Browse Topic: Transmission control units
Transmission tuning involves adjusting parameters within a vehicle's transmission control unit (TCU) or transmission control module (TCM) to optimize performance, efficiency, and driving experience. Transmission tuning is beneficial for optimizing performance, improving fuel efficiency, smoother shifting and enhancing drivability particularly when a vehicle's power output is increased or for specific driving conditions. Especially in offroad and agricultural machines, transmission tuning is vital to significantly improve vehicle performance during different operations. The process of transmission tuning is quite time consuming as multiple tuning iterations are required on the actual vehicle. A significant reduction in tuning time can be achieved using a simulation environment, which can mimic the actual vehicle dynamics and the real time vehicle behavior. In this paper, tuning during the forward and reverse motion of the tractor is described. A two-level PI control-based shift strategy is designed and implemented. In the two-level PI control, the first level calculates the transmission valve pressure setpoint based on the tractor acceleration error. In addition, the second level identifies the valve current based on the valve pressure error. The dynamics model of the tractor powertrain, which is called the plant model, was developed and a closed loop environment is established with the Simulink model. The tuning of the PI gains and the testing are performed in the plant model environment. The optimum PI gains are identified after multiple test iterations in the mentioned environment. The software then tested on the actual tractor with the optimum values and verified the shuttle shift performance. The results show that quick and comfortable shuttle shifts are achieved during the process of moving from the forward to reverse directions and vice versa.
Evaluating the impact of software changes on fuel consumption and emissions is a critical aspect of transmission development. To evaluate the trade-offs between performance improvements and potential negative effects on efficiency, a forward-looking Software-in-the-Loop (SiL) simulation has been developed. Unlike backward calculations that derive fuel consumption based solely on cycle speed and engine speed, this approach executes complete driving cycles as the Worldwide Harmonized Light-Duty Vehicle Test Cycle (WLTC) within a detailed SiL environment. By considering all relevant influencing factors in a dynamic simulation, the method provides a more accurate assessment of fuel consumption and emission differences between two versions of the transmission software. The significant contribution of this work lies in the high-fidelity integration of a real virtual Transmission Control Unit (vTCU) software within a comprehensive, validated forward-looking SiL environment. This approach enables precise delta comparisons that capture transient dynamic interactions, facilitating early, reliable software testing and validation.
This paper describes an optimal control method utilizing a Linear Quadratic Regulator (LQR) to control the torque during the gear shift on a multispeed electrified transmission to optimize for clutch actuator durability and shift performance. The dynamic state-space model of the system has been obtained using System-Identification. An LQR controller is formulated to minimize driveline oscillations and transmission-input-torque using the model by manipulating the electrical torque applied by the traction motor at the transmission input. The LQR controller is implemented in a simulation framework wherein the impact of vehicle parameters on the shift quality metrics is also assessed. Subjective and objective requirements are considered in the tuning process for the LQR controller. The LQR controller is utilized to generate profiled torque table calibrations. These calibrations are then deployed onto a production ready Transmission Control Unit and experimentally validated on a Class-8 Heavy Duty vehicle retrofitted with an electrified multispeed transmission. Experimental validation is performed at multiple Gross-Combination-Vehicle Weight (GCVW) configurations. Significant reduction of clutch actuation effort, shift time while maintaining adherence to subjective and objective shift quality metrics has been demonstrated compared to traditional S-Shaped torque profiling.
