JP5140109B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

The electric power steering device reduces the steering force by using the driving force of the motor as an auxiliary force. For this reason, if an abnormal auxiliary force is generated due to an abnormality of the control device, self-steering occurs, which is not preferable for safety.
In order to solve such a problem, an invention has been made to ensure safety even if a monitoring device is provided and the control device operates abnormally.
For example, in Patent Document 1, safety is ensured by providing a monitoring device that detects steering torque and limits motor driving in the direction opposite to the steering torque.
Further, in Patent Document 2, a main calculation unit that performs power steering control and a sub calculation unit that monitors the power calculation unit are provided, and even if the main calculation unit operates abnormally, the sub calculation unit limits the driving of the motor to ensure safety. The sex is secured.

Japanese Patent No. 3364135 JP 2009-132281 A

However, when configured as in Patent Document 1, safety can be ensured, but when steering is controlled based on information input via an in-vehicle LAN such as auto parking or lane keeping, motor control is limited by the monitoring device. There is a problem that the intended control cannot be performed.
Patent document 2 is an invention for solving the above-mentioned problem, but there is a problem in terms of cost, for example, it is necessary to provide an interface circuit for inputting the in-vehicle LAN to the sub-control device (monitoring device). .

  The present invention is intended to solve the above-described problems, and an object thereof is to provide an electric power steering device that realizes power steering control based on information input via an in-vehicle LAN with an inexpensive device. It is.

  An electric power steering apparatus according to the present invention includes a motor that generates a steering assist force, current detection means that detects a motor current flowing through the motor and outputs a motor current signal, and detects a steering torque of the steering wheel and outputs a torque signal. A torque detection means, a motor instruction current determination means for determining a motor current instruction value for the motor based on at least the torque signal, a control device including a motor current control means for controlling the motor current according to the motor current instruction value, and a torque signal; A monitoring device that detects an abnormality of the control device from the motor current signal and restricts the driving of the motor when the abnormality is detected, the monitoring device including a first region that is determined to be abnormal, and an increase rate of the motor current signal Based on the torque signal and the motor current signal. And performs area determination of the first to third, based on the.

  According to the present invention, control according to an instruction via an in-vehicle LAN, such as auto parking control and lane keeping control, and power steering control including control for improving the response and stability of power steering, control during normal operation It is possible to limit the motor current control and to ensure safety when there is an abnormality without limiting the motor.

It is a block diagram which shows the basic composition of the electric power steering apparatus concerning Embodiment 1 of this invention. 3 is a control block diagram of an EPS ECU according to Embodiment 1. FIG. 2 is a control block diagram of a main microcomputer and PI control in Embodiment 1. FIG. 3 is a diagram illustrating control characteristics of the electric power steering in Embodiment 1. FIG. FIG. 3 is a control block diagram of a sub-microcomputer in the first embodiment. FIG. 3 is a diagram showing a first area determined by a sub-microcomputer in the first embodiment. 6 is a diagram showing a second area determined by the sub-microcomputer in the first embodiment. FIG. 6 is a flowchart showing a second region determination processing unit in the first embodiment. FIG. 3 is a diagram illustrating first, second, and third areas determined by a sub-microcomputer in the first embodiment. FIG. 3 is a diagram showing a control characteristic locus when electric power steering is normal in the first embodiment. FIG. 3 is a diagram illustrating a control characteristic locus when the main microcomputer according to the first embodiment is abnormal in auto parking. It is a control block diagram of the submicrocomputer in Embodiment 2 of this invention. 10 is a flowchart showing processing of a second area determination unit in the second embodiment. It is a figure which shows the control characteristic locus | trajectory of electric power steering when responsiveness improvement control is added in Embodiment 2. FIG. It is a figure which shows the control characteristic locus | trajectory of an electric power steering when safety improvement control is added in Embodiment 2. FIG. It is a flowchart which shows the process of the 2nd area | region determination part in Embodiment 3 of this invention. It is a control block diagram of the submicrocomputer in Embodiment 4 of this invention. 15 is a flowchart showing processing of a second area determination unit in the fourth embodiment. FIG. 10 is a diagram illustrating setting of a current threshold reduction coefficient in the fourth embodiment. It is a figure which shows the change of the current threshold value in Embodiment 4. FIG. It is a flowchart which shows the process of the 2nd area | region determination part in Embodiment 5 of this invention. FIG. 10 is a diagram showing setting of a current threshold reduction coefficient in the fifth embodiment. It is a control block diagram of the main microcomputer in Embodiment 6, 8 of this invention. 18 is a flowchart showing processing of a right current limit calculation unit in the sixth embodiment. 18 is a flowchart showing processing of a left current limit calculation unit in the sixth embodiment. FIG. 10 is a block diagram of a current limit processing unit in a sixth embodiment. It is a control block diagram of the main microcomputer in Embodiment 7 of this invention. 18 is a flowchart showing processing of a right current limit calculation unit in the seventh embodiment. 18 is a flowchart showing processing of a left current limit calculation unit in the seventh embodiment. It is a flowchart which shows the process of the right current limiting calculating part in Embodiment 8 of this invention. 19 is a flowchart showing processing of a left current limit calculation unit in the eighth embodiment. FIG. 20 is a diagram illustrating setting of a current threshold reduction coefficient in the eighth embodiment.

Embodiment 1 FIG.
FIG. 1 shows the configuration of the electric power steering apparatus.
In the figure, 1 is a steering wheel, 2 is a steering shaft, 3 is a torque sensor that detects steering torque, 4 is a vehicle speed sensor, 5 is an EPS ECU that controls electric power steering, 6 is a motor that generates auxiliary steering force, 7 Is the gear that transmits the auxiliary force from the motor 6 to the steering shaft 2, 8 is the rack and pinion mechanism for transmitting the rotational force from the steering shaft 2 to the front wheels, 9 is the front wheel of the vehicle, and 10 is the power to the EPS ECU5 A battery 11 is an AP (auto parking) control ECU that sends a command signal to the EPS ECU to perform auto parking control.

