1. A controller of a heating, ventilation, and air conditioning (HVAC) system, comprising: a user interface configured to receive: an approximate relationship between each of a number of controlled variables of an HVAC system and each of a number of manipulated variables of the HVAC system; and a designation of one of the number of controlled variables as a primary controlled variable and the other controlled variables as secondary controlled variables; a memory; and a processor configured to execute executable instructions stored in the memory to: determine operating parameters for each of the number of manipulated variables that maintain the primary controlled variable at a particular set point or within a particular range based, at least in part, on the approximate relationship between the primary controlled variable and each respective manipulated variable; and determine operating parameters for each of the number of manipulated variables that maintain each of the secondary controlled variables at a particular set point or within a particular range based, at least in part, on: the approximate relationship between each respective secondary controlled variable and each respective manipulated variable; and the determined operating parameters for each of the number of manipulated variables that maintain the primary controlled variable.