JP6136803B2 - Motor control device and electric power steering device using the same - Google Patents

Description

  The present invention calculates each phase duty command value for controlling the motor current by control calculation, forms a PWM (pulse width modulation) signal corresponding to each phase duty command value, and outputs the PWM signal from the inverter to the motor. The present invention relates to a motor control device that is driven by applying a command current (voltage), and also relates to an electric power steering device that uses the motor control device to apply assist force by a motor to a steering system of a vehicle. In particular, a single current detection circuit (one shunt type current detection circuit) is arranged on the power input side or power output side (grounding side) of the inverter for PWM control, and at the timing of duty pattern switching, a rotation sensor By using the estimated motor angle value estimated from multiple previous motor angles (memory values) without using the motor angle signal detected in step 1, the noise is eliminated and the effect of fluctuations in the motor angle is prevented. The present invention relates to an inexpensive and low-noise motor control device and an electric power steering device using the same.

  An electric power steering device that applies a steering assist force (assist force) to a steering mechanism of a vehicle by a rotational force of a motor, a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. A steering assist force is applied to the vehicle. Such a conventional electric power steering device (EPS) performs feedback control of the motor current in order to accurately generate the torque of the steering assist force. In feedback control, the motor applied voltage is adjusted so that the difference between the steering assist command value (current command value) and the motor current detection value is small. In general, the adjustment of the motor applied voltage is performed by duty control of PWM control. This is done by adjusting the command value.

  The general configuration of the electric power steering apparatus will be described with reference to FIG. 1. A column shaft (steering shaft) 2 of the handle 1 is passed through a reduction gear 3, universal joints 4a and 4b, a pinion rack mechanism 5, and tie rods 6a and 6b. Furthermore, it is connected to the steering wheels 8L and 8R via the hub units 7a and 7b. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft 2 via the reduction gear 3. . The control unit (ECU) 100 that controls the electric power steering apparatus is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11. The control unit 100 calculates a current command value of an assist (steering assistance) command based on the steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel detected by the vehicle speed sensor 12, and compensates the current command value. The current supplied to the motor 20 is controlled by the voltage control value E subjected to. The vehicle speed Vel can also be received from a CAN (Controller Area Network) or the like.

  The control unit 100 is mainly composed of a CPU (or MPU or MCU). FIG. 2 shows general functions executed by programs in the CPU.

  The function and operation of the control unit 100 will be described with reference to FIG. 2. The steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel from the vehicle speed sensor 12 are input to the current command value calculation unit 101, and an assist map or the like is displayed. The current command value Iref1 is calculated using this. The calculated current command value Iref1 is limited by the maximum output limiting unit 102 based on the overheat protection condition and the like, and the current command value Iref2 whose maximum output is limited is input to the subtracting unit 103. The current command value calculation unit 101 and the maximum output limit unit 102 constitute a torque control unit.

The subtraction unit 103 obtains a deviation current Iref3 (= Iref2-Im) between the current command value Iref2 and the motor current Im of the motor 20 that is fed back, and the deviation current Iref3 is a current control unit 104 such as PI (proportional / integral). The controlled voltage control value E is input to the PWM control unit 105 to calculate the duty command value, and the motor 20 is driven via the inverter 106 by the PWM signal PS calculated from the duty command value. The PWM control unit 105 is input with a sawtooth phase carrier signal CS having a predetermined frequency generated by the carrier signal generation unit 107. The motor current Im of the motor 20 is detected by the current detection circuit 120 in the inverter 106, and the detected motor current Im is input to the subtraction unit 103 and fed back. When a brushless DC motor is used as the motor 20 in vector control or the like, for example, a resolver 21 is connected to the motor 20 as a rotation sensor, and an angular velocity calculation unit 22 that calculates a motor angular velocity ω from a motor angle (angle signal) θ. Is provided.
The inverter 106 that controls the motor current Im with the voltage control value E and drives the motor 20 uses a bridge circuit in which a semiconductor switching element (for example, FET) and the motor 20 are bridge-connected, and is based on the voltage control value E. Based on the determined duty command value of the PWM signal PS, the semiconductor switching element is ON / OFF controlled to control the motor current Im.