Next, the inside of the EPS ECU 5 will be described with reference to FIG. In the figure, the same reference numerals are the same as those in FIG.
501 is a torque sensor I / F (interface) circuit that inputs a signal from the torque sensor 3, 502 is an I / F circuit that inputs information via CAN from the vehicle speed sensor 4 or AP control ECU 11, and 503 is a power steering control The main microcomputer programmed to perform, 504 is an AND circuit for turning on the relay when both the output Drym of the main microcomputer and the output DryS of the sub-microcomputer described later output relay ON, and 505 drives the relay described later Relay drive circuit, 506 is a relay that cuts off the motor current when there is an abnormality, 507 is a shunt resistor that detects the current flowing through the motor 6, and 508 is a current detection that amplifies the potential difference generated at both ends of the shunt resistor 507 and inputs it to the main microcomputer 503 Circuit 509 is an AND circuit for driving the motor when both the main microcomputer and a sub-microcomputer described later output motor ON, and 510 is a motor driver described later. FET drive circuit for driving the circuit, 511 is a motor drive circuit in which transistors are bridged to control the current of the motor 6, 512 is a signal TRQ from the torque sensor I / F circuit 501, and a signal Imd from the current detection circuit 508 Is a sub-microcomputer that detects an abnormality in the main microcomputer 503 and restricts the motor current (motor OFF, relay OFF) when an abnormality occurs.

Next, the operation of the main microcomputer 503 will be described with reference to FIG.
In FIG. 3 (a), 503a takes in vehicle speed information and an auto parking control signal from the CAN bus, and obtains a vehicle speed signal Vsp1 and an auto parking control signal APSig, respectively. 503b is a torque signal input. A torque input processing unit that generates a torque signal TRQ1 by A / D-inputting the signal TRQ input from the I / F circuit 501 and adding the right torque signal to the positive value and the left torque signal to a negative value, 503c is the torque signal TRQ1 and the vehicle speed signal Vsp1 EPS instruction current determination unit for determining the power steering instruction current ImtEPS, 503d is an AP control unit for generating the auto parking control current ImtAP based on the auto parking control signal APSig, and 503e is the power steering instruction current ImtEPS and the auto parking control. An adder that adds the current ImAP to generate the motor current instruction value Imt1, and 503f compares the motor current instruction value Imt1 with a motor current detection signal Imd1, which will be described later. The motor current control unit that performs feedback control so that the motor current detection signal Imd1 coincides with the motor current instruction value Imt1 is a general PI controller shown in FIG. 3 (b) and outputs a motor current command value DmtM. .
A motor current input processing unit 503g performs A / D conversion on the signal Imd input from the motor current detection circuit 508, and generates a motor current detection signal Imd1 with the current in the right direction being positive and the current in the left direction being negative.
The EPS command current determination unit 503c has the characteristics as shown in FIG. 4. When steering in the right direction, a right current is generated according to the torque signal TRQ1, and a left current is generated in the left direction. In addition, since the current is set to change according to the vehicle speed signal Vsp1, optimal power steering control can be performed according to the vehicle speed.

Next, the operation of the sub-microcomputer 512 will be described with reference to FIG.
In the figure, 512a is a torque input processing unit that generates the torque signal TRQ2 by inputting the signal TRQ input from the torque sensor I / F circuit 501 and adding the right torque signal to the positive and the left torque signal to the negative value, and 512b is the motor current detection. A motor current input processor 512c generates a motor current signal Imd2 by converting the signal Imd input from the circuit 508 to A / D and generating a current in the right direction and a current in the left direction as a negative. 512c differentiates the motor current signal Imd2 Differentiator to obtain motor current change rate △ Imd2, 512d determines whether it is in the first area that is judged abnormal from torque signal TRQ2 and motor current signal Imd2, and if the condition is satisfied, F_A1 = 1 If not, F_A1 = 0 is output in the first region determination unit, and 512e is in the second region where it is determined that there is an abnormality from the torque signal TRQ2, the motor current signal Imd2, and the motor current change rate ΔImd2. If the condition is satisfied Is a second area determination unit that outputs F_A2 = 1, and F_A2 = 0 is output if not satisfied, and 512f is an OR process for the output F_A1 of the first area determination unit and the output F_A2 of the second area determination unit ORg, 512g is output when F_S1 of the OR operator continues for a predetermined time 1 (for example, 50 ms), F_S2 is set to 1, otherwise 1 is output, timer 1 is output 0, 512h is output of timer 1 F_S2 Relay output unit that outputs DryS = 1 when F_S2 is 1, output DryS = 0 when F_S2 is 1, 512i is output DmtS = 1 when F_S2 of timer 1 is 0, output DmtS = 0 when F_S2 is 1 It is a motor output part which outputs.

Next, the first area determination unit 512d will be described with reference to FIG.
In the figure, 21a is a region where the torque signal TRQ2 is greater than or equal to the first predetermined value Ta (eg, 3 Nm) in the right direction and the motor current signal Imd2 is in the left direction (Imd2 <0), and 21b is the first when the torque signal is in the left direction. 1 or more than the predetermined value Ta (left torque signal is represented by minus TRQ2 ≦ −Ta) and the motor current signal Imd2 is the rightward region (Imd2> 0), and the region where 21a and 21b are combined is the first region It is. The first region determination unit 512d outputs F_A1 = 1 when the torque signal TRQ2 and the motor current signal Imd2 are in the region 21a or 21b, and outputs F_A1 = 0 otherwise.

