JP5076415B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to a motor for interrupting the power supply line, which is inserted in a power supply line between an electric motor that applies a steering assist force to the steering system and a motor drive circuit that supplies electric power to the electric motor. The present invention relates to an electric power steering control device capable of avoiding a system down due to a malfunction of a relay circuit.

In this type of electric power steering control device, when an abnormality such as a short circuit failure occurs in a field effect transistor (FET) constituting the motor drive circuit, the electric motor may operate as an electromagnetic brake. In order to avoid this, each terminal voltage of the electric motor is detected, and when the terminal voltage exceeds a preset allowable range, it is determined that there is a fault such as a power fault or a ground fault, and the power supply line to the electric motor is determined. The motor relay inserted in is cut off, and the electric motor is prevented from acting as an electromagnetic brake (see, for example, Patent Document 1).
International Publication No. WO 98/58833 Pamphlet

  As described above, in a system in which a motor relay is inserted in the power supply line to the electric motor, a normally open type relay is used as the motor relay, and the electric motor is controlled by closing the motor relay when the system is activated. When an abnormality occurs, the motor relay is controlled to be in an open state to cut off the power supply to the electric motor, thereby preventing the electric motor from acting as an electromagnetic brake.

In such a system, the motor relay is normally closed when the system is started, but it is not confirmed whether the motor relay is reliably closed by this control, and the motor relay is closed. After the control is performed, the process shifts to the normal control for generating the steering assist force as it is.
For this reason, if the motor relay is not closed for some reason, even if the current control is performed after the shift to the normal control and the power supply to the electric motor is actually started, the motor relay is not opened. Since it remains in the state, power supply is not normally performed. As a result, the difference between the current command value to the electric motor and the current value actually flowing to the electric motor becomes large, and it is determined that an abnormality has occurred at this point.

For this reason, for example, if a motor relay does not close due to a continuity-inhibiting substance sandwiched between the contacts of the motor relay, the motor relay is closed even though the system itself has not failed. Therefore, there is a problem that the system is determined to be abnormal, and thereafter the system cannot be operated normally and the steering assist force cannot be generated.
In fact, when a motor relay operation confirmation test or the like is performed, a conduction-inhibiting substance that may have prevented contact connection inside the motor relay may be confirmed.

In the electric power steering control device, a motor relay is provided between the electric motor and a motor drive circuit for driving the electric motor, and a power source is also connected between the power source for supplying power to the motor drive circuit. A relay is provided, and the motor relay and the power relay usually use the same type of relay circuit in many cases.
When the motor relay and the power supply relay are composed of the same type of relay circuit, there is no difference in process, and therefore the possibility that a conduction inhibiting substance is mixed is considered to be equivalent. However, when an operation check test or the like is actually performed, no conduction abnormality has occurred in the power relay. This is because an inrush current flows when the power supply relay is turned on, and even if a conduction inhibiting substance is interposed between the relay contacts, it can be assumed that the inrush current is burned out. it can.

Originally, the motor relay is provided in order to prevent the electric motor from acting as an electromagnetic brake when an abnormality occurs. However, although the system itself is normal, it is detected as a motor relay failure due to the conduction-inhibiting substance, so it is determined that the system needs to be stopped, and the system can operate as an electric power steering device. After that, the driver is forced to perform a considerably heavy steering operation without power assist. This has a great impact on the future size increase of the vehicle and the system itself, and there has been a demand for an electric power steering control device that can operate reliably even if it takes some time to start up the control system. .
Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and it is possible to prevent the system from being down due to the influence of the conduction inhibiting substance even though the control system itself is normal. It is an object of the present invention to provide a possible electric power steering control device.

In order to achieve the above object, an electric power steering control device according to claim 1 of the present invention includes an electric motor that applies a steering assist force to a steering system, a motor drive circuit that drives and controls the electric motor, A motor relay circuit having a normally-open movable contact that cuts off a power supply line between the motor drive circuit and the electric motor; a conduction state detection unit that detects an actual conduction state of the motor relay circuit; The energizing means for energizing the motor relay circuit without going through the electric motor and the motor relay circuit in the non-conducting state by the conducting state detecting means even though the motor relay circuit is controlled to be in the conducting state. When this is detected, conducting the energization to activate the energization means to burn out the conduction-inhibiting substance that prevents conduction between the contacts of the motor relay circuit. And a recovery control means, the conducting recovery control means, the when the motor relay circuit in a conducting state detecting means detects that a non-conductive state, switching control means for a plurality of times opening and closing the motor relay circuit And detecting the conduction state each time the motor relay circuit is opened / closed a plurality of times by the opening / closing control means after the conduction state detection means detects that the motor relay circuit is in a non-conduction state. It is determined whether or not the continuity-inhibiting substance has been removed, and the continuity state detecting means detects that the motor relay circuit is in a continuity state until the motor relay circuit is opened and closed a predetermined number of times. If not, when the motor relay circuit is opened and closed a plurality of times while the energizing means is operated and energized by the energizing means When it is not detected that the motor relay circuit is in a conducting state by the conduction state detecting unit until the energization for a preset specified time by the energizing unit is completed by repeating the process of determining whether or not there is, The motor relay circuit is judged to be abnormal .

