阅读说明：本技术 扭矩波动补偿装置和方法 (Torque ripple compensation apparatus and method ) 是由 金仁赫 金奎河 郑贤熙 徐正薰 于 2020-02-21 设计创作，主要内容包括：一种扭矩波动补偿装置可以包括：扭矩测量单元,被配置为输出通过MDPS系统的扭矩传感器测量的扭矩；马达速度测量单元,被配置为输出通过MDPS马达的位置传感器测量的马达速度；控制单元,被配置为基于所述马达速度信息和测量的扭矩信息分别输出偏移信号和扭矩波动信号；和扭矩波动补偿单元,其被配置为合成从控制单元输出的多个扭矩波动信号,并且将扭矩波动补偿信号作为马达控制信号输出到所述MDPS马达,所述扭矩波动补偿信号用于补偿合成的扭矩波动信号。所述扭矩波动补偿装置能减小在驱动车辆的MDPS(马达驱动动力转向)系统的马达时出现的扭矩波动。(A torque ripple compensating device may include: a torque measurement unit configured to output a torque measured by a torque sensor of the MDPS system; a motor speed measurement unit configured to output a motor speed measured by a position sensor of the MDPS motor; a control unit configured to output an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively; and a torque ripple compensating unit configured to synthesize a plurality of torque ripple signals output from the control unit and output a torque ripple compensating signal as a motor control signal to the MDPS motor, the torque ripple compensating signal being for compensating the synthesized torque ripple signal. The torque ripple compensating apparatus can reduce torque ripple occurring when a motor of an MDPS (motor driven Power steering) system of a vehicle is driven.)

1. A torque ripple compensating device, comprising:

a torque measurement unit configured to output a torque measured by a torque sensor of an MDPS (motor driven power steering) system;

a motor speed measurement unit configured to output a motor speed measured by a position sensor of the MDPS motor;

a control unit configured to output an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively; and

a torque ripple compensation unit configured to synthesize a plurality of torque ripple signals output from the control unit and output a torque ripple compensation signal as a motor control signal to the MDPS motor, the torque ripple compensation signal being for compensating the synthesized torque ripple signal.

2. The torque ripple compensating device of claim 1, wherein the torque ripple signal includes at least a primary torque ripple signal and a secondary torque ripple signal.

3. The torque ripple compensating device of claim 1, wherein the control unit includes:

a fluctuation frequency generation unit configured to generate a torque fluctuation frequency using the motor speed;

a torque signal model application unit configured to generate a torque fluctuation estimation signal of the torque fluctuation frequency by applying a torque signal model to the torque fluctuation frequency;

a torque estimation unit configured to estimate a fluctuation torque from the generated torque fluctuation estimation signal and output the estimated torque;

a torque difference calculation unit configured to calculate a difference between the fluctuation torque and the measured torque by comparing the fluctuation torque estimated by the torque estimation unit and the measured torque acquired by the torque measurement unit;

a gain applying unit configured to multiply the gain set by the gain setting unit by the calculated torque difference and output a multiplication result; and

a torque ripple element output unit configured to apply the signal to which the gain is applied by the gain application unit to the estimation signal and generate a corrected estimation signal including all torque ripple elements.

4. The torque ripple compensating device of claim 3, wherein a measured torque signal and the ripple frequency are sampled and generated in each designated control cycle.

5. The torque ripple compensating device of claim 3, wherein the torque signal model is a matrix model, and an offset, a torque ripple 1, and a torque ripple 2 are distinguished according to an order set when the matrix model is established.

6. The torque ripple compensating device of claim 3, wherein the torque ripple element includes an offset, a torque ripple 1, and a torque ripple 2.

7. The torque ripple compensating device of claim 3, wherein the torque ripple compensating device feeds back the corrected estimation signal to the torque signal model applying unit so as to reflect the corrected estimation signal into the calculation of the torque estimation value.

8. A torque ripple compensation method, comprising:

outputting a torque measured by a torque sensor of the MDPS system;

outputting a motor speed measured by a position sensor of the MDPS motor;

outputting, by a control unit, an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively; and

synthesizing, by a torque ripple compensation unit, a plurality of torque ripple signals output from the control unit, and outputting a torque ripple compensation signal as a motor control signal to the MDPS motor, the torque ripple compensation signal being for compensating the synthesized torque ripple signal.

