Clutch Engagement Research Articles

On Dynamic Analysis and Prevention of Transmission Squawk in Wet Clutches

Abstract The genesis of clutch noise, encompassing squeaks, chatter, shudders, or judders, predominantly arises from friction-induced vibrations. As time progresses, the degradation of the clutch friction lining manifests due to diverse factors, such as the smearing of surface irregularities, elevated transmission fluid temperatures, fluctuating axial pressure, or aggressive shifting. Consequently, the slope of the friction curves tends to assume a negative gradient, giving rise to adverse damping effects like self-excited oscillations or stick-slip oscillations within the clutch pack. A lesser-discussed phenomenon, known as Squawking, occurs through analogous mechanisms discussed in this article. This article delves into investigating the occurrence of squawking noise observed in automatic transmission multi-disc clutches during low-speed up-shifts. The study discerns friction-induced vibrations as the primary contributor to squawk during the inertia phase of the clutch engagement cycle, a facet previously unidentified. During this phase, high-frequency weakly damped oscillating modes become self-excited due to the negative slope of the coefficient of friction versus slip speed curve. The coefficient of friction functions as negative damping during the inertia phase, where the energy dissipation from damping is insufficient to completely halt the oscillations, allowing them to persist at the natural frequency until clutch lock-up. Experimental data validates the proposed model and hypothesis, with results closely aligning with numerical simulations. The paper concludes by offering practical suggestions to prevent and mitigate squawk in automatic transmission wet clutches, with the aim of enhancing overall performance and reducing undesirable noise.

The Optimization and Control of the Engagement Pressure for a Helicopter Dry Clutch

The engagement quality of a helicopter dry clutch has a significant impact on the service life and overall flight performance of the helicopter. The engagement oil pressure is an important factor affecting the clutch engagement quality. Firstly, a nonlinear input–output dynamic model for the dry clutch is developed to investigate the optimization and control of dry clutch engagement pressure in this paper. Secondly, to efficiently obtain the optimal pressure curve, an optimal method combining the developed dynamic model with the state feedback gain of a linear quadratic optimization regulator (LQR) solver is proposed. Thirdly, considering that hydraulic actuators may struggle with tracking certain pressure curves, a hydraulic actuator for accurately tracking pressure curves based on fuzzy PID is proposed. The simulation results indicate that the developed hydraulic actuator exhibits an excellent tracking performance. Moreover, compared with linear and segmented pressure curves, the optimal pressure curve derived from the proposed method significantly reduces jerk, friction work, and engagement duration, resulting in improved helicopter dry clutch engagement quality.

Dynamical model for dog clutch shiftability

AbstractThe dog clutch offers advantages in mass and efficiency, but faces challenges in mismatch speed synchronization, which affects its shiftability. Face impact between dog teeth also reduces its lifespan. Our previous work introduced the kinematical shiftability condition that ensures impact-free gearshift but had limitations due to analysis assumptions. This study eliminates those assumptions, but uses a similar approach. Based on our previous work for dog clutch engagement dynamics, we develop the dynamical shiftability condition. Validation with full dog clutch dynamics showed an agreement. Employing another previous work that introduced shiftability map and parametric study method, we study system parameters impact on shiftability but based on the dynamical shiftability condition.

Modelling and application of typical nonlinear torsional elements in vibro-impact analysis of pickup truck driveline system

The torsional element method for the dynamic modelling of torsional system was proposed by Crowther and Zhang, which provides a modular modeling approach with high modeling efficiency and has a good application prospect in vibro-impact analysis of vehicle driveline system. The main purpose of this paper is to further enrich the element types of the torsional element method and to establish a nonlinear dynamic model for a pickup truck driveline system by applying the torsional element method to analyze the vibro-impact phenomenon. A general nonlinear clearance element with different contact stiffness and damping, a nonlinear friction element with smooth Stribeck effect and a nonlinear multistage stiffness-damping element with different torque transfer characteristics are developed. A dynamic lumped parametric model with 10 degrees of freedom for a pickup truck driveline system is established by assembling the developed nonlinear torsional elements. The transient vibro-impact phenomenon caused by the clearance, the stick-slip phenomenon caused by the friction and the transient hysteresis cycle phenomenon caused by the nonlinear multistage damper during transient engagement of clutch are numerically investigated. Furthermore, a real-vehicle experimental study is conducted to confirm the transient vibro-impact phenomenon in pickup truck driveline system during transient clutch engagement and to verify the correctness of the dynamic lumped parameter model. On these bases, the influence of the key parameters of the nonlinear torsional element on the transient vibro-impacts are investigated, the effective engineering countermeasures to reduce the vibro-impact of the vehicle driveline system are put forward.

