Control device, control method thereof, and electric power steering device

Abstract

To enhance operation feeling before and after a stroke end.SOLUTION: A control device is used for a vehicle including a steering wheel for steering a vehicle, a steering member for steering a steering wheel according to rotation of the steering wheel, and a steering actuator for applying steering force to the steering member and includes a control unit that outputs a drive signal for applying the steering force to the steering actuator on the bases of steering information of the steering wheel. When a rotation angle of the steering wheel reaches a predetermined control start angle, the control unit reduces the steering force until the steering member reaches a stroke end. When the steering member reaches the stroke end and rebounds, the control unit outputs a drive signal for increasing the steering force to the steering actuator.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a steering device mounted on an automobile, and more particularly to an electric power steering device that performs steering control by an electric motor. [Background technology]

[0002] In an electric power steering device, when the rack bar is steered until it approaches the stroke end, a phenomenon occurs in which the rack bar hits another structural material (e.g., a mechanical stopper mechanism) near the stroke end, causing an impact noise.

[0003] To address these issues, it has been proposed to reduce the output of the electric motor that provides an assist force for the rotation of the steering wheel before the rack bar hits another structural material, in order to reduce the impact when the rack bar hits another structural material.

[0004] For example, in Japanese Patent Laid-Open No. 2007-216745 (Patent Document 1), when it is determined that the rack bar has reached the stroke end, the upper limit of the target current value determined by the target current determination means is set to a predetermined value to limit the target current value. According to this, when it is detected that the rack bar has reached the stroke end, the upper limit of the target current value is set to a predetermined value, so that the generation of an excessive assist force can be prevented. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-216745 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the method described in Patent Document 1, the rebound after reaching the stroke end is not taken into consideration.

[0007] An object of the present invention is to provide an electric power steering device that improves the operational feel before and after the stroke end. [Means for solving the problem]

[0008] The present invention is characterized by: A control device is used in a vehicle equipped with a steering wheel for steering the vehicle, a steering member for steering the steered wheels in accordance with the rotation of the steering wheel, and a steering actuator for applying a steering force to the steering member, the control device including a control unit for outputting a drive signal for applying a steering force to the steering actuator based on steering information of the steering wheel, The control unit is a control device that outputs a drive signal to the steering actuator to reduce the steering force when the rotation angle of the steering wheel reaches a predetermined control start angle until the steering member reaches a stroke end, and to increase the steering force when the steering member reaches the stroke end and rebounds. is located. Effect of the Invention

[0009] According to the present invention, it is possible to provide an electric power steering device capable of improving the operational feel before and after the stroke end. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an external appearance of an electric power steering device; [Diagram 2] 2 is a vertical cross-sectional view of the electric power steering device shown in FIG. 1. [Diagram 3] 2 is a control block diagram showing a configuration of a controller used in the electric power steering device. FIG. [Figure 4] FIG. 2 is a block diagram showing a control block for determining an assist force (assist torque) according to an embodiment of the present invention. [Diagram 5] 5 is an explanatory diagram for explaining a torque correction steering wheel angle calculated by a torque correction steering wheel angle calculation block shown in FIG. 4. [Figure 6] FIG. 5 is a block diagram showing specific control blocks of the proportional-integral control processing block shown in FIG. 4. [Figure 7] 5 is a flowchart showing a control flow for implementing the function of a control block for determining a correction torque. [Figure 8] FIG. 7 is an explanatory diagram for explaining the torque correction handle angle obtained by the processing flow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0012] Before describing the embodiments of the present invention, the configuration of an electric power steering device on which the present invention is based will be described.

[0013] Figures 1 and 2 show an electric power steering device that detects the rotation angle, rotation direction, and rotation torque of the steering shaft separately from the drive (manual steering force) of a steering shaft (hereinafter referred to as rack bar) by a steering shaft rotated by a steering wheel, rotates an electric motor (corresponding to the steering actuator in the claims) based on these detection signals (corresponding to steering information in the claims), transmits the rotation of the electric motor to a nut, drives a rack bar stored in the nut, and assists the steering force.

[0014] The steering mechanism 1 includes a steering shaft 4 connected to a steering wheel (not shown) arranged in the driver's cab of the vehicle, a rack bar 5 as a steering axle linked to the steering wheel, and a conversion mechanism 6 that links the steering shaft 4 and the rack bar 5. The conversion mechanism 6 is a so-called rack and pinion mechanism that is composed of pinion teeth (not shown) formed on the outer periphery of the steering shaft 4 and rack teeth (not shown) formed on the outer periphery of the rack bar 5.

[0015] Here, the rack bar 5 represents a steering member, but the steering member can be a pitman arm in addition to the rack bar 5, and can further include, without being limited to these, a link mechanism provided between the steering actuator and the steering wheel, etc.

[0016] The steering shaft 4 has an input shaft 7 whose one axial end is connected so as to be rotatable integrally with the steering wheel, and an output shaft 8 whose one axial end is connected to the other axial end of the input shaft 7 via a torsion bar (not shown).

[0017] The rack bar 5 has both axial ends connected to a pair of steered wheels via tie rods 9 and a pair of knuckle arms, respectively. As a result, when the rack bar 5 moves in the axial direction, each knuckle arm is pulled via each tie rod 9, changing the direction of the pair of steered wheels.

[0018] The rack bar 5 is housed in a rack bar housing portion 11 of a substantially cylindrical rack housing 10 that constitutes a part of the housing 3 so as to be movable in the axial direction with both axial ends exposed to the outside. The rack housing 10 is formed by casting in such a way that it is divided into two parts in the axial direction, and a first housing 12 that houses one axial end side of the rack bar 5 and a second housing 13 that houses the other axial end side of the rack bar 5 are integrated by fastening them together with a plurality of bolts (not shown).

[0019] Furthermore, the rack bar accommodating portion 11 is composed of a first rack bar accommodating portion 14 that penetrates axially through the interior of the first housing 12, and a second rack bar accommodating portion 15 that penetrates axially through the interior of the second housing 13.

