Potential Energy Regeneration Research Articles

Boom Potential Energy Regeneration Method for Hybrid Hydraulic Excavators

Boom Potential Energy Regeneration Method for Hybrid Hydraulic Excavators

Design and energy analysis of novel hydraulic regenerative potential energy systems

Potential energy regeneration is an important hydraulic energy-saving technology in construction machinery. However, the existing hydraulic regenerative potential energy system (HRPES) is still limited by its large size, high cost, circuit interference, and so on. To solve the above problems, this paper intends to study novel HRPES by optimizing the hydraulic circuits and hydraulic components. First, we design four new HRPESs according to the working characteristics of energy recovery and energy reuse of construction equipment. Based on the load data of the 1.7-ton experimental excavator and the HRPES simulation model, the working characteristics of HRPES in the process of multicycle energy regeneration are studied. Finally, in addition to the conventional energy-saving efficiency, this paper proposes the recovery efficiency, reuse efficiency and regeneration efficiency to comprehensively analyse the energy efficiency characteristics of the four HRPESs. The results show that the energy-saving efficiencies of the four HRPESs are 16.02%, 22.84%, 21.95%, and 27.15% compared with traditional No-HRPES, and the regeneration efficiencies are 54.43%, 57.76%, 53.55%, and 57.97%, respectively. These results have an important reference for optimizing the structure of existing HRPES.

A Novel Electro-Hydraulic Compound Driving System With Potential Energy Regeneration Capability for Lifting Device

In order to realize the high energy efficiency and high performance motion control of the lifting device of construction machinery, this paper proposes an electro-hydraulic compound driving system that can regenerate the potential energy. In this new system, the high-power density combination of hydraulic cylinder with accumulator is used to balance the self-weight of the lifting device and recycle the gravitational potential energy directly. The green electro-mechanical actuator with high energy efficiency and control performance is used to control the motion of the lifting device. In addition, control valves are added to dynamically adjust the pressure of the two chambers of the hydraulic cylinder and increase the stiffness of the hydraulic system, which can restrain the impact of acceleration and deceleration of large inertia lifting device and rapid charging and discharging of accumulator on electro-mechanical actuator. Finally, a typical construction machinery excavator is structurally modified to build a test platform. The test results show that, under the same working conditions, the proposed electro-hydraulic compound driving system can further reduce energy consumption by 31% and reduce peak power by 15% than that of the high energy efficiency three-chamber hydraulic cylinder driving system with potential energy regeneration. The boom runs smoothly, and the velocity overshoot and fluctuation time are significantly reduced, realizing high performance driving of the lifting device with low energy consumption. The research results also have broad application prospects in missile erection devices, cranes, presses, and other equipment.

Simulated research on large-excavator boom based on hydraulic energy recovery

According to the working condition characteristics of a company's existing XE series 70-ton-large-scale crawler hydraulic excavator, a new hydraulic type is designed for the purpose of energy saving, which contains an accumulator as a reversible energy storage component and a variable pump/motor as an energy conversion element. This scheme belongs to the excavator boom potential energy regeneration method. When the boom is lowered, the accumulator and the pump/motor function, part of the hydraulic cylinder rodless cavity fluid entering the rod cavity and the other part filling the accumulator with fluid and driving the pump/motor to assist the engine's work. After the boom is lowered, the accumulator continues to supply liquid to the pump/motor which carries on assisting the engine to do work. Then the main hydraulic components of the system are modeled, together with building the simulated system model in LMS Imagine.Lab AMESim(Advanced Modeling Environment for performing Simulation of engineering systems). The result of simulation manifests that this system scheme can achieve the recovery of the potential energy of the boom and realize a better energy saving effect.

Potential Energy Recovery System for Electric Heavy Forklift Based on Double Hydraulic Motor-Generators

Heavy forklifts that are widely used in ports and stations have large gravitational potential energy at the lowering of the boom. As concerning the large rated power level, the engine is still the main power source for the heavy forklifts. With the increasingly stringent emissions regulations, the electric heavy forklift becomes an important choice. The structure and the working mode of an electric heavy forklift are introduced. Additionally the schematic of double hydraulic motor-generators is adopted to regenerate the potential energy when the boom is descending. The judge rule of the working mode and control strategy are analyzed. A test rig of a prototype electric heavy forklift is established. Control mode discrimination of potential energy regeneration, the control performance and the influence factors on regeneration efficiency are tested based on the test rig. The experimental results show that the discrimination method of the working mode of the proposed double hydraulic motor-generators with a potential energy regeneration system for potential energy is feasible. The descending of the lifting cylinder is consistent with the handle. The forklift can obtain the good following ability. Although the lifting cylinder descends at low velocity, the velocity is stable and the fluctuation of the rodless chamber pressure is within 0.1 MPa. With the increase of the load mass and descending velocity, the regeneration efficiency increases accordingly. The maximum efficiency is up to 74%. Hence, the proposed potential energy regeneration system is feasible and potential energy regeneration system does not affect the control performance of the boom.

