Rotation speed control device

Abstract

Even if the motor resolver itself in the vehicle is displaced relative to the drive wheels, the motor is controlled at a precise rotational speed corresponding to the rotational state of the drive wheels. [Solution] The rotation speed control device 10 is a rotation speed control device 10 for a motor 4 that drives the vehicle 1 while being elastically supported by the vehicle body 8, and comprises a relative rotation speed acquisition unit 11 that acquires the relative rotation speed ωre of the rotor 4r with respect to the stator 4s of the motor 4, a posture acquisition unit 12 that acquires the relative posture θst of the stator 4s with respect to the vehicle body 8, and a calculation unit 13 that calculates the rotation speed of the motor 4 as the absolute rotation speed ωab of the rotor 4r with respect to the vehicle body 8 by correcting the relative rotation speed ωre using the relative posture θst.

Description

[Technical Field]

[0001] This invention relates to a vehicle rotation speed control device. [Background technology]

[0002] Conventionally, devices have been proposed to correct errors in the rotation angle of motors mounted on electric vehicles. For example, Patent Document 1 discloses a device that detects the rotation angle of a motor with a resolver, calculates the error between a reference angle and the rotation angle of the motor detected by the resolver at predetermined time intervals, and corrects the rotation angle of the resolver by learning this error. In this conventional technology, a technique is employed to minimize the error by learning multiple past rotation angle errors, thereby reducing the influence of disturbance errors even if the learning data contains them. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-252789 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in motors mounted on vehicles, the resolver itself may be displaced relative to the drive wheels along with the motor as the vehicle moves. Therefore, even if errors in the rotation angle between the rotor and stator can be corrected, errors may occur in the rotation angle of the motor relative to the drive wheels, potentially making it impossible to control the motor at an accurate rotational speed (rpm: revolutions per minute) corresponding to the rotational state of the drive wheels.

[0005] This disclosure has been made in view of the above issues, and its purpose is to provide a rotational speed control device that can control the motor at an accurate rotational speed corresponding to the rotational state of the drive wheel, even when the motor resolver itself in the vehicle is displaced relative to the drive wheel. [Means for solving the problem]

[0006] To achieve the above objective, the rotational speed control device of the present disclosure is a rotational speed control device for a motor that drives a vehicle while being elastically supported by a vehicle body, and comprises: a relative rotational speed acquisition unit that acquires the relative rotational speed of the rotor with respect to the stator of the motor; a posture acquisition unit that acquires the relative posture of the stator with respect to the vehicle body; and a calculation unit that calculates the rotational speed of the motor as the absolute rotational speed of the rotor with respect to the vehicle body by correcting the relative rotational speed using the relative posture. [Effects of the Invention]

[0007] The rotational speed control device of this disclosure acquires the relative rotational speed of the stator and rotor in the motor, as well as the relative attitude of the stator with respect to the vehicle body. By performing a correction that subtracts the change in relative attitude from the relative rotational speed, the absolute rotational speed of the rotor corresponding to the rotational speed of the drive wheels attached to the vehicle body can be calculated. Therefore, according to the rotational speed control device of the present invention, even if the resolver of the motor in the vehicle is displaced relative to the drive wheels, the motor can be controlled at an accurate rotational speed corresponding to the rotational state of the drive wheels. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram of a vehicle to which the rotational speed control device described herein is applied. [Figure 2] This is a schematic diagram showing the relative displacement between the vehicle body and the e-axle. [Figure 3] This waveform schematically represents the changes in motor torque and stator speed. [Figure 4] This is a control block diagram illustrating the error correction procedure in a rotational speed control device.

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the content described below, and can be arbitrarily modified and implemented without changing the gist thereof. Also, the drawings used in the description of the embodiments schematically show the constituent members, and partial emphasis, enlargement, reduction, or omission has been performed for better understanding, and there are cases where the scale, shape, etc. of the constituent members are not accurately represented.