According to the first aspect of the present invention, when the motor relay circuit is controlled to be in the conductive state and the conductive state detecting means detects that the motor relay circuit is in the non-conductive state, the power supply means is activated. Then, the motor relay circuit is energized without going through the electric motor, and for example, the conduction-inhibiting substance that prevents conduction between the contacts of the motor relay circuit, such as foreign matter such as dust, is burned out, and the conductive state is brought about. Recovery is planned.
Further, when it is detected that the motor relay circuit is in a non-conduction state, the opening / closing operation of the motor relay circuit is performed by the opening / closing control means. Therefore, the conduction-inhibiting substance that prevents conduction between the contacts of the motor relay circuit is removed. It becomes possible.
In addition, after detecting that the motor relay circuit is in a non-conducting state, the motor relay circuit is in a conducting state by the conducting state detecting unit until the opening / closing control unit opens and closes the motor relay circuit a specified number of times. Is detected, that is, when the motor relay circuit is not in a conducting state even if the specified number of opening / closing operations are performed, the energizing means is activated to burn out the conduction inhibiting substance due to energization. In other words, after the conduction-inhibiting substance is removed by the opening and closing operation, the conduction-inhibiting substance is burned out by energization. Is avoided.
Furthermore, when it is not detected that the motor relay circuit is in a conducting state until the energization for a preset specified time by the energizing means is completed, that is, the motor relay circuit does not become in a conducting state even if energized for a specified time. Sometimes, it is determined that the motor relay circuit is abnormal.

The electric power steering control device according to claim 2 is characterized in that the conduction recovery control means controls the energization means so that the energization amount to the motor relay circuit gradually increases.
According to the second aspect of the present invention, the motor relay circuit is energized so that the energization amount to the motor relay circuit gradually increases.
According to a third aspect of the present invention, in the electric power steering control device, the continuity recovery control means limits the energization amount to the motor relay circuit to a value at which a movable contact cannot be welded to the motor relay circuit. It is characterized by.
According to the third aspect of the present invention, the energization amount to the motor relay circuit is limited to a value at which the movable contact cannot be welded to the motor relay circuit. The occurrence of welding is avoided.

According to a fourth aspect of the present invention , in the electric power steering control device, the motor drive circuit includes an H bridge circuit that controls a drive current to the electric motor, and an upper arm and a lower arm of each phase of the H bridge circuit; The electric motor is connected between the H bridge circuit and the electric motor, and the motor relay circuit is interposed between the H bridge circuit and the electric motor, wherein the energizing means includes the motor relay circuit and The current supply source connected between the electric motors and the switch means constituting the lower arm connected to the motor relay circuit, and the conduction recovery control means starts the current supply by the current supply source And the switch means are PWM controlled.

According to the fourth aspect of the present invention, the energizing means is constituted by the current supply source connected between the motor relay circuit and the electric motor, and the switch means constituting the lower arm and connected to the motor relay circuit. Because it is configured, energization is performed through a path consisting of a current supply source, a motor relay circuit, and switch means constituting the lower arm, and the amount of energization can be easily controlled by PWM control of the switch means. It becomes.

Furthermore, in the electric power steering control device according to claim 5 , the energization means includes a current supply source, and a plurality of switching elements for energization control connected in series between the current supply source and the motor relay circuit. The conduction recovery control means is characterized in that the plurality of switching elements are controlled to be cut off when the motor relay circuit is not energized, and the plurality of switching elements are controlled to be conducted when the motor relay circuit is energized.

According to the invention described in claim 5 , the energizing means includes a current supply source and a plurality of switching elements for energization control connected in series between the current supply source and the motor relay circuit. Yes. Then, the conduction recovery control means controls the switching of the plurality of switching elements when the motor relay circuit is not energized, and controls the conduction when energized. By providing a plurality of switching elements for energization control, even if a continuity abnormality that remains in a conductive state occurs in any of the switching elements, the motor relay is controlled by controlling the other switching elements to be cut off. The energization to the circuit is cut off.

