Power Split Transmission Research Articles

Modeling and control of a novel mechatronic model of a 750 kW-FSWT with power-splitting transmission using RBF neural network: a bond graph approach

This work addresses issues that appear from wind turbines equipped with frequency converters and presents a new fixed-speed wind turbine (FSWT) concept based on a split power transmission, along with a Mechatronic Control Model. The wind turbine rotor drives the first transmission shaft, while a servomotor with variable speed powers the second input. The differential gear transmission output is linked to the electric grid through an asynchronous generator. To optimize the power extracted from the wind energy while minimizing excessive dynamic loads on the wind turbine, a mechatronic control model of a 750 kW-FSWT is applied using a proportional and integral controller (PI). The paper suggests employing neural networks and evolutionary algorithms for determining appropriate PI gains. For collective servomotor control of a 750 kW-FSWT, a radial basis function (RBF) neural networks based on PI controller is proposed. To acquire an optimum dataset for RBF training, the particle swarm optimization (PSO) evolutionary algorithm is harnessed. The robustness and effectiveness of the proposed model and controller are verified and confirmed through simulation results. Hands-on experience is conducted using the 20-sim software package.

Analysis and design of multi-mode power split hybrid transmission scheme considering mode connection

For heavy-duty truck, multi-mode power split hybrid transmission scheme (MPSHTS) has good adaptability. However, the moment of inertia at both ends of the clutch is large. If there is a large speed difference in the clutch engagement process, it will increase clutch wear, engine stall and other problems. This paper proposed a new design method of multi-mode power split hybrid powertrain, which was different from the proof by exhaustion aiming at mode switching without speed difference. It included: the conditions for achieving mode connection without speed difference was obtained based on the lever method for dynamic characteristic analysis. Evaluation index for power split mechanisms that comprehensively considered power source and transmission system was established. Combining the mode connection conditions and the optimized basic configuration, the characteristic of no speed difference could be ensured by adjusting the power coupling mechanism. A multi-mode scheme based on optimized configuration and work mode requirements could be obtained. Finally, parameter matching and simulation verification on the designed scheme was carried out. It suggested that the designed system improved fuel economy by 4.14% compared with the original scheme.

Configuration of the Power Reflux Hydro-Mechanical Transmission System

The hydro-mechanical transmission system (HMTS) operates either in power split transmission mode (PSTM) or power reflux transmission mode (PRTM). Although PRTM is often ignored as a transition mode, this study reveals that the HMTS operating in the PRTM can accumulate the power input from the power source in the form of reflux power (in some references, scholars also refer to the reflux power as circulating power), thereby enabling the HMTS to exhibit a similar transmission performance as hydrodynamic transmission systems. Accordingly, this study applies the PRTM to the starting of construction vehicles and refers to the HMTS operating only in the PRTM as the power reflux hydro-mechanical transmission system (PHTS). By analyzing the internal relationship between the configuration and the power flow, transmission characteristics, energy storage mechanism, and energy loss mechanism of the PHTS, the optimal PHTS configuration suitable for construction vehicles was explored. The results indicate that reasonable configurations can enable the PHTS to significantly improve the efficiency of the construction vehicle transmission system, reducing energy consumption while ensuring power performance. Expanding the displacement ratio control range of the hydraulic speed regulation mechanism and combining the PRTM with the PSTM in an orderly manner can widen the high-efficiency range of the vehicle transmission system without increasing the number of vehicle gears.

Optimization design of load-sharing and light weight of the twin rotors concentric face gear power-split transmission system based on gear tooth matching condition