Next, the second area determination unit 512e will be described with reference to FIGS.
In FIG. 7A, 22a1 indicates that the torque signal TRQ2 is less than the first predetermined value Ta in the right direction (TRQ2 <Ta) and the current Imd2 is greater than or equal to the predetermined value Ia (for example, 5A) in the left direction (the left current is expressed as a negative value). So the area of Imd2 ≦ -Ia).
In FIG. 7B, 22a2 indicates that the torque signal TRQ2 is less than or equal to the second predetermined value Tb (eg, 1 Nm) in the left direction (the left torque signal is expressed as minus, so TRQ2 ≧ −Tb), and the current Imd2 is the predetermined value in the left direction. This is an area of Ia or more (Imd2 ≦ −Ia).
22b1 in FIG. 7 (a) and 22b2 in FIG. 7 (b) are regions existing at symmetrical positions of 22a1 and 22a2, respectively. FIG. 7 (c) is a superposition of FIG. 7 (a) and FIG. 7 (b).
As shown in the flowchart of FIG. 8, the second region discriminating unit 512e has the torque signal TRQ2 and the motor current signal Imd2 within the range 22a of FIG. 7C, and the motor current change rate ΔImd2 is a predetermined value Δ If it is greater than Imd2th (for example, 20 A / s) (if it is negative, it is △ Imd2 ≦-△ Imd2th), F_A2 = 1 is output (steps S101, S102, S103), and torque signal TRQ2 and motor current signal Imd2 Is in the range of 22b in FIG. 7C, and F_A2 = 1 is output when the motor current change rate ΔImd2 is greater than the predetermined value ΔImd2th (because it is a positive direction, ΔImd2 ≧ ΔImd2th) (steps S105, S106). , S103), otherwise F_A2 = 0 is output (steps S105, S106, S104).

  The output F_A1 of the first region determination unit and the output F_A2 of the second region determination unit described above are overlapped by the OR operation unit 512f of FIG. 5, and finally the state shown in FIG. The region, 22 is the second region, and the other portion 23 is the third region. The third area is a normal determination area.

Since the first embodiment is configured as described above, the first embodiment operates as follows.
First, the case of operating as power steering will be described.
When the steering wheel 1 is steered, a torque signal TRQ1 is obtained by the torque sensor 3, the torque signal input I / F circuit 501, and the torque input processing unit 503b.
Next, power steering command current ImtEPS is determined by EPS command current determination unit 503c. Specifically, as shown in FIG. 4, the power steering command current ImtEPS is determined according to the vehicle speed signal Vsp1 and the torque signal TRQ1 at that time.
When auto parking control is OFF, the output ImtAP of the AP control unit 503d is zero, so the final command current Imt1 is
Imt1 = ImtEPS
Thus, the power steering command current ImtEPS is energized to the motor 6 by the motor current control unit 503f.
In the case of right steering, current flows in the right direction as shown in FIG. The torque is transmitted to the steering shaft 2 via the gear 7 and acts as an auxiliary force. The reverse is true for left steering.

Next, the case where the auto parking control is operating will be described.
In auto parking, the command signal sent from the auto parking ECU 11 via CAN BUS is taken into EPS via the I / F circuit 502 and CAN communication circuit 503a, and converted into the motor current indication value ImtAP by the AP control unit 503d. The During the auto parking control, the steering wheel 1 is in the released state, so the power steering command current ImtEPS is zero. Therefore, the final indicated current Imt1 is
Imt1 = ImtAP
Thus, the current ImtAP is supplied to the motor 6 by the motor current control unit 503f.

FIG. 10 is a diagram in which the trajectory when operating as power steering and the trajectory when operating as auto parking are overwritten. The locus 31 is a power steering operation, and the locus 32 is an auto parking operation locus.
Since the current increases according to the torque during the power steering operation, the locus 31 is drawn, and during the auto parking operation, the torque signal TRQ1 is almost zero, and the locus 32 is drawn.

On the other hand, the sub-microcomputer 512 has the characteristics shown in FIG.
When the main microcomputer 512 operates as power steering, the locus 31 of FIG. 10 is drawn. Since this is in the range of the area 23 in FIG. 9, the sub-microcomputer 512 determines that it is normal and does not limit the motor current. As a result, power steering control as intended can be performed.
When the main microcomputer 512 operates as auto parking, the locus 32 of FIG. 10 is drawn. This enters region 22 of FIG. The region 22 does not limit the motor current if the current increase rate is equal to or less than the predetermined value ΔImd2th. Since the rate of increase in current is small when auto parking is operating normally, the sub-microcomputer does not limit the motor current. As a result, the intended auto parking control can be performed.

Next, a case where an excessive current suddenly flows due to a failure of the main microcomputer 512 or an abnormality of the AP ECU 11 will be described.
First, when an abnormal current flows in the steering direction during steering, it corresponds to the region 23 in FIG. 9, but since the steering force is only lightened, there is no danger and control is continued. When the current flows in the direction opposite to the steering direction, it corresponds to the region 21 in FIG. 9, so the sub-microcomputer 512 determines that there is an abnormality and limits (turns off) the motor current.
When the current flows in a state in which the steering is hardly performed, it corresponds to the region 22 in FIG. When an excessively large current flows suddenly, the current increase rate ΔImd2 exceeds a predetermined value ΔImd2th, so the sub-microcomputer 512 determines that there is an abnormality and limits the motor current (turns OFF).
When an excessive current suddenly flows, safety can be ensured by operating as described above.

Next, a case where the current gradually increases and reaches an excessive current due to a failure of the main microcomputer 512 or an abnormality of the AP ECU 11 will be described.
First, a case where an abnormal current flows in the steering direction during steering and a case where an abnormal current flows in the direction opposite to the steering direction are the same as the above-mentioned “when an excessively large current flows”, and thus the description thereof is omitted.
When the current flows in a state in which the steering is hardly performed, as described above, it corresponds to the region 22 in FIG. Since the abnormal current gradually increases, if the increase rate is equal to or less than the predetermined value ΔImd2th, the sub-microcomputer 512 does not detect the abnormality. However, when the steering wheel 1 starts to move on its own, the driver squeezes the steering wheel 1 to maintain the steering angle, and torque is generated. At this time, the locus becomes a curve 33 in FIG. If the abnormal current is in the right direction, the torque changes to the left, and if the abnormal current is in the left direction, the torque changes to the right. Therefore, the region 21 in FIG. 9 is entered. As a result, the sub-microcomputer 512 determines that there is an abnormality and limits (turns off) the motor current.