  When the motor 20 is a three-phase (U, V, W) brushless DC motor, details of the PWM control unit 105 and the inverter 106 are configured as shown in FIG. 3, for example. That is, the PWM control unit 105 inputs each phase carrier signal CS and calculates the voltage control value E to the PWM-Duty command values D1 to D6 for three phases (U, V, W) according to a predetermined formula. Part 105A and a gate drive part 105B that drives each gate of FET1 to FET6 with PWM-Duty command values D1 to D6 to turn on / off, and inverter 106 includes U-phase upper stage FET1 and lower stage FET4. And a three-phase bridge composed of an upper and lower arm composed of a V-phase upper stage FET 2 and a lower stage FET 5 and a W phase upper stage FET 3 and a lower stage FET 6, and a PWM-Duty command value D1 The motor 20 is driven by being turned ON / OFF at .about.D6. In addition, power is supplied to the inverter 106 from the battery 13 via the power relay 14.

  In such a configuration, it is necessary to measure the drive current of the inverter 106 or the motor current of the motor 20, but as one of the required items for the compactness, weight reduction, and cost reduction of the control unit 100, the current detection circuit 120 There is unification. A single shunt type current detection circuit is known as the unification of current detection circuits, and the configuration of the single shunt type current detection circuit 120 is as shown in FIG. 4 (for example, Japanese Patent Application Laid-Open No. 2009-131064). ). That is, one shunt resistor R1 is connected between the bottom arm of the FET bridge and the ground (GND), and a voltage drop caused by the shunt resistor R1 when a current flows through the FET bridge is an operational amplifier (differential amplifier circuit). ) 121 and resistors R2 to R4 are converted into a current value Ima, and further A / D converted at a predetermined timing by an A / D converter 122 through a filter composed of a resistor R6 and a capacitor C1, and a digital current value Im is obtained. It is designed to output. In addition, 2.5V which becomes a reference voltage is connected to the positive terminal input of the operational amplifier 121 through the resistor R5.

  When the current of each phase of UVW is detected by such a single shunt current detection circuit, for example, as shown in Japanese Patent Application Laid-Open No. 2010-279141 (Patent Document 1), determination of maximum duty, intermediate duty, and minimum duty is performed. And a method of sequentially rearranging the shifted carrier period is used. That is, the magnitude of the duty setting value of each phase is compared to determine the maximum phase, the intermediate phase, and the minimum phase, and the rising phase Y of the maximum phase carrier signal is determined with reference to the rising phase Y of the intermediate phase carrier signal. Advancing the phase by a certain amount, delaying the rising phase of the carrier signal of the smallest phase by a certain amount, and generating each phase PWM signal based on the carrier signal of each phase shifted from each other and the duty setting value of each phase In addition, current detection is performed in predetermined intervals Tu and Tw until the rising of each of the intermediate phase PWM signal and the minimum phase PWM signal. Thereby, the motor current of each phase can be detected by a single current detection circuit.

JP 2010-279141 A JP 2006-33903 A JP 2012-125106 A

  In the motor control device disclosed in Patent Document 1, the PWM rising timing is within the range of the carrier cycles TC1 and TC2 in FIG. 5 when the UVW3 phase is the maximum phase, intermediate phase, and minimum phase depending on the rotation angle of the motor. As shown in the figure, the signal rises in the order of U, V, and W. However, at the next moment, if the magnitude relationship of the duty of the UVW3 phase changes to the maximum of the U phase, the minimum of the V phase, and the middle of the W phase as shown in the range of the carrier cycle TC3 in FIG. The timing changes from U phase → V phase → W phase to U phase → W phase → V phase. Due to this change, an unintended duty variation shown in FIG. 5 temporarily occurs.

