JP3603991B2 - Electric power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering apparatus in which the power of an electric motor is directly applied to a steering system to reduce the steering force of a driver. In particular, the direction of a signal for driving the electric motor is opposite to the direction of steering torque depending on the presence or absence of a correction signal. More particularly, the present invention relates to an electric power steering device that performs correction control by driving an electric motor.
[0002]
[Prior art]
As disclosed in Japanese Patent Application Laid-Open No. Hei 6-305429, a conventional electric power steering apparatus converts an electric signal (steering torque signal) corresponding to a steering torque applied to a steering wheel into a target of a drive current (motor current) of a motor. The target value is further converted into a PWM (pulse width modulation) signal to drive and control a motor drive circuit (for example, a bridge circuit composed of switching elements), and the motor is driven via the motor drive circuit. The motor is driven by PWM, and a drive current corresponding to the target value flows to the electric motor.
[0003]
By driving the electric motor by PWM, the power of the electric motor is applied to the steering system as an auxiliary steering force (assist torque), and the driver's manual steering force is assisted by the auxiliary steering force to reduce the driver's steering force. .
[0004]
The electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 6-305429 reversely calculates a steering torque signal from a PWM signal and a driving current of a motor or a driving current of a motor, and calculates the steering torque signal and the steering applied to the steering wheel. The steering torque signal corresponding to the torque is compared, and if the back calculated steering torque signal does not match the steering torque signal, it is determined that there is an abnormality, and the operation of the motor drive circuit is stopped.
[0005]
As described above, the electric power steering apparatus disclosed in Japanese Patent Laid-Open No. 6-305429 discloses a motor driving current value corresponding to a steering torque due to an abnormal operation of a CPU constituting a main control system for driving the electric motor. Is determined to be abnormal, the drive of the electric motor can be stopped.
[0006]
Further, in the conventional electric power steering apparatus, a direction prohibition circuit is provided, and the electric motor is steered to steer the steered wheels (tires) to the right in accordance with the direction in which the steering torque is applied (for example, right steering). The motor current for rotating (for example, forward rotation) is allowed, but the motor current for reversely rotating the motor in the direction in which the steering torque is applied (for example, right steering) is a main control system (for example, There is also known one that determines that the operation of the CPU is abnormal and prohibits it.
[0007]
[Problems to be solved by the invention]
The electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 6-305429 discloses a steering torque signal applied to a steering wheel, a PWM signal generated in response to the steering torque signal, and a drive current (motor current) of the motor or a motor current. It compares the steering torque signal back-calculated from the drive current, and if they do not match, the drive of the motor is prohibited, so the main control system that drives the motor provides drive current corresponding to the vehicle behavior due to road surface conditions. To correct the target value of the (motor current), for example, to reduce the target value by the oversteer correction amount or the understeer correction amount according to the difference between the slip angle of the front wheel and the slip angle of the rear wheel (slip angle difference), The current flowing through the motor decreases below a desired motor current value, and the steering torque signal calculated from the motor current value and the steering torque signal applied to the steering wheel are reduced. It eliminated, there is a problem that would prohibit the driving of the motor despite the normal control of the correction control for a change in vehicle behavior.
[0008]
In addition, a conventional electric power steering device having a direction prohibition circuit prohibits a motor current that rotates a motor in a direction opposite to a steering torque direction.For example, a change in vehicle behavior is corrected by an oversteer correction amount or an understeer correction amount. In the case where the control amount by the control to be performed is large and the steering is stabilized by applying an auxiliary steering force (assist torque) to the steering system in a direction opposite to the direction of the steering torque from the electric motor, the direction inhibition circuit is activated. There is a problem that the driving of the electric motor is prohibited and the desired steering characteristics cannot be realized.
[0009]
As described above, depending on the road surface condition, it is required to apply a steering assist force in a direction opposite to the direction of the steering torque to realize a steering characteristic for stabilizing the vehicle behavior even when the driver's steering force is increased. ing.
[0010]
As described above, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-156528, the motor torque is applied in a direction to reduce the deviation between the azimuth in the traveling direction of the vehicle and the tangential azimuth of the road. This also occurs in the electric power steering device described above.
[0011]
SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to allow a motor to be driven when the operation of a main control system is normal even if the steering direction and the driving direction of the motor are different. An object of the present invention is to provide an electric power steering device capable of expanding the degree of freedom of characteristics.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, an electric power steering apparatus according to the present invention includes an electric motor that applies an auxiliary steering force to a steering system, a steering torque sensor that detects a steering torque of the steering system, and a motor current that flows through the electric motor. Motor current detection means for outputting a motor current signal; target current signal setting means for setting a target current signal based on at least a steering torque signal from a steering torque sensor; correction means for outputting a correction signal independently of the steering torque signal A motor control means having a drive control means for outputting a motor control signal based on a deviation signal between a basic target current signal obtained by correcting a target current signal with a correction signal and a motor current signal; and a reference signal based on at least a steering torque signal. Reference signal setting means for setting, a motor control signal by comparing the basic target current signal and the reference signal. In an electric power steering apparatus including a control unit having an output prohibiting unit for permitting or prohibiting the supply to the motor driving unit and a motor driving unit for driving the motor by the motor control signal, the output prohibiting unit includes a basic target current signal Output of the motor control signal is prohibited when the difference between the reference signal and the reference signal exceeds the reference value, and the reference value when the correction signal is generated is set to be larger than the reference value when the correction signal is not generated. It is characterized by the following.
[0013]
The output prohibiting means according to the present invention prohibits the output of the motor control signal when the difference between the basic target current signal and the reference signal exceeds a reference value, and sets the reference value when the correction signal is being generated by the correction signal. The motor drive means (bridge circuit) is set when the basic target current signal has an abnormal value due to an abnormality in the motor control means constituted by the microprocessor because the reference value is set to be larger than the reference value when no occurrence occurs. And the operation of the motor can be prohibited.