According to the electric power steering control device of the first aspect of the present invention, it is detected by the conduction state detecting means that the motor relay circuit is in the non-conduction state even though the motor relay circuit is controlled to the conduction state. In some cases, the energization means is activated and the energization is performed to burn out the conduction inhibiting substance that prevents conduction between the contacts of the motor relay circuit to the motor relay circuit without going through the electric motor. As a result, the motor relay circuit cannot be conducted, so that the possibility of the electric power steering control device being down can be reduced.
Further, when it is detected that the motor relay circuit is in a non-conducting state, the opening / closing control means opens and closes the motor relay circuit. It is possible to remove the conduction-inhibiting substance that hinders the above.
In addition, when it is detected that the motor relay circuit is in a non-conducting state, and it is not detected that the motor relay circuit is in a conducting state before the opening / closing control means opens and closes the motor relay circuit a specified number of times. Since the conduction-inhibiting substance is burned by energization by operating the energizing means, it is avoided that the conduction-inhibiting substance that can be removed by the opening / closing operation is burned by energization, and the power consumption is reduced accordingly. Can be planned.
Further, when the motor relay circuit does not become conductive until the energization of the predetermined time set by the energization means is completed, it is determined that the motor relay circuit is abnormal, so that the energization is avoided indefinitely. be able to.

Further, according to the electric power steering control device of the second aspect, since the motor relay circuit is energized so that the energization amount to the motor relay circuit gradually increases, a large current is suddenly applied to the motor relay circuit. It is possible to avoid premature wear and welding of the contacts due to the energization.
Further, according to the electric power steering control device of the third aspect, the energization amount to the motor relay circuit is limited to a value at which the welding of the movable contact cannot occur in the motor relay circuit. It is possible to avoid welding in the relay circuit.

Also, according to the electric power steering control apparatus according to claim 4, energization at a current source connected between the motor relay circuit and the electric motor, a switch means constituting the lower arm connected with the motor relay circuit Therefore, the current path composed of the current supply source, the motor relay circuit and the switch means constituting the lower arm can be easily formed, and the switch means can be easily controlled by PWM control. The energization amount can be controlled.

Furthermore, according to the electric power steering control device of the fifth aspect , since the plurality of switching elements for energization control connected in series between the current supply source and the motor relay circuit are provided, even any one of the switching elements In addition, even when a continuity abnormality that remains in the conductive state occurs, the energization to the motor relay circuit can be cut off by controlling the switching of the other switching elements.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, in which 1 is a steering wheel, and a steering force applied to the steering wheel 1 from a driver is transmitted to a steering shaft 2. . This steering shaft 2 has an input shaft 2a and an output shaft 2b, one end of the input shaft 2a is connected to the steering wheel 1, and the other end is one end of the output shaft 2b via a torque sensor 3 as torque detecting means. It is connected to.
The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6.

  The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured as a rack and pinion mechanism having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A reduction gear 10 that transmits an auxiliary steering force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The electric motor 12 that generates an auxiliary steering force for the steering system is connected to the reduction gear 10. The output shaft is connected.
The torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b is used. The torsional angular displacement is converted into an angular displacement and detected by, for example, a potentiometer. The torque detection value T output from the torque sensor 3 is input to the controller 13.

As shown in FIG. 2, the controller 13 has a steering assist control unit 17 having a microcomputer 16 that executes control processing of the electric motor 12 and a motor drive current I _M output from the microcomputer 16 in a known procedure. A motor drive circuit 18 that controls the drive current that is input and supplied to the electric motor 12, a motor current detection circuit 19 that detects the drive current flowing through the electric motor 12, a voltage detection circuit 25 between the motor terminals, and a voltage detection between the relay terminals A circuit 26 is provided.

Here, the motor driving circuit 18, an H-bridge circuit 20 formed of field effect transistors FET1 to FET4, to drive the gates of the respective field effect transistors FET1 to FET4 based on the motor driving current _{I M} that is output from the microcomputer 16 The FET gate drive circuit 21 is configured, and an internal voltage Vr generated inside the controller 13 is applied to a connection point between the field effect transistors FET1 and FET2, and the field effect transistors FET3 and FET4 are used for motor current detection described later. It is grounded via a shunt resistor 20r. An electric motor 12 is connected between a connection point of the field effect transistors FET1 and FET3 and a connection point of the field effect transistors FET2 and FET4, and a connection line between the connection point and the electric motor 12 is connected via a resistor. The internal voltage Vr is applied.

  The motor relay unit 40 includes a motor relay circuit 43 including a movable contact 41 and a relay coil 42 that energizes the movable contact 41, and a pnp type bipolar as an applied voltage control active element that controls an applied voltage to the relay coil 42. The movable contact 41 is connected between the connection point of the field effect transistors FET2 and FET4 of the H bridge circuit 20 and one input side of the electric motor 12, and one end of the relay coil 42 is grounded. The other end is connected to the collector terminal of the transistor TR. An internal voltage Vb is applied to the emitter terminal of the transistor TR, and a relay-on signal Ss from the microcomputer 16 is input to the base terminal. When this relay-on signal Ss is input, the transistor TR becomes conductive and relays. A voltage is applied to the coil 42 and the motor relay circuit 43 is controlled to be in a conductive state.

