JP2662953B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric steering apparatus that eliminates rotor inertia of an electric motor. (Prior Art) In the conventional electric power steering apparatus shown in FIG. 4, a torque sensor 2 is connected to a steering wheel 1, and this torque sensor 2 is connected to a function generator 3 and a differentiating circuit 4. A vehicle speed sensor 5 is also connected to the function generator 3 so that the function generator 3 outputs a torque signal according to the vehicle speed. The output signal of the function generator 3 and the output signal of the differentiating circuit 4 are added and input to the steering angle correction circuit 6. The steering angle sensor 7 is connected to the steering angle correction circuit 6, and the difference between the actual steering angle and the operation angle of the steering wheel 1 is corrected. The sign of the steering angle signal corrected as described above is discriminated by the sign discrimination circuit 8 and transmitted to the electric motor 9.
When a steering angle signal is transmitted to the electric motor 9, the electric motor 9 is driven according to the signal, and the tire 11 is transmitted through the speed reducer 10.
To steer. The differentiating circuit 4 is provided to correct a phase delay between the output signal of the torque sensor 2 and the motor torque of the electric motor 9. That is, since the inertia of the rotor acts on the electric motor 9, the phase of the motor torque b is delayed with respect to the torque signal a as shown in FIG. Therefore, the differentiating circuit 4 is provided to correct the delay. (Problems to be Solved by the Present Invention) In the conventional device as described above, when the handle is turned to a predetermined position and then the handle is released to release the handle, the magnet of the electric motor at that time is attracted. Cogging torque is generated by force. Since the cogging torque acts as a force against the return of the steering wheel, there is a problem that the return performance of the steering wheel is correspondingly deteriorated. It is an object of the present invention to provide an electric power steering device capable of canceling cogging torque. (Means for Solving the Problems) The present invention includes an electric power steering device that includes a function generation circuit that outputs an output torque signal according to running conditions such as a vehicle speed, and controls an electric motor with an output signal of the function generation circuit. Is assumed. On the premise of the above-described device, the present invention connects an angle sensor that detects a steering angle, an angle signal processing circuit that outputs a voltage signal according to the output of the angle sensor, and the angle signal processing circuit, An inverting circuit for inverting the output signal,
A limiter circuit that generates a voltage of an output signal of the inverting circuit by an attraction force of a magnet of the electric motor and limits the voltage to a set value for canceling a cogging torque acting as a force against the return of the steering wheel; It is characterized in that it has an addition circuit to which each signal of the circuit is input, and a motor drive circuit controlled according to the output signal of this addition circuit. (Operation of the Present Invention) Since the present invention is configured as described above, the signal output from the angle signal processing circuit is inverted by the inverting circuit. Moreover, the voltage output from the inverting circuit is limited by the limiter circuit to a set value for canceling the cogging torque. Therefore, when releasing the handle from the handle and returning it to the neutral position, the cogging torque is offset. (Effect of the Present Invention) According to the electric power steering device of the present invention,
When releasing the handle from the handle and returning it to the neutral position, the cogging torque generated by the attraction of the magnet of the electric motor and acting as a force against the return of the handle can be offset, thereby improving the return performance of the handle. be able to. In other words, it is possible to maintain almost the same return performance as in the case of manual steering. (Embodiment of the Present Invention) In the embodiment shown in FIGS. 1 to 3, the pinion 13 is connected to the tip of the steering input shaft 12 connected to the steering wheel H,
This pinion 13 is engaged with the rack 14. Both sides of the rack 14 are connected to knuckle arms 17 of wheels 16 via side rods 15. Further, a speed reducer 18 is connected to the electric motor m which can be rotated forward and backward. A pinion is provided on the output shaft side of the speed reducer 18 via an electromagnetic clutch 19.