[0020] In addition, bellows-shaped boots 16 are attached to both axial ends of the rack housing 10, straddling the tie rods 9. These boots 16 are made of an elastic material such as synthetic rubber to ensure a predetermined flexibility, and prevent water, dust, and the like from entering the housing 3.

[0021] The steering assist mechanism 2 includes an electric motor 17 which is a drive unit that generates a steering assist force (steering force), a transmission mechanism 18 which transmits the drive force of the electric motor 17 to the rack bar 5, various sensors which detect various state quantities of the power steering device, and a controller (corresponding to a control unit in the claims) 19 which drives and controls the electric motor 17 based on signals output by the various sensors. Here, the electric motor 17 and the transmission mechanism 18 constitute a steering actuator.

[0022] Among the various sensors, a steering angle sensor 20 that detects the steering angle (corresponding to the handle angle described later), which is the amount of rotation of the steering wheel from the neutral steering angle, and a torque sensor 21 that detects the torque input to the steering shaft 4 are both housed in a sensor housing 22, which is part of the housing 3 formed to surround the outer periphery of the steering shaft 4.

[0023] The steering angle sensor 20 is attached to the outer periphery of the input shaft 7 of the steering shaft 4, and detects the steering angle based on the rotation angle of the input shaft 7. The steering angle sensor 20 also has main and sub dual-system steering angle detection units 20a and 20b, each of which detects the steering angle.

[0024] The torque sensor 21 is provided so as to straddle between the input shaft 7 and the output shaft 8, and detects torque based on the amount of displacement of the relative rotation between the input shaft 7 and the output shaft 8. The torque sensor 21 also has main and sub dual-system torque detection units 21a and 21b, each of which detects steering torque. The steering angle sensor 20 and the torque sensor 21 are electrically connected to the controller 19 via a harness (not shown) provided along the outer periphery of the rack housing 10.

[0025] The electric motor 17 is a so-called three-phase AC motor that is driven based on three-phase AC power, and includes a motor housing 23 that constitutes a part of the housing 3, and a motor element provided inside the motor housing 23. The motor housing 23 has a cylindrical tubular portion 23a that houses the motor element therein, and first and second end wall portions 23b, 23c that each close an opening of the tubular portion 23a.

[0026] The motor elements include a cylindrical stator 26 fixed to the inner surface of the cylindrical portion 23a by shrink fitting or the like, a cylindrical rotor 27 arranged on the inner side of the stator 26 with a predetermined radial gap therebetween, and a motor shaft 28 fixed to the inner side of the rotor 27 so as to be rotatable integrally therewith and which outputs the rotation of the rotor 27.

[0027] Stator 26 is configured by winding U-phase, V-phase, and W-phase coils around a stator core (not shown) made of a plurality of laminated thin plates. In this embodiment, the coils are connected by a so-called Y connection (star connection), but they may also be connected by a delta connection.

[0028] The motor shaft 28 has both ends 28a, 28b exposed from the motor housing 23 via through holes formed in the first and second end wall portions 23b, 23c, respectively. Of these, the end 28a opposite the controller 19 faces inside a transmission mechanism accommodating portion 31 (described below) that accommodates the transmission mechanism 18. On the other hand, the other end 28b faces inside an accommodating portion 43 (described below) that accommodates the controller 19.

[0029] In addition, the motor shaft 28 is rotatably supported by a first ball bearing 29 provided between the outer peripheral surface on the one end 28a side and the inner peripheral surface of the through hole of the first end wall portion 23b, and a second ball bearing 30 provided between the outer peripheral surface on the other end 28b side and the inner peripheral surface of the through hole of the second end wall portion 23c.

[0030] The transmission mechanism 18 is accommodated in the transmission mechanism accommodating section 31 of the housing 3, and has an input side pulley 32, an output side pulley 33, a belt 34 wound between both pulleys 32, 33, and a ball screw mechanism 35 that converts the rotation of the output side pulley 33 into axial motion of the rack bar 5 while decelerating it.

[0031] The transmission mechanism accommodating section 31 is formed by joining a first transmission mechanism accommodating section 36 provided at the end of the first rack bar accommodating section 14 on the second housing 13 side and a second transmission mechanism accommodating section 37 provided at the end of the second rack bar accommodating section 15 on the first housing 12 side.

[0032] The input pulley 32 is formed in a cylindrical shape having a relatively small diameter compared to the output pulley 33, and is press-fitted and fixed to one end 28a of the motor shaft 28 of the electric motor 17 via a through hole formed therethrough on the inner periphery side.

[0033] The output pulley 33 is disposed on the outer periphery of the rack bar 5, and is connected to the rack bar 5 via a ball screw mechanism 35. More specifically, the output pulley 33 has a bottomed cylindrical shape with a relatively large diameter compared to the input pulley 32, and is fixed to the outer periphery of a nut 38 of the ball screw mechanism 35, which will be described later, so as to rotate integrally with the nut 38.

[0034] Belt 34 is an endless belt with glass fiber, steel wire, etc. embedded inside as a core material, and transmits the rotational force of input side pulley 32 to output side pulley 33 by rotating input side pulley 32 and output side pulley 33 synchronously.

[0035] The ball screw mechanism 35 includes a cylindrical nut 38 arranged on the outer periphery of the rack bar 5, a ball circulation groove 39 formed between the nut 38 and the rack bar 5, a plurality of balls 40 rollably arranged in the ball circulation groove 39, and a circulation mechanism (not shown) that circulates each ball 40 from one end side to the other end side of the ball circulation groove 39.

[0036] The nut 38 is rotatably supported via a ball bearing 41 accommodated in the first transmission mechanism accommodating portion 36. The ball bearing 41 has an inner race portion 41a formed integrally with the nut 38, an outer race portion 41b fixed to the inner circumferential surface of the first transmission mechanism accommodating portion 36, and a plurality of balls 41c rollably accommodated between the inner race portion 41a and the outer race portion 41b. Note that, although the present embodiment illustrates an example in which the inner race portion 41a is formed integrally with the nut 38, it is also possible for the inner race portion 41a and the nut 38 to be separate bodies.

