JP5181836B2 - Roll angle estimation device and electric power steering device - Google Patents

Description

  The present invention relates to a roll angle estimation device that estimates a roll angle of a vehicle body, and an electric power steering device including the roll angle estimation device.

When the roll angle of the vehicle body is detected by the gyro sensor and it is determined that the roll angle exceeds the predetermined value and the vehicle is in a rollover tendency, the rollover direction is suppressed, that is, if the vehicle is rolled to the right when viewed from the rear, it is moved to the right There is an electric power steering device that generates assist torque (see Patent Document 1).
On the other hand, the lateral acceleration of the vehicle body is estimated according to the vehicle speed and the yaw rate, the lateral acceleration is detected by a lateral acceleration sensor, and the roll angle of the vehicle body is estimated according to the difference between the estimated value of the lateral acceleration and the detected value. Some (see Patent Document 2) detect the vehicle height at the left and right wheel positions, and calculate the roll angle of the vehicle body from the difference between the left and right vehicle heights (see Patent Document 3).
Japanese Patent Laid-Open No. 2004-9812 JP 11-258260 A JP 2002-168620 A

  However, the conventional technique described in Patent Document 1 requires a dedicated sensor for detecting the roll angle, which increases the cost. In addition, as in the prior art described in Patent Document 2, when estimating the lateral acceleration of the vehicle body according to the vehicle speed and the yaw rate, when the change amount of the vehicle side slip angle becomes large, the change amount remains unchanged. Since this is an acceleration estimation error, the estimation accuracy decreases. Further, in the conventional example described in Patent Document 3, the roll angle of the vehicle body is calculated from the difference between the left and right vehicle heights. However, since the vehicle height sensor is not a general equipment, it is applied to a general passenger car. Is difficult.

  An object of the present invention is to estimate a roll angle of a vehicle body with high accuracy by using a sensor that is easily installed in a general passenger car.

The roll angle estimating device according to claim 1 is detected by a vertical load detecting means for detecting a vertical load acting on the left and right wheels, a lateral force detecting means for detecting a lateral force acting on the left and right wheels, and the vertical load detecting means. Estimation means for estimating the roll angle of the vehicle body according to the vertical load of the left and right wheels and the lateral force of the left and right wheels detected by the lateral force detection means.
The roll angle estimation device according to a second aspect is characterized in that the lateral force detecting means detects a perpendicular component of the lateral force with respect to a wheel traveling direction.

  According to a third aspect of the present invention, there is provided an electric power steering apparatus comprising: an electric motor capable of transmitting an assist torque to a steering system; and a control unit that drives and controls the electric motor according to a steering torque of a driver. A power steering device comprising the roll angle estimation device according to claim 1 or 2, wherein the control means is configured to detect the roll angle when the roll angle estimated by the roll angle estimation device exceeds a predetermined value. The electric motor is driven and controlled in a direction to suppress the above.

  According to the present invention, the roll angle of the vehicle body is estimated in accordance with the vertical load acting on the left and right wheels and the lateral force acting on the left and right wheels. The angle can be estimated with high accuracy. In other words, if it is a sensor that detects the vertical load and lateral force acting on the left and right wheels, it is equipped for other purposes such as stability control (side-slip prevention control), steering angle ratio variable device, four-wheel steering device, and steering-by-wire. Often used, diversion is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, the configuration of the present embodiment will be described.
FIG. 1 is a schematic configuration of an electric power steering apparatus. The steering wheel 1 is connected to the front wheels 5FL and 5FR via a steering shaft 2, a rack and pinion 3, and a tie rod 4 in this order, and an electric motor 7 is connected to the steering shaft 2 via a speed reducer 6. . The electric motor 7 is driven and controlled by the control device 8 to apply assist torque to the driver's steering operation.

The steering shaft 2 is provided with a torque sensor 11 that detects a steering torque T, and the wheels 5FL to 5RR detect vertical loads W _{FL to} W _RR and lateral forces F _{FL to} F _RR acting on the wheels 5FL to 5RR, respectively. A multi-load sensor 12 is provided. The multi-load sensor 12 measures a radial load and an axial load acting on a rolling bearing unit as described in, for example, JP-A-2005-98771. The basic principle is that when the contact angle of the rolling element to the outer ring and the inner ring changes according to the radial load and the axial load, the revolution speed of the rolling element changes. And are detected.
The control device 8 inputs the steering torque T, the vertical loads W _{FL to} W _RR , and the lateral forces F _{FL to} F _RR and executes a steering assist control process.

