KR20110114891A - Friction force calculation logic of motor driven power steering system and compensate friction therefor - Google Patents

Friction force calculation logic of motor driven power steering system and compensate friction therefor Download PDF

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Publication number
KR20110114891A
KR20110114891A KR1020100034274A KR20100034274A KR20110114891A KR 20110114891 A KR20110114891 A KR 20110114891A KR 1020100034274 A KR1020100034274 A KR 1020100034274A KR 20100034274 A KR20100034274 A KR 20100034274A KR 20110114891 A KR20110114891 A KR 20110114891A
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South Korea
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friction force
electric power
power steering
friction
steering system
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KR1020100034274A
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Korean (ko)
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권형주
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현대모비스 주식회사
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Priority to KR1020100034274A priority Critical patent/KR20110114891A/en
Publication of KR20110114891A publication Critical patent/KR20110114891A/en

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Abstract

The present invention relates to a friction force calculation logic of the electric power steering system and a friction compensation method using the same, and calculates the magnitude of the system friction force through the current of the steering motor measured by the current sensor and the rotation angle speed of the steering motor, The steering column torque is used to calculate the sign of the system friction force, and by multiplying the magnitude of the friction force by the sign of the friction force, the static friction force of the electric power steering system can be accurately calculated and quickly compensated.

Description

Friction force calculation logic of electric power steering system and friction compensation method using same {FRICTION FORCE CALCULATION LOGIC OF MOTOR DRIVEN POWER STEERING SYSTEM AND COMPENSATE FRICTION THEREFOR}

The present invention relates to a friction force calculation logic of the electric power steering system and a friction compensation method using the same. More specifically, the static friction force of the electric power steering system can be accurately calculated through the current, the rotation angle speed and the column torque of the steering motor. The present invention relates to a friction force calculation logic of an electric power steering system that can quickly compensate for this, and a friction compensation method using the same.

In general, Motor Driven Power Steering (MDPS) systems typically have a steering motor for generating auxiliary steering forces at the bottom of the steering wheel shaft, rather than the principle of operating the power handle by circulating oil through the operation of a power pump. When installed and started on the vehicle, the steering motor is activated to operate the power handle.

 This electric power steering system is not easy to drive the power handle by the steering motor, if the steering motor does not generate the necessary auxiliary steering force by the friction force generated when each steering component is driven.

To compensate for this, an electric power steering system with friction compensation logic is used. For example, in order to compensate for the frictional force of the rack-type electric power steering system, the mechanical frictional force generated when the rack, the steering gear and the respective components required for steering are operated is calculated by the direction of movement of the rack. And through the friction compensation lookup table, it is possible to calculate the friction force compensation value for the direction of movement of the rack.

Alternatively, the load value of the rack is measured through a load measuring device for calculating the load value of the separate rack, and the friction force compensation value is calculated through a compensation lookup table that stores a predetermined compensation value for the load value of the rack.

Since the frictional force compensation method of the electric power steering system always compensates for the constant frictional force according to the movement of the rack, the frictional force generated when the actual system is driven is not considered, and a significant error occurs between the frictional force calculated value and the actual frictional force.

SUMMARY OF THE INVENTION The present invention is to overcome the above-mentioned conventional problems, and an object of the present invention is to accurately calculate the static friction force for starting to drive the entire electric power steering system through the current of the steering motor, the rotation angle speed and the column torque. The present invention provides a friction force calculation logic of an electric power steering system and a friction compensation method using the same.

In addition, another object of the present invention can compensate for the static friction for starting to drive the electric power steering system, the steering heterogeneity generated when the steering motor is not easy to drive the power handle because it does not generate the necessary auxiliary steering force as necessary To provide a friction force calculation logic of the electric power steering system that can remove the and friction compensation method using the same.

In order to achieve the above object, the friction force calculation logic of the electric power steering system and the friction compensation method using the same in the frictional force logic for calculating the friction force generated in the electric power steering system, the steering motor current and the steering motor rotation angle Friction force magnitude calculating unit for calculating the magnitude of the frictional force generated in the electric power steering system through; and Friction force code calculating unit for calculating the sign of the frictional force generated in the electric power steering system through the column torque according to the driver's request; And a frictional force multiplier that calculates a system frictional force that is a frictional force of the electric power steering system by multiplying the magnitude of the frictional force by a sign of the frictional force.

