Feed forward technique and application for injection pressure control
A control method is provided for using a feed forward technique. The method includes, but is not limited to using a setpoint value of a controlled variable to calculate a compensation of the closed loop static error, summing said contribution to the setpoint value, operating an estimation of the closed loop error to obtain a feed forward contribution.
1. A control method for an operating parameter in an actual system plant using a feed forward technique, the control method comprising:
computing a closed loop static error compensation using a setpoint value for the operating parameter and a transfer function representative of the actual plant system;
computing a compensated setpoint value by adding the closed loop static error compensation and the setpoint value;
determining an actual value of the operating parameter from a sensor monitoring the actual system plant;
computing a controlled variable error by subtracting the actual value from the compensated setpoint value;
estimating a closed loop error of the compensated setpoint value;
computing a feed forward load contribution based on the controlled variable error and the estimated closed loop error;
computing a calculated load by adding the feed forward load contribution to an estimated load of the actual system plant;
computing an adjusted load by subtracting a measured load of the actual system plant from the calculated load; and
controlling the operating parameter based on the adjusted load.
2. The control method according to claim 1 , wherein the feed forward load contribution comprises a summation of a load integral contribution and a load proportional contribution, the control method further comprising:
computing the load integral contribution as a function of a difference between the controlled variable error and the estimated closed loop error; and
computing the load proportion contribution as a function of the controlled variable error.
3. The control method according to claim 1 , wherein the actual plant system comprises a fuel injection system having a fuel rail and wherein:
a fuel injection pressure (p) corresponds to the operating parameter;
a fuel quantity entering the fuel the fuel rail (Q in ) corresponds to the calculated load;
a fuel quantity exiting the fuel rail (Q out ) corresponds to the measured load; and
an integral of the quantity balance as follows:
Δ p ˜∫( Q in −Q out ) dt
corresponds to the transfer function.
4. A control apparatus for controlling an operating parameter of an actual system plant using a feed forward technique, the control apparatus comprising:
a sensor configured to measure the operating parameter;
an actuator configured to control the operating parameter; and
an electronic control unit in communication with the sensor and controlling the actual plant system, wherein the electronic control unit is configured to:
compute a closed loop static error compensation using a setpoint value for the operating parameter and a transfer function representative of the actual plant system;
compute a compensated setpoint value by adding the closed loop static error compensation and the setpoint value;
determine an actual value of the operating parameter measured by the sensor;
compute a controlled variable error by subtracting the actual value from the compensated setpoint value;
estimate a closed loop error of the compensated setpoint value;
compute a feed forward load contribution based on the controlled variable error and the estimated closed loop error;
compute a calculated load by adding the feed forward load contribution to an estimated load of the actual system plant;
compute an adjusted load by subtracting a measured load of the actual system plant from the calculated load; and
control the actuator for adjusting the operating parameter based on the adjusted load.
5. The control apparatus according to claim 4 , wherein the feed forward load contribution comprises a summation of a load integral contribution and a load proportional contribution, the electronic control unit is further configured to:
compute the load integral contribution as a function of a difference between the controlled variable error and the estimated closed loop error; and
compute the load proportion contribution as a function of the controlled variable error.
6. The control apparatus according to claim 4 , wherein the actual plant system comprises a fuel injection system having a fuel rail and wherein:
a fuel injection pressure (p) corresponds to the controlled variable;
a fuel quantity entering the fuel the fuel rail (Q in ) corresponds to the calculated load;
a fuel quantity exiting the fuel rail (Q out ) corresponds to the measured load; and
an integral of the quantity balance as follows:
Δ p ˜∫( Q in −Q out ) dt
corresponds to the transfer function.
7. A non-transitory computer readable medium comprising processor-executable instructions for reading data from a processor in communication with at least one sensor configured to measure an operating parameter of an actual system plant, the processor-executable instructions when executed on the processor in a control apparatus configure the control apparatus to:
compute a closed loop static error compensation using a setpoint value for the operating parameter and a transfer function representative of the actual plant system;
compute a compensated setpoint value by adding the closed loop static error compensation and the setpoint value;
determine an actual value of the operating parameter measured by the sensor;
compute a controlled variable error by subtracting the actual value from the compensated setpoint value;
estimate a closed loop error of the compensated setpoint value;
compute a feed forward load contribution based on the controlled variable error and the estimated closed loop error;
compute a calculated load by adding the feed forward load contribution to an estimated load of the actual system plant;
compute an adjusted load by subtracting a measured load of the actual system plant from the calculated load; and
control the operating parameter based on using the adjusted load.
8. The non-transitory computer readable medium according to claim 7 , wherein the feed forward load contribution comprises a summation of a load integral contribution and a load proportional contribution, and the processor-executable instruction when executed on the processor configured the control apparatus to
compute the load integral contribution as a function of a difference between the controlled variable error and the estimated closed loop error; and
compute the load proportion contribution as a function of the controlled variable error.
9. The non-transitory computer readable medium according to claim 7 , wherein the actual plant system comprises a fuel injection system having a fuel rail and wherein:
a fuel injection pressure (p) corresponds to the controlled variable;
a fuel quantity entering the fuel the fuel rail (Qin) corresponds to the calculated load;
a fuel quantity exiting the fuel rail (Qout) corresponds to the measured load; and
an integral of the quantity balance as follows:
Δ p ˜∫( Q in −Q out ) dt
corresponds to the transfer function.