JP2009190658A - Control device of electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a high-performance electric power steering device with simple structure having improved steering stability by providing a steering system with assisting torque for canceling torque steer by switching a control system corresponding to a vehicle state without monitoring driving torque of right and left wheels. <P>SOLUTION: In the control device of the electric power steering device for providing the steering mechanism of the vehicle with the assisting torque by drive of the motor driven by a current instruction value 1 calculated by a torque control part via a drive control part, a current instruction value 2 corresponding to the state of the vehicle is calculated and added to the current instruction value 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an electric power steering device in which a steering assist force by a motor is applied to a steering system of a vehicle, and in particular, electric power steering for reducing a torque steer state generated due to a tire state or a road surface condition at a sudden start. The present invention relates to an apparatus control device.

  An electric power steering device for assisting a vehicle steering device with a rotational force of a motor is applied to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. The auxiliary load is energized. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist force). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the motor current detection value becomes small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 5. It is connected to the tie rod 6. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is connected to the column shaft 2 via the reduction gear 3. ing. The control unit 30 that controls the power steering apparatus is supplied with electric power from the battery 14 and is also supplied with an ignition signal from the ignition key 11. The control unit 30 detects the steering torque value T detected by the torque sensor 10 and the vehicle speed. Based on the vehicle speed V detected by the sensor 12, an assist command steering assist command value I is calculated using an assist map or the like, and a current supplied to the motor 20 is calculated based on the calculated steering assist command value I. Control.

  The control unit 30 is mainly composed of a CPU (including an MPU (Micro Processor Unit) and MCU (Micro Controller Unit)), and general functions executed by a program inside the CPU are shown in FIG. Become.

  The function and operation of the control unit 30 will be described with reference to FIG. 6. The steering torque value T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12 are a current command value for calculating a current command value Iref. Input to the calculation unit 31. The current command value calculation unit 31 determines a current command value Iref that is a control target value of the current supplied to the motor 20 using an assist map or the like based on the input steering torque value T and vehicle speed V. The current command value Iref is input to the subtraction unit 32, and a deviation I (Iref-Im) from the fed-back motor current value Im is calculated, and the deviation is input to the PI control unit 33 for improving the characteristics of the steering operation. Entered. The steering assist command value Vref whose characteristics are improved by the PI control unit 33 is input to a motor drive circuit 34 including a PWM control unit and an inverter, and the motor 20 is PWM driven. The current value Im of the motor 20 is detected by the motor current detector 35 and fed back to the subtraction unit 32.

  In the general electric power steering apparatus as described above, when the vehicle starts suddenly, torque steer is generated depending on the tire condition and road surface condition. Torque steer is a phenomenon that occurs due to a moment difference around the kingpin when a sudden driving force is applied in a state where there is a difference in the tire condition on the left and right and the road surface condition on the FF vehicle. If it tries to turn, the handle is taken off, which is unfavorable because it gives the driver anxiety.

  Japanese Patent Laid-Open No. 9-207802 (Patent Document 1) discloses an apparatus for preventing the occurrence of such torque steer. The device described in Patent Document 1 is a device for compensating for torque steer in a vehicle having a power assist steering device, and includes characteristic sensing means for sensing an operation characteristic of the vehicle representing torque steer, and driver applied steering torque. A means for sensing and a control means for controlling the power assist steering device based on the sensed operating characteristic representing torque steer as well as based on the sensed driver applied steering torque to compensate for torque steer. is there.

  Moreover, it is disclosed by Unexamined-Japanese-Patent No. 2004-67040 (patent document 2), The apparatus of patent document 2 is for vehicles provided with the braking / driving force control means which controls the braking / driving force of a right-and-left wheel separately. An electric power steering device that sets an assist torque to be applied to the steering system based on a steering reaction force generated in the steering system, and the assist torque is determined by the braking / driving force of the left and right wheels controlled by the braking / driving force control means. It changes according to the difference.

Further, an apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-1481 (Patent Document 3) is an electric power steering apparatus that drives an electric motor in accordance with a steering torque of a steering wheel to perform auxiliary steering, and includes a vehicle wheel. A wheel speed detecting means for detecting the speed, a vehicle speed calculating means for calculating the vehicle body speed from the wheel speed detected by the wheel speed detecting means, and a target motor current according to the vehicle speed calculated by the steering torque and the vehicle speed calculating means. Assist control means for calculating the slip, means for calculating the slip amount of the left and right wheels from the wheel speed and body speed, and correcting the target motor current according to the slip amount of the left and right wheels calculated by the slip calculation means And a correcting means for performing.
JP-A-9-207802 JP 2004-67040 A JP 2005-1481 A

  In the devices disclosed in Patent Documents 1 and 2, it is necessary to sense the driving force torque to detect the torque steer state, and there is a problem in that the price of the system increases due to the structure of the driving force torque sensor.

