JP2009012551A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device having a controller capable of returning assist torque without providing sense of uneasiness due to the variation of steering torque to the operator when a control element of a steering system is returned to a normal state after being brought into an abnormal state. <P>SOLUTION: When the control element of the steering system is returned from the abnormal state to the normal state at a time point s1, and a state in which the torque is equal to or higher than a predetermined torque upper limit threshold TH is continued for a predetermined duration ta or longer and then a state in which the torque is less than a torque lower limit threshold TL (near neutral of steering) is continued for a predetermined duration tb or longer, the operator determines that he has experienced steering feeling by a gain G at that time. When the operator does not steer, he increases the gain G from zero to G1. Further, he gradually increases the gain from G1 to G2, G3, G4 ... for returning the assist torque. Since the assist torque is not changed during the steering, the sense of uneasiness due to the variation of steering torque is not provided to the operator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus, and in particular, suppresses a sudden change in assist torque that occurs when an abnormality occurs in a control element that constitutes a steering system and then returns to a normal state, and does not give a sense of incongruity to steering wheel operation. The present invention relates to an electric power steering apparatus including a control device.

  An electric power steering device for a vehicle detects a steering torque and a vehicle speed generated in a steering shaft by operating a steering handle, and drives a motor based on the detection signal to assist a steering force of the steering handle. is there. Such control of the electric power steering device is executed by a control device constituted by a microcomputer. The outline of the control is based on the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor. The magnitude of the current supplied to the motor is calculated, and the current supplied to the motor is controlled based on the calculation result.

  That is, when the steering wheel is operated and steering torque is generated, the control device supplies a large steering assist force when the detected vehicle speed is zero or low, and small steering when the detected vehicle speed is high. Calculate the control target value of the motor current according to the steering torque and the vehicle speed so as to supply the auxiliary force, perform feedback control so that the current that actually flows through the motor matches the control target value of the motor current, and according to the driving state The optimal steering assist force is given.

  In such an electric power steering device, when an abnormality occurs such as a steering system, for example, a motor overheating, a control device (ECU) overheating, or a power supply voltage dropping, the assist torque is limited or set to zero. There is one that avoids danger by performing fail-safe control to prevent the occurrence of secondary failure.

  In addition, when an abnormality occurs in a control element constituting the steering system and returns to a normal state, there is a case where control is performed to limit the supply due to the occurrence of an abnormality or raise the stopped assist torque to a specified value again. However, in such a case, the steering torque required for steering before and after the normal return of the control elements constituting the steering system is significantly different, so that the driver may feel uncomfortable when operating the steering wheel.

As a countermeasure, it has been proposed to provide means for preventing a sudden change in torque when the steering system returns to a normal state after an abnormality has occurred (see Patent Document 1).
Japanese Patent No. 3397065

  In the above-described conventional electric power steering apparatus, the means for preventing a sudden change in torque when the control element constituting the steering system returns to a normal state after an abnormality has occurred. The assist torque is changed during.

  For this reason, there is a problem that the driver must perform steering corresponding to changes in road conditions and assist torque. In particular, when the vehicle is passing a sharp curve, i.e., when it returns to normal with a high assist torque, even if the change in assist torque is small, the effect is large, and the driver may feel uneasy. There is.

  In addition, since the assist torque is raised under the condition that the steering torque is equal to or greater than a predetermined value (steering torque ≧ predetermined value), if the instantaneous sudden steering is repeated, the driver substantially experiences the steering torque. Before doing so, there is a risk of inconvenience of returning to the prescribed assist torque. An object of the present invention is to solve the above problems.

  SUMMARY OF THE INVENTION The present invention solves the above problems, and the invention of claim 1 is directed to a torque sensor that detects steering torque, a control device that controls motor current based on the detected steering torque, and assist torque to the steering mechanism. In an electric power steering apparatus having a motor to be supplied and generating an assist torque corresponding to the detected steering torque, an abnormality / recovery detection for detecting occurrence of abnormality of a control element constituting the steering system and normal return after occurrence of the abnormality And a gain setting means for outputting a gradually increasing gain on the condition that the driver experiences steering in a state where an assist torque based on the set gain is added and is not currently steering. The control device is configured to increase the gain set by the gain setting means when a normal return after occurrence of an abnormality of the control element is detected. An electric power steering apparatus characterized by controlling the motor so as to gradually increase the the assist torque based on the emissions.

  The control elements constituting the steering system include elements such as a battery and a motor, various sensors such as a torque sensor, a steering angle sensor, a motor angle sensor, a motor angular velocity sensor, a yaw rate sensor, and a temperature sensor, a power supply circuit, and a relay drive. Any one or more of various control unit (ECU) circuits such as a circuit, a sensor signal input circuit, a motor drive circuit, a motor current detection circuit, and a motor terminal voltage detection circuit are included.