[0010] FIG. 1 is a block diagram of a vehicle 1 to which a rotational speed control device 10 according to the present disclosure is applied. The vehicle 1 is an electric vehicle (EV) that travels by applying a driving force to a driving wheel W among a plurality of wheels W D and mainly includes a battery 2, an inverter 3, a motor 4, a reduction gear 5, a differential gear 6, an axle 7, a vehicle body 8, a plurality of elastic bodies 9, and a rotational speed control device 10. Note that the vehicle 1 may be a hybrid vehicle (HEV) or a plug-in hybrid vehicle (PHEV) that can be charged from the outside and supply power to the outside. Also, in addition to the illustrated configuration, the vehicle 1 is equipped with various components mounted on known electric vehicles.

[0011] The battery 2 is a power storage device composed of a lithium-ion battery or a nickel-metal hydride battery, and outputs the electric power required for driving the motor 4, and also supplies electric power to various electrical devices (not shown) mounted on the vehicle 1.

[0012] The inverter 3 is a power conversion device that converts DC power and AC power, and drives the motor 4 to rotate by converting the DC power output from the battery 2 into AC power and supplying it to the motor 4. Also, when the motor 4 generates regenerative power, the inverter 3 can charge the battery 2 by converting the AC power into DC power and supplying it to the battery 2.

[0013] The motor 4 is a driving motor that generates a driving force for driving the vehicle 1 when power is supplied from the inverter 3, and is also a motor generator (electric power generator) that can generate regenerative power during deceleration of the vehicle 1. The motor 4 includes a stator 4s, a rotor 4r, and a resolver R. The motor 4 is configured to measure and output the relative rotational speed of the rotor 4r with respect to the stator 4s by the resolver R (see FIG. 2).

[0014] The reduction gear 5 is a mechanism that increases the torque by reducing the rotational driving force (torque) output from the motor 4 by a reduction ratio N. The reduction ratio of the reduction gear 5 is appropriately set according to the output characteristics and performance of the motor 4.

[0015] The differential gear 6 is a mechanism for distributing the torque transmitted from the reduction gear 5 to the left and right drive wheels W according to the driving state of the vehicle 1. D

[0016] Here, the running drive system including the inverter 3, the motor 4, the reduction gear 5, and the differential gear 6 is integrated into a single housing as an e-axle E, thereby achieving a compact, lightweight, and low-cost configuration.

[0017] The axle 7 is a drive shaft for rotationally driving the left and right drive wheels W with the torque transmitted from the differential gear 6. D

[0018] The vehicle body 8 is a vehicle body frame that constitutes the skeleton of the vehicle 1 and includes a pair of left and right side members and a plurality of cross members (not shown). The vehicle body 8 also suspends the wheels W via a suspension (not shown).

[0019] ​​The multiple elastic bodies 9 are composed of, for example, spring bodies and are members that elastically support the e-axle E from multiple directions on the vehicle body 8. The multiple elastic bodies 9 can support the e-axle E on the vehicle body 8 while suppressing the shocks and vibrations transmitted between the vehicle body 8 and the e-axle E when the vehicle 1 is in motion. Note that the elastic bodies 9 are not limited to spring bodies and may be other shock-absorbing members such as rubber bushings.

[0020] The rotational speed control device 10 is an electronic control unit (ECU) that performs overall control of the vehicle 1, and is composed of input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and the like. The rotational speed control device 10 acquires information necessary for vehicle control from various components of the vehicle 1, such as the acceleration a of the vehicle 1 measured by the acceleration sensor Sa, and the tilt amount t of the vehicle 1 measured by the tilt sensor St.

[0021] Furthermore, the rotation speed control device 10 receives the rotation speed ω and motor torque T from the motor 4. M In addition to obtaining the necessary information, the rotational speed ω of the motor 4 is appropriately controlled via the inverter 3, as will be described in detail later. Furthermore, the rotational speed control device 10 has at least one of the known functions of traction control and anti-lock brake control, which prevent wheel slippage and locking, respectively.

[0022] In this embodiment, the rotation speed control device 10 includes a relative rotation speed acquisition unit 11, an attitude acquisition unit 12, a calculation unit 13, a torque acquisition unit 14, and a storage unit 15 as a functional module related to the rotation speed control of the motor 4.