The motor current detecting circuit 19 detects a driving current I _MD flowing through the electric motor 12 based on the voltage across the shunt resistor 20r. The motor terminal voltage detection circuit 25 inputs the potentials of the connection points of the field effect transistors FET2 and FET4 and the connection points of the field effect transistors FET1 and FET3, and detects the terminal voltage ΔVm of the electric motor 12 based on these. To do. The relay terminal voltage detection circuit 26 inputs the potentials of the movable contact 41 and the fixed contact 41a of the motor relay circuit 43, and detects the relay terminal voltage ΔVr, which is the voltage between the relay terminal contacts, based on these potentials. These detection signals are input to the microcomputer 16 via an A / D converter.

The inter-motor terminal voltage detection circuit 25 detects the inter-terminal voltage ΔVm of the electric motor 12 by arranging pull-up resistors at both ends of the motor line.
Similarly, the voltage detection circuit 26 between the relay terminals also inputs the potential at both ends of the motor relay circuit 43 to the connection point between the resistors of the known voltage dividing circuit, and generates an intermediate voltage obtained by dividing the internal voltage Vr. As a reference, the relay terminal voltage ΔVr of the motor relay circuit 43 is detected.
As a result, normality / abnormality can be determined even in an initial state where the motor drive circuit 18 is not driven or in a state where the motor relay circuit 43 is not in a conductive state.

  A forced energization circuit 50 is provided between the electric motor 12 and the motor relay circuit 43 to directly energize the motor relay circuit 43 from a battery (not shown). In this forced energization circuit 50, a resistor R50 having one end connected to the battery and field effect transistors FET11 and FET12 as switching elements for energization control are connected in series in this order, and the other end of the field effect transistor FET12 is The motor relay circuit 43 and the electric motor 12 are connected. A forced energization signal Sr from the microcomputer 16 is input to the gate terminals of the field effect transistors FET11 and FET12. When the forced energization signal Sr is input, the field effect transistors FET11 and FET12 are both in a conductive state, and an output current of a battery (not shown) is supplied to the motor relay circuit 43 via the resistor R50 and the field effect transistors FET11 and FET12. Then, energization to the fixed contact 41a of the motor relay circuit 43 is performed.

  Here, two field effect transistors FET11 and FET12 are connected in series in consideration of conduction failure of the field effect transistor FET as a switching element for energization control. However, the two switching switches for energization control are not necessarily used. It is not necessary to use an element, and this switching element may be one. As described above, when a plurality of switching elements for energization control are connected in series, the forced energization circuit 50 malfunctions when any of the switching elements has a conduction abnormality that remains in a conductive state. Since the possibility of doing so can be reduced, the reliability can be further improved.

The microcomputer 16 is activated when an ignition switch (not shown) is turned on, and controls the motor relay circuit 43 to a conduction state and executes an initial diagnosis process for confirming the conduction. Further, the microcomputer 16 executes the steering assist control process when the motor relay circuit 43 is controlled to be conductive by the initial diagnosis process, and detects the torque detection value T detected by the steering torque sensor 3 and the vehicle speed sensor 15. The detected vehicle speed V, the steering angle from the steering angle sensor 14 for detecting the steering angle φ of the steering wheel 1, the motor terminal voltage ΔVm detected by the motor terminal voltage detection circuit 25 and the relay terminal voltage detection circuit 26. Based on various detection signals such as the relay terminal voltage ΔVr, the steering assist command value I _M ^* for generating the steering assist force according to the torque detection value T and the vehicle speed detection value V by the electric motor 12 is a known procedure. in calculated by the calculated steering assist command value I _M ^* and the motor current detection value I _MD, Fidoba the drive current supplied to the electric motor 12 Calculating a motor driving current I _M to click control.

FIG. 3 is a flowchart showing an example of the processing procedure of the initial diagnosis processing.
In the microcomputer 16, when an ignition switch (not shown) is turned on and the microcomputer 16 is activated, this initial diagnosis process is executed.
First, in step S1, the motor relay circuit 43 is controlled to a conductive state. That is, the relay on signal Ss for operating the bipolar transistor TR is output. As a result, the bipolar transistor TR is turned on, the battery voltage is applied to the relay coil 42, the relay coil 42 is excited, and the movable contact 41 is activated.

  Next, the process proceeds to step S2, and it is confirmed whether or not the motor relay circuit 43 is in an on state, that is, a conduction state. This confirmation is made based on whether or not the relay terminal voltage ΔVr detected by the relay terminal voltage detection circuit 26 is substantially zero, that is, whether the voltages at both the contacts of the motor relay circuit 43 are equal. When the relay terminal voltage ΔVr is substantially zero, it is determined that the motor relay circuit 43 is in a conductive state, and the processing is ended as it is.

  On the other hand, when the motor relay circuit 43 is not in the conductive state, the process proceeds to step S3 to open / close the motor relay circuit 43. That is, the output of the relay on signal Ss to the motor relay circuit 43 is temporarily stopped and then output again. It should be noted that the number of opening / closing operations may be one or more. Then, an open / close counter N for counting the number of times the motor relay circuit 43 is opened / closed is incremented by “1”. The open / close counter N is reset to zero at the time of activation.

