Control Of Hydraulic Manipulators Research Articles

An Adaptive Robust Controller for Hydraulic Robotic Manipulators with a Flow-Mapping Compensator

Proportional directional control valves have flexible control functions for the control of various hydraulic manipulators. It is foreseeable that the application of proportional directional control valves will be further expanded. However, due to its own structure, its important parameter, flow gain, is complex, and it has a complex functional relationship with valve opening and temperature. The variable flow gain reduces the performance of a strictly derived nonlinear controller. Therefore, it is necessary to consider the nonlinearity of flow gain in the controller design. In order to solve the above problems, this paper proposes an adaptive robust controller for a hydraulic manipulator with a flow-mapping compensator, which takes into account the nonlinear flow gain and improves the performance of the nonlinear controller. First, we established an adaptive robust controller of the hydraulic manipulator to obtain the load flow of the control input valve. Then, the function of flow gain, input voltage, and temperature are calibrated offline using cubic polynomial, and the flow-mapping compensator is obtained. Finally, we calculate the input voltage based on the flow-mapping compensator and load flow. The flow-mapping compensator further reduces the uncertainty of the model and improves the robustness of the system. By using the proposed controller, the control accuracy of the hydraulic manipulator is significantly improved.

Robust position control of hydraulic manipulators using time delay estimation and nonsingular fast terminal sliding mode

A simple and robust tracking controller based on time delay estimation and nonsingular fast terminal sliding mode is proposed for the position control of hydraulic manipulator. The proposed controller does not require the mathematical model of hydraulic manipulator dynamics, which ensures that the method is simple and model free. Two elements, time delay estimation and nonsingular fast terminal sliding mode, are implemented in the proposed controller. Time delay estimation estimates the complex dynamics of the hydraulic manipulator, and nonsingular fast terminal sliding mode is implemented as the nonlinear desired error dynamic to ensure fast convergence and high trajectory tracking accuracy. Experiments are performed to verify the tracking performance of the method on a hydraulic manipulator. The results demonstrate that this method achieves faster and higher precision position tracking performance than a conventional time delay control with linear error dynamics.

Control of Hydraulic Manipulator with Consideration of Power Limitations On-Board Energy Source

In the paper we present results of theoretical and experimental research of properties of manipulators with electro hydraulic servo drives with energy sources of limited power. The danger of overloading the power sources and associated functional failures of the drive system are discussed. In order to solve the problem we propose a new structure of the control system and algorithms. This allows to effectively distribute available power between hydraulic drives. These control algorithms are based on a system with variable structure with actual fluid flow feedback. This paper presents analysis of the amplitude of the first harmonic and of oscillation frequency of the total flow in the steady state. This allows to give recommendations how to improve dynamic properties of a hydraulic manipulator. The proposed control laws solve the problem of coordination of motion of links of the manipulator for automatic distribution of power resources. Besides this, it creates favorable conditions for functioning of biotechnical system "human operator - hydraulic manipulator" with limited energy source.