[0023] The relative rotation speed acquisition unit 11 acquires the relative rotation speed ωre of the motor 4 from the resolver R. The attitude acquisition unit 12 acquires the relative attitude θst of the stator 4s with respect to the vehicle body 8 that changes as the displacement of the e-axle E changes (see FIG. 2). The calculation unit 13 calculates the rotation speed ω of the motor 4 as the absolute rotation speed ωab of the rotor 4r with respect to the vehicle body 8 by correcting the relative rotation speed ωre using the relative attitude θst. The torque acquisition unit 14 acquires the motor torque T M generated in the rotor 4r. The storage unit 15 stores in advance the correspondence relationship between the motor torque T M and the relative attitude θst when the vehicle 1 travels at a constant speed on a horizontal road surface.

[0024] The rotation speed control device 10 corrects the relative rotation speed ωre to the absolute rotation speed ωab by these functional modules so that the motor 4 rotates and drives at an appropriate rotation speed even when the e-axle E is displaced with respect to the vehicle body 8 as will be described in detail later.

[0025] FIG. 2 is a schematic diagram showing the relative displacement between the vehicle body 8 and the e-axle E. More specifically, FIG. 2 shows a state in which the e-axle E elastically supported on the vehicle body 8 via a plurality of elastic bodies 9 is displaced by the relative attitude θst with respect to the vehicle body 8 due to the driving reaction force T M ' of the motor 4. Here, the shapes and arrangements of the respective components are shown with significant simplification.

[0026] Here, the housing of the e-axle E, the stator 4s of the motor 4, and the resolver R are fixed to each other. On the other hand, the rotor 4r of the motor 4 rotates in conjunction with the axle 7 via the reduction gear 5 and the differential gear 6. For this reason, when the e-axle E is rotationally driven by the motor 4 with the motor torque T M , it receives the driving reaction force T M corresponding to the motor torque T M ' and is displaced by the relative attitude θst centered on the axle 7 with respect to the vehicle body 8.

[0027] FIG. 3 shows the motor torque T MAnd this is a waveform that schematically represents the change in stator rotational speed ωst. The relative attitude θst of the e-axle E is the motor torque T M When the magnitude changes, the motor torque T M The change will be proportional to this. At this time, the stator 4s of motor 4 will experience rotations equal to the stator rotational speed ωst, which is the time derivative of the relative posture θst, during the displacement process. As a result, motor 4 will have an error in rotational speed equivalent to the stator rotational speed ωst. Note that the relative posture θst is the motor torque T M Due to changes in size and other factors, the value may continue to fluctuate as vehicle 1 moves, and therefore cannot be ignored as a negligible amount.

[0028] Therefore, the rotational speed control device 10 according to this disclosure controls the motor 4 at an appropriate rotational speed by correcting the above error through the calculation described below. Figure 4 is a control block diagram showing the error correction calculation in the rotational speed control device 10.

[0029] The rotational speed control device 10 calculates the displacement of the e-axle E, which is suspended from the vehicle body 8 by multiple elastic bodies 9, as the relative attitude θst using a dynamic model M that models it as a spring-mass-damper system. In this dynamic model M, the axial rotational inertia Jst of the stator 4s, and the spring stiffness k and viscosity B parameters of the multiple elastic bodies 9 are used.

[0030] However, in this embodiment, the motor torque T M By pre-storing the relationship between the motor torque T and the relative attitude θst in the memory unit 15, the torque acquisition unit 14 sequentially acquires the motor torque T from the motor 4. M The relative posture θst can be obtained in the posture acquisition unit 12 by comparing the size of the elements in relation to the given relationship (first posture acquisition process).

[0031] Furthermore, in addition to the first attitude acquisition process described above, the attitude acquisition unit 12 is configured to acquire the relative attitude θst using the displacement x of the elastic body 9. More specifically, the attitude acquisition unit 12 expresses the force F acting on the e-axle E as F=kx, which is the relationship between the spring stiffness k of the elastic body 9 and the displacement x, and also expresses it as an equation of motion for the e-axle E that takes into account the weight m of the e-axle E, the acceleration a of the vehicle 1, and the acceleration g of gravity, thereby estimating the displacement x of each of the multiple elastic bodies 9. The attitude acquisition unit 12 also calculates the relative attitude θst of the e-axle E based on the displacement x of each elastic body 9 and its direction of displacement (second attitude acquisition process).

