Electromagnetic shock absorbers are mechatronic actuators designed to improve ride comfort and road holding in ground vehicles by introducing variable active and damping forces in the suspension. ...This feature difficults their testing, as the characterization test bench must adapt to this variable load feature. Moreover there is interest in testing them under realistic use scenarios. In this context, this work focuses on a hardware-in-the-loop implementation on a custom damper test bench to characterize rotary electromagnetic shock absorbers. First, the entire test bench is presented and described. The model of the plant is obtained together with a quarter car model of the target vehicle. Test bench bandwidth and instability issues are discussed. Then, a model following compensation method is proposed and simulated. Finally, the resulting approach is used to control a testbed, where the quarter car model is used to produce a realistic load duty cycle in real time. Experiments highlight the tracking performance of the test rig and its robustness against load variations.
In this article, the trajectory planning and high-precision motion control of an excavator based on the independent hydraulic system of the load port are studied. A trajectory planning algorithm ...based on the combination of a quintic non-uniform B-spline curve and improved sparrow algorithm and an oil inlet flow controller based on the time-varying secant barrier Lyapunov function (TSBLF) are designed. First, the traditional sparrow algorithm is innovatively improved in trajectory planning to make the generated trajectory time shorter, more stable and energy better. Then, the secant function and fixed time controller are first introduced in the design of the oil flow controller to ensure that the system error converges to the predefined boundary in finite time. At the same time, the RBF neural network is used to approximate the unmodeled error and disturbance of the system. Finally, the simulation verification is carried out with the common trenching conditions in the intelligent operation of the excavator. The results show that the generated trajectory has obvious advantages over the traditional sparrow algorithm. The trajectory tracking error can converge to the neighborhood near the equilibrium point in a fixed time while satisfying the constraints, and has high control accuracy.
Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of ...independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.
It is very well known that the use of a load-holding valve (LHV) in a hydraulic system introduces additional energy consumption. This article presented a simplified graphical method for analyzing the ...power requirements of hydraulic systems equipped with load-holding valves for overrunning load control. The method helps to understand the performance of load-holding valves during actuator movement. In addition, it allows visualization of the influence on the overall system consumption of the main parameters (pilot ratio, set pressure) and others such as flow rate, back pressure, and load force. The method is attractive because, with only the pressures at the three ports and the valve relief function curve, it is sufficient to evaluate the energy consumption and to define the power ratio as an index indicating the percentage of energy that is to be used to open the LHV valve. The method was applied to real cases, in particular to two types of lifting mobile machines. It was validated following several outdoor tests on two mobile machines where experimental data were obtained. During tests, both machines were equipped with a set of seven different performance LHV valves. The described method could be beneficial for hydraulic machine manufacturers engaged in designing lifting devices when selecting a suitable valve for energy efficiency applications, especially now that the trend towards electrification is a reality.
The search for alternative materials that can be used for parts of aircraft hydraulic systems has led to the idea of applying S32750 duplex steel for this purpose. This steel is mainly used in the ...oil and gas, chemical, and food industries. The reasons for this lie in this material's exceptional welding, mechanical, and corrosion resistance properties. In order to verify this material's suitability for aircraft engineering applications, it is necessary to investigate its behaviour at various temperatures since aircrafts operate at a wide range of temperatures. For this reason, the effect of temperatures in the range from +20 °C to -80 °C on impact toughness was investigated in the case of S32750 duplex steel and its welded joints. Testing was performed using an instrumented pendulum to obtain force-time and energy-time diagrams, which allowed for more detailed assessment of the effect of testing temperature on total impact energy and its components of crack initiation energy and crack propagation energy. Testing was performed on standard Charpy specimens extracted from base metal (BM), welded metal (WM), and the heat-affected zone (HAZ). The results of these tests indicated high values of both crack initiation and propagation energies at room temperature for all the zones (BM, WM, and HAZ) and sufficient levels of crack propagation and total impact energies above -50 °C. In addition, fractography was conducted through optical microscopy (OM) and scanning electron microscopy (SEM), indicating ductile vs. cleavage fracture surface areas, which corresponded well with the impact toughness values. The results of this research confirm that the use of S32750 duplex steel in the manufacturing of aircraft hydraulic systems has considerable potential, and future work should confirm this.
