC 31 steps down the power supply voltage VB applied from the DC power supply 16 to generate the operating power supply voltage for the microcomputer 32 and the pre-driver 33. The microcomputer 32 generates a control signal to drive the three-phase bridge circuit 34 via the pre-driver 33 in order to drive the second winding set of the electric motor M. This control signal controls the second winding set of the electric motor M, for example, using PWM control.

[0015] In the main drive system 12, the three-phase bridge circuit 34 is a drive circuit that supplies drive current to the energized phase windings, and the microcomputer 32 and pre-driver 33 are control circuit sections that control the drive circuit.

[0016] The switching circuits 14-5 and 14-6 are each composed of relays and switching elements connected to the wiring of each phase (UVW). Here, MOSFETs, which are semiconductor switching elements, are used and are controlled on / off by the microcomputer 32. During normal operation, all MOSFETs constituting these switching circuits 14-5 and 14-6 are turned on.

[0017] The switching circuit 14-1 has a switch unit 14-1a on the first main drive system 11 side and a switch unit 14-1b on the second main drive system 12 side, and the switching circuit 14-2 has a switch unit 14-2a on the first main drive system 11 side and a switch unit 14-2b on the second main drive system 12 side. Each of the switch units 14-1a, 14-1b, 14-2a, and 14-2b is composed of a relay or a switch element connected to the wiring of each phase. Here, MOSFETs which are semiconductor switch elements are used. For example, the MOSFETs constituting the switch units 14-1a and 14-2a are on / off controlled by the microcomputer 22. In addition, the MOSFETs constituting the switch units 14-1b and 14-2b are on / off controlled by the microcomputer 32.

[0018] Note that during normal operation, all the MOSFETs constituting these switching circuits 14-1 and 14-2 are off. As a result, the backup half-bridge circuit 13 is disconnected from the main drive systems 11 and 12.

[0019] The half-bridge circuit 13 functions as a backup circuit unit that replaces part of the three-phase bridge circuits 24 and 34 serving as the drive circuit units of the main drive systems. This half-bridge circuit 13 is configured by a half-bridge for one phase in the three-phase bridge circuit 24 or 34. When there is a failed phase in the three-phase bridge circuit 24 of the main drive system 11, a control signal is input from the microcomputer 22 to the half-bridge circuit 13 via the pre-driver 23 and the switch unit 14-1a of the switching circuit 14-1. Then, a PWM signal is output to the motor winding of the failed phase of the main drive system 11 via the switch unit 14-2a of the switching circuit 14-2.

[0020] On the other hand, when there is a faulty phase in the three-phase bridge circuit 34 of the main drive system 12, a control signal is input from the microcomputer 32 to the half-bridge circuit 13 via the pre-driver 33 and the switch unit 14-1b of the switching circuit 14-1. Then, a PWM signal is output to the motor winding of the faulty phase of the main drive system 12 via the switch unit 14-2b of the switching circuit 14-2.

[0021] Next, in the configuration as described above, the operation of switching to the backup system to continue driving when a failure (or abnormality) occurs in the main drive system will be described with reference to Figure 2. Figure 2 is a block diagram for explaining the backup operation when there is a failure or abnormality in the V-phase of the three-phase bridge circuit 34 of the second main drive system 12 in the electric motor drive control device shown in Figure 1.

[0022] As described above, in the normal operation state (state with no failure or abnormality), all the MOSFETs constituting the switching circuits 14-3 and 14-4 are controlled to be in the ON state by the microcomputer 22, all the MOSFETs constituting the switch unit 14-1a of the switching circuit 14-1 are set to the OFF state, and all the MOSFETs constituting the switch unit 14-2a of the switching circuit 14-2 are set to the OFF state. Further, all the MOSFETs constituting the switching circuits 14-5 and 14-6 are controlled to be in the ON state by the microcomputer 32, all the MOSFETs constituting the switch unit 14-1b of the switching circuit 14-1 are set to the OFF state, and all the MOSFETs constituting the switch unit 14-2b of the switching circuit 14-2 are set to the OFF state. As a result, the electric motor M is driven by the first and second main drive systems 11 and 12 under PWM control.

[0023] In response, when the microcomputer 32 detects a fault or abnormality in the V phase of the three-phase bridge circuit 34 of the second main drive system (indicated by an "x" in Figure 2), the microcomputer 32 switches MOSFET 14-5V and MOSFET 14-6V, which are connected to the V phase wiring of the three-phase bridge circuit 34, from the ON state to the OFF state. In addition, MOSFET 14-1bV, which is connected to the V phase wiring of the switch section 14-1b in the switching circuit 14-1, and MOSFET 14-2bV, which is connected to the V phase wiring of the switch section 14-2b in the switching circuit 14-2, are switched from the OFF state to the ON state.

[0024] Then, the microcomputer 32 supplies a PWM signal corresponding to the V phase of the three-phase bridge circuit 34 to the half-bridge circuit 13, as shown by the dashed arrow, to control it. This allows the X phase of the backup half-bridge circuit 13 to be replaced with the V phase inverter circuit in the three-phase bridge circuit 34 where an abnormality occurred, thereby enabling the electric motor M to continue operating.

[0025] Figure 3 is a flowchart of the backup operation when the electric motor drive control device shown in Figure 1 is applied to a vehicle's EPS system. Here, we will explain using the example of a case where the assist electric motor (two-winding motor) in the EPS system is driven by the first and second main drive systems 11 and 12, and when a failure or abnormality occurs in one of the drive systems, the system switches to the backup circuit 15 to continue driving.

