JP2008107248A - Test system for electric power steering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a test system capable of accurately simulating the provision of a steering reaction force even in an initial period of steering from the position of a linearly advancing state of a steering wheel in the case that an electric power steering apparatus is mounted to an actual vehicle. <P>SOLUTION: A steering operation force corresponding to an detected steering angle of the steering wheel 2 of the electric power steering apparatus 1 and an input vehicle speed is determined on the basis of a simulation model including the relation among the steering angle; the vehicle speed; and the steering reaction force. When it is determined that the steering wheel is in an initial period of steering from the position of a linearly advancing state, the determined steering reaction force is corrected in such a way that its magnitude may increase. An actuator 31 of a load providing mechanism 30 is controlled in such a way that a load corresponding to the determined steering reaction force may be provided for a steering force output part 7a if the steering wheel is not in the initial period of steering, and that a load corresponding to the corrected steering reaction force may be provided for the steering force output part 7a if the steering wheel is in the initial period of steering. A motor 10 for the generation of a steering assist force is controlled in such a way as to generate a steering assist force according to input vehicle speed and detected steering torque. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a test system used for performance evaluation of an electric power steering apparatus that applies a steering assist force by a motor.

In an electric power steering device, how to transmit road surface information as a steering reaction force to a driver is one of the important performances. Therefore, in the process of developing an electric power steering apparatus, performance evaluation is performed using a test system that applies a load that simulates a steering reaction force before mounting on an actual vehicle. In the test system, based on a vehicle simulation model including a relationship between a steering angle, a vehicle speed, and a steering reaction force, a steering reaction force corresponding to a detected steering angle of the steering wheel of the electric power steering device and an input vehicle speed is obtained. A load corresponding to the obtained steering reaction force is applied to the steering force output unit of the electric power steering device, and the steering auxiliary force generation of the electric power steering device is generated so as to generate the steering auxiliary force according to the input vehicle speed and the detected steering torque. The motor is controlled (see Patent Document 1).
JP 2005-172528 A

  However, when a load is applied to the electric power steering apparatus using the above-described conventional test system, there has been a problem that a change in steering torque at the beginning of steering from the straight traveling state position of the steering wheel is not properly simulated. For example, as shown in FIG. 8, in an electric power steering apparatus mounted on an actual vehicle traveling at a vehicle speed of 60 km / h, the relationship between time and steering angle is represented by a broken line, and the relationship between time and steering torque is represented by a solid line. expressed. On the other hand, as shown in FIG. 7, in an electric power steering apparatus to which a load is applied by a test system based on a simulation model of a vehicle traveling at a vehicle speed of 60 km / h, the relationship between time and steering angle is represented by a broken line. The solid line represents the relationship between time and steering torque according to the conventional example. When both are compared, the common point is that the steering torque increases as the steering angle increases. However, paying attention to the steering torque with respect to the steering angle at the beginning of steering from the straight-running position of the steering wheel, when the electric power steering device is mounted on a real vehicle, the steering angle change is very small (0 on the time axis in FIG. 8). In the test system, the steering torque starts to increase at the time point of 4 to 0.5 seconds (in the time axis in FIG. 7, around 1.0 second). The steering torque starts to increase at the time. That is, in the test system, there is a problem that the start-up of the steering torque at the beginning of steering from the straight-running position of the steering wheel is delayed as compared with the actual vehicle. It is an object of the present invention to provide a test system for an electric power steering apparatus that can solve such a problem.

The present invention includes a steering assist force generation motor, a torque sensor that detects a steering torque of a steering wheel, and a control device that controls the motor to generate a steering assist force according to the detected steering torque and the vehicle speed. A test system for an electric power steering device comprising a load applying mechanism including an actuator for applying a load to a steering force output unit in the electric power steering device; an angle sensor for detecting a steering angle of the steering wheel; A vehicle speed input unit for inputting a vehicle speed, a simulation model storage means including a relationship between a steering angle, a vehicle speed, and a steering reaction force, and a calculation means for obtaining a steering reaction force according to the detected steering angle and the input vehicle speed based on the simulation model And an input means to the control device for the vehicle speed input by the vehicle speed input unit, In the test system for an electric power steering apparatus in which the motor is controlled by the controller so that a steering assist force according to the steering torque obtained by the torque sensor and the input vehicle speed is generated, The determination means for determining whether or not the steering is initially started, and when the steering wheel is determined to be the initial steering start from the straight traveling state position, the magnitude of the steering reaction force obtained by the calculating means is increased. Correcting means for correcting the obtained steering reaction force, and when it is not determined that the steering wheel is at the beginning of steering from the straight traveling position, a load corresponding to the steering reaction force obtained by the computing means is the steering force. If it is given to the output unit and it is determined that it is the beginning of steering, the steering reaction force corrected by the correction means As response to the load applied to the steering force output section, and a controlling means for controlling the actuator.
The present invention is based on the following findings.
At the beginning of steering from the straight position of the steering wheel in an actual vehicle, even if the steering angle change is small due to the static frictional force and the steering reaction force based on viscosity in the system that transmits the movement of the steering wheel to the wheel Steering torque increases. In the conventional test system, since the influence of the steering reaction force based on such a static frictional force is not taken into consideration, the steering torque rises with respect to the steering angle at the beginning of steering from the straight traveling state position of the steering wheel. It was later than the actual case.
On the other hand, according to the present invention, when it is determined that the steering wheel starts from the straight-running position, the steering reaction force is increased by increasing the magnitude of the steering reaction force based on the simulation model. The static frictional force or the like in the transmission system is reflected in the simulation, so that the rise of the steering torque with respect to the steering angle can be prevented from being delayed from the actual case.