9. The torque ripple compensation method of claim 8, wherein the outputting, by the control unit, the offset signal and the torque ripple signal, respectively, comprises:

generating a torque ripple frequency using the motor speed;

generating a torque ripple estimation signal for the torque ripple frequency by applying a torque signal model to the torque ripple frequency;

estimating a torque from the generated torque fluctuation estimation signal and outputting the estimated torque;

calculating a difference between the estimated fluctuating torque and the measured torque by comparing the estimated fluctuating torque and the measured torque;

multiplying the preset gain by the calculated torque difference, and outputting a multiplication result; and

a corrected estimate signal including all torque ripple elements is generated by applying the gain application signal to the estimate signal.

10. The torque ripple compensation method of claim 9, wherein the torque signal model is a matrix model, and an offset, a torque ripple 1, and a torque ripple 2 are distinguished according to an order set when the matrix model is made.

11. The torque ripple compensation method of claim 9, wherein the torque ripple element includes an offset, a torque ripple 1, and a torque ripple 2.

12. The torque ripple compensation method of claim 9, further comprising feeding back the corrected estimation signal to apply the torque signal model to the torque ripple frequency in order to reflect the corrected estimation signal into the calculation of a torque estimate.

13. The torque ripple compensation method of claim 9, wherein the measured torque signal τ is modeled with an offset and torque ripple as shown in equation 1 below:

τ＝a₀a₁sin(N₁θ_m+φ₁)+…+a_nsin(N_nθ_m+φ_n)

wherein constant a₀Representing said offset, trigonometric function a_isin(N_iθ_m+φ_i) Represents the torque ripple, wherein i is 1,2, …, n, θ_mRepresenting the motor rotation angle, N_iθ_mRepresents a harmonic component with respect to the motor rotation angle, and a_iAnd phi_iRepresenting the magnitude and phase of the torque ripple, respectively.

14. The torque ripple compensation method of claim 9, wherein a measured torque signal and the ripple frequency are sampled and generated in each designated control cycle.

Technical Field

Embodiments of the present disclosure relate to a torque ripple (torque ripple) compensation apparatus and method, and more particularly, to a torque ripple compensation apparatus and method for reducing torque ripple occurring when a motor of an MDPS (motor driven power steering) system of a vehicle is driven.

Background

The MDPS system of the vehicle provides a portion of steering torque, which a driver needs to apply to a steering wheel when steering the vehicle, using an auxiliary power source, so that the driver can easily steer.

The MDPS system determines the driving condition of the vehicle by: a column torque sensor configured to measure a column torque of a driver input to a steering wheel; a steering angle sensor configured to measure a steering angle or a steering angular velocity of a steering wheel; and a vehicle speed sensor configured to measure a vehicle speed; and the MDPS system provides an assist torque through an electric motor (MDPS motor) based on a column torque applied to a steering shaft when a driver operates a steering wheel.

Generally, the MDPS motor is implemented as a 3-phase AC motor, and an Electronic Control Unit (ECU) of the MDPS system receives currents output into three phases of the MDPS motor through feedback and controls an inverter to output the 3-phase AC current through proportional-integral (PI) control to control driving of the MDPS motor. However, when the MDPS motor is driven, torque ripple or mechanical vibration may occur due to a mechanical structure based on the number of rotor poles or the number of stator slots. Since such motor torque fluctuations reduce NVH (noise, vibration, Harshness) performance of MDPS systems, improvements are needed.

As a method of preventing such torque fluctuations, a method of compensating for torque fluctuations based on a lookup table, using a system transfer function and a filter to compensate for torque fluctuations, or a method of compensating for torque fluctuations based on a torque sensor is generally used.

However, a lookup table-based motor (MDPS motor) control method, in which parameters extracted through a specific off-line experiment are used for motor control, can be easily applied to MDPS motor control, but there is a problem in that: parameter extraction may require separate test time and performance bias may occur due to system distribution.

In addition, the active disturbance compensation method uses a disturbance observer to estimate and compensate for torque fluctuations (mechanical vibrations) occurring in the MDPS system. The disturbance observer estimates the lumped disturbance of the system using the filter and the inverse transfer function of the normal system, and the performance of the disturbance observer is decided according to the design of the filter. At this time, when the filter is designed as a low-pass filter to estimate the torque ripple generated in the form of a trigonometric function, amplitude reduction and phase delay may occur.

When the offset of the torque sensor is removed using the high-pass filter as in the torque ripple compensation method based on the torque sensor, an additional operation is required to correct the distortion of the high-frequency signal. Further, although signal correction is performed, it may be difficult to restore the original signal. Furthermore, parameter estimation by integration requires a long convergence time and an additional algorithm to prevent divergence of the integrated signal.

Therefore, a method capable of reducing torque ripple without causing the above-described problems is required.

