JP3824527B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an on-vehicle electric power steering apparatus, and more particularly, to an electric motor having a self-diagnosis mechanism capable of performing an operation test on an AD converter that inputs various physical quantities (detection signals) such as steering torque. The present invention relates to a power steering device.
[0002]
[Prior art]
FIG. 5 is a control block diagram illustrating a functional configuration of a general electric power steering apparatus. A torque signal T ′ (analog signal) detected by the torque sensor 2 is input to a microcomputer (CPU) of the controller 7 as a digitized steering torque T via an A / D converter (A / D converter) 74. Is done. Thereafter, the torque signal is input to the phase compensator 70a realized by software executed by the microcomputer. After the phase compensation is performed, the torque signal is input to the assist command current setting unit 70b.
[0003]
The vehicle speed signal u is input to the assist command current setting unit 70b in a format digitized in advance by the vehicle speed sensor 6. Reference numeral 71 denotes a drive circuit for driving the motor 3, and 72 denotes a motor current detection circuit for measuring a measured value Ir of the drive current of the motor 3. The measured value Ir of the drive current is referred to by the PI control unit 70c in order to realize the PI control of the drive current.
[0004]
FIG. 6 is a graph schematically illustrating the operation of the assist command current setting unit 70b that determines the output characteristics of the auxiliary torque. For example, by determining the assist current command value Ia ^* based on the vehicle speed u and the steering torque T (digital signal) in this manner, an appropriate assist torque can be applied to the steering system.
[0005]
[Problems to be solved by the invention]
FIG. 7 is a configuration diagram illustrating a hardware configuration of the electric power steering apparatus. As can be seen from FIG. 5 and FIG. 6, in order to give an appropriate assist torque to the steering system, the normal operation of the A / D converter 74 is indispensable. For this reason, in the conventional apparatus, for example, the vehicle ignition / The A / D converter 74 is checked by checking whether a predetermined voltage (for example, 0 v, 5 v) output from the test constant power supply circuit 90 can be correctly confirmed on the CPU 75 side when the switch is turned on. The normal operation of was confirmed.
[0006]
For example, as described above, in the conventional apparatus, in order to confirm the normal operation of the A / D converter 74 at a predetermined timing during operation, the A / D converter 74 outputs a predetermined voltage (in a fixed state). In order to test whether there is a failure or not, it is necessary to install a test power supply (eg, constant power supply circuit 90 in FIG. 7) that outputs two kinds of voltages.
However, for example, the installation of the constant power supply circuit 90 for testing as shown in FIG. 7 requires corresponding parts cost and mounting space. Therefore, the system configuration capable of performing the test as described above is low in cost and small in size. It became one of the inhibition factors.
[0007]
A configuration without the constant power supply circuit 90 (FIG. 7) is also possible. However, under such a system configuration, when the A / D converter 74 does not operate normally, FIG. As shown in FIG. 5, there is no guarantee that the assist current Ia ^* (command value) can be accurately determined, which is not desirable.
[0008]
The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to configure a highly reliable electric power steering apparatus in a small size and at low cost.
[0009]
[Means for Solving the Problem, Action, and Effect of the Invention]
In order to solve the above problems, the following means are effective.
That is, the first means inputs A / D conversion by inputting a steering torque, a motor for applying assist torque to the steering mechanism to assist the steering of the vehicle, a torque sensor for detecting steering torque applied to the steering wheel, and the like. In an electric power steering apparatus having an A / D converter and a motor control device that controls driving of a motor, a pulse output device that outputs a predetermined signal and a predetermined signal output from the pulse output device are re-input from the A / D converter The verification line for testing whether the input signal input from the feedback line matches the predetermined signal, and the input signal does not match the predetermined signal as a result of the test by the verification unit In such a case, an abnormality processing means for stopping rotation of the motor, control of the motor, or power supply to the motor is provided.
[0010]
As the pulse output device, a constant voltage output circuit or the like that is basically provided in the motor control device (controller 7) can be used. As such a pulse output device, for example, a constant voltage output circuit for detecting an illegal operation of the CPU is used, or a part of a drive circuit 71 (FIG. 7) having a motor drive power source is used. It may be equal.
[0011]
Thereby, for example, it is not necessary to specially provide a test constant power supply circuit 90 as shown in FIG. 7, and an abnormality can be detected by the motor control unit alone. Therefore, according to the above means, a highly reliable electric power steering apparatus can be configured in a small size and at low cost.
