Patent Application
20190334465
The present invention claims priority under 35 U.S.C. § 119 to Japanese Application No. 2018-084111 filed on Apr. 25, 2018 the entire contents of which is incorporated herein by reference.
The present disclosure relates to a motor drive unit.
In a conventional electric vehicle or the like, a driving torque of a motor as the drive source is controlled. A method of controlling the driving torque has been known in which a current controller restricts current to protect an inverter, a motor, and the vehicle from overvoltage, overcurrent, and temperature rise, for example.
However, in a main driving motor of the vehicle, the vehicle is controlled according to the driving torque. Hence, the aforementioned current control by the current controller hinders determination of the actual torque amount of the vehicle, and may inhibit torque control based on the actual torque amount.
In view of the above problem, a motor controller disclosed as a conventional technique includes: a torque upper limit calculation processor that calculates a torque upper limit of the motor according to the rotational speed of the motor; and a torque instruction value liming portion that limits the torque instruction based on the torque upper limit, and calculates a motor driving torque instruction value based on the limited torque instruction.
However, in the conventional motor controller, since the torque upper limit is acquired from a table, the torque can be limited only by a fixed value that is set according to the rotational speed of the motor. For example, when the motor needs to be controlled to have low speed and high torque, such as when continuously traveling uphill or downhill for a certain period, when driving onto a step, or when maintaining a stopped state, the torque requires limitation that cannot be set by use of the table. Hence, the motor has to be stopped.
An example embodiment of a motor controller of the present disclosure is a motor drive that controls a motor based on an instruction torque. The motor drive includes limiting circuitry that calculates a limitation rate that limits the instruction torque. The instruction torque is limited based on the limitation rate calculated by the limiting circuitry. The motor drive also includes a controller that outputs electric power that drives the motor based on the limited instruction torque.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Hereinafter, example embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the dimensional ratio in the drawings is expanded for the sake of simple description, and may differ from the actual ratio.
The motor drive unit 100 includes a torque controller 110, a current limiting value setting portion 120, an adder 130, a controller 140, a two phase to three phase converter 150, an inverter 160, a three phase to two phase converter 170, a current sensor 180, and a limiting portion 300. Note that the torque controller 110, the current limiting value setting portion 120, and the like are an example of a controller. The motor drive unit 100 is preferably provided as hardware or a combination of hardware and software. Each of the current limiting value setting portion 120, the adder 130, the controller 140, the two phase to three phase converter 150, the inverter 160, the three phase to two phase converter 170, the current sensor 180, and the limiting portion 300 are preferably provided by circuitry. Alternatively, the functions of the current limiting value setting portion 120, the adder 130, the controller 140, the two phase to three phase converter 150, the inverter 160, the three phase to two phase converter 170, the current sensor 180, and/or the limiting portion 300 could be reproduced using software or a combination of hardware and software.
An unillustrated vehicle controller switches to torque control when the vehicle accelerates. The torque controller 110 receives input of an instruction torque (torque instruction value) Tq from the vehicle controller by controller area network (CAN) communication, other communication, or hard wire (wire communication).
The torque controller 110 calculates a target torque for controlling the rotational frequency of the motor 400 by multiplying the instruction torque Tq by a limitation rate Lmin from the limiting portion 300, and calculates each of a d-axis current instruction value Id and a q-axis current instruction value Iq based on the calculated target torque. The calculated d-axis current instruction value Id and q-axis current instruction value Iq are output to the current limiting value setting portion 120. For example, if the limitation rate Lmin from the limiting portion 300 is 0%, the target torque is also 0 Nm, and the current instruction value is also set to 0 A.
The current limiting value setting portion 120 sets a d-axis current instruction value Id* and q-axis current instruction value Iq* as upper limits based on the d-axis current instruction value Id and q-axis current instruction value Iq supplied from the torque controller 110. The d-axis current instruction value Id* and q-axis current instruction value Iq* are output to the adder 130, and are also output to the limiting portion 300 as parameters used to calculate a limitation rate L5.
The three phase to two phase converter 170 performs dq transformation on phase currents Iu, Iv, Iw detected by the current sensor 180 based on an angle signal θ (electrical angle) feedback from the angle sensor 410, and calculates a d-axis current value Id** and a q-axis current value Iq**. The converted d-axis current value Id** and q-axis current value Iq** are output to the adder 130, and are also output to the limiting portion 300 as parameters used to calculate the limitation rate L5.
The adder 130 calculates a difference between the d-axis current instruction value Id* from the current limiting value setting portion 120 and the d-axis current value Id** from the three phase to two phase converter 170. The calculated difference is output to the controller 140. Similarly, the adder 130 calculates a difference between the q-axis current instruction value Iq* from the current limiting value setting portion 120 and the q-axis current value Iq** from the three phase to two phase converter 170. The calculated differences are output to the controller 140.
