Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-02-26
2001-04-03
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S032000, C701S035000, C701S036000, C701S041000, C701S102000
Reexamination Certificate
active
06212447
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control system for a motor vehicle which is capable of adjusting variance or dispersion of characteristics intrinsic to individual control units, and more particularly, a control system for a motor vehicle for which reduction in manufacturing cost can be realized without impairing reliability by improving an internal adjusting mechanism.
BACKGROUND TECHNIQUES
In conjunction with the control system for a motor vehicle such as for a power steering system, an engine ignition control system and others, a control system for the motor vehicle which is designed for correcting an error peculiar to the system by resorting to the use of learning function is well known in the art, as is disclosed, for instance, in Japanese Unexamined Patent Application Publication No. 47471/1991 (JP-A-3-47471). However, in the control system for the motor vehicle equipped with such learning function, it is difficult to ensure reliability for the correcting control with high accuracy because of difficulty encountered in setting the conditions for learning.
Under the circumstances, there have been proposed a variety of apparatuses for adjusting variances of characteristics of individual systems in the course of assembling on the production line for ensuring reliability of correction with high accuracy.
In the following, adjustment of dispersion or variance of the characteristic of the control system for the motor vehicle as carried out on the production line and known heretofore will be described by taking as an example a motor-driven power steering control system.
FIG. 7
is a circuit diagram showing a conventional motor-driven power steering control system with several parts being shown in blocks.
Referring to
FIG. 7
, a steering effort assisting motor
40
(output unit) is electrically driven, being supplied with a motor current IM from a battery
41
, for thereby generating an assist torque to be applied to a steering wheel (not shown) of a motor vehicle.
Ripple components of the motor current IM is absorbed by a capacitor
42
of a large capacity (on the order of 1000 &mgr;F. to 3600 &mgr;F.), wherein the motor current IM is detected by means of a shunt resistor
43
. One terminal of the capacitor
42
is connected to the ground potential by way of a wiring conductor L
1
.
Further, the motor current IM is changed in dependence on magnitude and direction of the assist torque by means of a bridge circuit
44
which is constituted by a plurality of semiconductor switching elements (e.g. FETs) Q
1
to Q
4
.
The semiconductor switching elements Q
1
to Q
4
cooperate to constitute the bridge circuit
44
, being interconnected in the form of a bridge circuit by wiring conductor patterns P
1
and P
2
.
The bridge circuit
44
is connected to the shunt resistor
43
via the wiring conductor patterns P
1
and P
2
. Further, the output terminal of the bridge circuit
44
is realized by a wiring conductor pattern P
3
.
The motor
40
and the battery
41
are connected to the bridge circuit
44
by means of a connector
45
having a plurality of lead terminals. The motor
40
, the battery
41
, and the connector
45
are interconnected by external wiring conductors L
2
. The motor current IM can be interrupted by means of a normally opened relay
46
as occasion requires.
The relay
46
, the capacitor
42
and the shunt resistor
43
are interconnected by a wiring conductor pattern P
4
. The connector
45
is connected to the ground potential by a wiring conductor pattern P
5
. The wiring conductor pattern P
3
constituting the output terminals of the bridge circuit
44
is connected to the connector
45
.
The motor
40
is driven by a driving circuit
47
by way of the bridge circuit
44
. The driving circuit
47
is connected to an excitation coil of the relay
46
by way of a wiring conductor L
3
for driving the relay
46
. Further, the driving circuit
47
is connected to the bridge circuit
44
via wiring conductors L
4
.
The motor current IM is detected by a motor current detecting means
48
as a voltage appearing across the shunt resistor
43
. The driving circuit
47
and the motor current detecting means
48
constitute peripheral circuit elements of a microcomputer
55
which will be described hereinafter.
A steering torque T applied to the steering wheel is detected by a torque sensor
50
, while a speed V of a motor vehicle is detected by a vehicle speed sensor
51
.
The microcomputer
55
constitutes an electronic control unit (ECU) in cooperation with input/output control units (input/output interfaces) for arithmetically determining the assist torque on the basis of the steering torque T and the vehicle speed V while generating a rotating direction command Do and a current control quantity Io for controlling the bridge circuit
44
as a driving signal which corresponds to the assist torque and which is derived from a feedback signal indicating the motor current IM, wherein the rotating direction command Do and the current control quantity Io are outputted to the driving circuit
47
.
The microcomputer
55
includes a motor current determining means
56
, a subtracting means
57
and a PID (proportional-integral-differential) arithmetic means
58
.
The motor current determining means
56
is designed to generate the rotating direction command Do for the steering effort assisting motor
40
and a motor current command Im equivalent to the assist torque, while the subtracting means
57
is designed to arithmetically determine a current deviation &Dgr;I of the motor current IM from the motor current command Im.
The PID arithmetic means
58
arithmetically determines correcting quantities for the P (proportional) term, the I (integral) term and the D (differential) term, respectively, on the basis of the current deviation &Dgr;I, to thereby generate a current control quantity Io corresponding to a PWM (Pulse-Width Modulation) duty ratio.
Further, in addition to an A/D converter, a PWM timer circuit and others, the microcomputer
55
includes a self-diagnosis function known per se for carrying out constantly the self-diagnosis as to whether or not the system is operating normally, wherein upon occurrence of abnormality, the relay
46
is opened by way of the driving circuit
47
to thereby interrupt the motor current IM. The microcomputer
55
is connected to the driving circuit
47
by wiring conductors L
5
.
Next, description will be directed to operation of the conventional motor-driven power steering control system shown in FIG.
7
.
At first, the microcomputer
55
fetches the steering torque T and the vehicle speed V from the outputs of the torque sensor
50
and the vehicle speed sensor
51
, respectively, while fetching the motor current IM from the shunt resistor
43
as a feedback input quantity, to thereby arithmetically determine the rotating direction command Do and the current control quantity Io corresponding to the magnitude of the assist torque for the power steering on the basis of the steering torque T, the vehicle speed V and the motor current IM, wherein the rotating direction command Do and the current control quantity Io as determined are outputted to the driving circuit
47
via the wiring conductors L
5
.
In the steady driving state, the normally opened relay
46
is closed by the driving circuit
47
in response to the command supplied through the wiring conductor L
3
. However, upon inputting of the rotating direction command Do and the current control quantity Io, the PWM driving signals are generated to be applied to the individual semiconductor switching elements Q
1
to Q
4
, respectively, of the bridge circuit
44
via the wiring conductors L
4
.
Thus, the motor current IM is supplied to the motor
40
from the battery
41
by way of the external wiring conductors L
2
, the connector
45
, the relay
46
, the wiring conductor pattern P
4
, the shunt resistor
43
, the wiring conductor pattern P
1
, the bridge circuit
44
, the wiring conductor pattern P
3
, the connector
45
and the external wiring conductors L
2
. Th
Kishimoto Yuji
Kohge Shinichi
Cuchlinski Jr. William A.
Mancho Ronnie
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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