GB2306419A

GB2306419A - A steering control system.

Info

Publication number: GB2306419A
Application number: GB9622706A
Authority: GB
Inventors: Yong Hak Kim; Byeong Jo Lee; Jea Duk Kim
Original assignee: Mando Machinery Corp
Current assignee: Mando Machinery Corp
Priority date: 1995-10-31
Filing date: 1996-10-31
Publication date: 1997-05-07
Anticipated expiration: 2016-10-31
Also published as: GB2306419B; JPH09169281A; GB9622706D0; KR0140257B1; DE19644093A1; KR970020836A

Description

2306419 AN ELECTRONIC STEERING CONTROL SYSTEM FOR AUTOMOBILES AND A

CONTROL METHOD THEREOF

Background of invention

The invention is related to providing an electronic steering control system and a control inethod thereof for controlling an electronic control steerer to adjust the hydraulic pressure of a steering handle based on the travelling speed of automobiles.

Prior Art

Generally, a steering handle requires a greater operating force due to the friction generated between the wheels and the ground during the driving of the automobile, thereby causing the quick steering to be made difficult. To it, the light and quick steerer has been needed in the automobiles. Catching up with this needs, an electronic control steerer has been developed. The electronic control steerer reduces the operating force of the handle so as to select the steering gear, freely, thereby preventing the kick-back of the handle due to the impact against the road surface and reducing the shimmy motion of wheels during the rotating.

In other wordsI the electronic control steerer enables the catch-up of the automobiles in a manner that the operating fluid is fed to a steering control vale by a pump, and the steering control vale supplies the operating fluid to both sides of a power cylinder, selectively, according to the steering of drivers. it means that the catch-up force of the handle becomes lighter during the low speed travelling, the catch-up force is increased so as to 1 BAD ORIGINAL have a driver feel more heavy as the travelling speed becomes higher, thereby heightening the catch-up comfort of the driver. Also, it improves the on-center feel of the steering by which the catch-up force of the handle is positively adjusted according to the travelling speed of the automobile.

The-typical electronic control steerer is shown in Fig. 1, in which the operating fluid is distributed into two tubes by a pump P. The operating fluid passing through one tube is fed to a steering valve 1 and then to both sides of a power cylinder 2, selectively. The operating flow rate passing through the other tube is supplied through a hydraulic pressure control valve 5 to a repulsive force control 'device 6. And an electronic steering controller 4 controls the operation of the hydraulic pressure control valve 5 according to the travelling speed of the automobile which a sensor 3 detects, while it controls the force in the repulsive chamber of the repulsive force control device 6, thereby enabling the catch-up force to be positively controlled according to the travelling speed of the automobile.

As shown in Fig. 2, the steering control valve 1 generates the linear repulsive force according to the control hydraulic pressure of the flow rate, in which a pinion 11 is mounted in the inner of the steering control valve and a repulsive force piston 12 is assembled into a shaft S so as to be slidably moved in a radius direction. Thus, the piston 12 mounted on the rear surface of the pinion grasps around the outer periphery of the shaft S, tightly. A torsion bar 14 and the shaft 5 are coupled with each other by a center pin 15, and a body valve 16 and the pinion 11 are connected each other by means of a stopper pin 18, so that the driver feels 2 13A1) ORIGINAL the catch-up during the operating of the steering handle.

The electronic control steerer enables the torsion bar 14 to cause the anclular displacement and the edge of the shaft to form the orifice area corresponding to the angular displacement as well as to generate the hydraulic pressure corresponding to the orifice area, thereby providing the hydraulic pressure with the left and right cylinders of the steering control valve 2. Therefore, the electronic control steerer has its own inherent compensate gradient representing the control current characteristics of the steering valve to compensate for the flow rate according to the steering angular velocity. It means that the bypass hydraulic pressure is increased according to the travelling speed of the automobile and the bypass hydraulic pressure is reduced in a moment when the steering angular velocity occurs.