The controller 140 computes voltage instruction values Vd, Vq by performing proportional plus integral (PI) control computation, for example, such that the differences from the adder 130 converge to zero. The computed voltage instruction values Vd, Vq are output to the two phase to three phase converter 150.
The two phase to three phase converter 150 performs inverse dq transformation to transform the two phase voltage instruction values Vd, Vq into three phase voltage instruction values Vu, Vv, Vw of a u-phase, v-phase, and w-phase, based on an angle signal θ (electrical angle) feedback from the angle sensor 410. The three phase voltage instruction values Vu, Vv, Vw obtained by the inverse dq transformation are output to the inverter 160.
The inverter 160 has six bridge-connected switching elements. An insulated gate bipolar transistor (IGBT) may be used as the switching element, for example. The inverter 160 drives the switching element according to the three-phase PWM signal of a duty based on the three phase voltage instruction values Vu, Vw from the two phase to three phase converter 150, and thereby applies a voltage equivalent to the three phase voltage instruction values Vu, Vv, Vw to the motor 400. In the example embodiment, each switching element has a temperature sensor (not shown) for detecting a temperature T2 of the switching element. Additionally, a substrate on which the inverter 160 and other components are mounted has a temperature sensor (not shown) for detecting a temperature T3 of the substrate. Note that since the configuration of the above-mentioned three phase inverter circuit and the like is a known technique, detailed description is omitted.
The current sensor 180 detects the phase currents Iu, Iv, Iw supplied to the phases of the motor 400 from the inverter 160. The detected three phase currents Iu, Iv, Iw are output to the three phase to two phase converter 170.
The motor 400 is configured of a three-phase brushless motor, for example, and rotates by being driven by the inverter 160. In the example embodiment, the motor 400 has two temperature sensors (not shown), for example, for detecting a temperature T1 of the motor 400. Note that the number of temperature sensors is not limited to two.
The angle sensor 410 detects the angle signal θ according to a change in angle of the rotation axis of the motor 400. The detected angle signal θ is output to the two phase to three phase converter 150, the three phase to two phase converter 170, and a rotational speed calculator 230, for example. Note that a known angle detector such as a resolver or an MR sensor may be used as the angle sensor 410, for example.
The limiting portion 300 calculates the minimum limitation rate Lmin (output gain) based on limitation rates of multiple parameters such as the input phase currents Iu, Iv, Iw, a DC current I, and the temperature T1 of the motor 400. The limitation rate Lmin is a limiting value for limiting the instruction torque Tq to an optimal state depending on the traveling state of the vehicle. For example, if the limitation rate is 100%, the instruction torque Tq is set as the target torque, and the limitation is set such that the lower the limitation rate, the smaller the target torque. According to the example embodiment, since the instruction torque is limited by the limitation rate Lmin calculated by the limiting portion 300, even when the torque requires limitation that cannot be set by use of the conventional table storing torque upper limits, for example, the torque can be limited optimally.
The motor drive unit 100 also includes an adder 200, a speed controller 210, and the rotational speed calculator 230.
The unillustrated vehicle controller switches to rotational frequency control when the vehicle travels at low speed. The adder 200 receives input of an instruction rotational frequency ω* from the vehicle controller by CAN communication, other communication, or hard wire (wire communication). The adder 200 adds the input instruction rotational frequency ω* and a motor rotational speed ωe from the rotational speed calculator 230. The speed controller 210 controls speed based on information such as rotational frequency from the adder 200.
The converter 240 converts the analogue angle signal θ from the angle sensor 410 into digital data. Note that software having a conversion function or a device such as an R/D converter may be adopted as the converter 240. The angle sensor 0 degree learning portion 250 calculates a zero point from the angle of the motor 400 based on an input learning instruction. The adder 260 adjusts angle displacement between the motor 400 and the angle sensor 410, based on the angle signal θ from the converter 240 and zero-point information from the angle sensor 0 degree learning portion 250. The speed calculator 270 calculates the motor rotational speed ωe based on an electrical angle θe of the motor 400, for example. The calculated motor rotational speed ωe is output to the limiting portion 300 as a parameter used to calculate a limitation rate L4.
The DC current protector 310 acquires a DC current I of a power source such as a battery, for example. The cycle of acquiring the DC current I is 1 ms, for example. The DC current protector 310 calculates a limitation rate L1 of the acquired DC current I by use of a function graph for calculating the limitation rate L1. In addition, if the DC current protector 310 determines that the DC current I is abnormal after calculating the limitation rate L1, the DC current protector 310 notifies the user of warning and failure information. In the example embodiment, the notification may be made by sound, or by characters, image or the like displayed on a screen of a display, for example.
To calculate linear interpolation on the graph shown in
Where x represents the current DC current I, x0 represents a value that starts limitation of the DC current I, x1 represents a value that ends the limitation of the DC current I, y represents the limitation rate, y0 represents the minimum limitation rate L1, and y1 represents the maximum limitation rate L1.
