Shift Quality Research Articles

Application of Computer Simulation Technology in the Development of Tractor Transmission Systems

Tractors are the most important agricultural power machinery. With the development of tractors toward large-scale and electrification, the design of modern tractor transmission systems increasingly relies on computer simulation technology. However, tractor transmission systems, especially power-shift transmissions and CVTs, are highly complex industrial products that involve specialized knowledge from multiple disciplines. Engineers and researchers find it difficult to choose the correct mathematical model and grasp the trend of technological development when applying simulation technology. To address this issue, we conducted a systematic review of the field and carried out the following work: First, the types and basic principles of tractor transmission systems were introduced; Second, the modeling methods and applications of computer simulation technology in the structural optimization, power-shift control, and energy saving of tractor transmission systems were reviewed; Finally, the method of obtaining simulation parameters through system identification was introduced. Although computer simulation technology has been applied in the development of all tractor transmission systems, there are still some issues that need attention, such as the lack of established shift quality evaluation indicators and driving cycles suitable for tractors, which are crucial for the reliability of simulation results but are rarely studied. These issues need to be addressed in future work.

Improved energy utilization in heavy-duty automatic transmission: Advanced modeling and multi-objective optimization

In the current research of electro-hydraulic actuators for heavy-duty automatic transmissions, achieving accurate output is proven to be insufficient to meet growing demand. Aiming at this deficiency, this paper proposes a dynamic model, which combines detailed loss analysis and multi-objective optimization to further improve energy efficiency. Firstly, considering the key resistance factors, including viscous damping coefficient, spring constant and supply pressure, a dynamic model is established. Subsequently, the overall response of the model is verified based on the existing experimental data. In addition, the accuracy and stability time are used as evaluation indexes to analyze the influence of resistance on the function pattern. Finally, a multi-objective optimization method is used to balance the relationship between energy utilization efficiency, accuracy and shift quality. The slight changes in mechanical energy and stable time lead to a significant decrease in jerk by 22.11 %, which makes the shifting process smoother and effectively improves the shifting performance.

Experimental Investigation and Control of Driveline Torsional Vibrations during Clutch-to-Clutch Shifts of Electrified Vehicles

An electrified vehicle equipped with a stepped-ratio transmission and clutch(es) requires precise control of the clutch actuator(s) and power sources to achieve optimal gear shift performance, which is characterized by smooth and swift gear shifts. Owing to the absence of the smoothing effect of torque converters, dual-clutch transmission (DCT) powertrains are prone to inducing abrupt shift shocks—particularly during rapid clutch-to-clutch shifts. Balancing the smoothness and speed of shifts is a significant challenge and was the key focus of this study. Multiple experiments and model-based analyses were conducted to investigate the tradeoff between smoothness and shift time during the clutch-to-clutch shifts of a parallel-type hybrid electric vehicle with a dry DCT. Additionally, the adverse effects of inaccurate power-source control on shift quality were experimentally investigated. The results revealed the primary physical factors in terms of control causing torsional driveline oscillations in clutch-to-clutch shifts. According to these observations, a detailed quantitative guide including how to generate reference trajectories for shift control is proposed, with the aim of reducing the driveline torsional vibrations without compromising the shift time. The effectiveness of the proposed control strategy was demonstrated through real-time experiments on an electrified powertrain with a DCT using a dedicated test bench. This study provides valuable insights for optimizing the shift performance of electrified vehicles—particularly for managing torsional vibrations during clutch-to-clutch shifts.

