Method and apparatus to evaluate a starter motor for an internal combustion engine

• US 9,506,445 B2
• Filed: 01/30/2014
• Issued: 11/29/2016
• Est. Priority Date: 01/30/2014
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Ghoneim, Youssef A., Howell, Mark N.
• Primary Examiner(s): Cronin, Stephen K
• Assistant Examiner(s): MO, XIAO EN
• Application Number:
  US14/168,059
• Publication Number:
  US 20150211469A1
• Time in Patent Office: 1,034 Days
• Field of Search: 701/113, 123/179.3, 123/179.4, 318/490
• US Class Current: 1/1
• CPC Class Codes: F02N 11/0814 comprising means for controlling automatic idle-start-stop
• CPC Class Codes: F02N 11/0825 related to prevention of engine restart failure, e.g. disabling automatic stop at low battery state
• CPC Class Codes: F02N 11/087 Details of the switching means in starting circuits, e.g. relays or electronic switches
• CPC Class Codes: F02N 11/108 for diagnosis of the starter or its components
• CPC Class Codes: F02N 2200/022 Engine speed
• CPC Class Codes: F02N 2200/04 said parameters being related to the starter motor
• CPC Class Codes: F02N 2200/043 Starter voltage
• CPC Class Codes: F02N 2200/044 Starter current
• CPC Class Codes: F02N 2200/062 Battery current
• CPC Class Codes: F02N 2200/063 Battery voltage
• CPC Class Codes: F02N 2200/064 Battery temperature
• CPC Class Codes: F02N 2200/0801 Vehicle speed
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for monitoring the starter motor includes determining starter motor resistance associated with an engine starting event and determining a back-emf for the starter motor based upon the starter motor resistance. A state of health of the starter motor corresponding to the back-emf of the starter motor and engine cranking time is determined. Engine stop/start functionality is controlled based upon the state of health of the starter motor.

Claims

1. A method for monitoring an electrically-powered starter motor for a starter of an internal combustion engine, comprising:

determining a starter motor resistance associated with an engine starting event;

determining a back-emf for the starter motor based upon the starter motor resistance;

determining a state of health (SOH) of the starter motor corresponding to the back-emf of the starter motor and a measured engine cranking time; and

controlling engine stop/start functionality based upon the SOH of the starter motor.

2. The method of claim 1, wherein determining the back-emf for the starter motor based upon the starter motor resistance comprises employing the starter motor resistance to estimate back-emf in accordance with the following relationships:

y(t)=φ

(t)θ

=V_B(t)−

I_B{circumflex over (R)}_e

φ

(t)=N_spd,θ

=K_e

wherein V_B(t) is a battery voltage,

I_B is a battery current,

{circumflex over (R)}_e is an estimate of the starter motor resistance,

N_spd is a rotational speed of the starter motor, and

K_e is the estimated back-emf.

3. The method of claim 2, wherein the estimated starter motor resistance for the starting event is determined in accordance with the following relationship:

4. The method of claim 2, wherein employing the starter motor resistance to estimate back-emf further comprises applying a least-squares estimation routine to converge to the estimated back-emf for the battery current and the battery voltage during the engine starting event.

5. The method of claim 1, wherein determining the SOH of the starter motor comprises determining the state of health based upon a minimum SOH of a start/stop function availability SOH and a fault detection SOH, said minimum SOH adjusted based upon a ratio of a nominal engine cranking time and the measured engine cranking time.

6. The method of claim 5, wherein the start/stop function availability SOH is determined in accordance with the following relationship:

7. The method of claim 5, wherein the fault detection SOH is determined in accordance with the following relationship:

8. The method of claim 7, wherein the nominal starter motor resistance adjusted for starter motor temperature is determined in accordance with the following relationship:

R_{adj_nom} (T_SM)=R_nom(1+ρ

(T_sm −

T₀))

wherein R_{adj_nom}(T_SM) is the nominal starter motor resistance adjusted for a starter motor temperature T_SM,

R_nom is the nominal starter motor resistance at a nominal temperature T₀, and

ρ

is a temperature-based resistivity coefficient.