  In the device disclosed in Patent Document 3, the slip rate is obtained from the wheel speed, and the torque steer state is determined from the difference between the slip rates of the left and right wheels. However, there is a problem that it is impossible to accurately determine whether it is caused by the driver's arbitrary steering or torque steer only from the difference in slip rate.

  The present invention has been made under the circumstances described above, and an object of the present invention is to switch the control system according to the vehicle state with a simple and inexpensive system configuration without monitoring the driving torque of the left and right wheels. Another object of the present invention is to provide a control device for a high-performance electric power steering apparatus that aims to stabilize steering by giving an assist torque for canceling torque steer to a steering system.

  The present invention relates to a control device for an electric power steering apparatus that drives a motor with a current command value 1 calculated by a torque control section through a drive control section and applies assist torque to a steering mechanism of a vehicle by driving the motor. The above object of the present invention is achieved by calculating a current command value 2 according to the state of the vehicle and adding it to the current command value 1.

  The object of the present invention is more effective by estimating the state of the vehicle by steering torque, steering angle, wheel speed, vehicle speed, and accelerator opening, or by determining whether the vehicle state is torque steer. To be achieved.

  The present invention also provides an electric power steering apparatus that calculates a current command value 1 based on a steering torque and a vehicle speed, and applies an assist torque to a vehicle steering mechanism by driving a motor based on the current command value 1. Regarding the control device, the object of the present invention is to provide a torque differential control unit that obtains a differential value of the steering torque, a gain unit that gives a gain to the differential value, a vehicle state estimation unit that determines the state of the vehicle, This is achieved by providing a switching unit that switches the gain unit by a vehicle state estimation unit, and adding the current command value 2 that is the output of the switching unit to the current command value 1 to drive the motor.

  The state of the vehicle is estimated by the steering torque, the steering angle, the wheel speed, the vehicle speed, and the accelerator opening, or the gain unit is gain 1 and gain Kd (> 1), and can be switched under a predetermined condition. Or the state of the vehicle is detection of torque steer, and when the torque steer is detected, the gain unit is switched from gain 1 to gain Kd and output. This is achieved more effectively.

  Furthermore, the present invention provides an electric power steering apparatus that calculates a current command value 1 based on a steering torque and a vehicle speed, and applies an assist torque to a vehicle steering mechanism by driving a motor based on the current command value 1. Regarding the control device, the object of the present invention is to provide a torque differential control unit that obtains a differential value of the steering torque, a first gain unit that gives a gain to the differential value, a vehicle state estimation unit that determines the state of the vehicle, A first switching unit that switches the first gain unit according to a predetermined condition 1 of the vehicle state estimation unit, a damping control unit that obtains a damping value of the steering angle, a second gain unit that gives a gain to the damping value, A second switching unit that switches the second gain unit according to the predetermined condition 2 of the vehicle state estimation unit, and the current command value according to the state of the vehicle The current command values from the first switching unit and the second switching unit are added to or subtracted from each other, or the predetermined condition 1 is torque steer, or the predetermined condition 2 is the change rate of the steering angle and the This is achieved by setting based on the rate of change of the steering torque.

  According to the control device for the electric power steering apparatus according to the present invention, the assist for canceling the torque steer by switching the control system according to the vehicle state with a simple and inexpensive system configuration without monitoring the driving torque of the left and right wheels. Steering stability can be achieved by applying torque to the steering system.

  The wheel speed sensor is almost installed in recent vehicles, and it is not necessary to add a new one for this control, so that the cost is not increased.

  The present invention adds a condition that can be further determined as torque steer by comparing the steering angle signal estimated from the output of the steering angle sensor or the estimation of the steering angle with the difference between the left and right wheel speeds. Further, since the engine output is suddenly increased as a requirement for generating torque steer, the accuracy of determination as to whether the vehicle is in the torque steer state is improved by monitoring the driver's accelerator opening.

First, sudden start (rapid acceleration) is given as an overview of the torque steer generation mechanism, and this can be roughly estimated by measuring the rapid change Δα of the accelerator opening and the rapid change ΔV of the vehicle speed V. is there. In other words, in general, in an FF vehicle, the operation of opening the accelerator suddenly generates a rapid driving force and generates torque steer. As a result, a sudden change of the vehicle speed, that is, a sudden acceleration state occurs. Looking at the situation in more detail, the difference in left and right driving force should be seen as the difference in left and right wheel speeds after the vehicle has started to move. Therefore, by measuring the difference “ω _R −ω _L ” between the left and right wheel speeds, it can be estimated that the torque steer state. However, since only the condition of the wheel speed difference “ω _R −ω _L ” can be seen as a condition during turning, the present invention measures the difference “Δω _R −Δω _L ” of the wheel speed change rate, and there is this The condition is that torque steer occurs above a certain level. Incidentally, the vehicle speed of 0 [kph] is the initial state.

