JP5494628B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to an electric power steering control device that assists a driver to operate a steering wheel of a vehicle with a motor.

  Conventionally, the assist amount for assisting the operation of the steering wheel is calculated based on the steering torque generated by the steering wheel operation by the driver, and the assist amount is increased based on the steering angle so that the assist amount increases as the steering angle increases. There is known an electric power steering control device capable of reducing the burden on the driver when the driver greatly operates the steering wheel (that is, the steering angle is large) by setting an adjustment gain for adjusting the amount. (For example, refer to Patent Document 1).

JP 2000-43742 A

  However, the steering state of the vehicle changes not only by the steering angle but also by the steering torque and the rotational speed of the steering angle (steering angular velocity). For this reason, as in the technique described in Patent Document 1, when the assist amount is adjusted only by the steering angle, there is a problem that an unnatural steering feeling that does not appropriately reflect the driver's intention may occur.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique that enables assist control that appropriately reflects the driver's intention.

  In order to achieve the above object, an invention according to claim 1 is directed to an input shaft connected to a handle of a vehicle and rotating together with the handle, and transmitting the rotation of the input shaft to a steered wheel of the vehicle. An input transmission means for steering, a steering torque detection means for detecting a steering torque that is a torque in the rotational direction of the shaft applied to the input shaft, and an assist torque for assisting the operation of the steering wheel when the steering wheel is steered by the operation of the steering wheel. An electric power steering control device is provided in an electric power steering system including an input shaft or a motor for giving to input transmission means, and controls assist torque by controlling the motor.

  In the electric power steering control device according to claim 1, the assist amount calculating means calculates an assist amount indicating an assist torque having a value corresponding to the steering torque, based on the steering torque detected by the steering torque detecting means. The motor driving means drives the motor based on the assist amount calculated by the assist amount calculating means. The steering angular velocity detection means detects the steering angular speed which is the rotational speed of the steering angle of the steering wheel, and the steering state amount calculation means detects at least the steering torque detected by the steering torque detection means and the steering angular speed detection means. Based on the steering angular velocity, a steering state amount indicating the steering state of the vehicle is calculated. The assist amount calculating means changes the assist amount based on the steering state amount calculated by the steering state amount calculating means.

  In the electric power steering control device configured as described above, the assist amount is changed based on the steering state amount calculated based on the steering torque and the steering angular velocity. It is possible to change, and it is possible to realize assist control that more appropriately reflects the driver's intention.

  For example, when the assist amount calculation means is set so as to increase the assist amount in accordance with an increase in the steering angular velocity, the driver starts to turn the handle quickly from a state where the driver holds the handle at a certain handle angle. Then, the assist torque can be increased rapidly.

  That is, the steering wheel can be operated more easily when the steering wheel is turned faster than when the steering wheel is turned slowly, and the driver's intention to turn the steering wheel quickly can be appropriately reflected in the control.

Further, in the electric power steering control device according to claim 1, a steering angle detecting means detects the steering angle of the steering wheel, steering state quantity calculating means in addition to the steering torque and the steering angular velocity, further steering angle detection means based on the steering angle detected by, it calculates the steering state quantity.

  In the electric power steering control device configured as described above, the assist torque can be changed also by the steering angle of the steering wheel, and it is possible to realize the assist control more appropriately reflecting the driver's intention.

  For example, when the assist amount calculation means is set so as to increase the assist amount in accordance with the increase in the steering angle, an assist torque that increases in accordance with the steering angle is applied. In the case of increasing the steering angle, the assist torque can be gradually increased as the steering angle increases, and the steering wheel can be operated more easily as the steering wheel is increased.

In the electric power steering control device according to claim 1, the multiplication value of the first adjustment gain, the steering torque, and the steering angle that are set in advance, the second adjustment gain that is set in advance, the steering torque, and the steering are set. a value obtained by adding the multiplied value of the angular velocity is calculated as the steering state quantity.

  According to the electric power steering control device configured as described above, the calculation of the steering state amount can be performed simply by adding and multiplying the steering torque, the steering angle, and the steering angular velocity. Increase in processing load can be suppressed to the minimum necessary.