Aiming at the low efficiency of traditional mechanical cutting methods in hard coal seams, a multi-impact cutting technology was proposed, which was to design a hydraulic system inside the drum. In ...this paper, by analyzing the working process of the multi-impact drum, the corresponding mechanical model was established and the overall research plan was determined. A simulation experiment explored the working performance of the multi-impact drum under the action of multiple factors in cutting different hardnesses, using different impact frequencies and different drum speeds. The simulation results showed that the drum speed has the greatest influence on coal-breaking performance, followed by coal hardness, and the impact frequency of picks has the least influence on coal-breaking performance. In addition, a discrete element coal-breaking experiment with a traditional drum was carried out. The simulation results showed that the multi-point impact drum can improve coal-breaking performance by more than 20% compared with traditional drum in terms of coal-breaking capacity and cutting specific energy consumption. Finally, a simplified multi-impact drum industrial cutting test was carried out. The test results showed that the cutting resistance of the multi-impact drum was about 17.22% lower than when there was no impact. Considering that the simplified multi-impact cutting drum had a reduced impact pre-cracking effect on the coal, it can be considered that the results of the industrial test and the discrete element simulation test were still relatively consistent. The multi-impact cutting drum had good working performance under hard coal conditions.
Towards RL-Based Hydraulic Excavator Automation Egli, Pascal; Hutter, Marco
2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS),
2020-Oct.-24
Conference Proceeding
Odprti dostop
In this article we present a data-driven approach for automated arm control of a hydraulic excavator. Except for the link lengths of the excavator, our method does not require machine-specific ...knowledge nor gain tuning. Using data collected during operation of the excavator, we train a general purpose model to effectively represent the highly non-linear dynamics of the hydraulic actuation and joint linkage. Together with the link lengths a simulation is set up to train a neural network control policy for end-effector position tracking using reinforcement learning (RL). The control policy directly outputs the actuator commands that can be applied to the machine without unfounded filtering or modification. The proposed method is implemented and tested on a 12t hydraulic excavator, controlling its 4 main arm joints to track desired positions of the shovel in free-space. The results demonstrate the feasibility of directly applying control policies trained in simulation to the physical excavator for accurate and stable position tracking.
In this paper, a hydrostatic tidal turbine (HTT) is designed and modeled, which uses more reliable hydrostatic transmission to replace existing fixed ratio gearbox transmission. The HTT dynamic model ...is derived by integrating governing equations of all the components of the hydraulic machine. A nonlinear observer is proposed to predict the turbine torque and tidal speeds in real time based on extreme learning machine (ELM). A sensorless double integral sliding mode controller is then designed for the HTT to achieve the maximum power extraction in the presence of large parametric uncertainties and nonlinearities. Simscape design experiments are conducted to verify the proposed design, model, and control system, which show that the proposed control system can efficiently achieve the maximum power extraction and has much better performance than conventional control. Unlike the existing works on ELM, the weights and biases in the ELM are updated online continuously. Furthermore, the overall stability of the controlled HTT system including the ELM is proved and the selection criteria for ELM learning rates are derived. The proposed sensorless control system has prominent advantages in robustness and accuracy, and is also easy to implement in practice.
A model is developed for the synchronous brush drive of an airfield sweeper. This machine is equipped with a throttle flow divider that is not of gate-valve type, and employs a plunger-type control ...system. Methods are proposed for improving the static and dynamic properties of the synchronized system.
El Libro de cargo y descargo del Imperial Colegio de Tlatelolco fue sustraído del Museo Nacional a principios del siglo XX y después pasó desapercibido en la historiografía. Fue en la década de 1990 ...cuando salió a la luz pública y se vendió a un bibliófilo mexicano, pero en el proceso se pudo fotocopiar. Después de un análisis del manuscrito se localizaron las cuentas referentes a la construcción del caño que surtió agua al Imperial Colegio de Tlatelolco desde Tacuba. Esta etapa constructiva de 1581 a 1582 es desconocida, sin embargo, la información contenida en las cuentas permite conocer los nombres del maestro de obra, mer-caderes y comerciantes que proveyeron los materiales. Por las descripciones en las cuentas, se puede identificar que el sistema hidráulico se realizó por la superficie y de manera subterránea. Fueron fray Bernardino de Sahagún, fray Pedro de Oroz y fray Pedro Serrano quienes supervisaron la obra.
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