The related art of the present disclosure is disclosed in korean patent application laid-open No. 10-2016-.

Disclosure of Invention

Various embodiments relate to a torque ripple compensating apparatus and method for reducing torque ripple occurring when driving a motor of an MDPS (motor driven power steering) system of a vehicle.

In one embodiment, the torque ripple compensating device may include: a torque measurement unit configured to output a torque measured by a torque sensor of the MDPS system; a motor speed measurement unit configured to output a motor speed measured by a position sensor of the MDPS motor; a control unit configured to output an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively; and a torque ripple compensating unit configured to synthesize a plurality of torque ripple signals output from the control unit and output a torque ripple compensating signal as a motor control signal to the MDPS motor, the torque ripple compensating signal being for compensating the synthesized torque ripple signal.

The torque ripple signal may include at least a primary torque ripple signal and a secondary torque ripple signal.

The control unit may include: a fluctuation frequency generation unit configured to generate a torque fluctuation frequency using the motor speed; a torque signal model application unit configured to generate a torque fluctuation estimation signal of the torque fluctuation frequency by applying a torque signal model to the torque fluctuation frequency; a torque estimation unit configured to estimate a fluctuation torque from the generated torque fluctuation estimation signal and output the estimated torque; a torque difference calculation unit configured to calculate a difference between the fluctuation torque and the measured torque by comparing the fluctuation torque estimated by the torque estimation unit and the measured torque acquired by the torque measurement unit; a gain applying unit configured to multiply the gain set by the gain setting unit by the calculated torque difference and output a multiplication result; and a torque ripple element output unit configured to apply the signal to which the gain is applied by the gain application unit to the estimation signal and generate a corrected estimation signal including all the torque ripple elements.

The measured torque signal and the ripple frequency may be sampled and generated during each designated control cycle.

The torque signal model may be a matrix model, and the offset, the torque ripple 1, and the torque ripple 2 may be distinguished according to an order set when the matrix model is manufactured.

The torque ripple elements may include offset, torque ripple 1, and torque ripple 2.

The torque ripple compensating means may feed back the corrected estimation signal to the torque signal model applying unit to reflect the corrected estimation signal in the calculation of the torque estimation value.

In one embodiment, a torque ripple compensation method may include: outputting a torque measured by a torque sensor of the MDPS system; outputting a motor speed measured by a position sensor of the MDPS motor; outputting, by the control unit, an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively; and synthesizing, by a torque ripple compensation unit, a plurality of torque ripple signals output from the control unit, and outputting a torque ripple compensation signal as a motor control signal to the MDPS motor, the torque ripple compensation signal being for compensating the synthesized torque ripple signal.

The respectively outputting the offset signal and the torque ripple signal may include by the control unit: generating a torque ripple frequency using the motor speed; generating a torque ripple estimation signal of a torque ripple frequency by applying a torque signal model to the torque ripple frequency; estimating a torque from the generated torque fluctuation estimation signal and outputting the estimated torque; calculating a difference between the estimated fluctuating torque and the measured torque by comparing the estimated fluctuating torque and the measured torque; multiplying the preset gain by the calculated torque difference, and outputting a multiplication result; and generating a corrected estimate signal including all torque ripple elements by applying the gain application signal to the estimate signal.

The torque signal model may be a matrix model, and the offset, the torque ripple 1, and the torque ripple 2 may be distinguished according to an order set when the matrix model is manufactured.

The torque ripple elements may include offset, torque ripple 1, and torque ripple 2.

The torque ripple compensation method may further include feeding back the corrected estimation signal to apply a torque signal model to the torque ripple frequency so as to reflect the corrected estimation signal into the calculation of the torque estimation value.

The torque ripple compensation method of claim 9, wherein the measured torque signalModeled with offset and torque ripple, as shown in equation 1 below:

wherein constant a₀Representing an offset, trigonometric function a_isin(N_iθ_m+φ_i) Represents the torque ripple, wherein i is 1,2, …, n, θ_mRepresenting the motor rotation angle, N_iθ_mRepresents a harmonic component with respect to the motor rotation angle, and a_iAnd phi_iRepresenting the magnitude and phase of the torque ripple, respectively.

The measured torque signal and the ripple frequency are sampled and generated during each designated control cycle.

According to the embodiments of the present disclosure, the torque ripple compensating apparatus and method may reduce torque ripple occurring when driving a motor of an MDPS system of a vehicle.

Further, the torque ripple compensating apparatus and method can improve steering feel at low speed by torque ripple compensation.

Further, the torque ripple compensation apparatus and method may be applied to real-time torque ripple compensation logic without a separate compensation parameter extraction process.