[0026] First, when the vehicle's ignition switch (IGN SW) is turned on (step S1), an initial diagnosis of each main drive system 11,12 is performed (step S2). In the next step S3, it is determined whether the three-phase bridge circuits 24,34 are functioning correctly, and if they are deemed to be functioning correctly, a power relay (not shown) is turned on to start control (step S4).

[0027] Next, a command is received (step S5), and the steering angle of the vehicle is detected (step S6). Then, fault detection (or abnormality detection) of the main drive systems 11 and 12 is performed (step S7). Based on the fault detection result, it is determined whether the three-phase bridge circuits 24 and 34 are functioning normally or not (step S8).

[0028] If it is determined to be normal in step S8, a feedback process is performed (step S9) to calculate the current to be supplied to each winding set of the electric motor M (step S10). In the next step S11, calculations are performed for vector control of the assist electric motor M, and in step S12, a duty cycle calculation is performed to generate a PWM signal. Then, based on the results of these calculations, a PWM signal is output (step S13).

[0029] On the other hand, if it is determined in step S3 or step S8 that the three-phase bridge circuit 24 or 34 is abnormal, the faulty phase of the faulty three-phase bridge circuit is replaced with the backup half-bridge circuit 13 (step S14). Subsequently, the PWM settings of the microcomputer driving the faulty three-phase bridge circuit are performed (step S15), and the input of the PWM signal is switched (step S16).

[0030] In other words, the faulty phase is isolated and replaced with a half-bridge circuit. This replacement is performed by on / off control of the MOSFETs that constitute the switching circuit, as described above. Then, control of the backup half-bridge circuit 13 is performed in place of the faulty phase of the three-phase bridge circuit, thereby continuing control of the electric motor M.

[0031] Then, in step S17, it is determined whether the ignition switch (IGN SW) has been turned off. If it has been turned off, the process ends. If it has not been turned off, the process returns to step S5 and repeats the operations from step S5 to step S16 until the ignition switch is turned off.

[0032] With the drive control device for electric motors configured as described above, the backup system's microcomputer and pre-driver can be shared with the main drive system, resulting in a minimal configuration. Failures in the control system circuits, such as the microcomputer and pre-driver, which operate at low voltages, are mainly due to random failures and are relatively unlikely. In contrast, the switching elements such as MOSFETs that make up the three-phase bridge circuit (inverter circuit) have a relatively high failure rate due to the large thermal load caused by high currents. Furthermore, there is a possibility of upper and lower arm short-circuit failures due to incorrect switching of the upper and lower arms caused by disturbances, etc.

[0033] Therefore, by targeting three-phase bridge circuits (inverter circuits), which have a high failure rate, as the backup target, efficient backup becomes possible while suppressing the increase in circuit and system size that would otherwise be incurred by establishing a backup system. Moreover, since the backup system does not include a microcomputer or pre-driver, miniaturization and cost reduction can also be achieved.

[0034] Furthermore, by using a backup half-bridge circuit with fewer phases than the main drive system's half-bridge circuit and replacing each phase accordingly, further miniaturization becomes possible.

[0035] The configurations and methods described in the embodiments described above are merely schematic representations to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the embodiments described, and can be modified in various forms as long as it does not deviate from the scope of the technical idea set forth in the claims.

[0036] For example, we explained a configuration in which one phase of a three-phase bridge circuit (upper and lower arm half-bridge circuit) is replaced with the faulty phase of the main drive system, but it is also possible to provide two phases. In this case, it is possible to handle two locations or two faults (or abnormalities) in different phases of the main drive system.

[0037] Furthermore, the system may be configured to switch all drive circuit sections that experience a failure or malfunction in the main drive system to the backup circuit section. [Explanation of Symbols]

[0038] 10…Drive control device, 11…First main drive system, 12…Second main drive system, 13…Half-bridge circuit (backup circuit section), 14-1~14-6…Switching circuit, 15…Backup circuit section, 16…DC power supply, 21,31…Power supply IC (power supply circuit), 22,32…Microcomputer, 23,33…Pre-driver, 24,34…Three-phase bridge circuit (multi-phase bridge circuit), M…Electric motor

Claims

1. A drive control device for driving an electric motor having multiple sets of multiphase energized windings with multiple main drive systems, each having a drive circuit section that supplies drive current to the energized windings and a control circuit section that controls the drive circuit section, A backup circuit unit that backs up at least a part of the drive circuit unit, A switching circuit is provided to switch at least a part of the drive circuit to the backup circuit. When at least a portion of the drive circuit is replaced by the backup circuit, the backup circuit is controlled by the control circuit corresponding to the drive circuit that has been partially replaced. Each of the drive circuits of the aforementioned multiple main drive systems is equipped with a multiphase bridge circuit. The drive control device for an electric motor is characterized in that the backup circuit section comprises a half-bridge circuit, and the half-bridge circuit is connected to the input wiring of the drive signal of the multiphase bridge circuit and the energized phase winding via the switching circuit.

2. The drive control device for an electric motor according to Claim 1, characterized in that the switching circuit performs a switching to replace the faulty energized phase of the multiphase bridge circuit of the main drive system with the half-bridge circuit.

3. The drive control device for an electric motor according to claim 2, characterized in that the number of phases of the half-bridge circuit is less than the number of phases of the half-bridge circuit in the multi-phase bridge circuit of the main drive system.

4. The drive control device for an electric motor according to claim 2, characterized in that when a faulty phase is detected, the switching circuit disconnects the faulty energized phase of the multiphase bridge circuit of the main drive system and connects the half-bridge circuit to the energized phase winding corresponding to the faulty energized phase.

5. The drive control device for an electric motor according to claim 2, characterized in that when there is a faulty phase in the main drive system, the normal phase of the main drive system continues to operate together with the half-bridge circuit.

Images