[0014]
The output prohibiting means according to the present invention can set the reference value when the correction signal is generated to be larger than the reference value when the correction signal is not generated. Can be allowed to be driven even if the reference value that makes the reverse is large and the basic target current signal in the direction opposite to the steering torque is increased.
[0015]
The output prohibiting means according to the present invention includes: a deviation absolute value calculating means for calculating an absolute value of a difference between the basic target current signal and the reference signal; a signal detecting means for detecting that a correction signal is generated; Switching means for selecting one of the two reference values based on the detection signal from the means, and comparing means for comparing the absolute value from the deviation absolute value calculating means with the reference value selected by the switching means and outputting a prohibition signal. Output prohibition determining means.
[0016]
The output prohibiting means according to the present invention comprises: a deviation absolute value calculating means for calculating an absolute value of a difference between a basic target current signal and a reference signal; a signal detecting means for detecting that a correction signal is being generated; Switching means for selecting one of the two reference values based on the detection signal, and comparing means for comparing the absolute value from the deviation absolute value calculating means with the reference value selected by the switching means and outputting a prohibition signal. Since the prohibition determination means is provided, the operation of the motor driving means (bridge circuit) can be permitted or prohibited depending on the magnitudes of the basic target current signal and the reference signal and the presence or absence of the correction signal.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The present invention detects an abnormality of the motor control means based on a basic target current signal of the motor control means constituting the main control system and a reference signal for monitoring the operation of the motor control means, and inhibits driving of the motor. Even if the sign of the basic target current signal is different from the sign of the reference signal (direction of the steering torque), in the case of normal correction control depending on the presence or absence of the correction signal, driving of the motor in the opposite direction to the steering torque is permitted. Thus, the degree of freedom of the steering characteristics is increased.
[0018]
FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.
In FIG. 1, an electric power steering apparatus 1 includes a steering wheel 2, a steering shaft 3, a hypoid gear 4, a rack and pinion mechanism 5 including a pinion 5a and a rack shaft 5b, a tie rod 6, a front wheel 7 as a steered wheel, and an auxiliary torque. The motor includes a motor 8 that applies (auxiliary steering force) to a steering system, a control unit 13, a motor driving unit 14, and a motor current detecting unit 15.
[0019]
The electric power steering device 1 detects a yaw angular velocity acting on the vehicle, outputs a yaw angular velocity signal Y converted into an electric signal corresponding to the yaw angular velocity, a yaw angular velocity sensor 9, and detects a turning angle of the front wheels, A turning angle sensor 10 that outputs a turning angle signal δ converted to an electric signal corresponding to the turning angle of the front wheel, a vehicle speed sensor 11 that detects a vehicle speed and outputs a vehicle speed signal V converted to an electric signal corresponding to the vehicle speed, A steering torque sensor 12 that detects a steering torque acting on the steering wheel 2 and outputs a steering torque signal T converted into an electric signal corresponding to the steering torque.
The turning angle signal δ may be calculated from the steering angle of the steering shaft.
[0020]
The yaw rate signal Y, the turning angle signal δ, and the steering torque signal T each have a magnitude and a direction, and are supplied to the control unit 13.
The directions of the yaw angular velocity signal Y, the turning angle signal δ, and the steering torque signal T are positive (plus) in the clockwise direction and negative (minus) in the counterclockwise direction.
[0021]
When the steering wheel 2 is steered, the manual steering torque applied to the steering shaft 3 is converted into the axial linear motion of the rack shaft 5b by the rotation of the pinion 5a via the rack & pinion mechanism 5, and the tie rod 6 The steering of the front wheel 7 is changed.
[0022]
When the electric motor 8 is driven in response to the steering torque signal T to assist the manual steering torque, the electric motor torque is converted into an assist torque (assist torque) boosted via the hypoid gear 4 and the steering shaft 3 To reduce the steering force of the driver.
[0023]
The control means 13 comprises various arithmetic means, processing means, determination means, memory and the like based on a microprocessor, and generates at least a target current signal corresponding to the steering torque signal T. A motor control signal VO (for example, a mixed signal of an ON signal, an OFF signal, and a PWM signal) corresponding to a difference (negative feedback) from a motor current signal IMF corresponding to the motor current IM detected by the motor current detection unit 15 is generated. A motor control unit having a drive control unit is provided, and controls the driving of the motor drive unit so that the difference between the target current signal and the motor current signal IMF quickly becomes zero.
[0024]
The control unit 13 includes a slip angle difference estimating unit, a correction amount output unit, and the like. The control unit 13 includes, for example, a vehicle behavior determining unit that constitutes the correcting unit. The yaw angular velocity signal Y, the turning angle signal δ, the vehicle speed signal V, and the vehicle The difference (angle difference signal) between the slip angle of the front wheel and the slip angle of the rear wheel is estimated by calculation based on the dimensional parameter (wheel base), and the amount of understeer correction and the amount of understeer correction are calculated based on the magnitude of the difference (angle difference signal). An oversteer correction amount is determined, and a new target current signal obtained by correcting the target current signal with this correction amount is generated as a basic target current signal.
[0025]
Further, the control means 13 compares the direction (P) of the difference (angle difference signal) between the slip angle of the front wheel and the slip angle of the rear wheel (angle difference signal) and the direction (N) of the yaw angular velocity signal Y to determine the state of the vehicle (vehicle). (Behavior) is an understeer area or an oversteer area.
[0026]
Further, the control means 13 includes reference signal setting means for generating a reference signal corresponding to at least the steering torque.
The reference signal is set to be the same as the target current signal generated by the target current signal generator.
[0027]
The control means 13 determines an allowable range of the basic target current signal based on the magnitude and direction (polarity) of the basic target current signal from the motor control means and the reference signal from the reference signal setting means. An output prohibiting unit that prohibits the motor control signal VO to be supplied to the motor driving unit 14 when the allowable range is exceeded.
[0028]
The motor driving means 14 is constituted by a bridge circuit composed of switching elements such as four power FETs (field effect transistors) and insulated gate bipolar transistors (IGBTs), and PWM (pulse width modulation) based on the motor control signal VO. ) Is output, and the motor 8 is PWM-driven to rotate forward or reverse.