[0012]
Further, the second means connects the pulse output device to the reset IC for detecting the unauthorized operation of the CPU in the first means, and constantly outputs from the pulse output device to the reset IC as the predetermined signal. It is to use a fixed signal for detecting illegal operation.
[0013]
According to such means, the predetermined signal generation process and the verification verification process can be easily performed simultaneously. Also, according to such means, it is easy to always perform the predetermined signal generation process and the verification verification process in real time.
By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
(Example)
FIG. 1 is a system configuration diagram of an electric power steering apparatus 100 according to the present embodiment. A controller 7 operating as a motor control device inputs a vehicle speed signal (u: digital signal) from a vehicle speed sensor 6, and a torque signal (T ′) of a steering torque exerted on the steering wheel 1 by the driver from the torque sensor 2. : Analog signal) is input, and the drive current of the motor 3 is controlled so that the auxiliary torque corresponding to these detected values is output from the motor 3.
[0015]
FIG. 2 is a hardware configuration diagram of a motor control device (controller 7) included in the electric power steering apparatus 100 described above. Reference numeral 72 denotes a motor current detection circuit that measures the measured value Ir of the drive current of the motor 3. The reset IC 80 always receives the CPU irregular operation detection fixed signal V _out (lower left in the figure) output from the pulse output device 79, and when this signal is not received, the CPU 75 starts an unexpected operation. And a reset signal is sent to the CPU 75. This reset signal serves as a command signal for giving a restart interrupt to the CPU 75, and such a CPU improper operation detection mechanism is conventionally provided in a known microcomputer.
[0016]
In the hardware circuit (wiring, etc.) of the motor control device (controller 7) of the electric power steering apparatus 100 of the present invention, the most characteristic part is that a feedback line 81 is additionally provided for the output line of the pulse output device 79. It is in the point provided. The feedback line 81 is a line for re-inputting the predetermined signal (the fixed signal V _out ) output from the pulse output device 79 from the A / D converter 74 to the CPU 75. The feedback line 81 may be connected to a suitable free channel among the channels of the A / D converter 74. Hereinafter sometimes referred to as a signal that is the re-input an input signal V _in.
[0017]
Note that the reset IC 80 in FIG. 2 may be in a form built in the motor control device (controller 7). Also, the pulse output device 79, the A / D converter 74, etc. in FIG. 2 may be externally attached to the motor control device (controller 7). These differences only result in the problem of how far to see the components of the motor control device (controller 7).
However, FIG. 2 shows an example in which the pulse output device 79, the A / D converter 74, and the like are incorporated in advance in a single microcomputer. Under such a hardware configuration, the effect of the present invention can be entrusted with a relatively large cost.
[0018]
FIG. 3 is a flowchart of a control program that simultaneously realizes the generation process of the predetermined signal (V _out ) and the verification verification means of the present invention. This program is executed as an interrupt routine of a timer interrupt that occurs every 1 msec. The main variables used in this program are as follows.
(Main variables)
K: 1-bit variable. It becomes an argument of the arrays V (i) and N (i).
L: 1-bit variable. It becomes an argument of the array V (i).
V (i): An array having a constant value. Has a predetermined voltage value.
(Setting example: V (0) = 0 [v], V (1) = 5 [v])
N (i) ... Counter. Indicates the number of times that an illegal voltage value is continuously detected.
V _in ... Input voltage from the feedback line 81.
V _out ... Output voltage for reset IC80.
[0019]
In this control program, first, in step 210, the value of the variable L is inverted by calculating the exclusive OR of the variable L and the constant 1, and the value is stored in the variable K. The symbol XOR in step 210 is an operator of an instruction that calculates an exclusive OR. The initial value of the variable L at the time when the first timer interrupt at the time of system start-up may be 1 or 0.
In step 220, the value of the abnormal flag F is checked. The initial value of the flag F at the time of system startup is 0, and when an abnormal operation of the A / D converter 74 is detected, the value is changed to 1 (step 255).
[0020]
In step 230, to hold the input voltage V _in input from the feedback line 81 via the A / D converter 74 on CPU 75.
In step 240, the height of the input voltage V _in, checks whether substantially coincides with the constant V (K) (matching verification means).
In step 242, the value of the counter N (K) is set to zero.
On the other hand, in step 244, the value of the counter N (K) is incremented by one.