  When the control device detects a normal return after the occurrence of an abnormality of the control element, the control device multiplies the steering torque detected by the torque sensor by the gradually increasing gain set by the gain setting means, and gradually increases it. It is assumed that the assist torque is gradually increased by controlling the motor with a current command value calculated based on the steering torque.

  Further, when a normal return after occurrence of abnormality of the control element is detected, the control device is set by the gain setting means to a current command value calculated based on the steering torque detected by the torque sensor. It is assumed that the assist torque is gradually increased by multiplying the gradually increasing gain and controlling the motor with the gradually increasing current command value.

  When a normal return after the occurrence of an abnormality of the control element is detected, the control device uses a gain setting means to set the duty determined by the current command value calculated based on the steering torque detected by the torque sensor. It is assumed that the assist torque is gradually increased by multiplying the set gradually increasing gain and controlling the motor with the gradually increasing duty.

  The gain set by the gain setting means is set to 1 when no abnormality occurs in the control element, and is gradually decreased by a predetermined step when the abnormality is detected in the control element. When a normal return after the occurrence of an abnormality is detected in the control element, the driver experiences steering with an assist torque based on a set gain and is gradually increased by a predetermined step on condition that the driver is not currently steering. Gain.

  The gain set by the gain setting means when a normal return after occurrence of an abnormality in the control element is detected is a state in which the steering torque at a certain point in time exceeds a predetermined torque upper limit threshold for a predetermined time or more, and When the steering torque is below the predetermined torque lower limit threshold for a predetermined time or more, it is determined that the driver has experienced steering with the assist torque based on the gain set at that time, and It is a gain that is gradually increased by a predetermined level as a condition.

  When an abnormality is detected in the control element, the final target value of the gain that is gradually reduced by a predetermined level is zero.

  When a normal return after occurrence of an abnormality in the control element is detected, the final target value of the gain that is gradually increased by a predetermined level is the gain set before the occurrence of the abnormality of the control element.

  According to the present invention, when the steering system returns to a normal state after the occurrence of an abnormality in the steering system, the assist torque is not changed during steering, and the assist torque is gradually increased step by step on the condition that the steering is not currently performed. The assist torque can be restored without giving the driver anxiety due to fluctuations in the steering torque. Even when the abnormal state and the return to the normal state are repeated, the assist torque is slowly increased, so that the behavior of the vehicle not intended by the driver can be suppressed, the steering handle can be operated safely, and the steering It is possible to provide an electric power steering apparatus including a control device that does not give an uncomfortable feeling to the steering wheel operation.

  Embodiments of the present invention will be described below. FIG. 1 is a diagram for explaining an outline of the configuration of an electric power steering apparatus suitable for carrying out the present invention. A shaft 2 of a steering handle 1 passes through a reduction gear 4, universal joints 5a and 5b, and a pinion rack mechanism 7. Coupled to the steering wheel tyrod 8. A torque sensor 3 that detects the steering torque of the steering handle 1 is provided on the shaft 2, and a motor 9 that assists the steering force is coupled to the shaft 2 via a reduction gear 4.

  A control device 10 that controls the electric power steering device is supplied with an ignition key signal from a battery 14 via an ignition key 11 and is supplied with electric power from a parallel power supply line. The control device 10 calculates a current command value based on the steering torque detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and generates a current i supplied to the motor 9 based on the calculated current command value. Control. The control device 10 has a plurality of embodiments for gradually decreasing and gradually increasing the assist torque. Hereinafter, description will be made sequentially.

[Control Device of First Embodiment]
The control apparatus 10 of 1st Example is demonstrated. In the first embodiment, a substitute torque T2 is calculated by multiplying the detected torque T1 by a gain G for gradually decreasing or gradually increasing, and a current command value I1 is calculated based on the substitute torque T2, and the assist torque is gradually decreasing / gradually increasing. To do.

  FIG. 2 is a block diagram for explaining the control device 10 of the first embodiment and its peripheral circuit elements. The main part of the control device 10 is composed of a CPU. Here, functions executed by a program in the CPU are shown.

  Reference numeral 21 denotes a control element that constitutes a steering system that requires limitation of assist torque according to the present invention. Here, the sensors are a torque sensor, a steering angle sensor, a motor angle sensor, a motor angular velocity sensor, and a yaw rate sensor. Various sensors such as a temperature sensor are included. The ECU circuit includes various circuits such as a power supply circuit, a relay drive circuit, a sensor signal input circuit, a motor drive circuit, a motor current detection circuit, and a motor terminal voltage detection circuit that constitute the control device 10.