During the vehicle launch (i.e. moving the vehicle from “0” speed), the clutch would be slowly engaged by the Driver or Transmission Control Unit (in Automatic Transmission/Automatic Manual Transmission vehicle) for smooth torque transfer between engine and transmission. The clutch is designed to transfer max engine torque with min heat generation. During the clutch engagement, the difference in flywheel and gearbox input shaft speed is called the clutch slipping phase which then leads to a huge amount of energy being dissipated in terms heat due to friction. As a result, clutch surface temperature increases consistently, when the surface temperature crosses the threshold limit, the clutch wears out quickly or burns spontaneously. Hence it is crucial to predict the energy dissipation and temperature variation in various components of clutch assembly through virtual simulation. During the development process of the vehicle, the clutch is tested over many duty cycles to ensure the temperature, wear rate does not exceed the material thresholds. However, performing these tests for every prototype and for every variant can be expensive and time consuming. In this paper we have proposed a simulation methodology to replicate the vehicle test cycle (Hill- Fade test,) i.e. launching the vehicle on 15% grade followed by a cooling cycle and repeated over 150 cycles in the developed virtual simulation methodology using GT-SUITE application to accurately calculate the dissipated energy and the heat transfer through the components in the clutch housing. The developed simulation model can predict the surface temperature of clutch over the defined cycle, can predict the clutch life and can perform a Design Of Experiments analysis to optimize the vehicle or clutch parameter to meet the required customer targets. With the developed simulation model results and real-world vehicle testing results has been validated. The predicated simulation results have 90% correlation with the vehicle test data.
The eHorizon unit enables the possibility to get information of the road ahead in a defined prediction horizon. This data, like road gradient, curve radius, velocity limitation and road class, can be used by the onboard transmission control unit (TCU) via Controller Area Network (CAN) bus. This obtained predictive road information combined with the actual driving conditions can be used to optimize the shifting strategy by a model predictive control (MPC) algorithm which intends to reduce the fuel consumption. In order to solve the optimum problem inside the MPC with less memory, a pre-optimization based dynamic programming (PODP) approach is proposed. In this paper, the predictive gear selection (PGS) strategy will be compared to a conventional automatic gear shifting strategy in a simulation environment and validated on road by implementing it on a heavy-duty truck with a 16-speed automated manual transmission (AMT).
With increased vehicular traffic density a trend has been observed where customers have started preferring automatic transmission in place of its manual version. This Automatic transmission not only shifts the gear automatically, with the help of sensors and actuators, but they are also tuned for better performance of the vehicle in terms of fuel efficiency and emission. This all comes at the cost of power consumption from the battery, increment in cost, weight and complexity. The main parts of an automatic transmission include Torque Convertor, Sensors, Actuators, Transmission Control Unit (TCU) with the epicyclic gear-train being the heart of it. In terms of use in the automotive, a system of epicyclic gear-train can provide only 2 gear ratios. Ravigneaux gear-train is the modified version of epicyclic gear-train where there are two set of Planet gears and Sun gears or Ring gears thereby capable of giving 4 gear ratios with a single system. This paper discusses the design analysis and optimization of Ravigneaux Gear-train. To compare it with Simpson gear-train, simulation of both the gear-trains are done on MATLAB(Simulink), keeping all other parameters of the vehicle like gear ratios, engine and vehicle parameters etc same and the results are compared. Acceleration for both the vehicles were same as the within 8 sec vehicle crossed the 100 kmph mark. Nature of Engine Power curve is also same for both of them. Finally, a table top model of Ravigneaux gear-train is manufactured and its performance is experimentally observed. The results are compared with percentage change in the velocity ratio and it was found that the results are within 10% of the calculated value.
The mechanical properties of sandy road are quite different from those of hard surface road. For vehicle control systems such as EMS (engine management system), TCU (transmission control unit) and ABS (antilock brake system), the strategies and parameters set for solid surface road are not optimal for driving on sandy road. It is an effective way to improve the mobility of all-terrain vehicles by identifying sandy road online and shifting the control strategies and parameters of control systems to sandy sets. In this paper, a sandy road identification algorithm for SUVs is proposed. Firstly, the vehicle signals, such as engine torque and speed, gear position, wheel and vehicle speed, are acquired from EMS, TCU and ESP (electronic stability program) through CAN (controller area network) bus respectively. Based on the information and longitudinal force equilibrium equation, the travelling resistance of vehicle is estimated. The hydraulic torque converter is divided into several parts to calculate the acceleration resistance instead of using the rotational inertia coefficient. Then, the sandy road identification algorithm is proposed mainly based on the travelling resistance. Finally, real vehicle tests are carried out on different road conditions. After cone index penetrometer and soil hygrometer are used to measure the sandy test fields, performances of the travelling resistance estimation method and sandy road identification algorithm are validated. The results show that the identification algorithm designed in the paper can identify the sandy terrain effectively.