[0029]
The motor current detecting means 15 converts the motor current IM into a voltage using a resistor or a Hall element connected in series with the motor 8 and detects the voltage, and feeds back a motor current signal IMF corresponding to the motor current IM to the control means 13. (Negative feedback).
[0030]
FIG. 2 is a block diagram of a basic part of an electric power steering apparatus according to an embodiment of the present invention.
In FIG. 2, a control means 13 of the electric power steering apparatus 1 is constituted by a microprocessor, and comprises a target current signal setting means 21, a deviation calculation means 22, a drive control means 23, and a correction means which form a main control system. A motor control unit including a vehicle behavior determination unit 24 and a subtraction unit 25 is provided.
[0031]
Further, the control means 13 includes a reference signal setting means 16 and an output prohibiting means 17 constituted by a microprocessor or a digital circuit of discrete (discrete) components.
[0032]
The target current signal setting means 21 is configured by a memory such as a ROM, and stores in advance the steering torque signal T-target current signal IMS characteristic data using the vehicle speed signal V shown in FIG. When the vehicle speed signal V and the steering torque signal T are supplied from the torque sensor 12, respectively, the corresponding target current signal IMS data is read, and the target current signal IMS is supplied to the subtraction means 25.
Note that, as the vehicle speed signal V increases (Vl → Vm → Vh), the target current signal IMS shown in FIG. Set the behavior to be stable.
[0033]
The deviation calculation means 22 has a subtractor or a subtraction function, and a deviation ΔI (= IH−IMF) between the basic target current signal IH supplied from the subtraction means 25 and the motor current signal IMF supplied from the motor current detection means 15. ) And supplies the deviation signal ΔI (= IH−IMF) to the drive control means 23.
[0034]
The drive control unit 23 includes a PID controller, a motor control signal generation unit, and the like, and performs proportional (P), integral (I), and derivative (D) control on the deviation signal ΔI supplied from the deviation calculation unit 22, and then performs these operations. A PWM motor control signal VD corresponding to right steering or left steering of the steering wheel is generated based on a mixed signal obtained by mixing signals subjected to proportional / integral / differential (PID) control, and the output prohibiting means 17 outputs the motor control signal VD. To supply.
[0035]
The vehicle behavior determination unit (correction unit) 24 includes a slip angle difference estimation unit, a direction determination unit, a selection unit, an understeer correction amount output unit, an oversteer correction amount output unit, and the like, and includes a vehicle speed signal V supplied from the vehicle speed sensor 11, From the yaw angular velocity signal Y supplied from the yaw angular velocity sensor 9 and the steering angle signal δ supplied from the steering angle sensor 10, a difference (angular difference) between the front wheel slip angle (βf) of the vehicle and the rear wheel slip angle (βr) of the vehicle is obtained. βfr = βf−βr) to generate an understeer correction amount (DA) and an oversteer correction amount (DO) based on the angular difference signal (βfr), and to generate the understeer correction amount (DA) or the oversteer correction amount (DO). The corresponding correction signal ID is supplied to the subtracting means 25 and the output inhibiting means 17.
[0036]
FIG. 3 is a block diagram of a main part of the vehicle behavior determination means (correction means) according to the present invention.
3, the vehicle behavior determining means (correcting means) 24 includes a vehicle speed coefficient generating means 26, a slip angle difference estimating means 30, a selecting means 31, a direction determining means 32, an understeer correction amount output means 33, and an oversteer correction amount output means 34. , Multiplication means 35, multiplication means 36, addition means 37, angle difference change amount calculation means 39, and angle difference change coefficient generation means 40.
[0037]
The vehicle speed coefficient generating means 26 has a memory such as a ROM, and stores in advance the vehicle speed signal V and the characteristic data of the vehicle speed coefficient KR shown in FIG. The vehicle speed coefficient KR is read and provided to the multiplication means 35 and the multiplication means 36.
[0038]
The slip angle difference estimating means 30 has a memory and an arithmetic function, and is based on a vehicle speed signal V, a yaw angular speed signal Y, a turning angle signal δ, and a vehicle dimensional parameter L (for example, a wheel base) preset in the memory. , The difference βfr (= βf−βr) between the front wheel slip angle (βf) and the rear wheel slip angle (βr) is calculated, and the angle difference signal βfr is selected by the selection means 31, the direction determination means 32, and the angle difference change amount calculation means 39. To supply.
[0039]
(Equation 1)
βfr = Y * L / V−δ
[0040]
Since the front wheel slip angle (βf) and the rear wheel slip angle (βr) represent angles in the traveling direction of the tire based on the direction of the tire, when the steering wheel is turned clockwise, the direction of the front wheel tire is changed. On the other hand, the traveling direction of the tire is counterclockwise, and if the clockwise direction is positive (plus), the direction of the front wheel slip angle (βf) is negative (minus).
[0041]
Similarly, the rear wheel slip angle (βr) is also negative (minus), and the direction (sign) of the angle difference signal βfr is the absolute value | βr | of the rear wheel slip angle (βr) is the absolute value of the front wheel slip angle (βf). Until | βf | or more (| βr | ≧ | βf |), it is expressed as negative (minus).
Further, the lateral acceleration G may be used instead of the yaw angular velocity signal Y supplied to the direction determining means 32.
[0042]
The selection means 31 has a switch function of software control, switches the switch based on the determination signal HO supplied from the direction determination means 32, and outputs the angle difference signal βfr supplied from the slip angle difference estimation means 30 as an understeer correction amount. The output is supplied to the means 33 or the oversteer correction amount output means 34.
[0043]
The direction determining means 32 has a sign comparing function, and is based on the direction signal P of the angular difference signal βfr supplied from the slip angle difference estimating means 30 and the direction signal N of the yaw angular velocity signal Y supplied from the yaw angular velocity sensor 9. When the direction signal P and the direction signal N match (the sign is the same), for example, the determination signal HO at the H level is supplied to the selecting means 31, and the direction signal P and the direction signal N are different (the sign is different). In this case, for example, an L-level determination signal HO is supplied to the selection unit 31.