The friction force magnitude calculating unit stores a friction force according to a steering motor current, a first lookup table for outputting a friction force according to the steering motor current input, and a first derivative to differentiate the steering motor rotation angle and output a motor rotation angle speed. And a friction factor calculated according to a differentiator and a frictional coefficient according to the motor rotational angular velocity, and outputting a frictional coefficient according to the motor rotational angular velocity output from the first differentiator and the frictional force calculated through the first lookup table. It may include a friction force magnitude multiplier for calculating the magnitude of the friction force of the electric power steering system by multiplying the friction force coefficient calculated through the second lookup table.

The friction force code calculating unit differentiates a low pass filter that removes high frequency component noise from the column torque, the column torque from which the noise is removed through the low pass filter, and outputs a slope of the column torque. If the slope of the column torque output from the second differentiator is positive, the sign of the friction force generated by the electric power steering system is output as a positive (+), and if the slope is negative includes a sign calculator for outputting a negative sign (-) can do.

In addition, the friction force calculation logic and the friction compensation method using the electric power steering system according to the present invention to achieve the above object is to calculate the magnitude of the friction force generated in the electric power steering system through the steering motor current and the steering motor rotation angle. A friction force magnitude calculating step, a friction force code calculating step of calculating a sign of friction force generated in the electric power steering system through column torque according to a driver's request, and multiplying the magnitude of the friction force by a sign of the friction force, the electric power A friction force calculating step of calculating a system friction force, which is a friction force of a steering system, and a friction force compensation step of compensating friction force through a compensation motor torque in addition to the steering motor torque value calculated according to the steering demand torque of the driver and the speed of the vehicle. To include There.

The friction force calculation logic of the electric power steering system and the friction compensation method using the same according to the present invention accurately calculate the static friction force to start driving the entire electric power steering system through the current of the steering motor, the rotation angle speed and the column torque. Can be compensated quickly.

In addition, the friction force calculation logic of the electric power steering system and the friction compensation method using the same according to the present invention can compensate for the static friction for starting to drive the electric power steering system, the steering motor does not generate as much auxiliary steering force as necessary It is possible to eliminate the steering heterogeneity generated when the power handle driving is not easy.

1 is a block diagram showing the friction force calculation logic of the electric power steering system according to an embodiment of the present invention.
FIG. 2 is a graph illustrating an example of a first lookup table of the friction force calculation logic of FIG. 1.
3 is a graph illustrating an example of a second lookup table of the friction force calculation logic of FIG. 1.
4 is a flowchart illustrating a friction force compensation method using the friction force calculation logic of FIG. 1.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

1, there is shown a block diagram showing the friction force calculation logic of the electric power steering system according to an embodiment of the present invention.

As shown in FIG. 1, the friction force calculation logic 10 of the electric power steering system includes a friction force magnitude calculator 11, a friction force code calculator 12, and a friction force multiplier Xf. This electric power steering system is a rack type steering system. And since frictional force is generally proportional to normal force, the greater the thrust of the steering wheel, the greater the frictional force generated in the system. In addition, as the thrust of the rack increases, the auxiliary steering force also increases, so that the driving torque of the steering motor controlling the auxiliary steering also increases. That is, the frictional force generated in the electric power steering system is proportional to the driving torque of the steering motor, and the driving torque of the steering motor is expressed by the product of the steering motor current Im and the motor torque constant, so The friction force is calculated by

Therefore, in order to calculate the friction force generated in the electric power steering system, the friction force magnitude calculating unit 11 first measures the magnitude of the friction force generated in the electric power steering system through the current Im and the steering motor rotation angle Am of the steering motor. (F1) is calculated. At this time, the current Im of the steering motor is the current of the steering motor measured by the current sensor.

The friction force magnitude calculating unit 11 includes a first lookup table LUT1 that stores a change in frictional force with respect to a change in current of the steering motor. The first lookup table LUT1 receives a current Im of the steering motor, which is a current flowing through the steering motor, and outputs a frictional force F corresponding to the current Im of the steering motor. At this time, the current (Im) of the steering motor is proportional to the external load value. Therefore, the frictional force F corresponding to the current Im of the steering motor output from the first lookup table LUT1 is the amount of power loss due to an external load.

As shown in FIG. 2, the first lookup table LUT1 includes a graph representing a frictional force F with respect to a change in current Im of the steering motor. For example, if the current Im of the steering motor is Ia, the friction force F output through the first lookup table LUT1 at this time becomes Fa.

In addition, the friction force magnitude calculating unit 11 receives the rotation angle Am of the steering motor and differentiates it to calculate the rotation angular velocity Vm of the steering motor and the change of the rotation angular velocity Vm. And a second lookup table LUT2 that stores a change in the friction coefficient Rf relative to the second coefficient. The second lookup table LUT2 receives the rotation angular velocity Vm output from the first differentiator d1 and outputs a friction coefficient Rf corresponding to the rotation angular velocity Vm. This friction coefficient Rf is determined by the rotational angular velocity Vm of the steering motor as the friction coefficient of the electric power steering system.

