Method and system for determining engine state of a hybrid electric vehicle

• US 7,197,382 B2
• Filed: 04/19/2004
• Issued: 03/27/2007
• Est. Priority Date: 04/19/2004
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Syed, Fazal, McGee, Ryan, Davies, Kevin, Prema, Mukunda
• Primary Examiner(s): Tran; Dalena
• Application Number:
  US10/709,177
• Publication Number:
  US 20050230977A1
• Time in Patent Office: 1,072 Days
• Field of Search: 701/22, 716/2, 716/3, 716/5, 716/7, 716/18, 703/16, 706/13, 706/16, 706/33, 706/45, 180/65.1, 180/65.3, 180/65.5, 180/65.8
• US Class Current: 701/22
• CPC Class Codes: B60K 6/44 Series-parallel type
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 20/11 using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance utilising navigation and traffic information in the control strategy B60W20/12
• CPC Class Codes: F02D 2041/1411 using a finite or infinite state machine, automaton or state graph for controlling or modelling
• CPC Class Codes: F02D 41/26 using computer, e.g. microprocessor
• CPC Class Codes: F02N 11/0818 Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode
• CPC Class Codes: F02N 2300/30 characterised by the use of digital means
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A method and system of engine state determination includes a plurality of requestors each of which compares vehicle or environmental conditions to a requirement and outputs a request state variable. The requestors are grouped according to function or component and the request state variables are combined and simplified at the output of each group. A state machine receives the final combined and simplified request state, and evaluates it according to the active or inactive status of the requests. The state machine carries out the proper state transition and outputs the desired engine state to engine control algorithms that start or stop the engine as necessary.

Claims

1. A method for controlling on/off states of an engine in a hybrid electric vehicle powertrain, the method comprising the steps of:

generating a plurality of request state variables based on a comparison of vehicle operating conditions and requirements, each variable indicating an active or inactive status of a plurality of engine requests;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining the at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable;

evaluating the final request state variable to determine whether a change in engine state is desirable;

the step of evaluating the final request state variable comprising;

transitioning a state machine from an engine on state to an engine off state in accordance with a first predetermined relationship of engine request variables fpu, pu, ipu and fpd and otherwise maintaining the state machine in an engine on state; and

transitioning the state machine from an engine off state to an engine on state in accordance with a second predetermined relationship of engine request variables fpu, pu, ipu and fpd and otherwise maintaining the state machine in an engine off state, where fpd, pd, fpu, ipd, pu and ipu are engine request variables, which identify the active or inactive status of engine requests.

2. The method of claim 1 wherein the step of combining joins two or more request states through a bitwise OR operation.

3. The method of claim 2 wherein the step of simplifying includes an arbitration operation that follows the requests according to a predetermined priority.

4. The method of claim 1 wherein said engine requests are grouped in hierarchical levels through the combining and simplifying steps.

5. A method of controlling the on/off state of an engine in a hybrid electric vehicle powertrain comprising the following steps:

generating a plurality of reguest state variables based on a comparison of vehicle operating conditions and reguirements, each variable indicating the active or inactive status of each of a plurality of engine requests, the value of each request state variable being constrained to a set of fundamental request states;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable; and

evaluating the final request state variable to determine whether a change in engine state is desirable;

the step of evaluating the final request state variable includes the step of;

transitioning a state machine from an engine off state to an engine on state in accordance with the following expression;

(fpu+pu·

ipu)·

fpd

where fpu, pu, ipu and fpd are engine request variables identifying the active or inactive status of engine requests.

6. The method of claim 5 wherein each fundamental request state comprises a 6 bit binary word, each bit identifying whether an engine request state is active or inactive.