Research on a new energy-recovery system for hybrid hydraulic excavators

Hydraulic excavators, especially medium and large excavators, waste a lot of energy during the frequent lifting-lowering process of its boom. Recovery and regeneration the wasted energy is an important means to achieve energy saving and emission reduction of excavators. In this paper, a potential energy recovery and regeneration system based on a multi-cylinder structure working device is invented. Firstly, the theoretical analysis of the system, and the modeling and simulation research are carried out. Results show that under the same boom-single-action conditions, the energy-saving efficiency of the excavator equipped with energy recovery system can reach 33%, it has important reference significance for evaluating the energy efficiency of the new system.

Potential energy regeneration method and its engineering applications in large-scale excavators

Hydraulic excavators are essential excavation machines, with more than 3.8 million sets in use in the mining, and engineering and architectural engineering construction fields. However, during the working process, a large amount of gravitational potential energy is wasted, causing low energy efficiency and poor emissions. Taking a large-scale excavator as an example, during a certain 90° excavation process, the gravitational potential energy wastage of the working device is approximately 975.1 kJ, which amounts to at least 20% of the energy consumption of the entire machine, causing significant energy waste and serious pollution. And, during the boom lowering process, the changing rate of potential energy is about 406.4 kW. In order to improve the energy efficiency of hydraulic excavators, the recovery of this huge energy that changes rapidly with low cost and high efficiency is a big problem that must be solved. This paper proposes a gravitational potential energy recovery scheme with an energy conversion cylinder and a hydraulic accumulator. Using this scheme, the gravitational potential energy of the working device can be stored and reused directly, without increasing the cost and install power of the machine largely. In the study, first, the system parameters are designed, following which the multidisciplinary dynamic model of the hydraulic excavator is established. The influence of the accumulator parameters on the energy recovery ratio is studied based on the model. The results demonstrate that with the newly designed system more than 75.9% of the gravitational potential energy can be stored in the accumulator during the lowering process. Moreover, during a certain lifting process, the input energy to the pump can be reduced by 52%. On this basis, a 76 t hydraulic excavator test system is constructed using the above principle. The experimental results match strongly with the co-simulation results. The energy consumption can be reduced to approximately 238 kJ during a certain 90° excavation cycle, and the system can reduce the carbon dioxide emissions by 28088.4 kg per year. The energy-saving and emission-reduction effects are remarkable; furthermore, this principle can directly be applied to other lifting machines.

Novel potential energy regeneration systems for hybrid hydraulic excavators

This paper proposes a novel potential energy regeneration system (PERS) using a hydraulic accumulator and a valve–motor–generator for a hybrid hydraulic excavator (HHE). To analyze the dynamic performance of the proposed PERS, mathematical models are established. A numerical analysis is conducted to guide the parameters design of the key components in the PERS. The control strategy for the energy regeneration system (ERS) is discussed. Simulations are carried out in AMESim to validate the effectiveness of the novel PERS. The results demonstrate that the dynamic performance of the PERS is close to that of a throttle-governing system. The efficiency of the PERS is about 58%.

A novel hydraulic excavator boom driving system with high efficiency and potential energy regeneration capability

This paper proposes a new hydraulic excavator boom driving system using novel asymmetric pump to reduce energy consumption. Due to large throttling loss and gravitational potential wasting, conventional hydraulic excavator boom driving system has very low energy efficiency. This paper aims to improve the energy efficiency of the hydraulic excavator by reducing throttling loss and regenerating potential energy directly based on a novel pump controlled system. The system under consideration utilizes a novel asymmetric pump which has three ports, of which two are connected to the hydraulic cylinder, and the other one is connected to an accumulator. Thus, this system can regenerate the potential energy directly and can basically match the unequal flow rates of the single rod cylinder. The structure and working principle of the asymmetric pump controlled single rod cylinder system are studied in depth in this paper. To better demonstrate the performance of the proposed system, the popular independent metering circuit, which has been proposed to improve the efficiency of boom system, is used as a comparison. Moreover, experimental results of the two systems have been obtained based on a real 6-ton hydraulic excavator. The boom driving system of the excavator was first modified to the independent metering circuit to conduct experiment, and afterwards was modified to the proposed system. Experimental results show that, about 82.7% of the potential energy could be regenerated and reutilized by the proposed system. Compared with the independent metering circuit, the electric power consumption of the boom system during moving-up operation can be reduced by 76.1%. Furthermore, if the energy efficiency of the power source is considered, the energy consumption during the entire boom cylinder working cycle can be reduced by 75.0%. Finally, it is worth noting that the proposed system can be applied in all kinds of heavy-duty construction machineries, though only hydraulic excavator is experimented.