As shown in FIG. 3, the second lookup table LUT2 includes a graph representing a friction coefficient Rf with respect to a change in the rotational angular velocity Vm of the steering motor. For example, if the rotational angular velocity Vm of the steering motor is Va, the friction coefficient Rf output through the second lookup table LUT2 at this time is Ra.

The friction force magnitude calculating unit 11 multiplies the friction force F output from the first lookup table LUT1 and the friction coefficient Rf output from the second lookup table LUT2 by the friction force magnitude multiplier Xa. Outputs the magnitude (F1) of the frictional force generated by the electric power steering system.

The friction force code calculation unit 12 calculates a code F2 of the friction force generated in the electric power steering system through the column torque Tc according to the driver's request. The friction force code calculation unit 12 includes a low pass filter LPF for removing noise included in the column torque Tc. The low pass filter LPF removes noise that is a high frequency component from the column torque Tc, and outputs the column torque Tc from which the noise is removed.

In addition, the friction force code calculator 12 includes a second differentiator d2 for differentiating the column torque Tc from which the noise output from the low pass filter LPF is removed. The second differentiator d2 differentiates the column torque Tc from which the noise is removed and outputs the slope of the column torque Tc component.

In addition, the friction force code calculation unit 12 includes a code calculator S for calculating a code F2 of the friction force generated in the electric power steering system through the slope of the column torque Tc. The code calculator S outputs a sign of friction force as positive (+) when the slope of the column torque Tc output from the second differentiator d2 is positive, and when the slope of the column torque Tc is negative. , Sign of friction force is output as minus (-).

That is, the friction force code calculation unit 12 calculates the code F2 of the friction force of the electric power steering system through the column torque Tc. Since the sign F2 of the frictional force is calculated through the column torque which is the steering intention of the driver, it is calculated before the rack of the electric power steering system moves.

The friction force multiplier Xf is a friction force generated by the electric power steering system calculated by the friction force magnitude calculator 11 and the magnitude F1 of the friction force generated by the electric power steering system 11 calculated by the friction force magnitude calculating unit 11. The system friction force Ff is calculated by multiplying by the symbol F2.

This system frictional force Ff becomes a static frictional force for starting to drive the electric power steering system equal to the maximum static frictional force calculated by the current Im of the steering motor. In addition, when the torque of the static power is applied to the electric power steering system, the driving of the electric power steering system can be started.

Such friction force calculation logic of the electric power steering system of the present invention can accurately calculate the static friction force of the entire electric power steering system through the current of the steering motor, the rotation angle speed and the column torque. In addition, the friction force is calculated through the current of the steering motor, the rotation angle speed, and the column torque, so that the friction force can be calculated before the rack of the electric power steering system moves. Therefore, the friction force can be quickly compensated.

4, a flowchart illustrating a friction force compensation method using the friction force calculation logic of FIG. 1 is illustrated. The friction force compensation method of FIG. 4 will be described with reference to the friction force calculation logic of FIG. 1.

First, the magnitude F1 of the frictional force generated in the electric power steering system is calculated through the current Im of the steering motor and the rotation angle Am of the steering motor.

In order to calculate the magnitude of the frictional force F1, a current sensor for sensing the current of the steering motor is first sensed through the first lookup table LUT1 which stores the change of the frictional force with respect to the change of the current Im of the steering motor. The friction force (F) corresponding to the current (Im) of the steering motor measured through is calculated.

Then, through the second look-up table LUT2 that stores the change in the friction coefficient Rf with respect to the change in the rotational angular velocity Vm, the rotational angle Am that differentiates the rotational angle Am of the steering motor corresponds to the rotational angular velocity Vm. The friction coefficient Rf of the electric power steering system is calculated.

The magnitude F1 of the friction force is calculated by multiplying the friction force F and the friction coefficient Rf corresponding to the current Im of the steering motor.

Then, the sign F2 of the friction force generated in the electric power steering system is calculated through the column torque Tc according to the driver's request (S2). This frictional force symbol F2 becomes positive (+) when the slope of the column torque Tc, which is the derivative of the column torque Tc, is positive, and becomes negative (-) when the slope is negative.

Then, by multiplying the magnitude F1 of the friction force by the sign F2 of the friction force, the system friction force Ff, which is a friction force generated in the electric power steering system, is calculated (S3). This system frictional force Ff is a static frictional force for starting to drive the electric power steering system.