To improve the dynamic load-sharing performance and achieve lightweight, the twin rotors concentric face gear power-split transmission system (TRFGPSTS) was optimized. The gear tooth matching conditions of the system based on the design characteristics of power flow closed-loop and virtual constraint configuration of the system are established, and the basic parameters of each gear meet the requirements of the system load-sharing layout and synchronous meshing of each branch movement are calculated. Based on the lumped mass parameter method, combined with the calculation results of gear tooth matching, the 45-DOF bending torsional coupling dynamic model of the system was established considering time-varying meshing stiffness, support stiffness, manufacturing and installation errors, and other factors, and the influence of each factor on the dynamic load-sharing performance of the system was analyzed. Combined with the influence law of various factors, a multi-objective dynamic load-sharing optimization design model was established with the best dynamic load-sharing performance and the minimum system quality as the objective function. Through the weighted combination method, the global optimal solution of the system optimization design was determined, and the influence of each parameter on the optimization objective function was analyzed. The correctness of the results was verified by using the genetic algorithm based on Pareto frontier distribution. The results show that the dynamic load-sharing characteristics of the system become worse with the increase of error and torsional stiffness, and are more sensitive to the influence of various error parameters. The optimization process focuses on the geometric parameters such as the Module, the teeth Number, the Pressure angle, and the Tooth width of each gear, which can reflect the degree of influence on the dynamic load-sharing and lightweight of the system. After optimization, the dynamic load sharing coefficient (DLSC) was reduced to 1.017, and the overall geometric volume was reduced to 1.473 × 108 mm3. It provides a theoretical basis for the design and research of a new type of helicopter power transmission system with a compact structure, good maneuverability, and high reliability.

Model predictive control for multimode power-split hybrid electric vehicles: Parametric internal model with integrated mode switch and variable meshing losses

Model predictive control (MPC) is one of the most promising energy management strategies for hybrid electric vehicles. However, owing to constructive complexity, the multimode power-split powertrain requires dedicated mathematical tools to model the mode switch and transmission power losses within the internal model of the controller. Thus, the transmission losses are usually neglected and the mode switch is optimised through offline simulations. This paper proposes an MPC internal model relying on a parametric approach available in the literature, which provides a unique formulation for modelling any power-split transmission and assesses the transmission meshing losses. The objectives, which cover a gap in the literature, are: 1) to integrate the discrete problem of the mode switch in a continuous formulation of the internal model; 2) to compare MPC internal models with different complexity, and evaluate how the consideration of meshing losses and efficiency of the electric machines affect the controller performance. The results on a case study vehicle, i.e., the Chevrolet Volt, suggest that a simplified internal model deteriorates the fuel consumption performance by less than 2 %, while the integrated mode switch is comparable to the offline strategy.

Influence of errors and floating on static load-sharing characteristics of twin rotors concentric face-gear power-split transmission system

Influence of errors and floating on static load-sharing characteristics of twin rotors concentric face-gear power-split transmission system

Recovering and accumulating energy in regenerative braking of a garbage truck using hydro-mechanic power split transmission

Hydro-mechanical power-split transmissions (HPSTs) are a kind of continuously variable transmission; HPSTs integrated with the hydraulic energy recovery and accumulation function are the most coherent selection to im-prove the energy efficiency of the garbage truck. With an accumulator located in the speed-increasing hydraulic converter of the HPSTs, it is possible to recover and accumulate energy during braking and reuse energy when starting, accelerating or using other technologies in the process of garbage collection and transportation. Some results of simulation research and analysis of the energy recovery and accumulation process introduced in this paper can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks. In this study, the results of the simulation and analysis of the energy recovery and accumulation process were reported. Our findings can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks.

Control Design of a Hydraulic Cooling Fan Drive for Off-Road Vehicle Diesel Engine With a Power Split Hydraulic Transmission

The engine cooling fan drive is crucial for an engine as it ensures safe and efficient engine operation. In heavy-duty mobile machine, the engine cooling fan consumes a considerable amount of engine power. To meet high cooling demand a hydraulic fan drive is usually employed. A simple and cost-effective way is to use two fixed displacement hydrostatic units and a pressure relief valve where it has severe valve throttling losses. A more efficient way is to use a variable displacement pump to drive a fixed displacement motor. It eliminates valve throttling however the drive efficiency is still relatively low due to variable pump displacement control. Therefore, an engine cooling fan drive system with a power split hydraulic transmission was proposed in the previous study. The hydraulic transmission is a compact unit with both pumping and motoring functions. The fan speed is controlled by adjusting the transmission outlet pressure. Although previous results showed the system has relatively higher drive efficiency than conventional hydraulic fan drive at different fan speeds, the control design, and system dynamic performance have not yet been studied. Therefore, in this article, the control design of the cooling fan drive system with power split hydraulic transmission is studied. A feedforward controller based on transmission characteristics is designed to achieve better system performance. A hydraulic fan drive test bench is developed to evaluate system control design. The system dynamic performance with feedforward and feedback controls are compared through both simulation and experimental studies.

