EP0393650A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
High resolution pulse width modulation
Assignee: Vickers Inc
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Filing: 1990-04-19
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Granted: —
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Expires: 2010-04-19
Abstract
Abstract An electrohydraulic servo system in which a microprocessor-based controller directs a pulse width modulated control signal to a servo valve for controlling flow of hydraulic fluid therethrough. Duration of each pulse in the pulse width modulated control signal is separately controlled by selectively incrementing or decrementing duration of the pulse in increments of the microprocessor clock period. Signal transition is controlled by a timer interrupt in which time required to enter the interrupt routine is measured following generation of the interrupt, and further operation is delayed by a complementary time, so that control signal transition takes place a fixed preselected number of clock periods after generation of a timer interrupt. In this way, timer interrupt latency is eliminated, and resolution of the pulse width modulated signal is enhanced through individual duration control of the signal pulses while maintaining a fixed modulated signal period.
Inventors
- 👤 John A. Miller
- 👤 Richard S. Leemhuis
- 👤 Rajamouli Gunda
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 17:11
CPC Classifications
G; G05; G05B; G05B11/00; G05B11/01; G05B11/26; G05B11/28; G05B19/00; G05B19/02; G05B19/18; G05B19/19; G05B19/414; G05B19/4142; G05B2219/00; G05B2219/30; G05B2219/34; G05B2219/34045; G05B2219/34356; G05B2219/41; G05B2219/41301; G05B2219/42; G05B2219/42237
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
123 words
An electrohydraulic system comprising means (34) responsive to an electrical control signal (I) for variably controlling flow of hydraulic fluid, and microprocessor-based control means (12) including means for receiving an input command (R), means for generating a flow command (U) as a function of said input command (R) at a predetermined sampling frequency (1/T), and means (32) for directing a pulse width modulated control signal (I) to said signal-responsive means (84) as a function of said flow command (U) and at fixed frequency (1/P) greater than said sampling frequency (1/T; characterized in that said control and signal-directing means (12, 32) comprises means for separately controlling duration of individual pulses in said pulse width modulated control signal (I) while maintaining said fixed frequency (1/P).
Claim 2
Dependent Claim
123 words
An electrohydraulic system comprising means (34) responsive to an electrical control signal (I) for variably controlling flow of hydraulic fluid, and microprocessor-based control means (12) including means for receiving an input command (R), means for generating a flow command (U) as a function of said input command (R) at a predetermined sampling frequency (1/T), and means (32) for directing a pulse width modulated control signal (I) to said signal-responsive means (84) as a function of said flow command (U) and at fixed frequency (1/P) greater than said sampling frequency (1/T; characterized in that said control and signal-directing means (12, 32) comprises means for separately controlling duration of individual pulses in said pulse width modulated control signal (I) while maintaining said fixed frequency (1/P).
Claim 3
Dependent Claim
53 words
The system set forth in claim 1 wherein said microprocessor-based control means (12) includes a clock (29) having a fixed clock period (C), and wherein said separately-controlling means comprises means for selectively increasing or decrasing duration of individual pulses in said pulse width modulated control signal by increments of said clock period (C).
Claim 4
Dependent Claim
123 words
The system set forth in claim 2 wherein said microprocessor-based control means (12) includes means forming a pulse duration timer (28), means responsive to a signal from said timer (28) to initiate a control cycle, means responsive to said clock (29) for measuring a time interval as a first number of said clock periods (C) between said timer signal and initiation of said control cycle, means for delaying operation of said control cycle for a second number of said clock periods (C) complementary to said first number, means for changing state of said pulse width modulated control signal following said second number of clock periods, and means for reinitiating operation of said timer (28) for a duration corresponding to said individual pulse duration.
Claim 5
Dependent Claim
39 words
The system set forth in claim 3 wherein said separately-controlling means comprises means for delaying reinitiation of said timer (28) for a third number of said clock periods corresponding to desired increase or decrease of said individual pulse duration.
Claim 6
Dependent Claim
31 words
The system set forth in claim 2 wherein said selectively increasing or decreasing means comprises means for selectively increasing or decreasing each said pulse duration by a single clock period (C).
Claim 7
Dependent Claim
82 words
The system set forth in claim 1 wherein said microprocessor-based control means (12) comprises means forming a pulse duration timer (28), means responsive to a signal from said timer (28) to initiate a control cycle, means for measuring time interval between said timer signal and initiation of said control cycle, means for delaying operations of said control cycle for a time complementary to said interval, and means for changing state of said pulse width modulated control signal following said complementary time delay.
Claim 8
Dependent Claim
90 words
The electrohydraulic system set forth in claim 1 wherein said pulse duration timer (28) determines the duration of each pulse in a pulse width modulated control signal, means responsive to a signal from said timer to initiate a control cycle, means for measuring time interval between said timer signal and initiation of said control cycle, means for delaying operation of said control cycle for a time complementary to said time interval, and means responsive to operation of said controi cycle for changing state of said pulse width modulated control signal.