[0037] The ball circulation groove 39 is composed of a shaft side ball screw groove 39a having a spiral groove shape provided on the outer periphery of the rack bar 5, and a nut side ball screw groove 39b having a spiral groove shape provided on the inner periphery of the nut 38.

[0038] The controller 19 includes a control housing 42 that constitutes a part of the housing 3, and a control board 44 that is accommodated in an accommodating portion 43 of the control housing 42.

[0039] The control housing 42 has a cylindrical body 45 whose one end on the electric motor 17 side covers the outer periphery of the motor housing 23, and a cover 46 that closes the opening on the other end side of the body 45.

[0040] The control board 44 is constructed by forming conductor patterns on both the front and back sides of a substrate made of a non-conductive resin material such as glass epoxy resin, and mounting a large number of electronic and electrical components on these conductor patterns.

[0041] Although not shown in FIG. 2, a motor rotation angle sensor, which is one of various sensors, is provided on the control board 44 to detect a motor rotation angle, which is the rotation angle of the rotor 27 of the electric motor 17.

[0042] This motor rotation angle sensor detects the rotation angle of the motor shaft 28 (rotor 27) based on changes in a magnetic field generated by a magnet (not shown) attached to the other end 28b of the motor shaft 28. The motor rotation angle sensor also has a dual system of main and sub motor rotation angle detection units, each of which detects the rotation angle of the motor shaft 28.

[0043] Next, a configuration of the controller 19 that controls the electric motor 17 constituting the steering actuator used in the electric power steering device will be described.

[0044] Fig. 3 shows a hardware configuration of the controller 19 in Fig. 1. As shown in Fig. 3, the controller 19 includes a control microcontrol unit (control MCU) 51, a monitoring microcontrol unit (monitoring MCU) 52, a MOSFET pre-driver circuit 53, an inverter drive circuit 54 which is a motor drive circuit, a current detection circuit 55, a rotation angle detection circuit 56, and the like.

[0045] The control microcontroller unit 51 includes a CPU 57 which is an arithmetic device, a ROM 58 which is a memory, a RAM 59, an EEPROM (flash ROM) 60, an A / D converter 61, a CAN driver 62, a bus line 63, and the like.

[0046] The CPU 57 controls the electric motor 17 of the electric power steering device by executing various programs stored in the ROM 58. Therefore, the operations executed by the programs can be regarded as control functions.

[0047] The ROM 58 stores various programs executed by the CPU 57. Specifically, the ROM 58 stores a control program for executing a motor control process (steering process) for controlling the electric motor 17. Furthermore, the ROM 58 stores a diagnostic program for diagnosing the power steering device. The control program and the diagnostic program are used by the CPU 57 to execute predetermined control functions and diagnostic functions.

[0048] The RAM 59 is used as a working area when the CPU 57 executes a control program, and temporarily stores data required during the process and the results of the process. Similarly, when a diagnostic program is executed, the RAM 59 temporarily stores the diagnostic results as error codes.

[0049] The EEPROM 60 is a memory that can retain stored contents even after the power is cut off, and stores hardware-specific correction values ​​and error codes after executing diagnostic functions. In this case, the shutdown of the controller 19 is delayed by a shutoff function that cuts off the supply of power voltage, for the time it takes to transfer the error code from the RAM 59 to the EEPROM 60.

[0050] The A / D converter 61 receives steering angle information from the steering angle sensor 20, torque information from the torque sensor 21, current information of the electric motor 17 from the current detection circuit 55, and motor rotation angle information from the rotation angle detection circuit 56, and converts them into digital signals. It is also possible to estimate the steering angle from the rotation angle detection circuit 56.

[0051] The CAN driver 62 is connected to the CAN bus and is an interface for performing CAN communication with other controllers and sensors via the CAN bus. For example, the CAN driver 62 can receive a vehicle speed (V: vehicle speed pulse) from a vehicle speed sensor through CAN communication.

[0052] The MOSFET pre-driver circuit 53 converts the PWM control signals for each of the U, V, and W phases input from the control microcontrol unit 51 into positive and negative energization signals for each phase (Up, Un, Vp, Vn, Wp, Wn) and outputs them to the inverter drive circuit 54.

[0053] The inverter drive circuit 54 is an inverter drive circuit provided with bridge circuits each consisting of a pair of MOSFET switching elements for three phases, that is, for the U phase, the V phase, and the W phase, and a freewheeling diode is connected in parallel to each MOSFET switching element.

[0054] A DC voltage is applied to this bridge circuit from a battery 64 via a power supply relay 65. A conduction signal is input from a MOSFET pre-driver circuit 53 to a control terminal (gate terminal) of each MOSFET switching element.

[0055] The DC voltage applied to the inverter drive circuit 54 is converted into a three-phase AC voltage by the switching operation of the MOSFET switching elements in the inverter drive circuit 54, thereby driving the electric motor 17. Shunt resistors R1 and R2 are connected to the bridge circuit.

[0056] A current detection circuit 55 is connected to the shunt resistors R1 and R2, thereby detecting current information of the electric motor 17 and outputting it to an A / D converter 61. In addition, the rotation angle detection circuit 56 outputs an output signal from a motor rotation angle sensor 66, which detects the motor rotation angle, which is the rotation angle of the rotor of the electric motor 17, as motor rotation angle information to the A / D converter 61. This motor rotation angle sensor 66 has main and sub dual-system motor rotation angle detection units, each of which is configured to detect the rotation angle of the motor shaft 28.

[0057] Although not shown in the figure, the monitoring micro control unit 52 is equipped with a CPU, ROM, RAM, D / A converter, A / D converter, interface, etc., as is well known, and monitors runaway of the CPU 57 of the control micro control unit 51.