Adaptive coordinated control strategy for improving shift quality under different operating conditions

In order to improve the shift quality of vehicles under different operating conditions (such as road resistance coefficient and throttle opening), this paper proposes an adaptive coordinated control strategy. This strategy utilizes a Forgetting Factor Recursive Least Squares (FFRLS) to achieve online identification of the road resistance coefficient. Based on the changes in throttle pedal opening and road resistance coefficient during the vehicle’s shifting process, the strategy adaptively adjusts the coordinated control parameter (fuel cut-off time) to achieve optimal control of vehicle shifting under different operating conditions. To evaluate the shift quality, shift jerk, friction work, torque peak, and shift time are used as performance indicators. Based on a constructed simulation model of the powertrain system, the influence of different operating conditions on the performance indicators is analyzed, and the effect of coordinated control parameters on improving shift quality under different operating conditions is compared. Corresponding fuzzy rules are then established to achieve adaptive adjustment of the coordinated control parameters through fuzzy control, ensuring effective improvement of shift quality for vehicles under different operating conditions.

A Fast Optimizing Method of Clutch–Clutch Shift Calibration Parameters

Aiming at the drawbacks of the heavy workload and lengthy calibration cycle of transmission control unit (TCU) development, a fast optimizing and test method of clutch–clutch shift calibration parameters is developed based on the “V” development process. A controlled-object simulation model of a six-speed automatic transmission (6AT) is established, and the shift calibration parameters and shift quality evaluation system are studied. Therefore, a model-in-the-loop (MIL) calibration platform for key calibration parameters and evaluation indicators in the shift process is constructed. By setting the optimization target of evaluation indicators, the initial calibration parameters’ ranges are reduced. Finally, the TCU is flashed with the optimized calibration parameters, and a hardware-in-the-loop (HIL) test system is built to verify the shift quality. The same shift quality verification test is carried out in the vehicle. The test results show that the application of the MIL simulation platform can enable the batch simulation analysis of eight key shift calibration parameters, gradually refine the initial rough interval, and ensure shift quality. The shift calibration parameters are cross-validated in multiple development links, and the dependence on vehicle calibration is greatly reduced. The development cycle is effectively shortened to less than 6 months.

Controller Design for Electrohydraulic Actuator of Heavy-Duty Automatic Transmission Using Model Predictive Control Algorithm

High-quality shifting is an inelastic demand for the automotive industry, and it is worth exploring the design of controllers that can shift precisely according to the planned shifting strategy. This paper proposes a dynamic model of the automatic transmission up/downshift process, and the transfer function based on pressure is first given. The model was verified by comparing it with the experimentally obtained fluid pressure. Subsequently, a pressure control strategy suitable for heavy-duty automatic transmission shifting was explored by establishing a model predictive controller with pressure feedback control. Meanwhile, a Kalman filter-based observer was designed to solve the inconvenient installation of internal sensors. Finally, the proposed control model was optimised using a multi-objective genetic algorithm for the controller. The simulation results indicate that the proposed control strategy can be applied to heavy-duty vehicles for improving the shift quality.

Shift Quality Classifier Using Deep Neural Networks on Small Data with Dropout and Semi-Supervised Learning

Shift Quality Classifier Using Deep Neural Networks on Small Data with Dropout and Semi-Supervised Learning

Model Predictive Control for Automatic Transmission Upshift Inertia Phase

This article deals with model predictive control (MPC) design for automatic transmission (AT) upshift inertia phase, which aims to optimally coordinate the actions of oncoming (ONC) and off-going (OFG) clutches and engine and to facilitate calibration. The designed MPC strategy accounts for clutch actuation dynamics and constraints, while setting the tradeoff between three key and conflicting shift quality criteria: comfort; duration; and efficiency. The shift comfort and duration are ensured by minimizing output shaft torque and ONC clutch slip speed tracking errors, and the shift efficiency is reflected in clutch energy loss minimization on a prediction horizon. This allows for the calibration of the MPC performance through setting the inertia phase duration, the output shaft torque reference, cost function weighting coefficients, and constraints, rather than optimizing the shift control profiles themselves. The MPC problem is formulated as a constrained quadratic programming problem and efficiently solved online by an interior-point solver. The proposed MPC strategy is applicable to other transmissions with multiple actuators, such as parallel hybrid transmissions. The MPC system is examined through nonlinear powertrain model simulations for one to three shift and its performance is compared with an offline, multiobjective optimization-based control strategy. The MPC design flexibility and ease of calibration are demonstrated for different shift comfort and duration targets, as well as cost function tuning, and robustness with respect to clutch actuation parameter uncertainties is examined.