  As described above, in the first embodiment, the motor 6 that generates the steering assist force, the current detection means 508 that outputs the motor current detection signal Imd flowing through the motor 6, the steering torque of the handle 1 is detected, and the torque signal TRQ is obtained. Torque detection means 3 for outputting, motor instruction current determination means 503c for determining a motor current instruction value Imt1 for the motor 6 based on at least the torque signal TRQ, and motor current control means for controlling the motor current Imd according to the motor current instruction value Imt1 A control device (main microcomputer) 503 including 503f, and a monitoring device (sub-microcomputer) 512 that detects the abnormality of the control device 503 from the torque signal TRQ and the motor current signal Imd2, and restricts the driving of the motor 6 when the abnormality is detected. The monitoring device 512 determines that the first region 21 is determined to be abnormal, the second region 22 determines whether the motor current signal Imd2 is abnormal, and is normal based on the increase rate of the motor current signal Imd2. It has a third area 23, and performs the first to third area discrimination based on the torque signal TRQ and the motor current signal Imd2, and performs control according to instructions via the in-vehicle LAN such as auto parking control and lane keeping control. In power steering control with control to improve the response and stability of power steering, it is possible to ensure safety by limiting motor current control during abnormal operation without limiting control during normal operation .

In addition, since the increase rate of the motor current signal Imd2 is determined to be abnormal when it exceeds a predetermined value, if the control device fails and the motor current increases rapidly, the motor current increase rate exceeds the predetermined value. The monitoring device can determine that there is an abnormality and limit (cut off) the motor current. However, control based on in-vehicle LAN information such as auto parking has a slow current increase rate, so the motor current increase rate is less than a predetermined value and the monitoring device does not determine that there is an abnormality. As a result, the motor current is not limited and intended control is possible.
In addition, when a failure occurs such that the motor current gradually increases, torque is generated by the driver grasping the handle, and as a result, the first region 21 in which it is determined to be abnormal is entered. Can be restricted (blocked).
In other words, when an abnormal current suddenly occurs (when the steering wheel suddenly moves), it is difficult for the driver to react, but since the rate of increase of the motor current signal Imd2 is large, the monitoring device malfunctions in the second region 22 The motor current is limited. When the abnormal current increases gradually (when the handle moves slowly), the driver reacts and grips the handle to generate torque in the direction opposite to the motor current, thereby entering the first region 21. The motor current can be limited (cut off) by this, and safety can be ensured. Further, since the rate of increase of the motor current signal Imd2 is slow at the normal time, the monitoring device does not limit the motor current, so that intended control such as auto parking is possible.
Furthermore, by performing primary detection when the increase rate of the motor current signal Imd2 is equal to or greater than a predetermined value and determining that the primary detection state continues for a predetermined time as abnormal, it is possible to avoid erroneous detection while ensuring safety.

Embodiment 2. FIG.
Next, a second embodiment will be described. In the second embodiment, the processing of the sub-microcomputer 512 is made as shown in FIG.
In FIG. 12, 512j is a torque differentiator that differentiates the torque signal TRQ2 and calculates the rate of change ΔTRQ2, and 512k is determined to be abnormal from the torque signal TRQ2, torque change rate ΔTRQ2, motor current signal Imd2, and motor current rate of change ΔImd2. This is a second area determination unit that outputs F_A2 = 1 if the condition is satisfied if the condition is satisfied, and F_A2 = 0 is output if the condition is not satisfied. The description is omitted because it is the same as 1.

  Next, the operation of the second area determination unit 512k will be described. Also in the second embodiment, as in the first embodiment, the regions 22a and 22b in FIG. 7 (c) are determined, and the torque change rate ΔTRQ2 and the motor current change in that region as shown in the flowchart in FIG. If the signs of the rates ΔImd2 do not match, F_A2 = 1 is output (steps S201, S202, S203), and otherwise F_A2 = 0 is output (steps S201, S202, S204).

The configuration as described above works as follows.
Since the normal operation is the same as that of the first embodiment, the description thereof is omitted.
In general, in power steering, control using differential torque is used to improve responsiveness, and control using motor rotation speed is used to improve stability. When the control for improving the responsiveness is added to the basic control of the power steering shown in FIG. 4, the locus becomes as shown by 34 in FIG. Further, when the control for improving the stability is added to the basic control of the power steering of FIG. 4, the locus becomes as shown in 35 of FIG. In this way, current flows in the second quadrant and the fourth quadrant in both FIGS. Therefore, there is a possibility that the region 22 shown in FIG. In the second embodiment, in this region 22, a case where the sign of the torque signal change rate ΔTRQ2 and the motor current signal change rate ΔImd2 do not match is abnormal, but in FIGS. Since the signs of TRQ2 and motor current change rate ΔImd2 match, it is not judged abnormal. Therefore, the intended control becomes possible.

  Next, a case where an abnormal operation is performed will be described. When an abnormal operation occurs, the locus becomes like 33 in FIG. This is because the sign of the torque signal change rate ΔTRQ2 and the current change rate ΔImd2 is reversed, so that the sub-microcomputer 512 can determine that there is an abnormality and limit the motor current.

  As described above, in the second embodiment, the monitoring device (sub-microcomputer) 512 has the first region 21 determined to be abnormal, the torque differential signal obtained by calculating the torque signal change rate ΔTRQ2, A second area 22 in which the motor current differential signal obtained by calculating the rate of change ΔImd2 of the motor current signal is equal to or greater than a predetermined value and the signs do not match, and a third area 23 in which it is determined as normal. Since the first to third regions are determined based on the torque signal and the motor current signal, the monitoring device limits the motor current when the control device (main microcomputer) 503 is operating normally. Without control, the intended control is possible. On the other hand, if the control device malfunctions, the motor current is limited (cut off), so safety can be ensured.