[0058] In such an electric power steering device, as described above, when the rack bar is steered so as to approach the vicinity of the stroke end, the rack bar strikes another structural member (mechanical stopper mechanism) near the stroke end, which causes problems such as an impact sound due to the strike and an unintended rotation of the steering wheel due to rebound after the strike, resulting in an uncomfortable operation.

[0059] Therefore, in this embodiment, we propose an electric power steering device equipped with a steering force adjustment unit that outputs a drive signal to the steering actuator to reduce the steering force until the steering member reaches the stroke end when the rotation angle of the steering wheel (hereinafter, the rotation angle of the steering wheel may be referred to as the handle angle) reaches a predetermined control start angle, and outputs a drive signal to the steering actuator to increase the steering force when the steering member reaches the stroke end and bounces back.

[0060] In other words, when the rack bar approaches the stroke end, the steering force of the steering member (hereinafter referred to as assist torque) is reduced to suppress the impact noise caused by a collision, and when the rack bar bounces back, the assist torque of the steering member is increased to suppress the rebound of the rack bar and suppress unintended rotation of the steering wheel.

[0061] In particular, this embodiment is characterized in that the angle difference between the actual steering angle and a torque correction steering angle arbitrarily set based on the actual steering angle is calculated, and this angle difference is calculated as a negative correction torque and a positive correction torque using proportional-integral control, and the assist torque is corrected by the calculated correction torque. Here, the negative correction torque has a component that reduces the torque that urges the rack bar toward the stroke end, and the positive correction torque has a component that increases the torque that urges the rack bar toward the stroke end.

[0062] In this way, the negative and positive correction torques are calculated using proportional-integral control from the angle difference between the actual steering wheel angle and the torque correction steering wheel angle set based on this, and the assist torque is corrected by the calculated correction torques. Therefore, with a simple control logic and without the need to install any additional detection sensors, it is possible to suppress impact noise caused by hitting the road and unintended rotation of the steering wheel caused by bouncing back after hitting the road.

[0063] FIG. 4 shows a control block (steering force adjustment section) for determining the total assist torque to be applied to the electric motor.

[0064] 4, a normal assist torque calculation processing block (corresponding to a normal steering force generating unit in the claims) 70 calculates a normal assist torque based on input information such as the steering torque by the steering wheel, the steering angle, and the vehicle speed of the vehicle. Since the calculation of this normal assist torque is well known, a detailed description thereof will be omitted here.

[0065] The calculated normal assist torque and the steering force of the steering wheel by the driver (manual steering force) are combined to produce a rack axial force that displaces the rack bar 5, and this rack axial force steers the steered wheels. In this electric power steering device, the present embodiment adds the following torque correction function unit 71 (corresponding to the correction steering force generating unit in the claims).

[0066] The torque correction function unit 71 is composed of a torque correction handle angle calculation processing block 72 that determines a torque correction handle angle (θcom) generated based on the actual handle angle (θact), a proportional / integral control processing block 73 that determines a correction torque by proportional / integral control of the deviation (angle difference) between the actual handle angle (θact) and the torque correction handle angle (θcom), and an addition block 74 that adds the determined correction torque to the normal assist torque.

[0067] In the correction torque obtained by the torque correction function unit 71, a negative correction torque and a positive correction torque are generated. The negative correction torque reduces the normal assist torque, and the positive correction torque increases the normal assist torque to obtain a total assist torque. In other words, the negative correction torque acts in a direction that reduces the rack axial force, and the positive correction torque acts in a direction that increases the rack axial force.

[0068] Specifically, when the rack bar 5 approaches the stroke end, the normal assist torque is reduced by the negative correction torque to suppress the impact noise due to the collision. On the other hand, when the rack bar 5 bounces back, the normal assist torque is increased by the positive correction torque to suppress the rebound of the rack bar 5 and suppress unintended rotation of the steering wheel.

[0069] This function solves problems such as the generation of impact noise when hitting a bump, and unintended rotation of the steering wheel due to rebound after hitting the bump, resulting in an uncomfortable feeling when operating the wheel.

[0070] Next, the torque correction steering wheel angle (θcom) calculated in the torque correction steering wheel angle calculation processing block 72 will be described.

[0071] In FIG. 5, a torque correction steering wheel angle calculation process block 72 calculates a torque correction steering wheel angle (θcom) by adding and subtracting a predetermined correction angle (Δθ) to and from an input actual steering wheel angle (θact).

[0072] In other words, the correction angle (Δθ) is subtracted from the actual steering wheel angle (θact) to obtain the first torque correction steering wheel angle (θcom1), and the correction angle (Δθ) is added to the actual steering wheel angle (θact) to obtain the second torque correction steering wheel angle (θcom2). Therefore, following the change in the actual steering wheel angle (θact), the first torque correction steering wheel angle (θcom1) and the second torque correction steering wheel angle (θcom2) also change simultaneously, as shown by the movement of the arrow (P). Here, the correction angles (Δθ) are set to the same value, but they can also be set individually.

[0073] The torque correction handle angle calculation processing block 72 outputs a first torque correction handle angle (θcom1) when the rack bar 5 is in a direction approaching the stroke end, and outputs a second torque correction handle angle (θcom2) when the rack bar 5 is in a direction of bouncing back (this will be explained in the flowchart of FIG. 7). The first torque correction handle angle (θcom1) or the second torque correction handle angle (θcom2) is input to a proportional / integral control processing block 73 together with the actual handle angle (θact).

[0074] Fig. 6 shows the configuration of the proportional / integral control processing block 73. The actual steering wheel angle (θact) and the torque-corrected steering wheel angle (θcom) calculated in the torque-corrected steering wheel angle calculation processing block 72 are input to the proportional / integral control processing block 73. These inputs are subjected to a calculation of "(θcom)-(θact)" in a difference calculation unit 75 to find an angle difference. The angle difference is as shown in Fig. 8, and will be described later.