Nevertheless, the technology does not consider the influence of the steering angular velocity according to the travelling speed of the automobile at all. In other words, when the steering angular velocity occurs, the gradients for compensating for the quantity of the bypass hydraulic pressure are fixed in an one way independent of the travelling speed. in other words, when the compensating gradient is adapted by reference of the middle speed of the automobile, the compensating hydraulic pressure becomes too much during the high speed travelling, thereby making the light catch-up feel of the steering handle in a moment. On the contrary, when the compensating gradient is adapted by reference of the high speed of the automobile, the compensating hydraulic pressure becomes too less, thereby making the heavy catch-up feel of the steering handle.

3 BAD ORGINAL As a result, it has a problem in that if only one gradient for compensating for the flow rate is set, the driver feels strange since the areas that generates the steering angular velocity according to the travelling speed of the automobile are different from one another.

Also, a typical conventional steering force control device for power steering device is disclosed in Japanese Laid-open Publication No. 88242774 filed on July 10, 1988. The steering force control device is a type of a flow rate control apparatus that a solenoid valve adjusts the flow rate to be fed to a power cylinder and for computing the handle torque and the steering output torque based on information from a car speed sensor and performing the steering control based on the torque, in which a car speed V and a steering angle 0, changed momentarily according to the running state of an automobile, Is detected by a car speed sensor and a steering angle sensor to input the results to a resistor. After a car speed Va and a steering angle 0. stored in the resistor, are read, a CPU 51 computes a handle torque TMa responding to the car speed Va and the steering angle 6a from a characteristic map stored in an ROM. From the characteristic map stored in the ROM, the steering angle TS, responding to the car speed Va and the steering angle a is computed. The CPU computes a control current value, responding to the computed handle torque and steering output torque, from a characteristic map stored in the ROM. By means of a computed current value, a solenoid valve is controlled.

But, the technology also does not conside! the influence of the steering angular velocity according to the travelling speed of 4 BAD ORIG114AL the automobile at all. in other words, when the steering angular velocity occurs, the bypass hydraulic pressure is reduced in a moment independent of the travelling speed, and then the flow rate is reduced. It means that the disclosures of the publication is the same as the technology shown in Fig. 1. Herein, it is noted that the deficient flow rate is quickly compensated it the steering angular is changed during the travelling of the automobile.

A main object of the Invention is to provide an electronic steering control system including an electronic control steerer to control the hydraulic pressure of a steering handle based on the travelling speed of automobiles and a control method thereof.

The, other abiect of the invention is to provide an electronic steering control system and a control method thereof for calculating the compensating current according to an automobile speed, a steering angle and a steering angular velocity and for controlling the hydraulic pressure of the electronic control steerer.

Another object of the invention is to provide an electronic steering control system and a control method thereof for creating a compensating gradient to control the flow rate of the electronic control steerer according to the steering angular velocity to the automobile speed during the travelling.

SUMARY OF THE INVENTION

Accordingly, an electronic steering control system of the invention comprises an electronic steering control means for adjusting the flow rate to be fed to the left and right chambers of a power cylinder so as to give a catch-up force to a steering BAD'ORIGINAL handle; a first sensor for detecting the travelling speed of automobiles; a second sensor for detecting a steering angle during the travelling of the automobile; a throttle sensor for detecting the current applied according to the opening/closing angle of a throttle valve; an interface portion for converting the detected currants -from said sensors into voltages and outputting them; a control portion for processing said signals from said interface according to a system program in order to determine the current compensation gradient of the automobile speed, the steering absolute angle and the steering angular velocity during the travelling of the automobile; an operating portion for applying the power source to said electronic control steering means based on the signals of said control portion; a current feed-back portion for detecting the current flowing at said electronic control steering means and inputting the detected signal to said control portion; and a display operating portion for applying a power source to a light emitting diode(LED).