Next, the process proceeds to step S4. When the open / close counter N has not reached the specified value Nth, the process returns to step S2 to determine whether or not the motor relay circuit 43 is in a conductive state. The processes from step S2 to step S4 are repeated, and the opening / closing operation of the motor relay circuit 43 and the continuity determination are repeated.
When the open / close counter N reaches a specified value Nth (for example, “4”), the process proceeds from step S4 to step S5, and the forced energization counter M reaches a preset threshold value Mth (for example, “4”). Determine whether it has been reached. The forced energization counter M is a counter for measuring a period during which forced energization processing described later is performed, and is reset to zero at the time of activation.

If the forced energization counter M has not reached the threshold value Mth, the process proceeds to step S6. If the forced energization counter M is zero at this time, the process proceeds to step S7, and the field effect transistor of the forced energization circuit 50 is obtained. Forcibly energizing signal Sr for conducting these is output to FET 11 and FET 12 and the forcible energizing process is started.
In this forced energization process, only the field effect transistor FET4 connected to the movable contact 41 of the motor relay circuit 43 among the transistors in the lower arm of the H bridge circuit constituting the motor drive circuit 18 is subjected to PWM control, and other electric fields are controlled. The effect transistors FET1 to FET3 are kept open.

  Since the fixed contact 41a of the motor relay circuit 43 is energized by the forced energization circuit 50, the forced energization circuit 50, the motor relay circuit 43, and the field effect transistor FET4 are interposed between the battery voltage Vb and the ground. A current path connected in series is formed, and when the field effect transistor FET4 is subjected to PWM control in this state, a current corresponding to the duty ratio flows.

Here, when foreign matter such as dust is mixed between the movable contact 41 and the fixed contact 41a of the motor relay circuit 43, energization is performed through the foreign matter, and the foreign matter is generated by the energy of the energization current. Can be burned out.
Therefore, in the forced energization process, the field effect transistor FET4 is subjected to PWM control so that the energization current gradually increases, and foreign matter between the relay contacts is burned out. In addition, an upper limit value is provided for the energization current, and it is configured to avoid welding between the relay contacts. Here, the reason why the energization current is gradually increased is to prevent the contact from being quickly worn out and welded by the excessive current and to close the contact earlier.

  Next, the process proceeds to step S8, and after the above-described forced energization counter M is incremented by “1”, the process returns to step S2 to determine whether or not the motor relay circuit 43 is in a conductive state. While the conductive state is not established, the processing from step S2 to step S4 is repeated, and when the number of opening and closing operations N reaches the threshold value Nth, the process proceeds to step S5, and the forced energization counter M has not reached the threshold value Mth. Sometimes the forced energization counter M is not zero, so the process proceeds from step S5 to step S6 to step S8, and the forced energization counter M is incremented by “1” and then returns to step S2.

  While the motor relay circuit 43 is not in a conductive state, the energization amount by forced energization is increased while the motor relay circuit 43 is opened and closed, and the forced energization counter M reaches a threshold value Mth (for example, “4”). When the process proceeds from step S5 to step S10, it is determined that the motor relay circuit 43 is abnormal, and the process at the time of error determination is performed. For example, the output of the relay ON signal Ss to the motor relay circuit 43 is stopped, the motor relay circuit 43 is controlled to be in an open state, the forced energization process is stopped, and the forced energization circuit 50 is forced to the field effect transistors FET11 and FET12. The output of the energization signal Sr is stopped. Further, an alarm device (not shown) installed in the vicinity of the driver's seat is activated to notify the driver that the motor relay circuit 43 is abnormal in conduction. Then, the process ends.

FIG. 4 is a flowchart showing an example of a processing procedure of the steering assist control process, which is equivalent to a known steering assist control process. The microcomputer 16 executes the steering assist control process at a predetermined cycle set in advance.
That is, first, in step S11, various sensors and detection circuits such as the steering torque sensor 3, the vehicle speed sensor 15, the steering angle sensor 14, the motor current detection circuit 19, the voltage detection circuit 25 between motor terminals, and the voltage detection circuit 26 between relay terminals. , The process proceeds to step S12, and the steering assist command value I _M ^* is detected by a known procedure based on the torque detection value T detected by the steering torque sensor 3 and the vehicle speed detection value V detected by the vehicle speed sensor 15 ^. Is calculated.

Then, the process proceeds to step S13, and then proceeds estimated motor angular velocity ω in step S14 performs the following operation expression (1) based on the motor current detection value I _MD and motor terminal voltage .DELTA.Vm.
_{ω = (ΔVm-I MD ·} Rm) / K 0 ...... (1)
Here, Rm denotes a motor winding resistance of the electric motor 12, K ₀ is the electromotive force constant of the motor.