The pinion 20 is engaged with the rack 14. Further, the input shaft 12 is provided with a torque sensor 21 for detecting a steering torque acting on the input shaft 12, and an angle sensor 22 for detecting the steering angle. Further, a vehicle speed sensor 23 for detecting a vehicle speed of the vehicle,
An axial force sensor 24 for detecting the axial force of the rack 14 is provided, and these sensors are connected to the motor control device mc. The torque signal Tin detected by the torque sensor 21 is input to a torque signal processing circuit 25 provided in the motor control device mc and a torque sensor abnormality detection circuit 26. The signal V ₁ output from the torque signal processing circuit 25 is
The signal is input to a forward / reverse direction determination circuit 27 for determining the direction of the torque, and is also input to an absolute value circuit. The torque forward and reverse signal T ₀ which is output from the determination circuit 27 is inputted to the input port A ₁ microprocessor P striking the function generator circuit of the present invention. The signal V ₁ input to the absolute value circuit 28 is converted into an absolute value there. The absolute value | V ₁ | is converted into a digital value by the A / D conversion circuit 29. The torque level signal T ₁ which is converted into the digital value is input to the input port A ₂ of the microprocessor P, the torque level signal T _1, for example, in the case of 8bit, | V ₁ | = 0 is zero, | V ₁ | = max corresponds to 256. The vehicle speed signal v detected by the vehicle speed sensor 23 is transmitted to the vehicle speed signal processing circuit 30 of the motor control device mc and the vehicle speed sensor abnormality detection circuit.
Enter 31. The signal processed by the vehicle speed signal processing circuit 30 is transmitted to an interrupt port of the microprocessor.
Input to INT1. Note that the vehicle speed signal processing circuit 30 outputs a pulse train corresponding to the vehicle speed, for example, 0 pulses / sec, 40 km /
A pulse train of 40 pulse / sec at h and 100 pulse / sec at 100 km / h is output. When the pulse signal rises or falls, an interrupt is generated at the interrupt port INT1. The axial force signal detected by the axial force sensor 24 is sent to the axial force signal processing circuit 32 and the axial force sensor abnormality detection circuit 33 of the motor control device mc.
To enter. Then, the signal V ₃ processed in this axial force signal processing circuit 32, via the forward and reverse direction determining circuit 34, the axial force signal
Input to the input port A ₃ of the microprocessor P as F _0. Further, the output signals of the abnormality detection circuits 26, 31, and 33 are input to the interrupt port INT2 of the microprocessor P via the OR gate 35. From the output port C ₁ of the microprocessor P,
Output by the forward and reverse signals M ₀ to identify the rotational direction of the electric motor m, from the output port C _2, the output level signal M ₁ of the digital value is output, these output level signals M _0, M ₁ is
The torque output signal V ₄ is converted into an analog signal by the D / A conversion circuit 36, and the output signal V ₄ is input to the addition circuit 37. That is, the torque output signal output from the D / A conversion circuit 36 changes according to the steering torque, the vehicle speed, and the axial force. The angle sensor 22 is connected to an angle signal processing circuit 38 and an angle sensor abnormality detection circuit 39. The abnormality detection circuit 39 is connected to the OR gate 35. The angle signal processing circuit 38 is connected to a first differentiating circuit 40, and is further connected to a second differentiating circuit 41.
