Patent ID: 7232287

Claim:
A method of controlling a plurality of devices to respond to a demand, in which: (a) an initial demand instruction is established for each device, representing the device conditions required to achieve the demanded response; (b) the actual condition achieved by each device is detected; (c) a value representing the range of actual conditions is derived from the detected actual conditions, for comparison with a threshold value, wherein the range value is derived as the difference between the maximum and minimum values representing the actual conditions; (i) wherein when the range value is above the threshold value, a value representing the average of the actual conditions is derived, and further demand instructions are set in dependence on the average value; (A) wherein when the average value exceeds the average value derived from the conditions required to achieve the demanded response, the further demand instructions are set to achieve a reduced average value of the actual conditions; wherein the further demand instructions are set for at least some of the devices to achieve the minimum actual conditions of those devices; or (B) wherein when the average value is less than the average value derived from the conditions required to achieve the demanded response, the further demand instructions are set to achieve an increased value of the actual conditions; wherein the further demand instructions are set, for at least some of the devices, to achieve the maximum actual condition of those devices; (d) the result of the comparison is used to establish further demand instructions for independently controlling the devices; and steps (b), (c) and (d) are repeated until the demand is fulfilled, whereby the response of the devices to the demand is coordinated until the demand is fulfilled.