  The signals output from these control elements 21 are input to the abnormality / return detection unit 22, and the abnormality / return detection unit 22 determines whether or not an abnormality that requires limitation of the assist torque has occurred in the control element 21. And whether or not it has returned to normal after the occurrence of an abnormality. The abnormality / return detection unit 22 detects the above-described abnormality occurrence and normal return after the abnormality has occurred by a known means.

  The gain setting unit 23 obtains a gain G for gradually decreasing or increasing the torque T1 based on the detected torque T1 and a signal output from the abnormality / recovery detection unit 22 indicating abnormality occurrence or normal return after occurrence of abnormality. Compute and output by known means. When the abnormality / return detection unit 22 detects that no abnormality has occurred, the gain G = 1 is calculated and output.

  The gradual decrease / gradual increase unit 24 multiplies the torque T1 detected by the torque sensor 3 by the gain G output from the gain setting unit 23, and outputs the alternative torque T2 that is gradually decreased or increased. The current command value calculation unit 25 receives the alternative torque T2 and the vehicle speed detected by the vehicle speed sensor 12, and calculates a current command value I1 based on a predetermined calculation formula.

  In the adder 26, feedback control is performed to subtract the motor current detection value Im detected by the motor current detection circuit 29 from the current command value I1, and the resulting motor current control value I is output to the duty calculator 27. . The duty calculator 27 calculates a duty D1 corresponding to the motor current control value I.

  The motor drive circuit 28 is, for example, a known H bridge circuit in which semiconductor switching elements are bridge-connected, and a battery serving as a power source by controlling the semiconductor switching elements on and off based on the input duty D1 and the motor rotation direction signal. The current supplied from 14 is controlled to drive the motor 9.

  The motor current detection circuit 29 detects the motor current flowing through the motor 9, and the detected motor current Im is fed back to the adder 26 described above.

  With the above configuration, when no abnormality is detected in the control element 21, the gain setting unit 23 is set to gain G = 1, and the gradual decrease / gradual increase unit 24 adds the gain G to the torque T 1 output from the torque sensor 3. = 1 is multiplied. That is, the torque T1 output from the torque sensor 3 is directly input to the current command value calculation unit 25, and the gradual decrease / increase processing of the torque T1 is not performed.

  As a result, when the detected steering torque is large and the detected vehicle speed is zero or low, the current command value I1 is set large, and when the detected steering torque is small and the detected vehicle speed is fast, the current command value I1 is set. Since the command value I1 is set small, an optimum steering assist force corresponding to the traveling state can be applied to the steering shaft.

  When occurrence of an abnormality is detected in the control element 21, the gain setting unit 23 gradually decreases the gain from 1 to a predetermined gain (for example, 0) at a constant rate or at a predetermined rate over a predetermined time. The gain G is calculated and set, and the gradual decrease / gradual increase unit 24 multiplies the torque T1 output from the torque sensor 3 by the gradually decreasing gain G to output the alternative torque T2.

  That is, the current command value calculation unit 25 calculates the current command value I1 with the alternative torque T2 that gradually decreases. As a result, the current command value I1 gradually decreases and the assist torque gradually decreases, so that the fail-safe process can be performed safely without causing the driver to feel uncomfortable.

  When a normal return is detected after an abnormality has occurred in the control element 21, the gain setting unit 23 gradually increases the gain to a predetermined gain G (for example, 1) at a constant rate or at a predetermined rate. The gradually increasing gain G is calculated and set, and the gradually decreasing / gradually increasing unit 24 multiplies the torque T1 output from the torque sensor 3 by the gradually increasing gain G to output the alternative torque T2.

  That is, the current command value calculation unit 25 calculates the current command value I1 with the gradually increasing alternative torque T2. As a result, the current command value I1 gradually increases and the assist torque gradually increases. Therefore, it is possible to perform a process of safely returning to the normal assist torque without causing the driver to feel uncomfortable.

  As described above, when the occurrence of an abnormality is detected in the control element 21 or when normal return is detected after the occurrence of the abnormality, the gain G is gradually reduced and gradually increased. Is executed when the steering torque is not generated, and the assist torque is not changed during the steering (when the steering torque is generated).

  Here, if a signal that can identify the type of abnormality is output from the abnormality / return detection unit 22 to the gain setting unit 23, the gain G, or a predetermined time that gradually decreases or increases according to the type of abnormality, is appropriately set. It becomes possible to perform finer gradual reduction or gradual increase processing that is set and adapted to the type / property of the abnormality.

  FIG. 3 is a timing chart for explaining the assist control processing when the control element returns from the abnormality occurrence state to the normal state, and the horizontal axis indicates time.

  FIG. 3A shows the abnormality / normality of the control element, and shows that the abnormality occurrence state has returned to normal at time S1. FIG. 3B shows how the steering torque fluctuates, FIG. 3C shows how the gain G increases, and FIG. 3D shows how the assist torque fluctuates.