Further, when provided with a vehicle speed detecting means for detecting a speed of the vehicle is the electric power steering control device according to claim 1, as claimed in claim 2, the steering state quantity calculating means, the 1 of adjusting gain and the second adjustment gain at least one, may be calculated according to the speed of the vehicle detected by the vehicle speed detecting means.

  According to the electric power steering control device configured as described above, since the steering state amount is changed according to the vehicle speed, a more appropriate assist amount according to the vehicle speed can be calculated, and the appropriate vehicle speed is taken into consideration. It becomes possible to make it a characteristic.

1 is a configuration diagram showing a schematic configuration of an EPS system 1. FIG. 2 is a block diagram showing a schematic configuration of EPSECU 15. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram showing a schematic configuration of an electric power steering system 1 according to an embodiment to which the present invention is applied.

  An electric power steering system 1 (hereinafter referred to as an EPS (Electric Power Steering) system 1) assists the driver with the operation of the steering wheel 2 by a motor 6. The handle 2 is fixed to one end of a steering shaft 3, and a torque sensor 4 is connected to the other end of the steering shaft 3, and an intermediate shaft 5 is connected to the other end of the torque sensor 4.

  The torque sensor 4 is a sensor for detecting steering torque. Specifically, a torsion bar that connects the steering shaft 3 and the intermediate shaft 5 is provided, and a torque applied to the torsion bar is detected based on a twist angle of the torsion bar.

  The motor 6 assists the steering force of the handle 2. A worm gear is provided at the tip of the rotating shaft of the motor 6, and this worm gear meshes with a worm wheel provided on the intermediate shaft 5. Thereby, the rotation of the motor 6 is transmitted to the intermediate shaft 5. On the contrary, when the intermediate shaft 5 is rotated by the operation of the handle 2 or the reaction force from the road surface (road surface reaction force), the rotation is transmitted to the motor 6 and the motor 6 is also rotated.

  The other end of the intermediate shaft 5 opposite to the end to which the torque sensor 4 is connected is connected to the steering gear box 7. The steering gear box 7 is configured by a gear mechanism including a rack and a pinion gear (not shown), and the teeth of the rack mesh with a pinion gear provided at the other end of the intermediate shaft 5. Therefore, when the driver turns the handle 2, the intermediate shaft 5 rotates (that is, the pinion gear rotates), and the rack moves to the left and right. Tie rods 8 are attached to both ends of the rack, and the tie rods 8 reciprocate left and right together with the rack. Thereby, the direction of the tire 10 is changed by the tie rod 8 pulling or pushing the knuckle arm 9 ahead.

A steering angle sensor 11 that detects the steering angle θs of the steering wheel 2 and a vehicle speed sensor 12 that detects the vehicle speed V are provided at predetermined locations in the vehicle.
With this configuration, when the driver rotates the steering wheel 2, the rotation is transmitted to the steering gear box 7 via the steering shaft 3, the torque sensor 4, and the intermediate shaft 5. Then, in the steering gear box 7, the rotation of the intermediate shaft 5 is converted into the left-right movement of the tie rod 8, and the left and right tires 10 are steered by the movement of the tie rod 8.

  An electric power steering ECU (Electric Power Steering Electronic Control Unit) 15 (hereinafter referred to as EPSECU 15) is operated by electric power from a vehicle battery (not shown), and detects a steering torque Ts detected by the torque sensor 4 and a steering angle sensor 11. Based on the detected steering angle θs, a current command indicating a current value to be passed through the motor 6 is generated. Then, by applying a driving voltage Vd corresponding to the current command to the motor 6, an assist torque for assisting the driver's turning force of the steering wheel 2 (and thus the force of steering the two tires 10) is applied to the motor 6. generate.

