JP2009061844A - Motor controller for steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller for a steering device capable of preventing rapid reduction of assist force when an auxiliary power source is failed and ensuring action of electric equipment mounted on a vehicle by controlling load on a main power source. <P>SOLUTION: The motor controller for the steering device is provided with the main power source 4 for feeding electric power to the motor 1m of the steering device 1 of the vehicle; the auxiliary power source 9 capable of feeding electric power to the motor 1m; detection means 31, 32 for detecting failure of the auxiliary power source 9; and a control circuit 15 for gradually reducing the assist amount by the main power source 4 such that it becomes a predetermined assist amount after a predetermined time is passed from detection of failure when the failure of the auxiliary power source 9 is detected by the detection means 31, 32 when electric power is fed to the motor 1m by the main power source 4 and the auxiliary power source 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor control device for a steering device. More specifically, the present invention relates to a motor control device in a steering device that includes an auxiliary power source together with a main power source and uses the driving force of an electric motor.

  An electric power steering device mounted on a vehicle such as an automobile needs to pass a larger current through the motor as the required steering assist force is larger. Therefore, power is usually supplied to the motor from the in-vehicle battery, which is the main power source. However, when the terminal voltage of the main power source decreases due to an increase in load such as when entering the garage or parking, the auxiliary power previously stored is stored. A configuration has been proposed in which power is supplied from a power source to reduce the burden on the main power source (see, for example, Patent Document 1).

JP 2003-320942 A

By the way, when the power is supplied to the motor by the main power source (battery) and the auxiliary power source, if the auxiliary power source fails, the assist force suddenly decreases, so that the driver instantaneously feels the reaction force and the steering member The (steering wheel) becomes heavier and requires a lot of force for operation. When an operation is performed on the heavier steering member, the detected torque value increases, so the motor control device of the steering device tries to supply the necessary power from the battery.
However, if this state continues, it is conceivable that the terminal voltage of the battery decreases and power supply to other electrical devices of the vehicle becomes insufficient, affecting the operation of the electrical device.

  The present invention has been made in view of such circumstances, and prevents a sudden decrease in assist force when an auxiliary power source fails, and controls the load of the main power source to control the operation of electric equipment mounted on the vehicle. An object of the present invention is to provide a motor control device for a steering device that can be secured.

A motor control device for a steering device according to the present invention (hereinafter, also simply referred to as “motor control device”) includes a main power source that supplies power to a motor of a steering device for a vehicle,
An auxiliary power source capable of supplying power to the motor;
Detecting means for detecting a failure of the auxiliary power supply;
When power is supplied to the motor by the main power supply and the auxiliary power supply, when a failure of the auxiliary power supply is detected by the detection means, a predetermined assist amount is obtained after a predetermined time has elapsed since the failure was detected. And a control circuit for gradually reducing the amount of assist by the main power source.

  In the motor control device of the present invention, when power is supplied to the motor by the main power source and the auxiliary power source, when the auxiliary power source fails, the assist amount (assist force) is not drastically reduced and the original power is not reduced. The assist amount by only the main power source is gradually decreased over a predetermined time (for example, about 3 seconds). Therefore, when the auxiliary power supply is used together with the main power supply, even if the auxiliary power supply fails, the assist amount gradually decreases, so that the reaction force felt by the driver can be reduced. In addition, the main power assist amount is set to the main power original assist amount after a lapse of a predetermined time from the failure, so that the main power is consumed and its terminal voltage decreases, supplying power to other electrical equipment in the vehicle Can be prevented from becoming insufficient. As a result, a predetermined operation of the electric device can be ensured. In the present specification, the “assist amount by only the original main power supply” refers to the burden of the main power supply, that is, the assist amount when power is supplied to the motor by the main power supply and the auxiliary power supply. .

  In the control circuit, when the power is supplied to the motor by the main power source and the auxiliary power source, the assist amount by the main power source and the auxiliary power source is P, and the assist coefficient of the main power source is A (0 <A <1), When the assist coefficient of the auxiliary power source is (1-A), the assist amount at the time of failure detection is P, and the assist amount by the main power source is set to P × A after a predetermined time has elapsed since the failure detection. It can be configured to gradually decrease linearly. In this case, since the assist amount by the main power supply is gradually reduced so that the assist amount P at the time of failure detection becomes P × A after a predetermined time has elapsed, the reaction force felt by the driver can be reduced. Further, it is possible to prevent the main power from being consumed and the terminal voltage to be lowered, and the power supply to other electric devices of the vehicle becomes insufficient, thereby affecting the operation of the electric device.