  (1) When an abnormality occurrence state of the control element is detected, the gain G is gradually reduced to zero (0). Depending on the situation, it is immediately set to zero (see FIG. 3C).

  (2) When it is determined that the abnormality of the control element has returned to normal at time S1, the gain G is increased from zero (0) to G1 on the condition that steering torque is not generated (steering is completed) ( In this state, the input of a torque signal is awaited (see FIG. 3C).

  (3) A state where the torque is equal to or greater than the predetermined torque upper limit threshold TH (a value that is somewhat large as the torque) continues for a predetermined time ta or longer, and then a state that is less than the torque lower limit threshold TL (near the steering neutral position) continues for the predetermined time tb or longer. When this happens, it is determined that the driver has experienced a steering sensation with the gain G at that time.

  (4) Further, at time S2, the gain is increased from G1 to G2 on the condition that the steering torque is not generated (steering completion) (see FIG. 3C), and in this state, the torque signal is input. wait.

  (5) After that, the processes of (3) and (4) are repeated to increase the gain gradually in steps of G3 and G4, and finally the gain is repeated to Gn = target value (for example, Gn = 1). For example, in the case of return from overheat protection, etc., when a limit value for protection is set, a recovery process that loosens the limit value step by step is performed. As for the target value (eg, Gn = 1), the limit value allowed at that time becomes the target value.

  The gains G1, G2, G3... Gn are set at regular intervals. However, if the interval is not constant, it is not established, and settings such as unequal or gradually increasing the interval may be made.

  The torque upper threshold TH is set to an appropriate value in advance according to the vehicle type, vehicle grade, and the like. At this time, an appropriate value may be set in combination with each value of the gains G1 to Gn. It is not necessary to set the torque upper limit threshold TH to a constant value, and an appropriate value can be set individually. For example, TH1 = THn × G1, TH2 = THn × G2, and TH (n−1) = THn × G (n−1) may be set.

  The torque lower limit threshold value TL is a threshold value for determining whether or not the vehicle is in a steering state, and is determined in consideration of a value close to the steering neutral position but a dead zone of assist characteristics.

  The above-mentioned gains G1 to Gn, torque upper threshold TH, torque lower threshold TL, duration ta, duration tb, etc. may be stored in advance in a memory (not shown) of the control device.

  FIGS. 4 to 6 are flowcharts for explaining the assist control process executed by the control device 10 when the control element returns from the abnormality occurrence state to the normal state.

  First, the entire process will be described with reference to the flowchart of FIG. The ignition key (IG key) is turned on (step P11), the return flag B is reset (B ← 0) (step P12), the gain G is set to the reference value 1 (G ← 1) (step P13), and the torque upper threshold value TH Experience flag H is reset (H ← 0) (step P14), and durations ta and tb (see FIG. 3B) are reset (ta ← 0 and tb ← 0) (step P15).

  Here, “TH experience flag H” will be described. As described above, the state where the torque is equal to or greater than the predetermined torque upper limit threshold TH (a value that is somewhat large as torque) continues for the predetermined time ta or longer, and thereafter the state that is less than the torque lower limit threshold TL (near the steering neutral position) continues for the predetermined time tb or longer. When this happens, it is determined that the driver has experienced a steering sensation with the gain G at that time. The processing of predetermined times ta and tb, which will be described later, differs depending on whether or not the steering feeling at the gain G is experienced. For this reason, when it is determined that the steering feeling at the gain G is experienced, the TH experience flag H is set (see the flowchart of the duration processing shown in FIG. 6). The process of step P14 is resetting the TH experience flag H immediately after the ignition key (IG key) is turned on.

  It is determined whether the IG key is turned off (step P16). When it is not OFF, the output A of the abnormality / return detection unit 22 is read (step P17), and it is determined whether or not the output A indicates the occurrence of abnormality (A = 1?) (Step P18). Here, A = 1 indicates normality, and A = 0 indicates occurrence of abnormality.

  If the result of determination in step P18 is normal (A = 1), the state of the return flag B is determined (step P19), and if the return flag B is set (B = 1), the gain in the gain setting unit 23 G is gradually increased (step P20), and the process proceeds to step P21.

  If the return flag is not set (B ≠ 1) as a result of the determination in step P19, it is determined whether or not the gain G is the reference value (G = 1) (step P21), and the gain G is the reference value (G In the case of = 1), since the normal state has been restored, the process proceeds to Step P16 for the next assist control process. If it is determined in step P21 that the gain G is not the reference value (G = 1) (G ≠ 1), the duration process is executed (step P22), and the process proceeds to step P16.