Embodiment 3 FIG.
Next, a third embodiment will be described. In the third embodiment, the processing of the second area determination unit 512k in FIG. 12 is changed as in the flowchart in FIG. 16 with respect to the second embodiment.
First, in step S301, it is determined whether or not the torque signal signal TRQ2 and the motor current signal Imd2 are within the region 22a or the region 22b in FIG. Next, in the region 22a, it is determined whether or not the sign of the rate of change ΔTRQ2 of the torque signal signal and the rate of change ΔImd2 of the motor current signal match, and if they do not match, the rate of change of motor current ΔImd2 Is negative (step S302), if negative, output F_A2 = 1, otherwise F_A2 = 0 is output (steps S303, S304, S305). If it is in the region 22b, it is determined whether or not the sign of the change rate ΔTRQ2 of the torque signal signal and the change rate ΔImd2 of the motor current signal match (step S307). It is determined whether or not the rate ΔImd2 is positive. If it is positive, output F_A2 = 1 is output, otherwise F_A2 = 0 is output (steps S308, S309, S310).
With this configuration, F_A2 = 1 can be output when the absolute value of the current increases in the regions 22a and 22b, and F_A2 = 0 can be output otherwise.

With the configuration as described above, only the direction in which the absolute value of the current increases in the regions 22a and 22b can be determined as abnormal.
As described in the first and second embodiments, when an abnormality occurs, the locus changes in the direction in which the absolute value of the current increases as indicated by 33 in FIG. By determining only an increase in absolute value as abnormal as in the third embodiment, it is possible to further avoid malfunction of the sub-microcomputer 512.
In the third embodiment, the determination is made by increasing the motor current. However, the determination may be made by increasing the torque signal, or by increasing both the torque signal and the current.

  As described above, in the third embodiment, the monitoring device (sub-microcomputer) 512 has the torque differential signal and the motor current differential signal equal to or greater than a predetermined value in the second region 22 and the signs do not coincide with each other. Since the case where the absolute value of the current differential signal or both is increasing is determined to be abnormal, the monitoring device does not limit the motor current when the control device (main microcomputer) 503 is operating normally, Intended control is possible. However, when the control device operates abnormally, the motor current is limited (shut off), so that safety can be ensured.

Embodiment 4 FIG.
Next, a fourth embodiment will be described. In the fourth embodiment, the processing of the sub-microcomputer 512 is made as shown in FIG.
In FIG. 17, it is determined whether 512m is in the second region that is determined to be abnormal from the torque signal signal TRQ2 and the motor current signal Imd2, and if the condition is satisfied, F_A2 = 1 is satisfied. If not, the second area determination unit outputs F_A2 = 0.
Since others are the same as Embodiment 1, description is abbreviate | omitted.

  Next, the operation of the second area determination unit 512m will be described using the flowchart of FIG. First, in step S401, it is determined whether or not the torque signal TRQ2 and the current Imd2 are in the region 22a or 22b in FIG. 7C. If they are not in the region, the process branches to No. In step S402, the timer 2 is set. In step S403, the current threshold value Imd2th is set to the maximum current IMAX (for example, 50 A). Thereafter, in step S404, the output F_A2 is set to 0, and this process ends.

If the torque signal TRQ2 and the current signal Imd2 are in the region 22a or 22b in FIG. 7C, the process branches to Yes in step S401 and proceeds to step S405. In step S405, the timer 2 is incremented. In step S406, the elapsed time of the timer 2 is checked. If it is less than a predetermined value Time2th (for example, 50 ms), the process proceeds to step S403. If the elapsed time of the timer 2 is equal to or greater than the predetermined value Time2th, a threshold reduction coefficient kdec corresponding to the absolute value of the motor current signal Imd2 is determined in step S407. Next, in step S408, the decrease coefficient kdec calculated in step S407 is subtracted from the current threshold value Imd2th. Next, in step S409, it is checked whether or not the current threshold value Imd2th is less than a predetermined value Ia (for example, 5A). If it is less, the predetermined value Ia is substituted into the current threshold value Imd2th in step S410. In steps S409 and S410, the lower limit clipping is performed so that the current threshold value Imd2th does not become less than the predetermined value Ia. Next, in step S411, the absolute value of the motor current signal Imd2 is compared with the current threshold value Imd2th.If the absolute value of the motor current signal Imd2 is equal to or smaller than the current threshold value Imd2th, the process proceeds to step S404, and the output F_A2 Set to 0. If the absolute value of the motor current signal Imd2 is larger than the current threshold value Imd2th, the process branches to Yes in step S411, and the output F_A2 is set to 1 in step S412.
Thereafter, the processing of this flowchart is repeatedly performed at every calculation cycle.
When step S407 is set so that the decrease coefficient kdec increases as the current Imd2 increases as shown in FIG. 19, the current threshold value Imd2th decreases with time as shown in the timing chart of FIG.

With the configuration as described above, the following operation is performed.
Since the normal operation is the same as that of the first embodiment, the description thereof is omitted. Further, as described in the second embodiment, compensation control using torque differentiation is generally used to improve power steering response, and compensation control using motor rotation speed is used to improve stability. . Such a current is generated temporarily when the torque changes or while the motor is rotating.
By gradually lowering the current threshold value Imd2th from the maximum value IMAX as in the fourth embodiment, the intended control can be performed without hindering the compensation control.

  Next, a case where an abnormal operation occurs will be described. When an abnormal operation occurs, the locus becomes like 33 in FIG. 11 as in the first embodiment. Since this current continues, the state where the current Imd2 is equal to or greater than the current threshold value Imd2th continues. As a result, the sub-microcomputer can determine that there is an abnormality and limit the motor current.