Drawings

Fig. 1 is a diagram showing a schematic configuration of a torque ripple compensating device according to an embodiment of the present disclosure.

Fig. 2 is a diagram showing a detailed configuration of the control unit in fig. 1.

Fig. 3 to 5 show results obtained by a simulation using the torque ripple compensating device according to the embodiment of the present disclosure in fig. 1.

Detailed Description

Some example embodiments may be illustrated in the figures as functional blocks, units and/or modules, as is conventional in the relevant art. Those of ordinary skill in the art will appreciate that the blocks, units and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, processors, hardwired circuits, memory elements, wired connections, and so on. When the blocks, units, and/or modules are implemented by a processor or similar hardware, they may be programmed and controlled using software (e.g., code) to perform the various functions discussed herein. Alternatively, each block, unit and/or module may be implemented by dedicated hardware or as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed processors and associated circuitry) to perform other functions. Each block, unit and/or module of some example embodiments may be physically separated into two or more interacting and discrete blocks, units and/or modules without departing from the scope of the inventive concept. Furthermore, the blocks, units and/or modules of some example embodiments may be physically combined into more complex blocks, units and/or modules without departing from the scope of the inventive concept.

Hereinafter, a torque ripple compensating apparatus and method according to the present disclosure will be described below with reference to the accompanying drawings by way of various examples of embodiments. It should be noted that the drawings are not exact scale, and the thickness of lines or the size of components may be exaggerated for the purpose of descriptive convenience and clarity only. Further, terms used herein are defined by considering functions of the present disclosure, and may be changed according to custom or intention of a user or operator. Accordingly, the terms should be defined in light of the overall disclosure set forth herein.

In general, torque fluctuations of a motor (e.g., MDPS motor) are one of the factors that may cause an uncomfortable steering feel in a low-speed steering portion of the MDPS system.

Accordingly, the present disclosure provides a method that may reduce torque fluctuations of a motor through a control technique capable of estimating and compensating for torque fluctuations in real time.

Fig. 1 is a diagram showing a schematic configuration of a torque ripple compensating device according to an embodiment of the present disclosure. The torque ripple compensating apparatus includes a torque measuring unit 110, a motor speed measuring unit 120, a control unit 130, and a torque ripple compensating unit 140.

The torque measurement unit 110 outputs a torque measured by a torque sensor (not shown) of the MDPS system.

The motor speed measurement unit 120 outputs a motor speed measured by a position sensor (not shown) of the MDPS motor.

The control unit 130 outputs an offset signal and a torque ripple signal based on the motor speed information and the measured torque information, respectively.

At this time, the torque ripple signal includes at least primary and secondary torque ripple signals.

The torque ripple compensating unit 140 synthesizes the primary or secondary torque ripple signal output from the control unit 130 and outputs the torque ripple compensating signal, which is used to compensate the synthesized primary or secondary torque ripple signal, to a motor, i.e., an MDPS motor, as a motor control signal.

Fig. 2 is a diagram showing a detailed configuration of the control unit in fig. 1.

As shown in fig. 2, the control unit 130 includes a fluctuation frequency generation unit 131, a control period setting unit 132, a torque signal model application unit 133, a torque estimation unit 134, a torque difference calculation unit 135, a gain setting unit 136, a gain application unit 137, and a torque fluctuation element output unit 138.

The fluctuation frequency generation unit 131 generates a fluctuation frequency (i.e., a torque fluctuation frequency) using the motor speed (see the graph of fig. 3).

The torque ripple frequency is set to a multiple of the motor speed, Ni, where i is 1,2 …. This is because the fluctuation generated by the motor (i.e., the torque fluctuation) is generated in response to the speed of the motor, and therefore, as long as the motor speed is known, the frequency of the fluctuation generated in the motor can be acquired.

At this time, a fluctuation frequency (i.e., a torque fluctuation frequency) ω is generated in each prescribed control period (e.g., 1ms)_i(k)。

The torque signal model applying unit 133 applies the torque signal model a by applying the torque signal model a₀Torque ripple estimation signal applied to torque ripple frequency to generate torque ripple frequency

The torque estimation unit 134 estimates a signal from the generated torque fluctuationTo estimate the torque and output the estimated torque.

Torque signal model A₀Is a matrix model. Because the matrix model A is established₀An order is set so that the offset, the torque ripple 1, and the torque ripple 2 can be distinguished according to the order.

