Engine speed governor having improved low idle speed stability
First Claim
1. A method for controlling the speed of an internal combustion engine having an engine speed sensor for generating an engine speed signal indicative of the actual engine speed and a fuel system responsive to a fuel control signal to fuel the engine, the method comprising the steps of:
- generating a reference signal indicative of a reference engine speed;
comparing the engine speed signal to the reference signal to yield an error signal;
obtaining a fueling flow rate signal as a function of the error signal, the magnitude of the flow rate signal being indicative of a volume of fuel per unit time; and
generating a fuel control signal as a function of the fueling flow rate signal and the engine speed signal.
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Accused Products
Abstract
A system and method for controlling the speed of an engine, or a speed governor, receives an error signal indicative of the difference between the actual engine speed and a commanded engine speed. This error signal is passed through a linear controller that determines a fuel flow rate in units of volume per unit time. The fuel flow rate is a substantially linear function of engine speed, and more specifically engine speed error. The output of the linear controller is fed to a non-linear compensator that determines a fueling command signal as a non-linear function of actual engine speed and fuel flow rate. The speed governor can accurately control engine speeds at low idle conditions. In one embodiment, the non-linear compensator utilizes a three-dimensional table of fueling command values as a function of fuel flow rate and engine speed. In another embodiment, the compensator applies a transfer function utilizing low and high calibration speed values enveloping a low engine speed. In another feature of the invention, a speed sensing system applies a zero order sample and hold to a sensor pulse train to generate a preliminary speed signal. This preliminary speed signal is fed to a software-based first order sample and hold component that calculates an integrated error value, leading to a speed signal value that is substantially free from frequency aliasing.
69 Citations
17 Claims
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1. A method for controlling the speed of an internal combustion engine having an engine speed sensor for generating an engine speed signal indicative of the actual engine speed and a fuel system responsive to a fuel control signal to fuel the engine, the method comprising the steps of:
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generating a reference signal indicative of a reference engine speed;
comparing the engine speed signal to the reference signal to yield an error signal;
obtaining a fueling flow rate signal as a function of the error signal, the magnitude of the flow rate signal being indicative of a volume of fuel per unit time; and
generating a fuel control signal as a function of the fueling flow rate signal and the engine speed signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for controlling the speed of an internal combustion engine having an engine speed sensor for sensing actual engine speed and a fuel system having a flow control valve responsive to a fuel control signal to supply a quantity of fuel to the engine;
- the system comprising;
means for generating an error signal as a function of the difference between the actual engine speed and a reference speed;
a linear controller operable to generate a fuel flow signal in response to the error signal, said fuel flow signal indicative of a fuel volume per unit time; and
means for converting said fuel flow signal to a fuel control signal as a function of the actual engine speed, wherein said fuel control signal is indicative of a volume of fuel per actuation of the flow control valve of the fuel system. - View Dependent Claims (12, 13, 14, 15, 16)
where G is a predetermined gain value, N is the actual engine speed, and NMIN and NMAX are calibration speed values.
- the system comprising;
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15. The system for controlling the speed of an engine according to claim 14, wherein said calibration speed values envelope a low idle speed for the engine.
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16. The system for controlling the speed of an engine according to claim 11, wherein said means for converting includes:
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a three-dimensional table maintained in a memory, said table consisting of values for said fuel control signal as a function of said fuel control signal and the engine speed; and
a table look-up processor for extracting a fuel control signal value based on said inputs to said means for converting.
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17. A system for controlling the speed of an internal combustion engine having an engine speed sensor for generating a signal indicative of the actual engine speed and a fuel system with a flow control valve responsive to a fuel control signal to supply a quantity of fuel to the engine, the system comprising:
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means for generating an error signal as a function of the difference between the actual engine speed and a reference speed;
a linear controller receiving said error signal as an input and operable to generate a fuel flow signal as a substantially linear function of said error signal, said fuel flow signal indicative of a fuel volume per unit time; and
a non-linear compensator receiving said fuel flow signal and said actual engine speed signal as inputs and operable to generate a fuel control signal as a function of said fuel flow signal and the actual engine speed.
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Specification