This paper describes an approach to reduce development costs and time by frontloading of engineering tasks and even starting calibration tasks already in the early component conception phases of a vehicle development program. To realize this, the application of a consistent and parallel virtual development and calibration methodology is required. The interaction between vehicle subcomponents physically available and those only virtually available at that time, is achieved with the introduction of highly accurate real-time models on closed-loop co-simulation platforms (HiL-simulators) which provide the appropriate response of the hardware components. This paper presents results of a heterogeneous testing scenario containing a real internal combustion engine on a test facility and a purely virtual vehicle using two different automatic transmission calibration and hardware setups. The first constellation is based on an already validated vehicle model (A), including a physical dual-clutch transmission model (DCT), a semi-physical tire model and a vehicle dynamics model. With this standard configuration, the real-time model accuracy is initially illustrated by comparing the operating points distribution and the tailpipe emissions (diluted vs. undiluted) in “Worldwide harmonized Light vehicles Test Cycle” (WLTC) tests for the closed-loop setup at the engine test bench to the real vehicle on a chassis dynamometer. Furthermore, the achievable reproducibility with this in-the-loop approach regarding gaseous and particulate emissions is shown. Finally, the sensitivity and reproducibility of tailpipe emissions related to changes in the calibration set of the virtual “Transmission Control Unit” (TCU) are pointed out for this configuration in “Real Driving Emissions” (RDE) tests. In a second step, another vehicle model (B) is set up and also validated using extensive vehicle measurements. In contrast to model A, model B is equipped with an eight speed automatic transmission model, based on physical relations and an all-wheel drive drivetrain model. During the validation process of model B, several drivability and emission tests have been performed in a Model-in-the-Loop simulation environment. Afterwards, the validated transmission and TCU models were virtually installed into the vehicle model A, resulting in vehicle variant C. This physically nonexistent, virtual vehicle was then tested at the Engine-in-the-Loop test facility. The conceptually different results at the test bench are compared and discussed regarding the vehicle A setup. The potential and reproducibility of the Engine-in-the-Loop approach are shown by a compilation of the results for the variants A and C.
Shift selection devices are desired to be flexible for design and layout, in order to realize the next generation of cockpits for Lexus vehicles. In addition, refined shift operation feelings are also required to be suitable for Lexus vehicles. To meet these demands, the Lexus LC500 has been equipped with a shift-by-wire system, which replaces the mechanical linkage between the shift selector and transmission with electrical signals and an actuator. This shift-by-wire system will be installed in a wide variety of Lexus powertrain lineup, including conventional gas vehicles and hybrid vehicles. Therefore, the next generation shift-by-wire system for Lexus has been developed with high reliability and applicability. This technology will be essential when autonomous driving and autonomous parking systems are realized in the near future. To enable shifting of the parking mechanism in a simple configuration regardless of the engine operation state, shifting of the parking mechanism is performed by an add-on electric parking actuator, and shifting the driving force direction is performed by a transmission control unit in each powertrain system. The shift selection method basically follows an “h” pattern shift lever and a push-type parking switch, which Toyota has used in hybrid vehicles for many years. Additionally, emotional shift selection devices are even more in tune with the driver’s senses. The new flat type high-output parking actuator is developed to enable adoption of this system in rear-wheel drive (RWD) vehicles. This application has a difficult installation environment in terms of space and heat between the transmission and the floor tunnel, and also requires large torque to shift the parking mechanism because of the comparatively high vehicle weight. This paper outlines the new system and its major technologies.