  If the result of determination in step P18 is that an abnormality has occurred (A ≠ 1), the gain G after subtraction processing is output (step P23), the return flag B is set (B ← 1) (step P24), and the process proceeds to step P16. .

  The gain G gradually increasing process (gain processing subroutine) in the gain setting unit 23 shown in step P20 of the flowchart of FIG. 4 will be described with reference to the flowchart of FIG.

  The gain G is assumed to have a relationship of Gn> Gn-1> Gn-2> Gn-3...> G3> G2> G1.

  First, it is determined whether there is a relationship of (G ≧ G (n−1)) between the current gain G and the gain G (n−1) (step P31), and (G ≧ G (n−). 1) When the relationship of) is established, Gn (G ← Gn) is set to the gain G, THn (threshold corresponding to the gain G) (TH ← THn) is set to the torque upper threshold TH (Step P32), Move on to step P40. If it is determined in step P31 that the relationship (G ≧ G (n−1)) is not established, the process proceeds to step P33.

  Similarly, when there is a relationship of (G ≧ G (n−2)) between the current gain G and the gain G (n−2), Gn (G ← G (n−1)) is set to the gain G. Set, and set TH (n-1) (TH ← TH (n-1)) as the torque upper threshold TH, and the current gain G and the current torque upper threshold in the duration processing described later (see FIG. 6). (N-1) (m ← (n-1)) is set to the number m indicating TH (steps P33 and P34), and the process proceeds to step P40.

  Thereafter, the same processing is repeated, and when there is a relationship of (G ≧ G2) between the current gain G and the gain G2, G3 (G ← G3) is set to the gain G, and TH3 ( TH ← TH3) is set, 3 (m ← 3) is set to the number m indicating the current gain G and the current torque upper limit threshold TH (steps P35 and P36), and between the current gain G and the gain G1. When the relationship (G ≧ G1) is established, the gain G is set to G2 (G ← G2), the torque upper limit threshold TH is set to TH2, and the number indicating the current gain G and the current torque upper limit threshold TH 2 is set to m (m ← 2) (steps P37 and P38), and the process proceeds to step P40.

  If the relationship of (G ≧ G1) is not established between the current gain G and the gain G1 in the determination at Step P37, G1 (G ← G1) is set for the gain G, and TH1 is set for the torque upper limit threshold TH. Then, 1 (m ← 1) is set to the number m indicating the current gain G and the current torque upper limit threshold TH (step P39). The process proceeds to step P40, the return flag B is reset (B ← 0), the gain processing subroutine is terminated, and the process proceeds to step P21.

  The duration processing subroutine shown in step P22 of the flowchart of FIG. 4 will be described with reference to the flowchart of FIG.

  First, when the state where the torque is equal to or greater than a predetermined torque upper limit threshold TH (a value that is somewhat large as torque) continues for a predetermined time ta or longer, the driver experiences TH experience that is set as having experienced a steering sensation at the gain G at that time. It is determined whether or not the flag H is 1 (step P51). The TH experience flag H = 1 indicates that the steering feeling with the gain G at that time is experienced, and the TH experience flag H = 0 indicates that the steering feeling with the gain G at that time has not been experienced. Hereinafter, the TH experience flag H is simply referred to as “flag H”.

  If the flag H is 1 in the determination in step P51, it is determined whether or not there is a relationship of (T <TL) between the detected torque T and a preset torque lower limit threshold TL (step P52). If the relationship (T <TL) is not established, the duration tb is reset (tb ← 0) (step P58), and the process returns to the main routine (step P16).

  When the relationship of (T <TL) is established in the determination of step P52, it is determined whether or not there is a relationship of (tb ≧ t2) between the duration time tb and the preset time t2 (step P53). ), If the relationship of (tb ≧ t2) is not established, (tb + 1) is set as the duration tb (step P59), and the process returns to the main routine (step P16).

  If the relationship of (tb ≥t2) is established in the determination of step P53, in order to increase the gain, G (m + 1) (G ← G (m + 1)) is set as the gain G, and the gain G is set. Output (step P54), in order to increase the torque upper limit threshold TH, set TH (m + 1) (TH ← TH (m + 1)) as the torque upper limit threshold TH (step P55), and set the flag H to 0 ( Reset to H ← 0) (step P56), reset the durations ta and tb (ta ← 0, tb ← 0) (step P57), and return to the main routine (step P16).

  If it is determined in step P51 that the flag H is not 1, it is determined whether or not there is a relationship of (T ≧ TH) between the detected torque T and a preset upper threshold TH (step P60), If the relationship of T ≧ TH is not established, the duration ta is reset (ta ← 0) (step P64), and the process returns to the main routine (step P16).