  As described above, in the fourth embodiment, the monitoring device (sub-microcomputer) 512 continues the first region 21 that is determined to be abnormal and the state where the motor current signal Imd2 is equal to or greater than a predetermined value for a first predetermined time or longer. When the current threshold value Imd2th is generated so as to decrease from the maximum current value with the passage of time, and the motor current signal Imd2 exceeds the current threshold value Imd2th continues for a second predetermined time or more, it is determined as abnormal. This occurs temporarily because the second region 22 to be determined and the third region to be determined to be normal and the first to third regions are determined based on the torque signal and the motor current signal. It is possible to limit the current that flows for a long time, which leads to self-steering, without limiting the transient current, thus ensuring safety without impairing the controllability of the power steering. .

Embodiment 5 FIG.
Next, a fifth embodiment will be described. The fifth embodiment is different from the fourth embodiment in that the threshold reduction coefficient kdec is set according to the absolute value of the torque signal. This will be specifically described with reference to the flowchart of FIG.
Step S507 in the figure is the threshold reduction coefficient kdec setting process described above. The characteristic is set so that the coefficient kdec increases as the absolute value of the torque signal TRQ2 increases as shown in FIG. Yes. The rest is the same as in the fourth embodiment.

  As described above, in the fifth embodiment, the current threshold value Imd2th is decreased quickly when the torque signal TRQ2 is large, and is slowly decreased when the torque signal TRQ2 is small. The effect is obtained.

Embodiment 6 FIG.
Next, a sixth embodiment will be described. In the sixth embodiment, the processing FIG. 3A of the main microcomputer 503 is changed as shown in FIG. 23 in correspondence with the first embodiment.
In the figure, 503n is a right current limit value calculation unit that calculates a current limit value IlimitR in the right direction, 503o is a left current limit value calculation unit that calculates a current limit value IlimitL in the left direction, and 503p is generated by a current addition unit 503e. A current limit processing unit that clips the ImtSUM with the right current limit value IlimitR and the left current limit value IlimitL, and the others are the same as in the first embodiment.

Next, the processing of the right current limit value calculation unit 503n will be described using the flowchart of FIG. First, in step S601, it is determined whether or not the torque signal TRQ1 is greater than a predetermined value Ta in the left direction (the torque signal represents the left as a minus value, so in step S601, it is determined whether or not it is less than -Ta). If the condition is satisfied, the process branches to Yes. In step S602, 0 is substituted for the right current limit value IlimitR, and in step S603, the current threshold value Ia is substituted for the previous right current value Imt1Rz.
If the condition is not satisfied in step S601, the process proceeds to step S604, and it is determined whether or not the torque signal TRQ1 is equal to or less than a predetermined value Tb in the right direction. If the condition is satisfied, the process branches to Yes. In Step S605, it is determined whether or not the command current Imt1 is equal to or smaller than the predetermined value Ia. If it is equal to or smaller, the process branches to Yes. In Step S606, the right current limit value IlimtR is predetermined. Ia is substituted, and a predetermined value Ia is substituted for the previous right current value Imt1Rz in step S607.
If the condition is not satisfied in step S605, the process branches to No and proceeds to step S608. In step S608, the predetermined value kinc is added to the previous right current value Imt1Rz. Next, in step S609, it is determined whether the right current limit value IlimtR exceeds the maximum current value IMAX. If it exceeds, the maximum current value IMAX is substituted into the right current limit value IlimtR in step S610. If the condition is not satisfied in step S609, the process branches to No. In step S611, the current value Imt1 is substituted for the previous value of the right current.
If the condition is not satisfied in step S604, the maximum current value IMAX is substituted for the right current limit value IlimitR in step S612, and the predetermined value Ia is substituted for the previous right current value Imt1Rz in step S613.

  Next, the left current limit value calculation unit 503o will be described with reference to FIG. FIG. 25 shows the same process for the left current. In FIG. 25, the left and right sides are reversed with respect to FIG.

  Next, the current limit processing unit 503p in FIG. 23 will be described with reference to FIG. The current limit processing unit 503p includes a MIN processing unit 503q that selects and outputs the minimum value from the input values, and a MAX processing unit 503r that selects and outputs the maximum value from the input values. The maximum value clip and the minimum value (maximum value of the left current) are clipped with IlimitL to generate the indicated current Imt1.

Since it is configured as described above, the current limit process is as shown in FIG. 9 by the right current limit value calculation unit 503n, the left current limit value calculation 503o, and the current limit processing unit 503p. In other words, for the right current limit value IlimitR, when the torque signal is smaller than -Ta (area 21), the current current limit is 0 A, and when the torque signal exceeds Ia and Ia between -Ta and Tb and enters the area 22, The value is determined by a predetermined increase rate determined by kinc (for example, 20 A / s). The other region (region 23) can be energized up to the maximum current.
The left and right sides are reversed, but the same processing is performed.

With the configuration as described above, even if the EPS instruction current determination unit 503c and the AP control unit 503b output an instruction value that exceeds the limit, the current is finally limited by the current limit process of 503p.
Since the limiting processes 503n and 503o are set in accordance with the characteristics of the sub-microcomputer, as long as the main microcomputer operates normally, no motor current flows in the region where the sub-microcomputer determines abnormality. Therefore, it is possible to avoid malfunction of the sub-microcomputer while maintaining the same safety as in the first embodiment.

Embodiment 7 FIG.
Next, a seventh embodiment will be described. In the seventh embodiment, the processing of the main microcomputer is as shown in FIG. 27 corresponding to the second embodiment.
In the figure, 503s is a differential operation unit for differentiating the torque signal TRQ1 and calculating the torque change rate ΔTRQ1, and 503t is a current limit value IlimtR in the right direction from the torque signal TRQ1, torque change rate ΔTRQ1 and the motor current instruction value Imt1. Calculate the right current limit value calculation unit, 503u is the left current limit value calculation unit that calculates the current limit value IllimL in the left direction from the torque signal TRQ1, torque change rate ΔTRQ1, and motor current indication value Imt1, 503p is the current addition unit The current limit processing unit clips the ImtSUM generated in 503e with the right current limit value IllimitR and the left current limit value IlimitL, and the others are the same as in the second embodiment.

