Method for controlling discharge flow rate in a loss-in-weight scale

A method for controlling a discharge flow rate of a loss-in-weight scale comprising a meter, a motor, and a screw feeder using a calibration technique that reduces adjustment time, said method comprising:

• setting a plurality of consecutive sampling points, and setting a plurality of values of control output for the meter, each of said values of the control output corresponding to a respective one of the sampling points;
• operating the loss-in-weight scale with the values of the control output over time, including receiving weights of materials remaining in a weighing hopper of the loss-in-weight scale at the sampling points;
• calculating a functional relationship between the values of the control output and time such that applying different time values to the functional relationship results in output of different control values;
• calculating a functional relationship between the weights of materials remaining in the weighing hopper and time such that applying different time values to the functional relationship results in output of different expected weights of materials remaining in the weighing hopper;
• calculating a functional relationship between determined discharge flow rates of the screw feeder and the values of the control output by using the functional relationship between the values of the control output and time and the functional relationship between the weights and time such that applying different values of the control output to the functional relationship results in output of different discharge flow rates of the screw feeder;
• and
• operating the loss-in-weight scale according to the functional relationship between the discharge flow rates of the screw feeder and the values of the control output at a further time such that applying different desired discharge flow rates results in the loss-in-weight scale operating with different values of the control output;
• wherein a slope at any location on a curve corresponding to the functional relationship between the control output and time is less than or equal to a defined value for the loss-in-weight scale;
• and
• wherein the functional relationship between the control output and time is a linear, exponential, or quadratic curve relationship, or is a curve relationship that is obtained by an arbitrary combination of the linear, exponential, or quadratic curve relationship.

A loss-in-weight scale for controlling a discharge flow rate using a calibration technique that reduces adjustment time, said loss-in-weight scale comprising:

• a meter;
• a motor;
• a screw feeder;
• and
• one or more non-transitory electronic storage devices comprising software instructions, which when executed, configure one or more processors to:
• set a plurality of consecutive sampling points, and set a plurality of values of control output for the meter, each of said values of the control output corresponding to a respective one of the sampling points;
• operate the loss-in-weight scale with the values of the control output over time, including receiving weights of materials remaining in a weighing hopper of the loss-in-weight scale at the sampling points;
• calculate a functional relationship between the values of the control output and time such that applying different time values to the functional relationship results in output of different control values;
• calculate a functional relationship between the weights of materials remaining in the weighing hopper and time such that applying different time values to the functional relationship results in output of different expected weights of materials remaining in the weighing hopper;
• calculate a functional relationship between determined discharge flow rates of the screw feeder and the values of the control output by using the functional relationship between the values of the control output and time and the functional relationship between the weights and time such that applying different values of the control output to the functional relationship results in output of different discharge flow rates of the screw feeder;
• and
• operate the loss-in-weight scale according to the functional relationship between the discharge flow rates of the screw feeder and the values of the control output at a further time such that applying different desired discharge flow rates results in the loss-in-weight scale operating with different values of the control output;
• wherein a slope at any location on a curve corresponding to the functional relationship between the control output and time is less than or equal to a defined value for the loss-in-weight scale;
• and
• wherein the functional relationship between the control output and time is a linear, exponential, or quadratic curve relationship, or is a curve relationship that is obtained by an arbitrary combination of the linear, exponential, or quadratic curve relationship.