Claim 9
Dependent Claim
72 words
The system set forth in claim 7 wherein said microprocessor-based control means (28) further includes a clock (29) having a fixed clock period (C), wherein said interval-measuring means measures said interval as a first number of clock periods between said timer signal and initiation of said control cycle, and wherein said operation-delaying means comprises means for delaying said operation for a second number of said clock periods complementary to said first number.
Claim 10
Dependent Claim
32 words
The system set forth in claim 8 further comprising means for selectively increasing or decreasing duration of individual pulses in said pulse width modulated control signal by increments of said clock period.
Claim 11
Dependent Claim
30 words
The system set forth in claim 9 wherein said selectively increasing or decreasing means comprises means for selectively increasing or decreasing each said pulse duration by a single clock period.
Claim 12
Independent Claim
121 words
A method of generating a pulse width modulated control signal to a controllable device having a natural mechanical frequency, and employing digital control means (12) having a predetermined sampling period (T) and a clock (29) with a predetermined clock period (C), said method comprising the steps of (a) establishing a repeating pulse width modulation period (P) less than said sampling period (T) and at a frequency greater than said natural frequency, (b) collectively controlling duty cycle of said repeating pulse width modulation period (P) over each entire sampling period (T), and (c) individually controlling duration of each pulse in said pulse width modulation period (P) by increments of said clock period (C) while maintaining said pulse width modulation period (P) constant.
Claim 13
Independent Claim
121 words
A method of generating a pulse width modulated control signal to a controllable device having a natural mechanical frequency, and employing digital control means (12) having a predetermined sampling period (T) and a clock (29) with a predetermined clock period (C), said method comprising the steps of (a) establishing a repeating pulse width modulation period (P) less than said sampling period (T) and at a frequency greater than said natural frequency, (b) collectively controlling duty cycle of said repeating pulse width modulation period (P) over each entire sampling period (T), and (c) individually controlling duration of each pulse in said pulse width modulation period (P) by increments of said clock period (C) while maintaining said pulse width modulation period (P) constant.
Claim 14
Dependent Claim
64 words
The method set forth in claim 11 wherein said step (c) comprises the steps of (c1) selectively increasing width of one pulse in each cycle of said pulse width modulation period (P) by an incremental number of said clock periods (C), and (c2) decreasing width of the other puise in the same said cycle by the same said incremental number of clock periods (C).
Claim 15
Dependent Claim
13 words
The method set forth in claim 12 wherein said incremental number is one.
Claim 16
Dependent Claim
130 words
The method set forth in claim 12 wherein said step (a) comprises the steps of (a1) establishing a pulse width timer (28) in said digital control means (12) incremented by said clock period (C), (a2) loading said timer (28) with desired duration of a first pulse of said pulse width modulation period (P), (a3) upon time-out of said timer (28), entering an interrupt routine, (a4) measuring duration of said step (a3) as a first number of said clock periods (C), (a5) delaying operation of said interrupt routine for a second number of said clock periods (C) complementary to said first number. (a6) changing state of said pulse width modulated signal, and (a7) reloading said timer (28) with desired duration of a next pulse in said pulse width modulation period (P).
Claim 17
Dependent Claim
30 words
The method set forth in claim 14 wherein said step (c) comprises the step of delaying operation of said timer (28) by said incremental number of said clock periods (C).
Claim 18
Independent Claim
168 words
A method of generating a pulse width modulated control signal to a controllable device employing digital control means (12) having a clock (29) with a predetermined clock period (C), said method comprising the steps of (a) loading a pulse width timer (28) in said digital control means (12) with desired duration of a first pulse in said dpulse width modulated signal, (b) cycling said timer (28) with said clock period (C), (c) upon time-out of said timer (28), generating an interrupt in said digital control means (12), (d) entering a pulse width control cycle upon generation of said interrupt, (e) measuring time interval between said steps (c) and (d) as a first number of said clock periods (C), (f) delaying further operation for a second number of said clock periods (C) complementary to said first number, (g) changing state of said pulse width modulated signal, and (h) reloading said timer (28) in said step (a) with desired duration of a next pulse in said pulse width modulated signal.
Claim 19
Independent Claim
168 words
A method of generating a pulse width modulated control signal to a controllable device employing digital control means (12) having a clock (29) with a predetermined clock period (C), said method comprising the steps of (a) loading a pulse width timer (28) in said digital control means (12) with desired duration of a first pulse in said dpulse width modulated signal, (b) cycling said timer (28) with said clock period (C), (c) upon time-out of said timer (28), generating an interrupt in said digital control means (12), (d) entering a pulse width control cycle upon generation of said interrupt, (e) measuring time interval between said steps (c) and (d) as a first number of said clock periods (C), (f) delaying further operation for a second number of said clock periods (C) complementary to said first number, (g) changing state of said pulse width modulated signal, and (h) reloading said timer (28) in said step (a) with desired duration of a next pulse in said pulse width modulated signal.
References Cited (Backward Citations)
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