  When the relationship of (T ≧ TH) is established in the determination of step P60, it is determined whether or not there is a relationship of (ta ≧ t1) between the duration time ta and the preset time t1 (step P61). ), If the relationship of (ta.gtoreq.t1) is not established, (ta + 1) is set as the duration ta (step P63), and the process returns to the main routine (step P16).

  If the relationship of (ta.gtoreq.t1) is established in the determination of step P61, the flag H is set to 1 (H ← 1) (step P62), and the process returns to the main routine (step P16).

[Control Device of Second Embodiment]
FIG. 7 is a block diagram for explaining the control device 30 of the second embodiment and its peripheral circuit elements. The difference from the control device 10 of the first embodiment is that, in the first embodiment, a substitute torque T2 is calculated by multiplying the detected torque T1 by a gain G for gradually decreasing or gradually increasing, and the current based on the substitute torque T2 is calculated. Although the command value I1 is calculated, in the second embodiment, the current command value I1 is calculated based on the detected torque T1, and the calculated current command value I1 is multiplied by the gain G to obtain the alternative current command value I2. However, there is no particular difference in other points.

  Hereinafter, the same components as those of the control device 10 of the first embodiment are denoted by the same reference numerals and description thereof will be omitted, and the configuration of the control device 30 of the second embodiment will be described focusing on the differences.

  The signal output from the control element 21 is input to the abnormality return detection unit 22, and the abnormality return detection unit 22 determines whether or not an abnormality that requires limitation of the assist torque has occurred in the control element 21 and after the abnormality has occurred. It is detected whether it has returned to normal.

  The current command value calculation unit 31 receives the torque T1 detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and calculates a current command value I1 based on a predetermined arithmetic expression.

  Based on the detected torque T1 and a signal indicating the occurrence of abnormality or normal return after occurrence of an abnormality, the gain setting unit 23 gain G for gradually decreasing or increasing the current command value I1. Is calculated and output. When the abnormality return detection unit 22 detects that no abnormality has occurred, the gain G = 1 is output.

  The gradual decrease / gradual increase unit 32 multiplies the current command value I1 input from the current command value calculation unit 31 by the gain G output from the gain setting unit 23, and outputs a current command value I2 that is gradually decreased or increased.

  The adder 33 performs feedback control for subtracting the motor current detection value Im detected by the motor current detection circuit 29 from the current command value I2, and outputs the motor current control value I as a result to the duty calculation unit 34. . The duty calculator 34 calculates a duty D1 corresponding to the motor current control value I.

  The motor drive circuit 28 is, for example, a known H bridge circuit in which semiconductor switching elements are bridge-connected, and a battery serving as a power source by controlling the semiconductor switching elements on and off based on the input duty D1 and the motor rotation direction signal. The current supplied from 14 is controlled to drive the motor 9.

  The motor current detection circuit 29 detects the motor current flowing through the motor 9, and the detected motor current Im is fed back to the adder 33 described above.

  With the above configuration, when no abnormality is detected in the control element 21, the gain G = 1 is set in the gain setting unit 23, and the input current command value I 1 is output as it is from the gradual decrease / gradual increase unit 32. The As a result, when the detected steering torque is large and the detected vehicle speed is zero or low, the current command value I1 is set large, and when the detected steering torque is small and the detected vehicle speed is fast, the current command value I1 is set. Since the command value I1 is set small, an optimum steering assist force corresponding to the traveling state can be applied to the steering shaft.

  When occurrence of an abnormality is detected in the control element 21, the gain setting unit 23 gradually decreases the gain from 1 to a predetermined gain (for example, 0) at a constant rate or at a predetermined rate over a predetermined time. The gain G is calculated and set, and the gradual decrease / gradual increase unit 32 multiplies the current command value I1 by the gradually decreasing gain G to output the gradually decreased current command value I2. As a result, the current command value I2 gradually decreases and the assist torque gradually decreases, so that the fail-safe process can be performed safely without causing the driver to feel uncomfortable.

  When a normal return is detected after an abnormality has occurred in the control element 21, the gain setting unit 23 gradually increases the gain to a predetermined gain G (for example, 1) at a constant rate or at a predetermined rate. The gradually increasing gain G is calculated and set, and the gradually decreasing / gradually increasing unit 32 multiplies the current command value I1 by the gain G and outputs the gradually increased current command value I2. As a result, the current command value I2 gradually increases and the assist torque gradually increases. Therefore, it is possible to perform a process of safely returning to the normal assist torque without causing the driver to feel uncomfortable.

  As described above, when the occurrence of an abnormality is detected in the control element 21 or when normal return is detected after the occurrence of the abnormality, the gain G is gradually decreased / increased. It is executed when the steering torque is not generated, and the assist torque is not changed during the steering (when the steering torque is generated).