[0075] When the first torque correction handle angle (θcom12) and the second torque correction handle angle (θcom2) are input, the angle difference (±Δθ) is a constant value as shown in Fig. 5. However, as will be explained in the flowchart of Fig. 7, in the transition section between the first torque correction handle angle (θcom1) and the second torque correction handle angle (θcom2), the torque correction handle angle (θcom) before the transition begins continues to be used.

[0076] From the calculated angle difference, a proportional component is calculated in a proportional control section 76 of a proportional / integral control processing block 73, and an integral component is calculated in an integral control section 77. These proportional and integral components are added together in an adder 78 and output as a correction torque. Furthermore, as shown in Fig. 4, this correction torque is added to the normal assist torque and is applied to the electric motor as a total assist torque.

[0077] Here, if a "negative value" is derived from the calculation of "(θcom)-(θact)", a negative correction torque is generated as described above, and if a "positive value" is derived from the calculation of "(θcom)-(θact)", a positive correction torque is generated as described above.

[0078] Next, specific control of the torque correction function unit 71 having the above-mentioned functions will be explained with reference to Fig. 7 and Fig. 8. The torque correction function unit 71 is actually executed by control software of the control MCU 51 (see Fig. 3). Fig. 7 shows a specific processing flow, and Fig. 8 shows the change in the torque correction steering wheel angle (θcom) in the processing. Note that here, the neutral position of the steering wheel is set as the reference (=0°), and it is defined that the steering wheel angle increases as it approaches the stroke end side.

[0079] First, FIG. 8(a) shows the actual handle angle (θact), a first torque compensation handle angle (θcom1) set toward the neutral position by a predetermined compensation angle (-Δθ) from the actual handle angle (θact), and a second torque compensation handle angle (θcom2) set toward the stroke end by a predetermined compensation angle (+Δθ) from the actual handle angle (θact) in a state in which the rack bar 5 approaches the stroke end and bounces back after coming into contact with a structural material (stopper mechanism) near the stroke end.

[0080] The torque correction steering wheel angle (θcom) that is actually set is shown by a thick dashed line, and the angle difference between the torque correction steering wheel angle (θcom) and the actual steering wheel angle (θact) shown in Figure 8(b) is proportional-integral controlled to determine the correction torque.

[0081] Next, a specific process flow will be described with reference to the flowchart shown in Fig. 7. Here, the previous torque correction steering wheel angle value (θprv) used in the control steps described below is updated for each execution loop of the flowchart.

[0082] <Step S10> In step S10, it is determined whether the actual steering angle (θact) is greater than the control start angle (θsrt) by determining whether the steering wheel is rotated to move the rack bar 5 toward the stroke end.

[0083] The control start angle (θsrt) can be changed depending on the specifications of the vehicle, and the most suitable control start angle (θsrt) can be set. The control start angle (θsrt) can also be changed based on the angular velocity of the steering wheel operation rotation angle. When the steering wheel is rotated quickly, the rack bar 5 may quickly hit the structural material (stopper mechanism) at the stroke end. In this case, the greater the operation angular velocity, the more the control start angle (θsrt) should be shifted toward the neutral position.

[0084] Here, as described above, the actual steering angle (θact) being larger than the control start angle (θsrt) means that the steering wheel is rotated a great deal with respect to the neutral position of the steering wheel.

[0085] If it is determined in step S10 that the actual steering angle (θact) is smaller than the control start angle (θsrt) (NO), the process proceeds to step S11, and if it is determined that the actual steering angle (θact) is larger than the control start angle (θsrt) (YES), the process proceeds to step S12.

[0086] <Step S11> Since it is determined in step S10 that the actual steering angle (θact) is smaller than the control start angle (θsrt), the torque correction steering angle is set to the control start angle (θsrt) in step S11. This control start angle (θsrt) is set as the previous torque correction steering angle value (θprv) required for control when it is determined in step S10 that the actual steering angle (θact) is larger than the control start angle (θsrt).

[0087] In step S11, when the previous torque correction steering wheel angle value (θprv) is set, the process goes to RETURN and waits for the next execution timing.

[0088] <Step S12> In step S10, it is determined that the actual steering angle (θact) is greater than the control start angle (θsrt) (YES), so the steering wheel is rotated significantly. For example, this corresponds to the rotation of the steering wheel for "stationary steering" or for "reversal of steering". In this case, the rack bar 5 often hits the structural material (stopper mechanism) at the stroke end.

[0089] Then, in step S12, it is determined whether the previous torque correction handle angle value (θprv) is smaller than the first torque correction handle angle (θcom1). If it is determined that the previous torque correction handle angle value (θprv) is larger than the first torque correction handle angle (θcom1) (NO), the process proceeds to step S13. On the other hand, if it is determined that the previous torque correction handle angle value (θprv) is smaller than the first torque correction handle angle (θcom1) (YES), the process proceeds to step S15.

[0090] Here, the reason why it is determined that the previous torque correction handle angle value (θprv) is greater than the first torque correction handle angle (θcom1) (NO) is because the previous torque correction handle angle value (θprv), which is the control start angle (θsrt) set in step S11, is greater than the first torque correction handle angle (θcom1) obtained by subtracting the correction angle (Δθ) from the actual handle angle (θact).

[0091] <Step S13> Since it is determined in step S12 that the previous torque correction handle angle value (θprv) is greater than the first torque correction handle angle (θcom1) (NO), in step S13 it is determined whether the previous torque correction handle angle value (θprv) is greater than the second torque correction handle angle (θcom2). If it is determined in this determination that the previous torque correction handle angle value (θprv) is smaller than the second torque correction handle angle (θcom2) (NO), the process proceeds to step S14. On the other hand, if it is determined that the previous torque correction handle angle value (θprv) is greater than the second torque correction handle angle (θcom1) (YES), the process proceeds to step S16.