  At the beginning of steering from the straight traveling position of the steering wheel, the magnitude of the detected steering angle and the magnitude of the change speed of the detected steering angle are relatively small. Therefore, the present invention comprises means for storing a threshold value for the detected steering angle magnitude and means for storing a threshold value for the detected steering angle change speed, and stores the detected steering angle magnitude greater than zero. The steering wheel is at the beginning of steering from the straight traveling state position by the determination means when the detected steering angle change speed magnitude is less than the stored threshold value greater than zero. Is preferably determined. Thereby, it can be appropriately determined whether or not the steering wheel is at the beginning of steering from the straight traveling state position.

  As the steering angle increases, the influence of the static frictional force or the like in the system that transmits the movement of the steering wheel to the wheel decreases on the steering torque. Therefore, in the present invention, there is provided means for storing, as a correction characteristic, the relationship between the value before and after the correction of the steering reaction force by the correction means and the steering angle, and the calculation reaction means performs the steering reaction force based on the detected steering angle and the correction characteristic. It is preferable that the correction characteristic is determined so that the correction amount of the steering reaction force by the correction means decreases as the detected steering angle increases. As a result, the steering reaction force can be corrected appropriately.

  According to the test system of the present invention, it is possible to accurately simulate the application of the steering reaction force when the electric power steering device is mounted on an actual vehicle even at the beginning of steering from the straight traveling state position of the steering wheel. Appropriate performance evaluation of the steering device can be performed.

  FIG. 1 shows a test system for an electric power steering apparatus according to an embodiment of the present invention. The electric power steering device 1 to be tested includes a mechanism for transmitting the rotation of the steering wheel 2 by steering to the wheels so that the steering angle changes. The electric power steering apparatus 1 of the present embodiment is a known rack and pinion type, transmits the rotation of the steering wheel 2 to the pinion 5 via the steering shaft 4, moves the rack 6 engaged with the pinion 5, and moves the rack 6. The steering angle is changed by transmitting the movement to the wheels via the left and right tie rods 7. A steering assisting force generating motor 10 is provided which acts on a path for transmitting the rotation of the steering wheel 2 to the wheels. In the present embodiment, the rotation of the output shaft of the motor 10 is transmitted to the steering shaft 4 via the reduction gear mechanism 11 so that a steering assist force is applied. The motor 10 is connected to a control device 20 composed of an in-vehicle computer. A torque sensor 22 that detects the steering torque of the steering wheel 2 is connected to the control device 20. A vehicle speed sensor is connected to the control device 20 when the vehicle is mounted. The control device 20 controls the motor 10 so that a steering assist force corresponding to the steering torque obtained by the torque sensor 22 and the vehicle speed is generated. The steering shaft 4 of the present embodiment is divided into a steering wheel 2 side and a pinion 5 side and is connected by a torsion bar, and the torsion angle of the torsion bar, which is the difference between the steering angle of the steering wheel 2 and the rotation angle of the pinion 5. Further, the torque sensor 22 detects a steering torque obtained by multiplying the spring constant of the torsion bar.