In this investigation an innovative signal generator will be introduced, which enables the generation of transient control signals for the gearshift process. The signals are generated merely depending on scalar transmission control unit (TCU) calibration parameters. The signal generator replaces the comprehensive TCU software within the simulation environment. Thus no extensive residual bus simulation is required. Multiple experimental models represent the core part of the signal generator. To predict the system behavior of the underlying system, the models are trained using measured data from a powertrain with automatic transmission mounted on a test rig. The results demonstrate that the introduced signal generator is suitable to predict transient control signals for the gearshift operation accurately. In combination with an additional powertrain model it is possible to simulate the gearshift process and subsequently to evaluate the gearshift comfort. The signal generator allows a rapid implementation of a simulation environment for TCU calibration with less modeling effort in comparison with the implementation of the original TCU software. Due to a flexible approach, the signal generator offers to predict signals with any course. Hence, it also allows to predict gearshift-comfort relevant signals directly without using a powertrain model. In conclusion the introduced signal generator emphasizes an universal tool with high potential for model based calibration.
In order to improve the drivability and reduce the clutch friction loss, low-cost slope sensor is used in hill-start control of AMT vehicles. After the power spectrum analysis of the original signal and the design of the digital filter, the angle of the slope is obtained with short enough delay and small enough noise. By using this slope angle information, slope resistance force can be calculated online so that the vehicle can be prevented from sliding backward and optimal launch control can be realized. The digital filter of slope angle signal and the optimal controller of dry clutch engagement are embedded in the TCU (Transmission Control Unit) of a micro-car Geely Panda. Real-vehicle experiments are carried out with optimal clutch controller, which shows that the hill-start with low-cost slope sensor and optimal clutch controller can provide successful vehicle launch with little driveline shock. In addition, it can also avoid backward sliding and engine over-speed effectively. Furthermore, hill-start with low-cost slope sensor and optimal clutch controller can reduce clutch wear, extend the life of dry clutch and improve the drivability.
A control oriented model of a Dual Clutch Transmission was developed for real time Hardware In the Loop (HIL) applications. The model is an innovative attempt to reproduce the fast dynamics of the actuation system maintaining a step size large enough for real time applications. The model comprehends a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine sub-models; a stable real time simulation is achieved with a simplification of the model without losing physical validity. After an offline validation, the model was implemented in a HIL system and connected to the TCU (Transmission Control Unit) via two input-output boards, and to a load plate which comprehends all the actuators. The paper presents a selection of the several tests that have been performed for the development of the DCT controller: electrical failure tests on sensors and actuators, mechanical failure tests on hydraulic valves, clutches and synchronizers, and application tests comprehending all the main features of the control performed by the TCU, i.e. drive away and gear shift strategies, and interactions with the driver. Furthermore, the paper shows that the model is capable of reproducing the behavior of the real system during adaption procedures performed by the TCU under particular conditions, i.e. synchronizer position detection and clutch pressure characteristic detection. Being based on physical laws, in every condition the model simulates a plausible reaction of the system to the imposed failure or maneuver, as demonstrated by the possibility of performing a complete new software release test in fully automatic mode.