FIGS. 6A to 6J show an example of the operation. FIG. 6A shows a state in which the phase order of the V-phase duty command value is switched from the intermediate phase to the minimum phase at time t1. 6 (B) shows the V-phase current based on the V-phase Duty command value, and shows that the current fluctuation (distortion) due to the temporary Duty fluctuation generated by the phase switching occurs after time t1. ing. FIG. 6C shows a state in which the phase order of the W-phase duty command value is switched from the minimum phase to the intermediate phase at time t1, and FIG. 6D shows the W-phase current based on the W-phase duty command value. It shows that current fluctuation (distortion) due to phase switching occurs after time t1.
Thus, at the time point t1, fluctuation (distortion) occurs in the V-phase current and the W-phase current due to the temporary duty fluctuation caused by the switching of the PWM switching timing in the phase order of the V-phase and the W-phase. As shown in FIG. 6 (E), the motor angle fluctuates. As a result, the detected motor angle value fluctuates as shown in FIG. 6 (F), and the calculated current command value becomes as shown in FIG. 6 (G). fluctuate. As a result, as shown in FIGS. 6H to 6J, noise is generated due to fluctuations in the duty command value of each UVW phase, and sound and vibration are generated.

  As described above, the Duty phase sequence fluctuation due to the PWM phase shift occurs at the moment of the PWM phase shift, and this Duty phase sequence fluctuation causes the fluctuation (distortion) of the V phase current and the W phase current, for example. Causes fluctuations in the motor angle, thereby causing fluctuations in the detected motor angle value, and in response to fluctuations in the detected value, the torque control unit and the current control unit react to generate fluctuations in the current command value and the duty command value. . As a result, a series of feedback loops in which the V-phase current and the W-phase current further fluctuate are formed, causing an undesirable phenomenon in which sound and vibration are generated. The generation of sound and vibration in the electric power steering apparatus makes the driver uncomfortable and deteriorates steering performance.

  As a technique for reducing such a problem, it is conceivable to suppress the fluctuation by treating the fluctuating motor angle as noise and performing a certain filtering process.

  However, switching noise is generally considered as noise superimposed on a rotation (angle) signal of a rotation sensor such as a resolver. As a method for reducing such switching noise, for example, Japanese Patent Application No. 2006-33903 (patent) As disclosed in the literature 2), a method for reducing noise by averaging resolver output signals is generally known. However, if a filter that removes step-like noise due to PWM phase switching as described above is used, the resolver output signal itself may not be accurately reproduced. In the case of an electric power steering device, There is a problem that the steering performance becomes undesirable for the driver.

In the control device disclosed in Japanese Patent Application Laid-Open No. 2012-125106 (Patent Document 3), rotation detection related correction 1 and modulation rate related correction 2 are used to reduce angle detection noise due to switching noise. However, in the apparatus of Patent Document 3, since all signal processing is performed using the current value detected by the resolver, there is a problem that fluctuations in the resolver output signal itself directly affect the signal processing.
Furthermore, neither Patent Documents 2 and 3 disclose a motor current detection method, nor do they take into account the compactness, weight reduction, and cost reduction of the controller.
The present invention has been made under the circumstances as described above, and an object of the present invention is to detect a motor current using an inexpensive and compact one-shunt current detection circuit, and to detect a duty variation due to PWM phase shift as a PWM phase. Providing a motor control device that does not cause unpleasant phenomena such as noise and vibration without causing fluctuations in the current command value and duty command value even when it occurs at the moment of shifting, and an electric power steering device using the motor control device There is to do.

The present invention calculates each phase duty command value for controlling the motor current by control calculation, forms a PWM signal according to each phase duty command value, and controls the motor by an inverter based on the PWM signal. The motor control device is provided with a rotation sensor for driving and detecting a motor angle of the motor. The object of the present invention is to provide a one-shunt current detection circuit connected to the power source side or the ground side of the inverter. A comparison unit that compares the phase duty command values of each phase to determine a magnitude relationship;
Based on the magnitude relationship, a timing control unit that sequentially raises the rising or falling timing of the PWM signal in a predetermined order, and the rising order is changed according to a predetermined algorithm, and the rising order is changed. This is achieved only by providing a motor angle output unit that estimates a motor angle estimated value based on the past value of the rotation sensor and outputs the motor angle estimated value as the motor angle only at a predetermined timing.