Optimization Analysis on the Transmission Characteristics of Multipurpose Power Transmission Devices

Particularly crucial throughout the mode transition procedure is the transmission properties of hydro–mechanical composite transmission devices. This paper describes a multipurpose power transmission device that integrates hydrostatic, hydro-mechanical, and mechanical transmission and mainly discusses the transmission characteristic optimization problem from the perspective of speed regulation characteristics, shift strategy, and efficiency characteristics. The kinematic and dynamic analysis of the transmission system, the assembly scheme, and relevant parameters of the power transmission device are analyzed, and the speed regulation characteristic curve is obtained. The shift strategy of power transmission devices involving clutches and brakes during the whole speed regulation process and the best switch time of each component are found. The efficiency expression of the static pressure system is obtained from the efficiency model of the pump-control-motor system, and the efficiency of the multi-purpose power transmission device is obtained using the efficiency definition method. The fitting curves of hydrostatic system efficiency are determined using experimental data, and the efficiency of the hydro–mechanical composite power transmission system is obtained using the conversion mechanism method. The results show that the shift quality of power transmission devices can be improved greatly by controlling the switch sequence of clutches and brakes reasonably.

Study on the Influence of Machining Deviation of Vehicle Automatic Transmission Shifting Control Components on Calibration Parameters

An automatic transmission (AT) shift control model was completed by commercial code Simulation X based on AT shift control system mechanism. The AT shift process under condition of varied machining deviation was analysed by virtual calibration method based on this AT shift model. The results show that the machining deviation of AT shifting control component causes effect on the shift quality, especially affecting the shift impact during the shift process. The machining deviation is larger, accordingly the calibrated parameters such as the hydraulic pressure gradient and the control time increase. It is helpful to improve the shift quality to set the suitable calibration parameters of clutch shift according to different machining deviation.

Research on clutch position control based on backstepping method for small-sized tractors.

Tractors installed automated manual transmission can avoid discomfort for the drivers because of excessive limbs intervention as well as improve shift quality. Automatic clutch control is critical for the performance of the automated manual transmissions. For a good operation, precise and fast control of clutch position is mandatory. In order to meet these requirements, an enhanced strategy focused on the clutch is presented adopting a simple tracking control method based on the detailed models in this study. Clutch models including DC motor model and mechanical actuator model are established and transformed to a controllable model. On the basis of the control model, a clutch position tracking control scheme is proposed composed of motor control circuit and motor angle tracking controller designed according to the backstepping method. Simulations are carried out in comparation with the internal model control method, and the results demonstrate the effectiveness of the presented control scheme by superior rapidity and accuracy of the controller response for the clutch position tracking system.

Gear Shift Quality Enhancement Parameters in Light Commercial Vehicles

In the present scenario enhancements of human ergonomics in Light commercial vehicles are imperative to implement customer comfort in vehicle level. Thus the gear shift mechanism plays an important role in the interface between the driver and vehicle. An exact and smooth running gear shift feel typically depends on the combination of both internal and external shifting elements of the gearbox and Change shift operation(CSO) system. The objective of this paper is to explain the parameters that impacts the gear shift quality and how it is improved by taking multiple design iterations in Light commercial vehicle platform through both objective and subjective evaluations. These iterations are given better results on gear shift feel in dynamic as well as static condition. This lead us to facilitate better shift comfort to end users. The content of the paper is limited to the scope of gear shift quality improvements at manual transmission and change shift operation components.