  Next, the operation of the electric power steering control when the torque steer state is estimated will be described.

  When torque steer occurs, there are two main types of steering movement. One is the movement of the steering angle of the steering wheel when letting go, and the other is the torque change during steering. That is, the driver is aware that torque steer is occurring due to a change in torque or steering angle. Therefore, the electric power steering control only needs to assist in the direction of canceling the torque change or the direction of canceling the steering angle change only in the situation of the torque steer state. Furthermore, considering that it becomes difficult for the driver to recognize torque steer by making the steering wheel difficult to move, masking functions such as friction compensation, and actively adding viscous friction (damping control) Thus, the influence of torque steer can be reduced. In other words, in the state where the driver is not holding (releasing), the steering wheel moves, so the driver recognizes that torque steer has occurred, so it was determined that torque steer has occurred. If so, control the handle so that it does not move.

  The present invention has been made on the basis of the above premise, and an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A steering torque Th, a steering angle θ, a right wheel speed ω _R and a left wheel speed ω _L , a vehicle speed V, and an accelerator opening α are input to the control unit 100 for control. Unit 100 drives and controls motor 200. The control unit 100 inputs a steering torque Th, a steering angle θ, and a vehicle speed V, calculates a current command value Iref1, a steering torque Th, a steering angle θ, a wheel speed ω, a vehicle speed V, and an accelerator opening. When α is input, the change rate ΔTh of the steering torque Th by the driver per unit time, the change rate Δθ of the steering angle θ per unit time, the change rate Δω of the wheel speed ω per unit time, and the per unit time of the vehicle speed V A signal processing unit 130 for obtaining a rate of change ΔV of the engine and a rate of change Δα per unit time of the accelerator opening α, a rate of change ΔTh of the steering torque Th, a rate of change Δθ of the steering angle θ, a rate of change Δω of the wheel speed ω, a vehicle speed A vehicle state estimation unit 140 that estimates a vehicle state (torque steer) based on ΔV of V and a change rate Δα of the accelerator opening α, and a control command value I based on the vehicle state estimated by the vehicle state estimation unit 140 a control command value calculation unit 150 that calculates ref2, a current control unit 120 that drives and controls the motor 200 based on a control command value Iref3 obtained by adding the current command value Iref1 and the control command value Iref2 by the addition unit 101, and It has.

  The vehicle state estimation unit 140 estimates torque steer. For example, when the rate of change Δα of the accelerator opening α is small, the accelerator is gently depressed, and therefore torque steer is unlikely to occur. On the other hand, when the change rate Δα of the accelerator opening α is large, the driver is in a rough accelerator work, and the engine output is suddenly transmitted to the tire. In addition, the drive shaft is very long and there is a difference in torsional rigidity. Therefore, the drive torque transmitted to the tire is a different factor, and torque steer is generated.

  When torque steer is generated and detected by the vehicle state estimation unit 140, the control command value calculation unit 150 switches the control gain of a predetermined function. The control gain is obtained in advance as a test value that can reduce the torque steer, and the control gain is switched assuming two conditions: a condition that the driver is keeping the wheel or a condition that the driver is releasing her hand. Since the effect of torque steer is a torque change (handle is taken) and is transmitted to the driver under the steering holding condition, if it is determined that torque steer has occurred, the detected torque differential value (torque change rate) And a control gain for generating torque steer is a current command value Iref2. If it is determined that the control is to be let go, the influence of torque steer cannot be compensated based on the torque differential value, so that the movement of the steering angle θ, that is, the multiplication value of the steering angular speed and the control gain for occurrence of torque steer is The current command value Iref2 is obtained.

  In such a configuration, the operation will be described with reference to the flowchart of FIG.

First, in order to determine whether the driver is not rapid accelerator operation, it is determined whether the accelerator opening Δα is larger than the predetermined value alpha ₀ (step S1), the accelerator opening Δα predetermined value If α ₀ or less, the processing is stopped, and if the accelerator opening Δα is larger than the predetermined value α ₀ , whether the difference in the wheel speed ω due to the steering angle θ of the driver is determined according to the following equation (1). Determine (step S2).

sin (2θ / a) = 4L / E · (ω _L −ω _R ) / (ω _L + ω _R ) (1)
Here, a is a coefficient, L is a wheel base of the vehicle, and E is a tread width of the vehicle.