[Control Device of Third Embodiment]
FIG. 8 is a block diagram for explaining the control device 50 of the third embodiment and its peripheral circuit elements. The difference from the control device 10 of the first embodiment is that, in the first embodiment, a substitute torque T2 is calculated by multiplying the detected torque T1 by a gain G for gradually decreasing or gradually increasing, and the current based on the substitute torque T2 is calculated. Although the command value I1 is calculated, in the third embodiment, the current command value I1 is calculated based on the detected torque T1, the duty D1 is calculated based on the current command value I1, and the gain G is set to the calculated duty. However, there is no particular difference in other points.

  Hereinafter, the same components as those of the control device 10 of the first embodiment are denoted by the same reference numerals, description thereof is omitted, and the configuration of the control device 50 of the third embodiment will be described focusing on the differences.

  The signal output from the control element 21 is input to the abnormality return detection unit 22, and the abnormality return detection unit 22 determines whether or not an abnormality that requires limitation of the assist torque has occurred in the control element 21 and after the abnormality has occurred. It is detected whether it has returned to normal.

  The current command value calculation unit 51 receives the torque T1 detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and calculates a current command value I1 based on a predetermined arithmetic expression.

  The adder 52 performs feedback control to subtract the motor current detection value Im detected by the motor current detection circuit 29 from the current command value I1, and outputs the motor current control value I as a result to the duty calculation unit 53. . The duty calculator 53 calculates a duty D1 corresponding to the motor current control value I.

  The gain setting unit 23 calculates a gain G for gradually decreasing or gradually increasing the duty D1 based on the detected torque T1 and a signal output from the abnormality recovery detection unit 22 indicating the occurrence of abnormality or normal recovery after the abnormality has occurred. And output. When the abnormality return detection unit 22 detects that no abnormality has occurred, the gain G = 1 is output.

  The gradual decrease / gradual increase unit 54 multiplies the duty D1 input from the duty calculation unit 53 by the gain G output from the gain setting unit 23, and outputs a gradually decreased or gradually increased duty D2.

  The motor drive circuit 28 is, for example, a known H-bridge circuit in which semiconductor switching elements are bridge-connected, and a battery serving as a power source by ON / OFF controlling the semiconductor switching elements based on the input duty D2 and the motor rotation direction signal. The current supplied from 14 is controlled to drive the motor 9.

  The motor current detection circuit 29 detects the motor current flowing through the motor 9, and the detected motor current Im is fed back to the adder 52 described above.

  With the above configuration, when no abnormality is detected in the control element 21, the gain G = 1 is set in the gain setting unit 23, and the duty D 1 input from the gradual decrease / gradual increase unit 54 is output as it is (D 2 = D1).

  As a result, when the detected steering torque is large and the detected vehicle speed is zero or low, the current command value I1 is set large, and when the detected steering torque is small and the detected vehicle speed is fast, the current command value I1 is set. Since the command value I1 is set small, an optimum steering assist force corresponding to the traveling state can be applied to the steering shaft.

  When occurrence of an abnormality is detected in the control element 21, the gain setting unit 23 gradually decreases the gain from 1 to a predetermined gain (for example, 0) at a constant rate or at a predetermined rate over a predetermined time. The gain G is calculated and set, and the gradual decrease / gradual increase unit 54 multiplies the duty D1 by the gradually decreasing gain G, and outputs the gradually decreased duty D2. As a result, the duty D2 gradually decreases and the assist torque gradually decreases, so that the fail-safe process can be performed safely without causing the driver to feel uncomfortable.

  When a normal return is detected after an abnormality has occurred in the control element 21, the gain setting unit 23 gradually increases the gain to a predetermined gain G (for example, 1) at a constant rate or at a predetermined rate. The gradually increasing gain G is calculated and set, and the gradually decreasing / gradually increasing unit 54 multiplies the duty D1 by the gradually increasing gain G to output the gradually increasing duty D2. As a result, since the duty D2 gradually increases and the assist torque gradually increases, it is possible to perform a process of safely returning to the normal assist torque without causing the driver to feel uncomfortable.

  As described above, when the occurrence of an abnormality is detected in the control element 21 or when normal return is detected after the occurrence of the abnormality, the gain G is gradually decreased / increased. It is executed when the steering torque is not generated, and the assist torque is not changed during the steering (when the steering torque is generated).