The electric power steering is controlled by controlling the electric power steering system through a compensation motor torque that compensates by adding the system friction force Ff to the steering motor torque value calculated according to the driver's steering torque and the vehicle speed of the electric power steering system. Compensate for the frictional force generated in the system (S4). That is, since the static friction force for starting to drive the electric power steering system can be compensated, it is possible to eliminate the steering heterogeneity generated when the steering motor does not generate as much auxiliary steering force as necessary and the power handle driving is not easy.

What has been described above is just one embodiment for implementing the friction force calculation logic and friction compensation method using the electric power steering system according to the present invention, the present invention is not limited to the above embodiment, the following claims As claimed in the scope of the present invention, those skilled in the art to which the present invention pertains will have the technical spirit of the present invention to the extent that various modifications can be made.

10; Friction force calculation logic of the electric power steering system
11; Friction force magnitude calculation unit 11; Friction code calculator
Xf; Friction multiplier

Claims (4)

In the frictional logic that calculates the frictional force generated by the electric power steering system,
A friction force magnitude calculating unit configured to calculate a magnitude of friction force generated in the electric power steering system through a steering motor current and a steering motor rotation angle;
A friction force code calculation unit for calculating a sign of a friction force generated in the electric power steering system through column torque according to a driver's request; And
And a friction force multiplier for calculating a system friction force, which is a friction force of the electric power steering system, by multiplying the magnitude of the friction force by the sign of the friction force. The method according to claim 1,
The friction force magnitude calculation unit
A first lookup table storing a frictional force according to a steering motor current and outputting a frictional force according to the input steering motor current;
A first differentiator for differentiating the steering motor rotation angle to output a motor rotation angle speed;
A second lookup table storing a friction coefficient according to a motor rotational angular velocity and outputting a friction coefficient according to the motor rotational angular velocity output from the first differentiator; And
Electric power steering, characterized in that it comprises a friction force multiplier for calculating the magnitude of the frictional force of the electric power steering system by multiplying the frictional force calculated through the first lookup table and the frictional force coefficient calculated through the second lookup table. Friction force calculation logic in the system. The method according to claim 1,
The friction force code calculation unit
A low pass filter for removing high frequency component noise from the column torque;
A second differentiator outputting a slope of the column torque by differentiating the column torque from which noise is removed through the low pass filter; And
If the slope of the column torque output from the second differentiator is positive, the sign calculator outputs a sign of the friction force generated by the electric power steering system as positive (+), and if the slope is negative, a negative sign (-) Friction force calculation logic of an electric power steering system comprising a. A friction force magnitude calculating step of calculating a magnitude of friction force generated in the electric power steering system through the steering motor current and the steering motor rotation angle;
A friction force sign calculating step of calculating a sign of friction force generated in the electric power steering system through column torque according to a driver's request;
A friction force calculating step of calculating a system friction force which is a friction force of the electric power steering system by multiplying the magnitude of the friction force by a sign of the friction force; And
And a friction force compensating step of compensating the friction force through the compensating motor torque in addition to the steering motor torque value calculated according to the driver's steering request torque and the speed of the vehicle. Friction compensation method using logic.
KR1020100034274A 2010-04-14 2010-04-14 Friction force calculation logic of motor driven power steering system and compensate friction therefor KR20110114891A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104554423A (en) * 2013-10-22 2015-04-29 现代摩比斯株式会社 Friction compensation logic of motor driven power steering and method thereof
KR101583632B1 (en) * 2014-09-25 2016-01-08 현대모비스 주식회사 Friction compensation apparatus of motor driven power steering system and method thereof
CN118090015A (en) * 2024-04-26 2024-05-28 豫北转向系统(新乡)股份有限公司 Characterization method of friction force of electric steering pipe column

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104554423A (en) * 2013-10-22 2015-04-29 现代摩比斯株式会社 Friction compensation logic of motor driven power steering and method thereof
KR101583632B1 (en) * 2014-09-25 2016-01-08 현대모비스 주식회사 Friction compensation apparatus of motor driven power steering system and method thereof
CN106143596A (en) * 2014-09-25 2016-11-23 现代摩比斯株式会社 The friciton compensation logic of MDPS system and method
CN106143596B (en) * 2014-09-25 2018-12-25 现代摩比斯株式会社 The friciton compensation device and method of MDPS system
CN118090015A (en) * 2024-04-26 2024-05-28 豫北转向系统(新乡)股份有限公司 Characterization method of friction force of electric steering pipe column

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