In this paper, aimed at the problem of control accuracy when the traditional position-based impedance control is applied in the hydraulic drive unit (HDU) of legged robot, a kind of nonlinear ...model-based variable impedance parameters controller (MVIPC) is designed. First, the mathematical model of position-based impedance control for HDU is given. Second, the performance of traditional position-based impedance control is tested on the HDU performance test platform under different working conditions, and the experimental results show that the control accuracy of this control method needs to be improved greatly. Thirdly, the control idea of MVIPC is described, and the theoretical derivation is deduced. MVIPC considers the high-order dynamic characteristics of servo valve, pressure-flow nonlinearity of servo valve, oil compressibility and load characteristics. Finally, the control performance of MVIPC is verified on the HDU performance test platform. The experimental results show that MVIPC can significantly improve the performance of traditional position-based impedance control, and have an excellent adaptability under different working conditions. This research can provide an underlying control method of hydraulic systems during the robot locomotion.
•A broadband piezo-hydraulic actuator (PHA) was proposed for a variable swept wing (VSW).•The PHA driven by a resonant active valve piezoelectric pump was designed, fabricated and tested.•The ...composition and deformation of the PHA-Based VSW were presented and analyzed.•A dynamic model was established to reveal the variation laws of velocity and torque of the VSW.•The deformation operation of the PHA-Based VSW was successfully completed through the test.
Piezoelectric hydraulic actuators, instead of electromagnetic actuators, have a wide application prospect in the field of aerospace due to the merits of light weight, compact structure, non-magnetic interference, etc. Many researches have been devoted to boosting output powers of actuators with the help of large-scale piezoelectric stacks. However, the existing actuator operates at a relatively low frequency, limiting the output power improvement and the application. In this work, a high bandwidth piezo-hydraulic actuator (PHA) is proposed based on a resonant active valve piezoelectric pump with sandwich bending transducers (SBTs). The configuration and principle of the PHA are presented and analyzed. A tested setup of the PHA is established, and the maximum output velocity and thrust are measured to be 30.5 mm/s and 53.2 N under 1.6 kHz, and the output power reaches up to 294 mW under the load of 30 N. In addition, a variable swept wing (VSW) driven by the PHA is studied. The composition and deformation process of the PHA-Based VSW are discussed; the dynamic model of the PHA-Based VSW is derived; the tested results indicate that the maximum angular velocity and torque of the PHA-Based VSW are 1.135 rad/s and 1.701 N·m, and the swept angle range is 15.9° ∼ 64.1°
Display omitted
In this paper, the mathematical expressions of a second-order matrix sensitivity analysis (SOMSA) is derived. This method has higher accuracy and requires less calculation works than previous ...analysis methods. Based on the SOMSA, when the traditional force-based impedance control is applied in leg hydraulic drive system (LHDS) of legged robots, the effects of parameter variations on control performance are studied by sensitivity dynamic analysis under nine working conditions. Then, combined with two measurable sensitivity indexes, the results of the sensitivity dynamic analysis are studied quantitatively. Finally, the above results are verified experimentally by using LHDS test platform. The conclusions contribute to the optimization of the LHDS structure and provide theoretical references for compensation control strategies of the traditional force-based impedance control.
•New sensitivity analysis method called second-order matrix sensitivity analysis(SOMSA) is proposed.•Effects of parameter variations on control performance of force-based impedance control is studied.•Sensitivity dynamic analysis is conducted for twelve main parameters under nine working conditions.•Sensitivity dynamic analysis are studied quantitatively by combining with two measurable sensitivity indexes.
Due to the large energy consumption as well as poor controllability and other problems, the traditional cooling system has not been able to adapt to the development needs of construction machinery ...with the continuous upgrading of emission regulations. This paper introduces a hydraulic driven fan cooling system based on pilot operated electro-hydraulic proportional valve. In order to make the whole machine quickly reach the temperature required in the best working condition when the construction machinery starts working, controlling the fan at a lower speed can reduce the heat dissipation and save energy. The electronic control system will adjust the motor speed in time when the temperature of the fluid rises, and control the temperature in the best temperature range required. A one-dimensional simulation model of this stepless speed control system is established to predict the parameter sensitivity of the electro-hydraulic proportional valve and the dynamic performance of the system. The simulation shows that the fan speed of the system can reach the required speed in only 5s at the extreme high temperature of 40 °C; the fan input power of the system accounts for 65% of the system input power at −30 °C and reaches 80% at 40 °C. Three-dimensional simulation shows that the fan-front temperature-controlled cooling system for forklift truck has high heat dissipation efficiency and can be applied to other heavy machinery products.