[0092] Here, the reason why it is determined that the previous torque correction handle angle value (θprv) is smaller (NO) than the second torque correction handle angle (θcom2) is because the previous torque correction handle angle value (θprv), which is the control start angle (θsrt) set in step S11, is smaller than the second torque correction handle angle (θcom2) obtained by adding the correction angle (Δθ) to the actual handle angle (θact).

[0093] In this way, the "NO" judgments in steps S12 and S13 indicate that the previous torque correction handle angle value (θprv) is located between the first torque correction handle angle (θcom1) and the second torque correction handle angle (θcom2).

[0094] However, since the actual steering wheel angle (θact) increases with time as the steering wheel rotates, the first torque correction steering wheel angle (θcom1) and the second torque correction steering wheel angle (θcom2) also increase at the next execution timing. This causes the determinations in steps S12 and S13 to change.

[0095] <Step S14> If the determinations in steps S12 and S13 are "No," that is, if the previous torque correction handle angle value (θprv) is between the first torque correction handle angle (θcom1) and the second torque correction handle angle (θcom2), the torque correction handle angle (θcom) is set to the previous torque correction handle angle value (θprv) in step S14. Here, the previous torque correction handle angle value (θprv) is the control start angle (θsrt).

[0096] Therefore, by executing the processes of steps S12, S13, and S14, the torque correction steering angle (θcom) is set as shown in Fig. 8(a) from time (Ta) to time (Tb). Furthermore, the angle difference between the actual steering angle (θact) and the torque correction steering angle (θcom) at this time gradually becomes larger on the negative side between time (Ta) and time (Tb) as shown in Fig. 8(b).

[0097] Once the torque correction steering wheel angle (θcom) has been set, the process proceeds to step S17. Since the process from step S17 onwards is proportional-integral control, this will be described later.

[0098] <Step S15> When step S15 is executed, it is determined in step S12 that the previous torque correction handle angle value (θprv) is smaller than the first torque correction handle angle (θcom1) (YES). Here, the reason why it is determined that the previous torque correction handle angle value (θprv) is smaller than the first torque correction handle angle (θcom1) (YES) is as follows.

[0099] That is, with respect to the previous torque correction steering wheel angle value (θprv) set in step S14, the actual steering wheel angle (θact) increases with the passage of time (as the steering wheel rotates), and the first torque correction steering wheel angle (θcom1) also increases accordingly. Therefore, the previous torque correction steering wheel angle value (θprv) becomes smaller than the first torque correction steering wheel angle (θcom1), and as a result, the process proceeds to step S15.

[0100] In step S15, the torque correction handle angle (θcom) is set to the first torque correction handle angle (θcom1). This first torque correction handle angle (θcom1) becomes the previous torque correction handle angle value (θprv) at the next execution timing.

[0101] Therefore, the torque correction handle angle (θcom) is set to the first torque correction handle angle (θcom1) until it is determined in step S12 that the previous torque correction handle angle value (θprv) is greater than the first torque correction handle angle (θcom1) (NO).

[0102] Therefore, by executing the processes of steps S12 and S15, the first torque correction handle angle (θcom1) is set as shown in time (Tb) to time (Tc) in Fig. 8(a). The time (Tb) to time (Tc) is the section until the rack bar 5 contacts the structural material (stopper mechanism) at the stroke end, and this section needs to be a negative correction torque (torque that reduces the assist torque).

[0103] Therefore, the angle difference between the actual steering angle (θact) and the first torque correction steering angle (θcom1) at this time is maintained at a constant correction angle (Δθ) on the negative side between time (Tb) and time (Tc) as shown in Fig. 8(b). By setting a constant correction angle (Δθ) in this manner, even if the proportional gain is increased to improve tracking, the proportional component does not become excessively large.

[0104] When the first torque correction steering wheel angle (θcom1) is set, the process proceeds to step S17. Since the process from step S17 onwards is proportional-integral control, this will be described later.

[0105] <Step S16> In the previous step S15, the first torque correction handle angle (θcom1) is set until the rack bar 5 comes into contact with the structural material (stopper mechanism) at the stroke end. However, when the rack bar 5 comes into contact with the structural material (stopper mechanism) at the stroke end and bounces back, the actual handle angle (θact) changes in the direction toward the neutral position.

[0106] Therefore, while the previous torque correction handle angle value (θprv) is between the first torque correction handle angle (θcom1) and the second torque correction handle angle (θcom2), the above steps S12, S13, and S14 are executed. In this case, the first torque correction handle angle (θcom1) is set as the previous torque correction handle angle value (θprv).

[0107] In this manner, by executing the processes of steps S12, S13, and S14, the torque correction handle angle (θcom) is set as shown in Fig. 8(a) from time (Tc) to time (Te). Also, the angle difference between the actual handle angle (θact) and the torque correction handle angle (θcom) at this time gradually decreases toward the positive side between time (Tc) and time (Td) as shown in Fig. 8(b), and further gradually increases on the positive side between time (Td) and time (Te).

[0108] This is because the relationship between the torque correction steering angle (θcom) and the actual steering angle (θact) is reversed at time (Td). Once the torque correction steering angle (θcom) is set, the process proceeds to step S17. Since the process from step S17 onwards is proportional-integral control, this will be described later.

[0109] Next, when the time (Te) is reached, step S16 is executed. When step S16 is executed, it is determined in step S13 that the previous torque correction handle angle value (θprv) is greater than the second torque correction handle angle (θcom2) (YES). Here, the reason that it is determined that the previous torque correction handle angle value (θprv) is greater than the second torque correction handle angle (θcom2) (YES) is as follows.

[0110] That is, the previous torque correction handle angle value (θprv) set in step S15 is the first torque correction handle angle (θcom1). On the other hand, as time passes (the steering wheel rotates in the reverse direction due to the rebound of the rack bar), the actual handle angle (θact) becomes smaller, and accordingly the second torque correction handle angle (θcom2) also becomes smaller. For this reason, the previous torque correction handle angle value (θprv) becomes larger than the second torque correction handle angle (θcom2), and as a result, the process proceeds to step S16.