A method for controlling an electronic control steering means comprises steps of receiving the inputting signals including an automobile speed, a steering angle and a steering angular velocity from an automobile sensor and a steering angle sensor; calculating the current value to be applied to said electronic steering control means based on the inputting signals; detecting currents to be applied to a throttle valve and said electronic control steering means and processing the detected signals; and operating said electronic control steering means by applying the -compensating current based on the detected signals thereto.

6 BA OFLIGI9Al.

BRIEF DESCRIPTION OF DRAWINGS

The Invention now will be described in detail with reference to the attached drawings, in which; Fig. 1 is a block diagram schematically illustrating the configuration of a conventional electronic steering control system; Fig.- 2 is a cross-sectional view schematically illustrating a flow rate control valve adapted to the electronic steering control system; Fig. 3 is a bock diagram schematically illustrating an electronic steering BYSteM provided with an electronic control steerer according to the principal of the invention; Fig. 4 is a block diagram illustrating an electronic steering control portion adapted to the electronic steering control system according to the invention; Fig. 5 is a main flow chart illustrating the operation of controlling the electronic control steerer according to the invention; Fig. 6 is a flow chart illustrating the operation of calculating the automobile speed according to the invention; Fig. 7 is a flow chart illustrating the operation of calculating the compensating current value corresponding to the steering angle according to the invention; Fig. 8 is a flow chart illustrating the operation of calculating the compensating current value corresponding to the steering angular velocity according to the invention; and, Figs. 9A, 9B, 9C and 9D are compensating current -graphs based on the automobile speed, the steering angle and the steering angular velocity and a look-up table of the compensating current 7 BAD ORIGINAL based on the steering angular velocity.

DETAILED DESCRIPTION OF INVENTION

Fig. 3 is a view illustrating an electronic Control steerer and an electronic steering control portion adapted to an electronic steering. control system. The electronic control steerer 100 comprises a steering control valve 1 and a flow rate control valve 20. Herein, the explanation of the steering control valve 1 is omitted, since it is mentioned above. The flow rate control valve 20 includes a housing 2 integralled with a house 17 of the steering control valve 1. A spool 3 is mounted in the housing 2, one end of which is elastically supported against a spring 4 and the other end of which is connected to a solenoid 7 to be moved upward and downward therein. First groove 8 and second groove 9 is formed in the housing 2 to permit the spool 3 to be moved. The first groove 8 includes first flow passage 12 to be communicated with a right flow hydraulic pressure passage -31, while the second groove 9 includes second flow passage 13 to be communicated with a left hydraulic pressure passage 32. The spool 3 includes a both directional orifice 35 formed at the center to enable the flow rate to be freely moved between the first and second grooves 8 and 9. The electronic control steerer 100 is connected through flow lines L and R to a power cylinder 30 including left and right chambers 34 and 33, through a flow line 1 to a pump P and through a fluid returning line T to a tank 40. The tank 40 is cDnnected to the pump P, the furthermore explanation of which is described in detail in Japanese Patent Application No. 96-1690439 filec on June 28, 1996, U.S. A. Patent Application No. 8/670,129 filed on June 25, 1996 and 8 1310 ciaxGto Germany Patent Application No. 196 26 064.4 filed on June 28, 1996.

Therefore, when the steering handle is rotated rightward, the electronic control steerer 100 raises the hydraulic pressure of the right chamber to apply the high hydraulic pressure to the spring 4 of the-flow rate control valve 20. Then, the left chamber 34 is connected to the tank 40 to force the solenoid 7 to be positioned under the atmosphere pressure. On the contrary, when the steering handle is rotated leftward, the hydraulic pressure of the left chamber 34 is increased and the high hydraulic pressure is applied to the solenoid 7. Then, the right chamber 34 is connected to the tank 40 to force the spring 4 to be positioned under the atmosphere pressure. As described above, the electronic control steerer 100 has the both directional property to permit the fluid to be freely moved between the high hydraulic pressure portion and the low hydraulic pressure portion according to the left and right rotation of the steering handle. Thus, the hydraulic pressure formed by the orifice 35 has the equal characteristics to be moved between both directions.