[0032] In other words, the attitude acquisition unit 12 according to this disclosure can acquire the relative attitude θst of the e-axle E in two ways: a first attitude acquisition process and a second attitude acquisition process. For this reason, the attitude acquisition unit 12 can acquire, for example, the motor torque T when the vehicle 1 is traveling at a constant speed on a relatively level road surface. M Based on this, the first posture acquisition process, which references the memory unit 15, allows for the acquisition of the relative posture θst at high speed without performing computationally intensive calculations.

[0033] On the other hand, the attitude acquisition unit 12 performs the second attitude acquisition process without executing the first attitude acquisition process if the acceleration a of the vehicle 1 measured by the acceleration sensor Sa exceeds a predetermined acceleration threshold. Here, the predetermined acceleration threshold is the motor torque T in the storage unit 15 as the acceleration a increases. M This is a threshold value of acceleration a that is arbitrarily set in advance to determine if the relationship between the relative posture θst and the actual posture deviates from the actual one. As a result, the posture acquisition unit 12 can acquire the accurate relative posture θst of the e-axle E even when the force F acting on the e-axle E is greatly affected by the acceleration a.

[0034] Furthermore, the attitude acquisition unit 12 performs the second attitude acquisition process without executing the first attitude acquisition process if the amount of inclination t of the vehicle 1 measured by the inclination sensor St exceeds a predetermined inclination threshold. Here, the predetermined inclination threshold is the motor torque T stored in the storage unit 15 as the amount of inclination t increases. MThis is a threshold for the amount of inclination t that is set arbitrarily in advance to determine if the relationship between the relative attitude θst and the actual attitude deviates from the actual attitude. As a result, the attitude acquisition unit 12 can acquire the accurate relative attitude θst of the e-axle E even when the force F acting on the e-axle E is greatly affected by the amount of inclination t.

[0035] The calculation unit 13 then calculates the stator rotation speed ωst of the stator 4s relative to the vehicle body 8 by differentiating the relative attitude θst acquired by the attitude acquisition unit 12 with respect to time using the differentiator D, as shown in Figure 4. The calculation unit 13 also calculates the absolute rotation speed ωab by subtracting the stator rotation speed ωst from the relative rotation speed ωre acquired by the relative rotation speed acquisition unit 11 via the resolver R. As a result, the rotation speed control device 10 can feedback control the motor 4 based on the absolute rotation speed ωab relative to the vehicle body 8, regardless of the displacement of the e-axle E.

[0036] As described above, the rotational speed control device 10 according to this disclosure acquires the relative rotational speed ωre between the stator 4s and rotor 4r of the motor 4, and also acquires the relative attitude θst of the stator 4s with respect to the vehicle body 8, and performs a correction by subtracting the change in relative attitude θst from the relative rotational speed ωre, thereby controlling the drive wheels W attached to the vehicle body 8. D The absolute rotational speed ωab of the rotor 4r corresponding to the rotational speed can be calculated. Therefore, according to the rotational speed control device 10 of this disclosure, the resolver R of the motor 4 in the vehicle 1 is the drive wheel W D Even when displaced relative to the drive wheel W D The motor 4 can be controlled with a precise rotation speed according to its rotational state.

[0037] Furthermore, the rotation speed control device 10 controls the motor torque T when the vehicle 1 is traveling at a constant speed on a level road surface. M The correspondence between the rotor and the relative attitude θst is stored in advance, and the motor torque T generated in the rotor 4r is stored. MThe relative attitude θst can be obtained from the motor 4 by acquiring the corresponding relationship. As a result, the rotational speed control device 10 does not need to calculate the relative attitude θst each time, and the response speed of rotational speed control can be increased by the first attitude acquisition process.

[0038] Furthermore, the rotational speed control device 10 estimates the displacement x of each of the multiple elastic bodies 9 that support the motor 4 on the vehicle body 8, and performs a second attitude acquisition process to acquire the relative attitude θst using the displacement x. As a result, the rotational speed control device 10 can acquire an accurate relative attitude θst even in driving conditions where the relative attitude θst acquired in the first attitude acquisition process deviates from the actual one.