Pseudo-spectral optimization and model predictive control of vehicle shift process with dual clutch transmission

To improve the shift quality of dual clutch transmission (DCT) vehicles and reduce the jerk and sliding friction in the shift process, a real-time planning of clutch optimal engagement trajectory and control method in the shift process is proposed. This method combines pseudo-spectral optimization, machine learning, and model predictive control. First, considering the jerk, sliding friction work, and shift time as the optimization indices, the adaptive pseudo-spectral method is employed to optimize the engagement trajectory of the clutch during the shift process. Based on the optimal trajectory data set, a gradient boosting decision tree-based real-time planning method for the clutch target engagement trajectory is proposed. Second, a model predictive control strategy for the shift process is proposed based on the DCT system model to track the optimal target trajectory in real-time. Simulations and experiments reveal that the proposed target engagement trajectory planning method can plan the clutch target engagement trajectory for various accelerator pedal openings and initial clutch speed states in real-time, and the proposed model predictive control method can accurately track the target trajectory. Compared with the original vehicle strategy, under 35% and 65% accelerator pedal opening, the maximum absolute value of jerk produced by the proposed strategy was reduced by 31.06% and 31.46%, respectively, and the sliding friction work was reduced by 22.87% and 23.24%, respectively. The shift times of the proposed strategy under 35% and 65% accelerator pedal openings were 19.12% and 20.69% lower than that of the original vehicle strategy, respectively.

SBAR交班模式对外科护士交班质量及临床决策能力的影响

SBAR交班模式对外科护士交班质量及临床决策能力的影响

Analysis of HMCVT Shift Quality Based on the Engagement Characteristics of Wet Clutch

A wet clutch is the key shift part of the hydro-mechanical continuously variable transmission (HMCVT), and the working characteristics have an important influence on the shift quality of HMCVT. To reduce impact during the shift and improve engagement quality, this paper analyzed the influence of system oil pressure and the clutch’s working flow on the engagement characteristics of the wet clutch in terms of shift quality. Firstly, the engagement characteristics (including oil pressure variation characteristics and dynamic torque characteristics) of the wet clutch were tested with different working flows and system oil pressures based on the HMCVT shift clutch bench. Then, the shift impact and sliding friction work were used to evaluate the shift quality. An evaluation function was established based on the maximum shift impact and the maximum sliding friction work to obtain the optimal shift quality. Finally, a shift model was built using Simulation X to simulate the shift quality of nine groups of engagement characteristics. The results showed that increasing the working flow can reduce the wet clutch engagement time by 1.7 s at most, and increasing the system oil pressure can only reduce this by 0.1 s. The higher working flow and system oil pressure can increase the shift impact and reduce the sliding friction work. The combination of the working flow and system oil pressure with the minimum evaluation function value is (10 L/min, 2.0 MPa), and the shift quality is the best. The research can provide a reference for the design, shift control, and shift quality improvement of an HMCVT wet clutch.

Research on the law of dynamic shifting and coordinated section shifting of tractor full-power shift transmission

With the rapid development of China’s agricultural economy, the domestic research on full-power shift transmissions is still immature. In view of the problem of poor transmission shift quality, this paper proposes a tractor full-power shift transmission shifting coordination section law. A transmission dynamics model based on Matlab/Simulink was simulated and analyzed. The results show that the quality of shifting only is better than that of only changing sections, and the quality of shifting after shifting first is worse than that of shifting after shifting first. And selected only the shift and first shift after the two laws of the section, the shortening of the clutch engagement time during the shift only, the impact degree is reduced over time, the first decrease is increased, and the sliding friction work is increased. The change of time between the shift and the transition period, the impact is reduced with time, and the sliding friction work is increased.