МОДЕЛИРОВАНИЕ ДИНАМИЧЕСКИХ ПРОЦЕССОВ СИЛОВОЙ УСТАНОВКИ ЭЛЕКТРОГРУЗОВИКА МАЗ-4381ЕЕ С ИСПОЛЬЗОВАНИЕМ ПРОГРАММНОГО КОМПЛЕКСА MATLAB SIMULINK

A dynamic model of the battery power unit of the electric truck MAZ-4381EE with a two-speed gearbox is considered. The dynamic processes arising at gear shifting are investigated. The gearbox is switched by controlling the rotational speed of the traction electric motor synchronously with the process of switching on the synchronized gear coupling of the gearbox. When simulating the processes of gear shifting, dynamic loads, time of clutch engagement and synchronization of rotation frequencies of gearbox links, work and power of slipping of friction elements of the synchronizer are estimated. According to the simulation results, the necessity is shown for using feedbacks for controlling the traction electric motor and state parameters of synchronized gearbox couplings, and an algorithm is proposed for controlling the power electric drive of the electric truck, which provides minimum dynamic loads in the electric drive and low load of gearbox synchronizers.

Optimal Torque Control of the Launching Process with AMT Clutch for Heavy-Duty Vehicles

When launching a heavy-duty vehicle, torque and position control during automatic clutch engagement is critical, and the driver’s intention to launch and changes in the vehicle’s launching resistance make clutch control more complex. This paper analyses the automatic engagement process of automated mechanical transmission (AMT) clutches and proposes an optimal control of the clutch torque for launching heavy-duty vehicles. Firstly, a fuzzy neural network (FNN)-based vehicle launching states recognition (LSR) system is designed for distinguishing the driver’s launching intention and the vehicle’s launching equivalent moment of resistance. Secondly, jerk, friction work, and launching reserve power are taken as the performance indexes for clutch torque optimization, the weight coefficients of each performance index are adjusted according to the LSR results, and the optimal clutch torque is solved by using the minimum value principle based on the shooting method. Finally, simulations and tests are conducted to validate the strategy of optimizing clutch torque, and the impact of torque optimization on the position change during the engagement process is analyzed. The results indicate that under different driver’s intentions, vehicle masses, and road gradient conditions, the jerk, friction work, and slipping time of heavy vehicles during the launching process are improved by applying the optimization strategy.

Friction Coefficient of Wet Clutches as a Function of Service Mileage

As a core component for efficient variable speed transmission and energy saving, wet clutches are widely used in the transmission systems of energy-saving and new energy vehicles. However, with an increase in the service mileage of the wet clutch, the friction coefficient undergoes alterations. This leads to a deterioration of the control accuracy of the clutch transmission torque, which ultimately has a negative impact on the dynamic characteristics and driving safety of the entire vehicle. In order to understand the service behavior of the friction coefficient in a wet clutch, wet clutches with different service mileages were investigated experimentally and theoretically. The results show that as the service mileage increased, the hydrodynamic lubrication phase was extended. Analyses of the three-dimensional profile of the friction plate and the theoretical simulation of the friction revealed that the edge ridges of the friction pads were flattened. This increased the clutch engagement force when the asperities on the separator and friction plates came into contact.

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.

Plug‐In Hybrid Electric Vehicle Energy Management with Clutch Engagement Control via Continuous‐Discrete Reinforcement Learning

Energy management strategy (EMS) is a key technology for plug‐in hybrid electric vehicles (PHEVs). The energy management of certain series–parallel PHEVs involves the control of continuous variables, such as engine torque, and discrete variables, such as clutch engagement/disengagement. Herein, a control‐oriented model is established for a series–parallel plug‐in hybrid system with clutch engagement control from the perspective of mixed‐integer programming. Subsequently, an EMS based on continuous‐discrete reinforcement learning (CDRL), which enables simultaneous output of continuous and discrete variables, is designed. During training, state‐of‐charge (SOC) randomization is introduced to ensure that the hybrid system exhibits optimal energy‐saving performance in both high and low SOC. Finally, the effectiveness of the proposed CDRL strategy is verified by comparing EMS based on charge‐depleting charge‐sustaining (CD‐CS) with rule‐based clutch engagement control and dynamic programming (DP). In the simulation results, it is shown that, under a high SOC, the CDRL strategy proposed in this article can improve energy efficiency by 8.3% compared to CD‐CS, and the energy consumption is just 6.6% higher than the global optimum based on DP, while under a low SOC, the numbers are 4.1% and 3.9%, respectively.