  A load applying mechanism 30 including an AC servomotor 31 (actuator) for applying a load to the steering force output unit of the electric power steering apparatus 1 is provided. The steering force output portion 7a of the electric power steering apparatus 1 in this embodiment is constituted by the other end portion of one tie rod 7 having one end portion connected to the rack 6 via a universal joint 9 such as a ball joint. In an actual vehicle, wheels are connected to the steering force output portion 7a via a universal joint and a knuckle arm. The load applying mechanism 30 drives a ball screw 34 screwed to a ball nut 33 connected to the steering force output portion 7a via a universal joint 32 such as a ball joint by a motor 31 via a reduction gear mechanism 35. Thus, a load corresponding to the steering reaction force is applied to the steering force output unit 7a. Since the steering reaction force is mainly due to the self-aligning torque generated in proportion to the side slip angle of the front wheel, a force along the axial direction of the tie rod 7 (hereinafter referred to as “axial force”) acts on the tie rod 7 to cause the steering reaction force. Is applied to the steering force output unit 7a. Further, although the axial force in the actual vehicle is generated in each of the left and right tie rods 7, the steering reaction force felt by the driver is the sum of the left and right axial forces. Therefore, in this embodiment, the sum of the left and right axial forces is added to the tie rod 7 on one side. .

  The motor 31 is connected via a D / A converter 43 to a test control device 40 constituted by a personal computer. The test control device 40 is connected to an angle sensor 23 for obtaining a steering angle of the steering wheel 2 via an A / D converter 42, and further connected to a vehicle speed input unit 44 for inputting a vehicle speed. The vehicle speed input unit 44 can be configured by, for example, a keyboard switch or a brake pedal-like input switch. When the electric power steering device 1 controls the steering assist force generating motor 10 according to the steering angle, the angle sensor 23 provided in the electric power steering device 1 may be used.

  The test control device 40 functions as a means for storing a simulation model including the relationship between the steering angle, the vehicle speed, and the axial force corresponding to the steering reaction force, and the detected steering angle by the angle sensor 23 and the input vehicle speed by the vehicle speed input unit 44. It functions as a calculation means for obtaining an axial force corresponding to the above based on the stored simulation model. Further, the test control device 40 functions as a determination unit that determines whether or not the steering wheel 2 is initially started from the straight traveling state position, and is determined that the steering wheel 2 is the initial steering start from the straight traveling state position. In this case, it functions as correction means for correcting the obtained axial force so that the magnitude of the obtained axial force increases. Further, the test control device 40 controls the motor 31 so that the obtained axial force acts on the tie rod 7 when the steering wheel 2 is not initially started from the straight traveling state position, and the steering wheel 2 is steered from the straight traveling state position. If it is at the beginning, it functions as a control means for controlling the motor 31 so that the corrected axial force acts on the tie rod 7.

  The control device 20 and the test control device 40 are connected so that the vehicle speed input by the vehicle speed input unit 44 can be input to the control device 20, whereby the vehicle speed input to the control device 20 is input by the vehicle speed input unit 44. Functions as a means. The configuration of the vehicle speed input means to the control device 20 is not particularly limited. For example, the vehicle speed input unit 44 is directly connected to the control device 20 so that the vehicle speed input unit 44 is used as the vehicle speed input means to the control device 20. May function.

  The control device 20 controls the motor 10 based on the stored steering assist program so as to generate a steering assist force corresponding to the steering torque obtained by the torque sensor 22 and the input vehicle speed. In this embodiment, the steering assist force increases as the steering torque increases and the input vehicle speed decreases. However, the present invention is not limited to this. For example, the steering assist is performed according to the detected steering angle by the angle sensor 23. The force may be changed.

When simulating the state in which the steering reaction force is applied by the test system of the above embodiment, the electric power steering device 1 is fixed to a support base (not shown) in the same manner as being mounted on an actual vehicle. As the device 1, a device mounted on an ordinary passenger car having a body mass of more than 1000 kg is used. When the load is applied by the load applying mechanism 30, the self-aligning torque and the axial force of the tie rod 7 are obtained from the side slip angle of the front wheels in real time based on the simulation model. In this embodiment, the simulation model is an equivalent two-wheel model having front and rear wheels 50 and 51 in consideration of three degrees of freedom in the lateral direction, the yaw direction, and the roll direction, as shown in FIGS. The definitions of symbols used in this embodiment are as shown in Table 1 below. Further, the value corresponding to each symbol is positive when it corresponds to one of the left and right sides of the vehicle and one of the front and rear, and negative when it corresponds to the other side of the vehicle and the other side.

In the simulation model, the product of inertia in the x and z directions is zero, and the equation of motion around the vehicle center of gravity G is as shown in the following equations (1) to (3).

When the tire side slip angle in the wheel is minute, the wheel side force is proportional to the wheel side slip angle as shown in the following formulas (4) and (5).

In the present embodiment, the following equations (6) and (7) are used in consideration of dynamic characteristics from the occurrence of a skid angle to the occurrence of a lateral force in a tire constituting a wheel. That is, at a constant vehicle speed, the sum of the wheel lateral force and the value proportional to the time differential of the wheel lateral force is proportional to the wheel side slip angle.