  In step S14, a convergence control value Ic (= Kv · ω) is calculated by multiplying the estimated motor angular speed ω and the gain Kv set based on the vehicle speed detection value V, and then the process proceeds to step S15. A handle return control value Ih is calculated by executing a handle return control process. The steering wheel return control process may be performed by a known procedure. For example, the steering wheel return basic current value Ib corresponding to the steering angle θ detected by the steering angle sensor 14 is multiplied by the vehicle speed sensitive gain Gv corresponding to the vehicle speed detection value V. Thus, the steering wheel return basic control value Ibv is calculated.

  When the steering angular velocity θ ′ obtained by differentiating the steering angle θ is “0”, it is determined that the steering wheel 1 is stopped, and the steering wheel return control value Ih is set to “0”. When the steering angular velocity θ ′ is not “0” and the sign of the steering angle θ does not match the sign of the steering angular speed θ ′, it is during the steering wheel return to return the steering wheel 1 to the neutral position, that is, the straight traveling position. Judgment is made and the handle return basic control value Ibv is set as the handle return control value Ih. On the contrary, when the sign of the steering angle θ and the sign of the steering angular speed θ ′ match, it is determined that the steering wheel 21 is steered in the direction away from the neutral position, and the steering wheel return control value Ih is set to “0”. Set to.

Next, the process proceeds to step S16, where the torque detection value T is differentiated to calculate the center response improvement command value Ir for ensuring the stability in the assist characteristic dead zone and compensating for the static friction, and then the process proceeds to step S17. Then, the steering assist command value I _M ^* is added to the convergence control value Ic, the steering wheel return control value Ih, and the center response improvement compensation value Ir to calculate the steering assist compensation value I _M ^* ′, and then the process proceeds to step S18. To do.

In step S18, the steering assist compensation value I _M ^* ′ is differentiated to calculate a differential value Id for feedforward control. Then, the process proceeds to step S19, calculates a current deviation ΔI by subtracting the read in step S11 from the steering assist compensation value I _{M *} ^'motor current detection value I _MD, then the process proceeds to step S20, the current A proportional value ΔIp for proportional compensation control is calculated by performing a proportional calculation process on the deviation ΔI, and then the process proceeds to step S21 where an integral calculation process is performed on the current deviation ΔI to calculate an integral value ΔIi for integral compensation control.
Next, the process proceeds to step S22, where the motor current command value I _M (= Id + ΔIp + ΔIi) is calculated by adding the differential value Id, the proportional value ΔIp and the integral value ΔIi, and then the process proceeds to step S23. the calculated motor current command value I _M the processing is ended to the motor drive circuit 18.

Next, the operation of the above embodiment will be described.
When an ignition switch (not shown) is turned on, the microcomputer 16 performs a predetermined startup process and then starts the initial diagnosis process of FIG. 3 and outputs a relay-on signal Ss (step S1). As a result, the bipolar transistor TR becomes conductive, the battery voltage Vb is applied to the exciting coil 42, and the movable contact 41 is activated.
At this time, when the movable contact 41 and the fixed contact 41a are in a conductive state, the relay terminal voltage ΔVr detected by the relay terminal voltage detection circuit 26 becomes substantially zero. Since it is determined that the connection state is established, the process is terminated as it is from step S2.

Then, since the motor relay circuit 43 is in a conductive state and power can be supplied to the electric motor 12, the steering assist control process shown in FIG. 4 is executed, and the steering assist according to the torque detection value T and the vehicle speed detection value V is executed. The electric motor 12 is driven and controlled so that a force is generated.
On the other hand, if the voltage ΔVr between the relay terminals is not substantially zero after the motor relay circuit 43 is controlled to be in the conductive state, it is determined that there is a possibility that the motor relay circuit 43 has a continuity abnormality. After shifting to S3 and opening / closing the motor relay circuit 43, it is determined again based on the voltage ΔVr between the relay terminals (step S2). The process of step S4 is repeated, and the conduction state is confirmed each time the motor relay circuit 43 is opened and closed.

  By performing this opening / closing operation, the foreign matter sandwiched between the relay contacts of the motor relay circuit 43 is removed or the connection failure is eliminated, so that when the motor relay circuit 43 becomes conductive, the voltage ΔVr between the relay terminals is Since it becomes substantially zero, when this is detected, the processing is terminated as it is from step S2. Then, the steering assist control process shown in FIG. 4 is started. On the other hand, if the motor relay circuit 43 does not become conductive even though the motor relay circuit 43 has been opened and closed for the specified number of times Nth, it is difficult to remove foreign matters by the opening and closing operation of the motor relay circuit 43. In order to burn out foreign matter by forced energization.

  That is, the forced energization signal Sr is output to make the field effect transistors FET11 and FET12 of the forced energization circuit 50 conductive, and the forced energization process is started, and among the field effect transistors FET1 to FET4 of the motor drive circuit 18, While the FET 3 is in an open state, only the FET 4 is subjected to PWM control to form a current path including the forced energization circuit 50 to which the battery voltage Vb is applied, the motor relay circuit 43, and the field effect transistor FET4. (Step S5 to Step S7).