The demand for better driving comfort, fuel efficiency and reduced CO2 output has been becoming increasingly stringent. In response to such needs, we developed Transmission Electro-Hydraulic Control Module (TEHCM). For Automatic Transmission, expanding the lock-up control area is necessary to improve fuel efficiency. Meanwhile, lock-up control at lower speeds aggravates shift quality. To improve shift quality, Automatic Transmission Fluid (ATF) pressure control must be precise is needed. This can be accomplished by compensating for deviation in TEHCM, which integrates Transmission Control Unit (TCU) and the pressure control actuator, Variable Force Solenoid (VFS). However, there are two problems in installing TEHCM in compact vehicle. The first problem is the miniaturization of such TEHCM. Regarding modules that require a high electrical current to operate the VFS, thermal conductivity contradicts miniaturization. We applied a half-mold structure for TCU to accomplish high thermal conductivity. However, a half-mold structure entails the problem of delamination between ceramic substrate and mold resin, and between mold resin and heat sink. Therefore, the optimization of each material and the development of a new structure are necessary to resolve this problem. The second problem is preventing an increase in calibration time. Calibration must be done at high and low temperatures. However, the bigger the product size is, the longer the setting time. Therefore, a new structure, which reduces temperature dependency of the actuator dramatically, was developed. These technical innovations enable a new TEHCM which satisfies both fuel efficiency and shift quality to be miniaturized enough for accommodate all vehicle segments.
Dual Cultch Transmission (DCT) system has advantage both manual transmission and automatic transmission. As requirement of developing the DCT system is increasing, it is getting important to implement efficient On-Board Diagnosis (OBD) logic system to detect malfunction in vehicle to satisfy California Code Regulation (CCR 1968.2). To satisfy the CCR 1968.2, monitoring for circuit continuity and circuit faults shall be conducted continuously to detect Short to Circuit Ground (SCG), short to Circuit Battery (SCB) and Open error. In this paper, diagnostic logic for two clutches (clutch 1 and 2) and select, shift motor will be introduced to implement Transmission Control Unit (TCU) in DCT system. There are two methods to detect motor u/v/w-lines error. One is by using Application Specific Integrated Circuit (ASIC) diagnosis result and the other one is by software algorithm. Regarding diagnostic logic implemented in software algorithm, it will be derived by relationship between control duty and feedback current measured from motor u/v/w-lines and then from data measured from running vehicle, it will be shown that the diagnostic logic is reasonable to satisfy CCR 1968.2.
The battery electric vehicle (BEV) equipped with automatic mechanical transmission (AMT) can realize gear-shifting automatically based on the optimal shift schedule and thereby gains higher economy and dynamics performances as well as easy drivability. As one of electronic control systems in BEV, the AMT control system takes charge of drivetrain control and plays an important role. However, nowadays the development of electronic control systems in automobile industry is facing a variety of challenges which mainly arise from complex functional requirements and market pressure, and it's the same to the development of AMT control system. This paper presents a multi-layered and modular design approach for the development of AMT control system in a battery electric bus. The multi-layered design approach divides system into two high-level layers, each of which is then divided into a number of low-level layers. One high-level layer is the basic driver layer which is responsible for TCU (Transmission Control Unit) onboard devices driving and task scheduling; the other one is the advanced control layer which is responsible for advanced control strategy such as shift-decision making, shift timing control, fault handler and so on. The standardized application program interface (API) is applied to accomplish the interlayer interaction. Meanwhile, the modular design methodology is used in each layer to break down system function into modules, each of which accomplishes one sub-function and then is integrated to drive the complex function through sharing and combination and swapping. This modular design method allows system to be manageable for the purpose of implementation and maintenance. The modules in basic driver layer are developed in C language, while the modules in advanced control layer by MATLAB/Simulink/Stateflow tools. Finally, the experiment results are analyzed to show how the approach benefits the AMT control system development.
For efficiency improvements, the desire to reduce the mass of vehicle subsystems is far greater than the ability. As a result, off-highway suppliers must seek innovation and technological advances through other means. Given their sheer size and resulting weight, it is easy to see why losing a few pounds from a combine, dump truck, or track loader would not really help the overall mass of the vehicle. Given this conundrum, while a lightweight, compact off-highway vehicle may be the dream, in reality, the road to efficiency gains is not as straightforward. “Building an axle is not like a recipe,” said Michele Lazzaro, Director at Dromos, the Italian manufacturer of transmissions, drive axles, and suspensions for numerous industrial markets. “Axles or associated components need to be developed harmonically, not through a modular concept. You need an optimized solution, and the key to optimizing the weight is making the best use of the material possible. This means that when you look at the lightest possible solution, it probably won't work for mass-production products.”