Energy Management for Hybrid Electric Vehicles Using Safe Hybrid-Action Reinforcement Learning

Reinforcement learning has shown success in solving complex control problems, yet safety remains paramount in engineering applications like energy management systems (EMS), particularly in hybrid electric vehicles (HEVs). An effective EMS is crucial for coordinating power flow while ensuring safety, such as maintaining the battery state of charge within safe limits, which presents a challenging task. Traditional reinforcement learning struggles with safety constraints, and the penalty method often leads to suboptimal performance. This study introduces Lagrangian-based parameterized soft actor–critic (PASACLag), a novel safe hybrid-action reinforcement learning algorithm for HEV energy management. PASACLag utilizes a unique composite action representation to handle continuous actions (e.g., engine torque) and discrete actions (e.g., gear shift and clutch engagement) concurrently. It integrates a Lagrangian method to separately address control objectives and constraints, simplifying the reward function and enhancing safety. We evaluate PASACLag’s performance using the World Harmonized Vehicle Cycle (901 s), with a generalization analysis of four different cycles. The results indicate that PASACLag achieves a less than 10% increase in fuel consumption compared to dynamic programming. Moreover, PASACLag surpasses PASAC, an unsafe counterpart using penalty methods, in fuel economy and constraint satisfaction metrics during generalization. These findings highlight PASACLag’s effectiveness in acquiring complex EMS for control within a hybrid action space while prioritizing safety.

Study on Shifting Performance of Tractor Multi-Clutch under Different Engagement Rules

When shifting gears around a tractor’s power shift transmission, it is necessary to coordinate the control of multiple clutches and formulate a reasonable clutch engagement law to ensure the reliability and power of the power system. This paper explores the impact of different clutch engagement patterns on shifting characteristics in a power-shift tractor with multiple clutches. Shifting performance is comprehensively evaluated using indicators such as shifting time, impact degree, slip energies, and transmission output torque. The aim is to enhance the quality of power shifting, operational efficiency, and the service life of the transmission system. This paper takes the YTO TX4A transmission system as the research object, analyzes its working principle, and establishes a mathematical model of a power shift transmission system under different clutch engagement rules. This model of power shift transmission is established based on Matlab2021/Simulink and the AMESim2021 software platform. A simulation analysis is carried out for four clutches working simultaneously in a tractor’s advance gear II and lift gear III. The simulation results indicate that switching rule C is superior to switching rule A and switching rule B. Compared with the engagement scheme in which the torque exchange overlap time for both sets of clutches is 0.3 s, the scheme with a torque exchange overlap time of 0.15 s indicated a shifting time increase of 0.2 s, a slip energy increase of 4%, and a minimum output torque of the transmission increase of 2%. In the scheme with a torque exchange overlap time of 0 s, the shifting time increased by 0.15 s, the slip energy decreased by 13.5%, and the minimum output torque of the transmission decreased by 17%. Through the study of shifting performance under three different clutch engagement patterns, it is concluded that, during the shift from forward gear II to gear III in the YTO TX4A transmission system, appropriately reducing the torque exchange overlap time for both sets of clutches and avoiding simultaneous torque exchange can reduce the complexity of clutch control. This leads to smoother, more powerful, and more comfortable power shifting, effectively prolonging the service life of the transmission system.

Research on Mode Switching and Energy Management of Hybrid Electric Vehicle

Aiming at the optimization of mode switching control and energy management strategy for parallel hybrid electric vehicles, a mode switching control method and A-ECMS steady-state energy management strategy is proposed. Firstly, in order to effectively suppress the impact caused by mode switching, and a fuzzy controller is designed for clutch engagement displacement. Then, on the basis of ensuring the smoothness of mode switching, A-ECMS control strategy based on SOC feedback is established. Finally, Isight and Cruise are used to build a co-simulation platform, and multi-island genetic algorithm is used to study the influence of initial value selection of equivalent factor on the controller. The results show that the proposed mode switching control and energy management control strategy, combined with A-ECMS strategy, can effectively improve the vehicle fuel economy on the basis of ensuring the mode switching smoothness.