An electronic steering control portion 50 is connected to an automobile sensor 22 and a steering angle sensor 23 to receive the signals of the autonobile speed and the steering angle therefron, so that it controls the operation of the solenoid 7.

As shown in Fiq. 4, the electronic steering control portion 50 comprises a control portion 21 provided with a microprocessor etc. The control portion 21 includes an inputting portion connected through an interface portion 25 to an automobile speed sensor 22 for detecting the automobile speed, a steering angle sensor 23 for BAD ORiGINAL 9 1 detecting the steering angle and a throttle sensor 24 for detecting the opening angle of a throttle valve (not shown). The interface portion 25 converts the current signals detected into the voltage signals in the form of a square wave having a predetermined magnitude. The control portion 21 receives the inputting signals of each mensor from the interface portion 25 and processes them according to the system programming to apply the control signal to a solenoid operating portion 27, so that it controls the operation of the solenoid 7. The operating portion 27 enables a predetermined current to be applied to a solenoid coil 26 according to the control signal from the control portion 21. Then, the solenoid 7 moves the spool 3 to bypass the flow rate, so that the hydraulic pressure of the left and right chambers 34 and 34 is adjusted. A current feed-back portion 28 detects the current flowing at the solenoid coil 26 and feeds it back to the control portion 21. A display operating portion 29 includes a light emitting diode LED to be turn on/turn off according to the control signal from the control portion 21.

The electronic steering control portion 50 controls the electronic control steerer 100 according to the invention, the operating flow charts of which are shown in Figs. 5, 6, 7 and 8.

The electronic steering control portion 50 initialize the System at step 200 when an ignition key is turn on. Step 200 proceeds on step 210 to calculate the automobile speed. In order to obtain the exact automobile speed, as shown in Fig. 6, the Control portion 21 is provided with a plurality of P-,AM which are cooperated with an inner counter, so that the automobile speed is calculated by checking RAMs in turns per 1.42 second. In other Ithm.

lapp wards, it is determined at step 411 whether the time of 72ms, is elapsed after the starting of the automobile. if the predetermined time is elapsed, step 411 proceeds on step 412 to obtain the automobile speed, in a manner that each PAM stores the number of an automobile speed signal frequency counted by the inner counter for the time of 1.42 second. Next, in order to calculate the automobile speed during the travelling per 1.42 second, step 413 is performed to sum up all speed values stored in RAMs. The automobile speed calculated such like that has its own inherent gradient for compensating for the current applied to the solenoid valve 7 during the travelling of the automobile. For example, based an the automobile speed, the compensating current is l(A) from 0 to 60 Km/h, 0. 4(A) from 60 to 80 Km/h and O.l(A) at over 160 Km/h, which is referenced as lu.

After the compensating current value dependent upon the automobile speed is determined, the steering absolute angle is calculated at step 220. As shown in Fig. 7, it determines the gradient for compensating for the current applied to the electronic control steerer according to the signal from the steering angle sensor, when the automobile speed is over 40 Km/h.