•A hydraulic driven cooling system simulation model is developed.•Parameter sensitivity with pilot relief valve is analyzed.•Dynamic behavior of the system at extreme temperatures is predicted.•Heat transfer efficiency of the system is improved.•Thermal equilibrium temperature is well controlled.
Pump-controlled hydraulic cylinder drives may offer improved energy efficiency, compactness, and plug-and-play installation compared to conventional valve-controlled hydraulic systems and thus have ...the potential of replacing conventional hydraulic systems as well as electro-mechanical alternatives. Since the late 1980s, research into how to configure the hydraulic circuit of pump-controlled cylinder drives has been ongoing, especially in terms of compensating the uneven flow requirements required by a differential cylinder. Recently, research has also focused on other aspects such as replacing a vented oil tank with a small-volume pressurized accumulator including the consequences of this in terms of thermal behavior. Numerous references describe the advantages and shortcomings of pump-controlled cylinder drives compared to conventional hydraulic systems or electro-mechanical drives. This paper presents a throughout literature review starting from the earliest concepts based on variable-displacement hydraulic pumps and vented reservoirs to newer concepts based on variable-speed electric drives and sealed reservoirs. By classifying these drives into several proposed classes it is found that the architectures considered in the literature reduce to a few basic layouts. Finally, the paper compares the advantages and shortcomings of each drive class and seek to predict future research tasks related to pump-controlled cylinder drives.
One of the approaches to ensure friction stability in hydraulic precise pairs can be coating their components with low-friction materials with the friction coating method using a metal, e.g. brass. ...The article presents the method of applying brass on the steel surface of a hydraulic pair using friction. It discusses the technology of brass plating of hydraulic precise pairs and the results of laboratory tests involving friction-brasses hydraulic precise pairs. The factors impacting the quality of brass-coating process of hydraulic precise pairs and the requirements set for hydraulic precise pairs subject to friction-brassing were also discussed.
In this paper, attention was focused on identifying the components of the amplitude-frequency spectrum of pressure pulsations in a hydraulic system in which an external low-frequency mechanical ...vibration was subjected to a proportional hydraulic directional control valve. It was observed that an operating machine or device equipped with hydraulic valves is a source of mechanical vibrations with a wide frequency spectrum. The influence of these vibrations on the pressure pulsation spectrum was analyzed, identifying the components resulting from the forcing of the directional control valve spool. In addition, it was noted that the pressure pulsation spectrum includes components resulting from the pulsation of the displacement pump output feeding the hydraulic system. A description of these spectrum components was also made and, using the solution superposition method, the components of the pressure pulsation spectrum over a wide frequency range were identified.
The paper deals with the engineering design of lifting device weighing up to 3.5 tons. The first part is devoted to market research and the use of lifting equipment. Variant with a scissor ...construction and a hydraulic drive is chosen. The design itself follows. The machine composes five main parts: the lower frame, the scissor structure, the ramp, the mechanical lock and the drive mechanism. The individual chapters are devoted to design and analysis of these components.
Aimed at the negative effect of dynamics characteristics of leg hydraulic drive system (LHDS) on the accuracy of motion control of the hydraulic drive legged robot, a dynamics compensation control ...method is proposed. First, according to the mechanical structure of LHDS, the kinematics and statics models of LHDS are analyzed and obtained respectively. Based on the principle of force-based impedance control of LHDS, an impedance based motion control simulation model of LHDS is built and analyzed. The simulation results show that the dynamics characteristics have a great influence on the accuracy of impedance based motion control. Then, a dynamics compensation method considering gravity and inertia force is proposed to solve this problem. Finally, the effect of the dynamics compensation method is verified on the robot single leg test platform. The experimental results show that the compensation method reduces the negative effect of the dynamics characteristics of LHDS on impedance based motion control accuracy, and the position tracking accuracy of the robot’s foot end can be improved by more than 65%. The theory proposed in this paper provides a theoretical basis for the motion control of the whole robot prototype.
•An effective dynamics compensation control method of LHDS is proposed.•An impedance-based motion control simulation model of LHDS is built and analyzed.•The method reduces the negative effect of the dynamics characteristics of LHDS.
PDF
