Position sensor monitoring system

• US 4,920,939 A
• Filed: 02/27/1989
• Issued: 05/01/1990
• Est. Priority Date: 02/27/1989
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Ford Motor Company
• Inventors: Gale, Allan R.
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US07/316,191
• Time in Patent Office: 428 Days
• Field of Search: 123/361, 123/399, 123/479, 73/118.1, 324/208, 324/549, 364/431.11, 340/870.38, 340/438, 340/459
• US Class Current: 123/399
• CPC Class Codes: F02D 11/106 Detection of demand or actuation
• CPC Class Codes: F02D 2200/0404 Throttle position
• CPC Class Codes: F02D 2200/602 Pedal position
• CPC Class Codes: F02D 2400/08 Redundant elements, e.g. two sensors for measuring the same parameter
• CPC Class Codes: F02D 41/28 Interface circuits

Abstract

A condition monitoring system for a position sensor coupled to a control device in a throttle control system. The position sensor includes a potentiometer having a main resistor coupled across a source of electrical power and a wiper arm mechanically coupled to the control device and electrically coupled to the main resistor. An electrical signal is developed on the wiper arm which is directly proportional to the actual position of the control device. A sensing or monitoring resistor is connected in series between the main resistor and source of electrical power for providing a current measurement directly correlated with actual resistance of the main resistor. The voltage drop across the sense resistor is compared to a predetermined range for providing an indication of main resistor operation independently of wiper arm position.

Claims

1. An operating condition monitoring apparatus for a position sensor coupled to a control device, comprising:

said position sensor comprising a potentiometer having a main resistor coupled between a node and an electrical return, and a wiper arm responsive to actual position of the control device and electrically coupled to said main resistor;

a sense resistor connected in series between said node and a source of electrical power; and

comparison means for comparing electrical power through said sense resistor to a predetermined range to provide an indication of the operation of said main resistor independently of wiper arm position.

2. The apparatus recited in claim 1 wherein said control device comprises an operator actuable device.

3. The apparatus recited in claim 1 wherein said control device comprises an engine throttle plate.

4. An operating condition monitoring apparatus for a throttle control system in a motor vehicle, comprising:

a potentiometer for providing the throttle control system with an electrical signal related to position of a control device coupled to the throttle control system, said potentiometer including a main resistor coupled across a source of electrical power and a wiper arm responsive to actual position of said control device and electrically coupled to said main resistor for providing said electrical signal;

sensing means for sensing current flow through said main resistor thereby providing a measurement directly correlated with actual resistance of said main resistor independently of wiper arm position, said sensing means comprising a sense resistor connected in series between said main resistor and said source of electrical power; and

comparison means for comparing a voltage drop across said sense resistor to a predetermined range to provide an indication of operation of said main resistor independently of wiper arm position.

5. The apparatus recited in claim 4 wherein said control device comprises an operator actuable device.

6. The apparatus recited in claim 4 wherein said control device comprises an engine throttle plate.

7. The apparatus recited in claim 4 wherein said comparison means comprises:

a first operational amplifier having a positive input terminal coupled to a first voltage reference and a negative input terminal coupled to said sense resistor;

a second operational amplifier having a negative input terminal coupled to a second voltage reference and a positive input terminal coupled to said sense resistor; and

decoder means coupled to said first and second operational amplifiers for providing said indication of operation of said main resistor.

8. The apparatus recited in claim 4 further comprising an analog to digital converter coupled to said sensing means for providing said comparison means with a digital representation of said voltage drop across said sense resistor.

9. The apparatus recited in claim 8 further comprising derivative means coupled to said analog to digital converter for providing another indication of operation of said main resistor by calculating a derivative of said digital representation of said voltage drop across said sense resistor.

10. The apparatus recited in claim 8 further comprising means coupled to said analog to digital converter for providing an indication of wear in said main resistor by comparing differences between successive samples of said digital representation of said voltage drop across said sense resistor.

