Device for controlling construction machinery

A control device for construction machinery equipped with an engine and a variable displacement hydraulic pump driven by the engine, comprising:

• a first operating point calculation unit which calculates a plurality of combinations of engine rotational speed and engine torque with which demanded power of the engine can be generated and calculates system efficiency, as the product of energy efficiency of the engine and energy efficiency of the hydraulic pump, in each of the combinations according to discharge pressure of the hydraulic pump;
• a rotational speed calculation unit which calculates target rotational speed of the engine as the engine rotational speed in one of the combinations of the engine rotational speed, the engine torque and the system efficiency that is calculated by the first operating point calculation unit and includes desired system efficiency;
• and
• a displacement calculation unit which calculates target displacement of the hydraulic pump based on the target rotational speed calculated by the rotational speed calculation unit and demanded flow rate of the hydraulic pump.