As a result, the motor relay circuit 43 is energized through foreign matter or the like, and when foreign matter is mixed between the relay contacts, the foreign matter is burned out by the energized energy. Then, after incrementing the forced energization counter M, the process returns to step S2 to confirm the continuity again. When the continuity is not established, the motor relay circuit 43 is opened and closed again.
Then, while energizing the motor relay circuit 43, the motor relay circuit 43 is opened and closed, and the foreign matter is removed by burning the foreign matter due to energization or removing the foreign matter due to the opening and closing operation. When ΔVr becomes substantially zero, it is determined that the conduction state is established, and the process is terminated from step S2.

  On the other hand, when the energization to the motor relay 43 by the forced energization circuit 50 or the opening / closing operation of the motor relay 43 is not performed, the process starts from step S5 when the forced energization counter M reaches the threshold value Mth. The process proceeds to step S10, where the continuity abnormality of the motor relay circuit 43 is confirmed, the motor relay circuit 43 is controlled to be in an open state, and the continuity abnormality of the motor relay circuit 43 is activated to the driver by operating an alarm device (not shown). Notice. Further, the forced energization circuit 50 is deactivated, and the forced energization process is terminated.

  Thus, after controlling the motor relay circuit 43 to the conducting state, it is confirmed whether or not the conducting state is established. If it is not confirmed that the conducting state is established, the motor relay circuit 43 is opened and closed to perform relaying. Since the foreign matter sandwiched between the contacts is removed, or the motor relay circuit 43 is forcibly energized to burn out the foreign matter sandwiched between the relay contacts, the motor relay circuit 43 is determined to be abnormal in conduction. The possibility of being reduced can be reduced. Therefore, even though the electric power steering control device itself is normal, a foreign matter is caught between the relay contacts of the motor relay circuit 43, etc. The possibility of becoming can be reduced.

  In particular, in the case of mechanical relays that are designed to move through the relay piece, foreign matter mixed between the relay piece and the fixed contact can be removed by opening / closing the relay or burning the foreign matter due to energization of the relay. Therefore, when a conduction abnormality of the motor relay circuit 43 is detected, it is effective to recover the conduction abnormality by positively performing these operations.

In addition, since the motor relay circuit 43 is opened and closed in this way and burned out, it is not limited to foreign matters such as dust, but, for example, an oxide film formed on the contact surface of the motor relay circuit 43, etc. It is also possible to remove the continuity-inhibiting substance that prevents conduction between the contacts of the motor relay circuit 43.
Further, the motor relay circuit 43 is energized through the forced energization circuit 50 and not through the electric motor 12. Therefore, the electric motor 12 is not rotated by energizing the motor relay circuit 43, and it is not intended to avoid the driver from feeling uncomfortable due to the steering assist force acting on the steering wheel 1. Can do.

  Further, even when the energization control switching element for operating the forced energization circuit 50 is maintained in a conductive state due to an abnormality or the like, as shown in FIG. Since two connected field effect transistors FET11 and FET12 are provided, the motor relay circuit 43 is not energized unless both of them become abnormal. Therefore, it is possible to reduce the possibility that the motor relay circuit 43 is unintentionally energized due to an abnormality of the field effect transistor as the switching element for energization control.

Furthermore, when the forced energization is performed, the energization is performed so that the energization current gradually increases, so that it is possible to prevent early wear of the contacts and the occurrence of welding.
Whether the motor relay circuit 43 is in a conductive state is determined by measuring the voltage between the contacts of the motor relay circuit 43. Here, in the steering assist control process, drive control of the electric motor 12 is performed using the voltage between the terminals of the electric motor 12, and the terminal voltage of the electric motor 12 is connected to the motor relay circuit 43 of the electric motor 12. The measured voltage Vm− and the other voltage Vm + are measured. Therefore, since the voltage Vm− on the side connected to the motor relay circuit 43 can be used as the voltage on one terminal side of the motor relay circuit 43, the voltage on the other terminal side of the motor relay circuit 43 can be measured. That's fine. Therefore, it is possible to detect the voltage across the relay terminals of the motor relay circuit 43 without a significant circuit change.

Furthermore, since the motor relay circuit 43 is opened and closed after the foreign matter is burned out in the motor relay circuit 43, burnout of the foreign matter can be surely removed, and more effectively. Recovery to a conductive state can be achieved.
In the above embodiment, the case where the drive control of the electric motor 12 is performed using the voltage between the terminals of the electric motor 12 is described. However, the present invention is not limited to this, and the motor current detected by the motor current detection circuit 19 is described. Even when the drive control is performed based on the above, it can be applied.