Optimal Design of Power-On Downshift Control of Series-Parallel Hybrid Transmission Based on Motor Active Speed Regulation

Multi-speed transmission is the main development direction of hybrid transmission, which has brought higher shift quality requirements than traditional fuel vehicle transmission. However, there is less research on the shifting control of hybrid transmission, especially for the shifting control of dedicated hybrid transmission (DHT), which uses the wet clutch as a shift element. This paper studies the power-on downshift process of a two-speed series-parallel hybrid transmission, proposes a shifting control strategy based on motor active speed regulation, and deeply analyzes the causes of maximum impact during the shifting process. The results show that the reverse torque produced in the process of eliminating the remaining slip is the root cause of the maximum impact. On this basis, two optimization strategies are proposed to reduce the shift impact and improve the shift quality. The simulation results show that the proposed optimization strategies can effectively suppress the shift impact. In the meanwhile, for any control pressure of the OG (off-going) clutch in the speed phase within the range of (2.44–2.53 bar), a high shift quality in which the maximum impact is controlled lower than 10 m/s3 can be achieved, which has high engineering value and practical significance.

Research on shifting process control of automatic transmission

The shift quality of an automatic transmission directly affects the human-perceived comfort and the durability of the automatic transmission. In general, the inconsistency caused by manufacturing errors, life-cycle changes, or other changes in hydraulic characteristics are the main reason affecting the shift quality, which should be compensated by adaptive control in the shifting process. In this paper, we first provide an in-depth analysis of the relationship between proportional solenoid current, clutch pressure, speed and torque in the shifting process control. Then we propose two efficient adaptive control strategies for the torque phase and inertia phase, respectively. Both algorithms are tested and verified on a riot utility vehicle. The experimental results indicate that the adaptive control strategies proposed in this paper can effectively compensate the engine flare and the clutch tie-up of the torque phase, and keep the inertia phase within a proper time range.

Optimization of the Quality of the Automatic Transmission Shift and the Power Transmission Characteristics

We have established a simulation platform for the machine–electro-hydraulic coupling system of the transmission system and the control system to study the root causes of the problems of large shifting impact and slow change of the machine tool transmission system. The dynamic analysis of the gear shift work of the gearbox was carried out, and the main factors affecting its shift instability were studied. With the impact and sliding power as the optimization goals, the shift quality is optimized based on the multi-objective genetic algorithm. Through the shift experiment, it was found that the power interruption phenomenon during the shift process was eliminated after optimization, and the quality of the shift was improved. Simulated planetary row wheel gear meshing force was found in the same gear, and the second planetary row gear meshing force was the largest among the planetary rows. The stress of the node near the top of the tooth is greater than the stress of the node near the node circle and the root of the tooth, and the two sides of the tooth top are relatively larger than the intermediate stress. The dynamic simulation model of the planetary gearbox system with rigid–soft hybrid can obtain the stress distribution of the solar wheel at the maximum impact moment and the stationary stage, as well as the dynamic stress of the key nodes of the solar wheel, which lays the foundation for the fatigue strength and life prediction of the gear system.

Designing Comprehensive Shifting Control Strategy of Hydro-Mechanical Continuously Variable Transmission

The shift quality is one of the most important criteria for evaluating the operation and transportation of a hydro-mechanical continuously variable transmission (HMCVT) tractor. In this study, a comprehensive shifting control strategy of a hydro-mechanical continuously variable transmission in a high horsepower tractor is investigated for enhancing shift quality. The detailed mathematical model of the transmission assembly components, such as the pump-motor system, the clutch system and the equivalent gear shaft system of the hydro-mechanical continuously variable transmission, are established to analyze the exact shifting process. For different transmission systems, two different control methods are proposed to achieve precise control of the transmission. The double-loop control (PID-Model Predictive Control) is used for the pump-motor hydraulic system, which not only ensures the anti-interference of the control signal when the displacement is a fixed value but also improves the response characteristics and stability of the control output when the displacement ratio is variable. The PID control is used for oil pressure control of the clutch system, and experimental results reveal that a simple method can obtain better control performance. Finally, a comprehensive control strategy in the process of shifting is proposed, and the optimal control strategy is obtained by comprehensively adjusting the pump-motor hydraulic system and the clutch system at the shifting point. The results show that the shift acceleration under the optimal control strategy is 64.4% lower than that without control. The proposed control strategy can effectively reduce shift shock and Improve shift smoothness.