  Provided with a control device that can return the assist torque without causing the driver to feel uneasy due to fluctuations in the steering torque when the control element constituting the steering system returns to a normal state after an abnormal state has occurred. An electric power steering apparatus is provided.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the outline of a structure of the electric power steering apparatus suitable for implementing invention. The block diagram explaining the control apparatus of 1st Example, and its peripheral circuit element. The timing chart explaining the assist control process when returning from the abnormality occurrence state of the control element to the normal state. The flowchart explaining the assist control process performed with the control apparatus when returning from the abnormality occurrence state of a control element to a normal state (the 1). The flowchart explaining the assist control process performed with the control apparatus when it returns to a normal state from the abnormality occurrence state of a control element (the 2). The flowchart (the 3) explaining the assist control process performed with the control apparatus when it returns to a normal state from the abnormality occurrence state of a control element. The block diagram explaining the control apparatus of 2nd Example, and its peripheral circuit element. The block diagram explaining the control apparatus of 3rd Example, and its peripheral circuit element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Axis 3 Torque sensor 4 Reduction gear 5a, 5b Universal joint 7 Pinion rack mechanism 8 Tyrode 9 Motor 10 Control device (control device of 1st Example)
11 Ignition key (IG key)
DESCRIPTION OF SYMBOLS 12 Vehicle speed sensor 14 Battery 21 Control element which comprises steering system 22 Abnormal return detection part 23 Gain setting part 24 Gradual decrease / gradual increase part 25 Current command value calculation part 26 Adder 27 Duty calculation part 28 Motor drive circuit 29 Motor current detection circuit 30 Control device (control device of the second embodiment)
31 current command value calculation unit 32 gradual decrease / gradual increase unit 33 adder 34 duty calculation unit 50 control device (control device of third embodiment)
51 current command value calculation unit 52 adder 53 duty calculation unit 54 gradual decrease / gradual increase unit

Claims (9)

A torque sensor that detects steering torque, a control device that controls a motor current based on the detected steering torque, and a motor that supplies assist torque to the steering mechanism, and provides assist torque corresponding to the detected steering torque. In the electric power steering device to be generated,
Abnormality / return detection means for detecting the occurrence of abnormality of the control elements constituting the steering system and normal return after occurrence of the abnormality,
Gain setting means for outputting a gradually increasing gain on the condition that the driver experiences steering in a state where an assist torque based on the set gain is added and is not currently steering;
The control device controls the motor to gradually increase the assist torque based on a gradually increasing gain set by a gain setting means when a normal return after occurrence of abnormality of the control element is detected. Electric power steering device. The control elements constituting the steering system include elements such as a battery and a motor, torque sensors, steering angle sensors, motor angle sensors, motor angular velocity sensors, yaw rate sensors, temperature sensors and other various sensors, power supply circuits, relay drive circuits, The electric power steering according to claim 1, comprising any one or more of various control unit (ECU) circuits such as a sensor signal input circuit, a motor drive circuit, a motor current detection circuit, and a motor terminal voltage detection circuit. apparatus. When the control device detects normal return after occurrence of an abnormality of the control element, the control device multiplies the steering torque detected by the torque sensor by the gradually increasing gain set by the gain setting means, and gradually increases the steering torque. The electric power steering apparatus according to claim 1, wherein the assist torque is gradually increased by controlling the motor according to a current command value calculated based on the motor. The control device gradually increases the current command value calculated based on the steering torque detected by the torque sensor, which is set by the gain setting means, when normal return after occurrence of abnormality of the control element is detected. 2. The electric power steering apparatus according to claim 1, wherein the assist torque is gradually increased by multiplying the gain and controlling the motor with a gradually increased current command value. When a normal return after the occurrence of an abnormality of the control element is detected, the control device uses a gain setting means to set the duty determined by the current command value calculated based on the steering torque detected by the torque sensor. 2. The electric power steering apparatus according to claim 1, wherein the assist torque is gradually increased by multiplying a set gradually increasing gain and controlling the motor with the gradually increasing duty. The gain set by the gain setting means is set to 1 when no abnormality has occurred in the control element. When an abnormality has been detected in the control element, the gain is gradually reduced by a predetermined level. When a normal return after an abnormality has occurred in an element is detected, the driver experiences steering with an assist torque based on a set gain, and the gain is gradually increased by a predetermined step on condition that the driver is not currently steering The electric power steering apparatus according to claim 1, wherein: The gain set by the gain setting means when a normal return after the occurrence of an abnormality in the control element is detected means that the steering torque at a certain point in time exceeds a predetermined torque upper limit threshold for a predetermined time, and further, the steering torque Is less than the predetermined torque lower limit threshold for a predetermined period of time or longer, it is determined that the driver has experienced steering with assist torque based on the gain set at that time, and the vehicle is not currently steering. The electric power steering apparatus according to claim 1, wherein the gain is gradually increased by a predetermined level. The electric power steering apparatus according to claim 6 or 7, wherein when an abnormality is detected in the control element, the final target value of the gain that is gradually decreased by a predetermined level is zero. When a normal return after occurrence of an abnormality in the control element is detected, a final target value of the gain that is gradually increased by a predetermined level is a gain set before the occurrence of the abnormality of the control element. The electric power steering apparatus according to claim 6 or 7.

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