FIG. 2 is a block diagram of the steering assist control process.
First, the steering torque T input from the steering torque sensor 11 is input to the steering assist command value calculation unit 40 and the center response improvement unit 41, and the outputs of the steering assist command value calculation unit 40 and the center response improvement unit 41 are output. The result is input to the adder 42, and the addition result is input to the torque control calculation unit 43. The center responsiveness improvement unit 41 ensures stability in the assist characteristic dead zone and compensates for static friction. The output signal of the torque control calculation unit 43 is input to the motor loss current compensation unit 44, and the output is input to the maximum current limiting unit 46 via the adder 45, and the maximum current value is limited by the maximum current limiting unit 46 to control the current. Input to the unit 50. The motor loss current compensator 44 adds a current that does not appear in the motor output even when the motor current flows to improve the rise from the motor output torque 0, and the maximum current limiter 46 has a maximum current command value rated The current is limited. The output of the current control unit 50 is input to the H-bridge characteristic compensation unit 51, thereby driving the electric motor 7 via the current drive circuit 52.

  The motor current of the electric motor 7 is input to the motor angular velocity estimation unit 61, the current drive switching unit 62, and the current control unit 50 through the motor current offset correction unit 60, and the motor terminal voltage Vm is directly input to the motor angular velocity estimation unit 61. Entered. The angular velocity ωm estimated by the motor angular velocity estimator 61 is input to the motor angular acceleration estimator / inertia compensator 63, the motor loss torque compensator 64, and the yaw rate estimator 65. The output of the yaw rate estimator 65 is the convergence control. The outputs of the convergence controller 66 and the motor loss torque compensator 64 are added by the adder 67 and the addition result is input to the adder 42. The motor angular acceleration estimator / inertia compensator 63 eliminates the torque for accelerating / decelerating the motor inertia from the steering torque to obtain a steering feeling without inertia, and the convergence controller 66 improves the convergence of the yaw rate of the vehicle. In addition, the operation of the steering wheel 1 swinging is suppressed. The motor loss torque compensator 64 performs assist equivalent to the loss torque in the direction in which the loss torque of the motor 7 is generated, that is, the rotation direction of the motor 7. Further, a current dither signal generation unit 80 is provided, and outputs of the current dither signal generation unit 80 and the motor angular velocity estimation unit / inertia compensation unit 63 are added by an adder 81, and the addition result is input to the adder 45. Has been. The current dither signal generator 80 prevents the motor from sticking due to static friction. Further, a rollover suppression processing unit 90 is provided, and an output of the rollover suppression processing unit 90 is subtracted by the adder 45.

Here, the rollover suppression processing executed by the rollover suppression processing unit 90 as a process at predetermined time intervals (for example, 10 msec) will be described with reference to the flowchart of FIG.
First, in step S1, in front or rear wheel, it is loaded vertical load W _L and W _R, and the lateral force F _L and F _R exerted on the right and left wheels.

In the subsequent step S2, as shown in the following equation (1), the load movement amount ΔW in the left and right wheels is calculated according to the vertical loads W _L and W _R acting on the left and right wheels.
ΔW = W _L − (W _L + W _R ) / 2
= (W _L -W _R ) / 2 (1)

In step S3, as shown in the following equation (2), the load movement amount ΔW between the left and right wheels, and in accordance with the lateral force F _L and F _R exerted on the right and left wheels, to calculate the vehicle body roll angle phi. Figure 4 is a schematic diagram for explaining the vehicle body roll angle, from the following equation (2), the roll angle φ becomes larger the larger the load movement amount ΔW of the left and right wheels, as the lateral force F _L and F _R is greater The roll angle φ is reduced.
φ = {ΔW · d− (F _L + F _R ) h} / K (2)
φ: Roll angle [rad] d: Tread [m]
h: Roll center height [m] K: Roll rigidity [Nm / rad]

  In a succeeding step S4, it is determined whether or not the roll angle φ is larger than a predetermined value φth. If the determination result is φ ≦ φth, it is determined that the roll angle is within the allowable range, and the process returns to the predetermined main program as it is. On the other hand, if the determination result is φ> φth, it is determined that the vehicle body may roll over, and the process proceeds to step S5.

In step S5, the steering reaction force Tr is calculated according to the roll angle φ with reference to the map of FIG. In this map, when the roll angle φ is equal to or smaller than the predetermined value φth, the steering reaction force Tr is maintained at 0, and when the roll angle φ exceeds the predetermined value φth, the larger the roll angle φ is, the more the steering reaction force Tr becomes. growing.
In the subsequent step S6, the steering reaction force Tr is output to the adder 45, and then the process returns to the predetermined main program.

