Arousal level judging apparatus and method

• US 4,928,090 A
• Filed: 12/08/1988
• Issued: 05/22/1990
• Est. Priority Date: 12/09/1987
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Yoshinori, Takeshi, Kodama, Satoru, Ito, Masahiko, Yoshimi, Tomohisa
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US07/281,074
• Time in Patent Office: 530 Days
• Field of Search: 340/576, 340/575, 128/734
• US Class Current: 340/575
• CPC Class Codes: A61B 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: G08B 21/06 indicating a condition of sleep, e.g. anti-dozing alarms

Abstract

An arousal level judging apparatus has a skin potential level (SPL) detection device, a potential change detection device for detecting occurrance and convergence of a pulse of the signal from the SPL detection device, the pulse being caused by skin potential response (SPR), a storing device for storing the SPL value as a reference value, and a comparator for comparing SPL with the reference value to detect a SPL decrease to detect an arousal level decrease of a driver, etc. The reference value is renewed at every occurrance of SPR. When the SPL value indicates that the arousal level of the driver has been decreased, an alarm is caused to wake the driver up.

Claims

1. An arousal level judging apparatus comprising:

(a) skin potential level detection means for detecting a skin potential level of a human body;

(b) level change detection means for detecting a degree of change in a level of an output signal of said skin potential level detection means over a predetermined interval;

(c) a comparing means for comparing said degree from said level change detection means with a first predetermined value to detect a pulse-like change in said skin potential level;

(d) convergence detection means responsive to an output signal from said comparing means for detecting a non-pulse like portion in said skin potential level by analyzing successive changes of gradient determined by said degree from said level change detection means;

(e) storing means for storing said skin potential level as a reference value when said non-pulse like portion is detected by said convergence detection means; and

(f) arousal level detecting means responsive to said skin potential level from said skin potential level detection means and to said reference value from said storing means for determining arousal state and non-arousal state of said human body using the relationship between said skin potential level and said reference value.

2. An arousal level judging apparatus as claimed in claim 1, wherein said convergence detection means comprises:

a second comparing means for comparing said signal from said level change detection means with a second predetermined value which is of opposite sign to said first predetermined value; and

a third comparing means responsive to said second comparing means for comparing said signal from said level change detection means with a third predetermined value.

3. An arousal level judging apparatus as claimed in claim 1, further comprising an alarm means responsive to said arousal level detection means for alarming.

4. An arousal level judging apparatus as claimed in claim 1, further comprising an input means for inputting a difference data of said skin potential level between high and low arousal state, said arousal level detection means responsive to said data and using said data to evaluate said relationship between said skin potential level and said reference value.

5. An arousal level judging apparatus as claimed in claim 4, further comprising an alarm means responsive to said arousal level detection means for alarming.

6. An arousal level judging apparatus comprising:

(a) skin potential level detection means for detecting a skin potential level of a human body;

(b) level change detection means for detecting a degree of change in a level of an output signal of said skin potential level detection means over a predetermined interval;

(c) a comparing means for comparing said degree from said level change detection means with a first predetermined value to detect a pulse-like change in said skin potential level;

(d) convergence detection means responsive to an output signal from said comparing means for detecting a non-pulse like portion in said skin potential level by analyzing successive changes of gradient determined by said degree from said level change detection means;

(e) storing means for storing said skin potential level as a reference value when said non-pulse like portion is detected by said convergence detection means;

(f) a calculation means for obtaining a set point value by multiplying said reference value by a constant smaller than one; and

(g) arousal level detection means for determining a non-arousal state of said human body when said skin potential level is below said set point value and the gradient of the change of said skin potential level below said set point value is greater than a second predetermined value.

7. An arousal level judging apparatus as claimed in claim 6, wherein said convergence detection means comprises:

a second comparing means for comparing said signal from said level change detection means with a third predetermined value which is of opposite sign to said first predetermined value; and

a third comparing means responsive to said second comparing means for comparing said signal from said level change detection means with a fourth predetermined value.

8. An arousal level judging apparatus as claimed in claim 6, further comprising an alarm means responsive to said arousal level detection means for alarming.

9. A method of judging an arousal level comprising the steps of:

(a) detecting a skin potential level of a human body;

(b) detecting a skin potential response which is a pulse-like change in said skin potential level;

(c) determining a reference value as a skin potential level just after a convergence of said skin potential response, said convergence being a portion where said skin potential level reaches an end of said pulse-like change;

(d) calculating a decrease ratio of said skin potential level using said detected skin potential level and said reference value; and

(e) comparing said decrease ratio with a predetermined value to judge an arousal level of said human body.

10. An arousal level judging apparatus comprising:

(a) detection means for detecting a skin potential level of a human body;

(b) means for detecting a skin potential response, which is a pulse-like change in said skin potential level;

(c) storing means for storing a reference value which is a skin potential level just after a convergence of said skin potential response, said convergence being a portion where said skin potential level reaches an end of said pulse-like change;

(d) means for calculating a decrease ratio of said skin potential level using said detected skin potential level and said reference value; and

(e) comparing means for comparing said decrease ratio with a predetermined value to judge an arousal level of said human body.

11. An arousal level judging apparatus comprising:

(a) skin potential detection means having a pair of electrodes for detecting a skin potential level of a human body;

(b) computer means, responsive to said detection device, for;

(a) detecting a pulse-like change of said skin potential level, (b) storing a reference value which is a skin potential level just after an end of said pulse-like change, and (c) detecting a decrease of an arousal level on the basis of a decrease of said skin potential level from said reference value and producing an alarm signal indicative thereof; and

(c) alarm means, responsive to said alarm signal of said computer means for alarming when said decrease of an arousal level is detected by said computer means.

12. A method for detecting an end of a skin potential response of a skin potential level of a subject, comprising the steps of:

determining a gradient of said skin potential level;

setting an indication when said gradient is greater than a predetermined positive value; and

subsequently determining, after said indication is set, that the gradient is equal to a value close to zero, and determining said end of said skin potential response based thereupon.