Referring back to
Referring back to
The phase current protector 350 has an overcurrent detector 360, a current deviation detector 370, and a current sensor abnormality detector 380.
The overcurrent detector 360 acquires the phase currents Iu, Iv, Iw detected by the current sensor 180, and also acquires the DC current I of the power source. The cycle of acquiring the phase currents Iu, Iv, Iw, and the like is 1 ms, for example. The overcurrent detector 360 calculates a limitation rate L5a of the acquired phase currents Iu, Iv, Iw by using a function graph for calculating the limitation rate L5a. Similarly, the overcurrent detector 360 calculates a limitation rate L5b of the acquired DC current I of the power source by using a function graph for calculating the limitation rate L5b. Hereinbelow, a description will be given of a case of calculating the limitation rate L5a of the phase currents Iu, Iv, Iw.
The overcurrent detector 360 calculates the limitation rate L5b of the DC current I of the power source, too, by using the same linear pattern function graph as in
Referring back to
The current sensor abnormality detector 380 acquires the phase currents Iu, Iv, Iw detected by the current sensor 180. The cycle of acquiring the phase currents Iu, Iv, Iw, and the like is 1 ms, for example. The current sensor abnormality detector 380 calculates a limitation rate L5d of the phase currents Iu, Iv, Iw, too, by using the same linear pattern function graph as in
The phase current protector 350 selects the minimum limitation rate from among the limitation rates L5a, L5b calculated by the overcurrent detector 360, the limitation rate L5c calculated by the current deviation detector 370, and the limitation rate L5d calculated by the current sensor abnormality detector 380. The selected limitation rate is output to the selector 390 as the limitation rate L5. If it is determined that the phase currents Iu, Iv, Iw, and the like are abnormal, the phase current protector 350 notifies the user of warning and failure information.
The overspeed protector 340 acquires the motor rotational speed ωe from the rotational speed calculator 230. The cycle of acquiring the motor rotational speed ωe, and the like is 1 ms, for example. The overspeed protector 340 calculates the limitation rate L4 of the acquired motor rotational speed ωe, too, by using the same linear pattern function graph as in
The selector 390 compares the limitation rate L1 from the DC current protector 310, the limitation rate L2 from the overvoltage-low-voltage protector 320, the limitation rate L3 from the overheat protector 330, the limitation rate L4 from the overspeed protector 340, and the limitation rate L5 from the phase current protector 350, and selects the minimum limitation rate Lmin of the limitation rates L1 to L5. The selected limitation rate Lmin is output to the torque controller 110. According to the example embodiment, since the minimum limitation rate Lmin is selected, torque can be controlled with the strictest limitation.
As shown in
Next, in step S60, the DC current protector 310 calculates the limitation rate L1 based on the acquired DC current I of the power source. In in step S70, the overvoltage-low-voltage protector 320 calculates the limitation rate L2 based on the acquired power supply voltage V of the power source. In step S80, the overheat protector 330 calculates the limitation rate L3 based on the acquired temperature T1 of the motor 400, and the like. In step S90, the overspeed protector 340 calculates the limitation rate L4 based on the acquired motor rotational speed ωe. In step S100, the phase current protector 350 calculates the limitation rate L5 based on the acquired phase currents Iu, Iv, Iw flowing through the motor 400. Note that the steps S60 to S100 may be processed in parallel at the same time.
Next, in step S110, the selector 390 selects the minimum limitation rate Lmin of the calculated limitation rates L1 to L5, and outputs the selected limitation rate Lmin to the torque controller 110. In the example embodiment, such processing is repeated at predetermined intervals.
As has been described, according to the example embodiment, multiple parameters such as the temperatures T1 to T3, the DC current I of the power source, the power supply voltage V, the motor rotational speed ωe, and the phase currents Iu, Iv, Iw are taken into account, and the limitation rate of the parameter having the highest level of abnormality among the parameters can be selected as the minimum limitation rate Lmin to limit the instruction torque Tq. Accordingly, even when the torque requires limitation that cannot be set by use of the conventional table storing torque upper limits, for example, the instruction torque can be limited optimally. As a result, overcurrent, overvoltage, overspeed, or temperature rise, for example, can be surely suppressed during operation of the motor 400.
Note that the technical scope of the present disclosure is not limited to the above example embodiment, and includes various modifications of the above example embodiment without departing from the gist of the present disclosure. Although the above example embodiment describes an example of using five limitation rates L1 to L5, the disclosure is not limited to this. For example, the instruction torque Tq may be limited by using limitation rates of at least two or more parameters. The temperature acquired by the limiting portion 300 may be at least one or more of the temperature T1 of the motor 400, temperature T2 of the switching element, and temperature T3 of the substrate, or may be temperatures related to other parts of the motor drive unit 100.
While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-084111 | Apr 2018 | JP | national |