[0044]
When the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y are different (mismatch), for example, the yaw angular velocity signal Y is clockwise and the counterclockwise sliding angle (βf) of the front wheel is When the rear wheel is larger than the counterclockwise slip angle (βr), the direction signal N of the yaw angular velocity signal Y is plus (+) and the direction signal P of the angular difference signal βfr is minus (−), Upon determining that the vehicle behavior is in the understeer area, the selection means 31 selects the understeer correction amount output means 33 (displayed with a solid line).
[0045]
On the other hand, when the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y are the same (match), for example, the yaw angular velocity Y is clockwise, and the counterclockwise sliding angle (βr ) Is larger than the counterclockwise sliding angle (βf) of the front wheel, the direction signal N of the yaw angular velocity signal Y becomes plus (+) and the direction signal P of the angular difference signal βfr becomes plus (+). The selection means 31 selects the oversteer correction amount output means 34 (indicated by a broken line).
[0046]
The understeer region where the vehicle behavior is strong is a condition in which the vehicle does not turn any further even if the steering wheel is turned further from the current steering state, and the driver is strongly informed of the reaction force and the driver is advised that the steering wheel should be returned. This is the steering area.
[0047]
Since the correction of the reaction force is unnecessary in the weak understeer region, the dead zone region of the understeer correction amount DA with respect to the absolute value | βfr | of the angular difference signal βfr is set large as shown in FIG.
[0048]
On the other hand, the strong oversteer region of the vehicle is a state in which the vehicle may spin as it is, and makes the driver feel a strong reaction force to easily perform countersteering.
[0049]
The understeer correction amount output means 33 includes a memory such as a ROM, and stores in advance the characteristic data of the absolute value | βfr | of the angle difference signal and the understeer correction amount DA shown in FIG. When the signal βfr is supplied, the corresponding understeer correction amount DA is read, and the understeer correction amount signal DA is supplied to the multiplying means 35.
[0050]
The oversteer correction amount output means 34 has a memory such as a ROM, and stores in advance the characteristic data of the absolute value | βfr | of the angle difference signal and the oversteer correction amount DO shown in FIG. When the signal βfr is supplied, the corresponding oversteer correction amount DO is read, and the oversteer correction amount signal DO is supplied to the multiplying means 36.
[0051]
Note that the understeer correction amount DA and the oversteer correction amount DO each have their own dead zones as shown in FIGS. 11 and 12, so that optimum correction according to the understeer state or the oversteer state can be performed. .
[0052]
The multiplication means 35 has a multiplication function of software control, multiplies the vehicle speed coefficient KR, the understeer correction amount signal DA, and the angle difference change coefficient KV, and performs an understeer correction amount signal IDA (= KR * KV * DA) as a subtraction correction signal. ) Is supplied to the adding means 37.
[0053]
Since the understeer correction amount signal IDA corrects the understeer correction amount DA shown in FIG. 11 by the vehicle speed coefficient KR shown in FIG. 10, the understeer correction amount DA is set to 0 in the low vehicle speed region, and no correction is performed. In this case, it is possible to set the same as the characteristic of the understeer correction amount DA.
[0054]
The multiplication means 36 has a multiplication function of software control, multiplies the vehicle speed coefficient KR, the oversteer correction amount signal DO, and the angle difference change coefficient KV, and performs an oversteer correction amount signal IDO (= KR * KV * DO) as a subtraction correction signal. ) Is supplied to the adding means 37.
[0055]
Since the oversteer correction amount signal IDO corrects the oversteer correction amount DO shown in FIG. 12 with the vehicle speed coefficient KR shown in FIG. 10, the oversteer correction amount DO is not set to 0 in the low vehicle speed region, and is not corrected in the middle vehicle speed to the high vehicle speed region. It can be set to be the same as the characteristic of the oversteer correction amount DO.
Note that the oversteer correction amount DO is set to have a narrow dead zone and a small inclination compared to the understeer correction amount DA.
[0056]
The addition means 37 has an addition function of software control, and includes an understeer correction amount signal IDA (= KR * KV * DA) supplied from the multiplication means 35 and an oversteer correction amount signal IDO (= KR) supplied from the multiplication means 36. * KV * DO) and supplies either the understeer correction amount signal IDA or the oversteer correction amount signal IDO as the correction signal ID to the subtraction means 25 and the output inhibition means 17 shown in FIG.
[0057]
The angle difference change amount calculating means 39 has a differential calculating function, performs a differential calculation on the angle difference signal βfr supplied from the slip angle difference estimating means 30, and converts the angle difference change amount signal DV (= dβfr / dt) into the angular difference. It is supplied to the change coefficient generating means 40.
[0058]
The angle difference change coefficient generating means 40 has a memory such as a ROM, and stores in advance the characteristic data of the angle difference change amount DV and the angle difference change coefficient KV shown in FIG. 13, and is supplied with the angle difference change amount signal DV. Then, the corresponding angular difference change coefficient KV is read and supplied to the multiplying means 35 and the multiplying means 36.
[0059]
The angle difference change amount DV indicates a change in the angle difference signal βfr, and therefore indicates a temporal change in the vehicle behavior. Therefore, the understeer correction amount signal IDA (= KR * KV * DA) corresponding to the rapid change in the vehicle behavior. Alternatively, an oversteer correction amount signal IDO (= KR * KV * DO) can be generated.
[0060]
Returning to FIG. 2, the subtraction unit 25 has a subtraction function, and calculates the difference between the target current signal IMS supplied from the target current signal setting unit 21 and the correction signal ID supplied from the vehicle behavior determination unit 24 shown in FIG. IMS-ID) and supplies it to the deviation calculating means 22 and the output prohibition determining means 18 of the output prohibiting means 17 as a basic target current signal IH (= IMS-ID).