Further, the object of the present invention is that the predetermined order is the order of the maximum phase, the intermediate phase, and the minimum phase of the Duty command value, or the predetermined algorithm is a maximum phase, an intermediate phase of each phase, Phase change detection in which the rising order is also changed at the timing when the relationship of the minimum phase changes, or the motor angle output unit detects a change in the relationship of the maximum phase, intermediate phase, and minimum phase And a storage unit that stores the motor angle from the rotation sensor in a predetermined cycle, and a motor angle estimation unit that estimates the motor angle estimation value from a plurality of past values of the storage unit. Alternatively, this is achieved more effectively by the motor angle estimator estimating the estimated motor angle value by linear approximation, or when the rotation sensor is a resolver.
By mounting the motor control devices, the above-described electric power steering device can be achieved.

According to the present invention, at the PWM phase shift timing, the motor angle (angle signal) from the rotation sensor (for example, resolver) is not used, but the motor angle is obtained by linear approximation using a plurality of previous values stored in the storage unit. By estimating and using the estimated motor angle estimated value, it is possible to minimize or suppress the fluctuation of the detected motor angle, which is one of feedback loops that cause undesirable phenomena such as sound and vibration.
As a result, since current fluctuation (distortion) and motor angle fluctuation accompanying PWM phase switching do not affect the detected motor angle value, the current command value becomes a smooth command value waveform in which fluctuation of the detected motor angle value does not propagate. The duty command value can also obtain a smooth duty command value waveform that is not affected by the above fluctuation. Since the duty command value has a smooth waveform that is not affected by fluctuations in the detected motor angle value, it is possible to reduce or suppress the occurrence of an unpleasant phenomenon that is undesirable for the motor control device and the electric power steering device.

It is a lineblock diagram showing an outline of an electric power steering device. It is a block diagram which shows the general structural example of a control unit. It is a connection diagram which shows the structural example of a PWM control part and an inverter. It is a connection diagram which shows the structural example of a 1 shunt-type current detection circuit. It is a PWM phase diagram which shows a mode that the phase order of the PWM phase of a duty command value is changed. It is a time chart which shows the operation example of a conventional apparatus. It is a block block diagram which shows one Embodiment of this invention. It is a flowchart which shows the operation example of this invention. It is a flowchart which shows the operation example of motor angle estimation. It is a characteristic view which shows the effect of this invention.

  In the motor control device (electric power steering device) of the present invention, a single current detection circuit (one shunt type current detection circuit) is provided between the inverter and the power source or between the inverter and the ground (GND). . Then, in order to reliably detect the motor current of each phase of UVW with a single shunt type current detection circuit, the magnitude of the duty command value of each phase is compared to determine the maximum phase, intermediate phase, and minimum phase. The rising phase of the carrier signal of the largest phase is advanced by a fixed amount, and the rising phase of the carrier signal of the smallest phase is delayed by a fixed amount, and the phases of the phases shifted from each other. Each phase PWM signal is generated based on the carrier signal and the duty command value of each phase, and current detection is performed in a predetermined interval until each rising edge of the intermediate phase PWM signal and the minimum phase PWM signal.