9. The method of claim 7, wherein the nominal estimated back-emf adjusted for starter motor temperature is determined in accordance with the following relationship:

K_{e_adj_nom}(T_SM)=K_{e_nom}(1β

(T_SM−

T₀))

wherein K_{e_nom} is the nominal back-emf at a nominal temperature T₀,

K_{e_adj_nom}(T_SM) is the nominal back-emf at a starter motor temperature T_SM, and

β

is a temperature-based emf coefficient.

10. The method of claim 1, wherein controlling engine stop/start functionality based upon the SOH of the starter motor comprises disabling engine stop/start functionality for a present vehicle key-on cycle when the SOH of the starter motor is less than a first threshold SOH.

11. The method of claim 10, wherein controlling engine stop/start functionality based upon the SOH of the starter motor further comprises disabling engine stop/start functionality and alerting a vehicle operator when the SOH of the starter motor is less than a second threshold SOH, said second threshold SOH less than the first threshold SOH.

12. A method for monitoring a starter motor for an internal combustion engine configured to execute stop/start functions associated with autostop and autostart actions, comprising:

determining starter motor resistance associated with an engine starting event;

determining a back-emf for the starter motor based upon the starter motor resistance;

determining a state of health (SOH) of the starter motor corresponding to the back-emf of the starter motor, a measured engine cranking time, and starter motor temperature; and

disabling the engine stop/start functions for a present vehicle key-on cycle when the SOH of the starter motor is less than a first threshold SOH.

13. The method of claim 12, wherein determining the back-emf for the starter motor based upon the starter motor resistance comprises employing the starter motor resistance to estimate back-emf in accordance with the following relationships:

φ

(t)θ

=V_B(t)−

I_B{circumflex over (R)}_e

φ

(t)=N_spd,θ

=K_e

wherein V_B(t) is a battery voltage,

I_B is a battery current,

{circumflex over (R)}_e is an estimate of the starter motor resistance

N_spd is a rotational speed of the starter motor, and

K_e is the estimated back-emf.

14. The method of claim 13, wherein the estimated starter motor resistance for the starting event is determined in accordance with the following relationship:

15. The method of claim 13, wherein employing the starter motor resistance to estimate back-emf further comprises applying a least-squares estimation routine to converge to the estimated back-emf for the battery current and the battery voltage during the engine starting event.

16. The method of claim 12, wherein determining the SOH of the starter motor comprises determining the state of health based upon a minimum SOH of a start/stop function availability SOH and a fault detection SOH, said minimum SOH adjusted based upon a ratio of a nominal engine cranking time for the starter motor temperature and the measured engine cranking time.

17. The method of claim 16, wherein the start/stop function availability SOH is determined in accordance with the following relationship:

18. The method of claim 16, wherein the fault detection SOH is determined in accordance with the following relationship:

19. The method of claim 18, wherein the nominal starter motor resistance adjusted for starter motor temperature is determined in accordance with the following relationship:

R_{adj_nom}(T_SM)=R_nom(1+ρ

(T_SM−

T₀))

wherein R_{adj_nom}(T_SM) is the nominal starter motor resistance adjusted for a starter motor temperature T_SM,

R_nom is the nominal starter motor resistance at a nominal temperature T₀, and

ρ

is a temperature-based resistivity coefficient.

20. The method of claim 18, wherein the nominal estimated back-emf adjusted for temperature is determined in accordance with the following relationship:

K_{e_adj_nom}(T_SM)=K_{e_nom}(1−

β

(T_SM−

T₀))

wherein K_{e_nom} is the nominal back-emf at a nominal temperature T₀,

K_{e_adj_nom}(T_SM) is the nominal back-emf at a starter motor temperature T_SM, and

β

is a temperature-based emf coefficient.