Device and method for fast position control of a hydraulic actuator

A control system for controlling an actuator that is operable to be switched into an on state and an off state with pulse width modulation of a square wave signal, the control system comprising:

• a system parameter detection module configured to determine an actual system parameter on a first time schedule;
• a system desire module configured to determine a desired system parameter on a second time schedule;
• a computation module configured to run on a third time schedule, the computation module configured to:
• determine a position error difference between the actual system parameter and the desired system parameter, the third time schedule being configured to begin and to run the step of determining the position error difference each time that the system parameter detection module determines the actual system parameter and each time that the system desire module determines the desired system parameter;
• and
• determine a desired duty cycle of the square wave signal;
• a pulse width modulation output unit configured to output the square wave signal having the desired duty cycle;
• a command module configured to send a duty cycle command to the pulse width modulation output unit, the duty cycle command configured to cause the pulse width modulation output unit to output the square wave signal having the desired duty cycle;
• and
• a duty cycle determination module configured to determine an actual duty cycle of the square wave signal,
• wherein the computation module is further configured to determine whether a duty cycle difference between the actual duty cycle and the desired duty cycle exceeds a predetermined large error threshold;
• if the duty cycle difference exceeds the predetermined large error threshold, the computation module is configured to cause an immediate abortion of a current pulse repetition period of the square wave signal and cause the pulse width modulation output unit to start a new pulse repetition period of the square wave signal having the desired duty cycle;
• and if the duty cycle difference does not exceed the predetermined large error threshold, the command module is configured to allow the current pulse repetition period of the square wave signal to finish and to cause the pulse width modulation output unit to start the new pulse repetition period after the current pulse repetition period is finished.

A variable valve timing system for a motor vehicle, the variable valve timing system comprising:

• a camshaft configured to rotate and to control opening of a poppet valve;
• a camshaft phaser actuator defining a phaser cavity;
• a camshaft target wheel fixed to the camshaft and having a plurality of target edges;
• a camshaft sensor configured to sense the target edges;
• a pulse width modulated (PWM) control valve, the PWM control valve configured to be switched into an on state and an off state with pulse duration modulation of a square wave signal to control the flow of hydraulic fluid into and out of the phaser cavity to control an angular position of the camshaft with respect to a crankshaft;
• and
• a control system comprising:
• a camshaft angle detection module configured to determine an actual camshaft angle with respect to a crankshaft angle on a first time schedule based on feedback from the camshaft sensor including timing of sensing at least one target edge;
• a desired phase module configured to determine a desired camshaft angle with respect to the crankshaft angle on a second time schedule;
• a computation module configured to run on a third time schedule, the computation module configured to:
• determine a position error difference between the actual camshaft angle and the desired camshaft angle, the third time schedule being configured to begin and to run the step of determining the position error difference each time that the camshaft angle detection module determines the actual camshaft angle and each time that the desired phase module determines the desired camshaft angle;
• and
• determine a desired duty cycle of the square wave signal;
• a command module configured to send a duty cycle command to the PWM control valve, the duty cycle command configured to cause the PWM control valve to output the square wave signal having the desired duty cycle;
• and
• a duty cycle determination module configured to determine an actual duty cycle of the square wave signal, the computation module being further configured to determine whether a duty cycle difference between the actual duty cycle and the desired duty cycle exceeds a predetermined large error threshold;
• if the duty cycle difference exceeds the predetermined large error threshold, the computation module is configured to cause an immediate abortion of a current pulse repetition period of the square wave signal and cause the pulse width modulation output unit to start a new pulse repetition period of the square wave signal having the desired duty cycle;
• and if the duty cycle difference does not exceed the predetermined large error threshold, the command module is configured to allow the current pulse repetition period of the square wave signal to finish and to cause the pulse width modulation output unit to start the new pulse repetition period after the current pulse repetition period is finished.