It is determined at step 421 whether the automobile speed is over 40 Km/h. If the automobile speed is below 40 Km/h, step 421 proceeds on Step 421 to set the compensating current value at zero and to return to step 421. If the automobile speed is over 40 Km/h, step proceeds on step 423 to check whether the handle is in the neutral position, if the handle is not in the neutral position, the control performs step 422 to set the compensating current value at zero. If the handle is In the neutral position, the control BAD ORIGINAL d performs step 424 to judge whether the shifting signal between A phase of the on-center and B phase of the off -center is inputted. If the shifting signal from A phase into B phase or from B phase into A phase is inputted by one unit of t 100, the control performs steps 425 and 426 to determine the gradient for compensating for the current applied to the flow rate control valve as shown in Fig. 9B. For example, at below 80 Km/h the steering maximum absolute angle is 200 and at over 80 1Cm/h the steering maximum absolute angle is 600. Based on the steering absolute angle, the current compensating gradient is within the range of 0.01 to 0.04(A) according to the automobile speed of 70 to 80 Km/h, and the current compensating gradient is within the range of 0.04 to 0.172(A) according to the automobile speed of 80 to 160 Km/h. At that time, it takes below 1 second to reach the compensating current 0.l(A) during the performing of the shifting from A phase to 8 phase. On the contrary, it takes below 0.5 ms to reduce the compensating current 0.l(A) during the performing of the shifting from B phase to A phase. Also, when the steering absolute value is over 600 at the automobile speed of over 160 Km/h, the compensating current value is 0.172(A), which is not almostly changed. Therefore, the steering absolute angle is detected at steps 425 and 426 by one unit of 100, thereby determining the corresponding compensating current value, which is called lw.

Next, the control performs step 230 to determine the current compensating gradient based on the steering angular velocity. As shown in Fig. 8, the operating of the steering handle leads to the steering angular velocity during the travelling of the automobile. The period of the pulse signal from the steering angle sensor is 12 k BAD ORIGNAL measured in order to calculate the steering angular velocity. And it is determined at step 432 whether the steering angle is valid, or the steering angle is kept at the on-canter. If the steering angle is invalid, the control performs step 432 to set the compensating current at zero. If the steering angle is valid, it is determined at step 433 to determine whether the steering angle is changed over 200 from the current steering angle, or a driver has an intention to change the running lane. If the changing of the running lane is not intended, the control performs step 433 to compare the current steering angle with the previous one. If the detected steering angle is moved within 200, it is determined whether the steering handle is rotated to return to the neutral position. For example, the steering angle is changed from 300 to 200, it means that the steering handle is restored. Thus, at that case, the control performs step 434 to reduce the compensating current, rapidedly, until the steering handle reaches the neutral position, lest the steering handle should be passed by the neutral position. But, if the changing of the running lane occurs, the compensating current value to the steering angular velocity is calculated based on the automobile speed. As shown in Fig. 9C, the steering angular velocity has its own inherent gradient for compensating for the current applied to the flow rate control valve during the travelling of the automobile. For example, if the steering angular velocity is 8000 degree/sec at the automobile speed of 120 Km/h, the compensating current 1 p represents as 505(mA) in the look-up table as shown in Fig. 10. Thereafter, the control performs step 435 to determine whether 1Che steering angle is maintained at over t20 for over 10 second. Then, it means that 13 BAD ORIGINAL the automobile is running on the smooth curve road for a long time period. If the steering angle is maintained at below 200, the current compensating is, stopped based on the steering angular velocity at step 435. It means that the steering handle is returned to the neutral position. If the steering angle is maintained at over 20- for over 10 second, the control performs step 438 to increase the compensating current at a predetermined proportion, thereby improving the catch-up feel of the steering handle and relieving the driver's fatigue.

As described above, after the compensating current value is determined for each of the automobile speed, the steering angle and the steering angular velocity, the control performs step 240 to read the corresponding current value from the look-up table based on the compensating gradient. Step 240 goes on step 241 to sum up these current values Iu, lw and lp, in order to calculate the total current value 1. At that time, the control portion 21 is supposed to performs the PID operation to generate the PWM(Pulse Width Modulation) duty signal and then to apply it to the operating portion 27. Therefore, the predetermined compensating current 1 is applied to the flow rate control valve 20, so that the flow rate control valve 20 adjust the flow rate of the left and right chambers. Then, at step 243 the control portion receives the signals of the throttle valve voltage and the feed-back current that the feed-back portion 28 detects from the flow rate control valve 20. Therefore, the control portion 21 performs the PID operation based on the inputted signal parameters and-computes the PWM duty, minimizing the feed-back gain or FID gain on the compensating current for the steering angular velocity, thereby 14 Bp,D ORIGINAL determining the resulting compensating current valu.e. The control portion 21 generates the PWM duty signal, so that the compensating current determined is applied to the flow rate control valve 20.