Coupling mechanism and data-driven approaches for high power wet clutch torque modeling and analysis

We propose a hybrid model that integrates conventional mechanism methods with state-of-the-art data-driven techniques to study torque characteristics during the high power clutch engagement process. Experimental validations using clutch bench tests demonstrate that our hybrid model has an error of 7.0%, outperforming conventional mechanistic models and reducing the average error in predicting clutch torque by 12%. With this developed hybrid model, we systematically investigated the impact of oil pressure, oil temperature, and disc size on torque characteristics under various working conditions. Our findings reveal that pressure has the most significant impact on clutch torque. While the influence of the other two factors on overall clutch torque is relatively diminished, temperature can significantly change the viscous torque and disc size can markedly change torque generation time.

Mode transition prescribed performance control of connected hybrid electric vehicles based on driver intention fuzzy prediction

A novel hierarchical mode transition control (NHMTC) algorithm utilizing traffic information is investigated for realizing a superior dynamic and ride comfort performance of a connected hybrid electric vehicle (CHEV). The upper level includes the target vehicle velocity planning by model predictive control (MPC) considering less vehicle jerk based on the vehicle-to-infrastructure (V2I) information and the driving intention prediction by a type-2 fuzzy neural network (T2FNN) model using the planned target velocity. The lower level involves the automatic clutch system’s prescribed performance fixed-time controller (PPFTC) design and the desired velocity of the clutch engagement calculated by the predicted driving intention to improve the clutch position trajectory’s tracking accuracy and stability under the actual mode transition process. The comparison results with existing schemes under a co-simulation environment demonstrate the advantage and effectiveness of the designed NHMTC method.

Design of tractor virtual test system based on high-level architecture technology.

The limitations of the tractor virtual test system are evident in various aspects, including model reuse, system expansion, offsite interconnection, and virtual reality verification. To address these challenges, a distributed virtual test system for tractors based on the high-level architecture (HLA) is proposed. Involve analyzing the hardware structure and the tractor virtual test system, constructing the system federation and its members, and designing the federated object model (FOM) and simulation object model (SOM) tables. The system integrates multi-domain commercial software and enables real-time virtual testing through TCP/IP interconnection of multiple machines. To evaluate the system's performance, a virtual test of the tractor's reversing clutch engagement performance is conducted. The system's simulation performance and data transmission delay are thoroughly tested and analyzed. The results indicate that when the system's data volume reaches 5000KB, the data delay is 9.7ms, which satisfies the requirement of not exceeding 10ms for tractor virtual testing delay. The virtual test of the reversing clutch power reversal process demonstrates that it lasts 0.7s, with the vehicle speed changing from -3.5km/h to 3.5km/h, the forward gear piston oil pressure increasing from 0MPa to 5MPa, and the peak impact degree reaching 17m/s3. The slip work during the reversing process is measured to be 21kJ. Furthermore, the gray correlation method is employed to compare the virtual test results with the bench test results, confirming their consistency. The power reversal process exhibits relatively smooth speed changes overall. Therefore, the tractor power shift transmission (PST) reversing clutch virtual test model operates effectively within the HLA-based tractor virtual test system.

Defined extracellular matrix compositions support stiffness-insensitive cell spreading and adhesion signaling

Integrin-dependent adhesion to the extracellular matrix (ECM) mediates mechanosensing and signaling in response to altered microenvironmental conditions. In order to provide tissue- and organ-specific cues, the ECM is composed of many different proteins that temper the mechanical properties and provide the necessary structural diversity. Despite most human tissues being soft, the prevailing view from predominantly in vitro studies is that increased stiffness triggers effective cell spreading and activation of mechanosensitive signaling pathways. To address the functional coupling of ECM composition and matrix rigidity on compliant substrates, we developed a matrix spot array system to screen cell phenotypes against different ECM mixtures on defined substrate stiffnesses at high resolution. We applied this system to both cancer and normal cells and surprisingly identified ECM mixtures that support stiffness-insensitive cell spreading on soft substrates. Employing the motor-clutch model to simulate cell adhesion on biochemically distinct soft substrates, with varying numbers of available ECM-integrin-cytoskeleton (clutch) connections, we identified conditions in which spreading would be supported on soft matrices. Combining simulations and experiments, we show that cell spreading on soft is supported by increased clutch engagement on specific ECM mixtures and even augmented by the partial inhibition of actomyosin contractility. Thus, "stiff-like" spreading on soft is determined by a balance of a cell's contractile and adhesive machinery. This provides a fundamental perspective for in vitro mechanobiology studies, identifying a mechanism through which cells spread, function, and signal effectively on soft substrates.