7. A method of controlling the on/off state of an engine in a hybrid electric vehicle powertrain comprising the following steps:

generating a plurality of request state variables based on a comparison of vehicle operating conditions and requirements, each variable indicating the active or inactive status of each of a plurality of engine requests, the value of each request state variable being constrained to a set of fundamental request states;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable; and

evaluating the final request state variable to determine whether a chance in engine state is desirable;

the step of evaluating the final request state variable including the step of;

transitioning a state machine from an engine on state to an engine off state in accordance with the following expression;

fpd+pd·

fpu·

ipd·

pu

where fpd, pd, fpu, ipd, and pu are engine request variables identifying the active or inactive status of engine requests.

8. The method of claim 7 wherein each fundamental request state comprises a 6 bit binary word, each bit identifying whether an engine request state is active or inactive.

9. The method of claim 8 wherein the step of simplifying includes an arbitration operation that follows the requests according to a predetermined priority.

10. A method of controlling the on/off state of an engine in a hybrid electric vehicle powertrain comprising the following steps:

generating a plurality of request state variables based on a comparison of vehicle operating conditions and requirements, each variable indicating the active or inactive status of each of a plurality of engine requests, the value of each request state variable being constrained to a set of fundamental request states;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable;

evaluating the final request state variable to determine whether a chance in engine state is desirable;

the step of evaluating the final request state variable including the steps of;

transitioning a state machine from an engine on state to an engine off state in accordance with the following expression;

fpd+pd·

fpu·

ipd·

pu

and otherwise maintaining the state machine in an engine on state; and

transitioning said state machine from an engine off state to an engine on state in accordance with the following expression;

(fpu+pu·

ipu)·

fpd

and otherwise maintaining the state machine in an engine off state, where fpd, pd, fpu, ipd, pu, and ipu are engine request variables identifying the active or inactive status of engine requests.

11. The method of claim 10 wherein the step of combining joins two or more request states through a bitwise OR operation.

12. The method of claim 11 wherein the engine requests are grouped in hierarchical levels through the combination and simplification steps.

13. A method of controlling the on/off states of an engine in a hybrid electric vehicle powertrain comprising the following steps:

generating a plurality of request state variables based on a comparison of vehicle operating conditions and requirements, each variable indicating the active or inactive status of each of a plurality of engine requests, the value of each request state variable being constrained to a set of fundamental request states;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable; and

evaluating the final request state variable to determine whether a change in engine state is desirable;

the step of evaluating the final request state variable including the step of;

transitioning a state machine from an engine off state to an engine on state in accordance with a predetermined relationship of engine request variables fpu, pu, ipu and fpd, which identify an active status or an inactive status of engine requests.

14. A method of controlling the on/off state of an engine in a hybrid electric vehicle powertrain comprising the following steps:

generating a plurality of request state variables based on a comparison of vehicle operating conditions and requirements, each variable indicating the active or inactive status of each of a plurality of engine requests, the value of each request state variable being constrained to a set of fundamental request states;

prioritizing the active request state variables according to a predetermined schedule;

selecting at least two active request state variables of higher priority than other request state variables in the plurality of request state variables;

combining at least two request state variables to form a combined request state variable that contains active requests in the at least two request state variables;

simplifying the combined request state variable to eliminate any redundant requests and to resolve any conflicting requests;

providing a final request state variable;

evaluating the final request state variable to determine whether a change in engine state is desirable;

the step of evaluating the final request variable including the steps of;

transitioning a state machine from an engine on state to an engine off state in accordance with a first predetermined relationship of engine request variables and otherwise maintaining the state machine in an engine on state; and

transitioning the state machine from an engine off state to an engine on state in accordance with a second predetermined relationship of engine request variables and otherwise maintaining the state machine in an engine off state, the engine request variables identifying the active or inactive status of engine requests.

15. The method set forth in claim 14 wherein each fundamental request state comprises a 6 bit binary word, each bit identifying whether an engine request state is active or inactive.

16. The method set forth in claim 14 wherein the step of combining joins two or more request state variables through a bitwise OR operation.

17. The method set forth in claim 14 wherein the step of simplifying includes an arbitration operation that follows the requests according to a predetermined priority.

18. The method set forth in claim 14 wherein the engine requests are grouped in hierarchical levels through the combination and simplification steps.