As described above, the invention computes the compensating gradient& corresponding to the speed, the steering angle and the steering angular velocity in order to adjust the bypass flow rate of the electronic control steerer, thereby giving the good catch-up feel of the steering handle and securing the steering stability to drivers.

BAD ORiGINAL (L A I M S 1. An electronic steering control system comprising: an electronic control steering means for adjusting the flOW rate to be fed to the 'Left and right chambers of a power cylinder so as to give a catch-up force to a steering handle; a first sensor for detecting the travelling speed of an automobile; a second sensor for detecting a steering angle during the travelling of the automobile; a throttle sensor for detecting the current applied according to the opening/closing angle of a throttle valve; an interface portion for converting the detected currents from said sensors into valtages and outputting them; a control portion for processing said signals from said interface according to a system program in order to deternine the current compensation gradient of the automobile speed, the steering absolute angle and the steering angular velocity during the travelling of the automobile; an operating portion for applying the power source to said electronic control steering means based on the signals of said control portion; a current feed-back portion for detecting the current flowing at said electronic control steering means and inputting the detected signal to said control portion; and, a display operating portion for applyinU a power source to a light emitting diode(LED).

16 , 01

Claims

2. The electronic steering control system according to Claim 1, wherein:

said control portion including a plurality of RAMs to cooperate with an inner counter to store the number of an automobile speed signal frequency counted by said counter therein per 1.42 second in turns.

3. The electronic steering control system according to Claim 1, wherein: said control portlan calculates the steering angular velocity in a manner that an inner timer measures the period of a steering angle pulse signal.

4. A method for controlling an electronic control steering means comprising steps of: calculating the compensating current gradient for an automobile speed based on the automobile speed signals from an automobile speed sensor; determining a steering angle by one unit of 100, continuously, and calculating the compensating current gradient for steering absolute angle based on the steering angle signals from steering angle sensor: measuring the period of the steering angle signals from the steering angle sensor and calculating the compensating eu.-rent gradient for the steering angular velocity; calculating the total compensating current value by summing up said compensating current values -.or the automobile speed, the steering angle and the steering angular velocity; and, 17 L^Li ORIG --A detecting a throttle valve voltage and feed-back current from a flow rate control valve and performing the PID operation '-as-d on all marameters including said compensating current values f or the automobile speed, the steering angle and the steering angular velocity in order to determine the compensating current value.

5. The method for controlling an electronic control steering means according to Claim 4, wherein:

the automobile speed calculating step furthermore comprises steps of determining whether the time of 72ms is elapsed after the ignition key is turn on, enabling a counter to input/store the number of the automobile speed signal frequency into a plurality of RAM in turns per 1.42 second and calculating the automobile speed, summing up all the numbers of the automobile speed signal f recluency.

6. The method for controlling an electronic control steering means according to Claim 4, wherein:

the step of calculating the steering absolute angle furthermore comprise steps of determining whether the automobile speed is over 40Yn/h, determining whether the steering handle is in the neutral position, determining whether the on-center and the off-center is shifted into each other by 100, if the steering handle is in the neutral position, and determining the compensating current according to the steering angle.

7.

The method for controlling an electronic control steering is 130) C)nG044 means according to Claim 4, wherein:

the step of calculating the steering angular velocity furthermore comprises steps of determining whether the steering angle is valid, detecting the steering angular velocity when the steering angle is changed over 200 and calculating the compensating current based on the compensating current gradient of the steering angular velocity.

hAD ORIG^ 1 19