[0061]
The reference signal setting means 16 is composed of a memory such as a ROM. Like the target current signal setting means 21, the reference signal setting means 16 includes a steering torque signal T and a target of the target current signal IMS characteristic data with the vehicle speed signal V shown in FIG. The reference signal IRS, which has the same characteristics as the current signal IMS, is stored beforehand. When the vehicle speed signal V and the steering torque signal T are supplied from the vehicle speed sensor 11 and the steering torque sensor 12, respectively, the corresponding reference signal IRS Is supplied to the output prohibition determining means 18 of the output prohibiting means 17.
The reference signal IRS may be obtained from the steering torque signal T-target current signal IMS characteristic data different from that in FIG. 9. Also, the reference signal IRS has the same sign (direction) as the steering torque signal T, and It is also possible to set a constant value regardless of the absolute value.
[0062]
The output prohibiting unit 17 includes an output prohibiting determining unit 18 and a signal stopping unit 19.
The output prohibition determination means 18 has a subtraction function, a memory, a signal detection function, a switching function, and the like, and has a basic target current signal IH supplied from the deviation calculation means 25 of the motor control means and a reference supplied from the reference signal setting means 16. The prohibition signal SK is supplied to the signal stopping means 19 based on the difference from the signal IRS (= IH-IRS) and the correction signal ID supplied from the vehicle behavior determining means 24.
[0063]
FIG. 4 is a block diagram of a main part of an embodiment of the output prohibition determining means according to the present invention.
4, the output prohibition determining unit 18 includes a deviation absolute value calculating unit 41, a reference value storing unit 42, a signal detecting unit 43, a switching unit 44, and a comparing unit 45.
[0064]
The deviation absolute value calculation means 41 has a subtraction function and an absolute value calculation function, calculates a difference (= IH-IRS) between the basic target current signal IH and the reference signal IRS, performs an absolute value calculation process, and calculates a deviation absolute value. The value ΔIZ (= | IH-IRS |) is supplied to the comparing means 45.
[0065]
The reference value storage means 42 is configured by a memory such as a ROM, stores the reference value data K1 and the reference value data K2 in advance, reads out the reference value data K1 and the reference value data K2, and supplies the read data to the switching means 44.
[0066]
The reference value K1 is an absolute value, and in a state where the correction signal ID is generated, the deviation absolute value ΔIZ (= | IH-IRS |) between the basic target current signal IH and the reference signal IRS is an upper limit value at which normal control is performed. Set to.
In addition, the reference value K2 is an absolute value, and in a state where the correction signal ID is not generated, the absolute value of the deviation ΔIZ (= | IH−IRS |) between the basic target current signal IH and the reference signal IRS is a normal control. Set to the upper limit.
The reference value K1 (absolute value) is set to a value (| reference value K1 |> | reference value K2 |) larger than reference value K2 (absolute value).
[0067]
The signal detection unit 43 has a level comparison function such as a comparator, and compares and amplifies the correction signal ID supplied from the vehicle behavior determination unit 24 with a zero value or a low-level threshold to generate a correction signal ID. In this case, an H-level detection signal SO is supplied to the switching means 44.
When the correction signal ID has not been generated, the signal detection unit 43 supplies the L level detection signal SO to the switching unit 44.
[0068]
The switching unit 44 has a switching function, and when the detection signal SO of the H level is provided from the signal detection unit 43, selects the reference value K1 supplied from the reference value storage unit 42, and selects the reference value K (= K1). Is supplied to the comparing means 45.
On the other hand, when the L level detection signal SO is provided from the signal detection unit 43, the switching unit 44 selects the reference value K2 supplied from the reference value storage unit 42, and sets the comparison value 45 as the reference value K (= K2). To supply.
[0069]
The comparison means 45 has a comparison function, a buffer output function, and an inverter output function, and compares the deviation absolute value ΔIZ (= | IH-IRS |) supplied from the deviation absolute value calculation means 41 with the reference value K (K1 or K2). If the absolute value of the deviation ΔIZ exceeds the reference value K (K1 or K2), an L-level inhibition signal SK (SK1 or SK2) is supplied to the signal stopping means 19 shown in FIG.
[0070]
When the absolute difference value ΔIZ is equal to or smaller than the reference value K (K1 or K2), the comparing means 45 supplies an H-level prohibition signal SK (SK1 or SK2) to the signal stopping means 19.
[0071]
As an example, the L-level prohibition signal SK1 is a signal for prohibiting the forward rotation of the electric motor 8, and the L-level prohibition signal SK2 is a signal for prohibiting the reverse rotation of the electric motor 8.
In a normal control state, the inhibition signal SK (SK1, SK2) is always kept at the H level.
[0072]
For example, when the correction signal ID is generated, the basic target current signal IH is plus (+), and the difference absolute value ΔIZ exceeds the reference value K1 (ΔIZ> K1), the prohibition signal SK1 is set to L level, The signal SK2 is set to the H level, and the forward rotation of the electric motor 8 is prohibited.
[0073]
On the other hand, when the correction signal ID is generated, the basic target current signal IH is minus (-), and the deviation absolute value ΔIZ (−) is smaller than the reference value −K1 (ΔIZ <−K1), the inhibition signal SK1 is generated. The H level and the prohibition signal SK2 are set to the L level, and the reverse rotation of the motor 8 is prohibited.
[0074]
Further, when the correction signal ID is not generated, the basic target current signal IH is plus (+), and the deviation absolute value ΔIZ exceeds the reference value K2 (ΔIZ> K2), the prohibition signal SK1 is set to the L level and the prohibition signal is prohibited. The signal SK2 is set to the H level, and the forward rotation of the electric motor 8 is prohibited.
[0075]
On the other hand, when the correction signal ID is not generated, the basic target current signal IH is minus (−), and the deviation absolute value ΔIZ (−) is smaller than the reference value K2 (ΔIZ <−K2), the inhibition signal SK1 is set to H. The level and the prohibition signal SK2 are set to L level, and the reverse rotation of the electric motor 8 is prohibited.
