JP6752508B2 - Electric power steering device - Google Patents

Description

The present invention relates to an electric power steering device that assists steering operation by adding auxiliary torque.

The electric power steering device detects the steering torque by the driver and adds a predetermined auxiliary torque to the detected steering torque by the electric power steering motor. Then, in a general electric power steering device, the deviation of the current command value according to the steering torque detected by the torque sensor from the motor current of the electric power steering motor is proportionally and integratedly compensated by the proportional integration controller, and the power supply of the battery is supplied. The command voltage of the electric power steering motor is derived within the voltage range to drive and control the electric power steering motor to generate auxiliary torque.

However, when the driver operates the steering at high speed to the left or right, there is a period in which the motor current does not follow the current command value due to the induced voltage and control gain of the electric power steering motor, which causes the current command value. If a deviation occurs between the motor current and the motor current and the integration term increases with time, and the electric power steering device is in the rack-end state in such a situation, the steering cannot be operated any more and the motor rotates. since the speed is zero instantaneously, the induced voltage caused by the rotation of the electric power steering motor is rapidly extinguished, abrupt current flows to the motor by the integral term that has been increased, the so-called overshoot occurs However, the overcurrent caused by the overshoot causes the inconvenience that the drive circuit element that drives and controls the motor is damaged.

In order to eliminate such inconvenience, conventionally, an overshoot estimation means for estimating the overshoot of the motor current, a proportional sensitivity of the proportional / integral control means, and a proportional / integral coefficient setting means for controlling at least one of the integral gains are provided. An electric power steering device has been proposed (Patent Document 1).

Japanese Patent No. 323030 (paragraph 0030-0042, see FIG. 2)

However, the device described in Patent Document 1 described above requires an overshoot estimation means that takes a motor current as an input, determines whether the input motor current is greater than a predetermined value larger than the target current, and estimates an overshoot. Therefore, there is a problem that the configuration becomes complicated.

An object of the present invention is to make it possible to prevent overshoot in a rack-end state by a simple configuration in an electric power steering device.

In order to achieve the above object, the electric power steering device of the present invention includes a torque detection unit that detects the steering torque of the steering and the steering in the electric power steering device that assists the steering operation by adding an auxiliary torque. An electric power steering motor that generates auxiliary torque to be added to the torque detection means, a current command value setting unit that sets a current command value according to the torque detected by the torque detecting means, the current command value, and the motor current of the electric power steering motor. A proportional integration control unit that proportionally and integrally compensates for the deviation from the above, a motor drive unit that drives the electric power steering motor based on the output of the proportional integration control unit, and an induced voltage that estimates the induced voltage of the electric power steering motor. and a estimation unit, the proportional integral control unit, the integral term voltage by the proportional-integral compensation is controlled so as not to exceed the difference between the induced voltage and the power supply voltage estimated by the induced voltage estimation unit It features.

According to the present invention, since the electric power steering motor cannot apply a voltage higher than the power supply voltage of a battery or the like, the induced voltage Vr generated in the electric power steering motor with rotation is integrated with the proportional integration control unit. The sum (= Vr + Vi) with the term voltage Vi does not exceed the power supply voltage Vb. For example, the induced voltage Vr of the electric power steering motor is estimated by the induced voltage estimation unit based on the motor rotation speed, and the proportional integration control unit estimates the induced voltage Vr. , Electric power steering driven by the motor drive unit by controlling the integral term voltage Vi so that the integrated term voltage Vi does not exceed the difference between the induced voltage Vr estimated by the induced voltage estimator and the power supply voltage Vb. The drive voltage of the motor is always controlled to be equal to or lower than the power supply voltage Vb, and the simple configuration can prevent the occurrence of overshoot even in the rack-end state.

It is a block diagram of one Embodiment of the electric power steering apparatus which concerns on this invention. It is an operation explanatory view of FIG.

An embodiment of the electric power steering device according to the present invention will be described in detail with reference to FIGS. 1 and 2.

The electric power steering device (hereinafter, electric power steering is referred to as EPS) 1 of the present embodiment is configured as shown in FIG. That is, as shown in FIG. 1, it is the "torque detection unit" of the present invention that detects the steering torque of the steering (not shown) in the EPS ECU (Electric Control Unit) 3 having a microcomputer configuration that controls the EPS motor 2. The sensor output from the torque sensor 4 is input, the current command value corresponding to the current detected torque value is set by the current command value setting unit 31, and the deviation between the set current command value and the motor current of the EPS motor 2 is calculated. It is derived by the subtractor 32, and the derived deviation is proportionally / integrated compensated by the proportional integration control unit 33. At this time, the optimum relationship between the detected torque value and the current command value is experimentally obtained in advance, and is stored in the current command value setting unit 31 as a map, for example.