Formula (1) is satisfied because there is no slip in the tire in the actual situation. If it does not hold, there is a possibility that slip has occurred.

Therefore, if the above formula (1) is satisfied, it is determined that the difference is the wheel speed difference due to steering, and if the above formula (1) is not satisfied, the left and right wheel speed change rates Δω _L and Δω _R are further reduced. Is determined to determine whether torque steer is occurring (step S3). That is, it is determined whether or not the absolute value | Δω _R −Δω _L | of the difference between the change rate Δω _L of the left wheel speed and the change rate Δω _R of the right wheel speed is greater than a predetermined value ω ₀ , and the absolute value of the difference When | Δω _R −Δω _L | is smaller than the predetermined value ω ₀ , the difference in the change rate of the left and right wheel speeds is small and the possibility of torque steer is low.

On the other hand, when the absolute value | Δω _R −Δω _L | of the difference between the change rates of the left and right wheel speeds is greater than or equal to the predetermined value ω _{0 in} step S3, the change rate Δθ of the steering angle θ is greater than the predetermined value θ _0. It is determined whether or not the change rate ΔTh of the steering torque Th is larger than a predetermined value Th ₀ (step S4). When the change rate Δθ of the steering angle θ is smaller than the predetermined value θ ₀ and the steering torque Th is larger than the predetermined value Th ₀ , there is no change in the steering angle θ (Δθ≈0), and the change in the steering torque Th. Therefore, it is determined that the steering wheel is affected by torque steer and the torque differential control process is performed. If the rate of change Δθ of the steering angle θ is equal to or greater than the predetermined value θ ₀ , or the rate of change ΔTh of the steering torque Th is equal to or less than the predetermined value Th ₀ , there is a possibility of torque steer when releasing the steering angle. It is determined whether the change rate Δθ of θ is larger than the predetermined value θ ₀ and the change rate ΔTh of the steering torque Th is smaller than the predetermined value Th ₀ (step S5). When there is no change in the torque Th and the steering angle θ is moving, that is, in the hand-off state, it is determined that it is affected by torque steer and the damping control process is performed, and both conditions are not satisfied. Will be canceled.

  Here, the torque differential control process is executed by the configuration shown in FIG. 3, and the damping control process is executed by the configuration shown in FIG. 3 and FIG. 4 correspond to FIG. 1, and the torque control unit 110 of FIG. 1 includes a torque control unit 111 and a torque differentiation control unit 112 as shown in FIG. 3, or FIG. 1, the torque control unit 111 and the damping control unit 113 in FIG. 1 are configured by the torque control unit 111, the torque differentiation control unit 112, and the damping control unit 113. Both processes of damping control may be performed.

  First, the torque differential control process shown in FIG. 3 will be described. The torque differential control unit 112 in the torque control unit 110 performs a differential operation on the steering torque Th, treats it as a change rate ΔTh per unit time, and suppresses the torque change, that is, assists current command in a direction in which the torque change rate ΔTh decreases. Calculate the value. The torque change rate ΔTh from the torque differentiation control unit 112 is input to the gain units 151 (gain = 1) and 152 (gain Kd1> 1), and the output (= ΔTh) of the gain unit 151 is input to the contact point a1 of the switching unit 153. Then, the output of the gain unit 152 (= ΔTh × Kd1) is input to the contact b1 of the switching unit 153. The contacts a1 and b1 of the switching unit 153 are switched by the switching signal SW1 from the vehicle state estimation unit 140. When torque steer is detected, the switching signal SW1 is set to the contact b1 and the current command value that is an output from the switching unit 153 Iref2 is added and input to the adder 101.

  In such a configuration, at the normal time when torque steer is not generated, the switching signal SW1 sets the contact point of the switching unit 153 to a1, and the torque change rate ΔTh as it is as the current command value Iref. When torque steer is detected by the vehicle state estimation unit 140, the contact of the switching unit 153 is switched from “a1” to “b1” by the switching signal SW1, and ΔTh × Kd1 from the gain unit 152 is set as the current command value Iref2. Output. In steered situations, torque steering appears as an abrupt torque change, increasing the rate of torque change, and is usually used to compensate for the static friction felt at the start or return of steering. Even if the value is not larger than necessary for balance, it is necessary to actively suppress the torque change rate when torque steer occurs. Normally, the gain is set to “1” at the contact point a1, and the contact point is used during torque steer. In b1, the gain is set to Kd1 (> 1).