Tribo-thermal simulation study of AMT dry clutch assembly under the continuous sliding grinding condition

Electronic Mechanical Transmission (AMT) is an automatic transmission device that combines hydraulic automatic transmission (AT) with manual transmission (MT). AMT has the advantages of automatic transmission as well as high efficiency, low cost, simple structure, and easy manufacture in the traditional manual transmission system. In dry clutch engagement, the wear of the engagement surface should be minimized to achieve good performance. It is necessary to control some influencing factors during its use. When the car starts, the flywheel and driven disc in the clutch change from a separation state to a full engagement state. When joining, due to the increase in speed of the driven disc, relative sliding occurs between the drive and driven parts, which causes the temperature of the friction surface to rise. If the temperature is too high, the wear of friction plates will be increased, which will reduce the service life and working stability of the clutch. In this study, the coupling field transient analysis of the clutch under continuous sliding wear conditions is carried out, and the clutch temperature change and heat generated by friction are obtained by simulation calculation under the use of simulated clutch holding for 1s. Based on the results of the simulation, the factors that may affect the friction heat generation of the clutch are analyzed.

Research on wear law of friction plate of AMT dry clutch under continuous slip wear condition

In the process of operation, because the AMT dry clutch in the process of separation and combination of the slip wear stage, this stage will cause the clutch friction plate wear, resulting in the change of the clutch power transmission performance, but also lead to the change of the clutch engagement characteristics and affect the clutch control performance. Therefore, the purpose of this paper is to study the wear law of the friction plate of the AMT dry clutch, and it is of great significance to evaluate the change in clutch transmission performance and realize the precise control of the clutch. In this paper, the ANSYS analysis software system is used to build a finite element analysis model about the wear of the friction plate of the AMT dry clutch, and a simulation of the sliding wear condition. At the same time, the method of loading heat flux is used to simulate the temperature of the sliding wear condition. The thermal deformation caused by temperature is taken as the main influence factor. To carry on the wear simulation analysis of the clutch-driven disc friction plate. Finally, the wear law of the friction plate of the AMT dry clutch is obtained.

A hybrid transient/quasi-static model for wet clutch engagement

This work presents a comprehensive formulation of the equations governing the lubrication and the lock-up phases of an engaging wet clutch. A finite element model is established through the coupling of the Reynolds equation of the fluid film model with the dynamic force and torque equilibrium equations of the two-disc system. To solve the problem, an efficient hybrid simulation technique is introduced, capable of capturing the rapidly evolving transient phenomena at the start of the engagement phase, which later settles into a quasi-static one as the film thickness asymptotically decreases. The simulation tool is benchmarked against previously published results and is later used to investigate the effect of a newly introduced groove configuration utilising variable-width grooves. The proposed geometry is compared against the well-known radial groove configuration on the engagement characteristics, resulting into decreased hydrodynamic peak force by approximately 20%. The supremacy of the proposed groove design over the standard radial geometry is further verified through a newly introduced groove design criterion that takes into consideration the relative effect of squeeze and torsional Couette flows during the hydrodynamic phase of the engagement. Finally, a comprehensive parametric study is conducted to capture the effect of the groove width and depth on the engagement variables.

Coordinated clutch actuation for drivability improvement and energy management of a novel multi-mode hybrid electric vehicle and HIL validation

This article presents a novel architecture of a particular class, i.e., multi-mode hybrid electric propulsion systems that utilize two planetary gear sets, multiple clutches, two electric motors, and an internal combustion engine. Although this class of propulsion systems offers architectural compactness, improved fuel economy, and operational versatility, it faces a drivability issue arising from simultaneous clutch engagement and disengagement during mode shift events. Such drivability issues cannot be addressed by baseline motor-torque compensation-based coordinated control that is typically employed to address the drivability issues in power-split and parallel hybrid propulsion systems. Therefore, this article proposes an enhanced version of the coordinated control that includes the clutch’s torque capacity control. The enhanced coordinated control module augments with the energy management system, making the mode shift schedule drivable and near-optimal. A real-time hardware-in-the-loop test bench is developed to accurately evaluate the enhanced coordinated control’s impact on the energy management system’s performance. Test bench results demonstrate that the enhanced coordinated control is more effective than the baseline coordinated control in attenuating the propulsion system’s perturbations during mode shift events and making the overall mode shift schedule drivable. The enhanced energy management system consumes 7%–8% more fuel while transforming the mathematically optimal mode shift schedule into a drivable one.