And the second differentiating circuit 41 is connected to the adding circuit 37. The angle signal processing circuit 38 is connected to an inverting circuit 42 parallel to the first differentiating circuit 40, and the inverting circuit 42 is connected to the adding circuit 37 via a limiter circuit 43. And, from this adder circuit 37, the signal V ₅ for controlling the motor drive circuit 44 is outputted, the electric motor m in the signal V ₅
Is controlled. Thus, the output torque T of the electric motor m is a torque T ₁ used in the external work, can be decomposed into a torque T _M to be eaten by rotor inertia, the output torque is T =
That is, T ₁ + T _M. If the output torque T of the electric motor is constant, the larger the rotor inertia, torque T ₁ which are used for the external work is reduced. With such a torque T ₁ becomes smaller, since it must compensate the shortfall manually, the feel in hand inertial force of the rotor. However, the always T + T _M The Tokuru supplied, torque T ₁ always required by controlling the T _M as secure, it is possible to eliminate the influence of the rotor inertia. For example, the steering angle of the steering wheel H and theta, relationship if the rotation angle of the rotor and _{θ M θ M = cθ ...... (} 1) holds associated therewith. Here, c in the equation (1) is a constant. Then, when the rotor inertia and I _M, the _{T M = I M M = cI} M ...... (2). Therefore, do it a signal that raise the cI _M times the torque of the second derivative value of the steering angle of the steering wheel theta (steering angular acceleration) is added to the steering torque, it can be completely remove the influence of the rotor inertia of the motor. The present invention utilizes this principle, and the illustrated embodiment has a feature in this point. That is, the angle signal V ₂ detected by the angle sensor 22 is
Differentiation to obtain a differential value ₂ once in the first differentiating circuit 40, further together with obtaining a second derivative value ₂ by differentiating it with the second differentiating circuit 41, always the differential signal c _{4 2} to the adder circuit 37 Input and practice the above principle. Further, the angle signal processing circuit 38 is also connected to the inverting circuit 42, for example, to cut the handle H to the right, from the processing circuit 38 the signal V ₂ is output. Then, the signal V _2, as well as become -V ₂ is inverted by the inverting circuit 42, adds the signal -V ₂ is limited to a value -V ₂ 'as shown in FIG. 3 by the limiter circuit 43 Input to the circuit 37. Therefore, the signal V output from the addition circuit 37
_5, it comes to _{V 5 = V 4 + c 4} 2 -V 2 '. The reason for providing the inversion circuit 42 as described above is to apply a returning force of the handle H to improve the returning performance. That is, the characteristic shown by the solid line in FIG. 3 is a characteristic when the steering wheel is turned rightward and the hand is released from the handle at a predetermined position x when no return force is applied. As is clear from FIG. 3, when the handle H is released as described above, the torque in the right direction is lost and the torque returns. However, actually, when the handle H returns, it is generated by the attractive force of the magnet of the electric motor, and the return of the handle deteriorates due to the action of cogging torque or the like which is a force against the return of the handle. Therefore, in this embodiment, by adding the signal -V ₂ 'output by the inversion circuit 42, but which is adapted to cancel the return resistance of the handle by the cogging torque or the like, the characteristics in Figure 3 the broken lines Is shown. Since the reversal signal is constantly added, an extra load acts on the electric motor by the reversal torque.
If the capacity of the motor is set, there is almost no problem in practice. In any case, according to this embodiment, the electric motor m
The effect of the inertia of the rotor can be completely eliminated, and the return characteristic when the handle is released is also improved. The signal output from the output port C ₃ of the microprocessor P is input to the clutch drive circuit 45, the output signal of the drive circuit 45, so as to control the electromagnetic clutch 19. Further, from the output port C _4, but outputs a pulse indicating that the program is running normally, the output signal OR gate 35 via the watchdog processor 46
To be entered.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 show an embodiment of the present invention.
FIG. 2 is a block diagram of the control system, FIG. 3 is a graph showing the return characteristic of the steering wheel, FIGS. 4 and 5 show a conventional device, and FIG. 4 is a control system. Block diagram of the
FIG. 5 is a graph showing a phase delay between the torque signal and the motor torque. m: electric motor, P: microprocessor as function generating circuit, 22: angle sensor, 38: angle signal processing circuit, 40: first differential circuit, 41: second differential circuit, 42
…… Inverting circuit, 43 …… Limiter circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B62D 119: 00 137: 00 (56) References JP-A-61-98675 (JP, A) JP-A 62-34846 (JP, A)

Claims (1)

(57) [Claims] An electric power steering device that includes a function generating circuit that outputs an output torque signal according to running conditions such as a vehicle speed, and controls an electric motor with an output signal of the function generating circuit. An angle signal processing circuit that outputs a voltage signal in accordance with the output of the angle sensor, an inverting circuit connected to the angle signal processing circuit and inverting the output signal,
A limiter circuit that is generated by the attractive force of the magnet of the electric motor and limits a set value for canceling a cogging torque that is a force against the return of the handle, and an addition circuit that receives signals of the limiter circuit and the function generation circuit. And a motor drive circuit controlled according to the output signal of the adder circuit.