Next, the right current limit processing calculation unit 503t will be described with reference to the flowchart of FIG. First, in step S701, it is determined whether or not the torque signal TRQ1 is greater than a predetermined value Ta in the left direction (the torque signal represents the left as a minus value, so in step S601 it is determined whether or not it is less than -Ta). If the condition is satisfied, the process branches to Yes, and 0 is substituted for the right current limit value IlimitR in step S702.
If the condition is not satisfied in step S701, the process proceeds to step S703, and it is determined whether the torque signal TRQ1 is equal to or less than a predetermined value Tb in the right direction. If the condition is satisfied, the process branches to Yes. In Step S704, it is determined whether or not the command current Imt1 is equal to or larger than the predetermined value Ia. If it is equal to or lower, the process branches to Yes. In Step S705, the right current limit value IlimtR is predetermined. Assign the value Ia.
If step S704 is not satisfied, it is determined in step S706 whether or not the torque change rate ΔTRQ1 is 0 or more (increase in the right direction). If it has increased in the right direction, the right current limit value IlimitR is set to the maximum current IMAX. Set.
If the condition is not satisfied in step S706 (when the torque signal changes to the left), the process branches to No, and a predetermined value Ia is substituted for the right current limit value IlimitR in step S708.
If the condition is not satisfied in step S703, the process branches to No, and the maximum current IMAX is substituted for the right current limit value IlimitR in step S709.

  Next, the left current limit value calculation unit 503s will be described with reference to FIG. In FIG. 29, the same process is performed on the left current. The left and right sides are reversed with respect to FIG.

Since the current limiting processing unit 503p is the same as that of the sixth embodiment, the current limiting processing is as shown in FIG. 9 by configuring as described above. That is, for the right current limit value IlimitR, when the torque signal is smaller than -Ta (region 21), the torque is 0A when the torque signal is between -Ta and Tb and enters the region 22 exceeding Ia and Ia. When the signal changes in the right direction, the limit value becomes the maximum current IMAX, and when the signal changes in the left direction, the limit value becomes the predetermined value Ia. The other region (region 23) can be energized up to the maximum current.
The left and right sides are reversed, but the same processing is performed.

With the configuration as described above, even if the EPS instruction current determination unit 503c and the AP control unit 503b output an instruction value that exceeds the limit, the current is finally limited by the current limit process of 503p.
Since the limiting processes 503t, 503u, and 503p are set in accordance with the characteristics of the sub-microcomputer, as long as the main microcomputer is operating normally, no motor current flows in the area where the sub-microcomputer determines abnormality. Therefore, the malfunction of the sub-microcomputer can be avoided while maintaining the same safety as in the first embodiment.

Embodiment 8 FIG.
Next, an eighth embodiment will be described. In the eighth embodiment, the processing of the main microcomputer is as shown in FIG. 23 corresponding to the fifth embodiment, the right current limit value calculation unit 503n is as shown in FIG. 30, and the left current limit value calculation unit 503o is as shown in FIG. It is.

Next, the right current limit value calculation unit 503n will be described with reference to FIG.
First, in step S801, it is determined whether or not the torque signal TRQ1 is greater than a predetermined value Ta in the left direction (the torque signal represents the left as a minus value, so in step S801, it is determined whether or not it is less than -Ta). If the condition is satisfied, the process branches to Yes, and 0 is substituted for the right current limit value IlimitR in step S802. If the condition is not satisfied in step S801, the process proceeds to step S803, and it is determined whether the torque signal TRQ1 is equal to or less than a predetermined value Tb in the right direction. If the condition is satisfied, the process branches to Yes. In Step S804, it is determined whether or not the command current Imt1 is equal to or greater than the predetermined value Ia. If it is less, the process branches to Yes. In Step S805, the right current limit value IlimtR is maximized. Substitute the value IMAX.
If step S804 is not established, the process branches to No, and the reduction coefficient kdec is determined based on the absolute value of Imt1 in step S806. The characteristics of this reduction coefficient are shown in FIG.
Next, in step S807, the reduction coefficient kdec is reduced with respect to the right current limit value IlimitR. In step S808, it is determined whether the right current limit value IlimitR is less than the predetermined value Ia. If the condition is satisfied, the predetermined value Ia is substituted into the right current limit value IlimitR in step S809. If the condition is not satisfied in step S808, the process branches to No. If the condition is not satisfied in step S803, the maximum current IMAX is substituted for the right current limit value IlimitR in step S810.

  Next, the left current limiting unit 503o (FIG. 23) will be described with reference to FIG. FIG. 31 shows the same processing as that for the left current. The left and right sides are reversed with respect to FIG.

With the above configuration, the current limiting process is as shown in FIG. That is, for the right current limit value IlimitR, when the torque signal is smaller than -Ta (area 21), 0A, when the torque signal is between -Ta and Tb, IMAX, and when the command current Imt1 exceeds Ia and enters the area 22 The right current limit value IlimitR decreases from the maximum value to the predetermined value Ia at the speed indicated by the decrease coefficient kdec. The other region (region 23) can be energized up to the maximum current.
The left and right sides are reversed, but the same processing is performed.

With the configuration as described above, even if the EPS instruction current determination unit 503c and the AP control unit 503b output an instruction value that exceeds the limit, the current is finally limited by the current limit process of 503p.
Since the limiting processes 503n and 503o are set in accordance with the characteristics of the sub-microcomputer, as long as the main microcomputer operates normally, no motor current flows in the region where the sub-microcomputer determines abnormality. Therefore, the malfunction of the sub-microcomputer can be avoided while maintaining the same safety as in the first embodiment.

