Method and apparatus for pulse-modulated feedback control

A system comprising:

• a plant;
• a sensor coupled to sense an actual value signal corresponding to a quantity which is controllable by the plant;
• and
• a controller coupled to the plant for providing control signals to the plant and coupled to receive a signal from said sensor corresponding to the actual value signal, the controller comprising:
• a processor which receives a signal representative of a difference between a command signal value and actual signal value and in response to the value of the command value minus the actual value signal being greater than the upper margin of error, generating a first control signal having a first value;
• and in response to the value of the command signal minus the actual value signal being less than the lower margin of error, generating a second control signal having a second, different value and in response to the value of the actual value signal being neither greater than the command value plus the margin of error nor less than the command value minus the margin of error, generating a third control signal having a third value;
• and
• means for supplying one of the first, second or third control signals to an output port.

A controller comprising:

• a processor having an input coupled to receive a signal representative of a difference between a characteristic of a command signal and a characteristic of an actual signal and in response to the signal being greater than an upper margin of error, generating a first control signal having a first value which causes the system to produce a maximum system response;
• and in response to the signal being less than a lower margin of error, generating a second control signal having a second, different value which causes the system to produce a minimum system response and in response to the signal being neither greater than the upper margin of error nor less than the lower margin of error, generating a third control signal having a third value which causes the system to produce a substantially no response;
• and
• control signal output means for supplying one of the first, second or third control signals to an output port.

A method of controlling a system, the method comprising a repetitive sequence of the following:

• (a) obtaining an actual value signal corresponding to a quantity which is controllable by the system;
• (b) computing a difference value corresponding to a difference between a command value and the actual value;
• (c) in response to the difference value being greater than an upper margin of error, generating a first control signal having a first value;
• (d) in response to the difference value being smaller than a lower bound of error, generating a second control signal having a second, different value;
• (e) in response to the difference value being neither greater than the upper margin of error nor less than the lower margin of error, generating a third control signal having a third value;
• and
• (f) supplying one of the first, second or third control signals to the system for controlling the same.