  The EPS ECU 15 controls the motor 6 by directly controlling the drive voltage Vd applied to the motor 6. However, the EPS ECU 15 controls the EPS mechanism 70 driven by the motor 6 by controlling the motor 6. It can be said that the control object of the EPS ECU 15 is the EPS mechanism 70. The EPS mechanism 70 indicates the entire mechanism excluding the EPS ECU 15 and the motor 6 in the system configuration diagram shown in FIG. 1, that is, the entire mechanism that transmits the steering force of the handle 2 from the handle 2 to each tire 10. .

  Next, the internal configuration (control mechanism) of EPSECU 15 will be described using the block diagram of FIG. In FIG. 2, each block from the target assist torque calculation unit 20 to the motor drive circuit 50 excluding the motor 6 and the EPS mechanism 70 is realized by the EPS ECU 15. Of the blocks realized by EPSECU 15, each part excluding motor drive circuit 50 is actually realized when a CPU (not shown) included in EPSECU 15 executes a predetermined control program. That is, each block from the target assist torque calculation unit 20 to the current control unit 40 in FIG. 2 illustrates various functions realized by the CPU separately for each functional block. However, the realization of these blocks by software is merely an example, and it goes without saying that the blocks may be realized by hardware such as a logic circuit.

  As shown in FIG. 2, the ECU 15 calculates a target assist torque (target current) based on the steering torque Ts and the steering angle θs, and a target calculated by the target assist torque calculation unit 20. A deviation calculator 30 that calculates a current deviation that is a difference between the current and the actual current Im that actually flows through the motor 6, and a current command that indicates the amount of current that should be supplied to the motor 6 based on the current deviation and the actual current Im. And a motor drive circuit 50 for flowing a current corresponding to the current command to the motor 6 (actually applying the drive voltage Vd to the motor 6).

  Although not shown, a detection circuit including a detection element for detecting the actual current Im is provided inside the motor drive circuit 50 or in the energization path from the motor drive circuit 50 to the motor 6. The actual current Im is detected by the detection circuit.

  In addition, the target assist torque calculation unit 20 performs a steering state based on the phase compensator 21 that applies phase compensation to the steering torque Ts in order to stabilize the entire control system (control mechanism), and the steering torque Ts and the steering angle θs. A steering state amount calculation unit 22 that calculates the amount, a base assist calculation unit 23 that calculates a base assist torque that is a base of the target assist torque based on the steering state amount, and a value after phase compensation by the phase compensator 21 ( And a multiplier 24 for calculating a final target assist torque (target current) by multiplying the phase compensation torque) by the base assist torque by the base assist calculation unit 23.

  Note that the base assist calculation unit 23 actually has an assist map 23m in which assist torque gains with respect to the steering state amount are associated on a one-to-one basis, and the steering state input by linear interpolation based on the map. The base assist torque for the amount is calculated. In the present embodiment, a map is set in which the assist torque gain increases as the steering state amount increases.

  The steering state amount calculation unit 22 outputs a multiplier 61 that outputs a value obtained by multiplying the steering torque Ts by the steering angle θs, a differentiator 62 that calculates the steering angular velocity ωs based on the time change of the steering angle θs, and the steering torque. A multiplier 63 that outputs a value obtained by multiplying Ts by the steering angular velocity ωs, an amplifier 64 that amplifies and outputs an output value from the multiplier 61 with a predetermined adjustment gain α, and outputs an output value from the multiplier 63 to a predetermined value. An amplifier 65 that amplifies and outputs with the adjustment gain β, and an adder 66 that calculates the steering state quantity by adding the output value from the amplifier 64 and the output value from the amplifier 65 are provided. Therefore, the steering state amount calculation unit 22 outputs a steering state amount represented by (α × Ts × θs + β × Ts × ωs).

  Each of the amplifiers 64 and 65 has a map in which the adjustment gains α and β are associated with the vehicle speed V on a one-to-one basis, and the adjustment gain α for the input vehicle speed V is based on the maps. , Β is calculated.

