A controller for controlling at least a first air-conditioning system and a second air-conditioning system arranged for conditioning a common space, wherein a refrigerant circuit of the first air-conditioning system is separate from a refrigerant circuit of the second air-conditioning system, comprising: a multi-variable regulator to receive one or more setpoint signals and one or more measured value signals from the common space to determine control signals for controlling operations of first components of the first and the second refrigerant circuits to jointly and concurrently reduce at least one environmental error between the setpoint signals and the measured value signals; a first single-variable regulator to receive a first setpoint signal and a measured value signal of the operation of a second component of the first air-conditioning system and to determine a control signal for controlling the operation of the second component of the first air-conditioning system that reduces a first operational error of the second component of the first air-conditioning system; a second single-variable regulator to receive a second setpoint signal and a measured value signal of the operation of a second component of the second air-conditioning system and to determine a control signal for controlling the operation of the second component of the second air-conditioning system that reduces a second operational error of the second component of the second air-conditioning system; a memory storing a lookup structure mapping control signals controlling operations of a third component of the first air-conditioning system and a third component of the second air-conditioning system as a function of the control signals controlling operations of the first components of the first and the second air-conditioning systems; a processor to determine the control signals controlling operations of the third components of the first and the second air-conditioning systems by selecting the control signals from the lookup structure according to the control signals determined by the multi-variable regulator; and an electrical circuit for controlling the first and the second air-conditioning systems according to the determined control signals. a multi-variable regulator to receive one or more setpoint signals and one or more measured value signals from the common space to determine control signals for controlling operations of first components of the first and the second refrigerant circuits to jointly and concurrently reduce at least one environmental error between the setpoint signals and the measured value signals; a first single-variable regulator to receive a first setpoint signal and a measured value signal of the operation of a second component of the first air-conditioning system and to determine a control signal for controlling the operation of the second component of the first air-conditioning system that reduces a first operational error of the second component of the first air-conditioning system; a second single-variable regulator to receive a second setpoint signal and a measured value signal of the operation of a second component of the second air-conditioning system and to determine a control signal for controlling the operation of the second component of the second air-conditioning system that reduces a second operational error of the second component of the second air-conditioning system; a memory storing a lookup structure mapping control signals controlling operations of a third component of the first air-conditioning system and a third component of the second air-conditioning system as a function of the control signals controlling operations of the first components of the first and the second air-conditioning systems; a processor to determine the control signals controlling operations of the third components of the first and the second air-conditioning systems by selecting the control signals from the lookup structure according to the control signals determined by the multi-variable regulator; and an electrical circuit for controlling the first and the second air-conditioning systems according to the determined control signals.