Control of particle delivery in contamination test rig

A system for controlling delivery of contaminates, the system comprising:

• a conveyor configured to feed a plurality of contaminate particles from a hopper towards an airflow, the conveyor including a motor configured to drive the conveyor;
• a scale configured to measure the weight of contents of the hopper;
• a processor in communication with the motor and the scale, the processor configured to:
• cause the motor to rotate at a motor speed corresponding to a target mass flow rate;
• receive a plurality of weight measurements from the scale taken within a sliding window of time, each of the weight measurements having a corresponding one of a plurality of time points indicative of when the weight measurements were taken;
• apply linear regression to a data set comprising the time points as an independent variable and the weight measurements as a dependent variable, which results in a determination of a line fitting the data set;
• determine a current mass flow rate of the contaminate particles from the slope of the line fitting the data set;
• determine an estimated change in the motor speed needed to achieve the target mass flow rate, the estimated change determined from a predetermined mapping of flow rates to motor speeds, the estimated change based on the current mass flow rate and the target mass flow rate,
• wherein the estimated change is determined to be a fraction of a motor speed adjustment that the predetermined mapping of flow rates to motor speeds indicates from only the current mass flow rate and the target mass flow rate;
• and
• cause a change in the motor speed of the motor in accordance with the estimated change in the motor speed.

A method of controlling delivery of contaminates, the method comprising:

• determining a motor speed corresponding to a target mass flow rate from a predetermined mapping of flow rates to motor speeds;
• causing a motor, which drives a conveyor, to rotate at the motor speed,
• wherein the conveyor feeds contaminate particles from a hopper to an airflow in a mix line of a test rig for testing a test valve;
• weighing contents of the hopper at a plurality of time points within a sliding window of time by taking a plurality of weight measurements with a scale;
• determining a line that fits a data set by a processor applying linear regression to the data set, the data set comprising the time points as an independent variable and the weight measurements as a dependent variable;
• determining, by the processor, a current mass flow rate of the contaminate particles from the slope of the line fitting the data set;
• determining, by the processor, an estimated change in the motor speed by:
• determining a flow rate error as a difference between the current mass flow rate and a target mass flow rate;
• calculating a sensitivity slope as a change in motor speed divided by a change in flow rate at the current mass flow rate from the predetermined mapping of flow rates to motor speeds at the current mass flow rate;
• and
• calculating the estimated change in the motor speed to be the sensitivity slope multiplied by the flow rate error multiplied by a predetermined fraction;
• and
• causing, by the processor, a change in the motor speed of the motor in accordance with the estimated change in the motor speed.