  Based on the current deviation calculated by the deviation calculator 30, the current control unit 40 feedback-controls energization of the motor 6 so that the current deviation becomes 0, that is, the actual current Im matches the target current. An energization command is generated to Specifically, a current controller 41, which is a PI controller having proportional and integral elements, is provided, and the current controller 41 performs proportional and integral calculations on the input current deviation. Then, the current command is calculated. In addition to the current deviation, the actual current Im is also input to the current controller 41, and the current command value is calculated in consideration of the actual current Im. This current command actually indicates a drive voltage applied to the motor 6, and the current indicated by the current command flows to the motor 6 when the motor drive circuit 50 energizes the motor 6 in accordance with this current command. .

  In the EPS system 1 configured as described above, the target assist torque calculation unit 20 calculates a target current indicating a target assist torque having a value corresponding to the steering torque, based on the steering torque Ts detected by the torque sensor 4. The motor drive circuit 50 drives the motor 6 based on the calculated target current. In addition, the steering angle sensor 11 detects the steering angle θs, the differentiator 62 calculates the steering angular velocity ωs, and the steering state amount calculation unit 22 further based on the steering torque Ts, the steering angle θs, and the steering angular velocity ωs. The steering state quantity is calculated. Then, the target assist torque calculation unit 20 changes the target current indicating the target assist torque based on the calculated steering state quantity.

  Therefore, in order to change the target assist torque (target current) based on the steering state quantity calculated based on the steering torque Ts and the steering angular velocity ωs, the target assist torque is changed not only by the steering torque Ts but also by the steering angular velocity ωs. Thus, it is possible to realize assist control that more appropriately reflects the driver's intention.

  In the present embodiment, since (α × Ts × θs + β × Ts × ωs) is calculated as the steering state quantity, and the assist map 23m in which the assist torque gain increases as the steering state quantity increases, the steering angular velocity ωs is used. The target assist torque can be increased in accordance with the increase in. For this reason, when the driver starts turning the handle 2 quickly from a state where the driver holds the handle 2 at a certain handle angle, the target assist torque can be rapidly increased. That is, since the steering wheel 2 can be operated more easily when the steering wheel 2 is turned faster than when the steering wheel 2 is turned slowly, the driver's intention to turn the steering wheel 2 quickly can be appropriately reflected in the control.

  As a result, it is possible to realize the assist control that “when the steering wheel 2 is held, there is a firm response, and when the steering wheel 2 is intended to be turned quickly, the steering wheel 2 can be turned quickly”.

  Furthermore, when trying to stop the steering wheel 2 from the state in which the steering wheel 2 is turned, the steering angular velocity ωs decreases and the target assist torque decreases. Therefore, the intention of the driver is reflected more appropriately, It becomes easy to stop the handle 2.

  Further, in addition to the steering torque Ts and the steering angular velocity ωs, the steering state quantity is calculated based on the steering angle θs. Further, in the present embodiment, the assist map 23m is used in which (α × Ts × θs + β × Ts × ωs) is calculated as the steering state quantity, and the assist torque gain increases as the steering state quantity increases. When the driver gradually increases the steering wheel 2, the steering angular velocity ωs is small and the steering angle θs is gradually increased. For this reason, the contribution of the steering angular velocity ωs to the steering state quantity is small, and the target assist torque gradually increases as the steering angle θs increases, and the handle 2 can be operated more easily as the handle 2 is further increased. it can.

  The amplifiers 64 and 65 in the target assist torque calculation unit 20 calculate the adjustment gains α and β according to the vehicle speed V, respectively. Thereby, since the steering state amount is changed according to the vehicle speed V, a more appropriate base assist torque according to the vehicle speed V can be calculated, and an appropriate characteristic in which the vehicle speed V is considered can be obtained. .

  For example, by setting the adjustment gains α and β larger in a low speed range where there are many scenes where fast steering and steering with a large steering angle are performed, the burden during sudden steering or large steering can be reduced. Also, in high-speed areas where there are few scenes where fast steering or large steering angle steering is performed, the increase in assist torque can be suppressed by setting the adjustment gains α and β small, and steering is stabilized with a firm response. Can be made.