  As described above, the multi-load sensor 12 corresponds to the “vertical load detection means” and the “lateral force detection means”, and the processing in steps S1 to S3 corresponds to the “estimation means”. Further, the processes of steps S4 and S5 are included in the “control unit”.

Next, the effect of this embodiment is demonstrated.
The roll angle φ of the vehicle body is expressed by the above equation (2), and the tread d, the roll center height h, and the roll stiffness K are determined by the vehicle. The roll angle φ can be accurately estimated according to the lateral forces F _L and F _R to be performed.

The multi-load sensor 12 for detecting the vertical loads W _L and W _R acting on the left and right wheels and the lateral forces F _L and F _R includes stability control, steering angle ratio variable device, four-wheel steering device, steering by wire, etc. It is often equipped for the purpose of. Therefore, if the multi-load sensor 12 is provided, an increase in cost can be suppressed as compared to adding a dedicated sensor for detecting the roll angle and the vehicle height as in the prior art. Even if a new multi-load sensor 12 is newly added, as described above, it can be used for other purposes, which is more advantageous than adding a dedicated sensor for detecting the roll angle and the vehicle height. Therefore, it is easy to apply to general passenger cars.

  Thus, the roll angle φ of the vehicle body is estimated (step S3), and when the roll angle φ exceeds the predetermined value φth (determination in step S4 is “Yes”), the steering reaction force Tr is calculated (step S5). By subtracting this from the assist torque (step S6), the steering assist force is decreased and the steering reaction force against the driver is increased. Thereby, an increase in the steering angle is suppressed, an increase in the roll angle φ can be prevented, and as a result, a rollover of the vehicle body can be prevented. In addition, the driver can be alerted by increasing the steering reaction force.

In this embodiment, the single multi-load sensor 12 detects both the vertical load and the lateral force acting on the wheel. However, the present invention is not limited to this, and the vertical load and the lateral force are detected. It may be detected by an individual sensor.
Further, in the present embodiment, one of either the front or rear wheels, the load shift amount [Delta] W, and in accordance with the lateral force F _L and F _R, but to calculate the vehicle body roll angle phi, limited to It is not something. For example, the average value or larger select value of the load movement amount [Delta] W _R of the front wheel load movement amount [Delta] W _F and the rear wheels and [Delta] W, the lateral force of the lateral force F _FL (or F _FR) and rear wheels of the front wheels An average value with F _RL (or F _RR ) or a smaller selected value may be set as F _L (or F _R ). Here, the load movement amount ΔW is set to select high for the front and rear wheels, and the lateral force F _L (or F _R ) is set to select low for the front and rear wheels when the roll angle φ is different when there is a difference between the front and rear wheels. This is to select a larger value and promote rollover suppression.

  Further, in this embodiment, the subtraction of the steering reaction force Tr from the assist torque is performed by the adder 45, but the present invention is not limited to this, and may be executed by the adder 42. In short, it may be executed at any stage as long as a steering reaction force in the roll restraining direction can be applied to the assist torque finally output.

[Second Embodiment]
A steering assist control process executed in the present embodiment, as shown in FIG. 6, the rollover suppression processor 90, the vertical load W _FL to _W-RR, the lateral force F _FL to F _RR, the vehicle speed V, the steering angle δ is Entered.

  Further, as shown in FIG. 7, the rollover suppression process is performed in the same manner as in the first embodiment except that new steps S21 to S26 are performed instead of the above-described step S3.

First, in step S21, as shown in the following equation (3), a lateral acceleration y ″ is calculated according to the lateral forces F _{FL to} F _RR of each wheel.
y ″ = (F _FL + F _FR + F _RL + F _RR ) / m (3)
m: Body weight

In the subsequent step S22, the yaw rate γ is calculated according to the lateral forces F _{FL to} F _RR of each wheel, as shown in the following equation (4).
γ ′ = {L _F (F _FL + F _FR ) −L _R (F _RL + F _RR )} / I
γ = ∫ [{L _F (F _FL + F _FR ) −L _R (F _RL + F _RR )} / I] dt (4)
L _F : Distance from the center of gravity to the front axle L _R : Distance from the center of gravity to the rear axle I: Moment of inertia of the vehicle body