  According to the motor control device of the present invention, it is possible to prevent the assist force from rapidly decreasing when the auxiliary power source fails, and to control the load of the main power source to ensure the operation of the electric device mounted on the vehicle.

Hereinafter, embodiments of a motor control device of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a circuit diagram of a motor control device 2 of an electric power steering device 1 according to an embodiment of the present invention. In FIG. 1, a steering assist force is applied to a vehicle steering device 1s by a motor 1m. More specifically, the motor 1m is driven and controlled according to the output (steering torque) of a torque sensor such as a torsion bar type attached to a steering shaft (not shown) of the steering device 1s, and the steering shaft or steering gear (rack) Assist to pinion, rack shaft, etc. The motor drive circuit 3 supplies power to the motor 1m.

  The main power supply 4 is composed of an in-vehicle battery 4b and an alternator 4a, and a diode 6 is provided in the middle of a non-grounded electric circuit 5 that guides the main power supply 4 to the motor drive circuit 3. . A smoothing electrolytic capacitor 8 is provided between the cathode of the diode 6 and the ground side electric circuit 7.

  On the other hand, the auxiliary power source 9 is composed of an electric double layer capacitor (capacitor) and is connected in series to the main power source 4. A power feeding circuit (high potential side circuit) 10 of the auxiliary power source 9 is connected to the motor driving circuit 3 via a discharge control circuit 11. The discharge control circuit 11 includes a MOS-FET 11a and a PWM voltage source 11b. The discharge current can be controlled by PWM controlling the gate voltage. The anode of the diode 13 is connected to the low potential side of the auxiliary power supply 9 via the reactor 12, and the cathode of the diode 13 is connected to the power supply circuit 10 of the auxiliary power supply 9. In addition, a MOS-FET 14 is provided between the anode of the diode 13 and the ground-side electric circuit 7. The protective diode 14d is connected in parallel to or built in the MOS-FET 14. The gate of the MOS-FET 14 is driven by the gate drive circuit 20.

  The motor drive circuit 3, the discharge control circuit 11 and the gate drive circuit 20 operate in response to a command signal from the control circuit 15. The control circuit 15 is adapted to receive information on the steering torque of the steering wheel by the driver and the vehicle speed, and the control circuit 15 generates appropriate steering assist force in accordance with the information. The motor 1m is driven.

  When the MOS-FET 14 is in the on state, current flows from the alternator 4a through the reactor 12 and the MOS-FET 14, but when the MOS-FET 14 turns off, a high voltage is applied to the reactor so as to prevent magnetic flux change due to current interruption. Thus, the auxiliary power supply 9 is charged with a voltage obtained by boosting the output of the alternator 4a. In this way, the auxiliary power supply 9 can be charged by repeatedly turning on and off the MOS-FET 14.

  In the above configuration, when the required steering assist force is relatively small, the control circuit 15 turns off the discharge control circuit 11. Therefore, the voltage of the main power supply 4 is smoothed by the smoothing capacitor 8 and then supplied to the motor drive circuit 3. The motor drive circuit 3 drives the motor 1 m based on the control signal from the control circuit 15. On the other hand, the voltage of the auxiliary power supply 9 is not supplied to the motor drive circuit 3.

  Further, when the required steering assist force is relatively large and cannot be covered by the main power supply 4 alone, the control circuit 15 turns on the discharge control circuit 11. As a result, the current defined by the discharge control circuit 11 is supplied to the motor drive circuit 3 based on the voltage of the main power supply 4 and the auxiliary power supply 9 in series with each other.

  A current detector 31 for detecting a discharge current from the auxiliary power source 9 made of a capacitor is disposed in the power feeding circuit 10. A voltage detector 32 for detecting the voltage between the terminals of the auxiliary power supply 9 is provided. Each signal from the current detector 31 and the voltage detector 32 is transmitted to the control circuit 15.