A researcher from the Southwest Research Institute focuses on one of the most immediate and dramatic changes of powertrain design: the introduction of CVTs. The automotive drivetrain, after evolving little over the past 75 years, is undergoing a rapid and unprecedented metamorphosis. In light of the required reduction in fuel consumption and emissions levels set by legislation and reinforced by the reality of diminishing worldwide oil supplies, this accelerated transformation likely will continue for the next 20 years. Highlighting this transformation is the introduction of the continuously variable transmission (CVT), the change to 42-V electric systems, the introduction of hybrid-electric systems, and the electrification of many mechanical systems. According to researchers from the Southwest Research Institute, to fully realize the benefits of a CVT-configured powertrain, automotive engineers need to design engines with dramatically different operating and physical characteristics than those currently powering production vehicles. For the consumer, the benefits should include engines that are simpler and operate at higher efficiencies, but at higher average load and lower speed. These engines should produce fewer emissions, have a longer operating life, and cost less to make.
The new Mercedes-Benz SL moves into the 21st century with an industry-first production electrohydraulic braking system and a next-generation folding hardtop. Technology is the design ethic that has produced the new-generation Mercedes-Benz SL, just as it was with the first direct-fuel-injection gullwing SL of the early 1950s. But the latest Mercedes-Benz, the fifth-generation SL, reaches far higher levels of sophistication, with the introduction of an electrohydraulic brake-by-wire system (claimed as a “first” for a road car), advanced folding hardtop, and a structure with high aluminum content. Engine developments slated for production are believed to include a bi-turbo V12, and Mercedes-AMG is already offering a 5.5-L supercharged V8 producing 350 kW (470 hp). It is half a century since Mercedes embarked on its SL (sports, light) program when, at a Daimler-Benz Board meeting in June 1951, the decision was made to re-enter motor racing at Formula 1 and sports racing levels. For its first post-war sports racing car, it took the standard 3.0-L engine from the stately 300 sedan, almost doubled its output, “and built a tubular frame and aluminum body” around it. The result-the 300 SL-evolved along aerospace-engineering lines, the fine steel tubes that formed its structure being welded together by hand. And to ensure rigidity, top-hinged, upward-opening doors that formed part of the roof-similar to a fighter aircraft's canopy-provided access to an interior that had the distinct ambience of an aircraft cockpit. It was those doors-dubbed gullwing-more than any other facet of this extraordinary car that were to guarantee the 300 SL a truly unique position in automotive history.
This review of some of the more significant vehicles from this past year's motor shows showcases trends in design and technology from the world's automakers. Concepts highlighted here include some of the many vehicles introduced at acclaimed shows in Geneva, Seoul, Frankfurt, Tokyo, Detroit; and Chicago. One major trend from most of the venues was the distinct movement away from pure automobiles, many of the vehicles being station wagons, minivans, SUVs, or tall minicars or hybrids of one or more. When the first Seoul show was held back in 1995, Korea's personal transport was invariably sedan types. Now, the streets of Seoul, and elsewhere in the country, have more tall minis, minivans, and SUVs, with a sprinkle of sporty coupes. In Tokyo, there were plenty of concept vehicles-in fact more of them than ever before-and some significant new technologies, many in answer to the demands of an environmental and resource-conscious world. Another show car trend among the Japanese automakers was the B-pillarless body with centrally opening four doors. At the North American International Auto Show in Detroit, this year's crop of concept and production vehicles included a number of fuel-cell and hybrid electric vehicles and, again, many cross-over vehicles that blur the lines among traditional car and truck segments. At the 2000 Geneva Motor Show, there was a mix of aesthetic and technological exotica that few motor shows can match. This second in a two-part series highlights some of the more interesting designs and technologies covered by the AEI editors in the past year.
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