In the above embodiment, the case where the motor relay circuit 43 is opened / closed and the motor relay circuit 43 is energized has been described. However, the present invention is not limited to this, and only the opening / closing operation or only energization is performed. It is also possible to remove foreign matter with
In the above embodiment, the case where the motor relay circuit is interposed between the one terminal of the electric motor 12 and the motor drive circuit has been described. However, the present invention is not limited to this. Even when a motor relay circuit is inserted between each of the terminals and the motor drive circuit, the present invention can be applied. In this case, the other current supply line is also provided with a forced energization circuit. A current path including a forced energization circuit, a motor relay circuit, and an FET 3 connected to the motor relay circuit may be configured, and the forced energization circuit may be common to both power supply lines.

Furthermore, for example, a motor relay circuit interposed between a three-phase motor and a three-phase bridge circuit can be applied. In this case, too, the lower arm of each phase connected to the motor relay circuit is used. It is only necessary to form a current path for each phase.
Here, in the above embodiment, the relay terminal voltage detection circuit 26 and the process of step S2 in FIG. 3 correspond to the conduction state detection means, the forced energization circuit 50 and the transistor FET4 correspond to the energization means, and FIG. The processing from step S2 to step S10 corresponds to the conduction recovery control means.
Further, the processing in step S3 and step S4 in FIG. 3 corresponds to the opening / closing control means.
The forced energization circuit 50 corresponds to the current supply source, and the transistor FET4 corresponds to the switch means.

It is a schematic structure figure showing one embodiment of the present invention. FIG. 2 is a block diagram illustrating a specific configuration of the controller in FIG. 1. It is a flowchart which shows an example of the process sequence of the initial diagnosis process performed with the microcomputer of FIG. It is a flowchart which shows an example of the process sequence of the steering assistance control process performed with the microcomputer of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Torque sensor 8 Steering gear 10 Reduction gear 12 Electric motor 13 Controller 14 Steering angle sensor 15 Vehicle speed sensor 16 Microcomputer 18 Motor drive circuit 19 Motor current detection circuit 20 H bridge circuit 21 FET gate drive circuit 25 Motor Voltage detection circuit between terminals 26 Voltage detection circuit between relay terminals 41 Movable contact 41a Fixed contact 42 Relay coil 43 Motor relay circuit 50 Forced energization circuit TR Bipolar transistor

Claims (5)

An electric motor for applying a steering assist force to the steering system;
A motor drive circuit for driving and controlling the electric motor;
A motor relay circuit having a normally-open movable contact for cutting off a power supply line between the motor drive circuit and the electric motor;
Conduction state detecting means for detecting an actual conduction state of the motor relay circuit;
Energization means for energizing the motor relay circuit without going through the electric motor;
When the motor relay circuit is controlled to be in a conducting state, the conducting state detecting means detects that the motor relay circuit is in a non-conducting state, and the energizing means is operated to A conduction recovery control means for conducting electricity to burn out the conduction-inhibiting substance that prevents conduction between the contacts ,
The conduction recovery control means has an opening / closing control means for opening and closing the motor relay circuit a plurality of times when the conduction state detection means detects that the motor relay circuit is in a non-conduction state,
After detecting that the motor relay circuit is in a non-conductive state by the conductive state detecting means, the conductive state is determined by determining the conductive state every time the open / close control means opens and closes the motor relay circuit. The energization is performed when the conduction state detecting means does not detect that the motor relay circuit is in a conducting state until it is determined whether the motor relay circuit has been removed and the operation for opening and closing the motor relay circuit is performed a predetermined number of times. Actuate the means,
While conducting energization by the energization means, repeatedly performing a process of determining whether or not the motor relay circuit is opened and closed multiple times,
When the conduction state detection means does not detect that the motor relay circuit is in a conduction state before the conduction for a predetermined time set in advance by the conduction means, it is determined that the motor relay circuit is abnormal. An electric power steering control device.   2. The electric power steering control device according to claim 1, wherein the conduction recovery control means controls the energization means so that an energization amount to the motor relay circuit gradually increases.   3. The electric motor according to claim 1, wherein the continuity recovery control unit limits the amount of current supplied to the motor relay circuit to a value at which a movable contact cannot be welded to the motor relay circuit. Power steering control device. The motor drive circuit includes an H bridge circuit that controls a drive current to the electric motor, and the electric motor is connected between an upper arm and a lower arm of each phase of the H bridge circuit, and the H bridge circuit An electric power steering control device in which the motor relay circuit is inserted between the motor and the electric motor,
The energizing means includes a current supply source connected between the motor relay circuit and the electric motor, and a switch means constituting the lower arm connected to the motor relay circuit,
The electric power according to any one of claims 1 to 3 , wherein the conduction recovery control means controls the start of current supply by the current supply source and performs PWM control of the switch means. Steering control device. The energization means includes a current supply source and a plurality of switching elements for energization control connected in series between the current supply source and the motor relay circuit,
The conducting recovery control means, said when not energized to the motor relay circuit control block the plurality of switching elements, one of claims 1 to 4, at the time of energization, characterized in that conduction control the plurality of switching elements The electric power steering control device according to claim 1.

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