Control apparatus of power steering device

• US 20020120378A1
• Filed: 02/01/2002
• Published: 08/29/2002
• Est. Priority Date: 02/02/2001
• Status: Active Grant

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Kawada, Hideaki, Itakura, Yusuke, Endo, Shuji, Koiwai, Hisayoshi, Miyaura, Yasuhiko
• Granted Patent: US 6,658,333 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0484 for reaction to failures, e.g. limp home
• CPC Class Codes: B62D 5/049 detecting sensor failures

Abstract

A control apparatus of power steering device having functions of monitoring intermediate troubles such as offset or drift out of signal troubles of torque sensor, and limiting the current for limiting the assist function is presented. In a control apparatus of power steering device for controlling a motor on the basis of a current control value calculated from a steering assist command value calculated by calculating means on the basis of a steering torque generated on a steering shaft, and a current value of a motor for applying a steering assist force to a steering mechanism, wherein the difference of a main torque signal and a sub torque signal of a torque sensor for detecting the steering torque is stored preliminarily, and the difference of the main torque signal and the sub torque signal during operation is compared with the stored value, and at least the current control value is limited when the difference based on the comparison is a condition larger than a first prescribed value and continues for a time longer than a first prescribed time.

Claims

1. A control apparatus of a power steering device for controlling a motor on the basis of a current control value calculated from a steering assist command value calculated by calculating means on the basis of a steering torque generated on a steering shaft, and a current value of a motor for applying a steering assist force to a steering mechanism,

wherein a difference of a main torque signal and a sub torque signal of a torque sensor for detecting the steering torque is stored preliminarily, and the difference of the main torque signal and the sub torque signal during an operation is compared with the stored value, and at least the current control value is limited when the difference based on the comparison is a state larger than a first prescribed value and continues for a time longer than a first prescribed time.

2. A control apparatus of a power steering device according to claim 1, wherein an output of the current control value is stopped when the difference based on the comparison is larger than a second prescribed value which is larger than the first prescribed value and further the state continues for a time longer than a second prescribed time which is shorter than the first prescribed time.

3. A control apparatus of a power steering device according to claim 1, wherein a means for storing is a nonvolatile memory.

4. A control apparatus of a power steering device according to claim 1 or 2, wherein the limitation of the current control value is carried out according to a vehicle speed.

5. A control apparatus of a power steering device according to claim 4, wherein the limitation of the current control value is carried out by limiting a maximum current of the steering assist command value.

6. A control apparatus of a power steering device according to claim 4, wherein the limitation of the current control value is carried out by limiting a maximum current obtained by multiplying a prescribed gain with the steering assist command value.

7. A control apparatus of a power steering device according to claim 1 or 2, wherein the steering assist command value is calculated on the basis of an output of a normal mode characteristic map, and when the state of the difference based on the comparison being different from the first prescribed value continues for a time longer than the first prescribed time or the second prescribed time, the normal mode characteristic map is changed over to a torque sensor offset abnormal mode characteristic map.

8. A control apparatus of a power steering device according to claim 7, wherein an intermediate characteristic map is used so as to change without any sense of strangeness when changing over from the normal mode characteristic map to the torque sensor offset abnormal mode characteristic map.

9. A control apparatus of a power steering device according to claim 7, wherein the change over from the normal mode characteristic map to the torque sensor offset abnormal mode characteristic map is carried out by using a torque sensor offset abnormality detecting means.

10. A control apparatus of a power steering device according to claim 8, wherein the change over from the normal mode characteristic map to the intermediate characteristic map and the torque sensor offset abnormal mode characteristic map is carried out by using a torque sensor offset abnormality detecting means.

11. A control apparatus of a power steering device according to claim 9 or 10, wherein the torque sensor offset abnormality detecting means a first difference calculator for calculating the difference between the main torque signal and the sub torque signal, a memory for storing the difference from the first difference calculator through a changeover means, a second difference calculator for calculating a difference between a difference from the first difference calculator through the changeover means and the stored value from the memory, a comparator for comparing the difference from the second difference calculator with the first prescribed value and the second prescribed value and a time measuring means for measuring a lapse time of an output of the comparator.