Abstract
The series manipulator of the demolition robot has different working postures and large self-weight so that the bearing mass of the joint hydraulic cylinder is a variable value, and the change of mass affects the dynamic characteristics of the valve-controlled hydraulic cylinder system. In this paper, an equivalent mass estimation method of the big-arm joint hydraulic cylinder is given, and the natural frequency range of the big-arm hydraulic cylinder-load system is calculated. In order to suppress the influence of the change of the natural frequency and external disturbance of the hydraulic cylinder on the system, the linear active disturbance rejection control is adopted in the closed-loop position control. The simulation results show that the change of load mass of the joint hydraulic cannot be ignored when designing the joint position controller of multi-joint hydraulic manipulator. And the simulation tests prove that the linear active disturbance rejection control strategy keeps good dynamic characteristic and steady-state accuracy for the change of natural frequency and external disturbance of hydraulic cylinder and has good tracking performance for periodic sinusoidal signal. Linear active disturbance rejection control is robust in the variable mass control of the manipulator and meets the requirements of the joint position control of the heavy-duty hydraulic manipulator.
Highlights
Because of its breaking and shearing functions in harsh and complex environment, demolition robot has been widely used in the fields of construction, metallurgy and rescue, and its working mechanism is heavy-duty hydraulic series manipulator
When the manipulator is in different postures, the equivalent mass of the hydraulic cylinder loaded on the joint is changed
In the case of larger and smaller natural frequency of the big-arm hydraulic cylinder (40 and 85 rad/s), the position control system of the joint hydraulic cylinder is input with the sinusoidal periodic signals of 0.5 and 2.5 Hz, respectively, and the tracking performance of proportional–integral– derivative (PID) and linear active disturbance rejection control (LADRC) strategies on different periodic signals under different load masses of the hydraulic cylinder is compared
Summary
Because of its breaking and shearing functions in harsh and complex environment, demolition robot has been widely used in the fields of construction, metallurgy and rescue, and its working mechanism is heavy-duty hydraulic series manipulator. The load equivalent mass MB of the big-arm hydraulic cylinder is changed under different postures of the manipulator, resulting in a change value of the hydraulic-load natural frequency vh.
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