A Torque Conversion Solution to the Powertrain of Mobile Machine and Its Control Strategy

The demand for reducing fuel consumption and emission of mobile machines is increasing since they consume large amount of energy and generate huge exhaust each year. The wheel loader is a representative mobile machine and large wheel loader typically employs a hydrodynamic torque converter and an automatic transmission in the powertrain. The torque converter provides large torque amplification at low vehicle speed, however generates large amount of heat inside. This brings a challenge during frequent vehicle start and stop. In this study, an alternative torque conversion solution to the powertrain of mobile machine with a power split hydraulic transmission is proposed, where the hydraulic transmission is a substitute for the torque converter. It eliminates overheating problem by dissipating the heat inside through its outlet. The mathematical models of the proposed powertrain including the wheel drive and working function are developed. An engine-speed-based system optimization is conducted and a rule-based control strategy based on optimization results is developed. The engine operations and engine fuel consumptions with optimization-based and rule-based control strategies are compared using three different loading cycles (57 s, 30 s, 90 s). The results show the effectiveness of proposed powertrain solution and its control strategy.

Design of a Hybrid Electric Power-Split Transmission for Braking Energy Recovery in a Drilling Rig

Despite the promising potential of the hybrid electric power-split layout, its broader market penetration is prevented by the large number of feasible solutions and the constructive complexity, which overcomplicate the design process. Moreover, due to the lack of relevant literature references, the power-split transmissions design is even more difficult if concerning applications outside the automotive and agricultural sectors. In this paper, a general parametric model already available in the literature to design a single-mode power-split transmission with up to two planetary gear sets and six ordinary gear sets was applied to hybridize an oil drilling rig to recover energy braking during the gravity-driven lowering phases. This is the first power-split electric hybridization of a drilling rig. Two solutions differing in engine power size are presented. Thanks to the modularity of the model, the procedure enabled the optimization of the ICE, the electric machines, and the gear sets through decoupled design phases.

Effect of stiffness on load-sharing characteristics of twin rotors concentric face gear power-split transmission system

A twin rotors concentric face-gear power-split transmission system (TRCFGPSTS) applied to the core transmission mechanism of advanced aviation twin rotors helicopter was studied. The effects of torsional stiffness and support stiffness on the load-sharing characteristics of system were mainly studied. By comprehensively considering the factors such as manufacturing error and installation error, meshing stiffness, torsional stiffness, support stiffness and elastic deformation, and according to the power flow double closed-loop mechanical characteristics of this system, the static double closed-loop torsional angle elastic deformation coordination conditions are derived. The static load-sharing model was established by combining the moment balance equation of system. The load-sharing coefficient (LSC) and sensitivity parameters characterizing the load distribution of system were obtained. The effects of the torsional stiffness of the split-torsion shaft and the double-torsion shaft and the support stiffness of each gear on the load-sharing characteristics of the system were analyzed. The results show that the torsional stiffness of the split-torsion shaft and the double-torsion shaft has a great influence on LSC and sensitivity of the system, when its value is in the range of (1–1.6) × 105 N·m /rad and (2.4–4.3) ×105 N·m /rad, the system can meet the requirements of ± 5% of load-sharing characteristics under service conditions. Reducing the torsional stiffness of the split-torsion shaft can improve the load-sharing characteristics of the system, and the torsional stiffness of the right-branching double-shaft has little effect on the load-sharing characteristics of the left-branching of the system. The support stiffness of I-stage small cone angle face gear and Ⅲ-stage face gear is the most sensitive to LSC. With the increase of the support stiffness, the LSC first decreases and then gradually flattens, and the support stiffness of Ⅲ-stage face-gear has little effect on the I-stage LSC. The research results can provide a theoretical basis for the optimal design of load-sharing structure.