[0111] In step S16, the torque correction handle angle (θcom) is set to the second torque correction handle angle (θcom2). This second torque correction handle angle (θcom2) becomes the previous torque correction handle angle value (θprv) at the next execution timing.

[0112] Therefore, the torque correction handle angle (θcom) is set to the second torque correction handle angle (θcom2) until it is determined in step S13 that the previous torque correction handle angle value (θprv) is smaller than the second torque correction handle angle (θcom2) (NO).

[0113] Furthermore, in this state, when the actual steering angle (θact) returns to the control start angle (θsrt), the correction of the normal assist torque by the above-mentioned correction torque is terminated in step S10.

[0114] In this way, by executing the processes of steps S13 and S16, the second torque correction handle angle (θcom2) is set as shown in FIG. 8(a) from time (Te) to time (Tf). Furthermore, the angle difference between the actual handle angle (θact) and the second torque correction handle angle (θcom2) at this time is maintained at a constant correction angle (Δθ) on the positive side between time (Te) and time (Tf) as shown in FIG. 8(b). In this way, by setting a constant correction angle (Δθ), it is possible to prevent the proportional component from becoming excessively large even if the proportional gain is increased to improve tracking.

[0115] When the second torque correction steering wheel angle (θcom2) is set, the process proceeds to step S17. Since the process from step S17 onwards is proportional-integral control, this will be described later.

[0116] The above-described processing from step S12 to step S16 corresponds to the torque correction steering wheel angle calculation processing block 72 shown in Fig. 4. Once the torque correction steering wheel angle (θcom) is determined, proportional-integral control is executed from step S17 onwards.

[0117] <Step S17> In step S17, the angle difference between the actual steering wheel angle (θact) and the torque-corrected steering wheel angle (θcom) calculated in steps S12 to S16 is calculated. The calculated angle difference has the characteristics as shown in FIG. 8(b). Here, the angle difference is based on the actual steering wheel angle (θact), and the direction in which the rack bar 5 moves toward the stroke end is a negative angle difference, and the direction in which the rack bar 5 bounces back and moves away from the stroke end side at time (Td) is a positive angle difference. When the difference calculation is completed, the process proceeds to step S18.

[0118] <Step S18> In step S18, a calculation is performed to calculate the proportional and integral components based on the angle difference calculated in step S17. The calculation of the proportional and integral components is a well-known technique. When the calculation of the proportional and integral components is completed, the process proceeds to step S19.

[0119] <Step S19> In step S19, the proportional component and the integral component are added together to calculate the correction torque. As described above, the negative correction torque and the positive correction torque are calculated from the negative angle difference and the positive angle difference. The calculated correction torque is added to the normal assist torque to calculate the total assist torque, as shown in FIG. 4. This total assist torque is given to the electric motor as a drive current to assist steering.

[0120] The above-described processing from step S17 to step S19 corresponds to the proportional-integral control processing block 73 shown in FIG.

[0121] In the above-described embodiment, the absolute values ​​of the correction angle (-Δθ) set toward the neutral position side of the actual steering wheel angle (θact) and the correction angle (+Δθ) set toward the stroke end side of the actual steering wheel angle (θact) are set to the same value.

[0122] On the other hand, the correction angle (-Δθ) set on the neutral position side may be set to be larger than the correction angle (+Δθ) set on the stroke end side. When the correction angle (-Δθ) set on the neutral position side is set to be larger in this way, the assist torque in the direction of the stroke end can be reduced, so that the rebound of the rack bar itself is suppressed.

[0123] Also, the correction angle (+Δθ) set on the stroke end side may be set larger than the correction angle (-Δθ) set on the neutral position side. If the correction angle (+Δθ) set on the stroke end side is set larger in this way, the rebound of the rack bar is further suppressed. This makes it possible to further suppress the return of the handle due to the rebound.

[0124] In the above-described embodiment, an electric power steering device that applies an assist torque to a steering member by a steering actuator has been described. However, this technology can also be applied to a so-called steer-by-wire type electric power steering device in which the steering shaft is separated from the rack bar, the rotation angle, rotation direction, rotation torque, etc. of the steering shaft are detected, and the rotation of the electric motor is controlled based on these detection signals to directly drive the rack bar.

[0125] The present invention is a control device used in a vehicle equipped with a steering wheel for steering the vehicle, a steering member for steering the wheels in accordance with the rotation of the steering wheel, and a steering actuator for applying a steering force to the steering member, and includes a control unit that outputs a drive signal for applying a steering force to the steering actuator based on steering information of the steering wheel, and when the rotation angle of the steering wheel reaches a predetermined control start angle, the control unit outputs a drive signal to the steering actuator that reduces the steering force until the steering member reaches the stroke end, and increases the steering force when the steering member reaches the stroke end and bounces back.

[0126] This makes it possible to suppress the generation of impact noises due to hitting the road and the occurrence of unintended rotation of the steering wheel due to bouncing back after hitting the road, thereby improving the operating feel before and after the stroke end.

[0127] The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0128] 5...rack bar, 17...electric motor, 19...controller, 70...normal assist torque calculation processing block, 71...torque correction function unit, 72...torque correction handle angle calculation processing block, 73...proportional / integral control processing block, 74...addition block, 75...difference calculation unit, 76...proportional control unit, 77...integral control unit, 78...addition unit.