[0021]
In step 250, it is checked whether or not the value of the counter N (K) has reached 500. This boundary value may be an appropriate value of about 5 to 500. This value may be set to an appropriate value in consideration of the noise generation status in the system.
In step 255, the value of the abnormal flag F is set to 1.
In step 260, a subroutine for performing an abnormality process (eg, FIG. 4) is called and executed.
[0022]
In step 270, the output level _Vout of the pulse output device 79 is set (processing for generating a predetermined signal ( _Vout )).
In step 280, an output command is issued to the pulse output device 79.
In step 290, the value of L is inverted.
By the above processing, when the input voltage V _in is continued continuously about 1 second Floor unreasonable values unexpectedly, "abnormality processing" is executed. For example, setting the constant "V (0) = 0 [v ], V (1) = 5 [v] " If you have made a continuous input voltage V _in for more than one second to about 0 [v] , N (1) = 500 is detected by step 250.
[0023]
FIG. 4 is a flowchart of a control program for realizing the abnormal time processing means (motor stop processing) of this embodiment. This subroutine is desirably a process that can be executed within 1 msec in order not to adversely affect the reset IC 80.
For example, the drive power supply of the motor 3 may be turned off (step 175), or a warning lamp for alarming the abnormality may be turned on (step 178). In the above embodiment, when the desired process to be executed in the event of an abnormality cannot be executed within 1 msec, the process (corresponding abnormality process) is constituted by another task, and this timer interrupt routine It is desirable for system processing to devise such as executing asynchronously. Thereby, it is possible to maintain the waveform of the predetermined signal (fixed signal V _out ) constantly sent to the reset IC 80.
[0024]
With the configuration based on the above-described means of the present invention, a highly reliable electric power steering apparatus can be realized in a small size and at low cost.
Further, according to the above configuration, the operation abnormality of the A / D converter 74 is detected by adding (inserting) a small amount of processing in steps 220 to 260 (FIG. 3) to the conventional timer interrupt routine. It is possible to construct the means to do very simply.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an electric power steering apparatus 100 according to an embodiment of the present invention.
FIG. 2 is a hardware configuration diagram of a motor control device (controller 7) included in the electric power steering device 100.
FIG. 3 is a flowchart of a control program that simultaneously realizes predetermined signal generation processing and verification verification processing.
FIG. 4 is a flowchart of a control program for realizing the abnormal time processing means (motor stop processing) of the present invention.
FIG. 5 is a control block diagram illustrating a functional configuration of a general electric power steering apparatus.
FIG. 6 is a graph schematically illustrating the operation of an assist command current setting unit 70b that determines output characteristics of auxiliary torque.
FIG. 7 is a hardware configuration diagram of a general electric power steering apparatus.
[Explanation of symbols]
100 ... Electric power steering device 1 ... Steering wheel (handle)
2 ... Torque sensor 3 ... Electric motor 4 ... Reducer 5 ... Rack & pinion gear 6 ... Vehicle speed sensor 7 ... Controller (motor control device)
71 ... Drive circuit 72 ... Motor current detection circuit 74 ... A / D converter 79 ... Pulse output device 80 ... Reset IC
T: Steering torque (digital signal)
T '... Steering torque (analog signal)
u ... Vehicle speed (digital signal)
V _out ... Output signal V _in of the pulse output device ... Input signal Ir from the feedback line ... Motor drive current (measured value)
Ia ^* ... Motor drive current (command value)

Claims (2)

A motor for applying assist torque to assist the steering of the vehicle to the steering mechanism, a torque sensor for detecting the steering torque applied to the steering wheel, an A / D converter for inputting the steering torque and performing A / D conversion, In an electric power steering device having a motor control device for driving and controlling a motor,
A pulse output device for outputting a predetermined signal;
A feedback line for re-inputting the predetermined signal output from the pulse output device from the A / D converter;
Verification verification means for testing whether the input signal input from the feedback line and the predetermined signal match,
An abnormal-time processing means for stopping rotation of the motor, control of the motor or power supply to the motor when the input signal and the predetermined signal do not match as a result of the test by the verification verification means; An electric power steering device. The pulse output device is connected to a reset IC that detects unauthorized operation of the CPU,
2. The electric power steering apparatus according to claim 1, wherein the predetermined signal is a fixed signal for detecting an illegal operation that is constantly output from the pulse output device to the reset IC.

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