[0076]
Returning to FIG. 2, the signal stopping means 19 has a logical product operation function, and converts the motor control signal VD supplied from the drive control means 23 based on the prohibition signal SK supplied from the output prohibition determining means 18 to the motor control signal. It is supplied to the motor drive means 14 as a VO or is prohibited.
[0077]
FIG. 5 is a block diagram of a main part of an embodiment of the signal stopping means according to the present invention.
5, the signal stopping means 19 comprises two-input AND means 19A to 19D, and one input of each of the AND means 19A to 19D is provided with an electric motor supplied from the drive control means 23 shown in FIG. The four motor control signals VD1 to VD4 forming the control signal VD are input.
[0078]
FIG. 6 shows a block diagram of a main part of the drive control means.
6, the drive control unit 23 includes a PID controller 28 and a motor control signal generation unit 29.
The PID controller 28 performs P (proportional) control, I (integral) control, and D (differential) control on the deviation signal ΔI supplied from the deviation calculating means 22 shown in FIG. It is supplied to the control signal generating means 29.
[0079]
The motor control signal generating means 29 includes a PWM signal generating means and an on / off signal generating means. Based on the signal IC supplied from the PID controller 28, when the deviation signal ΔI is plus (+), the PWM signal VPWM is generated. VD1, VD2 of the ON signal VON, VD3 of the OFF signal VOF, and VD4 of the OFF signal VOF are supplied as motor control signals VD to one input of each of the AND means 19A to 19D of the signal stopping means 19.
[0080]
When the deviation signal ΔI is minus (−), the motor control signal generation means 29 outputs VD1 of the OFF signal VOF, VD2 of the OFF signal VOF, VD3 of the PWM signal VPWM, and VD4 of the ON signal VON to the signal stopping means 19. Is supplied to one input of each of the AND means 19A to 19D.
[0081]
Returning to FIG. 5, a prohibition signal SK1 supplied from the output prohibition determining unit 18 is input to the other input of each of the AND units 19A and 19B, and the other input of each of the AND units 19C and 19D is The prohibition signal SK2 supplied from the output prohibition determining means 18 is input.
[0082]
When the deviation absolute value ΔIZ supplied from the deviation absolute value calculation means 41 shown in FIG. 4 is equal to or smaller than the reference value K (K1 or K2) (ΔIZ ≦ K1, K2), both of the inhibition signals SK1, SK2 are at H level. The signal stopping means 19 receives the motor control signal VD (VD1, VD2, VD3, VD4) supplied from the motor control signal generating means 29 shown in FIG. 6 as it is, and controls the motor control signal VO (VO1, VO4, VO2, V03). Is output as
[0083]
When the deviation absolute value ΔIZ supplied from the deviation absolute value calculation means 41 exceeds the reference value K (K1 or K2) (ΔIZ> K1 or ΔIZ> K2), the basic target current on the side exceeding the reference value K The output of the motor control signals VD (VD1, VD2, VD3, VD4) of the AND means 19A to 19D to which the L-level prohibition signal SK1 or SK2 corresponding to the sign of the signal IH is input is prohibited.
[0084]
For example, when the correction signal ID is generated, the sign of the basic target current signal IH is plus (+), and the deviation absolute value ΔIZ exceeds the reference value K1 (ΔIZ> K1), the correction signal ID is supplied to the AND means 19A and 19B. The prohibition signal SK1 is set to the L level to prohibit the output of the motor control signals VD1 and VD2.
In this state, the prohibition signal SK2 supplied to the AND circuits 19C and 19D is set to the H level, the output of the motor control signals VD3 and VD4 is allowed, and the motor control signals VD3 and VD4 are output as the motor control signals V02 and V03.
[0085]
If the correction signal ID is not generated and the sign of the basic target current signal IH is minus (-), and the deviation absolute value .DELTA.IZ (-) falls below the reference value -K2 (.DELTA.IZ <-K2), the logic The prohibition signal SK2 supplied to the product means 19C and 19D is set to L level, and the output of the motor control signals VD3 and VD4 is prohibited.
In this state, the prohibition signal SK1 supplied to the AND means 19A and 19B is set to the H level, the output of the motor control signals VD1 and VD2 is permitted, and output as the motor control signals V01 and V02.
[0086]
As described above, the output prohibiting unit 17 according to the present invention prohibits the output of the motor control signal VD when the difference between the basic target current signal IH and the reference signal IRS exceeds the reference value K, and generates the correction signal ID. Since the reference value K2 when the correction signal ID is not generated is set smaller than the reference value K1 when the motor is turned on, an abnormality occurs in the motor control means constituted by the microprocessor, and the basic target current signal IH becomes an abnormal value. Is generated, the operation of the motor driving means (bridge circuit) 14 can be prohibited.
[0087]
The output prohibiting means 17 according to the present invention includes a deviation absolute value calculating means 41 for calculating an absolute value ΔIZ of a difference between the basic target current signal IH and the reference signal IRS, and a signal detecting means for detecting that the correction signal ID is generated. 43, switching means 44 for selecting one of the two reference values K1 and K2 based on the detection signal SO from the signal detection means 43, the absolute value ΔIZ from the deviation absolute value calculation means 41, and the reference value selected by the switching means 44. Since the output prohibition determining means 18 having the comparing means 45 for comparing the values K1 and K2 and outputting the prohibition signals SK1 and SK2 is provided, the magnitudes of the basic target current signal IH and the reference signal IRS, and the correction signal ID The operation of the motor driving means (bridge circuit) 14 can be permitted or prohibited depending on the presence or absence.
[0088]
FIG. 7 is an FET bridge circuit diagram constituting the motor driving means.
In FIG. 7, the motor driving means (FET bridge circuit) 14 includes four FETs (field effect transistors) Q1 to Q4.
Motor control signals V01 to V04 are supplied to gates G1 to G4 of FETs (field effect transistors) Q1 to Q4, respectively.