In the subsequent step S23, the side slip angle β of the vehicle body is calculated according to the lateral acceleration y ″, the yaw rate γ, and the vehicle speed V, as shown in the following equation (5).
β = ∫ {(y ″ / V) −γ} dt (5)

In the following step S24, as shown in the following equation (6), the front and rear wheel side slip angles β _F and β _R are calculated according to the side slip angle β of the vehicle body, the vehicle speed V, and the steering angle δ.
β _F + δ = β + (L _F · γ / V)
β _R = β + (L _R · γ / V) (6)

In the following step S25, as shown in the following formula (7), the cornering force of each wheel is determined according to the lateral forces F _{FL to} F _{RR of} each wheel, the side slip angles β _F and β _{R of} the front and rear wheels, and the steering angle δ. Fc _{FL to} Fc _RR are calculated. The cornering force corresponds to a component in the direction perpendicular to the wheel traveling direction in the lateral force.
Fc _FL = F _FL cos (β _F + δ)
Fc _FR = F _FR cos (β _F + δ)
Fc _RL = F _RL cosβ _R
Fc _RR = F _RR cosβ _R (7)

In step S26, as shown in the following equation (8), the load movement amount [Delta] W _F and [Delta] W _R, and in response to cornering force Fc _FL ~Fc _RR, it calculates the roll angle phi _F and phi _R of the front and rear wheels.
_{φ F = {ΔW F · d-} (Fc FL + Fc FR) h} / K
φ _R = {ΔW _R · d− (Fc _RL + Fc _RR ) h} / K (8)
As described above, the processing of steps S21 to S26 is included in the “estimating means”.

Next, the effect of this embodiment is demonstrated.
As in the first embodiment described above, by using the lateral force F _L and F _R of the left and right wheels, when estimating the roll angle phi, in a region the steering angle δ is large, there is a possibility that the error increases. Therefore, in this embodiment, the front and rear wheel roll angles φ _F and φ _R are calculated using the cornering forces Fc _{FL to} Fc _RR (steps S21 to S25). Accordingly, the roll angles φ _F and φ _R can be estimated more accurately even in a region where the change amount of the side slip angle β of the vehicle body is large or a region where the steering angle δ is large.

When the roll angles φ _F and φ _R of the front and rear wheels are estimated in this way, the average value or the larger selected value is compared with the predetermined value φth, and when it exceeds the predetermined value φth (the determination in step S4 is “Yes”) The steering reaction force Tr is calculated (step S5), and is subtracted from the assist torque (step S6), thereby reducing the steering assist force and increasing the steering reaction force for the driver. Thereby, an increase in the steering angle is suppressed, an increase in the roll angle φ can be prevented, and as a result, a rollover of the vehicle body can be prevented. In addition, the driver can be alerted by increasing the steering reaction force.

In the present embodiment, the roll angles φ _F and φ _R of the front and rear wheels are estimated, but the present invention is not limited to this, and only one of them may be used. If only the roll angle φ _{R of the} rear wheel is estimated, reading of the steering angle δ can be omitted.

It is a schematic block diagram of an electric power steering device. It is a block diagram which shows the steering assistance control process of 1st Embodiment. It is a flowchart which shows the rollover suppression process of 1st Embodiment. It is the schematic diagram explaining the roll angle of the vehicle body. It is a map used for calculation of steering reaction force. It is a block diagram which shows the steering assistance control process of 2nd Embodiment. It is a flowchart which shows the rollover suppression process of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Rack and pinion, 4 ... Tie rod, 5FL-5RR ... Wheel, 6 ... Reduction gear, 7 ... Electric motor, 8 ... Control device, 11 ... Torque sensor, 12 ... Multi load Sensor

Claims (3)

  Vertical load detecting means for detecting a vertical load acting on the left and right wheels, a lateral force detecting means for detecting a lateral force acting on the left and right wheels, a vertical load of the left and right wheels detected by the vertical load detecting means, and the lateral force A roll angle estimation device comprising: estimation means for estimating a roll angle of a vehicle body according to a lateral force of left and right wheels detected by a detection means.   The roll angle estimating device according to claim 1, wherein the lateral force detecting means detects a component perpendicular to the wheel traveling direction in the lateral force. An electric power steering apparatus comprising: an electric motor capable of transmitting an assist torque to a steering system; and a control unit that drives and controls the electric motor in accordance with a driver's steering torque,
The roll angle estimation device according to claim 1 or 2,
When the roll angle estimated by the roll angle estimation device exceeds a predetermined value, the control means drives and controls the electric motor in a direction to suppress the roll angle.

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