The gravitational potential energy regeneration system with closed-circuit of boom of hydraulic excavator

Considering the disadvantage of higher throttling loss for the open-circuit hydrostatic transmission at present, a novel gravitational potential energy regeneration system (GPERS) of the boom of hydraulic excavator, namely the closed-circuit GPERS, is proposed in this paper. The closed-circuit GPERS is based on a closed-circuit hydrostatic transmission and adopts a hydraulic accumulator as main energy storage element fabricated in novel configuration to recover the entire gravitational potential energy of the boom of hydraulic excavator. The matching parameter and control system design are carried out for the proposed system, and the system is modeled based on its physical attributes. Simulation and experiments are performed to validate the employed mathematical models, and then, the velocity and the pressure performance of system are analyzed. It is observed that the closed-circuit GPERS shows better velocity control of the boom and response characteristics. After that, the average working efficiency of the closed-circuit GPERS of boom is estimated under different load conditions. The results indicate that the proposed system is highly effective and that the average working efficiency in different load conditions varied from 60% to 68.2% for the experiment platform.

A novel hybrid control strategy for potential energy regeneration systems of hybrid hydraulic excavators

Excavators as a kind of typical construction machinery are widely used in all kinds of earthworks. Due to the low efficiency of the excavator, many enterprises and researchers have been committed to improving its efficiency. Energy regeneration system is an effective energy-saving technology, which has attracted much attention in recent years. However, the traditional energy regeneration system pays much attention to the energy saving, while the maneuverability is not fully considered. This article focuses on the maneuverability and the energy saving of the hybrid hydraulic excavator boom. A novel hybrid control method to guarantee the dynamic performance of the energy regeneration system, which is based on an electrical potential energy regeneration system, is proposed. A combined use of a torque controller for the permanent-magnet synchronous machine and a position controller for the proportional pressure valve makes the dynamic performance of the potential energy regeneration system insensitive to the influence from the direct current voltage, the capacity of the inverter as well as the cylinder speed, and achieves fast response and maximum energy regeneration simultaneously. To verify the effectiveness of the hybrid control method for the potential energy regeneration system, co-simulations are carried out in AMESim and Simulink. The results show that the dynamic performance of the potential energy regeneration system with the hybrid control method is close to a throttle-governing system and the regenerated potential energy is considerable.

Research on Key Technology of Oil-electric Hybrid Excavator

Due to energy crisis and environmental pollution in the world range,it is urgent to develop new solutions for excavators which are widely applied with low efficiency. As a well-known energy-saving solution,oil-electric hybrid driven technology which combines a diesel engine and an electric motor together has received significant breakthrough in vehicles,for engine efficiency can be improved and energy regeneration can be realized. There are many differences between excavators and vehicles such as load condition,regeneration approach,energy storage,operability and reliability. Therefore,it is necessary to investigate the hybrid driven technology of excavators specially. The key technologies of oil-electric hybrid excavators in China,abroad and especially in SKLoFP of Zhejiang University are reviewed on power hybridization mode and parameter optimization,power system control,electric swing and braking kinetic energy regeneration,boom potential energy regeneration and generator. The research results are validated in a prototype of 20 t hybrid excavator and can also be extended to other construction machinery.

Design and analysis of compound potential energy regeneration system for hybrid hydraulic excavator

Potential energy regeneration system, which shares an electrical energy storage device with power system, can further improve the fuel economy of hybrid construction machinery without much additional expense. However, the conventional potential energy regeneration system also results in poorer dynamic performance of actuators in comparison to throttle-governing system. In addition, the capacity of the regenerator should be large enough to avoid overload. Based on comprehensive consideration, this article presents a compound potential energy regeneration system that combines the regeneration device and throttle together. The regenerative torque is adaptive to load so as to keep the pressure drop over the throttle almost constant, and then the actuator can be governed by adjusting the opening of the throttle. The compound potential energy regeneration system is analyzed and evaluated using the frequency domain method and nonlinear simulation. Finally, experiments under different parameter conditions are carried out, and some useful design reference is provided. The simulation and experimental results show the effectiveness of the designed system as well as its control strategy.