Combined velocity and position control of large inertial hydraulic swing mechanism considering energy balance of supply and demand

The position of a conventional large inertial hydraulic swing system is controlled by the operator-in-loop, the production efficiency of which is poor, and the repetitive positioning precision is low owing to slow human reactions. To address this problem, this study proposes a combined velocity and position control strategy based on the independent metering control system. In this method, it is not necessary to change the conventional operation mode. If the required rotary angle is the same in each swing process, a precise desired position is provided as the input signal for closed-loop position control. If the required rotary angle is random, in order to be compatible with the handle operation mode used in mobile machines, a handle signal integral control method is proposed. Moreover, velocity feedback is used to improve the control accuracy, while differential pressure feedback is used to reduce the position overshoot. Meanwhile, to improve the system dynamic characteristics during the braking process, an energy balance principle is applied. The proposed strategy is verified with simulation and a 6 t hydraulic excavator. The simulation and experimental results demonstrate that a higher positioning accuracy can be achieved with different desired angular displacements. Furthermore, the position overshoot, and velocity and pressure fluctuation are avoided, while the dynamic characteristics are clearly improved. •In order to be compatible with the handle operation mode, a control method based on handle signal integral is proposed.•An electro-hydraulic velocity and position combined control strategy is proposed to improve the swing positioning accuracy.•The energy balance principle is further proposed to address the problem of large inertia swing system response lag.•The proposed control strategy can be applied to the control modes with the fixed or random desired rotation angle.•The research results can be applied to hydraulic excavators and other mobile machines with large inertial swing mechanisms.