1 Handle
2 Steering shaft
3 Torque sensor
4 Vehicle speed sensor
5 EPS ECU
6 Motor
7 Gear
8 Rack and pinion mechanism
9 Front wheel
10 battery
11 AP ECU
501 Torque signal input I / F circuit
502 CAN signal input I / F circuit
503 main microcomputer
503a CAN communication circuit
503b Torque input processing unit
503c EPS indication current determination unit
503d AP controller
503e Adder
503f Motor current controller
503g motor current input processor
503i motor current controller
503n Right current limit value calculator
503o Left current limit value calculator
503p current limit processor
503q MIN processing section
503r MAX processing unit Differential operation unit
503s Differential operation unit
503t right current limit value calculator
503u Left current limit value calculator
504 AND circuit
505 Relay drive circuit
506 Relay
507 shunt resistor
508 Current detection circuit
509 AND circuit
510 FET drive circuit
511 Motor drive circuit
512 sub-microcomputer
512a Torque input processor
512b Motor current input processor
512c differentiator
512d First region determination unit
512e Second region determination unit
512f OR operator
512g timer 1
512h relay output
512i motor output
512j torque differentiator
512k 2nd area judgment part
512m 2nd area judgment part

Claims (10)

A motor that generates steering assist force;
Current detection means for detecting a motor current flowing in the motor and outputting a motor current signal;
Torque detecting means for detecting steering torque of the steering wheel and outputting a torque signal;
A controller including motor instruction current determining means for determining a motor current instruction value for the motor based on at least the torque signal; and a motor current control means for controlling the motor current according to the motor current instruction value;
An abnormality of the control device is detected from the torque signal and the motor current signal, and a monitoring device that restricts driving of the motor when an abnormality is detected is provided.
The monitoring device
A first region that is determined to be abnormal;
A second region for determining abnormality or normality based on an increase rate of the motor current signal;
With a third area to determine normal,
An electric power steering apparatus characterized in that first to third region discrimination is performed based on the torque signal and the motor current signal. The monitoring device
2. The electric power steering apparatus according to claim 1, wherein in the second region, it is determined that the motor current signal is abnormal if the increase rate of the motor current signal is equal to or greater than a predetermined value, and is normal if the increase rate is less than the predetermined value. The monitoring device
2. The electric power steering according to claim 1, wherein in the second region, primary detection is performed when the rate of increase of the motor current signal is equal to or greater than a predetermined value, and an abnormality is determined when the primary detection state continues for a predetermined time. apparatus. A motor that generates steering assist force;
Current detection means for detecting a motor current flowing in the motor and outputting a motor current signal;
Torque detecting means for detecting steering torque of the steering wheel and outputting a torque signal;
A controller including motor instruction current determining means for determining a motor current instruction value for the motor based on at least the torque signal; and a motor current control means for controlling the motor current according to the motor current instruction value;
An abnormality of the control device is detected from the torque signal and the motor current signal, and a monitoring device that restricts driving of the motor when an abnormality is detected is provided.
The monitoring device
A first region that is determined to be abnormal;
When the torque differential signal obtained by calculating the rate of change of the torque signal and the motor current differential signal obtained by calculating the rate of change of the motor current signal are equal to or greater than a predetermined value and the signs do not match, it is determined as abnormal. A second region to
With a third area to determine normal,
An electric power steering apparatus characterized in that first to third region discrimination is performed based on the torque signal and the motor current signal. The monitoring device
In the second region, an abnormality occurs when the torque differential signal and the motor current differential signal are equal to or greater than a predetermined value and the signs do not match, and the absolute value of the torque differential signal and / or the motor current differential signal is increasing. The electric power steering apparatus according to claim 4, wherein the electric power steering apparatus is determined. A motor that generates steering assist force;
Current detection means for detecting a motor current flowing in the motor and outputting a motor current signal;
Torque detecting means for detecting steering torque of the steering wheel and outputting a torque signal;
A controller including motor instruction current determining means for determining a motor current instruction value for the motor based on at least the torque signal; and a motor current control means for controlling the motor current according to the motor current instruction value;
An abnormality of the control device is detected from the torque signal and the motor current signal, and a monitoring device that restricts driving of the motor when an abnormality is detected is provided.
The monitoring device
A first region that is determined to be abnormal;
When the state where the motor current signal is equal to or greater than a predetermined value continues for a first predetermined time or more, a current threshold value is generated so as to decrease from the maximum current value as time elapses, and the motor current signal is the current threshold value. A second region that is determined to be abnormal when a state exceeding the value continues for a second predetermined time or more;
With a third area to determine normal,
An electric power steering apparatus characterized in that first to third region discrimination is performed based on the torque signal and the motor current signal.   7. The electric power steering apparatus according to claim 6, wherein when the motor current signal is large, the current threshold value is decreased rapidly, and when the motor current signal is small, the current threshold value is decreased slowly.   7. The electric power steering apparatus according to claim 6, wherein when the torque signal is large, the current threshold value is decreased quickly, and when the torque signal is small, the current threshold value is decreased slowly. The first region is a region where the torque signal is equal to or greater than a first predetermined value and the motor current signal is in a direction opposite to the steering torque,
The second region includes a region where the torque signal is less than a first predetermined value, the motor current signal is in a direction opposite to a steering torque and the motor current signal is equal to or greater than a predetermined value, and the torque signal is a second predetermined value. Less than the region where the motor current signal is in the same direction as the torque signal and the region where the motor current signal is equal to or greater than a predetermined value,
The electric power steering apparatus according to any one of claims 1 to 8, wherein the third region is a region other than the first and second regions.   The clip processing for clipping so that the motor current instruction value does not become larger than a threshold value for judging abnormality of the monitoring device is performed in the control device. The electric power steering apparatus as described.

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