  In the present invention, switching of the phase order of the Duty pattern is detected, and only at the detected phase order switching timing, the motor angle (angle signal) detected by the resolver or the like is not used, and a plurality of stored values ( By using the estimated motor angle estimated from the (motor angle), it is possible to prevent or suppress the variation of the duty command value caused by the variation of the detected motor angle value at the phase sequence switching timing without passing through a special filter. Is possible. The motor angle detected by the resolver or the like is used as it is except for the timing of switching the duty pattern phase order.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 7 shows the configuration of an embodiment of the present invention corresponding to FIG. 2, and it corresponds to the duty of the PWM signal of each phase based on the voltage control value E and the carrier signal CS from the current control unit 104. The duty setting unit 130 for setting the duty command value DS is compared with the duty command value DS of each phase set by the duty setting unit 130, and the duty command value DS is the maximum phase with the maximum magnitude, the duty command value DS. A comparison unit 131 that determines an intermediate phase having a medium size and a minimum phase having a minimum duty command value DS and outputs a magnitude relationship signal SR, and a magnitude relationship signal SR and a carrier signal CS from the comparison unit 131 Based on the above, the rise or fall timing of the three-phase PWM signal is raised in a predetermined order, for example, in the order of maximum phase → intermediate phase → minimum phase of the duty command value DS, and the motor 20 is driven via the inverter 106 PWM signal P And a timing controller 132 for outputting.

Furthermore, a phase change detection unit 142 that detects that a change has occurred in the rising order of the three-phase PWM signal PS output from the timing control unit 132 and outputs a phase change signal PC when the change occurs, Only when the storage unit 141 that stores the motor angle θ from the resolver 21 in a predetermined cycle and the phase change signal PC is output from the phase change detection unit 142, the storage unit 141 reads the storage angle data θm of the past plural times. A motor angle estimator 140 is provided that estimates a motor angle by linear approximation and outputs a motor angle estimated value θe.
When the phase change signal PC is not output from the phase change detection unit 142, the motor angle θ of the resolver 21 is output as it is as the motor angle estimated value θe. That is, when the phase change signal PC is not output, the estimated motor angle θe = the motor angle θ. The current command value Iref2 calculated by the torque control unit 110 is input to the subtraction unit 103, and the current command value Iref3, which is a deviation from the motor current Im detected by the one-shunt current detection circuit 120, is the current control unit. 104 is input.

  Since the output from the resolver 21 is an analog signal, the storage unit 141 actually stores a digital value A / D converted by R / D conversion or the like as a motor angle θ at a predetermined sampling period. The motor angle estimation unit 140, the storage unit 141, and the phase change detection unit 142 constitute a motor angle output unit.

  In such a configuration, an example of the operation will be described with reference to the flowchart of FIG. In this flowchart, only the parts related to the present invention will be described.

  First, the duty setting unit 130 inputs the voltage control value E calculated by the current control unit 104 and the carrier signal CS generated by the carrier signal generation unit 107 (step S1), and enters the duty of the PWM signal of each phase. A corresponding duty command value DS is set (step S2). The duty command value DS set by the duty setting unit 130 is input to the comparison unit 131, the duty command value DS of each phase is compared, the maximum phase with the maximum duty command value DS, the magnitude of the duty command value DS The intermediate phase and the minimum phase with the smallest duty command value DS are determined and the magnitude relation signal SR is output (step S3).

  The timing control unit 132 receives the magnitude relation signal SR from the comparison unit 131, and sequentially raises the rising (or falling) timing of the three-phase PWM signal in a predetermined order (step S4). The predetermined order is, for example, the order of maximum phase → intermediate phase → minimum phase of Duty command value DS, or the order of minimum phase → intermediate phase → maximum phase. The PWM signal PS whose timing is controlled by the timing controller 132 is output (step S5), and the motor 20 is driven via the inverter 106 by the PWM signal PS (step S10).

  The motor current of each phase of the motor 20 is detected by the 1-shunt type current detection circuit 120 as described above (step S11), and the detected motor current detection value Im is fed back to the subtraction unit 103. The resolver 21 detects the motor angle θ (step S12), and the detected motor angle θ is stored in the storage unit 141 at a predetermined sampling period (step S13).