  In the embodiment described above, the steering shaft 3 is the input shaft in the present invention, the tire 10 is the steering wheel in the present invention, the intermediate shaft 5, the steering gear box 7, the tie rod 8, and the knuckle arm 9 are the input transmission means in the present invention. The torque sensor 4 is a steering torque detecting means in the present invention, the EPS ECU 15 is an electric power steering control device in the present invention, the target assist torque calculating section 20 is an assist amount calculating means in the present invention, and the motor drive circuit 50 is a motor driving means in the present invention. The steering angle sensor 11 is the steering angle detection means in the present invention, the differentiator 62 is the steering angular speed detection means in the present invention, the steering state quantity calculation unit 22 is the steering state quantity calculation means in the present invention, and the vehicle speed sensor 12 is the vehicle speed in the present invention. It is a detection means.

  The target assist torque is the assist torque in the present invention, the target current is the assist amount in the present invention, the adjustment gain α is the first adjustment gain in the present invention, and the adjustment gain β is the second adjustment gain in the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the above-described embodiment, the one that outputs the steering state quantity represented by (α × Ts × θs + β × Ts × ωs) is shown, but for example, (α × Ts + β × θs + γ × ωs) or (α × Ts + β A steering state quantity represented by (.times..theta.s.times..omega.s) may be output. Note that γ is an adjustment gain, which is the third adjustment gain in the present invention. Further, at least one of the adjustment gains α, β, γ may be calculated according to the vehicle speed V detected by the vehicle speed sensor 12.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering system, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Torque sensor, 5 ... Intermediate shaft, 6 ... Motor, 7 ... Steering gear box, 8 ... Tie rod, 9 ... Knuckle arm, 10 ... Tire, DESCRIPTION OF SYMBOLS 11 ... Steering angle sensor, 12 ... Vehicle speed sensor, 20 ... Target assist torque calculating part, 21 ... Phase compensator, 22 ... Steering state quantity calculating part, 23 ... Base assist calculating part, 23m ... Assist map, 24 ... Multiplier, DESCRIPTION OF SYMBOLS 30 ... Deviation calculator, 40 ... Current control part, 41 ... Current controller, 50 ... Motor drive circuit, 61, 63 ... Multiplier, 62 ... Differentiator, 64, 65 ... Amplifier, 66 ... Adder, 70 ... EPS Mecha

Claims (2)

An input shaft coupled to the vehicle handle and rotating with the handle;
Input transmission means for steering the steering wheel by transmitting rotation of the input shaft to the steering wheel of the vehicle;
Steering torque detection means for detecting a steering torque that is a torque in a shaft rotation direction applied to the input shaft;
An electric power steering system comprising: a motor for giving an assist torque for assisting the operation of the handle to the input shaft or the input transmission means during steering of the handle; and controlling the motor to control the motor An electric power steering control device for controlling assist torque,
An assist amount calculating means for calculating an assist amount indicating the assist torque having a value corresponding to the steering torque based on the steering torque detected by the steering torque detecting means;
Motor driving means for driving the motor based on the assist amount calculated by the assist amount calculating means;
Steering angular velocity detecting means for detecting a steering angular velocity which is a rotational velocity of the steering angle of the steering wheel;
Steering state amount calculation for calculating a steering state amount indicating the steering state of the vehicle based on at least the steering torque detected by the steering torque detection unit and the steering angular velocity detected by the steering angular velocity detection unit Means ,
Steering angle detection means for detecting the steering angle of the steering wheel,
The assist amount calculating means includes
Based on the steering state amount calculated by the steering state amount calculating means, the assist amount is changed ,
The steering state amount calculating means includes
In addition to the steering torque and the steering angular velocity, the steering state quantity is calculated based on the steering angle detected by the steering angle detection means,
A value obtained by adding a preset first adjustment gain, a multiplication value of the steering torque and the steering angle, and a preset second adjustment gain, a multiplication value of the steering torque and the steering angular velocity. An electric power steering control device that calculates the steering state quantity . Vehicle speed detecting means for detecting the speed of the vehicle,
The steering state amount calculating means includes
2. The electric power steering control device according to claim 1 , wherein at least one of the first adjustment gain and the second adjustment gain is calculated according to a speed of the vehicle detected by the vehicle speed detection unit. .