なお、単位ロール角あたりのロールステア量の値は本実施形態では定数と仮定して用いた。また、実車実験により操舵角入力に対するタイロッド７の変位に動特性がほとんどなかったため、操舵系は剛体とし、操舵角に対して前輪実舵角は以下の式（１２）に示すように比例関係とし、遅れがないものとする。

The sideslip angles of the front and rear wheels are expressed by the following formulas (8) to (11).

In this embodiment, the value of the roll steer amount per unit roll angle is assumed to be a constant. Moreover, since there was almost no dynamic characteristic in the displacement of the tie rod 7 with respect to the steering angle input in the actual vehicle experiment, the steering system is a rigid body, and the actual steering angle of the front wheels is proportional to the steering angle as shown in the following equation (12). Suppose there is no delay.

As shown in FIGS. 4 and 5, a value obtained by dividing the self-aligning torque around the kingpin 11 by the length of the knuckle arm 9 was used as the axial force acting on the tie rod 7 in the simulation model of this embodiment. The following formulas (13) and (14) show the relationship between the self-aligning torque and the axial force for two tires.

  The test control device 40 in the present embodiment determines whether or not the steering wheel 2 is initially started from the straight-running state position, so that the threshold value storage means for the detected steering angle θ and the change speed of the detected steering angle θ are determined. Functions as a threshold value storage means. In other words, the test control device 40 has the detected steering angle θ larger than zero and less than the stored threshold, and the detected steering angle θ change speed larger than zero and less than the stored threshold. Sometimes, it is determined that the steering wheel 2 is at the beginning of steering from the straight traveling position. Since the magnitude of the detected steering angle θ and the magnitude of the change speed of the detected steering angle θ are relatively small at the beginning of steering from the straight running state position of the steering wheel 2, the test control device 40 causes the steering wheel 2 to move from the straight running state position. It is possible to appropriately determine whether or not it is the beginning of steering. What is necessary is just to obtain | require each threshold value experimentally so that it can simulate appropriately. For example, P = 1 ° and Q = 10 ° / sec, where P is the threshold value of the detected steering angle θ and Q is the threshold value of the change speed of the detected steering angle θ.

Since the test control device 40 in the present embodiment corrects the axial force obtained from the equation (14) at the beginning of steering from the straight traveling state position of the steering wheel 2, the value before and after the correction of the axial force and the steering angle θ Is stored as a correction characteristic, and the axial force is corrected based on the correction characteristic and the detected steering angle θ. The correction characteristic is determined so that the amount of correction of the axial force decreases as the detected steering angle θ increases. For example, the correction characteristic is expressed by the following equation (15), where F is the axial force before correction obtained from equation (14), F ′ is the axial force after correction, and K is a coefficient. Here, the threshold value P for the magnitude of the detected steering angle θ is P = 1, and the coefficient K is 2 when the magnitude of the detected steering angle θ is zero, and the magnitude of the detected steering angle θ is 1. The detected steering angle θ becomes smaller as the magnitude of the detected steering angle θ increases so that it becomes 1, and when the detected steering angle θ reaches the threshold value P, F ′ = F.

  The flowchart of FIG. 6 shows a procedure for correcting the axial force F by the test control device 40. First, it is determined whether or not the detected steering angle θ is zero (step S1). If it is zero, no correction is performed, and if it is not zero, it is determined whether or not the detected steering angle θ is less than a threshold value P ( If it is less than the threshold value P, the correction is not performed. If it is less than the threshold value P, it is determined whether or not the magnitude of the change speed of the detected steering angle θ is less than the threshold value Q (step S3). If not, the correction is not performed, and if it is less than the threshold value Q, the axial force F is corrected using equation (15) (step S4).

  According to the test system of the above embodiment, when it is determined that the steering wheel 2 is initially started from the straight traveling state position, the magnitude of the axial force F based on the simulation model is increased, whereby the steering wheel 2 Static frictional force or the like in the system that transmits the motion to the wheel is reflected in the simulation, and the rise of the steering torque with respect to the steering angle can be prevented from being delayed from the actual case. Further, in the above embodiment, the amount of correction of the axial force decreases as the detected steering angle θ increases, so that static frictional force or the like in the system that transmits the movement of the steering wheel 2 to the wheels becomes steering torque. It is possible to simulate that the influence exerts becomes smaller as the steering angle increases, and the steering reaction force can be corrected appropriately.