  When the auxiliary power source (capacitor) 9 breaks down due to a short circuit due to a decrease in internal resistance, a ground fault of a terminal, or the like, a discharge current from the auxiliary power source 9 detected by the current detector 31 or a voltage detector 32 is detected. The voltage between the terminals of the auxiliary power supply 9 to be abruptly decreased or becomes zero. When the control circuit 15 determines that the auxiliary power supply 9 has failed based on the signals from the current detector 31 and the voltage detector 32, the control circuit 15 determines a predetermined assist amount only by the main power supply 4 after the predetermined time has elapsed (immediately before the failure of the auxiliary power supply). A PWM control signal is transmitted to the motor drive circuit 3 so that the assist amount is borne by the power supply 4). The motor drive circuit 3 adjusts the duty ratio according to the PWM control signal and supplies a predetermined amount of power to the motor 1m. The predetermined time is not particularly limited in the present invention, but is usually about 1 to 10 seconds in consideration of a reaction force received by the driver due to a decrease in steering assist force, consumption of main power, and the like.

  FIG. 2 is an explanatory diagram showing an example of the time variation of the assist amount by the main power supply and the auxiliary power supply. The horizontal axis indicates time (seconds) and the vertical axis indicates the assist coefficient A. The origin of the horizontal axis (zero) is when a failure of the auxiliary power supply is detected, the main power burden ratio (assist coefficient) of the motor auxiliary energy up to this time is 0.5, and the auxiliary power burden ratio (assist coefficient) is also the same 0.5. This ratio changes depending on the required steering assist force, and the assist power supply burden ratio (assist coefficient) increases as the required steering assist force increases.

  In the example shown in FIG. 2, if the assist amount until the auxiliary power supply failure is P, the main power supply bears 0.5P, and the auxiliary power supply bears 0.5P. When a failure of the auxiliary power supply is detected, the control circuit 15 drives the motor so that it gradually decreases linearly to the original assist amount of the main power supply, that is, the assist amount before the auxiliary power supply failure is 0.5P after 5 seconds. A PWM control signal is transmitted to the circuit 3. Therefore, the assist amount does not rapidly decrease and gradually decreases linearly from P to 0.5P, so that the reaction force felt by the driver can be reduced. In addition, the main power assist amount is set to the main power original assist amount after a lapse of a predetermined time from the failure, so that the main power is consumed and its terminal voltage decreases, supplying power to other electrical equipment in the vehicle Can be prevented from affecting the operation of the electrical device. Note that the change in the assist coefficient from the time of the auxiliary power supply failure until the lapse of a predetermined time is not limited to the linear change shown in FIG. 2, but can be changed, for example, in a curved line.

  If it is determined by the control circuit 15 that the auxiliary power supply 9 has failed, a failure signal is transmitted from the control circuit 15 to the alarm means 33. As the alarm means 33, a display means such as a liquid crystal display element, a plasma display element, a lamp, and a sound generating means such as a buzzer can be used in appropriate combination. When a failure signal from the control circuit 15 is received, the alarm means 33 assists the driver. Notify that the power supply 9 has failed.

  The steering device according to the present invention is not limited to an electric power steering device that applies a steering assist force to the steering mechanism by an electric motor. For example, a mechanical device between an operation member such as a steering wheel and the steering mechanism is used. Also included is a steer-by-wire system that eliminates the link and steers the steered wheels exclusively by the driving force of the electric motor.

It is a circuit diagram of one embodiment of a control device of a steering device of the present invention. It is explanatory drawing which shows the example of the time change of assist amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 1s Steering apparatus 1m Motor 2 Motor control apparatus 3 Motor drive circuit 4 Main power supply 4a Alternator 4b Car-mounted battery 9 Auxiliary power supply 15 Control circuit 31 Current detector 32 Voltage detector 33 Alarm means

Claims (2)

A main power source for supplying electric power to a motor of a vehicle steering device;
An auxiliary power source capable of supplying power to the motor;
Detecting means for detecting a failure of the auxiliary power supply;
When power is supplied to the motor by the main power supply and the auxiliary power supply, when a failure of the auxiliary power supply is detected by the detection means, a predetermined assist amount is obtained after a predetermined time has elapsed since the failure was detected. A motor control device for a steering device, comprising: a control circuit that gradually reduces an assist amount by the main power source.   In the control circuit, when the power is supplied to the motor by the main power source and the auxiliary power source, the assist amount by the main power source and the auxiliary power source is P, and the assist coefficient of the main power source is A (0 <A <1), When the assist coefficient of the auxiliary power source is (1-A), the assist amount at the time of failure detection is P, and the assist amount by the main power source is set to P × A after a predetermined time has elapsed since the failure detection. The motor control device for a steering device according to claim 1, wherein the motor control device is gradually decreased linearly.

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