Characteristic Investigation and Torque Distribution Diagram-Based Computational Method for Continuously Variable Power-Split Transmission

The key parameter of power-split transmission is the planetary ratio. To obtain various planetary ratios in one transmission system, people use complex systems with multiple planetary gear trains, clutches, and brakes. Another solution is replacing the planetary gear train with a planetary traction drive. However, the participation of the planetary traction drive brings about creep and spin motion, which increase the difficulty of precise calculation. In this study, we investigate the relationships between torques and speeds. Then, we derive the torque and speed distribution formulas that consider the influence of spin torque and creep motion. This study is the first step to precisely calculate the emerging power-split transmission with the planetary traction drive. Based on a contact model and a proposed torque distribution diagram method, this study proposes a fast computational method for calculating the performance of the new continuously variable power-split transmission. The results show that the proposed torque distribution diagram-based computational method is feasible, and the planetary traction drive can be a competitive power-split device for power-split transmission.

Machine-type communications in NOMA-based terahertz wireless networks

Terahertz (THz) band is one of the most promising aspects of wireless communication systems because of its potential to meet the growing demands for the envisioned next-generation of cellular communications. THz band connectivity can alleviate bandwidth shortages and transmit power constraints using multiple-input multiple-output (MIMO) systems. To obtain better throughput and enhanced spectral efficiency, non-orthogonal multiple access (NOMA) configuration can be incorporated into MIMO systems, as NOMA uses non-orthogonal resource allocation by assigning the same carrier frequency to multiple devices in the power domain. In this paper, we focus on 2 × 1 MIMO-NOMA and cooperative 2 × 1 MIMO-NOMA systems for THz spectrum in the downlink transmission. In order to evaluate the effectiveness of the proposed system architecture, we derive accurate data rate, transmission latency, and reliability expressions for 2 × 1 MIMO-NOMA system consists of critical and non-critical devices by leveraging finite block length theory. Moreover, we derive the closed-form expressions for power splitting coefficients, data rate, transmission latency, and reliability for the considered cooperative 2 × 1 MIMO-NOMA system. Extensive numerical results are presented to validate the feasibility of the proposed 2 × 1 MIMO-NOMA as well as the cooperative 2 × 1 MIMO-NOMA systems in the THz band.

A Hybrid–Electric Driveline for Agricultural Tractors Based on an e-CVT Power-Split Transmission

This paper proposes a full-hybrid driveline based on an electric continuously variable transmission (e-CVT), which is inspired by the car industry’s most successful solution. The paper describes the operating principle, the system architecture, and the control scheme of the proposed driveline. An analysis of four possible operating modes shows that the e-CVT driveline leads to a performance similar to that of conventional tractors, as well as unusual features such as power boost, full-electric mode, optimized auxiliary drive and electric power delivery capability. The compact layout proposed for the e-CVT also makes it possible to simplify the overall layout of the tractor, particularly during the installation of both the thermal engine and the cooling system.

Power Losses Minimization for Optimal Operating Maps in Power-Split HEVs: A Case Study on the Chevrolet Volt

The power-split architecture is the most promising hybrid electric powertrain. However, a real advantage in energy saving while maintaining high performance can be achieved only by the implementation of a proper energy management strategy. This requires an optimized functional design before and a comprehensive analysis of the powertrain losses after, which could be rather challenging owing to the constructive complexity of the power-split transmission, especially for multi-mode architecture with multiple planetary gearing. This difficulty was overcome by a dimensionless model, already available in the literature, that enables the analysis of any power-split transmission, even in full electric operation. This paper relies on this approach to find the operating points of the internal combustion engine and both electric machines which minimize the total power losses. This optimization is carried out for given vehicle speed and demanded torque, by supposing different scenarios in respect of the battery capability of providing or gathering power. The efficiency of the thermal engine and the electric machines is considered, as well as the transmission mechanical power losses. The aim is to provide a global efficiency map that can be exploited to extract data for the implementation of the most suitable real-time control strategy. As a case study, the procedure is applied to the multi-mode power-split system of the Chevrolet Volt.

Performance analysis of hydrodynamic mechanical power-split transmissions

The objective of this study was to evaluate the performance of 24 basic hydrodynamic mechanical power-split (HMPS) transmission designs effectively based on their torque multiplication capacities (TMCs) and efficiencies. Firstly, four schemes were preliminarily selected. Secondly, the matching between the four schemes and a reference wheel loader was considered, and an expression for the TMC was developed based on the traditional transmission and a second reference transmission. Thirdly, two performance metrics in terms of the TMC and efficiency – the average torque multiplication capacity (ATMC) and average efficiency – were defined to eliminate the couplings of four transmission parameters with the vehicle speed and speed ratio. Finally, the performances of the two best schemes and traditional hydrodynamic mechanical (HM) transmission were carefully compared. The results show that a transmission with power recirculation cannot present energy savings potential regardless of the ATMC, whereas a transmission with a power split can achieve an ATMC of 0.255, an average efficiency increment of 0.0143 in the short loading cycle, and a miniscule efficiency increment in the long loading cycle compared with the HM transmission.