[0089]
When the motor 8 is rotated forward, the PWM signal VPWM is supplied to the gate G1 of Q1 as the motor control signal VO1, and the ON signal VON is supplied to the gate G4 of Q4 as the motor control signal VO4. By supplying the off signal VOF as the motor control signals V02 and V03 to G3, the battery power supply VB (12V) → FET (field effect transistor) Q1 → terminal M1 → motor 8 → terminal M2 → FET (field effect transistor) Q4 → The motor current IM + flows through the ground (GND) path.
[0090]
When the motor 8 is rotated in the reverse direction, the PWM signal VPWM is supplied to the gate G2 of Q2 as the motor control signal VO2, and the ON signal VON is supplied to the gate G3 of Q3 as the motor control signal VO3. G1 and G4 are supplied with the off signal VOF as the motor control signals V01 and V04, so that the battery power supply VB (12V) → FET (field effect transistor) Q2 → terminal M2 → motor 8 → terminal M1 → FET (field effect transistor) ) A motor current IM− flows through a path of Q3 → ground (GND).
[0091]
The output prohibiting means 17 can control the driving of the motor 8 by allowing or prohibiting the motor control signals V01 to V04 supplied to the gates G1 to G4 of the FETs (field effect transistors) Q1 to Q4.
[0092]
Next, the operation of the output prohibiting means of the present invention will be described with reference to FIG.
FIG. 8 is an explanatory diagram of the operation of the output prohibiting means of the electric power steering device according to the present invention.
(A) is a waveform diagram of a detection signal SO for detecting the presence or absence of the correction signal ID, and (b) is a diagram showing a relationship between a difference (= IH-IRS) between the basic target current signal IH and the reference signal IRS and the reference values K1 and K2. (C) is a waveform diagram of a prohibition signal SK1, (d) is a waveform diagram of a prohibition signal SK2, and (e) is a diagram for explaining permission and prohibition of the motor currents IM + and IM-.
[0093]
FIG. 8 is an explanatory diagram in the case where the target current signal IMS is plus (+).
Also, the case where the target current signal IMS is minus (-) can be handled in the same way by reversing the signs of (b) and (e), so that the description is omitted.
[0094]
(A) shows a state in which the detection signal SO is at the L level and the correction signal ID is not generated from time 0 to time t3.
In addition, during a period from time t3 to time t10, the detection signal SO is at the H level, indicating that the correction signal ID is being generated.
[0095]
From time 0 to time t3 when the correction signal ID is not generated, the basic target current signal IH and the reference signal IRS are the same, and the difference (= IH−) between the basic target current signal IH and the reference signal IRS shown in FIG. IRS) is always 0 when the motor control means is operating normally.
[0096]
An abnormality occurs in the microprocessor constituting the motor control means between the time t1 and the time t2. For example, when the target current signal IMS has an abnormally large level (+ polarity side) and the reference signal IRS has a normal level. The difference between the basic target current signal IH and the reference signal IRS (= IH-IRS) also becomes a large level (+ polarity side) because the basic target current signal IH has an abnormally large level.
[0097]
On the other hand, from time 0 to time t3, the target current signal IMS is plus (+), the correction signal ID is not generated, and (IH-IRS) is the reference value K2 set when the correction signal ID is not generated. Therefore, the prohibition signal SK1 shown in the diagram (c) changes from H level to L level.
On the other hand, the inhibition signal SK2 shown in FIG.
[0098]
(E) When the target current signal IMS is larger than 0 (IMS> 0), the motor current IM shown in the figure shows a plus (+) polarity motor current IM + flowing between the time t1 and the time t2 due to the abnormality of the microprocessor. Although the excessive motor current IM + flows, the excessive motor current IM + between the time t1 and the time t2 can be prohibited by the L-level prohibition signal SK1.
The motor current IM (IM +, IM−) in FIG. 3E indicates whether or not the motor current IM + or the motor current IM− flows for convenience of description, and the magnitude of the current value is omitted.
[0099]
Next, in FIG. 5A, from time t3 to time t10 when the correction signal ID is generated, the plus (+) polarity target current signal IMS is changed to the plus (+) polarity correction signal ID (understeer shown in FIG. 3). Since the correction is performed by the correction amount signal IDA or the oversteer correction amount signal IDO), the basic target current signal IH has a smaller value (IH <IRS) than the reference signal IRS which is substantially the same as the target current signal IMS.
Note that the basic target current signal IH has a positive (+) polarity when the correction signal ID is smaller than the target current signal IMS (ID <IMS), and when the correction signal ID is larger than the target current signal IMS (ID> IMS). Has a negative (-) polarity.
[0100]
(B) The difference (= IH-IRS) between the basic target current signal IH and the reference signal IRS shown in the figure is always negative (-) polarity because the correction signal ID is generated, and the reference value is set to -K1. Is done.
[0101]
Between time t4 and time t5, a case where the correction signal ID is larger than the target current signal IMS (IMS <ID) is shown, and the basic target current signal IH (= IMS−), which is the difference between the target current signal IMS and the correction signal ID. ID) is minus (-).
[0102]
From time t4 to time t5, (IH-IRS) in the figure (b) is minus (-) but larger than the reference value -K1 (IH-IRS> -K1), and the inhibition signal SK1 in the figure (c). Also, the inhibition signal SK2 shown in FIG. 7D is kept at the H level, and the basic target current signal IH (= IMS-ID) is minus (-). Therefore, the motor current IM shown in FIG. Without this, the motor current IM- flows.
[0103]
Although the motor current IM- of minus (-) flows between time t6 and time t9, the difference (= IH-IRS) between the basic target current signal IH and the reference signal IRS in FIG. The value becomes excessively negative (-) due to the abnormality of the microprocessor and falls below the reference value -K1 (IH-IRS <-K1). Therefore, the prohibition signal SK1 shown in FIG. ) The prohibition signal SK2 in the figure becomes L level, and prohibits the minus (-) motor current IM- only between time t7 and time t8.