11. An apparatus for selecting a position sensor coupled to a control device in response to operating condition of the position sensor, comprising:

a primary position sensor coupled to the control device comprising a potentiometer having a main resistor coupled between a node and an electrical return, and a wiper arm responsive to actual position of the control device and electrically coupled to said main resistor;

a primary sense resistor connected in series between said node of said primary position sensor and a source of electrical power;

a secondary position sensor coupled to the control device comprising a potentiometer having a main resistor coupled between a node and an electrical return, and a wiper arm responsive to actual position of the control device and electrically coupled to said main resistor;

a secondary sense resistor connected in series between said node of said secondary position sensor and a source of electrical power;

comparison means for comparing a voltage drop across said primary sense resistor to a predetermined range and for comparing a voltage drop across said secondary sense resistor to a predetermined range to provide an indication of the operation of said main resistors in both said primary and said secondary position sensors independently of wiper arm position; and

selection means responsive to said comparison means for selecting between said primary position sensor and said secondary position sensor.

12. The apparatus recited in claim 11 wherein said control device comprises an operator actuable device.

13. The apparatus recited in claim 11 wherein said control device comprises an engine throttle plate.

14. A throttle control system having an operating condition monitoring, comprising:

a servo motor coupled to an engine throttle plate;

a controller coupled to said servo motor responsive to an input signal related to desired throttle position and also responsive to a feedback signal related to actual throttle position;

command means for generating said input signal in response to the mechanical position of a control device, said command means including a potentiometer having a main resistor coupled to a source of electrical power and a wiper arm responsive to the mechanical position of said control device and electrically coupled to said main resistor for generating said input signal;

a sense resistor coupled between said source of electrical power and said main resistor; and

comparison means for comparing electrical power through said sense resistor to a predetermined range to provide an indication of operating condition of said main resistor.

15. The apparatus recited in claim 14 wherein said comparison means comprises an analog window comparator circuit.

16. The apparatus recited in claim 14 wherein said comparison means comprises:

means for comparing a digital representation of said electrical power through said sense resistor to a digital value related to desired resistance limits of said main resistor.

17. A throttle control system having an operation condition indicator, comprising:

a servo motor coupled to an engine throttle plate;

a controller coupled to said servo motor responsive to an input signal related to desired throttle position and also responsive to a feedback signal related to actual throttle position;

feedback means for generating said feedback signal in response to the mechanical position of said engine throttle, said feedback means including a potentiometer having a main resistor coupled to a source of electrical power and a wiper arm responsive to the mechanical position of said engine throttle and electrically coupled to said main resistor for generating said feedback signal;

a sense resistor coupled between said source of electrical power and said main resistor;

conversion means for providing a digital signal related to a voltage drop across said sense resistor; and

comparison means for said digital signal to a predetermined range related to desired resistance limits of said main resistor to provide an indication of operating condition of said main resistor.

18. The apparatus recited in claim 17 further comprising derivative means coupled to said conversion means for providing another indication of operation of said main resistor by calculating a derivative of said digital signal.

19. The apparatus recited in claim 17 further comprising means coupled to said conversion means for providing an indication of wear in said main resistor by comparing differences between successive samples of said digital signal.

20. A throttle control system having an operation condition indicator, comprising:

a servo motor coupled to an engine throttle plate;

a controller coupled to said servo motor responsive to an input signal related to desired throttle position and also responsive to a feedback signal related to actual throttle position;

an actuator sensor for providing said input signal in response to position of an actuator, said actuator sensor including a potentiometer coupled to said actuator having a main resistor coupled to a source of electrical power and also having a wiper arm electrically coupled to said main resistor and responsive to position of said actuator for providing said input signal;

a first sense resistor coupled between said source of electrical power and said main resistor of said actuator sensor;

a throttle sensor for providing said feedback signal in response to mechanical position of said engine throttle, said throttle sensor including a potentiometer coupled to said throttle having a main resistor coupled to a source of electrical power and also having a wiper arm responsive to mechanical position of said throttle and electrically coupled to said main resistor for providing said feedback signal;

a second sense resistor coupled between said source of electrical power and said main resistor of said throttle sensor; and

comparison means for comparing a voltage drop across said first sense resistor to a predetermined range and for comparing a voltage drop across said second sense resistor to a predetermined range to provide an indication of operating condition in said main resistor of said actuator sensor and said main resistor of said throttle sensor.

21. The apparatus recited in claim 20 further comprising means coupled to said comparison means for providing a warning indication.