Characteristic sensitivity analysis of herringbone gear power-split transmission system

ABSTRACT The herringbone gear power-split transmission is widely used in high-speed and heavy-load transmission systems, and its dynamic analysis is becoming increasingly important. The characteristic sensitivity of a gear transmission system indicates the influence of the dynamic parameters on the natural frequency of the gear transmission system, and it functions as an important theoretical reference value in the dynamic design of a herringbone gear power-split transmission system. In this paper, the dynamic equations of a herringbone gear power-split transmission system for a ship are presented, and the natural frequencies and modal shapes are calculated based on the free torsional vibration differential equation. Subsequently, the modal shapes were classified into the coupling vibration model and the branch vibration model. The characteristic sensitivity was studied using modal analysis, and the characteristic sensitivity calculation equations for single and double root of natural frequency were deduced, and the characteristic sensitivity of the natural frequencies to the mesh stiffness was computed. Finally, the relationship between the modal strain energy and the characteristic sensitivity was analysed, and the physics essence of the characteristic sensitivity was revealed.

An Energy Efficient Power-Split Hybrid Transmission System to Drive Hydraulic Implements in Construction Machines

Abstract This paper proposes a novel hybrid power-split transmission to drive hydraulic implements in construction machinery. The highly efficient power-split hybrid transmission is combined with displacement-controlled (DC) actuators to eliminate throttling losses within the hydraulic system and achieve higher fuel savings. The architecture design, sizing, and power-management are addressed. Simulation results considering a realistic truck-loading cycle on a mini-excavator demonstrate the feasibility of the idea. A systematic comparison between the proposed system and the previously developed series–parallel hybrid is also carried out. The paper compares engine operation and fuel consumption of the previously mentioned hybrid system with the original nonhybrid load-sensing (LS) machine. It is shown that by implementing an efficient engine operation control, the proposed system can achieve up to 60.2% improvement in fuel consumption when compared to the original machine and consume 11.8% less than the previously developed series–parallel hybrid with DC actuation. Other advantages of the proposed solution include a much steadier engine operation, which open to the possibility of designing an engine for optimal consumption and emissions at a single operating point as well as greatly reduce pollutant emissions. A steadier prime mover operation should also benefit fully electric machines, as the battery would not be stressed with heavy transients.

Analysis of hybrid vehicle transmissions with any number of modes and planetary gearing: kinematics, power flows, mechanical power losses

This paper is focused on upgrading a unified parametric model, available in the literature, that can perform both the analysis and the design of Power-Split Continuously Variable Transmissions (PS-CVTs), which are particularly promising to deploy in the hybrid electric powertrain. In particular, this work is focused on the analysis of PS-CVTs and proposes a new matrix approach for identifying the basic functional parameters underlying the model from the constructive layout of the transmission. This new method does not rely on a case-specific formulation, thus befits any power-split transmission, regardless of the number of planetary and ordinary gear sets and their constructive arrangement. Moreover, it handles the clutches operations that perform the shift between different constructive layouts, therefore it is suitable even for multimode PS-CVTs.As a case study, we applied it to the complex multimode PS-CVT of the Cadillac CT6 and carried out a comprehensive analysis of its kinematics, mechanical power losses and power flows.

Rate optimization for relaying VLC system with simultaneous lightwave information and power transfer.

In this paper, the rate optimization problem in a relaying visible light communication system with simultaneous lightwave information and power transfer (SLIPT) is investigated, where the power splitting (PS) transmission strategy is adopted. The expressions of the transmission rate and energy harvesting at the target node are derived, based on which, the rate maximization problem is formulated. Then, this problem is solved by optimizing the PS factor, and a closed-form solution is given. Numerical results reveal that the existence of the relay node improves the system performance.