  The two-dot chain line in FIG. 7 shows the relationship between time and steering torque when a load whose axial force is simulated by the test system of the above embodiment is applied, and the time and steering torque in the electric power steering apparatus mounted on the actual vehicle. It can be confirmed that the relationship between and is simulated more appropriately than before.

  The present invention is not limited to the above embodiment. For example, the correction amount of the axial force does not necessarily change according to the detected steering angle θ, and the magnitude of the axial force increases when it is determined that the steering wheel 2 is at the beginning of steering from the straight traveling state position. It may be corrected as follows. For example, the corrected axial force F ′ may be obtained from the relationship of F ′ = Kc · F from the uncorrected axial force F and a fixed correction gain Kc (Kc> 1). The type of the electric power steering device to be tested by the test system of the present invention is not particularly limited. For example, the rotation of the steering wheel is transmitted from the steering shaft to the wheel via the link mechanism, or the ball screw integrated with the rack. A steering nut may be applied by driving a ball nut screwed to the motor by the output of a motor. Further, the configuration of the load applying mechanism is not particularly limited as long as it can apply a load to the steering force output unit of the electric power steering apparatus. For example, a load may be generated by a hydraulic actuator.

Configuration explanatory diagram of a test system for an electric power steering apparatus according to an embodiment of the present invention Plan view for explaining a simulation model in an embodiment of the present invention Front view for explaining a simulation model in an embodiment of the present invention Explanatory drawing of the action state of the self-aligning torque in the simulation model in the embodiment of the present invention Explanatory drawing of the action state of the axial force to the tie rod in the simulation model in the embodiment of the present invention The flowchart which shows the correction | amendment procedure of the axial force in embodiment of this invention The figure which represents the relationship between the time and steering angle in the electric power steering device which applied the load which simulated the steering reaction force, the relationship between the time and the steering torque according to the conventional example, and the relationship between the time and the steering torque according to this embodiment, respectively. The figure showing the relationship between the time and the steering angle and the relationship between the time and the steering torque in the electric power steering device mounted on the actual vehicle

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering wheel, 7a ... Steering force output part, 10 ... Motor for steering assist force generation, 20 ... Control device, 22 ... Torque sensor, 23 ... Angle sensor, 30 ... Load application mechanism, 31 ... AC servo motor (actuator), 40 ... Test control device (calculation means, control means, input means, storage means, determination means, correction means), 44 ... vehicle speed input section

Claims (3)

Electric power steering comprising a motor for generating steering assist force, a torque sensor for detecting steering torque of a steering wheel, and a control device for controlling the motor to generate steering assist force according to detected steering torque and vehicle speed A test system for the device,
A load applying mechanism including an actuator for applying a load to a steering force output unit in the electric power steering device;
An angle sensor for detecting a steering angle of the steering wheel;
A vehicle speed input unit for inputting the vehicle speed;
Means for storing a simulation model including the relationship between the steering angle, the vehicle speed, and the steering reaction force;
A calculation means for obtaining a steering reaction force according to the detected steering angle and the input vehicle speed based on the simulation model;
Input means to the control device of the vehicle speed input by the vehicle speed input unit,
In the test system for an electric power steering device in which the motor is controlled by the control device so that a steering assist force according to the steering torque obtained by the torque sensor and the input vehicle speed is generated.
Determining means for determining whether or not the steering wheel is initially started from the straight traveling state position of the steering wheel;
Correction means for correcting the obtained steering reaction force so that the magnitude of the steering reaction force obtained by the computing means increases when it is determined that the steering wheel is at the beginning of steering from the straight traveling state position; ,
When it is not determined that the steering wheel is at the beginning of steering from the straight traveling position, a load corresponding to the steering reaction force obtained by the calculation means is applied to the steering force output unit, and it is determined that the steering is at the beginning. Control means for controlling the actuator so that a load corresponding to the steering reaction force corrected by the correction means is applied to the steering force output unit. Test system. Means for storing a threshold value of the detected steering angle;
Means for storing a threshold value of the magnitude of the change speed of the detected steering angle,
When the magnitude of the detected steering angle is less than a threshold stored greater than zero and the magnitude of the change speed of the detected steering angle is less than a threshold stored greater than zero, the determination means causes the steering wheel to The test system for an electric power steering apparatus according to claim 1, wherein it is determined that the steering is initially started from the straight traveling state position. Means for storing the relationship between the value before and after the correction of the steering reaction force by the correction means and the steering angle as a correction characteristic;
A steering reaction force is corrected by the calculation means based on the detected steering angle and the correction characteristic,
3. The test system for an electric power steering apparatus according to claim 1 or 2, wherein the correction characteristic is determined so that the correction amount of the steering reaction force by the correction means decreases as the detected steering angle increases. .

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