  Next, the damping control process shown in FIG. 4 will be described. A damping control unit 113 in the torque control unit 110 inputs a steering angle θ (or steering angular velocity, motor angular velocity), and a damping signal Ds multiplied by a damping coefficient by the damping control unit 113 is a gain unit 151 (gain = 1) and 152 (gain Kd2> 1), the output (= Ds) of the gain unit 151 is input to the contact point a2 of the switching unit 153, and the output (= Ds × Kd2) of the gain unit 152 is input to the contact point b2 of the switching unit 153. Entered. The contacts a2 and b2 of the switching unit 153 are switched by the switching signal SW2 from the vehicle state estimation unit 140. When the above-described requirements in FIG. 2 are satisfied, the switching signal SW2 is the contact b2 and is an output from the switching unit 153. The current command value Iref2 is subtracted and input to the adder / subtractor 101.

  In such a configuration, by subtracting the current command value Iref2 from the current command value Iref1 obtained by the torque control unit 111, the motor assist can be braked and the steering system can be applied to the yaw motion of the vehicle. Convergence can be ensured by providing damping.

It is a block block diagram which shows the basic structural example of this invention. It is a flowchart which shows the operation example of this invention. It is a block block diagram which shows the structural example of the torque differential control of this invention. It is a block block diagram which shows the structural example of the damping control of this invention. It is a figure showing an example of composition of a general electric power steering device. It is a block block diagram which shows an example of a control unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Column shaft 3 Reduction gear 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 14 Battery 20, 200 Motor 30 Control unit 31 Current command value calculation part 32 Subtraction part 33 PI control part 34 Motor drive circuit 100 Control unit 110, 111 Torque Control Unit 112 Torque Differential Control Unit 113 Damping Control Unit 120 Current Control Unit 130 Signal Processing Unit 140 Vehicle State Estimation Unit 150 Control Command Value Calculation Units 151 and 152 Gain Unit 153 Switching Unit

Claims (10)

In a control device for an electric power steering apparatus that drives a motor through a drive control unit with a current command value 1 calculated by a torque control unit and applies assist torque to a steering mechanism of the vehicle by driving the motor, A control device for an electric power steering apparatus, wherein a current command value 2 corresponding to a state is calculated and added to the current command value 1. The control device for an electric power steering apparatus according to claim 1, wherein the state of the vehicle is estimated by a steering torque, a steering angle, a wheel speed, a vehicle speed, and an accelerator opening. 3. The control device for an electric power steering apparatus according to claim 1, wherein the state of the vehicle is a torque steer determination. In a control device for an electric power steering apparatus, which calculates a current command value 1 based on a steering torque and a vehicle speed, and applies an assist torque to a steering mechanism of a vehicle by driving a motor based on the current command value 1. A torque differential control unit that obtains a differential value of torque, a gain unit that gives a gain to the differential value, a vehicle state estimation unit that determines the state of the vehicle, and a switching unit that switches the gain unit by the vehicle state estimation unit; And a control device for the electric power steering apparatus, wherein the motor is driven by adding a current command value 2 which is an output of the switching unit to the current command value 1. The control device for the electric power steering apparatus according to claim 4, wherein the state of the vehicle is estimated by the steering torque, the steering angle, the wheel speed, the vehicle speed, and the accelerator opening. 6. The control device for an electric power steering apparatus according to claim 5, wherein the gain section has a gain of 1 and a gain Kd (> 1) and is switched under a predetermined condition. The electric power according to claim 6, wherein the state of the vehicle is detection of torque steer, and when the torque steer is detected, the gain unit is switched from the gain 1 to the gain Kd and output. Control device for steering device. In a control device for an electric power steering apparatus, which calculates a current command value 1 based on a steering torque and a vehicle speed, and applies an assist torque to a steering mechanism of a vehicle by driving a motor based on the current command value 1. A torque differential control unit that obtains a differential value of torque, a first gain unit that gives a gain to the differential value, a vehicle state estimation unit that determines the state of the vehicle, and a predetermined condition 1 of the vehicle state estimation unit A first switching unit that switches a gain unit; a damping control unit that obtains a damping value of the steering angle; a second gain unit that gives a gain to the damping value; A second switching unit that switches the gain unit, and the current command value 1 is set to the first switching unit and the second switching unit according to the state of the vehicle. Control device for an electric power steering apparatus characterized by subtracting the current command value. 9. The control device for an electric power steering apparatus according to claim 8, wherein the predetermined condition 1 is torque steer. The control device for an electric power steering apparatus according to claim 9, wherein the predetermined condition 2 is set based on a change rate of the steering angle and a change rate of the steering torque.

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