[0104]
As described above, when the correction signal ID is not generated and the difference between the basic target current signal IH and the reference signal IRS (= IH-IRS) exceeds the reference value K2, an abnormal phenomenon that does not occur in normal control occurs. It is possible to determine that an error has occurred in the microprocessor constituting the motor control means, inhibit the motor control signal VO generated due to the abnormality, and stop the motor current IM.
[0105]
When the correction signal ID is generated and the difference between the basic target current signal IH and the reference signal IRS (= IH-IRS) exceeds the reference value K1, an abnormal phenomenon that does not occur in the normal correction control occurs. It is possible to determine that an error has occurred in the microprocessor constituting the control means, inhibit the motor control signal VO generated due to the abnormality, and stop the motor current IM.
Note that the present invention can be applied to the electric power steering device disclosed in Japanese Patent Application Laid-Open No. 9-156528.
[0106]
【The invention's effect】
As described above, the output prohibiting means according to the present invention prohibits the output of the motor control signal when the difference between the basic target current signal and the reference signal exceeds the reference value, and also suppresses the output when the correction signal is generated. Since the reference value is set to be larger than the reference value when no correction signal is generated, if the motor control means constituted by the microprocessor becomes abnormal and the basic target current signal becomes an abnormal value, the motor It is possible to prohibit the operation of the driving means (bridge circuit) and prohibit the driving of the electric motor, thereby eliminating the instability of the steering characteristics due to the abnormal value of the basic target current signal.
[0107]
In addition, the motor current in the direction opposite to the target current signal by the correction signal can flow, and a larger reference value can be set than when no correction signal is generated. A large auxiliary steering force can be applied, and understeer correction and oversteer correction can be sufficiently performed to stabilize the vehicle behavior.
[0108]
Further, the output prohibiting means according to the present invention comprises: a deviation absolute value calculating means for calculating an absolute value of a difference between the basic target current signal and the reference signal; a signal detecting means for detecting that a correction signal is generated; Switching means for selecting one of the two reference values based on the detection signal from the means, and comparing means for comparing the absolute value from the deviation absolute value calculating means with the reference value selected by the switching means and outputting a prohibition signal. Output prohibition determining means, which allows or prohibits the operation of the motor driving means (bridge circuit) depending on the magnitude of the basic target current signal and the reference signal, and the presence or absence of the correction signal. Sufficient control can be performed to stabilize the vehicle behavior and obtain an optimal steering feeling.
[0109]
Therefore, the main microprocessor constituting the motor control means for determining the steering characteristics has an abnormality.
When power steering occurs, an electric power steering that prohibits assist and sets a large assist force in the direction opposite to the steering direction to expand the range of correction control and obtain steering characteristics for stabilizing vehicle behavior An apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.
FIG. 2 is a block diagram of an essential part of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 3 is a block diagram of a main part of a vehicle behavior determination unit (correction unit) according to the present invention.
FIG. 4 is a block diagram of a main part of an embodiment of an output prohibition determining means according to the present invention.
FIG. 5 is a block diagram of a main part of an embodiment of a signal stopping means according to the present invention.
FIG. 6 is a block diagram of a main part of the drive control means.
FIG. 7 is a circuit diagram of an FET bridge constituting motor driving means.
FIG. 8 is an explanatory diagram of the operation of the output prohibiting means of the electric power steering device according to the present invention.
FIG. 9 is a characteristic diagram of a steering torque signal T-target current signal IMS using a vehicle speed signal V as a parameter.
FIG. 10 is a characteristic diagram of a vehicle speed signal V and a vehicle speed coefficient KR.
FIG. 11 is a characteristic diagram of an angular difference signal | βfr | -understeer correction amount DA
FIG. 12 is a characteristic diagram of an angle difference signal | βfr | -oversteer correction amount DO
FIG. 13 is a characteristic diagram of an angle difference change amount DV-angle difference change coefficient KV.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 8 ... Electric motor, 9 ... Yaw angular velocity sensor, 10 ... Disconnection angle sensor, 11 ... Vehicle speed sensor, 12 ... Steering torque sensor, 13 ... Control means, 14 ... Electric motor drive means (FET bridge circuit), Reference numeral 15: motor current detecting means, 16: reference signal setting means, 17: output prohibiting means, 18: output prohibiting determining means, 19: signal stopping means, 21: target current signal setting means, 22: deviation calculating means, 23: driving Control means, 24: vehicle behavior determination means (correction means), 25: subtraction means, 41: deviation absolute value calculation means, 42: reference value storage means, 43: signal detection means, 44: switching means, 45: comparison means.

Claims (2)

A motor for applying an auxiliary steering force to a steering system, a steering torque sensor for detecting a steering torque of the steering system, a motor current detecting means for detecting a motor current flowing through the motor and outputting a motor current signal; Target current signal setting means for setting a target current signal based on a steering torque signal from a torque sensor, correction means for outputting a correction signal independently of the steering torque signal, and a basic target current signal obtained by correcting the target current signal with a correction signal Motor control means including a drive control means for outputting a motor control signal based on a deviation signal of the motor current signal and a reference signal setting means for setting a reference signal based on at least a steering torque signal, a basic target current signal and a reference signal And output inhibit means for permitting or inhibiting the supply of the motor control signal to the motor drive means. And control means for, in the electric power steering apparatus having a motor drive means for driving the electric motor by the motor control signal, and
The output prohibiting means prohibits the output of the motor control signal when the difference between the basic target current signal and the reference signal exceeds a reference value, and generates a correction signal based on the reference value when the correction signal is generated. An electric power steering apparatus characterized in that it is set to be larger than a reference value when there is no power steering. The output prohibiting means includes a deviation absolute value calculating means for calculating an absolute value of a difference between the basic target current signal and the reference signal, a signal detecting means for detecting that a correction signal is generated, and a detection signal from the signal detecting means. Output prohibition determination, comprising: switching means for selecting one of the two reference values based on the data, and comparing means for comparing the absolute value from the deviation absolute value calculating means with the reference value selected by the switching means and outputting a prohibition signal. 2. The electric power steering apparatus according to claim 1, further comprising means.

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