The torque difference calculation unit 135 compares the fluctuation torque estimated by the torque estimation unit 134And the measured torque measured by the torque measuring unit 110To calculate the fluctuation torqueAnd measuring torqueAnd multiplies the calculated difference by the gain L set by the gain setting unit 136 through the gain applying unit 137₀And outputs the multiplication result. The torque ripple element output unit 138 applies the signal to which the gain is applied via the gain application unit 137 to the estimation signalGenerate an estimation signal including all torque ripple elements (i.e., offset, torque ripple 1, and torque ripple 2)

The torque fluctuation element output unit 138 uses the measured torque signalCorrecting an estimated signalTo generate a corrected estimated signalAnd will estimate the signalFed back to the torque signal model application unit 133 to apply a corrected estimation signalReflecting to the torque ripple estimateIn the calculation of (2).

For reference, the gain L when multiplied by the gain applying unit 137₀When larger, the torque ripple estimation becomes faster, and when the gain L is larger₀When smaller, the torque ripple estimation becomes slower.

Hereinafter, the configuration and operation of the control unit 130 will be described in more detail.

In the present embodiment, the measured torque signal is subjected to offset and torque ripple as shown in the following equation 1Modeling is performed.

[ equation 1]

In equation 1, the constant a₀Representing an offset, trigonometric function a_isin(N_iθ_m+φ_i) Represents torque ripple, where i is 1,2, …, n.

Torque fluctuation model quilt tableShown as the angle of rotation theta relative to the motor_mHarmonic component N of_iθ_mAnd a is_iAnd phi_iRespectively, representing the magnitude and phase of the torque ripple.

At this time, since the rotation angle θ of the motor can be measured_mThus, the advancing angle N of the harmonic can be calculated_iθ_mBut need to be estimated as unknown: offset a₀Amplitude a of torque ripple_iAnd phase phi_i。

Thus, in the present embodiment, only the frequency of torque fluctuations in the state spaceMay be used to perform offset decoupling and torque ripple compensation.

I.e. will represent the measured torque signalIs defined as q₀＝a₀，q_i＝[q_isq_ic]^T。

Here, q is_is＝a_isin(N_iθ_m+φ_i) Andin addition, the frequency ω of the torque ripple_iIs calculated as

Therefore, when using the state variable q₀，q_iThe measured torque signal of equation 1 may be represented as the state space module of equation 2 below.

[ equation 2]

In the present embodiment, the torque fluctuation estimation logic is designed in consideration of digital control.

The continuous-time model of equation 2 can be discretized by a zero-order hold method, as shown in equation 3 below.

[ equation 3]

In equation 3, T denotes a control period, and k denotes a time point at which T ═ kT, where k is 0,1,2, …, ∞. For measuring torque signal in each control period TAnd the fluctuation frequency omega_i(κ) sampling.

In the present embodiment, the torque estimation unit 134 uses the estimation method of equation 4 below in order to separate the offset from the torque signal and estimate the torque ripple.

[ equation 4]

First, the torque estimation unit 134 uses a torque signal model a₀Generating an estimation signal

Because the matrix model A is established₀An order is set so that the offset, the torque ripple 1, and the torque ripple 2 can be distinguished according to the order.

Then, the torque estimation unit 134 uses the measured torque signalTo correct the estimated signalGenerating a corrected estimated signal

Then, the torque estimation unit 134 derives the corrected estimation signal from the corrected estimation signalTo calculate a torque ripple estimate

At this time, the gain L of the torque estimation unit 134₀Updated in the order represented by equation 5 below.

[ equation 5]

In equation 5, matrices Q and R are elements for determining the performance of the torque estimation unit 134.

In addition, the matrices P andis used to calculate the gain L for a given matrix Q and R₀Of (2) is used. Further, the matrix I represents an identity matrix.

Fig. 3 to 5 show results obtained by a simulation using the torque ripple compensating device according to the embodiment of the present disclosure in fig. 1. Fig. 3 is a graph showing the motor speed, and the fluctuation frequency generation unit 131 of the control unit 130 generates the torque fluctuation frequency using the motor speed.

Fig. 4 is a graph showing torque data before/after torque ripple compensation, and fig. 5 is a graph showing a frequency analysis result of the torque data.

Fig. 4 and 5 show that when comparing the graph before compensation (light color) and the graph after compensation (dark color), the primary torque fluctuation and the secondary torque fluctuation are significantly reduced.

In the present embodiment, the torque ripple compensating apparatus and method can reduce torque ripple occurring when the motor of the MDPS system of the vehicle is driven, and improve steering feel at low speed by torque ripple compensation.

Although the preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims. Therefore, the true technical scope of the present disclosure should be defined by the appended claims.