[0039] Furthermore, the rotational speed control device 10 can obtain the accurate relative attitude θst of the e-axle E even when the force F acting on the e-axle E is greatly affected by the acceleration a, by executing the second attitude acquisition process without executing the first attitude acquisition process when the acceleration a of the vehicle 1 exceeds a predetermined acceleration threshold.

[0040] Furthermore, when the tilt amount t of the vehicle 1 exceeds a predetermined tilt threshold, the rotation speed control device 10 executes the second attitude acquisition process without executing the first attitude acquisition process, thereby enabling the accurate relative attitude θst of the e-axle E to be acquired even when the force F acting on the e-axle E is greatly affected by the tilt amount t.

[0041] Furthermore, the rotational speed control device 10 is applied to a vehicle 1 having at least one of the functions of traction control and anti-lock brake control, and when rotational speed control of the motor 4 is required, it provides feedback control of the motor 4 using the absolute rotational speed ωab described above. As a result, the rotational speed control device 10 can accurately control the rotational speed of the motor 4 regardless of the displacement of the motor 4 relative to the vehicle body 8, even when preventing wheelspin during starting and acceleration of the vehicle 1, and when preventing wheel lock during sudden braking of the vehicle 1. [Explanation of Symbols]

[0042] 1 vehicle 2 batteries 3 Inverter 4 motors 4s stator 4r rotor 5 reduction gear 6 Differential Gear 7 axles 8 car bodies 9 Elastic body 10. Speed ​​control device 11. Relative rotation speed acquisition unit 12 Attitude acquisition part 13 Calculation Section 14 Torque acquisition unit 15 Storage section E e-axle W wheels W D Drive wheels ωre Relative rotation speed ωab Absolute rotation speed ωst Stator rotation speed R resolver θst relative posture

Claims

1. A rotation speed control device for a motor that drives a vehicle while being elastically supported by the vehicle body, A relative rotation speed acquisition unit that acquires the relative rotation speed of the rotor with respect to the stator of the motor, An attitude acquisition unit that acquires the relative attitude of the stator with respect to the vehicle body, A rotation speed control device comprising: a calculation unit that calculates the rotation speed of the motor as the absolute rotation speed of the rotor relative to the vehicle body by correcting the relative rotation speed using the relative posture.

2. A torque acquisition unit that acquires the torque generated in the rotor, The vehicle comprises a storage unit that pre-stores the correspondence between the torque and the relative posture when the vehicle is traveling at a constant speed on a level road surface, The rotational speed control device according to claim 1, wherein the attitude acquisition unit performs a first attitude acquisition process to acquire the relative attitude by comparing the torque acquired by the torque acquisition unit with the correspondence relationship.

3. A rotational speed control device according to claim 2, which is applied to a vehicle having a plurality of elastic bodies that support the motor from a plurality of directions on the vehicle body, The attitude acquisition unit is a rotation speed control device that estimates the displacement amount of each of the plurality of elastic bodies and executes a second attitude acquisition process to acquire the relative attitude using the displacement amounts.

4. A rotational speed control device according to claim 3, which is applied to a vehicle having an acceleration sensor for measuring the acceleration of the vehicle, The attitude acquisition unit is a rotation speed control device that, when the acceleration exceeds a predetermined acceleration threshold, executes the second attitude acquisition process without executing the first attitude acquisition process.

5. A rotation speed control device according to claim 3, which is applied to a vehicle having a tilt sensor for measuring the amount of tilt of the vehicle body, The attitude acquisition unit is a rotation speed control device that, when the amount of inclination exceeds a predetermined inclination threshold, executes the second attitude acquisition process without executing the first attitude acquisition process.

6. A rotational speed control device according to claim 1 or 2, applicable to a vehicle having at least one of the functions of traction control and anti-lock brake control, A rotation speed control device that, when rotation speed control of the motor is required, uses the absolute rotation speed calculated by the calculation unit to perform feedback control of the motor.

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