  On the other hand, the phase change detection unit 142 detects whether or not there is a phase change by changing the rising order based on the PWM signal PS (step S14), and when the phase change is detected. The phase change signal PC is output. The phase change signal PC is input to the storage unit 141 and the motor angle estimation unit 140. The motor angle estimation unit 140 reads a plurality of past motor angles θm from the storage unit 141 immediately before the phase change signal PC is input, The motor angle θe is estimated by linear approximation based on a plurality of motor angles θm (step S20). The estimated motor angle estimation value θe is output from the motor angle estimation unit 140 (step S30). When the phase change signal PC is not output from the phase change detection unit 142, the motor angle θ detected by the resolver 21 is output as it is as a motor angle estimated value θe (= θ).

  The flowchart of FIG. 9 shows details of the motor angle estimation in step S20. When the phase change signal PC is input from the phase change detection unit 142 (step S21), the storage unit 142 stores a plurality of past records. A value (motor angle θm) is read (step S22). The motor angle estimator 140 estimates the motor angle by a known linear approximation operation using the read past stored values (step S23), and outputs the estimated motor angle estimated value θe (step S24). .

  FIG. 10 shows the effect of the present invention in comparison with FIG. In the present invention, even if the motor angle θ fluctuates as shown in FIG. 10E due to the phase change, when the phase change occurs as shown in FIGS. 10A and 10C, the phase change detection unit Based on the phase change signal PC detected at 142, the motor angle estimation unit 140 estimates the motor angle from the past value θm of the motor angle θ by linear approximation or logarithmic approximation as shown in FIG. The estimated motor angle estimated value θe is used for the control calculation. Therefore, as shown in FIGS. 10 (G) to (J), the current command value and each phase duty command value do not vary, and a smooth current command value and each phase duty command value can be output. it can.

1 Handle 10 Torque Sensor 12 Vehicle Speed Sensor 13 Battery 20 Motor 21 Resolver 22 Angular Speed Calculation Unit 100 Control Unit (ECU)
101 Current Command Value Calculation Unit 102 Maximum Output Limiting Unit 104 Current Control Unit 105 PWM Control Unit 105A Duty Calculation Unit 105B Gate Drive Unit 106 Inverter 107 Carrier Signal Generation Unit 120 1 Shunt Type Current Detection Circuit 130 Duty Setting Unit 131 Comparison Unit 132 Timing Control unit 140 Motor angle estimation unit 141 Storage unit 142 Phase change detection unit

Claims (7)

Calculate each phase duty command value for controlling the motor current by control calculation, form a PWM signal according to each phase duty command value, drive the motor by an inverter based on the PWM signal, In the motor control device provided with the rotation sensor for detecting the motor angle of the motor,
A one-shunt current detection circuit is connected to the power supply side or ground side of the inverter,
A comparison unit that determines the magnitude relationship by comparing each phase Duty command value;
A timing controller that sequentially raises the rising or falling timing of the PWM signal in a predetermined order based on the magnitude relationship;
The rising order is changed according to a predetermined algorithm, and only at the timing when the rising order is changed, a motor angle estimated value is estimated based on the past value of the rotation sensor, and the motor angle estimated value is A motor angle output unit that outputs the motor angle;
A motor control device comprising: The motor control device according to claim 1, wherein the predetermined order is an order of a maximum phase, an intermediate phase, and a minimum phase of the duty command value. 3. The motor control device according to claim 1, wherein the predetermined algorithm is such that the order of the rising is also changed at a timing when a relationship between a maximum phase, an intermediate phase, and a minimum phase of each phase changes. The motor angle output unit includes a phase change detection unit that detects a change in the relationship between the maximum phase, intermediate phase, and minimum phase, a storage unit that stores a motor angle from the rotation sensor at a predetermined period, and The motor control device according to any one of claims 1 to 3, comprising a motor angle estimation unit that estimates the motor angle estimation value from a plurality of past values. The motor control device according to claim 4, wherein the motor angle estimation unit estimates the motor angle estimation value by linear approximation. The motor control device according to claim 1, wherein the rotation sensor is a resolver. An electric power steering apparatus comprising the motor control device according to any one of claims 1 to 6.

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