The proportional integration control unit 33 includes an integration element 33a having an integration gain (Ki) 33a1 and an integration term (1 / s) 33a2, and a proportional element 33b having a proportional gain (Kp), and outputs the integration element 33a and the proportional element 33b. Is added by the adder 34, and a gain provided to estimate the induced voltage proportionally from the output of the adder 34 and the output of the rotation speed sensor (not shown) that detects the rotation speed of the EPS motor 2. The induced voltage estimation element 35 of (Ke) is added by the adder 36, and a predetermined drive voltage is applied to the EPS motor 2 by the motor drive unit 37 composed of the H bridge circuit connected to the battery 5 mounted on the vehicle. To. Here, the induced voltage estimation element 35 corresponds to the "induced voltage estimation unit" in the present invention.

By the way, as shown in FIG. 1, in the present embodiment, the output of the induced voltage estimation element 35 is configured to be input to the integration term 33a2 of the integration element 33a, and the battery 5 input to the integration term 33a2. Based on the power supply voltage Vb of the above and the induced voltage Vr of the EPS motor 2 estimated by the induced voltage estimation element 35, the integrated term voltage Vi according to the integral term 33a2 is limited to the value obtained by subtracting the induced voltage Vr from the power supply voltage Vb. It has become so.

Now, when the electric power steering device is in the rack-end state while the driver is operating the steering wheel at high speed to the left or right, the voltage applied to the motor is the induced voltage Vr of the EPS motor 2 and the integrating element. It is the sum of the integration term voltage Vi according to the integration term 33a2 of 33a, but in the rack-end state, these sums exceed the power supply voltage Vb as shown in FIG. 2A, and overshoot occurs. At this time, the integration term voltage Vi is controlled to a value that does not exceed the difference between the power supply voltage Vb and the induced voltage Vr estimated by the induced voltage estimation element 35. Therefore, as shown in FIG. 2B, the motor The drive voltage of the EPS motor 2 driven by the drive unit 37 is always limited to the power supply voltage Vb or less, and overshoot does not occur.

Therefore, according to the above-described embodiment, since the EPS motor 2 cannot apply a voltage equal to or higher than the power supply voltage Vb of the battery 5, the induced voltage Vr generated in the EPS motor 2 with rotation and proportional integration control The sum (= Vr + Vi) of the integrated term voltage Vi by the unit 33 does not exceed the power supply voltage Vb, and based on the motor rotation speed, the induced voltage Vr of the EPS motor 2 is provided by the induced voltage estimation element 35 which is the induced voltage estimation unit. Is estimated, and the integral term voltage Vi that does not exceed the difference between the power supply voltage Vb and the induced voltage Vr estimated by the induced voltage estimation element 35 is derived by the integral term 33a2 of the proportional integration control unit 33, thereby driving the motor. The drive voltage of the EPS motor 2 driven by the unit 37 is always controlled to be equal to or lower than the power supply voltage Vb, and overshoot is performed even in the rack-end state by a simple configuration without providing an overshoot estimation means as in the conventional case. Can be prevented from occurring.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.

For example, in the embodiment described above, an induced voltage estimation unit and the induced voltage estimation element 35, but to detect the motor rotational speed has been described for the case of estimating the induced voltage of the EPS motor 2 by the rotation-side sensor, the induced voltage estimation element The input of 35 may be an induced voltage estimated value based on the motor applied voltage and the motor current, or the induced voltage itself.

1 ... EPS device (electric power steering device)
2 ... EPS motor (electric power steering motor)
3 ... EPSECU
4 ... Torque sensor (torque detector)
5 ... Battery 31 ... Current command value setting unit 33 ... Proportional integration control unit 33a2 ... Integration term 35 ... Induced voltage estimation element (Induced voltage estimation unit)
37 ... Motor drive unit Vb ... Power supply voltage Vr ... Induced voltage Vi ... Integral voltage

Claims (1)

In an electric power steering device that assists steering operation by adding auxiliary torque
A torque detector that detects the steering torque of the steering wheel and
An electric power steering motor that generates auxiliary torque applied to the steering, and
A current command value setting unit that sets a current command value according to the torque detected by the torque detecting means, and a current command value setting unit.
A proportional integration control unit that proportionally and integrally compensates for the deviation between the current command value and the motor current of the electric power steering motor.
A motor drive unit that drives the electric power steering motor based on the output of the proportional integration control unit,
It is provided with an induced voltage estimation unit that estimates the induced voltage of the electric power steering motor.
The proportional integration control unit
An electric power steering device characterized in that the integral term voltage by the proportional / integral compensation is controlled so as not to exceed the difference between the induced voltage and the power supply voltage estimated by the induced voltage estimation unit.

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