Pulse-width-modulating feedback control of electromagnetic actuators

Claim 1

A system for controlling the dynamics of an electromagnetic actuator having a related armature, coil and driver, in which the armature moves by activation of the related driver which energizes the related coil in response to a pulsed, driver-control waveform, certain aspects of the motion being affected by naturally occurring disturbances which cause the trajectory to depart from the ideal, the system comprising transducer means (2, 34, 53) to sense at least one state variable; digitizing means (3), connected to said transducer means (2), to digitize the transducer output; memory (6) for storing digital statements of the ideal trajectory; computer means (4), connected to said digitizing means (3) and to said memory (6), arranged to compare the digital transducer output with the digital statement of the ideal trajectory, and to provide a control signal which causes the driver-control waveform to be pulse-width modulated in response to the comparison; and a programmable time (7), responsive to the control signal, to produce the pulse-width-modulated, driver-control waveform; whereby the trajectory is urged, by pulse-width modulation, to seek the ideal.

Claim 2

A system for controlling the dynamics of an electromagnetic actuator having a related armature, coil and driver, in which the armature moves by activation of the related driver which energizes the related coil in response to a pulsed, driver-control waveform, certain aspects of the motion being affected by naturally occurring disturbances which cause the trajectory to depart from the ideal, the system comprising transducer means (2, 34, 53) to sense at least one state variable; digitizing means (3), connected to said transducer means (2), to digitize the transducer output; memory (6) for storing digital statements of the ideal trajectory; computer means (4), connected to said digitizing means (3) and to said memory (6), arranged to compare the digital transducer output with the digital statement of the ideal trajectory, and to provide a control signal which causes the driver-control waveform to be pulse-width modulated in response to the comparison; and a programmable time (7), responsive to the control signal, to produce the pulse-width-modulated, driver-control waveform; whereby the trajectory is urged, by pulse-width modulation, to seek the ideal.

Claim 6

A system for controlling the dynamics of a group of electromagnetic actuators, each actuator having a related armature, coil and driver, in which system an armature is displaceable from an intial position by electrical activation of the related coil, comprising: means to regulate the armature trajectory, in spite of naturally occurring disturbances, to conform to ideal values characteristic of an ideal trajectory, through pulse-width-modulation of the coil-energizing waveform, means to provide the coil-energizing waveform as a succession of pulses, denoted sequentially by the index i, which begin at fixed times t; with respect to the start of the actuation, and means to modulate each pulse to have a variable duration τ i determined on-the-fly as a function of a vector of state-variable errors e; observed at a pre-defined observation time t i fixed with respect to the start of said pulse, said errors being computed by reference to an ideal trajectory.

Claim 7

A system for controlling the dynamics of a group of electromagnetic actuators, each actuator having a related armature, coil and driver, in which system an armature is displaceable from an intial position by electrical activation of the related coil, comprising: means to regulate the armature trajectory, in spite of naturally occurring disturbances, to conform to ideal values characteristic of an ideal trajectory, through pulse-width-modulation of the coil-energizing waveform, means to provide the coil-energizing waveform as a succession of pulses, denoted sequentially by the index i, which begin at fixed times t; with respect to the start of the actuation, and means to modulate each pulse to have a variable duration τ i determined on-the-fly as a function of a vector of state-variable errors e; observed at a pre-defined observation time t i fixed with respect to the start of said pulse, said errors being computed by reference to an ideal trajectory.

Claim 8

A method for automatically deriving the control functions f required to achieve the desired regulation of actuator dynamics, including the following steps: calibrating the ideal trajectory, by firing the actuator in the absence of perturbations, using a nominal coil-energizing waveform made up of a series of pulses having pre-defined, nominal pulse widths τ i , whereby the ideal trajectory is generated, thereby allowing the state variables describing the ideal trajectory to be measured at the pre-defined observation timest i *, and the results to be stored as digital statements in memory; performing a trial-and-error procedure, for each pules i in the coil-energizing waveform, for the purpose of obtaining experimental data describing the control function f;, in which various combinations of state-variable errors e; for pulse i are deliberately and systematically produced at the observation time t t by means of perturbation parameters, each combination of perturbation parameters being applied while firing the actuator a number of times, with each actuation employing a slightly different width τ i of pulse i (all other pulses held fixed at their nominal widths), thereby to determine which values of pulse width τ i counteract the given combination of state-variable errors e; with adequate success, success being defined according to an acceptance criterion which is chosen to reflect the goals of the feedback-control system; and performing a statistical procedure for fitting the experimental data collected by the trial-and-error procedure, whereby the data relevant to each pulse of the coil-energizing waveform are fit separately with a piece-wise smooth function, thereby interpolating and extrapolating the experimental data, such that during subsequent, feedback-controlled operation, the appropriate values of pulse widths τ i may be determined for any given combination of the state-variable errors e;.

Claim 9

A method for automatically deriving the control functions f required to achieve the desired regulation of actuator dynamics, including the following steps: calibrating the ideal trajectory, by firing the actuator in the absence of perturbations, using a nominal coil-energizing waveform made up of a series of pulses having pre-defined, nominal pulse widths τ i , whereby the ideal trajectory is generated, thereby allowing the state variables describing the ideal trajectory to be measured at the pre-defined observation timest i *, and the results to be stored as digital statements in memory; performing a trial-and-error procedure, for each pules i in the coil-energizing waveform, for the purpose of obtaining experimental data describing the control function f;, in which various combinations of state-variable errors e; for pulse i are deliberately and systematically produced at the observation time t t by means of perturbation parameters, each combination of perturbation parameters being applied while firing the actuator a number of times, with each actuation employing a slightly different width τ i of pulse i (all other pulses held fixed at their nominal widths), thereby to determine which values of pulse width τ i counteract the given combination of state-variable errors e; with adequate success, success being defined according to an acceptance criterion which is chosen to reflect the goals of the feedback-control system; and performing a statistical procedure for fitting the experimental data collected by the trial-and-error procedure, whereby the data relevant to each pulse of the coil-energizing waveform are fit separately with a piece-wise smooth function, thereby interpolating and extrapolating the experimental data, such that during subsequent, feedback-controlled operation, the appropriate values of pulse widths τ i may be determined for any given combination of the state-variable errors e;.

Claim 10

A method for automatically deriving, through selective pulse-width-modulation of a succession of n pulses, the control functions f l ,..., f n and the acceptance windows Δ1, ..., Δ n-1 , comprising the following steps: (a) deriving an ideal trajectory in terms of n pulses having pre-defined widths: (b) deriving, by causing and measuring disturbances of actuator activity, a set of data points which partially describes the control function for pulse n, and at the same time circumscribes the acceptance window Δn-1; (c) iterating step (b) for earlier pulses n -1, ..., 1; (d) providing, through regression analysis, a complete description of the control functions fi, ..., f n ; whereby pulse-width modulation according to the control functions causes the actuator trajectory to seek the ideal.

Claim 11

A method for automatically deriving, through selective pulse-width-modulation of a succession of n pulses, the control functions f l ,..., f n and the acceptance windows Δ1, ..., Δ n-1 , comprising the following steps: (a) deriving an ideal trajectory in terms of n pulses having pre-defined widths: (b) deriving, by causing and measuring disturbances of actuator activity, a set of data points which partially describes the control function for pulse n, and at the same time circumscribes the acceptance window Δn-1; (c) iterating step (b) for earlier pulses n -1, ..., 1; (d) providing, through regression analysis, a complete description of the control functions fi, ..., f n ; whereby pulse-width modulation according to the control functions causes the actuator trajectory to seek the ideal.