Claims

1. The present invention is used in a vehicle equipped with a steering wheel for steering the vehicle, a steering member for steering the steered wheels in accordance with the rotation of the steering wheel, and a steering actuator for applying a steering force to the steering member, A control device including a control unit that outputs a drive signal for applying the steering force to the steering actuator based on steering information of the steering wheel, The control unit has a normal steering force generating unit that generates a normal steering force and a correction steering force generating unit that generates a correction steering force that corrects the normal steering force, when the rotation angle of the steering wheel reaches a predetermined control start angle, the corrective steering force generation unit generates a negative corrective steering force that reduces the normal steering force until the steering member reaches a stroke end, and generates a positive corrective steering force that increases the steering force when the steering member reaches the stroke end and rebounds, and outputs the positive corrective steering force to the steering actuator, Further, the correction steering force generating unit a torque correction handle angle calculation unit that calculates a first torque correction handle angle by subtracting a predetermined first correction angle from an actual handle angle, and a second torque correction handle angle by adding a predetermined second correction angle to the actual handle angle; a proportional / integral control unit that calculates an angle difference between the first torque correction steering wheel angle calculated by the torque correction steering wheel angle calculation unit or the second torque correction steering wheel angle and the actual steering wheel angle, and performs proportional / integral control on the angle difference to calculate the negative correction steering force or the positive correction steering force, The normal steering force generated by the normal steering force generating unit is corrected with the correction steering force obtained by the proportional / integral control unit. A control device comprising:

2. The control device according to claim 1 , The normal steering force generating unit applies the normal steering force to the steering member by the steering actuator, separately from the manual steering force applied to the steering member by the steering wheel. A control device comprising:

3. The control device according to claim 1, The torque correction steering wheel angle calculation unit calculates a torque correction steering wheel angle at a predetermined calculation cycle, and in the current calculation cycle, If the torque correction steering wheel angle calculated in the previous calculation cycle is smaller than the first torque correction steering wheel angle, the first torque correction steering wheel angle is output. If the torque correction steering wheel angle calculated in the previous calculation cycle is greater than the second torque correction steering wheel angle, the second torque correction steering wheel angle is output. When the torque correction steering wheel angle calculated in the previous calculation cycle is between the first torque correction steering wheel angle and the second torque correction steering wheel angle, the torque correction steering wheel angle calculated in the previous calculation cycle is output. A control device comprising:

4. A control device as claimed in claim 1, The torque correction steering wheel angle calculation unit sets the second correction angle to be larger than the first correction angle. A control device comprising:

5. A control device as claimed in claim 1, The torque correction steering wheel angle calculation unit sets the first correction angle to be larger than the second correction angle. A control device comprising:

6. A control device as claimed in claim 1, The control unit changes the control start angle according to the angular velocity of the rotation angle of the steering wheel. A control device comprising:

7. A control method for use in a vehicle equipped with a steering wheel for steering the vehicle, a steering member for steering wheels in accordance with rotation of the steering wheel, and a steering actuator for applying a steering force to the steering member, the control method being executed by a control unit that outputs a drive signal for applying the steering force to the steering actuator based on steering information of the steering wheel, When the rotation angle of the steering wheel reaches a predetermined control start angle, determining a first torque correction steering wheel angle by subtracting a predetermined first correction angle from an actual steering wheel angle, and a second torque correction steering wheel angle by subtracting a predetermined second correction angle from the actual steering wheel angle; determining an angle difference between the first torque correction steering wheel angle or the second torque correction steering wheel angle and the actual steering wheel angle; a step of obtaining a negative correction steering force or a positive correction steering force by performing proportional / integral control on the angle difference; correcting the steering force with the correction steering force obtained by the proportional-integral control unit; A control method for performing the above.

8. A steering member that steers the steering wheels in response to rotation of a steering wheel attached to a vehicle; a steering actuator that applies a steering force to the steering member; A control device for controlling the steering actuator, The control device includes a control unit that outputs a drive signal for applying the steering force to the steering actuator based on steering information of the steering wheel, and the control unit includes a normal steering force generation unit that generates a normal steering force, and a correction steering force generation unit that generates a correction steering force that corrects the normal steering force, the corrective steering force generation unit generates a negative corrective steering force that reduces the normal steering force until the steering member reaches a stroke end when the rotation angle of the steering wheel reaches a predetermined control start angle, and generates a positive corrective steering force that increases the steering force when the steering member reaches the stroke end and rebounds; Further, the correction steering force generating unit a torque correction handle angle calculation unit that calculates a first torque correction handle angle by subtracting a predetermined first correction angle from an actual handle angle, and a second torque correction handle angle by adding a predetermined second correction angle to the actual handle angle; a proportional / integral control unit that calculates an angle difference between the first torque correction steering wheel angle calculated by the torque correction steering wheel angle calculation unit or the second torque correction steering wheel angle and the actual steering wheel angle, and performs proportional / integral control on the angle difference to calculate the negative correction steering force or the positive correction steering force, The normal steering force generated by the normal steering force generating unit is corrected with the correction steering force obtained by the proportional / integral control unit. An electric power steering device comprising:

9. An electric power steering device as claimed in claim 8, The normal steering force generating unit applies the normal steering force to the steering member by the steering actuator, separately from the manual steering force applied to the steering member by the steering wheel. An electric power steering device comprising:

10. An electric power steering device as claimed in claim 9, The torque correction steering wheel angle calculation unit calculates a torque correction steering wheel angle at a predetermined calculation cycle, and in the current calculation cycle, If the torque correction steering wheel angle calculated in the previous calculation cycle is smaller than the first torque correction steering wheel angle, the first torque correction steering wheel angle is output. If the torque correction steering wheel angle calculated in the previous calculation cycle is greater than the second torque correction steering wheel angle, the second torque correction steering wheel angle is output. When the torque correction steering wheel angle calculated in the previous calculation cycle is between the first torque correction steering wheel angle and the second torque correction steering wheel angle, the torque correction steering wheel angle calculated in the previous calculation cycle is output. An electric power steering device comprising:

11. An electric power steering device as claimed in claim 9, The torque correction steering wheel angle calculation unit sets the second correction angle to be larger than the first correction angle. An electric power steering device comprising:

12. An electric power steering device as claimed in claim 8, The torque correction steering wheel angle calculation unit sets the first correction angle to be larger than the second correction angle. An electric power steering device comprising:

13. An electric power steering device as claimed in claim 8, The control unit changes the control start angle according to the angular velocity of the rotation angle of the steering wheel. An electric power steering device comprising:

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